PATENT DOCUMENT

Publication Number: US-10043776-B2
Application Number: US-201615182272-A
Country: US
Kind Code: B2

Title: Micro device transfer system with pivot mount

Abstract:
A micro pick up array mount includes a pivot platform to allow a micro pick up array to automatically align with a carrier substrate. Deflection of the pivot platform may be detected to control further movement of the micro pick up array.

Claims:
What is claimed is: 
     
       1. A micro pick up array mount comprising:
 a pivot platform; 
 a base laterally around the pivot platform, wherein the pivot platform is movable relative to the base; 
 a beam physically coupled with the pivot platform at an inner pivot and physically coupled with the base at an outer pivot; 
 a voltage source contact on the base; 
 an electrostatic voltage source contact on the pivot platform to transfer an operating voltage; 
 a source trace that connects the voltage source contact to the electrostatic voltage source contact; 
 a clamp contact on the base; 
 a clamping electrode on the pivot platform; and 
 a clamp trace that connects the clamp contact to the clamping electrode. 
 
     
     
       2. The micro pick up array mount of  claim 1 , further comprising a ribbon cable coupled to the voltage source contact and the clamp contact. 
     
     
       3. The micro pick up array mount of  claim 1 , wherein the outer pivot is on a base edge and the inner pivot is on a pivot platform edge, and the base edge is orthogonal to the pivot platform edge. 
     
     
       4. The micro pick up array mount of  claim 3 , further comprising second beam coupled with the base by a second outer pivot on a second base edge and coupled with the pivot platform by a second inner pivot on a second pivot platform edge. 
     
     
       5. The micro pick up array mount of  claim 3 , wherein the beam is coupled with the pivot platform at a second inner pivot and coupled with the base at a second outer pivot. 
     
     
       6. The micro pick up array mount of  claim 5 , wherein the inner pivot is across the pivot platform from the second inner pivot, and the outer pivot is across the pivot platform from the second outer pivot. 
     
     
       7. The micro pick up array mount of  claim 1 , wherein the inner pivot and the outer pivot each comprise silicon. 
     
     
       8. The micro pick up array mount of  claim 1 , further comprising:
 a second voltage source contact on the base; 
 a second electrostatic voltage source contact on the pivot platform to transfer a second operating voltage; and 
 a second source trace that connects the second voltage source contact to the second electrostatic voltage source contact. 
 
     
     
       9. The micro pick up array mount of  claim 1 , further comprising:
 a second clamp contact on the base; 
 a second clamping electrode on the pivot platform; and 
 a second clamp trace that connects the second clamp contact to the second clamping electrode. 
 
     
     
       10. The micro pick up array mount of  claim 1 , further comprising:
 a second voltage source contact on the base; 
 a second electrostatic voltage source contact on the pivot platform to transfer a second operating voltage; 
 a second source trace that connects the second voltage source contact to the second electrostatic voltage source contact; 
 a second clamp contact on the base; 
 a second clamping electrode on the pivot platform; and 
 a second clamp trace that connects the second clamp contact to the second clamping electrode. 
 
     
     
       11. A micro pick up array mount comprising:
 a pivot platform; 
 a base laterally around the pivot platform, wherein the pivot platform is movable relative to the base; 
 a plurality of beams physically coupled with the pivot platform and the base; 
 a pair of voltage source contacts on the base; 
 a pair of electrostatic voltage source contacts on the pivot platform to transfer operating voltages; 
 a pair of source traces that connect the pair of voltage source contacts to the pair of electrostatic voltage source contacts; 
 a pair of clamp contacts on the base; 
 a pair of clamping electrodes on the pivot platform; and 
 a pair of clamp traces that connect the pair of clamp contacts to the pair of clamping electrodes. 
 
     
     
       12. The micro pick up array mount of  claim 11 , wherein the pair of source traces and the pair of clamp traces run over the plurality of beams in a symmetric pattern. 
     
     
       13. The micro pick up array mount of  claim 11 , wherein the pivot platform, the base, and the plurality of beams comprise silicon. 
     
     
       14. The micro pick up array mount of  claim 11 , further comprising a ribbon cable coupled to a voltage source contact of the pair of voltage source contacts and a clamp contact of the pair of clamp contacts.

Description:
RELATED APPLICATION(S) 
     This application is a continuation application of U.S. patent application Ser. No. 13/715,557, filed on Dec. 14, 2012, now U.S. Pat. No. 9,391,042, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Field 
     The present invention relates to micro devices. More particularly, embodiments of the present invention relate to systems and methods for transferring a micro device from a carrier substrate. 
     Background Information 
     The feasibility of commercializing miniaturized devices such as radio frequency (RF) microelectromechanical systems (MEMS) microswitches, light-emitting diode (LED) display systems, and MEMS or quartz-based oscillators is largely constrained by the difficulties and costs associated with manufacturing those devices. Manufacturing processes typically include wafer based processing and transferring techniques. 
     Device transferring processes include transfer from a transfer wafer to a receiving wafer. One such implementation is “direct printing” involving one bonding step of an array of devices from a transfer wafer to a receiving wafer, followed by removal of the transfer wafer. Another such implementation is “transfer printing” involving two bonding/de-bonding steps. In transfer printing a transfer wafer may pick up an array of devices from a donor wafer and bond the devices to a receiving wafer. Following transfer, the transfer wafer may be removed using techniques that include laser lift-off (LLO), grinding or polishing, and etching. 
     Gimbal mechanisms have been used in wafer polishing equipment to facilitate evenly polishing a wafer. For example, passive gimbal mechanisms in polishing equipment facilitate alignment of wafers with a polishing pad. 
     SUMMARY OF THE DESCRIPTION 
     A micro pick up array mount and methods of using the micro pick up array mount to transfer an array of micro devices from a carrier substrate are disclosed. In an embodiment, the micro pick up array mount includes a pivot platform, a base laterally around the pivot platform, and a beam between the pivot platform and the base. The beam may be coupled with the pivot platform at an inner pivot and coupled with the base at an outer pivot. In an embodiment, the outer pivot is on a base edge and the inner pivot is on a pivot platform edge. The base edge may be orthogonal to the pivot platform edge. In an embodiment, a second beam may be coupled with the base by a second outer pivot on a second base edge and coupled with the pivot platform by a second inner pivot on a second pivot platform edge. In an embodiment, the beam is coupled with the pivot platform at a second inner pivot and coupled with the base at a second outer pivot. The inner pivot may be across the pivot platform from the second inner pivot, and the outer pivot may be across the pivot platform from the second outer pivot. In an embodiment, the inner pivots and the outer pivots comprise silicon. 
     In an embodiment, the micro pick up array mount includes a pivot platform electrostatic voltage source contact on the pivot platform and a base electrostatic voltage source contact on the base. The pivot platform electrostatic voltage source contact may be in electrical connection with the base electrostatic voltage source contact. The micro pick up array mount may also include a trace extending from the pivot platform electrostatic voltage source contact and placing the pivot platform electrostatic voltage source contact may be in electrical connection with the base electrostatic voltage source contact. 
     In an embodiment, the micro pick up array mount includes a bonding site on the pivot platform. The bonding site may include a clamp electrode in electrical connection with a base clamp contact on the base. In an embodiment, a trace extends from the clamp electrode and places the clamp electrode in electrical connection with the base clamp contact. In an embodiment, the bonding site may include a metal such as gold, copper, and aluminum. 
     In an embodiment, the micro pick up array mount includes a heating contact on the base and a heating element over the pivot platform in electrical connection with the heating contact. The micro pick up array mount may also include a temperature sensor on the pivot platform. 
     A micro device transfer system and methods of using the micro device transfer system to transfer an array of micro devices from a carrier substrate are disclosed. In an embodiment, the micro device transfer system includes a micro pick up array mount having a pivot platform, a base laterally around the pivot platform, and a beam between the pivot platform and the base. The beam may be coupled with the pivot platform at an inner pivot and coupled with the base at an outer pivot. The micro device transfer system may also include a micro pick up array having a substrate supporting an array of electrostatic transfer heads. The micro pick up array may be joinable with the micro pick up array mount. In an embodiment, the outer pivot may be on a base edge and the inner pivot may be on a pivot platform edge. The base edge may be orthogonal to the pivot platform edge. In an embodiment, the micro device transfer system includes a second beam coupled with the base by a second outer pivot on a second base edge and coupled with the pivot platform by a second inner pivot on a second pivot platform edge. In an embodiment, the beam may be coupled with the pivot platform at a second inner pivot and coupled with the base at a second pivot. The inner pivot may be across the pivot platform from the second inner pivot, and the outer pivot may be across the pivot platform from the second outer pivot. In an embodiment, the inner pivots and the outer pivots include silicon. In an embodiment, each electrostatic transfer head comprises a mesa structure including a top surface having a surface area in a range of 1 to 10,000 square micrometers. 
     In an embodiment, the micro device transfer system includes the micro pick up array having an electrode and a substrate electrostatic voltage source contact on the substrate. The substrate electrostatic voltage source connection may be in electrical connection with the electrode. In an embodiment, the micro device transfer system includes the micro pick up array mount having a pivot platform electrostatic voltage source contact on the pivot platform and a base electrostatic voltage source contact on the base. The pivot platform electrostatic voltage source contact may be in electrical connection with the base electrostatic voltage source contact. The micro pick up array mount may also include a first trace extending from the pivot platform electrostatic voltage source contact and placing the pivot platform electrostatic voltage source contact in electrical connection with the base electrostatic voltage source contact. Furthermore, the micro pick up array may also include a second trace extending from the substrate electrostatic voltage source contact and placing the substrate electrostatic voltage source contact in electrical connection with the electrode through the second trace. The substrate electrostatic voltage source contact may align with the pivot platform electrostatic voltage source contact to place the electrode in electrical connection with the base electrostatic voltage source contact. 
     In an embodiment, the micro device transfer system may include a base clamp contact on the base and in electrical connection with a clamp electrode on the pivot platform. The micro device transfer system may also include a trace extending from the clamp electrode and placing the clamp electrode in electrical connection with the base clamp contact. The clamp electrode may align with the substrate to electrostatically bond the micro pick up array to the pivot platform when voltage is applied to the clamp electrode from the base clamp contact through the trace. In an embodiment, the micro pick up array may attach to the pivot platform by a permanent bond, such as by a thermocompression bond. 
     In an embodiment, the micro device transfer system includes a heating contact on the base and a heating element over the pivot platform in electrical connection with the heating contact. The micro pick up array mount may also include a temperature sensor on the pivot platform. 
     A micro device transfer system and methods of using the micro device transfer system to transfer an array of micro devices from a carrier substrate are disclosed. In an embodiment, the micro device transfer system includes a transfer head assembly having a mounting surface. The micro device transfer system may also include a micro pick up array mount having a pivot platform, a base laterally around the pivot platform, and a beam that connects the base with the pivot platform, and a micro pick up array having a substrate supporting an array of electrostatic transfer heads. In an embodiment, the pivot platform may be deflectable toward the transfer head assembly when the base is mounted on the mounting surface and the micro pick up array is mounted on the pivot platform. In an embodiment, the transfer head assembly includes a sensor to detect deflection of the pivot platform toward the transfer head assembly. For example, the sensor may be a contact sensor to sense a deflected position of the pivot platform and the contact sensor can include a switch. Alternatively, the sensor may be a motion sensor to sense movement of the pivot platform. 
     In an embodiment, the micro device transfer system may include the transfer head assembly having an electrostatic voltage source connection, the micro pick up array mount having a pivot platform electrostatic voltage source contact and a base electrostatic voltage source contact, and the micro pick up array having a substrate electrostatic voltage source contact. The electrostatic voltage source connection may be aligned with the base electrostatic voltage source contact and the pivot platform electrostatic voltage source contact may be aligned with the substrate electrostatic voltage source contact. 
     In an embodiment, the micro device transfer system includes the transfer head assembly having a vacuum port coupled with a vacuum source to apply suction to the micro pick up array mount. In an embodiment, the transfer head assembly may have a clamping voltage source connection. The micro pick up array mount may have a clamp electrode on the pivot platform to apply an electrostatic force to the micro pick up array. In an embodiment, the micro pick up array mount may have a base clamp contact on the base in electrical connection with the clamp electrode. The micro pick up array mount may also have a trace extending from the clamp electrode and placing the clamp electrode in electrical connection with the base clamp contact. The clamp voltage source connection may be aligned with the base clamp contact and the substrate may be aligned with the clamp electrode to electrostatically bond the micro pick up array to the pivot platform when voltage is applied to the clamp electrode from the clamping voltage source connection through the base clamp. 
     In an embodiment, the micro device transfer system includes the transfer head assembly having a holding electrode coupled to an electrostatic voltage source to apply an electrostatic force to the micro pick up array mount and a clamping voltage source connection. Furthermore, the micro device transfer system may include the micro pick up array mount having a clamp electrode on the pivot platform to apply and electrostatic force to the micro pick up array. The micro pick up array mount may have a base clamp contact on the base in electrical connection with a clamp electrode on the pivot platform. The micro pick up array mount may have a trace extending from the clamp electrode to place the clamp electrode in electrical connection with the base clamp contact. The clamp voltage source connection may be aligned with the base clamp contact and the substrate may be aligned with the clamp electrode to electrostatically bond the micro pick up array to the pivot platform when voltage is applied to the clamp electrode from the clamping voltage source connection through the base clamp. 
     In an embodiment, each electrostatic transfer head includes a mesa structure having a top surface with a surface area in a range of 1 to 10,000 square micrometers. In an embodiment, the micro pick up array is attached to the pivot platform by a permanent bond that includes a thermocompression bond. 
     In an embodiment, the micro device transfer system includes the transfer head assembly having a heating connection and the micro pick up array mount having a heating contact on the base and a heating element over the pivot platform in electrical connection with the heating contact. 
     In an embodiment, a method includes moving a transfer head assembly toward a carrier substrate and contacting an array of micro devices on the carrier substrate with a micro pick up array having an array of electrostatic transfer heads. The micro pick up array may be mounted on a micro pick up array mount and the micro pick up array mount may be mounted on the transfer head assembly. The method may further include deflecting a pivot platform of the micro pick up array mount toward the transfer head assembly, sensing deflection of the pivot platform, stopping relative movement between the transfer head assembly and the carrier substrate, applying a voltage to the array of electrostatic transfer heads to create a grip pressure on the array of micro devices, and picking up the array of micro devices from the carrier substrate. In an embodiment, the method includes moving the transfer head assembly toward the pivot platform after sensing deflection and before stopping relative movement. In an embodiment, the method includes stopping relative movement between the transfer head assembly and the carrier substrate may occur after sensing deflection of the pivot platform with a plurality of sensors. In an embodiment, the method includes moving the transfer head assembly toward the carrier substrate for a set distance after sensing deflection of the pivot platform. In an embodiment, the method includes stopping relative movement between the transfer head assembly and the carrier substrate immediately in response to sensing deflection of the pivot platform. In an embodiment, the method includes actuating the transfer head assembly to further align the pivot platform to a plane of the carrier substrate by tipping or tilting the transfer head assembly after sensing deflection of the pivot platform. In an embodiment, the method includes applying heat to the array of electrostatic transfer heads while picking up the array of micro devices. 
     In an embodiment, a method includes moving a transfer head assembly toward a receiving substrate and contacting the receiving substrate with an array of micro devices carried by a micro pick up array. The micro pick up array may have an array of electrostatic transfer heads and be mounted on a micro pick up array mount that is mounted on the transfer head assembly. The method may also include deflecting a pivot platform of the micro pick up array mount toward the transfer head assembly, sensing deflection of the pivot platform, stopping relative motion between the transfer head assembly and the receiving substrate, removing a voltage from the array of electrostatic transfer heads, and releasing the array of micro devices onto the receiving substrate. In an embodiment, the method includes moving the transfer head assembly toward the pivot platform after sensing deflection and before stopping relative movement. In an embodiment, the method includes stopping relative movement between the transfer head assembly and the receiving substrate after sensing deflection of the pivot platform with a plurality of sensors. In an embodiment, the method includes moving the transfer head assembly toward the receiving substrate for a set distance after sensing deflection of the pivot platform. In an embodiment, the method includes stopping relative movement between the transfer head assembly and the receiving substrate immediately in response to sensing deflection of the pivot platform. In an embodiment, the method includes stopping relative movement between the transfer head assembly and the receiving substrate immediately in response to sensing deflection of the pivot platform. In an embodiment, the method includes actuating the transfer head assembly to further align the pivot platform to a plane of the receiving substrate by tipping or tilting the transfer head assembly after sensing deflection of the pivot platform. In an embodiment, the method includes applying heat to the array of micro devices before removing the voltage from the array of electrostatic transfer heads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustration of a mass transfer tool in accordance with an embodiment of the invention. 
         FIG. 2  is a side view illustration of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount in accordance with an embodiment of the invention. 
         FIG. 3A  is a side view illustration of a micro device transfer system having an array of electrostatic transfer heads positioned over and apart from an array of micro devices on a carrier substrate in accordance with an embodiment of the invention. 
         FIG. 3B  is a side view illustration of a micro device transfer system having an array of electrostatic transfer heads positioned over and in contact with an array of micro devices on a carrier substrate in accordance with an embodiment of the invention. 
         FIG. 4A  is a perspective view illustration of a micro pick up array mount having an electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 4B  is a side view illustration of a micro pick up array mount having an electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 4C  is a perspective view illustration of a micro pick up array mount having an electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 4D  is a perspective view illustration of a micro pick up array mount having an electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 4E  is a side view illustration of a micro pick up array mount having an electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 5A  is a perspective view illustration of a micro pick up array mount having a non-electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 5B  is a perspective view illustration of a micro pick up array mount having a non-electrostatic bonding site in accordance with an embodiment of the invention. 
         FIG. 6A  is a perspective view illustration of a micro pick up array mount having a beam laterally around a pivot platform and an auto-aligning behavior in accordance with an embodiment of the invention. 
         FIG. 6B  is a perspective view illustration of a micro pick up array mount having two beams laterally around a portion of a pivot platform and an auto-aligning behavior in accordance with an embodiment of the invention. 
         FIG. 6C  is a perspective view illustration of a micro pick up array mount having four beams between a pivot platform and a base, and an auto-aligning behavior, in accordance with an embodiment of the invention. 
         FIG. 7  is a side view illustration of a micro pick up array having a substrate supporting an array of electrostatic transfer heads in accordance with an embodiment of the invention. 
         FIG. 8A  is a side view illustration of a micro device transfer system including a micro pick up array mount electrostatically bonded with a micro pick up array in accordance with an embodiment of the invention. 
         FIG. 8B  is a side view illustration of a micro device transfer system including a micro pick up array mount electrostatically bonded with a micro pick up array in accordance with an embodiment of the invention. 
         FIG. 9A  is a side view illustration of a micro device transfer system including a micro pick up array mount permanently bonded with a micro pick up array in accordance with an embodiment of the invention. 
         FIG. 9B  is a side view illustration of a micro device transfer system including a micro pick up array mount permanently bonded with a micro pick up array in accordance with an embodiment of the invention. 
         FIG. 10A  is a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount in accordance with an embodiment of the invention. 
         FIG. 10B  is a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount in accordance with an embodiment of the invention. 
         FIG. 11  is a perspective view illustration of a transfer head assembly having multiple sensors to detect deflection of a micro pick up array mount in accordance with an embodiment of the invention. 
         FIG. 12  is a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount and the transfer head assembly having multiple sensors to detect deflection of the micro pick up array mount in accordance with an embodiment of the invention. 
         FIG. 13  is a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount and the micro pick up array mount deflected toward sensors on the transfer head assembly in accordance with an embodiment of the invention. 
         FIG. 14  is a flowchart illustrating a method of picking up an array of micro devices from a carrier substrate in accordance with an embodiment of the invention. 
         FIG. 15A  is a cross-sectional side view illustration of a micro device transfer system having a transfer head assembly moving toward a carrier substrate in accordance with an embodiment of the invention. 
         FIG. 15B  is a cross-sectional side view illustration of a micro device transfer system having an array of electrostatic transfer heads contacting an array of micro devices on a carrier substrate in accordance with an embodiment of the invention. 
         FIG. 15C  is a cross-sectional side view illustration of a micro device transfer system having a micro pick up array mount deflecting toward a transfer head assembly in accordance with an embodiment of the invention. 
         FIG. 15D  is a cross-sectional side view illustration of a micro device transfer system having an array of electrostatic transfer heads picking up an array of micro devices from a carrier substrate in accordance with an embodiment of the invention. 
         FIG. 16  is a flowchart illustrating a method of releasing an array of micro devices onto a receiving substrate in accordance with an embodiment of the invention. 
         FIG. 17A  is a cross-sectional side view illustration of a micro device transfer system having a transfer head assembly moving toward a receiving substrate in accordance with an embodiment of the invention. 
         FIG. 17B  is a cross-sectional side view illustration of a micro device transfer system having an array of electrostatic transfer heads carrying an array of micro devices contacting a receiving substrate in accordance with an embodiment of the invention. 
         FIG. 17C  is a cross-sectional side view illustration of a micro device transfer system having a micro pick up array mount deflecting toward a transfer head assembly in accordance with an embodiment of the invention. 
         FIG. 17D  is a cross-sectional side view illustration of a micro device transfer system releasing an array of micro devices onto a receiving substrate from an array of electrostatic transfer heads in accordance with an embodiment of the invention. 
         FIG. 18  is a schematic illustration of an exemplary computer system that may be used in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention describe systems and methods for transferring a micro device or an array of micro devices from a carrier substrate. For example, the micro devices or array of micro devices may be any of the micro LED device structures illustrated and described in related U.S. patent application Ser. Nos. 13/372,222, 13/436,260, 13/458,932, and Ser. No. 13/625,825. While some embodiments of the present invention are described with specific regard to micro LED devices, the embodiments of the invention are not so limited and certain embodiments may also be applicable to other micro LED devices and micro devices such as diodes, transistors, ICs, and MEMS. 
     In various embodiments, description is made with reference to the figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, in order to provide a thorough understanding of the present invention. In other instances, well-known processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the present invention. Reference throughout this specification to “one embodiment,” “an embodiment”, or the like, means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrase “one embodiment,” “an embodiment”, or the like, in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The terms “over”, “to”, “between” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over” or “on” another layer or bonded “to” another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers. 
     The terms “micro” device or “micro” LED structure as used herein may refer to the descriptive size of certain devices or structures in accordance with embodiments of the invention. As used herein, the terms “micro” devices or structures are meant to refer to the scale of 1 to 100 μm. However, embodiments of the present invention are not necessarily so limited, and certain aspects of the embodiments may be applicable to larger, and possibly smaller size scales. In an embodiment, a single micro device in an array of micro devices, and a single electrostatic transfer head in an array of electrostatic transfer heads both have a maximum dimension, for example length or width, of 1 to 100 μm. In an embodiment, the top contact surface of each micro device or electrostatic transfer head has a maximum dimension of 1 to 100 μm. In an embodiment, the top contact surface of each micro device or electrostatic transfer head has a maximum dimension of 3 to 20 μm. In an embodiment, a pitch of an array of micro devices, and a pitch of a corresponding array of electrostatic transfer heads is (1 to 100 μm) by (1 to 100 μm), for example a 20 μm by 20 μm, or 5 μm by 5 μm pitch. In one aspect, without being limited to a particular theory, embodiments of the invention describe micro device transfer heads and head arrays which operate in accordance with principles of electrostatic grippers, using the attraction of opposite charges to pick up micro devices. In accordance with embodiments of the present invention, a pull-in voltage is applied to a micro device transfer head in order to generate a grip pressure on a micro device and pick up the micro device. 
     In one aspect, embodiments of the invention describe systems and methods for the mass transfer of micro devices using a micro pick up array mount with a self-aligning capability. In an embodiment, the micro pick up array mount may include one or more pivots and beams to allow a mounted micro pick up array to automatically align to a carrier substrate or a receiving substrate when the system components are brought into contact, e.g., when electrostatic transfer heads supported by the micro pick up array contact an array of micro devices on the carrier substrate. Thus, the micro pick up array mount facilitates more complete and uniform contact between the array of electrostatic transfer heads and array of micro devices being transferred. In this manner, the self-aligning capability of the micro pick up array mount may allow for a simpler mass transfer tool design in which an expensive arrangement of sensors (such as spectral-interference laser displacement meters) and actuators may not be required for fine-alignment of the micro pick up array with the carrier or receiving substrate on the micron or sub-micron scale prior to picking up or releasing the array of micro devices. Thus, the self-aligning capability may reduce cost of system components, while also increasing the transfer rate of micro devices since fine-alignment may be accomplished by the self-aligning capability while picking up and releasing the array of micro devices. 
     In another aspect, embodiments of the invention describe systems and methods for the mass transfer of micro devices using sensors to sense system component deflections. A variety of sensors may be employed such as expensive spectral-interference laser displacement meters, or less expensive sensor switches that detect contact between system components. For example, a sensor may detect deflection of a micro pick up array mount when a mounted micro pick up array contacts a micro device on a carrier substrate, or when a micro device carried by the micro pick up array contacts a receiving substrate. More specifically, in an embodiment, relative movement between a transfer head assembly and a carrier substrate, or relative movement between the transfer head assembly and a receiving substrate, may be stopped in response to a sensed deflection. Movement may stop immediately upon detection, or upon a predetermined event following detection. Thus, contact between an array of micro devices and an array of electrostatic transfer heads or a receiving substrate may be monitored to control pick up and release of the array of micro devices. 
     In yet another aspect, embodiments of the invention describe systems and methods for the mass transfer of micro devices using system components having electrostatic voltage source connections and contacts that align to place the system components in electrical connection with each other. In an embodiment, an electrostatic voltage source connection of a transfer head assembly may be placed in electrical connection with an array of electrostatic transfer heads. More specifically, a voltage may be supplied from an electrostatic voltage source connection to the array of electrostatic transfer heads through various contacts and connectors, e.g., vias and traces, which align to create an operating voltage path traversing several components. An operating voltage applied to, e.g., an electrode of the electrostatic transfer head from the electrostatic voltage source connection, may allow the electrostatic transfer head to apply a grip pressure to a micro device. 
     In still another aspect, embodiments of the invention describes systems and methods for the mass transfer of micro devices using system components having clamping voltage source connections and contacts that align to join the system components with each other. In an embodiment, a clamping voltage source connection of a transfer head assembly may be placed in electrical connection with a clamp electrode of a micro pick up array mount. More specifically, a voltage may be supplied from a clamping voltage source connection to the micro pick up array through various contacts and connectors, e.g., vias and traces, which align to create a clamping voltage path traversing several components. A clamping voltage applied to the clamp electrode on the micro pick up array mount from the clamping voltage source connection may electrostatically hold a micro pickup array against the micro pick up array mount. 
     In another aspect, embodiments of the invention describe systems and methods for the mass transfer of micro devices using system components having heating mechanisms to apply heat to an array of micro devices. In an embodiment, the heating mechanism includes a resistive heating element on a micro pick up array mount. Heat may thus be delivered through the micro pick up array mount to one or more electrostatic transfer heads on a micro pick up array mounted on the micro pick up array mount, and into an array of micro devices gripped by the electrostatic transfer heads. In this manner, it is possible to transfer heat from a micro pick up array mount having a self-aligning capability to a micro device carried by the micro pick up array mount without excessively heating portions of the micro pick up array mount. 
     In yet another aspect, embodiments of the invention describe a manner for mass transfer of an array of pre-fabricated micro devices with an array of electrostatic transfer heads. For example, the pre-fabricated micro devices may have a specific functionality such as, but not limited to, a LED for light-emission, silicon IC for logic and memory, and gallium arsenide (GaAs) circuits for radio frequency (RF) communications. In some embodiments, arrays of micro LED devices which are poised for pick up are described as having a 20 μm by 20 μm pitch, or 5 μm by 5 μm pitch. At these densities a 6 inch substrate, for example, can accommodate approximately 165 million micro LED devices with a 10 μm by 10 μm pitch, or approximately 660 million micro LED devices with a 5 μm by 5 μm pitch. A transfer tool including an array of electrostatic transfer heads matching an integer multiple of the pitch of the corresponding array of micro LED devices can be used to pick up and transfer the array of micro LED devices to a receiving substrate. In this manner, it is possible to integrate and assemble micro LED devices into heterogeneously integrated systems, including substrates of any size ranging from micro displays to large area displays, and at high transfer rates. For example, a 1 cm by 1 cm array of electrostatic transfer heads can pick up and transfer more than 100,000 micro devices, with larger arrays of electrostatic transfer heads being capable of transferring more micro devices. 
       FIG. 1  is a perspective view illustration of a mass transfer tool for transferring micro devices from a carrier substrate shown in accordance with an embodiment of the invention. Mass transfer tool  100  includes a transfer head assembly  206  for picking up a micro device from a carrier substrate held by a carrier substrate holder  108  and for transferring and releasing the micro device onto a receiving substrate held by a receiving substrate holder  124 . A system of actuators operates to move the transfer head assembly  206  under the control of a computer system  150 . Furthermore, computer system  150  controls the actuators based on feedback inputs from various sensors. In some embodiments, mass transfer tool  100  may be any of the mass transfer tool embodiments illustrated and described in related U.S. patent application Ser. No. 13/607,031, which is hereby incorporated by reference. 
     Referring to  FIG. 2 , a side view illustration of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount is shown in accordance with an embodiment of the invention. Micro device transfer system  200  includes micro pick up array mount  202 , micro pick up array  204 , and transfer head assembly  206 . Each of these system components may be joined. For example, micro pick up array mount  202  may be retained on a mounting surface  208  of transfer head assembly  206 , and micro pick up array  204  may be retained on a mounting surface  205  of the micro pick up array mount  202 . In an embodiment, the components of micro pick up array system  200  may be electrically connected, such that an operating voltage path or clamping voltage path traverses multiple components. These aspects are described further below. 
     Referring to  FIG. 3A , a side view illustration of a micro device transfer system having an array of electrostatic transfer heads positioned over and apart from an array of micro devices on a carrier substrate is shown in accordance with an embodiment of the invention. Micro device transfer system  200  with micro pick up array  204  supporting array of electrostatic transfer heads  210  may be positioned over and apart from an array of micro devices (not shown) carried on carrier substrate  302 , which is held by carrier substrate holder  108 . In an initial state, micro pick up array  204  and carrier substrate  302  may have surfaces that are misaligned by an angle  304 . Furthermore, micro pick up array  204  is mounted on micro pick up array mount  202 . Micro pick up array mount  202  includes a pivot platform as described in more detail in the following description that allows for the self-alignment of micro pick up array  204  with the array of micro devices on the carrier substrate  302 . Thus, micro pick up array  204  is able to move relative to transfer head assembly  206 . 
     Referring to  FIG. 3B , a side view illustration of a micro device transfer system having an array of electrostatic transfer heads positioned over and in contact with an array of micro devices on a carrier substrate is shown in accordance with an embodiment of the invention. When micro pick up array  204  is moved toward carrier substrate  302  from the misaligned state shown in  FIG. 3A , the array of electrostatic transfer heads  210  may contact an array of micro devices on the carrier substrate  302  unevenly. For example, one side of array of electrostatic transfer heads  210  may contact the array of micro devices while another side may not. Alternatively, all of the electrostatic transfer heads  210  may make contact, but the pressure applied throughout the array of electrostatic transfer heads may be uneven. However, as described below, the forces imparted to array of electrostatic transfer heads  210  may tip and tilt the pivot platform, allowing array of electrostatic transfer heads  210  to align with the array of micro devices on carrier substrate  302 . That is, the pivot platform may rotate and translate about and along multiple axes to align with the contacting surface, e.g., carrier substrate  302 , such that complete and uniform contact is achieved. 
     Since the pivot platform self-aligns, pressure and/or contact distribution throughout micro pick up array  204  may be substantially uniform. Uniform pressure distribution can include even pressure and/or contact between the electrostatic transfer heads  210  and the micro devices on carrier substrate  302 . Such uniform pressure or contact may avoid damage to electrostatic transfer heads  210  or micro devices and it may enable the contact and transfer of all, or nearly all, of the micro devices. 
     Referring now to  FIG. 4A , a perspective view illustration is shown of a micro pick up array mount having an electrostatic bonding site in accordance with an embodiment of the invention. Micro pick up array mount  202  may be joined with, and placed between, micro pick up array  204  and transfer head assembly  206 , allowing relative movement between those components. Relative movement of  204 / 206  may result in automatic alignment of the array of electrostatic transfer heads  210  with an array of micro devices on a carrier substrate. As a result, the electrostatic transfer heads  210  may contact every corresponding micro device of the array of micro devices with uniform pressure. 
     In the embodiment illustrated, micro pick up array mount  202  includes base  402  and pivot platform  404 . In an embodiment, base  402  surrounds all or a part of pivot platform  404 . For example, base  402  may extend laterally around pivot platform  404 , as illustrated. In an alternative embodiment, base  402  does not surround pivot platform  404 . Base  402  and pivot platform  404  may be interconnected by one or more beams  406 . Each beam  406  may connect with base  402  and pivot platform  404  at one or more pivot locations, such as inner pivot  408 ,  414  and outer pivot  410 ,  416 . 
       FIG. 4A  shows both base  402  and pivot platform  404  having rectangular perimeters, however base  402  and pivot platform  404  may be shaped differently. For example, base  402  may be circular, hexagonal, oval, etc., without departing from the scope of this disclosure. Likewise, pivot platform  404  may be alternatively shaped. For example, pivot platform  404  may be circular, hexagonal, oval, etc. In an embodiment, base  402  and pivot platform  404  have conforming shapes, such that pivot platform  404  is nestled within the base  402  of the same shape. In other embodiments, base  402  and pivot platform  404  do not have conforming shapes. For example, base  402  may be circular and pivot platform  404  may be rectangular, resulting in additional gaps near the midpoint of each side of pivot platform  404 . Such mismatch may allow for beams  406  to be extended within the gap areas in order to provide larger bending arms, in accordance with the following disclosure. 
     Still referring to  FIG. 4A , beam  406  may extend from inner pivot  408  to outer pivot  410  laterally around pivot platform  404 . More particularly, beam  406  may conform to base  402  and pivot platform  404  by fitting between those components and substantially filling a void between those components. In at least one embodiment, the lateral extension of beam  406  provides a lever arm that allows adequate bending in beam  406  and torsion in pivots  408  and  410  to enable relative movement between base  402  and pivot platform  404  when forces are applied to those components. Bending in beam  406  includes a component orthogonal to base  402 , e.g., a z-direction component along axis  474 . 
     In an embodiment, the pivots of micro pick up array mount  202  are positioned to twist about multiple axes. For example, inner pivot  408  is positioned on pivot platform  404  at an edge that is orthogonal to an edge of base  402  on which outer pivot  410  is positioned. Thus, axes such as axis  470  and axis  472  running perpendicular to the edges that inner pivot  408  and outer pivot  410  are positioned on, are also orthogonal to each other. Resultantly, pivot platform  404  and base  402  may twist relative to each other along axes  470  and  472 . For example, pivot platform  404  can twist in a direction θ x  about axis  470 , relative to base  402 . Additionally, pivot platform  404  can twist in a direction θ y  about axis  472 , relative to base  402 . 
     Micro pick up array mount  202  may include pairs of pivots along an axis of torsion. For example, micro pick up array mount  202  may include inner pivot  414  positioned across pivot platform  404  from inner pivot  408 . Thus, pivot platform  404  may be supported along opposite sides by beam  406  at inner pivots  408  and  414 . Furthermore, pivot platform  404  may rotate about an axis, e.g., axis  472  running through inner pivot  408  and inner pivot  414  when a force is applied to the pivot platform offset from the axis. For example, pivot platform  404  may rotate in a direction θ y  about axis  472  when a force is applied to beam  406  near outer pivot  410 . Likewise, micro pick up array mount  202  may include outer pivot  416  positioned across pivot platform  404  from outer pivot  410 . Thus, the beam  406  connecting pivot platform  404  with base  402  may be supported along opposite sides by base  402  at outer pivots  410  and  416 . Furthermore, pivot platform  404  may rotate about an axis, e.g., axis  470 , running through outer pivot  410  and outer pivot  416  when a force is applied to the pivot platform offset from the axis. For example, pivot platform  404  may rotate in a direction θ x  about axis  470  when a force is applied to beam  406  near inner pivot  408 . Thus, pivots of micro pick up array mount  404  facilitate movement and automatic alignment between the base  402  and pivot platform  404 . The kinematics of micro pick up array mount  202  will be described further below. 
     In accordance with embodiments of the invention, micro pick up array mount  202  may be formed from one or more portions or parts. Several materials may be utilized for the micro pick up array mount  202 . Material selection for the micro pick up array mount is driven by the capability to deflect under applied load, thermal stability, and minimal spring mass. Table 1 lists relevant material properties for several candidate materials including silicon, silicon carbide, aluminum nitride, stainless steel, and aluminum. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Yield 
                 Flexure 
                   
                   
               
               
                   
                 Modulus 
                 Strength 
                 Ratio 
                 CTE 
                 Density 
               
               
                 Material 
                 (GPA) 
                 (MPa) 
                 (×10e−3) 
                 (ppm/° C.) 
                 (kg/m 3 ) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Silicon 
                 165 
                 2000 
                 12.1 
                 2.6 
                 2400 
               
               
                 Silicon Carbide 
                 410 
                 550 
                 1.3 
                 4.0 
                 3100 
               
               
                 Aluminum 
                 320 
                 320 
                 1.0 
                 4.5 
                 3260 
               
               
                 Nitride 
               
               
                 Stainless Steel 
                 190 
                 600 
                 3.2 
                 14 
                 8240 
               
               
                 316 
               
               
                 Aluminum 
                 70 
                 47 
                 0.7 
                 23 
                 2700 
               
               
                   
               
            
           
         
       
     
     Although each of the listed materials may be used for the micro pick up array mount, silicon has the largest flexure ratio, lowest CTE, and lowest density of the candidate materials. In addition, silicon may be formed with a variety of precision semiconductor manufacturing techniques. 
     Thus, in an embodiment, base  402 , pivot platform  404 , and beam  406  are formed from a silicon wafer to produce distinct regions. More specifically, known processes, such as deep etching, laser cutting, etc. may be used to form channels  412 . In at least one embodiment, channels  412  may therefore define the structure of micro pick up array mount  202  by providing separations between, e.g., base  402  and pivot platform  404  regions. 
     Referring to  FIGS. 4A-4B , micro pick up array mount  202  may include one or more pivot platform electrostatic voltage source contacts  420  on pivot platform  404 . Electrostatic voltage source contacts  420  may function to transfer the operating voltage to the array of electrostatic transfer heads on the micro pick up array  204  when operably connected with the micro pick up array mount  202 . In an embodiment, electrostatic voltage source contact(s)  420  are formed using a suitable technique such as, but not limited to, sputtering or electron beam evaporation of a conductive material (e.g., metal) onto a surface of pivot platform  404 . Referring now to  FIG. 4B , pivot platform each electrostatic voltage source contact  420  may further be placed in electrical connection with a landing pad  431  of a via structure  422 , which extends through the micro pick up array mount  202  to base electrostatic voltage source contact  433 . Furthermore, and more particularly, pivot platform electrostatic voltage source contact  420  may be placed in electrical connection with via  422  through trace  424 . Trace  424  connects pivot platform electrostatic voltage source contact  420  to landing pad  431 . As shown, trace  424  may run over one or more of the portions on the micro pick up array mounting side of micro pick up array mount  202 . For example, trace  424  may run over base  402 , beam  406 , and pivot platform  404 . Trace  424  may also be formed using a suitable technique such as sputtering or e-beam evaporation. In an embodiment, electrostatic voltage source contacts  420 , landing pads  431 , and traces  424  are simultaneously formed. In an embodiment, trace  424  may be a wire that is separate from, or bonded to a surface of, micro pick up array mount  202 , and which electrically connects pivot platform electrostatic voltage source contact  420  with landing pad  431 . 
     Micro pick up array mount  202  may further include an arrangement of dummy traces  425  on the same side of the micro pick up array mount  202  as traces  424 . As illustrated in  FIG. 4A , dummy traces  425  may mirror the arrangement of traces  424  on portions of the beams  406  or pivot platform  404  in order to balance residual and thermal stresses in micro pick up array mount  202 . More specifically, residual stresses from the fabrication of micro pick up array mount  202  depend in part on the composite structural characteristics of beams  406 . Traces  424  along beams  406  contribute to these characteristics, and residual stresses caused by, e.g., the cooling of beams  406  during fabrication, may therefore be different in beams  406  having traces  424  than beams  406  without traces  424 . This difference may result in, e.g., skewing of the self-aligning structure at ambient conditions. Alternatively, or in conjunction with these residual stresses, when heat is applied to micro pick up array mount  202 , beams  406  with traces  424  may behave differently, e.g., expand at a different rate, than beams  406  without traces  424 . Again, this may distort the micro pick up array structure. Dummy traces  425  give beams  406  without traces  424  similar composite structural characteristics as beams  406  with traces  424 . Thus, dummy traces  425  can balance or offset residual and thermal stresses throughout all of the beams  406  to avoid distortion of micro pick up array mount  202 . 
     Micro pick up array mount  202  may include one or more bonding sites to mount the micro pick up array  204  on the micro pick up array mount  202 . In an embodiment, a bonding site includes one or more clamping electrodes  430  located on a micro pick up array mounting surface  205  of pivot platform  404 . More particularly, the clamping electrodes  430  may be located on the same surface of pivot platform  404  on which pivot platform electrostatic voltage source contacts  420  are located. In an embodiment, the clamping electrodes  430  are formed simultaneously with electrostatic voltage source contacts  420 , landing pads  431 , and traces  424 . Clamp electrodes  430  may further be placed in electrical connection with a via structure  432 , which extends through the micro pick up array mount  202 . In the embodiment illustrated, the via structure  432  extends through the micro pick up array mount  202  to a landing pad  441  on a back surface, which is in electrical connection with a base clamp contact  442  by a trace  434 . As shown, trace  434  may run over one or more portions of the backside surface of micro pick up array mount  202  which connects with the transfer head assembly. For example, trace  434  may run over base  402 , beam  406 , and pivot platform  404 . Furthermore, in an embodiment, trace  434  may be a wire that is separate from, or bonded to a surface of, micro pick up array mount  202 , and which electrically connects base clamp contact  442  with via  432  and clamp electrode  430 . 
     Electrical components of micro pick up array mount  202  may be formed in numerous manners. For example, vias  422 ,  432  may be formed by drilling or etching a hole through base  402 , passivating the hole with an insulator, and forming a conductive material (e.g., metal) into the passivated hole to form via  422 ,  432  using a suitable technique such as sputtering, e-beam evaporation, electroplating, or electroless deposition. 
     In some embodiments, micro pick up array mount  202  may further be constructed to be secured or clamped to the transfer head assembly  206  with electrostatic principles. As shown in the embodiment illustrated in  FIGS. 4A-4E  and  FIG. 8A-10B , one or more clamp areas  450  may be formed on the backside of the micro pick up array mount  202  to align with the clamp electrodes  1010  of the transfer head assembly  206 . In accordance with the principles of electrostatic grippers, using the attraction of opposite charges, a dielectric layer may be formed over the clamp electrodes  1010  and/or the clamp areas  450 . Clamp areas  450  can be formed by a variety of methods and assume a variety of configurations. In one embodiment, clamp areas  450  are conductive pads, such as a metal or semiconductor film, formed on the back surface of the micro pick up array mount  202 . The conductive pads may be electrically isolated from the other active regions of the micro pick up array mount  202 . For example, insulating layers may be formed under, over, and around the conductive pads. 
     Referring to  FIG. 4C , a perspective view illustration of a micro pick up array mount having an electrostatic bonding site is shown in accordance with an embodiment of the invention. In some embodiments, micro pick up array mount  202  may include a heating contact  480  placed on base  402 . For example, heating contact  480  can be adjacent to clamp area  450  on the bottom surface of micro pick up array mount  202  to align with or otherwise be placed in electrical connection with a heating connection  1090  ( FIGS. 10A-10B ) of transfer head assembly  206 . Multiple heating contacts  480  may be used, for example, to pass current through one or more heating elements  484 . More specifically, heating element  484  may extend from a first heating contact  480  and over pivot platform  404  and/or beams  406  before terminating at, e.g., a second heating contact  480 . Thus, heating element  484  can carry electrical current between multiple heating contacts  480 . As current passes through heating element  484 , Joule heating causes the temperature of heating element  484  to rise. 
     In an embodiment, heating element  484  may be connected with heating contacts  480  by one or more heating leads  482 . Heating lead  482  can be sized and configured to dissipate less heat than heating element  484 , and thus, act as an electrical lead to carry electrical current from heating contacts  480  over portions of micro pick up array mount  202 , e.g., base  402  and beams  406 , without heating those portions significantly. For example, heating lead  482  may be a copper conductor. In this manner, heating of micro pick up array mount  202  can be isolated to areas having heating element  484 , such as pivot platform  404 . 
     Heating element  484  may be formed from a material and shape that is conducive to resistive heating. More particularly, heating element  484  can be formed to generate heat when an electrical current is passed through it. As an example, heating element  484  can be formed from a wire strand of molybdenum disilicide. The wire strand can be coiled or sinuously placed on the micro pick up array mount  202  to uniformly distribute heat across or throughout a surface or structure, e.g., pivot platform  404 . Heating element  484  may be insulated, for example by laminating over the element, to protect adjacent components from excessive heating and to direct heat into pivot platform  404 . 
     In an embodiment, micro pick up array mount  202  includes a temperature sensor to sense the temperature of micro pick up array mount  202  or nearby structures, e.g., a micro pick up array. For example, temperature sensor  440  may be located on the pivot platform to measure the temperature of the pivot platform  404 . Temperature sensor  440  may be potted or otherwise adhered or mechanically fixed to the pivot platform. In another embodiment, temperature sensor  440  may be located in a center of pivot platform  404  ( FIG. 4A ), a corner of pivot platform  404  ( FIG. 5A ), or on base  402  or beam  406 . In still other embodiments, temperature sensor  440  can be located on a front or back surface of pivot platform  404 , i.e., on a surface having landing pad  431  or on an opposing surface having landing pad  441 . The choice of location can be driven by considerations such as available space and whether the temperature sensor  440  will interfere with other functions, such as whether it will disrupt electrical charge in the electrostatic transfer heads  210 . For example, in an embodiment, temperature sensor  440  may be centered on the back surface of pivot platform  404  where the sensor will not mechanically interfere with bonding of the micro pick up array  204 . The temperature sensor  440  may be centered on platform  404  to closely approximate the peak temperature of micro pickup array  204 . Temperature variations due to convective heat loss may skew the measured temperature if sensor  440  is located in close proximity to the edge of pivot platform  404 . Temperature sensor  440  may be any of a variety of known temperature sensors, such as junction-type thermocouples, resistance temperature detectors, etc. 
     Referring to  FIGS. 4D-4E , in an embodiment, micro pick up array mount  202  includes base electrostatic voltage source contact  433  and base clamp contact  442  located on a same surface of micro pick up array mount  202 . For example, base electrostatic voltage source contact  433  and base clamp contact  442  can be located on a same side of micro pick up array mount  202  that electrostatic voltage source contacts  420  and clamping electrodes  430  are located. Furthermore, traces  424  can interconnect base electrostatic voltage source contact  433  and base clamp contact  442  with electrostatic voltage source contacts  420  and clamping electrodes  430 , respectively. Since the interconnected connections and contacts may be located on a same side of micro pick up array mount  202 , there is no need for vias  422 ,  432 . More particularly, traces  424  can run along the same side of micro pick up array mount  202  and over each of beams  406  in a symmetric pattern that balances the weight of traces  424  across beams  406 . 
     In an embodiment, given that base electrostatic voltage source contact  433  and base clamp contact  442  may be located on, e.g., the top surface of base  402 , base electrostatic voltage source contact  433  and base clamp contact  442  may be adjacently placed and connected with a separate electrical lead that extends to or from transfer head assembly  206 . For example, ribbon cable  460  having wires to make electrical connection between micro pick up array mount  202  and transfer head assembly  206  can be engaged with an insulation-displacement connector in electrical connection with base electrostatic voltage source contact  433  and base clamp contact  442 . Therefore, voltage can be applied to base electrostatic voltage source contact  433  and base clamp contact  442  through ribbon cable  460  from an external component, such as the transfer head assembly  206 . 
     Referring now to  FIG. 5A , a perspective view illustration of a micro pick up array mount having a non-electrostatic bonding site is shown in accordance with an embodiment of the invention. Most components of the micro pick up array mount  202 , such as pivot platform electrostatic voltage source contact  420  may be the same or similar to their counterparts in the embodiment of  FIG. 4A-4B . However, in this embodiment, the clamping electrodes  430  are replaced with bonding pad  500 . Bonding pad  500  may be formed of a variety of materials including polymers, solders, metals, and other adhesives to facilitate the formation of a permanent bond with another structure. In an embodiment, bonding pad  500  may include gold, copper, or aluminum to facilitate the formation of a thermocompression bond with an adjacent structure. For example, a gold-to-gold thermocompression bond may be formed between bonding pad  500  and an adjacent structure. However, a thermocompression bond is only one manner of forming a permanent bond between structures, and thus, bonding pad  500  may include other materials or mechanisms that facilitate the formation of a bond between the micro pick up array mount  202  and another part or structure. For example, direct bonding, adhesive bonding, reactive bonding, soldering, etc., may be used at numerous bonding sites having various shapes and sizes. 
     Referring to  FIG. 5B , a perspective view illustration of a micro pick up array mount having a non-electrostatic bonding site is shown in accordance with an embodiment of the invention. In an embodiment, micro pick up array mount  202  can include ribbon cables  460  in electrical communication with base electrostatic voltage source contact  433 . As discussed above, ribbon cables  460  can be electrically connected with an external component, such as an electrostatic voltage source of the transfer head assembly, which may eliminate the need for via  422  to deliver voltage to base electrostatic voltage source contact  433 . 
     As shown in  FIGS. 4A-4E , micro pick up array mount  202  may include heating element  484  disposed on a pivot platform surface opposite from electrostatic voltage source contacts  420  and clamping electrodes  430 . Thus, heat may be delivered through pivot platform  404  to electrostatic voltage source contacts  420  and clamping electrodes  430  or to a micro pick up array in contact with those contacts. 
     Referring now to  FIG. 6A , a perspective view illustration of a micro pick up array mount having a beam laterally around a pivot platform and an auto-aligning behavior is shown in accordance with an embodiment of the invention. As described above, micro pickup array mount  202  permits movement between platform  404  and base  402  along and about multiple axes as a result of bending of beams  406  and torsion of pivots  408 ,  410 ,  414 , and  416 . Bending of beams  406  can include a z-vector component, such as a component in the direction of axis  630 . Furthermore, pivot platform  404  may rotate about a first axis  602  due to twist in inner pivots  408 ,  414  and about axis  604  due to twist in outer pivots  410 ,  416 . Movement of pivot platform  404  in alternate planes is achieved through bending of beam  406 . For example, bending of beam  406  between inner pivot  414  and outer pivots  416  may cause pivot platform  404  to tilt away from the orientation shown in  FIG. 6A . Furthermore, bending of beam  406  may allow pivot platform  404  to translate in different directions, such as along axis  630 . Thus, pivot platform  404  may self-align to another surface by tipping, tilting, rotating, and translating from its original position relative to base  402 . 
     Translation of pivot platform  404  along axis  630  allows pivot platform  404  to move relative to base  402 , when base  402  remains fixed. In other words, movement of pivot platform  404  may result in an expansion, or telescoping, of micro pick up array mount  202  in the direction of axis  630 . This expansion may be defined by the deflection, or translation, of pivot platform  404  along axis  630 . In an embodiment, the potential amount of deflection relates to the degree of misalignment that may be accommodated between a micro pick up array and a carrier substrate, as will be more fully described below. Thus, in an embodiment, the range of motion of pivot platform  404  along axis  630  relative to base  402  may be in a range of about 1 to 30 micrometers. In another embodiment, the range of motion may be in a range of about 2 to 10 micrometers. Even more particularly, in an embodiment, pivot platform  404  may deflect approximately 10 micrometers away from base  402  along axis  630 . 
     Referring now to  FIG. 6B , a perspective view illustration of a micro pick up array mount having two beams laterally around a portion of a pivot platform and an auto-aligning behavior is shown in accordance with an embodiment of the invention. Micro pick up array mount  202  includes base  402  structurally connected with pivot platform  404  by beams  406  and  406 ′. Thus, in an embodiment, the beams  406  may be discontinuous and not completely laterally surround pivot platform  404 . More specifically, pivot platform  404  may be supported at one side by beam  406  connected with pivot platform  404  and base  402  at inner pivot  414  and outer pivot  416 , respectively. Similarly, pivot platform  404  may be supported at an opposite side by beam  406 ′ connected with pivot platform  404  and base  402  at inner pivot  414 ′ and outer pivot  416 ′. Alternative structure still allows for pivot platform  404  to tip and tilt relative to base  402 . More specifically, pivot platform  404  is able to rotate about axis  602  due to twisting in inner pivots  414 ,  414 ′, as well as rotate about axis  604  due to twisting in outer pivots  416 ,  416 ′. Furthermore, bending in beams  406 ,  406 ′ allow pivot platform to tilt in various other planes or translate along axes, e.g.,  630 . Thus, pivot platform  404  may self-align to another surface by tipping and tilting from its original position relative to base  402 . 
     Referring now to  FIG. 6C , a perspective view illustration of a micro pick up array mount having four beams between a pivot platform and a base, and an auto-aligning behavior, is shown in accordance with an embodiment of the invention. Micro pick up array mount  202  includes base  402  structurally connected with pivot platform  404  by beams  606 ,  608 ,  610 , and  612 . Thus, in an embodiment, multiple beams may support pivot platform  404 . As shown, each beam may have a substantially linear configuration, such that a single beam supports each side of pivot platform  404 . Beams  606 ,  608 ,  610 , and  612  may extend diagonally between pivot platform  404  and base  402  to provide a substantial moment or bending arm, but the beams may also extend orthogonally from pivot platform  404 , thereby minimizing the beam length. The multiple linear beam structure also permits pivot platform  404  to tip and tilt relative to base  402  in a manner similar to that discussed above. However, the mechanics of motion may be different from other embodiments, in that the linear beams may result in a stiffer structure. Thus, pivot platform  404  may still rotate about axis  602  or translate along axis  630 , for example, but the degree of movement may be less per unit force applied as opposed to some of the preceding structural embodiments. Nonetheless, pivot platform  404  may self-align to another surface by tipping and tilting from its original position relative to base  402 . 
     The preceding structural embodiments of micro pick up array mount  202  are intended to show the breadth of potential embodiments that are contemplated within the scope of this disclosure. Accordingly, these embodiments are in no way intended to be exhaustive, but are rather intended to suggest to one skilled in the art that a variety of beam structures and pivot configurations and placement may be used to achieve a self-aligning structure in which pivot platform  404  may move in multiple planes and along or about multiple axes relative to base  402 . 
     Having discussed the basic structure and function of micro pick up array mount  202 , further details will now be provided with respect to additional components that micro pick up array mount  202  may be mated to, assembled with, or otherwise combined to form a micro device transfer system. For example, micro pick up array mount  202  may be joined with a micro pick up array. Referring now to  FIG. 7 , a side view illustration of a micro pick up array having a substrate supporting an array of electrostatic transfer heads is shown in accordance with an embodiment of the invention. Micro pick up array  700  may include a base substrate  702 , formed from one or more of silicon, ceramics, and polymers, supporting an array of electrostatic transfer heads  703 . Each electrostatic transfer head  703  may include a mesa structure  704  including a top surface  708 , which may support an electrode  712 . However, electrode  712  is illustrative, and in another embodiment, mesa structure  704  can be wholly or partially conductive, such that electrode  712  is not necessary. A dielectric layer  716  covers a top surface of each mesa structure and electrode  712  if present. The top contact surface  718  of each electrostatic transfer head has a maximum dimension, for example a length or width of 1 to 100 μm, which may correspond to the size of a micro device to be picked up. 
     Mesa structure  704  protrudes away from base substrate  702  so as to provide a localized contact point of the top contact surface  718  to pick up a specific micro device during a pick up operation. In an embodiment, mesa structure  704  has a height of approximately 1 μm to 5 μm, or more specifically approximately 2 μm. In an embodiment, mesa structure  704  may have top surface  708  with surface area between 1 to 10,000 square micrometers. Mesa structure  704  may be formed in a variety of geometries, e.g., square, rectangular, circular, oval, etc., while maintaining this general surface area range. The height, width, and planarity of the array of mesa structures  704  on base substrate  702  are chosen so that each electrostatic transfer head  703  can make contact with a corresponding micro device during a pick up operation, and so that an electrostatic transfer head  703  does not inadvertently make contact with a micro device adjacent to an intended corresponding micro device during the pick up operation. 
     Still referring to  FIG. 7 , electrode lead  714  may place electrode  712  or mesa structure  704  in electrical connection with a terminal of via  720  and with substrate electrostatic voltage source contact  722 . Substrate electrostatic voltage source contact  722  of the micro pick up array  700  is formed to align with the electrostatic voltage source contacts  420  on the micro pick up array mount  202  to transfer the operating voltage to the array of electrostatic transfer heads  703  when operably connected with the micro pick up array mount  202 , as described in more detail with regard to  FIGS. 8-9  below. Electrode lead  714 , via  720 , and substrate electrostatic voltage source contact  722  may be formed using methods similar to those described above for other leads, vias, contacts, and connections. 
     In addition to operating in accordance with electrostatic principles to pick up micro devices, the micro pick up array  700  may further be constructed to be secured or clamped to the micro pick up array mount  202  with electrostatic principles. As shown in the embodiment illustrated in  FIG. 7 , one or more clamp areas  724  may be formed on the backside of the micro pick up array  700  to align with the clamp electrodes  430  of the micro pick up array mount  202 . In accordance with the principles of electrostatic grippers, using the attraction of opposite charges, a dielectric layer may be formed over the clamp electrodes  430  in the micro pick up array mount  202  and/or the clamp areas  724  on the micro pick up array  700 . Clamp areas  724  can be formed by a variety of methods and assume a variety of configurations. In one embodiment, clamp areas  724  are conductive pads, such as a metal or semiconductor film, formed on the back surface of the micro pick up array  700 . The conductive pads may be electrically isolated from the other active regions of the micro pick up array  700 . For example, insulating layers may be formed under, over, and around the conductive pads. In another embodiment, the clamp areas  724  may be integrally formed with the micro pick up array, for example bulk silicon, and electrically isolated from the other active regions of the micro pick up array  700 . 
     Referring to  FIG. 8A , a side view illustration of a micro device transfer system including a micro pick up array mount electrostatically bonded with a micro pick up array is shown in accordance with an embodiment of the invention. Micro pick up array system  800  includes micro pick up array mount  202  and micro pick up array  700 , which is joinable with micro pick up array mount  202 . More specifically, micro pick up array  700  may be both physically and electrically joined with micro pick up array mount  202 , as described below. 
     Micro pick up array  700  may be physically joined with micro pick up array mount  202  through a temporary bond. For example, clamp electrode  430  may be positioned adjacent to clamp areas  724  of substrate  702 . Upon applying an electrostatic voltage through the clamping voltage path from base clamp contacts  442  to clamp electrodes  430 , an electrostatic gripping pressure will be applied to substrate  702 , causing micro pick up array  700  to physically bond to micro pick up array mount  202 . This bond is reversible, in that discontinuation of the electrostatic voltage applied to clamp electrode  430  may remove the bond and release micro pick up array  700  from micro pick up array mount  202 . Thus, micro pick up array  700  will be temporarily adjoined to micro pick up array mount  202  to form micro device transfer system  800 . As described above, in accordance with the principles of electrostatic grippers, using the attraction of opposite charges, a dielectric layer is formed over the clamp electrodes  430  in the micro pick up array mount  202  and/or the clamp areas  724  on the micro pick up array  700 . 
     Micro pick up array mount  202  may also be operably joined with micro pick up array  700 . More particularly, substrate electrostatic voltage source contact  722  of micro pick up array  700  may be aligned with, and placed adjacent to, pivot platform electrostatic voltage source contact  420 . In this way, a voltage applied to base electrostatic voltage source connection  433  is transferred through the micro pick up array mount  202  to pivot platform electrostatic voltage source contact  420 , which is electrically connected to substrate electrostatic voltage source contact  722 , and to the array of electrostatic transfer heads  703 . Thus, micro pick up array mount  202  and micro pick up array  700  may be electrically connected to enable an electrostatic voltage to be applied through the operating voltage path from base electrostatic voltage source connection  433  to the array of transfer heads  703  in order to generate an electrostatic gripping force on an array of micro devices. 
     Heat can be delivered from micro pick up array mount  202  to micro pick up array  700  and/or to an array of micro devices gripped by micro pick up array  700  when those components are joined to form micro device transfer system  800 . As shown in  FIG. 8A , in an embodiment, heating contacts  480  on micro pick up array mount  202  can relay electrical current through heating leads  482  to heating element  484  (shown in  FIG. 8B ) on pivot platform  404 . In this manner, heating element  484  can be resistively heated. Thus, heat from heating element  484  on the bottom surface of micro pick up array mount  202  may transfer through pivot platform  404  to micro pick up array  700 . Furthermore, the heat delivered to micro pick up array  700  may dissipate through electrostatic transfer heads  210  into an array of micro devices gripped by electrostatic transfer heads  210 . 
     Referring to  FIG. 8B , a side view illustration of a micro device transfer system including a micro pick up array mount electrostatically bonded with a micro pick up array is shown in accordance with an embodiment of the invention. Micro pick up array  700  may include substrate electrostatic voltage source contact  722  and clamp areas  724  placed in electrical communication with electrostatic voltage source contacts  420  and clamp electrodes  430 , respectively. As discussed above electrostatic voltage source contacts  420  and clamp electrodes  430  may be interconnected with base electrostatic voltage source contact  433  and base clamp contact  442 , respectively. Furthermore, ribbon cable  460  can supply voltage to base electrostatic voltage source contact  433  and base clamp contact  442  from an external component, such as electrostatic voltage sources of a transfer head assembly  206 . Thus, a complete electrical pathway is formed between the electrostatic voltage sources and the substrate. 
     In an alternative embodiment, ribbon cables  462  can electrically connect with one or more contacts on the bottom surface of micro pick up array mount  202 . For example, ribbon cable  462  may supply electrical current to heating contacts  480 , and the electrical current can be relayed through heating leads  482  to raise the temperature of heating element  484 . In this manner, heat can be transferred from heating element  484  through pivot platform  404  to micro pick up array  700 . 
     In an alternative embodiment, an electrical lead of ribbon cables  462  may be connected with base electrostatic voltage source contact  433  or base clamp contact  442  when they are located on a bottom surface of micro pick up array mount  202 , such as their position in  FIG. 8A . In this case, an operating voltage and clamping voltage delivered through ribbon cables  462  may then be transferred to electrostatic voltage source contacts  420  and clamp electrodes  430  on a top surface of micro pick up array mount  202  through vias and traces. 
     Referring to  FIG. 9A , a side view illustration of a micro device transfer system including a micro pick up array mount permanently bonded with a micro pick up array is shown in accordance with an embodiment of the invention. Micro pick up array  700  may be permanently bonded to micro pick up array mount  202  to form micro device transfer system  900 . Micro pick up array mount  202  may include bonding pad  500 . Bonding pad  500  may be formed of a variety of materials including polymers, solders, metals, and other adhesives. To further facilitate bonding, a bonding pad  502  may be formed on substrate  702  in addition to, or alternative to bonding pad  500 . In an embodiment, bonding pads  500  and/or  502  are formed of a metallic material and the substrates micro pick up array mount  202  and micro pick up array  700  are bonded together with a thermocompression bond. Thus, in at least one embodiment, micro pick up array  700  may be permanently adjoined to micro pick up array mount  202  to form micro device transfer system  900 . Prior to permanently bonding micro pick up array mount  202  and micro pick up array  700 , the electrical contacts of those components may be aligned to ensure that the bonded components remain in electrical connection with one another. More particularly, alignment of pivot platform electrostatic voltage source contact  420  and substrate electrostatic voltage source contact  722  are aligned. 
     Heat can be delivered from micro pick up array mount  202  to micro pick up array  700  and/or to an array of micro devices gripped by micro pick up array  700  when those components are joined to form micro device transfer system  900 . As shown in  FIG. 9A , in an embodiment, heating contacts  480  on micro pick up array mount  202  can relay electrical current through heating leads  482  to heating element  484 . Heating element  484  can be resistively heated by the current, and heat may therefore transfer from heating element  484  on the bottom surface of micro pick up array mount  202  through pivot platform  404  to micro pick up array  700 . 
     In an alternative embodiment, an electrical lead of ribbon cables  462  may be connected with base electrostatic voltage source contact  433  when it is located on a bottom surface of micro pick up array mount  202 , such as its position in  FIG. 9A . In this case, an operating voltage delivered through ribbon cables  462  may then be transferred to electrostatic voltage source contacts  420  on a top surface of micro pick up array mount  202  through vias and traces. 
     Referring to  FIG. 9B , a side view illustration of a micro device transfer system including a micro pick up array mount permanently bonded with a micro pick up array is shown in accordance with an embodiment of the invention. Ribbon cables  460  can be placed in electrical communication with base electrostatic voltage source contact  433  to supply voltage from an external component, such as an electrostatic voltage source of the transfer head assembly  206 , through the various traces, contacts, and connections of micro pick up array mount  202  and micro pick up array  700 , into electrostatic transfer heads  703 . 
     In an embodiment, ribbon cable  462  can supply electrical current to heating contacts  480 , and the electrical current can be relayed through heating leads  482  to raise the temperature of heating element  484 . Thus, heat can be transferred from heating element  484  through pivot platform  404  to micro pick up array  700 . 
     Referring to  FIG. 10A , a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount is shown in accordance with an embodiment of the invention. As described above, micro pick up array  700  may be attached to micro pick up array mount  202  through either a temporary or a permanent bond. Similarly, micro pick up array mount  202  may be joined with transfer head assembly  206  in numerous ways. For example, an attachment may be formed pneumatically, electrostatically, or mechanically. 
     In an embodiment, micro pick up array mount  202  may be placed against mounting surface  208  of a transfer head assembly, and a holding mechanism of transfer head assembly  206  may be activated to retain micro pick up array mount  202 . For example, in at least one embodiment the micro pick up array mount  202  may be releasably attached and detached from the mounting surface  208  by applying a suction through vacuum port  1002  in mounting surface  208 . Vacuum port  1002  may be coupled with vacuum source  1004  for drawing suction on an object placed against mounting surface  208 . More particularly, when micro pick up array mount  202 , is positioned against mounting surface  208 , suction may be drawn through vacuum port  1002  to create a negative pressure within one or more vacuum channels  1006 . Thus, micro pick up array mount  202  may be pushed against the mounting surface  208  by the pressure difference between vacuum channel  1006  and the surrounding atmosphere. As a result, micro pick up array mount  202  attaches to mounting surface  208 . When the vacuum source is disconnected or the negative pressure in the vacuum channel  1006  is insufficient to retain micro pick up array mount  202 , the attachment is discontinued and the micro pick up array mount  202  may be released and removed. 
     In an alternative embodiment, micro pick up array mount  202  may be retained against mounting surface  208  by an electrostatic force. In such an embodiment, rather than applying suction to micro pick up array mount  202  through vacuum port  1002 , clamping electrode  1010  and lead  1007  may replace vacuum port  1002  and vacuum channel  1006 . Electrostatic voltage may be applied to clamping electrode  1010  from an electrostatic voltage source  1012 , which replaces the vacuum source  1004 . In such an embodiment, micro pick up array mount  202  may include a clamp area  450 . 
     Thus, when the clamp areas  450  are placed adjacent the clamping electrodes  1010 , an electrostatic force may be applied to retain the micro pick up array mount  202  against the mounting surface  208 . 
     Numerous other manners of retaining micro pick up array mount  202  may be used so that the use of vacuum or electrostatic clamping components is not required. For example, in yet another embodiment, one or more mechanical fasteners may be used to retain micro pick up array mount  202  against mounting surface  208 . As an example, screws can be placed in through holes formed in base  402  and threaded into counter bored holes in mounting surface  208  such that a head of the screw, e.g., of a cap screw, will retain the base  402  against the mounting surface  208 . Alternatively, clips can be used, such as spring loaded clips, to fasten the base against the mounting surface  208 . In this case, the clips can apply a fastening load to base  402  on the same side as of micro pick up array mount  202  that receives a micro pick up array  700 . Other mechanical retaining features such as pins may be used to retain micro pick up array mount  202  against mounting surface  208 . Additionally, alternative bonding mechanisms, such as adhesives can be used to retain the micro pick up array mount  202 . For example, an appropriate adhesive can be used to form a bond between mounting surface  208  and base  402 , depending on the materials used to form transfer head assembly  206  and micro pick up array mount  202 . 
     Transfer head assembly  206  may include electrical interconnects for supplying a clamping voltage to micro pick up array mount  202  for holding the micro pick up array  700 . For example, as described above, micro pick up array mount  202  may include clamp electrode  430  for applying a gripping pressure to micro pick up array  700 . In order to induce this gripping pressure, transfer head assembly  206  may supply an electrostatic voltage to base clamp contact  442 . More particularly, clamping voltage source connection  1040  of transfer head assembly  206  may supply voltage delivered from an electrostatic voltage source  1042  connected to clamping voltage source connection  1040  by wires or other electrical connections. As discussed above, the electrostatic voltage delivered to clamp electrode  430  permits micro pick up array mount  202  to physically join with micro pick up array  700 . 
     In another embodiment, micro pick up array  700  may alternatively be retained against micro pick up array mount  700  using vacuum. For example, in an embodiment, vacuum channels may run through transfer head assembly  206  and micro pick up array mount  202 , terminating in a vacuum port that apposes the back surface of micro pick up array  700 . The vacuum channels may form a singular conduit as a result of being aligned and sealed at the interfaces of the various components, using sealing components that are known in the art. Furthermore, channels may run through the wall of micro pick up array  700 , e.g., extending from base  402 , through the lengths of beams  406 , and into pivot platform  404 , eventually terminating at a mounting surface  205  of pivot platform  404 . In such an embodiment, the vacuum channels may be connected to a vacuum source (not shown) to create a suction that retains micro pick up array  700  against micro pick up array mount  202 . 
     Transfer head assembly  206  may also include electrical interconnects for supplying an operating voltage to the micro pick up array  700 . As described above, an electrostatic voltage may be the electrostatic transfer heads  703  of micro pick up array  700  to apply a gripping pressure to adjacent micro devices. In order to induce this gripping pressure, transfer head assembly  206  may supply an electrostatic voltage to substrate electrostatic voltage source contact  722  through micro pick up array mount  202 . More particularly, electrostatic voltage source connection  1060  may supply electrostatic voltage to base electrostatic voltage source contact  433  from an electrostatic voltage source  1062  connected with electrostatic voltage source connection  1060  by various wires or other electrical interconnects. As discussed above, the electrostatic voltage delivered to base electrostatic voltage source contact  433  may propagate through various vias, traces, and connections in the operating voltage path to the electrostatic transfer heads  703 . 
     Transfer head assembly  206  may further include electrical interconnects for supplying a heating current to micro pick up array mount  202 . As described above, an electrical current may be introduced to heating contacts  480  to raise the temperature of heating element  484 . Heating contacts  480  of micro pick up array mount  202  may be placed in electrical connection with heating connection  1090  of transfer head assembly  206  to receive the electrical current. More particularly, heating connection  1090  can transfer electrical current supplied by heating current source  1094  through heating connection leads  1092 . As discussed above, running electrical current through heating element  484  causes the element to generate heat that may transfer to micro pick up array  700  mounted on micro pick up array mount  202 . More particularly, heat may be transferred from heating element  484  to micro devices placed in contact with array of electrostatic transfer heads  703  on micro pick up array  700 . 
     Transfer head assembly  206  may further include recessed surface  1020 , which is generally configured to align with and receive pivot platform  404  and beams  406  when pivot platform  404  is deflected relative to base  402 . For example, recessed surface  1020  and sidewall profile  1104  are formed within the mounting surface  208  of the transfer head assembly  206  to form a cavity. Thus, pivot platform  404  may float over the cavity in the mounting surface  208 , which retains base  402 , for example, rigidly, using one or more of the retention techniques described above. 
     Micro device transfer system  200  may also include a sensor  1030  to detect deflection of the micro pick up array mount  202 . In an embodiment, sensor  1030  is fixed relative to transfer head assembly  206 . More particularly, sensor  1030  may include a threaded body that is screwed into a sensor channel  1032  extending from recessed surface  1020 . Furthermore, sensor  1030  may include probe  1034 , configured to extend beyond recessed surface  1020  in the direction of pivot platform  404 . Accordingly, when pivot platform  404  of micro pick up array mount  202  is undeflected, probe  1034  of sensor  1030  will remain in an extended state. Sensor  1030  may be a contact sensor and probe  1034  may be a spring-loaded probe of the contact sensor. The contact sensor may act as a switch or a feedback mechanism. For example, sensor  1030  may be a switch with a normally opened state when probe  1034  is in an extended position. 
     In an embodiment, sensor  1030  may effectively be a contact of an open circuit. In such a case, the open circuit may close when the contact is touched by pivot platform  404  or another conductive portion of micro pick up array mount  202 . More specifically, a source may supply voltage to a lead that extends from a positive terminal of the source to sensor  1030 . Furthermore, a lead may extend from a negative terminal of the source to a surface of micro pick up array mount  202 . The surface may be metallized, for example, to increase the local conductivity. Thus, when sensor  1030  contacts the surface of micro pick up array mount  202 , the circuit may close and current flows through the circuit. This current may be sensed by an external sensor, e.g., by a current sensor, that then delivers a signal to computer system  150  indicating whether the micro pick up array mount  700  has deflected into contact with sensor  1030 . 
     A contact sensor is only one example of a sensor that may be used to detect deflection of the micro pick up array mount  202 . For example, non-contact sensors, including laser interferometers capable of sensing absolute position of a remote object, may be used to detect when the pivot platform  404  has deflected from an original position and/or come into contact with recessed surface  1020 . In other embodiments sensor  1030  may include proximity sensors, optical sensors, and ultrasonic sensors. 
     One or more of these sensors may determine movement of pivot platform  404  without acting as a hard stop that prevents additional movement of pivot platform  404  as it deflects. In other words, sensor  1030 , whether of a contact or non-contact type, may detect movement of pivot platform  404  without impeding the deflection of pivot platform  404 . 
     Sensor  1030  may provide input and feedback to computer system  150  that controls various actuators of mass transfer tool  100 . For example, sensor  1030  may be connected with I/O ports of computer system  150  to deliver signals related to the sensor  1030  being in an open or closed state. Based on the sensor  1030  state, computer system  150  may determine whether a specific condition is met, e.g., whether micro pick up array mount  202  is in a deflected condition, and thus, may provide control signals to actuators or intermediate motion controllers to regulate the movement of mass transfer tool  100 . 
     Referring to  FIG. 10B , a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount is shown in accordance with an embodiment of the invention. Micro pick up array mount  202  illustrated in  FIG. 10B  may be retained against the mounting surface  208  of the transfer head assembly in any of the manners described above with regard to  FIG. 10A , such as mechanical fastening, adhesive, vacuum, electrostatic, etc. The electrical interconnects and supply routes of transfer head assembly  206  illustrated in  FIG. 10B  can be varied to incorporate ribbon cables. More particularly, ribbon cables  460  can include an electrical wire interconnecting base electrostatic voltage source contact  433  with electrostatic voltage source connection  1060 , as well as an electrical wire interconnecting base clamp contact  442  with clamping voltage source connection  1040 . Thus, voltage can be supplied to base electrostatic voltage source contact  433  and base clamp contact  442  from electrostatic voltage sources  1062  and  1042 , respectively. Furthermore, ribbon cables  462  can include an electrical wire interconnecting heating contact  480  with heating connection  1090 . Thus, electrical current can be supplied to heating contact  480  from heating current source  1094 . Ribbon cables  460  and  462  can also be used to communicate electrical signals for a variety of purposes between transfer head assembly  206  and micro pick up array mount  202 . For example, ribbon cables  460  and  462  can be used to transfer electrical signals from sensors, such as temperature sensor  440 , placed on a surface of micro pick up array mount  202  or micro pick up array  700 . Therefore, in an embodiment, micro pick up array mount  202  does not include vias to transfer voltage or current from transfer head assembly  206  to micro pick up array  700 . 
     Referring to  FIG. 11 , a perspective view illustration of a transfer head assembly having multiple sensors to detect deflection of a micro pick up array mount is shown in accordance with an embodiment of the invention. Several sensors  1030  may be located at various locations on transfer head assembly  206 . For example, sensors  1030   a - 1030   d  may be located in each corner of the recessed portion of mounting surface  208 , i.e., in each corner of recessed surface  1020 . Multiple sensors  1030  provides more response to deflection of micro pick up array mount  202  in that each sensor  1030  may sense deflection of a different area of micro pick up array mount  202 . For example, sensor  1030   a  in one corner of recessed surface  1020  may sense deflection of one corner of pivot platform  404  while sensor  1030  in another corner of recessed surface  1020  may sense deflection of another corner of pivot platform  404 . In this way, uneven deflection of pivot platform  404  relative to base  402  may be detected. 
     As mentioned above, pivot platform  404  may have a profile that is smaller than recessed portion profile  1104  to ensure that pivot platform  404  is able to deflect. Likewise, base profile  1202  of base  402 , indicated by a dotted line, may have a larger profile than recessed portion profile  1104  and therefore may remain rigidly fixed relative to mounting surface  208  even when a deflecting force is applied to pivot platform  404 . That is, base  402  may be apposed by mounting surface  208  to resist base  402  movement and facilitate relative movement between base  402  and deflected pivot platform  404 . Nonetheless, in at least one embodiment, a portion of base  402  could be smaller than recessed portion profile  1104  while still allowing pivot platform  404  to move relative to base  402 . 
     Referring to  FIG. 12 , a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount and the transfer head assembly having multiple sensors to detect deflection of the micro pick up array is shown in accordance with an embodiment of the invention. Further to the description provided above, base  402  may include an inner edge  1202  having a profile that is larger than, or equal to, recessed portion profile  1104 , indicated here by a wall of the recessed portion. Also, pivot platform  404  includes an outer edge  1204  having a profile that is smaller than recessed portion profile  1104 . Likewise, beam  406  may include an outer edge  1206  having a profile that is smaller than recessed portion profile  1104 . 
     Sensor  1210  and sensor  1212  are shown aligned with opposite corners of pivot platform  404 . Thus, sensors  1210  and  1212  will individually sense deflection of pivot platform  404 , and provide feedback related to pivot platform  404  position. More particularly, if a corner of pivot platform  404  adjacent to outer edge  1204  deflects, it will trigger sensor  1212 , which may either trigger a signal as an input to computer system  150 , or may act as a switch that directly controls a motor or other actuator that controls motion of the micro device transfer system relative to a carrier substrate or receiving substrate. Similarly, if a corner of pivot platform  404  adjacent to outer edge  1204  deflects, it will trigger sensor  1210  control motion. 
     Referring to  FIG. 13 , a cross-sectional side view illustration showing a portion of a micro device transfer system including a transfer head assembly holding a micro pick up array mount with a micro pick up array mounted on the micro pick up array mount and the micro pick up array mount deflected toward sensors on the transfer head assembly is shown in accordance with an embodiment of the invention. This embodiment illustrates a scenario in which pivot platform  404  is in a deflected state. Such deflection may occur, for example, when the array of electrostatic transfer heads  703  of micro pick up array  700  come into contact with an array of micro devices, a carrier substrate, a receiving substrate, or another external object. Pressure placed on the array of electrostatic transfer heads  703  causes deflection of pivot platform  404  and beam  406 . As a result, those components may move into the recessed profile  1104  of mounting surface  208 , eventually contacting and triggering sensors  1210  and  1212 . Although pivot platform  404  is shown as being flush with recessed surface  1020 , pivot platform  404  could be tilted. For example, array of electrostatic transfer heads  703  could contact a carrier substrate plane that is not parallel to recessed surface  1020 , and thus, as pivot platform  404  deflects into recessed portion  1020 , it may tilt and trigger only one of the sensors, or depress one sensor more than another. Sensors  1210  and  1212  may be configured to sense such uneven deflection of pivot platform  404  and to provide feedback to control motion of the mass transfer tool  100  accordingly. 
     Referring to  FIG. 14 , a flowchart illustrating a method of picking up an array of micro devices from a carrier substrate is shown in accordance with an embodiment of the invention. For illustrational purposes, the following description of  FIG. 14  is also made with reference to the embodiments illustrated in  FIGS. 15A-15D . At operation  1401 , transfer head assembly  206  is moved toward carrier substrate  302 . Referring to  FIG. 15A , a cross-sectional side view illustration of a micro device transfer system having a transfer head assembly moving toward a carrier substrate is shown in accordance with an embodiment of the invention. The micro pick up array  700  may be mounted on micro pick up array mount  202 , which is held against transfer head assembly  206 . As shown, pivot platform  404  may be undeflected, with a gap between an upper surface of pivot platform  404  and one or more sensors  1212 . Furthermore, the micro device transfer system is shown prior to contact being made between the array of electrostatic transfer heads  703  and the array of micro devices  1501  carried on the carrier substrate  302 , and thus, there is a gap between those components. In this state, transfer head assembly  206  may be connected with various actuators of mass transfer tool  100 , which move transfer head assembly  206  toward carrier substrate  302  under the direct or indirect control of computer system  150 . 
     Referring again to  FIG. 14 , at operation  1405 , electrostatic transfer heads  703  carried on micro pick up array  700  contact an array of micro devices  1501  on carrier substrate  302 . Referring to  FIG. 15B , a cross-sectional side view illustration of a micro device transfer system having an array of electrostatic transfer heads contacting an array of micro devices on a carrier substrate is shown in accordance with an embodiment of the invention. As an example, mass transfer tool  100  actuators have moved transfer head assembly  206  toward carrier substrate  302  until the gap between the array of micro devices  1501  and electrostatic transfer heads  703  has closed. However, pivot platform  404  remains undeflected, and therefore, the gap between sensor  1212  and the upper surface  405  of pivot platform  404  remains unchanged from the state shown in  FIG. 15A . Although shown in alignment, at this point one or more electrostatic transfer heads  703  may not be in contact with the array of micro devices  1501 . 
     Referring again to  FIG. 14 , at operation  1410 , pivot platform  404  of micro pick up array mount  202  deflects toward transfer head assembly  206  as the transfer head assembly  206  continues to move toward the carrier substrate. Referring to  FIG. 15C , a cross-sectional side view illustration of a micro device transfer system having a micro pick up array mount deflecting toward a transfer head assembly is shown in accordance with an embodiment of the invention. As shown, the upper surface  405  of pivot platform  404  has contacted and depressed sensor(s)  1212 . Base  402  has remained in contact with mounting surface  208  of transfer head assembly  206 . However, beam  406  has bent and/or twisted to enable pivot platform  404  to deflect toward sensor(s)  1212 . 
     Referring again to  FIG. 14 , at operation  1415 , the deflection of pivot platform  404  is sensed. As shown in  FIG. 15C , sensor  1212  is contacted and depressed by upper surface of pivot platform  404 . The depression of sensor  1212  may trigger a signal transmission to computer system  150 , the signal indicating that pivot platform  404  has deflected. Sensor  1212  may detect a single location on pivot platform  404 . Thus, in an embodiment, sensor  1212  indicates whether pivot platform  404  has deflected, but may not indicate whether the deflection is uniform across the entire pivot platform  404 . However, in an alternative embodiment, several sensors  1212  may be used, and thus, additional information regarding the orientation of pivot platform  404  may be evaluated and supplied to computer system  150  to further control movement of mass transfer tool  100  and the micro device transfer system. 
     At operation  1420 , relative movement between transfer head assembly  206  and carrier substrate  302  may be stopped. In an embodiment, as shown in  FIG. 15C , pivot platform  404  has deflected with an upper surface  405  nearly parallel to recessed surface  1020 . However, in other embodiments, pivot platform  404  may be tilted relative to recessed surface  1020 . Relative movement between transfer head assembly  206  and carrier substrate  302  may be stopped immediately upon detecting deflection of pivot platform  404 , or movement of transfer head assembly  206  can be continued after and detection prior to stopping the relative movement. For example, computer system  150  can control actuators of mass transfer tool  100  to cause movement of transfer head assembly  206  for a predetermined time or distance after detecting deflection. This additional range of motion following detection may ensure that complete contact is made between all, or almost all, of the electrostatic transfer heads and micro devices. Thus, detection of deflection can be an input in a chain of inputs that lead to halting movement of the transfer head assembly  206 . 
     In accordance with embodiments of the invention, information obtained from the sensor(s)  1212  can be used to operate the mass transfer tool  100  in a variety of fashions. In one embodiment, the tool may be operated in a drive to contact fashion in which the relative movement between the transfer head assembly  206  and carrier substrate stops only when all sensors have detected deflection. In another embodiment, relative movement is continued a set distance after a specific number of sensors have detected deflection. By way of example, once a first sensor or all of the sensors have detected deflection, the relative movement may be continued for a set distance such as 10 nm to 1 μm. The set distance may vary based upon size of the micro devices, size of the electrostatic transfer heads, as well as the size and elastic modulus of the micro pick up array mount  202 . In another embodiment, relative movement is stopped as soon as deflection is detected by any sensor. In yet another embodiment, upon detection of deflection of only a subset of the sensors, the transfer head assembly  206  may be actuated to further align the pivot platform  404  with the carrier substrate plane by tipping or tilting the transfer head assembly  206 . 
     Still referring to  FIG. 15C , the movement of transfer head assembly  206  may be stopped in a state where each electrostatic transfer head  703  is in contact with an apposing micro device  1501 . In some embodiments or instances, this may not occur. However, in at least one embodiment, the deflection of pivot platform  404  facilitates this uniform contact to allow transferring an array of micro devices  1501  completely without damaging electrostatic transfer heads  703  or micro devices  1501 . 
     Referring again to  FIG. 14 , at operation  1425 , a voltage may be applied to the array of electrostatic transfer heads  703  to create a grip pressure on the corresponding array of micro devices  1501  on carrier substrate  302 . As shown in  FIG. 15C , with electrostatic transfer heads  703  placed in contact with micro devices  1501 , an electrostatic voltage may be applied to electrostatic transfer heads  703  through various contacts and connectors, e.g., vias and traces, of the micro pick up array mount  202  and micro pick up array  700 . More specifically, voltage may be transmitted from electrostatic voltage source  1062 , through the electrostatic voltage source connection  1060  of transfer head assembly  206 , through base electrostatic voltage source connection  433  and pivot platform electrostatic voltage source contact  420  into substrate electrostatic voltage source contact  722  before reaching electrostatic transfer heads  703 . As a result, a gripping pressure is applied to the array of micro devices  1501  from the array of electrostatic transfer heads  703 . 
     Referring again to  FIG. 14 , at operation  1430 , the array of micro devices on carrier substrate  302  is picked up from carrier substrate  302 . Referring to  FIG. 15D , a cross-sectional side view illustration of a micro device transfer system having an array of electrostatic transfer heads picking up an array of micro devices from a carrier substrate is shown in accordance with an embodiment of the invention. Actuators of mass transfer  100  may be controlled by computer system  150  to cause transfer head assembly  206  to retract from carrier substrate  302 . During retraction, pivot platform  404  may return toward an undeflected state, as beams  406  release stored energy and spring back to an initial configuration. Simultaneously, sensor  1212  may extend past recessed surface  1020  to an initial configuration. During pick up, the electrostatic voltage supplied to electrostatic transfer heads  703  persists, and thus, micro devices  1501  are retained on electrostatic transfer heads  703  and removed from carrier substrate  302 , once transfer head assembly  206  is sufficiently retracted. 
     During the pick up process described with respect to  FIG. 14 , heating element  484  on micro pick up array mount  202  may be heated. For example, heating element  484  can be resistively heated to transfer heat to micro pick up array  700  and to micro devices in contact with electrostatic transfer heads  210 . Heat transfer can occur before, during, and after picking up the array of micro devices from carrier substrate  302 . 
     Following pick up of micro devices  1501  from carrier substrate  302 , mass transfer tool  100  may be controlled by computer system  150  to move micro devices  1501  toward a receiving substrate in order to complete the transfer of the micro devices. For example, actuators and sensors of mass transfer tool  100  may be used to position transfer head assembly  206  over a receiving substrate held by a receiving substrate holder  124 . After re-positioning the transfer head assembly  206  to prepare for transferring, the following process may be performed. 
     Referring to  FIG. 16 , a flowchart illustrating a method of releasing an array of micro devices onto a receiving substrate is shown in accordance with an embodiment of the invention. For illustrational purposes, the following description of  FIG. 16  is also made with reference to the embodiments illustrated in  FIGS. 17A-17C . At operation  1601 , transfer head assembly  206  is moved toward a receiving substrate on receiving substrate holder  124 . Referring to  FIG. 17A , a cross-sectional side view illustration of a micro device transfer system having a transfer head assembly moving toward a receiving substrate is shown in accordance with an embodiment of the invention. Pivot platform  404  may be undeflected, with a gap between an upper surface  405  of pivot platform  404  and one or more sensors  1212 . The micro pick up array  700  may be mounted on micro pick up array mount  202 , which is retained against transfer head assembly  206  in one of the manners described above. Furthermore, array of electrostatic transfer heads  703  grips array of micro devices  1501 , however, a gap exists between array of micro devices  1501  and receiving substrate  1702 . In this state, transfer head assembly  206  may be moved toward receiving substrate  1702  by mass transfer tool  100  under the control of computer system  150 . 
     Referring again to  FIG. 16 , at operation  1605 , the array of micro devices carried by electrostatic transfer heads  703  contacts the receiving substrate. The micro pick up array  700  may be mounted on micro pick up array mount  202 , which may be held against transfer head assembly  206  in one of the manners described above. Referring to  FIG. 17B , a cross-sectional side view illustration of a micro device transfer system having an array of electrostatic transfer heads carrying an array of micro devices contacting a receiving substrate is shown in accordance with an embodiment of the invention. Transfer head assembly  206  has moved toward receiving substrate  1702  until the gap between the array of micro devices  1501  and receiving substrate  1702  has closed. However, pivot platform  404  remains undeflected, and therefore, the gap between sensor  1212  and the upper surface of pivot platform  404  remains unchanged from the state shown in  FIG. 17A . Although shown in alignment, at this point one or more micro devices  1501  may not be in contact with receiving substrate  1702 . 
     Referring again to  FIG. 16 , at operation  1610 , pivot platform  404  of micro pick up array mount  202  deflects toward transfer head assembly  206  as the transfer head assembly  206  continues to move toward the carrier substrate. Referring to  FIG. 17C , a cross-sectional side view illustration of a micro device transfer system having a micro pick up array mount deflecting toward a transfer head assembly is shown in accordance with an embodiment of the invention. As shown, the upper surface  405  of pivot platform  404  has contacted and depressed sensor(s)  1212 . Base  402  has remained in contact with mounting surface  208  of transfer head assembly  206 . However, beam  406  has bent or twisted to deflect away from receiving substrate  1702  such that pivot platform  404  deflects toward sensor(s)  1212 . 
     Referring again to  FIG. 16 , at operation  1615 , the deflection of pivot platform  404  may be sensed. As shown in  FIG. 17C , sensor  1212  is contacted and depressed by upper surface of pivot platform  404 . The depression of sensor  1212  may trigger a signal transmission to computer system  150 , the signal indicating that pivot platform  404  has deflected. Sensor  1212  may detect a single location on pivot platform  404 . Thus, in an embodiment, sensor  1212  indicates whether pivot platform  404  has deflected, but may not indicate whether the deflection is uniform across the entire pivot platform  404 . However, in an alternative embodiment, several sensors  1212  may be used, and thus, additional information regarding the orientation of pivot platform  404  may be evaluated and supplied to computer system  150  to control movement of mass transfer tool  100  and the micro device transfer system. 
     In an embodiment, such as the one shown in  FIG. 17C , pivot platform  404  has deflected with an upper surface  405  nearly parallel to recessed surface  1020 . However, in other embodiments, pivot platform  404  may be tilted relative to recessed surface  1020 . Relative movement between transfer head assembly  206  and carrier substrate  302  may be stopped at operation  1620  in a variety of embodiments. For example, relative movement may be stopped immediately upon detecting deflection of pivot platform  404 , or movement of transfer head assembly  206  can be continued after detection. Computer system  150  can control mass transfer tool  100  to move transfer head assembly  206  for a predetermined time or distance after detecting deflection. This additional range of motion following detection may ensure that complete contact is made between all, or almost all, of the micro devices and the receiving substrate. Thus, detection of deflection can be an input in a chain of inputs that lead to halting movement of the transfer head assembly  206 . 
     In accordance with embodiments of the invention, information obtained from the sensor(s)  1212  can be used to operate the mass transfer tool  100  in a variety of fashions. In one embodiment, the tool may be operated in a drive to contact fashion in which the relative movement between the transfer head assembly  206  and receiving substrate stops only when all sensors have been detected deflection. In another embodiment, relative movement is continued a set distance after a specific number of sensors have detected deflection. By way of example, once a first sensor or all of the sensors have detected deflection, the relative movement may be continued for a set distance such as 10 nm to 1 μm. The set distance may vary based upon size of the micro devices, electrostatic transfer heads, as well as the size and elastic modulus of the micro pick up array mount  202 . In another embodiment, relative movement is stopped as soon as deflection is detected by any sensor. In yet another embodiment, upon detection of deflection of only a subset of the sensors, the transfer head assembly  206  may be actuated to further align the pivot platform  404  with the receiving substrate plane by tipping or tilting the transfer head assembly  206  or receiving substrate. 
     Referring again to  FIG. 16 , at operation  1625 , heat may be applied to the array of micro devices. For example, heating element  484  may be resistively heated as described above to transfer heat through micro pick up array mount  202  into the array of electrostatic transfer heads  703  that appose micro devices  1501 . Micro devices  1501  may be heated throughout the placement process described with respect to  FIG. 16 . Maintaining an elevated temperature of micro pick up array mount  202  in this manner can avoid some problems that arise from temperature variations in an operating environment. However, more particularly, micro devices  1501  may be heated after deflection of pivot platform  404  is sensed and/or after micro devices  1501  are in contact with receiving substrate  1702 . In an embodiment, each electrostatic transfer head  703  in the array is heated uniformly, e.g., to a temperature of 50 degrees Celsius, 180 degrees Celsius, 200 degrees Celsius, or even up to 350 degrees Celsius. These temperatures can cause melting or diffusion between micro devices  1501  and receiving substrate  1702 . 
     Referring again to  FIG. 16 , at operation  1630 , the voltage may be removed from the array of electrostatic transfer heads  703 . As shown in  FIG. 17C , with micro devices  1501  in contact with receiving substrate  1702 , the electrostatic voltage may be removed from electrostatic transfer heads  703 . For example, the electrostatic voltage was applied to electrostatic transfer heads  703  through various contacts and connectors, e.g., vias and traces of the micro pick up array mount  202  and micro pick up array  700  may be discontinued or removed. 
     Referring again to  FIG. 16 , at operation  1635 , the array of micro devices may be released onto the receiving substrate. Referring to  FIG. 17D , a cross-sectional side view illustration of a micro device transfer system releasing an array of micro devices onto a receiving substrate from an array of electrostatic transfer heads is shown in accordance with an embodiment of the invention. After electrostatic voltage is removed from electrostatic transfer heads  703 , the grip pressure between electrostatic transfer heads  703  and micro devices  1501  is attenuated, and thus micro devices  1501  may release onto an adjacent surface of receiving substrate  1702 . Following release of micro devices  1501 , mass transfer tool  100  may be controlled to retract transfer head assembly  206  from receiving substrate  1702 . During retraction, pivot platform  404  may return toward an undeflected state, as beams  406  spring back to an initial configuration. Simultaneously, sensor  1212  may extend past recessed surface  1020  to an initial configuration. 
     Transfer head assembly  206  may continue to lift away from receiving substrate  1702 . Thus, a gap will occur between electrostatic transfer heads  703  and micro devices  1501 , as micro devices  1501  are released onto receiving substrate  1702 . Subsequently, transfer head assembly  206  may be moved back toward carrier substrate  302  to continue the transfer process by transferring another array of micro devices  1501 , as described above. 
     Referring to  FIG. 18 , a schematic illustration of an exemplary computer system that may be used is shown in accordance with an embodiment of the invention. Portions of embodiments of the invention are comprised of or controlled by non-transitory machine-readable and machine-executable instructions which reside, for example, in machine-usable media of a computer control system  150 . Computer system  150  is exemplary, and that embodiments of the invention may operate on or within, or be controlled by a number of different computer systems including general purpose networked computer systems, embedded computer systems, routers, switches, server devices, client devices, various intermediate devices/nodes, stand-alone computer systems, and the like. 
     Computer system  150  of  FIG. 18  includes an address/data bus  1810  for communicating information, and a central processor unit  1801  coupled to bus  1810  for processing information and instructions. System  150  also includes data storage features such as a computer usable volatile memory  1802 , e.g. random access memory (RAM), coupled to bus  1810  for storing information and instructions for central processor unit  1801 , computer usable non-volatile memory  1803 , e.g. read only memory (ROM), coupled to bus  1810  for storing static information and instructions for the central processor unit  1801 , and a data storage device  1804  (e.g., a magnetic or optical disk and disk drive) coupled to bus  1810  for storing information and instructions. System  150  of the present embodiment also includes an optional alphanumeric input device  1806  including alphanumeric and function keys coupled to bus  1810  for communicating information and command selections to central processor unit  1801 . System  150  also optionally includes an optional cursor control device  1807  coupled to bus  1810  for communicating user input information and command selections to central processor unit  1801 . System  150  of the present embodiment also includes an optional display device  1805  coupled to bus  1810  for displaying information. 
     The data storage device  1804  may include a non-transitory machine-readable storage medium  1808  on which is stored one or more sets of instructions (e.g. software  1809 ) embodying any one or more of the methodologies or operations described herein. Software  1809  may also reside, completely or at least partially, within the volatile memory  1802 , non-volatile memory  1803 , and/or within processor  1801  during execution thereof by the computer system  150 , the volatile memory  1802 , non-volatile memory  1803 , and processor  1801  also constituting non-transitory machine-readable storage media. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Metadata:
Filing Date: 20160614
Publication Date: 20180807
Grant Date: 20180807
Priority Date: 20121214
Inventors: GOLDA, DARIUSZ
HIGGINSON, JOHN A.
BIBL, ANDREAS
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L33/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T279/23", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/75725", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/75", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L2224/7598", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/351", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/1461", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12041", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/75843", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2224/75843", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L25/167", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10H20/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2924/1461", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12041", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/7598", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/351", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2224/75725", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T279/23", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T279/23", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/7598", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/351", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2224/75725", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/1461", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12041", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/1461", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/351", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12041", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2924/12042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/7598", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L2224/75725", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01L24/97", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L24/75", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L24/75", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L24/75", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 50931075