Abstract:
A method and apparatus for fabricating one or more electronic devices from wafer, die or other holder including designing a plurality of electronic devices ( 805 ), wherein each of the electronic devices is encapsulated in a cell and designing a plurality of tethers ( 825 ). Each tether includes a first end and a second end. The method includes selecting an attachment point ( 835, 860 ) on each of the plurality of electronic devices, attaching the first end of each of the plurality of tethers to one of the attachment points, selecting a plurality of anchor points ( 835, 860 ), attaching the second end of each of the plurality of tethers to one of the anchor points. The method includes determining a fracture condition ( 835 ) for each electronic device that breaks the tether at the first end ( 865 ). The fracture condition is same for a group of electronic devices in the plurality of electronic devices.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC §119(e)(1) of Provisional Application No. 60/989,230, filed Nov. 20, 2007, incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to releasing microelectronic devices in a cell of wafer, die, or other holder after fabrication. More particularly, the invention relates to detaching of components or devices attached to the frame of the cell by one or more tethers. Still more particularly, the invention relates to parallel and selective detethering of components or devices such as micro-electromechanical devices (MEMS) devices in the cells using vibratory agitation. 
       BACKGROUND OF THE INVENTION 
       [0003]    Manufacture of microelectronic devices (each device may be composed of one or more components) such as integrated circuits, System on Chip (SOC), MEMS devices, polymeric devices includes fabrication of the devices/components on a wafer, die, or other holders (e.g. polymeric holder). Each device is located on a cell of the wafer, die, or other holder surrounded by the cell frame that is attached to the wafer, die, or other holder. Fabrication of the devices is usually performed using high throughput manufacturing so that multiple devices may be formed on the substrate of a wafer, die, or other holder without damage to the devices&#39; microstructures formed on the substrate. 
         [0004]    Design and fabrication of microelectronic devices includes anchor structures that connect the device to the cell and cell frame so that the device is not damaged or lost during the fabrication and transportation process. In order to be used, after the devices have been fabricated on the wafer, die, or other holder, each microelectronic device has to be released from the cell and cell frame. Some approaches to releasing the device connected to the cell and cell frame include mechanical probing, mechanical sawing, thermal diffusion, laser dicing, lithography and chemical releasing to break the attachments. However, such techniques result in low throughput release of devices since typically large numbers of devices cannot be released at the same time. Furthermore, these techniques require sensory vision feedback, may not result in complete separation of the devices from the cell and cell frame, and may introduce defects in the device caused by lubricants, heat, particles and stresses generated during the separation process. Different applications of integrated circuits, SOC, MEMS devices, polymeric devices or components may each require different approaches to releasing the device attached to the cell and cell frame. Thus, in any given fabrication process line, multiple pieces of equipment may be needed for different device types and application adding to the expense and complexity of the fabrication line. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with some embodiments of the invention, a method for forming an electronic device includes designing a tether, wherein the tether includes a first end and a second end; selecting an attachment point on the electronic device; attaching the first end of the tether to the attachment point, wherein the electronic device is encapsulated in a cell; selecting an anchor point; attaching the second end of the tether to the anchor point; determining fracture conditions that break the tether at the first end; agitating the cell at the fracture conditions to break the tether at the first end; and separating the electronic device from the cell. 
         [0006]    In accordance with some other embodiments of the invention, a method comprises designing a plurality of electronic devices, wherein each of the electronic devices is encapsulated in a cell of a wafer, die or other holder; designing a plurality of tethers, wherein each tether includes a first end and a second end; selecting an attachment point on each of the plurality of electronic devices; attaching the first end of each of the plurality of tethers to one of the attachment points; selecting a plurality of anchor points; attaching the second end of each of the plurality of tethers to one of the anchor points; determining a fracture condition for each electronic device that breaks the tether at the first end, wherein the fracture condition is same for a group of electronic devices in the plurality of electronic devices; agitating the wafer, die or other holder at one of the fracture conditions to selectively and in parallel break the tether at the first end of one or more electronic devices; and separating the one or more electronic devices from the wafer, die or other holder. 
         [0007]    In accordance with some embodiments of the invention, a holding device comprises a plurality of electronic devices, wherein each of the electronic devices is encapsulated in a cell; a plurality of tethers, wherein each tether includes a first end and a second end; an attachment point on each of the plurality of electronic devices, wherein the first end of each of the plurality of tethers connects to one of the attachment points; a plurality of anchor points in each cell, wherein the second end of each of the plurality of tethers connects to one of the anchor points; and wherein fracture conditions for each electronic device break the tether at the first end, wherein the fracture conditions are the same for a group of electronic devices in the plurality of electronic devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows device top view connected to the frame of a cell with a tether; 
           [0009]      FIG. 2  is a schematic of different tethered devices fabricated in two columns of a wafer, die, or other holder; 
           [0010]      FIG. 3  is a schematic of MEMS devices tethered at different angles and notches fabricated on a wafer; 
           [0011]      FIG. 4  shows mechanical modeling and time response of tethered devices in  FIGS. 2 and 3 ; 
           [0012]      FIG. 5  is a graph of frequency versus stress showing detether frequencies of four devices; 
           [0013]      FIG. 6(   a ) shows tether fracture points of a device with two different tethers at different modal frequencies; 
           [0014]      FIG. 6(   b ) is a graph of stress at neck of tether versus frequency at different damping; 
           [0015]      FIG. 7(   a ) shows a microgripper device in a unit cell; 
           [0016]      FIG. 7(   b ) shows four groups of microgripper cells in an array with each group having same tether and anchor location; 
           [0017]      FIG. 7(   c ) is a graph of stress at neck of tether versus frequency for the four groups of cells shown in  FIG. 7(   b ); 
           [0018]      FIG. 8  shows a flowchart for design and anchor of tethers to cell frames in accordance with some embodiments of the invention; 
           [0019]      FIG. 9(   a ), in accordance with some embodiments of the invention, shows an application of detethering in a vibratory agitation system; 
           [0020]      FIG. 9(   b ), in accordance with some embodiments of the invention, shows a vibratory agitation system coupled to control circuitry; 
           [0021]      FIG. 10  shows use of agitation system of  FIG. 9(   a ) for detethering to release large quantities of MEMS devices for self assembly; and 
           [0022]      FIG. 11  shows, in accordance with some embodiments of the invention, an application of detethering in a safety inertial sensor. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]    Referring to  FIG. 1 , a top view of a microelectronic device  115  connected to the frame  100  of a cell with a cantilever beam (hereinafter “tether”)  110  is shown. The microelectronic device  115  may be an integrated circuit device, SOC device, MEMS device, polymeric device or any other type of device that can be fabricated. A device may be composed of one or more components. In accordance with some embodiments of the invention, the process technology used to fabricate the microelectronic device may be microtechnology, nanotechnology or smaller. In some other embodiments of the inventions, the process technology may be centimeter technology or larger. One end of the tether of length L includes a neck  107  that may be coupled to the device  115  at an angle θ 1  in accordance with some embodiments of the invention. The angle θ 1  focuses concentration of the stress caused by vibratory agitation at the neck  107  of the tether to detach the device from the tether. Notch  122 , described in greater detail below, may also help focus concentration of the stress caused by vibratory agitation at the neck  107  of the tether to detach the device from the tether. Device  115  may be modeled with a center of gravity  103  and point mass m at the center of gravity. The angle of the center of gravity from the beam lateral axis z may be defined as β, the angle that the device travels upon fracture from the tether. Tether  110  may connect to cell frame  100  at anchor  120 . Vertical axis x along the cell frame may be perpendicular to lateral axis z. Agitation vector  125  applied to excite anchor  120  may be at an angle θ 2  from vertical axis x. 
         [0024]    In accordance with some embodiments of the invention, tether  110  may be a linear breadth tapered cantilever beam, prismatic cantilever beam, tapered cantilever beam of truncated wedges, tapered cantilever beam of truncated cone, doubly-tapered cantilevered beam, or group of cantilever beams truncated at different shape-functions. 
         [0025]    Turning now to  FIG. 2 , a schematic of various different devices attached to cell frame by different tethers fabricated on a wafer, die, or other holder  200  is shown. Separation of a device from its tether is caused by applying external oscillatory displacement to the wafer, die, or other holder that encapsulates the cells. Each cell includes one or more devices attached to the cells frame by one or more tethers. Each wafer, die, or other holder may include a large number of cells as shown in FIG.  2 —shaking the wafer, die, or other holder with directional agitation transmits forces to the tethered devices. Sufficient frequencies and amplitudes of the directional agitation produce inertial forces on the device that cause breaks on the tether attached to the device at a predefined location. 
         [0026]    As shown in  FIG. 2 , devices A 1  and A 2   205  are identical devices with identical tethers  207  attaching the devices to cell frame  202 . In accordance with some embodiments of the invention, upward/downward directional agitation  240  causes same anchor excitation to devices  205  and tethers  207  causing simultaneous fracture at the neck of each tether. In accordance with some other embodiments, directional agitation  240  may be at a different angle. Thus, monolithic parallel releasing of identical devices with identical tethers may be accomplished by application of fracture conditions to simultaneously generate fracture stress in the tether. 
         [0027]      FIG. 2  may also be used to illustrate selective detethering of different devices attached by different tethers to cell frame. Modification of the design of the device and tether causes the dynamic response of the device and tether in each cell to vary under same directional agitation  240 . Thus, devices A 1 , A 2 , and A 3   205  are the same but because tether  210  is different from tethers  207 , devices A 1  and A 2  fracture from tethers  207  at a one directional agitation frequency f 1 . However, device A 3  fractures from tether  210  at another directional agitation frequency f 2 . Similarly, device B 1  and B 2  are identical but attached to their respective cell frames by different tethers  220  and  225 . Tethers  220  and  225  are attached to device B 1  and B 2  at different angles θat the neck of the tether. The different tether designs and tether angle of attachment θ to the device result in different agitation frequency f 3  and f 4  for devices B 1  and B 2   215  fracturing from tethers  220  and  225 . 
         [0028]    A different agitation frequency f 5  for directional agitation vector  240  may be needed for device fracturing from tether even if device and tether are same but orientation of cell frame is different as shown in cell  230 . Thus, devices A 1 , A 2 , and A 4   205  are the same and tethers  207  are the same but because the orientation of cell frame  230  is different from cell frame  202  on wafer, die, or other holder  200 , directional agitation  240  frequency f 5  different from f 1  causes device A 4  in cell  230  to fracture from tether  207 . Alternatively, rotation of the wafer, die, or other holder  200  with respect to tether anchors allows transmitting in-plane agitation causing device A 4  to fracture from tether  207 . Thus, applying directional agitation frequency f 1  to tether  207  in cell  202  that is ninety degrees to directional agitation vector  240 , device A 1  and A 2  will fracture from tether  207  but device A 4  in cell  230  will not fracture from tether  207 . Rotating the wafer, die, or other holder counterclockwise so tether  207  in cell  230  is at ninety degree angle to directional agitation vector  240  and agitating at frequency f 1  will, for example, cause device A 4  in cell  230  to fracture from tether  207 . 
         [0029]    Referring to  FIG. 3 , a schematic of MEMS devices tethered at different angles and notches fabricated on a wafer are shown. The tethers shown in  FIG. 3  are of different lengths and maximum width at tether anchor, minimum width at tether neck connection to device. The shape  310  of the device at the tether neck connection and angle θ 1    320  of the device to the tether defines the notch (see  FIG. 1   122 ) that creates maximum stress concentration at the point of attachment of tether to the device. 
         [0030]    Different tether lengths, angle θ 1  and notch shape are shown in  FIG. 3 : 1) long tether  302  with θ 1  at 90 degree angle; 2) short tether  305  with θ 1  at 45 degree angle; 3) short tether  308  with θ 1  at 90 degree angle; 4) long tether with concave notch  310  that results in angle θ 1  at 45 degrees; 5) long tether without a notch  315  results in angle θ 1  at 90 degrees; 6) long tether  320  without device attached at neck of tether after detethering; and 7) long tether with convex notch  325  that may accommodate any shape device at any of different angles θ 1 . The notch shown in  310  and  325  allows the device to easily break from tether during directional agitation but is strong enough to hold device during fabrication and handling processes. 
         [0031]    Turning now to  FIG. 4 , mechanical modeling and time response of tethered devices of  FIGS. 1-3  is shown. The parameters shown in  FIGS. 1-3  are some of the parameters that may be investigated in the design and characterization of a tethered device. Variation of these and other design parameters discussed in more detail below provides a wide range of desired operating conditions for frequencies and amplitudes to detether devices and also leads to different tether shapes. This disclosure is meant to encompass all such different tether shapes based on the microfracture analysis of these and other design parameters. 
         [0032]    In  FIG. 4 , cell  405  is depicted as anchor  120  moving with up and down directional agitation  423  that may be maximum relative displacement D  426  as shown in time response plot  415 . Device mass  420  is attached to anchor  120  through tether  110  and moves relative to displacement reference  421 . The motion of device mass  420  may be a sinusoidal motion  422  along displacement reference  421  as shown in time response plot  415 . Equivalent model  410  of cell  405  shows device mass  420  coupled to anchor  120  through equivalent viscous damping  424  and equivalent elastic spring  425  that together model the behavior of tether  110 . Device mass  420  has displacement  422  that may be a sinusoidal motion  422 . Anchor  120  in equivalent model  410  has displacement  423  by up and down directional agitation as shown in time response plot  415 . 
         [0033]    Turning now to  FIG. 5 , a semi-log graph of frequency versus stress for detether frequencies of four groups of devices Devices  1 -Devices  4  is shown. In accordance with some embodiments of the invention,  FIG. 5  may allow determination of the critical frequencies f 1 -f 4  upon which successful parallel and selective detethering of one group of devices from the four groups takes place. The devices in the four groups of devices may be fabricated on the same wafer, die, or other holder as shown in  FIGS. 2-3 . As shown in  FIG. 5 , each group of devices has unique detethering conditions that do not overlap with other group of devices. Design of the device attachment and tether for Devices 1 -Devices 4  includes a fracture threshold  530  (σ yield ) min  stress above which the device breaks from the tether. The design of each group of devices attachment and tether occurs so that the frequencies of tether fracture at notch for each group of devices do not overlap, allowing parallel and selective detethering of one group of devices. Thus, for example, devices in group Devices 1  fracture at frequency f 1    510  with concentrated stress σ 1 ; devices in group Devices 2  fracture at frequency f 2    515  with concentrated stress σ 2 ; devices in group Devices 3  fracture at frequency f 3    520  with concentrated stress σ 3 ; and devices in group Devices 4  fracture at frequency f 4    525  with concentrated stress σ 4 . 
         [0034]    Finite element modeling, lumped modeling, and other analytical approaches allow determination of mechanical signatures including directional agitation frequency and amplitude to break the device from the tether at the neck.  FIG. 6(   a ) shows tether fracture points of the same device with two different tethers (attached one at a time and not at the same time) at different modal frequencies using finite element modeling. Each type of tether oscillates at a fundamental frequency (first modal) and harmonic frequencies (second modal, third modal, fourth modal, and so on). A look-up table may be generated for each design of tether and device attachment to the tether indicating the modal frequencies at which stress is optimally applied to the neck of the tether allowing the device to cleanly break from the tether. 
         [0035]    In  FIG. 6(   a ), stresses on tether attached to device is shown for several modal frequencies. Model  1  prismatic tether  605  with directional agitation  615  at first modal frequency causes principal stress concentration to take place at a distance  620  from the neck edge. Thus, the device after breaking from the model  1  tether  605  could still have some portion of the tether attached to it. Model  2  tapered tether  610  with directional agitation  625  at first modal frequency causes principal stress concentration to take place at fracture point  627  at neck of tether close to device body. Thus, first modal frequency agitation of model  2  tether results in a fracture free from left over tether attached to the device. As can be seen in  FIG. 6(   a ), second modal frequency agitation  630  of model  2  tapered tether results in a fracture point  632  slightly farther from the neck of the tether as compared to fracture point  627  caused by first modal frequency agitation. Third modal frequency agitation  635  of model  2  tapered tether results in multiple fracture points  637  at various distances from the neck of the tether. Based on the finite element modeling of the model  2  tapered tether, agitating the tether at first modal frequency results in the cleanest fracture at neck of tether close to device body. As mentioned above, performing modal frequency fracture analysis for each design of tether and device attachment to the tether allows creation of a look-up table that includes the optimal modal frequency of agitation for a device to cleanly break from its tether. 
         [0036]    Referring now to  FIG. 6(   b ), a graph of stress at neck of tether versus frequency at different damping ratios for model  2  tapered tether and device A from  FIG. 6(   a ) is shown. Material damping and air damping of the agitation reduces the amplitude of maximum stress at the neck of the tether while still allowing the device to break from the tether. Lower amplitude agitation because of damping may result in a cleaner break at the tether neck while reducing potential damage to the device for packaged devices that are vacuum sealed and unpackaged devices.  FIG. 6(   b ) shows model  2  tether and device A stress at neck of device for agitation over a range of frequencies with various damping ratios. With zero damping ratio, a sharp, high intensity maximum amplitude peak at f 1  exceeds the stress fracture threshold  650  and results in the detethering of the device. Applying damping ratio of 0.1 results in smaller intensity amplitude peak at f 3    655  that exceeds stress fracture threshold  650  and results in detethering of the device. In accordance with some embodiments of the invention, because the effect of damping reduces the amplitude of maximum stress at the neck of the tether, external introduction of damping effect may be advantageous. Thus, for example, in detethering of MEMS devices on a wafer, die, or other holder, use of vacuum to create damping effect may result in smaller intensity amplitude peak at modal frequency. 
         [0037]    Finite element modeling of a complex MEMS device as shown in  FIGS. 7(   a )- 7 ( c ) such as a microgripper  710  in cell may also be performed. Cells  1  group  720 , cells  2  group  725 , cells  3  group  730  and cells  4  group  740  as shown in  FIG. 7(   b ) may be detethered in parallel but selective manner using unique tethers needing distinct signatures for fracture that may be obtained by modal analysis for array of complex devices. In  FIG. 7(   b ) each microgripper is identical, however the tether and anchor location is different for each cell group. Each cell in cells  1  group includes a microgripper  710  attached by model  2  tether shown in  FIG. 6(   a ) at 90 degree perpendicular angle to left side cell frame anchor. Cells  2  group  725  includes a microgripper  710  attached by a different tether at a non-perpendicular angle with respect to left side cell frame anchor. Cells  3  group  730  and cells  4  group  740  each include a microgripper  710  attached by a tether longer then the tethers used in cells  1  group and cells  2  group. Both cells  3  group and cells  4  group tethers are identical and attached at non-perpendicular angles to top side cell frame anchor. Direction, frequency and amplitude of input agitation  750  is shown in  FIG. 7(   b ) as amplitude of 10 and frequency f corresponding to ω=2πf. 
         [0038]    In accordance with some embodiments of the invention, each device or component in a cell may be attached by a single tether or multiple tethers of the same or different geometry to different anchoring locations in the cell. Each tether may form different angles θ 1  (defined in  FIG. 1 ) with the device or component in the cell. 
         [0039]      FIG. 7(   c ) is a graph of stress at neck of tether versus frequency f for cells  1  group, cells  2  group, cells  3  group and cells  4  group shown in  FIG. 7(   b ). The direction of agitation  750  is perpendicular to cells  1  group tethers horizontal direction. The tether in cells  2  group is at an angle with respect to the direction of agitation  750 . The graph of stress versus frequency in  FIG. 7(   c ) for cells  1  group and cells  2  group shows a similar modal response pattern for the two groups with a slight shift in frequency for the peaks of the two modal response patterns. As can be seen in  FIG. 7(   c ), cells  3  group and cells  4  group with longer tethers than the other two groups and anchored at different angles to the top side of the cell frame have different modal response pattern with stress peaks at frequencies different from cells  1  group and cells  2  group. Thus, as mentioned above, directional input agitation conditions of varying amplitudes and frequencies for selective detethering can be determined for identical complex MEMS devices connected to cell frames with different tethers. The determined directional input agitation conditions may be applied to the identical complex MEMS devices to detether the devices without causing damage or failure to the complex devices. 
         [0040]    Turning now to  FIG. 8 , a flowchart for design and anchor of tethers to cell frames in accordance with some embodiments of the invention is shown. In accordance with some embodiments, each cell in the wafer, die, or other holder may include a microelectronic device. Furthermore, some embodiments of the device may be attached to the cell frame by one or more tethers. In some other embodiments, each device may include a number of components with each component attached by a tether to the cell frame. As discussed above, the location of the tethers attachment to the component and the cell frame may be determined by finite element modeling analysis so that detethering of the component(s) takes place at directional agitation input of certain frequency and amplitude ( FIG. 7(   b )). In accordance with some other embodiments of the invention, the location of the tethers attachment to the component and the cell frame so that detethering of the component(s) takes place at directional agitation input of certain frequency and amplitude may also be determined by look-up tables created by experimental feasibility studies as discussed above. 
         [0041]    In  FIG. 8 , a microelectronic device/component is designed for a particular application in block  805 . In corresponding block  810 , during design of the microelectronic device/component, the device/component enclosed in the cell is also modeled in finite element modeling software such as ANSYS™ or an equivalent functionality software product. Finite element modeling of the device/component identifies structural and dynamic characteristics such as the shape of the device, presence of notch ( FIG. 3   310 ) at prospective tether connection location, susceptibility of the device to shaking and agitation and so on. In block  820 , the structural and dynamic characteristics of the device/component is used to define general performance specifications such as frequency/amplitude upper and lower bounds, optimal tether attachment location and other features for use in tether design and attachment. Performance measures such as detethering at certain frequencies, number of components in a device, type of device/components, tether(s) geometry, attachment locations to cell frame and device/component, detethering of multiple similar/different components at a specified frequency are defined in block  815 . In block  825 , the tether is parametrically modeled in finite element software and attached on cell frame and device/component. Design optimization process is performed in block  830 -block  855  to identify optimal design variables values that meet performance measures. Design variables are defined in block  830  and assigned initial values. As discussed in detail above, design variables may be tether geometric parameters, attachment locations on cell frame and device/component. Parametric model of tether and attachment on cell frame and device/component are updated based on design variables initial values in block  835 . Static/dynamic modal analysis to determine directional agitation frequency and amplitude for breaking the tether also occurs in block  835 . In block  840 , the results of the modal analysis are assessed to evaluate whether performance measures have been satisfied. The results of the modal analysis may also define new values for the design variables in block  840 . In block  850 , a determination of whether performance measures have been satisfied occurs. If performance measures have not been satisfied, control moves to block  845  in which the design variable values are modified using various approaches to identify the new values for the design variables. The parametric model of tether and attachment on cell frame and device/component are updated with the new values of the design variables. Static/dynamic modal analysis is then performed in block  835  and the results of the analysis are assessed in block  840 . This loop is repeated until performance measures are satisfied or until a number of iterations is reached. The design optimization process is stopped if a number of iterations is reached to prevent infinite loops as there may be a possibility that the desired performance measures cannot be met with the selected range of design variables values, attachment point(s) or desired frequency/amplitude of detethering. If a number of iterations has been reached, then control is passed to block  825  (not shown in  FIG. 8 ) and a model of tether with different parameters (e.g. different number of tethers) is create, new design variable values are defined and the loop  835 - 850  is repeated. The design optimization process is stopped in block  855  if performance measures are satisfied or if the maximum number of iterations has been reached. The results of the design optimization process are incorporated into the device/component and final tether model in finite element modeling software in block  860 . In block  865 , the final design of one or more tethers and attachment(s) to cell frame and device/components is evaluated to determine if breaking of the tether(s) occurs in the proper place at neck of tether. An analysis in block  865  is performed of the final design to verify that the input directional agitation does not cause damage or failure to the device/component(s) but rather only causes detethering of the device/components. In block  870 , if device/component(s) failure is detected, then the tether geometry, attachment location, number of tethers, and input frequencies/amplitudes are redefined, and the design variables are redefined. A new optimization analysis is performed until satisfactory detethering without device/component(s) damage or failure is observed. 
         [0042]      FIG. 9(   a ), in accordance with some embodiments of the invention, shows an application of detethering in a vibratory agitation system for microelectronics fabrication line. The apparatus of  FIG. 9(   a ) allows parallel and selective detethering of microelectronic devices on wafer  912 . The apparatus includes actuator blocks to provide controlled vibratory directional agitations at various frequencies and amplitudes. In some embodiments of the invention, the actuators may be piezoactuators, electromagnetic actuators, sonic actuators, or any type of actuator that can generate a controlled frequency. In the embodiment shown in  FIG. 9(   a ), cubes of stacked piezoactuators  920 ,  940  are sandwiched between a rigid frame  910  and a rotary disc  980 . Piezoactuator  920  can generate directional agitation out of plane and piezoactuator  940  can generate directional agitation in plane. Intermediate adapter  930  is placed between piezoactuators  920  and  940 . Intermediate adapter  960  is present between piezoactuator  940  and locking mechanism  970 . Locking mechanism  970  attaches to rotary disc  980 . Rotary disc  980  holds wafer  912  along axis of alignment  913  and changes the angle θ  914  relative to axis of alignment  913  of in-plane directional agitation with respect to tethered devices. The rotary disc  980  includes a mechanical clamper or suction  990  mounted on the rotary disc and is used to hold the wafer  912 . Rotary disc  980  also includes mechanical stopper/barrier  915  that may be used to “hammer” against the wafer to encourage additional conditions for simultaneous release of microelectronic devices. The released devices are caught by template  910  that sorts the devices as the non-sticking conveyor belt  911  moves on wheels  950 . 
         [0043]    Turning now to  FIG. 9(   b ), in accordance with some embodiments of the invention, shows a vibratory agitation system  952  coupled to control circuitry. In accordance with some embodiments of the invention, the agitation system  952  may be the apparatus shown in  FIG. 9(   a ) and described above. Agitation system  952  may include transducers  956 , one or more electromagnetic actuators  954  and one or more piezoelectric actuators  958 . The actuators are able to generate vibratory directional agitation over a wide range of frequencies and amplitudes that may be needed to detether different microelectronic devices attached to cell frames. Transducers  956  outputs 3-coordinated force-gauge values and three-coordinated accelerometer values that are conditioned in signal conditioning circuit  962  and output to data acquisition cards  978 . A user at user interface  972  coupled to controller  974  including personal computer (PC)  976  after performing the technique shown in flowchart of  FIG. 8  may select proper parameters for controlled directional agitation. The parameters for controlled directional agitation are converted to signals that are generated by waveform generators  982  and output channels  984 . The signals from waveforms generator  982  after power amplification  966  and matching  964  are sent to agitation system  952  and read back from accelerometer and force gauges in transducers  956 . The signals from output channels  984  after auxiliary subsystems  968  are sent to agitation system  952  and read back from accelerometer and force gauges in transducers  956 . As mentioned above, 3-coordinated force-gauge values and three-coordinated accelerometer values are conditioned in signal conditioning circuit  962  and out to data acquisition cards  978  to close the system and monitor the directional agitation in three dimensions. Auxiliary subsystems  968  may include (not shown in  FIG. 9(   b )) a pneumatic subsystem to hold wafers through vacuum chuck, cool down shakers, and other devices to perform related tasks. Auxiliary subsystems  968  may also include gas control system to control the gas around the wafer and thermal system to regulate wafer temperature at desired values. 
         [0044]      FIG. 10  shows use of agitation system of  FIG. 9(   a ) for detethering to release large quantities of MEMS devices  1010  for DNA based self assembly  1020 . In accordance with some embodiments of the invention, the MEMS devices may be fabricated from Silicon on Insulator (SOI) by Deep Reactive Ion Etching (DRIE) process. In some other embodiments of the invention, the MEMS devices may be fabricated by laser bulk micromachining, lithography, PolyMUMPS, microinjection, hot embossing, and so on. Based on assembly principles, the MEMS devices stochastically organize themselves to form certain robotics systems. 
         [0045]    Referring now to  FIG. 11 , in accordance with some embodiments of the invention, an application of detethering in a safety inertial sensor is shown. In accordance with some embodiments, cell  1108  containing safety inertial sensor includes double tethers  1103  separated by an angle of θ  1104 . In accordance with some other embodiments of the invention, safety inertial sensor  1130  includes double tethers  1135  separated by angle θ=180 degrees. The safety inertial sensors include conductive pads  1101 , proof mass  1102  attaching the double tethers  1103 , electrical signal  1106 , and circuits  1107 . Directional agitation  1105  is applied to the cell including the safety inertial sensor  1108 . Electrode tethers  1103  are fabricated with their free ends attached to proof mass  1102 . The proof mass  1102  has at least one conductive layer that passes electrical signal  1106 . In  FIG. 11 , the electrode tethers  1103  and proof mass  1102  in cell  1108  are completing an electronic circuit. At a specified external directional agitation  1105 , the resulting stress on the neck of the electrode tethers causes them to break, creating an open circuit that prevents the electrical signal  1106  from reaching other circuits (not shown in  FIG. 11 ). 
         [0046]    Applications of the safety inertial sensor may be as a disposable packaged MEMS device to secure the safety of electrical circuits in harsh environments. The safety inertial sensor has various advantages over accelerometers and force sensors that can be used for the same purpose. These advantages include simple principle of operation that relies only on the mechanical signature, capability to cover wide range of harsh conditions, reduced design complexity, compact size, reliability, ease of packaging and low cost. 
         [0047]    While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.