Wireless in-situ real-time measurement of electrostatic chucking force in semiconductor wafer processing

Embodiments disclosed herein include an apparatus for measuring chucking force and methods of using such apparatuses. In an embodiment, the apparatus for measuring a chucking force comprises a substrate having a chucking surface, where the chucking surface is the surface that is supported by a chuck. In an embodiment, the apparatus further comprises a plurality of sensors over the chucking surface, where the plurality of sensors are thin film sensors with a thickness that is less than a thickness of the substrate. In an embodiment, the apparatus further comprises a wireless communication module electrically coupled to each of the plurality of sensors.

BACKGROUND

Field

Embodiments relate to the field of semiconductor manufacturing and, in particular, to methods and apparatuses for measuring the chucking force in-situ and in real-time.

Description of Related Art

In the processing of substrates, such as semiconducting wafers, the wafers are secured to a chuck during processing. Currently, there is no way to accurately measure the chucking force across the wafer. The only way to monitor the chucking force is to reduce the chucking voltage until the force is not sufficient to hold the wafer to the electrostatic chuck, and backside helium flow increases. Such a process only provides a measure of the minimum chucking voltage to secure the wafer. Accordingly, it is not possible to measure chucking force uniformity. Additionally, it is not possible to compare the chucking force between chambers in order to provide chamber matching information.

As such, the substrates being processed are over-chucked. That is, the chucking force applied to the substrates is substantially larger than is necessary in order to guarantee that the substrate is properly secured. Such over-chucking leads to damage of the chucking surface of the substrate (i.e., the backside of the wafer) being processed and to the chuck itself. Accordingly, there is an increase in particle generation and a reduced useable lifespan of the chuck.

SUMMARY

Embodiments disclosed herein include an apparatus for measuring chucking force and methods of using such apparatuses. In an embodiment, the apparatus for measuring a chucking force comprises a substrate having a chucking surface, where the chucking surface is the surface that is supported by a chuck. In an embodiment, the apparatus further comprises a plurality of sensors over the chucking surface, where the plurality of sensors are thin film sensors with a thickness that is less than a thickness of the substrate. In an embodiment, the apparatus further comprises a wireless communication module electrically coupled to each of the plurality of sensors.

Embodiments disclosed herein may also comprise a system for measuring the real-time chucking forces on a substrate. In an embodiment, the system comprises a processing tool with a chamber and a support surface in the chamber for securing substrates with a chucking force. In an embodiment, the system further comprises a substrate with a chucking surface, where the chucking surface is secured to the support surface by the chucking force. In an embodiment, a plurality of sensors are positioned over the chucking surface of the substrate. The sensors measure the chucking force. In an embodiment, the system may further comprise a wireless communication module electrically coupled to the plurality of sensors, where the wireless communication module transmits chucking force data outside of the chamber.

Embodiments may also comprise a method of optimizing a semiconductor fabrication process recipe. In an embodiment, the method comprises placing a substrate having a plurality of thin film sensors on a chucking surface of the substrate on a support surface in a processing tool. The method may also comprise securing the substrate to the support surface with a chucking force, where the plurality of thin film sensors provide a measurement of the chucking force across a surface of the substrate. In an embodiment, the method may further comprise executing a process recipe in the processing tool, and obtaining chucking force measurements from the plurality of sensors during execution of the process recipe. In an embodiment, the method may further comprise using the chucking force measurements to modify the process recipe.

DETAILED DESCRIPTION

Systems that include substrates with thin-film sensors over a chucking surface of the substrate and methods of using such thin-film sensors to measure a chucking force profile over the chucking surface are described in accordance with various embodiments. In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments. It will be apparent to one skilled in the art that embodiments may be practiced without these specific details. In other instances, well-known aspects are not described in detail in order to not unnecessarily obscure embodiments. Furthermore, it is to be understood that the various embodiments shown in the accompanying drawings are illustrative representations and are not necessarily drawn to scale.

As noted above, there are currently no tools that can be used to measure the chucking force applied to a chucking surface of a substrate. Accordingly, substrates need to be over-chucked in order to guarantee that the substrate is properly secured during processing. Such over-chucking results in damage to the chucking surface of the substrate and damage to the chuck itself.

Accordingly, embodiments disclosed herein include a substrate with a plurality of thin-film sensors distributed across the chucking surface of the substrate. In accordance with an embodiment, the thin-film sensors have a thickness that is substantially less than the thickness of the substrate (e.g., 100 μm or less). As such, embodiments disclosed herein provide the ability to measure the chucking force without affecting the form factor of standard wafer dimensions.

Additionally, embodiments may also include a wireless communication module that allows for the chucking force profile to be monitored in real-time. Accordingly, measurement of a chucking force profile during a process recipe may be obtained. This is particularly beneficial since RF plasma processing may alter the chucking force across the substrate. In a particular embodiment, the wireless communication module may operate at a frequency that does not interact with the RF plasma (e.g., 2.4 GHz) in order to more accurately monitor the chucking force that will be experienced by device wafers being processed in the processing tool.

As such, embodiments disclosed herein include sensor substrates that substantially match the form factor and behavior of device wafers during execution of a processing recipe. The sensor substrates, therefore, provide an accurate representation of the chucking force experienced by device wafers. Accordingly, such sensor substrates may be used to optimize the chucking force in order to minimize damage to the chucking surface of device wafers and/or to minimize damage to the chuck itself. Embodiments, therefore, provide reduced particle generation and increased chuck lifespans. Embodiments may also allow for improved chamber matching since each chamber may be calibrated to provide a uniform chucking force across chambers.

Referring now toFIG. 1, a cross-sectional schematic of a processing tool100is shown, in accordance with an embodiment. In an embodiment, the processing tool100may include a support surface130on which a substrate120is supported. The substrate120may comprise a chucking surface122that is in direct contact with the support surface130and a second surface124that is opposite from the chucking surface122. The support surface130may include a mechanism for providing a chucking force F to secure the substrate120to the support surface130. In a particular embodiment, the support surface130may be an electrostatic chuck (ESC), a vacuum chuck, a heater pedestal, or any other support surface used in semiconductor manufacturing environments. In an embodiment, the support surface130may be one or more of a Coulombic chuck, a Johnson-Rahbek (J-R) chuck, a monopolar ESC, and a bipolar ESC. In an embodiment, the support surface130may include sealing bands132around the perimeter of the support surface130and a plurality of mesas134within the sealing bands132. The sealing bands132and the mesas134may provide channels through which fluids (e.g., helium) may be flown for thermal management purposes, as is known in the art.

As noted above, the standard practice to secure the substrate120to the support surface130involves over-chucking the substrate120. That is, the chucking force F applied to the substrate120is greater than necessary to secure the substrate120to the support surface130since there is currently no way to monitor the chucking force. The over-chucking results in damage to the chucking surface122of the substrate120and damage to the sealing bands132and the mesas134.

Accordingly, embodiments disclosed herein include a substrate with a plurality of thin-film sensors distributed across the chucking surface. For example,FIG. 2Ais a plan view illustration of the chucking surface222of a sensor substrate220, in accordance with an embodiment. In an embodiment, the sensor substrate220may have substantially the same form factor as devices wafers. For example, the sensor substrate220may have a diameter (e.g., 150 mm, 200 mm, 300 mm, 450 mm, or the like) that substantially matches the diameter of the device wafers. In an embodiment, a thickness of the sensor substrate220may also substantially match the thickness of the device wafers. In an embodiment, the sensor substrate220may also comprise the same material as the device wafers. For example, the sensor substrate220may comprise a silicon substrate.

In an embodiment, the chucking surface222may comprise a plurality of thin-film sensors228distributed across the chucking surface222. Distributing the thin-film sensors228across the chucking surface222allows for the chucking force across the sensor substrate220to be obtained. This is particularly beneficial since the chucking force may be non-uniform across the chucking surfaces222(e.g., due to variations in the support surface130, variations in the plasma process, or the like). Accurate mapping of the chucking force profile across the chucking surface222allows for fine adjustments to the chucking force to be made in order to optimize process recipes, provide chamber matching, minimize particle generation, and/or minimize damage to the support surface130.

In the illustrated embodiment, seventeen thin-film sensors228are shown. However, it is to be appreciated that any number of thin-film sensors228may be included on the sensor substrate220. For example, one or more thin-film sensors228, tens of thin-film sensors228, hundreds of thin-film sensors228, or thousands of thin-film sensors228may be formed over the chucking surface222of the sensor substrate220in order to provide the desired resolution of the chucking force mapping. In a particular embodiment, a total surface area of the thin-film sensors228may be approximately 30% or less, 20% or less, or 10% or less of the total surface area of the chucking surfaces222. Accordingly, embodiments allow for larger proportions of the chucking surface222to match the actual chucking surfaces of device wafers in order to provide a more accurate representation of the chucking forces experienced by device wafers. Furthermore, while schematically represented as being square in shape, it is to be appreciated that the thin-film sensors228may be any desired shape or shapes.

Referring now toFIG. 2B, a cross-sectional illustration of a sensor substrate220is shown, in accordance with an embodiment. In the illustrated embodiment, the plurality of thin-film sensors228are shown as being substantially embedded in the sensor substrate220. For example, surfaces229of the thin-film sensors228may be substantially coplanar with the chucking surfaces222of the sensor substrate220.

In an embodiment, the plurality of thin-film sensors228may be electrically coupled (e.g., with conductive traces223) to a wireless communication module225. In an embodiment, the wireless communication module225may comprise a transceiver for communicating wirelessly with a device located outside of the processing tool being monitored by the sensor substrate220. The wireless communication may be implemented at any frequency and/or with any suitable wireless communication protocol (e.g., WiFi, Bluetooth, Zigbee, or the like). In a particular embodiment, the frequency used by the wireless communication module225may be significantly greater than the frequency at which a plasma source operates in order to minimize interference with the plasma. For example, the wireless communication module225may operate at 2.4 GHz, which is substantially above the frequency commonly used for RF plasma generation.

In an embodiment, the wireless communication module225may also comprise other circuitry and/or components. For example, the wireless communication module225may also comprise a power source (e.g., a battery) for operating the thin-film sensors228and/or for enabling wireless communication. In other embodiments, a power source may be a separate component distinct from the wireless communication module225. In an embodiment, the wireless communication module225may also comprise a memory, a processor, or any other passive or active circuitry blocks. As shown inFIG. 2B, the wireless communication module225may be embedded in the sensor substrate220. That is, all or substantially all of the wireless communication module225may be below the second (i.e., top) surface224of the sensor substrate220.

Referring now toFIG. 2C, a cross-sectional illustration of a sensor substrate220is shown, in accordance with an additional embodiment. The sensor substrate220inFIG. 2Cmay be substantially similar to the sensor substrate220inFIG. 2B, with the exception that the thin-film sensors228and the wireless communication module225are not embedded in the sensor substrate220.

As shown, the thin-film sensors228may be disposed over the chucking surface222. That is, the bottom surface229of the thin-film sensors228(i.e., the surface that interfaces with the support surface of the chuck) is not substantially coplanar with the chucking surface222of the sensor substrate220. However, it is to be appreciated that the thickness T of the thin-film sensors228is substantially smaller than the thickness of the sensor substrate220in order to minimize any effects attributable to the thin-film sensors. For example, the thickness T of the thin-film sensors228may be 100 μm or less, 50 μm or less, or 25 μm or less.

In an embodiment, the wireless communication module225may also not be embedded in the sensor substrate220. For example, the wireless communication module225may be positioned over the second (i.e., top) surface224of the sensor substrate220. In such an embodiment, the sensor substrate220may only comprise electrical traces223to connect the thin-film sensors228to the wireless communication module225. That is, in some embodiments, no active circuitry may be embedded in the sensor substrate220, and any components (e.g., the thin-film sensors228and the wireless communication module225) may be positioned over the chucking surface222or the second surface224of the sensor substrate220.

Referring now toFIG. 3, a schematic of a thin-film sensor328is shown, in accordance with an embodiment. In an embodiment, thin-film sensor328is a force sensor. The force sensor may comprise a body that has an electrical resistance R that varies with the amount of compressive force F applied to the body. In a particular embodiment, the electrical resistance R may be correlated to a pressure (i.e., force F divided by the area of the thin-film sensor) applied to the thin-film sensor328. For example, as the force F (and pressure) increases, the resistance R may also change with a known relationship (e.g., the resistance R may be inversely proportional to the pressure (i.e., force F divided by area of the thin-film sensor) applied to the thin-film sensor328. Accordingly, the compressive force (i.e., the chucking force) can be determined by monitoring the resistance of the thin-film sensor328. In an embodiment, the thin-film sensor328may comprise any suitable material that exhibits such a relationship between force and resistance. For example, the thin-film sensor328may comprise semiconductor material that can be deposited as an ink or a film that is sandwiched between conductive pads, traces, or the like.

Referring now toFIG. 4, a cross-sectional schematic of a processing tool450that is being monitored with a sensor substrate420is shown, in accordance with an embodiment. The processing tool450may comprise a chamber451suitable for semiconductor processing. In a particular embodiment, the chamber451may be a vacuum chamber suitable for processing operations in which a plasma455is induced. In other embodiments, the processing tool450may be any processing tool that is used in semiconductor fabrication applications, and may omit the presence of a chamber. For example, the processing tool450may be a heater pedestal, or the like.

In an embodiment, the processing tool450may comprise a support surface430. The support surface430may be an ESC, a vacuum chuck, or the like. In an embodiment, the support surface430may be one or more of a Coulombic chuck, a J-R chuck, a monopolar ESC, and a bipolar ESC. In an embodiment, the support surface430may include sealing bands432around the perimeter of the support surface430and a plurality of mesas434within the sealing bands432. The sealing bands432and the mesas434may provide channels through which fluids (e.g., helium) may be flown for thermal management purposes, as is known in the art.

In an embodiment, a sensor substrate420may be disposed on the support surface430. That is, a chucking surface422of the sensor substrate420may interface with the support surface430. The sensor substrate420may be a sensor substrate such as those described above with respect toFIGS. 2A-2C. For example, the sensor substrate420may comprise a plurality of thin-film sensors428disposed across the chucking surface422of the sensor substrate420. In a particular embodiment, the thin-film sensors428may be arranged such that they are positioned between the sealing bands432and the sensor substrate420and/or between the mesas434and the sensor substrate420. Accordingly, as a chucking force F is applied to the sensor substrate the thin-film sensors428will provide a chucking force profile across the chucking surface422of the sensor substrate420.

In an embodiment, the chucking force profile may be transmitted in substantially real-time by a wireless communication module425of the sensor substrate420. For example, wireless communication453may be transmitted to a receiver457located outside of the processing tool450. In an embodiment, the frequency of the wireless communication453may be different than the frequency of the plasma455in order to minimize or eliminate any adverse interference with the plasma455. For example, the wireless communication453may be transmitted at 2.4 GHz using a Bluetooth compatible communication protocol.

Referring now toFIG. 5, a schematic of a processing tool550and a receiver557used to generate and use a chucking force profile is shown, in accordance with an embodiment. As shown, the processing tool may comprise a chamber551and a support surface530. The chamber and support surface530may be substantially similar to embodiments described above with respect toFIG. 4. In an embodiment, a sensor substrate520that comprises a plurality of thin-film sensors528may be supported by the support surface530. The thin-film sensors528are illustrated with a dashed line in order to indicate that the thin-film sensors528are positioned between a chucking surface of the sensor substrate520and the support surface530.

In an embodiment, the sensor substrate520may be communicatively coupled to a receiver557outside of the processing tool550(e.g., with a wireless communication signal553). In an embodiment, the receiver557may include a sensor interface558for receiving raw data from the thin-film sensors528. In an embodiment, the sensor interface558may convert electrical signals (e.g., resistance values) into a measure of force. While shown as being part of the receiver557outside of the processing tool550, it is to be appreciated that the sensor interface558may also be implemented as a component on the sensor substrate520and the raw data from the thin-film sensors528may be processed prior to being transmitted to the receiver557.

After processing by the sensor interface558, the processed data may be displayed and/or stored in memory as a chucking force profile by the chucking force module559. The chucking force profile provides a visual representation of the chucking force across the surface of the sensor substrate520. Furthermore, the chucking force profile may change over time. That is, the chucking force experienced by a given thin-film sensor may change during the execution of a process recipe. The change of the chucking force profile over time may also be captured (e.g., displayed and/or stored in memory) by the chucking force module559.

In an embodiment, the chucking force module559may also comprise software that utilizes the chucking force profile (or profiles) in order to provide instructions/modifications561to a database562for future use. For example, the instructions/modifications may include one or more of modifications to a process recipe, chamber matching information, end of useable life determinations for the support surface, or the like.

Referring now toFIG. 6, a process flow diagram of a process670for modifying a process recipe using a chucking force profile generated with a sensor substrate is shown, in accordance with an embodiment. In an embodiment, process670may being with operation671which includes placing a substrate with sensors on a chucking surface onto a support surface in a processing tool. Process670may continue with operation672which comprises securing the substrate to the support surface with a chucking force. In an embodiment, process670may then continue with operation673which comprises executing a process recipe in the processing tool. In an embodiment, process670may also comprise operation674which includes measuring the chucking force with the sensors in real-time during execution of the process recipe. Since the chucking force is measured in real-time, the changes to the chucking force that occur during changing processing conditions during the process recipe may be monitored. In an embodiment, process670may then include operation675which comprises modifying the process recipe based on the chucking force measurements. For example, the process recipe may be modified by increasing or decreasing the chucking force applied to the substrate.

Referring now toFIG. 7, a block diagram of an exemplary computer system760of a processing tool is illustrated in accordance with an embodiment. In an embodiment, the computer system760may be used as the receiver that is communicatively coupled to the sensor substrate. In an embodiment, computer system760is coupled to and controls processing in the processing tool. Computer system760may be connected (e.g., networked) to other machines in a network761(e.g., a Local Area Network (LAN), an intranet, an extranet, or the Internet). Computer system760may operate in the capacity of a server or a client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. Computer system760may be a personal computer (PC), a tablet PC, a set-top box (STB), a Personal Digital Assistant (PDA), a cellular telephone, a web appliance, a server, a network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated for computer system760, the term “machine” shall also be taken to include any collection of machines (e.g., computers) that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies described herein.

In an embodiment, computer system760includes a system processor702, a main memory704(e.g., flash memory, etc.), a static memory706(e.g., flash memory, etc.), and a secondary memory718(e.g., a data storage device), which communicate with each other via a bus730.

System processor702represents one or more general-purpose processing devices such as a microsystem processor, central processing unit, or the like. System processor702may also be one or more special-purpose processing devices. System processor702is configured to execute the processing logic726for performing the operations described herein.

The computer system760may further include a system network interface device708for communicating with other devices or machines. The computer system760may also include a video display unit710(e.g., a liquid crystal display (LCD), a light emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device712(e.g., a keyboard), a cursor control device714(e.g., a mouse), and a signal generation device716(e.g., a speaker).

The secondary memory718may include a machine-accessible storage medium731(or more specifically a computer-readable storage medium) on which is stored one or more sets of instructions (e.g., software722) embodying any one or more of the methodologies or functions described herein. The software722may also reside, completely or at least partially, within the main memory704and/or within the system processor702during execution thereof by the computer system760, the main memory704and the system processor702also constituting machine-readable storage media. The software722may further be transmitted or received over a network761via the system network interface device708.

In the foregoing specification, specific exemplary embodiments have been described. It will be evident that various modifications may be made thereto without departing from the scope of the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.