Online monitoring method and system for wafer-level film stress, storage medium, electronic equipment and computer program product

Abstract

The invention discloses an online monitoring method and system for wafer-level film stress, a storage medium, electronic equipment and a computer program product, and relates to the technical field of semiconductor manufacturing and detection. The online monitoring method comprises the following steps: transmitting a first signal to at least one surface wave sensor of a wafer, wherein the at least one surface wave sensor is arranged on the back surface of the wafer; receiving a second signal generated by the at least one surface wave sensor according to the first signal; demodulating the second signals to obtain the center frequency offset of each second signal; determining the strain of the wafer at the position of the at least one surface wave sensor according to the center frequency offset; and determining the stress of the film according to the strain of the wafer at the position of the at least one surface wave sensor, the film being arranged on the front surface of the wafer.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing and detection, and specifically to an online monitoring method, system, storage medium, electronic device and computer program product for wafer-level thin film stress. Background Art

[0002] During the semiconductor film preparation process, the film is prone to stress due to the lattice adaptation of the wafer and the film and the inconsistency of the thermal expansion coefficients of the wafer and the film. The stress generated by the film may cause the wafer to warp or even crack, thus affecting the performance of the film.

[0003] At present, the main methods for characterizing and measuring wafer-level thin film stress include non-contact methods such as laser interferometry, X-ray diffraction, and Raman spectroscopy, as well as contact methods such as surface profilometers.

[0004] However, the inventors of the present application have discovered that both the non-contact method and the contact method are off-line measurement methods or require major modifications to the coating equipment to achieve online measurement. Summary of the invention

[0005] According to one aspect of the present application, the present application provides an online monitoring method for wafer-level thin film stress. The online monitoring method for wafer-level thin film stress includes: transmitting a first signal to at least one surface wave sensor of a wafer, wherein at least one surface wave sensor is arranged on the back side of the wafer; receiving a second signal generated by at least one surface wave sensor according to the first signal; demodulating the second signal to obtain a center frequency offset of each second signal; determining the strain of the wafer at the location of at least one surface wave sensor according to the center frequency offset; determining the stress of the thin film according to the strain of the wafer at the location of at least one surface wave sensor, wherein the thin film is arranged on the front side of the wafer.

[0006] According to some embodiments of the present application, after the step of determining the stress of the film based on the strain of the wafer where at least one surface wave sensor is located, the method may further include: determining the stress change of the film based on the stress of the film.

[0007] According to some embodiments of the present application, the surface wave sensor is a surface acoustic wave sensor.

[0008] According to one aspect of the present application, an online monitoring system for wafer-level thin film stress is provided. The wafer is arranged in a coating chamber, and an observation window is provided on the side wall of the coating chamber. The online monitoring system for wafer-level thin film stress includes a signal transceiver, at least one surface wave sensor and a processor. The signal transceiver is arranged outside the coating chamber and within a preset range of the observation window, and the signal transceiver transmits a first signal. At least one surface wave sensor is arranged on the back of the wafer, each surface wave sensor is connected to a first antenna, the first antenna receives the first signal, at least one surface wave sensor generates and sends a second signal according to the first signal, and the first antenna receives and transmits the second signal. The signal transceiver also receives and transmits the second signal transmitted by the first antenna; the processor receives the second signal transmitted by the signal transceiver, the processor determines the center frequency offset of the second signal, the processor determines the strain of the wafer at the location of at least one surface wave sensor according to the center frequency offset, and determines the stress of the film according to the strain of the wafer at the location of at least one surface wave sensor; wherein the film is arranged on the front of the wafer.

[0009] According to some embodiments of the present application, the processor further determines a stress change of the film based on the stress of the film.

[0010] According to some embodiments of the present application, the first signal is a radio frequency signal, and the surface wave sensor converts the radio frequency signal into a surface acoustic wave signal.

[0011] According to some embodiments of the present application, the surface wave sensor converts a radio frequency signal into a surface acoustic wave signal through an interdigital transducer.

[0012] According to one aspect of the present application, the present application provides a non-volatile computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can implement the online monitoring method of wafer-level thin film stress as described above.

[0013] According to one aspect of the present application, the present application provides an electronic device, comprising: one or more processors; a storage device for storing one or more programs, which, when the one or more programs are executed by one or more processors, enables the one or more processors to implement the online monitoring method of wafer-level thin film stress as described above.

[0014] According to one aspect of the present application, the present application provides a computer program product, comprising: a computer program stored on a computer-readable storage medium; the computer program includes program instructions, and when the program instructions are executed by a computer, the computer executes the online monitoring method of wafer-level thin film stress as described above.

[0015] According to one aspect of the present application, the present application also provides a wafer processing system, and the wafer processing system includes the online monitoring system for wafer-level thin film stress described above.

[0016] Through the above-mentioned technical solution, the present application can realize non-contact measurement of wafer-level thin film stress based on wireless signal transmission by setting a surface wave sensor on the back of the wafer. Compared with traditional contact measurement, this solution causes less damage to the wafer and film. The present application can realize online monitoring of wafer-level thin film stress through wireless signal transmission. The present solution does not require modification of the coating equipment and is economical and practical. The present application can improve the coating efficiency of the coating process and improve the closed-loop effect of the coating process through real-time online monitoring of wafer-level thin film stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic flow chart of an online monitoring method 1000 for wafer-level thin film stress according to an embodiment of the present application is shown;

[0019] Figure 2 A schematic flow chart showing an online monitoring method 2000 for wafer-level thin film stress according to an embodiment of the present application;

[0020] Figure 3 A schematic structural diagram of an online monitoring system 300 for wafer-level thin film stress according to an embodiment of the present application is shown;

[0021] Figure 4 A schematic diagram showing a surface wave sensor disposed on the back side of a wafer according to an embodiment of the present application;

[0022] Figure 5 A schematic diagram showing the connection between a surface acoustic wave sensor and a first antenna according to an embodiment of the present application;

[0023] Figure 6 A schematic structural diagram of a surface acoustic wave sensor according to an embodiment of the present application is shown;

[0024] Figure 7 Another structural schematic diagram of a surface acoustic wave sensor according to an embodiment of the present application is shown.

[0025] Reference numerals:

[0026] Coating chamber 1; wafer stage 2; sputtering target 3; wafer 4; observation window 5.

[0027] An online monitoring system 300 for wafer-level thin film stress.

[0028] Signal transceiver 31; surface wave sensor 32; processor 33.

[0029] Signal transmitting module 311; second antenna 312.

[0030] First antenna 321 ; IDT 322 ; Reflection grating 323 .

[0031] Demodulator 331; processing host 332. DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0033] The described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other modes, components, materials, devices, etc. may be adopted. In these cases, known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0034] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0035] The terms "first", "second" and the like in the specification and claims of this application and the above drawings are used to distinguish different objects rather than to describe a specific order.

[0036] The following is a clear and complete description of the technical solution of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0037] The inventor of the present application has found that the contact method in the current characterization and measurement method of wafer-level thin film stress is very easy to damage the film, and the non-contact method requires a specific optical path and expensive instruments to measure. In addition, the current technical solutions for characterization and measurement of thin film stress are all offline measurement methods or require major modifications to the coating equipment to achieve online measurement. For example, to transform the equipment using the laser interferometer method into an online measurement device, it is necessary to open a hole in the coating equipment and install a laser interferometer.

[0038] Thin film stress is a type of stress generated during a process. Online characterization of thin film stress can provide control for a closed-loop process, effectively improving the performance of the thin film and thus the yield of the final product.

[0039] According to one aspect of the present application, the present application provides an online monitoring method 1000 for wafer-level thin film stress, see Figure 1 The method 1000 includes steps S110 to S150. Exemplarily, the method 1000 may be performed by an online monitoring system for wafer-level thin film stress, and the online monitoring system may be a terminal device (such as a host or server, etc.) with data processing capabilities.

[0040] In step S110 , a first signal is transmitted to at least one surface wave sensor of a wafer, wherein the at least one surface wave sensor is disposed on a back side of the wafer.

[0041] According to an exemplary embodiment, an operator may set at least one surface wave sensor on the back side of a wafer to be coated. The back side of the wafer may be the substrate side of the wafer, or the side opposite to the surface of the wafer to be coated.

[0042] For example, operators can form a surface wave sensor by depositing a piezoelectric film on the back of a wafer, or by bonding a surface wave sensor to the back of a wafer using a temperature-resistant tape. The distribution locations of the surface wave sensors may include the center of the wafer, radial directions at different radii, and tangential directions. The number of surface wave sensors can be determined based on factors such as the area of ​​the wafer, the material of the film, and the stress monitoring requirements.

[0043] Optionally, the surface wave sensor may be a surface acoustic wave sensor, which has the advantage of being able to transmit signals online, so that the present application can monitor the film stress during the coating process in real time.

[0044] For example, the surface acoustic wave strain sensors may be distributed at different radial positions of the wafer and symmetrically distributed about the center of the wafer. For example, the strain sensitive direction of the surface acoustic wave sensor may be along the radial direction and the tangential direction of the wafer.

[0045] For example, in step S110, the online monitoring system transmits a first signal to at least one surface wave sensor of the wafer. The first signal may be a radio frequency signal, which includes a specific radio frequency band to excite the surface wave sensor (such as a surface acoustic wave sensor) to generate a surface acoustic wave.

[0046] The online monitoring system can transmit a first signal to at least one surface wave sensor before, during, and after the film coating process of the thin film. The online monitoring system can also transmit the first signal to at least one surface wave sensor multiple times at different times during the film coating process of the thin film.

[0047] In step S120 , a second signal generated by at least one surface wave sensor according to the first signal is received.

[0048] According to an example embodiment, the surface wave sensor can receive a first signal transmitted by the online monitoring system through a first antenna electrically connected thereto, and after receiving the first signal, the surface wave sensor converts the radio frequency signal of the first signal into a surface acoustic wave signal. For example, the surface acoustic wave sensor can convert the radio frequency signal of the first signal into a surface acoustic wave signal through an internal interdigital transducer (IDT).

[0049] The interdigital transducer can receive the first signal from the first antenna and convert the radio frequency signal of the first signal into a surface acoustic wave signal. The interdigital transducer can send the surface acoustic wave signal to a reflection grating inside the surface acoustic wave sensor. After receiving the surface acoustic wave signal, the reflection grating reflects the surface acoustic wave signal to the interdigital transducer. After receiving the surface acoustic wave signal from the reflection grating, the interdigital transducer can convert the surface acoustic wave signal into a radio frequency signal, thereby generating a second signal.

[0050] The second signal includes information about the strain of the wafer between the IDT and the reflection grating at the moment when the first signal is received, that is, includes information about the strain of the wafer at the position where the surface acoustic wave sensor is located at that moment.

[0051] Because the propagation speed of the surface acoustic wave signal and the radio frequency signal is much greater than the speed of thin film deposition, the time error can be ignored.

[0052] Exemplarily, the second signal is a radio frequency signal.

[0053] The IDT sends the second signal to the first antenna, and the SAW sensor receives and transmits the second signal based on the first antenna. In step S120, the online monitoring system receives the second signal generated and sent by the SAW sensor.

[0054] In step S130, the second signals are demodulated to obtain a center frequency offset of each second signal.

[0055] According to example embodiments, the online monitoring system may determine the center frequency offset of the second signal based on the center frequency of the second signal before coating.

[0056] For example, in step S130, the online monitoring system may perform demodulation based on a demodulator, which may be a network analyzer, which demodulates the second signal by scanning the frequency spectrum density to obtain the center frequency offset of the second signal at that moment.

[0057] In step S140, the strain of the wafer at a location where at least one surface wave sensor is located is determined according to the center frequency offset.

[0058] For example, in step S140, the online monitoring system can calculate the strain of the wafer at the location of at least one surface wave sensor according to the center frequency offset of the second signal by the following formula:

[0059]

[0060] Among them, ▽f is the frequency change; ε is the strain of the wafer; S is the proportional coefficient of the surface acoustic wave sensor, also known as the sensitivity of the surface acoustic wave sensor.

[0061] In step S150, the stress of the thin film is determined according to the strain of the wafer at a location where at least one surface wave sensor is located, wherein the thin film is disposed on the front side of the wafer.

[0062] According to an example embodiment, the front side of the wafer may be a film-coated surface of the wafer. For example, in step S150, the online monitoring system may calculate and determine the stress of the film according to Hooke's law:

[0063] σ r =M f ·ε r ;

[0064] σ t =M f ·ε t ;

[0065] Among them, M f is the biaxial Young's modulus of the film; ε r is the radial strain of the wafer, which can be considered equivalent to the radial strain of the film; εt is the wafer tangential strain, which can be considered equivalent to the tangential strain of the film; σ r is the radial stress of the film; σ t is the tangential stress of the film.

[0066] Through the above-mentioned embodiments, the present application can realize non-contact measurement of wafer-level thin film stress based on wireless signal transmission by setting a surface wave sensor on the back of the wafer. Compared with traditional contact measurement, this solution causes less damage to the wafer and film. The present application can realize online monitoring of wafer-level thin film stress through wireless signal transmission. The present solution does not require modification of the coating equipment and is economical and practical. The present application can improve the coating efficiency of the coating process and improve the closed-loop effect of the coating process through real-time online monitoring of wafer-level thin film stress.

[0067] Optionally, the present application provides an online monitoring method 2000 for wafer-level thin film stress, see Figure 3 The method 2000 includes steps S210 to S260. Exemplarily, the method 2000 may be performed by an online monitoring system for wafer-level thin film stress, and the online monitoring system may be a terminal device (such as a host or server, etc.) with data processing capabilities.

[0068] Steps S210 to S250 in the wafer-level thin film stress online monitoring method 2000 are the same as steps S110 to S150 in the wafer-level thin film stress online monitoring method 1000 , and are not described in detail herein.

[0069] In step S260, the stress change of the film is determined according to the stress of the film.

[0070] According to example embodiments, the online monitoring system may determine the stress change of the thin film based on the stress of the thin film before coating.

[0071] For example, in step S260, the online monitoring system may determine the stress change of the film according to the determined film stress.

[0072] According to an example embodiment, the online monitoring system may calculate the difference between the stress of the thin film at different times and the stress of the thin film before coating, thereby determining the stress change of the thin film at different times.

[0073] Through the above-mentioned embodiments, the present application can determine the stress change of the film according to the stress of the film, thereby realizing real-time monitoring of the stress change of the film.

[0074] According to one aspect of the present application, an online monitoring system 300 for wafer-level thin film stress is provided. Figure 3The coating device includes a coating chamber 1, a wafer table 2 and a sputtering target 3 are arranged inside the coating chamber 1, a wafer 4 can be coated on the wafer table 2 inside the coating chamber 2, and the sputtering target 3 deposits a thin film on the front side of the wafer 4. The front side of the wafer 4 can be a wafer coating surface. The back side of the wafer 4 can be a wafer substrate surface, or can be a surface opposite to the wafer coating surface.

[0075] See also Figure 3 An observation window 5 may be opened on the side wall of the coating chamber 1 . The observation window 5 is usually transparent, and the operator can observe the coating process through the observation window 5 .

[0076] According to an example embodiment, see Figure 3 The wafer-level thin film stress online monitoring system 300 includes a signal transceiver 31 , at least one surface wave sensor 32 and a processor 33 .

[0077] According to an exemplary embodiment, the signal transceiver 31 is disposed outside the coating chamber 1 and within a preset range of the observation window 5. The signal transceiver 31 transmits a first signal to at least one surface wave sensor 32.

[0078] The preset range of the observation window 5 is intended to define a specific spatial area, which allows the first signal emitted by the signal transceiver 31 to be effectively transmitted to the surface wave sensor 32 after penetrating the observation window 5 , and enables the first signal to be received by the surface wave sensor 32 .

[0079] The first signal may be a radio frequency signal, which includes a specific radio frequency band to excite a surface wave sensor (such as a surface acoustic wave sensor) to generate a surface acoustic wave.

[0080] According to an example embodiment, see Figure 3 and Figure 4 The signal transceiver 31 includes a signal transmitting module 311 and a second antenna 312. The signal transmitting module 311 transmits a first signal to at least one surface wave sensor 32 in response.

[0081] According to an exemplary embodiment, at least one surface wave sensor 32 is disposed on the back side of the wafer 4, and the surface wave sensor 32 may be formed by depositing a piezoelectric film on the back side of the wafer 4, or by bonding the surface wave sensor 32 on the back side of the wafer 4 using a temperature-resistant tape. The distribution positions of the surface wave sensors 32 may include the center of the wafer 4, radial directions at different radial positions, and tangential directions. The number of surface wave sensors 32 may be determined based on factors such as the area of ​​the wafer, the material of the film, and the monitoring requirements for stress.

[0082] Exemplarily, the surface wave sensor 32 can be a surface acoustic wave sensor, which has the advantage of being able to transmit signals online, so that the present application can monitor the film stress during the coating process in real time. Exemplarily, the surface acoustic wave strain sensor can be distributed at different radial positions of the wafer and symmetrically distributed about the center of the wafer. Exemplarily, the strain sensitive direction of the surface acoustic wave sensor is along the radial and tangential directions of the wafer.

[0083] As an example, Figure 4 As shown, the operator uses a temperature-resistant tape to bond eight surface wave sensors 32 to the back side of the wafer.

[0084] Exemplarily, the eight surface wave sensors 32 may be surface acoustic wave sensors a to h.

[0085] The surface acoustic wave sensor a and the surface acoustic wave sensor b form a group, the strain sensitive direction of the surface acoustic wave sensor a is along the radial direction r of the wafer, and the strain sensitive direction of the surface acoustic wave sensor b is along the tangential direction t of the wafer.

[0086] The surface acoustic wave sensor c and the surface acoustic wave sensor d form a group. The strain sensitive direction of the surface acoustic wave sensor c is along the radial direction r of the wafer, and the strain sensitive direction of the surface acoustic wave sensor d is along the tangential direction t of the wafer.

[0087] The surface acoustic wave sensor e and the surface acoustic wave sensor f form a group. The strain sensitive direction of the surface acoustic wave sensor e is along the radial direction r of the wafer, and the strain sensitive direction of the surface acoustic wave sensor f is along the tangential direction t of the wafer.

[0088] The surface acoustic wave sensor g and the surface acoustic wave sensor h form a group. The strain sensitive direction of the surface acoustic wave sensor g is along the radial direction r of the wafer, and the strain sensitive direction of the surface acoustic wave sensor h is along the tangential direction t of the wafer.

[0089] For example, the signal transmitting module 311 transmits a first signal to the surface acoustic wave sensors a to h.

[0090] Optionally, the signal transmitting module 311 may transmit a first signal to at least one surface wave sensor 32 before, during, and after the film coating process of the thin film. The signal transmitting module 311 may also transmit a first signal to at least one surface wave sensor 32 multiple times at different times during the film coating process of the thin film.

[0091] For example, the signal transmitting module 311 transmits the first signal to the surface acoustic wave sensor a to the surface acoustic wave sensor h at time T0 before coating. The signal transmitting module 311 transmits the first signal to the surface acoustic wave sensor a to the surface acoustic wave sensor h at time T2 during coating.

[0092] According to an example embodiment, see Figure 5 Each surface wave sensor 32 is connected to a first antenna 321. The first antenna 321 and the surface wave sensor 32 can be connected by welding or wire bonding. The first antenna 321 receives the first signal. At least one surface wave sensor 32 generates and sends a second signal according to the first signal.

[0093] Optionally, the first signal may be a radio frequency signal, and the surface wave sensor 32 converts the radio frequency signal into a surface acoustic wave signal. For example, after receiving the first signal, the surface wave sensor 32 converts the radio frequency signal of the first signal into a surface acoustic wave signal through an interdigital transducer (IDT) 322. Figure 5 The surface acoustic wave sensor (surface wave sensor 32 ) further includes an interdigital transducer 322 and a reflection grating 323 .

[0094] As an example, see Figure 6 , the surface acoustic wave sensor (surface wave sensor 32) may include an interdigital transducer 322 and a reflection grating 323. The interdigital transducer 322 may receive the first signal from the first antenna 321 and convert the radio frequency signal of the first signal into a surface acoustic wave signal. The interdigital transducer 322 may send the surface acoustic wave signal to the reflection grating 323. After receiving the surface acoustic wave signal, the reflection grating 323 reflects the surface acoustic wave signal to the interdigital transducer 322. After receiving the surface acoustic wave signal from the reflection grating 323, the interdigital transducer 322 may convert the surface acoustic wave signal into a radio frequency signal, thereby generating a second signal.

[0095] As another example, see Figure 7 The surface acoustic wave sensor (surface wave sensor 32) may also include two interdigital transducers 322 and two reflection gratings 323. The two interdigital transducers 322 are respectively connected to the two reflection gratings 323 to achieve the transmission of the surface acoustic wave signal. The surface acoustic wave sensor (surface wave sensor 32) is provided with two interdigital transducers 322 to enhance the strength of the radio frequency signal and the surface acoustic wave signal.

[0096] The second signal includes the strain information of the wafer 4 between the IDT 322 and the reflection grating 323 at the moment when the first signal is received, that is, includes the strain information of the wafer 4 at the position where the SAW sensor 32 is located at that moment.

[0097] Because the propagation speed of the surface acoustic wave signal and the radio frequency signal is much greater than the speed of thin film deposition, the time error can be ignored. The second signal is a radio frequency signal.

[0098] The IDT 322 sends the second signal to the first antenna 321 , and the first antenna 321 receives and transmits the second signal.

[0099] For example, after the first antenna 321 connected to the surface acoustic wave sensor a receives the first signal 1, it sends the first signal 1 to the interdigital transducer 322 inside the surface acoustic wave sensor a. The interdigital transducer 322 converts the radio frequency signal of the first signal 1 into a surface acoustic wave signal. The interdigital transducer 322 sends the surface acoustic wave signal to the reflection grating 323. After the reflection grating 323 receives the surface acoustic wave signal, it reflects the surface acoustic wave signal to the interdigital transducer 322. After receiving the surface acoustic wave signal from the reflection grating 323, the interdigital transducer 322 can convert the surface acoustic wave signal into a radio frequency signal, thereby generating the second signal 1. The interdigital transducer 322 sends the second signal 1 to the first antenna 321, and the first antenna 321 transmits the second signal 1.

[0100] The process of surface acoustic wave sensor b to surface acoustic wave sensor h generating second signal 2 to second signal 8 respectively is the same as that of surface acoustic wave sensor a, and will not be described in detail here.

[0101] According to an example embodiment, see Figure 3 , the signal transceiver 31 also receives and transmits the second signal transmitted by the first antenna 321. For example, the second antenna 312 receives the second signal 1-second signal 8 generated by the surface acoustic wave sensor a-surface acoustic wave sensor h at time T1 according to the first signal 1-first signal 8 transmitted by the signal transmitting module 311 at time T0; the second antenna 312 receives the second signal 1-second signal 8 generated by the surface acoustic wave sensor a-surface acoustic wave sensor h at time T3 according to the first signal 1-first signal 8 transmitted by the signal transmitting module 311 at time T2.

[0102] The processor 33 receives the second signal transmitted by the signal transceiver. For example, the processor 33 receives the second signal 1 to the second signal 8 transmitted by the second antenna 312.

[0103] According to an example embodiment, see Figure 3 The processor 33 includes a demodulator 331 and a processing host 332. The processor 33 determines the center frequency offset of the second signal. For example, the processor 33 can determine the center frequency offset of the second signal based on the center frequency of the second signal received at time T1 before coating.

[0104] Exemplarily, the demodulator 331 may be a network analyzer, and the network analyzer may demodulate the second signal by scanning the frequency spectrum density to obtain the center frequency offset of the second signal at that moment.

[0105] For example, the demodulator 331 (network analyzer) demodulates the second signal 1 to the second signal 8 to obtain:

[0106] The center frequency offset of the second signal 1 at time T3: ▽f 1 =-0.00013MHz;

[0107] The center frequency offset of the second signal 2 at time T3: ▽f 2 = -0.0001375MHz;

[0108] The center frequency offset of the second signal 3 at time T3: ▽f 3 = -0.000191MHz;

[0109] The center frequency offset of the second signal 4 at time T3: ▽f 4 = -0.000198MHz;

[0110] The center frequency offset of the second signal 5 at time T3: ▽f 5 = -0.0002125MHz;

[0111] The center frequency offset of the second signal 6 at time T3: ▽f 6 = -0.000237MHz;

[0112] The center frequency offset of the second signal 7 at time T3: ▽f 7 = -0.0002575MHz;

[0113] The center frequency offset of the second signal 8 at time T3: ▽f 8 =-0.000265MHz.

[0114] Among them, ▽f 1 is the center frequency offset of the second signal 1 at time T3, ▽f 2 is the center frequency offset of the second signal 2 at time T3, ▽f 3 is the center frequency offset of the second signal 3 at time T3, ▽f 4 is the center frequency offset of the second signal 4 at time T3, ▽f 5 is the center frequency offset of the second signal 5 at time T3, ▽f 6 is the center frequency offset of the second signal 6 at time T3, ▽f 7 is the center frequency offset of the second signal 7 at time T3, ▽f 8 is the center frequency offset of the second signal 8 at time T3.

[0115] According to an exemplary embodiment, the processor 33 determines the strain of the wafer 4 at the location of the at least one surface wave sensor 32 according to the center frequency offset. For example, the processing host 332 calculates the strain of the wafer 4 at the location of the at least one surface wave sensor 32 according to the center frequency offset of the second signal by the following formula:

[0116]

[0117] Wherein, ▽f is the frequency change; ε is the strain of the wafer 4; and S is the proportional coefficient of the surface acoustic wave sensor, also known as the sensitivity of the surface acoustic wave sensor.

[0118] According to an exemplary embodiment, the processing host 332 calculates the radial strain r and the tangential strain t of the wafer 4 at the location of the at least one surface wave sensor 32 according to the center frequency offset of the second signal by using the following formula:

[0119]

[0120] Among them, ε r is the radial strain of the wafer; t is the strain in the wafer tangential direction t.

[0121] For example, S is the proportionality coefficient (or sensitivity) of the surface acoustic wave sensor, which is related to the type of the surface acoustic wave sensor. S can be set to 0.00005MHz / με. The processing host 332 determines the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor a at time T3 based on the center frequency offset of the second signal 1 as: ε r1 =260με;

[0122] The processing host 332 determines the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor b at time T3 according to the center frequency offset of the second signal 2 as: ε t1 =2.75με;

[0123] The processing host 332 determines the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor c at time T3 according to the center frequency offset of the second signal 3 as: ε r2 =3.82με;

[0124] The processing host 332 determines the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor d at time T3 according to the center frequency offset of the second signal 4 as: ε t2 =3.96με;

[0125] The processing host 332 determines the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor e at time T3 according to the center frequency offset of the second signal 5 as: εr3 =4.25με;

[0126] The processing host 332 determines the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor f at time T3 according to the center frequency offset of the second signal 6 as: ε t3 =4.74με;

[0127] The processing host 332 determines the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor g at time T3 according to the center frequency offset of the second signal 7 as: ε r4 =5.15με;

[0128] The processing host 332 determines the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor h at time T3 according to the center frequency offset of the second signal 8 as: ε t4 =5.30με.

[0129] Among them, ε r1 is the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor a at time T3, ε t1 is the tangential strain t of wafer 4 at the location of surface acoustic wave sensor b at time T3, ε r2 is the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor c at time T3, ε t2 is the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor d at time T3, ε r3 is the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor e at time T3, ε t3 is the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor f at time T3, ε r4 is the radial strain r of the wafer 4 at the location of the surface acoustic wave sensor g at time T3, ε t4 is the tangential strain t of the wafer 4 at the location of the surface acoustic wave sensor h at time T3.

[0130] According to an exemplary embodiment, the processor 33 determines the stress of the film based on the strain of the wafer 4 at the location of the at least one surface wave sensor 32. For example, the processing host 332 can calculate the stress of the film based on Hooke's law:

[0131] σ r =M f ·ε r ;

[0132] σ t =M f ·ε t ;

[0133] Among them, M fis the biaxial Young's modulus of the film; ε r is the radial strain of the wafer, which can be considered equivalent to the radial strain of the film; ε t is the wafer tangential strain, which can be considered equivalent to the tangential strain of the film; σ r is the radial stress of the film; σ t is the tangential stress of the film.

[0134] For example, M f M is the biaxial Young's modulus of the film, which is related to the type, temperature, and crystal structure of the film. f The value can be 120GPa.

[0135] For example, processing host 332 determines that:

[0136] The radial r stress of the film at the location of the surface acoustic wave sensor a at time T3: r1 =312MPa;

[0137] The tangential stress t of the film at the location of the surface acoustic wave sensor b at time T3: t1 =330MPa;

[0138] The radial r stress of the film at the location of the surface acoustic wave sensor c at time T3: r2 =458.4MPa;

[0139] The tangential stress of the film at the location of the surface acoustic wave sensor d at time T3: t2 =475.2MPa;

[0140] The radial r stress of the film at the location of the surface acoustic wave sensor e at time T3: r3 =510MPa;

[0141] The tangential stress t of the film at the location of the surface acoustic wave sensor f at time T3: t3 =568.8MPa;

[0142] The radial r stress of the film at the location of the surface acoustic wave sensor g at time T3: r4 =618MPa;

[0143] The tangential stress of the film at the location of the surface acoustic wave sensor h at time T3: t4 =636MPa.

[0144] Then, the processing host 332 determines:

[0145] The stress of the film at the location of the SAW sensor a and the SAW sensor b at time T3 is:

[0146] The stress of the film at the location of the SAW sensor c and the SAW sensor d at time T3 is:

[0147] The stress of the film at the location of the SAW sensor e and the SAW sensor f at time T3 is:

[0148] The stress of the film at the location of the SAW sensor g and the SAW sensor h at time T3 is:

[0149] Then, the processing host 332 calculates the stress of the film at time T3 as:

[0150]

[0151] Among them, σ 1 is the stress of the film at the location of SAW sensor a and SAW sensor b at time T3, σ 2 is the stress of the film at the location of the SAW sensor c and the SAW sensor d at time T3, σ 3 is the stress of the film at the location of the SAW sensor e and SAW sensor f at time T3, σ 4 is the stress of the film at the location of the surface acoustic wave sensor g and the surface acoustic wave sensor h at time T3, and σ is the stress of the film at time T3.

[0152] Through the above-mentioned embodiments, the present application can realize non-contact measurement of wafer-level thin film stress based on wireless signal transmission by setting a surface wave sensor on the back of the wafer. Compared with traditional contact measurement, this solution causes less damage to the wafer and film. The present application can realize online monitoring of wafer-level thin film stress through wireless signal transmission. The present solution does not require modification of the coating equipment and is economical and practical. The present application can improve the coating efficiency of the coating process and improve the closed-loop effect of the coating process through real-time online monitoring of wafer-level thin film stress.

[0153] Optionally, the processor 33 may also determine the stress change of the film according to the determined film stress. For example, the processing host 332 may calculate the difference between the stress of the film at different times, thereby determining the stress change of the film at different times. For another example, the processing host 332 may use the stress of the film before coating as a reference, calculate the difference between the stress at different times and the stress of the film at time T0 (which is 0), thereby determining the stress change of the film at different times.

[0154] For example, the processing host 332 determines the stress σ of the film at time T0 0 =0, the stress of the film at time T3 σ=691.28MPa, then the processing host 332 determines the stress change of the film at time T3 ▽σ=691.28MPa.

[0155] Through the above-mentioned embodiments, the present application can determine the stress change of the film according to the stress of the film, thereby realizing real-time monitoring of the stress change of the film.

[0156] According to another aspect of the present application, the present application also provides a non-volatile computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the online monitoring method of wafer-level thin film stress as described above can be implemented.

[0157] According to another aspect of the present application, the present application also provides an electronic device, comprising: one or more processors; a storage device for storing one or more programs, when the one or more programs are executed by one or more processors, the one or more processors are enabled to implement the online monitoring method of wafer-level thin film stress as described above.

[0158] According to another aspect of the present application, the present application also provides a computer program product, including: a computer program stored on a computer-readable storage medium; the computer program includes program instructions, and when the program instructions are executed by the computer, the computer executes the online monitoring method of wafer-level thin film stress as described above.

[0159] According to another aspect of the present application, the present application further provides a wafer processing system, and the wafer processing system includes the online monitoring system for wafer-level thin film stress described above.

[0160] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions of the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for online monitoring of wafer-level thin film stress, characterized in that: The online monitoring method comprises: transmitting a first signal to at least one surface wave sensor of a wafer, wherein the at least one surface wave sensor is disposed on a back side of the wafer; receiving a second signal generated by the at least one surface wave sensor based on the first signal; Demodulating the second signals to obtain a center frequency offset of each of the second signals; Determining the strain of the wafer at a location of the at least one surface wave sensor according to the center frequency offset; The stress of the thin film is determined based on the strain of the wafer at the location of the at least one surface wave sensor, wherein the thin film is disposed on the front side of the wafer.

2. The online monitoring method according to claim 1, characterized in that: After determining the stress of the film according to the strain of the wafer at the location of the at least one surface wave sensor, the online monitoring method further comprises: According to the stress of the film, a stress change of the film is determined.

3. The online monitoring method according to claim 1, characterized in that: The surface wave sensor is a surface acoustic wave sensor.

4. An online monitoring system for wafer-level thin film stress, characterized in that: The wafer is arranged in a coating chamber, and an observation window is provided on the side wall of the coating chamber. The online monitoring system comprises: A signal transceiver is arranged outside the coating chamber and within a preset range of the observation window, and the signal transceiver transmits a first signal; at least one surface wave sensor, disposed on the back side of the wafer, each of the surface wave sensors being connected to a first antenna, the first antenna receiving the first signal, the at least one surface wave sensor generating and sending a second signal according to the first signal, the first antenna receiving and transmitting the second signal; The signal transceiver also receives and transmits a second signal transmitted by the first antenna; a processor, receiving a second signal transmitted by the signal transceiver, the processor determining a center frequency offset of the second signal, the processor determining a strain of the wafer at a location where the at least one surface wave sensor is located according to the center frequency offset, and the processor determining a stress of the film according to the strain of the wafer at a location where the at least one surface wave sensor is located; Wherein, the film is arranged on the front side of the wafer.

5. The online monitoring system according to claim 4, characterized in that: The processor also determines a stress change of the film based on the stress of the film.

6. The online monitoring system according to claim 5, characterized in that: The first signal is a radio frequency signal, and the surface wave sensor converts the radio frequency signal into a surface acoustic wave signal.

7. The online monitoring system according to claim 6, characterized in that: The surface wave sensor converts the radio frequency signal into the surface acoustic wave signal through an interdigital transducer.

8. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the online monitoring method for wafer-level thin film stress is implemented as described in any one of claims 1-3.

9. An electronic device, characterized in that: include: one or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the online monitoring method for wafer-level thin film stress as described in any one of claims 1-3.

10. A computer program product, characterized in that It comprises a computer program stored on a computer-readable storage medium, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer is caused to execute the online monitoring method for wafer-level thin film stress as claimed in any one of claims 1 to 3.

11. A wafer processing system, characterized in that: An online monitoring system for wafer-level thin film stress comprising any one of claims 4-7.

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