Wafer surface film thickness online detection method and device

Abstract

The invention discloses a wafer surface film thickness on-line detection method and device, and the method comprises the steps: transmitting a grating signal to a wafer through a grating device, receiving a reflection signal outputted by the reflection of the grating signal on the surface of the wafer, and judging whether the wafer is in a horizontal state or not; if yes, when the wafer is driven to rotate for spin coating treatment, alternately applying excitation signals to the first capacitive sensor and the second capacitive sensor; acquiring a differential capacitance value between the first capacitive sensor and the second capacitive sensor in real time, and synchronously acquiring dynamic gaps between the wafer and the first capacitive sensor and between the wafer and the second capacitive sensor; and according to the differential capacitance value, the dynamic gap and the dielectric constant of the film layer material coated on the surface of the wafer, the thickness distribution of the film layer on the surface of the wafer is analyzed and calculated through impedance spectroscopy. According to the invention, the precision of wafer surface film thickness detection can be effectively improved, and the problem that the precision is not high when a capacitance sensor is adopted to carry out capacitance detection on the wafer surface film in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of wafer detection, and in particular to an online detection method and device for the thickness of a wafer surface film. Background Art

[0002] As semiconductor process nodes continue to shrink to below 5nm, the thickness uniformity of thin films on the wafer surface has become a core factor affecting device performance and reliability.

[0003] The current mainstream online detection technology has the following defects:

[0004] Insufficient anti-interference ability: Single-point capacitance sensors are easily affected by wafer rotation vibration, temperature drift and electromagnetic noise, resulting in measurement signal distortion. In particular, the error is significantly amplified under high-speed rotation conditions (>500rpm).

[0005] Low resolution of multilayer films: The capacitance detection method based on single-frequency excitation cannot distinguish the dispersion characteristics of the material's dielectric constant. There is an interlayer coupling error in the thickness calculation of the multilayer film structure. Actual measurements show that the resolution limit of two layers of 5nm thickness is only ±3nm.

[0006] Therefore, the prior art still has the problem of low accuracy when using a capacitive sensor to perform capacitance detection on a film layer on a wafer surface. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an online detection method for the thickness of the wafer surface film layer, aiming to improve the accuracy of the detection of the wafer surface film layer thickness, so as to solve the problem of low accuracy when using capacitive sensors to perform capacitance detection on the wafer surface film layer in the existing technology.

[0008] A first aspect of the present invention is to provide a method for online detection of wafer surface film thickness, the method comprising:

[0009] emitting a grating signal toward the wafer through a preset grating device, receiving a reflection signal output by the grating signal reflected on the wafer surface, and determining whether the wafer is in a horizontal state at a current time node according to the reflection signal;

[0010] If it is determined that the wafer is in a horizontal state at the current time node, when the wafer is driven to rotate for the coating process, an excitation signal is alternately applied to the preset first capacitive sensor and the second capacitive sensor;

[0011] Acquire the differential capacitance value between the first capacitance sensor and the second capacitance sensor in real time, and synchronously acquire the dynamic gap between the wafer and the first capacitance sensor and the second capacitance sensor;

[0012] According to the differential capacitance value, the dynamic gap and the dielectric constant of the film material coated on the wafer surface, the thickness distribution of the film layer on the wafer surface is calculated through impedance spectrum analysis.

[0013] According to one aspect of the above technical solution, the grating device includes a first grating device and a second grating device, wherein the first grating device is arranged on one side of the wafer rotation horizontal plane, and the second grating device is arranged in the peripheral direction of the wafer, and the optical paths of the first grating device and the second grating device are perpendicular;

[0014] The step of transmitting a grating signal toward the wafer through the grating device, receiving a reflection signal output by the grating signal reflected on the wafer surface, and determining whether the wafer is in a horizontal state at a current time node according to the reflection signal includes:

[0015] After the wafer is fixed to the rotating table, the first grating device is controlled to transmit a first grating signal toward the wafer along an axial direction, and receive a first reflection signal output by the first grating signal reflected on the wafer surface;

[0016] controlling the second grating device to transmit a second grating signal radially toward the wafer, and receiving a second reflected signal output by the second grating signal reflected on the wafer surface;

[0017] It is determined whether the wafer is in a horizontal state at a current time node according to the first reflection signal and the second reflection signal.

[0018] According to one aspect of the above technical solution, the step of determining whether the wafer is in a horizontal state at a current time node based on the first reflection signal and the second reflection signal includes:

[0019] Calculating a phase difference between the first reflected signal and the second reflected signal according to the first reflected signal and the second reflected signal;

[0020] The tilt angle of the wafer is calculated according to the phase difference between the first reflection signal and the second reflection signal, so as to determine whether the wafer is in a horizontal state at a current time node according to the tilt angle of the wafer.

[0021] According to one aspect of the above technical solution, when the wafer is driven to rotate for the coating process, the step of alternately applying an excitation signal to the first capacitive sensor and the second capacitive sensor includes:

[0022] Acquiring the type of the film layer coated on the surface of the wafer, and automatically matching the corresponding excitation mode according to the film layer type;

[0023] When the wafer is driven to rotate for the coating process, the first capacitive sensor and the second capacitive sensor are controlled to output corresponding excitation signals toward the wafer according to the pre-matched excitation mode.

[0024] According to one aspect of the above technical solution, the excitation mode includes a sweep mode and a pulse mode.

[0025] According to one aspect of the above technical solution, in the frequency sweep mode, the first capacitive sensor and the second capacitive sensor are controlled to perform linear frequency sweep alternately in the range of 1 MHz to 10 GHz;

[0026] In the pulse mode, the first capacitive sensor and the second capacitive sensor are controlled to alternately output 10ns level pulse excitation.

[0027] According to one aspect of the above technical solution, in the step of calculating the thickness distribution of the wafer surface film layer by impedance spectroscopy analysis based on the differential capacitance value, the dynamic gap and the dielectric constant of the film layer material coated on the wafer surface, the step of calculating the thickness distribution of the wafer surface film layer by impedance spectroscopy analysis includes:

[0028] A capacitance-frequency response model is established, and the real and imaginary spectra of the dielectric constant at different frequencies are used to separate the thickness contributions of the multilayer films in the wafer surface film layer, so as to determine the thickness distribution of the wafer surface film layer based on the thickness contributions of the multilayer films.

[0029] According to one aspect of the above technical solution, the calculation formula for the thickness of a single film is:

[0030]

[0031] Where h is the thickness of the single-layer film, C is the differential capacitance, that is, the capacitance difference between the first capacitance sensor and the second capacitance sensor, d0 is the dynamic gap value, and ε r (f) Obtained by traversing a preset material database, or taking the arithmetic mean of the dielectric constants at multiple frequencies.

[0032] The second aspect of the present invention is to provide an online detection device for the thickness of the film layer on the surface of a wafer. The device is integrated in a wafer coating machine and is used to perform online detection of the film thickness when coating a thin film on the wafer. The device includes a grating device, a first capacitance sensor and a second capacitance sensor. The first capacitance sensor and the second capacitance sensor are symmetrically arranged on both sides of the horizontal plane of wafer rotation, and the grating device emits a grating signal toward the wafer.

[0033] A second aspect of the present invention is to provide an online detection device for wafer surface film thickness, the device further comprising:

[0034] A mounting bracket, the mounting bracket being fixed on a moving arm of a wafer coating machine, the moving arm being movable between a coating station and a developing station in the wafer coating machine;

[0035] The mounting bracket is in a U-shape and includes a first mounting portion, a second mounting portion, and a support portion connected between the first mounting portion and the second mounting portion. The first capacitive sensor is disposed at the bottom of the first mounting portion, and the second capacitive sensor is disposed at the top of the second mounting portion.

[0036] Furthermore, the grating device includes a first grating device and a second grating device, wherein the first grating device is disposed at the bottom of the first mounting portion, and the second grating device is disposed on the inner side wall of the supporting portion.

[0037] Compared with the prior art, the method and device for online detection of wafer surface film thickness shown in the present invention have the following beneficial effects:

[0038] This invention innovatively combines grating positioning and differential capacitance sensing technology to provide a high-precision, high-stability online solution for measuring the thickness of film layers on wafer surfaces. The grating device determines the wafer's horizontal state in real time, and the symmetrically arranged dual capacitance sensors dynamically compensate for mechanical vibration and tilt errors, significantly improving the stability of the detection benchmark. The differential capacitance design effectively suppresses environmental electromagnetic interference and temperature drift, stimulates the dispersion response of the film material through multi-frequency excitation signals, and accurately calculates the thickness of single or multi-layer films through impedance spectrum analysis, breaking through the accuracy bottleneck of traditional single-frequency detection. It is particularly suitable for non-contact measurement of nano-scale ultra-thin films in advanced processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0040] Figure 1 Schematic diagram of the process of an online detection method for wafer surface film thickness according to one embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the structure of an online detection device for wafer surface film thickness according to one embodiment of the present invention;

[0042] Figure 3 This is a structural diagram of an online detection device for wafer surface film thickness integrated into a wafer coating machine in one embodiment of the present invention. DETAILED DESCRIPTION

[0043] To make the objectives, features, and advantages of the present invention more readily apparent, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] Example 1

[0046] See also Figure 1 The first embodiment of the present invention provides a method for online detection of wafer surface film thickness, the method comprising steps S10 to S40:

[0047] Step S10: emitting a grating signal toward the wafer through a preset grating device, receiving a reflection signal outputted by the grating signal reflected on the wafer surface, and determining whether the wafer is in a horizontal state at a current time node according to the reflection signal.

[0048] First of all, it should be explained that the online detection method for the wafer surface film thickness shown in this embodiment is applied to an online detection device for the wafer surface film thickness, which is integrated in a wafer coating machine and is used to detect the thickness of the film layer coated on the wafer surface, thereby determining the film layer distribution on the wafer surface.

[0049] Among them, the device includes a grating device, which is used to emit a grating signal toward the wafer and receive a reflected signal output by the grating signal reflected on the wafer surface, so that it can determine whether the wafer is currently in a tilted state based on the comparison value between the grating signal and the reflected signal. If it is in a tilted state, the wafer position needs to be readjusted so that the wafer is in a horizontal state before online detection of the film thickness on the wafer surface can be performed.

[0050] Specifically, the grating device is used to emit multiple infrared rays and output grating signals. The multiple infrared rays are parallel to each other. When the multiple infrared rays are irradiated on the wafer surface, reflection will be generated. The grating device then receives the reflected signal of the infrared light and compares the grating signal with the reflected signal to determine whether the wafer is fixed in a horizontal state at the current time node. If so, the next step is to perform online detection of the thickness of the film layer on the wafer surface. Otherwise, the wafer position needs to be readjusted to make it horizontal.

[0051] In this embodiment, the steps of transmitting a grating signal toward the wafer through the grating device, receiving a reflection signal output by the grating signal reflected on the wafer surface, and determining whether the wafer is in a horizontal state at a current time point according to the reflection signal include:

[0052] After the wafer is fixed to the rotating table, the first grating device is controlled to transmit a first grating signal toward the wafer along an axial direction, and receive a first reflection signal output by the first grating signal reflected on the wafer surface;

[0053] controlling the second grating device to transmit a second grating signal radially toward the wafer, and receiving a second reflected signal output by the second grating signal reflected on the wafer surface;

[0054] It is determined whether the wafer is in a horizontal state at a current time node according to the first reflection signal and the second reflection signal.

[0055] The step of determining whether the wafer is in a horizontal state at a current time node according to the first reflection signal and the second reflection signal includes:

[0056] Calculating a phase difference between the first reflected signal and the second reflected signal according to the first reflected signal and the second reflected signal;

[0057] The tilt angle of the wafer is calculated according to the phase difference between the first reflection signal and the second reflection signal, so as to determine whether the wafer is in a horizontal state at a current time node according to the tilt angle of the wafer.

[0058] Specifically, the grating device includes a first grating device and a second grating device. The first grating device is configured on the axial side of the irradiated wafer, and the second grating device is configured on the radial side of the irradiated wafer, that is, the first grating device and the second grating device maintain a vertical state, at least keeping the optical paths of the first grating device and the second grating device perpendicular to each other. When the wafer is fixed, the first grating device and the second grating device simultaneously output grating signals to the wafer, including outputting the first grating signal to the axial side of the wafer and the second grating signal to the radial side of the wafer. Then, the first grating device and the second grating device respectively receive the first reflection signal and the second reflection signal reflected by the wafer, and the first reflection signal and the second reflection signal are jointly used to determine whether the wafer is currently fixed and whether it is tilted or in a horizontal state.

[0059] More specifically, by setting a first grating device and a second grating device perpendicular to the first grating device, the phase difference of the dual grating reflection signal is calculated, and then the tilt angle of the wafer is calculated based on the phase difference of the dual grating reflection signal, so as to judge whether the wafer is tilted or in a horizontal state based on the tilt angle of the wafer.

[0060] Moreover, when the wafer is driven to rotate, the first grating device and the second grating device can still be used to dynamically determine whether the wafer is in a horizontal state. Specifically, during the rotation of the wafer, the first grating device and the second grating device continuously output the first grating signal and the second grating signal, and then continuously receive the first reflection signal and the second reflection signal, thereby outputting the real-time tilt angle θ of the wafer to eliminate the mechanical error of wafer placement.

[0061] In this embodiment, if it is determined by the dual grating reflection signal that the wafer is in a horizontal state, this embodiment will enter the online detection of the thickness of the film layer on the wafer surface.

[0062] Step S20 : If it is determined that the wafer is in a horizontal state at the current time node, when the wafer is driven to rotate for the coating process, an excitation signal is alternately applied to a preset first capacitance sensor and a second capacitance sensor.

[0063] In this embodiment, when the wafer is driven to rotate for the coating process, the step of alternately applying an excitation signal to the first capacitive sensor and the second capacitive sensor includes:

[0064] Acquiring the type of the film layer coated on the surface of the wafer, and automatically matching the corresponding excitation mode according to the film layer type;

[0065] When the wafer is driven to rotate for the coating process, the first capacitive sensor and the second capacitive sensor are controlled to output corresponding excitation signals toward the wafer according to the pre-matched excitation mode.

[0066] Among them, a mixed excitation mode is adopted by alternately applying excitation signals to the first capacitive sensor and the second capacitive sensor, including a sweep mode and a pulse mode. In the sweep mode, the first capacitive sensor and the second capacitive sensor are controlled to perform linear sweep frequency alternately according to 1MHz-10GHz; and in the pulse mode, the first capacitive sensor and the second capacitive sensor are controlled to alternately output 10ns-level pulse excitation.

[0067] Specifically, in this embodiment, before driving the wafer to rotate and coat, the first grating device will first output the first grating signal and the received first reflection signal to determine the type of the required coating film layer, such as dielectric film SiO2, metal film Cu, compound film SiN, etc. The detection range is from 1nm to 10μm. According to the film type of the coating film, the excitation mode is automatically switched. Specifically, in the sweep mode, the first capacitance sensor and the second capacitance sensor are controlled to perform linear sweep according to the alternating frequency of 1MHz-10GHz for multi-layer film separation of the wafer surface film layer. In the pulse mode, the first capacitance sensor and the second capacitance sensor are controlled to alternately output 10ns pulse excitation to suppress the skin effect, which is particularly suitable for the excitation of metal films.

[0068] Step S30 , collecting the differential capacitance value between the first capacitance sensor and the second capacitance sensor in real time, and synchronously acquiring the dynamic gaps between the wafer and the first capacitance sensor and the second capacitance sensor.

[0069] In this embodiment, after determining the film type of the required coating film layer and automatically switching the excitation mode according to the film type, and controlling the first capacitive sensor and the second capacitive sensor to output excitation signals according to the preset excitation mode, the first capacitance value and the second capacitance value output by the first capacitive sensor and the second capacitive sensor are respectively obtained, and then the differential capacitance value of the first capacitive sensor and the second capacitive sensor is calculated based on the first capacitance value and the second capacitance value.

[0070] In the process of real-time acquisition and calculation of differential capacitance values, the dynamic gaps between the wafer and the first capacitance sensor and the second capacitance sensor will also be obtained synchronously. Real-time measurement can be performed using a laser rangefinder or a fiber optic interferometer.

[0071] Specifically, in this embodiment, the first capacitance sensor is integrated with the first fiber optic interferometer to design a common optical path, and the second capacitance sensor is integrated with the second fiber optic interferometer to design a common optical path. The dynamic gap value d0 between the first capacitance sensor, the second capacitance sensor and the wafer is directly calculated using the interference signal received by the fiber optic interferometer, and a joint correction is performed to eliminate the influence of mechanical vibration.

[0072] In step S40 , the thickness distribution of the film layer on the wafer surface is calculated by impedance spectrum analysis according to the differential capacitance value, the dynamic gap, and the dielectric constant of the film layer material coated on the wafer surface.

[0073] In this embodiment, the step of calculating the thickness distribution of the film layer on the wafer surface by impedance spectroscopy analysis based on the differential capacitance value, the dynamic gap and the dielectric constant of the film layer material coated on the wafer surface includes:

[0074] A capacitance-frequency response model is established, and the real and imaginary spectra of the dielectric constant at different frequencies are used to separate the thickness contributions of the multilayer films in the wafer surface film layer, so as to determine the thickness distribution of the wafer surface film layer based on the thickness contributions of the multilayer films.

[0075] Among them, the calculation formula for the thickness of a single film is:

[0076]

[0077] Where h is the thickness of the single-layer film, C is the differential capacitance, that is, the capacitance difference between the first capacitance sensor and the second capacitance sensor, d0 is the dynamic gap value, and ε r (f) Obtained by traversing a preset material database, or taking the arithmetic mean of the dielectric constants at multiple frequencies.

[0078] Furthermore, in this embodiment, the dynamic gap value d0 is corrected by the following formula:

[0079] d0=d measured -Δd vibration ;

[0080] Where Δd vibration It is calculated by real-time measurement of wafer vibration amplitude using a fiber optic interferometer.

[0081] As an example, when the film layer coated on the wafer surface is a SiO2 thin film, by determining the excitation mode, 1 MHz and 10 GHz excitations are applied to the first and second capacitive sensors respectively, and the measured capacitances are C1 and C2. The corresponding dielectric constant is calculated using the following formula:

[0082]

[0083] Then substitute it into the above calculation formula for the thickness of a single film to calculate h, thereby calculating the film thickness of the film layer on the surface of the wafer.

[0084] In summary, this embodiment innovatively integrates grating positioning and differential capacitance sensing technology to provide a high-precision, high-stability online solution for wafer surface film thickness detection. The horizontal state of the wafer is determined in real time by the grating device, and the mechanical vibration and tilt error are dynamically compensated by the symmetrically arranged dual capacitance sensors, which significantly improves the stability of the detection benchmark. The differential capacitance design effectively suppresses environmental electromagnetic interference and temperature drift, stimulates the dispersion response of the film material through multi-frequency excitation signals, and accurately calculates the thickness of single or multi-layer films in combination with impedance spectrum analysis, breaking through the accuracy bottleneck of traditional single-frequency detection. It is particularly suitable for non-contact measurement of nano-scale ultra-thin films in advanced processes.

[0085] Furthermore, the system enables real-time monitoring of the entire wafer surface while it is rotating. The synergistic effect of the grating's rapid response and high-frequency capacitor sampling dynamically generates thermal maps of film thickness distribution, providing data support for closed-loop control of key processes such as deposition and polishing. By providing real-time feedback on film thickness distribution, the system optimizes process parameter adjustment efficiency and reduces wafer rejection due to uneven film thickness. Furthermore, the system is compatible with complex industrial environments and meets the demands of demanding scenarios such as vacuum and high-temperature environments.

[0086] It also boasts strong scalability and adaptability to various scenarios. Through dynamic dielectric constant matching, it supports the detection of multiple materials, including metals, dielectrics, and compounds. Combined with a cross-validation mechanism that combines grating reflection signals with capacitance fluctuations, it can identify surface contamination or abnormal areas, reducing the risk of false detection. Non-contact measurement avoids damage to the wafer surface and is particularly suitable for the detection of flexible materials and three-dimensional stacked structures, providing reliable technical support for intelligent and high-yield management of semiconductor manufacturing processes.

[0087] Example 2

[0088] See also Figure 2 and Figure 3 The second embodiment of the present invention provides an online detection device for the thickness of a film layer on the surface of a wafer. The device 100 is integrated in a wafer coating machine and is used to perform online detection of the thickness of a film layer when coating a thin film on a wafer. The device 100 includes a grating device, a first capacitance sensor 101 and a second capacitance sensor 102. The first capacitance sensor 101 and the second capacitance sensor 102 are symmetrically arranged on both sides of the horizontal rotation plane of the wafer 300. The grating device irradiates and emits a grating signal toward the wafer 300.

[0089] In this embodiment, the device further includes:

[0090] The mounting bracket 200 is fixed on a movable arm 400 of the wafer coating machine, and the movable arm 400 is movable between the coating station and the developing station in the wafer coating machine;

[0091] Among them, the mounting bracket 200 is in a U shape, including a first mounting portion 201, a second mounting portion 202, and a support portion 203 connecting the first mounting portion 201 and the second mounting portion 202. The first capacitance sensor 101 is disposed at the bottom of the first mounting portion 201, and the second capacitance sensor 102 is disposed at the top of the second mounting portion 202;

[0092] In addition, the grating device includes a first grating device 103 and a second grating device 104. The first grating device 103 is disposed at the bottom of the first mounting portion 201, and the second grating device 104 is disposed on the inner sidewall of the support portion 203.

[0093] Specifically, in this embodiment, a mounting bracket 200 made of a metal material is provided and fixed on a moving arm 400 in a wafer coating and developing machine. The first capacitance sensor 101 is disposed at the bottom of the first mounting portion 201 of the mounting bracket 200, such that the signal emitting end of the first capacitance sensor 101 faces the axial top surface of the wafer 300. The second capacitance sensor 102 is disposed at the top of the second mounting portion 202 of the mounting bracket 200, such that the signal emitting end of the second capacitance sensor 102 faces the axial bottom surface of the wafer 300. The differential capacitance value is determined by the first capacitance sensor 101 and the second capacitance sensor 102, so as to determine the thickness of the film layer 301 on the surface of the wafer 300. In addition, the first grating device 103 of the grating device is disposed at the bottom of the first mounting portion 201, such that the first grating device 103 faces the axial top surface of the wafer 300, and the second grating device 104 of the grating device is disposed on the inner sidewall of the support portion 203, such that the second grating device 104 faces the radial side surface of the wafer 300. Through grating positioning, mechanical vibration and tilt errors can be dynamically compensated, improving the stability of the detection basis.

[0094] In summary, this embodiment innovatively integrates grating positioning and differential capacitance sensing technologies, providing a high-precision and high-stability online solution for detecting the thickness of the film layer on the wafer surface. The horizontal state of the wafer is determined in real time by the grating device. Combining the symmetrically arranged dual capacitance sensors to dynamically compensate mechanical vibration and tilt errors significantly improves the stability of the detection reference. The differential capacitance design effectively suppresses environmental electromagnetic interference and temperature drift. By exciting the dispersion response of the film layer material with multi-frequency excitation signals and combining impedance spectrum analysis to accurately calculate the thickness of single-layer or multi-layer thin films, the accuracy bottleneck of traditional single-frequency detection is broken through, especially suitable for non-contact measurement of nano-scale ultra-thin film layers in advanced processes.

[0095] Throughout this specification, references to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. Throughout this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0096] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for online detection of wafer surface film thickness, characterized in that: The method comprises: emitting a grating signal toward the wafer through a preset grating device, receiving a reflection signal output by the grating signal reflected on the wafer surface, and determining whether the wafer is in a horizontal state at a current time node according to the reflection signal; If it is determined that the wafer is in a horizontal state at the current time node, when the wafer is driven to rotate for the coating process, an excitation signal is alternately applied to the preset first capacitive sensor and the second capacitive sensor; Acquire the differential capacitance value between the first capacitance sensor and the second capacitance sensor in real time, and synchronously acquire the dynamic gap between the wafer and the first capacitance sensor and the second capacitance sensor; According to the differential capacitance value, the dynamic gap and the dielectric constant of the film material coated on the wafer surface, the thickness distribution of the film layer on the wafer surface is calculated through impedance spectrum analysis.

2. The online detection method for wafer surface film thickness according to claim 1, characterized in that: The grating device includes a first grating device and a second grating device, wherein the first grating device is arranged on one side of the wafer rotation horizontal plane, and the second grating device is arranged in the peripheral direction of the wafer, and the optical paths of the first grating device and the second grating device are perpendicular; The step of transmitting a grating signal toward the wafer through the grating device, receiving a reflection signal output by the grating signal reflected on the wafer surface, and determining whether the wafer is in a horizontal state at a current time node according to the reflection signal includes: After the wafer is fixed to the rotating table, the first grating device is controlled to transmit a first grating signal toward the wafer along an axial direction, and receive a first reflection signal output by the first grating signal reflected on the wafer surface; controlling the second grating device to transmit a second grating signal radially toward the wafer, and receiving a second reflected signal output by the second grating signal reflected on the wafer surface; It is determined whether the wafer is in a horizontal state at a current time node according to the first reflection signal and the second reflection signal.

3. The online detection method for wafer surface film thickness according to claim 2, characterized in that: The step of determining whether the wafer is in a horizontal state at a current time node according to the first reflection signal and the second reflection signal includes: Calculating a phase difference between the first reflected signal and the second reflected signal according to the first reflected signal and the second reflected signal; The tilt angle of the wafer is calculated according to the phase difference between the first reflection signal and the second reflection signal, so as to determine whether the wafer is in a horizontal state at a current time node according to the tilt angle of the wafer.

4. The online detection method for wafer surface film thickness according to claim 1, characterized in that: When the wafer is driven to rotate for the coating process, the step of alternately applying an excitation signal to the first capacitive sensor and the second capacitive sensor comprises: Acquiring the type of the film layer coated on the surface of the wafer, and automatically matching the corresponding excitation mode according to the film layer type; When the wafer is driven to rotate for the coating process, the first capacitive sensor and the second capacitive sensor are controlled to output corresponding excitation signals toward the wafer according to the pre-matched excitation mode.

5. The online detection method for wafer surface film thickness according to claim 4, characterized in that: The excitation mode includes a sweep mode and a pulse mode.

6. The online detection method for wafer surface film thickness according to claim 5, characterized in that: In the frequency sweep mode, controlling the first capacitive sensor and the second capacitive sensor to perform linear frequency sweep alternately in the range of 1 MHz to 10 GHz; In the pulse mode, the first capacitive sensor and the second capacitive sensor are controlled to alternately output 10ns level pulse excitation.

7. The online detection method for wafer surface film thickness according to any one of claims 1 to 6, characterized in that: The step of calculating the thickness distribution of the film layer on the wafer surface by impedance spectrum analysis according to the differential capacitance value, the dynamic gap and the dielectric constant of the film layer material coated on the wafer surface comprises: A capacitance-frequency response model is established, and the real and imaginary spectra of the dielectric constant at different frequencies are used to separate the thickness contributions of the multilayer films in the wafer surface film layer, so as to determine the thickness distribution of the wafer surface film layer based on the thickness contributions of the multilayer films.

8. The online detection method for wafer surface film thickness according to claim 7, characterized in that: The calculation formula for the thickness of a single film is: Where h is the thickness of the single-layer film, C is the differential capacitance, that is, the capacitance difference between the first capacitance sensor and the second capacitance sensor, d0 is the dynamic gap value, and ε r (f) Obtained by traversing a preset material database, or taking the arithmetic mean of the dielectric constants at multiple frequencies.

9. An online detection device for wafer surface film thickness, characterized in that: The device is integrated into a wafer coating machine and is used to perform online detection of film thickness when coating a thin film on a wafer. The device includes a grating device, a first capacitance sensor, and a second capacitance sensor. The first capacitance sensor and the second capacitance sensor are symmetrically arranged on both sides of the horizontal plane of wafer rotation. The grating device emits a grating signal toward the wafer.

10. The on-line detection device for wafer surface film thickness according to claim 9, characterized in that: The device further comprises: A mounting bracket, wherein the mounting bracket is fixedly connected to a movable arm in a wafer coating machine, and the movable arm moves between a coating station and a developing station in the wafer coating machine; The mounting bracket is in a U-shape and includes a first mounting portion, a second mounting portion, and a support portion connected between the first mounting portion and the second mounting portion. The first capacitive sensor is disposed at the bottom of the first mounting portion, and the second capacitive sensor is disposed at the top of the second mounting portion. Furthermore, the grating device includes a first grating device and a second grating device, wherein the first grating device is disposed at the bottom of the first mounting portion, and the second grating device is disposed on the inner side wall of the supporting portion.

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