CN116852252A - Wafer film thickness measuring method and chemical mechanical polishing equipment - Google Patents

Abstract

The invention discloses a wafer film thickness measurement method and chemical mechanical polishing equipment. The wafer film thickness measurement method includes: collecting a reflection spectrum in the initial stage of polishing, and obtaining the number of spectral peaks or troughs of the reflection spectrum; based on For the number of spectral peaks or troughs, the FFT algorithm or spectral fitting algorithm can be used to calculate the wafer film thickness.

Description

A wafer film thickness measurement method and chemical mechanical polishing equipment

Technical field

The invention relates to the technical field of chemical mechanical polishing, and in particular to a wafer film thickness measurement method and chemical mechanical polishing equipment.

Background technique

Wafer manufacturing is a key link restricting the development of ultra/extremely large-scale integrated circuit (i.e., chip, IC, Integrated Circuit) industry. As Moore's Law continues, the feature sizes of integrated circuits continue to shrink and approach theoretical limits, and wafer surface quality requirements become increasingly stringent. Therefore, the control of defect size and quantity in the wafer manufacturing process becomes increasingly stringent. Chemical Mechanical Planarization (CMP) is a global surface planarization technology used to reduce the impact of wafer thickness changes and surface topography during the semiconductor manufacturing process. Because CMP can accurately and uniformly planarize wafers to the required thickness and flatness, it has become the most widely used surface planarization technology in the semiconductor manufacturing process.

The chemical mechanical polishing process uses a carrier head to press the wafer onto the surface of the polishing pad, relying on the relative movement between the wafer and the polishing pad and the abrasive particles in the polishing fluid to achieve polishing of the wafer surface. Some polishing processes require the removal of non-metallic layers. For the control of non-metallic polishing processes, offline measurement equipment is generally used to measure the film thickness of the non-metallic layer. Parameters such as changes in film thickness before and after wafer polishing are obtained to establish a model, and then measurements are made. The previous value of wafer film thickness is used for feedback control of polishing pressure, polishing time, etc.

It is very important to control the polishing end point during the chemical mechanical polishing process, that is, to determine whether the film layer has been flattened to the desired flatness or thickness, or to determine when the required amount of material has been removed. In the existing technology, due to the different reliability of different solution algorithms in different optical ranges, there will be deviations in the real-time measurement accuracy of the system.

Contents of the invention

Embodiments of the present invention provide a wafer film thickness measurement method and chemical mechanical polishing equipment, aiming to solve at least one of the technical problems existing in the prior art.

A first aspect of the embodiment of the present invention provides a wafer film thickness measurement method, which includes:

Collect the reflection spectrum in the initial stage of polishing, and obtain the number of spectral peaks or troughs of the reflection spectrum;

Based on the number of spectral peaks or troughs, the FFT algorithm or the spectral fitting algorithm is selected to calculate the wafer film thickness.

In some embodiments, if the number of spectral peaks or troughs is greater than a preset threshold, the FFT algorithm is selected to solve the reflection spectrum;

If the number of spectral peaks or troughs is not greater than the preset threshold, a spectrum fitting algorithm is used to solve the reflection spectrum.

In some embodiments, the spectrum fitting algorithm includes:

During the polishing process, a measurement spectrum is generated based on the collected reflection spectrum;

Select the spectral group of the reference spectrum that is closest to the measured spectrum;

The film thickness corresponding to the spectrum group of the closest reference spectrum is estimated as the film thickness of the wafer.

In some embodiments, the reference spectrum is:

Among them, n is the refractive index; λ is the wavelength; a, b, and c are constants, which are related to the material and thickness of the measurement sample.

In some embodiments, the following formula is used to select the maximum value among them, thereby selecting the spectrum group of the reference spectrum that is closest to the measured spectrum:

Among them, x _i is the abscissa value of the fitted theoretical spectrum, generally the wavelength, i = 1, 2,..., n; y _i is the relative reflectance value of the measured spectrum at wavelength x _i , y (x _i ) is The relative reflectance value of the fitted theoretical spectrum at wavelength _xi .

In some embodiments, the FFT algorithm includes:

Perform fast Fourier transform on the reflection spectrum, perform time domain-frequency domain transformation, and extract the relationship between its frequency components and spectrum intensity;

The thickness function is used to convert the relationship between frequency components and spectrum intensity to generate the relationship between thickness and spectrum intensity.

A second aspect of the embodiment of the present invention provides a chemical mechanical polishing equipment, which includes:

A polishing disc, used to be provided with a polishing pad for polishing the wafer;

A carrying head, used to hold the wafer and press the wafer on the polishing pad, and the carrying head is provided with a temperature detection unit;

an optical measurement device for detecting the reflectance spectrum obtained from the wafer during polishing;

A control device used to implement the wafer film thickness measurement method as described above.

In some embodiments, the obtained reflection spectrum information includes the number of spectral peaks or troughs of the reflection spectrum.

A third aspect of the embodiment of the present invention provides a control device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the computer program When implementing the steps of the wafer film thickness measurement method as described above.

A third aspect of the embodiment of the present invention provides a computer-readable storage medium that stores a computer program. When the computer program is executed by a processor, the wafer film thickness measurement as described above is implemented. Method steps.

The beneficial effects of embodiments of the present invention include:

a. By collecting reflection spectrum information at the beginning of polishing, judging the specific algorithm model to be used based on the characteristics of the reflection spectrum, and using a priori algorithm switching method to avoid measurement errors caused by mismatch between the actual measured film thickness and the algorithm. , effectively ensuring the accuracy of measurement;

b. Perform fast Fourier transform on the reflection spectrum, perform time domain-frequency domain transformation, and extract the relationship between its frequency component and spectrum intensity; use the thickness function to convert the relationship between the frequency component and spectrum intensity to generate the relationship between thickness and spectrum intensity. relationship to accurately obtain the film thickness of the wafer;

c. By integrating the light intensity calibration unit, the reference light intensity signal can be obtained at any time. On the one hand, it is convenient to monitor the status of the white light measurement module integrated inside the polishing unit. On the other hand, the PM cycle is reduced, which has a certain effect on productivity improvement. .

Description of the drawings

The advantages of the present invention will become clearer and easier to understand through the detailed description combined with the following drawings, but these drawings are only schematic and do not limit the scope of the present invention, wherein:

Figure 1 shows a chemical mechanical polishing equipment provided by an embodiment of the present invention;

Figure 2 shows a chemical mechanical polishing equipment provided by an embodiment of the present invention;

Figure 3 shows a main control module provided by an embodiment of the present invention;

Figure 4 shows the relationship between reflection spectrum and film thickness;

Figure 5 shows the process steps of a wafer film thickness measurement method provided by an embodiment of the present invention.

Detailed ways

The technical solution of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described here are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are illustrative and exemplary and should not be understood as limiting the implementation of the present invention and the scope of protection of the present invention. . It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of this application can be combined with each other. In addition to the embodiments recorded here, those skilled in the art can also adopt other obvious technical solutions based on the disclosure of the claims and the specification of this application. These technical solutions include the use of any modifications to the embodiments recorded here. Obvious technical solutions for substitutions and modifications. It should be understood that, unless otherwise specified, in order to facilitate understanding, the following description of specific embodiments of the present invention is based on the natural state in which the relevant equipment, devices, components, etc. are in an original static state without external control signals and driving forces. describe.

In addition, it should be noted that terms used in this application such as front, back, up, down, left, right, top, bottom, front, back, horizontal, vertical, etc. to express orientation are only for convenience of explanation and are used for convenience. To aid in understanding of relative position or orientation and are not intended to limit the orientation of any device or structure.

In order to illustrate the technical solution of the present invention, the following description will be made with reference to the accompanying drawings and in combination with the embodiments.

In this application, chemical mechanical polishing (Chemical Mechanical Polishing) is also called chemical mechanical planarization (Chemical Mechanical Planarization), and wafer (wafer) is also called wafer, silicon wafer, substrate or substrate, etc., and its meaning is It is equivalent to the actual effect.

As shown in Figure 1, the chemical mechanical polishing equipment includes a carrying head 10 for holding the wafer w and driving the wafer w to rotate, a polishing disc 20 covered with a polishing pad 21, a dresser 30 for dressing the polishing pad 21, and Liquid supply part 40 for supplying polishing liquid.

During the chemical mechanical polishing process, the carrier head 10 presses the wafer w onto the polishing pad 21 covered by the polishing disk 20 , and the carrier head 10 rotates and reciprocates along the radial direction of the polishing disk 20 to make contact with the polishing pad 21 The surface of the wafer w is gradually thrown away, and at the same time, the polishing disk 20 rotates, and the liquid supply part 40 sprays polishing liquid on the surface of the polishing pad 21 . Under the chemical action of the polishing liquid, the wafer w is rubbed against the polishing pad 21 through the relative movement of the carrying head 10 and the polishing disk 20 to perform polishing. During polishing, the dresser 30 is used to dress and activate the surface topography of the polishing pad 21 . The dresser 30 can be used to remove impurity particles remaining on the surface of the polishing pad 21 , such as abrasive particles in the polishing liquid and waste material falling off the surface of the wafer w, etc., and can also smoothen the surface deformation of the polishing pad 21 caused by grinding. .

As shown in FIG. 2 , the chemical mechanical polishing equipment also includes an optical measurement device 50 . The optical measurement device 50 is disposed under the surface of the polishing disk 20 and rotates with the polishing disk 20 to achieve online measurement while polishing. The polishing pad 21 is provided with a light-transmissive opening, and the opening penetrates the polishing pad 21 , thereby providing an optical path that can pass through the polishing pad 21 . The light emitted by the optical measurement device 50 irradiates the surface of the wafer w on the polishing pad 21 through the opening and receives the reflected light of the wafer w through the window to determine the non-metallic film thickness of the wafer w according to the spectrum of the reflected light.

During polishing of wafer w, the carrier head 10 presses the wafer w on the polishing pad 21 and the carrier head 10 reciprocates along the radial direction of the polishing disc 20 , and the optical measurement device 50 follows the rotation of the polishing disc 20 , so the optical measurement device 50 The position of the sampling point measured on the wafer w is constantly changing, so that optical measurement signals at different radial positions of the wafer w can be obtained.

In one embodiment of the present invention, the optical measurement device 50 is used to measure the non-metallic film thickness of the wafer during the CMP process. It includes: an online optical measurement component and a reference optical measurement component. The online optical measurement component includes: The first optical sensor 51 and the first window 52 for measuring the non-metallic film thickness of the wafer. The reference optical measurement component includes a second optical sensor 53 for obtaining calibration light intensity, a second window 54, a calibration piece 55 and a shield. components.

The online optical measurement component follows the rotation of the polishing disc 20 to achieve online non-metallic film thickness measurement while polishing. The first optical sensor 51 is arranged inside the polishing disc 20 , and the first window 52 is embedded above the first optical sensor 51 accordingly. Inside the polishing pad 21 , the light path of the first optical sensor 51 illuminates the wafer through the first window 52 .

In one embodiment, the first optical sensor 51 is disposed inside the polishing disc 20, and a receiving groove is provided on the surface of the polishing disc 20. The first optical sensor 51 is placed in the receiving groove, and the first optical sensor 51 passes through the first optical fiber. Connect the main control module 60. The first window 52 is embedded in the surface of the polishing pad, and the first window 52 is disposed directly above the first optical sensor 51 . Specifically, the polishing pad 21 is provided with a through opening at a corresponding position directly above the first optical sensor 51 , and the first window 52 is inserted into this opening.

The light emitted by the first optical sensor 51 irradiates the surface of the wafer w on the polishing pad 21 through the first window 52 and receives the reflected light of the wafer w via the first window 52 to determine the intensity of the surface of the wafer w according to the spectrum of the reflected light. Non-metallic film thickness.

Reference optical measurement components are used to calibrate the light intensity. As shown in FIG. 2 , the reference optical measurement component is installed inside the polishing disc 20 . The reference optical measurement component includes a second optical sensor 53 , a second window 54 , a calibration piece 55 and a shielding component. The second optical sensor 53 , the second window 54 , the calibration piece 55 and the shielding assembly are all located inside the polishing disc 20 . The second optical sensor 53 is used to obtain calibrated light intensity. Specifically, the calibration chip 55 is a standard silicon chip and is used to calibrate the light intensity.

The second optical sensor 53 and the second window 54 are placed oppositely, and the calibration sheet 55 is in contact with the side of the second window 54 away from the second optical sensor 53 . In other words, the calibration sheet 55 is in close contact with the second window 54 and located at The second window 54 is on a side away from the second optical sensor 53 .

Specifically, as shown in FIG. 2 , as a specific example, the detection end of the second optical sensor 53 faces downward, the second window 54 is located below the second optical sensor 53 , and the upper surface of the second window 54 is in contact with the second optical sensor. The detection end of 53 is opposite, the lower surface of the second window 54 is close to the calibration piece 55, there is no gap between the calibration piece 55 and the lower surface of the second window 54, the light path of the second optical sensor 53 is emitted downward through the second window 54 It reaches the calibration sheet 55 and is reflected by the calibration sheet 55 to obtain the calibrated light intensity.

Of course, as another implementation, the detection end of the second optical sensor 53 can also be directed upward, and the second window 54 is located above the second optical sensor 53 , so that the lower surface of the second window 54 is in contact with the second optical sensor 53 The detection end is opposite, the upper surface of the second window 54 is close to the calibration piece 55, and there is no gap between the calibration piece 55 and the upper surface of the second window 54. In this case, the light path of the second optical sensor 53 is emitted upward. The second window 54 reaches the calibration sheet 55 and is reflected by the calibration sheet 55 . Alternatively, the detection end of the second optical sensor 53 can also face the front, back, left, rear or even in an oblique direction, as long as one side of the second window 54 faces the detection end of the second optical sensor 53 and the other side of the second window 54 It suffices to be close to the calibration piece 55. As long as the optical path to obtain the calibrated light intensity can be achieved, it is within the protection scope of the present application. The relative positions between the second optical sensor 53, the second window 54 and the calibration piece 55 are not limited to the above. listed.

In addition, the first window 52 and the second window 54 are exactly the same, that is, the size, thickness, material, shape, etc. of the first window 52 and the second window 54 are exactly the same. Furthermore, the linear distance between the first optical sensor 51 and the first window 52 is consistent with the linear distance between the second optical sensor 53 and the second window 54 .

During chemical mechanical polishing, the wafer w is pressed on the polishing pad 21 by the carrying head 10 . When the wafer passes through the first window 52 , it is in close contact with the upper surface of the first window 52 . Therefore, when the first optical sensor 51 measures the wafer, the optical path of the emitted light passing through the first window 52 to the wafer surface is the same as the optical path of the second optical sensor 53 emitting light passing through the second window 54 to the surface of the calibration sheet 55 when measuring the calibration sheet 55 . , the optical paths of the two optical paths are the same, only the measurement objects are different, and other interference is eliminated, so that the measurement of the calibration piece 55 can be used as a reference, and the signal measured by the second optical sensor 53 can be used to obtain the calibration light intensity.

As shown in FIG. 2 , the blocking component is used to achieve blocking between the second optical sensor 53 and the second window 54 . In one embodiment, the shielding assembly includes a light blocking member 56 and a driving module 57 . The driving module 57 is connected to the light blocking member 56 and can drive the light blocking member 56 to move between the second optical sensor 53 and the second window 54 . The light blocking member 56 can be moved between the second optical sensor 53 and the second window 54 to block the light path between the second optical sensor 53 and the second window 54; the light blocking member 56 can also be moved out of the second optical sensor 53 and the second window 54. between the second windows 54 to make the light path between the second optical sensor 53 and the second window 54 unobstructed. The light-blocking member 56 can be made of light-absorbing material, and its surface does not reflect light. The driving module 57 is connected to the main control module 60 so that the movement of the light blocking member 56 can be controlled under program control. Specifically, the driving module 57 can control the light blocking member 56 to swing and move in and out between the second optical sensor 53 and the second window 54 .

As shown in Figure 2, in one embodiment of the present invention, the first optical sensor 51 and the second optical sensor 53 are respectively connected to the main control module 60 through optical fibers. The main control module 60 is located inside the polishing disc 20 and rotates with the polishing disc 20 . The main control module 60 is connected to other devices located outside the polishing disc 20 through rotary joints. The connecting wires of the main control module 60 lead out the electrical signals through the rotary joint, thereby avoiding damage caused by twisting of the wires.

As shown in FIG. 3 , the main control module 60 includes a light source 61 , a detection unit 62 , a data collection and communication unit 63 , a central processing unit 64 and an external interface 65 .

In one embodiment, the first optical sensor 51 and the second optical sensor 53 are respectively connected to the same light source 61 and the same detection unit 62 through optical paths with equal optical lengths to avoid introducing other interference factors and ensure that the second optical sensor 53 obtains The light intensity can be used as a calibration light intensity.

Specifically, as shown in FIG. 3 , the first optical sensor 51 and the second optical sensor 53 are respectively connected to the light source 61 and the detection unit 62 through an X-shaped optical fiber. Among them, the input end of one side of the X-type optical fiber is connected to the light source 61, the output end of one side of the X-type optical fiber is connected to the detection unit 62, one of the input and output ends of the other side of the The other input and output terminal on one side is connected to the second optical sensor 53 . Thus, the light source 61 signal provided by the light source 61 is divided into two identical optical input signals through two completely symmetrical optical paths with equal optical paths and reaches the first optical sensor 51 and the second optical sensor 53 .

Specifically, the light source 61 signal output by the light source 61 is divided into two identical signals through a symmetrical optical path, namely the first optical input signal and the second optical input signal; the first optical sensor 51 receives the first optical input signal, and the second optical input signal. The optical sensor 53 receives a second optical input signal, and the first optical input signal received by the first optical sensor 51 is exactly the same as the second optical input signal received by the second optical sensor 53 .

Further, the first optical sensor 51 outputs a first optical output signal and sends it to the detection unit 62, the second optical sensor 53 outputs a second optical output signal and sends it to the detection unit 62, and the transmission route of the first optical output signal and the second optical output signal is Symmetry and equal optical path avoid other interference.

As shown in Figure 3, the light source 61 and the detection unit 62 are respectively connected to the data collection and communication unit 63. The data collection and communication unit 63 is respectively connected to the central processing unit 64 and the external interface 65. The central processing unit 64 is also connected to the external interface 65.

During chemical mechanical polishing, the light-blocking member 56 is programmed to move between the second optical sensor 53 and the second window 54. The light emitted by the second optical sensor 53 is absorbed by the light-blocking member 56 and cannot return, that is, no reflected light is generated. The second optical sensor 53 does not feedback signals and has no interference with the optical signal collected by the first optical sensor 51. The light emitted by the first optical sensor 51 is reflected by the wafer through the first window 52 and is received by the first optical sensor 51. At this time, The detection unit 62 receives only the first optical output signal collected by the second optical sensor 53, so that the film thickness of the wafer can be obtained.

During equipment maintenance, after replacing the polishing pad 21, place a light-absorbing sheet above the first window 52. The light emitted by the first optical sensor 51 is absorbed by the light-absorbing sheet and does not produce reflected light. The first optical sensor 51 does not feedback a signal. In addition, The light blocking member 56 is set by the program to move away so that there is no obstruction between the second optical sensor 53 and the second window 54 . The light emitted by the second optical sensor 53 passes through the second window 54 and is reflected by the calibration sheet 55 and is reflected by the second optical sensor 53 Receiving, at this time, the detection unit 62 receives only the second optical output signal collected by the second optical sensor 53, thereby obtaining the calibrated light intensity.

In order to solve the problem of light intensity drift of the light source 61, the light intensity needs to be calibrated before measurement. This application proposes a built-in optical light intensity signal calibration device based on X-type optical fiber for calibrating the light intensity of the light source 61.

The optical measurement device provided by the embodiment of the present invention can obtain the reference light intensity signal at any time by integrating the light intensity calibration unit. On the one hand, it is convenient to monitor the status of the white light measurement module integrated inside the polishing unit, and on the other hand, it reduces the PM cycle. , which has a certain effect on improving productivity.

On the other hand, based on the above chemical mechanical polishing equipment, embodiments of the present invention also provide a wafer film thickness measurement method, including:

Collect the reflection spectrum in the initial stage of polishing, and obtain the number n of spectral peaks or troughs of the reflection spectrum;

Based on the number of spectral peaks or troughs, the FFT algorithm or the spectral fitting algorithm is selected to calculate the wafer film thickness.

Among them, FFT is the Fast Fourier Transform, which is the collective name for efficient and fast calculation methods that use computers to calculate the Discrete Fourier Transform (DFT).

In one embodiment, a wafer film thickness measurement method further includes:

If the number n of spectral peaks or troughs is greater than the preset threshold N, that is, n>N, the FFT algorithm is used to solve the reflection spectrum;

If the number n of spectral peaks or troughs is not greater than the preset threshold N, that is, n≤N, the spectrum fitting algorithm is used to solve the reflection spectrum.

Among them, the preset threshold N is determined to be a certain constant through experience such as test data.

As shown in Figure 4, when white light is used to measure the thickness of the non-metallic film on the wafer surface, the characteristic values in the reflection spectrum obtained by the optical measurement device are related to the thickness of the film on the wafer surface. As shown in Figure 4, the 270nm film thickness Among the characteristic values of the reflection spectrum, there is one extreme point (i.e. spectral peak or trough); among the characteristic values of the reflection spectrum of the 500nm film thickness, there are three extreme points; among the characteristic values of the reflection spectrum of the 1040nm film thickness, There are 5 extreme points; according to the number of extreme points (that is, the number of spectral peaks or troughs), the corresponding spectrum analysis algorithm can be selected to improve the reliability of the measurement results.

As shown in Figure 5, the specific steps of the wafer film thickness measurement method include:

Step S01, start polishing;

Step S02, collect reflection spectrum;

Step S03, perform signal processing, obtain the number n of spectral peaks or troughs of the reflection spectrum, and determine the relationship between the number n and the preset threshold N to determine whether n>N is satisfied;

Step S04, if n>N is satisfied, use the FFT algorithm to solve the reflection spectrum to obtain the wafer film thickness;

Step S05, if n>N is not satisfied, use a spectrum fitting algorithm to solve the reflection spectrum to obtain the wafer film thickness;

Step S06, determine whether the polishing end point is reached based on the obtained wafer film thickness, and if the end point is reached, polishing is completed;

Step S07, if the end point is not reached, continue polishing and return to step S02 to re-execute the wafer film thickness measurement method.

Further, in one embodiment, the spectrum fitting algorithm includes:

During the polishing process, a measurement spectrum is generated based on the collected reflection spectrum;

Select the spectral group of the reference spectrum that is closest to the measured spectrum;

The film thickness corresponding to the spectrum group of the closest reference spectrum is estimated as the film thickness of the wafer.

In addition, before using the spectrum fitting algorithm, spectral groups of multiple reference spectra corresponding to different film thicknesses need to be prepared in advance.

In this embodiment, the reference spectrum is:

Among them, n is the refractive index; λ is the wavelength; a, b, c are constants, which are related to the material and thickness of the measured sample.

In this embodiment, the following formula is used to select the maximum value, thereby selecting the spectrum group of the reference spectrum that is closest to the measured spectrum:

Among them, x _i is the abscissa value of the fitted theoretical spectrum, generally the wavelength, i = 1, 2,..., n; y _i is the relative reflectance value of the measured spectrum at wavelength x _i , y (x _i ) is The relative reflectance value of the fitted theoretical spectrum at wavelength _xi .

In one embodiment, the FFT algorithm includes:

Perform fast Fourier transform on the reflection spectrum, perform time domain-frequency domain transformation, and extract the relationship between its frequency components and spectrum intensity;

The thickness function is used to convert the relationship between frequency components and spectrum intensity to generate the relationship between thickness and spectrum intensity.

In summary, the wafer film thickness measurement method provided in this application collects reflection spectrum information at the beginning of polishing, determines the specific algorithm model to be used based on the characteristics of the reflection spectrum, and uses a priori algorithm switching to avoid measurement errors. Measurement error caused by mismatch between actual film thickness and algorithm. The present invention proposes a priori algorithm pattern recognition model to solve the problem of accuracy of spectral fitting algorithm and FFT algorithm for wafer film thickness calculation in different thickness ranges. During the polishing process, the corresponding spectral information processing algorithm model can be automatically identified and switched based on the collected spectral information. Establish a priori model judgment feedback process to realize adaptive adjustment of the polishing process calculation algorithm model based on prior values. Based on the logical judgment of analytical data and prior values, select the most appropriate thickness calculation algorithm to reduce factors. The measurement error caused by the excessive range of the polishing process enables accurate thickness identification and end point judgment within a large range.

The drawings in this specification are schematic diagrams to assist in explaining the concept of the present invention, schematically showing the shapes of various parts and their mutual relationships. It should be understood that, in order to clearly show the structure of various components of the embodiments of the present invention, the drawings are not drawn to the same scale, and the same reference numbers are used to represent the same parts in the drawings.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" or the like is intended to be incorporated into the description of the implementation. An example or example describes a specific feature, structure, material, or characteristic that is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above 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.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the invention. The scope of the invention is defined by the claims and their equivalents.

Claims (10)

1. A wafer film thickness measurement method, characterized by comprising: Collect the reflection spectrum in the initial stage of polishing, and obtain the number of spectral peaks or troughs of the reflection spectrum; Based on the number of spectral peaks or troughs, the FFT algorithm or the spectral fitting algorithm is selected to calculate the wafer film thickness. 2. The wafer film thickness measurement method according to claim 1, characterized in that, If the number of spectral peaks or troughs is greater than the preset threshold, the FFT algorithm is used to solve the reflection spectrum; If the number of spectral peaks or troughs is not greater than the preset threshold, a spectrum fitting algorithm is used to solve the reflection spectrum. 3. The wafer film thickness measurement method according to claim 1, wherein the spectrum fitting algorithm includes: During the polishing process, a measurement spectrum is generated based on the collected reflection spectrum; Select the spectral group of the reference spectrum that is closest to the measured spectrum; The film thickness corresponding to the spectrum group of the closest reference spectrum is estimated as the film thickness of the wafer. 4. The wafer film thickness measurement method as claimed in claim 3, wherein the reference spectrum is: Among them, n is the refractive index; λ is the wavelength; a, b, and c are constants, which are related to the material and thickness of the measurement sample. 5. The wafer film thickness measurement method according to claim 3, characterized in that the following formula is used to select the maximum value, thereby selecting the spectrum group of the reference spectrum that is closest to the measured spectrum: Among them, x _i is the abscissa value of the fitted theoretical spectrum, generally the wavelength, i = 1, 2,..., n; y _i is the relative reflectance value of the measured spectrum at wavelength x _i , y (x _i ) is The relative reflectance value of the fitted theoretical spectrum at wavelength _xi . 6. The wafer film thickness measurement method according to claim 1, wherein the FFT algorithm includes: Perform fast Fourier transform on the reflection spectrum, perform time domain-frequency domain transformation, and extract the relationship between its frequency components and spectrum intensity; The thickness function is used to convert the relationship between frequency components and spectrum intensity to generate the relationship between thickness and spectrum intensity. 7. A chemical mechanical polishing equipment, characterized in that it includes: A polishing disc, used to be provided with a polishing pad for polishing the wafer; A carrying head, used to hold the wafer and press the wafer on the polishing pad, and the carrying head is provided with a temperature detection unit; an optical measurement device for detecting the reflectance spectrum obtained from the wafer during polishing; A control device used to implement the wafer film thickness measurement method according to any one of claims 1 to 6. 8. The chemical mechanical polishing equipment of claim 1, wherein the obtained reflection spectrum information includes the number of spectral peaks or troughs of the reflection spectrum. 9. A control device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and when the processor executes the computer program, the claims are implemented The steps of the wafer film thickness measurement method described in any one of 1 to 6. 10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the wafer according to any one of claims 1 to 6 is implemented. Steps of film thickness measurement method.