Wafer thickness measuring device and method

Abstract

The invention discloses a wafer thickness measuring device and method, and relates to the technical field of optics, the wafer thickness measuring device comprises an infrared low-coherence light source, a beam splitter prism, a reflector, a carrying table, a driving part, an infrared detector and a data processing unit, and a light beam emitted by the infrared low-coherence light source is split by the beam splitter prism and then enters the reflector and a wafer to be measured; the light is reflected by the reflector and the wafer to be detected along the original path, then enters the beam splitter prism and enters the infrared detector after passing through the beam splitter prism; the driving part is connected with the reflector and used for driving the reflector to move back and forth relative to the beam splitter prism, and the data processing unit is connected with the driving part and the infrared detector and used for obtaining a signal spectrum according to scanning information of the driving part and light signal intensity information measured by the infrared detector and obtaining peak position information of two interference signals in the signal spectrum. And obtaining the thickness of the to-be-measured wafer according to the peak position information and the refractive index of the to-be-measured wafer. According to the wafer thickness measuring device and method, accurate measurement of the wafer thickness can be realized.

Description

Technical Field

[0001] The present application relates to the field of optical technology, and in particular to a wafer thickness measurement device and method. Background Art

[0002] In the field of semiconductor manufacturing, wafer thickness parameters directly affect the yield and product performance of semiconductor devices. Especially in the production process of power semiconductor products such as IGBT (insulated gate bipolar transistor), accurate measurement of wafer thickness data has become a key link in ensuring process accuracy and product quality.

[0003] Among the current mainstream wafer thickness measurement methods, contact measurement can easily introduce mechanical stress and cause wafer damage due to the direct contact between the measuring probe and the wafer surface. At the same time, it is limited by the probe accuracy and measurement force control, resulting in large measurement errors. Although Fourier transform spectroscopy is a non-contact measurement technology, its measurement spot size is large and can only provide average thickness data for macro areas, which is difficult to meet the measurement needs of local micro areas. In addition, the spectral resolution bottleneck of Fourier transform spectroscopy significantly restricts the measurement range. When the wafer thickness exceeds a certain threshold, the resolution accuracy of the spectral signal will drop significantly, and effective measurement cannot be achieved. Summary of the Invention

[0004] The purpose of this application is to provide a wafer thickness measurement device and method, which can accurately measure the thickness of the wafer without the need for direct contact with the wafer during measurement, thereby avoiding damage to the wafer.

[0005] The embodiment of the present application is implemented as follows:

[0006] According to a first aspect of an embodiment of the present application, a wafer thickness measuring device is provided, comprising an infrared low-coherence light source, a beam splitter prism, a reflector, a carrier, a driver, an infrared detector, and a data processing unit, wherein the carrier is used to carry a wafer to be measured, wherein a light beam emitted by the infrared low-coherence light source is split by the beam splitter prism to form a first light beam and a second light beam, which are incident on the reflector and the wafer to be measured respectively, and the first light beam and the second light beam are reflected by the reflector and the wafer to be measured and then incident on the beam splitter prism and then on the infrared detector after passing through the beam splitter prism; the driver is transmission-connected to the reflector and used to drive the reflector to move back and forth relative to the beam splitter prism to correspondingly change the optical path of the first light beam; the data processing unit is electrically connected to the driver and the infrared detector and used to obtain a signal spectrum based on scanning information of the driver and light signal intensity information measured by the infrared detector, and obtain peak position information of two interference signals in the signal spectrum through a peak-finding algorithm, and further used to calculate the thickness of the wafer to be measured based on the peak position information and the refractive index of the wafer to be measured.

[0007] As an implementation method, the infrared low-coherence light source, the beam splitter prism and the carrier are arranged in sequence along the thickness direction of the wafer to be measured, and the reflector, the beam splitter prism and the infrared detector are arranged in sequence along a direction perpendicular to the thickness direction of the wafer to be measured.

[0008] As an implementable embodiment, the coherence length of the infrared low-coherence light source is smaller than the thickness of the wafer to be measured.

[0009] As an implementable embodiment, the infrared low-coherence light source is a superluminescent diode or a broadband infrared light source.

[0010] As an implementable embodiment, the beam splitter prism is a 50:50 beam splitter prism.

[0011] As an implementation method, the scanning information includes position-time data or optical path difference data of the driving element.

[0012] As an implementable embodiment, the response speed of the infrared detector matches the scanning speed of the driving member.

[0013] As an implementation method, the two interference signals include a first interference signal and a second interference signal, the first interference signal being an interference signal when the optical path of the first light beam is equal to the optical path of the second light beam reflected by the upper surface of the wafer to be measured, and the second interference signal being an interference signal when the optical path of the first light beam is equal to the optical path of the second light beam reflected by the lower surface of the wafer to be measured.

[0014] As an implementable method, the peak finding algorithm includes a Gaussian fitting method, a centroid method or a threshold search method.

[0015] According to a second aspect of the embodiments of the present application, a wafer thickness measurement method is provided, which is used in the above-mentioned wafer thickness measurement device.

[0016] The beneficial effects of the embodiments of the present application include:

[0017] The wafer thickness measuring device includes an infrared low-coherence light source, a beam splitter prism, a reflector, a carrier, a driving component, an infrared detector and a data processing unit. The carrier is used to carry a wafer to be measured. A light beam emitted by the infrared low-coherence light source is split by the beam splitter prism to form a first light beam and a second light beam, which are incident on the reflector and the wafer to be measured respectively. The first light beam and the second light beam are reflected by the reflector and the wafer to be measured and then incident on the beam splitter prism and then incident on the infrared detector after passing through the beam splitter prism. The driving component is transmission-connected to the reflector and is used to drive the reflector to move back and forth relative to the beam splitter prism to correspondingly change the optical path of the first light beam. The data processing unit is electrically connected to the driving component and the infrared detector and is used to obtain a signal spectrum based on scanning information of the driving component and light signal intensity information measured by the infrared detector, and obtain peak position information of two interference signals in the signal spectrum through a peak-finding algorithm. The data processing unit is also used to calculate the thickness of the wafer to be measured based on the peak position information and the refractive index of the wafer to be measured. The wafer thickness measurement device provided in the present application utilizes the interference characteristics of infrared low-coherence light and combines it with high-precision displacement control of the driving component (such as nanometer-level stepping accuracy) to achieve submicron or even nanometer-level thickness measurement accuracy; the wafer thickness measurement device provided in the present application also uses optical reflection and interference, and does not directly contact the wafer to be measured throughout the entire measurement process, fundamentally eliminating the risk of mechanical damage and protecting the integrity of the wafer to be measured, thereby improving the yield rate and product reliability of the wafer to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is one of the structural schematic diagrams of the wafer thickness measurement device provided in an embodiment of the present application;

[0020] Figure 2 The second structural diagram of the wafer thickness measurement device provided in an embodiment of the present application;

[0021] Figure 3 A schematic diagram of the signal spectrum provided in an embodiment of the present application.

[0022] Icon: 1-infrared low-coherence light source; 2-beam splitter prism; 3-reflector; 4-driving element; 5-wafer to be tested; 6-infrared detector. DETAILED DESCRIPTION

[0023] The embodiments set forth below represent the information necessary to enable those skilled in the art to practice the embodiments and illustrate the best mode for practicing the embodiments. After reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically set forth herein. It should be understood that these concepts and applications fall within the scope of the present disclosure and the appended claims.

[0024] It should be understood that when an element (such as a layer, region or substrate) is referred to as being “on” or “extending onto” another element, it can be directly on or directly extend onto the other element, or intervening elements may be present. Similarly, it should be understood that when an element (such as a layer, region or substrate) is referred to as being “over” or “extending onto” another element, it can be directly on or extend directly over the other element, or intervening elements may be present.

[0025] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" are intended to include the plural forms as well. It should also be understood that when used herein, the term "comprising" indicates the presence of the recited features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0026] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. It should also be understood that the terms used herein should be interpreted as having the same meaning as in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense, unless otherwise explicitly defined herein.

[0027] Wafer thickness parameters directly affect the yield rate and product performance of semiconductor devices. Accurately measuring wafer thickness data has become a key link in ensuring process accuracy and product quality. Existing wafer thickness measurement methods can be divided into two categories: contact measurement and non-contact measurement. Contact measurement, due to the direct contact between the measurement probe and the wafer surface, can easily introduce mechanical stress and cause wafer damage. At the same time, it is limited by probe accuracy and measurement force control, resulting in large measurement errors. Although Fourier transform spectroscopy is a non-contact measurement technology, its measurement spot size is large and can only provide average thickness data for macroscopic areas, which is difficult to meet the measurement needs of local micro-areas. In addition, the spectral resolution bottleneck of Fourier transform spectroscopy significantly restricts the measurement range. When the wafer thickness exceeds a certain threshold, the resolution accuracy of the spectral signal will drop significantly, making effective measurement impossible.

[0028] In order to solve the problems of contact measurement easily damaging wafers and limited accuracy of non-contact measurement in existing wafer thickness measurement methods, please refer to Figures 1 to 3 The present application provides a wafer thickness measurement device and method based on the principle of infrared low-coherence interference, which can accurately measure the thickness of the wafer without the need for direct contact with the wafer during measurement, thus avoiding damage to the wafer.

[0029] Specifically, if Figures 1 to 3 As shown, in the first aspect of an embodiment of the present application, a wafer thickness measuring device is provided, comprising an infrared low-coherence light source 1, a beam splitter 2, a reflector 3, a carrier, a driving component 4, an infrared detector 6 and a data processing unit. The carrier is used to carry a wafer 5 to be measured. The light beam emitted by the infrared low-coherence light source 1 is split by the beam splitter 2 to form a first light beam and a second light beam which are incident on the reflector 3 and the wafer 5 to be measured respectively. The first light beam and the second light beam are reflected by the reflector 3 and the wafer 5 to be measured and then enter the beam splitter 2 and pass through the beam splitter 2 before entering the infrared detector 6.

[0030] The driving member 4 is connected to the reflector 3 in a transmission manner and is used to drive the reflector 3 to move back and forth relative to the beam splitter prism 2 to correspondingly change the optical path of the first light beam. The data processing unit is electrically connected to the driving member 4 and the infrared detector 6 and is used to obtain a signal spectrum based on the scanning information of the driving member 4 and the light signal intensity information measured by the infrared detector 6, and to obtain the peak position information of the two interference signals in the signal spectrum through a peak finding algorithm, and is also used to calculate the thickness of the wafer 5 to be measured based on the peak position information and the refractive index of the wafer 5 to be measured.

[0031] It should be noted that the wafer thickness measuring device is designed based on the principle of infrared low-coherence interference. By optimizing the optical path design and signal processing algorithm, non-contact measurement of wafer thickness is achieved. The infrared low-coherence light source 1 emits an infrared light beam with a short coherence length characteristic. After entering the beam splitter 2, it is divided into two beams: the first beam is directed to the reflector 3, and the second beam is directed to the wafer to be measured 5 placed on the stage. After the first beam is reflected by the reflector 3, it returns to the beam splitter 2 along the original path. The second beam penetrates the wafer to be measured 5, and after being reflected on the upper and lower surfaces of the wafer to be measured 5, it returns to the beam splitter 2 along the original path. Then it re-converges at the beam splitter 2, and interference occurs due to the optical path difference, and is finally received by the infrared detector 6.

[0032] The driving element 4 (such as a high-precision linear motor or piezoelectric ceramic driver) is connected to the reflector 3 and can accurately control the forward and backward movement of the reflector 3 along the optical axis of the beam splitter prism 2 to correspondingly change the optical path of the first light beam. On the one hand, the data processing unit receives the displacement scanning information of the driving element 4 and records the position change of the reflector 3; on the other hand, it collects the light signal intensity information of the infrared detector 6 and converts it into a signal spectrum. Through the peak-finding algorithm, the data processing unit can accurately identify the peak position information of the two interference signals in the signal spectrum, combine it with the known refractive index of the wafer 5 to be measured, and use the optical thickness calculation formula (such as: wafer thickness = optical path difference / (2×refractive index)) to finally calculate the actual physical thickness of the wafer 5 to be measured.

[0033] The linear motion of reflector 3 precisely changes the optical path (e.g., displacement accuracy reaches ±1nm when driven by piezoelectric ceramics). Combined with the short coherence length of infrared low-coherence light (e.g., 10μm), a significant interference signal is only generated when the optical path difference between the two beams approaches zero. This allows the device to distinguish between reflected light from the top and bottom surfaces of wafer 5 under test. Even if an oxide layer or coating exists on the surface of wafer 5 under test, the dual peak position can be used to accurately calculate the thickness, overcoming the limitations of traditional laser interferometers for transparent materials.

[0034] Traditional non-contact measurement methods (such as Fourier transform spectroscopy) have a large measurement spot size, which is difficult to meet the measurement needs of local small areas. In addition, when the wafer thickness exceeds a certain threshold, the resolution accuracy of the spectral signal will drop significantly, and effective measurement cannot be achieved. The wafer thickness measurement device provided in this application utilizes the interference characteristics of infrared low-coherence light and combines the high-precision displacement control of the drive element 4 (such as nanometer-level stepping accuracy) to achieve submicron or even nanometer-level thickness measurement accuracy, thereby meeting the stringent requirements of advanced semiconductor manufacturing for wafer thickness consistency.

[0035] In addition, traditional contact measurement methods (such as probe measurement) may scratch the wafer surface due to pressure or friction, especially causing irreversible damage to ultra-thin wafers (<100μm) or sensitive film layers of processed wafers. At the same time, due to the limitations of probe accuracy and measurement force control, there are large measurement errors. The wafer thickness measurement device provided in this application uses optical reflection and interference, and does not directly contact the wafer 5 to be measured during the entire measurement process, fundamentally eliminating the risk of mechanical damage and protecting the integrity of the wafer 5 to be measured, thereby improving the yield rate and product reliability of the wafer 5 to be measured.

[0036] The high-speed scanning capability of the driver 4 (e.g., 1000 displacements per second), combined with the real-time calculations of the data processing unit, enables a single measurement to be completed in seconds. When used with a rotating stage, it can also measure multiple points on the surface of the wafer 5 under test, creating a thickness distribution map to help detect warpage or uneven thickness. This improves efficiency dozens of times compared to traditional contact measurement, meeting the rapid testing needs of production lines.

[0037] The optical measurement method provided in this application is not limited by the material of the wafer 5 being measured. Whether it is a semiconductor substrate such as silicon, silicon carbide, or sapphire, or an optical material such as quartz or glass, as long as the refractive index is known, the device can accurately measure the thickness. The data processing unit's algorithm automatically adapts to different material properties, reducing measurement errors caused by material differences and enhancing the device's versatility.

[0038] As an implementable method, Figure 1 and Figure 2 As shown, the infrared low coherence light source 1, the beam splitter prism 2 and the carrier are arranged in sequence along the thickness direction of the wafer 5 to be measured, and the reflector 3, the beam splitter prism 2 and the infrared detector 6 are arranged in sequence along the direction perpendicular to the thickness direction of the wafer 5 to be measured.

[0039] It should be noted that if Figure 1 and Figure 2 As shown, the infrared low-coherence light source 1, the beam splitter prism 2 and the carrier (or the wafer to be measured 5) are coaxially arranged along the thickness direction (or vertical direction) of the wafer to be measured 5, and the light beam emitted by the infrared low-coherence light source 1 is split by the beam splitter prism 2 to form a second light beam, which is vertically downwardly projected toward the wafer to be measured 5 on the carrier, and the second light beam is respectively reflected on the upper surface and the lower surface of the wafer to be measured 5 and returns to the beam splitter prism 2 along the original path; the reflector 3, the beam splitter prism 2 and the infrared detector 6 are arranged along a direction perpendicular to the thickness direction of the wafer to be measured 5 (or horizontal direction), and the light beam emitted by the infrared low-coherence light source 1 is split by the beam splitter prism 2 to form a first light beam, which is horizontally projected to the left toward the reflector 3, and is reflected by the reflector 3 and returns to the beam splitter prism 2 along the original path, and the two beams of reflected light are reunited at the beam splitter prism 2, and interference occurs due to the optical path difference, and is finally received by the infrared detector 6 located on the right side in the horizontal direction.

[0040] The orthogonal optical path layout makes the device structure more compact and easy to integrate into the wafer transmission line or detection platform. Among them, the reflector 3 in the horizontal optical path only reflects the first light beam without contacting the wafer 5 to be measured, avoiding the wear of the traditional contact probe; the infrared low-coherence light source 1 and the infrared detector 6 in the vertical optical path are isolated by the dichroic prism 2, reducing the damage to the detector caused by direct exposure to strong light. In addition, the design of the vertical and horizontal orthogonal optical paths reduces the impact of interference such as environmental vibration and airflow on the measurement. For example, the movement of the reflector 3 in the horizontal optical path only changes the optical path of the first light beam along the horizontal direction, and the second light beam along the vertical direction in the vertical optical path always vertically impinges on the surface of the wafer 5 to be measured, avoiding measurement deviations caused by optical path tilt.

[0041] As an implementation method, the coherence length of the infrared low-coherence light source 1 is smaller than the thickness of the wafer 5 to be measured.

[0042] It should be noted that when the infrared light beam emitted by the infrared low-coherence light source 1 is split by the beam splitter prism 2 and then perpendicularly incident on the wafer 5 to be tested, the resulting second beam is reflected from the upper and lower surfaces of the wafer 5 to be tested, respectively, forming two beams of reflected light. Because the thickness of the wafer 5 to be tested is greater than the coherence length of the infrared low-coherence light source 1, the optical path difference between the two reflected light beams (approximately twice the wafer thickness) exceeds the coherence range of the infrared low-coherence light source 1. Therefore, no interference signals are generated between the two reflected light beams.

[0043] At the same time, the optical path difference between the first light beam from the reflector 3 and the reflected light from a certain surface (such as the upper surface or the lower surface) of the wafer 5 to be measured can be adjusted by the drive 4 to be less than the coherence length, thereby generating a clear interference signal. For example, when the reflector 3 is moved so that the optical path difference between the reference light beam and the reflected light from the upper surface of the wafer 5 to be measured is less than or equal to the coherence length, the two interfere with each other; continue to move the reflector 3, and when the optical path difference between the reference light beam and the reflected light from the lower surface of the wafer 5 to be measured is less than or equal to the coherence length, interference occurs again. By recording the positions of the two interference peaks, the coordinates of the upper and lower surfaces of the wafer 5 to be measured can be determined, and then the thickness of the wafer 5 to be measured can be calculated.

[0044] As one possible implementation method, the infrared low-coherence light source 1 is a superluminescent diode or a broadband infrared light source. Both light sources have the characteristics of a short coherence length (typically a few microns to tens of microns) and a wide spectral bandwidth (e.g., 30-100 nm). In the wafer thickness measurement device, the infrared light beam emitted by this type of light source is split into two beams by a beam splitter prism 2, which are respectively directed to a reflector 3 and a wafer to be measured 5. The short coherence characteristics of this type of light source are used to accurately distinguish the light reflected from the upper and lower surfaces of the wafer.

[0045] As an implementation method, the beam splitter prism 2 is a 50:50 beam splitter prism 2 .

[0046] It should be noted that the beam splitter 2 adopts a 50:50 splitting ratio design, that is, the incident light beam will be evenly divided into two beams when passing through the beam splitter 2, 50% of the light intensity is directed to the reflector 3 (reference light path), and the other 50% of the light intensity is directed to the wafer to be measured 5 (measurement light path). This splitting ratio makes the light intensity of the two beams of light almost equal, ensuring that the interference signal with the best contrast is generated during the interference process. Specifically, when the light beam emitted by the infrared low-coherence light source 1 is incident on the 50:50 beam splitter prism 2, the semi-transparent and semi-reflective film layer inside the beam splitter prism 2 will evenly distribute the energy of the light beam to form a first light beam and a second light beam with similar intensities. The two beams of light are respectively reflected by the reflector 3 and the wafer to be measured 5 and then return to the beam splitter prism 2, producing clear interference fringes on the infrared detector 6.

[0047] In one embodiment, the scanning information includes position-time data or optical path difference data of the driver 4. The data processing unit can collect these two types of scanning information and synchronously correlate them with the light signal intensity data of the infrared detector 6 to create a light intensity-optical path difference signal spectrum, providing key input for subsequent thickness calculations.

[0048] It should be noted that the scanning information of the driver 4 may include position-time data. That is, during the scanning process, the driver 4 (such as a linear motor) records the spatial position coordinates of the reflector 3 (such as the displacement along the optical axis) and the corresponding timestamp in real time. For example, when the driver 4 moves at a speed of 100 μm / s, the position is recorded every 10 ms (e.g., x = 0 μm at t = 0 ms, and x = 1 μm at t = 10 ms), forming a position-time sequence.

[0049] The scanning information from driver 4 can also include optical path difference data. Since the displacement of reflector 3 directly changes the optical path of the first light beam (optical path difference = 2 × displacement of reflector 3), driver 4 can convert position data into optical path difference data using a displacement sensor (such as a grating ruler). For example, when reflector 3 moves 5 μm, the optical path difference increases by 10 μm (round-trip path). This data directly corresponds to the optical path change in interferometry.

[0050] As one possible implementation, the response speed of infrared detector 6 is matched to the scanning speed of driver 4. This matching ensures that infrared detector 6 can capture the intensity changes of the interference signal during the movement of reflector 3 in real time, avoiding signal distortion caused by sampling lag or advance. For example, if the response speed of infrared detector 6 is insufficient (e.g., with a sampling frequency of only 1 kHz) when driver 4 is scanning rapidly, critical interference peak information will be missed, resulting in errors in thickness calculation.

[0051] As an implementation method, the two interference signals include a first interference signal and a second interference signal. The first interference signal is an interference signal when the optical path of the first light beam is equal to the optical path of the second light beam reflected by the upper surface of the wafer 5 to be measured. The second interference signal is an interference signal when the optical path of the first light beam is equal to the optical path of the second light beam reflected by the lower surface of the wafer 5 to be measured.

[0052] It should be noted that the present application utilizes the short coherence characteristics of the infrared low-coherence light source 1, and interference is generated only when the optical path difference is within the coherence length, ensuring that the first interference signal and the second interference signal uniquely correspond to the reflections of the upper surface and lower surface of the wafer 5 to be tested, respectively. Specifically, when the driver 4 drives the reflector 3 to move to a certain position, the optical path of the first light beam (reflected by the reflector 3) is equal to the optical path of the second light beam reflected by the upper surface of the wafer 5 to be tested. At this time, the optical path difference between the two beams of light falls within the coherence length of the infrared low-coherence light source 1, resulting in interference. The light intensity signal received by the infrared detector 6 forms a first peak, i.e., the first interference signal; the driver 4 continues to move the reflector 3. When the optical path of the first light beam (reflected by the reflector 3) is equal to the optical path of the second light beam reflected by the lower surface of the wafer 5 to be tested, the two beams of light interfere again, and the infrared detector 6 receives a second peak, i.e., the second interference signal.

[0053] As an implementable method, the peak finding algorithm includes a Gaussian fitting method, a centroid method or a threshold search method.

[0054] like Figures 1 to 3 As shown, a second aspect of the embodiment of the present application provides a wafer thickness measurement method for the above-mentioned wafer thickness measurement device, the method comprising:

[0055] S01: The driving member 4 drives the reflective mirror 3 to move forward and backward relative to the beam splitter prism 2 to correspondingly change the optical path of the first light beam;

[0056] S02: The infrared detector 6 measures the light signal intensity information;

[0057] S03: The data processing unit obtains a signal spectrum based on the scanning information of the driving member 4 and the light signal intensity information measured by the infrared detector 6;

[0058] S04: The data processing unit obtains peak position information of two interference signals in the signal spectrum through a peak search algorithm;

[0059] S05: The data processing unit calculates the thickness of the wafer 5 to be measured according to the peak position information and the refractive index of the wafer 5 to be measured.

[0060] It should be noted that where the wafer thickness measurement method provided in this embodiment is identical to the specific structure of the wafer thickness measurement device described above, those skilled in the art can infer the wafer thickness measurement method based on the description of the specific structure of the wafer thickness measurement device described above, and this application will not repeat the description. Since the wafer thickness measurement method provided in this embodiment is used for the above-mentioned wafer thickness measurement device, the wafer thickness measurement method has the same beneficial effects as the above-mentioned wafer thickness measurement device, and will not be repeated here.

[0061] The above description is merely an optional embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

[0062] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

Claims

1. A wafer thickness measuring device, characterized in that: The device comprises an infrared low-coherence light source, a beam splitter prism, a reflector, a carrier, a driving component, an infrared detector, and a data processing unit. The carrier is used to carry a wafer to be tested. A light beam emitted by the infrared low-coherence light source is split by the beam splitter prism to form a first light beam and a second light beam, which are incident on the reflector and the wafer to be tested respectively. The first light beam and the second light beam are reflected by the reflector and the wafer to be tested, and then are incident on the beam splitter prism and incident on the infrared detector after passing through the beam splitter prism. The driving member is in transmission connection with the reflector, and is used to drive the reflector to move forward and backward relative to the beam splitter prism to correspondingly change the optical path of the first light beam. The data processing unit is electrically connected to the driving member and the infrared detector, and is used to obtain a signal spectrum based on the scanning information of the driving member and the light signal intensity information measured by the infrared detector, and obtain the peak position information of the two interference signals in the signal spectrum through a peak finding algorithm, and is also used to calculate the thickness of the wafer to be measured based on the peak position information and the refractive index of the wafer to be measured.

2. The wafer thickness measuring device according to claim 1, wherein: The infrared low-coherence light source, the beam splitter prism and the carrier are sequentially arranged along the thickness direction of the wafer to be measured, and the reflector, the beam splitter prism and the infrared detector are sequentially arranged along a direction perpendicular to the thickness direction of the wafer to be measured.

3. The wafer thickness measuring device according to claim 1, wherein: The coherence length of the infrared low-coherence light source is smaller than the thickness of the wafer to be measured.

4. The wafer thickness measuring device according to claim 1, wherein: The infrared low-coherence light source is a superluminescent diode or a broadband infrared light source.

5. The wafer thickness measuring device according to claim 1, wherein: The beam splitter prism is a 50:50 beam splitter prism.

6. The wafer thickness measuring device according to claim 1, wherein: The scanning information includes position-time data or optical path difference data of the driving element.

7. The wafer thickness measuring device according to claim 1, wherein: The response speed of the infrared detector matches the scanning speed of the driving member.

8. The wafer thickness measuring device according to claim 1, wherein: The two interference signals include a first interference signal and a second interference signal. The first interference signal is an interference signal when the optical path of the first light beam is equal to the optical path of the second light beam reflected by the upper surface of the wafer to be measured. The second interference signal is an interference signal when the optical path of the first light beam is equal to the optical path of the second light beam reflected by the lower surface of the wafer to be measured.

9. The wafer thickness measuring device according to claim 1, wherein: The peak finding algorithm includes Gaussian fitting method, centroid method or threshold search method.

10. A wafer thickness measurement method, characterized in that: Used in the wafer thickness measuring device according to any one of claims 1 to 9.

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