Wafer thickness measuring method and system and storage medium

Abstract

The invention relates to a wafer thickness measuring method and system and a storage medium, and the method comprises the following steps: S1, providing a plurality of wafers with metal layers; s2, non-metal area planning is carried out on the surface of the wafer based on the materials and structures of different layers of the wafer, and a non-metal area of the wafer is determined; s3, selecting a predetermined measurement point in the non-metal area of the wafer, and measuring the predicted thickness of the predetermined measurement point by adopting an infrared spectrum interference measurement method; s4, slicing the non-metal area where the predetermined prediction point of each wafer is located, and measuring the actual thickness of each wafer slice; s5, determining the average offset of the predicted thickness of each wafer based on the difference between the predicted thickness and the actual thickness of each wafer; and S6, performing offset compensation on the predicted thickness of the to-be-detected wafer based on the average offset in the subsequent wafer thickness measurement process to obtain a thickness measurement result closer to the real thickness of the to-be-detected wafer, thereby effectively improving the accuracy of wafer thickness measurement in the Inline process.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor production, and in particular relates to a wafer thickness measurement method, system and storage medium. Background Art

[0002] In the field of semiconductor device manufacturing, wafer thickness is a key parameter that directly affects the performance and reliability of the device. With the continuous miniaturization of integrated circuits, higher requirements are placed on the accurate measurement of wafer thickness. At present, the measurement of wafer thickness mainly relies on two methods: offline measurement and inline measurement.

[0003] Among them, the traditional Offline measurement method can provide more accurate measurement results, but it usually requires the wafer to be removed from the production line for separate measurement, which not only increases production costs, but may also cause secondary contamination and damage to the wafer. Inline measurement mainly relies on infrared (IR) spectral interferometry. This method obtains wafer thickness information by penetrating infrared light through different materials and receiving reflected signals, which can avoid contamination and damage to the wafer, but the device still has obvious defects. On the one hand, since infrared light waves cannot penetrate thick metal layers, the existing Inline wafer thickness measurement method cannot measure wafers with thick metal layers. On the other hand, when infrared light penetrates thin metal layers, the signal will be interfered, which affects the accuracy of the measurement results and thus affects the performance and reliability of the final product. Summary of the invention

[0004] The purpose of the present invention is to solve one of the above technical problems and to provide a wafer thickness measurement method, system and storage medium.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A wafer thickness measurement method is used to detect the thickness of a wafer with a metal layer in an Inline semiconductor process, comprising the following steps:

[0007] S1: providing a plurality of wafers with metal layers;

[0008] S2: Plan the non-metallic area on the wafer surface based on the material and structure of different layers of the wafer to determine the non-metallic area of ​​the wafer;

[0009] S3: Select a predetermined measurement point in the non-metallic area of ​​the wafer, allow infrared light of different wavelengths to pass through the interferometer and illuminate the predetermined measurement point on the surface of the wafer, penetrate and reflect at different layers at the predetermined measurement point, and the reflected light waves of each layer interfere with each other to form characteristic interference fringes. Use a photometer to analyze the interference fringes and the infrared spectrum of the reflected light waves of each layer to calculate the predicted thickness of the wafer;

[0010] S4: Slicing the non-metallic area of ​​each wafer where the predetermined predicted point is located, and measuring the actual thickness of each wafer slice;

[0011] S5: determining an average offset of the predicted thickness of each wafer based on the difference between the predicted thickness and the actual thickness of each wafer;

[0012] S6: providing a wafer to be inspected, repeating steps S2 to S3 to obtain a predicted thickness of the wafer to be inspected, and performing offset compensation on the predicted thickness of the wafer to be inspected based on the average offset to obtain a thickness measurement result of the wafer to be inspected.

[0013] In some embodiments of the present invention, step S3 specifically includes the following steps:

[0014] S31: Selecting a predetermined measurement point in a non-metallic area of ​​the wafer;

[0015] S32: using an infrared light source to emit infrared light of different wavelengths, and the infrared light of different wavelengths passes through the interferometer line and irradiates a predetermined measurement point on the surface of the wafer;

[0016] S33: adjusting the position of the reflector in the interferometer to generate interference light with different optical path differences;

[0017] S34: using a detector to receive the interference light and generate an interference pattern including information about the variation of light intensity with the optical path difference;

[0018] S35: performing fast Fourier transform calculation on the interference pattern, converting the time domain spectrum into a frequency domain spectrum, and obtaining an infrared spectrum diagram with wavelength or wave number as a function;

[0019] S36: Extracting the predicted thickness of the wafer based on the obtained infrared spectrum.

[0020] In some embodiments of the present invention, in step S3, multiple predetermined measurement points are selected, the infrared spectra of the reflected light waves of each layer at each predetermined detection point are compared and analyzed, the point with the least metal interference is selected, and the predicted thickness of the wafer is calculated based on the infrared spectrum of the point with the least metal interference.

[0021] In some embodiments of the present invention, the distance from each predetermined measurement point to the center of the wafer is different.

[0022] In some embodiments of the present invention, in step S3, after the infrared spectrum of the reflected light waves of each layer is obtained, a filter is used to filter out the noise therein.

[0023] In some embodiments of the present invention, in step S4, a contact height gauge is used to measure the actual thickness of each wafer slice.

[0024] Some embodiments of the present invention further provide a wafer thickness measurement method system, which is used to implement the above-mentioned wafer thickness measurement method, including:

[0025] The area planning module is used to plan the non-metal area on the wafer surface based on the material and structure of different layers of the wafer to determine the non-metal area of ​​the wafer;

[0026] Interference measurement module, used to obtain infrared spectra of light waves reflected by different material layers at predetermined measurement points on the wafer surface;

[0027] A predicted thickness calculation module, used to calculate the predicted thickness of the wafer based on the infrared spectrum measured by the interferometric measurement module;

[0028] An offset compensation module, for determining an average offset based on the difference between the predicted thickness and the actual thickness of different wafers;

[0029] The result output module is used to compensate the predicted thickness of the wafer to be inspected based on the average offset calculated by the offset compensation module, and output the thickness measurement result of the wafer to be inspected.

[0030] In some embodiments of the present invention, the interferometric measurement module includes a laser transmitter, an interferometer, and a photometer;

[0031] The laser transmitter is used to generate infrared light waves with a predetermined wavelength and coherence;

[0032] The interferometer includes at least a beam splitter, a reflector and a detector;

[0033] The beam splitter is used to split the light emitted by the laser light source into two beams, one of which is used as a reference beam and the other is used as a measurement beam;

[0034] The reflector includes at least two surfaces, one of which is fixed and the other is movable, and is used to change the optical path difference to generate interference fringes;

[0035] a detector for detecting and analyzing a fringe pattern formed by interference of the reference beam and the measurement beam;

[0036] The photometer is used to calculate the predicted thickness of the wafer based on the infrared spectrum of the beam reflected off the wafer surface and the fringe pattern measured by the detector.

[0037] In some embodiments of the present invention, the interference measurement module further includes a filter, which is used to filter out noise in the infrared spectrum of the reflected light waves of each layer.

[0038] Some embodiments of the present invention further provide a storage medium storing a program executable by a processor, wherein the program executable by the processor is used to implement the above-mentioned wafer thickness measurement method when executed by the processor.

[0039] The beneficial effects of the present invention are:

[0040] The present invention selects multiple wafers, adopts infrared spectral interferometry to measure the predicted thickness of the non-metallic area of ​​the wafer, adopts a physical method to measure the actual thickness of the non-metallic area slice, and calculates the average offset of the measurement by comparing the predicted thickness and the actual thickness of the multiple wafers. Then, in the subsequent wafer thickness measurement process, the predicted thickness measured by the infrared spectral interferometry is compensated based on the average offset, so as to obtain a measurement result closer to the actual thickness of the wafer, and effectively improves the accuracy of wafer thickness measurement in the Inline process. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 The figure is a flow chart of a wafer thickness measurement method. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0045] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0046] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and the accompanying drawings.

[0047] As attached Figure 1As shown, in an illustrative embodiment of a wafer thickness measurement method of the present invention, the measurement method is used to measure the thickness of a wafer with a metal layer in a real-time (Inline) process, and includes the following steps.

[0048] S1: Provide multiple wafers with metal layers. In this embodiment, the multiple wafers with metal layers are n consecutive wafers in the same batch of wafers to be tested, where n is a natural multiple of the number of chambers of the previous process tool into which the multiple wafers of the same batch enter.

[0049] In some embodiments of the present invention, step S1 also requires cleaning the surfaces of multiple wafers to ensure that the surfaces of the wafer samples to be tested are clean and flat, free of impurities and bubbles, thereby ensuring that the light can be correctly reflected and interfered during the measurement process to obtain accurate thickness data.

[0050] S2: Based on the material and structure of different layers of the wafer, non-metallic areas are planned on the wafer surface to determine the non-metallic areas of the wafer.

[0051] S3: Adjust the interferometric measurement equipment to the appropriate working mode and determine the appropriate measurement parameters and optical system settings. Specifically, select parameters such as spectral range and acquisition speed.

[0052] Place the wafer on the measuring table of the interferometer and fix its position so that it maintains stable contact with the optical system, ensure that the sample is parallel to the measuring table, and use infrared spectroscopy interferometry to measure the predicted thickness of the non-metallic area of ​​the wafer. Select predetermined measurement points in the non-metallic area of ​​the wafer, and allow infrared light of different wavelengths to pass through the interferometer and illuminate the predetermined measurement points on the surface of the wafer. Penetration and reflection occur in different layers at the predetermined measurement points, and the reflected light waves of each layer interfere with each other to form characteristic interference fringes. Use a photometer to analyze the interference fringes and the infrared spectrum of the reflected light waves of each layer to calculate the predicted thickness of the wafer.

[0053] During the measurement process, the mapping error is analyzed and corrected by adjusting the position of the reference mirror in the interferometric measurement device or the position of the predetermined measurement point to reduce the impact of the mapping error on the measurement result and ensure the accuracy of the measurement result.

[0054] In some embodiments of the present invention, step S3 specifically includes the following steps:

[0055] S31: Select at least one predetermined measurement point in the non-metallic area of ​​the wafer.

[0056] S32: Using an infrared light source to emit infrared light of different wavelengths, the infrared light of different wavelengths passes through the interferometer line and irradiates a predetermined measurement point on the surface of the wafer.

[0057] S33: Adjust the position of the reflector in the interferometer to generate interference light with different optical path differences.

[0058] S34: Using a detector to receive the interference light and generate an interference pattern containing information about the variation of light intensity with the optical path difference.

[0059] S35: Perform fast Fourier transform calculation on the interference pattern, convert the time domain spectrum into a frequency domain spectrum, and obtain an infrared spectrum diagram with wavelength or wave number as a function.

[0060] S36: Extracting the predicted thickness of the wafer based on the obtained infrared spectrum.

[0061] In some embodiments of the present invention, in step S3, multiple predetermined measurement points are selected, the infrared spectra of the reflected light waves of each layer at each predetermined detection point are compared and analyzed, and a point with the least metal interference is selected, and the predicted thickness of the wafer is calculated based on the infrared spectrum of the point with the least metal interference. By measuring at predetermined measurement points at different distances, the thickness distribution of the wafer can be more comprehensively understood, which is helpful for detecting and compensating for the non-uniformity of the wafer.

[0062] Furthermore, in the process of selecting a plurality of predetermined measurement points, it is ensured that the distance from each predetermined measurement point to the center of the wafer is different, so as to reflect the overall thickness of the entire wafer.

[0063] In some embodiments of the present invention, in step S3, after obtaining the infrared spectrum of the reflected light waves of each layer, a filter is used to filter out the noise therein. Using the filter to filter out the noise improves the quality of the infrared spectrum data, thereby improving the accuracy of the thickness prediction.

[0064] S4: Slice the non-metallic area where the predetermined predicted point of each wafer is located, and measure the actual thickness of each wafer slice.

[0065] Specifically, in step S4, a contact altimeter is used to measure the actual thickness of each wafer slice. In this embodiment, the contact altimeter is used to measure the actual thickness, which provides an accurate verification method, helps to calibrate and optimize the measurement results, and improves the accuracy of the overall measurement.

[0066] In some embodiments of the present invention, the thickness of the wafer can also be measured by using other wafer thickness measurement technologies that are highly accurate and not easily affected by the metal layer, such as a WD4000 wafer measurement system and a high-precision laser confocal technology.

[0067] S5: Determine an average offset of the predicted thickness of each wafer based on the difference between the predicted thickness and the actual thickness of each wafer, wherein the average offset is an average value of the difference between the predicted thickness and the actual thickness of each wafer.

[0068] S6: providing a wafer to be inspected, repeating steps S2 to S3 to obtain a predicted thickness of the wafer to be inspected, and performing offset compensation on the predicted thickness of the wafer to be inspected based on the average offset calculated in step S5 to obtain a thickness measurement result of the wafer to be inspected.

[0069] The present invention provides a method for measuring the thickness of a wafer with a metal layer in an Inline semiconductor process, which solves the problem that a traditional IR spectral interferometry method cannot penetrate a thick metal layer, thereby improving the measurement accuracy and process efficiency.

[0070] Some embodiments of the present invention further provide a wafer thickness measurement method system for implementing the above-mentioned wafer thickness measurement method, including a region planning module, an interference measurement module, a predicted thickness calculation module, an offset compensation module and a result output module.

[0071] Among them, the area planning module is used to plan the non-metallic area on the wafer surface based on the material and structure of different layers of the wafer to determine the non-metallic area of ​​the wafer.

[0072] The interferometric measurement module is used to obtain the infrared spectrum of light waves reflected by different material layers at predetermined measurement points on the wafer surface.

[0073] The predicted thickness calculation module is used to calculate the predicted thickness of the wafer based on the infrared spectrum measured by the interference measurement module.

[0074] The offset compensation module is used to determine the average offset based on the difference between the predicted thickness and the actual thickness of different wafers.

[0075] The result output module is used to compensate the predicted thickness of the wafer to be inspected based on the average offset calculated by the offset compensation module, and output the thickness measurement result of the wafer to be inspected.

[0076] In some embodiments of the present invention, the interference measurement module includes a laser transmitter, an interferometer and a photometer.

[0077] The laser transmitter is used to generate infrared light waves with a predetermined wavelength and coherence.

[0078] An interferometer includes at least a beam splitter, a reflector and a detector.

[0079] The beam splitter is used to split the light emitted by the laser light source into two beams, one of which is used as a reference beam and the other as a measurement beam.

[0080] The reflector includes at least two surfaces, one of which is fixed and the other is movably arranged to change the optical path difference to generate interference fringes.

[0081] A detector is used to detect and analyze the fringe pattern formed by the interference of the reference beam and the measurement beam.

[0082] The photometer is used to calculate the predicted thickness of the wafer based on the infrared spectrum of the beam reflected off the wafer surface and the fringe pattern measured by the detector.

[0083] In some embodiments of the present invention, the interference measurement module further includes a filter, and the filter is used to filter out noise in the infrared spectrum of the light waves reflected by each layer.

[0084] Some embodiments of the present invention further provide a storage medium storing a program executable by a processor, wherein the program executable by the processor is used to implement the above-mentioned wafer thickness measurement method when executed by the processor.

[0085] Finally, it should be noted that: the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0086] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A wafer thickness measurement method for measuring the thickness of a wafer with a metal layer in an Inline semiconductor process, characterized in that: The following steps are involved: S1: providing a plurality of wafers with metal layers; S2: Plan the non-metallic area on the wafer surface based on the material and structure of each material layer of the wafer to determine the non-metallic area of ​​the wafer; S3: Selecting a predetermined measurement point in the non-metallic area of ​​the wafer, allowing infrared light of different wavelengths to pass through the interferometer and illuminate the predetermined measurement point on the surface of the wafer, penetration and reflection occur in each material layer at the predetermined measurement point, and the reflected light waves of each layer interfere with each other to form characteristic interference fringes, and using a photometer to analyze the interference fringes and the infrared spectrum of the reflected light waves of each layer to calculate the predicted thickness of the wafer; S4: Slicing the non-metallic area of ​​each wafer where the predetermined predicted point is located, and measuring the actual thickness of each wafer slice; S5: determining an average offset of the predicted thickness of each wafer based on the difference between the predicted thickness and the actual thickness of each wafer; S6: providing a wafer to be inspected, repeating steps S2 to S3 to obtain a predicted thickness of the wafer to be inspected, and performing offset compensation on the predicted thickness of the wafer to be inspected based on the average offset to obtain a thickness measurement result of the wafer to be inspected.

2. The wafer thickness measurement method according to claim 1, characterized in that: The step S3 specifically comprises the following steps: S31: Selecting a predetermined measurement point in a non-metallic area of ​​the wafer; S32: using an infrared light source to emit infrared light of different wavelengths, wherein the infrared light of different wavelengths passes through an interferometer line and irradiates a predetermined measurement point on the surface of the wafer; S33: adjusting the position of the reflector in the interferometer to generate interference light with different optical path differences; S34: using a detector to receive the interference light and generate an interference pattern including information about the variation of light intensity with the optical path difference; S35: performing fast Fourier transform calculation on the interference pattern, converting the time domain spectrum into a frequency domain spectrum, and obtaining an infrared spectrum diagram with wavelength or wave number as a function; S36: Extracting the predicted thickness of the wafer based on the obtained infrared spectrum.

3. The wafer thickness measurement method according to claim 1 or 2, characterized in that: In step S3, multiple predetermined measurement points are selected, the infrared spectra of the reflected light waves of each layer at each predetermined detection point are compared and analyzed, and the point with the least metal interference is selected, and the predicted thickness of the wafer is calculated based on the infrared spectrum of the point with the least metal interference.

4. The wafer thickness measurement method according to claim 3, characterized in that: The distance from each predetermined measurement point to the center of the wafer is different.

5. The wafer thickness measurement method according to claim 1 or 2, characterized in that: In step S3, after obtaining the infrared spectrum of the reflected light waves of each layer, a filter is used to filter out the noise therein.

6. The wafer thickness measurement method according to claim 1, characterized in that: In step S4, a contact height gauge is used to measure the actual thickness of each wafer slice.

7. A wafer thickness measurement method system, used to implement the wafer thickness measurement method according to any one of claims 1 to 6, characterized in that: include: The area planning module is used to plan the non-metal area on the wafer surface based on the material and structure of different layers of the wafer to determine the non-metal area of ​​the wafer; Interference measurement module, used to obtain infrared spectra of light waves reflected by different material layers at predetermined measurement points on the wafer surface; A predicted thickness calculation module, used to calculate the predicted thickness of the wafer based on the infrared spectrum measured by the interference measurement module; An offset compensation module, for determining an average offset based on the difference between the predicted thickness and the actual thickness of different wafers; The result output module is used to compensate the predicted thickness of the wafer to be inspected based on the average offset calculated by the offset compensation module, and output the thickness measurement result of the wafer to be inspected.

8. The wafer thickness measurement system according to claim 7, characterized in that: The interference measurement module includes a laser transmitter, an interferometer and a photometer; The laser transmitter is used to generate infrared light waves with predetermined wavelength and coherence; The interferometer at least includes a spectroscope, a reflector and a detector; The beam splitter is used to split the light emitted by the laser light source into two beams, one of which is used as a reference beam and the other is used as a measurement beam; The reflector comprises at least two surfaces, one of which is fixed and the other is movable, for changing the optical path difference to generate interference fringes; The detector is used to detect and analyze the fringe pattern formed by the interference of the reference beam and the measurement beam; the photometer is used to calculate the predicted thickness of the wafer based on the infrared spectrum of the beam reflected on the wafer surface and the fringe pattern measured by the detector.

9. The wafer thickness measurement system according to claim 7 or 8, characterized in that: The interference measurement module also includes a filter, which is used to filter out noise in the infrared spectrum of the reflected light waves of each layer.

10. A storage medium storing a program executable by a processor, characterized in that: The processor-executable program is used to implement the wafer thickness measurement method according to any one of claims 1 to 6 when executed by the processor.

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