End point detection method and device based on multiple light beams

Abstract

The invention provides an end point detection method and equipment based on multiple light beams. The method is applied to semiconductor processing. The method comprises the steps that the wavelength # imgabs3 # of any incident light beam in multiple light beams is calculated through the target wafer film thickness # imgabs0 # corresponding to a wafer grinding end point, the refractive index # imgabs1 # of a wafer film and the incident angle # imgabs2 # of the light beams; the wavelength # imgabs4 # and the wavelength # imgabs5 # are at least utilized to establish a corresponding relation curve of the wafer film thickness and the reflectivity, the reflectivity changes periodically along with the thickness, and a point corresponding to the target wafer film thickness # imgabs7 # in the corresponding relation curve established by the wavelength # imgabs6 # is within a preset range in the curve; and irradiating at least two light beams containing the wavelength # imgabs8 # and the wavelength # imgabs9 # to the surface of the wafer film, and monitoring whether the thickness of the wafer film reaches the target wafer film thickness # imgabs11 # or not by utilizing the reflectivity corresponding to the target wafer film thickness # imgabs10 # and the corresponding relation curve. According to the invention, the end point detection sensitivity and the measurement accuracy are improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor processing, and in particular to a method and device for detecting an endpoint based on multiple light beams. Background Art

[0002] Wafers are one of the foundations of the semiconductor industry and are mainly used to produce various semiconductor devices, such as integrated circuits, optoelectronic components, and micro-electromechanical systems. Their thickness has an important impact on the performance of the devices. According to different requirements for measurement accuracy and measurement range, many wafer thickness measurement methods have emerged, such as ellipsometry and reflectance spectroscopy. Under the premise of meeting the basic measurement accuracy, the current wafer thickness measurement methods often have problems such as high cost and complex principles. It is a difficult problem in the field of thin film thickness measurement to achieve wafer thickness measurement while taking into account economic cost and measurement accuracy.

[0003] In order to solve the above problems, a dual-beam optical film thickness measurement method is proposed in the prior art. This method can more accurately measure the thickness of the film by using two light beams of different wavelengths for interference. This method is simple in principle and low in cost, and can effectively reduce the errors that may occur when measuring a single wavelength, thereby improving the accuracy of the measurement. However, the limitation of this method is that the wavelength is not limited, which leads to large measurement errors at some film thickness value locations.

[0004] The multi-beam optical film thickness measurement method requires at least two light sources with different wavelengths, and different reflectivity and film thickness correspondence curves are established for the two light beams. After using the two light beams to obtain the reflectivity at the same thickness, the film thickness is obtained by matching the reflectivity and film thickness correspondence curve. The choice of the wavelengths of the two light sources will have a great impact on the accuracy of the measurement results. When the film thickness is near the position where the change rate of the reflectivity and film thickness correspondence curve is small, the film thickness is not sensitive to the change of reflectivity, which will lead to a decrease in the accuracy of the thickness measurement.

[0005] Therefore, how to select a dual-beam or multi-beam light source with a suitable wavelength for endpoint detection is a technical problem that urgently needs to be solved. Summary of the invention

[0006] In view of this, the present application provides an endpoint detection method based on multiple light beams, comprising: Target wafer film thickness corresponding to the wafer grinding end point , the refractive index of the wafer film , the incident angle of the light beam Calculate the wavelength of any incident beam in a multi-beam ; At least using wavelength and wavelength The corresponding relationship curves between wafer film thickness and reflectivity are established respectively, where the reflectivity changes periodically with thickness and the wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding point is within a predetermined range in the curve; During the wafer grinding process, the wavelength and wavelength At least two light beams are irradiated onto the wafer film surface, and the target wafer film thickness is determined by using the target wafer film thickness. The corresponding reflectivity and the corresponding relationship curve monitor whether the thickness of the wafer film reaches the target wafer film thickness .

[0007] Optionally, the predetermined range is a range extending forward and backward by T15 / 12 from the maximum gradient point in the curve as the midpoint, where T1 is the wavelength. The period of the corresponding relationship curve.

[0008] Optionally, determining the wavelength of any incident beam in the multiple beams include: The wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], is the initial phase, and m is taken as an arbitrary value through Get wavelength The value range of In wavelength Choose a value from the range of values ​​to get the wavelength .

[0009] Optionally, the predetermined range is a range extending forward and backward by T1 / 12 from the maximum gradient point in the curve as the midpoint, where T1 is the wavelength. The period of the corresponding relationship curve.

[0010] Optionally, determining the wavelength of any incident beam in the multiple beams include: The wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], is the initial phase, and m is taken as an arbitrary value through Get wavelength The value range of In wavelength Choose a value from the range of values ​​to get the wavelength .

[0011] Optionally, the wavelength The value range is T2 / 12, which is the range extending forward and backward from the extreme point in the curve as the midpoint, where T2 is the wavelength The period of the corresponding relationship curve.

[0012] Optionally, the method further comprises determining the wavelength in the following manner: : The wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], take any value for m and pass Get wavelength The value range of is the initial phase; In wavelength Choose a value from the range of values ​​to get the wavelength .

[0013] Optionally, using wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding point is the point with the maximum gradient in the curve.

[0014] Alternatively, the wavelength at the point of maximum gradient is calculated as follows : ; where m∈[ ], take any value for m and get the wavelength , The initial phase.

[0015] Optionally, using wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding points are the extreme points in the curve.

[0016] Optionally, the wavelength is calculated as follows : ; where m∈[ ], take any value for m to get the wavelength , The initial phase.

[0017] Optionally, the wavelength With wavelength The ratio of the two is not equal and is within a preset ratio range.

[0018] Optionally, the preset ratio range is 1.2~1.5.

[0019] Optionally, using the target wafer film thickness The corresponding reflectivity and the corresponding relationship curve monitor whether the thickness of the wafer film reaches the target wafer film thickness ,include: At least real-time acquisition of the wavelength of the wafer film surface and wavelength The reflectivity r1 and reflectivity r2 of the reflected light; By real-time monitoring of whether the reflectivity r1 at the current moment meets the wavelength Target wafer film thickness The corresponding reflectivity, and whether the reflectivity r2 is consistent with the wavelength Target wafer film thickness The corresponding reflectivity is used to determine whether the target wafer film thickness is reached. .

[0020] Accordingly, the present application provides a multi-beam based endpoint detection device, comprising: a processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor executes the above-mentioned multi-beam based endpoint detection method.

[0021] The present application also provides a chemical mechanical polishing device for performing chemical mechanical polishing on a wafer and executing the above-mentioned multi-beam-based endpoint detection method during the grinding process.

[0022] The endpoint detection method and device provided in the present application use multiple wavelength light beams for endpoint detection, and determine the wavelength of at least one incident light beam among the multiple light beams used based on the grinding endpoint thickness, ensuring that the grinding endpoint thickness in the corresponding relationship curve between the wafer film thickness and the reflectivity corresponding to the light beam is at or near the maximum gradient point, so as to improve the sensitivity of the endpoint detection.

[0023] In another technical solution of the present application, while solving the multiple solution problem of measuring film thickness by a single wavelength method, the relationship between multiple wavelengths is further determined, thereby improving the accuracy of measurement.

[0024] The technical solution of the present application is also applicable to the precise measurement of the thickness of single-layer films and multi-layer films. When measuring, the incident light beam enters the wafer surface after passing through only the air medium, which is the film thickness measurement of a single-layer film. When measuring, the incident light beam not only passes through the air medium, but also passes through glass, water or other light-transmitting media before entering the wafer surface, which is the film thickness measurement of a multi-layer film. Since the operation of the wavelength determined by this solution is not affected by the above-mentioned media, it can be applied to the precise measurement of the thickness of single-layer films and multi-layer films. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a flow chart of a multi-beam based endpoint detection method in an embodiment of the present invention; Figure 2 is the wavelength in the embodiment of the present invention The corresponding relationship curve between wafer film thickness and reflectivity is established; Figure 3 Schematic diagram of the film thickness detection principle based on a single-wavelength light beam in an embodiment of the present invention; Figure 4 A corresponding relationship curve between wafer film thickness and reflectivity established for two light beams in an embodiment of the present invention; Figure 5 A schematic diagram of a wavelength value range in an embodiment of the present invention; Figure 6 FIG. 4 is a schematic diagram of another wavelength value range in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] like Figure 1As shown, an embodiment of the present invention provides a method for endpoint detection based on multiple light beams, which is executed by an electronic device such as a computer or a server, and includes the following operations: S1, using the target wafer film thickness corresponding to the wafer grinding end point , the refractive index of the wafer film , the incident angle of the light beam Calculate the wavelength of any incident beam in a multi-beam The wafer film can be silicon dioxide, silicon carbide, etc. Incident angle The value range of is (0, 90°), preferably (0, 30°).

[0030] According to the principles of thin film optics, in an air environment, there is the following relationship between the film thickness and reflectivity of the wafer: ; Where R represents the reflectivity of the wafer, A, B and are coefficients related to the refractive index of the wafer surface material and can be obtained by substituting relevant parameters. . is the film refractive index, represents the film thickness, is the wavelength of incident light, Represents the incident angle of the light beam.

[0031] It can be seen from the above formula that in the measurement environment of a single-layer film or a multi-layer film, the corresponding relationship curve between the film thickness and the reflectivity changes periodically.

[0032] S2, at least using wavelength and wavelength The corresponding relationship curves between wafer film thickness and reflectivity are established respectively, where the reflectivity changes periodically with thickness and the wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding point is within a predetermined range in the curve.

[0033] Specifically, a mathematical model can be used to establish a corresponding relationship curve between thickness and reflectivity. Given different thickness values, the mathematical model can be used to calculate the corresponding reflectivity. It is a fixed parameter in the mathematical model and one of the factors affecting the curve. In step S1, the thickness is used Calculated wavelength Based on wavelength In the obtained curve, the thickness Located within the above range.

[0034] Figure 2 To use wavelength The corresponding relationship curve between wafer film thickness and reflectivity is established, where the horizontal axis is the wafer film thickness d and the vertical axis is the reflectivity R. The curve shows a periodic law, that is, the reflectivity shows a periodic change with the thickness. Near the peak of the curve, the reflectivity R has a small change rate with the thickness of the wafer film. The sensitivity of the film thickness measurement is very low here, so the target wafer film thickness It should be far away from the extreme points; at the midpoint between the two extreme values, the reflectivity R has the largest thickness change rate for the wafer film to be measured, and the sensitivity of the film thickness measurement is very high here.

[0035] Taking a cycle as an example, there is a maximum point and a minimum point, so the purpose of this embodiment is to set a suitable wavelength so that the target wafer film thickness The corresponding point is far away from the extreme point, and the closer it is to the maximum gradient point of the curve, the better the measurement effect is. For example, it can be within the range of wafer film thickness corresponding to the reflectivity R1~R2.

[0036] S3, during the wafer grinding process, will contain wavelength and wavelength At least two light beams are irradiated onto the wafer film surface, and the wafer film thickness is The corresponding reflectivity and corresponding relationship curve monitor whether the thickness of the wafer film reaches the target wafer film thickness .

[0037] like Figure 3 As shown in the figure, regarding the principle of single wavelength film thickness measurement, the light beam is emitted to the plane reflector 1, and the plane reflector 1 can be adjusted so that the light beam is incident at an angle of The light is incident on the surface of the wafer (the wafer includes a wafer substrate 3 and a wafer film 2), and the reflected light of the wafer film 2 is received by the photodiode 4 and converted into a current signal and input into the signal processing circuit. The photocurrent is converted into a voltage signal by a current-voltage (IV) conversion circuit, the voltage signal is amplified and filtered, and then the amplified and filtered voltage signal is AD converted to obtain a voltage value, and the reflectivity value can be obtained according to the voltage value.

[0038] The thickness of the wafer film can be obtained by matching the reflectivity value with the above correspondence curve. Due to the periodic characteristics, the measurement result corresponding to the single wavelength light beam is multiple periodic thickness values.

[0039] Based on the above principle, endpoint detection is performed. For example, during the grinding process of the wafer for CMP treatment, the thickness of the wafer film gradually decreases, and the target wafer film thickness This is the end point of grinding. The incident light is set for the grinding end point, so at least the wavelength The measurement results corresponding to the incident light can accurately detect that the thickness of the wafer film reaches the target wafer film thickness. At the same time, due to the wavelength With wavelength Different, so that the same target wafer film thickness , the corresponding reflectances in the thickness and reflectance correspondence curves established based on the two wavelengths are different. In one case, when the reflectances of the two beams reach the corresponding curves at the same time When the corresponding reflectivity reaches the grinding end point.

[0040] According to the above content, when the film thickness value at the polishing end point is at the maximum value of the gradient, the sensitivity is the highest; when it is at the extreme point, the sensitivity is the lowest. Therefore, in order to improve the measurement accuracy, it is necessary to ensure that at least one of the wavelengths corresponding to the polishing end point is near the maximum value of the gradient, so that the wavelength selection can be determined according to the polishing end point.

[0041] Further, in one embodiment, step S3 includes: S31, at least respectively collect the wavelength of the wafer film surface in real time and wavelength The reflectivity r1 and reflectivity r2 of the reflected light; S32, by real-time monitoring whether the reflectivity r1 at the current moment meets the wavelength Target wafer film thickness The corresponding reflectivity, and whether the reflectivity r2 is consistent with the wavelength Target wafer film thickness The corresponding reflectivity is used to determine whether the target wafer film thickness is reached. .

[0042] by Figure 4 For example, based on wavelength and wavelength The corresponding relationship curve between wafer film thickness and reflectivity is established, with the horizontal axis being the wafer film thickness and the vertical axis being the reflectivity. In the curve, the target wafer film thickness is d12, and the corresponding reflectivity is r1; wavelength In the curve, the target wafer film thickness is d22, and the corresponding reflectivity is r2, d12=d22. During the polishing process, the thickness of the wafer film changes, causing the reflectivity to change accordingly. The reflectivity of the light beam is r1, and at the same time, the reflectivity of the wafer film surface to the wavelength If the reflectivity of the light beam is r2, it can be determined that the target wafer film thickness (polishing end point) may have been reached at that moment.

[0043] About the wavelength of another beam , in order to ensure the target wafer film thickness For wavelength and wavelength The only solution is, in the preferred embodiment, the wavelength With wavelength The ratio of the two is not equal and is within a preset ratio range.

[0044] For multiple incident beams, the wavelength of one of the incident beams can be determined first. , and then select another with wavelength according to the above preset ratio In addition, there may be more incident light beams, and the wavelengths of the other incident light beams may be in accordance with the above-mentioned preset proportional relationship between each other, or may be respectively proportional to the wavelength It complies with the above preset proportional relationship.

[0045] As a preferred embodiment, the preset ratio range of the wavelength values ​​of the two beams of light is 1.2 to 1.5. or . Since the polishing endpoint detection module matches the measured voltage and reflectivity, and determines the film thickness value through the reflectivity. Due to the influence of signal noise and circuit resolution, the voltage fluctuation value of the existing measuring equipment is conservatively estimated to be within 4mV. At this time, the corresponding reflectivity fluctuation value is 0.02. Therefore, within the measurement range, when the reflectivity deviations corresponding to different wavelengths under the two film thicknesses are less than 0.02, the measurement system cannot distinguish the accurate film thickness value. Through traversal calculation, it is found that when the ratio of the two wavelengths is between 1.2 and 1.5, a unique solution can be obtained in the range of 0-1000nm.

[0046] Specifically, at least two light beams are used to measure the multiple solutions of the measurement results. However, when the wavelengths of the two light beams are too close, such as Take 610nm, wavelength Take 630nm, ignore the incident angle, and the wavelength is The corresponding period is 210nm, the wavelength The corresponding period is 216nm. At this time, within the film thickness range of 0-500nm, the film thickness-reflectivity change trends at different wavelengths are basically the same. The voltage values ​​of the two wavelengths corresponding to some different film thickness values ​​are very close. Coupled with the influence of signal noise and circuit resolution, it is easy to cause the measurement results to be unrecognizable, or the existing acquisition equipment may not be able to detect the difference in reflectivity, resulting in unrecognizable measurement results. For example, the reflectivity values ​​of the two wavelengths at a film thickness of 103nm are 18.55 and 18.37 respectively, and the reflectivity values ​​of the two wavelengths at a film thickness of 313nm are 18.55 and 18.39. Therefore, in this case, the two film thickness values ​​are likely to correspond to the same measurement result, and it is impossible to identify which film thickness value it is.

[0047] When the wavelengths of the two beams differ greatly, especially when the wavelengths are multiples, such as Take 340nm, wavelength Take 680nm, ignore the incident angle, and the wavelength is The corresponding period is 117nm, the wavelength The corresponding period is 234nm, and the lowest common multiple of the period is 234nm. Therefore, the thickness value will have the same solution every 234nm, that is, the measured reflectivity of the two beams at multiple moments meets the reflectivity r1 and reflectivity r2, but only one moment of these moments actually reaches the target wafer film thickness. Therefore, other means are needed to distinguish the moment when the polishing ends.

[0048] In some embodiments, if the wavelength and wavelength When the value of causes the polishing endpoint thickness values ​​to appear at multiple moments during the measurement process, the actual polishing endpoint can be determined based on the period corresponding to any wavelength, the predicted initial film thickness, and the target thickness. Specifically, for example, if the wavelength is known The corresponding cycle is T, the initial thickness of the wafer film is d0, and the target thickness (polishing end point) is d1. Then d0-d1 can be calculated to get the thickness difference, and then it can be determined how many cycles (number of cycles) are required from the initial thickness to reach the target thickness. During the measurement, the change cycle of the reflectivity is counted. When the polishing end point thickness value d1 is detected at a certain moment, it is determined whether the current cycle count reaches the cycle number. If it does not reach the cycle number, d1 has not been reached at the current moment. Until the polishing end point thickness value d1 is detected at a certain moment and the cycle count reaches the above cycle number, it is determined that d1 has actually been reached at this moment.

[0049] In addition to the above-mentioned embodiment, it is also possible to detect that the reflectivity r1 at a certain time corresponds to the wavelength Target wafer film thickness The corresponding reflectivity, and at the same time the reflectivity r2 conforms to the wavelength Target wafer film thickness When the reflectivity is equal to the corresponding reflectivity, polishing is stopped and offline detection is used to verify whether the current thickness is d1; alternatively, it is also possible to ensure that the difference between the current thickness and the target thickness is less than one cycle before using the multi-beam measurement method for measurement.

[0050] The above judgment methods are only examples for some specific application scenarios. In actual applications, other methods can be used to solve the above multiple solution problems according to different application scenarios.

[0051] when When , R is at the maximum gradient position; when When R has an extreme value, the appropriate incident light wavelength can be optimized. , so that a more obvious and stable signal can be obtained during the measurement process.

[0052] In one embodiment, the wavelength The predetermined range is the range of T15 / 12 extending forward and backward from the maximum gradient point in the curve as the midpoint, T1 is the wavelength The period of the corresponding relationship curve.

[0053] Specifically, according to the measurement accuracy of the existing measurement equipment for electrical signals, when the target wafer film thickness is When the reflectivity is within T1 / 12 before and after the extreme point of the corresponding curve, the change rate of the corresponding electrical signal will be reduced to a few millivolts because the change rate of the reflectivity in this range is too small. The existing measurement accuracy is difficult to distinguish the change of a few millivolts, so there will be recognition errors, or although the actual thickness has changed, the electrical signal collection result has not changed. Therefore, only when the wavelength is determined, the target wafer film thickness is deliberately avoided. The measurement accuracy can be improved by placing it T1 / 12 before and after the extreme point, that is, the point with the maximum gradient in the curve is within the range of T15 / 12 extending forward and backward from the middle point.

[0054] Further, in step S1, the wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], is the initial phase, and m is taken as an arbitrary value through Get wavelength For example, if m is 0 and get The upper limit of m is 0 and get The lower limit of the wavelength is obtained Similarly, m can be 1, 2, ..., n to obtain the corresponding value range.

[0055] Then at the wavelength Choose a value from the range of values ​​to get the wavelength When the wafer film thickness reaches When, wavelength The measurement result obtained by the light beam is located at a relatively large rate of change in the corresponding curve, thereby ensuring the accuracy of the end point detection.

[0056] In one embodiment, the wavelength The predetermined range is the range of T1 / 12 extending forward and backward from the maximum gradient point in the curve as the midpoint, where T1 is the wavelength The period of the corresponding relationship curve.

[0057] As mentioned above, due to the influence of the repeatability measurement error of the voltage signal, when the difference in reflectivity is less than 0.02 (i.e., the difference in voltage is less than 4mV), the film thickness value is difficult to distinguish. Therefore, the points with a reflectivity difference of less than 0.02 under adjacent 1nm can be set as points near the extreme point. The range of this number of points is 1 / 12 of the period extending before and after the extreme point; and at the maximum gradient, the difference in reflectivity is 0.07 (i.e., 28mV), at which time the sensitivity of the film thickness is the greatest. Therefore, the points with a reflectivity difference of more than 0.06 under adjacent 1nm can be set as points near the maximum gradient, and the number of points is 1 / 12 of the period extending before and after the maximum gradient point.

[0058] like Figure 5 As shown, taking one cycle as an example, the wavelength Make the target wafer film thickness Located between the thickness d5 and the thickness d6, the size of this range is 1 / 6 of the curve period T1.

[0059] In the predetermined range of the curve of this embodiment, the change rate of the thickness value with the reflectivity value is large enough to change the wafer film thickness to Within this range, the target wafer film thickness The detection is sensitive enough.

[0060] Further, in step S1, the wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], is the initial phase, and m is taken as an arbitrary value through Get wavelength For example, if m is 0 and get The upper limit of m is 0 and get The lower limit of the wavelength is obtained Similarly, m can be 1, 2, ..., n to obtain the corresponding value range.

[0061] Then at the wavelength Choose a value from the range of values ​​to get the wavelength When the wafer film thickness reaches When, wavelength The measurement result obtained by the light beam is located at a relatively large rate of change in the corresponding curve, thereby ensuring the accuracy of the end point detection.

[0062] About the wavelength of another beam , in this embodiment, the wavelength The value range is T2 / 12, which is the range extending forward and backward from the extreme point in the curve as the midpoint, where T2 is the wavelength The period of the corresponding relationship curve.

[0063] like Figure 6 As shown, taking one cycle as an example, the wavelength Make the target wafer film thickness Located between the thickness d3 and the thickness d4, the size of this range is 1 / 6 of the curve period T2.

[0064] Further, the wavelength can be determined as follows : ; Among them, m∈[ ], take values ​​for m, and pass and Get wavelength The value range of is the initial phase. As an example, m can be 0 and ,get The upper limit of m is 1 and ,get The lower limit of Similarly, m can be set to 1…n to obtain the corresponding value range. Then in the wavelength Choose a value from the range of values ​​to get the wavelength .

[0065] According to wavelength When the wafer film thickness is When the phase difference is a certain amount, the wavelength The measurement results obtained by the beam are located at a relatively large rate of change in the corresponding curve, which can ensure that the wafer film thickness and When the difference is a certain amount, the measurement value of at least one beam has a higher accuracy.

[0066] In this embodiment, the target wafer film thickness is defined in the film thickness-reflectivity curve. The wavelength is calculated accurately based on the range of corresponding points and wavelength The value range of can not only avoid the area with small reflectivity change, but also obtain a more stable relationship between reflectivity and wafer film thickness in the area with more sensitive reflectivity change, thereby significantly improving the accuracy and reliability of wafer endpoint detection.

[0067] In one embodiment, the wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding point is the point with the maximum gradient in the curve, that is, the midpoint between two adjacent maximum and minimum points in the corresponding relationship curve.

[0068] In this embodiment, the point in the curve where the thickness value has the largest change rate with the reflectivity value is taken as the target wafer film thickness. , thereby significantly improving the accuracy and reliability of wafer endpoint detection.

[0069] Furthermore, in step S1, the wavelength at the maximum gradient point is calculated as follows: : ; Among them, m∈[ ], take any value for m and get the wavelength , The initial phase.

[0070] At the same time, using wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding points are the extreme points in the curve.

[0071] Furthermore, the wavelength is calculated as follows: : ; where m∈[ ], and the wavelength can be obtained by taking any value of m , The initial phase.

[0072] In the technical solution of the present application, the selection of wavelength is only related to the parameters of the film to be measured itself, and has nothing to do with the medium between the film to be measured and the incident light beam. That is, the technical solution of the present application can realize accurate measurement of the endpoint detection of the thickness of single-layer films and multi-layer films.

[0073] As an example, suppose the target wafer film thickness corresponding to the wafer grinding end point is =200nm, let =0; when m=2, the incident angle is ignored, The range is 537.6-635.3nm, which can make Located near the maximum gradient point in the curve, preferably 582.4nm (the position of the maximum gradient point); when m=2, the incident angle is ignored, The range is 436.8-499.2nm, which can make Located near the extreme point in the curve, preferably 465.9nm (extreme point position). This ensures that the film thickness at at least one wavelength near the polishing end point is sensitive to the change in reflectivity, thereby further improving the accuracy of end point detection.

[0074] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0075] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0076] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0077] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0078] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A multi-beam endpoint detection method, characterized in that: include: Target wafer film thickness corresponding to the wafer grinding end point , the refractive index of the wafer film , the incident angle of the light beam Calculate the wavelength of any incident beam in a multi-beam ; At least using wavelength and wavelength The corresponding relationship curves between wafer film thickness and reflectivity are established respectively, where the reflectivity changes periodically with thickness and the wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding point is within a predetermined range in the curve; During the wafer grinding process, the wavelength and wavelength At least two light beams are irradiated onto the wafer film surface, and the target wafer film thickness is determined by using the target wafer film thickness. The corresponding reflectivity and the corresponding relationship curve monitor whether the thickness of the wafer film reaches the target wafer film thickness .

2. The method according to claim 1, characterized in that The predetermined range is a range extending forward and backward by T15 / 12 from the maximum gradient point in the curve as the midpoint, where T1 is the wavelength The period of the corresponding relationship curve.

3. The method according to claim 2, characterized in that Determine the wavelength of any incident beam in the multi-beam include: The wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], is the initial phase, and m is taken as an arbitrary value through Get wavelength The value range of In wavelength Choose a value from the range of values ​​to get the wavelength .

4. The method according to claim 2, characterized in that: The predetermined range is a range extending forward and backward by T1 / 12 with the maximum gradient point in the curve as the midpoint.

5. The method according to claim 4, characterized in that Determine the wavelength of any incident beam in the multi-beam include: The wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], is the initial phase, and m is taken as an arbitrary value through Get wavelength The value range of In wavelength Choose a value from the range of values ​​to get the wavelength .

6. The method according to any one of claims 2 to 5, characterized in that: wavelength The value range is T2 / 12, which is the range extending forward and backward from the extreme point in the curve as the midpoint, where T2 is the wavelength The period of the corresponding relationship curve.

7. The method according to claim 6, characterized in that It also includes determining the wavelength as follows : The wavelength is calculated as follows The value range of is: ; Among them, m∈[ ], take any value for m and pass Get wavelength The value range of is the initial phase; In wavelength Choose a value from the range of values ​​to get the wavelength .

8. The method according to claim 1, characterized in that Using wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding point is the point with the maximum gradient in the curve.

9. The method according to claim 8, characterized in that The wavelength at the point where the gradient is maximum is calculated as follows : ; where m∈[ ], take any value for m and get the wavelength , The initial phase.

10. The method according to claim 6, characterized in that Using wavelength The target wafer film thickness in the established corresponding relationship curve The corresponding points are the extreme points in the curve.

11. The method according to claim 10, characterized in that It also includes the calculation of wavelength as follows : ; where m∈[ ], take any value for m to get the wavelength , The initial phase.

12. The method according to claim 1, characterized in that wavelength With wavelength The ratio of the two is not equal and is within a preset ratio range.

13. The method according to claim 12, characterized in that The preset ratio range is 1.2~1.

5.

14. The method according to claim 1, characterized in that Using the target wafer film thickness The corresponding reflectivity and the corresponding relationship curve monitor whether the thickness of the wafer film reaches the target wafer film thickness ,include: At least real-time acquisition of the wavelength of the wafer film surface and wavelength The reflectivity r1 and reflectivity r2 of the reflected light; By real-time monitoring of whether the reflectivity r1 at the current moment meets the wavelength Target wafer film thickness The corresponding reflectivity, and whether the reflectivity r2 is consistent with the wavelength Target wafer film thickness The corresponding reflectivity is used to determine whether the target wafer film thickness is reached. .

15. An endpoint detection device based on multiple light beams, characterized in that: include: A processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor executes the multi-beam based endpoint detection method as described in any one of claims 1-14.

16. A chemical mechanical polishing device, characterized in that: Used to perform chemical mechanical polishing on a wafer, and to execute the multi-beam based endpoint detection method described in any one of claims 1 to 14 during the grinding process.

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