Method and system for detecting the depth of a surface damage layer of a silicon wafer

Abstract

The present disclosure relates to a method and system for detecting a damage layer depth of a silicon wafer surface, the method comprising cleaving the silicon wafer in a diametrical direction to obtain a semi-circular silicon wafer portion, irradiating a side portion of the cleaved surface of the silicon wafer portion adjacent to a diametrical edge with a laser beam, photographing the irradiated portion in a reflection direction in which the laser beam is reflected via the irradiated portion, and analyzing an image formed by the photographing to obtain the damage layer depth of the silicon wafer surface at the portion. By the method and system, the detection cost is reduced and the detection time is shortened.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor processing and manufacturing technology, and more specifically, to a method and system for detecting the depth of a damage layer on a silicon wafer surface. Background Technology

[0002] During silicon wafer manufacturing, machining processes such as tumbling, slicing, grinding, and polishing inevitably introduce mechanical damage to the wafer surface. This mechanical damage disrupts the original monocrystalline layer, and if not removed promptly, it can adversely affect the quality of products produced by subsequent processing. Therefore, it is necessary to accurately measure the depth of the mechanical damage in order to determine parameters such as the amount of material removed during subsequent processes.

[0003] Given that the depth of such mechanical damage is relatively small, it is difficult to accurately detect its specific depth directly using existing equipment such as microscopes and infrared spectrometers. Currently, methods such as "angle polishing" are often used for detection. In angle polishing, the silicon wafer is first split into multiple pieces along its cleavage direction to serve as measurement samples. Then, the measurement samples are angle polished at an angle to form a bevel, and an etching solution is used to etch the bevel so that the surface damage of the silicon wafer can be better displayed on the bevel. Here, angle polishing acts as an "amplifier." By measuring the length of the damage on the bevel using a microscope and multiplying it by the sine of the polishing angle, the depth of the damaged layer can be determined.

[0004] However, the aforementioned "angle polishing method" requires the silicon wafer to be split into multiple small samples before subsequent testing. Furthermore, the samples must be erected, polished, and etched during testing, which makes the testing destructive and results in higher costs. The entire process is also quite complex, leading to a longer testing time. This makes it difficult to promptly feed the test results back to the production front end so that product quality can be adjusted based on the test results. Summary of the Invention

[0005] This section provides a general overview of this disclosure, rather than a full disclosure of the entire scope or all features of this disclosure.

[0006] One object of this disclosure is to provide a method for detecting the depth of damage layers on the surface of silicon wafers that can reduce detection costs.

[0007] Another object of this disclosure is to provide a method for detecting the depth of a damage layer on a silicon wafer surface that can shorten the detection time.

[0008] To achieve one or more of the above objectives, according to one aspect of this disclosure, a method for detecting the depth of a damage layer on a silicon wafer surface is provided, comprising:

[0009] The silicon wafer is cleaved along the diameter to obtain a semi-circular portion of the silicon wafer;

[0010] The side of the cleavage surface of a silicon wafer is irradiated with a laser beam near the diameter edge.

[0011] The image is taken of the irradiated area in the direction of reflection of the laser beam from the irradiated area on the side; and

[0012] The captured images are analyzed to determine the depth of the damage layer on the surface of the silicon wafer at that location.

[0013] In the above-described method for detecting the depth of the damage layer on the surface of a silicon wafer, irradiating the side of the cleavage surface of a portion of the silicon wafer with a laser beam may include irradiating the portion with a laser beam in a direction perpendicular to the cleavage surface.

[0014] In the above-described method for detecting the depth of the damage layer on the surface of a silicon wafer, irradiating the side portion of the cleavage surface of the silicon wafer portion with a laser beam may include irradiating multiple portions of the side portion with a laser beam.

[0015] In the above-described method for detecting the depth of the damage layer on the surface of a silicon wafer, the plurality of locations can be symmetrically distributed relative to the center of the silicon wafer portion.

[0016] In the above-described method for detecting the depth of the damage layer on the surface of a silicon wafer, the laser beam can move relative to the cleavage surface in a direction parallel to the diameter edge, so that the laser beam can irradiate the entire side.

[0017] In the aforementioned method for detecting the depth of the damage layer on the surface of a silicon wafer, cleaving the silicon wafer along the diameter direction can include cleaving along the crystal orientation in the diameter direction. <110> The silicon wafer is cleaved.

[0018] In the above-mentioned method for detecting the depth of the damage layer on the surface of a silicon wafer, cleaving the silicon wafer along the diameter direction may include blowing nitrogen gas onto the cleaving surface during the cleaving process to prevent impurities from adhering to the cleaving surface.

[0019] In the above-described method for detecting the depth of the damage layer on the surface of a silicon wafer, the laser beam can be focused into a spot that appears as a micrometer-sized spot when irradiating the side.

[0020] According to another aspect of this disclosure, a system for detecting the depth of a damage layer on a silicon wafer surface is provided, comprising:

[0021] A cleaving unit, used to cleave a silicon wafer along the diametrical direction to obtain a semi-circular silicon wafer portion;

[0022] An irradiation unit is used to irradiate the side of the cleavage surface of a silicon wafer portion adjacent to the diameter edge using a laser beam;

[0023] A shooting unit, used to capture images of the irradiated area in the reflection direction of the laser beam reflected from the irradiated area on the side; and

[0024] The processing unit is used to analyze the captured image to obtain the depth of the damage layer on the surface of the silicon wafer at that location.

[0025] The system described above for detecting the depth of the damage layer on the surface of a silicon wafer may further include a moving unit for enabling the irradiation unit and the imaging unit to move synchronously relative to the cleavage surface in a direction parallel to the diameter edge.

[0026] According to the detection method disclosed herein, the depth of the damage layer on the silicon wafer surface is determined by irradiating the cleavage surface of a semi-circular silicon wafer portion with a laser beam and identifying the bright and dark areas. This method only requires splitting the silicon wafer into two semi-circular portions and selecting one for detection, eliminating the need to cleave the wafer into many small pieces, thus reducing damage to the silicon wafer. Furthermore, the other semi-circular portion can be recycled, further reducing detection costs. In addition, the detection method of this disclosure uses relatively fewer cleavage procedures, eliminating the need for polishing, etching, and other operations, thus simplifying the entire process, shortening the detection time, and enabling multi-location detection without further cleavage, further reducing detection time. This facilitates timely feedback of detection results to the production front end for product quality adjustments based on the results.

[0027] The above-described features and advantages, as well as other features and advantages, of this disclosure will become clearer from the following detailed description of exemplary embodiments of the disclosure in conjunction with the accompanying drawings. Attached Figure Description

[0028] Figure 1 This is a flowchart of a method for detecting the depth of a damage layer on a silicon wafer surface according to an embodiment of the present disclosure;

[0029] Figure 2 The silicon wafer to be inspected is schematically shown in a top view, where the cleavage direction is indicated by dashed lines;

[0030] Figure 3 A three-dimensional diagram schematically illustrates a semi-circular silicon wafer portion obtained through cleavage;

[0031] Figure 4 The principle of detecting the depth of the damage layer on the surface of a silicon wafer is illustrated schematically.

[0032] Figure 5 The schematic diagram illustrates the detection process when a laser beam is irradiated in a direction perpendicular to the cleavage plane; and

[0033] Figure 6 This is a top view of the cleavage plane, which schematically shows the surface damage of the silicon wafer reflected on the cleavage plane. Detailed Implementation

[0034] The present disclosure will now be described in detail with reference to the accompanying drawings and exemplary embodiments. It should be noted that the following detailed description of the present disclosure is for illustrative purposes only and is not intended to limit the scope of the disclosure.

[0035] Currently, the "angle polishing method" is frequently used to measure the depth of damage layers on silicon wafer surfaces. However, as mentioned earlier, this method requires cleaving the silicon wafer into numerous small samples, severely damaging the wafer and making recycling difficult, resulting in high testing costs. Furthermore, angle polishing testing of small samples requires vertical mounting, polishing, and etching, making the process complex and time-consuming. When performing multi-location testing, the overall testing time is even longer, hindering timely feedback of results to the production line for product quality adjustments.

[0036] Therefore, referring to Figures 1 to 6 According to one aspect of this disclosure, a method for detecting the depth of a damage layer on a silicon wafer surface is provided, comprising:

[0037] The silicon wafer 1 is cleaved along the diameter direction to obtain a semi-circular silicon wafer portion 2;

[0038] The side portion 21a of the adjacent diameter edge 10 of the cleavage surface 21 of the silicon wafer portion 2 is irradiated using a laser beam 3;

[0039] The laser beam 3 is photographed in the direction of reflection of the irradiated portion A via the side portion 21a; and

[0040] The depth of the damage layer at location A on the surface 11 of the silicon wafer 1 is obtained by analyzing the captured image.

[0041] It is worth noting that when a laser beam is used to irradiate the surface of a silicon wafer, for an undamaged or ideal silicon wafer surface, the laser beam will be completely reflected, meaning that reflected light will only be generated in the direction of reflection. In this case, when viewed from the direction of reflection, the irradiated area will appear completely bright. However, when there is damage to the surface, because the damage causes a sudden change in the surface refractive index, when the laser beam irradiates the damaged area, the damage will induce scattered light, and the laser will not be completely reflected. That is, in addition to being reflected in the direction of reflection, reflected light will also be generated in other directions. Therefore, when viewed from the direction of reflection, the irradiated area will not appear completely bright; instead, the brightness of the damaged area will be darker. In this way, the location of the damage can be identified based on the position of the relatively darker area.

[0042] To measure the depth of the damage layer on the silicon wafer surface, the present disclosure further involves cleaving the silicon wafer to obtain a semi-circular wafer portion. This allows the surface damage to be exposed on the cleavage surface in its extension direction perpendicular to the wafer surface, such as... Figure 6 As shown by the short line extending downwards from the diameter side 10, the depth of the damage layer can be determined by irradiating the side of the cleavage surface adjacent to the diameter side where the damage is located in the extension direction with a laser beam, based on the change in brightness at the irradiated area. In other words, when the cleavage surface is irradiated with a laser beam, the laser beam will irradiate the entire length of the damage in the extension direction. Since the damaged area is darker than the undamaged area, the depth of the damage layer on the silicon wafer surface at the irradiated area can be obtained based on the length of the dark area.

[0043] In this method, only two semi-circular wafer portions need to be split into two, and one portion needs to be inspected, without having to dissect the wafer into many smaller pieces. This reduces damage to the wafer, and the other semi-circular wafer portion can be recycled, further reducing inspection costs. Furthermore, the inspection method disclosed herein uses fewer dissecting procedures, eliminating the need for polishing, etching, and other operations. Therefore, the entire process is simpler, the inspection time is shorter, and multi-location inspection can be performed without further dissecting, further shortening the inspection time. This facilitates timely feedback of inspection results to the production line for adjustments to product quality.

[0044] Specifically, in the detection method disclosed herein, such as Figure 2 and Figure 3As shown, silicon wafer 1 is cleaved into two semi-circular silicon wafer portions 2 along the diameter direction indicated by dashed lines, and either of these two semi-circular silicon wafer portions 2 can be selected as the object of inspection. As mentioned above, obtaining the cleavage surface 21 through cleavage exposes silicon wafer surface damage in its extension direction perpendicular to the silicon wafer surface, thereby allowing the depth of the damage layer in this extension direction to be detected by the inspection method of this disclosure.

[0045] It should be noted that no heat treatment or oxidation treatment is performed on silicon wafer 1 in this detection method. The detection method disclosed herein targets surface damage of silicon wafers, while heat treatment or oxidation treatment will cause defects inside the silicon wafer to nucleate and grow. This will cause internal defects and surface defects to appear simultaneously, making it difficult to distinguish surface damage and seriously affecting the detection of the depth of the surface damage layer of the silicon wafer.

[0046] It can be imagined that, due to crystal orientation <110> The silicon wafer 1 has fewer dislocations, making cleavage along this crystal direction less prone to problems such as fragmentation. Therefore, cleaving the silicon wafer 1 along the diameter direction can include cleaving along the crystal direction in the diameter direction. <110> The silicon wafer 1 is cleaved.

[0047] In addition, nitrogen gas can be blown onto the cleavage surface 21 during the cleavage process, which can prevent impurities from adhering to the cleavage surface 21 and thus adversely affecting subsequent laser beam irradiation detection.

[0048] In the detection method disclosed herein, such as Figure 4 As shown, a laser beam 3 can be generated using, for example, an irradiation unit 100 of a laser. The laser beam 3 irradiates the cleavage surface 21 in the plane in which the silicon wafer portion 2 is located. The laser beam 3 can be incident at a certain angle relative to the cleavage surface 21, and the imaging unit 200 of, for example, an optical imaging device can be used to image the portion A irradiated by the laser beam 3 in the reflection direction. Thus, the thickness of the damage layer on the surface of the silicon wafer 1 can be detected.

[0049] Understandably, this angle can be any angle greater than 0 and less than 180°, as long as it can illuminate the cleavage surface and be reflected by the illuminated part on it.

[0050] In embodiments of this disclosure, such as Figure 5 As shown, the laser beam 3 can be used to irradiate part A in a direction perpendicular to the cleavage plane 21.

[0051] In this case, an image of the part A irradiated by the laser beam 3 can be captured in the reflection direction, which is also perpendicular to the cleavage plane 21, so that the part A irradiated by the laser beam 3 can be observed from the best angle, so as to more conveniently and accurately determine the depth of the damage layer on the silicon wafer surface.

[0052] In embodiments of this disclosure, a laser beam 3 can be used to irradiate multiple locations on the side 21a of the cleavage surface 21 adjacent to the diameter edge 10. In this way, the depth of the damage layer at multiple locations on the surface of the silicon wafer 1 in the diameter direction can be detected, so as to more accurately assess the damage condition of the silicon wafer surface.

[0053] It is conceivable that the plurality of portions can be symmetrically distributed with respect to the center of the silicon wafer portion 2. Furthermore, the plurality of portions can be equidistantly distributed in the diametrical direction (or cleavage direction), or, as needed, the plurality of portions can be concentrated at the desired detection location. This facilitates obtaining more accurate evaluation results.

[0054] It is also conceivable that the entire side portion 21a can be detected in the cleavage direction according to the above detection method, that is, the multiple parts can be all parts of the side portion 21a in the cleavage direction.

[0055] In this regard, it is conceivable that the laser beam 3 can move relative to the cleavage surface 21 in a direction parallel to the diameter edge 10, so that the laser beam 3 can irradiate the entire side 21a.

[0056] In this regard, on the one hand, the laser beam 3 can be moved relative to the cleavage surface 21 in a direction parallel to the diameter edge 10, so that the entire side portion 21a can be irradiated.

[0057] In this case, it is understandable that as the laser beam 3 moves, the laser beam 3 will irradiate all parts of the side 21a of the cleavage surface 21 in the direction parallel to the diameter edge 10, that is, as it moves, it will irradiate the entire side 21a in the direction (i.e., the cleavage direction). On the other hand, the position for photographing the irradiated part A must also move synchronously with the movement of the laser beam 3 so as to always keep the part A photographed in the reflection direction.

[0058] On the other hand, the cleavage surface 21 can be moved relative to the laser beam 3 in a direction parallel to the diameter side 10, so that the laser beam 3 can irradiate the entire side 21a.

[0059] In this case, the laser beam 3 and the position for photographing the irradiated part A can be fixed, and only the silicon wafer part 2 needs to be moved, that is, the cleavage surface 21 of the silicon wafer part 2 needs to be moved.

[0060] Furthermore, it is conceivable that when the laser beam 3 is incident at a non-right angle relative to the cleavage surface 21, the position of the light source that generates the laser beam 3 can be fixed. It is only necessary to adjust the angle of the laser beam 3 relative to the cleavage surface 21 to irradiate the entire side 21a, and move the position for photographing the irradiated part A so that it is always in the reflection direction.

[0061] In embodiments of this disclosure, the laser beam 3 can be focused such that it forms a micrometer-sized spot when irradiating the side portion 21a.

[0062] Typically, a silicon wafer is 775 μm thick, and the diameter of the laser beam used may be, for example, around 100 μm. The depth of surface damage on the silicon wafer is generally only a few micrometers, or even less than 1 μm. In this case, when the laser beam 3 is used to irradiate part A of side 21, the size of the dark area characterizing the damage depth may also be only a few micrometers, making it difficult to clearly observe and determine the damage depth. In the embodiments of this disclosure, by focusing the laser beam 3 into a micrometer-sized spot, the dark area characterizing the damage depth can be more clearly displayed in the spot, thereby facilitating a clear and accurate determination of the damage depth.

[0063] According to another aspect of this disclosure, a system for detecting the depth of a damage layer on a silicon wafer surface is also provided, comprising:

[0064] A cleaving unit, used to cleave a silicon wafer along the diametrical direction to obtain a semi-circular silicon wafer portion;

[0065] An irradiation unit is used to irradiate the side of the cleavage surface of a silicon wafer portion adjacent to the diameter edge using a laser beam;

[0066] An imaging unit is used to image the irradiated portion in the reflection direction of the laser beam reflected from the irradiated portion on the side; and

[0067] The processing unit is used to analyze the captured image to obtain the depth of the damage layer on the surface of the silicon wafer at that location.

[0068] In embodiments of this disclosure, the system may further include a moving unit for enabling the irradiation unit and the imaging unit to move synchronously relative to the cleavage surface in a direction parallel to the diameter edge.

[0069] In other words, the moving unit allows the irradiation unit and the imaging unit to move relative to the cleavage surface in a direction parallel to the diameter edge, and the movement of the irradiation unit and the imaging unit is synchronous. It is also conceivable that the moving unit can be configured such that the cleavage surface can move relative to the irradiation unit and the imaging unit in a direction parallel to the diameter edge, and the relative positions of the irradiation unit and the imaging unit are fixed.

[0070] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for detecting the depth of a damaged layer on the surface of a silicon wafer, characterized in that, The silicon wafer has not undergone heat treatment or oxidation treatment, and the method includes: The silicon wafer is cleaved along the diameter to obtain a semi-circular portion of the silicon wafer; At least one portion of the side of the cleavage surface of the silicon wafer portion is irradiated with a laser beam adjacent to the diameter edge, the laser beam irradiating the entire length of the damage in the extension direction, and the laser beam forming an incident angle with respect to the cleavage surface. The irradiated portion is photographed in the direction of reflection of the laser beam from the irradiated portion of the side; and The image is analyzed, and the depth of the damage layer on the surface of the silicon wafer at the location is obtained based on the length of the dark area where the brightness is dimmed due to the scattered light caused by the damage at the incident angle.

2. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 1, characterized in that, The step of irradiating the side of the cleavage surface of the silicon wafer portion with a laser beam includes irradiating the portion with the laser beam in a direction perpendicular to the cleavage surface.

3. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 1 or 2, characterized in that, The irradiation of the side portion of the cleavage surface of the silicon wafer portion with a laser beam includes irradiating multiple portions of the side portion with the laser beam.

4. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 3, characterized in that, The plurality of portions are symmetrically distributed with respect to the center of the silicon wafer portion.

5. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 1 or 2, characterized in that, The laser beam can move relative to the cleavage surface in a direction parallel to the diameter edge, so that the laser beam can irradiate the entire side portion.

6. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 1 or 2, characterized in that, The cleaving of the silicon wafer along the diameter direction includes cleaving along the crystal direction in the diameter direction. <110> The silicon wafer is cleaved.

7. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 1 or 2, characterized in that, The cleaving of the silicon wafer along the diameter direction includes blowing nitrogen gas onto the cleaving surface during the cleaving process to prevent impurities from adhering to the cleaving surface.

8. The method for detecting the depth of a damaged layer on a silicon wafer surface according to claim 1 or 2, characterized in that, The laser beam is focused so that it forms a micrometer-sized spot when it illuminates the side.

9. A system for detecting the depth of a damaged layer on the surface of a silicon wafer, characterized in that, The silicon wafer has not undergone heat treatment or oxidation treatment, and the system includes: A cleaving unit, used to cleave a silicon wafer along the diametrical direction to obtain a semi-circular silicon wafer portion; An irradiation unit is used to irradiate at least one portion of the side of the cleavage surface of the silicon wafer portion adjacent to the diameter edge using a laser beam, the laser beam irradiating the entire length of the damage in the extension direction, and the laser beam forming an incident angle relative to the cleavage surface. An imaging unit is configured to image the irradiated portion in the reflection direction of the laser beam reflected from the irradiated portion via the side portion; and The processing unit is used to analyze the image formed by the capture and, based on the length of the dark area whose brightness is dimmed due to the scattered light caused by the damage at the incident angle, obtains the depth of the damage layer on the surface of the silicon wafer at the location.

10. The system for detecting the depth of a damage layer on a silicon wafer surface according to claim 9, characterized in that, It also includes a moving unit for enabling the irradiation unit and the imaging unit to move synchronously relative to the cleavage surface in a direction parallel to the diameter edge.

Images