Method for evaluating a cut ingot

Abstract

The present application provides an evaluation method for cutting a crystal ingot. The evaluation method includes the following steps. A plurality of sampling points are set on a test piece of the crystal ingot. Then, a plurality of observation planes are set. Each observation plane is formed by at least two adjacent sampling points. After that, the average value of the measured values of the sampling points included in each observation plane is calculated. And the observation plane corresponding to the minimum average value is taken as the reference plane for cutting the crystal ingot.

Description

Technical Field

[0001] This invention relates to a semiconductor manufacturing process, and more particularly to an evaluation method for dicing ingots. Background Technology

[0002] In the semiconductor industry, the process of manufacturing wafers involves first forming an ingot, and then slicing the ingot to obtain wafers. The process of slicing the ingot to form wafers directly determines the number of wafers and has a more direct impact on the number of wafers produced in the later stages of semiconductor manufacturing. Therefore, improving the quality of ingot slicing can consequently increase the economic benefits of the semiconductor industry. Summary of the Invention

[0003] This invention relates to an evaluation method for cutting crystal ingots, which can obtain a better infeed reference surface and thus reduce the breakage rate of the slices.

[0004] According to an embodiment of the present invention, an evaluation method for cutting an ingot includes: setting a plurality of sampling points on an inspection piece; setting a plurality of observation surfaces, wherein each observation surface is formed by at least two adjacent sampling points; calculating a first average value of the measured values ​​of the sampling points included in each observation surface, wherein the measured values ​​of the sampling points are obtained by sampling with a measuring instrument; and using the observation surface corresponding to the smallest first average value as a cutting reference surface.

[0005] In the evaluation method for cutting ingots according to an embodiment of the present invention, after taking the observation surface corresponding to the smallest first average value as the cutting reference surface, the method further includes: setting multiple slicing paths for the remaining sampling points that do not constitute the cutting reference surface in a manner parallel to the cutting reference surface; calculating a second average value of the measured values ​​of the sampling points included in each slicing path; and determining multiple slicing parameters corresponding to each slicing path based on the second average value of each slicing path.

[0006] In the evaluation method for dicing ingots according to an embodiment of the present invention, the step of determining the dicing parameters corresponding to each dicing path based on the second average value of each dicing path includes: obtaining a reference index corresponding to each dicing path based on the second average value of each dicing path; and obtaining the dicing parameters corresponding to each dicing path based on the reference index of each dicing path.

[0007] In the evaluation method for cutting ingots according to an embodiment of the present invention, the slicing parameters include wire cutting speed, roller oscillation angle, roller speed, and ingot movement speed.

[0008] In an evaluation method for cutting an ingot according to an embodiment of the present invention, the step of setting the observation surface includes: setting the observation surface in an annular region located on the test piece, wherein the inner radius of the annular region is 60% of the radius of the test piece, and the outer radius of the annular region is 99% of the radius of the test piece.

[0009] In an evaluation method for cutting an ingot according to an embodiment of the present invention, the step of setting the observation surface includes: setting the observation surface in an annular region located on the test piece, wherein the inner radius of the annular region is 75% of the radius of the test piece, and the outer radius of the annular region is 85% of the radius of the test piece.

[0010] In the evaluation method for cutting ingots according to an embodiment of the present invention, the step of setting the observation surface includes: setting the observation surface on the circumference of the test piece, wherein the distance from the circumference to the center point of the test piece is 80% of the radius of the test piece.

[0011] In the evaluation method for cutting crystal ingots according to an embodiment of the present invention, the test piece is a slice of one of the head or tail ends of the crystal ingot.

[0012] Based on the above, the present invention can determine the ingot cutting reference surface according to the test wafer of the ingot, thereby further reducing the wafer breakage rate and optimizing the wafer geometry. Attached Figure Description

[0013] Figure 1 This is a perspective view of a crystal ingot cutting process according to an embodiment of the present invention;

[0014] Figure 2 This is a flowchart of an evaluation method for cutting crystal ingots according to an embodiment of the present invention;

[0015] Figure 3 This is a schematic diagram of a test piece according to an embodiment of the present invention;

[0016] Figure 4 This is a schematic diagram of the setting of the observation surface according to an embodiment of the present invention;

[0017] Figure 5 This is a schematic diagram of an annular region according to an embodiment of the present invention;

[0018] Figure 6 This is a schematic diagram of a slice path according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures

[0020] 110: Fixture

[0021] 120: Crystal Ingot

[0022] 130, 140: Rollers

[0023] 150: Cutting line

[0024] 300: Test film

[0025] 310, 310-1~310-12: Sampling points

[0026] 410~440: Observation surface

[0027] 510: Circular area

[0028] 610-611: Slice Path

[0029] C: Center

[0030] D: knife entry direction

[0031] d1: Outer radius

[0032] d2: Inner radius

[0033] S205~S220: Steps in the evaluation method for cutting crystal ingots Detailed Implementation

[0034] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same component reference numerals are used in the drawings and description to denote the same or similar parts.

[0035] Figure 1 This is a perspective view of an ingot cutting process according to an embodiment of the present invention. Please refer to... Figure 1 In this embodiment, a fixing device 110, rollers 130 and 140, and a cutting wire 150 are used as cutting tools to cut the ingot 120. The ingot 120 is, for example, a silicon carbide ingot, but is not limited thereto. Here, the fixing device 110 is used to fix the ingot 120. The cutting wire 150 includes steel wire and abrasive grains (e.g., diamond particles) on the steel wire. The cutting wire 150 is wound around the rollers 130 and 140, and multiple cutting sections are defined. The cutting wire 150 is used to repeatedly cut the ingot 120 to cut the ingot 120 into tens to hundreds of wafers. In this embodiment, the cutting wire 150 is used to cut the ingot 120, but it is not limited thereto. In other embodiments, the ingot 120 can also be cut by a knife, laser, water jet, or other means.

[0036] Before cutting ingot 120, the X-ray rocking curve distribution on the test piece of ingot 120 can be obtained using measuring equipment. This distribution can then be analyzed and statistically analyzed using electronic devices to adjust relevant parameters during cutting. The quality of the ingot 120 slice is related not only to the parameter design and equipment status during cutting but also to the quality of the ingot 120 itself. The entry point of the cutting tool is particularly important during the cutting process. The following example illustrates the evaluation method used for cutting ingot 120.

[0037] Figure 2 This is a flowchart of an evaluation method for cutting a crystal ingot according to an embodiment of the present invention. In step S205, a plurality of sampling points are set on an inspection piece of the crystal ingot 120. Here, the inspection piece is, for example, a slice of one of the head or tail ends of the crystal ingot 120, and the number of sampling points is preferably greater than 48, and the sampling points are evenly distributed.

[0038] For example, Figure 3 This is a schematic diagram of a test piece according to an embodiment of the present invention. Please refer to... Figure 3 Multiple sampling points 310 are set in the test piece 300. Figure 3 The diagram shows 51 sampling points 310. The number of sampling points 310 is for illustrative purposes only and is not a limitation.

[0039] Next, in step S210, multiple observation surfaces are set. Here, each observation surface is formed by at least two adjacent sampling points, and the minimum number of observation surfaces is set to 4, but more than 4 observation surfaces can also be set. Figure 4 This is a schematic diagram illustrating the setting of an observation surface according to an embodiment of the present invention. Please refer to... Figure 4 The observation surfaces 410 to 440 are each formed by three adjacent sampling points. Observation surface 410 includes sampling points 310-1 to 310-3, observation surface 420 includes sampling points 310-4 to 310-6, observation surface 430 includes sampling points 310-7 to 310-9, and observation surface 440 includes sampling points 310-10 to 310-12.

[0040] For example, the observation surface can be set within the annular region of the test piece 300. That is, the observation surface is set using the sampling points within the annular region. For example, Figure 5 This is a schematic diagram of an annular region according to an embodiment of the present invention. The center C of the inspection piece 300 is taken as the center of the annular region 510, and the inner radius of the annular region 510 is d2, and the outer radius is d1. In this embodiment, the inner radius d2 of the annular region 510 is set to 60% of the radius of the inspection piece 300, and the outer radius d1 is set to 99% of the radius of the inspection piece 300.

[0041] However, in other embodiments, the inner radius d2 of the annular region 510 is set to 75% of the radius of the test piece 300, and the outer radius d1 is set to 85% of the radius of the test piece 300.

[0042] In addition, in other embodiments, the observation surface may also be set on the circumference of the test piece 300. The distance from the circumference to the center C of the test piece 300 is 80% of the radius of the test piece 300.

[0043] After that, in step S215, the first average value of the measurement values of the sampling points 310 included in each observation surface (410 to 440) is calculated. Here, the measurement value of the sampling point is obtained by sampling with a measuring instrument. For example, the measuring instrument samples the X-ray rocking curve of the sampling point 310, and then obtains the full width at half maximum (FWHM) of each sampling point 310, that is, the measurement value. The measuring instrument 110 includes a diffractometer, such as an X-ray diffractometer (XRD) or an optical instrument, such as FRT or Tropel, which are respectively used to measure the wafer to obtain the full width at half maximum (FWHM) of different positions in each wafer. The full width at half maximum can represent the crystal quality. Therefore, the full width at half maximum is measured here as the basis for judgment.

[0044] For Figure 4 example, calculate the average value (the first average value a1) of the full width at half maximum of the sampling points 310-1 to 310-3 included in the observation surface 410, calculate the average value (the first average value a2) of the full width at half maximum of the sampling points 310-4 to 310-6 included in the observation surface 420, calculate the average value (the first average value a3) of the full width at half maximum of the sampling points 310-7 to 310-9 included in the observation surface 430, and calculate the average value (the first average value a4) of the full width at half maximum of the sampling points 310-10 to 310-12 included in the observation surface 440.

[0045] After that, in step S220, the observation surface corresponding to the smallest first average value is used as the tool entry reference surface. That is, the observation surface corresponding to the smallest value among the first average values a1 to a4 is used as the tool entry reference surface. Assume a2 < a1 < a3 < a4, then the observation surface 420 is taken as the tool entry reference surface.

[0046] After obtaining the tool entry reference surface, the slicing parameters can be further adjusted. Here, the remaining sampling points that do not form the tool entry reference surface are used to set a plurality of slicing paths in a manner parallel to the tool entry reference surface. Then, calculate the second average value of the measurement values of the sampling points included in each slicing path, and determine the plurality of slicing parameters corresponding to each slicing path according to the second average value of each slicing path.

[0047] Figure 6 This is a schematic diagram of a slice path according to an embodiment of the present invention. Please refer to... Figure 6 The cutting direction D is determined based on the cutting reference plane (i.e., the observation plane 420), and the slicing paths 601 to 611 are set. The second average value of each slicing path is calculated using the measurement values ​​obtained by sampling point 310 using a measuring instrument. For example, the average value (second average value) of the half-width at half-height of the three sampling points included in slicing path 601 is calculated.

[0048] The corresponding reference index is obtained by looking up the second average value in a table. Then, the corresponding slicing parameters are obtained based on the reference index. For example, an index lookup table and a parameter lookup table can be pre-established in the electronic device. The index lookup table includes multiple reference indexes, each with a corresponding numerical range. The parameter lookup table includes multiple reference indexes and their corresponding slicing parameters. After obtaining the second average value for each slicing path, the index lookup table is used to determine which range the second average value falls within, thereby obtaining the corresponding reference index. Next, the corresponding slicing parameters are obtained from the parameter lookup table based on the reference index. The slicing parameters include the cutting speed of the cutting line 150, the oscillation angle of the rollers 130 and 140, the oscillation speed of the rollers 130 and 140, and the moving speed of the ingot 120 (i.e., the downward movement speed of the fixing device 110 that holds the ingot 120).

[0049] For example, with Figure 1 The cutting tool shown is used such that the ingot 120 is positioned with the observation surface 420 facing down, and cutting begins from the entry direction D. Assume that cutting paths 601 to 611 have corresponding cutting parameters A601 to A611. Between the edge of the ingot 120 and cutting path 601, the cutting tool is set using pre-defined cutting parameters. Between cutting paths 601 and 602, cutting parameter A601 is used; between cutting paths 602 and 603, cutting parameter A602 is used, and so on, to adjust the cutting parameters of the cutting tool accordingly.

[0050] In summary, this invention can determine the ingot's cutting reference surface based on the ingot's inspection wafer, thereby reducing the wafer breakage rate and optimizing wafer geometry. Furthermore, since ingots may exhibit varying hardness at different locations, using the same slicing parameters for the same ingot during the slicing process can lead to wafer cracks, wafer breakage, and other problems, resulting in a decrease in production yield. Therefore, the above embodiments also propose a method for adjusting cutting parameters, thereby improving production yield. In addition, the above embodiments can also adjust cutting parameters for different ingots.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An evaluation method for diced crystal ingots, characterized in that, include: Multiple sampling points are set on the test strip; Multiple observation surfaces are defined, wherein each observation surface is formed by at least two adjacent sampling points; Calculate a first average of the measurements at the sampling points included in each of the observation surfaces, wherein the measurements at the sampling points are obtained by sampling the X-ray rocking curves of the sampling points using a measuring instrument; and The observation surface corresponding to the smallest first average value is used as the cutting reference surface.

2. The evaluation method for cutting ingots according to claim 1, characterized in that, After using the observation surface corresponding to the smallest of the first average values ​​as the cutting reference surface, the method further includes: The remaining sampling points that do not constitute the tool entry reference surface are used to set multiple slicing paths in a manner parallel to the tool entry reference surface; Calculate a second average of the measurements taken at the sampling points included in each slice path; and Based on the second average value of each slice path, a plurality of slice parameters corresponding to each slice path are determined.

3. The evaluation method for diced crystal ingots according to claim 2, characterized in that, The step of determining the slice parameter corresponding to each slice path based on the second average value of each slice path includes: A reference index corresponding to each slice path is obtained based on the second average value of each slice path; and Based on the reference index for each slice path, the slice parameters corresponding to each slice path are obtained.

4. The evaluation method for diced crystal ingots according to claim 2, characterized in that, The slicing parameters include the cutting speed of the cutting line, the oscillation angle of the roller, the oscillation speed of the roller, and the movement speed of the ingot.

5. The evaluation method for diced ingots according to claim 1, characterized in that, The steps for setting the observation surface include: The observation surface is set within an annular region of the test piece, wherein the inner radius of the annular region is 60% of the radius of the test piece, and the outer radius of the annular region is 99% of the radius of the test piece.

6. The evaluation method for diced ingots according to claim 1, characterized in that, The steps for setting the observation surface include: The observation surface is set within an annular region of the test piece, wherein the inner radius of the annular region is 75% of the radius of the test piece, and the outer radius of the annular region is 85% of the radius of the test piece.

7. The evaluation method for diced ingots according to claim 1, characterized in that, The steps for setting the observation surface include: The observation surface is set on the circumference of the test piece, wherein the distance from the circumference to the center point of the test piece is 80% of the radius of the test piece.

8. The evaluation method for diced ingots according to claim 1, characterized in that, The test piece is a slice from one of the head or tail ends of the crystal ingot.

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