TWI855564B - A system and method for detecting the depth of a peripheral damage layer of a silicon wafer - Google Patents

Abstract

An embodiment of the present invention discloses a system and method for detecting the depth of a peripheral damage layer of a silicon wafer, the system comprising: a cross-section acquisition device, the cross-section acquisition device is used to acquire a cross-section of the silicon wafer, wherein the cross-section is perpendicular to the silicon wafer; a measuring device, the measuring device is used to measure the diameter of the silicon wafer and to measure the cross-sectional dimension of the cross-section in a first direction parallel to the silicon wafer; a dimension acquisition device, the dimension acquisition device is used to acquire the dimension of the peripheral damage layer in the cross-section and in the first direction; and a calculating device, the calculating device is used to calculate the depth of the peripheral damage layer according to the diameter, the cross-sectional dimension and the damage layer dimension.

Description

A system and method for detecting the depth of a peripheral damage layer of a silicon wafer

The present invention relates to the field of semiconductor silicon wafer production, and in particular to a system and method for detecting the depth of the peripheral damage layer of a silicon wafer.

In the silicon wafer manufacturing process, mechanical processing processes such as rolling, cutting, grinding, and polishing will inevitably introduce mechanical damage to the main surface and side surface of the silicon wafer, thereby forming a main surface damage layer and a peripheral damage layer in the silicon wafer. These mechanical damages destroy the original single crystal layer. If they cannot be removed in time, they will affect the quality of the products produced by the subsequent processing process. In this case, it is necessary to accurately measure the depth of the mechanical damage layer so as to determine the parameters such as the removal amount involved in removing the damage layer in the subsequent steps.

It is known that the depth of this kind of mechanical damage is relatively small, and it is not easy to directly and accurately detect the specific depth by the equipment in the relevant technology. At present, for the main surface damage layer of the silicon wafer, the "angle polishing method" is often used for detection. In this angle polishing method, the silicon wafer needs to be split into multiple pieces as measurement samples, and then the measurement sample is angle polished at an oblique angle to form an inclined surface, and the inclined surface is etched with an etching liquid so that the defects in the main surface damage layer of the silicon wafer can be better displayed on the inclined surface. Here, angle polishing plays the role of an "amplifier" of the damage layer, that is, the length of the damage layer on the inclined surface is measured by a microscope and multiplied by the sine value of the polishing angle, and the depth of the damage layer can be obtained.

However, the above-mentioned "angle polishing method" requires that the silicon wafer be split into multiple small samples before subsequent testing. In addition, the samples formed by splitting are small and cannot be compatible with standard etching machines. During etching, auxiliary tools such as special clamps or glove boxes are required, which is very inconvenient to operate. In addition, if the damage depth at multiple locations on the edge of the silicon wafer needs to be measured, it is necessary to repeatedly perform operations such as standing, polishing, and etching on multiple samples, which makes the overall measurement time longer. The peripheral damage layer of the silicon wafer can also be inspected using the above-mentioned "angle polishing method", but the above-mentioned problems in this method also exist when inspecting the thickness of the peripheral damage layer. Moreover, the peripheral damage layer and the main surface damage layer are perpendicular to each other, so the required inspection surfaces are also perpendicular to each other. Therefore, the inspection surface obtained by the polishing device of the main surface damage layer inspection system is not suitable for the inspection of the peripheral damage layer.

In order to solve the above technical problems, the embodiment of the present invention hopes to provide a system and method for detecting the depth of the peripheral damage layer of a silicon wafer, which can avoid the various problems caused by the above-mentioned "angle polishing method" and can obtain the detection surface required for detecting the depth of the peripheral damage layer.

The technical solution of the present invention is implemented as follows:

In a first aspect, the present invention provides a system for detecting the depth of a peripheral damage layer of a silicon wafer, the system comprising: a cross-section acquisition device, the cross-section acquisition device is used to acquire a cross-section of the silicon wafer, wherein the cross-section is perpendicular to the silicon wafer; a measuring device, the measuring device is used to measure the diameter of the silicon wafer and the cross-sectional dimension of the cross-section in a first direction parallel to the silicon wafer; a dimension acquisition device, the dimension acquisition device is used to acquire the dimension of the peripheral damage layer in the cross-section and in the first direction; and a calculation device, the calculation device is used to calculate the depth of the peripheral damage layer according to the diameter, the cross-sectional dimension and the damage layer dimension.

In a second aspect, an embodiment of the present invention provides a method for detecting the depth of a peripheral damage layer of a silicon wafer, the method comprising: obtaining a cross section of the silicon wafer, wherein the cross section is perpendicular to the silicon wafer; measuring the diameter of the silicon wafer and measuring the cross-sectional dimensions of the cross section in a first direction parallel to the silicon wafer; obtaining the dimensions of the peripheral damage layer in the cross section and in the first direction; and calculating the depth of the peripheral damage layer according to the diameter, the cross-sectional dimensions and the damage layer dimensions.

The embodiment of the present invention provides a system and method for detecting the depth of the peripheral damage layer of a silicon wafer. Compared with the "angle polishing method", a cross section can be obtained on the basis of a complete silicon wafer without splitting the silicon wafer, thereby reducing the process steps in the detection process. In addition, since the silicon wafer can maintain its integrity, it can be compatible with a standard etching machine, thereby simplifying the operation. Finally, the position of the cross section in the silicon wafer can be selected as needed, avoiding the obtained detection surface being only suitable for detecting the thickness of the main surface damage layer.

1: System

10: Cross-section acquisition device

11: Cutting unit

12: Polishing unit

121: Clamping mechanism

122: Polishing pad

122X: Center axis

123: Driving mechanism

20: Measuring device

30: Size acquisition device

31: Measurement unit

32: Computing unit

40: Computing device

FD: First Direction

L1: Cross-sectional dimensions

L2: Damage layer size

L2-1: Size of the first damage layer

L2-2: Second damage layer size

L3, L4: Dimensions

S: Cross section

D: Diameter

d: depth

W: Silicon wafer

CS: Cutting surface

MS: Main Surface

PS: Polished surface

DE: Defect

DL: Peripheral damage layer

DL-1: First peripheral damage layer

DL-2: Second peripheral damage layer

T: Tangent

SD: Distance

WX: Center axis

701-704: Steps

FIG1 is a schematic diagram of a system for detecting the depth of the peripheral damage layer of a silicon wafer in combination with a front view of a silicon wafer according to an embodiment of the present invention; FIG2 is an illustrative schematic diagram showing a calculation method adopted by a calculation device in accordance with an embodiment of the present invention; FIG3 is an illustrative schematic diagram showing the "depth" of a cross section toward the center of a silicon wafer in accordance with an embodiment of the present invention; FIG4 is a schematic diagram of a system for detecting the peripheral damage layer of a silicon wafer in combination with a front view of a silicon wafer according to an embodiment of the present invention. FIG5 is a schematic diagram of a system for detecting the depth of a peripheral damage layer of a silicon wafer according to an embodiment of the present invention; FIG5 is a schematic diagram of a cross-sectional acquisition device of a system for detecting the depth of a peripheral damage layer of a silicon wafer in combination with a front view of a profile change of a silicon wafer; FIG6 is a schematic diagram of a polishing unit of a system for detecting the depth of a peripheral damage layer of a silicon wafer according to an embodiment of the present invention; FIG7 is a schematic diagram of a method for detecting the depth of a peripheral damage layer of a silicon wafer according to an embodiment of the present invention.

The following will combine the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention.

Referring to FIG. 1 , an embodiment of the present invention provides a system 1 for detecting the depth d of the peripheral damage layer DL of a silicon wafer W. In FIG. 1 , the peripheral damage layer DL of the silicon wafer W is schematically shown by the dot-filled area. The system 1 may include: a cross-section acquisition device 10, the cross-section acquisition device 10 is used to acquire a cross section S of the silicon wafer W, wherein the cross section S is perpendicular to the silicon wafer W. It can be understood that the silicon wafer W is in a flat or planar shape, and being perpendicular to the silicon wafer W means being perpendicular to the plane in which the silicon wafer W is located, so the vertical here means being perpendicular to the plane. In addition, FIG. 1 shows that the cross section S of the silicon wafer W is perpendicular to the plane in which the silicon wafer W is located. The cross section S is indicated by a thick solid line in the front view of the silicon wafer; a measuring device 20, which is used to measure the diameter D of the silicon wafer W and the cross-sectional dimension L1 of the cross section S in the first direction FD parallel to the silicon wafer W; a dimension acquisition device 30, which is used to acquire the damage layer dimension L2 of the peripheral damage layer DL in the cross section S and in the first direction FD; a calculating device 40, which is used to calculate the depth d of the peripheral damage layer DL according to the diameter D, the cross-sectional dimension L1 and the damage layer dimension L2.

For the system 1 according to the embodiment of the present invention, compared with the "angle polishing method", the cross section S can be obtained on the basis of the complete silicon wafer W, without splitting the silicon wafer W, reducing the process steps in the detection process. In addition, since the silicon wafer W can maintain its integrity, it can be compatible with a standard etching machine, thereby simplifying the operation. Finally, the position of the cross section S in the silicon wafer W can be selected as needed, avoiding the obtained detection surface being only suitable for detecting the thickness of the damaged layer on the main surface.

In order to simplify the calculation process of the depth d by the calculation device 40, in an optional embodiment of the present invention, the calculation device 40 can calculate the depth d using the following formula (1):

In this regard, please refer to FIG. 2 specifically. It can be seen from the triangle area filled with horizontal lines in FIG. 2 that:

From the triangle area filled with vertical lines in Figure 2, we can see that:

In addition, it is easy to understand:

Combining the above formulas (2), (3) and (4) can obtain formula (1), so that it is no longer necessary to calculate the dimensions L3 and L4 shown in Figure 2, thereby simplifying the calculation process of the depth d calculated by the calculation device 40.

The "depth" of the above-mentioned section S toward the center of the silicon wafer W can be arbitrary, but on the other hand, the depth of the damaged layer caused by machining is usually shallow. In this regard, in an optional embodiment of the present invention, referring to FIG. 3, corresponding to a silicon wafer W with a diameter of 300 mm, the distance SD between the section S and the tangent T parallel to the section S and tangent to the outer peripheral profile PC of the silicon wafer W can be between 3 mm and 5 mm. In this way, when, for example, the section S is completely obtained by polishing the silicon wafer W, the polishing amount and the time required can be minimized to the greatest extent, thereby improving production efficiency.

It is understandable that, for the peripheral damage layer DL of the silicon wafer W, the depth d at different circumferential positions may be different. In order to make the depth d detected by the system 1 more accurate, in an optional embodiment of the present invention, referring to FIG. 4 , the size acquisition device 30 may include: a measuring unit 31, the measuring unit 31 is used to measure the first peripheral damage layer DL in the section S. -1 measures the first damage layer size L2-1 in the first direction FD and measures the second damage layer size L2-2 of the second peripheral damage layer DL-2 in the section S in the first direction FD; a calculation unit 32, the calculation unit 32 is used to calculate the average value of the first damage layer size L2-1 and the second damage layer size L2-2 as the damage layer size L2.

As described above, in the "angle polishing method", the sample needs to be angle polished to form an inclined surface, the purpose of which is to make the defects in the damaged layer better appear on the inclined surface for easy measurement. In this regard, as described above, the cross section S can be completely obtained by polishing the silicon wafer W. However, in an optional embodiment of the present invention, the size acquisition device 30 also obtains the defect DE existing in the peripheral damaged layer DL and appearing in the cross section S. The defect layer size L2, and referring to FIG5, in which the defect DE is schematically shown by filling the points at the periphery of the silicon wafer W, the cross-section acquisition device 10 may include: A cutting unit 11, which is used to cut the silicon wafer W in a plane perpendicular to the silicon wafer W to obtain a cut surface CS of the silicon wafer W; a polishing unit 12, which is used to polish the cut surface CS to obtain a polished surface PS that is conducive to showing the defect DE.

In this way, compared with the case where the cross section S is obtained entirely by polishing the silicon wafer W, the required polishing amount is reduced to the greatest extent. Although the cut surface CS obtained by cutting is relatively rough as shown in FIG5, the defect DE still cannot be revealed. However, the production efficiency is improved by reducing the amount of processing required for the time-consuming polishing process.

For the above-mentioned polishing unit 12, in an optional embodiment of the present invention, referring to FIG6, the polishing unit 12 may include: a clamping mechanism 121, the clamping mechanism 121 is used to clamp the silicon wafer W by contacting the main surface MS of the silicon wafer W; a polishing pad 122; a driving mechanism 123, the driving mechanism 123 is used to drive the polishing pad 122 to move relative to the clamping mechanism 121, for example, as shown in FIG6, the polishing pad 122 is rotated around its own central axis 122X to polish the silicon wafer W clamped by the clamping mechanism 121.

In addition, it may be necessary to obtain multiple polishing surfaces PS at different positions in the circumferential direction of the silicon wafer W. For example, a polishing surface PS is obtained every 45° in the circumferential direction, that is, a total of 8 polishing surfaces PS are obtained and these 8 polishing surfaces PS are evenly distributed in the circumferential direction of the silicon wafer W, so as to detect a more comprehensive depth d of the circumferential damage layer DL. In this case, for the polishing unit 12, see FIG6 , the silicon wafer W can be set to be able to rotate around its own central axis WX relative to the clamping mechanism 121. In this way, after each polishing operation to obtain a polished surface PS, the clamping mechanism 12 only needs to loosen the silicon wafer W and rotate the silicon wafer W 45°. Finally, the clamping mechanism 12 clamps the silicon wafer W again, and then the previous polishing operation can be repeated to obtain another polished surface PS.

Referring to FIG. 7 and in combination with FIG. 1 , the embodiment of the present invention further provides a method for detecting the depth of a peripheral damage layer DL of a silicon wafer W, the method may include: 701: obtaining a cross section S of the silicon wafer W, wherein the cross section S is perpendicular to the silicon wafer W; 702: measuring the diameter D of the silicon wafer W and measuring the cross-sectional dimension L1 of the cross section S in a first direction FD parallel to the silicon wafer W; 703: obtaining the damage layer dimension L2 of the peripheral damage layer DL in the cross section S and in the first direction FD; 704: calculating the depth d of the peripheral damage layer DL according to the diameter D, the cross-sectional dimension L1 and the damage layer dimension L2.

Optionally, as described above in conjunction with FIG. 2 , the depth d may be calculated using the following formula:

Optionally, referring to FIG. 4 , obtaining the damage layer size L2 of the peripheral damage layer DL in the section S and in the first direction FD may include: measuring the first damage layer size L2-1 of the first peripheral damage layer DL-1 in the section S in the first direction FD and measuring the second damage layer size L2-2 of the second peripheral damage layer DL-2 in the section S in the first direction FD; calculating the average value of the first damage layer size L2-1 and the second damage layer size L2-2 as the damage layer size L2.

Optionally, the damage layer size L2 is obtained according to the defect DE existing in the peripheral damage layer DL and appearing in the cross section S, and referring to FIG5 , the cross section S of the silicon wafer W can be obtained by: cutting the silicon wafer W in a plane perpendicular to the silicon wafer W to obtain a cut surface CS of the silicon wafer W; polishing the cut surface CS to obtain a polished surface PS that is conducive to showing the defect DE.

It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.

The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person of ordinary skill in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the patent application.

1: System

10: Cross-section acquisition device

20: Measuring device

30: Size acquisition device

40: Computing device

FD: First Direction

L1: Cross-sectional dimensions

L2: Damage layer size

S: Cross section

D: Diameter

d: depth

W: Silicon wafer

DL: Peripheral damage layer

Claims (8)

A system for detecting the depth of a peripheral damage layer of a silicon wafer, the system comprising: a cross-section acquisition device, the cross-section acquisition device is used to acquire a cross-section of the silicon wafer, wherein the cross-section is perpendicular to the silicon wafer; a measuring device, the measuring device is used to measure the diameter of the silicon wafer and the cross-sectional dimension of the cross-section in a first direction parallel to the silicon wafer; a dimension acquisition device, the dimension acquisition device The device is used to obtain the size of the peripheral damage layer in the cross section and in the first direction; the calculation device is used to calculate the depth of the peripheral damage layer according to the diameter, the cross-sectional size and the damage layer size; wherein, the diameter is set to D, the cross-sectional size is L1, and the damage layer size is L2, then the calculation device calculates the depth d using the following formula:

A system for detecting the depth of the peripheral damage layer of a silicon wafer as described in claim 1, wherein, corresponding to a silicon wafer with a diameter of 300 mm, the distance between the cross section and a tangent line parallel to the cross section and tangent to the outer peripheral contour of the silicon wafer is between 3 mm and 5 mm. A system for detecting the depth of the peripheral damage layer of a silicon wafer as described in claim 1, wherein the size acquisition device includes: a measuring unit, the measuring unit is used to measure the first damage layer size of the first peripheral damage layer in the cross section in the first direction and measure the second damage layer size of the second peripheral damage layer in the cross section in the first direction; a calculating unit, the calculating unit is used to calculate the average value of the first damage layer size and the second damage layer size as the damage layer size. A system for detecting the depth of the peripheral damage layer of a silicon wafer as described in claim 1, wherein the size acquisition device acquires the size of the damage layer according to the defects existing in the peripheral damage layer and appearing in the cross section, and the cross section acquisition device includes: a cutting unit, which is used to cut the silicon wafer in a plane perpendicular to the silicon wafer to obtain the cut surface of the silicon wafer; and a polishing unit, which is used to polish the cut surface to obtain a polished surface that is conducive to showing the defect. A system for detecting the depth of the peripheral damage layer of a silicon wafer as described in claim 4, wherein the polishing unit includes: a clamping mechanism for clamping the silicon wafer by contacting the main surface of the silicon wafer; a polishing pad; and a driving mechanism for driving the polishing pad to move relative to the clamping mechanism to polish the silicon wafer clamped by the clamping mechanism. A method for detecting the depth of a peripheral damage layer of a silicon wafer, the method comprising: obtaining a cross section of the silicon wafer, wherein the cross section is perpendicular to the silicon wafer; measuring the diameter of the silicon wafer and measuring the cross-sectional dimension of the cross section in a first direction parallel to the silicon wafer; obtaining the dimension of the peripheral damage layer in the cross section and in the first direction; calculating the depth of the peripheral damage layer according to the diameter, the cross-sectional dimension and the damage layer dimension; wherein, assuming that the diameter is D, the cross-sectional dimension is L1, and the damage layer dimension is L2, the depth d is calculated using the following formula:

A method for detecting the depth of a peripheral damage layer of a silicon wafer as described in claim 6, wherein obtaining the damage layer size of the peripheral damage layer in the cross section and in the first direction comprises: measuring a first damage layer size of a first peripheral damage layer in the cross section in the first direction and measuring a second damage layer size of a second peripheral damage layer in the cross section in the first direction; calculating an average value of the first damage layer size and the second damage layer size as the damage layer size. A method for detecting the depth of a peripheral damage layer of a silicon wafer as described in claim 6, wherein the size of the damage layer is obtained based on a defect existing in the peripheral damage layer and appearing in the cross section, and the cross section of the silicon wafer is obtained, including: cutting the silicon wafer in a plane perpendicular to the silicon wafer to obtain a cut surface of the silicon wafer; polishing the cut surface to obtain a polished surface that is conducive to showing the defect.

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