A method for measuring the size of oxygen precipitation in silicon wafers

Abstract

The present invention relates to a method for measuring the size of oxygen precipitates in a silicon wafer. The method comprises obtaining the LSE size of defects on the surface of the silicon wafer, dividing the defects into a first defect group and a second defect group based on the LSE size, and calculating the size of the oxygen precipitates in the silicon wafer according to the LSE size. The method for measuring oxygen precipitates of the present invention can quickly and accurately obtain the actual size of the oxygen precipitates on a silicon wafer to be tested containing a large amount of oxygen precipitates, thereby saving time and reducing costs.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor materials, and in particular relates to a method for measuring the size of oxygen precipitation in a silicon wafer. Background Art

[0002] Oxygen precipitation is a common defect in silicon wafers, typically caused by the precipitation of supersaturated oxygen during crystal cooling. On the one hand, oxygen precipitation plays an important role in improving silicon wafer performance, not only serving as an effective gettering site for metal impurities, but also enhancing the mechanical properties of the silicon wafer. On the other hand, when oxygen precipitation is too large, it may also cause dislocation and slip. At the same time, when it is located in the device area, it may also affect the conductivity of the area. Therefore, it is very important to control the density and size of oxygen precipitation, which requires appropriate characterization methods.

[0003] Localized Light Scattering (LLS) scanning is a commonly used surface defect detection method. Combined with HCl vapor etching, it can detect and identify native defects, obtaining the latex sphere equivalent (LSE) size of the surface defect on the silicon wafer under test. However, the LSE size here refers to the size of the etch pit, not the actual size of the oxygen precipitate.

[0004] Scanning Electron Microscope (SEM) detection is a commonly used defect morphology analysis method. Based on the LLS scanning results, the defects can be observed and measured to obtain the actual size of the oxygen precipitation.

[0005] Laser scattering tomography (LST) is another common method for defect measurement. However, the measurement results are affected by factors such as laser power and recognition algorithms, and the actual size of oxygen precipitates cannot be directly determined. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for measuring the size of oxygen precipitates in silicon wafers, so as to achieve the purpose of quickly and accurately measuring the size of oxygen precipitates in silicon wafers.

[0007] The present invention provides a method for measuring the size of oxygen precipitates in a silicon wafer. The method comprises obtaining the LSE size of defects on the surface of the silicon wafer, dividing the defects into a first group of defects and a second group of defects based on the LSE size, and calculating the size of the oxygen precipitates in the silicon wafer based on the LSE size.

[0008] Preferably, the size of the first group of defective oxygen precipitates (S actual ) and its LSE size (S LSE) satisfies the following relationship: S actual =0.548×S LSE –16.736; For the second group of defects, the size of oxygen precipitates and their LSE size satisfy the following relationship: S actual =0.392×S LSE –15.718.

[0009] More preferably, the LSE size of the first group of defects is less than 62 nm, and the LSE size of the second group of defects is greater than or equal to 62 nm.

[0010] Preferably, the LSE size is obtained by an LLS (Surface Light Scattering Scanning) method or an LST (Laser Scattering Tomography) method.

[0011] Preferably, the LLS method comprises the following steps:

[0012] (1) Chemical Mechanical Polishing (CMP) and RCA cleaning of the silicon wafer to be tested;

[0013] (2) etching the silicon wafer to be tested processed in step (1) with HCl vapor in a chemical vapor deposition (CVD) chamber;

[0014] (3) Perform LLS test on the etched silicon wafer to obtain the LSE size.

[0015] Preferably, the equipment used for the vapor phase etching in step (2) is ASM Epsilon2000.

[0016] Preferably, in step (2), the etching temperature is 800-1000° C., the gas flow rate is 300-1000 sccm, and the etching time is 0-8 min.

[0017] Preferably, the device used for the LLS test in step (3) is KLA-Tencor Surfscan SP5 TM .

[0018] Preferably, the recipe used for the LLS test in step (3) is Defect_Etch, the recognition lower limit is set to 50 nm, and the edge removal width is set to 3 mm.

[0019] Preferably, the LST method comprises the following steps:

[0020] (1) Splitting the ground silicon wafer to be tested, performing LST scanning on its cross section to obtain the LST size of the defect;

[0021] (2) Based on the LST size of the defect obtained in step (1), the corresponding LSE size is calculated by the formula: S LSE =0.424×S LST +36.288.

[0022] Preferably, the LST scanning device in step (1) is SEMILAB IR-LST-2500.

[0023] Preferably, the laser power of the LST scan in step (1) is set to 0.3 mw, and the detection threshold is set to 1.03.

[0024] There are two methods for measuring the size of oxygen precipitation in the present invention. The overall process is as follows: Figure 1 shown.

[0025] Beneficial effects

[0026] The method for measuring oxygen precipitation of the present invention can quickly and accurately obtain the actual size of the oxygen precipitation of the silicon wafer to be tested containing a large amount of oxygen precipitation, thereby saving time and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 4 is an overall flow chart of the method for measuring the size of oxygen precipitates of the present invention.

[0028] Figure 2 (a) LLS image of the silicon wafer to be tested after CMP, RCA cleaning and HCl vapor etching, (b) SEM image of the defect, and (c) magnified SEM image of the defect in Example 1 of the present invention.

[0029] Figure 3 is the size of oxygen precipitates (S) of (a) the first group of defects and (b) the second group of defects in Example 1 of the present invention actual ) and the corresponding LSE size (S LSE ) relationship.

[0030] Figure 4 is the LST size (S) of the silicon wafer to be tested in (a) in Example 2 of the present invention LST ), (b) S LST With the corresponding S LSE relationship. DETAILED DESCRIPTION

[0031] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0032] Example 1

[0033] The method for measuring the size of oxygen precipitates in this embodiment comprises the following steps:

[0034] (1) Perform CMP treatment and RCA cleaning on the silicon wafer to be tested.

[0035] (2) The silicon wafer to be tested is subjected to HCl vapor etching using an ASM Epsilon 2000, with an etching temperature of 800-1000°C, a gas flow rate of 300-1000 sccm, and an etching time of 0-8 min;

[0036] (3) Perform LLS testing on the etched silicon wafer using KLA-Tencor Surfscan SP5 TM The recipe used in the LLS test is Defect_Etch, the lower limit of recognition is set to 50nm, and the edge removal width is set to 3mm. The scanning results are as follows Figure 2 As shown, Figure 2 (a) is the LLS image of the silicon wafer to be tested after CMP, RCA cleaning and HCl vapor etching. Figure 2 (b) SEM is used to Figure 2 Observation results of defects in (a), Figure 2 (c) is the magnified SEM image of the defects. From the morphology, these defects are all oxygen precipitation. The LSE size of the defects on the silicon wafer surface is obtained from the LLS scanning results.

[0037] (4) According to the LSE size, the defects are divided into the first group of defects and the second group of defects. The size of oxygen precipitation is calculated by the corresponding formula. The first group of defects: S actual =0.548×S LSE –16.736; Second set of defects: S actual =0.392×S LSE –15.718. At the same time, the oxygen precipitation in the center of the etch pit can be directly measured by SEM results to obtain the actual size of the oxygen precipitation. The relationship between them is: Figure 3 (a) and Figure 3 (b) shows that the red line in the figure is the result calculated according to the formula, and the dots are the results obtained by SEM measurement. It can be seen that the two are basically consistent.

[0038] Example 2

[0039] As an alternative measurement method, LST measures the cross section rather than the surface, and can be used directly on polished silicon wafers without undergoing CMP and RCA cleaning. The method for measuring the size of oxygen precipitates in this embodiment includes the following steps:

[0040] (1) The ground silicon wafer to be tested is split and its cross section is scanned by LST. The equipment is SEMILAB IR-LST-2500, the laser power is set to 0.3mw, the detection threshold is set to 1.03, and the LST size of the defect is obtained. Taking R = 130mm as an example, the results are as follows Figure 4 (a)

[0041] (2) Based on the LST size, the formula S LSE =0.424×S LST The corresponding LSE size is calculated by +36.288, which is basically consistent with the actual LLS measurement value. Figure 4 As shown in (b), the dotted line is the result calculated according to the formula, and the bar graph is the result obtained by LLS measurement.

[0042] (3) According to the LSE size calculated in step (2), the defects are divided into the first group of defects and the second group of defects, and the actual size of the oxygen precipitate is calculated using the formula: actual ) and its LSE size (S LSE ) satisfies the following relationship: S actual =0.548×S LSE –16.736; For the second group of defects, the size of oxygen precipitates and their LSE size satisfy the following relationship: S actual =0.392×S LSE –15.718.

Claims

1. A method for measuring the size of oxygen precipitates in a silicon wafer, the method comprising: obtaining the LSE size of defects on the silicon wafer surface; classifying the defects into a first group of defects and a second group of defects based on the LSE size; and calculating the size of the oxygen precipitates in the silicon wafer based on the LSE size; wherein the size of the oxygen precipitates in the first group of defects and their LSE size satisfy the following relationship: S actual = 0.548 × S LSE –16.736, the LSE size of the first group of defects is less than 62 nm; for the second group of defects, the size of the oxygen precipitate and its LSE size satisfy the following relationship: S actual = 0.392 × S LSE –15.718, the LSE size of the second group of defects is greater than or equal to 62 nm.

2. The method for measuring the size of oxygen precipitates in silicon wafers according to claim 1, wherein: The LSE size is obtained by the LLS method or the LST method.

3. The method for measuring the size of oxygen precipitates in silicon wafers according to claim 2, wherein: The LLS method comprises the following steps: (1) Chemical mechanical polishing and RCA cleaning of the silicon wafer to be tested; (2) etching the silicon wafer to be tested processed in step (1) with HCl vapor in a chemical vapor deposition chamber; (3) Perform LLS test on the etched silicon wafer to obtain the LSE size.

4. The method for measuring the size of oxygen precipitates in a silicon wafer according to claim 3, wherein: In step (2), the etching temperature is 800-1000° C., the gas flow rate is 300-1000 sccm, and the etching time is 0-8 min.

5. The method for measuring the size of oxygen precipitates in a silicon wafer according to claim 3, wherein: The recipe used for the LLS test in step (3) is Defect_Etch, the recognition lower limit is set to 50 nm, and the edge removal width is set to 3 mm.

6. The method for measuring the size of oxygen precipitates in a silicon wafer according to claim 2, wherein: The LST method comprises the following steps: (1) Split the ground silicon wafer to be tested, perform LST scanning on its cross section, and obtain the LST size of the defect; (2) Based on the LST size of the defect obtained in step (1), the corresponding LSE size is calculated using the formula: S LSE =0.424 × S LST +36.

288.

7. The method for measuring the size of oxygen precipitates in a silicon wafer according to claim 6, wherein: In step (1), the laser power of the LST scan is set to 0.3 mW, and the detection threshold is set to 1.03.

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