Method for determining defect type in single crystal silicon wafer
By combining LST with short-time heat treatment, the defect type of single-crystal silicon wafer is determined by particle density and/or size, which solves the problems of long detection time and high cost in the existing technology and achieves efficient and low-cost defect type differentiation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZING SEMICON CORP
- Filing Date
- 2022-12-05
- Publication Date
- 2026-05-26
AI Technical Summary
Existing methods for detecting defects in single-crystal silicon wafers have high requirements for silicon wafers, complex processes, long detection times, and high costs.
A laser scattering tomography (LST) combined with short-time heat treatment method was used to determine the V-rich, Pv, I-rich and Pi regions by performing initial measurements and heat treatment on As-Grown silicon wafers, and then measuring them again using particle density and/or particle size.
It enables efficient and stable differentiation of defect types in monocrystalline silicon wafers, reducing the requirements for silicon wafers, shortening inspection time, and lowering process costs.
Smart Images
Figure CN115985798B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for determining the type of defects in a single-crystal silicon wafer. Background Technology
[0002] In the Czochralski (CZ) single-crystal silicon manufacturing process, polycrystalline silicon raw material is placed in a quartz crucible and heated to melt into a silicon solution. A seed crystal is then immersed in the molten silicon, and the seed crystal is pulled upwards by rotation, causing the silicon at the interface between the seed crystal and the molten silicon to solidify and crystallize. As the seed crystal is pulled upwards, a single-crystal silicon ingot is formed. The intrinsic defects within single-crystal silicon grown using the CZ method are affected by the pulling speed and thermal field distribution during crystal growth. Depending on the crystallization pulling conditions, the distribution of intrinsic defects follows the order of V-rich region, OISF region, Pv region, Pi region, and I-rich region, starting from the high-speed side. The V-rich region is characterized by a higher concentration of voids due to insufficient silicon atoms on the high-speed side under the pulling conditions; the I-rich region is characterized by a higher concentration of dislocations and excess silicon atom blocks due to the presence of excess interstitial silicon atoms on the low-speed side under the pulling conditions. In addition, the OISF region is a region where defects known as OISF (Oxidation Induced Stacking Fault) are distributed in a ring shape when viewed in a cross-section (within the wafer plane) perpendicular to the crystal growth axis.
[0003] Since Pv and Pi regions are the desired defect-free areas on silicon wafers, and NPS (Nearly Perfect Crystal) is defined as a region that does not produce void defects and LEP (Large Etch Pit), it can be divided into Pi and Pv regions. Therefore, the demand for NPS is increasing. This demonstrates the importance of characterizing the presence and types of defects in silicon wafers.
[0004] Currently, commonly used methods for silicon wafer defect detection include Localized Light Scattering (LLS) scanning technology. By combining LLS with vapor phase etching, native defects can be detected and identified. However, vapor phase etching requires a certain level of cleanliness on the silicon wafer surface, necessitating polishing, cleaning, and etching steps to achieve the required surface cleanliness. Laser Scattering Tomography (LST) can also measure defects, but it primarily relies on measuring the biomolecular density (BMD) after heat treatment (mainly measuring the density and size of oxygen deposits). However, BMD, formed by oxygen deposits, typically requires two heat treatment steps: 4 hours at 800°C and 16 hours at 1000°C, which is time-consuming and increases process costs.
[0005] In summary, current defect detection methods have high requirements for silicon wafers and complex processes for defect partitioning types, and the detection time is long and the cost is high. Summary of the Invention
[0006] The purpose of this invention is to provide a method for determining the type of defects in a single-crystal silicon wafer, which can solve the problem that current defect detection methods have high requirements for the silicon wafer in terms of defect partitioning types.
[0007] To address the above problems, this invention provides a method for determining the type of defects in a single-crystal silicon wafer, comprising the following steps:
[0008] The particles in an As-Grown silicon wafer are measured using LST to obtain a first measurement result, and a V-rich region is determined based on the first measurement result and a first preset density value; and
[0009] The silicon wafer is heat-treated, and the particles in the silicon wafer are measured again using LST to obtain a second measurement result. The Pv region, I-rich region and Pi region are determined based on the second measurement result, a second preset density value and a third preset density value.
[0010] Optionally, the first measurement result includes particle density, and the method for determining the V-rich region based on the first measurement result, a first preset density value, and the first measurement result is as follows:
[0011] The regions in the first measurement results where the particle density is greater than the first preset density value are identified as V-rich regions.
[0012] Optionally, the atmosphere for heat treatment of the silicon wafer is argon, the process temperature is 800℃~1000℃, the process time is 2 hours~4 hours, and the oxygen content of the silicon wafer is 5ppma~20ppma.
[0013] Optionally, the second measurement result includes particle density, and the method for determining the Pv region, I-rich region, and Pi region based on the second measurement result, the second preset density value, and the third preset density value is as follows:
[0014] The region in the second measurement result where the particle density is greater than the second preset density value is determined as the Pv region;
[0015] The region in the second measurement result where the particle density is between the second preset density value and the third preset density value is defined as the I-rich region; and
[0016] The region in the second measurement result where the particle density is less than the third preset density value is determined as the Pi region.
[0017] Optionally, the first preset density value is 2×10 6 cm -3 ~10 7 cm -3 The second preset density value is 4×10 6 cm -3 ~4×10 7 cm -3 The third preset density value is 5×10 5 cm -3 ~3×10 6 cm -3 .
[0018] On the other hand, the present invention provides a method for determining the type of defects in a single-crystal silicon wafer, comprising the following steps:
[0019] The particles in an As-Grown silicon wafer are measured using LST to obtain a third measurement result, and the V-rich region is determined based on a first preset size, a fourth preset density value, and the third measurement result; and
[0020] The silicon wafer is heat-treated, and the particles in the silicon wafer are measured again using LST to obtain a fourth measurement result. Based on the fourth measurement result, the second preset size, the fifth preset density value, and the sixth preset density value, the Pv region, the I-rich region, and the Pi region are determined.
[0021] Optionally, the third measurement result includes particle density and particle size, and the method for determining the V-rich region based on the first preset size, the fourth preset density value, and the third measurement result is as follows:
[0022] The region in the third measurement result where the particle density is greater than the fourth preset density value and the particle size is greater than the first preset size is determined to be a V-rich region.
[0023] Optionally, the atmosphere for heat treatment of the silicon wafer is argon, the process temperature is 800℃~1000℃, the process time is 2 hours~4 hours, and the oxygen content of the silicon wafer is 5ppma~20ppma.
[0024] Optionally, the fourth measurement result includes particle density and particle size, and the method for determining the Pv region, I-rich region, and Pi region based on the fourth measurement result, the second preset size, the fifth preset density value, and the sixth preset density value is as follows:
[0025] The region in the fourth measurement result where the particle density is greater than the fifth preset density value is determined as the Pv region;
[0026] The region in the fourth measurement result where the particle density is between the fifth and sixth preset density values, and the particle size is larger than the second preset size, is defined as an I-rich region; and
[0027] The region in the fourth measurement result where the particle density is less than the sixth preset density value and the particle size is greater than the second preset size is determined to be the Pi region.
[0028] Optionally, the first preset size is 20nm to 25nm, the second preset size is 30nm to 40nm, and the fourth preset density value is 5×10⁻⁶. 5 cm -3 ~5×10 6 cm -3 The fifth preset density value is 4×10 7 cm -3 ~10 8 cm -3 The sixth preset density value is 0 to 4 × 10⁻⁶. 6 cm -3 .
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] 1. Based on LST measurement results, the four types of regions in a single-crystal silicon wafer—V-rich, Pv, Pi, and I-rich—can be accurately and effectively distinguished by using particle density or by using both particle density and particle size. This makes the test results clearly distinguishable, and the test stability and repeatability are high, thereby reducing the requirements of the defect partitioning type on the silicon wafer.
[0031] 2. Using short-time heat treatment combined with LST measurement method can have the advantages of high efficiency and low cost in characterizing defects in silicon wafers. Shortening the heat treatment time can significantly reduce the time required for silicon wafer heat treatment, reduce process complexity, and reduce process cost. Attached Figure Description
[0032] Figure 1 This is a flowchart illustrating a method for determining the type of defect in a single-crystal silicon wafer according to Embodiment 1 of the present invention.
[0033] Figure 2 This is a flowchart illustrating a method for determining the type of defect in a single-crystal silicon wafer, as provided in Embodiment 2 of the present invention. Detailed Implementation
[0034] The following will provide a more detailed description of a method for determining the type of defects in a single-crystal silicon wafer according to the present invention. The invention will now be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.
[0035] For clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not detailed in detail, as they would obscure the invention with unnecessary detail. It should be understood that in the development of any actual embodiment, numerous implementation details must be made to achieve the developer's specific objectives, such as changes from one embodiment to another according to limitations related to the system or business. Furthermore, it should be understood that such development work may be complex and time-consuming, but is merely routine work for those skilled in the art.
[0036] To make the objectives and features of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to conveniently and clearly assist in illustrating the objectives of the embodiments of the present invention.
[0037] Example 1
[0038] Figure 1This is a flowchart illustrating a method for determining the type of defect in a single-crystal silicon wafer, as provided in this embodiment. Figure 1 As shown, this embodiment provides a method for determining the type of defects in a single-crystal silicon wafer, including the following steps:
[0039] Step S11: Measure the particles in the As-Grown silicon wafer using LST to obtain a first measurement result, and determine the V-rich region based on the first measurement result and a first preset density value; and
[0040] Step S12: Perform heat treatment on the silicon wafer, and measure the particles in the silicon wafer again using LST to obtain a second measurement result. Determine the Pv region, I-rich region and Pi region based on the second measurement result, the second preset density value and the third preset density value.
[0041] The following provides a detailed description of a method for determining the type of defect in a single-crystal silicon wafer provided in this embodiment.
[0042] First, step S11 is executed, using LST to measure the particles in the As-Grown state silicon wafer (i.e., the silicon wafer in a state where no heat treatment has been performed after pulling a single crystal silicon rod) to obtain a first measurement result, and then determining the V-rich region based on the first preset density value and the first measurement result.
[0043] This step specifically includes:
[0044] First, a single-crystal silicon ingot is obtained using the Czochralski single-crystal silicon manufacturing process;
[0045] Next, the single-crystal silicon ingot is cut along the axial direction, that is, the single-crystal silicon ingot is cut longitudinally;
[0046] Next, after longitudinal cutting, shape and flatness processing is performed to obtain silicon wafers in the As-Grown state;
[0047] Next, LST (Laser Scattering Tomography) was used to measure the particles in the cross-section of the As-Grown silicon wafer to obtain a first measurement result. This first measurement result includes particle density, where the particles include both void and non-void defects.
[0048] Next, a V-rich region is determined based on a first preset density value and the first measurement result. Specifically, if there is a region in the first measurement result where the particle density is greater than the first preset density value, then that region is determined to be a V-rich region. The first preset density value can be 2 × 10⁻⁶. 6 cm-3 ~10 7 cm -3 Preferably, the first preset density value is 8×10 6 cm -3 .
[0049] Next, step S12 is performed to heat-treat the silicon wafer, and the particles in the silicon wafer are measured again using LST to obtain a second measurement result. Based on the second measurement result, the defect areas in the silicon wafer are divided into regions with the second preset density value and the third preset density value as boundaries. The second measurement result in this step has obvious distinguishability, high measurement stability, and high repeatability (i.e., high reproducibility).
[0050] This step specifically includes the following steps:
[0051] First, the silicon wafer is heat-treated. The atmosphere during the heat treatment process includes, but is not limited to, argon. The process temperature is 800℃~1000℃, and the process time is 2 hours~4 hours. Preferably, the process temperature is 950℃, and the process time is 3 hours. The oxygen content of the silicon wafer is 5ppma~20ppma. Compared to the existing technology's heat treatment for BMD (with or without oxygen precipitation) growth, which requires heating at 800℃ for 4 hours and at 1000℃ for 16 hours, this embodiment only requires the defects to grow to a level that the LST can detect and distinguish. It does not require sufficient oxygen precipitation to grow and measure its density, thus improving the heat treatment process for BMD growth, significantly reducing the time required for silicon wafer heat pretreatment, and lowering process costs.
[0052] Next, the particles in the heat-treated silicon wafer are measured again using LST to obtain a second measurement result. This second measurement result also includes the particle density.
[0053] Next, based on the second measurement result, the second preset density value, and the third preset density value, the Pv region, the I-rich region, and the Pi region are determined. Specifically,
[0054] If the second measurement result shows a region where the particle density is greater than the second preset density value, then that region is determined to be the Pv region. The second preset density value is 4 × 10⁻⁶. 6 cm -3 ~4×10 7 cm -3 Preferably, the second preset density value is 8×10. 6 cm -3 .
[0055] If the second measurement result shows a region where the particle density falls between the second preset density value and the third preset density value, then this region is determined to be the I-rich region, wherein the third preset density value can be 5 × 10⁻⁶. 5 cm -3 ~3×10 6 cm -3 Preferably, the third preset density value is 10. 6 cm -3 .
[0056] If there is a region in the second measurement result where the particle density is less than the third preset density value, then that region is determined to be the Pi region.
[0057] The following example illustrates the method for determining the defect type in four sample silicon wafers (i.e., sample silicon wafer 1, sample silicon wafer 2, sample silicon wafer 3, and sample silicon wafer 4).
[0058] First, before heat treatment, the particle density at the center of four sample silicon wafers was measured using LST, and the first measurement result was obtained: the total particle density of sample silicon wafer 1, sample silicon wafer 2, sample silicon wafer 3, and sample silicon wafer 4 was 1.34 × 10⁻⁶. 7 cm -3 0, 0, 8.52×10 5 cm -3 Because the particle density of sample silicon wafer 1 is greater than the first preset density value of 8 × 10⁻⁶. 6 cm -3 The sample silicon wafer 1 meets the criteria for V-rich region type. Therefore, the center position of the sample silicon wafer 1 is determined to be a V-rich region. Sample silicon wafers 2, 3, and 4 do not meet the criteria. Therefore, the particles in sample silicon wafers 2, 3, and 4 need to be heat-treated and further measured.
[0059] Next, LST was used again to measure the particles in sample silicon wafers 2, 3, and 4, and a second measurement result was obtained, namely, the total particle density of sample silicon wafers 2, 3, and 4, which was 8.72 × 10⁻⁶. 7 cm -3 2.84×10 5 cm -3 4.83×10 6 cm -3 Because the particle density of sample silicon wafer 2 is greater than the second preset density value of 8 × 10⁻⁶. 6 cm -3The sample silicon wafer 2 meets the criteria for Pv region type, therefore, the center position of the sample silicon wafer 2 is determined to be a Pv region; since the particle density of the sample silicon wafer 3 is less than the third preset density value of 10... 6 cm -3 The sample silicon wafer 3 meets the criteria for determining the Pi region type; therefore, the center position of sample silicon wafer 4 is determined to be a Pi region. Since the particle density of sample silicon wafer 4 is 10... 6 cm -3 ~8×10 6 cm -3 Between these points, the condition meets the criteria for determining the I-rich region type. Therefore, the center position of sample silicon wafer 4 is determined to be an I-rich region.
[0060] When the above measurement results were detected by combining LLS and vapor phase etching to determine defects in sample silicon wafers 1, 2, 3, and 4, it was found that the measurement results of the two determination methods were consistent.
[0061] Example 2
[0062] Figure 2 This is a flowchart illustrating a method for determining the type of defect in a single-crystal silicon wafer, as provided in this embodiment. Figure 2 As shown, this embodiment provides a method for determining the type of defects in a single-crystal silicon wafer, including the following steps:
[0063] Step S21: Measure the particles in the As-Grown silicon wafer using LST to obtain a third measurement result, and determine the V-rich region based on the first preset size, the fourth preset density value, and the third measurement result; and
[0064] Step S22: Perform heat treatment on the silicon wafer, and measure the particles in the silicon wafer again using LST to obtain a fourth measurement result. Determine the Pv region, I-rich region and Pi region based on the fourth measurement result, the second preset size, the fifth preset density value and the sixth preset density value.
[0065] The following provides a detailed description of a method for determining the type of defect in a single-crystal silicon wafer provided in this embodiment.
[0066] First, step S21 is executed, using LST to measure the particles in the As-Grown silicon wafer to obtain a third measurement result, and the V-rich region is determined based on the first preset size, the fourth preset density value and the third measurement result.
[0067] This step specifically includes:
[0068] First, the particles in the As-Grown silicon wafer are measured using LST to obtain a third measurement result. This third measurement result includes particle density and particle size. The particles include both void and non-void defects.
[0069] Next, the V-rich region is determined based on the first preset size, the fourth preset density value, and the third measurement result. Specifically, if the third measurement result shows a region where the particle density is greater than the fourth preset density value and the particle size is greater than the first preset size, then that region is determined to be a V-rich region. The first preset size is 20nm to 25nm, preferably 25nm, to filter out larger particles. Larger particle sizes increase the likelihood of void defects, thereby improving measurement accuracy. The fourth preset density value can be 5 × 10⁻⁶. 5 cm -3 ~5×10 6 cm -3 Preferably, the fourth preset density value is 10. 6 cm -3 .
[0070] Next, step S22 is performed to heat-treat the silicon wafer and measure the particles in the silicon wafer again using LST to obtain a fourth measurement result. Based on the fourth measurement result, the second preset size, the fifth preset density value, and the sixth preset density value, the Pv region, the I-rich region, and the Pi region are determined.
[0071] This step specifically includes the following steps:
[0072] First, the silicon wafer is heat-treated. The atmosphere during the heat treatment process includes, but is not limited to, argon. The process temperature is 800℃~1000℃, and the process time is 2 hours~4 hours. Preferably, the process temperature is 950℃, and the process time is 3 hours. The oxygen content of the silicon wafer is 5ppma~20ppma. Compared to the existing technology's heat treatment for BMD (with or without oxygen precipitation) growth, which requires heating at 800℃ for 4 hours and at 1000℃ for 16 hours, this embodiment only requires the defects to grow to a level that the LST can detect and distinguish. It does not require sufficient oxygen precipitation to grow and measure its density, thus improving the heat treatment process for BMD growth, significantly reducing the time required for silicon wafer heat pretreatment, and lowering process costs.
[0073] Next, the particles in the heat-treated silicon wafer are measured again using LST to obtain a fourth measurement result. This fourth measurement result also includes particle density and particle size.
[0074] Next, based on the fourth measurement result, the second preset size, the fifth preset density value, and the sixth preset density value, the Pv region, the I-rich region, and the Pi region are determined. Specifically,
[0075] If the fourth measurement result contains a region where the particle density is greater than the fifth preset density value, then that region is determined to be a Pv region. The fifth preset density value can be 4 × 10⁻⁶. 7 cm -3 ~10 8 cm -3 Preferably, the fifth preset density value is 5×10⁻⁶. 7 cm -3 .
[0076] If the fourth measurement result contains a region where the particle density is between the fifth and sixth preset density values, and the particle size is larger than the second preset size, then this region is determined to be an I-rich region. The sixth preset density value can be 0 to 4 × 10⁻⁶. 6 cm -3 Preferably, the sixth preset density value is 10. 6 cm -3 The second preset size can be 30nm to 40nm, preferably 40nm.
[0077] If the fourth measurement result contains a region where the particle density is less than the sixth preset density value and the particle size is greater than the second preset size, then the region is determined to be the Pi region.
[0078] In this step, the measurement results are presented using a particle size-particle number bar chart, which clearly and intuitively displays key information. The particle density of the fourth measurement result and the particle density of the third measurement result can also be calculated from the bar chart.
[0079] In summary, this invention provides a method for determining defect types in monocrystalline silicon wafers. Based on LST measurement results, it accurately and effectively distinguishes four regions—V-rich, Pv, Pi, and I-rich—in monocrystalline silicon wafers using particle density or a combination of particle density and size. This results in clearly distinguishable test results, high test stability, and high repeatability, thereby reducing the requirements on silicon wafers for defect partitioning. Furthermore, the use of short-time heat treatment combined with LST measurement offers advantages in terms of high efficiency and low cost for silicon wafer defect characterization. The shortened heat treatment time significantly reduces the required heat treatment time for silicon wafers, lowering process complexity and costs.
[0080] Furthermore, it should be noted that, unless otherwise specified or indicated, the terms "first" and "second" in the specification are used only to distinguish the various components, elements, steps, etc. in the specification, and are not used to indicate the logical or sequential relationships between the various components, elements, steps, etc.
Claims
1. A method for determining the type of defects in a single-crystal silicon wafer, characterized in that, Includes the following steps: The particles in the As-Grown silicon wafer are measured using LST to obtain a first measurement result, and the V-rich region is determined based on the first measurement result and a first preset density value. as well as The silicon wafer is heat-treated, and the particles in the silicon wafer are measured again using LST to obtain a second measurement result. The second measurement result includes particle density. Based on the second measurement result, a second preset density value, and a third preset density value, the Pv region, I-rich region, and Pi region are determined. The determination method is as follows: The region in the second measurement result where the particle density is greater than the second preset density value is determined as the Pv region; The region in the second measurement result where the particle density is between the second preset density value and the third preset density value is determined as the I-rich region; as well as The region in the second measurement result where the particle density is less than the third preset density value is determined as the Pi region.
2. The determination method as described in claim 1, characterized in that, The first measurement result includes particle density, and the method for determining the V-rich region based on the first measurement result, a first preset density value, and the first measurement result is as follows: The regions in the first measurement results where the particle density is greater than the first preset density value are identified as V-rich regions.
3. The determination method as described in claim 1, characterized in that, The silicon wafer is subjected to heat treatment in an argon atmosphere at a process temperature of 800°C to 1000°C for 2 to 4 hours, and the oxygen content of the silicon wafer is 5 ppma to 20 ppma.
4. The determination method as described in claim 1, characterized in that, The first preset density value is 2x10 6 cm -3 The second preset density value is 4x10 7 cm -3 The third preset density value is 5x10 6 cm -3 The fourth preset density value is 3x10 7 cm -3 The fifth preset density value is 2x10 5 cm -3 The sixth preset density value is 4x10 6 cm -3 .
5. A method for determining the type of defects in a single-crystal silicon wafer, characterized in that, Includes the following steps: The particles in the As-Grown silicon wafer are measured using LST to obtain a third measurement result, and the V-rich region is determined based on the first preset size, the fourth preset density value and the third measurement result. as well as The silicon wafer is heat-treated, and the particles in the silicon wafer are measured again using LST to obtain a fourth measurement result. The fourth measurement result includes particle density and particle size. Based on the fourth measurement result, a second preset size, a fifth preset density value, and a sixth preset density value, the Pv region, I-rich region, and Pi region are determined. The method for determining the Pv region, I-rich region, and Pi region is as follows: The region in the fourth measurement result where the particle density is greater than the fifth preset density value is determined as the Pv region; The region in the fourth measurement result where the particle density is between the fifth and sixth preset density values and the particle size is larger than the second preset size is determined to be an I-rich region; as well as The region in the fourth measurement result where the particle density is less than the sixth preset density value and the particle size is greater than the second preset size is determined to be the Pi region.
6. The determination method as described in claim 5, characterized in that, The third measurement result includes particle density and particle size. The method for determining the V-rich region based on the first preset size, the fourth preset density value, and the third measurement result is as follows: The region in the third measurement result where the particle density is greater than the fourth preset density value and the particle size is greater than the first preset size is determined to be a V-rich region.
7. The determination method as described in claim 5, characterized in that, The silicon wafer is subjected to heat treatment in an argon atmosphere at a process temperature of 800°C to 1000°C for 2 to 4 hours, and the oxygen content of the silicon wafer is 5 ppma to 20 ppma.
8. The determination method as described in claim 5, characterized in that, The first preset size is 20nm-25nm, the second preset size is 30nm-40nm, the fourth preset density value is 5x10 5 cm -3 ~5x10 6 cm -3 , the fifth preset density value is 4x10 7 cm -3 ~10 8 cm -3 , and the sixth preset density value is 0-4x10 6 cm -3 .