Silicon wafer with low oxygen content and low microdefect content, application of silicon wafer and method for detecting silicon wafer

Abstract

The invention belongs to the field of solar photovoltaics, and particularly relates to a silicon wafer with low oxygen content and low microdefect content, application of the silicon wafer and a method for detecting the silicon wafer. According to the silicon wafer with low oxygen content and low microdefect content, when the oxygen content in the silicon wafer is lower than 25 ppma, the COP (coefficient of performance) size is 100-200 nm, and the content is 1500-2000 / wafer; when the oxygen content in the silicon wafer is lower than 18 ppma, the COP (coefficient of performance) size is 60-150 nm, and the content is 1000-1400 pieces per wafer. The silicon wafer provided by the invention has the advantages of long service life, high use efficiency and higher stability when being applied to a photovoltaic power generation system. Meanwhile, the silicon wafer is low in preparation cost and beneficial to wide production and application. The detection method is wide in application range, high in accuracy and high in detection efficiency.

Description

Technical Field

[0001] This invention belongs to the field of solar photovoltaics, specifically relating to a silicon wafer with both low oxygen content and low micro-defect content, its application, and a method for testing silicon wafers. Background Technology

[0002] With traditional energy sources becoming increasingly depleted and environmental concerns rising, clean energy solar cells have garnered significant attention. As the photovoltaic industry rapidly develops, market demand for monocrystalline silicon is constantly increasing, especially regarding the quality of silicon wafers. The growing photovoltaic industry is driving the demand for high-efficiency monocrystalline silicon wafers. In terms of market size, the global market for high-efficiency monocrystalline silicon wafers for photovoltaic applications has maintained steady growth over the past few years, particularly in major photovoltaic countries such as China, the United States, and Japan, where demand is robust. From a technological perspective, continuous advancements in the production technology of high-efficiency monocrystalline silicon wafers have significantly improved product performance, providing strong support for the further development of the photovoltaic industry. Among these factors, oxygen content and micro-defect content are key factors affecting photovoltaic cell efficiency.

[0003] The oxygen content directly affects the lifespan of silicon wafers and the efficiency of solar cells. Silicon wafers with excessively high oxygen content still contain numerous micro-defects even after high-temperature annealing. This results in severe carrier recombination within the wafer, a shorter minority carrier lifetime, lower open-circuit voltage, and consequently, lower solar cell conversion efficiency. Furthermore, silicon wafers with high oxygen content are more prone to the thermal donor effect. The generation of thermal donors alters the carrier concentration, further impacting the conversion efficiency of the solar cell.

[0004] Micro-defects during crystal growth are a significant factor affecting wafer quality. They can act as getter sites, effectively adsorbing metallic impurities introduced during crystal growth, such as… Figure 1 As shown, under the same metallic atmosphere, silicon wafers with more micro-defects will retain more metallic impurities. COP is an octahedral void-type native micro-defect in silicon wafers. As a recombination center for charge carriers, it accelerates charge carrier recombination. At the same time, it may damage the integrity of the gate oxide in the device, causing problems such as PN junction leakage, reducing the lifespan of solar cells, and even affecting the stability of photovoltaic power generation systems.

[0005] Patent CN101514485A discloses a method and equipment for preparing low-oxygen-content silicon crystals, using the Chucklausky method to prepare silicon crystals, treating environmentally polluting reducing gases, and including a tail gas harmless treatment device connected to the outlet of a flashback retardant. However, this patent does not further study the prepared low-oxygen-content silicon crystals, nor does it study silicon wafers with low micro-defects. Patent CN117712204A discloses a low-oxygen silicon wafer and its preparation method. This invention relates to silicon wafers in batteries and battery modules, and includes relevant research and limitations on specific data such as the total oxygen content and antimony concentration of the silicon wafer itself, but it does not include relevant research and limitations on the low micro-defect aspect of the silicon wafer. Developing photovoltaic silicon wafers with both low oxygen content and low micro-defect content not only helps improve the performance and efficiency of photovoltaic cells, but also helps reduce production costs and improve the economics and market competitiveness of photovoltaic energy. Therefore, researching and developing a silicon wafer with both low oxygen content and low micro-defect content has significant practical implications. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of high oxygen content and numerous defects in silicon wafers in the prior art, which affect their lifespan in solar cells. This invention proposes a silicon wafer with both low oxygen content and low micro-defect content, as well as its application and a method for testing silicon wafers.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides a silicon wafer with both low oxygen content and low micro-defect content. When the oxygen content in the silicon wafer is less than 25 ppma, the COP size is 100-200 nm and the content is 1500-2000 pieces / wafer. When the oxygen content in the silicon wafer is less than 18 ppma, the COP size is 60-150 nm and the content is 1000-1400 pieces / wafer.

[0009] In this invention, the oxygen content is measured in parts per million (ppma) or parts per billion (ppba) and can be detected by any method known to those skilled in the art, typically Fourier transform infrared spectroscopy. Because silicon single crystal growth is highly stable, there is generally no significant gradient distribution in the radial direction of the silicon wafer. Therefore, the oxygen content measured at any point on the silicon wafer surface can represent the oxygen content of the entire wafer.

[0010] Furthermore, when the oxygen content is below 14 ppma, the COP size is less than 65 nm.

[0011] The detection limit of the laser scanning particle size analyzer of this invention is 65nm. When the COP size is less than 65nm, the laser scanning particle size analyzer will display that there is no COP.

[0012] Furthermore, the resistance of the silicon wafer is 0.5-20.0 Ω·cm.

[0013] Secondly, the present invention provides an application of a silicon wafer with both low oxygen content and low micro-defect content as described above in solar photovoltaic cells.

[0014] Thirdly, the present invention provides a method for detecting the size and quantity of COPs on a silicon wafer, comprising the following steps:

[0015] S.1. Clean the silicon wafer using SC1 solution;

[0016] S.2. The size and quantity of COPs present on the silicon wafer surface are characterized using a laser scanning particle size analyzer.

[0017] Furthermore, the time for cleaning the silicon wafer in step S.1 is 0.5-1.5 hours.

[0018] Furthermore, the SC1 solution mentioned in step S.2 contains NH3·H2O, H2O2, and H2O.

[0019] Furthermore, the volume ratio of NH3·H2O:H2O2:H2O in the SC1 solution is 1:1:5.

[0020] The beneficial effects of this invention are mainly reflected in:

[0021] (1) The present invention provides a silicon wafer with both low oxygen content and low micro-defect content. The low oxygen content and low micro-defect characteristics make the silicon wafer beneficial to increasing the service life and efficiency of solar photovoltaic cells and increasing the stability of photovoltaic power generation system.

[0022] (2) The present invention provides a silicon wafer with low cost, which is conducive to its widespread production and use in the market and to improving the economic efficiency and market competitiveness of photovoltaic energy. Therefore, the application of this silicon wafer has strong practical significance.

[0023] (3) The detection method described in this invention has high sensitivity and small size detection capability, and can quickly and non-destructively measure silicon wafers, and is applicable to a wide range of silicon wafers. Attached Figure Description

[0024] Figure 1 This diagram illustrates the retention of metallic impurities in silicon wafers with different micro-defect concentrations under the same metallic atmosphere.

[0025] Figure 2 This is a schematic diagram of the COP dimensions of silicon wafers with different oxygen contents.

[0026] Figure 3 This is a schematic diagram showing the COP (Coefficient of Performance) of silicon wafers with different oxygen contents. Detailed Implementation

[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. Unless otherwise specified, the methods used in the embodiments of the present invention are conventional methods, and the reagents used are commercially available.

[0028] Example 1:

[0029] 1. Experimental Methods:

[0030] Under the same process conditions, three boron-doped p-type silicon single crystals with a diameter of 200 mm, a crystal orientation of 100, a resistivity of 0.5-20.0 Ω·cm were grown using the Czochralski method. Among them, the oxygen content of single crystal 1 was 18-25 ppma; the oxygen content of single crystal 2 was 14-18 ppma; and the oxygen content of single crystal 3 was 14 ppma and below.

[0031] After the three single crystals were rounded, silicon wafers were cut from the same locations on each crystal (i.e., at the same distance from the shoulder of the single crystal). These wafers were then chemically and mechanically polished to produce polished silicon wafers. The resistivity of the three types of silicon wafers was measured using the four-probe method and was approximately 15 Ω·cm. The oxygen concentration in the three types of silicon wafers was measured using Fourier transform infrared spectroscopy.

[0032] The three types of silicon wafers were cleaned in an SC1 solution (NH3·H2O:H2O2:H2O=1:1:5) at 80℃ for 1 hour. After drying, the COP (Coefficient of Particle Size) of the silicon wafers was measured using a KLA-SP2 laser particle size analyzer to obtain information on the quantity and size distribution of COP. This device has a size resolution of 65nm. As mentioned earlier, the size of COP is typically between 80-200nm. Therefore, if the silicon wafer does not show COP detected by the laser particle size analyzer, it can be considered that the silicon wafer does not contain COP.

[0033] 2. Results Analysis:

[0034] Figure 2 The image shows the COPs distribution obtained after scanning the silicon wafer using a laser particle size analyzer. Figure 2 The COP size data for silicon wafers with different oxygen contents are shown. Figure 3The data on the number of COPs (Chip Optimizers) for silicon wafers with different oxygen contents are displayed. Specifically, when the oxygen content in the silicon wafer is below 25 ppma, the COP size is 100-200 nm, and the content is 1500-2000 pieces / wafer; when the oxygen content in the silicon wafer is below 18 ppma, the COP size is 60-150 nm, and the content is 1000-1400 pieces / wafer; when the oxygen content is below 14 ppma, the COP size is less than 65 nm.

[0035] As can be seen, compared with the number of COPs and the average size of silicon wafers 1 and 2, silicon wafer 3, with an oxygen content of 14 ppma or less, does not contain COPs. That is, within the detection range, the COP size is less than 65 nm, which can be called a near-perfect silicon wafer.

Claims

1. A silicon wafer with both low oxygen content and low micro-defect content, characterized in that, When the oxygen content in the silicon wafer is less than 25 ppma, the COP size is 100-200 nm and the content is 1500-2000 pieces / wafer; when the oxygen content in the silicon wafer is less than 18 ppma, the COP size is 60-150 nm and the content is 1000-1400 pieces / wafer.

2. A silicon wafer with both low oxygen content and low micro-defect content as described in claim 1, characterized in that, When the oxygen content is below 14 ppma, the COP size is less than 65 nm.

3. A silicon wafer with both low oxygen content and low micro-defect content as described in claim 2, characterized in that, The resistance of the silicon wafer is 0.5-20.0 Ω·cm.

4. The application of a silicon wafer with both low oxygen content and low micro-defect content as described in claims 1-3 in solar photovoltaic cells.

5. A method for detecting the COP size and quantity of a silicon wafer, characterized in that, Includes the following steps: S.

1. Clean the silicon wafer using SC1 solution; S.

2. The size and quantity of COPs present on the silicon wafer surface are characterized using a laser scanning particle size analyzer.

6. The method for detecting the COP size and quantity of a silicon wafer as described in claim 5, characterized in that, The silicon wafer is cleaned for 0.5-1.5 hours as described in step S.

1.

7. The method for detecting the COP size and quantity of a silicon wafer as described in claim 5, characterized in that, The SC1 solution mentioned in step S.2 contains NH3·H2O, H2O2, and H2O.

8. The method for detecting the COP size and quantity of a silicon wafer as described in claim 7, characterized in that, The volume ratio of NH3·H2O:H2O2:H2O in the SC1 solution is 1:1:5.

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