Method for improving OISF defect of 8-inch light phosphorus-doped single crystal and product thereof

Abstract

The invention belongs to the technical field of semiconductor material processing, and particularly relates to a method for improving an OISF defect of an 8-inch light phosphorus-doped single crystal and a product thereof, and the method comprises the following steps: in the crystal pulling process, reducing the pulling speed, flattening a solid-liquid interface, balancing the growth rate and the release of thermal stress, so as to reduce the thermal stress and inhibit the formation of the OISF defect; the liquid opening distance is increased, the increase of the liquid opening distance enables the crystal to experience a slower cooling rate in the growth process so as to reduce the accumulation of thermal stress, so that the dislocation defect in the crystal is reduced, dislocation is a potential nucleation point of OISF, and therefore, the increase of the liquid opening distance can inhibit the formation of the OISF defect; after the crystal growth is finished, the cooling rate is increased, so that a crystal bar quickly passes through a temperature interval, the generation of O2V is reduced, the generation of OISF defects is avoided, oxygen atoms are in a solid solution state in the silicon crystal at high temperature, and the higher cooling rate can inhibit the diffusion and aggregation of oxygen, reduce the formation of oxygen precipitates, reduce the density of the OISF defects and also avoid the generation of the OISF defects; therefore, the OISF defect of the 8-inch light phosphorus-doped single crystal is reduced, and the electrical property of the 8-inch light phosphorus-doped single crystal is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material processing, and in particular relates to a method for improving OISF defects of an 8-inch lightly phosphorus-doped single crystal and a product thereof. Background Art

[0002] As a key foundational material in the semiconductor industry, Czochralski silicon single crystals play a crucial role in the manufacturing of high-power devices and integrated circuits. Their excellent electrical properties and favorable physical characteristics make them an indispensable component of modern electronic technology. High-power devices play a core role in energy conversion and power transmission, while integrated circuits are the foundation for the complex functions of various electronic devices. Therefore, the quality and performance of Czochralski silicon single crystals are directly related to the stability, reliability, and overall performance of these devices and circuits.

[0003] As a key type of Czochralski silicon single crystal, 8-inch lightly phosphorus-doped single crystals, with their moderate size, excellent electrical properties, and low production cost, play a crucial role in semiconductor manufacturing. They can meet the production needs of mid- and low-end integrated circuits and some specific high-power devices, playing a significant role in promoting the diversified development of the semiconductor industry and reducing the cost of electronic products.

[0004] During the growth of 8-inch lightly phosphorus-doped single crystals, a supersaturation of point defects occurs at the solid-liquid interface. During cooling, some of these point defects transform into microdefects, while any remaining defects that remain serve as nucleation centers during the subsequent high-temperature oxidation process. During thermal oxidation, self-interstitial atoms are generated at the silicon-silicon dioxide interface. These self-interstitial atoms diffuse into these nucleation centers, gradually forming oxidation-induced stacking faults (OISFs). OISFs typically take the form of boat-, bow-, or rod-shaped etch pits. These specific pit shapes can damage the crystal structure of the 8-inch lightly phosphorus-doped single crystal, affecting its electrical properties. Summary of the Invention

[0005] In view of this, the present invention provides a method and product for improving the OISF defects of 8-inch lightly phosphorus-doped single crystals, so as to solve the above-mentioned technical problem caused by the easy formation of oxidation induced stacking faults (OISF) when pulling 8-inch lightly phosphorus-doped single crystal products in the prior art.

[0006] To achieve the above objectives, this application adopts the following scheme: A method for improving OISF defects in 8-inch lightly phosphorus-doped single crystals comprises: reducing the pulling speed during the equal diameter process to flatten the solid-liquid interface, balancing the growth rate with the release of thermal stress, reducing thermal stress, and inhibiting the formation of OISF defects; increasing the liquid nozzle distance to allow the crystal to experience a slower cooling rate during growth, thereby reducing the accumulation of thermal stress and thus reducing dislocation defects in the crystal; and increasing the cooling rate after crystal growth to allow the crystal rod to quickly pass through the temperature range and avoid the generation of OISF defects.

[0007] Preferably, the pulling speed is reduced to 0.4 mm / min-1.0 mm / min.

[0008] Preferably, the liquid port distance is increased to 25 mm-45 mm.

[0009] Preferably, the temperature in the temperature range is 900°C-1050°C.

[0010] Preferably, the cooling rate after the crystal growth is completed is increased to 10 mm / min-25 mm / min.

[0011] Preferably, the pulling speed is reduced to 0.6 mm / min-0.8 mm / min, the liquid nozzle distance is increased to 30 mm-40 mm, and the cooling rate after the crystal growth is completed is increased to 15 mm / min-20 mm / min.

[0012] Preferably, during the equal diameter process, the crucible rotation speed is 1 rpm-2 rpm, and the crystal rod rotation speed is 6.5 rpm-8 rpm.

[0013] Preferably, during the iso-diameter process, the furnace pressure is 7KPa-9KPa, and the argon flow rate is 100slm-150slm.

[0014] The single crystal product was prepared according to the above method for improving the OISF defects of 8-inch lightly phosphorus-doped single crystal.

[0015] In the above-mentioned method for improving the OISF defects of 8-inch lightly phosphorus-doped single crystals, during the isodiameter process, that is, during crystal growth, the pulling speed is first reduced to make the solid-liquid interface flat, balance the growth rate with the release of thermal stress, thereby reducing thermal stress and inhibiting the formation of OISF defects. Then, the distance between the amorphous crystal in the melt and the melt surface, namely the liquid nozzle distance, is increased. The increase in the liquid nozzle distance can cause the crystal to experience a slower cooling rate during growth, thereby reducing the accumulation of thermal stress and thus reducing dislocation defects in the crystal. Dislocations are potential nucleation sites for OISF. Therefore, increasing the liquid nozzle distance will inhibit the formation of OISF defects. After the completion of crystal growth, the cooling rate is increased to allow the crystal rod to pass through the temperature range quickly, reducing the generation of O2V, thereby avoiding the generation of OISF defects. At high temperatures, oxygen atoms are in a solid solution state in the silicon crystal. The faster cooling rate will inhibit the diffusion and aggregation of oxygen, reduce the formation of oxygen precipitates, reduce the density of OISF defects, and also avoid the generation of OISF defects, thereby reducing the OISF defects of the 8-inch lightly phosphorus-doped single crystal and improving its electrical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a macroscopic image of a crystal rod slice prepared in the embodiment.

[0017] Figure 2 This is a macroscopic image of the crystal rod slice prepared in the comparative example. DETAILED DESCRIPTION

[0018] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. Preferred embodiments of the present application will also be described. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] A method for improving OISF defects in 8-inch lightly phosphorus-doped single crystals comprises: reducing the pulling speed during the equal diameter process to flatten the solid-liquid interface, balancing the growth rate with the release of thermal stress, reducing thermal stress, and inhibiting the formation of OISF defects; increasing the liquid nozzle distance to allow the crystal to experience a slower cooling rate during growth, thereby reducing the accumulation of thermal stress and thus reducing dislocation defects in the crystal; and increasing the cooling rate after crystal growth to allow the crystal rod to quickly pass through the temperature range and avoid the generation of OISF defects.

[0021] Ingot growth is primarily determined by the pulling rate. Excessively fast pulling rates can lead to uneven oxygen distribution within the crystal, forming localized enriched zones and increasing the likelihood of OISF defects. Therefore, in this embodiment, the pulling rate is reduced to flatten the solid-liquid interface. This also increases the axial temperature gradient at the crystallization interface, creating a certain degree of undercooling. This provides sufficient growth momentum for the single crystal and reduces the likelihood of OISF defects. The liquid-inlet distance, the distance between the amorphous crystals in the melt and the melt surface, affects the longitudinal growth rate, surface shape, and crystal quality. A larger liquid-inlet distance results in a slower cooling rate during crystal growth, reducing the accumulation of thermal stress. This reduced thermal stress reduces defects such as dislocations within the crystal. Dislocations are potential nucleation sites for OISF defects. Therefore, increasing the liquid-inlet distance suppresses OISF defect formation. By increasing the liquid-inlet distance and reducing the pulling rate, end flow and impurity fluctuations are suppressed, microscopic defects are reduced, the distribution of oxygen content is controlled, and thermal stress within the crystal is reduced, thus controlling the density of OISF defects while ensuring crystal quality. Increasing the cooling rate of the crystal rod allows the crystal rod to pass through the temperature range quickly, reducing the generation of O2V and thus avoiding the generation of OISF defects. At high temperatures, oxygen atoms are in a solid solution state in the silicon crystal. A faster cooling rate will inhibit the diffusion and aggregation of oxygen, reduce the formation of oxygen precipitation, and reduce the density of OISF defects, thereby reducing the OISF defects of the 8-inch lightly phosphorus-doped single crystal, improving its electrical properties and increasing its yield.

[0022] In a specific embodiment, the pulling speed is reduced to 0.4 mm / min-1.0 mm / min. If the pulling speed is too high, the single crystal will produce structural defects, resulting in lattice distortion. Excessive pulling speed may cause uneven distribution of oxygen in the crystal, forming local enrichment areas and increasing the probability of OISF defects. Therefore, in this embodiment, it is more appropriate to reduce the pulling speed to 0.4 mm / min-1.0 mm / min. The appropriate pulling speed will make the solid-liquid interface flat, balance the growth rate and the release of thermal stress, reduce thermal stress, and inhibit the formation of defects. The temperature gradient is gentle, allowing oxygen to partially diffuse to the surface or be evenly distributed, reducing supersaturation, reducing oxygen precipitation, and further reducing the formation of OISF defects.

[0023] The nozzle distance is increased to 25mm-45mm. Generally, a smaller nozzle distance results in faster liquid phase changes, which in turn increases the growth rate and, consequently, the ingot growth rate. Similarly, a larger nozzle distance reduces the ingot growth rate. However, a smaller nozzle distance may enhance thermal convection in the melt, leading to a more uneven distribution of impurities (such as metal contamination) and oxygen. Furthermore, a smaller nozzle distance shortens the diffusion path of oxygen from the crucible to the growth interface, increasing the oxygen content in the crystal and, in turn, forming oxygen precipitates, which serve as nucleation centers for OISF defects. Therefore, increasing the nozzle distance to 25mm-45mm is more appropriate.

[0024] Specifically, the temperature range is 900°C-1050°C. Generally, if a silicon single crystal ingot is cooled for too long or too slowly within the 900°C-1050°C range, a large amount of O2V will be generated, which will become the nucleation site for OISF defects. Therefore, after crystal growth is completed, the cooling rate is increased to 10mm / min-25mm / min to allow the ingot to quickly pass through the 900-1050°C temperature range to avoid the generation of OISF defects. Furthermore, at high temperatures, oxygen atoms are in a solid solution state in the silicon crystal. A faster cooling rate will inhibit the diffusion and aggregation of oxygen, reduce the formation of oxygen precipitates, and thus reduce the density of OISF defects.

[0025] Preferably, the pulling speed is reduced to 0.6 mm / min-0.8 mm / min, the liquid nozzle distance is increased to 30 mm-40 mm, and the cooling rate after the completion of crystal growth is increased to 15 mm / min-20 mm / min.

[0026] Specifically, in the equal diameter process, the crucible rotation speed is 1 rpm-2 rpm, the crystal rod rotation speed is 6.5 rpm-8 rpm, the furnace pressure is 7 KPa-9 KPa, and the argon flow rate is 100 slm-150 slm.

[0027] By controlling the crystal rotation / pot speed ratio, melt turbulence can be suppressed and the uniformity of solute distribution at the solid-liquid interface can be improved; high-flow argon gas effectively carries volatiles (such as SiO and CO), reduces interfacial impurity adsorption, and lowers dislocation density.

[0028] The single crystal product prepared according to the above method for improving the OISF defects of 8-inch lightly phosphorus-doped single crystal has fewer surface defects, oxidation-induced stacking faults (0ISF) are largely eliminated, and has excellent electrical properties.

[0029] The following is a detailed description of the technical solutions and effects of the present invention. It should be noted that the following examples are only intended to further explain the present invention and do not limit the technical solutions of the present invention. Example

[0030] When pulling an 8-inch lightly phosphorus-doped crystal rod using the original process, the pulling speed is controlled at 0.4-1.0 mm / min and the liquid nozzle distance is 25-45 during the crystal pulling stage. After the crystal growth is completed, the cooling rate of the silicon single crystal rod in the range of 900℃-1050℃ is 10-25 mm / min. Under these conditions, the crystal rod is pulled and cut into single crystal silicon wafers. After heat treatment at 1100℃ for 2 hours, the wafers are preferentially etched. The macroscopic picture is as follows: Figure 1 As shown, the yield of single crystal silicon pulled using the method provided in this embodiment is statistically shown in Table 1.

[0031] Comparative Example When pulling an 8-inch lightly phosphorus-doped crystal rod using the original process, the pulling speed is controlled at 0.6-1.2 mm / min and the liquid nozzle distance is 20-35 during the crystal pulling stage. After the crystal growth is completed, the cooling rate of the silicon single crystal rod in the range of 900℃-1050℃ is 5-15 mm / min. Under these conditions, the crystal rod is pulled and cut into single crystal silicon wafers. After heat treatment at 1100℃ for 2 hours, the wafers are preferentially etched. The macroscopic picture is as follows Figure 2 As shown, the yield of single crystal silicon pulled using the method provided in this embodiment is statistically shown in Table 1.

[0032] Table 1 Statistics of single crystal yields of examples and comparative examples

[0033] Figure 2 Circular oxidation-induced stacking faults (OISF) can be observed with the naked eye. Figure 1 As can be seen from the figure, the surface defects of the crystal rod are greatly improved, and the oxidation induced stacking fault (0ISF) is also largely eliminated. The above comparison proves that the solution provided by this application can effectively improve the OISF defect problem when pulling 8-inch lightly phosphorus-doped crystal rods. Table 1 shows that the single crystal yield can be effectively improved when the crystal rod is pulled using this method in the embodiment.

[0034] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A method for improving OISF defects in 8-inch lightly phosphorus-doped single crystals, characterized in that: During the equal diameter process, the pulling speed is reduced to make the solid-liquid interface flat, balance the growth rate and the release of thermal stress, reduce thermal stress, and inhibit the formation of OISF defects; the liquid mouth distance is increased so that the crystal experiences a slower cooling rate during the growth process to reduce the accumulation of thermal stress, thereby reducing dislocation defects in the crystal; after the crystal growth is completed, the cooling rate is increased so that the crystal rod passes through the temperature range quickly to avoid the generation of OISF defects.

2. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 1, characterized in that: Reduce the pulling speed to 0.4mm / min-1.0mm / min.

3. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 1, characterized in that: Increase the liquid port distance to 25mm-45mm.

4. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 1, characterized in that: The temperature in the temperature range is 900°C-1050°C.

5. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 4, characterized in that: The cooling rate after the crystal growth is completed is increased to 10 mm / min-25 mm / min.

6. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 4, characterized in that: Reduce the pulling speed to 0.6mm / min-0.8mm / min, increase the liquid nozzle distance to 30mm-40mm, and increase the cooling rate after the crystal growth is completed to 15mm / min-20mm / min.

7. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 1, characterized in that: During the equal diameter process, the crucible speed is 1rpm-2rpm, and the crystal rod speed is 6.5rpm-8rpm.

8. The method for improving OISF defects of 8-inch lightly phosphorus-doped single crystal according to claim 1, characterized in that: During the isodiameter process, the furnace pressure is 7Kpa-9Kpa, and the argon flow rate is 100slm-150slm.

9. A single crystal product prepared by the method for improving OISF defects in 8-inch lightly phosphorus-doped single crystals according to any one of claims 1 to 8.

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