Crystal pulling method for reducing defect of heavily arsenic-doped COP and single-crystal crystal bar

Abstract

The invention provides a crystal pulling method for reducing heavy arsenic-doped COP defects and a single-crystal crystal bar, and belongs to the technical field of single-crystal silicon crystal pulling, the crystal pulling method comprises a doping step, a temperature testing step, a crystal seeding step, a shoulder enlarging step, a shoulder rotating step and an equal-diameter step which are carried out in sequence, in the doping step, the doping amount of each kilogram of total doping amount is 7.2-7.7 g, and the doping amount of each kilogram of total doping amount is 7.2-7.7 g; in the process that the arsenic is gasified along with the rising of the furnace temperature, most of the arsenic gas is taken away by argon and blown to a solid-liquid interface to be uniformly fused into crystals, and only a small part of the arsenic gas is fused into a melt to form impurities; in the shouldering step, the shouldering angle is kept between 20 degrees and 35 degrees by adopting a mode of reducing the temperature of a melt in a gradient manner, so that lattice stress caused by high-concentration arsenic doping is released, dislocation is avoided, fluctuation of a crystal growth interface is reduced, heat can be uniformly conducted in the radial direction of a crystal bar, an accumulation area of COP defects is reduced, and the yield of the crystal bar is improved. And generation of COP defects is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of single-crystal silicon crystal pulling, and particularly relates to a crystal pulling method and a single-crystal ingot for reducing heavily doped arsenic COP defects. Background Art

[0002] Heavily doped arsenic single-crystalline silicon has important applications in semiconductor device manufacturing. However, during the Cz method growth process, due to the large lattice stress caused by high-concentration arsenic doping, a large number of crystal originated particles (COP) defects are easily generated. COP defects will seriously affect the electrical performance and reliability of devices. Currently, the industry mainly reduces COP defects by optimizing the thermal field design and adjusting crystal pulling parameters; Existing ones, such as the Chinese invention patent with the application number "CN202310926929.6" discloses a method for improving single-crystal silicon micro-defects. During the crystal ingot pulling process, the thermal field with a cooling system includes a water-cooled thermal shield. An annular water-cooled cavity is opened in the water-cooled thermal shield, and the annular water-cooled cavity has the same shape as the water-cooled thermal shield. Cold water at a predetermined temperature is introduced into the annular water-cooled cavity in the water-cooled thermal shield, so that when the pulling speed V is the same, the temperature gradient G between the center and the edge of the solid-liquid interface is approximately 1, so that there will be no accumulation areas of two different point defects on the cross-section of the single crystal, and thus the formation of COP defects is suppressed, reducing the particle defects (COP) in the single crystal. However, when using the above technical solution to pull heavily doped arsenic single-crystalline silicon, due to introducing cold water at a predetermined temperature into the annular water-cooled cavity in the water-cooled thermal shield and a constant pulling speed, the temperature gradient G between the center and the edge of the solid-liquid interface is approximately 1, resulting in the inability to release the lattice stress caused by high-concentration arsenic doping, and thus the effect of reducing COP defects in heavily doped arsenic single-crystalline silicon is poor. Summary of the Invention

[0003] In view of this, aiming at the above deficiencies, it is necessary to propose a crystal pulling method for reducing heavily doped arsenic COP defects to reduce COP defects in heavily doped arsenic single-crystalline silicon; It is also necessary to provide a single-crystal ingot.

[0004] On the one hand, the present invention provides a crystal pulling method for reducing heavily doped arsenic COP defects, including the following steps, S1: Perform the doping step, temperature testing step, seed crystal pulling step, shoulder forming step, shoulder turning step, and constant diameter step in sequence. In the doping step, the doping amount input per kilogram of the total doping amount is 7.2 grams - 7.7 grams; S2: In the shoulder forming step, adopt a method of gradually reducing the melt temperature to keep the shoulder forming angle between 20° and 35°, so as to release the lattice stress caused by high-concentration arsenic doping, and thereby reduce the generation of COP defects.

[0005] Preferably, the method of gradually decreasing the melt temperature is specifically to decrease the temperature by 2°C - 3°C every 15 min - 25 min.

[0006] Preferably, in the shoulder releasing step, the argon flow rate is 115 slm - 125 slm, the furnace pressure is 15 Kpa - 17 Kpa, the drawing speed is 0.8 mm / min - 0.9 mm / min, and the crucible rotation speed is 2.5 rpm - 3.5 rpm.

[0007] Preferably, in the shoulder releasing step, a horizontal magnetic field with a magnetic field strength of 2000 GS - 3000 GS is applied to avoid segregation of high-concentration arsenic.

[0008] Preferably, in the shoulder turning step, the drawing speed is 1.5 mm / min - 2 mm / min.

[0009] Preferably, in the equal diameter step, the drawing speed is 0.7 mm / min - 1 mm / min.

[0010] On the other hand, the present invention provides a single crystal ingot, which is drawn by the crystal pulling method for reducing heavy-doped arsenic COP defects described in the above aspect.

[0011] As can be seen from the above technical solutions, a crystal pulling method for reducing heavy-doped arsenic COP defects provided by the present invention includes a doping step, a temperature testing step, a seed crystal introducing step, a shoulder releasing step, a shoulder turning step, and an equal diameter step that are carried out in sequence. In the doping step, the doping amount input per kilogram of the total doping input is 7.2 g - 7.7 g, so that during the process of arsenic gasifying as the furnace temperature rises, most of the arsenic gas will be carried away by argon and blown towards the solid-liquid interface to be uniformly incorporated into the crystal, and only a small part of the arsenic gas will be incorporated into the melt to form impurities; In the shoulder releasing step, the shoulder releasing angle is maintained between 20° - 35° by using a method of gradually decreasing the melt temperature, so as to release the lattice stress caused by high-concentration arsenic doping to avoid dislocation generation, reduce the fluctuation of the crystal growth interface, enable heat to be uniformly conducted along the radial direction of the ingot, reduce the accumulation area of COP defects, and thus reduce the generation of COP defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flowchart of the crystal pulling method for reducing heavy-doped arsenic COP defects provided by an embodiment of the present invention.

[0013] Figure 2 It is a detection result diagram of COP defects of the first heavy-doped arsenic ingot obtained by an embodiment of the method of the present invention.

[0014] Figure 3 It is a detection result diagram of COP defects of the second heavy-doped arsenic ingot obtained in Comparative Example 1.

[0015] Figure 4 It is a detection result diagram of the COP defects of the third arsenic-doped crystal bar obtained in Comparative Example 2. Specific Embodiments

[0016] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with the embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0017] Please refer to Figure 1 , on the one hand, the present invention provides a crystal pulling method for reducing COP defects of heavily arsenic-doped, including the following steps, S1: Perform the doping step, temperature testing step, crystal seeding step, shoulder releasing step, shoulder turning step, and equal diameter step in sequence. In the doping step, the doping amount input per kilogram of the total doping amount is 7.2 g - 7.7 g; S2: In the shoulder releasing step, adopt the method of gradually reducing the melt temperature to keep the shoulder releasing angle between 20° and 35°, so as to release the lattice stress caused by high-concentration arsenic doping, thereby reducing the generation of COP defects.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The crystal pulling method for reducing COP defects of heavily arsenic-doped provided by the present invention includes the doping step, temperature testing step, crystal seeding step, shoulder releasing step, shoulder turning step, and equal diameter step performed in sequence. In the doping step, the doping amount input per kilogram of the total doping amount is 7.2 g - 7.7 g, so that during the process of arsenic gasifying as the furnace temperature rises, most of the arsenic gas will be carried away by argon and blown to the solid-liquid interface to be evenly incorporated into the crystal, and only a small part of the arsenic gas will be incorporated into the melt to form impurities; In the shoulder releasing step, adopt the method of gradually reducing the melt temperature to keep the shoulder releasing angle between 20° and 35°, so as to release the lattice stress caused by high-concentration arsenic doping to avoid the generation of dislocations, reduce the fluctuation of the crystal growth interface, enable heat to be evenly conducted along the radial direction of the crystal bar, reduce the accumulation area of COP defects, and thereby reduce the generation of COP defects.

[0019] In one embodiment, the method of gradually reducing the melt temperature is specifically to reduce 2°C - 3°C every 15 min - 25 min.

[0020] In one embodiment, in the shoulder releasing step, the argon flow rate is 115 slm - 125 slm, the furnace pressure is 15 Kpa - 17 Kpa, the pulling speed is 0.8 mm / min - 0.9 mm / min, and the crucible rotation speed is 2.5 rpm - 3.5 rpm.

[0021] In one embodiment, in order to avoid strong thermal convection caused by too high melt temperature, resulting in segregation of arsenic element due to uneven distribution at the solid-liquid interface, during the shoulder broadening step, a horizontal magnetic field with a magnetic field intensity of 2000 GS - 3000 GS is applied to avoid segregation of high-concentration arsenic.

[0022] In one embodiment, during the shoulder transition step, the pulling speed is 1.5 mm / min - 2 mm / min.

[0023] In one embodiment, during the equal diameter step, the pulling speed is 0.7 mm / min - 1 mm / min.

[0024] On the other hand, the present invention provides a single crystal ingot, which is drawn by the crystal pulling method for reducing heavy-doped arsenic COP defects described in the above aspect.

[0025] Through the examples of the method of the present invention and the comparative examples of the traditional method, the technical solutions and technical effects of the present invention are further illustrated. It should be noted that the following experimental examples are only for further explaining the present invention and do not limit the technical solutions of the present invention.

[0026] Example: Using a CV type single crystal furnace, an 8-inch single crystal is drawn with a crystal orientation of <100>. The ratio of the doping amount to the total feeding amount is doped according to 7.5 g / kg, where the feeding amount is 120 kg and the doping amount is 900 g. First, the polysilicon raw material is loaded into a quartz crucible. In a vacuum environment, argon is used as a protective gas, and the polysilicon is heated to above 1420 °C. Then, this temperature is maintained for a period of time to melt the silicon material. After changing from solid state to liquid state, a doping step is carried out. After the doping is completed, under an argon flow rate of 120 slm, a furnace pressure of 16 Kpa, and a crucible rotation speed of 3 rpm, a temperature measurement step is carried out to obtain the test temperature, and the crystal seeding step is carried out at a pulling speed of 0.85 mm / min. After the crystal seeding step is completed, a horizontal magnetic field with a magnetic field intensity of 2400 GS is applied, and the melt temperature is reduced at a rate of 2.2 °C every 20 min to keep the shoulder broadening angle at 25° for the shoulder broadening step. During the shoulder transition step, the pulling speed is increased to 1.8 mm / min. During the equal diameter step, the pulling speed is reduced to 0.8 mm / min. Then, the crystal growth process is completed by tailing and cooling to obtain the first heavy-doped arsenic ingot. The first heavy-doped arsenic ingot is cut into silicon wafers with a thickness of 1 mm and mechanically polished. One silicon wafer is randomly selected from the head, middle, and tail positions of the first heavy-doped arsenic ingot to obtain the first head silicon wafer, the first middle silicon wafer, and the first tail silicon wafer. The SP1 detection of COP defects is carried out on the first head silicon wafer, the first middle silicon wafer, and the first tail silicon wafer. The detection results are as Figure 2 shown.

[0027] Comparative Example 1: Using a CV type single crystal furnace, an 8-inch single crystal was pulled, with a crystal orientation of <100>. The ratio of the doping amount to the total feeding amount was doped at 5.8 g / kg. The feeding amount was 120 kg and the doping amount was 700 g. First, the polysilicon raw material was placed in a quartz crucible. In a vacuum environment, argon was used as the protective gas, and the polysilicon was heated to above 1420 °C. Then, this temperature was maintained for a period of time to melt the silicon material. After changing from the solid state to the liquid state, the doping step was carried out. After the doping was completed, under an argon flow rate of 120 slm, a furnace pressure of 14 Kpa, and a crucible rotation speed of 3 rpm, the temperature measurement step was carried out to obtain the test temperature, and the seed crystal pulling step was carried out at a pulling speed of 0.85 mm / min. After the seed crystal pulling step was completed, the melt temperature was decreased at a rate of 2.5 °C every 20 min to keep the shoulder angle at 37° for the shoulder forming step. In the shoulder turning step, the pulling speed was increased to 1.8 mm / min. In the constant diameter step, the pulling speed was decreased to 0.8 mm / min. Then, the finishing and cooling were carried out to complete the crystal growth process, obtaining a doubly arsenic-doped crystal bar. The doubly arsenic-doped crystal bar was cut into silicon wafers with a thickness of 1 mm and mechanically polished. One silicon wafer was randomly selected from the head, middle, and tail positions of the doubly arsenic-doped crystal bar, respectively, to obtain the second head silicon wafer, the second middle silicon wafer, and the second tail silicon wafer. The second head silicon wafer, the second middle silicon wafer, and the second tail silicon wafer were subjected to SP1 detection for COP defects, and the detection results are as Figure 3 shown.

[0028] Comparative Example 2: Using a CV type single crystal furnace, an 8-inch single crystal was pulled, with a crystal orientation of <100>. The ratio of the doping amount to the total feeding amount was doped at 3.5 g / kg. The feeding amount was 120 kg and the doping amount was 420 g. First, the polysilicon raw material was placed in a quartz crucible. In a vacuum environment, argon was used as the protective gas, and the polysilicon was heated to above 1420 °C. Then, this temperature was maintained for a period of time to melt the silicon material. After changing from the solid state to the liquid state, the doping step was carried out. After the doping was completed, under an argon flow rate of 135 slm, a furnace pressure of 12 Kpa, and a crucible rotation speed of 3 rpm, the temperature measurement step was carried out to obtain the test temperature, and the seed crystal pulling step was carried out at a pulling speed of 0.85 mm / min. After the seed crystal pulling step was completed, the melt temperature was decreased at a rate of 2.1 °C every 20 min to keep the shoulder angle at 35° for the shoulder forming step. In the shoulder turning step, the pulling speed was increased to 1.8 mm / min. In the constant diameter step, the pulling speed was decreased to 1 mm / min. Then, the finishing and cooling were carried out to complete the crystal growth process, obtaining a triply arsenic-doped crystal bar. The triply arsenic-doped crystal bar was cut into silicon wafers with a thickness of 1 mm and mechanically polished. One silicon wafer was randomly selected from the head, middle, and tail positions of the triply arsenic-doped crystal bar, respectively, to obtain the third head silicon wafer, the third middle silicon wafer, and the third tail silicon wafer. The third head silicon wafer, the third middle silicon wafer, and the third tail silicon wafer were subjected to SP1 detection for COP defects, and the detection results are as Figure 4 shown.

[0029] Please refer to Figure 3 and Figure 4 , it can be clearly observed that there are obvious COP defects in the heavily arsenic-doped crystals obtained in Comparative Example 1 and Comparative Example 2. Please refer to Figure 2 , it can be found that the COP defects in the heavily arsenic-doped crystals obtained in the examples of the method of the present invention basically disappear. From the above comparison, it can be proved that in the present application, on the one hand, in the doping step, the doping amount input per kilogram of the total doping amount is 7.2 g - 7.7 g, so that most of the arsenic gas will be carried away by argon and blown towards the solid-liquid interface and evenly incorporated into the crystal during the process of arsenic gasification as the furnace temperature rises, and only a small part of the arsenic gas will be incorporated into the melt to form impurities. On the other hand, the shoulder angle is maintained between 20° and 35° by adopting the method of gradually decreasing the melt temperature, so that the lattice stress caused by high-concentration arsenic doping can be released to avoid dislocation generation, reduce the fluctuation of the crystal growth interface, enable heat to be evenly conducted along the radial direction of the crystal rod, reduce the accumulation area of COP defects, and then reduce the generation of COP defects, which well solves the technical problem of generating more COP defects during the pulling of heavily arsenic-doped crystal rods and effectively improves the quality of heavily arsenic-doped crystal rods.

[0030] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A crystal pulling method for reducing heavily doped arsenic COP defects, characterized in that: It includes the following steps. S1: Successively perform the doping step, temperature testing step, seed crystal drawing step, shoulder releasing step, shoulder turning step, and equal diameter step. In the doping step, the doping amount input per kilogram of the total doping amount is 7.2 g - 7.7 g. S2: In the shoulder releasing step, adopt the method of gradually decreasing the melt temperature to keep the shoulder releasing angle between 20° and 35°, so as to release the lattice stress caused by high-concentration arsenic doping, thereby reducing the generation of COP defects.

2. The crystal pulling method for reducing heavily doped arsenic COP defects as described in claim 1, characterized in that: The method of gradually decreasing the melt temperature is specifically to decrease 2°C - 3°C every 15 min - 25 min.

3. The crystal pulling method for reducing heavily doped arsenic COP defects as described in claim 1 or 2, characterized in that: In the shoulder releasing step, the argon flow rate is 115 slm - 125 slm, the furnace pressure is 15 Kpa - 17 Kpa, the drawing speed is 0.8 mm / min - 0.9 mm / min, and the crucible rotation speed is 2.5 rpm - 3.5 rpm.

4. The crystal pulling method for reducing heavily doped arsenic COP defects according to claim 1, characterized in that: In the shoulder releasing step, a horizontal magnetic field with a magnetic field strength of 2000 GS - 3000 GS is also applied to avoid segregation of high-concentration arsenic.

5. The crystal pulling method for reducing heavily doped arsenic COP defects according to claim 1, characterized in that: In the shoulder turning step, the drawing speed is 1.5 mm / min - 2 mm / min.

6. The crystal pulling method for reducing heavily doped arsenic COP defects according to claim 1, characterized in that: In the equal diameter step, the drawing speed is 0.7 mm / min - 1 mm / min.

7. A single crystal ingot, characterized in that: It is drawn by the crystal pulling method for reducing the COP defects of heavily doped arsenic as described in any one of claims 1 - 6.

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