Method for controlling resistivity drop amplitude of low-resistance heavily-doped single crystal

Abstract

The invention provides a method for controlling the resistivity drop amplitude of a heavily doped single crystal, and relates to the technical field of heavily doped crystal pulling, in the crystal pulling process, after the curing rate, through common adjustment of the pulling speed, pressure and argon, a crystal bar with the resistivity drop amplitude being less than or equal to 0.4 m omega when the resistivity is below low resistance is pulled; wherein the pulling speed is kept unchanged, the change amplitude of unit pressure is 5Kpa / 100mm to 30Kpa / 100mm, and the change amplitude of unit argon is 10slm / 100mm to 40slm / 100mm, as the current process cannot directly obtain that the head resistance is low resistance, after a certain curing rate, when the resistivity of a crystal bar reaches low resistance, the pulling speed, the pressure and the argon are jointly adjusted, so that the qualification rate is improved, and the production cost is reduced. Meanwhile, the stability is improved, and the standard deviation is reduced (N is equal to 10).

Description

Technical Field

[0001] The present invention belongs to the technical field of heavily doped crystal pulling, and in particular relates to a method for controlling the resistivity reduction range of a low-resistance heavily doped single crystal. Background Art

[0002] One of the key quality control requirements of heavily doped single crystals is resistivity. The highest goal of resistivity control is that the resistivity distribution from beginning to end can meet the specification requirements. Taking 8-inch heavily doped arsenic as an example, the common resistivity specification distribution is 0-6mΩ, of which 2-3mΩ and 3-4mΩ are the main ones. For heavily doped single crystals, it is important to completely control the resistivity within the specification range. When the head resistance is ≥3mΩ and the resistivity range is ≥0.6mΩ, conventional control means can fully meet the requirements. The conventional control means is to control the pressure gradient. When the head resistivity requirement is high, the pressure is reduced, and vice versa. High pressure, when the resistivity range is large, the pressure gradient is set smaller, and vice versa, to ensure that the resistivity of the entire crystal rod is within the required range. However, when the head resistance is ≤3mΩ or the resistivity range is ≤0.6mΩ, conventional control methods cannot fully meet the control requirements and can only partially meet the requirements. When the head resistance is smaller or the resistivity range is smaller, the conventional control methods can control the resistivity to a shorter qualified length within the required range, and the stability cannot be guaranteed, that is, the qualified rate (the ratio of the weight of the resistivity within the required range / total weight) is unstable and has a large dispersion, which cannot meet the quality control requirements.

[0003] However, when the head resistivity is below the low resistance or the resistivity range is required to be ≤0.4mΩ, conventional control methods are not applicable, because the lower the resistivity range, the higher the pressure needs to be adjusted, but the equipment and thermal field have certain limitations, which makes it impossible to increase the pressure, and when the pressure reaches a certain critical value, the resistivity no longer changes, and the correlation between the increase in pressure and the resistivity becomes very weak; therefore, it is necessary to explore a method that can control the resistivity range of the crystal rod to ≤0.4mΩ when the resistivity is below the low resistance, so as to improve the pass rate. Summary of the invention

[0004] In view of this, the present invention provides a method for controlling the resistivity reduction range of a low-resistance heavily-doped single crystal.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for controlling the resistivity reduction range of a low-resistance heavily doped single crystal, wherein during the crystal pulling process, after the solidification rate, the pulling speed, pressure, and argon gas are jointly adjusted to pull a crystal rod with a resistivity reduction range of ≤0.4 mΩ when the resistivity is below the low resistance; Among them: the pulling speed remains unchanged, the unit pressure changes within a range of 5Kpa / 100mm-30Kpa / 100mm, and the unit argon changes within a range of 10slm / 100mm-40slm / 100mm.

[0006] Preferably, the pressure needs to be adjusted below a critical pressure value, and the argon gas needs to be adjusted between critical argon gas flow rates.

[0007] Preferably, the pulling speed remains unchanged after the solidification rate, and the pulling speed is 0.3 mm / min-0.7 mm / min.

[0008] Preferably, the pressure is 30-50 KPa, and the argon gas is 40-200 slm.

[0009] Preferably, when the resistivity is determined and the magnitude of the resistivity decreases, the pulling speed decreases as the magnitude of the resistivity decreases; When the resistivity is determined and the resistivity decreases, the unit pressure change increases as the resistivity decreases. When the resistivity is determined and the resistivity drop amplitude is required to decrease, the unit argon gas change amplitude increases as the resistivity drop amplitude decreases.

[0010] Preferably, compared with the resistivity decrease of 0.4 mΩ, for every 0.1 mΩ decrease in the resistivity, the pulling speed decreases by 10%-40%; the unit pressure change increases by 0.5-3.5 times; and the unit argon change increases by 0.5-3.5 times.

[0011] Preferably, the resistivity decreases by no less than 0.2 mΩ.

[0012] Preferably, within the same length range, the unit pressure change amplitude and the unit argon change amplitude do not change at the same time.

[0013] Preferably, the unit pressure change amplitude and the unit argon change amplitude vary when the solidification rate is 200-500mm.

[0014] Preferably, the pressure changes first and the argon changes later.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for controlling the resistivity reduction range of a low-resistance heavily-doped single crystal. In the process of pulling the crystal, after the solidification rate, the pulling speed, pressure and argon are jointly adjusted to pull a crystal rod with a resistivity reduction range of ≤0.4 mΩ when the resistivity is below the low resistance; wherein: the pulling speed remains unchanged, the unit pressure variation range is between 5 Kpa / 100mm-30 Kpa / 100mm, and the unit argon variation range is between 10 slm / 100mm-40 slm / 100mm. Since the current process cannot directly obtain the head resistance as low resistance, after a certain solidification rate, when the resistivity of the crystal rod reaches the low resistance, the pulling speed, pressure and argon are jointly adjusted to exert a synergistic effect, so as to meet the resistivity distribution requirements under low resistance and narrow range, and maintain stable distribution, thereby improving the qualified rate, and at the same time improving the stability and reducing the standard deviation (N=10). BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the resistivity distribution diagram of Example 1.

[0017] Figure 2 This is the resistivity distribution diagram of comparative example A.

[0018] Figure 3 The normal distribution diagram of the qualified rate comparison of Example 1 and Comparative Example A is shown in FIG.

[0019] Figure 4 This is the resistivity distribution diagram of Example 2.

[0020] Figure 5 This is the resistivity distribution diagram of comparative example B.

[0021] Figure 6 The normal distribution diagram of the qualified rate comparison of Example 2 and Comparative Example B is shown in FIG.

[0022] Figure 7 This is the resistivity distribution diagram of Example 3. DETAILED DESCRIPTION

[0023] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0024] A method for controlling the resistivity reduction range of a low-resistance heavily doped single crystal, wherein during the crystal pulling process, after the solidification rate, the pulling speed, pressure, and argon gas are jointly adjusted to pull a crystal rod with a resistivity reduction range of ≤0.4 mΩ when the resistivity is below the low resistance; Among them: the pulling speed remains unchanged, the unit pressure changes within a range of 5Kpa / 100mm-30Kpa / 100mm, and the unit argon changes within a range of 10slm / 100mm-40slm / 100mm.

[0025] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for controlling the resistivity reduction range of a low-resistance heavily-doped single crystal. In the process of pulling the crystal, after the solidification rate, the pulling speed, pressure and argon are jointly adjusted to pull a crystal rod with a resistivity reduction range of ≤0.4 mΩ when the resistivity is below the low resistance; wherein: the pulling speed remains unchanged, the unit pressure variation range is between 5 Kpa / 100mm-30 Kpa / 100mm, and the unit argon variation range is between 10 slm / 100mm-40 slm / 100mm. Since the current process cannot directly obtain the head resistance as low resistance, after a certain solidification rate, when the resistivity of the crystal rod reaches the low resistance, the pulling speed, pressure and argon are jointly adjusted to exert a synergistic effect, so as to meet the resistivity distribution requirements under low resistance and narrow range, and maintain stable distribution, thereby improving the qualified rate, and at the same time improving the stability and reducing the standard deviation (N=10).

[0026] Specifically, for heavily doped arsenic, the low resistance head resistivity is below 2.5 mΩ, for heavily doped antimony, the low resistance head resistivity is below 15 mΩ, and for heavily doped red phosphorus, the low resistance head resistivity is below 1.1 mΩ.

[0027] Specifically, the curing rate is greater than or equal to 0 and less than 100%.

[0028] Specifically, the solidification rate refers to the ratio of the solid part weight to the total weight after the single crystal is taken out. The size of the solidification rate depends on the required specification head resistivity. The larger the head resistivity, the smaller the solidification rate. Unit pressure change range: pressure change value / (change range / 100), expressed as pressure change per 100mm, unit: Kpa / 100mm, ± value indicates direction, + value indicates increase, - value indicates decrease; Unit argon gas change range: argon gas change value / (change range / 100), expressed as argon gas change per 100mm, unit: slm / 100mm, ± value indicates direction, + value indicates increase, - value indicates decrease.

[0029] Furthermore, the pressure needs to be adjusted below the critical pressure value, and the argon needs to be adjusted between the critical argon flow values; the critical pressure value is related to the thermal field and the specific configuration of the equipment, and the maximum critical argon flow rate is related to the thermal field and the specific configuration of the equipment.

[0030] Furthermore, the pulling speed remains unchanged after the solidification rate, and the pulling speed is 0.3 mm / min-0.7 mm / min.

[0031] Furthermore, the pressure is 30-50 KPa, and the argon gas is 40-200 slm.

[0032] Furthermore, when the resistivity is determined and the resistivity drop is required to decrease, the pulling speed decreases as the resistivity drop decreases. There is a correlation between the pulling speed and the resistivity drop. During the growth of a single crystal, the edge cools faster than the center. Due to the segregation effect, on a cross section, the impurity concentration in the center is higher than that at the edge, resulting in a lower resistivity at the center. When the pulling speed increases, the edge cools faster, resulting in a lower resistivity at the center. Therefore, there is a correlation between the pulling speed and the resistivity.

[0033] When the resistivity is determined and the resistivity drop is required to decrease, the unit pressure change increases as the resistivity drop decreases. When the pressure increases, the volatilization of impurities in the solution is suppressed, the volatilization amount of impurities is reduced, and the resistivity distribution follows the segregation effect more. Therefore, there is a correlation between the pressure change and the resistivity. The pressure setting should be below the critical pressure value. Above the critical pressure value, the correlation between the pressure increase and the resistivity becomes very weak.

[0034] When the resistivity is determined and the resistivity drop is required to decrease, the unit argon change increases as the resistivity drop decreases; the increase in argon will inhibit the volatilization of impurities in the solution, the volatilization of impurities will decrease, and the resistivity distribution will follow the segregation effect more. Therefore, there is a correlation between the change in argon and the resistivity. The setting of argon should be between the critical values ​​of argon. Outside the critical values ​​of argon, the correlation between the change in argon and the resistivity becomes very weak.

[0035] Furthermore, compared with the resistivity decrease of 0.4 mΩ, for every 0.1 mΩ decrease in the resistivity, the pulling speed decreases by 10%-40%; the unit pressure change increases by 0.5-3.5 times; and the unit argon change increases by 0.5-3.5 times.

[0036] Furthermore, the resistivity decreases by no less than 0.2 mΩ.

[0037] Furthermore, within the same length range, the unit pressure change amplitude and the unit argon change amplitude do not change at the same time to ensure smooth growth of the single crystal.

[0038] Furthermore, the unit pressure change amplitude and the unit argon change amplitude change when the solidification rate is 200mm-500mm.

[0039] Furthermore, the pressure changes first and the argon changes later.

[0040] Furthermore, the heavily doped single crystal is heavily doped with phosphorus, heavily doped with antimony, or heavily doped with arsenic.

[0041] The use of the present invention is described by the following examples. Embodiment 1:

[0042] A Hanhong 2408 single crystal furnace with a 24-inch hot field was used. The furnace type was the same in the following embodiments and comparative examples. An 8-inch heavily arsenic-doped crystal rod was pulled by MCZ, wherein: crystal rotation was 12 rpm; crucible rotation was 2 rpm; doping ratio was 10 times; Gap was 30 mm; head resistance was required to be 2.5 mΩ, resistivity control range was required to be 0.4 mΩ, actual resistivity of the crystal rod head was 2.7 mΩ, solidification rate was 30%, and multi-parameter method was used for control. The pulling speed was 0.56 mm / min, unit pressure variation was 5 Kap / 100 mm, pressure variation range was 40-20 KPa, variation interval was 400 mm, unit argon variation was 10 slm / 100 mm, argon variation range was 150-120 KPa, variation interval was 300 mm, and the pulling was performed 10 times to obtain an equal-diameter crystal rod control effect as shown in FIG. Figure 1 As shown (experimental group A), Figure 1 The horizontal axis represents the length of the single crystal with equal diameter, and the vertical axis represents the resistivity.

[0043] Comparative Example A The head resistance is required to be 2.5 mΩ, and the resistivity control range is required to be 0.4 mΩ. The actual resistivity of the crystal rod head is 2.7 mΩ, and the solidification rate is 30%. It is controlled only by pressure, and the unit pressure change range is 6.7 Kap / 100 mm, the pressure change range is 40 Kpa-20 Kpa, and the change interval is 300 mm. Others are the same as in Example 1. After 10 times of pulling, the control effect of the equal-diameter crystal rod is obtained. Figure 2 As shown, Figure 2 The horizontal axis represents the length of the single crystal with equal diameter, and the vertical axis represents the resistivity.

[0044] Depend on Figure 1 , Figure 2 It can be seen that, through the control method of Example 1 of the present invention, the single crystal length of the pulled crystal rod after the solidification rate reaches 30% is all controlled within the required resistivity range.

[0045] The qualified rates of Example 1 and Comparative Example A were compared, and the mean, range and standard deviation of the two were compared. The qualified rate was rounded, such as Figure 3 As shown, the fitted histogram made with Mintab can intuitively express the difference between the two sets of data. The horizontal axis is the pass rate, and the vertical axis is the percentage of an interval in the total sample.

[0046] Depend on Figure 3It can be seen that the mean value in comparative example A is 40%, the range is 16%, and the standard deviation is 5.42%; the mean value in example 1 is 55%, the range is 9%, and the standard deviation is 3.33%. Under the premise of a curing rate of 30%, the maximum qualified rate of example 1 is 55%. Under the same goal, the mean value of the control group and the experimental group represents the improvement of the qualified rate, and the range and standard deviation represent the improvement of stability. Embodiment 2:

[0047] Use Hanhong 2408 single crystal furnace, 24-inch hot field, MCZ to pull 8-inch heavily doped arsenic crystal rods, including: crystal rotation 12rpmm; crucible rotation 2rpm; doping ratio 10 times; Gap30mm; required head resistance: 2.2mΩ, resistivity required control range: 0.2mΩ, actual resistivity of crystal rod head 2.7mΩ, solidification rate 60%, multi-parameter method control, pulling speed 0.36mm / min, unit pressure change range 20Kap / 100mm, pressure change range: 40-20Kpa, change interval: 100mm, unit argon change range 30slm / 100mm, argon change range: 150-120Kpa, change interval: 100mm, pull 10 times; get equal diameter crystal rod control effect as shown Figure 4 As shown (experimental group B), Figure 4 The horizontal axis represents the length of the single crystal with equal diameter, and the vertical axis represents the resistivity.

[0048] Comparative Example B The head resistance is required to be 2.2 mΩ, and the resistivity control range is required to be 0.2 mΩ. The actual resistivity of the crystal rod head is 2.7 mΩ, and the solidification rate is 60%. It is controlled only by pressure, and the unit pressure change range is 10.0 Kap / 100 mm, the pressure change range is 40 Kpa-20 Kpa, and the change interval is 200 mm. Others are the same as in Example 1. After 10 times of pulling, the control effect of the equal-diameter crystal rod is obtained. Figure 5 As shown, Figure 5 The horizontal axis represents the length of the single crystal with equal diameter, and the vertical axis represents the resistivity.

[0049] Depend on Figure 4 , Figure 5 It can be seen that, through the control method of Example 2 of the present invention, the single crystal lengths of the pulled crystal rods after the solidification rate reaches 60% are all controlled within the required resistivity range.

[0050] The qualified rates of Example 2 and Comparative Example B were compared, and the mean, range and standard deviation of the two were compared. The qualified rate was rounded, such as Figure 6 As shown, the fitted histogram made with Mintab can intuitively express the difference between the two sets of data. The horizontal axis is the pass rate, and the vertical axis is the percentage of an interval in the total sample.

[0051] Depend on Figure 6 It can be seen that the mean value in comparative example B is 15%, the range is 11%, and the standard deviation is 3.72%; the mean value in example 2 is 35%, the range is 4%, and the standard deviation is 1.60%. Under the premise of a curing rate of 30%, the maximum qualified rate of example 2 is 35%. Under the same goal, the mean difference between the control group and the experimental group represents the improvement of the qualified rate, and the range and standard deviation represent the improvement of stability. Embodiment 3:

[0052] Use Hanhong 2408 single crystal furnace, 24-inch hot field, MCZ to pull 8-inch heavily doped arsenic crystal rods, including: crystal rotation 16rpmm; crucible rotation 6rpm; doping ratio 9 times; Gap25mm; required head resistance: 1.1mΩ, resistivity required control range: 0.3mΩ, actual resistivity of crystal rod head is 1.2mΩ, solidification rate 50%, multi-parameter method control, pulling speed is 0.64mm / min, unit pressure change range is 5Kap / 100mm, pressure change range: 30-15Kpa, change interval: 300mm, unit argon change range is 20slm / 100mm, argon change range: 120-80Kpa, change interval: 200mm, pull 5 times, get equal diameter crystal rod control effect as shown Figure 7 As shown, Figure 7 The horizontal axis represents the length of the single crystal with equal diameter, and the vertical axis represents the resistivity.

[0053] By using the control method of the present invention, the 8-inch red phosphorus can be controlled within 1.1-0.8 mΩ after the curing rate reaches 50%, and before that, there is basically no qualified part of the red phosphorus in the range of 1.1-0.8 mΩ.

[0054] It can be seen from Examples 1, 2, and 3 that this patent can be applied not only to heavily arsenic-doped single crystals, but also to heavily antimony-doped and heavily red phosphorus-doped single crystals, and can be used in 4-12 inches.

[0055] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for controlling the decrease in resistivity of a low-resistance heavily doped single crystal, characterized in that: During the crystal pulling process, after the solidification rate, the pulling speed, pressure, and argon gas are adjusted together to pull a crystal rod with a resistivity drop of ≤0.4mΩ when the resistivity is below the low resistance; Among them: the pulling speed remains unchanged, the unit pressure changes within a range of 5Kpa / 100mm-30Kpa / 100mm, and the unit argon changes within a range of 10slm / 100mm-40slm / 100mm.

2. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 1, characterized in that: The pressure needs to be adjusted below a critical pressure value, and the argon gas needs to be adjusted between critical argon gas flow rates.

3. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 1, characterized in that: The pulling speed remains unchanged after the solidification rate, and the pulling speed is 0.3 mm / min-0.7 mm / min.

4. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 1, characterized in that: The pressure is 30-50Kpa, and the argon gas is 40-200slm.

5. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 1, characterized in that: When the resistivity is determined and the resistivity decreases, the pulling speed decreases as the resistivity decreases. When the resistivity is determined and the resistivity decreases, the unit pressure change increases as the resistivity decreases. When the resistivity is determined and the resistivity drop amplitude is required to decrease, the unit argon gas change amplitude increases as the resistivity drop amplitude decreases.

6. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 5, characterized in that: Compared with the resistivity decrease of 0.4mΩ, for every 0.1mΩ decrease in the resistivity, the pulling speed decreases by 10%-40%; the unit pressure change increases by 0.5-3.5 times; the unit argon change increases by 0.5-3.5 times.

7. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 5, characterized in that: The resistivity decrease is not less than 0.2 mΩ.

8. The method for controlling the resistivity reduction of a low-resistance heavily doped single crystal according to claim 1, characterized in that: Within the same length range, the unit pressure change amplitude and the unit argon change amplitude do not change at the same time.

9. The method for controlling the resistivity reduction range of a low-resistance heavily doped single crystal according to claim 1 or 8, characterized in that: The unit pressure variation range and the unit argon variation range vary when the solidification rate is 200-500mm.

10. The method for controlling the resistivity reduction range of a low-resistance heavily-doped single crystal according to claim 9, characterized in that: The pressure changes first, and the argon changes later.

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