Preparation method of detector-grade high-purity germanium single crystal

Abstract

The invention relates to a preparation method of a detector-grade high-purity germanium single crystal. The preparation method comprises the following steps: putting corroded 12N high-purity germanium polycrystal into a crucible; vacuumizing, introducing nitrogen for purging, and maintaining the pressure; switching to introduce hydrogen, maintaining exhaust, and maintaining flow type vacuum; heating to 950-1000 DEG C under flowing type vacuum, and melting the material; lowering the seed crystal to a distance from the liquid level, and preheating the seed crystal; starting crucible rotation and crystal rotation which are opposite in rotation direction, inserting the seed crystal into the liquid surface, performing seeding, shouldering and equal-diameter growth, and pulling to grow an initial crystal bar; s7, cooling the lifting furnace to 935 to 945 DEG C, and keeping the temperature for 30 to 60 minutes; s8, starting the crucible rotation and the crystal rotation which are opposite in rotation direction again, so that the initial crystal bar is completely immersed under the liquid level; raising the temperature to completely melt the initial crystal bar again; pulling and growing a product crystal bar under the condition of maintaining crucible rotation and crystal rotation in opposite rotation directions; and cooling, stopping crystal rotation and crucible rotation, enabling the interior of the pulling furnace to reach normal pressure, opening the pulling furnace, and cutting off the product crystal bar.

Description

Technical Field

[0001] The present disclosure relates to the field of crystal growth, and more specifically to a method for preparing detector-grade high-purity germanium single crystal. Background Art

[0002] High purity germanium detectors have incomparable advantages in detecting radiation, especially x-rays and gamma-rays, such as good energy resolution, high detection effect, and stable performance. The carrier concentration of detector-grade high purity germanium single crystals must be ≤2E10 cm -3 The higher the detector efficiency, the smaller the crystal carrier concentration is required. The lateral uniformity of resistivity will affect the electrical performance of the detector. In order to obtain a detector with high detection efficiency, it is necessary to have a crystal carrier concentration of ≤2E10 cm -3 On this basis, the crystal purity and lateral uniformity of crystal resistivity are improved. Summary of the invention

[0003] In view of the problems existing in the background technology, an object of the present disclosure is to provide a method for preparing a detector-grade high-purity germanium single crystal, which can improve the crystal purity and the lateral uniformity of the crystal resistivity.

[0004] Thus, a method for preparing detector-grade high-purity germanium single crystals includes the following steps: S1, loading the etched 12N high-purity germanium polycrystals into the crucible of a pulling furnace; S2, evacuating and purging with high-purity nitrogen, then stopping evacuating and nitrogen, and maintaining pressure; S3, switching to high-purity hydrogen and maintaining exhaust to maintain a flowing vacuum in the pulling furnace; S4, raising the temperature of the pulling furnace to 950-1000°C under the flowing vacuum to precipitate the 12N high-purity germanium polycrystals in the crucible. The material is melted into a melt; S5, after the material is melted, the seed crystal is lowered to 10-20mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30min; S6, the crucible rotation and the crystal rotation of the seed crystal are turned on in opposite directions, and the seed crystal is inserted into the liquid surface 10-20mm, and an aperture appears, and seeding, shouldering and equal diameter growth are performed, and the initial crystal rod with a diameter of Φ20-50mm and a length of 100-150mm of the equal diameter part is grown by pulling. Then, the initial crystal rod is separated from the liquid surface, and the crucible rotation and crystal rotation are stopped; S7, the pulling furnace is cooled to 935-945℃, and maintained for 30-60min, so that the liquid surface of the melt in the crucible remains in a molten state; S8, the crucible rotation and crystal rotation in the opposite direction are turned again, so that the initial crystal rod descends and is completely immersed under the liquid surface and the distance from the bottom of the crucible is 10-20mm, and the immersion time is 30-60min; S9, the pulling furnace is heated to 950-1000℃, and the initial crystal rod is re- Completely melt into the crucible; S10, after the initial crystal rod is completely melted into the crucible, while maintaining the crucible rotation and crystal rotation in opposite directions, carry out crystal induction, neck shrinkage, thin neck, shoulder release, equal diameter, and tailing, and pull and grow the product crystal rod; S11, after the end of step S10, cool down, turn off the crystal rotation and crucible rotation, stop passing hydrogen, switch to nitrogen filling and maintain exhaust, so that the pulling furnace reaches normal pressure, then stop filling nitrogen and stop exhausting, open the pulling furnace, and cut the product crystal rod.

[0005] The beneficial effects of the present disclosure are as follows: in the method for preparing detector-grade high-purity germanium single crystals according to the present disclosure, the initial crystal rod grown in step S6 plays a stirring role in step S8; the diameter of the grown initial crystal rod is Φ20-50mm and the length is 100-150mm. If the diameter is too small, in step S8, the initial crystal rod will melt quickly during stirring, and the melt cannot be fully stirred. If the diameter of the initial crystal rod is too large, the remaining melt in the crucible is relatively small, and the amount of germanium that is fully stirred is relatively small. The relatively small amount of melt has limited contact with the hydrogen that maintains the flowing vacuum in the pulling furnace, which is not conducive to the hydrogen taking away impurities. If the length of the initial crystal rod is too short, it is also not conducive to the stirring of step S8. If the length of the initial crystal rod is too long, the bottom of the crucible will exist, causing the bottom of the crucible to break. The risk of cracking; in step S7, after the initial crystal rod growth is completed, the pulling furnace is cooled to 935-945°C, so that the melt in the crucible is kept at the lowest temperature of the molten state to prevent the temperature from being too high to melt the initial crystal rod used for stirring in step S8; in step S8, the initial crystal rod is completely immersed in the liquid surface, and the crystal rotation is set opposite to the crucible rotation. The initial crystal rod stirs the melt, increases the contact area between the melt and hydrogen, and the germanium is passivated, and the impurities are active, thereby taking away the impurities from the 12N high-purity germanium polycrystal in the melt, purifying the melt in the crucible before the pulling growth, and improving the purity of the crystal of the product crystal rod pulled and grown in step S10. Moreover, the stirring in step S8 makes the components in the melt evenly distributed, so that the crystal of the product crystal rod pulled and grown in step S10 has improved lateral uniformity in resistivity. That is to say, the preparation method of detector-grade high-purity germanium single crystal disclosed in the present invention can improve the crystal purity and lateral uniformity of crystal resistivity. DETAILED DESCRIPTION

[0006] It will be understood that the disclosed embodiments are merely examples of the present disclosure, which may be implemented in various forms, and therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to implement the present disclosure in various ways.

[0007] [Preparation method of detector-grade high-purity germanium single crystal]

[0008] The method for preparing detector-grade high-purity germanium single crystal according to the present disclosure comprises the following steps:

[0009] S1, loading the corroded 12N high purity germanium polycrystal into the crucible of the pulling furnace;

[0010] S2, evacuate and purge with high-purity nitrogen, then stop evacuating and purge with nitrogen, and maintain pressure;

[0011] S3, switch to introduce high-purity hydrogen and maintain exhaust to maintain a flowing vacuum in the pulling furnace;

[0012] S4, under a flowing vacuum, the pulling furnace is heated to 950-1000°C to polycrystallize the 12N high-purity germanium in the crucible into a melt;

[0013] S5, after the melting is completed, the seed crystal is lowered to 10-20 mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30 minutes;

[0014] S6, start the crucible rotation and the seed crystal rotation in opposite directions, insert the seed crystal 10-20 mm below the liquid surface, and an aperture appears, and then seeding, shouldering and equal diameter growth are performed, and an initial crystal rod with a diameter of Φ20-50 mm and a length of 100-150 mm is grown by pulling. After the equal diameter is reached, the initial crystal rod is separated from the liquid surface, and the crucible rotation and the crystal rotation are stopped;

[0015] S7, the pulling furnace is cooled to 935-945°C and maintained for 30-60 minutes to keep the liquid surface of the melt in the crucible in a molten state;

[0016] S8, start the crucible rotation and crystal rotation in opposite directions again, so that the initial crystal rod descends and is completely immersed under the liquid surface and is 10-20 mm away from the bottom of the crucible. The immersion time is 30-60 min;

[0017] S9, the pulling furnace is heated to 950-1000°C to completely melt the initial crystal rod into the crucible again;

[0018] S10, after the initial crystal rod is completely melted into the crucible, seeding, necking, neck thinning, shoulder release, equal diameter, and tailing are performed while maintaining the crucible rotation and crystal rotation in opposite directions, and the product crystal rod is grown by pulling;

[0019] S11, after step S10 is completed, cool down, turn off the crystal turner and the crucible turner, stop passing hydrogen, switch to nitrogen filling and maintain exhaust, so that the pulling furnace reaches normal pressure, then stop filling nitrogen and stop exhausting, open the pulling furnace, and cut the product crystal rod.

[0020] In the method for preparing detector-grade high-purity germanium single crystal according to the present disclosure, the initial crystal rod grown in step S6 plays a stirring role in step S8; the diameter of the grown initial crystal rod is Φ20-50mm and the length is 100-150mm. If the diameter is too small, in step S8, the initial crystal rod will melt quickly during stirring, and the melt cannot be fully stirred. If the diameter of the initial crystal rod is too large, the remaining melt in the crucible is relatively small, and the amount of germanium that is fully stirred is relatively small. The relatively small amount of melt has limited contact with the hydrogen that maintains the flowing vacuum in the pulling furnace, which is not conducive to the hydrogen taking away impurities. If the length of the initial crystal rod is too short, it is also not conducive to the stirring of step S8. If the length of the initial crystal rod is too long, there will be a risk of the bottom of the crucible being damaged and the bottom of the crucible being broken. In step S7, after the initial crystal rod growth is completed, the pulling furnace is cooled to 935-945°C, so that the melt in the crucible is kept at the lowest temperature of the molten state to prevent the temperature from being too high to melt the initial crystal rod used for stirring in step S8; in step S8, the initial crystal rod is completely immersed in the liquid surface, and the crystal rotation is set opposite to the crucible rotation. The initial crystal rod stirs the melt, increasing the contact area between the melt and hydrogen, germanium passivation, and impurities are active, thereby taking away impurities from the 12N high-purity germanium polycrystal in the melt, purifying the melt in the crucible before pulling growth, and improving the purity of the crystal of the product crystal rod pulled and grown in step S10. Moreover, the stirring in step S8 makes the components in the melt evenly distributed, so that the crystal of the product crystal rod pulled and grown in step S10 has improved lateral uniformity in resistivity. That is to say, the preparation method of detector-grade high-purity germanium single crystal disclosed in the present invention can improve the crystal purity and lateral uniformity of crystal resistivity.

[0021] In step S1, for example, etching is performed using 68% HNO in a volume ratio of 1:4. 3 :49% HF mixed solution.

[0022] In step S2, for example, vacuum is first drawn, and then high-purity nitrogen is introduced. The pulling furnace is purged by vacuuming and nitrogen filling for multiple times. After the purging is completed, vacuuming and nitrogen filling are stopped, and then the pressure is maintained. Specifically, in step S2, vacuuming and nitrogen filling are performed 3-5 times, and each time the vacuum is drawn to below 1Pa, the purity of the high-purity nitrogen is 7N, the pressure is maintained for 2h, and the pressure of the pressure maintenance is 1×10 -4 Below Pa.

[0023] In step S3, for example, the pressure of the flowing vacuum is 0.095-0.105 MPa.

[0024] In step S5, for example, the net impurity carrier concentration of the seed crystal is less than 2E11cm -3 .

[0025] In one example, in step S6, step S8 and step S10, the rotation speed of the crucible rotation and the crystal rotation is 1-5 rpm, and in step S6 and step S10, the pulling speed is 20-24 mm / h.

[0026] For example, in step S3, the purity of hydrogen is 9N; in step S11, the purity of nitrogen is 7N.

[0027] [test]

[0028] Example 1

[0029] The method for preparing the detector-grade high-purity germanium single crystal of Example 1 adopts the following steps:

[0030] S1, the etched 12N high purity germanium polycrystal is loaded into the crucible of the pulling furnace, and the etching is carried out using 68% HNO with a volume ratio of 1:4. 3 :49% HF mixed solution;

[0031] S2, first evacuate the vacuum, then pass high-purity nitrogen with a purity of 7N, and evacuate and fill with nitrogen 4 times, each time evacuating the vacuum to 1Pa to achieve the purge of the pulling furnace. After the purge is completed, stop evacuating the vacuum and stop passing high-purity nitrogen, and then maintain the pressure for 2h. The pressure of the pressure is 1×10 -4 Pa;

[0032] S3, switch to introduce high-purity hydrogen with a purity of 9N and maintain exhaust to maintain a flowing vacuum in the pulling furnace, and the pressure of the flowing vacuum is 0.1MPa;

[0033] S4, under a flowing vacuum, the pulling furnace is heated to 980° C. to polycrystallize the 12N high-purity germanium in the crucible into a melt;

[0034] S5, after the melting is completed, the seed crystal is lowered to 15 mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30 min. The net impurity carrier concentration of the seed crystal is 5E10 cm -3 ;

[0035] S6, start the crucible rotation and the seed crystal rotation in opposite directions, insert the seed crystal 15mm below the liquid surface, and an aperture appears, and then seeding, shoulder release and equal diameter growth are performed, and an initial crystal rod with a diameter of Φ35mm and a length of 125mm is grown by pulling. After the equal diameters are obtained, the initial crystal rod is separated from the liquid surface, and the crucible rotation and the crystal rotation are stopped. The rotation speed of the crucible rotation and the crystal rotation is 4rpm, and the pulling speed is 22mm / h;

[0036] S7, the pulling furnace is cooled to 940°C and maintained for 45 minutes to keep the liquid surface of the melt in the crucible in a molten state;

[0037] S8, start the crucible rotation and crystal rotation in opposite directions again, the rotation speed of the crucible rotation and crystal rotation is 4rpm, so that the initial crystal rod is lowered and completely immersed under the liquid surface and the distance from the bottom of the crucible is 20mm, and the immersion time is 45min;

[0038] S9, the pulling furnace is heated to 980°C to completely melt the initial crystal rod into the crucible again;

[0039] S10, after the initial crystal rod is completely melted into the crucible, seeding, necking, neck thinning, shoulder release, equal diameter, and tailing are performed while maintaining the crucible rotation and crystal rotation in opposite directions, and the product crystal rod is grown by pulling. The rotation speed of the crucible rotation and crystal rotation is 4 rpm, and the pulling speed is 22 mm / h;

[0040] S11, after step S10 is completed, cool down, turn off the crystal turner and crucible turner, stop passing hydrogen, switch to filling nitrogen with a purity of 7N and maintain exhaust, so that the pulling furnace reaches normal pressure, then stop filling nitrogen and stop exhausting, open the pulling furnace, and cut the product crystal rod.

[0041] Comparative Example 1

[0042] Except that steps S6 to S9 are not performed and there is no initial crystal rod in step S10, the rest is the same as in Example 1. That is, Comparative Example 1 belongs to the conventional direct pulling method.

[0043] A whole disc with a thickness of 1 mm was taken from the head and tail ends of the equal-diameter section of the product crystal rod prepared by Example 1 and Comparative Example 1, and then a square piece of 10 mm×10 mm was taken from the center and edge of the disc, and two square pieces were used to test the carrier concentration (the average of the two square pieces) and the lateral uniformity of resistivity (the absolute value of the resistivity difference of the two square pieces divided by the sum of the resistivities of the two square pieces). The carrier concentration and the lateral uniformity of resistivity were tested by HL9900 produced by Toho Technology, USA.

[0044] Table 1 shows the test results of carrier concentration and resistivity lateral uniformity of Example 1 and Comparative Example 1.

[0045] Table 1 Test results of carrier concentration and resistivity lateral uniformity of Example 1 and Comparative Example 1

[0046]

[0047] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.

Claims

1. A method for preparing detector-grade high-purity germanium single crystal, characterized in that: Includes steps: S1, loading the corroded 12N high purity germanium polycrystal into the crucible of the pulling furnace; S2, evacuate and purge with high-purity nitrogen, then stop evacuating and purge with nitrogen, and maintain pressure; S3, switch to introduce high-purity hydrogen and maintain exhaust to maintain a flowing vacuum in the pulling furnace; S4, under a flowing vacuum, the pulling furnace is heated to 950-1000°C to polycrystallize the 12N high-purity germanium in the crucible into a melt; S5, after the melting is completed, the seed crystal is lowered to 10-20 mm from the liquid surface of the melt in the crucible, and the seed crystal is preheated for 30 minutes; S6, start the crucible rotation and the seed crystal rotation in opposite directions, insert the seed crystal 10-20mm into the liquid surface, and an aperture appears, and then seeding, shoulder release and equal diameter growth are performed, and an initial crystal rod with a diameter of Φ20-50mm and a length of 100-150mm is grown by pulling. After the equal diameters are obtained, the initial crystal rod is separated from the liquid surface, and the crucible rotation and the crystal rotation are stopped; S7, the pulling furnace is cooled to 935-945°C and maintained for 30-60 minutes to keep the liquid surface of the melt in the crucible in a molten state; S8, start the crucible rotation and crystal rotation in opposite directions again, so that the initial crystal rod descends and is completely immersed under the liquid surface and is 10-20 mm away from the bottom of the crucible. The immersion time is 30-60 min; S9, the pulling furnace is heated to 950-1000°C to completely melt the initial crystal rod into the crucible again; S10, after the initial crystal rod is completely melted into the crucible, seeding, necking, neck thinning, shoulder release, equal diameter, and tailing are performed while maintaining the crucible rotation and crystal rotation in opposite directions, and the product crystal rod is grown by pulling; S11, after step S10 is completed, cool down, turn off the crystal turner and the crucible turner, stop passing hydrogen, switch to nitrogen filling and maintain exhaust, so that the pulling furnace reaches normal pressure, then stop filling nitrogen and stop exhausting, open the pulling furnace, and cut the product crystal rod.

2. The method for preparing detector-grade high-purity germanium single crystal according to claim 1, characterized in that: In step S1, a mixed solution of 68% HNO3:49% HF in a volume ratio of 1:4 is used for etching.

3. The method for preparing detector-grade high-purity germanium single crystal according to claim 1, characterized in that: In step S2, vacuum is first drawn, and then high-purity nitrogen is introduced. The pulling furnace is purged by vacuuming and filling with nitrogen multiple times. After the purging is completed, the vacuuming and the introduction of high-purity nitrogen are stopped, and then the pressure is maintained.

4. The method for preparing detector-grade high-purity germanium single crystal according to claim 3, characterized in that: In step S2, vacuum-fill with nitrogen 3-5 times, vacuuming to below 1Pa each time, the purity of high-purity nitrogen is 7N, the pressure is maintained for 2h, and the pressure of the pressure is 1×10 -4 Below Pa.

5. The method for preparing detector-grade high-purity germanium single crystal according to claim 1, characterized in that: In step S3, the pressure of the flowing vacuum is 0.095-0.105 MPa.

6. The method for preparing detector-grade high-purity germanium single crystal according to claim 1, characterized in that: In step S5, the net impurity carrier concentration of the seed crystal is less than 2E11cm -3 .

7. The method for preparing detector-grade high-purity germanium single crystal according to claim 1, characterized in that: In step S6, step S8 and step S10, the rotation speed of the crucible and the crystal is 1-5 rpm. In step S6 and step S10, the pulling speed is 20-24 mm / h.

8. The method for preparing detector-grade high-purity germanium single crystal according to claim 1, characterized in that: In step S3, the purity of hydrogen is 9N; In step S11, the purity of nitrogen is 7N.

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