A method for preparing high-purity germanium single crystal with controlled defects

Abstract

The application discloses a preparation method of high-purity germanium single crystal controlling defects, and relates to the technical field of high-purity single crystal defect control of semiconductors. ‑3 Pa, a mixed protective gas with a volume fraction of 95% H2 and 5% Ar is introduced at a flow rate of 0.1-0.3 L / min, and the straight pulling furnace is baked at 900 DEG C for 2 h; S2, 10-13N high-purity germanium polycrystal raw materials are loaded, and the temperature is raised to 945-950 DEG C for melting at a constant temperature for 40 min; S3, a 13N dislocation-free seed crystal with a [100] crystal direction and a crystal direction deviation of less than 0.5 DEG is used to perform necking treatment, and the necking diameter is 2-3 mm and the length is 15-20 mm; S4, the shoulder is released at a cooling rate of 10-15 DEG C / h, and the shoulder angle is 45-60 DEG. ‑2 The dislocation density is stably controlled in the range of 1000-5000 cm-2, the optimal range of the detector is matched, V2H deep trap enrichment and carrier capture loss aggravation caused by too low dislocation density are avoided, leakage current rise caused by too high dislocation density is prevented, and the performance optimal window of the high-purity germanium detector is accurately matched.

Description

Technical Field

[0001] This invention relates to the field of defect control technology for high-purity single crystal semiconductors, specifically a method for preparing high-purity germanium single crystals with controlled defects. Background Technology

[0002] High-purity germanium single crystals are core materials for advanced equipment such as high-purity nuclear radiation detectors, dark matter detectors, and gamma-ray imaging systems. Detectors are extremely sensitive to the dislocation density range of germanium single crystals: 1000–5000 cm⁻¹. -2 The optimal range is defined as such; values ​​that are too high or too low will degrade detector performance.

[0003] When the dislocation density is too low, there is insufficient dislocation network pinning and dispersion of V2H defects within the crystal, and no pathways can be provided for hydrogen diffusion. This leads to the enrichment of deep V2H traps, exacerbated carrier trapping losses, decreased charge collection efficiency, and a significant deterioration in energy spectrum resolution. When the dislocation density is too high, a large number of recombination traps will form in the dislocation core and strain region, causing carrier losses themselves. This, combined with residual V2H defects, creates a double negative impact, simultaneously increasing device leakage current and baseline noise, severely degrading detector performance, and failing to meet the requirements for high-resolution energy spectrum detection.

[0004] Conventional constant-diameter growth processes result in temperature fluctuations > ±0.5℃, high interfacial thermal stress, easy dislocation multiplication, and difficulty in stable density control. Furthermore, the use of single isothermal annealing can only eliminate some macroscopic stress and cannot precisely control the dislocation density, making it difficult to stably fall within the 1000–5000 cm⁻² range. This leads to large differences in dislocation density between batches and in different regions within the crystal, resulting in significant fluctuations in detector performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-purity germanium single crystals with controlled defects, so as to overcome the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-purity germanium single crystal with controlled defects, comprising the following steps:

[0007] S1. Evacuate the straight-pull furnace to ≤1×10 -3 Pa, a mixed protective gas of 95% H2 and 5% Ar by volume is introduced at a flow rate of 0.1-0.3 L / min, and baked at a constant temperature of 900℃ for 2 hours;

[0008] S2. Heat the 10-13N high-purity germanium polycrystalline raw material to 945–950℃ and melt it at a constant temperature for 40 minutes.

[0009] S3. Using a 13N dislocation-free seed crystal with a

[100] crystal orientation and a crystal orientation deviation of <0.5°, a necking treatment is performed with a necking diameter of 2–3 mm and a length of 15–20 mm.

[0010] S4. Perform shoulder setting at a cooling rate of 10–15℃ / h, with a shoulder setting angle of 45–60°.

[0011] S5. Maintain a mixed protective gas atmosphere, control the solid-liquid interface temperature gradient to 5–8℃ / cm, the lifting speed to 0.8–1.2mm / h, and the rotation speed to 5–10rpm; control the temperature in real time throughout the process, and strictly control the temperature fluctuation to <±0.2℃.

[0012] S6. After single crystal growth is complete, allow it to cool naturally to room temperature without removing it or opening the furnace. Perform step annealing in situ, specifically including:

[0013] The temperature is increased to 590-610℃ at a rate of 4.5-5.5℃ / min and held at that temperature for 1.8-2.2h to release residual macroscopic thermal stress from the growth process.

[0014] The temperature is lowered to 390-410℃ at a rate of 2.5-3.5℃ / min, and held at that temperature for 3.8-4.2 hours to promote dislocation slip, coalescence, and annihilation, thereby precisely controlling the dislocation density to 1000–5000 cm⁻¹. -2 interval;

[0015] The temperature is lowered to 190-210℃ at a rate of 1.5-2.5℃ / min and held at that temperature for 0.8-1.2h to stabilize the crystal structure and avoid the formation of new defects.

[0016] S7. After annealing, the furnace is naturally cooled to room temperature, and the 13N high-purity germanium single crystal with controllable dislocation density is obtained after exiting the furnace.

[0017] Preferably, in step S1, the Czochralski furnace is evacuated to 8×10⁻⁶ ℃. -4 Pa – 1 × 10 -3 Pa, the mixed protective gas flow rate is 0.1–0.2 L / min.

[0018] Preferably, in step S2, 13N high-purity germanium polycrystalline raw material is loaded, and the melting temperature is 946–949℃.

[0019] Preferably, in step S3, the necking diameter is 2.2–2.8 mm and the length is 16–19 mm.

[0020] Preferably, in step S4, the cooling rate is 11–14℃ / h and the shoulder angle is 48–55°.

[0021] Preferably, in step S5, the temperature gradient is 5.5–7℃ / cm, the lifting speed is 0.9–1.1mm / h, the rotation speed is 6–9rpm, and the temperature fluctuation is ≤±0.18℃.

[0022] Preferably, in step S6, the error of the heating and cooling rate at each stage does not exceed ±0.5℃ / min, and the error of the holding time does not exceed ±10min.

[0023] Preferably, the dislocation density of the prepared 13N high-purity germanium single crystal is 1000–5000 cm⁻², the residual stress is completely eliminated, and the content of carbon, oxygen and nitrogen impurities is maintained at the 13N level.

[0024] In the above technical solution, the beneficial effect provided by the present invention is that by driving dislocation slip, merging and annihilation in the core heat preservation section at 390–410℃ during three-stage stepped annealing, the dislocation density is stably controlled at 1000–5000 cm⁻¹. -2 The optimal range of the detector is precisely matched to avoid both excessively low dislocation density leading to the enrichment of V2H deep traps and increased carrier trapping losses, and excessively high dislocation density causing an increase in leakage current.

[0025] The in-situ furnace-free annealing method avoids the additional thermal stress and new defects introduced by traditional furnace transfer and secondary loading. It can completely eliminate residual macroscopic thermal stress from crystal growth, stabilize the crystal lattice structure, and the closed annealing process does not introduce carbon, oxygen, and nitrogen impurities, thus maintaining the ultra-high purity of 13N. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0027] Figure 1 This is a process flow diagram of the present invention;

[0028] Figure 2 The low-temperature Hall effect detection diagrams for Embodiment 1 and Comparative Examples 1-6 of the present invention are shown below.

[0029] Figure 3 This is a crystal defect detection diagram from Embodiment 1 of the present invention;

[0030] Figure 4 This is a crystal defect detection diagram of Comparative Example 1 of the present invention;

[0031] Figure 5 This is a crystal defect detection diagram of Comparative Example 2 of the present invention;

[0032] Figure 6 This is a crystal defect detection diagram of Comparative Example 3 of the present invention;

[0033] Figure 7 This is a crystal defect detection diagram of Comparative Example 4 of the present invention;

[0034] Figure 8 This is a crystal defect detection diagram of Comparative Example 5 of the present invention;

[0035] Figure 9 This is a crystal defect detection diagram of Comparative Example 6 of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Please see Figure 1-9 All annealing parameter gradient comparison experiments provided in this embodiment of the invention follow the single variable principle to ensure the comparability of experimental results.

[0038] Example 1:

[0039] Vacuum 8×10 -4 Baking at 95% H2 + 5% Ar, 0.12 L / min, and 900℃ for 2 hours;

[0040] 13N germanium polycrystalline, melted at 948℃ for 40 min;

[0041]

[100] Seed crystal, necked φ2.5mm, length 18mm;

[0042] Cool down by 12℃ / h, and lower the shoulder angle to 50°.

[0043] Temperature fluctuation ±0.18℃, temperature gradient 6℃ / cm, lifting speed 1.0mm / h, rotation speed 8rpm;

[0044] Increase the temperature to 600℃ at 5℃ / min and hold for 2 hours; decrease the temperature to 400℃ at 3℃ / min and hold for 4 hours; decrease the temperature to 200℃ at 2℃ / min and hold for 1 hour; then cool and remove from the furnace.

[0045] Finished product testing: Purity 4.404e9cm -3 Dislocation density 2333 cm³ -2 The residual stress is completely eliminated, the leakage current is low, and the energy resolution is high, which meets the optimal requirements of the detector.

[0046] Comparative Example 1: Single Isothermal Annealing

[0047] Annealing was changed to: holding at 650℃ for 4 hours, then allowing to cool naturally.

[0048] Comparative Example 2: Elimination of the 400℃ constant temperature section

[0049] Two-stage annealing: 600℃ / 2h → directly cool down to 200℃ / 1h to remove the temperature-controlled dislocation segment in the core.

[0050] Comparative Example 3: Medium temperature > 410℃

[0051] Only the temperature node is changed to 415℃, the rest remain unchanged.

[0052] Comparative Example 4: Temperature Fluctuations

[0053] Temperature fluctuation during constant diameter growth is ±0.6℃.

[0054] Comparative Example 5: Shortening the heat preservation time at 400℃

[0055] The 400℃ heat preservation time has been changed from 4 hours to 2 hours, with the rest remaining unchanged.

[0056] Comparative Example 6: Non-in-situ annealing

[0057] After growth is complete, the furnace is removed, transported, and loaded into the furnace a second time, and then the same three-stage annealing parameters are used.

[0058] Example 1 4.404e9 2333 This plan A complete set of parameters is properly matched, and stress, dislocations, and defects are controlled in a coordinated manner. Comparative Example 1 5.582e9 8292 Compared to traditional single annealing High-temperature annealing alone cannot precisely control dislocations, resulting in incomplete stress release and a significant excess of dislocation density. Comparative Example 2 4.333e9 6917 Verification of the core role of mid-temperature segment control dislocation Without the 400℃ fine-tuning step, dislocations cannot effectively recombine and annihilate, leading to uncontrolled density and defect enrichment. Comparative Example 3 4.788e9 792 Verification core temperature window High temperatures lead to dislocation annihilation; insufficient dislocation mesh fails to confine V2H defects, resulting in degraded detection performance. Comparative Example 4 4.060e9 10471 Temperature fluctuations during equal diameter growth The interface exhibits high thermal stress, facilitates dislocation multiplication, makes density control difficult, and generates dislocation lines. Comparative Example 5 4.245e9 5417 Verification of asymmetric heat preservation time Insufficient insulation in the core temperature control section leads to inadequate dislocation convergence and recombination, resulting in an overall high density. Comparative Example 6 9.030e9 3750 Verify the advantages of in-situ annealing process Impurities are introduced during transport, and new stresses are generated during secondary loading, resulting in impurity loss and significant batch-to-batch fluctuations in dislocation density.

[0059] In summary, based on the comparative experiments of Example 1 and the six groups of single-variable comparative proportions, the following core conclusions can be drawn:

[0060] Compared to the single isothermal annealing in Comparative Example 1, this method can reduce the dislocation density from 8292 cm⁻¹. -2 Reduced to 2333cm -2 Precisely landing at 1000–5000cm -2 The detector's optimal range is found, while residual thermal stress from growth is eliminated more thoroughly.

[0061] In Comparative Example 2, the dislocation density increased to 6917 cm⁻¹ after this segment was removed. -2 In contrast, dislocations cannot effectively recombine and annihilate; in Comparative Example 3, dislocations undergo partial annihilation at temperatures exceeding 410℃, with a length of only 792 cm⁻¹. -2 If the value is below the optimal range, it will lead to insufficient V2H defect confinement ability, which will degrade the detector performance.

[0062] Gradual heating and cooling rates, along with sufficient intermediate-temperature holding time, are essential for effective temperature control. In Comparative Example 4, a uniform heating and cooling rate introduces additional thermal stress, causing dislocations to multiply significantly to 10471 cm⁻¹. -2 ;

[0063] In Comparative Example 5, shortening the medium-temperature insulation time resulted in insufficient dislocation convergence and recombination, with the density exceeding the upper limit of the optimal range.

[0064] In-situ annealing is significantly superior to off-situ annealing. In Comparative Example 6, off-situ annealing, which involves reloading the furnace after exiting the furnace, introduces external impurities, reduces crystal purity, and generates new thermal stress, leading to increased batch-to-batch fluctuations in dislocation density. In-situ annealing without opening the furnace can stably maintain a purity of 13N, resulting in stronger process consistency.

[0065] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity germanium single crystals with controlled defects, characterized in that, Includes the following steps: S1. Evacuate the straight-pull furnace to ≤1×10 -3 Pa, a mixed protective gas of 95% H2 and 5% Ar by volume is introduced at a flow rate of 0.1-0.3 L / min, and baked at a constant temperature of 900℃ for 2 hours; S2. Heat the 10-13N high-purity germanium polycrystalline raw material to 945–950℃ and melt it at a constant temperature for 40 minutes. S3. Using a 13N dislocation-free seed crystal with a [100] crystal orientation and a crystal orientation deviation of <0.5°, a necking treatment is performed with a necking diameter of 2–3 mm and a length of 15–20 mm. S4. Perform shoulder setting at a cooling rate of 10–15℃ / h, with a shoulder setting angle of 45–60°. S5. Maintain a mixed protective gas atmosphere, control the solid-liquid interface temperature gradient to 5–8℃ / cm, the lifting speed to 0.8–1.2mm / h, and the rotation speed to 5–10rpm; control the temperature in real time throughout the process, and strictly control the temperature fluctuation to <±0.2℃. S6. After single crystal growth is complete, allow it to cool naturally to room temperature without removing it or opening the furnace. Perform step annealing in situ, specifically including: The temperature is increased to 590-610℃ at a rate of 4.5-5.5℃ / min and held at that temperature for 1.8-2.2h to release residual macroscopic thermal stress from the growth process. Cool to 390-410℃ at a rate of 2.5-3.5℃ / min, hold at that temperature for 3.8-4.2h, and adjust the dislocation density to the range of 1000–5000cm-2. The temperature is lowered to 190-210℃ at a rate of 1.5-2.5℃ / min and held at that temperature for 0.8-1.2h to stabilize the crystal structure and avoid the formation of new defects. S7. After annealing, the furnace is naturally cooled to room temperature, and the 13N high-purity germanium single crystal with controllable dislocation density is obtained after exiting the furnace.

2. The method for preparing high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, In step S1, the Czochralski furnace is evacuated to 8×10⁻⁶ ℃. -4 Pa – 1 × 10 -3 Pa.

3. The method for preparing a high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, In step S2, 13N high-purity germanium polycrystalline raw material is selected, with a melting temperature of 946–949℃.

4. The method for preparing a high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, In step S3, the necking diameter is 2.2–2.8 mm and the length is 16–19 mm.

5. The method for preparing a high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, In step S4, the cooling rate is 11–14℃ / h, and the shoulder angle is 48–55°.

6. The method for preparing a high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, In step S5, the temperature gradient is 5.5–7℃ / cm, the lifting speed is 0.9–1.1mm / h, the rotation speed is 6–9rpm, and the temperature fluctuation is ≤±0.18℃.

7. The method for preparing a high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, In step S6, the error in the heating and cooling rate of each stage shall not exceed ±0.5℃ / min, and the error in the holding time shall not exceed ±10min.

8. The method for preparing a high-purity germanium single crystal with controlled defects according to claim 1, characterized in that, The dislocation density of the prepared 13N high-purity germanium single crystal is 1000–5000 cm⁻¹. -2 .

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