Processing methods to improve the utilization rate of high-purity germanium crystals

Abstract

A processing method for improving the utilization rate of high-purity germanium crystals includes the following steps: S1, taking slices from the head and tail sections of the high-purity germanium crystal obtained by the Czochralski method for Hall effect testing to obtain a purity qualified section; S2, taking slices from the head and tail sections with qualified purity and performing dislocation defect and deep-level impurity tests; S3, based on the dislocation defects at the head and tail sections of the purity qualified section, rolling the crystal from the point where the diameter of the dislocation defect at the tail section is qualified and not less than the minimum diameter of the planar detector towards the middle section of the purity qualified section; S4, based on the deep-level impurity content at the head and tail sections of the purity qualified section, rolling the crystal from the point where the diameter of the deep-level impurity content at the head section is qualified and not less than the minimum diameter of the planar detector towards the middle section of the purity qualified section; S5, the inverted frustum at the tail section, the frustum shape at the head section, and the cylindrical shape between the inverted frustum at the tail section and the frustum shape at the head section are high-purity germanium qualified crystals; S6, cutting.

Description

Technical Field

[0001] This disclosure relates to the field of germanium crystals, and more specifically to a processing method for improving the utilization rate of high-purity germanium crystals. Background Technology

[0002] High-purity germanium crystals (13N germanium single crystals) are the core material for manufacturing high-purity germanium detectors and are widely used in nuclear physics, particle physics, astrophysics, nuclear safety, and national defense. They are used in applications with carrier concentrations ≤2E¹⁰ cm⁻¹. -3 Under these conditions, the usable size of high-purity germanium crystals is determined by crystal defects (such as dislocation defects) and the content of deep-level impurities. The existing processing method is to use a rounding technique to obtain a portion of equal diameter that simultaneously satisfies the requirements of carrier concentration, dislocation defects, and deep-level impurity content. However, this method has limited utilization of high-purity germanium crystals, resulting in significant waste and high costs. Summary of the Invention

[0003] In view of the problems existing in the background art, one object of this disclosure is to provide a processing method for improving the utilization rate of high-purity germanium crystals, which can improve the utilization rate of high-purity germanium crystals, reduce waste of high-purity germanium crystals, and reduce costs.

[0004] Therefore, a processing method for improving the utilization rate of high-purity germanium crystals includes the following steps: S1, taking slices from the head and tail sections of the high-purity germanium crystal obtained by the Czochralski method and performing Hall effect testing to obtain a purity qualified section; S2, taking slices from the head and tail sections with qualified purity and performing dislocation defect and deep-level impurity testing; S3, based on the dislocation defects at the head and tail sections of the purity qualified section, starting from the qualified diameter of the dislocation defects at the tail section (which is not less than the minimum diameter of the planar detector) and rolling it towards the middle part of the purity qualified section, forming an inverted frustum shape at the tail of the purity qualified section; S4, ... Based on the deep-level impurity content at the head and tail of the purity qualified section, the crystal is rolled from the head where the deep-level impurity content is qualified and the diameter is not less than the minimum diameter of the planar detector, towards the middle part of the purity qualified section. The rolling forms a frustum shape at the head of the purity qualified section; S5, the inverted frustum at the tail, the frustum shape at the head, and the cylinder between the inverted frustum at the tail and the frustum shape at the head are high-purity germanium qualified crystals; S6, according to the detector size requirements, the inverted frustum at the tail, the frustum shape at the head, and the cylinder between the inverted frustum at the tail and the frustum shape at the head of the qualified crystal are cut.

[0005] The beneficial effects of this disclosure are as follows: For the tail of a high-purity germanium crystal, processing (i.e., rounding) can be directly performed from the tail to the head in a laterally outward direction, provided that the purity meets the requirements (i.e., the carrier concentration in the Hall test is qualified). This not only combines with the variation of dislocation defects but also maximizes the utilization of the tail portion with qualified deep-level impurity content in the rounded crystal. Similarly, for the head of a high-purity germanium crystal, processing (i.e., rounding) can be directly performed from the head to the tail in a laterally outward direction, provided that the purity meets the requirements (i.e., the carrier concentration in the Hall test is qualified). This not only combines with the variation of deep-level impurity content but also maximizes the utilization of the head portion with qualified dislocation defects in the rounded crystal. Based on this principle, the aforementioned processing method for improving the utilization rate of high-purity germanium crystals disclosed in this disclosure can be implemented. After step S6 is completed, the frustum at the tail and the frustum at the head of the qualified crystal can be further processed into planar detectors of different sizes, while the cylindrical shape between the frustum at the tail and the frustum at the head can be further processed into a coaxial detector. This improves the utilization rate of high-purity germanium crystals, reduces waste, and lowers costs. Attached Figure Description

[0006] Figure 1 This is a schematic flowchart of the processing method for improving the utilization rate of high-purity germanium crystals according to this disclosure.

[0007] Figure 2 This is a photograph of dislocation defects at the head and tail of an example purity-compliant segment. Detailed Implementation

[0008] It will be understood that the disclosed embodiments are merely examples of this disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are intended only as the basis for the claims and as an illustrative basis to teach those skilled in the art how to implement this disclosure in various ways.

[0009] Reference Figure 1 and Figure 2 The processing method for improving the utilization rate of high-purity germanium crystals according to this disclosure includes the following steps:

[0010] S1. Take slices from the head and tail of the high-purity germanium crystal obtained by the Czochralski method and perform Hall effect tests to obtain the section with qualified purity.

[0011] S2, take samples from the head and tail sections with qualified purity and perform dislocation defect and deep-level impurity tests.

[0012] S3, based on the dislocation defects at the head and tail of the purity-qualified section (refer to...). Figure 2 Starting from the point at the tail end where the dislocation defect has a qualified diameter and the diameter is not less than the minimum diameter of the planar detector, the material is rolled round towards the middle part of the purity qualified section, forming an inverted frustum shape at the tail end of the purity qualified section.

[0013] S4. Based on the deep-level impurity content at the head and tail of the purity qualified section (refer to Tables 1 to 4 below), start rolling the material from the diameter of the head where the deep-level impurity content is qualified and the diameter is not less than the minimum diameter of the planar detector, and roll it towards the middle part of the purity qualified section. The rolling forms a frustum shape at the head of the purity qualified section.

[0014] S5, the inverted frustum at the tail, the frustum at the head, and the cylindrical shape between the inverted frustum at the tail and the frustum at the head are qualified high-purity germanium crystals.

[0015] S6, according to the detector size requirements, cut the inverted frustum at the tail, the frustum at the head, and the cylinder between the inverted frustum at the tail and the frustum at the head of the qualified crystal.

[0016] In high-purity germanium crystals obtained by the Czochralski method, along the longitudinal direction (head and tail relative to each other), dislocation defects gradually decrease from the tail to the head, while the content of deep-level impurities decreases from the head to the tail in the opposite direction. Along the transverse direction perpendicular to the longitudinal direction, in any transverse section, dislocation defects gradually decrease from the edge to the center, and the content of deep-level impurities also gradually decreases from the edge to the center. Figure 2 As shown in Tables 1 to 4 (the results in Tables 1 to 4 are for p-type high-purity germanium crystals), the variation of dislocation defects and deep-level impurity content is the same in any transverse cross-section. Thus, at the tail end of the high-purity germanium crystal, dislocation defects have a maximum value, while the deep-level impurity content is within acceptable limits; at the head end of the high-purity germanium crystal, the deep-level impurity content has a maximum value, while the dislocation defects are within acceptable limits. Therefore, for the tail of a high-purity germanium crystal, processing (i.e., rounding) can be directly started from the tail to the head in a laterally outward direction, provided that the purity meets the requirements (i.e., the carrier concentration in the Hall test is qualified). This not only combines with the aforementioned changes in dislocation defects but also maximizes the utilization of the qualified deep-level impurity content in the rounded tail of the qualified crystal. Similarly, for the head of a high-purity germanium crystal, processing (i.e., rounding) can be directly started from the head to the tail in a laterally outward direction, provided that the purity meets the requirements (i.e., the carrier concentration in the Hall test is qualified). This not only combines with the aforementioned changes in deep-level impurity content but also maximizes the utilization of the qualified dislocation defect content in the rounded tail of the qualified crystal. Figure 1As shown. Based on this principle, the aforementioned processing method for improving the utilization rate of high-purity germanium crystals disclosed herein can be implemented. After step S6, the frustum at the tail and the frustum at the head of the qualified crystal can be further processed into planar detectors of different sizes, while the cylindrical shape between the frustum at the tail and the frustum at the head can be further processed into a coaxial detector. This improves the utilization rate of high-purity germanium crystals, reduces waste, and lowers costs.

[0017] Table 1. Fitting results of DLTS detection at the head edge.

[0018] impurity center ΔE(eV) <![CDATA[sigma(cm 2 )]]> <![CDATA[N T (cm -3 )]]> <![CDATA[Cu s (1)]]> 0.009 1.60E-20 2.15E+09 Cu-H(1) 0.052 1.42E-15 1.96E+09 Cu-H(2) 0.017 2.24E-15 1.09E+09 <![CDATA[Cu s (2)]]> 0.297 5.19E-14 2.15E+08 total 5.42E+09

[0019] Table 2. Fitting results of DLTS detection at the center of the head.

[0020] impurity center ΔE(eV) <![CDATA[sigma(cm 2 )]]> <![CDATA[N T (cm -3 )]]> <![CDATA[Cu s (1)]]> 0.046 1.34E-16 2.53E+09 Cu-H(1) 0.172 1.57E-15 1.34E+09 Cu-H(2) 0.333 4.34E-13 2.79E+08 <![CDATA[Cu s (2)]]> 0.315 1.16E-13 2.64E+08 total 4.41E+09

[0021] Table 3. Fitting results of DLTS detection at the tail edge.

[0022] impurity center ΔE(eV) <![CDATA[sigma(cm 2 )]]> <![CDATA[N T (cm -3 )]]> <![CDATA[Cu s (1)]]> 0.041 1.97E-17 7.89E+08 Cu-H(1) 0.040 1.87E-21 1.39E+08 Cu-H(2) 0.117 7.90E-21 2.08E+08 <![CDATA[Cu s (2)]]> 0.167 9.55E-16 4.89E+08 total 1.63E+09

[0023] Table 4. Fitting results of DLTS detection at the tail center.

[0024] impurity center ΔE(eV) <![CDATA[sigma(cm 2 )]]> <![CDATA[N T (cm -3 )]]> <![CDATA[Cu s (1)]]> 0.011 5.60E-20 8.00E+08 Cu-H(1) 0.050 5.07E-16 3.56E+08 Cu-H(2) 0.178 4.39E-15 2.11E+08 <![CDATA[Cu s (2)]]> 0.314 1.39E-13 1.34E+08 total 1.50E+09

[0025] In step S1, the Hall effect test is used to determine the carrier concentration, where the carrier concentration is ≤2E10cm⁻¹. -3 This serves as the basis for determining the purity level. Hall effect testing and sample collection can be performed according to CN115825682A.

[0026] In step S2, the sampling and testing of dislocation defects can be referenced in CN115825682A. For example, for p-type high-purity germanium crystals, the qualification criterion for dislocation defects is that the dislocation density of the dislocation sample is ≤10000 cm⁻¹. -2 For n-type high-purity germanium crystals, the acceptable standard for dislocation defects is that the dislocation density of the dislocation sample is ≤5000 cm⁻¹. -2 In addition to dislocation density, dislocation defects can also increase the requirements for dislocation lines, as shown in the reference. Figure 1 Dislocation lines appear at the edge of the tail. For example, the requirement for dislocation lines is that the ratio of the sum of the lengths of all dislocation lines in the dislocation sample to the radius of the dislocation sample is ≤3.

[0027] In step S2, the sampling and testing of deep-level impurity content can be referenced in CN115825682A. For example, for p-type high-purity germanium crystals, the deep-level impurity content (i.e., deep-level impurity concentration) corresponds to N in Tables 1 to 4. T The total value) ≤ 4.5E+09cm -3For n-type high-purity germanium crystals, the deep-level impurity content is <5.0E+08cm. -3 .

[0028] In steps S3 and S4, for example, the minimum diameter of the planar detector is 10 mm.

[0029] Furthermore, it should be noted that the order of steps S3 and S4 is not restricted; step S3 can be executed first and step S4 later, or step S4 can be executed first and step S3 later, or steps S3 and S4 can be executed simultaneously. The rounding process can be performed by supplementary testing and statistical analysis of dislocation defects and deep-level impurity content in the middle portion of the same batch of high-purity germanium crystals to determine the bevel angle during rounding.

[0030] Several exemplary embodiments have been described in detail above, but this document is not intended to limit itself to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined to form several other combinations, which are not shown for simplicity.

Claims

1. A processing method for improving the utilization rate of high-purity germanium crystals, characterized in that, Including the following steps: S1. Take slices from the head and tail of the high-purity germanium crystal obtained by the Czochralski method and perform Hall effect tests to obtain the section with qualified purity. S2, take samples from the head and tail sections with qualified purity and perform dislocation defect and deep-level impurity tests. S3, based on the dislocation defects at the head and tail of the purity qualified section, start from the qualified diameter of the dislocation defect at the tail and the diameter is not less than the minimum diameter of the planar detector and roll it towards the middle part of the purity qualified section. The rolling forms an inverted frustum shape at the tail of the purity qualified section. S4. Based on the deep-level impurity content at the head and tail of the purity qualified section, start rolling the material from the diameter of the head where the deep-level impurity content is qualified and the diameter is not less than the minimum diameter of the planar detector toward the middle part of the purity qualified section. The rolling forms a frustum shape at the head of the purity qualified section. S5, the inverted frustum at the tail, the frustum at the head, and the cylindrical shape between the inverted frustum at the tail and the frustum at the head are qualified high-purity germanium crystals. S6, according to the detector size requirements, cut the inverted frustum at the tail, the frustum at the head, and the cylinder between the inverted frustum at the tail and the frustum at the head of the qualified crystal.

2. The processing method for improving the utilization rate of high-purity germanium crystals according to claim 1, characterized in that, The minimum diameter of the planar detector is 10mm.

Images