Method for detecting deep level defects of high purity germanium single crystal of detector grade

Abstract

A kind of detector grade high purity germanium monocrystal deep energy level defect detection method includes the following steps: detector grade high purity germanium monocrystal is p-type germanium monocrystal, Hall sample and dislocation sample are taken in the head of p-type germanium monocrystal respectively to carry out carrier concentration and dislocation density detection, DLTS sample is taken in the head of the remaining crystal of p-type germanium monocrystal;Processing;Sputtering dot tin film as Schottky electrode on the front of DLTS sample, the back of DLTS sample is connected with copper sheet using tin foil, the surface contour of copper sheet is greater than DLTS sample, the part of tin foil covering and contacting the back of DLTS sample is used as ohmic electrode, the area of the part is more than ten times the area of dot tin film, so as to form detection sample;Detection: contact detection, if the contact of Schottky electrode and ohmic electrode is not a problem, then carry out normal temperature IV curve detection, if detection sample forms Schottky contact, then carry out DLTS spectrum signal detection, if DLTS spectrum signal is good, then start to carry out complete low temperature DLTS detection to obtain DLTS spectrum.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of germanium, and more particularly to a method for detecting deep level defects of a detector-grade high-purity germanium single crystal. BACKGROUND

[0002] High-purity germanium single crystal material is the most high-end and most difficult-to-produce material in the germanium series products, with a purity of 13N, and is the core material for manufacturing high-purity germanium detectors. Compared with other detectors, high-purity germanium detectors have incomparable advantages such as good energy resolution, high detection efficiency, and strong stability, and have become indispensable instruments and equipment in nuclear physics, particle physics, inspection and quarantine, biomedicine, and national security, with a broad market application prospect.

[0003] DLTS (Deep Level Transient Spectroscopy) is an important technical means for researching and detecting semiconductor impurities, defect deep levels, and interface states in the field of semiconductors.

[0004] However, since DLTS detection is a non-standard detection, different detection samples need to be designed for different materials to ensure effective detection results. At present, there is no report on the detection of deep level defects of detector-grade high-purity germanium single crystals using DLTS equipment, so the detection method of deep level defects of detector-grade high-purity germanium single crystals needs to be developed. SUMMARY

[0005] In view of the problems in the background art, the purpose of the present disclosure is to provide a method for detecting deep level defects of a detector-grade high-purity germanium single crystal, which can realize the detection of deep level defects of a detector-grade high-purity germanium single crystal.

[0006] Therefore, a method for detecting deep level defects of a detector-grade high-purity germanium single crystal includes the following steps: S1, sampling: the detector-grade high-purity germanium single crystal is a p-type germanium single crystal, and a Hall sample and a dislocation sample are taken from the head of the p-type germanium single crystal for carrier concentration and dislocation density detection, respectively; if the carrier concentration of the Hall sample of the p-type germanium single crystal is < 2E10 cm -3 and the dislocation density of the dislocation sample of the p-type germanium single crystal is < 10000 cm -2, then the DLTS sample is taken from the head of the remaining crystal of the p-type germanium single crystal; S2, processing: the DLTS sample is surface ground, polished, etched to a mirror surface, washed with pure water, and dried; S3, electrode preparation: a round dot tin film is sputtered on the front surface of the DLTS sample, the round dot tin film serving as a Schottky electrode, a tin foil is used to connect a copper sheet to the back surface of the DLTS sample, the tin foil at least partially covers and contacts the back surface of the DLTS sample, the surface contour of the copper sheet is larger than that of the DLTS sample, the part of the tin foil covering and contacting the back surface of the DLTS sample serves as an ohmic electrode, and the area of the part of the tin foil covering and contacting the back surface of the DLTS sample is more than ten times the area of the round dot tin film; thus forming a detection sample; S4, detection, the detection sample is placed in the sample stage of the DLTS detection device, the positive probe of the sample stage contacts the Schottky electrode of the detection sample, the negative probe of the sample stage contacts the part of the copper sheet exceeding the surface contour of the DLTS sample, then contact detection is performed to determine whether the contact between the Schottky electrode and the ohmic electrode is problematic, if the contact between the Schottky electrode and the ohmic electrode is not problematic, normal temperature IV curve detection is performed, if the detection sample forms a Schottky contact, DLTS spectrum signal detection is performed, and if the DLTS spectrum signal is good, complete low-temperature DLTS detection is started to obtain the DLTS spectrum.

[0007] Thus, a detection method for detecting deep energy level defects of a detector-grade high-purity germanium single crystal includes the following steps: S1, sampling: the detector-grade high-purity germanium single crystal is an n-type germanium single crystal, a Hall sample and a dislocation sample are taken from the tail of the n-type germanium single crystal for carrier concentration and dislocation density detection, respectively, if the carrier concentration of the Hall sample of the n-type germanium single crystal is < 2E10 cm -3 and the dislocation density of the dislocation sample of the n-type germanium single crystal is < 5000 cm -2, then the DLTS sample is taken from the tail of the remaining crystal of the n-type germanium single crystal; S2, processing: the DLTS sample is subjected to surface grinding, polishing, etching to a mirror surface, washed with pure water, and then dried; S3, electrode preparation: a circular dot gold film is sputtered on the front surface of the DLTS sample, and then annealing heat treatment is performed, the circular dot gold film serving as a Schottky electrode, a tin foil is used to connect a copper sheet to the back surface of the DLTS sample, the tin foil at least partially covers and contacts the back surface of the DLTS sample, the surface contour of the copper sheet is larger than that of the DLTS sample, the part of the tin foil covering and contacting the back surface of the DLTS sample serves as an ohmic electrode, and the area of the part of the tin foil covering and contacting the back surface of the DLTS sample is more than ten times the area of the circular dot gold film; thus forming a detection sample; S4, detection: the detection sample is placed on a sample stage of a DLTS detection device, a positive probe of the sample stage contacts the Schottky electrode of the detection sample, a negative probe of the sample stage contacts the part of the copper sheet exceeding the surface contour of the DLTS sample, and then contact detection is performed to determine whether the contact between the Schottky electrode and the ohmic electrode is problematic, if the contact between the Schottky electrode and the ohmic electrode is not problematic, normal-temperature IV curve detection is performed, if the detection sample forms a Schottky contact, DLTS spectrum signal detection is performed, and if the DLTS spectrum signal is good, complete low-temperature DLTS detection is started to obtain a DLTS spectrum.

[0008] The beneficial effects of the present disclosure are as follows: based on the above-mentioned two kinds of detector-grade high-purity germanium single crystal deep level defect detection methods, the detector-grade high-purity germanium single crystal deep level defect detection can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a graph showing the IV curve at normal temperature for the p-type germanium single crystal of Example 1.

[0010] Figure 2 is a graph of the IV curve at normal temperature for the Schottky electrode and the ohmic electrode of the p-type germanium single crystal of Comparative Example 1.

[0011] Figure 3 is a graph of the DLTS spectrum signal at 160K for the p-type germanium single crystal of Example 1.

[0012] Figure 4 is a graph of the DLTS spectrum signal at 160K for the p-type germanium single crystal of Comparative Example 1.

[0013] Figure 5 is a graph of the DLTS spectrum signal at 160K for the p-type germanium single crystal of Comparative Example 2, when the area of the part of the tin foil covering and contacting the back surface of the DLTS sample is five times the area of the circular dot tin film.

[0014] Figure 6is a graph of DLTS spectrum for p-type high-purity germanium single crystal in the range of 10K-160K of Example 1.

[0015] Figure 7 is a graph of DLTS spectrum for p-type high-purity germanium single crystal in the range of 10K-160K of Comparative Example 2.

[0016] Figure 8 is a graph of DLTS spectrum signal for n-type germanium single crystal at 160K of Example 2.

[0017] Figure 9 is a graph of DLTS spectrum for n-type high-purity germanium in the range of 10K-160K of Example 2. DETAILED DESCRIPTION

[0018] [Method for detecting deep level defects of detector-grade high-purity germanium single crystal-p-type germanium single crystal]

[0019] The method for detecting deep level defects of detector-grade high-purity germanium single crystal for p-type germanium single crystal comprises the steps of:

[0020] S1, sampling: the detector-grade high-purity germanium single crystal is a p-type germanium single crystal, a Hall sample and a dislocation sample are taken at the head of the p-type germanium single crystal for carrier concentration and dislocation density detection, respectively, if the carrier concentration of the Hall sample of the p-type germanium single crystal is <2E10 cm -3 and the dislocation density of the dislocation sample of the p-type germanium single crystal is <10000 cm -2 , then a DLTS sample is taken at the head of the remaining crystal of the p-type germanium single crystal;

[0021] S2, processing: the DLTS sample is surface ground, polished, and etched to a mirror surface, washed with pure water, and blown dry;

[0022] S3, electrode preparation: a circular point tin film is sputtered on the front surface of the DLTS sample, the circular point tin film serves as a Schottky electrode, a tin foil is used to connect a copper sheet on the back surface of the DLTS sample, the tin foil at least partially covers and contacts the back surface of the DLTS sample, the surface contour of the copper sheet is larger than that of the DLTS sample, the part of the tin foil covering and contacting the back surface of the DLTS sample serves as an ohmic electrode, the area of the part of the tin foil covering and contacting the back surface of the DLTS sample is more than ten times the area of the circular point tin film, and then annealing is performed, thereby forming a detection sample;

[0023] S4, Detection: Place the test sample into the sample stage of the DLTS detection equipment. The positive probe 5 of the sample stage contacts the Schottky electrode of the test sample, and the negative probe of the sample stage contacts the portion of the copper sheet that extends beyond the outer contour of the DLTS sample surface. Then, perform electrode contact detection to determine if there is a problem with the contact between the Schottky and ohmic electrodes. If there is no problem with the contact between the Schottky and ohmic electrodes, perform room temperature IV curve detection. If the test sample forms a Schottky contact, perform DLTS spectral analysis.

[0024] If the DLTS spectrum signal is good, then a complete low-temperature DLTS detection is performed to obtain the 0DLTS spectrum.

[0025] In one embodiment, in step S1, the sampling specifications of the Hall sample are (8-12mm)×(8-12mm)×(1-2mm), the sampling specifications of the dislocation sample are the thickness of the entire cross-section of the head of the p-type germanium single crystal × (3-5mm), and the sampling specifications of the DLTS sample are (15-20mm)×(15-20mm)×(3-5mm).

[0026] 5. In step S1, the carrier concentration of the Hall sample is detected using an HL9900 from Toho Technology, USA. Tin particles are pressed into the four corners of the Hall sample, followed by annealing heat treatment to create good ohmic contacts. Then, an IV test is performed on the HL9900. If no problems are found, a low-temperature Hall effect test is performed to determine the carrier concentration. Specifically, the annealing heat treatment involves placing the sample in a 7N nitrogen annealing furnace at a temperature of 300-400℃ for 20-30 minutes.

[0027] In step S1, the dislocation density is determined by milling the dislocation sample flat and smooth on both sides using a milling machine.

[0028] Polish to a mirror finish, clean with pure water, and immerse the dislocation sample in a constant-temperature etching solution at 5-15℃ for 5-10 minutes. Then, examine it under a metallographic microscope. The etching solution is hydrofluoric acid: nitric acid: 10% copper nitrate = 2:1:1 (volume ratio).

[0029] Similarly, in one embodiment, in step S2, the etching solution used for etching is hydrofluoric acid: nitric acid: 10% copper nitrate = 2:1:1 (volume ratio).

[0030] In step S3, in an embodiment, corresponding to the sampling specification of the DLTS sample sheet (i.e. (15-20mm) x (15-20mm) x (3-5mm) as mentioned above), the diameter of the round tin film is 1-2mm, and the thickness is 100-200nm, the tin foil is taken with the same profile as the DLTS sample sheet (i.e. (15-20mm) x (15-20mm)) to completely contact and cover the back of the DLTS sample sheet, and the thickness of the tin foil is 30-50μm.

[0031] 0In step S3, the area of the part of the tin foil covering and contacting the back of the DLTS sample sheet is more than ten times the area of the round tin film, which can effectively obtain the DLTS spectrum signal in step S4, and the comparison is referred to Figure 3 and Figure 5 .

[0032] In step S3, by increasing the copper sheet and the surface profile of the copper sheet is larger than the surface profile of the DLTS sample sheet, on the one hand, the protection of the copper sheet to the tin foil is increased, so that the stability of the ohmic electrode is enhanced, and on the other hand, the resistance to vibration of the helium cooling stage from low temperature during the entire DLTS detection process is increased, and the stability of the contact between the tin foil and the back of the DLTS sample sheet is improved. The size of the surface profile of the copper sheet can be determined by the contact between the negative probe of the sample stage and the part of the copper sheet that exceeds the surface profile of the DLTS sample sheet. The thickness of the copper sheet can be determined by ensuring that the copper sheet has a certain overall hardness to resist deformation caused by the vibration of the helium cooling stage at low temperature. Specifically, the thickness of the copper sheet is 0.5-1mm.

[0033] In an embodiment, in step S3, the back of the DLTS sample sheet is connected to the copper sheet by the tin foil: wearing clean gloves, placing the tin foil between the back of the DLTS sample sheet and the copper sheet, and squeezing the DLTS sample sheet and the copper sheet from both sides with hands to connect the DLTS sample sheet, the tin foil and the copper sheet together.

[0034] In step S3, by annealing treatment, the germanium sheet is in better contact with the Schottky electrode and the ohmic electrode, and the IV curve maintains the diode characteristic, as compared in Figure 1 and Figure 2 .

[0035] In an embodiment, in step S3, the annealing is as follows: the front surface of the DLTS sample sheet with a sputtered tin film is upward, the copper sheet is below the tin foil, and it is placed in a 7N nitrogen annealing furnace with a temperature of 300-400℃ for 20-30min.

[0036] It is noted that in step S3, since the round tin film and the tin foil are both made of tin, they can be annealed at one time, thereby saving detection time and improving detection efficiency.

[0037] In step S4, the electrode contact test is directly performed by using the DLTS device itself. In the detecting method of the deep energy level defects of the detector-grade high-purity germanium single crystal of the present disclosure, the DLTS device is the digital deep energy level transient spectrometer DLTS of the American Sula Technologies Company, which can directly display that the capacitance value of the test sample is stable within 1%, indicating that the contact of the Schottky electrode and the ohmic electrode is determined to be no problem.

[0038] In step S4, the room temperature IV curve test is performed. If the IV curve of the detected sample is nonlinear (for example Figure 1 ), it indicates that the Schottky contact is formed.

[0039] In step S4, the DLTS spectrum signal detection is performed at the maximum point of the low temperature range of the complete low temperature DLTS detection. For example, if the low temperature range is 10-160K, the DLTS spectrum signal detection is performed at 160K. In this way, the complete low temperature DLTS detection can be directly continued under the condition that the DLTS spectrum signal obtained by the DLTS spectrum signal detection is good, so that the complete low temperature DLTS detection does not need to wait or re-adjust to the maximum point of the low temperature range as the starting point to start again, thereby saving the detection time and improving the detection efficiency.

[0040] In step S4, the good DLTS spectrum signal is determined by whether the spectrum signal figure output by the DLTS forms a good exponential curve, and the thinner the exponential curve, the better the DLTS spectrum signal, for example, as shown in Figure 3 .

[0041] In step S4, the low temperature temperature range of the complete low temperature DLTS spectrum detection is provided by the DLTS device itself. The sample table of the digital deep energy level transient spectrometer DLTS of the American Sula Technologies Company has a temperature-adjustable helium gas cooling table connected with a compressor, and the low temperature temperature range of the complete low temperature DLTS spectrum detection is 10K-160K.

[0042] [Detecting method of deep energy level defects of detector-grade high-purity germanium single crystal-n-type germanium single crystal]

[0043] For n-type germanium single crystal, the detecting method of deep energy level defects of detector-grade high-purity germanium single crystal includes the following steps:

[0044] S1, sampling: the detector-grade high-purity germanium single crystal is an n-type germanium single crystal, and the Hall sample and the dislocation sample are taken from the tail of the n-type germanium single crystal for carrier concentration and dislocation density detection. If the carrier concentration of the Hall sample of the n-type germanium single crystal is <2E10 cm -3 and the dislocation density of the dislocation sample of the n-type germanium single crystal is <5000 cm -2Then, the DLTS sample is taken from the tail of the remaining crystal of the n-type germanium single crystal;

[0045] S2, processing: surface grinding, polishing, etching to mirror surface are performed on the DLTS sample, then the DLTS sample is washed with pure water and dried by blowing.

[0046] S3, electrode preparation: a circular gold film is sputtered on the front surface of the DLTS sample, and then annealing heat treatment is performed, so that the circular gold film serves as a Schottky electrode; a tin foil is used to connect a copper sheet to the back surface of the DLTS sample, the tin foil at least partially covers and contacts the back surface of the DLTS sample, the surface contour of the copper sheet is larger than that of the DLTS sample, the part of the tin foil covering and contacting the back surface of the DLTS sample serves as an ohmic electrode, the area of the part of the tin foil covering and contacting the back surface of the DLTS sample is more than ten times the area of the circular gold film, and then annealing treatment is performed, thereby forming a detection sample.

[0047] S4, detection: the detection sample is placed on the sample stage of the DLTS detection device, the positive probe of the sample stage contacts the Schottky electrode of the detection sample, the negative probe of the sample stage contacts the part of the copper sheet that exceeds the surface contour of the DLTS sample, and then electrode contact detection is performed to determine whether the contact between the Schottky electrode and the ohmic electrode is problematic, if the contact between the Schottky electrode and the ohmic electrode is not problematic, then normal temperature IV curve detection is performed, if the detection sample forms a Schottky contact, then DLTS spectrum signal detection is performed, if the DLTS spectrum signal is good, then complete low-temperature DLTS detection is started to obtain the DLTS spectrum.

[0048] Similarly, in an embodiment, in step S1, the sampling specifications of the Hall sample are (8-12 mm) x (8-12 mm) x (1-2 mm), the sampling specifications of the dislocation sample are the entire cross section of the tail of the n-type germanium single crystal x (3-5 mm) in thickness, and the sampling specifications of the DLTS sample are (15-20 mm) x (15-20 mm) x (3-5 mm).

[0049] Similarly, in step S1, the carrier concentration of the Hall sample is detected by HL9900 of Toho Technology Company, USA, tin particles are pressed on the four corners of the Hall sample, annealing heat treatment is performed to form a good ohmic contact, then IV test is performed on the HL9900, after no problem, low-temperature Hall detection is performed to determine the carrier concentration. Specifically, the annealing heat treatment is as follows: the sample is placed in a 7N nitrogen annealing furnace, the temperature is 300-400℃, and the time is 20-30 min.

[0050] Similarly, in step S1, after the dislocation sample piece is milled and polished to be smooth and flat, and then polished to a mirror surface, the dislocation sample piece is washed with pure water, and then placed in a constant temperature etching solution at 5-15°C for etching for 5-10 min, and then detected on a metallographic microscope. The etching solution is hydrofluoric acid: nitric acid: 10% copper nitrate = 2:1:1 (volume ratio).

[0051] Similarly, in an embodiment, in step S2, the etching solution used for etching is hydrofluoric acid: nitric acid: 10% copper nitrate = 2:1:1 (volume ratio).

[0052] In step S3, in an embodiment, corresponding to the sampling specification of the DLTS sample piece (i.e. (15-20mm) x (15-20mm) x (3-5mm) as mentioned above), the diameter of the round gold film is 1-2mm, and the thickness is 100-200nm, the tin foil has the same profile as the DLTS sample piece (i.e. (15-20mm) x (15-20mm)) to completely contact and cover the back surface of the DLTS sample piece, and the thickness of the tin foil is 30-50μm.

[0053] In step S3, the area of the part of the tin foil covering and contacting the back surface of the DLTS sample piece is more than ten times the area of the round gold film, which can effectively obtain the DLTS spectrum signal in step S4.

[0054] Similarly, in step S3, by increasing the copper sheet and the surface profile of the copper sheet being larger than the surface profile of the DLTS sample piece, on the one hand, the protection of the copper sheet to the tin foil is increased, so that the stability of the ohmic electrode is enhanced, and on the other hand, the resistance to vibration of the helium cooling stage from low temperature during the entire DLTS detection process is increased, and the stability of the contact between the tin foil and the back surface of the DLTS sample piece is improved. The size of the surface profile of the copper sheet can be determined by the contact between the negative probe of the sample stage and the part of the copper sheet that exceeds the surface profile of the DLTS sample piece, and the thickness of the copper sheet can be determined by ensuring that the copper sheet has a certain overall hardness to resist deformation caused by the vibration of the helium cooling stage at low temperature. Specifically, the thickness of the copper sheet is 0.5-1mm.

[0055] Similarly, in an embodiment, in step S3, the back surface of the DLTS sample piece is connected to the copper sheet by the tin foil as follows: wearing clean gloves, placing the tin foil between the back surface of the DLTS sample piece and the copper sheet, and squeezing the DLTS sample piece and the copper sheet from both sides with hands to connect the DLTS sample piece, the tin foil and the copper sheet together.

[0056] In step S3, the germanium wafer is better contacted with the Schottky electrode and the ohmic electrode by annealing heat treatment and annealing treatment, and the IV curve keeps the diode characteristic. However, since the round dot gold film and the tin foil are different materials, in step S3, the annealing heat treatment is performed after sputtering the round dot gold film, and then the annealing treatment is performed after connecting the copper sheet with the tin foil on the back of the DLTS wafer.

[0057] In an embodiment, in step S3, the annealing heat treatment is that the front of the DLTS wafer with the sputtered round dot gold film is placed upward in a 7N nitrogen annealing furnace for annealing, the temperature is 1100-1150℃, and the time is 20-30min.

[0058] In an embodiment, in step S3, the annealing treatment is that the round dot gold film of the DLTS wafer is upward, the copper sheet is below the tin foil, and the DLTS wafer is placed in a 7N nitrogen annealing furnace, the temperature is 300-400℃, and the time is 20-30min.

[0059] Similarly, in step S4, the electrode contact test is directly performed by using the function of the DLTS equipment. In the detection method of the deep level defects of the detector-grade high-purity germanium single crystal disclosed in the present disclosure, the DLTS equipment is a digital deep level transient spectrometer DLTS of Sula Technologies Company, USA, which can directly display that the capacitance value of the test sample is stable within 1%, which means that the contact of the Schottky electrode and the ohmic electrode is determined to be no problem.

[0060] Similarly, in step S4, the normal temperature IV curve test is performed, and if the IV curve of the test sample is nonlinear, it means that the Schottky contact is formed.

[0061] Similarly, in step S4, the DLTS spectrum signal detection is performed at the maximum point of the complete low-temperature DLTS detection low-temperature range, for example, if the low-temperature range is 10-160K, the DLTS spectrum signal detection is performed at 160K, which is convenient for directly continuing the complete low-temperature DLTS detection under the condition that the DLTS spectrum signal obtained by the DLTS spectrum signal detection is good, so that the complete low-temperature DLTS detection does not need to wait or re-adjust to the maximum point of the low-temperature range as the starting point to start again, thereby saving the detection time and improving the detection efficiency.

[0062] Similarly, in step S4, the good DLTS spectrum signal is determined by whether the spectrum signal figure output by the DLTS forms a good exponential curve, and the thinner the exponential curve line is, the better the DLTS spectrum signal is, for example, as shown in Figure 8 .

[0063] Similarly, in step S4, the low-temperature temperature range of the complete low-temperature DLTS spectrum detection is provided by the DLTS equipment itself, and the sample table of the digital deep level transient spectrum DLTS of the American Sula Technologies Company is provided with a temperature-adjustable helium gas cooling table connected with a compressor, and the low-temperature temperature range of the complete low-temperature DLTS spectrum detection is 10K-160K.

[0064] [TEST]

[0065] Embodiment 1

[0066] For the p-type germanium single crystal, the detection method of the deep level defect of the detector-grade high-purity germanium single crystal comprises the following steps:

[0067] S1, sampling:

[0068] The detector-grade high-purity germanium single crystal is a p-type germanium single crystal, and a Hall sample and a dislocation sample are taken from the head of the p-type germanium single crystal for carrier concentration and dislocation density detection. The sampling specification of the Hall sample is 10mm×10mm×2mm, and the sampling specification of the dislocation sample is the entire cross section of the head of the p-type germanium single crystal×4mm in thickness. The carrier concentration of the Hall sample is detected by the HL9900 of the American Toho Technology Company, tin particles are pressed on the four corners of the Hall sample, annealing heat treatment is performed to make the Hall sample form a good ohmic contact, then IV test is performed on the HL9900, after no problem, low-temperature Hall detection is performed to determine the carrier concentration. The annealing heat treatment specifically comprises: being placed in a 7N nitrogen annealing furnace, the temperature is 350℃, and the time is 25min. After the dislocation sample is milled and polished to be smooth on both sides by a milling machine, the dislocation sample is polished to a mirror surface, washed clean with pure water, placed in a constant-temperature etching liquid at 10℃ for etching for 10min, and then detected on a metallographic microscope. The etching liquid is hydrofluoric acid:nitric acid:10% copper nitrate=2:1:1(by volume ratio);

[0069] If the carrier concentration of the Hall sample of the p-type germanium single crystal is <2E10cm -3 and the dislocation density of the dislocation sample of the p-type germanium single crystal is <10000cm -2 , then a DLTS sample is taken from the head of the remaining crystal of the p-type germanium single crystal, and the sampling specification of the DLTS sample is 18mm×18mm×4mm.

[0070] S2, processing:

[0071] The DLTS sample is surface ground, polished, etched (the etching liquid is hydrofluoric acid:nitric acid:10% copper nitrate=2:1:1(by volume ratio)) to a mirror surface, washed with pure water, and blown dry.

[0072] S3, electrode preparation:

[0073] Sputtering tin film on the front side of the DLTS sample, the diameter of the tin film is 1.5mm, and the thickness is 150nm. The tin film serves as a Schottky electrode. A clean glove is used to place the tin foil between the back side of the DLTS sample and the copper sheet. The DLTS sample and the copper sheet are pressed together from both sides by hand, so that the back side of the DLTS sample is connected to the copper sheet by the tin foil. The tin foil has the same contour as the DLTS sample (i.e. 18mm x 18mm to completely contact and cover the back side of the DLTS sample). The thickness of the tin foil is 40μm. The surface contour of the copper sheet is 10mm larger than that of the DLTS sample. The thickness of the copper sheet is 0.75mm. The part of the tin foil that covers and contacts the back side of the DLTS sample serves as an ohmic electrode. Then annealing is performed. The front side of the DLTS sample with sputtered tin film is placed upwards, and the copper sheet is placed below the tin foil. The sample is placed in a 7N nitrogen annealing furnace at a temperature of 350℃ for 25min, thereby forming a detection sample;

[0074] S4, detection:

[0075] The detection sample is placed in the sample stage of the DLTS detection equipment. The positive probe of the sample stage contacts the Schottky electrode of the detection sample, and the negative probe of the sample stage contacts the part of the copper sheet that exceeds the surface contour of the DLTS sample. Then electrode contact detection is performed to determine whether the contact of the Schottky electrode and the ohmic electrode is problematic. The electrode contact test is directly performed using the self-function of the DLTS equipment. In the detector-level high-purity germanium single crystal deep level defect detection method of the present disclosure, the DLTS equipment is a digital deep level transient spectrometer DLTS of Sula Technologies Company, USA. The DLTS equipment can directly display that the capacitance value of the test sample is stable within 1%, which indicates that the contact of the Schottky electrode and the ohmic electrode is not problematic;

[0076] If the contact of the Schottky electrode and the ohmic electrode is not problematic, the DLTS equipment performs normal temperature IV curve detection. If the IV curve of the detection sample is nonlinear, it indicates that a Schottky contact is formed;

[0077] If the detection sample forms a Schottky contact, the DLTS equipment performs DLTS spectrum signal detection. The DLTS spectrum signal detection is performed at the maximum point 160K in the low temperature range of complete low temperature DLTS detection. The DLTS spectrum signal is good, and whether a good exponential curve is formed in the spectrum signal diagram output by the DLTS. The sample stage of the digital deep level transient spectrometer DLTS of Sula Technologies Company, USA, has a temperature-adjustable helium cooling table connected with a compressor. The low temperature range of complete low temperature DLTS spectrum detection is 10K-160K;

[0078] If the DLTS spectrum signal is good, the DLTS device starts to conduct the low-temperature DLTS detection in the complete low-temperature range of 10-160 K to obtain the DLTS spectrum.

[0079] Comparative Example 1

[0080] Except that annealing is not conducted in step S3, the rest is the same as Example 1.

[0081] Comparative Example 2

[0082] Except that the size of the tin foil in step S3 is 5 times the area of the round-point tin film, the rest is the same as Example 1.

[0083] Figure 1 and Figure 2 The DLTS device conducts the normal-temperature IV curve detection result of Example 1 and Comparative Example 1 in step S4, respectively, from which it can be seen that Figure 1 and Figure 2 It can be seen from the comparison of Figure 3 and Figure 4 The DLTS spectrum signal detection result of Example 1 and Comparative Example 1 in step S4, respectively, from which it can be seen that Figure 4 and Figure 3 Since step S3 of Comparative Example 1 does not adopt annealing, the DLTS spectrum signal of subsequent step S4 cannot show the exponential curve, and thus the complete low-temperature DLTS spectrum detection cannot be conducted.

[0084] Figure 3 and Figure 5 The DLTS spectrum signal detection result of Example 1 and Comparative Example 2 in step S4, respectively, from which it can be seen that Figure 3 and Figure 5 It can be seen from the comparison of Figure 5 The area of the part of the tin foil covering and contacting the back surface of the DLTS sample of Comparative Example 2 is 5 times the area of the round-point tin film, although the exponential curve trend can be seen, the line of the exponential curve is very thick.

[0085] Figure 6 The DLTS spectrum of Example 1 is given, which can clearly reveal the clear and explicit peak representing the deep energy level defect. Figure 7 The DLTS spectrum of Comparative Example 2 is given. Based on the comparison of Figure 3 and Figure 5 Further based on the comparison of Figure 6 and Figure 7 Since the DLTS spectrum signal of Comparative Example 2 is poor, the peak value in the further obtained DLTS spectrum is less and not obvious.

[0086] Example 2

[0087] The detection method of the deep level defects of the detector-grade high-purity germanium single crystal for the n-type germanium single crystal comprises the following steps:

[0088] S1, sampling:

[0089] The detector-grade high-purity germanium single crystal is an n-type germanium single crystal, and a Hall sample and a dislocation sample are taken from the tail of the n-type germanium single crystal for carrier concentration and dislocation density detection. The sampling specification of the Hall sample is 10 mm x 10 mm x 2 mm, and the sampling specification of the dislocation sample is the entire cross section of the tail of the n-type germanium single crystal x 4 mm in thickness. The carrier concentration of the Hall sample is detected by HL9900 of Toho Technology Company, USA. Tin particles are pressed on the four corners of the Hall sample, annealing heat treatment is performed to form a good ohmic contact, then IV test is performed on the HL9900, after no problem, low-temperature Hall detection is performed to determine the carrier concentration. The annealing heat treatment is specifically as follows: put into a 7N nitrogen annealing furnace, the temperature is 350℃, and the time is 25 min. The dislocation density is polished flat and smooth by a milling machine after the dislocation sample is polished to a mirror surface, cleaned with pure water, placed in a constant temperature etching liquid at 10℃ for etching for 10 min, and then detected on a metallographic microscope. The etching liquid is hydrofluoric acid: nitric acid: 10% copper nitrate = 2:1:1 (volume ratio);

[0090] If the carrier concentration of the Hall sample of the n-type germanium single crystal is < 2E10 cm -3 and the dislocation density of the dislocation sample of the n-type germanium single crystal is < 5000 cm -2 , then a DLTS sample is taken from the tail of the remaining crystal of the n-type germanium single crystal, and the sampling specification of the DLTS sample is 18 mm x 18 mm x 4 mm;

[0091] S2, processing: the DLTS sample is surface ground, polished, etched (the etching liquid is hydrofluoric acid: nitric acid: 10% copper nitrate = 2:1:1 (volume ratio)) to a mirror surface, washed with pure water, and dried;

[0092] S3, electrode preparation:

[0093] Sputtering gold film on the front surface of the DLTS sample, the diameter of the gold film is 1.5 mm and the thickness is 150 nm, and then annealing heat treatment is performed, the front surface of the DLTS sample with sputtered gold film is placed upwards in a 7N nitrogen annealing furnace for annealing, the temperature is 1125℃ and the time is 25 min, the gold film is used as a Schottky electrode; tin foil is placed between the back surface of the DLTS sample and the copper sheet with clean gloves, and the DLTS sample and the copper sheet are pressed from both sides to connect them together, thus the back surface of the DLTS sample is connected to the copper sheet with tin foil, the tin foil has the same outline as the DLTS sample (i.e. 18 mm x 18 mm to completely contact and cover the back surface of the DLTS sample), the thickness of the tin foil is 40 μm, the surface outer contour of the copper sheet is larger than the surface outer contour of the DLTS sample by 10 mm, the thickness of the copper sheet is 0.75 mm, and the part of the tin foil covering and contacting the back surface of the DLTS sample is used as an ohmic electrode, then annealing treatment is performed, the DLTS sample with gold film upwards and the copper sheet below the tin foil is placed in a 7N nitrogen annealing furnace, the temperature is 350℃ and the time is 25 min, thus forming a detection sample;

[0094] S4, detection:

[0095] The detection sample is placed in the sample stage of the DLTS detection equipment, the positive probe of the sample stage contacts the Schottky electrode of the detection sample, and the negative probe of the sample stage contacts the part of the copper sheet that exceeds the surface outer contour of the DLTS sample, then electrode contact detection is performed to determine whether the contact of the Schottky electrode and the ohmic electrode is problematic, and the electrode contact test is directly performed by using the self-function of the DLTS equipment. In the detector level high-purity germanium single crystal deep level defect detection method of the present disclosure, the DLTS equipment is a digital deep level transient spectroscopy DLTS of Sula Technologies Company, USA, which can directly display that the capacitance value of the test sample is stable within 1%, which means that the contact of the Schottky electrode and the ohmic electrode is not problematic;

[0096] If the contact of the Schottky electrode and the ohmic electrode is not problematic, the DLTS equipment performs normal temperature IV curve detection, and if the IV curve of the detection sample is nonlinear, it means that the Schottky contact is formed;

[0097] If the sample forms a Schottky contact, the DLTS device detects the DLTS spectrum signal, and the DLTS spectrum signal detection is performed at the maximum point 160K in the low temperature range of the complete low temperature DLTS detection, and the DLTS spectrum signal is good, and whether the DLTS output spectrum signal graph forms a good exponential curve, wherein the sample table of the digital deep level transient spectroscopy DLTS of the American Sula Technologies company is connected with the temperature adjustable helium gas cooling table with a compressor, and the low temperature temperature range of the complete low temperature DLTS spectrum detection is 10K-160K.

[0098] If the DLTS spectrum signal is good, the DLTS device starts to perform the complete low temperature range of 10-160K low temperature DLTS detection to obtain the DLTS spectrum.

[0099] Figure 8 The DLTS spectrum signal detection result in step S4 of example 2 is shown. Figure 9 The DLTS spectrum obtained in step S4 of example 2 is given.

Claims

1. A method for detecting deep-level defects in detector-grade high-purity germanium single crystals, comprising the following steps: S1, Sampling: The detector-grade high-purity germanium single crystal is a p-type germanium single crystal. Hall sample and dislocation sample are taken from the head of the p-type germanium single crystal for carrier concentration and dislocation density detection, respectively. If the carrier concentration of the Hall sample of the p-type germanium single crystal is <2E10cm -3 Furthermore, the dislocation density of the p-type germanium single crystal dislocation sample is <10000 cm⁻¹. -2 Then, a DLTS sample is taken from the head of the remaining crystal of the p-type germanium single crystal. S2, Processing: Grind, polish, and etch the DLTS sample to a mirror finish, then wash with pure water and dry. S3, Electrode preparation: A dotted tin film is sputtered on the front side of the DLTS sample, serving as a Schottky electrode. A copper sheet is connected to the back side of the DLTS sample using tin foil, with the tin foil at least partially covering and contacting the back side of the DLTS sample. The outer contour of the copper sheet is larger than the outer contour of the DLTS sample. The portion of the tin foil covering and contacting the back side of the DLTS sample serves as an ohmic electrode, and the area of ​​the portion of the tin foil covering and contacting the back side of the DLTS sample is more than ten times the area of ​​the dotted tin film. Annealing is then performed to form the test sample. S4, Detection: Place the test sample into the sample stage of the DLTS detection equipment. The positive probe of the sample stage contacts the Schottky electrode of the test sample, and the negative probe of the sample stage contacts the portion of the copper sheet that extends beyond the outer contour of the DLTS sample surface. Then, a contact test is performed to determine if there is a problem with the contact between the Schottky electrode and the ohmic electrode. If there is no problem with the contact between the Schottky electrode and the ohmic electrode, a room temperature IV curve test is performed. If the test sample forms a Schottky contact, a DLTS spectrum signal test is performed. If the DLTS spectrum signal is good, a complete low-temperature DLTS test is started to obtain the DLTS spectrum.

2. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 1, characterized in that, In step S1, the sampling specifications of the Hall sample are (8-12mm)×(8-12mm)×(1-2mm), the sampling specifications of the dislocation sample are the entire cross-section of the head of the p-type germanium single crystal × (3-5mm) thickness, and the sampling specifications of the DLTS sample are (15-20mm)×(15-20mm)×(3-5mm).

3. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 1, characterized in that, In step S3, the copper sheet is connected to the back of the DLTS sample with tin foil: wearing clean gloves, place the tin foil between the back of the DLTS sample and the copper sheet, and squeeze the DLTS sample and the copper sheet from both sides by hand to connect the DLTS sample, tin foil and copper sheet together.

4. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 1, characterized in that, In step S1, the sampling dimensions of the DLTS sample are (15-20mm)×(15-20mm)×(3-5mm); In step S3, the diameter of the dot tin film is 1-2 mm and the thickness is 100-200 nm. The tin foil is made of (15-20 mm) × (15-20 mm) with the same outline as the DLTS sample to completely contact and cover the back of the DLTS sample. The thickness of the tin foil is 30-50 μm.

5. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 1, characterized in that, In step S3, the annealing is performed as follows: the DLTS sample with the sputtered tin film facing up and the copper sheet below the tin foil is placed in a 7N nitrogen annealing furnace at a temperature of 300-400℃ for 20-30 minutes.

6. A method for detecting deep-level defects in detector-grade high-purity germanium single crystals, comprising the following steps: S1, Sampling: The detector-grade high-purity germanium single crystal is an n-type germanium single crystal. Hall sample and dislocation sample are taken from the tail of the n-type germanium single crystal for carrier concentration and dislocation density detection, respectively. If the carrier concentration of the Hall sample of the n-type germanium single crystal is <2E10cm -3 Furthermore, the dislocation density of the n-type germanium single crystal dislocation sample is <5000 cm⁻¹. -2 Then, a DLTS sample is taken from the tail of the remaining crystal of the n-type germanium single crystal. S2, Processing: Grind, polish, and etch the DLTS sample to a mirror finish, then wash with pure water and dry. S3, Electrode preparation: A dotted gold film is sputtered onto the front side of the DLTS sample, followed by annealing heat treatment. The dotted gold film serves as a Schottky electrode. A copper sheet is connected to the back side of the DLTS sample using tin foil. The tin foil at least partially covers and contacts the back side of the DLTS sample. The outer contour of the copper sheet is larger than the outer contour of the DLTS sample. The portion of the tin foil covering and contacting the back side of the DLTS sample serves as an ohmic electrode. The area of ​​the portion of the tin foil covering and contacting the back side of the DLTS sample is more than ten times the area of ​​the dotted gold film. After annealing, a test sample is formed. S4, Detection: Place the test sample into the sample stage of the DLTS detection equipment. The positive probe of the sample stage contacts the Schottky electrode of the test sample, and the negative probe of the sample stage contacts the part of the copper sheet that extends beyond the outer contour of the DLTS sample surface. Then, a contact test is performed to determine whether there is a problem with the contact between the Schottky electrode and the ohmic electrode. If there is no problem with the contact between the Schottky electrode and the ohmic electrode, a room temperature IV curve test is performed. If the test sample forms a Schottky contact, a DLTS spectrum signal test is performed. If the DLTS spectrum signal is good, a complete low-temperature DLTS test is started to obtain the DLTS spectrum.

7. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 6, characterized in that, In step S1, the sampling specifications of the Hall sample are (8-12mm)×(8-12mm)×(1-2mm), the sampling specifications of the dislocation sample are the thickness of the entire cross section of the tail of the n-type germanium single crystal × (3-5mm), and the sampling specifications of the DLTS sample are (15-20mm)×(15-20mm)×(3-5mm).

8. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 6, characterized in that, In step S3, the copper sheet is connected to the back of the DLTS sample with tin foil: wearing clean gloves, place the tin foil between the back of the DLTS sample and the copper sheet, and squeeze the DLTS sample and the copper sheet from both sides by hand to connect the DLTS sample, tin foil and copper sheet together.

9. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 6, characterized in that, In step S1, the sampling dimensions of the DLTS sample are (15-20mm)×(15-20mm)×(3-5mm); In step S3, the diameter of the dot gold film is 1-2 mm and the thickness is 100-200 nm. The tin foil is made of (15-20 mm) × (15-20 mm) with the same outline as the DLTS sample to completely contact and cover the back of the DLTS sample. The thickness of the tin foil is 30-50 μm.

10. The method for detecting deep-level defects in detector-grade high-purity germanium single crystals according to claim 6, characterized in that, In step S3, the annealing heat treatment is as follows: the DLTS sample with the sputtered gold dot film facing up is placed in a 7N nitrogen annealing furnace for annealing at a temperature of 1100-1150℃ for 20-30 minutes. In step S3, the annealing process is as follows: the gold dot film of the DLTS sample is facing upwards, the copper sheet is below the tin foil, and it is placed in a 7N nitrogen annealing furnace at a temperature of 300-400℃ for 20-30 minutes.

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