A method for detecting P-type and N-type of zone-melted germanium ingot

Abstract

This invention discloses a method for detecting P-type and N-type germanium ingots in a zone-melted process. The germanium ingot to be tested is placed between a heat source and a thermal imager. The heat source is turned on, and the thermal imager scans the ingot. If the displayed image can penetrate the germanium ingot, the scanned area is N-type; if the displayed image shows a striped shadow, the scanned area is P-type. This method cleverly utilizes the infrared transmittance of N-type germanium (which P-type germanium does not possess). By scanning with an infrared thermal imager, P-type material can be detected quickly and accurately, thereby accelerating the detection process and reducing the workload of inspection personnel. It offers high accuracy and clearly identifies the boundary between P-type and N-type, avoiding P-type residue and reducing N-type loss, thus improving product quality, saving costs, and preventing waste. Simultaneously, it improves detection efficiency and testing accuracy, achieving a testing accuracy below 0.5 mm.

Description

Technical Field

[0001] This invention relates to a method for detecting P-type and N-type zone-melted germanium ingots, belonging to the field of materials testing technology. Background Technology

[0002] Zone-refined germanium ingots are high-purity germanium ingots obtained through zone refining from reduced germanium ingots or recycled germanium single crystals (with a resistivity greater than or equal to 50 Ω·m at 20±0.5℃). Zone-refined germanium ingots are the raw materials for producing infrared and photovoltaic germanium single crystals. Generally, high-purity zone-refined germanium ingots have an N-type conductivity, but P-type high-purity zone-refined germanium ingots can also appear at the head or tail of the ingot. In actual production, N-type zone-refined germanium ingots are considered qualified, while P-type ingots are considered unqualified and need to be removed. When inspecting incoming P- and N-type germanium ingots, the probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" is used. This method is inconvenient and time-consuming, requiring continuous point testing within a region to distinguish the P-type area, and it is difficult to accurately determine the boundary between P- and N-type, leading to P-type residue or N-type loss in the germanium ingot. Summary of the Invention

[0003] This invention provides a method for detecting P-type and N-type zone-melted germanium ingots to solve the problem of low detection efficiency caused by probe spot testing.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for detecting P-type and N-type germanium ingots in zone-melted ingots involves placing the germanium ingot to be tested between a heat source and a thermal imager, turning on the heat source, and using the thermal imager to scan and image. If the displayed image can penetrate the germanium ingot, it indicates that the scanned area is N-type; if the displayed image shows a striped dark shadow, it indicates that the scanned area is P-type.

[0006] The application's "image penetrating germanium ingot" refers to the fact that the germanium ingot is similar to cloaking, allowing the heat source behind the germanium ingot to be seen through it.

[0007] The above method is simple to operate and highly efficient.

[0008] The temperature of the heat source is controlled between 50℃ and 95℃. If the temperature exceeds this range, the imaging effect will be unclear. A more preferable temperature range is 70℃ to 85℃.

[0009] To facilitate testing and improve accuracy, the heat source and thermal imager are positioned on opposite sides of the germanium ingot to be tested, with the distance between the ingot and the heat source ranging from 10mm to 100mm. If this distance is exceeded, the imaging effect will be unclear. A more preferable distance between the germanium ingot and the heat source is 20mm to 50mm. The distance between the germanium ingot and the thermal imager lens is 500mm to 1200mm; if this distance is exceeded, the imaging effect will be poor. A more preferable distance between the germanium ingot and the thermal imager lens is 800mm to 1200mm.

[0010] The thermal imagers described in this application are: long-wave uncooled thermal imagers, manual / automatic uncooled thermal imagers, and handheld / non-handheld thermal imagers.

[0011] For ease of operation, as one specific implementation scheme, the method for detecting P-type and N-type zone-melted germanium ingots includes the following steps:

[0012] 1) Turn on the heat source and control the temperature at 50℃~95℃. Place the germanium ingot to be tested between the heat source and the thermal imager. The germanium ingot to be tested should be 10mm~100mm away from the heat source, and the lens of the thermal imager should be 500mm~1200mm away from the germanium ingot to be tested.

[0013] 2) Turn on the thermal imager and display system, and adjust the focus of the thermal imager until the image on the screen is clear;

[0014] 3) Move the thermal imager to scan the entire germanium ingot. If the displayed image can penetrate the germanium ingot, it indicates that the scanned area is N-type; if the displayed image is a striped shadow, it indicates that the scanned area is P-type.

[0015] In the above scheme, thermal imaging is performed after the heat source temperature has stabilized. During testing, the temperature of the germanium ingot under test is not critical; imaging can begin as soon as the heat source temperature stabilizes.

[0016] In step 1), the heat source can be turned on first, and then the germanium ingot to be tested can be placed in; alternatively, the germanium ingot to be tested can be placed in and then the heat source can be turned on. It is important to ensure that the temperature of the heat source itself reaches the set temperature and stabilizes before imaging, and that the germanium ingot to be tested is located between the heat source and the thermal imager during imaging.

[0017] Any techniques not mentioned in this invention are based on existing technologies.

[0018] This invention provides a method for detecting P-type and N-type germanium ingots in a zone-melted process. It cleverly utilizes the infrared transmittance of N-type germanium (a characteristic lacking in P-type germanium). By scanning with an infrared thermal imager, P-type material can be detected quickly and accurately, thus accelerating the detection process and reducing the workload of inspection personnel. The method boasts high accuracy and clearly identifies the boundary between P-type and N-type ingots, preventing P-type residue, reducing N-type loss, improving product quality, saving costs, and avoiding waste. Simultaneously, it improves detection efficiency and testing accuracy, achieving a precision below 0.5 mm. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the method for detecting P-type and N-type germanium ingots in the zone melting process according to the present invention; Detailed Implementation

[0020] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0021] In each case: the germanium ingots to be tested were all commercially available products with a resistivity greater than 50 Ω·m; the thermal imager was a CGMO-M-641219 manufactured by Zhongge Technology Co., Ltd.; and the display system was an IRT_TAS_LT_MICROШ from Arrow Electronics.

[0022] Example 1

[0023] The following method is used to detect the P-type and N-type of germanium ingots in the test zone:

[0024] Turn on the heat source and maintain the temperature at 50℃. Place the germanium ingot to be tested 50mm away from the heat source, and position the thermal imager lens 800mm away from the ingot, with the ingot positioned between the heat source and the thermal imager. Turn on the long-wave uncooled thermal imager and display system. Adjust the thermal imager's focus until the image on the display screen is clear. Move the thermal imager to scan the entire germanium ingot. A striped shadow appears on the top 2cm of the ingot, indicating a P-type germanium ingot with a clear outline and a measurement accuracy below 0.5mm. Mark the P-type area with a marker. The remaining portion is an N-type germanium ingot, ready for cutting. The inspection takes 10 seconds.

[0025] Comparative Example 1

[0026] The probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" was used to directly test the germanium ingot in Example 1. The measurement result showed that the 1.9cm length of the germanium ingot head was P-type, and the test took more than 2 minutes.

[0027] The probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" was used to test the germanium ingot under test in Example 1. Point tests were performed in the areas identified as N-type in Example 1, and the results showed that all were N-type. Point tests were performed in the areas identified as P-type in Example 1, and the results showed that all were P-type, proving that the accuracy of the method in Example 1 reached 100%.

[0028] Since Comparative Example 1 is a point-based test, it is difficult to accurately determine the boundary between P-type and N-type, resulting in a measurement error that is significantly higher than that of Example 1. The measurement result shows that the 1.9cm length of the germanium ingot head is P-type, while in reality, the germanium ingot head has a 2cm length of P-type, resulting in the 0.1cm length of the P-type germanium ingot head not being cut cleanly, which in turn affects the product quality.

[0029] Example 2

[0030] The following method is used to detect the P-type and N-type of germanium ingots in the test zone:

[0031] Turn on the heat source and maintain the temperature at 70℃. Place the germanium ingot to be tested 50mm away from the heat source, and position the thermal imager lens 1000mm away from the ingot. The ingot should be positioned between the heat source and the thermal imager. Turn on the long-wave uncooled thermal imager and display system. Adjust the thermal imager's focus until the image on the display screen is clear. Move the thermal imager to scan the entire germanium ingot. A strip-shaped dark shadow appearing 1cm from the tail of the ingot indicates a P-type germanium ingot, with a clear outline and a measurement accuracy below 0.5mm. Mark the P-type area with a marker; the others are N-type germanium ingots, ready for cutting. The inspection takes 10 seconds.

[0032] Comparative Example 2

[0033] The probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" was used to test the germanium ingot to be tested in Example 2. That is, this example and Example 2 are the same germanium ingot to be tested. The test result is that the length of 1 cm at the tail of the germanium ingot is P-type, and the test time is 2 minutes.

[0034] The probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" was used to test the germanium ingot in Example 2. Point tests were performed in the areas identified as N-type in Example 2, and the results showed that all samples were N-type. Point tests were also performed in the areas identified as P-type in Example 2, and the results showed that all samples were P-type. This proves that the accuracy of the method in Example 2 is 100%.

[0035] Example 3

[0036] The following method is used to detect the P-type and N-type of germanium ingots in the test zone:

[0037] Turn on the heat source and set the temperature to 80℃. Place the germanium ingot to be tested 50mm away from the heat source, and position the thermal imager lens 900mm away from the ingot. The ingot should be positioned between the heat source and the thermal imager. Turn on the long-wave uncooled thermal imager and display system. Adjust the focus until the image on the display screen is clear. Move the thermal imager to scan the entire germanium ingot. A 0.6cm length at the tail and a 1cm length in the middle of the ingot will show a striped shadow, indicating a P-type germanium ingot. The outline of the striped shadow should be clear, with a measurement accuracy below 0.5mm. Mark the P-type area with a marker. The rest are N-type germanium ingots, ready for cutting. The inspection time is 10 seconds.

[0038] With the heat source temperature controlled at 80℃ and the thermal imager lens positioned 900mm from the germanium ingot, the image was clearest when the distance between the germanium ingot and the heat source was varied, ranging from 20mm to 50mm. Similarly, with the distance controlled at 50mm and the thermal imager lens positioned 900mm from the germanium ingot, the image was clearest when the heat source temperature was varied, ranging from 70℃ to 85℃. Finally, with the distance controlled at 50mm and the heat source temperature controlled at 80℃, the image was clearest when the distance between the germanium ingot and the thermal imager lens was varied, ranging from 800mm to 1000mm.

[0039] Comparative Example 3

[0040] The probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" was used to test the germanium ingot to be tested in Example 3. That is, this example and Example 3 are the same germanium ingot to be tested. The test results show that the length of 0.7 cm at the tail and 1 cm in the middle of the germanium ingot indicates that it is a P-type germanium ingot. The test time is 3 minutes.

[0041] The probe point contact rectification method in GB / T 1550-1997 "Test Method for Conductivity Type of Intrinsic Semiconductor Materials" was used to test the germanium ingot in Example 3. Point tests were performed in the areas identified as N-type in Example 3, and the results showed that all were N-type. Point tests were also performed in the areas identified as P-type in Example 3, and the results showed that all were P-type. This proves that the accuracy of the method in Example 3 is 100%.

[0042] Since Comparative Example 3 is a point-based test, it is difficult to accurately determine the boundary between P-type and N-type, resulting in a measurement error that is significantly higher than that of Example 3. The measurement result shows that the 0.7cm length of the germanium ingot tail is P-type, while in reality, only 0.6cm of the germanium ingot tail is P-type, resulting in an extra 0.1cm of N-type material being cut off at the tail, causing material loss.

Claims

1. A method for detecting P-type and N-type zone-melted germanium ingots, characterized in that: The germanium ingot to be tested is placed between the heat source and the thermal imager. The heat source is turned on and the thermal imager is used to scan and image. If the image can penetrate the germanium ingot, it indicates that the scanned area is N-type. If the image shows a striped shadow, it indicates that the scanned area is P-type. The test accuracy is below 0.5mm. The heat source temperature is controlled between 50℃ and 95℃; The distance between the germanium ingot to be tested and the heat source is 10mm to 100mm; The distance between the germanium ingot to be tested and the lens of the thermal imager is 500mm to 1200mm.

2. The method for detecting P-type and N-type zone-melted germanium ingots as described in claim 1, characterized in that: The heat source temperature is controlled between 70℃ and 85℃.

3. The method for detecting P-type and N-type zone-melted germanium ingots as described in claim 1 or 2, characterized in that: The distance between the germanium ingot to be tested and the heat source is 20mm to 50mm.

4. The method for detecting P-type and N-type zone-melted germanium ingots as described in claim 1 or 2, characterized in that: The distance between the germanium ingot to be tested and the lens of the thermal imager is 800mm to 1000mm.

5. The method for detecting P-type and N-type zone-melted germanium ingots as described in claim 1 or 2, characterized in that: The thermal imagers are: long-wave uncooled thermal imagers, manual / automatic uncooled thermal imagers, and handheld / non-handheld thermal imagers.

6. The method for detecting P-type and N-type zone-melted germanium ingots as described in claim 1 or 2, characterized in that: Includes the following steps: 1) Turn on the heat source and control the temperature at 50℃~95℃. Place the germanium ingot to be tested between the heat source and the thermal imager. The germanium ingot to be tested should be 10mm~100mm away from the heat source, and the lens of the thermal imager should be 500mm~1200mm away from the germanium ingot to be tested. 2) Turn on the thermal imager and display system, and adjust the focus of the thermal imager until the image on the screen is clear; 3) Move the thermal imager to scan the entire germanium ingot. If the displayed image can penetrate the germanium ingot, it indicates that the scanned area is N-type; if the displayed image is a striped shadow, it indicates that the scanned area is P-type.

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