Method for locally doping aluminum on surface of silicon substrate, aluminum-doped silicon substrate and PN junction
By depositing a silicon nitride masking film on the surface of a silicon substrate and controlling the temperature, the problems of uneven aluminum doping and device warping in the prior art have been solved, achieving uniform aluminum doping on the surface of the silicon substrate and improving product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHUZHOU CRRC TIMES SEMICON CO LTD
- Filing Date
- 2024-12-13
- Publication Date
- 2026-04-10
AI Technical Summary
Existing aluminum doping processes are difficult to achieve selective doping and suffer from problems such as aluminum impurity penetration and device warping.
A silicon nitride masking film is deposited on the surface of a silicon substrate, a doping window is formed by etching, and the temperature of the aluminum doping process is controlled to achieve localized uniform doping of aluminum on the surface of the silicon substrate.
This method achieves uniform doping of aluminum on the silicon substrate surface, avoiding warping and improving the product yield.
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Figure CN121843431A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor, in particular to a method for locally doping aluminum on the surface of a silicon substrate, a silicon substrate doped with aluminum and a PN junction. BACKGROUND
[0002] In the manufacturing process of gate-commutated thyristors, ordinary thyristors and other devices, local doping of aluminum impurities is sometimes required to form a complex PN junction. However, there are few ways to achieve local doping in the current aluminum doping process.
[0003] The existing technology has two directions. On the one hand, silicon dioxide is used as a masking film on the surface of the device. However, research has found that silicon dioxide cannot prevent aluminum impurities from penetrating during the aluminum doping process, and cannot effectively mask the effect.
[0004] On the other hand, wet etching is mainly used to remove part of the aluminum impurities on the surface of the device to form a complex PN junction. However, multiple etching can cause the device to warp, and there is a risk of uneven and insufficient etching.
[0005] Therefore, there is an urgent need for a method for locally doping aluminum in the existing technology to achieve selective doping of aluminum impurities during the aluminum doping process. SUMMARY
[0006] To solve the above problems in the prior art, the present application provides a method for locally doping aluminum on the surface of a silicon substrate, a silicon substrate doped with aluminum and a PN junction.
[0007] The present application deposits a masking film layer on the surface of a silicon substrate and etches the masking film layer to obtain a doping window, which can experimentally dope aluminum locally on the surface of a silicon substrate. However, when silicon nitride is used as a masking film, the uniformity of aluminum doping is poor during aluminum doping. The present application controls the temperature of the aluminum doping process to achieve uniform doping of aluminum in the doping area.
[0008] In a first aspect, the present application provides a method for locally doping aluminum on the surface of a silicon substrate, comprising the following steps:
[0009] (1) depositing a silicon nitride masking film layer on the surface of a silicon substrate;
[0010] (2) etching the silicon nitride masking film layer to obtain a silicon substrate with a doping window;
[0011] (3) placing metallic aluminum in a reaction tube, heating the reaction tube to a first temperature, vaporizing the metallic aluminum and diffusing it to the surface of the reaction tube, and then cooling the reaction tube; placing the silicon substrate with the doping window in the reaction tube, heating the reaction tube to a second temperature under vacuum conditions, and doping the aluminum on the surface of the reaction tube into the silicon substrate, and then cooling the reaction tube to obtain a silicon substrate doped with aluminum;
[0012] The second temperature is 950–1150℃;
[0013] (4) Remove the masking film layer on the surface of the aluminum-doped silicon substrate to obtain a partially aluminum-doped silicon substrate.
[0014] This invention uses silicon nitride as a masking film, which effectively prevents aluminum from penetrating during the aluminum doping process. Furthermore, by controlling the aluminum doping temperature, uniform aluminum doping in the silicon substrate can be ensured.
[0015] As a specific embodiment of the present invention, in step (3), the reaction tube is heated to a first temperature under vacuum conditions.
[0016] In a specific embodiment of the present invention, in step (3), the first temperature is 850-1150°C; preferably 900-1150°C.
[0017] The present invention maintains the reaction tube under vacuum conditions and heats the reaction tube, which can prevent the oxidation of metallic aluminum and avoid the gas from hindering the diffusion of aluminum.
[0018] As a specific embodiment of the present invention, in step (3), under vacuum conditions in the reaction tube, the holding time at the first temperature is 1000-2500 min.
[0019] As a specific embodiment of the present invention, in step (3), under vacuum conditions in the reaction tube, the holding time at the second temperature is 1 to 800 min.
[0020] The vacuum conditions of this invention refer to a vacuum degree greater than 1×10⁻⁶. -1 Pa (gauge pressure). Vacuum degree can be 1×10⁻⁶. -1 Pa ~ 1×10 -4 Pa. Specifically, the vacuum level is 1 × 10⁻⁶. -2 Pa.
[0021] The present invention can satisfy the diffusion of aluminum to the surface of the reaction tube under a limited holding time at a first temperature.
[0022] The present invention can ensure that aluminum is uniformly doped into the silicon substrate under a limited holding time at a second temperature.
[0023] In a specific embodiment of the present invention, in step (3), the reaction tube is heated to the first temperature at a heating rate of 2 to 8 °C / min.
[0024] In a specific embodiment of the present invention, in step (3), the reaction tube is heated to the second temperature at a heating rate of 2 to 8 °C / min.
[0025] In a specific embodiment of the present invention, in step (3), the reaction tube is cooled at a cooling rate of 0.5 to 3 °C / min.
[0026] In a specific embodiment of the present invention, the reaction tube can be a silicon tube. The reaction tube has a closable, cuboid or cylindrical structure with a cavity.
[0027] In a specific embodiment of the present invention, the thickness of the masking film is 50–200 nm. Preferably, the thickness of the masking film is 100–200 nm.
[0028] As a specific embodiment of the present invention, the deposition method of the masking film is chemical vapor deposition.
[0029] As a specific embodiment of the present invention, the purity of the metallic aluminum is 99.999% to 99.9999%.
[0030] In a specific embodiment of the present invention, in step (4), HF or H3PO4 is used for cleaning to remove the masking film layer on the surface of the aluminum-doped silicon substrate. Specifically, the silicon substrate containing the masking film can be placed in hydrofluoric acid and cleaned for 3 to 30 minutes to remove the masking film layer on the surface of the silicon substrate. The use of HF or H3PO4 to clean the masking film layer in the present invention will not cause side reactions.
[0031] In the process of aluminum doping, the present invention can perform local doping at different locations multiple times on the surface of a silicon substrate to achieve a diverse distribution of aluminum impurities on the surface of the silicon substrate.
[0032] In a second aspect, the present invention provides an aluminum-doped silicon substrate, which is prepared using the aluminum local doping method provided in the first aspect of the present invention.
[0033] In a specific embodiment of the present invention, the surface concentration of aluminum in the aluminum-doped silicon substrate is 7–120 mV, and the depth of aluminum doping is 2–200 μm.
[0034] Surface concentration refers to the concentration of surface carriers in a substrate. It is generally measured using a four-probe test stage and is usually expressed as a voltage value. The higher the voltage value, the lower the surface carrier concentration.
[0035] The depth of aluminum doping in the silicon substrate was measured using an extended resistance test bench.
[0036] Thirdly, the present invention provides a PN junction, the preparation method of which includes the aluminum local doping method provided in the first aspect of the present invention.
[0037] Specifically, an aluminum-doped silicon substrate is prepared using the aluminum local doping method of the first invention. However, because the aluminum doping is very shallow, the PN junction formed with the N-type silicon substrate does not have sufficient voltage withstand capability. Typically, it is necessary to allow aluminum impurities to thermally diffuse into the silicon substrate under prolonged high-temperature conditions to increase the PN junction depth and obtain a PN junction with a voltage withstand capability that meets the application requirements.
[0038] Compared with the prior art, the present invention has the following beneficial effects.
[0039] This invention achieves localized aluminum doping by depositing a silicon nitride masking film on the surface of a silicon substrate, followed by etching doping windows using photolithography. Aluminum can be doped at the windows, but not below the masking film. Furthermore, by controlling the temperature of the isothermal section during the aluminum doping process, the problem of uneven aluminum doping when silicon nitride is used as a masking film is solved.
[0040] The method for localized aluminum doping on the silicon substrate surface of this invention does not cause silicon substrate warping and can achieve uniform doping according to application requirements. This method can improve product yield. Attached Figure Description
[0041] Figure 1 This invention provides a method for localized aluminum doping on a silicon substrate surface and the preparation of a PN junction in one embodiment.
[0042] Figure 2 This is a box plot showing the relationship between the temperature and surface concentration number in the isothermal section of the aluminum doping process of this invention. Detailed Implementation
[0043] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.
[0044] Example 1
[0045] A silicon nitride layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. Doping windows were then etched into the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0046] Aluminum doping was performed on a silicon substrate with a doping window. 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 960℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated. The temperature was increased to 960℃ at a heating rate of 5℃ / min and held for 60min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min to complete the aluminum doping process, resulting in an aluminum-doped silicon substrate.
[0047] The aluminum-doped silicon substrate was removed, and the silicon nitride film on the surface of the silicon substrate was removed by HF cleaning to obtain an aluminum-doped silicon substrate.
[0048] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0049] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0050] The test results were as follows: the value at the center point was 98.14mV, and the values at the other five points were 100.62mV, 99.28mV, 96.78mV, 99.60mV, and 103.29mV, respectively.
[0051] In addition, when testing the surface concentration of aluminum in the masking region of the silicon substrate, the probe could not detect the surface concentration of aluminum in the masking region, indicating that there is no aluminum doping under the masking film.
[0052] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 3.11 μm using a spread resistance test stage (SRP).
[0053] Example 2:
[0054] A silicon nitride layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. Doping windows were then etched into the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0055] Aluminum doping was performed on a silicon substrate with a doping window. 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 1050℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated. The temperature was increased to 1050℃ at a heating rate of 5℃ / min and held for 60min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min to complete the aluminum doping process, resulting in an aluminum-doped silicon substrate.
[0056] The aluminum-doped silicon substrate was removed, and the silicon nitride film on the surface of the silicon substrate was removed by HF cleaning to obtain an aluminum-doped silicon substrate.
[0057] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0058] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0059] The test results were as follows: the value at the center point was 51.37mV, and the values at the other five points were 51.92mV, 48.89mV, 51.41mV, 50.90mV, and 48.65mV, respectively.
[0060] In addition, when testing the surface concentration of aluminum in the masking region of the silicon substrate, the probe could not detect the surface concentration of aluminum in the masking region, indicating that there is no aluminum doping under the masking film.
[0061] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 3.92 μm using a spread resistance test stage (SRP).
[0062] Example 3:
[0063] A silicon nitride layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. Doping windows were then etched into the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0064] Aluminum doping was performed on a silicon substrate with a doping window. 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 1140℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated. The temperature was increased to 1140℃ at a heating rate of 5℃ / min and held for 60min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min to complete the aluminum doping process, resulting in an aluminum-doped silicon substrate.
[0065] The aluminum-doped silicon substrate was removed, and the silicon nitride film on the surface of the silicon substrate was removed by HF cleaning to obtain an aluminum-doped silicon substrate.
[0066] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0067] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0068] The test results were as follows: the center point was 8.05mV, and the other five points were 8.06mV, 8.04mV, 8.02mV, 8.07mV, and 8.08mV, respectively.
[0069] In addition, when testing the surface concentration of aluminum in the masking region of the silicon substrate, the probe could not detect the surface concentration of aluminum in the masking region, indicating that there is no aluminum doping under the masking film.
[0070] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 8.96 μm using a spread resistance test stage (SRP).
[0071] Example 4:
[0072] A silicon nitride layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. Doping windows were then etched into the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0073] Aluminum doping was performed on a silicon substrate with a doping window. 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 960℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated. The temperature was increased to 960℃ at a heating rate of 5℃ / min and held for 160min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min to complete the aluminum doping process, resulting in an aluminum-doped silicon substrate.
[0074] The aluminum-doped silicon substrate was removed, and the silicon nitride film on the surface of the silicon substrate was removed by HF cleaning to obtain an aluminum-doped silicon substrate.
[0075] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0076] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0077] The test results were as follows: the value at the center point was 61.84mV, and the values at the other five points were 60.83mV, 62.02mV, 60.55mV, 61.09mV, and 62.25mV, respectively.
[0078] In addition, when testing the surface concentration of aluminum in the masking region of the silicon substrate, the probe could not detect the surface concentration of aluminum in the masking region, indicating that there is no aluminum doping under the masking film.
[0079] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 3.88 μm using a spread resistance test stage (SRP).
[0080] Example 5:
[0081] A silicon nitride layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. Doping windows were then etched into the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0082] Aluminum doping was performed on a silicon substrate with a doping window. 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 960℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated. The temperature was increased to 960℃ at a heating rate of 5℃ / min and held for 700min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min to complete the aluminum doping process, resulting in an aluminum-doped silicon substrate.
[0083] The aluminum-doped silicon substrate was removed, and the silicon nitride film on the surface of the silicon substrate was removed by HF cleaning to obtain an aluminum-doped silicon substrate.
[0084] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0085] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0086] The test results were as follows: 26.88mV at point 1 of the midline, and 26.41mV, 26.84mV, 26.57mV, 26.01mV, and 26.4mV at the other 5 points, respectively.
[0087] In addition, when testing the surface concentration of aluminum in the masking region of the silicon substrate, the probe could not detect the surface concentration of aluminum in the masking region, indicating that there is no aluminum doping under the masking film.
[0088] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 6.99 μm using an extended resistance test stage (SRP).
[0089] Comparative Example 1:
[0090] A silicon nitride layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. Doping windows were then etched into the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0091] Aluminum doping was performed on a silicon substrate with a doping window. 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 900℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated. The temperature was increased to 900℃ at a heating rate of 5℃ / min and held for 60min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min to complete the aluminum doping process, resulting in an aluminum-doped silicon substrate.
[0092] The aluminum-doped silicon substrate was removed, and the silicon nitride film on the surface of the silicon substrate was removed by HF cleaning to obtain an aluminum-doped silicon substrate.
[0093] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0094] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0095] The test results showed that the voltage at point 1 of the midline was 169.7mV, and the voltages at the other 5 points were 158.2mV, 152.5mV, 141.1mV, 142.3mV, and 129.1mV, respectively.
[0096] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 3.02 μm using an extended resistance test stage (SRP).
[0097] Comparative Example 2:
[0098] To dope a silicon substrate with aluminum, 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 900℃ at a heating rate of 5℃ / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min. At room temperature, a silicon substrate with a diameter of 75mm was placed in the silicon tube. After evacuating the furnace, the temperature was increased to 900℃ at a heating rate of 5℃ / min and held for 60min. The temperature was then decreased to room temperature at a cooling rate of 1℃ / min, thus completing the aluminum doping process and obtaining an aluminum-doped silicon substrate.
[0099] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0100] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0101] The test results showed that the voltage at point 1 of the midline was 60.92mV, and the voltages at the other 5 points were 61.58mV, 62.90mV, 65.12mV, 63.32mV, and 64.25mV, respectively.
[0102] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 3.81 μm using a spread resistance test stage (SRP).
[0103] Comparative Example 3:
[0104] A silicon dioxide layer with a thickness of 150 nm was deposited on the surface of a circular silicon substrate with a diameter of 75 mm using chemical vapor deposition. The doped windows were then etched on the silicon nitride layer using photolithography. The substrate was then cleaned using RCA cleaning technology to obtain a silicon substrate with doped windows.
[0105] To dope a silicon substrate with aluminum, 0.1g of metallic aluminum was placed in a silicon tube, which was then placed in a vacuum furnace. After evacuating the furnace, the temperature was increased to 960°C at a heating rate of 5°C / min and held for 1500min. The temperature was then decreased to room temperature at a cooling rate of 1°C / min. At room temperature, the silicon substrate with the doping window was placed into the silicon tube, and the vacuum furnace was evacuated again. The temperature was increased to 960°C at a heating rate of 5°C / min and held for 60min. The temperature was then decreased to room temperature at a cooling rate of 1°C / min, thus completing the aluminum doping process and obtaining the aluminum-doped silicon substrate.
[0106] The surface concentration of aluminum in an aluminum-doped silicon substrate was determined using a four-probe method.
[0107] Six points were tested on the aluminum-doped silicon substrate. One point was measured at the center, and five points were measured on the circular silicon substrate with 10 mm of edge removed. The angle between each point was 72°.
[0108] The test results showed that the value at the center point was 37.21mV, and the values at the other five points were 36.17mV, 35.31mV, 36.56mV, 35.59mV, and 35.10mV, respectively.
[0109] In addition, the surface concentration of aluminum in the masking area of the silicon substrate was tested. The circular silicon substrate was trimmed by 15 mm, and 5 points were measured, with each point spaced at an angle of 72°.
[0110] The test results for the five points were 38.51mV, 37.27mV, 37.62mV, 39.09mV, and 37.81mV, respectively.
[0111] The doping depth of aluminum in an aluminum-doped silicon substrate was measured to be 6.87 μm using a spread resistance test stage (SRP).
[0112] Figure 2Box plots showing the relationship between temperature and surface concentration in the isothermal section of aluminum doping in Embodiment 1 and Comparative Example 1 of this invention. Figure 2 The narrower the square block along the Y-axis, the better the uniformity of aluminum doping. Figure 2 It can be seen that in Example 1, the constant temperature of 960℃ was used during the aluminum doping process, resulting in better uniformity of aluminum doping on the silicon substrate surface.
[0113] Comparing Examples 1-5 of the present invention with Comparative Example 1, it can be found that the present invention can solve the problem of poor uniformity of aluminum doping when silicon nitride is used as a masking film by increasing the process temperature of the aluminum doping process.
[0114] Compared with Comparative Example 2, Examples 1-5 show that the present invention can achieve localized doping of aluminum doping process, and the uniformity can also be similar when the surface concentration level is similar.
[0115] Compared with Comparative Example 3, under the same conditions, in Examples 1-5, silicon nitride as a masking film layer can effectively prevent aluminum doping compared with silicon dioxide as a masking film.
[0116] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.
Claims
1. A method of local doping of aluminum on a surface of a silicon substrate, characterized in that, The method comprises the following steps: (1) depositing a silicon nitride mask layer on the surface of a silicon substrate; (2) etching the silicon nitride mask layer to obtain a silicon substrate with a doped window; (3) placing aluminum in a reaction tube, heating the reaction tube to a first temperature, vaporizing the aluminum and diffusing the aluminum to the surface of the reaction tube, and then cooling the reaction tube; placing the silicon substrate with the doped window in the reaction tube, heating the reaction tube to a second temperature under vacuum, and then cooling the reaction tube, so as to obtain an aluminum-doped silicon substrate; the second temperature is 950-1150℃; (4) removing the mask layer on the surface of the aluminum-doped silicon substrate to obtain a locally aluminum-doped silicon substrate.
2. The aluminum local doping method of claim 1, wherein, In step (3), the reaction tube is heated to the first temperature under vacuum; and / or, in step (3), the first temperature is 850-1150℃; and / or, in step (3), the holding time of the first temperature is 1000-2500 min under vacuum; and / or, in step (3), the holding time of the second temperature is 1-800 min under vacuum.
3. The aluminum local doping method according to claim 1 or 2, wherein In step (3), the reaction tube is heated to the first temperature at a heating rate of 2-8℃ / min; and / or, in step (3), the reaction tube is heated to the second temperature at a heating rate of 2-8℃ / min; and / or, in step (3), the reaction tube is cooled at a cooling rate of 0.5-3℃ / min.
4. The aluminum local doping method according to claim 1 or 2, wherein The thickness of the mask layer is 50-200 nm.
5. The method of claim 4, wherein the aluminum partial doping is performed by a method comprising: The deposition method of the mask layer is chemical vapor deposition.
6. The method of claim 4, wherein the aluminum partial doping is performed by a method comprising: The purity of the aluminum is 99.999%-99.9999%.
7. The method of claim 6, wherein the aluminum partial doping is performed by a method comprising: In step (4), HF or H3PO4 is used for cleaning to remove the mask layer on the surface of the aluminum-doped silicon substrate.
8. An aluminum-doped silicon substrate, characterized by, The aluminum-doped silicon substrate is prepared by the method of any one of claims 1-7.
9. The silicon substrate of claim 8, wherein, The surface concentration of aluminum in the aluminum-doped silicon substrate is 7-120 mV, and the doping depth of aluminum is 2-200 μm.
10. A PN junction, characterized by The method for preparing the PN junction comprises the method of any one of claims 1-8.