Processing method before mercury C-V test of N-type silicon epitaxial wafer
By treating N-type silicon epitaxial wafers with hydrofluoric acid, alkaline and acidic cleaning solutions, combined with drying and oxide layer growth, the problem of unstable measurement results in wet chemical processes was solved, achieving highly stable and accurate mercury CV testing.
Patent Information
- Application Number
- CN202511512666.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-02-03
AI Technical Summary
Traditional wet chemical processes are difficult to control effectively in the pretreatment of N-type silicon epitaxial wafers for mercury CV testing. This results in residual water stains on the surface, affecting the accuracy and repeatability of the measurement results, leading to excessively low phase angles and large fluctuations in the measurement results.
The surface of the N-type silicon epitaxial wafer was cleaned using hydrofluoric acid, alkaline cleaning solution and acidic cleaning solution, and a stable oxide layer was formed by drying and oxide layer growth treatment, including infrared drying and ion wind purging.
It significantly improves the stability and accuracy of mercury CV testing on N-type silicon epitaxial wafers, with single-point repeatability testing stability improved by more than 10 times, avoiding the problems of measurement result fluctuation and poor repeatability.
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Figure CN121463786A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of N-type silicon epitaxial wafer, in particular to a processing method for N-type silicon epitaxial wafer before mercury C-V test. BACKGROUND
[0002] Semiconductor silicon has been used as a basic material for modern electronic industry for a long time, and epitaxial technology is widely used in semiconductor discrete devices and integrated circuits. The resistivity and uniformity of the epitaxial layer directly affect the electrical performance and yield of the device.
[0003] Currently, the common method for detecting the resistivity of the epitaxial layer is mercury C-V method, the principle of which is: a Schottky junction is formed by the contact between metal and the surface of the silicon epitaxial wafer, and the resistivity of the silicon epitaxial wafer is calculated by measuring the Schottky barrier capacitance under the action of high-frequency electric field. It should be noted that in order to obtain a good Schottky barrier, the sample to be tested needs to be pretreated to ensure that its surface morphology meets the test requirements.
[0004] In actual production, N-type silicon epitaxial products account for more than 95% of the total amount of silicon epitaxial products, and the surface pretreatment process of the sample has a significant impact on the accuracy, stability and repeatability of the mercury C-V test resistivity value. Therefore, the pretreatment process of N-type silicon epitaxial wafer before mercury C-V test has become one of the current research hotspots in the industry.
[0005] Currently, the mainstream processing method for N-type epitaxial wafer in the industry is wet chemical process, the specific process of which is as follows: after the epitaxial product is processed, the natural oxide layer on the surface of the sample is removed by HF, and then the sample is cleaned by deionized high-purity water, and then immersed in a strong oxidizing chemical solution, usually chromium acid or high-temperature hydrogen peroxide, to form a thin oxide layer on the surface of the sample; then the sample is washed with high-purity water and dried with a rinsing and drying machine, and finally subjected to mercury C-V test.
[0006] However, the traditional wet chemical process has obvious shortcomings: on the one hand, the strong oxidizing chemical reagent used is difficult to effectively control in terms of purity and concentration; on the other hand, water stains are easily left on the surface of the sample after the process. These problems often lead to the situation that the phase angle of the N-type silicon epitaxial wafer is too low during mercury C-V test, resulting in large fluctuations in the measurement results and poor repeatability, which not only makes the resistivity test results lose reference value, but also may cause defective products to flow into the next process or customer end, causing cost waste. SUMMARY
[0007] In order to solve the problems of the prior art, the present application provides a processing method for N-type silicon epitaxial wafer before mercury C-V test, which avoids the situation that the phase angle of the N-type silicon epitaxial wafer is too low during mercury C-V test, resulting in large fluctuations in the measurement results and poor repeatability.
[0008] The application adopts the technical scheme that a kind of N-type silicon epitaxial wafer mercury C-V test before processing method, comprising the following steps: S1, take hydrofluoric acid solution to the N-type silicon epitaxial wafer for surface cleaning after epitaxial growth, and wash the N-type silicon epitaxial wafer surface residual hydrofluoric acid with clean water; S2, take alkaline cleaning solution to the N-type silicon epitaxial wafer for surface cleaning, and wash the N-type silicon epitaxial wafer surface residual alkaline cleaning solution with clean water; Wherein, the alkaline cleaning solution is mixed by ammonia, hydrogen peroxide and water; S3, take acid cleaning solution to the N-type silicon epitaxial wafer for surface cleaning, and wash the N-type silicon epitaxial wafer surface residual acid cleaning solution with clean water; Wherein, the acid cleaning solution is mixed by hydrochloric acid, hydrogen peroxide and water; S4, dry processing to the N-type silicon epitaxial wafer; S5, the N-type silicon epitaxial wafer after dry processing is transferred to dry Pre-CV processing area, and the N-type silicon epitaxial wafer surface is grown oxide layer.
[0009] As a further optimization of the application, the flushing time of clean water in S1, S2 and S3 is less than or equal to 10s.
[0010] As a further optimization of the application, the volume ratio of ammonia, hydrogen peroxide and water is 1:2-5:30.
[0011] As a further optimization of the application, the temperature of the alkaline cleaning solution is 60-70℃.
[0012] As a further optimization of the application, the volume ratio of hydrochloric acid, hydrogen peroxide and water is 1:0.5-2:30.
[0013] As a further optimization of the application, the method of S4 comprises: dehydration treatment is carried out on the N-type silicon epitaxial wafer obtained in S3; infrared drying is carried out on the dehydrated N-type silicon epitaxial wafer.
[0014] As a further optimization of the application, the drying time of the infrared drying is 50-100s, and the drying temperature is 60-70℃.
[0015] As a further optimization of the application of a kind to be treated before N-type silicon epitaxial wafer mercury C-V test method: the method of S5 includes: using vacuum suction pen to place infrared dried N-type silicon epitaxial wafer on quartz boat, and the quartz boat and N-type silicon epitaxial wafer are transferred to dry Pre-CV processing cavity; The dry Pre-CV processing cavity is vacuumized; Oxygen is introduced into the dry Pre-CV processing cavity in a vacuum environment and ionized, so that an oxide layer is generated on the surface of the N-type silicon epitaxial wafer; The N-type silicon epitaxial wafer after generating the oxide layer is ion wind swept.
[0016] As a further optimization of the application of a kind to be treated before N-type silicon epitaxial wafer mercury C-V test method: the N-type silicon epitaxial wafer after generating the oxide layer is ion wind swept by using ion wind machine, and the sweeping time is 10-30 min.
[0017] As a further optimization of the application of a kind to be treated before N-type silicon epitaxial wafer mercury C-V test method: the vacuum degree of the dry Pre-CV processing cavity is less than 50mtorr.
[0018] Compared with the prior art, the beneficial effects of the present application are:
[0019] The present application can avoid the situation that the phase angle of the N-type silicon epitaxial wafer is too low during mercury C-V test, resulting in large fluctuation of measurement results and poor repeatability. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 The process flow chart of the present application is shown in the figure; Figure 2 The data graph of the same wafer different point phase angle test of the N-type silicon epitaxial wafer treated by the conventional wet C-V pretreatment process is shown in the figure; Figure 3 The data graph of the same wafer different point phase angle test of the N-type silicon epitaxial wafer treated by the present application is shown in the figure. DETAILED DESCRIPTION
[0021] The technical solutions of the present application will be further described in detail below in combination with specific embodiments. The parts not described and disclosed in detail in each embodiment of the present application should be understood as the prior art known or should be known by those skilled in the art.
[0022] As Figure 1As shown, a processing method of N-type silicon epitaxial wafer before mercury C-V test includes steps S1-S5.
[0023] S1, take hydrofluoric acid solution to clean the surface of N-type silicon epitaxial wafer after epitaxial growth, and use clean water to flush the residual hydrofluoric acid on the surface of N-type silicon epitaxial wafer.
[0024] This step uses HF tank to clean the surface of N-type silicon epitaxial wafer after epitaxial growth. The function of HF tank is to remove the natural oxide layer on the surface of N-type silicon epitaxial wafer, so as to avoid the influence of uneven natural oxide layer on the original surface of the sample on the test result. The temperature of hydrofluoric acid solution in the HF tank is normal temperature, the HF tank has solution circulation function, the circulation amount is 7-17 L / min, and the volume ratio of hydrofluoric acid to water is 1:5-20. The HF tank is mainly composed of containing tank, circulation system and bearing mechanism, etc. The HF tank is a conventional prior art in the field, and will not be described in detail here. This step uses QDR tank to flush the residual hydrofluoric acid on the surface of N-type silicon epitaxial wafer, and the flushing time is ≤10 s. The QDR tank is mainly composed of spraying area, overflow area, flow equalizing plate, quick exhaust cylinder, nozzle and pipeline, etc. The QDR tank is a conventional prior art in the field, and will not be described in detail here.
[0025] S2, take alkaline cleaning solution to clean the surface of N-type silicon epitaxial wafer, and use clean water to flush the residual alkaline cleaning solution on the surface of N-type silicon epitaxial wafer. The alkaline cleaning solution is mixed by ammonia, hydrogen peroxide and water. The volume ratio of ammonia, hydrogen peroxide and water is 1:2-5:30. This step uses alkaline cleaning solution in SC-1 tank to clean N-type silicon epitaxial wafer for the first time, removes particles and contamination on the surface of N-type silicon epitaxial wafer, and the cleaning time is ≤10 s. This step can oxidize organic residues on the surface of the wafer to form carbon dioxide, water, etc., so as to avoid the influence of organic residues on the surface of the sample on the mercury C-V test result in the later period; at the same time, a small amount of ammonia can form a complex with the metal on the surface of the sample, such as Au, Ag, Cu, Ni, Zn, Cr, etc., such as Cu(NH3)4 2+ , in order to prepare for the removal of metal ions in the next step; the temperature of the alkaline cleaning solution is 60-70℃. The SC-1 tank is a conventional prior art in the field, and its specific structure will not be described in detail here. The bottom of the SC-1 tank is configured with megasonic with power greater than or equal to 300W, and the tank body has solution circulation function with circulation amount of 7-17 L / min. This step uses QDR tank to flush the residual alkaline cleaning solution on the surface of N-type silicon epitaxial wafer.
[0026] S3, the N-type silicon wafer is cleaned with an acidic cleaning solution, and the N-type silicon wafer is rinsed with clean water to remove the residual acidic cleaning solution on the surface of the N-type silicon wafer. The acidic cleaning solution is prepared by mixing hydrochloric acid, hydrogen peroxide and water. The volume ratio of hydrochloric acid, hydrogen peroxide and water is 1:0.5-2:30. The temperature of the acidic cleaning solution is room temperature. The N-type silicon wafer is cleaned for the second time with the acidic cleaning solution in the SC-2 tank, and the alkali ions on the surface of the N-type silicon wafer and the insoluble hydroxide cations formed in the above-mentioned alkaline cleaning solution are removed. This step is used to remove the alkali ions and Al 3+ , Fe 3+ , Mg 2+ , etc. After the treatment in step S2, these alkali ions and metal ions form insoluble hydroxide cation precipitates on the wafer surface. After soaking in the solution in step S3, soluble complexes are formed, thereby removing the residual metal ions on the wafer surface and avoiding the influence of metal residues on the mercury C-V test results. The SC-2 tank is a conventional prior art in the field, and its specific structure will not be described in detail here. The tank body of the SC-2 tank has a solution circulation function, and the circulation amount is 7-17 L / min. This step uses the QDR tank to rinse the residual acidic cleaning solution on the surface of the N-type silicon wafer, and the rinsing time is ≤10 s.
[0027] S4, the N-type silicon wafer is dried. This step uses a slow pull level IR drying tank to dry the N-type silicon wafer. The slow pull level IR drying tank is a conventional prior art in the field, and its specific structure will not be described in detail here.
[0028] The method of S4 specifically includes steps S41 and S42.
[0029] S41, the N-type silicon wafer obtained in S3 is subjected to dehydration treatment; S42, the dehydrated N-type silicon wafer is subjected to infrared drying.
[0030] First, the N-type silicon wafer obtained in S3 is subjected to dehydration treatment in the slow pull level IR drying tank. The mechanical arm of the slow pull level IR drying tank lifts the N-type silicon wafer and separates it from the water surface in the slow pull level IR drying tank. The lifting speed of the mechanical arm is 0.5-1.0 mm / s, and the water temperature in the slow pull level IR drying tank is 30-35℃. The slow pull level IR drying tank uses the surface tension of water to separate the water on the surface of the N-type silicon wafer. Then the dehydrated N-type silicon wafer is subjected to infrared drying in the slow pull level IR drying tank. The drying time of infrared drying is 50-100 s, and the drying temperature is 60-70℃. The slow pull level IR drying tank does not need to add additional chemical reagents, which is safe and environmentally friendly. It avoids water marks and ensures the cleanliness of the surface of the N-type silicon wafer. This step prepares for the next step and avoids the influence of water marks on the surface of the silicon wafer on the mercury C-V test in the later period.
[0031] S5, transferring the N-type silicon epitaxial wafer after drying treatment to a dry Pre-CV processing area, and growing an oxide layer on the surface of the N-type silicon epitaxial wafer. The method of S5 includes steps S51 to S54.
[0032] S51, placing the N-type silicon epitaxial wafer after infrared drying on a quartz boat by using a vacuum suction pen, and transferring the quartz boat and the N-type silicon epitaxial wafer to a dry Pre-CV processing cavity. Up to 3 N-type silicon epitaxial wafers can be placed on the quartz boat, and a distance exists between each N-type silicon epitaxial wafer.
[0033] S52, vacuumizing the dry Pre-CV processing cavity; the vacuum degree of the dry Pre-CV processing cavity is less than 50mtorr, and the air leakage rate is less than 50mTorr / min.
[0034] S53, introducing oxygen into the dry Pre-CV processing cavity in a vacuum environment and ionizing to generate an oxide layer on the surface of the N-type silicon epitaxial wafer; the specific process and parameters are as shown in Table 1.
[0035] Table 1 Process parameter table Step sequence Process time Gas / flow rate (sccm) Chamber pressure (torr) RF power (W) 1 30-60S O2: 180-200 0.9 0 2 350-450S O2: 180-200 0.9 800 3 80-120S O2: 180-200 0.485 800 4 20-40S O2: 180-200 0.485 0 5 50-80S N2:400-600 0 0
[0036] S54, after the oxide layer is generated on the surface of the N-type silicon epitaxial wafer, the quartz boat is taken out by using a special quartz boat holding fork tool, and the N-type silicon epitaxial wafer after generating the oxide layer is ion wind swept. The N-type silicon epitaxial wafer after generating the oxide layer is ion wind swept by using an ion wind machine, and the sweeping time is 10-30min. The ion wind machine is used for sweeping, which can neutralize static electricity, avoid secondary adsorption of static electricity by air flow, and achieve more thorough cleaning effect. The N-type silicon epitaxial wafer after sweeping is placed in a special transfer wafer box by using a vacuum suction pen, and is transferred to a mercury C-V test post for epitaxial layer resistivity test.
[0037] Compared with the conventional wet C-V pretreatment process, the processing method provided by the present application can significantly improve the pretreatment effect of N-type silicon epitaxial wafer mercury C-V test. The stability and accuracy of the N-type silicon epitaxial wafer treated by the processing method in mercury C-V test are greatly improved. After the same N-type silicon epitaxial wafer is treated by the new method, the stability of single point repeated test is improved by more than 10 times compared with the wet process. The comparison data of different sample single point repeated 10 times measurement are shown in Table 2; the data of the same sample different point phase angle test of the N-type silicon epitaxial wafer treated by the conventional wet C-V pretreatment process are shown in Table 3; and the data of the same sample different point phase angle test of the N-type silicon epitaxial wafer treated by the present application are shown in Table 4. Figure 2 Figure 3
[0038] Table 2 Comparison data of different sample single point repeated 10 times measurement
[0039] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for pretreatment of N-type silicon epitaxial wafers before mercury CV testing, characterized in that, Includes the following steps: S1. Take hydrofluoric acid solution to clean the surface of the N-type silicon epitaxial wafer after epitaxial growth, and rinse the surface of the N-type silicon epitaxial wafer with water to remove residual hydrofluoric acid. S2. Use alkaline cleaning solution to clean the surface of the N-type silicon epitaxial wafer, and rinse the surface of the N-type silicon epitaxial wafer with clean water to remove any residual alkaline cleaning solution. The alkaline cleaning solution is composed of ammonia, hydrogen peroxide, and water. S3. Use acidic cleaning solution to clean the surface of the N-type silicon epitaxial wafer, and rinse the surface of the N-type silicon epitaxial wafer with clean water to remove any residual acidic cleaning solution. The acidic cleaning solution is composed of hydrochloric acid, hydrogen peroxide, and water. S4. Dry the N-type silicon epitaxial wafer; S5. The dried N-type silicon epitaxial wafer is transferred to the dry Pre-CV processing area, and an oxide layer is grown on the surface of the N-type silicon epitaxial wafer.
2. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 1, characterized in that, The rinsing time with clean water in S1, S2 and S3 is less than or equal to 10 seconds.
3. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 1, characterized in that, The volume ratio of ammonia, hydrogen peroxide, and water is 1:2 to 5:
30.
4. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 1, characterized in that, The temperature of the alkaline cleaning solution is 60–70°C.
5. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 1, characterized in that, The volume ratio of hydrochloric acid, hydrogen peroxide, and water is 1:0.5 to 2:
30.
6. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 1, characterized in that, S4's methods include: The N-type silicon epitaxial wafer obtained in S3 was subjected to dehydration treatment; The dehydrated N-type silicon epitaxial wafer is then subjected to infrared drying.
7. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 6, characterized in that, The infrared drying process involves a drying time of 50–100 seconds and a drying temperature of 60–70°C.
8. The pretreatment method for mercury CV testing of N-type silicon epitaxial wafers as described in claim 1, characterized in that, S5 methods include: The infrared-dried N-type silicon epitaxial wafer was placed on a quartz boat using a vacuum suction pen, and the quartz boat and the N-type silicon epitaxial wafer were transferred into a dry Pre-CV processing chamber. The dry Pre-CV processing chamber is evacuated; Oxygen is introduced into the dry Pre-CV processing chamber in a vacuum environment and ionized, resulting in the formation of an oxide layer on the surface of the N-type silicon epitaxial wafer. The N-type silicon epitaxial wafer after the oxide layer is formed is ionized and purged.
9. The pretreatment method for mercury CV testing of an N-type silicon epitaxial wafer as described in claim 8, characterized in that, The N-type silicon epitaxial wafer after the oxide layer is formed is purged with ion air using an ion blower for 10 to 30 minutes.
10. The pretreatment method for mercury CV testing of an N-type silicon epitaxial wafer as described in claim 8, characterized in that, The vacuum level of the dry Pre-CV processing chamber is less than 50 mtorr.