Method for detecting silicon single crystal OISF-ring

Abstract

According to the method for detecting the OISF-ring of the silicon single crystal, firstly, the surface of a silicon wafer to be detected is evenly coated with an oxidation induced dislocation nucleating agent to obtain a first silicon wafer, the oxidation induced dislocation nucleating agent is an acid radical solution containing transition metal ions, secondly, the first silicon wafer is placed in a high-temperature environment at the preset temperature to be subjected to heat treatment for the preset time, and then the first silicon wafer is subjected to heat treatment for the preset time to obtain the OISF-ring of the silicon single crystal. The method comprises the following steps: cleaning a silicon wafer to be detected to obtain a second silicon wafer, carrying out mixed acid cleaning on the second silicon wafer to obtain a third silicon wafer, removing a surface oxide film of the silicon wafer to be detected, putting the third silicon wafer into an oxidation induced fault exposing agent for preferential corrosion to obtain a detected silicon wafer, and finally conveying the detected silicon wafer to a spotlight in a darkroom. In the heat treatment process, transition metal ions serve as nucleation centers of oxidation induced faults, the heat treatment time is shortened, the oxidation induced faults can wrap the transition metal ions to form nucleation and grow, the OISF-ring of the silicon wafer cannot be covered even if mechanical damage exists on the surface of the silicon wafer to be detected, and the detection accuracy of the OISF-ring on the surface of the silicon wafer to be detected is improved. And the detection result is clearer.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon wafer quality detection, and in particular to a method for detecting silicon single crystal OIS F-ring. Background Art

[0002] Oxidation-induced stacking faults (OISF) are important evaluation parameters in silicon single crystals. OISFs are usually distributed in a ring shape, called OISF-ring. The presence of OISFs will increase the reverse current and affect device performance, so the detection of OISF-ring must be strictly controlled to prevent defective products from flowing into customers.

[0003] The existing method for detecting OIS F-ring defects in silicon wafers is to place the cut silicon wafer to be tested in a wet oxygen atmosphere at 1000-1200°C for heat treatment for 60-120 minutes to nucleate and grow the oxidation-induced stacking fault defects of the silicon wafer to be tested, and then expose the defects through preferential etching. However, since the surface state of the cut silicon wafer to be tested is poor and there is mechanical damage, the mechanical damage will cover the OIS F-ring on the surface of the silicon wafer, resulting in unclear OIS F-ring detection results on the surface of the silicon wafer, affecting the judgment of the inspectors. Summary of the invention

[0004] In view of this, in order to address the above shortcomings, it is necessary to propose a method for detecting the OIS F-ring of silicon single crystals to solve the technical problem that mechanical damage on the surface of the silicon wafer will cover the OIS F-ring defects of the silicon wafer, resulting in unclear detection results and thus affecting the judgment.

[0005] A method for detecting silicon single crystal OIS F-ring, comprising the following steps: Step 1: evenly apply an oxidation-induced stacking fault nucleating agent on the surface of a silicon wafer to be tested to obtain a first silicon wafer; The oxidation-induced stacking fault nucleating agent is an acid radical solution containing transition metal ions; Step 2: placing the first silicon wafer in a high temperature environment at a predetermined temperature for a predetermined time to obtain a second silicon wafer, wherein the transition metal ions serve as nucleation centers of oxidation-induced stacking faults, and the oxidation-induced stacking faults wrap the transition metal ions to nucleate and grow, so that the mechanical damage on the surface of the second silicon wafer will not cover the OISF-ring of the silicon wafer; Step 3: Clean the second silicon wafer with mixed acid to obtain a third silicon wafer, and remove the surface oxide film of the silicon wafer to be tested; Step 4: placing the third silicon wafer in an oxidation-induced stacking fault revealing agent for preferential etching to obtain a test silicon wafer; Step 5: Place the test silicon wafer under a spotlight in a dark room, turn on the spotlight and observe the OISF-ring on the surface of the test silicon wafer.

[0006] Preferably, in step 1, the transition metal ion is a chromium ion, a manganese ion, an iron ion, a cobalt ion, a nickel ion, a copper ion, a zinc ion, a palladium ion, a silver ion, a platinum ion, or a gold ion.

[0007] Preferably, in step 1, the transition metal ions are copper ions, and the oxidation-induced stacking fault nucleating agent is an acid copper solution.

[0008] Preferably, the concentration of copper ions in the oxidation-induced stacking fault nucleating agent is 700-1000 ppma.

[0009] Preferably, in step 2, the predetermined temperature is 600-900° C., and the predetermined time is 5-10 min.

[0010] Preferably, in step 3, the mixed acid solution consists of hydrofluoric acid, nitric acid, acetic acid and water, and the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water in the mixed acid solution is (1-2):(3-4):(1-2):(3-4).

[0011] Preferably, in step 3, after the temperature of the second silicon wafer drops to room temperature, it is cleaned with the mixed acid solution for 1-5 minutes.

[0012] Preferably, in step 4, the oxidation-induced stacking fault revealing agent is composed of chromic acid solution, nitric acid, acetic acid and hydrofluoric acid, wherein the volume ratio of chromic acid solution, nitric acid, acetic acid and hydrofluoric acid is 1:1:(1-3):(2-4).

[0013] Preferably, in step 4, the oxidation-induced stacking fault revealing agent is composed of chromic acid solution, copper acid solution, nitric acid, acetic acid and hydrofluoric acid, wherein the volume ratio of chromic acid solution, copper acid solution, nitric acid, acetic acid and hydrofluoric acid is 1:(1-3):1:(1-3):(2-4).

[0014] Preferably, in step 4, the oxidation-induced stacking fault revealing agent is prepared by mixing a chromic acid solution and a hydrofluoric acid solution, wherein the volume ratio of the chromic acid solution to the hydrofluoric acid solution is 1:(1-3).

[0015] It can be seen from the above technical scheme that the method for detecting OISF-ring of silicon single crystal provided by the present invention is that before heat treatment, an oxidation-induced stacking fault nucleating agent is first evenly applied on the surface of the silicon wafer to be detected to obtain a first silicon wafer. The oxidation-induced stacking fault nucleating agent is an acid radical solution containing transition metal ions. During the heat treatment process, the transition metal ions serve as nucleation centers of oxidation-induced stacking faults, promoting the formation of oxidation-induced stacking faults. On the one hand, the heat treatment time is greatly shortened. On the other hand, the oxidation-induced stacking faults will wrap the transition metal ions to nucleate and grow. Even if there is mechanical damage on the surface of the silicon wafer to be detected, it will not cover the OISF-ring of the silicon wafer, making the detection result clearer. The detection personnel can accurately judge that the mixed acid cleaning after the heat treatment is to remove the oxide film on the surface of the silicon wafer to prevent the influence of the oxide film on preferential corrosion, so that the oxidation-induced stacking fault revealing agent can etch the OISF-ring more effectively to highlight the OISF-ring on the surface of the silicon wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a method for detecting OIS F-ring of a silicon single crystal provided in an embodiment of the present invention.

[0017] Figure 2 This is a diagram of the test results of an embodiment of the method of the present invention.

[0018] Figure 3 This is a comparative test result diagram of the traditional method. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Please see Figure 1 , a method for detecting silicon single crystal OIS F-ring, comprising the following steps: Step 1: evenly apply an oxidation-induced stacking fault nucleating agent on the surface of a silicon wafer to be tested to obtain a first silicon wafer; The oxidation-induced stacking fault nucleating agent is an acid radical solution containing transition metal ions; Step 2: placing the first silicon wafer in a high temperature environment at a predetermined temperature for a predetermined time to obtain a second silicon wafer, wherein the transition metal ions serve as nucleation centers of oxidation-induced stacking faults, and the oxidation-induced stacking faults wrap the transition metal ions to nucleate and grow, so that the mechanical damage on the surface of the second silicon wafer will not cover the OISF-ring of the silicon wafer; Step 3: Clean the second silicon wafer with mixed acid to obtain a third silicon wafer, and remove the surface oxide film of the silicon wafer to be tested; Step 4: placing the third silicon wafer in an oxidation-induced stacking fault revealing agent for preferential etching to obtain a test silicon wafer; Step 5: Place the test silicon wafer under a spotlight in a dark room, turn on the spotlight and observe the OISF-ring on the surface of the test silicon wafer.

[0021] Compared with the prior art, the present invention has the following beneficial effects: Before heat treatment, an oxidation-induced stacking fault nucleating agent is uniformly applied on the surface of the silicon wafer to be tested to obtain a first silicon wafer. The oxidation-induced stacking fault nucleating agent is an acid radical solution containing transition metal ions. During the heat treatment process, the transition metal ions serve as nucleation centers of oxidation-induced stacking faults, promoting the formation of oxidation-induced stacking faults. On the one hand, the heat treatment time is greatly shortened. On the other hand, the oxidation-induced stacking faults will wrap the transition metal ions to nucleate and grow. Even if there is mechanical damage on the surface of the silicon wafer to be tested, it will not cover the OISF-ring of the silicon wafer, making the test result clearer. The test personnel can accurately judge that the mixed acid cleaning after heat treatment is to remove the oxide film on the surface of the silicon wafer to prevent the influence of the oxide film on preferential corrosion, so that the oxidation-induced stacking fault revealing agent can etch the OISF-ring more effectively and highlight the OISF-ring on the surface of the silicon wafer.

[0022] In one embodiment, in step 1, the transition metal ions are chromium ions, manganese ions, iron ions, cobalt ions, nickel ions, copper ions, zinc ions, palladium ions, silver ions, platinum ions, or gold ions. The transition metal ions attached to the surface of the silicon wafer to be tested will become the nucleation center of the OISF-ring, promoting the formation of oxidation-induced stacking faults.

[0023] In one embodiment, in step 1, the transition metal ions are copper ions, and the oxidation-induced stacking fault nucleating agent is an acid copper solution. The copper ions can diffuse rapidly throughout the entire silicon wafer to be tested under high temperature conditions, while at room temperature, the copper ions will exist on the surface of the silicon wafer in the form of precipitation.

[0024] In one embodiment, the concentration of copper ions in the acid copper solution is 700-1000 ppma. At this concentration, copper ions can be effectively diffused to the entire silicon wafer to be tested, while avoiding insufficient diffusion of copper ions or even excessive copper ions that cause waste.

[0025] In one embodiment, in step 2, the predetermined temperature is 600-900°C, and the predetermined time is 5-10 minutes. Within the predetermined temperature range and the predetermined time range, the transition metal ions can be completely diffused throughout the entire silicon wafer, and the oxidation-induced stacking faults in the silicon wafer can wrap the transition metal ions to nucleate and grow completely.

[0026] In one embodiment, in step 3, the mixed acid solution consists of hydrofluoric acid, nitric acid, acetic acid and water, and the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water in the mixed acid solution is (1-2):(3-4):(1-2):(3-4).

[0027] In one embodiment, in step 3, after the temperature of the second silicon wafer drops to room temperature, the transition metal ions in the second silicon wafer will precipitate or precipitate in the form of a transition metal-silicon complex, so that the OISF-ring in the second silicon wafer is wrapped with the precipitate of the transition metal ions or precipitated together in the form of a transition metal-silicon complex, and is washed with the mixed acid solution for 1-5 minutes to remove the oxide film on the surface of the second silicon wafer to prevent the influence of the oxide film on preferential corrosion, thereby allowing the oxidation-induced stacking fault revealing agent to etch the OISF-ring more effectively and highlight the OISF-ring on the surface of the silicon wafer.

[0028] In one embodiment, in step 4, the oxidation-induced stacking fault revealing agent is composed of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid, wherein the volume ratio of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid is 1:1:(1-3):(2-4), and the third silicon wafer is placed in the oxidation-induced stacking fault revealing agent and preferentially corroded for 5 minutes to obtain a test silicon wafer, so that the OISF-ring on the surface of the test silicon wafer is clearer, which is convenient for distinguishing the OISF-ring on the surface of the test silicon wafer.

[0029] In one embodiment, in step 4, the oxidation-induced stacking fault revealing agent is composed of chromic acid solution, copper acid solution, nitric acid, acetic acid, and hydrofluoric acid, wherein the volume ratio of chromic acid solution, copper acid solution, nitric acid, acetic acid, and hydrofluoric acid is 1: (1-3): 1: (1-3): (2-4), and the third silicon wafer is placed in the oxidation-induced stacking fault revealing agent and preferentially corroded for 10 minutes to obtain a test silicon wafer, so that the OISF-ring on the surface of the test silicon wafer is clearer, which is convenient for distinguishing the OISF-ring on the surface of the test silicon wafer and improving the accuracy of the detection.

[0030] In one embodiment, in step 4, the oxidation-induced stacking fault revealing agent is prepared by mixing a chromic acid solution and a hydrofluoric acid solution in the following manner: Step 1: Dissolve 10-20 grams of potassium dichromate in 200-400 ml of water to obtain a chromic acid solution; Step 2: Mix the chromic acid solution and the 49% hydrofluoric acid solution in a volume ratio of 1: (1-3) to obtain the oxidation induced stacking fault revealing agent, and place the third silicon wafer in the oxidation induced stacking fault revealing agent for preferential corrosion for 5 minutes to obtain a test silicon wafer, so that the OISF-ring on the surface of the test silicon wafer is clearer, which is convenient for distinguishing the OISF-ring on the surface of the test silicon wafer and improving the accuracy of the detection.

[0031] The following examples of the method of the present invention and comparative examples of the conventional method are used to demonstrate the detection process and results of silicon wafer OIS F-ring.

[0032] Take a 12-inch silicon wafer with mechanical damage on the surface and cleave it into four pieces evenly with a diamond pen. Take two of them, one is marked as silicon wafer No. 1 to be tested, and the other is marked as silicon wafer No. 2 to be tested. Silicon wafer No. 1 to be tested is tested by the method of the present invention, and silicon wafer No. 2 to be tested is tested by the traditional method.

[0033] 1. Example: First, the No. 1 silicon wafer to be tested is placed in a NaOH solution with a mass fraction of 8% for alkaline washing for 10 minutes to remove dirt and grease on the surface of the No. 1 silicon wafer to be tested. Then, the surface of the No. 1 silicon wafer to be tested is rinsed with deionized water to remove the residual NaOH solution on the surface of the No. 1 silicon wafer to be tested. Next, 1g of copper nitrate is dissolved in 100-300ml of water to obtain an oxidation-induced stacking fault nucleating agent with a copper ion concentration of 700-1000ppma, and 2-5 drops of the oxidation-induced stacking fault nucleating agent are dropped on the surface of the No. 1 silicon wafer to be tested. The surface of the silicon wafer No. 1 to be tested is uniformly wiped with a dust-free cloth to the entire surface of the oxidation-induced stacking fault nucleating agent. It is left to stand for 1-2 minutes to dry to obtain the first silicon wafer. The first silicon wafer is then placed on a quartz boat. When the temperature of the muffle furnace rises to 900°C, the quartz boat is placed in the muffle furnace with a quartz boat fork. After heat treatment for 5-10 minutes, the quartz boat is taken out to obtain the second silicon wafer. The copper ions serve as the nucleation center of the oxidation-induced stacking fault to promote the formation of OISF-ring. The second silicon wafer is then naturally cooled to room temperature. At room temperature, copper ions will precipitate on the surface of the second silicon wafer in the form of precipitation, so that the OISF-ring wraps the copper ions and precipitates together. After the second silicon wafer is cooled, it is corroded with a mixed acid solution for 1-5 minutes to remove the oxide film on the surface of the second silicon wafer to obtain a third silicon wafer. The mixed acid solution is composed of hydrofluoric acid, nitric acid, acetic acid and water, wherein the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water is (1-2): (3-4): (1-2): (3-4). Then the obtained third silicon wafer is placed in an oxidation-induced stacking fault revealing agent. After 5-10 minutes of selective etching, the No. 1 test silicon wafer is obtained. The oxidation-induced stacking fault revealing agent is composed of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid, wherein the volume ratio of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid is 1:1:(1-3):(2-4). Finally, the No. 1 test silicon wafer is cleaned with deionized water and the surface water droplets are blown clean with an air gun and then sent to the darkroom of the inspection room for inspection. During the inspection, the No. 1 test silicon wafer is placed under a spotlight, and the spotlight is turned on to observe the surface of the No. 1 test silicon wafer. The test results are shown in FIG. Figure 2 There is a clear 4mm ring on the surface of the No. 1 test silicon wafer.

[0034] 2. Comparative example: First, the silicon wafer No. 2 to be tested is placed in a NaOH solution with a mass fraction of 8% for alkaline washing for 10 minutes to remove dirt and grease on the surface of the silicon wafer No. 2 to be tested, and then placed in a mixed acid solution for pickling to remove the damaged layer on the surface of the silicon wafer No. 2 to be tested. The mixed acid solution is composed of hydrofluoric acid, nitric acid, acetic acid and water, wherein the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water is (1-2): (3-4): (1-2): (3-4). Then, the silicon wafer No. 2 to be tested is rinsed with deionized water. After the water droplets are blown off the surface with an air gun, the No. 2 silicon wafer to be tested is placed in an oxidation furnace under a dry oxygen atmosphere of 600-900℃, and the temperature is raised to 1000-1200℃ at a rate of 5-20℃ / min in the dry oxygen atmosphere, and then kept constant for 60-120min in a wet oxygen atmosphere, and then dry oxygen is introduced and the temperature is lowered to 600-900℃ at a rate of 1-5℃ / min. At 600-900℃, the No. 2 silicon wafer to be tested is taken out of the furnace, and then the No. 2 silicon wafer to be tested is In a solution of 49% HF and water in a volume ratio of 1: (1~1.5), fully react for 2~3 minutes to remove the oxide film on the surface of the silicon wafer, and rinse the No. 2 silicon wafer to be tested with overflowing deionized water to remove the residual solution on the surface of the No. 2 silicon wafer to be tested. Then put the No. 2 silicon wafer to be tested into the prepared preferential etching solution, take it out after full contact for 5-10 minutes, and rinse the residual solution on the surface of the No. 2 silicon wafer to be tested with overflowing deionized water to obtain the No. 2 test silicon wafer. The preferential etching solution used is composed of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid, wherein the volume ratio of chromic acid solution: nitric acid: acetic acid: hydrofluoric acid is 1: 1: (1~3): (2~4). After preferential etching, rinse it with deionized water and blow off the surface water droplets with an air gun. Finally, send the No. 2 test silicon wafer to the darkroom of the inspection room for inspection. During the inspection, put the No. 2 test silicon wafer under the spotlight, turn on the spotlight to inspect the surface of the No. 2 test silicon wafer, and the inspection results are shown in Figure 3 There is a 4mm ring on the surface of the No. 2 silicon wafer.

[0035] It can be seen from the examples of the method of the present invention and the comparative examples of the conventional method that, on the one hand, the heat treatment time in the examples is shorter than that in the comparative examples and the process is simpler, and the detection efficiency of the examples is higher. On the other hand, the detection results of the comparative examples are Figure 3 The OISF-ring boundary is fuzzy, and the mechanical damage on the surface will interfere with the OISF-ring judgment result. The test results obtained by the embodiment are as follows: Figure 2 In the process, the OISF-ring on the surface of the silicon wafer can be clearly observed, and the judgment result will not be affected by mechanical damage on the surface of the silicon wafer.

[0036] The modules or units in the device of the embodiment of the present invention can be combined, divided and deleted according to actual needs. The above disclosure is only the preferred embodiment of the present invention, and of course it cannot be used to limit the scope of the rights of the present invention. Those skilled in the art can understand that all or part of the processes of the above embodiment are implemented, and the equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for detecting silicon single crystal OIS F-ring, characterized in that: The following steps are involved: Step 1: evenly apply an oxidation-induced stacking fault nucleating agent on the surface of a silicon wafer to be tested to obtain a first silicon wafer; The oxidation-induced stacking fault nucleating agent is an acid radical solution containing transition metal ions; Step 2: placing the first silicon wafer in a high temperature environment at a predetermined temperature for a predetermined time to obtain a second silicon wafer, wherein the transition metal ions serve as nucleation centers of oxidation-induced stacking faults, and the oxidation-induced stacking faults wrap the transition metal ions to nucleate and grow, so that the mechanical damage on the surface of the second silicon wafer will not cover the OISF-ring of the silicon wafer; Step 3: Clean the second silicon wafer with mixed acid to obtain a third silicon wafer, and remove the surface oxide film of the silicon wafer to be tested; Step 4: placing the third silicon wafer in an oxidation-induced stacking fault revealing agent for preferential etching to obtain a test silicon wafer; Step 5: Place the test silicon wafer under a spotlight in a dark room, turn on the spotlight and observe the OISF-ring on the surface of the test silicon wafer.

2. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In step 1, the transition metal ion is a chromium ion, a manganese ion, an iron ion, a cobalt ion, a nickel ion, a copper ion, a zinc ion, a palladium ion, a silver ion, a platinum ion, or a gold ion.

3. The method for detecting silicon single crystal OIS F-ring according to claim 2, characterized in that: In the step 1, the transition metal ions are copper ions, and the oxidation-induced stacking fault nucleating agent is an acid copper solution.

4. The method for detecting silicon single crystal OIS F-ring according to claim 3, characterized in that: The concentration of copper ions in the oxidation-induced stacking fault nucleating agent is 700-1000 ppma.

5. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In step 2, the predetermined temperature is 600-900° C., and the predetermined time is 5-10 minutes.

6. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In step 3, the mixed acid solution is composed of hydrofluoric acid, nitric acid, acetic acid and water, and the volume ratio of hydrofluoric acid, nitric acid, acetic acid and water in the mixed acid solution is (1-2): (3-4): (1-2): (3-4).

7. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In the step 3, after the temperature of the second silicon wafer drops to room temperature, it is cleaned with the mixed acid solution for 1-5 minutes.

8. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In step 4, the oxidation-induced stacking fault revealing agent is composed of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid, wherein the volume ratio of chromic acid solution, nitric acid, acetic acid, and hydrofluoric acid is 1:1:(1-3):(2-4).

9. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In step 4, the oxidation-induced stacking fault revealing agent is composed of chromic acid solution, copper acid solution, nitric acid, acetic acid, and hydrofluoric acid, wherein the volume ratio of chromic acid solution, copper acid solution, nitric acid, acetic acid, and hydrofluoric acid is 1:(1-3):1:(1-3):(2-4).

10. The method for detecting silicon single crystal OIS F-ring according to claim 1, characterized in that: In the step 4, the oxidation-induced stacking fault revealing agent is prepared by mixing a chromic acid solution and a hydrofluoric acid solution, wherein the volume ratio of the chromic acid solution to the hydrofluoric acid solution is 1:(1-3).

Images