Method for controlling edge pollution of wet etching silicon wafer

Abstract

The invention discloses a wet etching silicon wafer edge pollution control method, and relates to the technical field of semiconductors, and the wet etching silicon wafer edge pollution control method comprises the following steps: 1, preprocessing a silicon wafer; 2, calibrating the levelness of the equipment; step 3, implementing a corrosion process; 4, performing post-corrosion treatment on the silicon wafer; 5, quality detection and control; and 6, waste liquid treatment and processing completion. The two gradienters are mounted on the mechanical arm, so that the two gradienters can perform horizontal balance control on the mechanical arm and the corrosion cage in real time, the probability of inclination of the corrosion cage is reduced, and the stability during silicon wafer processing is effectively improved; therefore, the probability that the edge of the silicon wafer is rubbed with the inner wall of the clamping groove of the corrosion cage to cause stains is reduced, the processing quality of the silicon wafer is further improved, and the applicability is high.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for controlling contamination at the edge of a wet-etched silicon wafer. Background Art

[0002] The overall technological level of semiconductor processing represents the highest level of manufacturing development. The wet acid etching process is a crucial step in semiconductor processing. Due to the unique and hazardous nature of this process, the degree of smudges produced on the edges of silicon wafers during the etching process is often difficult to control. Analyzing and addressing the various smudges that occur on the edges of silicon wafers during the acid etching process is urgent.

[0003] The existing technology has the following problems:

[0004] Existing semiconductor silicon wafer processing arms are not equipped with a level. The machine's supporting arm supports the specialized etching cage that holds the silicon wafer. The level of the entire arm directly affects the level of the acid etching machine's etching cage. Without a level to measure the horizontal accuracy of the supporting arm, if the two robotic arms appear to be unevenly aligned during processing, the etching cage may tilt without being detected in time. As the silicon wafer rotates in the etching cage, it rubs against the inner wall of the slot, one side against the left side and the other against the right side. This high friction can cause scratches on the chamfered edges of the silicon wafer. Summary of the Invention

[0005] The present invention provides a method for controlling contamination at the edge of a wet-etched silicon wafer to solve the problems raised in the above-mentioned background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for controlling contamination at the edge of a wet-etched silicon wafer comprises the following steps:

[0008] Step 1: Silicon wafer pretreatment;

[0009] Step 2: Equipment level calibration;

[0010] Step 3: Implementation of corrosion process;

[0011] Step 4: Post-etching treatment of silicon wafers;

[0012] Step 5: Quality inspection and control;

[0013] Step 6: Waste liquid treatment and processing are completed.

[0014] A further improvement of the technical solution of the present invention is that the step 1 further includes the following steps:

[0015] A1: RCA cleaning, standard SC-1 (NH4OH / H2O2 / H2O) to remove organic matter and particles, SC-2 (HCl / H2O2 / H2O) to remove metal ions;

[0016] A2: Use dilute hydrofluoric acid (0.5% to 1%) to remove the natural oxide layer (SiO2) at room temperature. The etching time is controlled within 5-30 seconds (adjusted according to the thickness of the oxide layer, the rate is about ), exposing a clean silicon surface;

[0017] A3: Rinse with deionized water (DI Water) and gently brush the edge of the silicon wafer with a soft brush to remove particles and impurities at the chamfer (to prevent impurities from increasing edge friction) and thoroughly remove any cleaning chemical residue.

[0018] A4: Blow dry with nitrogen (N2) (temperature 80℃~100℃) or spin dry: obtain a dry and clean surface. The drying time should be controlled within 1~2 minutes.

[0019] A further improvement of the technical solution of the present invention is that the step 2 further includes the following steps:

[0020] B1: Start the machine, run the robotic arm without load to a horizontal position, observe the position of the bubbles on both sides of the spirit level, and center the bubbles by adjusting the leveling screws (or hydraulic support) at the bottom of the machine (deviation ≤ 0.1 grid). After calibration, record the spirit level reading as the process benchmark. Calibrate the robotic arm of the acid etching machine (used to support the etching cage), and install bubble levels (accuracy ≥ 0.5mm / m) symmetrically at both ends of the arm to monitor the horizontal status in real time.

[0021] B2: An automatic alarm is set between the corrosion cage and the robotic arm. When the level detects that the deviation exceeds the threshold, the machine automatically pauses and alarms (response time < 100ms).

[0022] A further improvement of the technical solution of the present invention is that the step three further includes the following steps:

[0023] C1: Use a Teflon (PTFE) corrosion cage to hold the silicon wafer and ensure that the silicon wafer is not loose in the slot (to avoid rotational friction);

[0024] C2: Prepare an HNA mixture with a formula of HF:HNO3:CH3COOH=1:6:3. The temperature is controlled at 25±0.5°C (constant temperature water bath). The ratio of nitric acid to HF (HNO3:HF) affects the corrosion uniformity: when the ratio is greater than 3:1, the oxidation-corrosion reaction is more balanced, and the incidence of edge stains can be reduced by 20% to 30%.

[0025] C3: Pour the HNA mixture into the corrosion cage;

[0026] C4: Control the temperature of the etching solution at 80℃±5℃ (constant temperature water bath), the time is calculated according to the target depth (eg, 5μm / min), the rotation speed is: 20-50rpm, the stirring method is uniform rotation of the corrosion cage + gentle circulation of the solution, and the bubble offset of the spirit level is kept ≤0.5mm during the rotation. If the offset is out of tolerance, suspend the calibration immediately. If the edge of the silicon wafer is over-corroded (thickness deviation>5%): reduce the HF concentration to 8%, or shorten the etching time to 8 minutes, and check whether the spirit level is offset by more than 0.5mm during the process. If the etching rate is insufficient (the target depth is not reached), Reach): The temperature can be raised to 85°C (not exceeding 90°C to avoid boiling of the solution), or the HNO3 ratio must be increased to 35%, but the calibration time must be extended to 10 minutes to ensure levelness. For every 10°C increase in temperature, the corrosion rate increases by about 2 times: at 80°C, the typical corrosion rate is 500nm / min (HF=10%, HNO3=30% ratio). The constant temperature accuracy must be strictly controlled to avoid local overheating and uneven edge corrosion. Corrosion time and depth conversion: If the target corrosion depth is 5μm, at 80°C and standard ratio, the required time is about 10 minutes;

[0027] C5: After the silicon wafer etching is completed, quickly move it out of the etching tank and immerse it in flowing DI water for ≥5 minutes, then tilt and rinse the etching cage slot.

[0028] A further improvement of the technical solution of the present invention is that the step 4 further includes the following steps: D1: by overflow cleaning or spray cleaning, rinse multiple times with ultrapure water (resistivity > 18 MΩ·cm) for a period of 5 to 10 minutes, with a spray pressure of 0.2 to 0.5 MPa, to ensure that the surface liquid residue is completely removed;

[0029] D2: Blow dry with nitrogen (N2) (temperature 80℃~100℃) or spin dry: obtain a dry and clean surface, and control the drying time to 1~2 minutes.

[0030] A further improvement of the technical solution of the present invention is that the step five further includes the following steps: E1: corrosion rate test: using a step profiler to measure the thickness difference before and after corrosion and calculate the rate (such as a target rate of 1 μm / min);

[0031] E2: Surface uniformity: Use a microscope (OM or SEM) to observe whether there is uneven etching, bumps or residue on the surface;

[0032] E3: Defect detection: Use laser scanning microscopy (LSCM) to check for microcracks or damage introduced by corrosion.

[0033] A further improvement of the technical solution of the present invention is that: the step six further includes the following steps: F1: storing the silicon wafer after inspection;

[0034] F2: Acidic waste liquid needs to be neutralized to pH 6-8, and fluoride ions (F-) need to be removed by CaCl2 precipitation (generating CaF2), and then discharged after meeting environmental emission standards.

[0035] Due to the adoption of the above technical solution, the present invention has the following technical advancements compared to the prior art:

[0036] 1. The present invention provides a method for controlling contamination at the edge of a wet-etched silicon wafer. By pre-treating the silicon wafer and calibrating the level of the robotic arm and the etching cage before processing the silicon wafer, the stability of the silicon wafer during processing can be effectively improved, the probability of friction between the silicon wafer and the card slot can be reduced, and the production quality of the silicon wafer can be improved.

[0037] 2. The present invention provides a method for controlling contamination at the edge of a wet-etched silicon wafer. By installing two spirit levels on a robotic arm, the two spirit levels can control the horizontal balance of the robotic arm and the corrosion cage in real time, thereby reducing the probability of the corrosion cage tilting and effectively improving the stability of silicon wafer processing. This reduces the probability of residual stains caused by friction between the edge of the silicon wafer and the inner wall of the corrosion cage slot, further improving the processing quality of the silicon wafer and having strong applicability.

[0038] 3. The present invention provides a method for controlling contamination at the edge of a wet-etched silicon wafer. By installing an automatic alarm between the etching cage and the robotic arm, the platform can automatically pause and alarm when the level instrument detects that the deviation exceeds the threshold, thereby effectively reducing the probability of deviation in silicon wafer processing and further improving applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0040] The present invention is described in further detail below in conjunction with the embodiments:

[0041] Example 1

[0042] like Figure 1 As shown, the present invention provides a method for controlling contamination at the edge of a wet-etched silicon wafer, and the method comprises the following steps:

[0043] Step 1: Silicon wafer pretreatment;

[0044] Step 2: Equipment level calibration;

[0045] Step 3: Implementation of corrosion process;

[0046] Step 4: Post-etching treatment of silicon wafers;

[0047] Step 5: Quality inspection and control;

[0048] Step 6: Waste liquid treatment and processing are completed.

[0049] Step 1 also includes the following steps:

[0050] A1: RCA cleaning, standard SC-1 (NH4OH / H2O2 / H2O) to remove organic matter and particles, SC-2 (HCl / H2O2 / H2O) to remove metal ions;

[0051] A2: Use dilute hydrofluoric acid (0.5% to 1%) to remove the natural oxide layer (SiO2) at room temperature. The etching time is controlled within 5-30 seconds (adjusted according to the thickness of the oxide layer, the rate is about ), exposing a clean silicon surface;

[0052] A3: Rinse with deionized water (DI Water) and gently brush the edge of the silicon wafer with a soft brush to remove particles and impurities at the chamfer (to prevent impurities from increasing edge friction) and thoroughly remove any cleaning chemical residue.

[0053] A4: Blow dry with nitrogen (N2) (temperature 80℃~100℃) or spin dry: obtain a dry and clean surface. The drying time should be controlled within 1~2 minutes.

[0054] Step 2 also includes the following steps:

[0055] B1: Start the machine, run the robotic arm without load to a horizontal position, observe the position of the bubbles on both sides of the spirit level, and center the bubbles by adjusting the leveling screws (or hydraulic support) at the bottom of the machine (deviation ≤ 0.1 grid). After calibration, record the spirit level reading as the process benchmark. Calibrate the robotic arm of the acid etching machine (used to support the etching cage), and install bubble levels (accuracy ≥ 0.5mm / m) symmetrically at both ends of the arm to monitor the horizontal status in real time.

[0056] B2: An automatic alarm is set between the corrosion cage and the robotic arm. When the level detects that the deviation exceeds the threshold, the machine automatically pauses and alarms (response time < 100ms).

[0057] Step three also includes the following steps:

[0058] C1: Use a Teflon (PTFE) corrosion cage to hold the silicon wafer and ensure that the silicon wafer is not loose in the slot (to avoid rotational friction);

[0059] C2: Prepare an HNA mixture with a formula of HF:HNO3:CH3COOH=1:6:3. The temperature is controlled at 25±0.5°C (constant temperature water bath). The ratio of nitric acid to HF (HNO3:HF) affects the corrosion uniformity: when the ratio is greater than 3:1, the oxidation-corrosion reaction is more balanced, and the incidence of edge stains can be reduced by 20% to 30%.

[0060] C3: Pour the HNA mixture into the corrosion cage;

[0061] C4: Control the temperature of the etching solution at 80℃±5℃ (constant temperature water bath), the time is calculated according to the target depth (eg, 5μm / min), the rotation speed is: 20-50rpm, the stirring method is uniform rotation of the corrosion cage + gentle circulation of the solution, and the bubble offset of the spirit level is kept ≤0.5mm during the rotation. If the offset is out of tolerance, suspend the calibration immediately. If the edge of the silicon wafer is over-corroded (thickness deviation>5%): reduce the HF concentration to 8%, or shorten the etching time to 8 minutes, and check whether the spirit level is offset by more than 0.5mm during the process. If the etching rate is insufficient (the target depth is not reached), Reach): The temperature can be raised to 85°C (not exceeding 90°C to avoid boiling of the solution), or the HNO3 ratio must be increased to 35%, but the calibration time must be extended to 10 minutes to ensure levelness. For every 10°C increase in temperature, the corrosion rate increases by about 2 times: at 80°C, the typical corrosion rate is 500nm / min (HF=10%, HNO3=30% ratio). The constant temperature accuracy must be strictly controlled to avoid local overheating and uneven edge corrosion. Corrosion time and depth conversion: If the target corrosion depth is 5μm, at 80°C and standard ratio, the required time is about 10 minutes;

[0062] C5: After the silicon wafer etching is completed, quickly move it out of the etching tank and immerse it in flowing DI water for ≥5 minutes, then tilt and rinse the etching cage slot.

[0063] Step 4 also includes the following steps:

[0064] D1: Use overflow cleaning or spray cleaning, rinse multiple times with ultrapure water (resistivity > 18MΩ·cm) for 5 to 10 minutes, and spray pressure: 0.2 to 0.5MPa to ensure that the surface liquid residue is completely removed;

[0065] D2: Blow dry with nitrogen (N2) (temperature 80℃~100℃) or spin dry: obtain a dry and clean surface, and control the drying time to 1~2 minutes.

[0066] Step 5 also includes the following steps:

[0067] E1: Corrosion rate test: Use a step profiler to measure the thickness difference before and after corrosion and calculate the rate (e.g. target rate 1μm / min);

[0068] E2: Surface uniformity: Use a microscope (OM or SEM) to observe whether there is uneven etching, bumps or residue on the surface;

[0069] E3: Defect detection: Use laser scanning microscopy (LSCM) to check for microcracks or damage introduced by corrosion.

[0070] 7. The method for controlling contamination of a silicon wafer edge during wet etching according to claim 1, wherein said step 6 further comprises the following steps:

[0071] F1: Store the inspected silicon wafers;

[0072] F2: Acidic waste liquid needs to be neutralized to pH 6-8, and fluoride ions (F-) need to be removed by CaCl2 precipitation (generating CaF2), and then discharged after meeting environmental emission standards.

[0073] In this embodiment, the stability of the corrosion cage is improved by calibrating the level of the corrosion cage and the robotic arm carrying the corrosion cage before processing. At the same time, the two spirit levels can control the horizontal balance of the robotic arm in real time, effectively improving the stability of the corrosion cage, thereby effectively reducing the probability of stains on the edge of the silicon wafer, improving the production quality of the silicon wafer, and being able to promptly treat and discharge the acidic waste liquid after processing is completed to prevent pollution to the environment, and has strong applicability.

[0074] While the present invention has been generally described above, modifications and improvements are readily apparent to those skilled in the art. Therefore, modifications and improvements that do not depart from the spirit of the present invention are intended to be within the scope of the present invention.

Claims

1. A method for controlling contamination at the edge of a wet-etched silicon wafer, characterized by: The method for controlling contamination of a wet-etched silicon wafer edge comprises the following steps: Step 1: Silicon wafer pretreatment; Step 2: Equipment level calibration; Step 3: Implementation of corrosion process; Step 4: Post-etching treatment of silicon wafers; Step 5: Quality inspection and control; Step 6: Waste liquid treatment and processing are completed.

2. The method for controlling contamination of a wet-etched silicon wafer edge according to claim 1, wherein: The step 1 further comprises the following steps: A1: RCA cleaning, standard SC-1 (NH4OH / H2O2 / H2O) to remove organic matter and particles, SC-2 (HCl / H2O2 / H2O) to remove metal ions; A2: Use dilute hydrofluoric acid (0.5% to 1%) to remove the natural oxide layer (SiO2) at room temperature. The etching time is controlled within 5-30 seconds (adjusted according to the thickness of the oxide layer, the rate is about ), exposing a clean silicon surface; A3: Rinse with deionized water (DIWater) and gently brush the edge of the silicon wafer with a soft brush to remove particles and impurities at the chamfer (to prevent impurities from increasing edge friction) and thoroughly remove any cleaning chemical residue. A4: Blow dry with nitrogen (N2) (temperature 80℃~100℃) or spin dry: obtain a dry and clean surface. The drying time should be controlled within 1~2 minutes.

3. The method for controlling contamination of a wet-etched silicon wafer edge according to claim 1, wherein: The step 2 further comprises the following steps: B1: Start the machine, run the robotic arm without load to a horizontal position, observe the position of the bubbles on both sides of the spirit level, and center the bubbles by adjusting the leveling screws (or hydraulic support) at the bottom of the machine (deviation ≤ 0.1 grid). After calibration, record the spirit level reading as the process benchmark. Calibrate the robotic arm of the acid etching machine (used to support the etching cage), and install bubble levels (accuracy ≥ 0.5mm / m) symmetrically at both ends of the arm to monitor the horizontal status in real time. B2: An automatic alarm is set between the corrosion cage and the robotic arm. When the level detects that the deviation exceeds the threshold, the machine automatically pauses and alarms (response time < 100ms).

4. The method for controlling contamination of a wet-etched silicon wafer edge according to claim 1, wherein: The step three further comprises the following steps: C1: Use a Teflon (PTFE) corrosion cage to hold the silicon wafer and ensure that the silicon wafer is not loose in the slot (to avoid rotational friction); C2: Prepare an HNA mixture with a formula of HF:HNO3:CH3COOH=1:6:

3. The temperature is controlled at 25±0.5°C (constant temperature water bath). The ratio of nitric acid to HF (HNO3:HF) affects the corrosion uniformity: when the ratio is greater than 3:1, the oxidation-corrosion reaction is more balanced, and the incidence of edge stains can be reduced by 20% to 30%. C3: Pour the HNA mixture into the corrosion cage; C4: Control the temperature of the etching solution at 80℃±5℃ (constant temperature water bath), the time is calculated according to the target depth (eg, 5μm / min), the rotation speed is: 20-50rpm, the stirring method is uniform rotation of the corrosion cage + gentle circulation of the solution, and the bubble offset of the spirit level is kept ≤0.5mm during the rotation. If the offset is out of tolerance, suspend the calibration immediately. If the edge of the silicon wafer is over-corroded (thickness deviation>5%): reduce the HF concentration to 8%, or shorten the etching time to 8 minutes, and check whether the spirit level is offset by more than 0.5mm during the process. If the etching rate is insufficient (the target depth is not reached), Reach): The temperature can be raised to 85°C (not exceeding 90°C to avoid boiling of the solution), or the HNO3 ratio must be increased to 35%, but the calibration time must be extended to 10 minutes to ensure levelness. For every 10°C increase in temperature, the corrosion rate increases by about 2 times: at 80°C, the typical corrosion rate is 500nm / min (HF=10%, HNO3=30% ratio). The constant temperature accuracy must be strictly controlled to avoid local overheating and uneven edge corrosion. Corrosion time and depth conversion: If the target corrosion depth is 5μm, at 80°C and standard ratio, the required time is about 10 minutes; C5: After the silicon wafer etching is completed, quickly move it out of the etching tank and immerse it in flowing DI water for ≥5 minutes, then tilt and rinse the etching cage slot.

5. The method for controlling contamination of a wet-etched silicon wafer edge according to claim 1, wherein: The step four also The following steps are involved: D1: Use overflow cleaning or spray cleaning, rinse multiple times with ultrapure water (resistivity > 18MΩ·cm) for 5 to 10 minutes, and spray pressure: 0.2 to 0.5MPa to ensure that the surface liquid residue is completely removed; D2: Blow dry with nitrogen (N2) (temperature 80℃~100℃) or spin dry: obtain a dry and clean surface, and control the drying time to 1~2 minutes.

6. The method for controlling contamination of a wet-etched silicon wafer edge according to claim 1, wherein: The step five further comprises the following steps: E1: Corrosion rate test: Use a step profiler to measure the thickness difference before and after corrosion and calculate the rate (e.g. target rate 1μm / min); E2: Surface uniformity: Use a microscope (OM or SEM) to observe whether there is uneven etching, bumps or residue on the surface; E3: Defect detection: Use laser scanning microscopy (LSCM) to check for microcracks or damage introduced by corrosion.

7. The method for controlling contamination of a wet-etched silicon wafer edge according to claim 1, wherein: The step six further comprises the following steps: F1: Store the inspected silicon wafers; F2: Acidic waste liquid needs to be neutralized to pH 6-8, and fluoride ions (F-) need to be removed by CaCl2 precipitation (generating CaF2), and then discharged after meeting environmental emission standards.

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