High-voltage diode silicon block table top cleaning treatment process

Abstract

The invention relates to a high-voltage diode silicon block mesa cleaning treatment process, which can perform deep treatment on a mesa damage layer, can perform quantitative management on the corrosion depth, and meanwhile, is uniform and controllable in silicon block mesa corrosion shape, so that the reverse breakdown voltage of a device is improved, and the surface electric leakage of the device is reduced. According to the technical scheme, mixed acid is adopted for silicon block table-board treatment. The composition, proportion and specific treatment process of the mixed acid are researched and determined. The process for cleaning the solder oxide layer on the surface of the silicon block after mixed acid treatment is studied and determined. The method has the advantages that a novel silicon block cleaning treatment process is adopted, and the high-voltage reject ratio of a product in the TMTT full-number test procedure is 6% and is reduced by 9% compared with the high-voltage reject ratio of 15% in the prior art.

Description

Technical Field

[0001] The invention relates to a silicon block table pickling process before high-voltage diode silicon block lead welding, and in particular to a high-voltage diode silicon block table cleaning process. Background Art

[0002] After alloying, the silicon stack of the high-voltage diode production line is cut and cleaned to form a silicon block. Before the silicon block is welded with the lead, it must be cleaned on the table. The purpose of the process is to remove the surface damage layer during the cutting process, remove the solder oxide layer at both ends of the silicon block, and ensure the weldability between the silicon wafer and the lead. Previously, the surface cleaning process only used concentrated H2SO4 and HF treatment, which did not adequately treat the silicon block surface damage layer, ultimately affecting the high-voltage electrical performance of the product, resulting in a high high-voltage defect rate in the TMTT full test. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a high-voltage diode silicon block table cleaning process, which performs deep treatment on the table damage layer and can quantitatively manage the corrosion depth. At the same time, the corrosion shape of the silicon block table is uniform and controllable to increase the reverse breakdown voltage of the device and reduce the surface leakage of the device.

[0004] A high-voltage diode silicon block table cleaning process, Step 1: Mixed acid corrosion: Pour the tube core into the tube core container to the position of the indicator line, open the corrosion bracket, remove the corrosion basket, unscrew the upper cover, pour the tube core into the tube core container, tighten the upper cover, place it in the corrosion bracket, and repeat this operation until the corrosion bracket is full; The mechanical arm swing frequency is 45±2 times / min, the mixed acid treatment temperature is 18±2℃, and the corrosion time is set to 4~6 minutes, which is set according to different models; hang the corrosion bracket on the swing arm of the pickling vibrator, turn on the vibrator switch, and start corrosion; After the corrosion is finished and the music alarm sounds, press the "reset" switch to raise the swing arm, take down the bracket, and shake the bracket up and down in the mixed acid solution for 3 times; Step 2, first wash: After the mixed acid etching is completed, quickly immerse the etching bracket in the jet water tank and shake it up and down vigorously for 10 to 15 times; Place the etching bracket on the swing arm of the second water washing tank, start the switch, and the swing frequency is 80±2 times / min; the cleaning time is 2 minutes; After the washing is finished and the musical alarm sounds, press the "reset" switch to raise the handle, remove the bracket and place it in the washing tank; Step 3: Determination of corrosion amount: Open the corrosion bracket, take down a corrosion basket, unscrew the top cover, use tweezers to pick up 4 tube cores and place them on the projector. Perform corrosion measurement and inspection under the projector according to the "Tube Core Corrosion Test Method". Test 2 points on each tube core and check whether there is any abnormality in the corrosion shape of the tube core under a microscope. Silicon block corrosion requirements: The corrosion control standard is 60±10μm; if the average corrosion value is lower than the standard value, additional corrosion should be performed; Step 4: Nitric Acid Corrosion: The ratio of dilute nitric acid in the nitric acid tank is: 68% nitric acid: pure water = 1:5; the volume of the nitric acid tank is 30L; Tighten the upper cover of the corrosion basket and put it back into the empty space of the corrosion bracket. Place the corrosion bracket on the swing arm of the nitric acid cleaning tank and start the switch. The swing arm frequency is 45±2 times / min. The cleaning time is 2 minutes. After the musical alarm sounds, press the "reset" switch and remove the bracket; Step 4, second wash: Immerse the bracket in the third water tank, immerse the bracket to the bottom of the water, swing and clean it 10 to 15 times, then hang the bracket on the vibrator swing arm above the water tank, start the switch, the swing frequency is 60±2 times / min, and the cleaning time is 3 minutes; After the musical alarm sounds, press the "reset" switch and remove the bracket; Step 4, third wash: Hang the corrosion bracket on the vibrator swing arm above the fourth water tank, start the switch, the swing frequency is 60±2 times / min, and the cleaning time is 3 minutes; After the musical alarm sounds, press the "reset" switch, remove the bracket and place it in the water tank; Step 5: Isopropyl alcohol rinsing: Transfer 6 baskets of silicon blocks on the corrosion bracket into the stainless steel wire mesh; The stainless steel wire mesh is placed in the first isopropanol tank and immersed for 2 minutes; The stainless steel wire mesh is placed in the second isopropanol tank and rinsed for 2 minutes; Step 6: Drying in nitrogen storage box: Place the silicon block and the stainless steel wire mesh into a nitrogen storage box for drying. The nitrogen flow rate is 100L / min, the temperature is set at 60±5℃, and the drying time is 6min. Step 7. After the operation is completed, turn off the pure water and cut off the power supply of the cooling device.

[0005] In step 1, the etching bracket includes 6 etching baskets. If more than 25 etching baskets are used for mixed acid etching, the etching liquid should be replaced. The mixed acid liquid will decrease after each etching, so replenishing liquid should be continuously added to the red line in the mixed acid tank.

[0006] Method for testing the amount of corrosion on the tube core in step 3: a) Turn on the projector main power switch and lighting power switch; b) Place the tube core on the filter paper on the glass plate on the work surface just below the lens, and rotate the lifting hand wheel to adjust the focus until the tube core is clear under the microscope; c) Adjust the direction of the tube core so that the end surface of the tube core is parallel to the horizontal X-axis and the vertical center line of the tube core is perpendicular to the horizontal X-axis; d) Move the working platform in the X-axis direction, align the vertical line of the lowest point of a corroded vertical surface of the tube core to be measured with the Y-axis, and clear the X-axis coordinate; e) Move the workbench in the X-axis direction so that the vertical line of the highest point of a corroded vertical surface of the tube core is aligned with the Y-axis. The value displayed on the X-axis is the corrosion amount of the tube core; f) Turn off the lighting power switch when the test is completed; g) Remove the tested die from the work surface, place it in a designated container, and dispose of it as scrap; h) After finishing the work, turn off the power switch of the projector; i) Clean the projector work surface and swing arm.

[0007] The weight ratio of the mixed acid is nitric acid: hydrofluoric acid: glacial acetic acid = 6:3:2.

[0008] Preparation before operation: Wear labor protection equipment: wear protective masks / protective glasses, masks, long rubber boots, latex gloves, and aprons; Check whether the exhaust status is good before operation, and start work after confirming that the exhaust is working normally; Check the pre-corrosion equipment: Check that the pre-corrosion equipment freezer pump has no abnormal sound, the freezing tank, the inside of the equipment and the pure water pipeline have no leakage, the swing of the mechanical arm mechanism of each station is normal, and check the pure water flow of each immersion tank, which is required to be controlled at 15±2L / min; Pour 45L of mixed acid into the acid tank, turn on the refrigerator, and set the mixed acid temperature controller to 18±2℃; place an empty corrosion bracket on the swing arm and swing it up and down. After the acid temperature is constant, measure the mixed acid temperature with a mercury thermometer. The actual temperature should meet 18±2℃; Check the corrosion basket, which should be free of damage or deformation; Check the model, batch number and quantity of the chip you received.

[0009] The advantages of the present invention are ingenious design and complete and reasonable process. Mixed acid is used to treat the silicon block table through the mixed acid composition, ratio and specific treatment process; the process of cleaning the solder oxide layer on the surface of the silicon block after the mixed acid treatment; the silicon block cleaning treatment process. The high-voltage defective rate of the product in the TMTT full test process is 6%, which is 9% lower than the previous high-voltage defective rate of 15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a qualified product of corrosion modeling of the tube core under the microscope.

[0011] Figure 2 It is the second qualified product of the corrosion modeling of the tube core under the microscope.

[0012] Figure 3 It is a defective product of the corrosion modeling of the tube core under the microscope.

[0013] Figure 4 It is the second defective product of the corrosion modeling of the tube core under the microscope.

[0014] Figure 5 It is a schematic diagram showing the operation of the tube core corrosion test method. DETAILED DESCRIPTION

[0015] The following is an explanation and introduction with reference to the accompanying drawings.

[0016] 1. Job Description 1.1 Equipment and Materials 1.1.1 Tube core (silicon block) etching equipment, refrigerator, projector, nitrogen drying box, tube core etching basket, and etching bracket.

[0017] 1.1.2 The tube core after appearance selection.

[0018] 1.2 Chemicals: Mixed acid (nitric acid: hydrofluoric acid: glacial acetic acid = 6:3:2), isopropyl alcohol, and pure water.

[0019] 1.3 Preparation 1.3.1 Wear labor protection equipment: wear protective masks / protective glasses, masks, long rubber boots, latex gloves, and aprons.

[0020] 1.3.2 Before operation, check whether the exhaust status is good, and start work after confirming that the exhaust is working normally.

[0021] 1.3.3 Check the pre-corrosion equipment: Check that there is no abnormal sound from the refrigeration pump of the pre-corrosion equipment, that there is no leakage in the freezing tank, inside the equipment and in the pure water pipeline, that the swing of the mechanical arm mechanism of each station is normal, and check the pure water flow rate of each immersion tank, which is required to be controlled at (15±2) L / min.

[0022] 1.3.4 Pour 45L of mixed acid into the acid tank, turn on the refrigerator, and set the mixed acid temperature controller to (18±2)℃. Place an empty corrosion bracket on the swing arm and swing it up and down. After the acid temperature is constant, measure the mixed acid temperature with a mercury thermometer. The actual temperature should meet (18±2)℃.

[0023] 1.3.5 Check the corrosion basket. The corrosion basket should be free of damage and deformation.

[0024] 1.3.6 Check the model, batch number and quantity of the chip received.

[0025] 1.4 Formal Assignment 1.4.1 Mixed acid corrosion 1.4.1.1 Pour the cores into the core container to the indicated line, open the corrosion tray, remove the corrosion basket, unscrew the top cover, pour the cores in the special container, tighten the top cover, place it in the corrosion tray, and repeat this operation until the corrosion tray is full (6 baskets).

[0026] 1.4.1.2 The mechanical arm swing frequency is 45±2 times / min, the mixed acid treatment temperature is 18±2℃, and the corrosion time is set to 4~6 minutes (depending on the model). Hang the corrosion bracket on the swing arm of the pickling vibrator, turn on the vibrator switch, and start corrosion. (If the mixed acid corrosion exceeds 25, the corrosion liquid should be replaced).

[0027] 1.4.1.3 After the corrosion is completed and the musical alarm sounds, press the "reset" switch to raise the swing arm, remove the bracket, and shake the bracket up and down in the mixed acid solution for 3 times.

[0028] (The mixed acid liquid will decrease with each corrosion, so replenishing liquid should be continuously added until it reaches the red line in the mixed acid tank).

[0029] 1.4.2 First wash 1.4.2.1 After the mixed acid corrosion is completed, quickly immerse the corrosion bracket in the jet water tank and shake it up and down vigorously for 10 to 15 times. If sampling and measurement are required at this time, proceed to the sampling and measurement step in 5.3. After the sampling is completed, proceed to the next step.

[0030] 1.4.2.2 Place the corrosion bracket on the swing arm of the second washing tank, start the switch, and the swing frequency is 80±2 times / min. The cleaning time is 2 minutes.

[0031] When washing is finished and the musical alarm sounds, press the "reset" switch to raise the handle, remove the bracket and place it in the washing tank.

[0032] 1.4.3 Determination of corrosion amount 1.4.3.1 Open the corrosion bracket, take down a corrosion basket, unscrew the top cover, use tweezers to pick up 4 tube cores and place them on the projector. Under the projector, perform corrosion measurement and inspection according to the "Tube Core Corrosion Test Method". Test 2 points on each tube core. Figure 1-4 "Check the corrosion shape of the tube core under a microscope for any abnormalities.

[0033] 1.4.3.2 Test method for core corrosion: a) Turn on the projector main power switch (POWER) and the lighting power switch (CONTOUR).

[0034] b) Place the tube core on the filter paper on the glass plate on the workbench just below the lens, and rotate the lifting hand wheel to adjust the focus until the tube core is clear under the microscope.

[0035] c) Adjust the direction of the tube core to the following figure, as shown in the attached Figure 5 The AC side is parallel to the X-axis; the BD side is perpendicular to the X-axis.

[0036] d) Move the working platform in the X-axis direction, align one surface of the measured length (such as BD) with the Y-axis, and clear the X coordinate.

[0037] e) Move the workbench in the X-axis direction to align the other side of the tube core (such as CE) with the Y-axis. At this time, the X-axis display value (such as BC) is the corrosion amount of the tube core.

[0038] f) After the test is completed, turn off the lighting power switch (CONTOUR).

[0039] g) Remove the tested die from the work surface, place it in a designated container, and dispose of it as scrap.

[0040] h) After finishing work, turn off the projector power switch (POWER).

[0041] i) Clean the projector work surface and swing arm.

[0042] 1.4.3.3 Silicon block corrosion requirements: The corrosion control standard is 60±10μm. If the average corrosion value is lower than the standard value, additional corrosion should be carried out.

[0043] 1.4.4 Nitric acid corrosion 1.4.4.1 The ratio of dilute nitric acid in the nitric acid tank is: 68% nitric acid: pure water = 1:5. The volume of the nitric acid tank is 30L.

[0044] 1.4.4.2 Tighten the upper cover of the corrosion basket and put it back into the empty space of the corrosion bracket. Place the corrosion bracket on the swing arm of the nitric acid cleaning tank and start the switch. The swing arm frequency is 45±2 times / min. The cleaning time is 2 minutes.

[0045] 1.4.4.3 After the music sounds, press the “Reset” switch and remove the bracket.

[0046] 1.4.5 Second washing 1.4.5.1 Immerse the bracket in the third water tank, immerse the bracket to the bottom of the water, swing and clean it 10 to 15 times, then hang the bracket on the vibrator arm above the water tank, start the switch, the swing frequency is 60±2 times / min, and the cleaning time is 3 minutes.

[0047] 1.4.5.2 After the music sounds, press the “Reset” switch and remove the bracket.

[0048] 1.4.6 Third washing 1.4.6.1 Hang the corrosion bracket on the vibrator swing arm above the fourth water tank, start the switch, the swing frequency is 60±2 times / min, and the cleaning time is 3 minutes.

[0049] 1.4.6.2 After the music sounds, press the “reset” switch, remove the bracket and place it in the washing tank.

[0050] 1.4.7 Isopropyl alcohol immersion 1.4.7.1 Transfer the 6 baskets of silicon blocks on the corrosion rack into the stainless steel wire mesh.

[0051] 1.4.7.2 Place the stainless steel wire mesh in the first isopropanol tank and soak for 2 minutes.

[0052] 1.4.7.3 Place the stainless steel wire mesh in the second isopropyl alcohol tank and soak for 2 minutes.

[0053] 1.4.8 Nitrogen storage box drying The silicon block and the stainless steel wire mesh were placed in a nitrogen storage box for drying. The nitrogen flow rate was 100 L / min, the temperature was set at 60 ± 5 °C, and the drying time was 6 min.

[0054] 1.4.9 After the operation is completed, turn off the pure water and cut off the power supply of the cooling device.

[0055] Cut off the main power switch, seal the mixed acid tank with a cover, clean up the work site, and scrap the scattered cores.

Claims

1. A high-voltage diode silicon block table cleaning process, characterized in that: Step 1: Mixed acid corrosion: Pour the tube core into the tube core container to the position of the indicator line, open the corrosion bracket, remove the corrosion basket, unscrew the upper cover, pour the tube core into the tube core container, tighten the upper cover, place it in the corrosion bracket, and repeat this operation until the corrosion bracket is full; The mechanical arm swing frequency is 45±2 times / min, the mixed acid treatment temperature is 18±2℃, and the corrosion time is set to 4~6 minutes, which is set according to different models; hang the corrosion bracket on the swing arm of the pickling vibrator, turn on the vibrator switch, and start corrosion; After the corrosion is finished and the music alarm sounds, press the "reset" switch to raise the swing arm, take down the bracket, and shake the bracket up and down in the mixed acid solution for 3 times; Step 2, first wash: After the mixed acid etching is completed, quickly immerse the etching bracket in the jet water tank and shake it up and down vigorously for 10 to 15 times; Place the etching bracket on the swing arm of the second water washing tank, start the switch, and the swing frequency is 80±2 times / min; the cleaning time is 2 minutes; After washing is finished and the musical alarm sounds, press the "reset" switch to raise the handle, remove the bracket and place it in the washing tank; Step 3: Determination of corrosion amount: Open the corrosion bracket, take down a corrosion basket, unscrew the top cover, use tweezers to pick up 4 tube cores and place them on the projector. Perform corrosion measurement and inspection under the projector according to the "Tube Core Corrosion Test Method". Test 2 points on each tube core and check whether there is any abnormality in the corrosion shape of the tube core under a microscope. Silicon block corrosion requirements: The corrosion control standard is 60±10μm; if the average corrosion value is lower than the standard value, additional corrosion should be performed; Step 4: Nitric Acid Corrosion: The ratio of dilute nitric acid in the nitric acid tank is: 68% nitric acid: pure water = 1:5; the volume of the nitric acid tank is 30L; Tighten the upper cover of the corrosion basket and put it back into the empty space of the corrosion bracket. Place the corrosion bracket on the swing arm of the nitric acid cleaning tank and start the switch. The swing arm frequency is 45±2 times / min. The cleaning time is 2 minutes. After the music alarm sounds, press the "reset" switch and remove the bracket; Step 4, second wash: Immerse the bracket in the third water tank, immerse the bracket to the bottom of the water, swing and clean it 10 to 15 times, then hang the bracket on the vibrator swing arm above the water tank, start the switch, the swing frequency is 60±2 times / min, and the cleaning time is 3 minutes; After the music alarm sounds, press the "reset" switch and remove the bracket; Step 4, third wash: Hang the corrosion bracket on the vibrator swing arm above the fourth water tank, start the switch, the swing frequency is 60±2 times / min, and the cleaning time is 3 minutes; After the musical alarm sounds, press the "reset" switch, remove the bracket and place it in the water tank; Step 5: Isopropyl alcohol rinsing: Transfer 6 baskets of silicon blocks on the corrosion bracket into the stainless steel wire mesh; The stainless steel wire mesh is placed in the first isopropanol tank and immersed for 2 minutes; The stainless steel wire mesh is placed in the second isopropanol tank and rinsed for 2 minutes; Step 6: Drying in nitrogen storage box: Place the silicon block and the stainless steel wire mesh into a nitrogen storage box for drying. The nitrogen flow rate is 100L / min, the temperature is set at 60±5℃, and the drying time is 6min. Step 7. After the operation is completed, turn off the pure water and cut off the power supply of the cooling device.

2. A high-voltage diode silicon block table cleaning process according to claim 1, characterized in that: In step 1, the etching bracket includes 6 etching baskets. If more than 25 etching baskets are used for mixed acid etching, the etching liquid should be replaced. The mixed acid liquid will decrease after each etching, so replenishing liquid should be continuously added to the red line in the mixed acid tank.

3. A high-voltage diode silicon block table cleaning process according to claim 1, characterized in that: Method for testing the amount of corrosion on the tube core in step 3: a) Turn on the projector main power switch and lighting power switch; b) Place the tube core on the filter paper on the glass plate on the work surface just below the lens, and rotate the lifting hand wheel to adjust the focus until the tube core is clear under the microscope; c) Adjust the direction of the tube core so that the end surface of the tube core is parallel to the horizontal X-axis and the vertical center line of the tube core is perpendicular to the horizontal X-axis; d) Move the working platform in the X-axis direction, align the vertical line of the lowest point of a corroded vertical surface of the tube core to be measured with the Y-axis, and clear the X-axis coordinate; e) Move the workbench in the X-axis direction so that the vertical line of the highest point of a corroded vertical surface of the tube core is aligned with the Y-axis. The value displayed on the X-axis is the corrosion amount of the tube core; f) Turn off the lighting power switch when the test is completed; g) Remove the tested die from the work surface, place it in a designated container, and dispose of it as scrap; h) After finishing the work, turn off the power switch of the projector; i) Clean the projector work surface and swing arm.

4. A high-voltage diode silicon block table cleaning process according to claim 1, characterized in that: The weight ratio of the mixed acid is nitric acid: hydrofluoric acid: glacial acetic acid = 6:3:

2.

5. A high-voltage diode silicon block table cleaning process according to claim 1, characterized in that: Preparation before operation: Wear labor protection equipment: wear protective masks / protective glasses, masks, long rubber boots, latex gloves, and aprons; Check whether the exhaust status is good before operation, and start work after confirming that the exhaust is working normally; Check the pre-corrosion equipment: Check that the pre-corrosion equipment freezer pump has no abnormal sound, the freezing tank, the inside of the equipment and the pure water pipeline have no leakage, the swing of the mechanical arm mechanism of each station is normal, and check the pure water flow of each immersion tank, which is required to be controlled at 15±2L / min; Pour 45L of mixed acid into the acid tank, turn on the refrigerator, and set the mixed acid temperature controller to 18±2℃; place an empty corrosion bracket on the swing arm and swing it up and down. After the acid temperature is constant, measure the mixed acid temperature with a mercury thermometer. The actual temperature should meet 18±2℃; Check the corrosion basket, which should be free of damage or deformation; Check the model, batch number and quantity of the chip you received.

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