Method for improving metal on edge of silicon wafer

Abstract

The invention relates to a method for improving metal at the edge of a silicon wafer, which belongs to the technical field of silicon wafer processing and comprises the following operation steps of: 1, spraying pure water on a second-hand wafer box for 5 minutes at the flow rate of 25 Lpm; secondly, hydrochloric acid is soaked in a pure water soaking tank, and the second-hand tablet box is soaked for 30 min; and 3, spraying pure water on the second-hand film box for 10 minutes, wherein the flow rate of the pure water is 40 Lpm. Fourthly, the second-hand piece box is subjected to rotary spin-drying, the rotating speed is 300 Rpm, and the spin-drying time is 10 min. 5, the second-hand tablet box is put into a closed drying oven to be dried, the drying temperature ranges from 62 DEG C to 65 DEG C, and the drying time is 30 min. And 6, putting a clean silicon wafer into the cleaned and dried second-hand wafer box, and detecting the metal level of the edge of the silicon wafer. The problem that the wafer box cleaning machine cannot clean the second-hand wafer box is solved. After hydrochloric acid with the dilution concentration of 0.4% is added into the cleaning tank of the wafer box cleaning machine, Al and Fe element metal pollution is effectively reduced, and the second-hand wafer box metal level is improved, so that the silicon wafer edge metal level is improved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon wafer processing, and in particular to a method for improving metal at the edge of a silicon wafer. Background Art

[0002] With the growing development of the semiconductor industry, the integration level of ICs is constantly increasing, the feature size of chips is shrinking, and the requirements for the metal level of silicon wafers are becoming higher and higher. Metal contamination has a great adverse effect on the performance of silicon wafers. For example, metal contamination can cause leakage current in the pn structure, which in turn leads to a decrease in the breakdown voltage of the oxide and a reduction in the carrier life cycle. Organic contaminants may cause unexpected hydrophobic properties on the surface and edges of the wafer, increase the roughness of the surface and edges, produce haze, and damage the growth of the epitaxial layer. If the contaminants are not removed first, it will also affect the cleaning effect of metal contamination.

[0003] The surface metal content of domestic 12-inch silicon wafers has reached 10E7 atoms / cm². After comparing and analyzing the data with those of competing companies, the edge metal content of 12-inch silicon wafers performed poorly, with the performance varying from company to company. The better performers can reach below 10E8 atoms / cm², while the worse performers are at the level of 10E9 to 10E11 atoms / cm². The concentration of Al, Fe, and Ti elements is high, which is related to the fact that some silicon wafer manufacturers use second-hand FOSB wafer boxes for shipment.

[0004] Currently, most wafer fabs have generally used second-hand wafer boxes for shipment. Second-hand wafer boxes come from various FAB factories. Since some second-hand wafer boxes have undergone certain metal-contaminated processes in the FAB factories, the metal level of the second-hand wafer boxes is poor, mainly concentrated in the Al and Fe elements relative to other elements.

[0005] The silicon wafer is placed in a used wafer box. The contact position between the silicon wafer and the wafer box is mainly concentrated at the edge of the silicon wafer. The metal cleanliness of the groove inside the used wafer box will be directly affected. The current wafer box cleaning machine mainly uses pure water as the cleaning agent, and uses spraying or ultrasonic immersion for cleaning. Since no chemical liquid is added, the cleaning effect on metal pollution is very limited. The grooves inside the wafer box are more likely to harbor dirt due to their dense structure, making it more difficult to remove metal pollution. Summary of the invention

[0006] The present invention mainly solves the deficiencies in the prior art and provides a method for improving the metal at the edge of a silicon wafer, which has the advantages of convenient operation and good improvement effect, and solves the problem that a wafer box cleaning machine cannot clean a used wafer box. By adding hydrochloric acid with a diluted concentration of 0.4% into the cleaning tank of the wafer box cleaning machine, the metal pollution of Al and Fe elements is effectively reduced, the metal level of the used wafer box is improved, and thus the metal level at the edge of the silicon wafer is improved.

[0007] The above technical problems of the present invention are mainly solved by the following technical solutions: A method for improving the edge metal of a silicon wafer comprises the following steps: Step 1: Spray the used film box with pure water for 5 minutes, with a pure water flow rate of 25Lpm.

[0008] Step 2: Add hydrochloric acid to the pure water immersion tank and soak the used film box for 30 minutes.

[0009] Step 3: Spray the used film box with pure water for 10 minutes, with a pure water flow rate of 40Lpm.

[0010] Step 4: The second-hand film box is spun and dried at a speed of 300 Rpm and a drying time of 10 minutes.

[0011] Step 5: Put the used film box into a closed oven for drying at a temperature of 62-65°C and a drying time of 30 minutes.

[0012] Step 6: Place clean silicon wafers in the cleaned and dried second-hand wafer box and check the metal level at the edge of the silicon wafers.

[0013] Preferably, the amount of hydrochloric acid added is 5 L, and the dilution concentration of the hydrochloric acid added is 0.4%.

[0014] Preferably, the used wafer box with silicon wafers is vacuum-packed with a layer of PO plastic bag on the outside and a layer of aluminum foil bag on the inside, placed in a high humidity and high temperature test box for deterioration test, and taken out after standing for 24 hours to detect the increase in particles on the surface of the silicon wafer.

[0015] PO plastic bags are moisture-proof, high temperature resistant, corrosion-resistant, and wear-resistant. They can effectively prevent the corrosion of filming materials and prevent contamination by ionizing radiation.

[0016] Preferably, water is injected into the cleaned recovery film box until the water level is above the handle, the box is tightly covered, shaken and left to stand for 3 hours, and then the metal content in the water is detected using a particle counter or ICP-MS.

[0017] The particle counter detects the number of 0.2um particles in each milliliter of water. The qualified standard is 0.2um≤150ea / ml, and the actual measured value is 30-40ea / ml. The metals detected by ICP-MS include Na, Mg, K, Ca, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Pb. The qualified standard is ≤100ppt, and the actual measured values ​​are all ≤10ppt.

[0018] Preferably, nitrogen is used for blowing while the used film box is being spin-dried.

[0019] Preferably, the nitrogen dust-proof drying time is 12 to 16 minutes, and the nitrogen flow rate is 55 to 66 LPM.

[0020] Preferably, the spin drying is performed with an interval of 2 minutes to alternate between left and right rotation directions.

[0021] Preferably, the concentration of surfactant TSC-1 added to the pure water immersion tank is about TSC-1:H2O=1:1100~1:1300.

[0022] Preferably, the water temperature for spraying the used film box with pure water is 30°C, and the water temperature for soaking in the pure water soaking tank is 45°C.

[0023] The present invention can achieve the following effects: The present invention provides a method for improving the metal at the edge of a silicon wafer. Compared with the prior art, the method has the advantages of convenient operation and good improvement effect, and solves the problem that a wafer box cleaning machine cannot clean a used wafer box. By adding hydrochloric acid with a diluted concentration of 0.4% into the cleaning tank of the wafer box cleaning machine, the metal pollution of Al and Fe elements is effectively reduced, the metal level of the used wafer box is improved, and thus the metal level of the silicon wafer edge is improved. DETAILED DESCRIPTION

[0024] The technical solution of the invention is further specifically described below through embodiments.

[0025] Embodiment 1: A method for improving the edge metal of a silicon wafer, comprising the following steps: Step 1: Spray the used film box with pure water for 5 minutes, with a pure water flow rate of 25Lpm. The water temperature for spraying the used film box with pure water is 30℃.

[0026] Step 2: Add hydrochloric acid in the pure water soaking tank, and soak the used film box for 30 minutes. The amount of hydrochloric acid added is 5L, and the dilution concentration of hydrochloric acid added is 0.4%. The water temperature for soaking in the pure water soaking tank is 45℃.

[0027] Step 3: Spray the used film box with pure water for 10 minutes, with a pure water flow rate of 40Lpm. The water temperature for spraying the used film box with pure water is 30℃.

[0028] Pour water into the cleaned recycling film box until the water level is above the handle, close the lid, shake it and let it stand for 3 hours, then use a particle counter to detect or use ICP-MS to detect the metal content in the water.

[0029] Step 4: The second-hand film box is spun and dried at a speed of 300 Rpm for 10 minutes. The rotation direction is alternately changed to the left and right every 2 minutes.

[0030] The used film box is spun and dried at the same time with nitrogen blowing. The nitrogen dust-proof drying time is 14 minutes, and the nitrogen flow rate is 62 LPM.

[0031] Step 5: Put the used film box into a closed oven for drying at a temperature of 64°C for 30 minutes.

[0032] Step 6: Put clean silicon wafers into the cleaned and dried second-hand wafer box and test the metal level at the edge of the silicon wafer. Use a layer of PO plastic bag on the outside and a layer of aluminum foil bag on the inside to vacuum pack the second-hand wafer box with silicon wafers, put it into a high humidity and high temperature test box for deterioration test, take it out after standing for 24 hours, and test the increase of particles on the surface of the silicon wafer.

[0033] Embodiment 1: A method for improving the edge metal of a silicon wafer, comprising the following steps: Step 1: Spray the used film box with pure water for 5 minutes, with a pure water flow rate of 25Lpm. The water temperature for spraying the used film box with pure water is 30℃.

[0034] Step 2: Add hydrochloric acid in the pure water soaking tank, and soak the used film box for 30 minutes. The amount of hydrochloric acid added is 5L, and the dilution concentration of hydrochloric acid added is 0.4%. The water temperature for soaking in the pure water soaking tank is 45℃.

[0035] The concentration of surfactant TSC-1 added to the pure water immersion tank is approximately TSC-1:H2O=1:1200.

[0036] Step 3: Spray the used film box with pure water for 10 minutes, with a pure water flow rate of 40Lpm. The water temperature for spraying the used film box with pure water is 30℃.

[0037] Pour water into the cleaned recycling film box until the water level is above the handle, close the lid, shake it and let it stand for 3 hours, then use a particle counter to detect or use ICP-MS to detect the metal content in the water.

[0038] Step 4: The second-hand film box is spun and dried at a speed of 300 Rpm for 10 minutes. The rotation direction is alternately changed to the left and right every 2 minutes.

[0039] The used film box is spun and dried at the same time with nitrogen blowing. The nitrogen dust-proof drying time is 14 minutes, and the nitrogen flow rate is 62 LPM.

[0040] Step 5: Put the used film box into a closed oven for drying at a temperature of 64°C for 30 minutes.

[0041] Step 6: Put clean silicon wafers into the cleaned and dried second-hand wafer box and test the metal level at the edge of the silicon wafer. Use a layer of PO plastic bag on the outside and a layer of aluminum foil bag on the inside to vacuum pack the second-hand wafer box with silicon wafers, put it into a high humidity and high temperature test box for deterioration test, take it out after standing for 24 hours, and test the increase of particles on the surface of the silicon wafer.

[0042] In summary, the method for improving the metal on the edge of silicon wafers has the advantages of convenient operation and good improvement effect, and solves the problem that the wafer box cleaning machine cannot clean the second-hand wafer box. By adding 0.4% diluted hydrochloric acid into the cleaning tank of the wafer box cleaning machine, the metal pollution of Al and Fe elements is effectively reduced, the metal level of the second-hand wafer box is improved, and thus the metal level of the silicon wafer edge is improved.

[0043] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A method for improving the edge metal of a silicon wafer, characterized in that The steps are as follows: Step 1: Spray the used film box with pure water for 5 minutes, with a pure water flow rate of 25Lpm; Step 2: Soak the used film box in hydrochloric acid in a pure water immersion tank for 30 minutes; Step 3: Spray the used film box with pure water for 10 minutes, with a pure water flow rate of 40Lpm; Step 4: The second-hand film box is spun and dried at a speed of 300 Rpm for 10 minutes; Step 5: Put the used film box into a closed oven for drying at a temperature of 62-65°C for 30 minutes; Step 6: Place clean silicon wafers in the cleaned and dried second-hand wafer box and check the metal level at the edge of the silicon wafers.

2. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: The amount of hydrochloric acid added is 5L, and the dilution concentration of the hydrochloric acid added is 0.4%.

3. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: The used wafer box with silicon wafers is vacuum-packed with a layer of PO plastic bag on the outside and a layer of aluminum foil bag on the inside, and placed in a high-humidity and high-temperature test box for deterioration testing. After standing for 24 hours, it is taken out and the increase in particles on the surface of the silicon wafer is detected.

4. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: Pour water into the cleaned recycling film box until the water level is above the handle, close the lid, shake it and let it stand for 3 hours, then use a particle counter to detect or use ICP-MS to detect the metal content in the water.

5. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: Nitrogen is used to blow air while the used film box is being spun and dried.

6. The method for improving the edge metal of a silicon wafer according to claim 4, characterized in that: The nitrogen dust-proof drying time is 12 to 16 minutes, and the nitrogen flow rate is 55 to 66 LPM.

7. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: Spin and dry alternately between left and right rotation directions every 2 minutes.

8. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: The concentration of surfactant TSC-1 added to the pure water immersion tank is approximately TSC-1:H2O=1:1100~1:1300.

9. The method for improving the edge metal of a silicon wafer according to claim 1, characterized in that: The water temperature for spraying the used film boxes with pure water is 30°C, and the water temperature for soaking in the pure water soaking tank is 45°C.