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How does chip photoresist require HMDS oven?

First: The necessity of HMDS pretreatment system: in semiconductor production process, lithography is an important process of integrated circuit graphics transfer. The quality of coating directly affects the quality of lithography, and the coating process is particularly important. most of the photoresist in the photoresist coating process is hydrophobic, while the hydroxyl groups and residual water molecules on the surface of the silicon wafer are hydrophilic, which results in poor adhesion between the photoresist and the silicon wafer, especially the positive adhesive. the developer will invade the junction of photoresist and silicon wafer when developing, easy to cause drift strip, float glue and so on, and lead to the failure of photoresist transfer. at the same time, wet corrosion is prone to lateral corrosion. Adhesive HMDS( hexamethylene disilazane) can improve this condition. After coating the HMDS on the surface of silicon wafer, the compounds with siloxane as the main body can be formed by oven heating. It successfully changed the surface of silicon wafer from hydrophilic to hydrophobic, and its hydrophobic base can be well combined with photoresist and play the role of coupling agent.

Second, the application field of HMDS pretreatment system: a layer of HMDS. is evenly coated on the surface of silicon wafer before leveling glue

Function: reduce the contact angle of silicon wafer after HMDS treatment, then reduce the difficulty of spreading the time glue on the surface of silicon wafer, improve the adhesion between photoresist and silicon wafer, and reduce the amount of photoresist.

Third: The principle of HMDS pretreatment system: the pretreatment system can evenly coat the surface of silicon wafer and substrate by parameters such as working temperature, processing time and holding time of oven HMDS pretreatment process HMDS, which reduces the contact angle of silicon wafer after treatment, reduces the amount of photoresist and improves the adhesion between photoresist and silicon wafer.

Forth, HMDS the general work flow of the pretreatment system :
1. First set the oven working temperature
2. Open the vacuum pump to pump the vacuum, after the vacuum in the cavity reaches a certain vacuum degree
3. Start filling in nitrogen, After a certain low vacuum is reached, the process of vacuuming and filling nitrogen is carried out again, After reaching the set number of times filled with nitrogen, So that the silicon wafer is fully heated, Reduce the moisture on the surface of the wafer
6. Then start vacuuming again
7. Heating the HMDS pipe
8. After filling the HMDS gas to the set time, Stop filling HMDS liquid
9. The three-sided heating box makes the temperature reach 150 degrees or so 10 degrees, Enable the wafer to react fully with the HMDS
11. When the set holding time is reached, Start vacuuming again
12. Fill in nitrogen, Complete the whole process

Remark: remove the moisture on the surface of the silicon wafer, Then HMDS OH reaction with the surface, On the surface of a silicon wafer, Eliminate hydrogen bonding, so that the polar surface becomes a nonpolar surface. entire reaction continued until steric hindrance (larger trimethylsilyl) prevented its further reaction v. tail gas emissions etc.: excess HMDS steam (tail gas) will be pumped out by a vacuum pump, Discharge into special exhaust gas collection pipeline. Special treatment is required when there is no special exhaust gas collection pipeline.
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