Ashing process using an atmospheric pressure, DBD-generated plasma

摘要

We present an atmospheric pressure plasma processing for ashing photo-resist (PR) layer in the flat panel display and semiconductor manufacturing. Removal of various PR materials on LCD process and IC chip process was investigated by making use of a dielectric barrier discharge (DBD) plasma device, which has a large number of gasflowing holes. The nitrogen DBD plasma was generated with a mixture of compressed dry air (CDA) and SF6. To prevent thermal shrinkage of PR layer, samples were maintained below the hard baking temperature. Uniformity and reproducibility have been tested as a function of treatment time. Eventually, we obtained the ash rate of about 600 nm/min for negative color filter PR, and 450 nm/min for KrF and I-line PR at the CDA concentration of 1%, SF6 concentration of 0.5%, and the carrier N2 gas flow rate 1500 liters per minute (lpm) when the applied power is about 8 kW. a-Si layer loss which strongly depends on the fluorine radicals was about 5nm/min in the given conditions which is an acceptable level in the process. Also, high-dose implanted PR stripping (HDIS) processing has been developed from the same plasma source. To avoid the popping (so called violent defects) of HDI wafer at high temperature, it is necessary to control the gas-exit temperature from plasma device. HDIS processing has been divided by 2steps. First step is heavily carbonized layer pretreatment at low temperature (105°C) and following virgin photoresist stripping step is a wellknown high speed ashing process. For the first step, reductive gas recipes were applied to volatilize Arsenic accumulated inner the crust layers. The next step is high temperature (300°C) process using fluorine free chemicals for no polysilicon loss. At optimized condition, DBD-generated plasma source can effectively remove HDI photo resist, showing chemically clean surface in the XPS data.