Wet chemical cleaning for damaged layer removal inside the deep sub-micron contact hole

Wet chemical cleaning inside the deep sub-micron contact hole after reactive ion etching (RIE) and resist removal by O₂ plasma ashing was investigated systematically. By optimizing the composition of a cleaning solution, it was found that buffered hydrofluoric acid (BHF) which consists of both a low HF concentration (about 0.1 wt%) and the high NH₄F concentration (about 40 wt%) and also contains both surfactant (40-80 ppm) and hydrogen peroxide (~5 wt%) was the most effective for the cleaning process. It was found that this cleaning solution can simultaneously remove the sidewall protecting deposition films which adhere on the contact hole sidewall, and the damaged layer which is formed on the Si substrate surface during RIE, and the native oxide film which grows on the Si surface at the contact hole base during resist mask removal after RIE. Moreover, it was found that during cleaning, the enlargement of a 0.4 μm contact hole can be kept within 200 Å, and micro-roughness generation at the Si surface of the contact hole base can be prevented. It was confirmed that this cleaning solution is very effective for decreased contact resistance and increased yield in the semiconductor device manufacturing process