Ion-implanted photoresist removal using water/carbon dioxide mixtures at elevated temperature and pressure

The ability of water and water/1% carbon dioxide mixtures to remove ion-implanted photoresist from silicon substrates was investigated. Photoresist with implant levels up to 2×1015/cm2 of boron and phosphorus were stripped effectively at a temperature of 165 °C and a pressure of 58.6 bar (850 psi) by both water and water/carbon dioxide. Removal of photoresist at low implant levels (2×1012/cm2) proceeded rapidly, while samples at higher dose levels (>2×1015/cm2) had a thin carbonized layer at the photoresist surface that inhibited the removal rate. Removal of this carbonized layer required approximately 2 min for water/carbon dioxide and approximately 8 min for water, while complete removal of the remaining photoresist film took less than 30 min for both fluids. Patterned, arsenic-implanted (1×1016/cm2) photoresist layers were removed by water/carbon dioxide at 200 °C, 850 psi, 3 ml/min flow rate, and 30 min exposure. Under all conditions investigated, water/carbon dioxide proved more effective than pure w...