Thermally Activated Gas-Phase Chemical Reactions in a Single-Wafer Wet Clean Process

Abstract

We investigate an alternative approach to conventional high dose ion-implanted photoresist strip and clean that replaces a remote plasma strip with a thermally activated, atmospheric gas-phase oxidation process and replaces sulfuric-peroxide mixture (SPM) chemistry with a de-ionized water/ozone (DIO3) chemistry. The gas phase oxidation process is first characterized in a mini-test chamber. Then the alternative dry and wet clean sequence is entirely processed in a modified single-wafer wet clean chamber. The atmospheric dry O3/O2 gas mixture decomposes and reacts with the ion-implanted photoresist wafer that is heated above 300 °C from the backside. 9,000 Å/min and 600 Å/min removal rates are measured on 193 nm photoresist and high dose implanted crust, respectively. Silicon reactivity from ellipsometry measurements is lower than a typical remote oxygen plasma based on ~1 Å silicon loss. The integrated process completely removes 5E15-1E16 at/cm2 high dose implanted 193 nm photoresist with no residue remaining on patterned substrates.