Selective Removal of Small Particles by Wet Cleaning Without Pattern Damage

摘要

The drastic shrinking of semiconductor linewidths has led to a need for new wafer cleaning strategies in the FEOL. For past technology generations, particle removal has been accomplished typically using the SC1 (NH_4OH/H_2O_2/H_2O) solution in conjunction with megasonic energy in a wet bench, or by DI water with a high pressure jet or megasonic nozzle in a wafer scrubber. However, such techniques have been found to damage patterns, particularly narrow polysilicon gate lines. Furthermore, the etching of oxide associated with SC1, which facilitates particle removal by an undercutting mechanism, has recently become a concern due to increasingly strict oxide budgets. An alternative technique using an atomized liquid spray nozzle on a single wafer platform is proposed. Small droplets are able to effect particle removal without damage to sensitive patterns, by control of their carrier gas (N2) flow rate. Mechanisms for particle removal will be discussed. Results using this technique show particle removal comparable to megasonics can be achieved. Furthermore, 90nm and 65nm polysilicon gate structures were processed with high particle removal efficiency and no damage, as were Aluminum lines. Effects of the N_2 flow rate on particle removal and damage performance will be presented. The physical mechanism of atomized spray enables chemical etching of oxides to be minimized without sacrificing particle removal efficiency. Results using this technique in conjunction with chemistry, to further improve particle removal, will be presented. Results over a large range of particle sizes will be shown. Specific applications will be discussed.