Ashing of Ion-Implanted Resist Layer

Abstract

The stripping method of high-dose ion-implanted resist layers was studied on the basis of the chemical structure of carbonized layers formed by ion implantation and that of residues remaining on the wafer surface after O2 plasma ashing. The chemical structure of the carbonized layer was observed with solid NMR and that of residues was analyzed with XPS. A decrease in the etching rate of the high-dose ion-implanted resist was caused by carbonization of polymers of the resist. Residues were mainly formed during O2 plasma ashing by chemical reaction between oxygen and implanted species, i.e., the main component of residues was oxide of the implanted species. On the basis of these results, to remove the high dose ion implanted resist without damage, we developed a two-step ashing process which was composed of H2 RIE and downstream ashing, and achieved the purpose.

Relationship between the Thermal Hardening of Ion-Implanted Resist and the Resist Removal Using Atomic Hydrogen

“…The resist-removal rate was obtained by dividing the resist film thickness by the resist removal time. The sample size was 1cm 2 . The hydrogen-nitrogen mixed gas (H 2 :N 2 =10:90vol%) inflow rate was 300sccm, the total pressure in the chamber was 21.3Pa (the hydrogen pressure in the chamber was 2.13Pa), the distance from the top of the catalyst to the substrate was 20mm, and the hot catalyst temperature was 1950°C.…”

Polyimides

“…The method is very much the same as using a mask, but higher degrees of accuracy are obtained as the photosensitive material's exposure and development are done with coherent short wavelength light. The combination of step reduction, increased accuracy, and less complexity while maintaining good dielectric, mechanical, and thermal properties have spurred the development of photosensitive polyimides (PSPIs) used with these photoimaging methods (206,207).…”

Removal of ion-implanted photoresists on GaAs using two organic solvents in sequence

“…It is known that photoresist components react with implanted cations to afford highly cross-linked polymers during the ion implantation process [12,13]. In addition, when the implantation dose is above 1 × 10 15 atoms/cm 2 , the cross-linked photoresist produces an amorphous carbonized crust and residue [12,14] that are not easily removed using conventional organic solvents [15,16]. Heavily implanted photoresists have been removed via dry plasma ashing with a subsequent wet chemical treatment at elevated temperatures [17,18].…”