Masahiro Ogasawara

Influence of Gas Chemistry and Ion Energy on Contact Resistance

Reactive ion etching (RIE) damage in contact hole etching is studied. The significant oxidation retardation layer (ORL) on Si surfaces is observed followed by high V pp (peak-to-peak voltage of 380 kHz RF) RIE. The depth of the ORL is linearly proportional to V pp, and it consists of a Si–C bond layer, according to X-ray photoelectron spectroscopy (XPS) analysis. The increase in contact resistance is found to be due to the existence of the ORL, using the sacrificial oxidation method and secondary ion mass spectroscopy (SIMS) analysis. The etch chemistries based on fluorocarbon-containing gas mixtures are characterized in terms of contact resistance and ORL. When hydride-containing gas mixtures are used in RIE, the contact resistance is low and the ORL depth is small. When CO-containing gas mixtures are used, the contact resistance is high and ORL depth is large. These different properties result from the different amounts of carbon implanted at the silicon surface.