Self-assembled-monolayer film islands as a self-patterned-mask for SiO₂ thickness measurement with atomic force microscopy

A novel method for measuring ultrathin (2-12 nm) SiO₂ film thickness is discussed. The process consists of: (1) formation of octadecyltrichlorosilane (OTS) self-assembled-monolayer (SAM) islands on SiO₂ of which thickness to be measured, (2) removal of the SiO₂ layers not covered by the OTS-SAM islands, and (3) measurement of the height difference between the etched and nonetched areas by atomic-force-microscopy. The OTS film is good resist against HF and its islands can be regarded as self-patterned-mask. Practical usefulness is demonstrated not only by the compatibility of the measured values but also by the short measurement period resulting from the -~-directness of the method.