Durable ultraviolet sensors using highly oriented diamond films

We fabricated vacuum ultraviolet (VUV) sensors using highly oriented diamond (HOD) films and studied their long-term stability to evaluate the feasibility of the sensors for practical use. The sensors are composed of a pair of interdigitated Pt electrodes on the HOD film surfaces, and sealed in the industrially standard can packages. Xenon (Xe) excimer lamps (λ = 172 nm) and low-pressure mercury (Hg) lamps (λ = 185 nm) were used as the radiation sources. It was demonstrated that the output signal of the sensors is reproducible and stable over 700 h under the intense VUV irradiation from Xe excimer lamps. The results of low-pressure Hg lamp measurements showed that the sensors were sensitive only to the 185-nm radiation irrespective of the presence of the 254-nm radiation that is five to ten times more intense than the 185-nm radiation. It is thus concluded that the present HOD film sensors make possible a continuous monitoring of the intense VUV radiation sources, and can be applicable to dry cleaning of silicon wafers or glass substrates in semiconductor industry and flat panel display manufacturing processes, respectively.