Semiconductor device having beam structure

Abstract

Abstract PURPOSE:To set the resonant frequency of a beam with the same accuracy by forming a plurality of beams of the same length on a semiconductor substrate and then changing the thickness. CONSTITUTION:P<+> layers 2-4 and an n<+> layer 5 are provided on the n type Si substrate, and gate oxide films 22 are formed by selectively opening windows 20 and 21 through an SiO2. Next, an Si3N4 is provided at a beam forming part, a PSG island is formed, a doped poly Si 11 is superposed, and further an Si3N4 mask 15 is applied. An SiO2 16 of a thickness of a high accuracy is provided by oxidation by controlling the temperature and the time. The mask 15 and the film 16 are removed. The thickness of a cantilever beam is changed by repeating the above processes. Then, an Al wiring 9 is provided and covered with a PSG, and an Si mask 19 is applied. The PSG's above and below the cantilever beam 12 of a oscillation frequency detection part 18 are removed by etching, and finally the Si 19 is removed by dry etching with CF4+O2. The resonant frequency of the cantilever beam is proportional to a thickness t/ a length l<2>, but in the case of a short beam, relative dimensional accuracy is poor, and resonant frequency accuracy is also unsatisfactory. However it is easy to keep thickness constant, and accordingly higher and lower resonant frequencies can be set with the same accuracy by changing the thickness.

Inventors

• 👤 Takeshi Oguro
• 👤 大黒　健
• 👤 Toshiaki Shinohara
• 👤 俊朗 篠原

Bibliographic Details