| 摘要 |
PURPOSE:To form a semiconductor pressure transducer having a strain-generating part with a uniform plate pressure, a dispersion-free pressure sensitivity and well-uniformized characteristics by a method wherein an insulating film, which has its peripheral part formed thicker than its central part and an etching rate according to an etching liquid smaller than that of a substrate, is adhered on a region of the substrate surface where no mask is adhered. CONSTITUTION:A low-impurity concentration layer 2 is epitaxially grown on one surface of a high-concentration single crystal Si substrate 1 by the amount of the thickness of a strain-generating part, which is finally needed, strain gages 3 which each consist of different conductive type layers are formed in this layer and an oxide film 4 having an electrical insulation property is provided on the other surface of the substrate. Moreover, an Au metal film 5 containing Ni or Cr is adhered thereon, the central part of this film is removed by the amount of the diameter-D region of a recessed part to be formed and the oxide film under the lower side of the region is also removed by 1/4 or more of the D. When the Si substrate 1 of such a construction is dipped in an etching liquid 6 in the mixing ratio: 1:9 of hydrofluoric acid to pure water and is electrochemically etched by impressing a D/C voltage between a platinum cathode 7 and the substrate, the etching liquid reaches a concentration boundary surface 11 in the central part ahead of the etching liquid in the peripheral part and finally, the etching liquid in the peripheral part also reaches the concentration boundary surface 11 to end the formation of the recessed part 12. As the etching rate of the low-impurity concentration layer 2 is a sufficient smaller one of about 1/100 or thereabouts compared to that of the high-concentration Si substrate 1, a flat bottom surface 13 is produced.
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