| 摘要 |
PURPOSE:To form a strain-generating part with a uniform thickness of a pressure transducer by a method wherein a mask having a resistance to a long-time etching is used and a recessed part up to a P-N junction surface is formed by utilizing an effect that the electrochemical etching on the P-N junction to be inversely biased by an applied voltage stops. CONSTITUTION:A boron-doped P-type low-impurity concentration layer 3 is epitaxially grown on one surface of an n<+> high-concentration single crystal Si substrate 1, moreover a phosphorus-doped n-type low-impurity concentration layer 4 is epitaxially grown thereon and strain gages 2 consisting of a P-type layer are formed in this layer. An insulating oxide film 5 is provided on the peripheral part of the surface of the substrate 1 on the opposite side to these strain gages 2 and the upper part of that is coated with a corrosion-resistant metal film 6 like a metal film containing Ni or Cr to use a mask. The substrate coated with such a mask is put in an etching liquid (hydrofluoric liquid) 7 in the mixing rate=1:9 of hydrofluoric acid to pure water, a platinum cathode 8 is arranged opposing to the substrate surface adhered with the mask, a several-V D/C voltage set the substrate on the positive side is impressed between the substrate 1 and the cathode 8, with the substrate made positive, by means of a power source 9 to etch the substrate electrochemically, and an etching part 12 shown by dotted oblique lines is removed. Thereby, a substrate for a pressure transducer having a strain-generating part 11 can be obtained.
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