ファインセラミッグスのフォトエッチングのための高温リン酸エッチャントの組成制御

抄録

The controllability of the composition of open-beaker phosphoric acids was studied at temperatures in a range from 200 to 300°C. The composition of phosphoric acid and alumina etch rates was measured under the following conditions; (1) water addition, (2) mixed solution with sulphuric acid, and (3) subboiling condensed phosphoric acid (CPA). Adding water to boiling phosphoric acid and thus keeping the acid at the constant boiling point provided a constant acid composition because further dehydration and condensation were avoided. Mixing phosphoric acid with H₂SO₄ up to about 50vol% has the same effect when water is added. A constant acid composition produces constant etch rates throughout the entire etching period. This enables the estimation of the depths of etch and the amounts of side etching. This, in turn, provides good etching accuracy. The CPA shows further condensation and composition change due to heating even though the acid is kept at temperatures below the boiling point.