A new lift-off metallization technique for high speed bipolar LSI´s

A new lift-off technique, employing PIQ^®as the lift-off layer with an Mo mask and reactive RF sputter etching for patterning, is developed to provide two level, highly packed interconnection metallization. The minimum pitches of the first and second level metallization and via-holes are 5, 7 and 7 µm, respectively. The technique has the following advantages: (1) Fine patterns are obtained since the metallization layer is deposited through sharply edged reverse masks accurately formed by sputter etching the PIQ layer. (2) PIQ withstands the high temperatures up to about 350 °C required for the metallization layer deposition. (3) The lift-off layer can be removed in much less time than with usual methods because Mo electrolysis is used. (4) The via-hole pitch is reduced to 7 µm, by the adoption of the lift-off step for the second level.