Dry etching of through substrate via holes for GaAs MMIC’s

Through substrate via’s are essential in many GaAs monolithic microwave integrated circuits (MMIC’s). They allow for increased circuit complexity and provide low inductance grounding. A dry etch process is described which has been used for etching vias through 0.2 mm thick GaAs substrates. Freon 12 (CCl2F2) is used at high pressure in a RIE mode at 13.6 MHz. Polymer formation has been identified to be the key to controlling the hole profile.