Simultaneous formation of via hole and tube structures for GaAs monolithic microwave integrated circuits

摘要

A method of simultaneously forming recesses for via holes and tube structures in a substrate is provided in a common etching step by defining a mask pattern for the via hole as a single aperture and by defining a mask pattern for the tub structure as a plurality of thin slots. The slots are chosen to have a smaller cross-sectional dimension than the corresponding dimension for the single aperture. Etchant brought into contact with the substrate will etch the substrate at a slower rate in the slots than in the single aperture such that the via hole will etch completely through the substrate whereas, the tub structure will be etched only partially through the substrate. Conductive material is provided in the tub structure and via hole, and a layer of conductive material is disposed thereover, to provide a heat sink/ground plane conductor. Electrical contact is provided between the frontside of the substrate and the heat sink/ground plane conductor through the via hole, whereas a low thermal impedance path is provided through the tub structure between a heat dissipating element supported on the frontside of the substrate and the heat sink/ground plane conductor.