Laser-Assisted InP Via Etching For Microwave Device and Circuit Applications

There is a widespread interest in developing improved via hole etching techniques due to the importance of vias, especially in the fabrication of relatively high density MMIC's (Monolithic Microwave Integrated Circuits) and millimeter-wave circuits. Conventional dry etching techniques are not suitable in this application because of their extremely low etch rates in In-based compounds. Current technology uses a process for etching vias in GaAs microwave device structures based on a chemical etching technique' which produces low aspect ratio vias, malung it difficult to achieve the close spacing required by microwave circuits. High aspect ratio vias have been previously achieved using laser assisted photoelectrochemical etching-', however, the etch rates were very slow, rendering the process industrially impractical. To date there has not been any information on an industrially viable via etching technique for microwave and millimeter-wave applications.