A NEW TECHNIQUE TO STRENGTHEN SILICON MICROMACHINED PRESSURE SENSOR
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2002-Apr-01
In a piezoresistive pressure sensor, a deep cavity is etched using chemicals such as NaOH or KOH to product a thin diaphragm. These chemicals etch along well-defined crystal planes, creating sharp cor- ners inside the cavity. These corners result in a stress concentration which reduces the strength of the struc- ture and limits over-pressure capability especially for back/cavity-side pressure applications. In the past, an additional isotropic wet etch (HNOs, HF and acetic acid) was used to round these corners to increase burst pressure strength. In this paper we present a dry etch method and compare it to the conventional wet etch method for increasing device strength. We will also discuss a variation ofthis dry etch technique as applied to direct wafer bonded wafers.