Semiconductor structure having a monocrystalline member overlying a cavity in a semiconductor substrate and process therefor

• US 6,013,933 A
• Filed: 05/30/1997
• Issued: 01/11/2000
• Est. Priority Date: 05/30/1997
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Mirza, Amir Raza, Foerstner, Juergen August, Hughes, Henry Guenther
• Primary Examiner(s): Meier, Stephen D.
• Application Number:
  US08/866,588
• Time in Patent Office: 956 Days
• Field of Search: 257/415, 257/417
• US Class Current: 257/415
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A process for forming a sensor (10) such as an accelerometer includes the steps of forming an epitaxial layer (14) on a semiconductor substrate (12), patterning a portion of the epitaxial layer to provide a monocrystalline finger (20,22), wherein the finger has a height (43) at least twice its width (44), and forming a cavity (40) under at least a portion of the finger to expose a bottom surface (38) of the finger using an etchant with an etch selectivity for the semiconductor substrate relative to the epitaxial layer of greater than about 10:1. The distance (42) from the bottom of the cavity to the bottom surface of the member is greater than about 5 microns. The accelerometer is useful for lateral acceleration sensing and is built in bulk silicon at the surface of the substrate.

Claims

1. A monolithic semiconductor sensor structure comprising:

a semiconductor layer overlying a semiconductor substrate, wherein a portion of said semiconductor layer provides a monocrystalline member and another portion of said semiconductor layer extends from and cooperates with a portion of the semiconductor substrate so that the lattice structure of the semiconductor layer matches the lattice structure of the semiconductor substrate; and

a cavity disposed under at least a portion of said member that exposes a bottom surface of said member, wherein said cavity has a cavity surface and a distance from said bottom surface to said cavity surface is greater than about 5 microns.

2. The semiconductor structure of claim 1 wherein said member has a height and a width and said height is at least twice said width.

3. The semiconductor structure of claim 1 wherein said semiconductor layer has an opposite conductivity type from said semiconductor substrate.

4. The semiconductor structure of claim 1 wherein said structure is an accelerometer.

5. The semiconductor structure of claim 1 wherein said structure is a chemical sensor.