Z-axis angular rate micro electro-mechanical systems (MEMS) sensor

• US 20050066728A1
• Filed: 07/15/2004
• Published: 03/31/2005
• Est. Priority Date: 09/25/2003
• Status: Abandoned Application

• Current Assignee: Kionix Incorporated (ROHM Co., Ltd.)
• Original Assignee: Kionix Incorporated (ROHM Co., Ltd.)
• Inventors: Nenadic, Nenad, Chojnacki, Eric P., Stirling, Nathan L., Nistor, Vasile, Shen-Epstein, June P.
• Application Number:
  US10/891,755
• Publication Number:
  US 20050066728A1
• Time in Patent Office: Days
• US Class Current: 73/514.160
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

An oscillatory angular rate MEMS sensor is described for sensing rotation about the “Z-axis”. Embodiments are either coupled-mass tuning-fork or single oscillating-mass in nature. The sensor includes mechanical and electrical function integration, and is preferably manufactured by a unique MEMS fabrication process.

Claims

1. A sensor, having orthogonal x-, y-, and z-axes, for detecting a rate of rotation about the z-axis comprising:

a substrate; and

a gross mass, symmetrical with respect to the x-axis and the y-axis, suspended from the substrate by a plurality of exterior anchor points, and comprising;

at least one proof mass, symmetrical with respect to the x-axis and the y-axis;

a driven frame surrounding each proof mass and attached to its proof mass and external anchor points by a plurality of flexures;

a set of drive banks and a first set of sense banks for each driven frame for oscillating along the x-axis;

a second set of sense banks attached to each proof mass for detecting Coriolis motion along the y-axis; and

a plurality of electrode routing configurations connected to the set of drive banks and the first and second sets of sense banks;

wherein at least part of the sensor is made by a trench isolation process comprising the steps of;

a) providing a material;

b) patterning the material with a first dielectric layer;

c) etching the material to produce at least one isolation trench;

d) filling the isolation trench with a second dielectric layer;

e) planarizing the first and second dielectric layers;

f) patterning and etching a via to expose the substrate for an electrical connection;

g) depositing a metal layer into the via and onto the dielectric layers;

h) patterning the metal layer to create the plurality of electrode routing configurations; and

i) patterning, etching, passivating, and releasing a plurality of structural elements including the proof mass, each driven frame, and the flexures.

2. The sensor of claim 1, wherein the gross mass comprises one proof mass.

3. The sensor of claim 1, wherein the gross mass further comprises two proof masses, two driven frames, and a coupling spring between the two driven frames to allow frame motion predominantly along the x-axis in anti-phase motion such that Coriolis-induced anti-phase motion of the proof masses along the y-axis results.

4. The sensor of claim 1, wherein the metal layer comprises aluminum.

5. The sensor of claim 1, wherein at least one driven frame comprises at least one electrical crossover element and at least one electrical isolation segment.

6. The sensor of claim 1, wherein each drive bank and each sensor bank is a capacitive comb.

7. The sensor of claim 1 further comprising a plurality of external bond pads electrically connected to the sensor by a plurality of current paths, wherein the current paths cross at a plurality of crossover points.

8. The sensor of claim 7, wherein at least one crossover point is made by the trench isolation process.

9. The sensor of claim 1, wherein the material is selected from the group consisting of:

a) a single crystal silicon wafer;

b) a silicon on insulator wafer;

c) a polysilicon wafer; and

d) an epitaxial wafer.