Method of Forming a Micromachined Device Using an Assisted Release

Abstract

A method of forming a micromachined device embeds a first material within a sacrificial material, and then removes such first material to form a channel through the sacrificial material. The method then directs a sacrificial material removal fluid through the channel. The sacrificial material removal fluid removes at least a portion of the sacrificial material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing advantages of the invention will be appreciated more fully from the following further description thereof with reference to the accompanying drawings. Those drawings are as described below.

FIG. 1 schematically shows a cross-sectional view of a MEMS device formed by illustrative embodiments of the invention. This view also corresponds to step 206 of the method of FIG. 2.

FIG. 2 shows a process of forming the MEMS device of FIG. 1 in accordance with illustrative embodiments.

FIG. 3 schematically shows a cross-sectional view of the MEMS device during fabrication corresponding to method step 200.

FIG. 4 schematically shows a cross-sectional view of the MEMS device during fabrication corresponding to method step 202.

FIG. 5 schematically shows a cross-sectional view of the MEMS device during fabrication corresponding to method step 204.

Claims

1. A method of forming an inertial sensor, the method comprising: forming a sacrificial layer above a substrate, the sacrificial layer having a first material and a second material;forming a mass after forming a sacrificial layer, at least a portion of the sacrificial layer being between the mass and the substrate;removing the first material from the sacrificial layer to produce a channel within the sacrificial layer, at least a portion of the channel being between the substrate and the mass; anddirecting a second material removal fluid through the channel to remove at least a portion of the second material, directing releasing the mass.

2. The method as defined by claim 1 wherein the second material at least partially encapsulates the first material.

3. The method as defined by claim 1 wherein the second material removal fluid does not pass through the movable member.

4. The method as defined by claim 1 further comprising forming a flow path to the first material, removing comprising directing a first material removal fluid through the flow path to the first material.

5. The method as defined by claim 4 wherein directing a second material removal fluid through the channel comprises directing the second material removal fluid through the flow path and the channel.

6. The method as defined by claim 1 wherein the first material comprises polysilicon and the second material comprises an oxide.

7. The method as defined by claim 1 wherein the mass is substantially free of holes therethrough.

8. A method of forming a micromachined device, the method comprising: embedding a first material within a sacrificial material;removing at least a portion of the first material to form a channel through the sacrificial material; anddirecting a sacrificial material removal fluid through the channel, the sacrificial material removal fluid removing at least a portion of the sacrificial material.

9. The method as defined by claim 8 further comprising: forming a movable element that is supported by the sacrificial material, the movable element being released when at least a portion of the sacrificial material is removed.

10. The method as defined by claim 9 wherein the sacrificial material removal fluid does not pass through the movable element.

11. The method as defined by claim 8 further comprising forming a flow path to the first material, removing comprising directing a first material removal fluid through the flow path to the first material.

12. The method as defined by claim 11 wherein directing a sacrificial material removal fluid through the channel comprises directing the sacrificial material removal fluid through the flow path and the channel.

13. The method as defined by claim 11 wherein the first material comprises polysilicon and the first material removal fluid comprises xenon difluoride.

14. The method as defined by claim 8 wherein the sacrificial material comprises an oxide, and the sacrificial material removing fluid comprises an oxide etchant.

15. The method as defined by claim 8 wherein the micromachined device includes an inertial sensor.

16. A method of forming a MEMS inertial sensor, the method comprising: providing a substrate that supports a sacrificial layer;forming a mass wherein the sacrificial layer is positioned between the mass and the substrate;forming a channel through at least a portion of the sacrificial layer, at least a portion of the channel being between the mass and the substrate; andafter forming the channel, releasing the mass.

17. The method as defined by claim 16 wherein forming a channel comprises: forming the sacrificial layer with a first material and a second material;removing the first material from the sacrificial layer to produce the channel.

18. The method as defined by claim 17 wherein releasing the mass comprises directing a second material removal fluid through the channel to remove at least a portion of the second material.

19. The method as defined by claim 16 wherein the substrate is part of a SOI wafer.

20. The method as defined by claim 16 wherein the inertial sensor is one of an accelerometer or a gyroscope.