Process for manufacturing a micro-electro-mechanical device, and mems device

Patent metadata

Field	Value
Publication number	US-2021363000-A1
Application number	US-202117320993-A
Country	US
Kind code	A1
Filing date	May 14, 2021
Priority date	May 20, 2020
Publication date	Nov 25, 2021
Grant date	—

Abstract

A process for manufacturing a MEMS device includes forming a first structural layer of a first thickness on a substrate. First trenches are formed through the first structural layer, and masking regions separated by first openings are formed on the first structural layer. A second structural layer of a second thickness is formed on the first structural layer in direct contact with the first structural layer at the first openings and forms, together with the first structural layer, thick structural regions having a third thickness equal to the sum of the first and the second thicknesses. A plurality of second trenches are formed through the second structural layer, over the masking regions, and third trenches are formed through the first and the second structural layers by removing selective portions of the thick structural regions.

First claim

1 . A process for manufacturing a MEMS device, comprising:
forming a first structural layer of semiconductor material on a substrate, the first structural layer having a first thickness; forming a plurality of first trenches extending through the first structural layer and defining first functional elements; forming masking regions on the first structural layer, the masking regions being separated from each other by first openings; forming a second structural layer of semiconductor material on the first structural layer and on the masking regions, the second structural layer having a second thickness, being in direct contact with the first structural layer at the first openings and forming, together with the first structural layer, thick structural regions of the semiconductor material having a third thickness equal to the sum of the first and the second thicknesses; forming a plurality of second trenches extending through the second structural layer, over the masking regions; and forming a plurality of third trenches extending through the first and the second structural layers by removing selective portions of the thick structural regions.

2 . The process according to claim 1 , wherein the second trenches delimit first functional regions having the second thickness, and the third trenches delimit second functional regions having the third thickness, the process further comprising:
removing selective portions of the second structural layer to form cavities over the masking regions while forming third trenches, forming third regions having the first thickness.

3 . The process according to claim 1 , wherein forming the second trenches and forming the third trenches includes forming the second and third trenches using a single etching mask.

4 . The process according to claim 1 , wherein forming the second trenches and forming the third trenches includes forming the second and third trenches using two distinct etching masks.

5 . The process according to claim 1 , wherein the third trenches have a greater width than the second trenches.

6 . The process according to claim 1 , wherein forming masking regions includes forming a masking sacrificial layer and patterning the masking sacrificial layer.

7 . The process according to claim 1 , further comprising removing the masking regions and forming first gap zones between the first and the second structural layers.

8 . The process according to claim 7 , comprising:
forming a sacrificial anchoring layer over the substrate prior to forming the first structural layer, the sacrificial anchoring layer having anchoring openings; and removing the masking regions, the removing the masking regions including removing the sacrificial anchoring layer and forming second gap zones between the first structural layer and the substrate.

9 . The process according to claim 1 , comprising forming a vertical stop structure including forming a bottom abutment region in the first structural layer and forming an upper abutment region in the second structural layer, the bottom abutment region having the first thickness and being delimited, at least partially, by a first trench belonging to the plurality of first trenches or by a lower portion of an abutment trench belonging to the plurality of third trenches and the upper abutment region overlying the bottom abutment region, and being separated from the bottom abutment region by a first gap zone of the plurality of first gap zones.

10 . The process according to claim 9 , wherein the upper abutment region is delimited by a second trench belonging to the plurality of second trenches or by an upper part of the abutment trench.

11 . The process according to claim 1 , wherein forming a plurality of first trenches includes defining first functional elements and forming a plurality of second trenches includes defining second functional elements.

12 . A MEMS device, comprising:
a substrate; a first structural layer having a first thickness and extending on the substrate; a second structural layer having a second thickness and extending on the first structural layer; a plurality of first trenches extending through the first structural layer and defining first functional elements; a plurality of second trenches extending through the second structural layer and defining second functional elements overlying the first functional elements; and a plurality of third trenches extending through the first and the second structural layers, wherein the first and the second structural layers form a supporting structure, having a third thickness equal to the sum of the first and the second thicknesses, anchored to the substrate and supporting the first and the second functional elements, and wherein a first gap zone extends between the first and the second functional elements and surrounds the supporting structure.

13 . The MEMS device according to claim 12 , further comprising:
a vertical stop structure including a bottom abutment region and an upper abutment region overlying the bottom abutment region, wherein the bottom abutment region extends in the first structural layer, having the first thickness and being delimited, at least partially, by a first trench belonging to the plurality of first trenches or by a lower portion of an abutment trench belonging to the plurality of third trenches, and wherein the upper abutment region extends in the second structural layer, having the second thickness, and separated from the bottom abutment region by an abutment gap area.

14 . The MEMS device according to claim 13 , wherein the upper abutment region is delimited by a second trench belonging to the plurality of second trenches or by an upper part of the abutment trench.

15 . The MEMS device according to claim 12 , further comprising:
first functional regions having the second thickness and delimited by the second or the third trenches; second functional regions having the third thickness and delimited by the third trenches; and third functional regions having the first thickness and delimited by the first trenches or by lower portions of the third trenches.

16 . The MEMS device according to claim 12 , wherein the second functional elements have a width that is greater than a width of the first functional elements.

17 . A method, comprising:
forming a plurality of first trenches extending through a first semiconductor layer and defining first functional elements, the first semiconductor layer having a first thickness; forming masking regions on the first semiconductor layer, the masking regions being separated from each other by openings; forming a second semiconductor layer on the first semiconductor layer and on the masking regions, the second semiconductor layer directly contacting the first semiconductor layer at the openings; forming a plurality of second trenches extending through the second semiconductor layer and at least partially exposing portions of the masking regions; forming a cavity and a plurality of third trenches by selectively removing portions of the second semiconductor layer, the cavity overlying at least one of the masking regions, the plurality of third trenches extending from the cavity through the second semiconductor layer.

18 . The method according to claim 17 , wherein forming the second trenches and forming the third trenches includes forming the second and third trenches using a single etching mask.

19 . The method according to claim 17 , wherein forming the second trenches and forming the third trenches includes fo

Assignees

• St Microelectronics Srl

Inventors

• Allegato Giorgio
• Corso Lorenzo
• Gelmi Ilaria
• Valzasina Carlo

Classifications

• B81B2201/0235

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• B81C1/00015 Primary

  for manufacturing microsystems · CPC title

• B81B2201/0242

  Gyroscopes · CPC title

• B81C2201/00

  Manufacture or treatment of microstructural devices or systems · CPC title

• B81B2201/02

  Sensors · CPC title