Process for forming a buried cavity in a semiconductor material wafer and a buried cavity

• US 6,992,367 B2
• Filed: 11/12/2003
• Issued: 01/31/2006
• Est. Priority Date: 02/29/2000
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Villa, Flavio, Corona, Pietro, Barlocchi, Gabriele, Sacchi, Enrico, Erratico, Pietro
• Primary Examiner(s): Wilson, Allan R.
• Application Number:
  US10/712,211
• Publication Number:
  US 20040106290A1
• Time in Patent Office: 811 Days
• Field of Search: 257/528, 257531-532, 257534-536
• US Class Current: 257/531
• CPC Class Codes: B81C 1/00404 Mask characterised by its size, orientation or shape

Abstract

The process comprises the steps of forming, on top of a semiconductor material wafer, a holed mask having a lattice structure and comprising a plurality of openings each having a substantially square shape and a side with an inclination of 45° with respect to the flat of the wafer; carrying out an anisotropic etch in TMAH of the wafer, using said holed mask, thus forming a cavity, the cross section of which has the shape of an upside-down isosceles trapezium; and carrying out a chemical vapor deposition using TEOS, thus forming a TEOS layer which completely closes the openings of the holed mask and defines a diaphragm overlying the cavity and on which a suspended integrated structure can subsequently be manufactured.

Claims

1. A structure comprising:

a buried cavity in a semiconductor material body having a shape, in cross section, in which a top wall, including a lattice having a first and a second layer, is approximately parallel with a horizontal plane of the semiconductor material body, side walls slope inward from the top wall to a bottom wall, and the bottom wall is approximately parallel with the top wall, and wherein said lattice has a plurality of interstitial openings filled with polycrystalline silicon.

2. The structure according to claim 1, wherein said first layer comprises silicon-dioxide, and said second layer comprises silicon-nitride.

3. The structure according to claim 1, wherein said top wall of said buried cavity further comprises a grown layer, and wherein communication openings extend through said grown layer and said lattice layer to said buried cavity.

4. The structure according to claim 1, wherein each of said plurality of interstitial openings has a square shape, as viewed from above the horizontal plane of the semiconductor material body.

5. The structure according to claim 1, wherein each of said plurality of interstitial openings has a rectangular shape, as viewed from above the horizontal plane of the semiconductor material body.

6. The structure according to claim 1, wherein said lattice is oriented to an angle of between 44°

and 46°

with respect to a flat of said semiconductor material body.

7. The structure according to claim 1, wherein said lattice is oriented to an angle of between 30°

and 60°

with respect to a particular crystallographic plane of said semiconductor material body.

8. A structure, comprising:

a semiconductor material body;

a cavity formed within the body, the cavity having a substantially planar lower surface lying in a plane that is approximately parallel to a plane of an upper surface of the body;

a cover over the cavity comprising a polycrystalline-silicon coating layer formed on the upper surface of the body; and

a communication opening extending in the cover as far as the cavity.

9. The structure of claim 8 wherein the cover further comprises a lattice layer formed on the upper surface of the body.

10. The structure of claim 8, further comprising a layer grown on the polycrystalline-silicon layer.

11. A structure, comprising:

a semiconductor material body;

a cavity formed within the body;

a cover over the cavity comprising a lattice layer having a plurality of openings, formed on an upper surface of the body, and a polycrystalline-silicon coating layer formed on the lattice layer, the coating layer closing the plurality of openings; and

a communication opening extending through the coating layer in the cover as far as the cavity.

12. The structure of claim 11, further comprising a layer grown on the polycrystalline-silicon layer.