Integrated differential pressure sensor and manufacturing process thereof

• US 20060260408A1
• Filed: 05/04/2006
• Published: 11/23/2006
• Est. Priority Date: 05/06/2005
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Corona, Pietro, Barlocchi, Gabriele, Villa, Flavio Francesco, Baldo, Lorenzo
• Granted Patent: US 7,763,487 B2
• Time in Patent Office: Days
• US Class Current: 73/715
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0045 Diaphragm associated with a buried cavity

Abstract

A process for manufacturing an integrated differential pressure sensor includes forming, in a monolithic body of semiconductor material having a first face and a second face, a cavity extending at a distance from the first face and delimiting therewith a flexible membrane, forming an access passage in fluid communication with the cavity, and forming, in the flexible membrane, at least one transduction element configured so as to convert a deformation of the flexible membrane into electrical signals. The cavity is formed in a position set at a distance from the second face and delimits, together with the second face, a portion of the monolithic body. In order to form the access passage, the monolithic body is etched so as to form an access trench extending through it.

Claims

1. A process for manufacturing an integrated differential pressure sensor, comprising:

forming, in a monolithic body of semiconductor material having a first face and a second face, a cavity extending at a distance from said first face and extending at a distance from said second face, the cavity delimiting, with said first face, a flexible membrane, and delimiting, with said second face, a portion of said monolithic body;

forming an access passage in fluid communication with said cavity, including etching said monolithic body to form an access trench extending through said monolithic body; and

forming, in said flexible membrane, at least one transduction element configured to convert a deformation of said flexible membrane into electrical signals.

2. The process according to claim 1, wherein forming said cavity comprises:

digging trenches within said monolithic body the trenches delimiting structures of semiconductor material;

growing, from said structures, a closing layer of semiconductor material to close said trenches; and

performing a thermal treatment such as to cause migration of the semiconductor material of said structures and transform said trenches into said cavity.

3. The process according to claim 1, wherein etching said monolithic body comprises performing an etching from said second face as far as said cavity.

4. The process according to claim 3, further comprising, prior to forming the access passage:

forming an oxidation trench extending between said first face and said cavity; and

oxidizing walls of said cavity through said oxidation trench to form a stop oxide layer therein.

5. The process according to claim 1, wherein forming the access passage further comprises forming a connection channel buried within said monolithic body, laterally with respect to, and in fluid communication with, said cavity, prior to etching said monolithic body.

6. The process according to claim 5, wherein etching said monolithic body comprises performing an etching from said second face as far as said connection channel.

7. The process according to claim 5, wherein etching said monolithic body comprises performing an etching from said first face as far as said connection channel.

8. The process according to claim 7, further comprising:

arranging said monolithic body in a first portion of a package, having a second portion defining, with said first portion, an internal space facing said flexible membrane; and

mechanically coupling said first portion to said second portion so as to fluidally connect said internal space to a first opening of said package and to provide a fluid-tight insulation between said first opening and said access trench.

9. The process according to claim 8, wherein mechanically coupling comprises fluidally connecting said access trench to a second opening of said package.

10. The process according to claim 1, wherein forming at least one transduction element comprises forming piezoresistive elements or capacitive elements.

11. An integrated differential pressure sensor, comprising:

a monolithic body of semiconductor material having a first face and a second face;

a cavity buried within said monolithic body and extending in said monolithic body at a distance from said first face and delimiting, with said first face, a flexible membrane, said cavity extending at a distance from said second face and delimiting, with said second face, a portion of said monolithic body;

an access passage in fluid communication with said cavity, said access passage including an access trench extending through said monolithic body; and

at least one transduction element formed in said flexible membrane and configured so as to convert a deformation of said flexible membrane into electrical signals.

12. The sensor according to claim 11, wherein said access trench extends between said second face and said cavity.

13. The sensor according to claim 11, wherein said access passage further comprises a buried connection channel, formed within said monolithic body, laterally with respect to, and in fluid communication with, said cavity.

14. The sensor according to claim 13, wherein said access trench extends between said second face and said connection channel.

15. The sensor according to claim 13, wherein said access trench extends between said first face and said connection channel.

16. The sensor according to claim 11, wherein said at least one transduction element is a piezoresistive element or a capacitive element.

17. A pressure sensor system comprising:

an integrated differential pressure sensor, said integrated differential pressure sensor including

a monolithic body of semiconductor material having a first face and a second face,

a cavity buried within said monolithic body and extending in said monolithic body at a distance from said first face and delimiting, with said first face, a flexible membrane, said cavity extending at a distance from said second face and delimiting, with said second face, a portion of said monolithic body,

an access passage in fluid communication with said cavity, said access passage having

a buried connection channel, formed within said monolithic body, laterally with respect to, and in fluid communication with, said cavity, and

an access trench extending through said monolithic body, said access trench extending between said first face and said connection channel, and

at least one transduction element formed in said flexible membrane and configured so as to convert a deformation of said flexible membrane into electrical signals; and

a package housing said monolithic body, said package including a first portion and a second portion mechanically coupled and defining an internal space facing said flexible membrane, said internal space being fluidally connected to a first opening of said package, and being insulated in a fluid-tight way from said access trench via fluid-tight means.

18. The pressure sensor system according to claim 17, wherein said fluid-tight means comprise a seal ring made of elastomeric material, arranged between said package and said monolithic body.

19. The pressure sensor system according to claim 17, wherein said package comprises a second opening fluidally connected to said access trench.

20. The pressure sensor system according to claim 17, wherein said at least one transduction element is a piezoresistive element or a capacitive element.

21. A process for manufacturing an integrated differential pressure sensor using a monolithic body of semiconductor material having a first face and a second face, the process comprising:

forming a cavity within the monolithic body and positioned a first distance from the first face and a second distance from the second face, the cavity delimiting in conjunction with the first face a flexible membrane and delimiting in conjunction with the second face a portion of the monolithic body, the cavity being delimited by internal walls;

forming an oxidation trench extending between the first face and the cavity;

oxidizing the internal walls of the cavity through the oxidation trench to form a stop oxide layer thereon;

forming an access passage in fluid communication with the cavity; and

forming, in the flexible membrane, at least one transduction element configured to convert a deformation of the flexible membrane into electrical signals.

22. The process according to claim 21, wherein forming the cavity comprises:

forming trenches within the monolithic body, the trenches delimiting structures of semiconductor material;

growing, from the structures, a closing layer of semiconductor material to close the trenches; and

performing a thermal treatment to cause migration of the semiconductor material of the structures and transform the trenches into the cavity.

23. The process according to claim 21, wherein forming an access passage comprises etching an access trench in the monolithic body, the access trench extending from the second face of the monolithic body to the cavity.

24. The process according to claim 21, wherein forming at least one transduction element comprises forming a piezoresistive element.

25. An integrated differential pressure sensor, comprising:

a monolithic body of semiconductor material having a first face and a second face;

a cavity buried within the monolithic body and positioned a first distance from the first face and a second distance from the second face, the cavity delimiting in conjunction with the first face a flexible membrane and delimiting in conjunction with the second face a portion of the monolithic body, the cavity being delimited by internal walls, the internal walls being oxidized;

an access passage in fluid communication with the cavity; and

at least one transduction element formed in the flexible membrane and configured to convert a deformation of the flexible membrane into electrical signals.

26. The sensor according to claim 25, wherein the access passage comprises an access trench extending between the second face and the cavity.

27. The sensor according to claim 25, wherein the access passage comprises an access trench extending between the first face and the cavity.

28. The sensor according to claim 25, wherein the access passage comprises a buried connection channel formed within said monolithic body, the buried connection channel being in fluid communication with the cavity.

29. The sensor according to claim 28, wherein the access passage further comprises an access trench extending between the second face and the buried connection channel.

30. The sensor according to claim 28, wherein the access passage further comprises an access trench extending between the first face and the buried connection channel.