Sensor usable in ultra pure and highly corrosive environments

• US 7,152,478 B2
• Filed: 05/16/2003
• Issued: 12/26/2006
• Est. Priority Date: 07/20/2000
• Status: Expired due to Term

• Current Assignee: Entegris Incorporated
• Original Assignee: Entegris Incorporated
• Inventors: Cucci, Gerald R., Diaz, Jorge Andres Diaz, Peterson, Thomas
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US10/440,433
• Publication Number:
  US 20040040382A1
• Time in Patent Office: 1,320 Days
• Field of Search: 737/00, 737/02, 737/08, 737/14, 737/15, 737/16, 737/291, 737/292, 737/56
• US Class Current: 73/715
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 19/0627 Protection against aggressive medium in general
• CPC Class Codes: G01L 19/0681 Protection against excessive heat
• CPC Class Codes: G01L 19/069 Protection against electromagnetic or electrostatic interferences
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0052 of piezoresistive elements circuits therefor G01L9/06
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

The electrical pin lead structure and brazing technique of the present invention provide a brazed lead in a sensor that adheres well to a semiconductor substrate while facilitating lateral flexibility without joint fatigue or breakage. In one example embodiment, the pin lead includes a coil head that is brazed to a silicon layer on a sapphire substrate using a silver-copper-palladium braze material. An advantage to this approach is the ability to both braze the pin lead to the diaphragm and seal the diaphragm to the ceramic backing plate with a high temperature glass in a single process step. Further, the palladium in the braze composition is a factor in reducing surface tension between the metal lead and semiconductor substrate during cooling to avoid stress fractures in the substrate.

Claims

1. A sensor having a non-porous outer surface, said sensor comprising:

a backing plate that includes apertures extending therethrough;

a diaphragm;

a sensing element disposed over an inner surface of the diaphragm;

at least one electrical lead extending through at least one aperture and coupled to the sensing element on the diaphragm, the electrical lead having a coil head adapted for brazing over the inner surface of the diaphragm with a high temperature braze composition; and

a glass layer adapted to be bonded by glassing to the backing plate and the diaphragm, the glass layer having both a high bond strength and a high melt temperature that is at or above 700°

C., wherein the glass layer bonds the backing plate to the diaphragm and the coil head is brazed to the sensing element.

2. The sensor of claim 1, wherein the at least one electrical lead has a coefficient of expansion similar to that of the diaphragm to reduce stresses on the diaphragm as the braze composition and the lead are cooled after being subjected to a single high temperature melting operation.

3. The sensor of claim 1, wherein the at least one electrical lead is formed into a coil spring from a wire selected from the group consisting of nickel and KOVAR.

4. The sensor of claim 1, wherein the braze composition comprises copper, silver and palladium.

5. The sensor of claim 1, further comprising:

bond pads disposed between said glass layer and said non-porous diaphragm; and

windows formed in said glass layer providing access to said bond pads, wherein said electrical leads are brazed to said bond pads.

6. The sensor of claim 5, wherein said bond pads comprise a titanium layer and a diffusion barrier and the diaphragm is comprised of sapphire.

7. An electrical lead member configured for use in connection with a semiconductor element disposed on an insulating substrate, the electrical lead comprising a coiled lead member, a portion of the coiled member adapted to be brazed to the semiconductor element on the substrate.

8. The lead member of claim 7, wherein the coiled member is located at the end of a shaft of an electrical lead member and is comprised of a coiled spring member adapted to be bonded to the semiconductor element.

9. The lead member of claim 7, wherein the coiled member is a coiled spring member.

10. The lead member of claim 9, wherein the coiled spring member is comprised of a plurality of coils, the coils at an end being more closely spaced than the coils in the middle.

11. A method of bonding an electrical lead to a semiconductor device comprising the steps of:

forming an electrical lead comprised of a coiled member;

applying a braze composite material on the substrate surface;

locating a portion of the coiled member on the braze material and on a substrate surface such that a shaft of the lead is substantially perpendicular to the surface of the substrate; and

heating the braze composite material to a sufficiently high temperature such that the braze material melts and the coiled member adheres to the substrate surface as the braze material cools.

12. The method of claim 11, wherein forming the coiled member includes a coil head formed from a plurality of coils.

13. The method of claim 11, further comprising cooling the braze material over time to avoid a stress fracture in the substrate.

14. The method of claim 11, wherein forming the coiled member includes forming a coil head on the electrical lead.

15. The method of claim 11, further comprising the step of adding a weight on the sensor before heating the braze material.

16. A method for bonding an electrical lead to a semiconductor device comprising the steps of:

forming an electrical lead comprised of a coiled member;

providing a backing plate that includes apertures extending therethrough;

providing a substrate having a semiconductor element thereon and adapted to be coupled with the backing plate;

providing a glass layer adapted to be bonded by glassing to the backing plate and the substrate, the glass layer comprised of a high bond strength and high melt temperature material;

applying a braze composite material in the apertures of the backing plate; and

locating the coiled member of the electrical lead through at least one aperture in the backing plate and adjacent the braze material, such that a portion of the lead is protruding from the backing plate; and

heating the braze composite material and the glass layer to a sufficiently high temperature such that the coiled member is brazed to the substrate and the backing plate and the substrate are glassed together.

17. The method of claim 16, wherein the electrical lead is comprised of the coiled member and a shaft.

18. The method of claim 16, further comprising the step of adding a weight on the sensor before heating the braze material.