Hydrostatic pressure transducer

• US 5,187,984 A
• Filed: 04/26/1991
• Issued: 02/23/1993
• Est. Priority Date: 04/27/1990
• Status: Expired due to Fees

• Current Assignee: Schlumberger Industries Incorporated (SLB)
• Original Assignee: Schlumberger Industries Incorporated (SLB)
• Inventors: Contreras, Sylvie, Mosser, Vincent, Robert, Jean-Louis
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US07/691,906
• Time in Patent Office: 669 Days
• Field of Search: 73/706, 73/708, 73/720, 73/721, 73/717, 73/723, 73/726, 73/727, 73/753, 73/754, 73/DIG. 4, 338/4, 29/621.1, 374/143
• US Class Current: 73/708
• CPC Class Codes: G01L 19/0092 Pressure sensor associated with other sensors, e.g. for measuring acceleration or temperature G01L9/025, G01L9/045, G01L9/065, G01L9/085, G01L9/105, G01L9/125, G01L19/02, G01L19/04 take precedence; measuring two or more variable G01D21/02; temperature sensors with pressure compensation G01K1/26
• CPC Class Codes: G01L 9/0052 of piezoresistive elements circuits therefor G01L9/06
• CPC Class Codes: G01L 9/045 with electric temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A monolithic pressure and/or temperature transducer comprises at least two sensitive semiconductor layers of III-V material sensitive to pressure and to temperature and supported by a common substrate of III-V material, which two layers comprise: a first layer doped with donor type impurities at a first concentration and having a first resistivity as a function of pressure and of temperature; and a second layer doped with donor type impurities at a second concentration different from the first concentration and having a second resistivity as a function of pressure and of temperature, which second resistivity depends on temperature in a different manner than the first resistivity.

Claims

1. A monolithic pressure and/or temperature transducer comprising at least two sensitive semiconductor layers of III-V material are sensitive to pressure and to temperature, and which are supported by a common substrate of III-V material, said at least two sensitive layers comprising:

a first layer doped with donor type impurities at a first concentration and having a first resistivity as a function of pressure and of temperature; and

a second layer doped with donor type impurities at a second concentration different from the first concentration, said second concentration being at least one order of magnitude greater than said first concentration and having a second resistivity as a function of pressure and of temperature, which second resistivity depends on temperature in a different manner than the first resistivity, wherein said first and second pressure and temperature sensitive layers are of substantially the same composition.

2. A transducer according to claim 1, wherein the sensitive layers are made of Al_x Ga_1-x As, where the aluminum fraction x is selected to lie in the range 0.22 to 0.40, and wherein the substrate is made of GaAs.

3. A transducer according to claim 2, wherein x lies in the range 0.30 to 0.35.

4. A transducer according to claim 2, wherein the first sensitive layer is made of Al_x Ga_1-x As that is N-doped to a concentration ≦

10¹⁷ atoms/cm³, and wherein the second sensitive layer is made of Al_x Ga_1-x As that is N-doped to a concentration ≧

10¹⁸ atoms/cm³.

5. A transducer according to claim 4, comprising, overlying the GaAs substrate:

a buffer layer of GaAs that is not intentionally doped;

a separator layer of Al_z Ga_1-z As that is not intentionally doped and in which the aluminum fraction z increases smoothly from 0 to x;

a bottom active layer of Al_x Ga_1-x As that is N-doped;

a separator layer of Al_y Ga_1-y As that is not intentionally doped where 0.25≦

y≦

0.50 and y>

x;

a top active layer of Al_x Ga_1-x As that is N-doped;

a protective layer of Al_t Ga_1-t As that is not intentionally doped, with 0.22≦

t≦

0.60;

a contact-making layer of N-doped GaAs; and

a metal contact layer.

6. A transducer according to claim 1, wherein the sensitive layers are doped with ions of elements from column IV-B of the periodic table.

7. A transducer according to claim 1, wherein the two sensitive layers overlie each other and are separated by a separator layer of III-V material having a forbidden band of greater width than that of the sensitive layers.

8. A transducer according to claim 7, wherein the separator layer is made of Al_y Ga_1-y As which is not intentionally doped, where y is greater than x and is selected to lie in the range 0.25 to 0.50.

9. A transducer according to claim 8, wherein y is equal to 0.40.

10. A transducer according to claim 7, comprising both a first resistive device comprising a first zone of the first sensitive layer and a zone of the second sensitive layer that overlie each other and that are separated by the separator layer, and a second resistive device comprising a second zone of said first sensitive layer.

11. A transducer according to claim 10, wherein the first resistive device further includes a first pair of metal contacts established on the zone of the second sensitive layer and separated from each other, and wherein the second resistive device includes a second pair of metal contacts established on the second zone of the first sensitive layer, and separated from each other.

12. A transducer according to claim 7, wherein the sensitive layer having the lower concentration of doping ions is situated between the other sensitive layer and the substrate.