Patent US4288775A successfully refreshed from Google Patents.
US4288775A
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Device and method of manufacturing a relative humidity sensor and temperature sensor
Assignee: Individual
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Filing: 1979-11-09
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Granted: 1981-09-08
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Expires: 1999-11-09
Abstract
Abstract Sensor and method of fabricating a sensor for detecting relative humidity with a substantially linear response from 0% to 100% and also detecting temperature. The sensor utilizes a unique essentially pure Al 2 0 3 layer which has a disordered crystalline structure and a density gradient which varies from a low density at its lower surface to a higher density at its upper surface which together produce the desired linear response to relative humidity. The method of producing the unique essentially pure Al 2 O 3 layer includes anodizing with an ac current in a solution of approximately 6.4 normal acid at a starting temperature of 21° C. and allowing the temperature of the anodizing solution to rise with the process to vary the density of the Al 2 O 3 layer. The Al 2 O 3 layer is neutralized in a base solution, washed in boiling water and alcohol to neutralize the Al 2 O 3 layer and remove impurities. The sensor is employed as a three-terminal semiconducting device which is biased with dc current, allowing implementation with standard ICs and LSI circuitry. Application of a biasing current on the top electrode allows the RH sensor to be operated simultaneously as a temperature sensor.
Inventors
- 👤 Paul F. Bennewitz
- 👤 Matt C. Bennewitz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:17
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/12; G01N27/121; G01K; G01K7/00; G01K7/16; G01K7/18; H; H10; H10N; H10N99/00
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
175 words
A semiconductor for use as a sensor for detecting relative humidity comprising: a lower electrode formed from a noble metal; an essentially pure layer of Al 2 O 3 having a thickness ranging from approximately 120 angstroms to 5000 angstroms deposited on said lower electrode, said layer of Al 2 O 3 having a disordered crystalline structure and a density gradient which varies progressively through the thickness of said layer of Al 2 O 3 from a less dense structure at the lower surface of said layer of Al 2 O 3 adjacent said lower electrode to a more dense structure at the upper surface of said layer of Al 2 O 3 ; an upper electrode deposited on said upper surface of said layer of Al 2 O 3 , said upper electrode having a thickness ranging from approximately 7 A to approximately 1000 A; whereby said disordered crystalline structure and said density gradient of said layer of Al 2 O 3 function to produce a linear response to relative humidity from said sensor.
Claim 2
Dependent Claim
175 words
A semiconductor for use as a sensor for detecting relative humidity comprising: a lower electrode formed from a noble metal; an essentially pure layer of Al 2 O 3 having a thickness ranging from approximately 120 angstroms to 5000 angstroms deposited on said lower electrode, said layer of Al 2 O 3 having a disordered crystalline structure and a density gradient which varies progressively through the thickness of said layer of Al 2 O 3 from a less dense structure at the lower surface of said layer of Al 2 O 3 adjacent said lower electrode to a more dense structure at the upper surface of said layer of Al 2 O 3 ; an upper electrode deposited on said upper surface of said layer of Al 2 O 3 , said upper electrode having a thickness ranging from approximately 7 A to approximately 1000 A; whereby said disordered crystalline structure and said density gradient of said layer of Al 2 O 3 function to produce a linear response to relative humidity from said sensor.
Claim 3
Dependent Claim
42 words
The semiconductor of claim 1 further comprising: a substrate; a chrome layer deposited on said substrate between said substrate and said lower electrode; a chrome layer deposited between said layer of Al 2 O 3 and said lower electrode and said substrate.
Claim 4
Dependent Claim
15 words
The semiconductor of claim 1 wherein said upper electrode is formed from a noble metal.
Claim 5
Dependent Claim
13 words
The semiconductor of claim 1 wherein said upper electrode is formed from nickel.
Claim 6
Dependent Claim
13 words
The semiconductor of claim 1 wherein said upper electrode is formed from indium.
Claim 7
Dependent Claim
197 words
A semiconductor for use as a sensor for detecting relative humidity and temperature simultaneously comprising: a lower electrode formed from a noble metal; an essentially pure layer of Al 2 O 3 having a thickness ranging from approximately 120 angstroms to 5000 angstroms deposited on said lower electrode, said layer of Al 2 O 3 having a disordered crystalline structure and a density gradient which varies progressively through the thickness of said layer of Al 2 O 3 from a less dense structure at the lower surface of said layer of Al 2 O 3 adjacent said lower electrode to a more dense structure at the upper surface of said layer of Al 2 O 3 ; an upper electrode deposited on said upper surface of said layer of Al 2 O 3 , said upper electrode having a thickness ranging from approximately 7 A to approximately 1000 A; whereby said disordered crystalline structure and said density gradient of said layer of Al 2 O 3 function to produce a linear response to relative humidity from said sensor and said upper electrode displays a change in resistance to changes in temperature when biased with a dc source.
Claim 8
Dependent Claim
197 words
A semiconductor for use as a sensor for detecting relative humidity and temperature simultaneously comprising: a lower electrode formed from a noble metal; an essentially pure layer of Al 2 O 3 having a thickness ranging from approximately 120 angstroms to 5000 angstroms deposited on said lower electrode, said layer of Al 2 O 3 having a disordered crystalline structure and a density gradient which varies progressively through the thickness of said layer of Al 2 O 3 from a less dense structure at the lower surface of said layer of Al 2 O 3 adjacent said lower electrode to a more dense structure at the upper surface of said layer of Al 2 O 3 ; an upper electrode deposited on said upper surface of said layer of Al 2 O 3 , said upper electrode having a thickness ranging from approximately 7 A to approximately 1000 A; whereby said disordered crystalline structure and said density gradient of said layer of Al 2 O 3 function to produce a linear response to relative humidity from said sensor and said upper electrode displays a change in resistance to changes in temperature when biased with a dc source.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-09-07 | 1985-03-09 | 1985-09-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-07 | 1989-03-09 | 1989-09-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-07 | 1993-03-09 | 1993-09-08 | $7700.00 | Window Closed / Lapsed |