US5041191A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Diffusion barrier for thin film hybrid circuits
Assignee: Boeing Co
•
Filing: 1989-11-13
•
Granted: 1991-08-20
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Expires: 2009-11-13
Abstract
Abstract A thin film resistor and method of making employs tungsten or tungsten titanium alloy as an alectrically conductive diffusion barrier between the nickel chromium resistor and the gold conductor. A solution of cupric sulfate, ammonium hydroxide, glycerol and deionized water is used to remove the unwanted diffusion barrier without damaging the thin film resistor materials, thereby preserving precision resistance values.
Inventors
- 👤 James C. Watson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:52
CPC Classifications
C; C23; C23F; C23F1/00; C23F1/10; C23F1/14; C23F1/32; C23F1/38; H; H01; H01C; H01C17/00; H01C17/28; H01C17/288; H10; H10D; H10D84/00; H10D84/01; H10D86/00; H10D86/01; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49099
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
116 words
A method for preventing degradation of thin film nickel chromium alloy resistors owing to voids caused by chromium diffusion into the conductor for the resistor, comprising the steps of: establishing a thin film layer of nickel chromium alloy on an insulator surface of a support; forming a diffusion barrier comprising at least tungsten overlaying said thin film; establishing a conductor layer over said diffusion barrier; and, patterning the layers and the thin film to form at least a discrete resistor; and, utilizing a solution of: ______________________________________
cupric sulfate (CUSO.sub.4)
5 grams
ammonium hydroxide (NH.sub.4 OH)
10 milliliters
glycerol 150 milliliters
deionized water 125 milliliters
______________________________________ to remove the undesired tungsten without appreciably affecting the nickel chromium.
Claim 2
Independent Claim
116 words
A method for preventing degradation of thin film nickel chromium alloy resistors owing to voids caused by chromium diffusion into the conductor for the resistor, comprising the steps of: establishing a thin film layer of nickel chromium alloy on an insulator surface of a support; forming a diffusion barrier comprising at least tungsten overlaying said thin film; establishing a conductor layer over said diffusion barrier; and, patterning the layers and the thin film to form at least a discrete resistor; and, utilizing a solution of: ______________________________________
cupric sulfate (CUSO.sub.4)
5 grams
ammonium hydroxide (NH.sub.4 OH)
10 milliliters
glycerol 150 milliliters
deionized water 125 milliliters
______________________________________ to remove the undesired tungsten without appreciably affecting the nickel chromium.
Claim 3
Dependent Claim
10 words
The method of claim 1, wherein: the conductor is gold.
Claim 4
Dependent Claim
13 words
The method of claim 2, wherein: the diffusion barrier comprises tungsten titanium alloy.
Claim 5
Dependent Claim
50 words
An etchant for removing tungsten and tungsten titanium alloy from a composite structure including a layer of nickel chromium without adversely affecting the nickel or chromium, comprising a solution of: ______________________________________
cupric sulfate (CUSO.sub.4)
5 grams
ammonium hydroxide (NH.sub.4 OH)
10 milliliters
glycerol 100 milliliters
deionized water 125 milliliters.
______________________________________
Claim 6
Dependent Claim
50 words
An etchant for removing tungsten and tungsten titanium alloy from a composite structure including a layer of nickel chromium without adversely affecting the nickel or chromium, comprising a solution of: ______________________________________
cupric sulfate (CUSO.sub.4)
5 grams
ammonium hydroxide (NH.sub.4 OH)
10 milliliters
glycerol 100 milliliters
deionized water 125 milliliters.
______________________________________
Claim 7
Independent Claim
150 words
A method of fabricating a precision thin film resistor comprising the steps of: establishing a thin film layer of approximately 250-300 Å thickness of nickel chromium alloy on an insulator surface of a support; forming a diffusion barrier for said layer comprising at least a layer of tungsten having a thickness of approximately 500 Å-1000 Å overlaying said thin film layer; establishing a conductor layer over said diffusion barrier having a thickness of approximately 2000 Å or more; heating the thin film layer, diffusion barrier and conductor layer to a temperature less than 300° C. to stabilize the resistor value; employing photographic masking and etching techniques to pattern the layers to form said resistor; and utilizing a solution of: ______________________________________
cupric sulfate (CUSO.sub.4)
5 grams
ammonium hydroxide (NH.sub.4 OH)
10 milliliters
glycerol 100 milliliters
deionized water 125 milliliters
______________________________________ to remove the undesired tungsten without appreciably affecting the nickel chromium.
Claim 8
Independent Claim
150 words
A method of fabricating a precision thin film resistor comprising the steps of: establishing a thin film layer of approximately 250-300 Å thickness of nickel chromium alloy on an insulator surface of a support; forming a diffusion barrier for said layer comprising at least a layer of tungsten having a thickness of approximately 500 Å-1000 Å overlaying said thin film layer; establishing a conductor layer over said diffusion barrier having a thickness of approximately 2000 Å or more; heating the thin film layer, diffusion barrier and conductor layer to a temperature less than 300° C. to stabilize the resistor value; employing photographic masking and etching techniques to pattern the layers to form said resistor; and utilizing a solution of: ______________________________________
cupric sulfate (CUSO.sub.4)
5 grams
ammonium hydroxide (NH.sub.4 OH)
10 milliliters
glycerol 100 milliliters
deionized water 125 milliliters
______________________________________ to remove the undesired tungsten without appreciably affecting the nickel chromium.
Claim 9
Dependent Claim
19 words
The method of claim 5 wherein: tungsten titanium alloy is substituted for said at least a layer of tungsten.
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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) | 1994-08-19 | 1995-02-18 | 1995-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-19 | 1999-02-18 | 1999-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-19 | 2003-02-18 | 2003-08-20 | $7700.00 | Window Closed / Lapsed |