Patent US4943540A successfully refreshed from Google Patents.
US4943540A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for selectively wet etching aluminum gallium arsenide
Assignee: Nokia Bell Labs
•
Filing: 1988-12-28
•
Granted: 1990-07-24
•
Expires: 2008-12-28
Abstract
Abstract A method for selectively etching higher aluminum concentration AlGaAs in the presence of lower aluminum concentration AlGaAs or GaAs, preferably at room temperature. The AlGaAs is first cleaned with a solution of NH 4 OH and rinsed. The AlGaAs is then etched in a solution of HF. If photoresist is used on the AlGaAs, the photoresist may first be baked to increase the adhesion of the photoresist to the AlGaAs and to "toughen" the photoresist to reduce undercutting thereof. Agitation is applied to the AlGaAs or the etchant to assist in the uniform etching of the AlGaAs.
Inventors
- 👤 Fan Ren
- 👤 Nitin J. Shah
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 11:48
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/69; H10P50/691; H10P50/693; H10P50/695; H10P50/60; H10P50/64; H10P50/642; H10P50/646; Y; Y10; Y10S; Y10S148/00; Y10S148/051; Y10S148/056
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
104 words
A method of manufacturing a semiconductor device, which includes etching AlGaAs on an wafer, CHARACTERIZED BY THE STEPS OF: depositing a masking layer over the AlGaAs; patterning the masking layer to expose regions of the AlGaAs to be etched; cleaning the exposed AlGaAs regions with a solution of ammonium hydroxide (NH 4 OH); etching the AlGaAs regions with a solution of diluted hydrofluoric acid (HF) at a predetermined temperature or less; wherein the predetermined temperature is approximately the boiling temperature of the diluted HF solution, the concentration of HF 48% or less, and the concentration of aluminum in the AlGaAs is 60% or less.
Claim 2
Independent Claim
104 words
A method of manufacturing a semiconductor device, which includes etching AlGaAs on an wafer, CHARACTERIZED BY THE STEPS OF: depositing a masking layer over the AlGaAs; patterning the masking layer to expose regions of the AlGaAs to be etched; cleaning the exposed AlGaAs regions with a solution of ammonium hydroxide (NH 4 OH); etching the AlGaAs regions with a solution of diluted hydrofluoric acid (HF) at a predetermined temperature or less; wherein the predetermined temperature is approximately the boiling temperature of the diluted HF solution, the concentration of HF 48% or less, and the concentration of aluminum in the AlGaAs is 60% or less.
Claim 3
Dependent Claim
47 words
The method for selectively etching AlGaAs recited in claim 1, wherein the masking layer is photoresist, and FURTHER CHARACTERIZED BY THE STEP OF: baking the photoresist prior to the etching step; wherein the baking of the photoresist increases the adhesion of the photoresist to the AlGaAs layer.
Claim 4
Dependent Claim
19 words
The method for selectively etching AlGaAs recited in claim 2, wherein the photoresist is baked in a non-reactive atmosphere.
Claim 5
Dependent Claim
32 words
The method for selectively etching AlGaAs recited in claim 3, wherein the non-reactive atmosphere is N 2 and the baking occurs at a temperature of approximately 110° C. for approximately 30 minutes.
Claim 6
Dependent Claim
19 words
The method for selectively etching AlGaAs recited in claim 1, wherein the predetermined temperature is less than 80° C.
Claim 7
Dependent Claim
18 words
The method for selectively etching AlGaAs recited in claim 5, wherein the predetermined temperature is substantially room temperature.
Claim 8
Dependent Claim
26 words
The method for selectively etching AlGaAs recited in claim 1, wherein the NH 4 OH is diluted in water at a concentration of 1:1 or less.
Claim 9
Dependent Claim
24 words
The method for selectively etching AlGaAs as recited in claim 1, FURTHER COMPRISES THE STEP OF: agitating the wafer or the diluted HF etchant.
Claim 10
Independent Claim
111 words
A method of manufacturing a semiconductor device, which includes etching AlGaAs on a wafer, CHARACTERIZED BY THE STEPS OF: depositing photoresist over the AlGaAs; patterning the photoresist to expose the AlGaAs where the AlGaAs is to be etched; baking the photoresist; cleaning the exposed AlGaAs with a solution of ammonium hydroxide (NH 4 OH) diluted with water at a concentration of 1:1 or less; etching the AlGaAs with a solution of diluted hydrofluoric acid (HF) at a predetermined temperature or less; wherein the predetermined temperature is approximately the boiling temperature of the diluted HF solution and the baking of the photoresist increases the adhesion of the photoresist to the AlGaAs layer.
Claim 11
Independent Claim
111 words
A method of manufacturing a semiconductor device, which includes etching AlGaAs on a wafer, CHARACTERIZED BY THE STEPS OF: depositing photoresist over the AlGaAs; patterning the photoresist to expose the AlGaAs where the AlGaAs is to be etched; baking the photoresist; cleaning the exposed AlGaAs with a solution of ammonium hydroxide (NH 4 OH) diluted with water at a concentration of 1:1 or less; etching the AlGaAs with a solution of diluted hydrofluoric acid (HF) at a predetermined temperature or less; wherein the predetermined temperature is approximately the boiling temperature of the diluted HF solution and the baking of the photoresist increases the adhesion of the photoresist to the AlGaAs layer.
Claim 12
Dependent Claim
19 words
The method for selectively etching AlGaAs recited in claim 9, wherein the photoresist is baked in a non-reactive atmosphere.
Claim 13
Dependent Claim
32 words
The method for selectively etching AlGaAs recited in claim 10, wherein the non-reactive atmosphere is N 2 and the baking occurs at a temperature of approximately 110° C. for approximately 30 minutes.
Claim 14
Dependent Claim
19 words
The method for selectively etching AlGaAs recited in claim 9, wherein the predetermined temperature is less than 80° C.
Claim 15
Dependent Claim
18 words
The method for selectively etching AlGaAs recited in claim 12, wherein the predetermined temperature is substantially room temperature.
Claim 16
Dependent Claim
24 words
The method for selectively etching AlGaAs recited in claim 9, FURTHER CHARACTERIZED BY THE STEP OF: agitating the wafer or the diluted HF etchant.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-07-23 | 1994-01-22 | 1994-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-23 | 1998-01-22 | 1998-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-23 | 2002-01-22 | 2002-07-24 | $7700.00 | Window Closed / Lapsed |