US5773369A
Expired / Lapsed
US
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Photoelectrochemical wet etching of group III nitrides
Assignee: University of California
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Filing: 1996-04-30
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Granted: 1998-06-30
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Expires: 2016-04-30
Abstract
Abstract A method of processing semiconductor films and layers, especially Group III Nitride films, has been achieved, using laser-enhanced, room-temperature wet etching with dilute etchants. Etch rates of a few hundred Å/min up to a few thousand Å/min have been achieved for unintentionally doped n-type Group III Nitride films grown by MOCVD on a sapphire substrate. The etching is thought to take place photoelectrochemically with holes and electrons generated by incident illumination from 4.5 mW of HeCd laser power enhancing the oxidation and reduction reactions in an electrochemical cell.
Inventors
- 👤 Evelyn Lynn Hu
- 👤 Milan Singh Minsky
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:51
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/60; H10P50/61; H10P50/617; C; C25; C25F; C25F3/00; C25F3/02; C25F3/12; C25F3/14
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
127 words
A method of wet etching a Group III Nitride semiconductor layer, comprising the steps of: overlaying the Group III Nitride semiconductor layer with a mask, wherein the mask defines a pattern to be transferred to the Group III Nitride semiconductor layer and facilitates a flow of photogenerated carriers from an area of the Group III Nitride semiconductor layer to be etched; immersing the Group III Nitride semiconductor layer in an etchant solution, the etchant solution being unable to etch the Group III Nitride semiconductor layer, the etchant solution further being unheated; and illuminating the immersed Group III Nitride semiconductor layer using an optical source containing frequencies above the bandgap of the Group III Nitride semiconductor layer, wherein the step of illuminating etches the Group III Nitride layer.
Claim 2
Independent Claim
127 words
A method of wet etching a Group III Nitride semiconductor layer, comprising the steps of: overlaying the Group III Nitride semiconductor layer with a mask, wherein the mask defines a pattern to be transferred to the Group III Nitride semiconductor layer and facilitates a flow of photogenerated carriers from an area of the Group III Nitride semiconductor layer to be etched; immersing the Group III Nitride semiconductor layer in an etchant solution, the etchant solution being unable to etch the Group III Nitride semiconductor layer, the etchant solution further being unheated; and illuminating the immersed Group III Nitride semiconductor layer using an optical source containing frequencies above the bandgap of the Group III Nitride semiconductor layer, wherein the step of illuminating etches the Group III Nitride layer.
Claim 3
Dependent Claim
31 words
The method of claim 1, wherein the method further comprises the step of coupling the mask to a conductive path which draws electrons from the mask to a higher electrical potential.
Claim 4
Dependent Claim
21 words
The method of claim 1, wherein a sidewall of the area to be etched substantially mirrors the geometry of the mask.
Claim 5
Dependent Claim
14 words
The method of claim 1, wherein an etch rate exceeds 100 angstroms per minute.
Claim 6
Dependent Claim
18 words
The method of claim 1, wherein the temperature of the etchant solution is less than 40 degrees centigrade.
Claim 7
Dependent Claim
22 words
The method of claim 1, wherein the mask comprises at least one of the group comprising: gold; silver; titanium; or composite metals.
Claim 8
Dependent Claim
15 words
The method of claim 1, wherein the power of the optical source is 4.5 mW.
Claim 9
Dependent Claim
30 words
The method of claim 1, wherein a concentration of the etchant solution is less than the concentration required to etch the Group III Nitride semiconductor layer without the optical source.
Claim 10
Dependent Claim
22 words
The method of claim 1, wherein the type of etchant solution is selected from the group comprising: Potassium Hydroxide; and Hydrochloric Acid.
Claim 11
Dependent Claim
15 words
The method of claim 1, wherein the Group III Nitride semiconductor layer comprises a heterostructure.
Claim 12
Independent Claim
121 words
A method of etching a Group III Nitride layer, comprising the steps of: overlaying the Group III Nitride layer with a mask, wherein the mask ensures an unimpeded flow of photogenerated carriers from an area of the layer to be etched; immersing the Group III Nitride layer in an etchant solution, the etchant solution being unable to etch the Group III Nitride layer, the etchant solution further being unheated; coupling the mask to a conductive path which draws electrons from the mask to a higher electrical potential; and illuminating the immersed Group III Nitride layer using an optical source containing frequencies above the bandgap of the Group III Nitride layer, wherein the step of illuminating etches the Group III Nitride layer.
Claim 13
Independent Claim
121 words
A method of etching a Group III Nitride layer, comprising the steps of: overlaying the Group III Nitride layer with a mask, wherein the mask ensures an unimpeded flow of photogenerated carriers from an area of the layer to be etched; immersing the Group III Nitride layer in an etchant solution, the etchant solution being unable to etch the Group III Nitride layer, the etchant solution further being unheated; coupling the mask to a conductive path which draws electrons from the mask to a higher electrical potential; and illuminating the immersed Group III Nitride layer using an optical source containing frequencies above the bandgap of the Group III Nitride layer, wherein the step of illuminating etches the Group III Nitride layer.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2001-06-29 | 2001-12-29 | 2002-06-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-06-29 | 2005-12-29 | 2006-06-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-06-29 | 2009-12-29 | 2010-06-30 | $7700.00 | Window Closed / Lapsed |