US3849217A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of manufacturing high frequency diode
Assignee: Unisys Corp
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Filing: 1973-03-09
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Granted: 1974-11-19
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Expires: 1993-03-09
Abstract
Abstract High frequency diodes are manufactured by methods in which extended dual mesas are formed upon semiconductor or other substrates, one mesa incorporating the active junction and another supporting the active mesa in reduced parasitic capacitive relation, with the substrate supporting the combination of mesas and with an efficient heat sink cooperating with the active mesa. Novel ring shaped diodes made according to the method feature a high degree of circular symmetry and therefore freedom from burn out, thermal compression bonding being used to perfect the bond between the active mesa and a diamond heat sink. Symmetry of the diode is assured by use of a photoresist mask generation technique employing a reduced rate of evaporation of the photoresist solvent.
Inventors
- 👤 H Kroger
- 👤 C Potter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:14
CPC Classifications
H; H10; H10W; H10W40/00; H10W40/10; H10D; H10D99/00; H10W99/00; Y; Y10; Y10S; Y10S438/00; Y10S438/942; Y10S438/948; Y10S438/95
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
144 words
THE METHOD OF MAKING HIGH FREQUENCY DIODE DEVICE FROM A BODY OF SEMICONDUCTOR MATERIAL HAVING TYPE N+ CONDUCTIVITY AND HAVING AN EPITAXIAL LAYER OF TYPE N CONDUCTIVITY, THE METHOD COMPRISING: FORMING A LAYER OF TYPE OF P CONDUCTIVITY MATERIAL AT A SURFACE OF SAID EPITAXIAL LAYER, FORMING A METAL LAYER OF CROMIUM OVER SAID SURFACE, FORMING A METAL LAYER OF GOLD OVER SAID CHROMIUM LAYER, FORMING A RING SHAPE PHOTORESIST MASK OVER SAID GOLD LAYER, SUBSTANTIALLY REMOVING BY ETCHING SAID METAL LAYERS EXCEPT WHERE PROTECTED BY SAID RING SHAPED MASK FOR FORMING CONTIGUOUS METAL RING LAYERS, UNDERCUTTING SAID CONTIGUOUS METAL RING LAYERS BY ETCHING SAID SEMICONDUCTOR BODY FOR GENERATING A FIRST ANNULAR MESA PROJECTING FROM SAID BODY FOR SUPPORTING SAID METAL RING LAYERS, REMOVING BY ETCHING SUBSTANTIALLY ALL PARTS OF SAID METAL RING LAYERS OVERHANGING SAID FIRST ANNULAR MESA, AND REMOVING SAID PHOTORESIST MASK.
Claim 2
Independent Claim
144 words
THE METHOD OF MAKING HIGH FREQUENCY DIODE DEVICE FROM A BODY OF SEMICONDUCTOR MATERIAL HAVING TYPE N+ CONDUCTIVITY AND HAVING AN EPITAXIAL LAYER OF TYPE N CONDUCTIVITY, THE METHOD COMPRISING: FORMING A LAYER OF TYPE OF P CONDUCTIVITY MATERIAL AT A SURFACE OF SAID EPITAXIAL LAYER, FORMING A METAL LAYER OF CROMIUM OVER SAID SURFACE, FORMING A METAL LAYER OF GOLD OVER SAID CHROMIUM LAYER, FORMING A RING SHAPE PHOTORESIST MASK OVER SAID GOLD LAYER, SUBSTANTIALLY REMOVING BY ETCHING SAID METAL LAYERS EXCEPT WHERE PROTECTED BY SAID RING SHAPED MASK FOR FORMING CONTIGUOUS METAL RING LAYERS, UNDERCUTTING SAID CONTIGUOUS METAL RING LAYERS BY ETCHING SAID SEMICONDUCTOR BODY FOR GENERATING A FIRST ANNULAR MESA PROJECTING FROM SAID BODY FOR SUPPORTING SAID METAL RING LAYERS, REMOVING BY ETCHING SUBSTANTIALLY ALL PARTS OF SAID METAL RING LAYERS OVERHANGING SAID FIRST ANNULAR MESA, AND REMOVING SAID PHOTORESIST MASK.
Claim 3
Dependent Claim
64 words
The method described in claim 1 wherein the step of removing by etching said metal layers comprises the steps of: removing by etching said gold layer except where protected by said ring shaped mask for forming a gold ring layer, and removing by etching said chromium layer except where said chromium layer lies below said gold ring layer for forming a chromium ring layer.
Claim 4
Dependent Claim
50 words
The method described in claim 2 wherein the step of removing by etching substantially all parts of said metal ring layers overhanging said first annular mesa comprises: removing by etching said overhanging parts of said gold ring layer, and removing by etching said ovErhanging parts of said chromium ring layer.
Claim 5
Dependent Claim
66 words
The method described in claim 3 including the additional steps of: forming a ring shaped photoresist mask over a continuous portion of said gold ring layer, removing by etching peripheral portions of said metal ring layers except where protected by said ring shaped mask for forming decreased width contiguous metal ring layers, undercutting said decreased width contiguous metal ring layers by etching, and removing said mask.
Claim 6
Independent Claim
178 words
The method of making a high frequency diode device from a body of semiconductor material having type n+ conductivity and an epitaxial layer having type n conductivity, the method comprising: forming a layer of type p conductivity material at a first free surface of said epitaxial layer, forming a base layer of gold at a second free surface of said type n+ semiconductor material, forming a metal layer of chromium over said first surface, forming a metal layer of gold over said metal layer of chromium, forming a ring shaped photoresist mask over said metal layer of gold, substantially removing by etching said metal layers except where protected by said ring shaped mask for forming contiguous metal ring layers, undercutting said contiguous metal ring layers by etching away said semiconductor body to said base layer of gold for generating a first annular mesa projecting from said base layer of gold for supporting said contiguous metal ring layers, removing by etching substantially all parts of said contiguous metal ring layers overhanging said annular mesa, and removing said photoresist mask.
Claim 7
Independent Claim
178 words
The method of making a high frequency diode device from a body of semiconductor material having type n+ conductivity and an epitaxial layer having type n conductivity, the method comprising: forming a layer of type p conductivity material at a first free surface of said epitaxial layer, forming a base layer of gold at a second free surface of said type n+ semiconductor material, forming a metal layer of chromium over said first surface, forming a metal layer of gold over said metal layer of chromium, forming a ring shaped photoresist mask over said metal layer of gold, substantially removing by etching said metal layers except where protected by said ring shaped mask for forming contiguous metal ring layers, undercutting said contiguous metal ring layers by etching away said semiconductor body to said base layer of gold for generating a first annular mesa projecting from said base layer of gold for supporting said contiguous metal ring layers, removing by etching substantially all parts of said contiguous metal ring layers overhanging said annular mesa, and removing said photoresist mask.
Claim 8
Dependent Claim
117 words
The method described in claim 5 including the additional steps of: forming an annular photoresist mask covering a continuous portion of a surface of said contiguous metal gold ring layer, substantially removing by etching said contiguous metal ring layer except where protected by said ring shaped mask for forming contiguous metal ring layers of reduced width, undercutting said contiguous metal ring layers of reduced width by etching said semiconductor body for generating a mesa of reduced width on said semiconductor body for supporting said contiguous metal ring layers of reduced width, removing by etching substantially all parts of said contiguous metal ring layers of reduced width overhanging said mesa of reduced width, and removing said photoresist mask.
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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) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |