EP0091548A2
Expired / Lapsed
EP
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Semiconductor structure comprising a mesa region, process for forming a semiconductor mesa; vertical field effect transistor and method of forming a vertical semiconductor device
Assignee: International Business Machines Corp
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Filing: 1983-02-23
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Granted: —
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Expires: 2003-02-23
Abstract
Abstract The thickness of a conformal coating (7) over an originally formed mesa (6) is used to define a shoulder (10) in a finally formed mesa. The shoulder permits an electrode (11) to be precisely positioned at a location between the base and the top of the mesa. A vertical field effect transistor has a mesa serving as the channel region and a gate electrode positioned at a shoulder of the mesa. The stepped mesa is formed (Figures 1 to 8) by providing a conformal coating (7) on the sides of an original mesa (6) of constant cross-section, rendering the material surrounding the original mesa semi-insulating, and downwardly eroding the material surrounding the original mesa using the conformal coating as a mask to form a final mesa consisting of an upper part which was the original mesa and a lower part of greater cross-section than the upper part.
Inventors
- 👤 Thomas Nelson Jackson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 15:30
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/01; H10D30/061; H10D30/80; H10D30/87; H10D30/871; H10D62/00; H10D62/10; H10D62/113; H10D62/115; H10D62/116; H10P; H10P50/00; H10P50/69; H10P50/691
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
47 words
A semiconductor structure comprising a mesa region (6) epitaxial to and extending from a substantially planar portion (9) characterised by the mesa (6) having a step (10) therein so that the lower part of the mesa has a greater cross-section than the upper part of the mesa.
Claim 2
Dependent Claim
47 words
A semiconductor structure comprising a mesa region (6) epitaxial to and extending from a substantially planar portion (9) characterised by the mesa (6) having a step (10) therein so that the lower part of the mesa has a greater cross-section than the upper part of the mesa.
Claim 3
Dependent Claim
28 words
A semiconductor structure as claimed in claim 1, in which said planar portion is a layer epitaxial to a substrate (2) having a higher conductivity than the layer.
Claim 4
Dependent Claim
15 words
A semiconductor structure as claimed in claim 1 or claim 2, composed of gallium arsenide.
Claim 5
Dependent Claim
21 words
A semiconductor structure as claimed in any preceding claim, in which the material in the area surrounding the mesa is semi-insulating.
Claim 6
Dependent Claim
50 words
A vertical field effect transistor comprising a semiconductor structure as claimed in any preceding claim, a Schottky barrier contact to the lower part of the mesa, the lower part serving as the channel region of the transistor, and individual ohmic contacts to the substrate and the top of the mesa.
Claim 7
Dependent Claim
28 words
A vertical field effect transistor as claimed in claim 5, in which there is a Schottky barrier contact on both sides of the lower part of the mesa.
Claim 8
Dependent Claim
85 words
A process of forming a semiconductor mesa with a lower part having a greater cross-section than the upper part of the mesa, the process comprising forming an original mesa of constant cross-section, providing a conformal coating on the sides of the original mesa, and downwardly eroding the material surrounding the original mesa using the conformal coating as a mask to form a final mesa consisting of an upper part which was the original mesa and a lower part of greater cross-section than the upper part.
Claim 9
Dependent Claim
85 words
A process of forming a semiconductor mesa with a lower part having a greater cross-section than the upper part of the mesa, the process comprising forming an original mesa of constant cross-section, providing a conformal coating on the sides of the original mesa, and downwardly eroding the material surrounding the original mesa using the conformal coating as a mask to form a final mesa consisting of an upper part which was the original mesa and a lower part of greater cross-section than the upper part.
Claim 10
Dependent Claim
26 words
A process as claimed in claim 7, in which the character of the material surrounding the original mesa is modified prior to it being downwardly eroded.
Claim 11
Dependent Claim
24 words
A process as claimed in claim 8, in which the material surrounding the original mesa is rendered semi-insulating prior to it being downwardly eroded.
Claim 12
Dependent Claim
74 words
A process as claimed in any of claim 7 to 9, in which the conformal coating is provided on the sides of the original mesa by forming a conformal coating on the top and sides of, and the area surrounding, the original mesa and downwardly etching away the conformal coating to remove it from the top of the original mesa and the area surrounding it but not from the sides of the original mesa.
Claim 13
Dependent Claim
31 words
A process as claimed in any of claim 7 to 10, in which the semiconductor is composed of gallium arsenide and the conformal coating consists of silicon nitride and/or silicon dioxide.
Claim 14
Dependent Claim
67 words
A process of forming a vertical semiconductor device including providing a semiconductor body with a mesa by a process as claimed in any of claim 7 to 11, coating the mesa and the area surrounding it with a metal layer and dissolving away the conformal coating on the sides of the mesa so that the portions of the metal layer overlying the conformal coating are lifted off.
References Cited (Backward Citations)
No citation records indexed.
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