US3893147A
Expired / Lapsed
US
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Multistate varactor
Assignee: Westinghouse Electric Corp
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Filing: 1973-09-05
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Granted: 1975-07-01
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Expires: 1993-09-05
Abstract
Abstract A multistate varactor is provided on a diffused semiconductor substrate having a plurality of spaced apart emitter zones forming PN junctions with a diffused base portion of the semiconductor. Interzone spacing between emitter zones permits control of two or more states of capacitance by applying a reverse bias voltage between the emitter and base of the device. The voltage-variable capacitor has a relatively high perimeter to area ratio, and interzone spacing is substantially less than the width of the zones to permit spreading of adjacent depletion layers together under reverse bias voltage across the PN junction. The device achieves an excellent figure of merit as to the ratio of high capacitance to low capacitance with a correspondingly low differential in the transition voltage between states. The semiconductor varactor can be made using existing diffusion and photomasking techniques, with a triplediffused PNP device in a complementary bipolar process being preferred. The multistate varactor can be used in phased array radar, frequency shift keying, voltage controlled oscillator, RF digital transmission, and multichannel voltage controlled tuner applications.
Inventors
- 👤 David W Williams
- 👤 Phillip L Peyton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:43
CPC Classifications
H; H10; H10D; H10D1/00; H10D1/60; H10D1/62; H10D1/64
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
153 words
A multistate voltage-variable capacitor comprising a semiconducting substrate having a main surface; a diffused portion with a concentration gradient decreasing inwardly from the main surface; at least three spaced-apart diffused first zones forming corresponding PN junctions with the said portion of the capacitor, successive ones of said first zones being separated by corresponding, different interzone spacings, each of not more than 5 microns and establishing for the associated, adjacent ones of said first zones, first and second capacitance states having a predetermined transition voltage therebetween with respect to a reverse bias voltage applied between said first zones and the said portion, and the successive spacings differing respectively in amount thereby to establish corresponding, different transition voltages; and means for applying a selectively adjustable reverse bias voltage between the said portion and said first zones for controlling the capacitance of said capacitor in accordance with said capacitance states and said corresponding, different transition voltages.
Claim 2
Dependent Claim
153 words
A multistate voltage-variable capacitor comprising a semiconducting substrate having a main surface; a diffused portion with a concentration gradient decreasing inwardly from the main surface; at least three spaced-apart diffused first zones forming corresponding PN junctions with the said portion of the capacitor, successive ones of said first zones being separated by corresponding, different interzone spacings, each of not more than 5 microns and establishing for the associated, adjacent ones of said first zones, first and second capacitance states having a predetermined transition voltage therebetween with respect to a reverse bias voltage applied between said first zones and the said portion, and the successive spacings differing respectively in amount thereby to establish corresponding, different transition voltages; and means for applying a selectively adjustable reverse bias voltage between the said portion and said first zones for controlling the capacitance of said capacitor in accordance with said capacitance states and said corresponding, different transition voltages.
Claim 3
Dependent Claim
37 words
The capacitor of claim 1 wherein said substrate comprises a P-type semiconductor, the said portion is formed by an N-type diffusion through said main surface of said substrate, and said first zones comprise diffused P+ first zones.
Claim 4
Dependent Claim
59 words
The capacitor of claim 2 wherein the substrate consists essentially of P-type silicon and where the first zones are diffused into planar regions of the diffused N-type portion with a concentration gradient decreasing inwardly from the main surface, thereby forming sidewalls in the first zones, said sidewalls having a higher capacitance per unit area than the corresponding planar regions.
Claim 5
Dependent Claim
208 words
A semiconductor multistate device for use as a voltage variable capacitor comprising a semiconductor substrate having a main surface and including a first conductivity-type region diffused therein from said main surface and an opposite conductivity-type region comprising at least three spaced zones diffused into said first conductivity-type region, said at least three zones each defining a PN-type junction with said first conductivity-type region and each of said zones having a relatively high perimeter:area ratio, successive ones of said zones being separated by interzone spaces each thereof substantially less than the width of said zones and sufficiently closely spaced to permit spreading of the depletion layer of a given said zone into the corresponding depletion layer of an adjacent zone at a corresponding, transition value of reverse bias voltage applied to the PN junction of said adjacent zone and the successive interzone spacings between successive said zones differing respectively in amount to define corresponding, different transition voltages; means for applying a bias voltage across said PN junctions, whereby increasing reverse bias voltage across the PN junctions formed by said zones causes the corresponding depletion layers of adjacent zones to spread together at corresponding, different predetermined transition voltages, said spreading substantially reducing interior sidewall capacitance between the successive, corresponding zones.
Claim 6
Dependent Claim
208 words
A semiconductor multistate device for use as a voltage variable capacitor comprising a semiconductor substrate having a main surface and including a first conductivity-type region diffused therein from said main surface and an opposite conductivity-type region comprising at least three spaced zones diffused into said first conductivity-type region, said at least three zones each defining a PN-type junction with said first conductivity-type region and each of said zones having a relatively high perimeter:area ratio, successive ones of said zones being separated by interzone spaces each thereof substantially less than the width of said zones and sufficiently closely spaced to permit spreading of the depletion layer of a given said zone into the corresponding depletion layer of an adjacent zone at a corresponding, transition value of reverse bias voltage applied to the PN junction of said adjacent zone and the successive interzone spacings between successive said zones differing respectively in amount to define corresponding, different transition voltages; means for applying a bias voltage across said PN junctions, whereby increasing reverse bias voltage across the PN junctions formed by said zones causes the corresponding depletion layers of adjacent zones to spread together at corresponding, different predetermined transition voltages, said spreading substantially reducing interior sidewall capacitance between the successive, corresponding zones.
Claim 7
Dependent Claim
13 words
The device of claim 4 wherein the semiconductor substrate is a P-type semiconductor.
Claim 8
Dependent Claim
153 words
A multistate voltage-variable capacitor comprising: a semiconductor substrate of one conductivity type; saiD substrate having diffused therein at least three zones having an opposite conductivity type, successive said zones being spaced apart by different amounts thereby defining corresponding, different interzone spacings, said zones and said substrate forming a plurality of PN junctions; and means for applying a selectively variable electric potential between each of said zones and said substrate thereby to establish a reverse bias across each of said PN junctions, each said zone developing a depletion layer in said substrate which increases in extent as a function of the magnitude of the reverse bias, and successive said zones being spaced whereby the depletion layer for each zone overlaps the depletion layer for a next adjacent zone at a predetermined voltage, the successive, different interzone spacings defining successive, different predetermined voltages at which the respective depletion layers of said successive, adjacent zones overlap.
Claim 9
Dependent Claim
153 words
A multistate voltage-variable capacitor comprising: a semiconductor substrate of one conductivity type; saiD substrate having diffused therein at least three zones having an opposite conductivity type, successive said zones being spaced apart by different amounts thereby defining corresponding, different interzone spacings, said zones and said substrate forming a plurality of PN junctions; and means for applying a selectively variable electric potential between each of said zones and said substrate thereby to establish a reverse bias across each of said PN junctions, each said zone developing a depletion layer in said substrate which increases in extent as a function of the magnitude of the reverse bias, and successive said zones being spaced whereby the depletion layer for each zone overlaps the depletion layer for a next adjacent zone at a predetermined voltage, the successive, different interzone spacings defining successive, different predetermined voltages at which the respective depletion layers of said successive, adjacent zones overlap.
Claim 10
Dependent Claim
14 words
A multistate voltage-variable capacitor as in claim 6 wherein said zones are electrically interconnected.
Claim 11
Dependent Claim
16 words
A multistate voltage-variable capacitor as in claim 7, wherein said zones contain an impurity concentration gradient.
Claim 12
Dependent Claim
33 words
A multistate voltage-variable capacitor as in claim 7, wherein said PN junctions between said zones and said substrate include planar areas and sidewall areas, said sidewall areas being larger than said planar areas.
References Cited (Backward Citations)
CA816339A
Cited
US3544862A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-06-30 | 1978-12-30 | 1979-07-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-30 | 1982-12-30 | 1983-07-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-30 | 1986-12-30 | 1987-07-01 | $7700.00 | Window Closed / Lapsed |