Solid state RF switch with high cutoff frequency
First Claim
Patent Images
1. An RF solid state switch, comprising:
- (A) a plurality of adjacent semiconductor fingers each having first and second ends and an intermediate body portion, with one of said ends constituting a source region and the other of said ends constituting a drain region;
(B) each said finger having a width W, where W is less than around 5000 Å
;
(C) each said finger having an oxide layer on the surface thereof;
(D) each said finger having a resistive gate layer on said oxide layer;
(E) said resistive gate layer having a sheet resistance ρ
g in the range of 100,000 to on the order of 5×
106 ohms per square; and
(F) respective electrical contacts in electrical communication with said gate layer, and said source and drain regions.
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Abstract
A solid state microwave switch having a plurality of adjacent parallel fingers covered with an oxide layer. One end of a finger is an N+ source region while the other end is an N+ drain region, with a current conducting N region between them. The oxide layer is covered with a gate layer to which a gate signal is applied for control of current between the N+ regions through the N region. The gate layer is highly resistive and has a sheet resistance on the order of millions of ohms per square. The length from the source to drain region is around 2 μm, and the fingers are spaced with a pitch of around 1 μm.
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Citations
15 Claims
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1. An RF solid state switch, comprising:
-
(A) a plurality of adjacent semiconductor fingers each having first and second ends and an intermediate body portion, with one of said ends constituting a source region and the other of said ends constituting a drain region;
(B) each said finger having a width W, where W is less than around 5000 Å
;
(C) each said finger having an oxide layer on the surface thereof;
(D) each said finger having a resistive gate layer on said oxide layer;
(E) said resistive gate layer having a sheet resistance ρ
g in the range of 100,000 to on the order of 5×
106 ohms per square; and
(F) respective electrical contacts in electrical communication with said gate layer, and said source and drain regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
(A) said sheet resistance ρ
g is at least 5×
106 ohms per square.
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3. A switch according to claim 1 wherein:
(A) said first and second ends, and said intermediate body portion are all of the same conductivity type, with said first and second ends having a higher doping concentration than said intermediate body portion.
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4. A switch according to claim 1 wherein:
(A) the length of said intermediate body portion between said source and drain regions is on the order 2 μ
m.
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5. A switch according to claim 1 wherein:
(A) the pitch of said adjacent semiconductor fingers is on the order of 1 μ
m.
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6. A switch according to claim 1 wherein:
(A) the thickness of said oxide layer is on the order of 100 Å
to 1000 Å
.
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7. A switch according to claim 1 wherein:
(A) the thickness of said gate layer is on the order of 100 Å
to 1000 Å
.
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8. A switch according to claim 1 wherein:
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(A) said semiconductor fingers are of silicon; and
(B) said gate layer is a polysilicon.
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9. A switch according to claim 1 wherein:
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(A) said fingers extend for a distance D; and
(B) said extended fingers are parallel to one another.
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10. A switch according to claim 1 wherein:
(A) said switch is operated in the enhancement mode of operation whereby a positive gate voltage applied to said gate layer will turn said switch on.
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11. An RF solid state switch, comprising:
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(A) a plurality of adjacent vertical semiconductor fingers each having first, second and third layers with said first layer constituting one of a source or drain region and said third layer constituting the other of a source or drain region;
(B) said fingers extending from, and having a common one of said source or drain regions, so as to define fingers having distal ends, as well as horizontal interfinger portions;
(C) each said finger having a width W, where W is less than around 5000 Å
;
(D) each said finger having an oxide layer on the vertical surfaces thereof and in said horizontal interfinger portions;
(E) each said finger having a resistive gate layer on said oxide layer so as to extend along said vertical surfaces, as well as along said horizontal interfinger portions;
(F) said resistive gate layer which extends along said vertical surfaces having a sheet resistance μ
g in the range of 100,000 to on the order of 5×
106 ohms per square;
(G) said resistive gate layer which extends along said horizontal interfinger portions constitutes a gate pad having a sheet resistance lower than said resistive gate layer which extends along said vertical surfaces; and
(H) respective electrical contacts in electrical communication with said gate layer, and said source and drain regions. - View Dependent Claims (12, 13, 14, 15)
(A) said first, second and third layers are of the same conductivity type, with said first and third layers having higher doping concentrations than said second layer.
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13. A switch according to claim 11 wherein:
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(A) said resistive gate layer has a sheet resistance of at least 5×
106 ohms per square; and
(B) said gate pad has a sheet resistance which is around 1000 times lower than that of said gate layer.
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14. A switch according to claim 13 which includes:
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(A) a gate pad contact, for application of a control signal, in electrical communication with said gate pad;
(B) said gate pad contact being metallic.
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15. A switch according to claim 11 wherein:
(A) said distal ends of said fingers are in electrical communication with a common contact.
Specification