US4929570A
Expired / Lapsed
US
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Selective epitaxy BiCMOS process
Assignee: National Semiconductor Corp
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Filing: 1989-01-19
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Granted: 1990-05-29
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Expires: 2009-01-19
Abstract
Abstract A process for fabricating both bipolar and complementary field effect transistors in an integrated circuit is disclosed. The process begins with a structure having a P type substrate 10, an N type epitaxial layer 15, and an intervening N type buried layer 12. The process includes the steps of removing all of the epitaxial layer 15 and all of the buried layer 12 from regions of the substrate where NMOS devices are to be formed, to thereby leave second regions of the epitaxial layer 15 and buried layer 12 having sidewalls 21 protruding above the substrate 10. A layer of silicon dioxide 25 is formed at least over the sidewalls of the protruding regions, and then a further epitaxial deposition of silicon is employed to reform the epitaxial layer 28 over the first regions, which epitaxial layer 28 is separated from the previously formed epitaxial layer 15 by the silicon dioxide isolation 25. The process continues by fabricating bipolar and field effect transistors in separate ones of the first and second regions.
Inventors
- 👤 Paul J. Howell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 16:42
CPC Classifications
H; H10; H10D; H10D1/00; H10D1/40; H10D1/47; H10D84/00; H10D84/01; H10D84/0107; H10D84/0109; H10D84/0123; H10D84/0126; H10D84/0165; H10D84/02; H10D84/03; H10D84/038; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/018; H10W10/10
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
255 words
In a structure having a semiconductor substrate of first conductivity type, an epitaxial layer of second conductivity type, and a buried layer of second conductivity type separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: (a) removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate, said step of removing further comprising the steps of: (i) masking the second regions of the epitaxial layer with an etch-resistant material by forming a first layer of silicon dioxide on the epitaxial layer and a layer of silicon nitride on the silicon dioxide; and (ii) etching the epitaxial layer and the buried layer to expose the substrate in the first regions; (b) forming a layer of insulating material at least over the sidewalls of the second regions; (c) depositing semiconductor material over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the insulating material; (d) implanting first conductivity type impurity into the first regions, the second regions being protected by the layer of silicon nitride; and (e) forming at least one first channel type field effect transistor in one of the first regions and one bipolar transistor in one of the second regions.
Claim 2
Dependent Claim
255 words
In a structure having a semiconductor substrate of first conductivity type, an epitaxial layer of second conductivity type, and a buried layer of second conductivity type separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: (a) removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate, said step of removing further comprising the steps of: (i) masking the second regions of the epitaxial layer with an etch-resistant material by forming a first layer of silicon dioxide on the epitaxial layer and a layer of silicon nitride on the silicon dioxide; and (ii) etching the epitaxial layer and the buried layer to expose the substrate in the first regions; (b) forming a layer of insulating material at least over the sidewalls of the second regions; (c) depositing semiconductor material over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the insulating material; (d) implanting first conductivity type impurity into the first regions, the second regions being protected by the layer of silicon nitride; and (e) forming at least one first channel type field effect transistor in one of the first regions and one bipolar transistor in one of the second regions.
Claim 3
Dependent Claim
15 words
A method as in claim 1 wherein the step of etching comprises reactive ion etching.
Claim 4
Dependent Claim
17 words
A method as in claim 1 wherein each of the substrate and the epitaxial layer comprise silicon.
Claim 5
Dependent Claim
30 words
A method as in claim 3 wherein the step of forming a layer of insulating material comprises oxidizing at least the sidewalls of the second regions to form silicon dioxide.
Claim 6
Dependent Claim
35 words
A method as in claim 4 wherein the step of forming a layer of insulating material is followed by a step of etching the insulating material from the first regions except at a periphery thereof.
Claim 7
Dependent Claim
24 words
A method as in claim 1 wherein the step of forming a layer of insulating material comprises depositing silicon dioxide using chemical vapor deposition.
Claim 8
Dependent Claim
30 words
A method as in claim 6 wherein the step of forming a layer of insulating material is followed by a step of etching the insulating material from the first regions.
Claim 9
Dependent Claim
39 words
A method as in claim 7 wherein the step of etching the insulating material is followed by a step of implanting first conductivity type impurity into the first regions, the second regions being protected by the silicon nitride mask.
Claim 10
Dependent Claim
53 words
A method as in claim 1 wherein the step of forming bipolar and field effect transistors comprises oxidizing the epitaxial layer in both the first and second regions to form a layer of oxide, said oxide layer forming a layer of gate oxide in regions where field effect transistors are to be formed.
Claim 11
Dependent Claim
29 words
A method as in claim 9 wherein the step of oxidizing the epitaxial layer is followed by a step of defining polycrystalline silicon gate electrodes on the gate oxide.
Claim 12
Dependent Claim
40 words
A method as in claim 10 wherein the step of defining polycrystalline silicon gate electrodes is followed by a step of using the polycrystalline silicon gate electrodes as a mask to implant sources and drains of the field effect transistors.
Claim 13
Dependent Claim
36 words
A method as in claim 11 wherein following the step of using the polycrystalline silicon gate electrodes as a mask, a step of forming silicon dioxide spacer regions on sides of the gate electrodes is performed.
Claim 14
Dependent Claim
27 words
A method as in claim 12 wherein following the step of forming the spacer regions, a step of applying a silicide-forming metal to the structure is performed.
Claim 15
Dependent Claim
40 words
A method as in claim 12 wherein the step of forming silicon dioxide spacer regions comprises: oxidizing the semiconductor structure; and anisotropically etching the structure to remove the thereby formed silicon dioxide from the structure except from the spacer regions.
Claim 16
Dependent Claim
30 words
A method as in claim 1 wherein the step of forming bipolar and field effect transistors comprises forming a collector sink extending to the buried layer in a second region.
Claim 17
Dependent Claim
32 words
A method as in claim 15 wherein the step of forming a collector sink is followed by a step of implanting a base region of the bipolar transistor into the second region.
Claim 18
Dependent Claim
30 words
A method as in claim 16 wherein the step of implanting a base region is followed by a step of defining a polycrystalline silicon emitter contact to the bipolar transistor.
Claim 19
Dependent Claim
20 words
A method as in claim 1 wherein the step of forming bipolar and field effect transistors further comprises forming resistors.
Claim 20
Dependent Claim
27 words
A method as in claim 18 wherein the step of forming resistors comprises oxidizing one of the first or second regions to form a field oxide region.
Claim 21
Dependent Claim
32 words
A method as in claim 19 wherein the step of oxidizing one of the first or second regions is followed by the step of depositing polycrystalline silicon on the field oxide region.
Claim 22
Dependent Claim
178 words
In a structure having a P conductivity type silicon substrate, an N conductivity type epitaxial layer, and an N conductivity type buried layer separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate; oxidizing at least the sidewalls of the second regions to form silicon dioxide; implanting P type impurity into the substrate in the first regions to form a P conductivity type buried layer in the first regions; depositing silicon over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the silicon dioxide; and forming bipolar transistors in the second regions and field effect transistors in each of the first and second regions.
Claim 23
Dependent Claim
178 words
In a structure having a P conductivity type silicon substrate, an N conductivity type epitaxial layer, and an N conductivity type buried layer separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate; oxidizing at least the sidewalls of the second regions to form silicon dioxide; implanting P type impurity into the substrate in the first regions to form a P conductivity type buried layer in the first regions; depositing silicon over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the silicon dioxide; and forming bipolar transistors in the second regions and field effect transistors in each of the first and second regions.
Claim 24
Dependent Claim
26 words
The method as recited in claim 1 further comprising the step of forming a second channel type field effect transistor in one of said second regions.
Claim 25
Dependent Claim
225 words
In a structure having a semiconductor substrate of first conductivity type, an epitaxial layer of second conductivity type, and a buried layer of second conductivity type separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate; forming a layer of insulating material at least over the sidewalls of the second regions; depositing semiconductor material over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the insulating material; forming at least one bipolar, one field effect transistor and one resistor in the first and the second regions, the step of forming a resistor further comprising the step of oxidizing one of the first or second regions to form a field oxide region; depositing polycrystalline silicon on the field oxide region; and protecting a region of the polycrystalline silicon to be a resistor and introducing impurity into two spaced apart regions of the polycrystalline silicon to thereby provide electrical connections to the resistor.
Claim 26
Dependent Claim
225 words
In a structure having a semiconductor substrate of first conductivity type, an epitaxial layer of second conductivity type, and a buried layer of second conductivity type separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate; forming a layer of insulating material at least over the sidewalls of the second regions; depositing semiconductor material over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the insulating material; forming at least one bipolar, one field effect transistor and one resistor in the first and the second regions, the step of forming a resistor further comprising the step of oxidizing one of the first or second regions to form a field oxide region; depositing polycrystalline silicon on the field oxide region; and protecting a region of the polycrystalline silicon to be a resistor and introducing impurity into two spaced apart regions of the polycrystalline silicon to thereby provide electrical connections to the resistor.
Claim 27
Dependent Claim
168 words
In a structure having a semiconductor substrate of first conductivity type, an epitaxial layer of second conductivity type, and a buried layer of second conductivity type separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate; forming a layer of insulating material at least over the sidewalls of the second regions; depositing semiconductor material over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the insulating material; and forming at least one first channel type field effect transistor in one of the second regions and one bipolar transistor in one of the first regions.
Claim 28
Dependent Claim
168 words
In a structure having a semiconductor substrate of first conductivity type, an epitaxial layer of second conductivity type, and a buried layer of second conductivity type separating the substrate from the epitaxial layer, a method of fabricating both bipolar and field effect transistors comprising: removing all of the epitaxial layer and all of the buried layer from first regions where first channel type field effect transistors are desired to thereby leave second regions of the epitaxial layer and buried layer having sidewalls protruding above the substrate; forming a layer of insulating material at least over the sidewalls of the second regions; depositing semiconductor material over at least the first regions to thereby reform the epitaxial layer over the first regions, the epitaxial layer in the second regions being separated from the epitaxial layer in the first regions by the insulating material; and forming at least one first channel type field effect transistor in one of the second regions and one bipolar transistor in one of the first regions.
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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) | 1993-05-28 | 1993-11-27 | 1994-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-05-28 | 1997-11-27 | 1998-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-05-28 | 2001-11-27 | 2002-05-29 | $7700.00 | Window Closed / Lapsed |