US5185276A
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Method for improving low temperature current gain of bipolar transistors
Assignee: International Business Machines Corp
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Filing: 1991-04-23
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Granted: 1993-02-09
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Expires: 2011-04-23
Abstract
Abstract A method for improving the low temperature current gain of silicon bipolar transistors by implanting a first and a second impurity of the same conductivity type into the base region to provide a high doping level base that increases bandgap narrowing without decreasing freeze-out activation energy. The second impurity is selected to have a higher ionization energy that that of the first impurity. The second impurity thereby freezes out sooner than the first impurity resulting in the freeze-out activation energy being equal to or greater than the energy with only the first impurity.
Inventors
- 👤 Tze-Chiang Chen
- 👤 John D. Cressler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:17
CPC Classifications
H; H10; H10D; H10D10/00; H10D10/01; H10D10/051; H10D10/40; H10D62/00; H10D62/80; H10D62/83; H10D62/834; G; G09; G09G; G09G2300/00; G09G2300/02; G09G2300/023; G09G2320/00; G09G2320/02; G09G2320/0271; G09G2320/0276; Y; Y10; Y10S; Y10S148/00; Y10S148/002; Y10S148/01; Y10S438/00; Y10S438/914; Y10S438/918; Y10S438/919
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
130 words
A method of improving the gain at a temperature of below about 80K of a bipolar transistor having an emitter region and a collector region of a first conductivity type and a base region of a second conductivity type opposite to said first type sandwiched between said emitter and collector regions, said base region having an intrinsic and an extrinsic region, comprising the step of: introducing a first and second impurity of said second conductivity type into said intrinsic base region, said second impurity having an ionization energy of at least approximately 0.010 eV greater than said first impurity such that the base region has an activation energy at said low temperature at least approximately equal to the activation energy of the base region doped with only the first impurity.
Claim 2
Independent Claim
130 words
A method of improving the gain at a temperature of below about 80K of a bipolar transistor having an emitter region and a collector region of a first conductivity type and a base region of a second conductivity type opposite to said first type sandwiched between said emitter and collector regions, said base region having an intrinsic and an extrinsic region, comprising the step of: introducing a first and second impurity of said second conductivity type into said intrinsic base region, said second impurity having an ionization energy of at least approximately 0.010 eV greater than said first impurity such that the base region has an activation energy at said low temperature at least approximately equal to the activation energy of the base region doped with only the first impurity.
Claim 3
Dependent Claim
34 words
The method of claim 1 wherein the difference in ionization energy between said first and second impurities of said second conductivity type is in the range of between about 0.010 eV and 0.20 eV.
Claim 4
Dependent Claim
53 words
The method of claim 1 wherein said first conductivity type is n-type and said second conductivity type is p-type and wherein said first p-type impurity is selected from the group consisting of boron, Ga and Al, and said second p-type impurity is selected from the group consisting of indium, gallium, Al and Tl.
Claim 5
Dependent Claim
28 words
The method of claim 3 wherein said transistor is formed on a silicon substrate and said first p-type impurity is boron and said second p-type impurity is indium.
Claim 6
Dependent Claim
16 words
The method of claim 4 wherein the concentrations of boron and indium are about the same.
Claim 7
Dependent Claim
42 words
The method of claim 1 wherein said first conductivity type is p-type and said second conductivity type is n-type and wherein said first n-type impurity is selected from the group consisting of P and As, and said second n-type impurity is Bi.
Claim 8
Dependent Claim
28 words
The method of claim 6 wherein said transistor is formed on a silicon substrate and said first n-type impurity is P and said second n-type impurity is Bi.
Claim 9
Dependent Claim
16 words
The method of claim 7 wherein the concentrations of P and Bi are about the same.
Claim 10
Dependent Claim
56 words
The method of claim 1 wherein the concentration of said first impurity of said second conductivity type is in the range of about 1×10 17 to 5×10 18 cm -3 and the concentration of said second impurity of said second conductivity type is in the range of about 1×10 17 to 5×10 18 cm -3 .
Claim 11
Dependent Claim
19 words
The method of claim 1 wherein said first and second impurities of said second conductivity type are introduced simultaneously.
Claim 12
Dependent Claim
20 words
The method of claim 1 wherein said first and second impurities of said second conductivity type are introduced in succession.
Claim 13
Dependent Claim
21 words
The method of claim 1 wherein said first and second impurities of said second conductivity type are introduced by ion implantation.
Claim 14
Dependent Claim
19 words
The method of claim 1 wherein said first and second impurities of said conductivity type are introduced by MBE.
Claim 15
Dependent Claim
19 words
The method of claim 1 wherein said first and second impurities of said conductivity type are introduced by CVD.
Claim 16
Independent Claim
112 words
A method of improving the gain at a low temperature of below about 80K of a bipolar transistor having an emitter region and a collector region of a first conductivity type and a base region doped with a first impurity of a second conductivity type opposite to said first type sandwiched between said emitter and collector regions, comprising the step of: introducing a second impurity of said second conductivity type into said base region, said second impurity having an ionization energy of at least approximately 0.010 eV greater than said first impurity and being of a concentration to provide a gain at said lower temperature in the range of 20 to 100.
Claim 17
Independent Claim
112 words
A method of improving the gain at a low temperature of below about 80K of a bipolar transistor having an emitter region and a collector region of a first conductivity type and a base region doped with a first impurity of a second conductivity type opposite to said first type sandwiched between said emitter and collector regions, comprising the step of: introducing a second impurity of said second conductivity type into said base region, said second impurity having an ionization energy of at least approximately 0.010 eV greater than said first impurity and being of a concentration to provide a gain at said lower temperature in the range of 20 to 100.
Claim 18
Dependent Claim
34 words
The method of claim 26 wherein the difference in ionization energy between said first and second impurities of said second conductivity type is in the range of between about 0.010 eV and 0.20 eV.
Claim 19
Dependent Claim
34 words
The method of claim 15 wherein the concentration of said second impurity of said second conductivity type is sufficient to provide bandgap narrowing at said low temperature in the range of about 60 meV.
Claim 20
Dependent Claim
23 words
The method of claim 17 wherein the concentration of the first and second impurities of the second conductivity type are about the same.
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| 3.5 Years (Year 4) | 1996-02-09 | 1996-08-10 | 1997-02-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-02-09 | 2000-08-10 | 2001-02-09 | $3760.00 | Window Closed / Lapsed |
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