US5356837A
Expired / Lapsed
US
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Method of making epitaxial cobalt silicide using a thin metal underlayer
Assignee: International Business Machines Corp
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Filing: 1993-10-29
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Granted: 1994-10-18
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Expires: 2013-10-29
Abstract
Abstract An epitaxial cobalt silicide film is formed using a thin metal underlayer, which is placed underneath a cobalt layer prior to a heating step which forms the silicide film. More specifically, a refractory metal layer comprising tungsten, chromium, molybdenum, or a silicide thereof, is formed overlying a silicon substrate on a semiconductor wafer. A cobalt layer is formed overlying the refractory metal layer. Next, the wafer is annealed at a temperature sufficiently high to form an epitaxial cobalt silicide film overlying the silicon substrate. Following this annealing step, a cobalt-silicon-refractory metal alloy remains overlying the epitaxial cobalt silicide film. This silicide is then used to form a shallow P-N junction by dopant out-diffusion. First, either a P or N-type dopant is implanted into the silicide film so that substantially none of the dopant is implanted into the underlying silicon substrate. After implanting, the dopant is out-diffused from the silicide film into the underlying silicon substrate at a drive temperature sufficiently high to form the desired P-N junction.
Inventors
- 👤 Peter J. Geiss
- 👤 Thomas J. Licata
- 👤 Herbert L. Ho
- 👤 James G. Ryan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 15:04
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/01; H10D64/011; H10D64/0111; H10D64/0112; C; C30; C30B; C30B1/00; C30B29/00; C30B29/10; H10P; H10P32/00; H10P32/10; H10P32/14; H10P32/1408; H10P32/1414; H10P32/17; H10P32/171
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
76 words
A process for forming an epitaxial cobalt silicide film in a semiconductor device, comprising the steps of: forming a refractory metal layer comprising tungsten, chromium, molybdenum, a mixture thereof, or a silicide of tungsten, chromium, or molybdenum, said refractory metal layer formed overlying a silicon substrate; forming a cobalt layer overlying said refractory metal layer; and annealing said cobalt layer at a temperature sufficiently high to form said epitaxial cobalt silicide film overlying said silicon substrate.
Claim 2
Dependent Claim
76 words
A process for forming an epitaxial cobalt silicide film in a semiconductor device, comprising the steps of: forming a refractory metal layer comprising tungsten, chromium, molybdenum, a mixture thereof, or a silicide of tungsten, chromium, or molybdenum, said refractory metal layer formed overlying a silicon substrate; forming a cobalt layer overlying said refractory metal layer; and annealing said cobalt layer at a temperature sufficiently high to form said epitaxial cobalt silicide film overlying said silicon substrate.
Claim 3
Dependent Claim
22 words
The process of claim 1 wherein said step of annealing also forms a cobalt-silicon-refractory metal alloy overlying said epitaxial cobalt silicide film.
Claim 4
Dependent Claim
33 words
The process of claim 1 wherein said step of forming a refractory metal layer and said step of forming a cobalt layer are performed consecutively in situ without removal from a vacuum environment.
Claim 5
Dependent Claim
12 words
The process of claim 1 wherein said refractory metal layer is tungsten.
Claim 6
Dependent Claim
17 words
The process of claim 1 wherein said refractory metal layer consists essentially of tungsten, chromium, or molybdenum.
Claim 7
Dependent Claim
13 words
The process of claim 1 wherein said refractory metal layer is tungsten silicide.
Claim 8
Dependent Claim
18 words
The process of claim 1 wherein said refractory metal layer is sputtered or evaporated onto said silicon substrate.
Claim 9
Dependent Claim
18 words
The process of claim 1 wherein said cobalt layer is sputtered or evaporated onto said refractory metal layer.
Claim 10
Dependent Claim
16 words
The process of claim 1 wherein said step of annealing is performed using rapid thermal annealing.
Claim 11
Dependent Claim
20 words
The process of claim 1 wherein said formed refractory metal layer has a thickness of about 0.5 to 2.5 nm.
Claim 12
Dependent Claim
19 words
The process of claim 1 wherein said formed cobalt layer has a thickness of about 5 to 20 nm.
Claim 13
Dependent Claim
21 words
The process of claim 1 wherein said step of annealing is performed at a temperature of at least about 550° C.
Claim 14
Dependent Claim
21 words
The process of claim 12 wherein said step of annealing is performed at a temperature between about 750° and 900° C.
Claim 15
Dependent Claim
18 words
The process of claim 13 wherein said step of annealing is performed for at least about 20 seconds.
Claim 16
Dependent Claim
18 words
The process of claim 1 wherein said epitaxial cobalt silicide film has a resistivity of about 15 micro-ohm-cm.
Claim 17
Independent Claim
62 words
A method for forming a shallow P-N junction by dopant out-diffusion from an epitaxial cobalt silicide film formed on a silicon substrate, comprising the steps of: implanting a dopant into said epitaxial cobalt silicide film; and out-diffusing said dopant from said epitaxial cobalt silicide film into said silicon substrate by annealing at a drive temperature sufficiently high to form said P-N junction.
Claim 18
Independent Claim
62 words
A method for forming a shallow P-N junction by dopant out-diffusion from an epitaxial cobalt silicide film formed on a silicon substrate, comprising the steps of: implanting a dopant into said epitaxial cobalt silicide film; and out-diffusing said dopant from said epitaxial cobalt silicide film into said silicon substrate by annealing at a drive temperature sufficiently high to form said P-N junction.
Claim 19
Dependent Claim
23 words
The method of claim 16 wherein said dopant is implanted so that substantially none of said dopant is implanted into said silicon substrate.
Claim 20
Dependent Claim
15 words
The method of claim 16 wherein said dopant comprises boron, gallium, phosphorous, antimony, or arsenic.
Claim 21
Dependent Claim
20 words
The method of claim 16 wherein said epitaxial cobalt silicide film is formed according to the process of claim 1.
Claim 22
Dependent Claim
15 words
The method of claim 16 wherein said drive temperature is at least about 800° C.
Claim 23
Dependent Claim
18 words
The method of claim 20 wherein said step of out-diffusing is performed for at least about 15 seconds.
Claim 24
Dependent Claim
66 words
A process for forming an epitaxial cobalt silicide film in a semiconductor device, comprising the steps of: forming a tungsten metal layer on a silicon substrate; forming a cobalt layer on said tungsten metal layer; and annealing said cobalt and tungsten layers at a temperature greater than about 550° C. for a time period sufficient to form said epitaxial cobalt silicide film on said silicon substrate.
Claim 25
Dependent Claim
66 words
A process for forming an epitaxial cobalt silicide film in a semiconductor device, comprising the steps of: forming a tungsten metal layer on a silicon substrate; forming a cobalt layer on said tungsten metal layer; and annealing said cobalt and tungsten layers at a temperature greater than about 550° C. for a time period sufficient to form said epitaxial cobalt silicide film on said silicon substrate.
Claim 26
Dependent Claim
16 words
The process of claim 22 wherein said annealing temperature is between about 750° and 900° C.
Claim 27
Dependent Claim
21 words
The process of claim 23 wherein said step of annealing is performed for a time period greater than about 20 seconds.
Claim 28
Dependent Claim
33 words
The process of claim 22 wherein said step of forming a tungsten metal layer and said step of forming a cobalt layer are performed consecutively in situ without removal from a vacuum environment.
Claim 29
Dependent Claim
19 words
The process of claim 23 wherein said tungsten metal layer has a thickness of about 0.5 to 2.5 nm.
Claim 30
Dependent Claim
18 words
The process of claim 26 wherein said cobalt layer has a thickness of about 5 to 20 nm.
Claim 31
Dependent Claim
21 words
The process of claim 23 wherein said step of annealing further forms a cobalt-silicon-tungsten alloy overlying said epitaxial cobalt silicide film.
Claim 32
Independent Claim
105 words
A method for forming a shallow P-N junction by dopant out-diffusion from an epitaxial cobalt silicide film, comprising the steps of: forming a tungsten metal layer on a silicon substrate; forming a cobalt layer on said tungsten metal layer; annealing said cobalt and tungsten layers at a temperature greater than about 550° C. for a time period sufficient to form said epitaxial cobalt silicide film on said silicon substrate; implanting a dopant into said epitaxial cobalt silicide film; and out-diffusing said dopant from said epitaxial cobalt silicide film into said silicon substrate by annealing at a drive temperature sufficiently high to form said P-N junction.
Claim 33
Independent Claim
105 words
A method for forming a shallow P-N junction by dopant out-diffusion from an epitaxial cobalt silicide film, comprising the steps of: forming a tungsten metal layer on a silicon substrate; forming a cobalt layer on said tungsten metal layer; annealing said cobalt and tungsten layers at a temperature greater than about 550° C. for a time period sufficient to form said epitaxial cobalt silicide film on said silicon substrate; implanting a dopant into said epitaxial cobalt silicide film; and out-diffusing said dopant from said epitaxial cobalt silicide film into said silicon substrate by annealing at a drive temperature sufficiently high to form said P-N junction.
Claim 34
Dependent Claim
16 words
The method of claim 29 wherein said annealing temperature is between about 750° and 900° C.
Claim 35
Dependent Claim
21 words
The method of claim 30 wherein said step of annealing is performed for a time period greater than about 20 seconds.
Claim 36
Dependent Claim
23 words
The method of claim 29 wherein said dopant is implanted so that substantially none of said dopant is implanted into said silicon substrate.
Claim 37
Dependent Claim
15 words
The method of claim 30 wherein said drive temperature is at least about 800° C.
Claim 38
Dependent Claim
18 words
The method of claim 29 wherein said step of out-diffusing is performed for at least about 15 seconds.
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| 3.5 Years (Year 4) | 1997-10-17 | 1998-04-18 | 1998-10-18 | $2000.00 | Window Closed / Lapsed |
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