US5219773A
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US
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Method of making reoxidized nitrided oxide MOSFETs
Assignee: Massachusetts Institute of Technology
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Filing: 1991-12-03
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Granted: 1993-06-15
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Expires: 2011-12-03
Abstract
Abstract A method of fabricating a field-effect device having a gate dielectric of reoxidized nitrided oxide (RNO) provides an inversion layer mobility much higher than that of conventional RNO devices. A conductivity structure such as a metal oxide semiconductor field-effect transistor (MOSFET) is formed in a semiconductor substrate and provided with a gate dielectric of RNO. The formation of the device may or may not make use of rapid thermal processing techniques. Once formed, the device is irradiated with ionizing radiation. A voltage potential may be maintained across the gate dielectric during irradiation to further improve the inversion layer mobility. Post-radiation annealing is then performed at a controlled temperature.
Inventors
- 👤 Gregory J. Dunn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 10:13
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/60; H10D64/66; H10D64/68; H10D64/693; H10D30/00; H10D30/01; H10D30/021; H10D30/0411; H10D64/01; H10D64/013; H10D64/01302; H10D64/01332; H10D64/01336; H10D64/0134; H10D64/01344; H10P; H10P14/00; H10P14/60; H10P14/66; H10P14/662; H10P34/00; H10P34/40; H10P34/42; Y; Y10; Y10S; Y10S438/00; Y10S438/91
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
126 words
A method of fabricating a field-effect semiconductor device, the method comprising: providing a semiconductor substrate having a channel region of a first conductivity type; providing a gate dielectric of reoxidized nitrided oxide adjacent the channel region of the substrate; forming in the substrate a conductivity structure having regions of a second conductivity type different than said first conductivity type, the regions being at least partially separated in the substrate by said channel region; irradiating the reoxidized nitrided oxide gate dielectric with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the substrate and gate dielectric at about 400° C. or greater for a duration in the order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 2
Independent Claim
126 words
A method of fabricating a field-effect semiconductor device, the method comprising: providing a semiconductor substrate having a channel region of a first conductivity type; providing a gate dielectric of reoxidized nitrided oxide adjacent the channel region of the substrate; forming in the substrate a conductivity structure having regions of a second conductivity type different than said first conductivity type, the regions being at least partially separated in the substrate by said channel region; irradiating the reoxidized nitrided oxide gate dielectric with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the substrate and gate dielectric at about 400° C. or greater for a duration in the order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 3
Dependent Claim
13 words
A method according to claim 1 wherein the field-effect device is a MOSFET.
Claim 4
Dependent Claim
17 words
A method according to claim 1 wherein the field-effect semiconductor device is a floating gate memory device.
Claim 5
Dependent Claim
16 words
A method according to claim 1 wherein providing a semiconductor substrate comprises providing a silicon substrate.
Claim 6
Dependent Claim
17 words
A method according to claim 1 wherein providing a semiconductor substrate comprises providing a p-type semiconductor substrate.
Claim 7
Dependent Claim
21 words
A method according to claim 1 wherein the annealing of the substrate and gate dielectric is at about 400° C.-475° C.
Claim 8
Dependent Claim
27 words
A method according to claim 1 wherein annealing the substrate and gate dielectric comprises annealing at a temperature which is dependent on the duration of the annealing.
Claim 9
Dependent Claim
26 words
A method according to claim 1 wherein forming a gate dielectric of reoxidized nitrided oxide comprises initially forming said gate dielectric from a silicon dioxide material.
Claim 10
Dependent Claim
24 words
A method according to claim 8 wherein forming a gate dielectric of reoxidized nitrided oxide comprises exposing said gate dielectric to an ammonia atmosphere.
Claim 11
Dependent Claim
25 words
A method according to claim 9 wherein the exposing of said gate dielectric to an ammonia atmosphere is done in at a relatively high temperature.
Claim 12
Dependent Claim
22 words
A method according to claim 10 wherein said relatively high temperature is within a range of about 1000° C. to 1200° C.
Claim 13
Dependent Claim
23 words
A method according to claim 9 wherein the time of said exposure to the ammonia atmosphere is approximately 15 minutes at atmospheric pressure.
Claim 14
Dependent Claim
22 words
A method according to claim 9 wherein the time of said exposure to the ammonia atmosphere is decreased with increased ambient pressure.
Claim 15
Dependent Claim
32 words
A method according to claim 9 wherein forming a gate dielectric of reoxidized nitrided oxide includes exposing the gate dielectric to an oxygen atmosphere after it is exposed to said ammonia atmosphere.
Claim 16
Dependent Claim
31 words
A method according to claim 14 wherein the exposing of said gate dielectric to an oxygen atmosphere is done at a relatively high temperature of about 900° C. to 1200° C.
Claim 17
Dependent Claim
21 words
A method according to claim 14 wherein the time of said oxygen exposure is decreased as the ambient pressure is increased.
Claim 18
Dependent Claim
21 words
A method according to claim 1 further comprising maintaining a voltage potential across the channel region while irradiating the gate dielectric.
Claim 19
Dependent Claim
20 words
A method according to claim 17 wherein the voltage potential on the gate dielectric is a minimum of 1 MV/cm.
Claim 20
Dependent Claim
27 words
A method according to claim 1 wherein irradiating the gate dielectric with ionizing radiation comprises irradiating the gate dielectric with a minimum dose of about 10 Mrad.
Claim 21
Independent Claim
157 words
A method of fabricating a field-effect semiconductor device, the method comprising: providing a semiconductor substrate having a channel region of a first conductivity type, the channel region being adjacent a first surface of the substrate; providing a silicon dioxide gate dielectric on the first surface of the substrate adjacent the channel region; nitriding the gate dielectric to form a nitrided oxide gate dielectric; reoxidizing the nitrided oxide gate dielectric to form a reoxidized nitrided oxide gate dielectric; forming regions of a second conductivity type in said substrate, the regions being along the first surface of the substrate and being separated by said channel region; irradiating the reoxidized nitrided oxide gate dielectric with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the substrate and gate dielectric at about 400° C. or greater for a duration in the order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 22
Independent Claim
157 words
A method of fabricating a field-effect semiconductor device, the method comprising: providing a semiconductor substrate having a channel region of a first conductivity type, the channel region being adjacent a first surface of the substrate; providing a silicon dioxide gate dielectric on the first surface of the substrate adjacent the channel region; nitriding the gate dielectric to form a nitrided oxide gate dielectric; reoxidizing the nitrided oxide gate dielectric to form a reoxidized nitrided oxide gate dielectric; forming regions of a second conductivity type in said substrate, the regions being along the first surface of the substrate and being separated by said channel region; irradiating the reoxidized nitrided oxide gate dielectric with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the substrate and gate dielectric at about 400° C. or greater for a duration in the order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 23
Dependent Claim
27 words
A method according to claim 20 further comprising providing a conductive gate adjacent to the gate dielectric to the side of the dielectric away from the substrate.
Claim 24
Dependent Claim
17 words
A method according to claim 21 wherein providing a conductive gate comprises providing a doped polysilicon gate.
Claim 25
Dependent Claim
29 words
A method according to claim 21 further comprising providing metal contacts for providing electrical conduction paths to the gate and to each of the regions of second conductivity type.
Claim 26
Dependent Claim
18 words
A method according to claim 20 wherein providing a silicon dioxide gate dielectric includes using rapid thermal processing.
Claim 27
Dependent Claim
25 words
A method according to claim 20 wherein the nitriding of the gate dielectric is accomplished at a temperature within the range of 700° C.-1300° C.
Claim 28
Dependent Claim
20 words
A method according to claim 20 wherein irradiation of the gate dielectric uses radiation of less than about 500 Mrad.
Claim 29
Dependent Claim
18 words
A method according to claim 20 wherein the annealing temperature is within the range of 400° C.-1200° C.
Claim 30
Dependent Claim
14 words
A method according to claim 20 wherein the annealing temperature is about 400° C.
Claim 31
Dependent Claim
22 words
A method according to claim 20 wherein annealing the substrate and gate dielectric comprises annealing in an ambient atmosphere of inert gas.
Claim 32
Dependent Claim
12 words
A method according to claim 29 wherein said ambient atmosphere includes nitrogen.
Claim 33
Dependent Claim
14 words
A method according to claim 20 wherein the field-effect semiconductor device is a MOSFET.
Claim 34
Dependent Claim
17 words
A method according to claim 20 wherein the field-effect semiconductor device is a floating gate memory device.
Claim 35
Independent Claim
74 words
A method of improving the inversion layer mobility of an n-channel MOSFET with a reoxidized nitrided oxide gate dielectric, the method comprising: irradiating the MOSFET with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the MOSFET at about 400° C. or greater after said irradiating of the MOSFET for a duration in the order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 36
Independent Claim
74 words
A method of improving the inversion layer mobility of an n-channel MOSFET with a reoxidized nitrided oxide gate dielectric, the method comprising: irradiating the MOSFET with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the MOSFET at about 400° C. or greater after said irradiating of the MOSFET for a duration in the order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 37
Independent Claim
164 words
A method of fabricating a MOSFET comprising: providing a semiconductor substrate having a channel region of a first conductivity type forming a silicon dioxide gate dielectric on a surface of the substrate adjacent the channel region; exposing the gate dielectric to an ammonia atmosphere at a relatively high temperature to form a nitrided oxide gate dielectric; exposing the gate dielectric to an oxygen atmosphere at a relatively high temperature to form a reoxidized nitrided oxide gate dielectric; forming a source region and a drain region each of a second conductivity type in the semiconductor substrate such that the source and drain regions are separated in the substrate by said channel region; irradiating the reoxidized nitrided oxide gate dielectric with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the substrate and gate dielectric at about 400° C. or greater for a duration int he order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
Claim 38
Independent Claim
164 words
A method of fabricating a MOSFET comprising: providing a semiconductor substrate having a channel region of a first conductivity type forming a silicon dioxide gate dielectric on a surface of the substrate adjacent the channel region; exposing the gate dielectric to an ammonia atmosphere at a relatively high temperature to form a nitrided oxide gate dielectric; exposing the gate dielectric to an oxygen atmosphere at a relatively high temperature to form a reoxidized nitrided oxide gate dielectric; forming a source region and a drain region each of a second conductivity type in the semiconductor substrate such that the source and drain regions are separated in the substrate by said channel region; irradiating the reoxidized nitrided oxide gate dielectric with ionizing radiation sufficient to create electron-hole pairs in the gate dielectric; and annealing the substrate and gate dielectric at about 400° C. or greater for a duration int he order of thirty minutes such that there is a significant improvement in inversion layer mobility rate.
References Cited (Backward Citations)
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1996-06-14 | 1996-12-14 | 1997-06-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-14 | 2000-12-14 | 2001-06-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-14 | 2004-12-14 | 2005-06-15 | $7700.00 | Window Closed / Lapsed |