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US4098924A Expired / Lapsed US ⏱️ 0.0 years remaining

Gate fabrication method for mnos memory devices

Assignee: Westinghouse Electric Corp
•
Filing: 1976-10-19
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Granted: 1978-07-04
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Expires: 1996-10-19
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Abstract

Abstract An improved method for growing the silicon oxide memory insulator of an MNOS memory transistor is disclosed. The oxide is grown by passing a mixture of inert gas and anhydrous HCL over the substrate while the temperature is maintained within a predetermined range.

Inventors

  • 👤 Raymond M. McLouski
  • 👤 Philip R. Reid

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-27 13:05
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/01; H10D64/013; H10D64/01302; H10D64/01332; H10D64/01336; H10D64/01346; H10D30/00; H10D30/01; H10D30/021; H10D30/0413; H10P; H10P95/00

Claims Analysis

Total Claims: 23
Claim 1
Independent Claim 127 words
A method of growing an insulating layer from a thin oxide layer formed on a silicon substrate to improve the memory window and reduce the rate of memory decay of a device in which said layer and substrate is utilized, comprising the steps of: heating the substrate on which the layer is formed in a furnace chamber of approximately 600° to 900° centigrade through which a substantially pure inert gas is flowing at a selected rate; introducing anhydrous HCL into the furnace at a selected rate to subject the heated oxide layer to a predetermined percentage mixture of the inert gas and the anhydrous HCL; eliminating the anhydrous HCL from the mixture upon the expiration of a selected period of time; and permitting the substrate to cool.
Claim 2
Independent Claim 127 words
A method of growing an insulating layer from a thin oxide layer formed on a silicon substrate to improve the memory window and reduce the rate of memory decay of a device in which said layer and substrate is utilized, comprising the steps of: heating the substrate on which the layer is formed in a furnace chamber of approximately 600° to 900° centigrade through which a substantially pure inert gas is flowing at a selected rate; introducing anhydrous HCL into the furnace at a selected rate to subject the heated oxide layer to a predetermined percentage mixture of the inert gas and the anhydrous HCL; eliminating the anhydrous HCL from the mixture upon the expiration of a selected period of time; and permitting the substrate to cool.
Claim 3
Dependent Claim 16 words
A method according to claim 1 wherein the furnace has a temperature of approximately 750° centigrade.
Claim 4
Dependent Claim 33 words
A method according to claim 1 wherein the predetermined mixture of the inert gas and the anhydrous HCL is in the ratio of approximately 99% of the inert gas and 1% anhydrous HCL.
Claim 5
Dependent Claim 12 words
A method according to claim 1 wherein the inert gas is nitrogen.
Claim 6
Dependent Claim 34 words
A method according to claim 1 wherein the substrate is subjected to the mixture of anhydrous HCL and the inert gas for approximately 10 minutes for a flow rate of 1 liter per minute.
Claim 7
Dependent Claim 37 words
A method according to claim 1 wherein the substrate is subjected to the inert gas flow prior to the introduction of the anhydrous HCL for approximately 5 minutes for a flow rate of 1 liter per minute.
Claim 8
Dependent Claim 40 words
A method according to claim 1 wherein the substrate is subjected to the inert gas subsequent to the elimination of the anhydrous HCL for a period of approximately 1 minute for a flow rate of approximately 1 liter per minute.
Claim 9
Dependent Claim 25 words
A method according to claim 1 wherein the cooling step is performed by cooling the substrate to ambient temperature subsequent to removal from the furnace.
Claim 10
Dependent Claim 16 words
A method according to claim 1 wherein the said insulating layer is a gate oxide layer.
Claim 11
Dependent Claim 26 words
A method according to claim 1 wherein the said insulating layer is a memory oxide layer of an MNOS device which utilizes tunnelling to store charges.
Claim 12
Independent Claim 134 words
A method of processing a thin oxide portion of an MNOS memory transistor to provide a device having a DC memory window of approximately 12 volts and a memory decay rate of approximately 0.35 to 0.1 volts per decade, comprising the steps of: subjecting the MNOS substrate having previously formed drain and source regions and an overlying thick and thin oxide portion to a furnace temperature of approximately between 600° to 900° centigrade in an atmosphere of a flowing inert gas; changing the inert gas atmosphere to a flowing atmosphere of approximately 1% anhydrous HCL and 99% inert gas after a first predetermined time interval; changing the anhydrous HCL and inert gas atmosphere to an inert gas atmosphere after a second predetermined time interval; and cooling the substrate after a third predetermined time interval.
Claim 13
Independent Claim 134 words
A method of processing a thin oxide portion of an MNOS memory transistor to provide a device having a DC memory window of approximately 12 volts and a memory decay rate of approximately 0.35 to 0.1 volts per decade, comprising the steps of: subjecting the MNOS substrate having previously formed drain and source regions and an overlying thick and thin oxide portion to a furnace temperature of approximately between 600° to 900° centigrade in an atmosphere of a flowing inert gas; changing the inert gas atmosphere to a flowing atmosphere of approximately 1% anhydrous HCL and 99% inert gas after a first predetermined time interval; changing the anhydrous HCL and inert gas atmosphere to an inert gas atmosphere after a second predetermined time interval; and cooling the substrate after a third predetermined time interval.
Claim 14
Dependent Claim 16 words
A method according to claim 11 wherein the furnace has a temperature of approximately 750° centigrade.
Claim 15
Dependent Claim 35 words
A method according to claim 12 wherein the thin portion of the oxide layer is formed by etching a portion of the thick oxide layer, said thin portion being the residual oxide layer after etching.
Claim 16
Dependent Claim 12 words
A method according to claim 11 wherein the inert gas is nitrogen.
Claim 17
Dependent Claim 16 words
A method according to claim 11 wherein the second predetermined time interval is approximately 10 minutes.
Claim 18
Dependent Claim 16 words
A method according to claim 11 wherein the first predetermined time interval is approximately 5 minutes.
Claim 19
Dependent Claim 16 words
A method according to claim 11 wherein the third predetermined time interval is approximately 1 minute.
Claim 20
Dependent Claim 17 words
A method according to claim 11 wherein the cooling step is carried out in an ambient atmosphere.
Claim 21
Dependent Claim 43 words
A method according to claim 11 wherein the thick portion of the oxide layer is greater than one hundred Angstroms and the thin portion of the oxide layer prior to the first named step is in the neighborhood of eight to ten Angstroms.
Claim 22
Independent Claim 131 words
A method of processing a thin oxide layer formed on a silicon substrate, comprising the steps of: subjecting the substrate on which the layer is formed to a furnace chamber having a temperature between approximately 600° and 900° centigrade through which an inert gas is flowing for approximately 5 minutes for a rate of approximately 1 liter per minute for a chamber of approximately ten square inches in cross section; introducing anhydrous HCL into the heated chamber for approximately 10 minutes for a mixture of 99% inert gas and 1% HCL for an approximate rate of one liter per minute; continuing the flow of inert gas in the furnace chamber for approximately 1 minute for a flow rate of approximately 1 liter per minute; and removing the substrate from the furnace.
Claim 23
Independent Claim 131 words
A method of processing a thin oxide layer formed on a silicon substrate, comprising the steps of: subjecting the substrate on which the layer is formed to a furnace chamber having a temperature between approximately 600° and 900° centigrade through which an inert gas is flowing for approximately 5 minutes for a rate of approximately 1 liter per minute for a chamber of approximately ten square inches in cross section; introducing anhydrous HCL into the heated chamber for approximately 10 minutes for a mixture of 99% inert gas and 1% HCL for an approximate rate of one liter per minute; continuing the flow of inert gas in the furnace chamber for approximately 1 minute for a flow rate of approximately 1 liter per minute; and removing the substrate from the furnace.

References Cited (Backward Citations)

US3647535A Cited
US3692571A Cited
US3719866A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1981-07-03 1982-01-02 1982-07-04 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1985-07-03 1986-01-02 1986-07-04 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1989-07-03 1990-01-02 1990-07-04 $7700.00 Window Closed / Lapsed

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