US6066531A
Expired / Lapsed
US
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Method for manufacturing semiconductor memory device
Assignee: Sharp Corp
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Filing: 1998-06-18
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Granted: 2000-05-23
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Expires: 2018-06-18
Abstract
Abstract A method for manufacturing a semiconductor memory device, including the steps of: forming a plurality of stripes comprising a first floating gate material film and a ion implantation protective film, covering one longitudinal side wall of the stripes with a resist pattern; removing a given width of the other side wall of the first floating gate material film by an isotropic etching in use of the resist pattern as a mask; forming an impurity region of low concentration by implanting impurity ions of a second conductivity type into the semiconductor substrate of the first conductivity type in use of the ion implantation protective film as a mask in a tilted direction after removing the resist pattern; and forming asymmetrical impurity regions on both sides of the stripe like first floating gate material film as viewed in the cross section along the direction perpendicular to the longitudinal direction of the stripes. According to the above-mentioned method, without using a side wall spacer, a semiconductor memory device provided with asymmetrical impurity regions having precisely desired forms can be obtained.
Inventors
- 👤 Yukiharu Akiyama
- 👤 Takuji Tanigami
- 👤 Shinichi Sato
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:21
CPC Classifications
H; H10; H10B; H10B41/00; H10B41/30
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
270 words
A method for manufacturing a semiconductor memory device, comprising the steps of: forming a gate insulating film, a first floating gate material film and an ion implantation protective film in this order over the surface of a semiconductor substrate of a first conductivity type; forming a first resist pattern on the ion implantation protective film; forming a plurality of stripes comprising the first floating gate material film and the ion implantation protective film, the stripes being spaced apart from each other by a given distance, by etching in use of the first resist pattern as a mask; forming a second resist pattern to cover one longitudinal side wall of the stripes after removing the first resist pattern; removing a given width of the other side wall of the first floating gate material film by an isotropic etching with the second resist pattern used as a mask; forming an impurity region of a low concentration by implanting impurity ions of a second conductivity type into the semiconductor substrate of the first conductivity type with the ion implantation protective film used as a mask in a tilted direction after removing the second resist pattern; and forming asymmetrical impurity regions on both sides of the stripe like first floating gate material film as viewed in the cross section along the direction perpendicular to the longitudinal direction of the stripes by implanting impurity ions of the second conductivity type into the semiconductor substrate of the first conductivity type with the ion implantation protective film used as a mask in the direction perpendicular to the semiconductor substrate to form an impurity region of high concentration.
Claim 2
Independent Claim
270 words
A method for manufacturing a semiconductor memory device, comprising the steps of: forming a gate insulating film, a first floating gate material film and an ion implantation protective film in this order over the surface of a semiconductor substrate of a first conductivity type; forming a first resist pattern on the ion implantation protective film; forming a plurality of stripes comprising the first floating gate material film and the ion implantation protective film, the stripes being spaced apart from each other by a given distance, by etching in use of the first resist pattern as a mask; forming a second resist pattern to cover one longitudinal side wall of the stripes after removing the first resist pattern; removing a given width of the other side wall of the first floating gate material film by an isotropic etching with the second resist pattern used as a mask; forming an impurity region of a low concentration by implanting impurity ions of a second conductivity type into the semiconductor substrate of the first conductivity type with the ion implantation protective film used as a mask in a tilted direction after removing the second resist pattern; and forming asymmetrical impurity regions on both sides of the stripe like first floating gate material film as viewed in the cross section along the direction perpendicular to the longitudinal direction of the stripes by implanting impurity ions of the second conductivity type into the semiconductor substrate of the first conductivity type with the ion implantation protective film used as a mask in the direction perpendicular to the semiconductor substrate to form an impurity region of high concentration.
Claim 3
Dependent Claim
17 words
The method of claim 1, wherein the impurity ions of the second conductivity type are arsenic ions.
Claim 4
Dependent Claim
13 words
The method of claim 1, wherein the stripes are formed by anisotropic etching.
Claim 5
Dependent Claim
27 words
The method of claim 1, wherein the stripes are formed so that they are spaced apart from each other by a distance of 0.18 to 0.65 μm.
Claim 6
Dependent Claim
25 words
The method of claim 1, wherein the other side of the first floating gate material film is removed by 0.15 to 0.25 μm in width.
Claim 7
Dependent Claim
43 words
The method of claim 1, wherein the impurity ions of the second conductivity type implanted in the tilted direction are implanted into the silicon substrate in a tilted angle of 5 to 50° with respect to the line perpendicular to the semiconductor substrate.
Claim 8
Dependent Claim
31 words
The method of claim 1, wherein an oxide film is formed by selective oxidation of the semiconductor substrate which is not covered with the stripes, after forming the asymmetrical impurity regions.
Claim 9
Dependent Claim
21 words
The method of claim 7, wherein the oxide film has approximately the same height as the first floating gate material film.
Claim 10
Dependent Claim
77 words
The method of claim 1, further comprising steps of: after forming the impurity regions and removing the ion implantation protective film, forming a second floating gate material film, an insulating film and a control gate material film in this order over the entire surface of the semiconductor substrate; and forming a first floating gate, a second floating gate and a control gate by etching with a third resist pattern of a given shape used as a mask.
Claim 11
Dependent Claim
17 words
The method of claim 9, wherein the first floating gate is covered with the second floating gate.
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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) | 2003-05-23 | 2003-11-22 | 2004-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-05-23 | 2007-11-22 | 2008-05-23 | $3760.00 | Window Closed / Lapsed |
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