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US4957878A Expired / Lapsed US ⏱️ 0.0 years remaining

Reduced mask manufacture of semiconductor memory devices

Assignee: Micron Technology Inc
•
Filing: 1988-05-02
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Granted: 1990-09-18
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Expires: 2008-05-02
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Abstract

Abstract A dynamic randon access memory (DRAM) is formed in a series of masking steps, during which a first layer of polysilicon is anisotropically etched. After the anisotropic etch, junctions are added to the polysilicon through doping techniques. A second layer of polysilicon is then deposited and is isotropically etched. By the sequence, critical dimensions are established at preliminary mask layers and subsequent layers do not require the high degree of criticality of dimension.

Inventors

  • 👤 Tyler A. Lowrey
  • 👤 Randal W. Chance

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-28 00:00
CPC Classifications
H; H10; H10B; H10B12/00; H10B12/01

Claims Analysis

Total Claims: 4
Claim 1
Independent Claim 177 words
Method of forming semiconductor circuit memory devices which include, as a part of each device, a plurality of memory cells and active circuit elements to control signals, the cells and active circuit elements forming a repeating pattern on the device, the method comprising: (a) preparing a silicon wafer and establishing the wafer as a substrate; (b) forming an initial oxide on the wafer; (c) establishing buried contact of rings in the initial oxide; (d) deposit a polysilicon layer on said initial oxide layer and buried contact openings, and patterning said polysilicon layer to simultaneously form gate electrodes and bitlines connected to substrate through the buried contact openings; (e) applying a second oxide layer over the gate electrodes and bitlines; (f) applying a third oxide layer on the second oxide layer; (g) anisotropically etching the second and third oxide layers to form oxide sidewall spacers on the gate electrodes while leaving an oxide layer on top portions of said gate electrodes; (h) forming capacitor plates after said anisotropic etch; (i) forming electrical connections between the various device regions.
Claim 2
Dependent Claim 177 words
Method of forming semiconductor circuit memory devices which include, as a part of each device, a plurality of memory cells and active circuit elements to control signals, the cells and active circuit elements forming a repeating pattern on the device, the method comprising: (a) preparing a silicon wafer and establishing the wafer as a substrate; (b) forming an initial oxide on the wafer; (c) establishing buried contact of rings in the initial oxide; (d) deposit a polysilicon layer on said initial oxide layer and buried contact openings, and patterning said polysilicon layer to simultaneously form gate electrodes and bitlines connected to substrate through the buried contact openings; (e) applying a second oxide layer over the gate electrodes and bitlines; (f) applying a third oxide layer on the second oxide layer; (g) anisotropically etching the second and third oxide layers to form oxide sidewall spacers on the gate electrodes while leaving an oxide layer on top portions of said gate electrodes; (h) forming capacitor plates after said anisotropic etch; (i) forming electrical connections between the various device regions.
Claim 3
Dependent Claim 19 words
Method as described in claim 1, further comprising: doping the substrate in the region of the buried contact openings.
Claim 4
Dependent Claim 22 words
Method as described in claim 1, further comprising: said preparation of the wafer including predoping the wafer to provide a P-type material.

References Cited (Backward Citations)

US4280271A Cited
US4341009A Cited
US4366613A Cited
US4441247A Cited
US4417325A Cited
US4463491A Cited
US4536943A Cited
US4464824A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1993-09-17 1994-03-19 1994-09-18 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1997-09-17 1998-03-19 1998-09-18 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 2001-09-17 2002-03-19 2002-09-18 $7700.00 Window Closed / Lapsed

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