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Trench Capacitor Dram Cell with Source Region Diffused from Boron Doped Polisilicon Strap

IP.com Disclosure Number: IPCOM000111179D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Fujisawa, K: AUTHOR [+2]

Abstract

Disclosed is a new CMOS Dynamic Random Access Memory (DRAM) process in which the source region of the transfer FET is formed by diffusion from a boron doped polysilicon strap.

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This is the abbreviated version, containing approximately 76% of the total text.

Trench Capacitor Dram Cell with Source Region Diffused from Boron
Doped Polisilicon Strap

      Disclosed is a new CMOS Dynamic Random Access Memory (DRAM)
process in which the source region of the transfer FET is formed by
diffusion from a boron doped polysilicon strap.

      The Figure shows the cross-section of the new DRAM memory cell.
A process sequence consists of the following steps:

1.  Forming trench capacitor (1).

2.  Growing SiO2 (LOCal Oxidation of Silicon (LOCOS) or Shallow
    Trench Isolation (STI)) isolation (2).

3.  Depositing boron-doped poly Si, oxidizing and patterning to form
    boron-doped poly Si strap (3).

4.  Forming nitride spacer (4) or oxidizing the poly Si strap

5.  Growing gate oxide.

6.  Depositing n-type poly Si (5), tungsten silicide (6) and Low
    Pressure Chemical Vapor Deposition (LPCVD) SiO2 (7).

7.  Patterning the gate electrode.

8.  Forming nitride spacer (8) on the gate electrode edges.

9.  Ion-imlanting Complementary Metal Oxide Semiconductor Field
    Effect Transistor (CMOSFET) drain region and annealing for
    activation.  In this step, the source region is formed by
    diffusion from the poly Si starp (3).

10. Blanket-depositing CVD insulator film.

11. Etching contact holes, depositing and patterning wiring metal.

This process has three advantages:

1.  As the source junction is formed by diffusion from the
    boron-doped poly-Si (3), process damage is much less than in the
    case...