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High Density Dynamic Random-Access Memory Cell Compatible with Bicmos

IP.com Disclosure Number: IPCOM000102319D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

El-Kareh, B: AUTHOR

Abstract

A mesa type of trench dynamic random-access memory (DRAM) cell is described which connects an array device substrate to a wafer substrate by means of a P+ polysilicon-filled trench plate.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

High Density Dynamic Random-Access Memory Cell Compatible with Bicmos

       A mesa type of trench dynamic random-access memory (DRAM)
cell is described which connects an array device substrate to a wafer
substrate by means of a P+ polysilicon-filled trench plate.

      It is essential to have a means for connecting a device
substrate to a fixed potential while providing a high density memory
array which allows the merger of DRAM/SRAM/LOGIC BICMOS technologies.
Utilizing advanced ground rules, a memory cell layout is shown in the
figure which facilitates technology mergers. To fabricate an array of
these cells, a process sequence is shown which yields a high density
DRAM cell compatible with BICMOS. The bipolar portion of the
technology is not described here since it follows standard processing
techniques.
      1)   A p-type substrate is chosen for illustration purposes.
      2)   A heavily doped n-well (subcollector) is either deposited
as a "blanket" or defined with a mask, depending on the bipolar
isolation technique being utilized.
      3)   An n-type epitaxy is grown.
      4)   Insulating layers are deposited to define deep trenches
using  well-known techniques. The trenches extend beneath the n-well
region, as shown.
      5)   For isolation, the trench floor is implanted with a
medium- to-heavy dose of boron. Implantation is done at normal
incidence.
      6)   The trench node insulator stack is grown next.
  ...