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Browse Prior Art Database

Tapered Insulator Storage Trench

IP.com Disclosure Number: IPCOM000103086D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Kenney, DM: AUTHOR [+2]

Abstract

To avoid parasitic leakage current collected on junctions in trench structures, e.g., at the top of a trench capacitor, a nonconformal insulator is added to thin insulating layers to create a thicker coating on top edges while retaining benefits of thin insulation (high capacitance) elsewhere in the structure.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 89% of the total text.

Tapered Insulator Storage Trench

      To avoid parasitic leakage current collected on junctions in
trench structures, e.g., at the top of a trench capacitor, a
nonconformal insulator is added to thin insulating layers to create a
thicker coating on top edges while retaining benefits of thin
insulation (high capacitance) elsewhere in the structure.

      Thus, opportunity is created to optimize storage insulator
thickness by using thinner than usual insulator thickness in the
lower portion of the trench while making insulator thickness greater
than usual in the upper portion where most leakage current
originates.

      Referring to the figure, silicon substrate 2 is etched to form
a trench, oxidized to form insulator layer 4, conformally coated with
insulator layer 6, e.g., silicon nitride, in a conventional storage
trench process which includes adjacent diffusion 8.  Next, a
nonconformal layer of insulator 10, e.g., silicon dioxide, is
deposited.  In a conventional process, a final layer 12 of silicon
dioxide is conformally deposited.  Note that a change in deposition
process parameters may be used to cause a change from nonconformal to
nearly conformal coating, thereby combining deposition of layers 10
and 12 into a single process step.

      Thus, a three-layer thin insulator covers most of the trench
capacitor sidewall area to achieve high capacitance with no shorts.
Thicker insulation covers the upper portion of the trench where high
fields can cr...