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Simplified Trench Sidewall Doping Process

IP.com Disclosure Number: IPCOM000103144D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 53K

Publishing Venue

IBM

Related People

Harmon, D: AUTHOR [+2]

Abstract

By use of electron cyclotron resonance (ECR) oxide deposition for masking and ECR trench wall impurity deposition, very deep and narrow trench walls are doped in a relatively small number of process steps.

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Simplified Trench Sidewall Doping Process

      By use of electron cyclotron resonance (ECR) oxide deposition
for masking and ECR trench wall impurity deposition, very deep and
narrow trench walls are doped in a relatively small number of process
steps.

      Figures 1a and 2a are cross sections used in describing a
process for doping entire trench sidewalls.  Figures 1b and 2b are
used in describing a process for doping upper portions of trench
sidewalls.

      Referring to Fig. 1a, a trench is cut in silicon substrate 10
by conventional means.  Silicon dioxide (SiO2) is deposited by ECR
which leaves only a thin, porous film on vertical walls while
depositing a much thicker, high quality (non-porous) masking film 12
on horizontal surfaces.  Then, a brief isotropic etch is used to
remove the SiO2 from the vertical walls.

      Referring to Fig. 2a, an appropriate impurity is deposited on
all exposed surfaces, preferably at a relatively low temperature
afforded by ECR.  The impurity is then driven into trench sidewalls
by an anneal to form doped regions 14.  Impurity deposited on
horizontal surfaces is held on and in SiO2 12 and may be removed, if
required, by etching away masking film 12.  Conventional processing
is resumed, for instance with formation of a dielectric coating on
the trench interior and filling the trench with doped silicon (not
shown).

      Referring to Fig. 1b, the trench in substrate 10 is coated with
dielectric 16, filled w...