INITIAL PLASMA TREATMENT FOR VERTICAL DRY ETCHING OF SIO2

TRAITEMENT A L'AIDE D'UN PLASMA AVANT LA GRAVURE A SEC VERTICALE DE SIO2

English Abstract

A method of making a semiconductor device is disclosed wherein a plasma
treatment is carried out prior to carrying out an etch step.

Claims

Claims
1. A method of making a semiconductor device wherein a plasma treatment
is carried out prior to carrying out an etch step.

2. A method as claimed in claim 1, wherein the plasma treatment is carried
out with an oxygen or inert gas plasma.

3. A method as claimed in claim 1, wherein said etch step is carried out to
produce vertical sidewalls.

4. A method as claimed in claim 3, wherein said etch step is a dry plasma
etch.

5. A method as claimed in claim 1, wherein said semiconductor device is a
photonic device.

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Description

CA 02349033 2001-05-28
Initial plasma treatment for vertical dry etching of Si02
Background of the Invention
I. Field of the Invention
This invention relates to a method of making semiconductor devices, and in
particular photonic devices with vertical sidewalls.
2. Description of Related Art
The verticality of Si02 sidewalls is critical, particularly for photonic
devices. The
verticality depends on the sample temperature. It i;> imperative to have a
good
control of the sample's temperature. However, the sample being etched does not
reach a stable-constant temperature before ~ 1 min after starting the plasma
(temperature rise induced by ion bombardment); leaving rounded edges (non-
verticality near the top of the sidewalk).
Present technology either does nor recognize this problem (and associated
advantages) or simply tries to live with it. Present technology is not capable
of
providing deep, fast and good control of verticality in etching Si02.
Summary of the Invention
According to the present invention there is provided a method of making a
semiconductor device wherein a plasma treatment is carried out prior to
carrying
out an etch step.
It has been found surprisingly that by the inventive technique of adding a
plasma
treatment just before the etch step, a dramatic improvement in the verticality
of
etched sidewalk can be obtained.
By using an 02 plasma or any inert gas, the sample is. brought to a constant
temperature before starting the real plasma etching conditions.
The process parameters (particularly the temperaturEa) should remain constant
during etching.
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CA 02349033 2001-05-28
Brief Description of the Drawings
The invention will now be described in more detail, by way of example, only
with
reference to the accompanying drawings, in which:-
Figure 1 is an SEM image of a Si02 ridge etched with a non-constant sample
temperature, in particular showing a rounded rough edge just below the surface
or
the hardmask; and
Figure 2 is an SEM image of a Si02 ridge etched with the new process at stable
sample temperature.
Detailed Description of the Invention
20 During the manufacture of a photonic device vertical Si02 sidewails are
formed by
etching using a conventional dry plasma etching technique. Just prior to
carrying
out the dry etch step, a simple and efficient plasma treatment is performed
just
before the etch step. During subsequent etching the :process parameters, and
in
particular the temperature, are maintained constant.
By using an OZ plasma or any inert gas plasma, the sample is brought to a
constant
temperature before starting the plasma etch process.
The following SEM image shown in Figures 1 and 2 illustrate the improvement
obtained using the new process: Figure 1 shows a rounded edge induced by a non
constant etching temperature, while the Figure 2 shows a sharp edge obtained
by
using the novel process. It will be seem that the edge is sharp, the straight
sidewall
starts just below the hardmask.
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Representative Drawing