Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1999-06-30
2002-02-26
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C156S345420, C438S716000, C438S729000
Reexamination Certificate
active
06350698
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10 188672 filed Jul. 03, 1998, which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a dry etching apparatus used in fabrication of super LSIs, and so forth, for micro processing of a pattern by exciting and activating a gas with electric-discharge plasma to make it interact with a substance on a wafer and then evacuating it, and also relates to a method for dry-etching a substrate.
2. Description of the Related Art
Along with progressive miniaturization of semiconductor devices, for the purpose of enabling processing of finer patterns than those heretofore realized dy dry etching apparatuses as their manufacturing apparatuses, further improvements are under progress with employment of a method ensuring highly even electric discharge of a plasma and realization of high-speed evacuation. Together with improvements of such etching techniques, reduction of particles for preventing defects in micro-sized patterns during processing is an important factor required in manufacturing apparatuses. In order to prevent products of reaction as a major source of particles from accumulating in a reaction chamber during processing, there is a movement toward reducing parts in the reaction chamber and simplifying the flow of reaction products.
An example of conventional dry etching apparatuses is shown in FIG.
1
. Shown here is a substrate susceptor by reference numeral
101
. The substrate susceptor
101
mainly comprises a lower electrode
111
, an annular focus ring
112
, and so on. The lower electrode
111
has formed on its top surface a groove
113
for a cool gas, and the groove
113
is connected to a cool gas supply/exhaust line
114
. Helium gas, for example, is used as the cool gas. Provided inside the lower electrode
111
are a cooling tank
115
containing a refrigerant and a wafer push-up mechanism
116
located in a central position. The lower electrode
111
is connected to a high-frequency power source
118
via a capacitor
119
.
Further referring to
FIG. 1
, reference numeral
102
denotes an upper end portion of the reaction chamber. The upper end portion
102
of the reaction chamber is dome-shaped, and a coil
123
fitting on the outer circumferential surface of the dome-shaped upper end portion
102
is connected with its one end to a high-frequency power source
121
via a capacitor
122
and with the other end to the ground.
Still referring to
FIG. 1
, reference numeral
110
denotes a wafer to be processed by etching. The wafer
110
is transported by a carrier arm, not shown, and put on the substrate susceptor
101
at a position where the inner circumferential surface of the focus ring
112
functions as positional definition thereof. Additionally, etching gas inlets and exhaust gas outlets, not shown, are provided at lateral locations relative to the position where the wafer
110
lie. A predetermined etching gas is supplied through the inlets into the reaction chamber, and electric-discharge plasma is generated in the reaction chamber held under a predetermined low pressure and a predetermined temperature held in the reaction chamber by applying high-frequency voltages to the lower electrode
111
and the high-frequency coil
123
from high-frequency power sources
118
,
121
. The electric-discharge plasma excites and activates the etching gas to have it interact with a substance on the wafer and thereby invite etching. In this process, flows of the etching gas from the inlets move along the contour of the dome-shaped upper end portion
102
as shown by arrows in
FIG. 1
first to the central portion, there turn their directions to move downward through the plasma region
133
, then turn their directions near the surface of the wafer
110
to move laterally while licking the surface of the wafer
110
, and finally move to the exhaust gas outlets.
In the above-introduced dry etching apparatus using electric-discharge plasma, a complex electric-discharge mechanism occupies the space just above the wafer, and the etching gas inlets are located at lateral positions relative to the wafer. Therefore, the etching gas circulates through the plasma region
133
. As a result, reaction products which should be discharged by flows of the gas are re-dissociated by the plasma and adhere to any in the reaction chamber. More specifically, stagnation occurs in the gas flows at the stepped portion of the focus ring
112
surrounding the wafer
110
, and reaction products accumulate there as shown at
132
in FIG.
1
and may cause generation of dust due to re-dissociation of the reaction products
132
.
For the purpose of overcoming the problem, namely, preventing re-adhesion of reaction products, there is proposed a dry etching apparatus smoothing gas flows by removing any step disturbing evacuation of the gas, like that on the focus ring, from the portion around the wafer.
FIG. 2
shows such a dry etching apparatus removing the focus ring to make a flat plane. In
FIG. 2
, elements and parts common to those of the apparatus shown in
FIG. 1
are labeled with common reference numerals.
In case of the dry etching apparatus shown in
FIG. 2
, the upper end portion
102
of the reaction chamber is configured as a flat plate, and the coil
123
fitting on the outer circumferential surface of the flat upper end portion
102
is connected with its one end to the high-frequency power source
121
via the capacitor
122
and with the other end to the ground. Additionally, an upper electrode
124
is attached onto the flat upper end portion
102
. The upper electrode
124
has formed diffusion holes
125
distributed all over its area to introduce an etching gas, and these diffusion holes
125
are connected to an etching gas inlet tube
126
.
In the dry etching apparatus having the above-explained structure, the etching gas supplied through the diffusion holes
125
falls down from the respective diffusion holes
125
through the plasma region
133
to the proximity of the wafer, there changes its direction to move transversely while licking the surface of the wafer
110
, and finally moves to the exhaust gas outlets.
However, the dry etching apparatus shown in
FIG. 2
also fails to remove the possibility that not a small amount of reaction products accumulate along the perimeter of the substrate susceptor
101
around the wafer
110
as shown at
132
in
FIG. 2
, and dust is generated due to re-dissociation of the reaction products
132
. On the other hand, since this apparatus removes any step like that made by the focus ring for the purpose of making smooth gas flows, it has no means to mechanically determine the setting position of the wafer
110
transported there, and therefore involves the possibility that the wafer is offset from the proper setting position as shown by the broken line and an arrow in
FIG. 2
, for example, and thereby disables its transport. As reviewed above, conventional dry etching apparatuses were compelled to determine the structure of the substrate susceptor so as to preferentially select one at the cost of the other of the requirements, namely, preventing generation of particles in the reaction chamber and ensuring reliable transport of wafers, and no dry etching apparatus satisfying both these requirements has been proposed heretofore.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a dry etching apparatus capable of minimizing adhesion of reaction products, or any other matters, which will become a source of particles, and simultaneously ensuring stable transport, and to provide a method for dry-etching substrates by using the dry etching apparatus.
According to the invention of the second claim, there is provided a dry etching apparatus characterized in that a substrate susceptor has a portion for contact with a wafer, having a diameter not larger than the diameter of the wafer, and no element is pro
Powell William A.
Sonnenschein Nath & Rosenthal
Sony Corporation
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