Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-04-22
2001-01-23
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230AN, C118S7230ER, C118S7230ER
Reexamination Certificate
active
06176969
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a baffle plate of a dry etching apparatus for manufacturing semiconductor devices, and more particularly, a baffle plate for minimizing the vacuum level fluctuations in a process chamber, as well as minimizing the accumulation of particles that are generated as by-products of the semiconductor device fabrication process.
2. Description of the Related Art
Generally, semiconductor devices are manufactured by forming multiple layers on a semiconductor substrate wafer, and forming circuit patterns thereon according to the desired electrical properties of a specified semiconductor device.
The patterns on the semiconductor substrate are typically formed by selectively removing portions of the layers on the semiconductor substrate using an etching process.
Conventional etching processes are categorized as wet etching (using chemicals), dry etching (using plasma), and reactive ion etching, which is a type of dry etching with improved plasma efficiency.
A conventional reactive ion etching apparatus is shown in
FIG. 1
, and includes an upper electrode
12
and a lower electrode
14
, to which high frequency power is applied for forming the plasma inside a process chamber
10
. When power is applied to the lower electrode
14
the upper electrode
12
functions as ground. The lower electrode
14
is located under the chuck for mounting the wafer W. A transfer apparatus
28
transports the wafers to and from the chuck.
A magnetic coil
15
surrounds the process chamber
10
in order to generate a magnetic field during the etching process. A gas supply line
16
is provided on the upper electrode
12
for supplying, to the process chamber
10
, a reaction gas and other gases required for the etching process.
A vacuum chamber
24
is disposed under the process chamber
10
, with the vacuum chamber
24
being connected to a vacuum pump
18
for forming the vacuum in the process chamber
10
. Valves
20
and
22
are connected between the vacuum chamber
24
and the vacuum pump
18
. Gate valve
20
is selectively opened/closed in conjunction with the operation of the vacuum pump
18
. Vacuum control valve
22
controls the degree or level of the vacuum in the vacuum chamber
24
. This is accomplished by controlling the opening angle of the vacuum control valve
22
.
A vacuum indicator
26
is connected to the vacuum chamber
24
for readily displaying the degree of vacuum in the vacuum chamber
24
. The vacuum indicator
26
senses the degree of vacuum in the vacuum chamber
24
, and inputs it to a controlling part (not shown). Accordingly, the controlling part controls the opening/closing of the vacuum control valve
22
, which in turn controls the degree of vacuum in the vacuum chamber
24
.
In this embodiment, the degree of vacuum in the process chamber
10
should basically be the same as the degree of vacuum in the vacuum chamber
24
, which can easily be ascertained by the vacuum indicator
26
display.
A baffle plate
30
is disposed between the process chamber
10
and the vacuum chamber
24
, and has slits for discharging the non-reacting gases and polymer by-products remaining inside the process chamber
10
to the vacuum chamber
24
. The baffle plate
30
essentially surrounds the chuck of the lower electrode
14
, such that the inner circumference of the baffle plate
30
confronts the outer circumference of the chuck. To effect a wafer transfer, the chuck would descend from this engaged position, move toward the transfer apparatus
28
, and thereafter the wafer is mounted on the chuck. The chuck then moves back toward the baffle plate
30
and then rises to the engaged position confronting the baffle plate
30
.
As shown in
FIG. 2
the baffle plate
30
comprises a plurality of slits
34
formed radially in the annular ring portion
32
of the baffle plate
30
and spaced a certain distance from each other. In the conventional baffle plate, 360 slits are provided.
As shown in
FIG. 3
the slit
34
has three distinct sections. The upper
40
part of the slit
34
has an inclined surface, with the widest portion facing the process chamber
10
and thereafter converging as it approaches the middle part. The middle part is vertically formed with a constant width. The lower part facing the vacuum chamber
24
is also vertically formed, but with a constant width greater than that of the middle part.
As described above, the non-reacting gases and polymer
36
by-products remaining inside the process chamber
10
are discharged into the vacuum chamber
24
through the slits
34
of the baffle plate
30
. However, as shown in
FIG. 3
, not all the polymer by-products are discharged to the vacuum chamber
24
, and a certain amount of polymer
36
remains on the annular ring
32
and slits
34
.
As one could readily see, if the width of the middle part of the slit
34
is A (e.g., 0.8 mm) the polymer
36
deposits serve to reduce the width of the opening to something less than A, which then hinders the remaining non-reacted gases in the process chamber
10
from being discharged to the vacuum chamber
24
.
The remaining non-reacted gases in the process chamber
10
changes the degree of vacuum in the process chamber
10
. Accordingly, the degree of vacuum as indicated by the vacuum indicator
26
and the degree of vacuum in the process chamber
10
are different.
For example, if initially about 35 mTorr of vacuum is formed inside the process chamber
10
and the vacuum chamber
24
, as the etching process proceeds the degree of vacuum in the process chamber
10
increases to above 35 mTorr due to the polymer
36
by-products generated and attached to the annular ring
32
and slits
34
, while the vacuum indicator
26
senses the vacuum in the vacuum chamber
24
as 35 mTorr. As shown in
FIG. 4
, the etch rate is inversely proportional to the length of the etching process time due to the changes in the degree of vacuum in the process chamber
10
, that is, the etch rate is decreased.
In particular, during an etching process to form contact holes in an oxide film (SiO
2
film) on a semiconductor substrate using CHF
3
as the main reaction gas, and CO as the supplementary gas, polymer
36
by-products are rapidly generated which thereafter adhere to the surface of the annular ring
32
and slits
34
. More specifically, the CHF
3
supplied as the main reaction gas is dissociated in the plasma state into CHF
2
+F* (* : radical), that is, the active radical F* reacts with an etched layer, SiO
2
, forming Si
x
F
y
and O
2
. The O
2
then reacts with the CO supplied as the supplementary gas, thereby generating the polymer
36
by-product.
Accordingly, the degree of vacuum in the process chamber
10
changes due to the polymer
36
attached on the annular ring
32
and the slits
34
, but this change, as described above, is not accurately reflected at the vacuum indicator
26
, whereby the etching process is inadvertently permitted to proceed at decreased etch rate.
FIG. 5
depicts contact holes formed through a certain layer
44
on a semiconductor substrate wafer W having a gate electrode
40
and a field oxide film
43
. Because of the decreased etch rate, however, the bottom
42
portion of the contact hole does not reach the wafer, or the width of the contact hole is too small to perform its intended function.
In addition, the polymer
36
adhered to the annular ring
32
and slits
34
serves as source of contaminating particles, which thereafter adhere to the wafer inside the process chamber
10
and cause process failures during the etching process.
In summary, an etching apparatus having a conventional baffle plate suffers from two main problems. One is the degree of vacuum inside the process chamber changes due to the attached polymer deposits. The other is the polymer deposits serve as a source of contaminating particles, thereby resulting in a decrease in the productivity and reliability of the semiconductor device manufacturing process.
SUMMARY OF THE INVENTION
The present invention is
Choi Jong-wook
Park Jeong-hyuck
Dang Thi
Jones Volentine, LLC
Samsung Electronics Co,. Ltd.
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