Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
2001-06-28
2002-06-25
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230IR
Reexamination Certificate
active
06409877
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for plasma etching. More particularly, it relates to an apparatus and method for plasma etching wherein a target film is etched by a plasma generated with a high-frequency induction field produced by a spiral coil disposed in opposing relationship with a sample stage provided in a chamber.
With the increasing miniaturization of a semiconductor integrated circuit element in recent years, exposing light with a shorter wavelength has been used in a lithographic step. At present, the use of a KrF excimer laser (with a wavelength of 248 nm) or an ArF excimer laser (with a wavelength of 193 nm) is becoming prevalent.
As the wavelength of exposing light becomes shorter, the reflectivity of light reflected from a substrate after exposing a resist film becomes higher so that the reflected light from the substrate is more likely to cause variations in the size of a resist pattern. To prevent the reflected light from being incident on the resist film, there has recently been used a process wherein an organic bottom anti-reflective coating (hereinafter referred to as ARC) is formed under the resist film. The ARC process is primarily used in the manufacturing of a semiconductor element in a high-performance device with design rules whereby a gate width is 0.25 &mgr;m or less.
In the ARC process, it is necessary to etch the ARC after a resist pattern is formed by a conventional lithographic technique. Of a variety of plasma etching apparatus used to etch the ARC, an apparatus for inductively coupled plasma (ICP) etching with a spiral coil is used frequently.
As examples of the inductively coupled apparatus for plasma etching, an apparatus for inductively coupled plasma etching having a planar coil (see U.S. Pat. No. 4,948,458), an apparatus for inductively coupled plasma etching with a dome-shaped coil (see U.S. Pat. No. 5,614,055), and the like are known.
Referring to
FIG. 10
, a conventional apparatus for inductively coupled plasma etching having a planar single spiral coil will be described.
As shown in
FIG. 10
, a sample stage
2
as a lower electrode to which high-frequency power is applied is disposed in the lower portion of a grounded chamber
1
having an inner wall covered with an insulator such as ceramic, alumina, or quartz. A semiconductor substrate
3
as a sample to be etched is placed on the sample stage
2
. The chamber
1
is provided with gas inlet ports (not shown) for introducing etching gas into the chamber
1
via a mass flow controller and with a gas outlet port
5
connected to a turbo pump for setting pressure in the chamber
1
to the order of 0.1 Pa to 10 Pa.
A single spiral coil
4
of inductively-coupled type is disposed atop the chamber
1
externally thereof in opposing relationship with the sample stage
2
. The single spiral coil
4
has one end connected to a high-frequency power source via a matching circuit (not shown) and the other end connected to a wall of the chamber
1
and thereby grounded. The arrangement allows the single spiral coil
4
to generate a high-frequency induction field so that etching gas introduced into the chamber
1
is changed into a plasma. The etching gas changed into the plasma is guided by high-frequency power applied to the sample stage
2
toward the target film on the semiconductor substrate
3
held by the sample stage
2
so as to etch the target film.
When the present inventors performed an etching process. with respect to an ARC as the target film by using a plurality of inductively coupled apparatus for plasma etching each having the planar single spiral coil
4
mentioned above, the problem occurred that the inplane uniformity of the etching rate varied with the different apparatus for plasma etching, though they were of the same model.
The inplane uniformity of the etching rate is defined as the degree of variations in etching rate across the surface of the target film and expressed as 3&sgr;/&mgr;×100 (%), where &sgr; is the standard deviation of a data value and &mgr; is the mean value of the data value. When variations in data value exhibit a normal distribution, 3&sgr; represents a deviation including 99.74% of the data value. The following equation (1) shows 3&sgr; and &mgr; specifically.
3
σ
=
3
∑
i
=
1
n
(
Xi
-
μ
)
2
n
Equation
1
where
μ
:
mean
value
=
∑
i
=
1
n
Xi
n
n
:
number
of
samples
Xi
:
i
-
th
data
value
.
Conditions for the plasma etching process when the inplane uniformity of the etching rate was measured by using the conventional apparatus for plasma etching are as shown in Table 1.
In Table 1, ICP denotes high-frequency power applied to the single spiral coil
4
and RF denotes high-frequency power applied to the sample stage
2
.
TABLE 1
N
2
/O
2
30/30 (sccm)
ICP/RF
350/50 (W)
PRESSURE
8 (mTorr)
TEMPERATURE OF SAMPLE STAGE
10 (° C.)
The models of apparatus for inductively coupled plasma etching and the inplane uniformities of the respective etching rates are as shown in Table 2. As shown in FIG.
18
(
a
), etching was performed with respect to the ARC
11
as a target film formed on the semiconductor substrate
10
.
TABLE 2
APPARATUS MODEL
UNIFORMITY
APPARATUS A
±4.5%
APPARATUS B
±2.1%
APPARATUS C
±5.6%
APPARATUS D
±5.1%
APPARATUS E
±3.3%
APPARATUS F
±6.8%
APPARATUS G
±2.6%
As will be understood from Table 2, the inplane uniformities of the etching rates for the ARC
11
were ±4.5% for the apparatus A, ±2.1% for the apparatus B, ±5.6% for the apparatus C, ±5.1% for the apparatus D, ±3.3% for the apparatus E, ±6.8% for the apparatus F, and ±2.6% for the apparatus G and not constant.
The etching rate which is inferior in inplane uniformity causes variations in the actual amount of etching across the surface of the target film. If the actual amount of etching varies across the surface of the target film, an adverse effect is produced such as variations in the characteristics of a FET in the case of forming the gate electrode of the FET by etching.
SUMMARY OF THE INVENTION
In view of the foregoing, it is therefore an object of the present invention to improve the inplane uniformity of an etching rate when etching is performed with respect to a target film by using an apparatus for plasma etching and to reduce variations in the inplane uniformity of the etching rate from apparatus to apparatus for plasma etching of the same model.
As a result of various examinations of the above apparatus A to G, the present inventors found that the positional relationship between the single spiral coil
4
and the gas outlet port
5
varied with the different models of apparatus.
Assuming that the positional relationship between the single spiral coil
4
and the gas outlet port
5
affects the uniformity of the etching rate, the present inventors examined the varying positional relationship between the single spiral coil
4
and the gas outlet port
5
and found that the varying positional relationship between the single spiral coil
4
and the gas outlet port
5
caused uneven distribution of reactive radicals over the plasma generation region in the chamber
1
. A description will be given below to the finding.
First, as shown in
FIG. 11
, it is assumed that the single spiral coil
4
consists of three portions which are: a coil portion
4
a
contributing directly to the generation of a high-frequency induction field; a power-source-side withdrawn portion
4
b
positioned between the coil portion
4
a
and the high-frequency power source
6
, and a ground-side withdrawn portion
4
c
positioned between the coil portion
4
a
and a ground source
7
. It is also assumed that the coil portion
4
a
consists of two regions separated by a first line L
1
linking a power-source connection point A between
Dang Thi
Matsushita Electronics Corporation
McDermott & Will & Emery
LandOfFree
Apparatus and method for plasma etching does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for plasma etching, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for plasma etching will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2915188