Plasma process apparatus

Details Plasma process apparatus Plasma process apparatus

2001-01-12

2003-09-16

Hassanzadeh, Parviz (Department: 1763)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

With microwave gas energizing means

C156S345420, C156S345360, C118S7230MW, C118S7230MR, C118S7230MA, C315S111210

Reexamination Certificate

active

06620290

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma process apparatuses, and more particularly, to a plasma process apparatus for use in fabrication of a semiconductor device, a liquid crystal display device or the like.
2. Description of the Background Art
Conventionally, a plasma process apparatus with a capacitively-coupled plasma source has been utilized for fabricating a semiconductor device, a liquid crystal display device or the like, in which a pair of electrodes are placed within a process chamber and supplied with high-frequency power of 13.56 MHz as means of plasma excitation. In such an apparatus, an object being processed is placed on one of the electrodes. If the object being processed is conductive, it is possible to excite plasma using direct-current (DC) power even with such a capacitively-coupled type apparatus.
Recently, in an effort to realize a more advanced, highly productive device fabrication technique, a plasma process apparatus incorporating a plasma source capable of exciting so-called “high density plasma” has been developed extensively. Although plasma exciting means based on a variety of principles can be employed for such an apparatus, the one utilizing microwave is highly advantageous. When employing the microwave, besides the fact that the high density plasma as mentioned above can be obtained, it becomes unnecessary to provide a process chamber with an electrode for introduction of power necessary at least for plasma excitation. This eliminates a possibility of contamination of impurities associated with the electrode material. In addition, the plasma excited with the microwave has a potential that is lower than the plasma obtained by the capacitively-coupled type apparatus, which leads to another advantage that influx of energy particles to the surface of the object being processed can be controlled to a greater extent.
With conventional apparatuses, however, it has been difficult to realize a plasma state that permits uniform processing of a relatively wide area. A number of techniques have been proposed to address this problem.
One of the techniques is disclosed in Japanese Patent Laying-Open No. 11-111493.
FIGS. 16 and 17
schematically show vertical and horizontal cross sectional views, respectively, of a plasma process apparatus disclosed therein.
Referring to
FIGS. 16 and 17
, the plasma process apparatus includes, among others, a reaction chamber
120
, a microwave introduction window
102
, a stage
107
, a dielectric line
111
, a microwave distributor
113
, a microwave waveguide
114
, and a microwave oscillator
115
.
The inside of metal reaction chamber
101
constitutes a reaction chamber
120
, whose top is sealed airtight by microwave introduction window
102
. Within reaction chamber
120
a stage
107
is placed for holding thereon a semiconductor substrate
108
as an object being processed. A high-frequency power supply is connected to stage
107
. Four partitioned dielectric lines
111
are provided above microwave introduction window
102
, with a prescribed spacing (air gap
112
) provided therebetween. An outer periphery of each dielectric line
111
is covered with a metal plate
116
. Each dielectric line
111
has its side connected to microwave waveguide
114
via microwave distributor
113
. Microwave oscillator
115
is attached to the end of microwave waveguide
114
.
In the operation of this apparatus, the interior of reaction chamber
120
is first evacuated down to a required level of pressure, followed by introduction of reaction gas therein via a gas feed tube. Microwave are then oscillated at microwave oscillator
115
, which are led via waveguide
114
to microwave distributor
113
.
The microwave divided at microwave distributor
113
are led to respective dielectric lines
111
in phase with the same power. The microwave led to dielectric lines
111
pass through air gap
112
and introduced into reaction chamber
120
via microwave introduction window
102
. With the introduction of the microwave, plasma is produced within reaction chamber
120
, whereby plasma processing (etching) is applied on the surface of substrate
108
placed on stage
107
.
Other techniques to realize uniform plasma processing in a relatively wide area are disclosed, e.g., in Japanese Patent Laying-Open No. 8-316198, Japanese Patent Publication No. 7-105385 and Japanese Patent No. 2641450.
Japanese Patent Laying-Open No. 8-316198 discloses a plasma process apparatus wherein microwave oscillated by a single microwave oscillator are branched and transmitted via a plurality of dielectric layers into a reaction chamber.
Japanese Patent Publication No. 7-105385 discloses a plasma process apparatus wherein a plurality of waveguides are connected to the upper part of a process chamber, and a plurality of microwave oscillators are respectively connected to the waveguides, whereby a plurality of microwave are controlled independently from each other.
Japanese Patent No. 2641450 discloses a plasma process apparatus that is similar to the one disclosed in Japanese Patent Publication No. 7-105385 in that each waveguide requires a respective set of microwave oscillator. The difference therebetween is only the way of plasma excitation.
Microwaves generally refer to electro-magnetic waves of frequencies of 1-30 GHz. However, in the field of engineering, waves of VHF band (30-300 MHz), UHF band (0.3-3 GHz) and milliwave band (30-300 GHz) can be handled in the same manner as the microwaves of the general definition. Hence, in this specification, the electromagnetic waves of these frequency bands are collectively referred to as the microwaves.
The techniques disclosed in the references above have disadvantages as follows.
First, in the plasma process apparatus of Japanese Patent Laying-Open No. 11-111493 as shown in
FIGS. 16 and 17
, microwave in phase with the same power are introduced into four partitioned dielectric lines
111
. Of microwave introduction window
102
, however, in a region SA that is closer to a sidewall
101
b
of reaction chamber
101
and in a region SB farther from the sidewall
101
b
, there are differences in the potential states and in the manners of excited particle generation/dissipation within the plasma. Accordingly, load impedance of the plasma immediately beneath the region SA differs from that beneath the region SB, thereby hindering a uniform plasma process.
In the plasma process apparatus of Japanese Patent Laying-Open No. 8-316198, the dielectric layer is partitioned only into two parts. This is insufficient for uniformly processing a substrate of wide area. Even if the number of partition of the dielectric layer is increased, load impedance differs in different positions as in the case of Japanese Patent Laying-Open No. 11-111493, which again hinders the uniform plasma process.
In Japanese Patent Publication No. 7-105385 and Japanese Patent No. 2641450, one microwave oscillator is required for a respective waveguide. In general, it is more advantageous from the standpoint of cost saving to prepare, instead of a plurality of oscillators each of low power level, one powerful oscillator capable of supplying the equivalent power. Accordingly, the apparatuses disclosed in these references are disadvantageous in terms of cost saving, and will become more disadvantageous if they are to be used to process a substrate of large area.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a cost-effective plasma process apparatus that allows a uniform plasma process even if plasma produced within a reaction chamber exhibits different load impedance in different positions.
The plasma process apparatus according to the present invention applies a plasma process on a substrate employing reaction gas that has been excited to a plasma state by microwaves. The plasma process apparatus includes a chamber and a plurality of microwave introduction windows. With a substrate held therein, the chamber has a main wall facing the surface of the substrate and a sidewall

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