Plasma processor

Details Plasma processor Plasma processor

2000-02-18

2002-03-19

Dang, Thi (Department: 1763)

Adhesive bonding and miscellaneous chemical manufacture

Differential fluid etching apparatus

With microwave gas energizing means

C118S7230MW, C204S298380

Reexamination Certificate

active

06358361

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a plasma processing apparatus wherein a semiconductor substrate, a glass substrate for a liquid crystal display and so on is etched, ashed or otherwise processed by a plasma generated by using a microwave.
BACKGROUND ART
A plasma generated by adding energy from outside to a reacting gas is widely used in a manufacturing process of an LSI, an LCD and so on. Especially in a process of dry etching, use of the plasma is an indispensable core technology. Generally, exciting means for generating the plasma uses either a microwave having a frequency of 2.45 GHz for example, or an RF (radio frequency) having a frequency of 13.56 MHz for example. The former has an advantage over the latter in that a plasma of a higher density can be obtained. However, in a plasma processing apparatus using the microwave, it was difficult to generate the plasma in a wide area and at a uniform density. Yet, because of the above-mentioned advantage that a plasma of a higher density can be obtained in such a plasma apparatus, there has been a requirement for an apparatus capable of processing a large size of the semiconductor substrate, the glass substrate for LCD and other materials. In order to meet the requirement, the applicant of the present invention proposed in Japanese Patent Application Laid-Open No. 62-5600 (1987), Japanese Patent Application Laid-Open No. 62-99481 (1987), and so on, a following apparatus:
FIG. 1
is a sectional side view of a plasma apparatus of the same type as disclosed in Japanese Patent Application Laid-Open No. 62-5600 (1987) and Japanese Patent Application Laid-Open No. 62-99481 (1987).
FIG. 2
is a plan view thereof. A reactor
41
in the shape of a rectangular box is entirely made of aluminum. The reactor
41
has an upper opening sealed airtight by a seal plate
44
for introducing a microwave. The seal plate
44
is made of a dielectric such as silica glass or alumina, i.e. which is heat resistant, transmittable by microwaves, as well as having a small rate in dielectric loss.
The reactor
41
has an upper portion connected with and covered by a cover member
50
in the shape of a rectangular box. The cover member
50
has a ceiling portion attached with a dielectric plate
51
. There is an air gap
53
between the dielectric plate
51
and the seal plate
44
. The dielectric plate
51
is made of such a dielectric like as a fluororesin such as Teflon (registered trademark), a polyethylene resin, a polystyrene resin and so on, being formed into a plate having a substantially pentagon in the shape of a rectangle portion combined with a triangle portion, with an apex of the pentagon provided with a projected portion. The projected portion is inserted into a waveguide
61
connected to a circumferential surface of the cover member
50
. The waveguide
61
is connected to a microwave generator
60
. A microwave emitted from the microwave generator
60
is guided by the waveguide
61
into the projected portion of the dielectric plate
51
.
As has been described above, the projected portion of the dielectric plate
51
has a base end continuing to the substantially triangular tapered portion
51
a
as viewed from above. The microwave entered from the projected portion reaches the tapered portion
51
a
, expands widthwise of the tapered portion, and propagates throughout the whole of the dielectric plate
51
. Then, the microwave reflects on an end surface of the cover member
50
opposing the waveguide
61
. The incident wave is superimposed on the reflected wave, forming a standing wave in the dielectric plate
51
.
The reactor
41
has an inner space as a processing chamber
42
. The processing chamber
42
has a circumferential wall formed with a through hole fitted with a pipe
45
, through which a necessary gas is introduced into the processing chamber
42
. The processing chamber
42
has a bottom wall having a center portion provided with a table
43
for placing a work W to be processed by the plasma. The table
43
is connected to a high frequency power source
47
via a matching box
46
. Further, the bottom wall of the reactor
41
is formed with exhaust holes
48
so that an atmosphere inside the processing chamber
42
is exhausted from the exhaust holes
48
.
By using the plasma apparatus of the above constitution, a surface of the work W can be etched according to the following steps: First, inner gas is exhausted from the exhaust holes
48
, bringing the processing chamber
42
into a partial vacuum of a desired pressure. Then, the reactive gas is supplied through the pipe
45
into the processing chamber
42
. Then, the microwave generator
60
is activated to generate a microwave, and the microwave is introduced through the waveguide
61
into the dielectric plate
51
. When introduced, the microwave is allowed by the tapered portion
51
a
to expand uniformly within the dielectric plate
51
, forming a standing wave within the dielectric plate
51
. The standing wave forms a leakage electric field below the dielectric plate
51
, which introduces through the air gap
53
and seal plate
44
into the processing chamber
42
. In such a manner, the microwave propagates inside the processing chamber
42
, generating the plasma within the processing chamber
42
.
The table
43
is applied with a high frequency wave by the high frequency power source
47
via the matching box
46
, so that a bias electric potential is generated. The bias electric potential draws ions within the plasma onto the work W at an accelerated speed to etch the surface of the work W. According to the above, if a diameter of the reactor
41
is increased for a capacity to process the work W having a large size, it is possible to uniformly introduce the microwave to all regions of the reactor
41
. Therefore, a uniform anisotropic etching can be performed even to the large sized work W.
There is a problem however: As has been described above, according to the prior art plasma processing apparatus, in order to uniformly expand the microwave throughout the dielectric plate
51
, there is provided the seal plate
44
, as well as the tapered portion
51
a
formed as part of the dielectric plate
51
projecting horizontally from an edge portion of the reactor
41
. Size of the tapered portion
51
a
is determined in accordance with the area of the dielectric plate
51
, i.e. the diameter of the processing chamber
42
. As a result, when the prior art plasma processing apparatus is to be installed, there is a problem that an extra horizontal space must be provided for housing the tapered portion
51
a
which projects out of a perimeter of the reactor
41
.
On the other hand, there has been a trend to increase the size of the work W, and there is a requirement for the reactor
41
having an increased diameter. Further, at the same time, there is a requirement that such an apparatus should not demand for extra space for installation; in other words, the apparatus must be installed within as small space as possible. However, according to the prior art apparatus as described above, the size of the tapered portion
51
a
depends on the diameter of the reactor
41
, and therefore if the diameter of the reactor
41
is increased, the size of the tapered portion
51
a
must be made accordingly longer. As a result, the requirements conflicted against each other, i.e. a demand for a plasma processing apparatus having an increased diameter of the reactor
41
yet capable of being installed within as small space as possible.
Further, according to the prior art plasma processing apparatus, the circumferential wall of the reactor
41
for example is earthed so as to serve as a earthed electrode for the table
43
which is applied with the high frequency wave. However, with such an arrangement, there is another problem in that the inner surface of the circumferential wall of the reactor
41
is hit and damaged by the ions from within the plasma, decreasing life of the reactor
41
. Still further, when the circumferential wall of the reactor
41
is earthed, t

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