Coating apparatus – Gas or vapor deposition
Reexamination Certificate
1999-11-26
2002-06-11
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
C118S7230AN, C118S7230AN
Reexamination Certificate
active
06402847
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a dry processing apparatus such as a film forming apparatus or etching apparatus, and a dry processing method.
A CVD (chemical vapor deposition) apparatus, which is an example of the dry processing apparatus, is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 10-70088. In this CVD apparatus, a liner made of an insulating material is provided between the main chamber and a pumping flow path arranged around the chamber, for the purpose of shutting heat or plasma. Thus, the generation of a precipitate in the pumping flow path is suppressed.
In the above-described CVD apparatus, a process gas flows through a nozzle of a shower head to a chamber of a processing region. The process gas flown into the chamber traverses an edge of a wafer placed on a lower electrode to flow outwards in a radial direction of the wafer, and goes over a centering situated at a ring-like shelf portion formed on the outer circumference of an upper section of the lower electrode. Then, the gas flows into the pumping flow path, and proceeds through the outer circumference of the processing chamber. After that, the gas is exhausted by a vacuum pump device connected to the process chamber.
In such a CVD apparatus, when the film forming process is continued, depositions accumulate on the inner wall of the chamber or in the pumping flow path, and thus an unevenness is created in the electro-conductivity of the chamber and the flow of the gas. As a result, the surface of a thin film formed on the wafer is adversely affected in terms of evenness or the like. In order to avoid this, when depositions accumulate to have a certain thickness or more in, for example, the vicinity of the lower electrode in the chamber, it becomes necessary to remove such deposition by cleaning with the process gas which is made to flow. Such a cleaning operation is carried out periodically.
However, between the film formation and cleaning, the flow rate of the process gas, the distance between the shower head and the lower electrode, and the like varies, and therefore the flowing manner of the process gas varies to become uneven, and there created some sections in the pumping flow path, where they cannot be easily cleaned. Therefore, drawbacks such as that a cleaning time is prolonged and dusts are easily created in sections in the pumping flow path, where the gas flow is stagnant.
Further, when the introduction of the process gas is stopped just after the completion of the process and the gas is exhausted to ultimate pressure, the gas exhaustion becomes, in some cases, uneven depending upon the position of the exhaust outlet, thus unsettling the gas flow rate distribution. For this reason, dusts generated in the space above the wafer during the process pass above the wafer for a long distance until the ultimate pressure is obtained by exhaustion, and therefore the probability that dusts attach onto the surface of the wafer increases.
Meanwhile, there is a CVD apparatus having a chamber in which a lower electrode on which a wafer is placed, is contained, and a gas introduction path is provided for the upper section of the chamber, whereas an exhaustion hole is made in the lower section thereof. In such the apparatus, an exhaustion plate having a plurality of exhaustion holes is provided at a central portion of the chamber so as to uniform the gas flow around the wafer. However, this technique entails a drawback in which depositions are attached to the exhaust plate, thus making the time required to remove the depositions longer. Thus, the utility of the process gas is low.
Further, dusts and the like, which are created from peeled-off depositions once attached to the surface of, for example, the inner wall of the chamber, attach to a wafer being subjected to film formation.
In the meantime, another example of the dry process apparatus is an etching device, which generates activated species such as of radicals or ions by plasma generated by exciting the process gas (medium gas), and carries out the etching of the wafer, which is an object to be processed.
As shown in
FIG. 25
, the etching apparatus
301
has a chamber
302
, into which a process gag such as fluorocarbon is introduced, for example, over the upper end side, from a gas supply tube path
303
.
In the chamber
302
, a process stage
305
is provided as a holding means for holding a wafer W. The process stage
305
is designed to hold a wafer W with its upper end surface, and the holding section which holds the wafer W serves as a lower electrode
306
. To the lower electrode
306
, an RF power
307
provided on an outer side of the chamber
302
is electrically connected, so as to make it possible to apply a high-frequency voltage to the lower electrode
306
.
In a lower side of the chamber
302
, a gas exhaust pipe path
308
for exhausting a gas introduced to the chamber
302
and for maintaining the inside of the chamber at a predetermined pressure, is provided. The gas exhaust pipe path
308
is connected to a suction means, which is not shown, thereby the interior of the chamber
302
can be vacuum-suctioned.
In such an etching apparatus
301
, the process gas introduced from the gas supply tube path
303
is excited into plasma by the RF power
307
which applies power to the lower electrode
306
, and the activated species such as activated atoms (radicals) and ions, generated by the plasma, are carried by the gas flow directed to the gas exhaustion pipe path
308
, thereby processing the wafer W placed on the lower electrode
306
.
In usual cases, the gas flow rate within the apparatus is high on the exhaustion side, and therefore the etching rate is biased within the surface of the wafer W in some cases, depending upon the type of the process.
Further, as to the relationship between the gas flow rate and the etching rate on the surface of the wafer W placed in the process chamber, the process gas supplied from the gas supply inlet into the process chamber is allowed to pass above the surface of the wafer W placed on the lower electrode
306
, and then exhausted from the gas exhaust pipe path
308
. With this structure, the flow of the process gas on the surface of the wafer W is faster on the exhaust pipe path
308
side, whereas it is slower on the opposite side. In processes in which activated species are sufficiently supplied, the etching rate within the surface can be made uniform. However, in processes with an insufficiently amount of activated species generated, a great number of activated species move across the section where the gas flow is fast, thus increasing the etching rate there. As a result, the etching amount becomes uneven.
In order to prevent such an unevenness of the etching amount, the following technique has been proposed. That is, a baffle plate
309
is provided at a position between an circumferential wall of the process stage
305
in the chamber
302
, and the inner wall of the chamber
302
so as to uniform the gas flow by suppressing the bias of the gas flow, which occurs due to the position where the gas exhaustion pipe path
308
is situated, and to restrict the passing of the plasma (charged particles) to the exhaust pipe path
308
side.
The baffle plate
309
is designed to be situated between the circumferential wall of the process stage
305
and the inner wall of the chamber
302
, and therefore it has a ring-like shape. Further, the baffle plate
309
has slits
310
formed therein to be directed outwards from the center of the diameter of the ring-like shape. Each slit
310
is formed to have such a width that it is no more than two times the sheath thickness of the plasma generated within the chamber
302
, and this structure prevents plasma from being exhausted as it is allowed to pass the exhaust pipe tube
308
.
The cross sectional shape of each slit
310
is as shown in
FIG. 26
, and it is designed that the width is made narrow on one surface side (upper side in the figure), whereas the width is made wide on the other surface side (lower side) s
Nishimura Hiroshi
Onoue Seiji
Saito Makoto
Takagi Shigeyuki
Tohno Ichiro
Kabushiki Kaisha Toshiba
MacArthur Sylvia R
Mills Gregory
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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