Coating apparatus – Gas or vapor deposition – Work support
Reexamination Certificate
2000-09-27
2002-08-13
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
Work support
C118S725000, C118S724000, C156S345510, C156S345520, C156S345530
Reexamination Certificate
active
06432208
ABSTRACT:
TECHNICAL FIEND
The present invention relates to plasma processing apparatuses and, more particularly, to a plasma processing apparatus for applying a process using plasma to a substrate to be processed such as a semiconductor wafer placed on a placement table in a vacuum process chamber.
BACKGROUND ART
In a manufacturing process of semiconductor devices, plasma is used so as to promote ionization or chemical reaction of process gases in various processes such as etching, CVD or sputtering. Generally, in a processing apparatus using a plasma, a placement table is installed in a hermetically sealed processing chamber so as to place a semiconductor wafer on the placement table to apply a process to the semiconductor wafer.
FIG. 1
is an illustration showing a structure of a conventional typical plasma processing apparatus. In the plasma processing apparatus, a placement table
204
is installed in the center of a process chamber
200
, which is a vacuum chamber, via a support member
202
. The semiconductor wafer W as a substrate to be processed is placed on a placement surface
204
a
of the placement table
204
, which is formed in a disc-like shape.
The replacement table
204
is provided with an electrostatic attracting (chucking) function so as to attracts and retain the semiconductor wafer W by an electrostatic force. In this processing apparatus, an upper portion of at least the placement surface
204
a
of the placement table
204
is constituted by an insulating material, and an electrode
206
is provided therein. An appropriate voltage is applied to the electrode
206
from a direct current power source
208
provided outside the process chamber
200
so as to have the placement surface
204
a
attract and retain the semiconductor wafer W by an electrostatic force.
In the process chamber
200
, a plasma P is generated above the placement table
204
by an appropriate method, and is lead near the surface of the semiconductor wafer W. At the same time, a predetermined process gas is introduced into the process chamber
200
. The molecules of the introduced process gas are excited by the plasma P, thereby promoting fine processing such as a film deposition or an etching.
Ions and electrons in the plasma P can be incident on the surface of the wafer W in a vertical direction by applying a high-frequency bias voltage to the electrode
206
of the placement table
204
. Thereby, directionality (anisotropy) can be provided to a fine processing by the plasma processing, which improves an accuracy of processing. In order to apply the high-frequency bias voltage, a normally 23.5 MHz high-frequency power source
210
is provided outside the process chamber
200
.
The placement table
204
is installed, via an O-ring, on the support member
202
, which is formed in a disc-like or cylindrical shape. A gap (space)
214
formed inside the O-ring
212
is separated from the depressurized process space in the process chamber
200
. A power supply line and the like connected to the placement table
204
from outside extend through a through hole (not shown in the figure) formed in the support member
202
and the gap
214
.
The support member
202
is a block made of a material having a high heat-conductivity such as aluminum, and has a coolant passage
202
a
therein. A coolant (for example, water) of a predetermined temperature (for example, 25° C.) is supplied to the coolant passage
202
a
via a pipe (not shown in the figure) from a cooling apparatus (not shown in the figure) provided outside the process chamber
200
. Thereby, the entire support member
202
is maintained at a predetermined temperature.
A heat of plasma transmitted to the placement table
204
via the semiconductor wafer W transmitted to the support member
202
from the placement table
204
via the gap
214
. Then, the heat of plasma is absorbed by the coolant flowing through the coolant passage
202
a
formed in the support member
202
, and is released to outside the chamber by the cooling apparatus. By this heat releasing mechanism, the temperature of the placement table
204
is maintained at a predetermined setting temperature (normally, equal to or lower than 200° C.).
The reason for maintaining the setting temperature at a temperature equal to or lower than 200° C. is that the O-ring
212
is in contact with a back surface of the placement table
204
. That is, the O-ring
212
is formed by an elastic resin and a heat resistant temperature thereof is about 200° C. at maximum.
Maintaining the setting temperature of the placement table
204
at a temperature equal to or lower than 200° C. causes a large temperature difference between the placement table
204
and the semiconductor wafer W. In a general plasma process, a temperature of the wafer W is 400° C., and, thus, it is necessary to provide a temperature difference of about 200° C. between the two. The temperature difference is provided by contacting surfaces of the two and a thermal resistance of a space between the two.
It should be noted that a resistance heating element (not shown in the figure) may be provided inside the placement table
204
, and an electrical control of an amount of heat generated by the resistance heating element is performed according to a temperature feedback function (not shown in the figure).
In the above-mentioned plasma process chamber, the temperature of the placement table
204
can be maintained at the setting temperature with a considerably high accuracy by the cooling by the support member
202
and the temperature control by heating by the equipped resistance heating element.
However, the with respect to the temperature of the wafer W which is an object whose temperature is to be controlled, it is difficult to compensate for with a fine thermal response in consideration of a temperature change caused by fluctuation in the plasma density and variation in a quality between individual wafers since the temperature difference between the semiconductor wafer W and the placement table
204
. That is, it is difficult to maintain the temperature of the wafer W at a stable and uniform temperature.
Additionally, when starting the plasma processing, it is necessary to raise the temperature of the semiconductor wafer W to a temperature (setting temperature), at which the process can be started, after the semiconductor wafer W is placed on the placement table
204
. This period is referred as a preheat time. If the temperature difference between the semiconductor wafer W and the placement table
204
is large as mentioned above, it is difficult to enhance the throughput since the preheat time is increased.
DISCLOSURE OF INVENTION
It is a general object of the present invention to provide an improved and useful plasma processing apparatus in which the above-mentioned problems.
A more specific object of the present invention is to provide a plasma processing apparatus which can obtain high throughput by reducing a preheat time from placement of a substrate to be processed on a placement table until the process is started.
In order to achieve the above-mentioned objects, there is provided according to the present invention a plasma processing apparatus for performing a process using a plasma with respect to a substrate to be processed within a depressurized process chamber, comprising:
a placement table, provided in said process chamber, having a placement surface for placing said substrate to be processed thereon and a back surface opposite to the placement surface; and
a support member supporting said placement table,
characterized in that said support member is provided between said placement table and a wall of said process chamber; said support member defines a space, which is separated from a process space of said process chamber, by being airtightly connected to said placement table and being airtightly connected to said process chamber; and said support member separates a connection part between said support member and the wall of said process chamber from said placement table by a predetermined distance so as to provide a
Iwabuchi Katsuhiko
Kawajiri Tetsuya
Kawakami Satoru
Kuwajima Ryo
Ushikoshi Ryusuke
Hassanzadeh P.
Mills Gregory
Pillsbury & Winthrop LLP
Tokyo ELectron Limited
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