Coating apparatus – Control means responsive to a randomly occurring sensed... – Responsive to attribute – absence or presence of work
Reexamination Certificate
2002-11-19
2004-11-02
Crispino, Richard (Department: 1734)
Coating apparatus
Control means responsive to a randomly occurring sensed...
Responsive to attribute, absence or presence of work
C118S679000, C118S712000, C118S321000, C118S323000
Reexamination Certificate
active
06811613
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technique of feeding coating liquid to various substrates such as a semiconductor wafer, a glass substrate for liquid crystal display or a reticle substrate for photomask, to form a liquid film of the coating liquid on the surface of such a substrate.
2. Description of the Background Art
Conventionally, the coating process of resist liquid performed to obtain a desired circuit pattern in manufacturing of a semiconductor device or the like has been carried out by a so-called spin coating method. This method is to form a liquid film (resist film) on the entire surface of a wafer by feeding coating liquid from a nozzle provided above a middle portion of the wafer, which is a substrate to be processed, horizontally held by a rotatable spin chuck or the like, while rotating the wafer for diffusion of the resist liquid by the centrifugal force of the wafer.
To accommodate the recently-increasing demand of miniaturization of circuit patterns, it is required to reduce the thickness of the resist film. In the spin coating method, the number of rotations of the wafer has been increased to meet such a requirement. If the wafer is rotated at a high speed, however, turbulent flow is likely to occur on the wafer surface especially when the wafer has a large size. The turbulent flow would cause unevenness of the film thickness on the entire wafer, which would make difficult to reduce the size of a pattern. Accordingly, the inventors have studied application of a coating film forming apparatus not using the spin coating method.
FIG. 23
shows an example of a nozzle unit in which a nozzle and a driving mechanism for moving the nozzle in the X-direction (from side to side) are integrated. A case body
11
shown in
FIG. 23
is constituted by a front portion
12
and a rear portion
13
. The upper and lower surfaces of front portion
12
are each provided with a slit
14
(not shown for the lower surface side), which defines the direction of movement of a coating liquid feed tube
15
provided through slit
14
. A nozzle portion
16
for discharging the coating liquid downward is arranged at a tip of coating liquid feed tube
15
. Coating liquid feed tube
15
and nozzle portion
16
are configured to move back and forth within an area defined by slit
14
, by actuation of a belt driving portion
17
provided in rear portion
13
.
At the coating process, nozzle portion
16
is moved back and forth (a scan is performed) in the X-direction as described above, while a wafer W placed below nozzle portion
16
is intermittently fed in the Y-direction. Further, the width of movement in the X-direction is changed in accordance with the width of a region to be fed with coating liquid, every time the intermittent feeding in the Y-direction is performed, to allow the coating liquid to be fed onto the surface of wafer W in the manner of a so-called single stroke of the blush.
However, as the method above is to form a liquid film on the entire wafer surface by lining up linear coated regions side by side, scanning time per one row of nozzle portion
16
must be shortened in order to reduce the total time required. For the time reduction, it is effective to move nozzle portion
16
at a high speed. Such operation, however, causes large vibration at e.g. belt driving portion
17
, which is propagated to pulsate the coating liquid in coating liquid feed tube
15
, causing variation in the pressure within coating liquid feed tube
15
. The change in the pressure in coating liquid feed tube
15
is directly reflected in the discharge pressure of the coating liquid at nozzle portion
16
, resulting in non-uniform feeding of the coating liquid from discharge opening
16
a
of nozzle portion
16
, as shown in FIG.
26
.
SUMMARY OF THE INVENTION
The present invention was made to solve the problems described above, and an object of the invention is to provide a technique that allows, in forming of a coating film on the surface of a substrate by feeding coating liquid onto the substrate while moving a nozzle portion from side to side, stabilization of discharge of the coating liquid and formation of a coating film having high in-plane uniformity in the film thickness.
In order to solve the problems above, various approaches have been presented such as provision of a shock-absorbing movable body (balancer) at belt driving portion
17
, which moves in a direction opposite and symmetrical to the movement of nozzle portion
16
, or application of high pressure air to the periphery of a guide member (not shown) of nozzle portion
16
for suppressing mechanical friction at moving of nozzle portion
16
. It was, however, difficult to completely remove vibration itself propagated to nozzle portion
16
, and thus variation in the discharge pressure could not be sufficiently reduced by such approaches. The present inventors, therefore, have continuously pursued the reasons therefor, and have made an attempt to form a line of coating liquid on the surface of the wafer while moving nozzle portion
16
at 1 m/sec in the apparatus described above, and measure the surface height of the line with respect to time at the section of interest, to find that the surface has regular concave and convex portions at frequency of e.g. 200 Hz. This is assumed to be one cause of the vibration, since the frequency corresponds to the cycle at which groove
18
a
on the surface of belt
18
is engaged with tooth
19
a
on the surface of a cam
19
in belt driving portion
17
shown in
FIGS. 27A and 27B
. As illustrated, grooves
18
a
and teeth
19
a
are both formed in parallel, and it is assumed that the vibration occurs when the tip of tooth
19
a
touches the inner surface of groove
18
a
, which is repeated.
According to one aspect of the present invention, a coating film forming apparatus includes a substrate holding portion holding a substrate, a nozzle portion feeding coating liquid to the substrate held by the substrate holding portion via a discharge opening formed at a tip, a coating liquid feed path feeding coating liquid to the nozzle portion, a channel connecting the discharge opening and the coating liquid feed path in the nozzle portion and having a section larger in a diameter than the discharge opening, a pressure loss portion causing pressure loss in the coating liquid flowing through the channel, a first driving portion moving said nozzle portion in a first direction (side-to-side direction) along a substrate surface, and a second driving portion intermittently moving said nozzle portion relative to the substrate in a second direction (back-and-forth direction) crossing said first direction. The nozzle portion is moved in the side-to-side direction to apply the coating liquid linearly on the substrate surface, and is intermittently moved relative to the substrate such that the linear coated regions are lined up in the back-and-forth direction.
In such a structure, even if pulsation occurs in the coating liquid feed path due to vibration caused at the first driving portion at moving of the nozzle portion in the side-to-side direction, the pressure loss portion in the nozzle portion can absorb the pulsation, preventing propagation of the vibration to the discharge opening side. Accordingly, the discharge pressure of the coating liquid at the discharge opening is stabilized, so that a coating film having a high in-plane uniformity in the film thickness can be formed on the substrate surface. For the pressure loss portion, preferably, a filtering member is used, and specifically, a tubular body formed by layering a plurality of porous bodies, having one end opened may be used. In addition to the effects described above, such a structure allows removal of impurities from the coating liquid as the coating liquid passes through the filtering member, so that a coating film having high purity can be formed on the substrate, improving a product yield.
Moreover, the nozzle portion may be a sphere provided with a channel having a portion with a circula
Kawafuchi Yoshiyuki
Kitano Takahiro
Koga Norihisa
Takei Toshichika
Crispino Richard
Koch, III George R.
Tokyo Electron Limited
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