Coating apparatus – With means to centrifuge work
Reexamination Certificate
1999-03-13
2001-01-30
Edwards, Laura (Department: 1734)
Coating apparatus
With means to centrifuge work
C118S056000, C118S319000, C118S320000, C118S500000, C134S902000
Reexamination Certificate
active
06179915
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The invention relates to a track coater unit cup set, which is utilized in IC fabrication processes, especially in a spinning process; and more particularly to a modified track coater unit cup set in which the induced solvent spraying accuracy and the resulted cleanliness on the wafer in the involving process can be greatly improved by little reworking on the cup set profile.
(2) Description of the Prior Art
In the coating processes of a wafer in the semi-conductor industry, spin coating is the general application in adding a thin film or membrane on the wafer. Such a thin film can be a photoresist, etching agent, or the like to coat over the wafer surface. In the spin application of the art, the wafer is positioned upon a vacuum susceptor, and the chemical solvent to form the film is dropped from top of the wafer while it rotates with the susceptor driven by a rotation mechanism. During the spinning, at least a spray post located under the susceptor is used to provide cleaning solvent spray onto the rim of the wafer, so that the chemical residues over the rim can be washed out at the same time. By proving such a cleaning spray, possible inaccurate problems close to rim of the wafer can be reduced to a minimum.
In the conventional arrangement of a spin facility, it generally involves a track coater unit cup set to work with the cleaning solvent spray for reducing the possibility of the solvent contaminating the wafer or the spin facility
Referring now to
FIG. 1
, a track coater unit cup set and the related part of the rotation mechanism are shown exposedly. As shown, the track coater unit cup set
1
on top of the rotation mechanism
2
is a kit with three circular parts. The first part is a hollow concave base cup
11
capable of anchoring on the rotation mechanism
2
, the second is a hollow convex inner cup
13
located on top of the base cup
11
, and the third is a hollow convex outer cup
15
to envelope the inner cup
13
and to be placed on top of the base cup
11
. In piling the track coater unit cup set I onto the rotation mechanism
2
for application, the base cup
11
is firstly fixed to the rotation mechanism
2
. Secondly, the inner cup
13
with the maximum diameter less than that of the base cup
11
is placed on top of the base cup
11
. Thirdly, engage a susceptor
21
with a shaft
23
over the inner cup
13
, in which the shaft
23
is extended from the rotation mechanism
2
and through the hollow openings of the base cup
11
and the inner cup
13
. The susceptor
21
is used to carry a wafer (not shown in
15
FIG. 1
) on top for undertaking a spin coating process. Finally, the outer cup
15
is used to go with the base cup
11
for forming an internal space in between to include the inner cup
13
and the susceptor
21
as well as the wafer thereinside.
Referring now to
FIG. 2
, a cross sectional view of the assembly of the track coater unit cup
1
and the rotation mechanism
2
is shown. As shown, the base cup
11
rides on the rotation mechanism
2
and has the central opening for top of the rotation mechanism
2
to penetrate. The base cup
11
further includes two concentric circular grooves: an inner circular groove
111
and an outer circular groove
113
. An inner wall of the inner circular groove
111
is defined as an inner groove wall
115
. On the other hand, the outer surface of the inner cup
13
is used as a flow-leading surface. As shown in
FIG. 2
, the inner cup
13
has an inner downward protruding ring
1311
for engaging with the inner groove wall
115
of the base cup
11
through a first step-shape engaging structure established along the meshing interface
1110
between the top edge of the inner groove wall
115
and the lower end of the protruding ring
1311
. The outer lower end of the inner cup
13
is designed to suspend in the outer circular groove
113
of the base cup
11
, so that the cleaning solvent can be led into the outer circular groove
113
through the outer surface of the inner cup
13
, after the solvent hitting the rim of the wafer
3
. The accumulated cleaning solvent is then led out through a hole (not shown in figures) on the bottom of the outer circular groove
113
. The upper central opening of the inner cup
13
is defined as an upper opening
131
, through which the driving shaft
23
of the rotation mechanism
2
can penetrate. At the upper end of the shaft
23
, there locates the susceptor
21
for vacuuming the wafer
3
on top thereof. The area of the upper opening
131
is no more than either that of the top of the rotation mechanism
2
or that of the wafer
3
. The outer cup
15
is used to enclose totally the outer circular groove
113
of the base cup
11
. Generally, the lower end of the outer cup
15
engages with the top end of the outer wall of the outer circular groove
113
(also the outer wall of the base cup
11
) through a second step-shape engaging structure
1113
formed in-between. The upper central opening of the outer cup
15
is defined as a top opening
151
. The space formed between the outer cup
15
and the inner cup
13
is defined as a working space
350
, in which the wafer
3
undergoes the coating process. The rim of the outer cup
15
to form the upper opening
151
further includes a ring of short inward tip
153
protruding into the working space
350
. The purpose of the inward tip
153
is to substantially smooth out the airflow introduced into the working space
350
through the upper opening
151
.
During a coating process, the susceptor
21
as well as the wafer
3
is rotated by the shaft
23
of rotation mechanism
2
. Photoresist or other chemical for forming a thin film on the wafer
3
is added through the top opening
151
. By the rotation induced centrifugal force, photoresist or other chemical can be spread to cover the whole wafer
3
. In order to achieve smoothness and to avoid possible splash of the photoresist and other chemical, a ventilation system (not shown in figures) for vacuuming the working space
350
can be provided to the bottom of the base cup
11
. To avoid the photoresist or other chemical to residue at the rim of the wafer
3
(which may induce particle contamination and the planarization problems on the wafer
3
thereafter), the rotation mechanism
2
usually includes a pair of spray posts
25
for providing cleaning solvent spray
251
onto the rim of the wafer
3
. For the spray
251
to penetrate the upper opening
131
and arrive at the rim of the wafer
3
, the inner cup
13
further has a pair of respective apertures
133
located along the inner rim thereof. The cleaning solvent spray
251
is provided by the spray posts
25
, hits the rim of the wafer
3
, and then drops between the inner cup
13
and the outer cup
15
. The cleaning solvent together with the residue photoresist or other chemical then flow into the outer circular groove
113
of the base cup
11
. Finally, the cleaning solvent together with the residue photoresist or other chemical are led out of the track coater unit cup set
1
from the bottom of the base cup
11
.
In the aforesaid structure, the track coater unit cup set
1
generally has two disadvantages. One is the misalignment problem between the spray
251
and the aperture
133
, and the other is the aggregation and solidification of the solvent at the comer close to and at the inward tip
153
.
Regarding the misalignment between the spray
251
and the apertures
133
, the problem results from the angular shifting between the base cup
11
and the engaged inner cup
13
, due to the vibration caused the driving system of the rotation mechanism
2
. Furthermore, the light weight on the inner cup
13
(usually made of plastic or non-metallic material), which contributes to less normal force on the meshing interface
1110
and thus less friction force thereon to prevent from the relative motion between the inner cup
13
and the base cup
11
, makes worse the angular shifting problem. As a consequence of the angular shifting, the spray
251
inject
Edwards Laura
Liauh W. Wayne
ProMos Technology, Inc
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