Coating apparatus – With means to centrifuge work
Reexamination Certificate
2002-10-10
2004-05-18
Lorengo, J. A. (Department: 1734)
Coating apparatus
With means to centrifuge work
C118S730000, C118S313000, C118S315000, C118S320000, C239S450000, C427S255230, C427S425000, C427S426000, C427S240000
Reexamination Certificate
active
06736896
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to spin coating apparatus used to coat a photoresist on a semiconductor wafer substrate in the fabrication of semiconductor integrated circuits. More particularly, the present invention relates to a new and improved gas purge arm which facilitates a diffuse spray pattern of nitrogen purge gas against a substrate surface after a photoresist coating process in a spin coating apparatus.
BACKGROUND OF THE INVENTION
The fabrication of various solid state devices requires the use of planar substrates, or semiconductor wafers, on which integrated circuits are fabricated. The final number, or yield, of functional integrated circuits on a wafer at the end of the IC fabrication process is of utmost importance to semiconductor manufacturers, and increasing the yield of circuits on the wafer is the main goal of semiconductor fabrication. After packaging, the circuits on the wafers are tested, wherein non-functional dies are marked using an inking process and the functional dies on the wafer are separated and sold. IC fabricators increase the yield of dies on a wafer by exploiting economies of scale. Over 1000 dies may be formed on a single wafer which measures from six to twelve inches in diameter.
Various processing steps are used to fabricate integrated circuits on a semiconductor wafer. These steps include deposition of a conducting layer on the silicon wafer substrate; formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal interconnection pattern, using standard lithographic or photolithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby etching the conducting layer in the form of the masked pattern on the substrate; removing or stripping the mask layer from the substrate typically using reactive plasma and chlorine gas, thereby exposing the top surface of the conductive interconnect layer; and cooling and drying the wafer substrate by applying water and nitrogen gas to the wafer substrate.
The numerous processing steps outlined above are used to cumulatively apply multiple electrically conductive and insulative layers on the wafer and pattern the layers to form the circuits. The final yield of functional circuits on the wafer depends on proper application of each layer during the process steps. Proper application of those layers depends, in turn, on coating the material in a uniform spread over the surface of the wafer in an economical and efficient manner.
During the photolithography step of semiconductor production, light energy is applied through a reticle mask onto a photoresist material previously deposited on the wafer to define circuit patterns which will be etched in a subsequent processing step to define the-circuits on the wafer. Because these circuit patterns on the photoresist represent a two-dimensional configuration of the circuit to be fabricated on the wafer, minimization of particle generation and uniform application of the photoresist material to the wafer are very important. By minimizing or eliminating particle generation during photoresist application, the resolution of the circuit patterns, as well as circuit pattern density, is increased.
Photoresist materials are coated onto the surface of a wafer by dispensing a photoresist fluid typically on the center of the wafer as the wafer rotates at high speeds within a stationary bowl or coater cup of a spin coating apparatus. The coater cup catches excess fluids and particles ejected from the rotating wafer during application of the photoresist. The photoresist fluid dispensed onto the center of the wafer is spread outwardly toward the edges of the wafer by surface tension generated by the centrifugal force of the rotating wafer. This facilitates uniform application of the liquid photoresist on the entire surface of the wafer.
Spin coating of photoresist on wafers is carried out in an automated track system using wafer handling equipment which transport the wafers between the various photolithography operation stations, such as vapor prime resist spin coat, develop, baking and chilling stations. Robotic handling of the wafers minimizes particle generation and wafer damage. Automated wafer tracks enable various processing operations to be carried out simultaneously. Two types of automated track systems widely used in the industry are the TEL (Tokyo Electron Limited) track and the SVG (Silicon Valley Group) track.
A typical conventional spin coating apparatus for coating semiconductor wafers with a photoresist liquid is generally indicated by reference numeral
8
in
FIGS. 1 and 2
. The spin coating apparatus
8
includes a coater cup
3
which includes a top opening
6
and partially encloses a wafer support stage or chuck
1
on which is supported the wafer
2
. A chemical dispensing system
10
includes a nitrogen gas spray arm
12
, an acid dispensing arm
13
and a deionized (DI) water spray arm
14
, each of which extends from a corresponding arm slot
7
in an arm mount
11
. As shown in
FIG. 2
, each of the arms
12
,
13
,
14
is capable of swinging or pivoting from a stored position on the side of the coater cup
3
, over the top of the coater cup
3
for dispensing the corresponding liquid through the top opening
6
onto the wafer
2
. In operation, the chuck
1
rotates the wafer
2
at high speeds, typically as high as 4,000 rpm, either after or as the liquid photoresist (not shown) is dispensed onto the center of the spinning wafer
2
, through the top opening
6
. By operation of centrifugal force imparted to the wafer
2
by the rotating chuck
1
, the dispensed photoresist liquid is spread across and uniformly coated on the surface of the wafer
2
. Exhaust solvent gases and photoresist particles generated during the process are vented from the coater cup
3
through an exhaust pipe
4
which may be connected to an exhaust manifold
5
.
After the liquid photoresist is applied to the wafer
2
, the acid dispensing arm
13
sweeps over the center of the coater cup
3
and back to the “home” position on the side of the coater cup
3
as acid is dispensed from the arm
13
through the top opening
6
onto the surface of the spinning wafer
2
at a pressure of typically about 0.3 psi. This step removes excess photoresist, as well as photoresist particles, from the wafer
2
. Next, the water spray arm
14
sweeps over the center of the coater cup
3
and back to the “home” position on the side of the coater cup
3
to spray DI water, at a pressure of typically about 20-40 psi, through the top opening
6
and onto the wafer
2
to remove residual acid from the wafer
2
. Finally, the nitrogen gas spray arm
12
is initially positioned over the center of the coater cup
3
and then sweeps back to the “home” position on the side of the coater cup
3
to blow nitrogen gas, at a pressure of typically about 15 psi, onto the surface of the spinning wafer
2
. This final step dries most of the DI water remaining on the wafer
2
.
As shown in
FIG. 3
, the nitrogen spray arm
12
includes a central dispensing tube
15
that terminates in a nozzle opening
16
at the end of the nitrogen spray arm
12
. The nozzle opening
16
typically has a relatively small diameter of about 1.0 mm to about 1.5 mm, and this tends to eject the nitrogen gas onto the surface of the wafer
2
in a narrow, forceful stream
18
. The nitrogen gas stream
18
tends to blow or splash water droplets
17
from localized areas on the surface of the wafer
2
contacted directly by the nitrogen gas stream
18
while spreading the water droplets
17
to adjacent areas on the wafer
2
. Consequently, some of the water droplets
17
remain on the wafer
2
, forming chemical and water spots on the surface of the wafer
2
after the cleaning process. Chemical and water spots remaining on the wafer
2
after the photoresist application process tend to adversely affect device performance and reduce the yield of devices on the wafer
2
.
Lazor Michelle Acevedo
Lorengo J. A.
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
LandOfFree
Gas spray arm for spin coating apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas spray arm for spin coating apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas spray arm for spin coating apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3215445