Photocopying – Projection printing and copying cameras – With temperature or foreign particle control
Reexamination Certificate
2003-01-15
2004-07-20
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
With temperature or foreign particle control
Reexamination Certificate
active
06765645
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to tools for removing a pellicle from a reticle or mask on a semiconductor wafer substrate in the fabrication of semiconductor integrated circuits. More particularly, the present invention relates to a new and improved de-pellicle tool which is capable of removing a pellicle from a mask without touching the mask.
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.
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. 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.
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 the 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.
Reticles must remain meticulously clean for the creation of perfect images during its many exposures to pattern a circuit pattern on a substrate. The reticle may be easily damaged such as by dropping of the reticle, the formation of scratches on the reticle surface, electrostatic discharge (ESD), and particles. ESD can cause discharge of a small current through the chromium lines on the surface of the reticle, melting a circuit line and destroying the circuit pattern.
FIG. 1
illustrates a cross-section of a reticle
10
, having a mask material layer
12
and a chrome pattern
14
provided in the form of the desired circuit configuration on the mask material
12
. During a lithography process, an optically-transparent pellicle film
16
, which may be covered on both surfaces with antireflective coatings
18
, is typically positioned about 5-10 mm above the reticle
10
to prevent airborne particles
20
from falling on the reticle
10
and thus, damaging the reticle
10
and causing an imaging defect.
As shown in
FIG. 2
, the pellicle film
16
is tightly stretched on a sealed frame
17
which is supported on the surface of the reticle
10
. After the exposure, the pellicle frame
17
is removed from the underlying reticle
10
typically by operation of a conventional, manual de-pellicle tool
24
. The conventional de-pellicle tool
24
includes an elongated handle
25
on the end of which is provided a head
26
mounted on rollers
27
. A lift pin
28
extends forwardly from the head
26
. Accordingly, as shown in
FIGS. 2-2B
, the pellicle frame
17
is initially raised from the surface of the reticle
10
by resting the rollers
27
on the peripheral surface portion of the reticle
10
and inserting the lift pin
28
into a pin opening
22
extending into the pellicle frame
17
. Next, as shown in
FIG. 2B
, the rollers
27
act as a fulcrum as the handle
25
is lowered to raise the pin lift pin
28
in the pin opening
22
and partially lift the frame
17
from the reticle
10
. Finally, the pellicle frame
17
is typically manually grasped and completely removed from the reticle
10
.
One of the problems associated with use of the conventional, hand-operated de-pellicle tool
24
to remove the pellicle frame
17
from the reticle
10
is that the rollers
27
frequently scratch the surface of the reticle
10
as the tool
24
is moved forwardly to insert the lift pin
28
into the pin opening
22
. Accordingly, a device is needed for raising a pellicle from a reticle without scratching and otherwise damaging the reticle.
An object of the present invention is to provide a new and improved de-pellicle tool for removing a pellicle film from a reticle.
Another object of the present invention is to provide a new and improved de-pellicle tool which prevents scratching or other damage to a reticle during the removal of a pellicle film from the reticle.
Still another object of the present invention is to provide a de-pellicle tool which requires minimal contact of the tool with a reticle for the removal of a pellicle frame and pellicle film from the reticle.
Yet another object of the present invention is to provide a new and improved de-pellicle tool which utilizes multiple lift pins to simultaneously lift a pellicle frame completely from the surface of a reticle.
A still further object of the present invention is to provide a de-pellicle tool which facilitates ease in removing a pellicle frame from a reticle.
Yet another object of the present invention is to provide a de-pellicle tool which facilitates quick, easy, low-risk and efficient removal of a pellicle frame from a reticle.
SUMMARY OF
Chang Chi-Chang
Chiu Bill
Ho Ming-Tao
Lee Kuang-Yang
Adams Russell
Esplin D. Ben
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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