Photography – Fluid-treating apparatus – Fluid application to one side only of photographic medium
Reexamination Certificate
2002-04-18
2003-05-06
Mathews, Alan A. (Department: 2851)
Photography
Fluid-treating apparatus
Fluid application to one side only of photographic medium
C118S052000, C118S058000, C118S300000
Reexamination Certificate
active
06558053
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to substrate processing apparatus for processing substrates such as semiconductor wafers and glass substrates for liquid crystal displays. More particularly, the invention relates to a coating technique for supplying a coating solution such as a photoresist solution to form a film of coating solution on substrates.
(2) Description of the Related Art
Drawbacks of the Prior Art:
(I) A series of coating processes for forming a film of photoresist, for example, on a substrate may broadly be divided into the following processes. A first process is a “coverage process” for supplying a photoresist solution to the substrate to cover the entire surface of the substrate with the photoresist solution. A second process is a “leveling process” for making the photoresist solution on the substrate into a film. A third process is a “drying process” for drying the film of photoresist solution formed on the substrate. A fourth process, carried out as necessary, is a “removing process” for removing unwanted parts of the photoresist adhering to edges on the upper or front surface of the substrate having the film of photoresist formed thereon, and the photoresist adhering to the back surface of the substrate.
A conventional substrate processing apparatus having a coating unit carries out the above first to third processes or first to fourth processes consecutively with the single coating unit. Where, for example, a substrate processing apparatus has a spin coating unit for coating a substrate in a spin, the coating unit includes a spin chuck rotatable about a vertical axis while holding the substrate in horizontal posture, a coating solution supply nozzle for supplying a photoresist solution to the substrate held by the spin chuck, and a solvent supply nozzle for supplying a solvent to the back surface and edges of the substrate. The substrate processing apparatus having such a single coating unit consumes approximately 60 seconds in processing one substrate.
Incidentally, photoresists of the chemical amplification type that are becoming the mainline solution today are susceptible to the influence of a chemical contamination caused by atmospheric ammonia and the like. To minimize the time in which a substrate is exposed to atmosphere, the above substrate processing apparatus having the coating unit is connected with an exposing apparatus (i.e. stepper) that prints patterns on the substrate with a photoresist film formed thereon, to constitute an “in-line system” widely employed for consecutively performing a series of operations from a coating process to an exposing process.
The exposing apparatus connected to the substrate processing apparatus consumes approximately 30 seconds in processing one substrate. To secure a throughput equal to that of the exposing apparatus, the conventional substrate processing apparatus is provided with a plurality of (e.g. two) coating units for carrying out the first to third processes (or first to fourth processes) concurrently.
The coating units of the conventional substrate processing apparatus must form photoresist films on substrates with an average film thickness and a thickness distribution within specified ranges. For this purpose, coating conditions such as resist discharge, resist temperature, and temperature and humidity within the coating unit are adjusted for each coating unit.
However, circuit patterns printed and developed on the substrates with the photoresist films formed thereon by the respective coating units show that serious variations in quality such as precision of the developed patterns occur among the substrates.
(II) Conventional substrate processing apparatus may have various coating units for performing a coating process by supplying a coating solution such as a photoresist solution to substrates. One such example is a thermal transfer type coating unit that first supplies a coating solution to an applicator sheet, applies the sheet to a substrate to supply the coating solution to the substrate, and separates the sheet from the substrate after heat treatment, thereby transferring a coating film from the sheet to the substrate. Another example is a scan type coating unit having a slit nozzle that discharges a coating solution while scanning or sweeping over a substrate maintained still, to supply the coating solution to the substrate. A third type of coating unit is what is known as a spin coater that supplies a coating solution adjacent the center of a substrate spinning at high speed, spreading the coating solution from the center of the substrate by the centrifugal force of the substrate to form a film of coating solution over the entire surface of the substrate.
A photolithographic procedure where the coating solution is a photoresist solution, for example, includes a series of processes such as (1) supplying the photoresist solution to the substrate to form a photoresist film on the substrate (coating process), (2) an exposing process for exposing the substrate coated with the photoresist film, and (3) developing the exposed substrate (developing process).
Usually, the coating process (1) and developing process (3) are carried out in the same substrate processing apparatus using a coating unit, while the exposing process (2) is carried out by an exposing apparatus which is an external processing apparatus associated with the substrate processing apparatus. Substrates are transferred between the substrate processing apparatus and exposing apparatus through an interface forming a part of the substrate processing apparatus.
However, such a conventional construction has the following drawbacks.
The substrate having undergone the coating process (1) could be exposed in a defective manner (i.e. defocused) in the exposing apparatus.
That is, where different positions on the surface of the substrate are at different heights from the lens of the exposing apparatus, the variations in the height could exceed the depth of focus of the lens, thereby causing a blur. This results in a defective exposure to affect the uniformity in line width of patterns obtained from the exposing process. Conventionally, such a defective exposure is considered due to particles adhering to the surface of the substrate, or ununiformity of the photoresist film formed on the substrate. To avoid the defective exposure, it is conventional practice to clean the surface of the substrate before the coating process or, in the case of a spin coater, adjust the spinning speed of the substrate to uniform the photoresist film. However, such surface cleaning alone has proved no ultimate solution to the defective exposure.
(III) Improved throughput in particular among the processing capabilities of the substrate processing apparatus is desired nowadays. For this purpose, measures have been taken not only to improve transport capability but to increase the number of processing units for performing the same series of processes in parallel.
FIG. 1
is a conceptual diagram of a parallel processing in which step A is carried out concurrently by using two processing units. Step A has a processing time of 60 seconds, for example. This apparatus has an improved throughput of 30 seconds owing to the parallel processing. However, such a technique of parallel processing relying on an increased number of processing units entails disadvantages of increased cost and enlargement of the apparatus.
A technique for overcoming such disadvantages has been proposed in Japanese Patent No. 3164739, for example. In the technique proposed in this patent, a process is divided to reduce the processing time consumed by each step, thereby to reduce the number of parallel processing units. Thus, throughput may be maintained while achieving a cost reduction and compactness of the apparatus.
FIG. 2
is a conceptual diagram of an apparatus using such a technique. In this apparatus, step A is divided into step B (with a processing time of 30 seconds) and step C (with a processing time of 30 seconds) to be carried out in series by
Aoki Kaoru
Inagaki Yukihiko
Kodama Mitsumasa
Matsunaga Minobu
Mitsuhashi Tsuyoshi
Dainippon Screen Mfg. Co,. Ltd.
Mathews Alan A.
Ostrolenk Faber Gerb & Soffen, LLP
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