Photography – Fluid-treating apparatus – Fluid application to one side only of photographic medium
Reexamination Certificate
2001-04-18
2002-06-11
Rutledge, D (Department: 2851)
Photography
Fluid-treating apparatus
Fluid application to one side only of photographic medium
C396S611000, C396S627000, C118S052000, C427S240000
Reexamination Certificate
active
06402399
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a developing method and a developing apparatus, and more particularly, to a method and developing apparatus for performing a developing process by applying developing solution to a surface of a substrate such as a semiconductor wafer.
To manufacture a semiconductor device, photolithography technique is used. In the photolithography technique, photoresist is coated on a semiconductor wafer, thereby forming a photoresist film on one surface of the wafer. The photoresist film is exposed to a predetermined circuit pattern and then developed. Thus, a predetermined pattern photoresist film is formed on the wafer.
In general, the wafer is developed in the following manner. First, the developing solution is continuously applied from a nozzle to the photoresist film to which the circuit pattern has been exposed. The applied developing solution forms a layer, which contacts that surface of the photoresist film. The layer of developing solution is maintained on the resist film for a prescribed time, by continuously applying the developing solution.
Recently, a linear nozzle
100
of the type shown in
FIG. 7
is used to apply developing solution in order to save the developing solution and to apply a developing solution uniformaly over an entire surface of the wafer. The linear nozzle
100
has a number of discharge holes
101
arranged in a straight line. To develop the resist film formed on a wafer
102
, the nozzle
100
is moved to face the wafer
102
. The nozzle
100
applies the developing solution through the holes
101
onto the wafer
102
, in the form of parallel streams. When the streams of developing solution merge on the surface of the resist film to form a film-like stream, then, the wafer
102
is slowly rotated by 180°. After the developing solution layer covers the entire surface of the resist film, the rotation speed of the wafer
102
is increased.
The conventional method of developing the resist film by the use of the linear nozzle
100
is, however, disadvantageous in the following respects:
(1) It takes some time until the developing solution
103
spreads all over the pattern-forming surface of the wafer
102
. This is because the wafer
102
is rotated only after the developing solution
103
is applied onto the resist film. Consequently, that part of the resist film, which first contacts the developing solution
103
may differ from any other part of the resist film in terms of resolution.
To be more specific, the parallel streams of developing solution
103
applied through the holes
101
merge together on the resist film, forming a film-like stream. The wafer
100
must be rotated only after the developing solution forms a film-like stream. It is therefore impossible to rotate the wafer
102
before or at the same time the developing solution
103
first contacts the photoresist film. As a consequence, that part of the resist film, which first contacts the solution
103
, may be developed to excess, unlike any other part of the resist film.
(2) Second, much attention must be now pad to the influence of the first impact given by the developing solution
103
that first contacts the resist film.
That is, when the valve connected to the linear nozzle
100
is opened to supply the developing solution
103
to the nozzle
100
, the pressure on the solution
103
increases momentarily. Thus, the streams of developing solution applied from the nozzle
100
give the first impact to the wafer
102
. Consequently, that part of the resist film, which first contacts the solution
103
, is developed to excess, unlike any other part of the resist film.
The circuit patterns recently designed and formed on the wafer consist of very fine elements arranged in high density, and the resist film must be processed with high resolution. This is why the influence of the first impact, which has hitherto been neglected, now needs to be considered.
As described above, the conventional developing method is disadvantageous in view of the non-uniform development of the resist film, which results not only from the different timings of applying the developing solution to the resist film, but also from the influence of the first impact of developing solution.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing. Its object is to provide a developing method and a developing apparatus, which solves various problems arising in applying a developing solution on a wafer, thereby to properly develop the photoresist film formed on the wafer.
More particularly, the object of the invention is to provide a developing method and a developing apparatus, in which no time lag in the application of developing solution for the parts of the resist film takes place, making it possible to develop the photoresist film uniformly.
Another object of the invention is to provide a developing method and a developing apparatus, which prevent the first impact of the developing solution on the photoresist film from impairing the developing of the photoresist film.
To attain the objects of the invention, a developing method according to the first aspect of the invention comprises the steps of: holding a substrate in a substantially horizontal position, the substrate coated with a photoresist film which has a pattern-exposed region where a circuit pattern is formed by light exposure; and developing the photoresist film by applying, at a time, a developing solution to the entire pattern-exposed region of the photoresist film.
In the cross-sectional area of the photoresist film, which can be applied with the developing solution at a time, is larger than in the conventional method in which the solution is applied by the linear nozzle. The developing solution can be therefore applied at a lower speed to the pattern-forming region of the resist film. Hence, it is possible to reduce the influence that the first impact of solution imposes on the resist film.
The developing solution may be is applied to the resist film, in the form of parallel streams. However, the streams of solution merge on the resist film, forming a layer of solution thereon more quickly than in the conventional method. Therefore, the substrate can be rotated before the start of applying the developing solution to the photoresist film, and at a higher speed than in the conventional developing method. Moreover, this effectively reduces the influence of the first impact of developing solution.
With the developing method of the invention it is possible to apply the developing solution, almost at a time, to the entire pattern-exposed region of the resist film. Thus, no time lag in the application of solution for the parts of the resist film takes place. This makes it possible to develop the resist film uniformly. As a result, the resist film can have uniform resolution over its entire pattern-exposed region.
In the developing method of the invention, if the developing solution is applied at a higher rate, the developing solution can be uniformaly applied over the entire photoresist film without rotating the substrate.
According to the second aspect of the present invention, there is provided a developing apparatus which comprises: a substrate holding mechanism for holding a substrate in a substantially horizontal position, the substrate coated by a photoresist film which has a pattern-exposed region where a circuit pattern is formed by light exposure; a solution discharging unit having a number of discharge tubes, each having a distal end opposing the pattern-exposed region of the photoresist film; a solution applying mechanism for applying the developing solution to the pattern-exposed region of the photoresist film through the discharge tubes; and a control section for controlling the solution applying mechanism, thereby to apply the developing solution to the entire pattern-exposed region substantially at a same time.
Comprising these components, the developing apparatus can perform the developing method according to the first aspect of the invention. The appar
Nishikido Shuuichi
Sakamoto Kazuo
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