Semiconductor device manufacturing: process – With measuring or testing
Reexamination Certificate
1999-08-27
2001-12-25
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
With measuring or testing
C438S007000, C430S030000
Reexamination Certificate
active
06333203
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of forming a resist pattern in a step of a process of manufacturing a semiconductor device, and more specifically to a method of determining the thickness of a resist film and the structure and thickness of a film underlying the resist film, which can be applied to, for example, a photolithographic step.
Conventionally, in a step during the manufacture of a semiconductor device, a photoresist film formed on a semiconductor substrate is exposed to light, in order to form a pattern of the photoresist on the semi-conductor substrate (that is, a semiconductor wafer). At the time of the exposure, the light energy is absorbed into the photoresist film in a certain distribution in the depth direction of the photoresist film. In this manner, a standing wave which corresponds to the wavelength of the light during the exposure is created in the resist film.
Due to the occurrence of the standing wave during the exposure, an irregularity (of recesses and projections) that resembles the shape of the standing wave is created on the side wall of the resist pattern obtained developing the exposed resist.
When the shape of a standing wave is created on the side wall of a resist pattern as described above, some problems may occur. For example, measurements of the pattern of the underlying layer that is etched using a resist pattern as a mask may vary from one another. In order to avoid such problems, the side wall of the resist pattern should be made as smooth as possible. Accordingly, the occurrence of a standing wave within a resist film, as described above, should be inhibited or at least suppressed. This can be achieved by optimizing the thickness of the resist film and the structure and thickness of the film underlying the resist in advance by simulation.
In the meantime, in order to accurately observe the state of occurrence of a standing wave within a resist film by simulation, it is necessary to obtain a number of resist parameters with high accuracy, such as the type of the resist, the dissolving speed of the resist, the diffusion length of the acid depending upon the temperature of the post exposure bake (PEB), etc.
However, it is very difficult to obtain all these parameters accurately, and further, with the conventional simulation technique, there has been no methods of quantitatively determining the shape of a resist after calculating the resist shape. Therefore it has not been possible to optimize the parameters such as the thickness of the resist film and the structure and thickness of the film underlying the resist.
As described above, the conventional method of forming a resist pattern entails such a problem that the occurrence of a standing wave within a resist film cannot be avoided, i.e., the conditions such as the thickness of the resist film and the structure and thickness of the film underlying the resist film cannot be optimized in advance by simulation.
BRIEF SUMMARY OF THE INVENTION
The present invention has been proposed as a solution to the above-described problems of the conventional technique, and the object is to provide a method of forming a resist pattern that is capable of optimizing the thickness of the resist film, the thickness of the film underlying the resist film, and the structure of the underlying resist film under a condition where the type of the resist has been determined, in order to minimize the occurrence of a standing wave within the resist film.
According to the present invention, there is provided a method of forming a resist pattern, comprising the steps of calculating a light intensity profile of a latent image formed in a resist film in a depth direction by an exposure; slicing the light intensity profile of the latent image in the depth direction of the resist film at a desired position; obtaining a maximum value and a minimum value of light intensity of a latent image at the position where the latent image profile is sliced; calculating the contrast of the latent image on the basis of the maximum and minimum values of the light intensity of the latent image; and determining a thickness of the resist film and a thickness of an underlying film under the resist film to have values such that the contrast becomes a predetermined value or less; and forming a resist pattern on the semiconductor substrate on the basis of the values of the determined thickness.
In the method of forming a resist pattern, according to the present invention, the position where the latent image profile is sliced may be the position of an edge defining a resist pattern size.
In the method of forming a resist pattern, according to the present invention, the predetermined value of the contrast may be determined with correlation to an experimental value.
In the method of forming a resist pattern, according to the present invention, the predetermined value of the contrast may be 0.3 or less.
In the method of forming a resist pattern, according to the present invention, the predetermined value of the contrast of the latent image may be a threshold contrast value.
In the method of forming a resist pattern, according to the present invention, the thickness of the film underlying the resist film may include the thickness of an anti-reflection film formed on and under the resist film.
In the method of forming a resist pattern, according to the present invention, the determining step further may include determination of the structure of the film underlying the resist film. The position where the latent image profile is sliced may be the position of an edge defining a resist pattern size. The predetermined value of the contrast may be determined with correlation to an experimental value. The predetermined value of the contrast may be 0.3 or less. The predetermined value of the contrast of the latent image may be a threshold contrast value. The thickness of the film underlying the resist film may include a thickness of an anti-reflection film formed on and under the resist film. The structure of the underlying film may include one layer constituting the underlying film. The structure of the underlying film may include a plurality of superposed layers constituting the underlying film. The structure of the underlying film may include a material for one layer constituting the underlying film. The structure of the underlying film may include materials for a plurality of superposed layers constituting the underlying film. The structure of the underlying film may further include an anti-reflection coating film. The structure of the underlying film further may include a material for layer constituting the underlying film. The structure of the underlying film further may include materials for a plurality of superposed layers constituting the underlying film. The structure of the underlying film further may include a material for the anti-reflection coating film.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5472829, 19951200
patent: 5763124, 19980600
Hashimoto Koji
Nojima Shigeki
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Le Dung A
Nelms David
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