Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2001-11-13
2004-09-28
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S791000
Reexamination Certificate
active
06797647
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for fabricating an organic thin film that will serve as a resist film, an anti-reflection film or the likes.
As the systems bearing complex semiconductor integrated circuits have been downsized, it is becoming increasingly difficult to print complex circuit patterns onto a small semiconductor chip by the pattern lithography method that uses a resist pattern, namely, a patterned resist film, as a mask. As the wavelength of the energy beam used in the pattern lithography method becomes shorter, the beam which has passed through the photosensitive organic film serving as a resist film is reflected at higher reflectivity off the surface of the film to be etched (formed under the resist film). Then, undesired areas in the photosensitive organic film (the areas which should not be irradiated with the energy beam) other than the target areas for exposure may be subject to unintentional exposure.
To solve this problem, a method for reducing the reflection of the energy beam that has passed through the photosensitive organic film has been proposed in which an organic film that absorbs the energy beam is coated on the film to be etched as an anti-reflection film prior to the formation of the photosensitive organic film serving as a resist film.
FIGS. 9A and 9B
are sectional views illustrating steps of an organic thin film fabrication method according to the prior art.
Referring now to
FIG. 9A
, the semiconductor substrate
100
on which a film to be etched (not shown) has been formed is first subjected to wet-cleaning to remove particles that have stuck on the surface of the semiconductor substrate
100
when the film to be etched is formed, for example. To be more specific, the semiconductor substrate
100
is turned while a cleaning liquid
102
is supplied from a nozzle
101
onto the semiconductor substrate
100
.
Next, as shown in
FIG. 9B
, an organic film
103
, which will serve as a resist film or an anti-reflection film, is formed on the semiconductor substrate
100
of which wet-cleaning has been completed.
As the design rule for electronic devices becomes increasingly fine in recent years, it has become hard to form fine resist patterns when the photosensitive organic film serving as a resist film is thick. Besides, if the organic film serving as an anti-reflection film is thick, the resist film is subjected to undesired etching. To solve such a problem and enable to provide fine resist patterns, a few methods have been proposed for forming a thin organic film serving as a resist film or an anti-reflection film.
At least the same or higher levels of uniformity in film thickness are required in forming an organic thin film, compared with the case of forming an organic thick film.
Then it is necessary to increase the content of solvent in the organic material used in forming the organic thin film, in order to make viscosity of the organic material low. However, if the content of solvent in the organic material is raised, the uniformity of film thickness is more likely to be affected by the heat of vaporization of solvent (Japanese Patent Laid-Open Publication No. Hei. 8-186072).
In addition to the above-mentioned drawback, the inventors of the present invention have found another problem that if an organic thin film is formed 100 nm or less in thickness on a silicon nitride film or silicon nitride oxide film that is deposited as a hard mask or an inorganic anti-reflection film, a coating pattern running radially from the wafer center to its peripherals shows up (hereafter, coating unevenness) on the fabricated organic thin film. An organic thin film that has such coating unevenness cannot be used as a resist film or an anti-reflection film.
SUMMARY OF THE INVENTION
In view of the foregoing, it is, therefore, an object of the present invention to provide a method for forming organic thin films, using an organic material of a low viscosity, of uniform thickness and free of such coating unevenness, when forming an organic thin film onto the silicon nitride film or silicon nitride oxide film.
In order to attain the above object, a first method for fabricating an organic thin film according to the present invention comprises the steps of: forming an undercoating film made of silicon nitride or silicon nitride oxide on a substrate; wet-cleaning the undercoating film using a cleaning liquid; irradiating far ultraviolet ray onto the undercoating film of which wet-cleaning has been completed; and forming an organic thin film with a thickness of about 100 nm or thinner on the undercoating film onto which far ultraviolet ray has been irradiated by turning the substrate and providing a liquid organic material onto the substrate.
According to the first method for fabricating an organic thin film of the present invention, the undercoating film made of silicon nitride or silicon nitride oxide is wet-cleaned; far ultraviolet ray is irradiated onto the undercoating film; and then the organic thin film with a thickness of about 100 nm or thinner is formed on the undercoating film. Then compared with the conventional organic thin film fabrication method that conducts no irradiation of far ultraviolet ray onto the undercoating film, coating unevenness is unlikely to show up in the resulting organic thin film even when an organic material of low viscosity is employed. Therefore, the uniformity of thickness of the organic thin film can be improved. When the organic thin film is formed as a resist film or anti-reflection film, it becomes possible to make fine resist patterns. Then it becomes also possible to provide electronic devices of finer design rules.
A second method for fabricating an organic thin film according to the present invention comprises the steps of:
forming an undercoating film made of silicon nitride or silicon nitride oxide on a substrate; wet-cleaning the undercoating film using a cleaning liquid; and forming an organic thin film with a thickness of about 100 nm or thinner on the undercoating film, of which wet-cleaning has been completed, by turning the substrate and providing a liquid organic material onto the substrate; wherein the organic material contains at least one solvent selected from the group consisting of propylene glycol monomethyl ether acetate, propylene glycol monomethyl-ether, ethyl lactate, ethyl methoxy propionate, ethyl ethoxy propionate, 2-heptanone, ethyl pyruvate, diethylene glycol monomethyl ether, methyl cellosolve acetate, propylene glycol monoethyl ether acetate, ethyl methoxy propionate, methyl lactate and methyl pyruvate.
According to the second method for fabricating an organic thin film of the present invention, the undercoating film made of silicon nitride or silicon nitride oxide is wet-cleaned and then organic thin film with a thickness of about 100 nm or thinner is formed on the undercoating film by the use of an organic material containing at least one solvent selected from the group consisting of propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, methyl methoxy propionate, ethyl ethoxy propionate, 2-heptanone, ethyl pyruvate, diethylene glycol monomethyl ether, methyl cellosolve acetate, propylene glycol monoethyl ether acetate, ethyl methoxy propionate, methyl lactate and methyl pyruvate. Then, compared with the conventional organic thin film fabrication method that does not use an organic material containing the above solvent, coating unevenness is unlikely to show up in the resulting organic thin film even when an organic material of low viscosity is employed and therefore the uniformity of the thickness of the organic thin film can be improved. When the organic thin film is formed as a resist film or anti-reflection film, it becomes thereby possible to make the resist pattern finer. Then it also becomes possible to provide electronic devices of finer design rules.
Further, compared with the first method of the invention, the second method does not need the irradiation process of far ultraviolet ray onto the undercoating film.
Shono Tomofumi
Yamashita Kazuhiro
Fourson George
Kebede Brook
Matsushita Electric - Industrial Co., Ltd.
McDermott Will & Emery LLP
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