Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
1998-06-17
2001-02-20
Duda, Kathleen (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S326000
Reexamination Certificate
active
06190840
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a resist pattern forming method used in manufacturing a semiconductor device and the like. In this specification, a resist means a photoresist.
In a photolithography process, a super-resolution exposure technique using a phase-shifting mask and the like must be applied to form a fine pattern with a width smaller than the wavelength of exposure light.
A Levenson phase-shifting mask comprises, e.g., a transparent substrate, light-shielding members arranged parallel to each other on the transparent substrate at predetermined intervals, and phase shifters arranged every other interval between adjacent light-shielding members. The Levenson phase-shifting mask is formed to attain a phase difference of 180° between exposure light transmitted through a transmitting portion not having a phase shifter, and exposure light transmitted through an adjacent transmitting portion having a phase shifter.
Of phase-shifting masks, the Levenson phase-shifting mask can form a periodic, high-density resist pattern at a higher resolution. With the use of the Levenson phase-shifting mask, a larger depth of focus (DOF) can be obtained.
However, when, e.g., the core of a semiconductor device is to be formed using the Levenson phase-shifting mask, transmitting portions having phase shifters or transmitting portions not having phase shifters may be partially adjacent to each other because the core pattern is complicated. No phase difference can be formed at the location where transmitting portions of the same type are adjacent to each other. At this location, the resolution cannot be increased. For this reason, the core pattern is formed with a relatively large size, whereas the cell pattern is generally formed with a size as small as possible.
In general, exposure light transmitted through a photomask diffracts or interferes, varying in intensity and the like. That is, the intensity of exposure light incident on a resist film is not uniform but varies at the entire irradiated portion. The intensity distribution (image intensity distribution) depends on diffraction and interference conditions, i.e., the pattern size and pattern density (duty ratio) of a light-transmitting portion formed on the photomask. Therefore, optimum conditions, such as the optimum exposure dose, for exposing the resist film formed on the substrate depend on the size and the density. Accordingly, it is difficult to expose both core and cell portions under optimum conditions in simultaneously forming them.
This problem occurs not only in the use of the Levenson phase-shifting mask but also in the use of a general photomask. Therefore, demands arise for a larger margin for exposure conditions such as the exposure dose in order to form a pattern at a higher precision in manufacturing a semiconductor device.
Prior to the exposure, a resist film must be formed on a substrate. A resist film is formed on the entire coating surface of a substrate by a spin coating method as a conventional resist coating method. The resist film is also applied on an alignment mark used to align the substrate, a photomask, and the like in exposure. As a result, the alignment precision decreases, and no resist pattern can be formed at a high precision.
In addition, since the resist film is formed on a region, such as the alignment mark, where no resist film need be formed, a larger amount of resist is required, resulting in high cost.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a resist pattern forming method capable of forming a resist pattern at a high precision.
It is another object of the present invention to provide a resist pattern forming method capable of widening the margin for exposure conditions and increasing the throughput in simultaneously forming regions having different pattern sizes and different pattern densities.
It is still another object of the present invention to provide a resist pattern forming method capable of increasing the alignment precision in exposure.
It is still another object of the present invention to provide a resist pattern forming method capable of contributing to a cost reduction.
According to the present invention, there is provided a resist pattern forming method comprising the steps of forming a resist film on one major surface of a substrate, irradiating the resist film with exposure light via a photomask to expose the resist film, and developing the exposed resist film, wherein the photomask includes a first pattern portion having a light-transmitting portion, and a second pattern portion having a light-transmitting portion different in at least one of a pattern size and a pattern density from the first pattern portion, and the step of forming the resist film comprises forming first and second regions respectively corresponding to the first and second pattern portions of the resist film to have different thicknesses.
According to the present invention, there is provided a resist pattern forming method comprising the steps of forming a resist film selectively on part of one major surface of a substrate, thereby forming an applied region and a non-applied region in the major surface of the substrate, exposing the resist film using a photomask, and developing the exposed resist film.
According to the present invention, there is provided a resist pattern forming method comprising the steps of forming a resist film on one major surface of a substrate irradiating the resist film with exposure light via a photomask to expose the resist film, and developing the exposed resist film, wherein the resist film is made by using a positive resist, the major surface of the substrate consists of a first region where an intensity substantially equal to an intensity of the exposure light incident on the photomask is observed, and a second region as the other portion, and the resist film forming step comprises applying the resist on the second region, without applying on at least part of the first region.
According to the present invention, there is provided a resist pattern forming method comprising the steps of forming a resist film on one major surface of a substrate, irradiating the resist film with exposure light via a photomask to expose the resist film, and developing the exposed resist film, wherein the resist film is made by using a negative resist, the major surface of the substrate consists of a first region where an intensity of the exposure light observed is substantially equal to zero, and a second region as the other region, and the resist film forming step comprises applying the resist on the first region, without applying on at least part of the second region.
Additional object 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 object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinbefore.
REFERENCES:
patent: 5702848 (1997-12-01), Spence
patent: 196 33 407 (1998-02-01), None
patent: 738 925 (1996-10-01), None
patent: 7-321001 (1995-12-01), None
patent: 7-320999 (1995-12-01), None
Ito Shin'ichi
Kawano Kenji
Okumura Katsuya
Barreca Nicole
Duda Kathleen
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
LandOfFree
Resist pattern forming method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Resist pattern forming method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Resist pattern forming method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597710