Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2000-08-30
2002-10-08
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S192000, C430S193000, C430S270100
Reexamination Certificate
active
06461785
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a composition for a positive type photoresist for manufacturing microscopic circuit patterns such as liquid crystal display circuits or semiconductor integrated circuits and, more particularly, to a composition for a positive type photoresist, including polymer resin that produces a photoresist layer, photosensitive chemical and solvents.
(b) Description of the Related Art
For producing tiny circuit patterns such as those used in liquid crystal display (LCD) circuits or semiconductor integrated circuits, a photoresist composition is uniformly coated or applied on an insulator layer or a conductive metal layer on a substrate. The coated or applied substrate is then exposed through a mask to some form of radiation, such as ultraviolet light, electrons, or X-rays. And the exposed substrate is developed to produce a desired pattern. The patterned photoresist film is used as a mask to remove the insulator layer or the conductive metal layer. Then the remaining photoresist layer is removed to complete the microscopic circuit pattern onto the substrate surface. Photoresist compositions are classified into negative and positive types depending on whether the exposed areas of photoresist coating become insoluble or soluble. Recently, positive type photoresist compositions have been preferred, because they can form firmer patterns.
The important properties of photoresist compositions for commercial use are photosensitivities, contrast, resolution, adhesivity to the substrate, remainder ratio, and safety.
Photosensitivity refers to the speed how fast the photoresist responds to the light. Higher photosensitivity is required, particularly in applications where a number of exposures are performed to form multiple patterns by a repeated process. The other examples are when reduced light is used, like the projection exposure techniques that use light passed through a series of lenses and mono-chromatic filters.
Contrast refers to a ratio between the percentage of film loss in the exposed development area and the percentage of film loss on the unexposed area. Ordinarily, development of an exposed resist coated substrate is continued until the coating on the exposed area is completely dissolved away. Thus, development contrast can be determined simply by measuring the percentage of the film coating loss in the unexposed areas when the exposed coating areas are removed entirely.
Resolution refers to the capability of a photoresist composition how finely to reproduce the mask image utilized during exposure on the developed exposed spaces. In many industrial applications, particularly in the manufacture of LCDs or semiconductor integrated circuits, a photoresist is required to provide a high degree of resolution for very fine line and space widths of 1 &mgr; or less.
Generally, photoresist composition includes a polymer resin for producing a photoresist layer, photosensitive chemicals, and a solvent. Various attempts have been made previously to improve the photosensitivity, contrast, resolution, and the safety of positive photoresist compositions. For example, U.S. Pat. No. 3,666,473 discloses the compound of a mixture of two phenol formaldehyde novolak resins together with a typical photosensitive chemical. U.S. Pat. No. 4,115,128 discloses that an organic acid cyclic anhydride was added to the phenolic resin and naphthoquinone diazide photosensitive chemical to increase photosensitivity. U.S. Pat. No. 4,555,069 discloses that novolak resin and o-quninone diazide photosensitive chemical and propylene glycol alkyl ether acetate solvent are used for higher photosensitivity and for increased safety.
Various solvents have been developed to improve physical properties of the photoresist composition and work safety. For example, ethylene glycol mono ethyl ether acetate or ethyl lactate, propylene glycol mono ethyl ether acetate may be used as solvent. However, the photoresist composition including ethyl lactate exhibits poor adhesivity to the substrate and it is difficult to be coated on a substrate uniformly. Ethylene glycol mono ethyl ether acetate or propylene glycol mono ethyl ether acetate is toxic and generates an unpleasant odor during the process. Accordingly, there is still a need for photoresist compositions that are suitable for various industrial applications, without sacrificing any one of the properties of photosensitivity, contrast, resolution, or solubility of polymer resin.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a composition for a positive type photoresist that exhibits high photosensitivity, remainder ratio, contrast, resolution, and substrate adhesivity for varieties of industrial applications.
It is another object to provide a composition for a positive type photoresist that is safe, without unpleasant odor, and environmentally friendly.
These and other objects may be achieved by a composition for positive type photoresist of the present invention. This composition includes a polymer resin for forming a photoresist layer, a photosensitive chemical that changes solubility of the photoresist layer when exposed to some form of radiation, and a solvent of 3-methoxybutyl acetate, 2-heptanone, and 4-butyrolactone. The polymer resin is preferably a novolak resin and the photosensitive chemical is preferably a diazide-type compound. The ratio of 3-methoxybutylacetate:2-heptanone:4-butyrolactone is 50 to 70 parts by weight 3-methoxybutylacetate to 5 to 15 parts by weight 2-heptanone to 2 to 10 parts by weight 4-butyrolactone.
DETAILED DESCRIPTION OF THE INVENTION
The useful polymer resins employed in a photoresist composition of the present invention are well known in the related arts. A novolak resin, an exemplary polymer resin, may be employed in a photoresist composition of the present invention. The novolak resin is produced by reacting aromatic alcohol such as phenol, meta and/or para cresol with formaldehyde. To improve the photoresist, the molecular weight of the resin may be controlled by adjusting the ratio among high, medium or low molecular resins depending on the purpose of the photoresist.
The useful diazide compound for a photosensitive chemical may be produced by reacting polyhydroxy benzophenone with a diazide-based compound such as 1,2-naphtoquinonediazide, or 2-diazide- 1 -naphtol-5-sulfonic acid.
The solvent includes 3-methoxybutyl acetate, 2-heptanone and 4-butyrolactone. The ratio of 3-methoxybutyl acetate:2-heptanone:4-butyrolactone is preferably 50 to 70 parts by weight 3-methoxybutyl acetate to 5 to 15 parts by weight 2-heptanone to 2 to 10 parts by weight 4-butyrolactone, and more preferably 55 to 65 parts by weight 3-methoxybutyl acetate to 7 to 13 parts by weight 2-heptanone to 2 to 5 parts by weight 4-butyrolactone.
3-methoxybutyl acetate more than the above range decreases the viscosity of the composition and reduces the thickness of the photoresist layer as well as deteriorate the remainder ratio. On the other hand, 3-methoxybutyl acetate less than the above range increases the viscosity and increases the thickness of the layer too much while reducing. 2-heptanone more than the above range makes, the composition difficult to use because of it's unpleasant odor, and decreases the viscosity of the composition while reducing the thickness of the layer thins. On the other hand, 2-heptanone less than the above range increases the viscosity of the composition too much and reduces the photosensitivity. 4-butyrolactone more than and reduces the above range deteriorate the remainder ratio. 4-butyrolactone less than the above range reduces the solubility of the photosensitive chemical such that the homogeneous composition is not obtained and easily produces particles on the substrate.
In the present invention, the photoresist composition includes preferably about 10 to about 25 wt % of the polymer resin, about 4 to 10 wt % of the photosensitive chemical, and 65 to 85 wt % of the solvent.
If the amount of the polymer resin is less than 10 w
Ju Jin-Ho
Kang Sung-Chul
Kim Ki-Soo
Lee Yu-Kyung
Nah Yun-Jung
Chu John S.
McGuireWoods LLP
Park Hae-Chan
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