Radiation-sensitive composition of chemical amplification type

Details Radiation-sensitive composition of chemical amplification type Radiation-sensitive composition of chemical amplification type

2000-07-03

2002-03-19

Ashton, Rosemary (Department: 1752)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Radiation sensitive composition or product or process of making

C430S914000, C430S921000, C568S028000, C568S034000, C568S035000

Reexamination Certificate

active

06358665

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemically amplified radiation sensitive composition, and more particularly to the so-called “photoresist” for the manufacture of electronic components, printing plates, and three-dimensional micro objects.
2. Background Art
An increase in the processor speed attained by the development of microelectronic devices with higher integration density in the electronic industry has lead to a demand for further improved radiation sensitive compositions. That is, an improvement in properties, such as resolution of photoresists and dimensional accuracy of images, has been required for satisfying demands in the microelectronic device production industry.
According to the Rayleigh's equation
R=k
1
*&lgr;/NA
wherein R denotes the ultimate resolution, k
1
is a constant, &lgr; is the wavelength of the light source used in exposure, and NA is the numerical aperture of the illuminating optical system, use of a light source having shorter wavelength in exposure can most effectively enhance the ultimate resolution. This has been effectively applied to the transition of irradiation technology from g-line (436 nm) to i-line (365 nm), and has pushed the resolution limits of conventional near UV irradiation technology to below 0.30 &mgr;m. With the need to produce even smaller features, shorter wavelength radiation, such as deep UV (DUV) radiation (150-320 nm), has become employed. Photons generated from DUV radiation exhibit higher energy than those generated from near UV radiation sources. Therefore, the number of photons per unit energy is smaller, leading to a demand for radiation sensitive compositions with higher sensitivity.
Radiation sensitive compositions called “chemically amplified photoresists” are known in the art, and are advantageous in that the catalytic imaging process can provide high photosensitivity. By virtue of high photosensitivity and high resolution, the chemically amplified radiation sensitive compositions are being substituted for conventional radiation sensitive compositions and being spread. The chemically amplified radiation sensitive compositions comprise a radiation sensitive acid generating agent (photoacid generator; hereinafter often referred to as “PAG”) which generates an acid. Upon exposure, this PAG releases an acid which catalyzes a layer dissolution reaction in the case of positive-working photoresists and catalyzes a crosslinking reaction in the case of negative-working photoresists.
Positive-working chemically amplified photoresists are the so-called “two component systems” which basically comprise: (1) a resin which has been rendered insoluble in alkaline solutions by masking at least a part of the water soluble groups on the resin with an acid cleavable protective group; and (2) a PAG. Optionally, low molecular weight or phenol derivatives masked with acid cleavable protective groups described below are added to further improve the lithographic performance. This system is known as a “three component chemically amplified radiation sensitive composition. Upon exposure, the PAG produces a strong acid capable of cleaving the bond between protective group and the resin, resulting in the formation of an alkali-soluble resin. Acid molecules produced from the PAG upon exposure are not consumed by a single reaction for cleaving the protective group from the resin, and one acid molecule produced during the exposure can cleave a large number of protective groups from the resin. This contributes to the high sensitivity of chemically amplified radiation sensitive compositions.
Many two or three component positive-working photoresist compositions comprising polyhydroxystyrene resins or phenol derivatives having polyfunctional groups have been described in patents and literature. In the case of positive-working two component photoresist compositions, the phenolic groups of the polymer are partly or fully protected by acid-cleavable protective groups, for example, t-butoxycarbonyl groups (U.S. Pat No. 4,491,628), t-butoxycarbonylmethyl groups (U.S. Pat. No. 5,403,695), t-butyl groups, trimethylsilyl groups, tetrahydropyranyl groups (U.S. Pat. No. 5,350,660), 2-(alkoxyethyl) groups (U.S. Pat. No. 5,468,589 and U.S. Pat. No. 5,558,971, and U.S. Pat. No. 5,558,976), or combinations thereof. A co- or terpolymer of hydroxystyrene with (meth)acrylic acid, wherein the carboxylic acid is partly or fully protected by acid-cleavable groups, such as t-butyl groups (U.S. Pat. No. 4,491,628, U.S. Pat. No. 5,482,816, and U.S. Pat. No. 5,492,793), amyl groups, or tetrahydropyranyl groups, has also been regarded as useful for positive-working two component photoresist compositions. The addition of dissolution inhibitors, which have been protected in the same manner as described above, to the positive-working photoresist composition is described in U.S. Pat. No. 5,512,417 and U.S. Pat. No. 5,599,949.
In the case of negative-working photoresists, a crosslinking agent, such as hexamethoxy methylmelamine, is added to an alkali soluble phenolic resin (U.S. Pat. No. 5,376,504 and U.S. Pat. No. 5,389,491). The acid produced from the PAG upon exposure induces a crosslinking reaction in the exposed areas.
As is apparent from the foregoing description, PAG plays an important role in the imaging process for both positive-working and negative-working chemically amplified resists, because PAG governs light response properties, such as absorption of light or quantum yield of acid formation, and, in addition, governs the properties of the produced acid, such as acid strength, mobility, or volatility. Useful PAGs for both positive-working and negative-working chemically amplified resists include ionic onium salts, particularly iodonium salts or sulfonium salts with strong non-nucleophilic anions (U.S. Pat. No. 4,058,400 and U.S. Pat. No. 4,933,377), for example, hexafluoroantimonate and trifluoromethane sulfonate (U.S. Pat. No. 5,569,784) or aliphatic/aromatic sulfonates (U.S. Pat. No. 5,624,787). In addition, many non-ionic PAGs producing the above mentioned sulfonic acids have been described for both positive-working and negative-working chemically amplified photoresist materials (U.S. Pat. No. 5,286,867 and U.S. Pat. No. 5,338,641). Further, certain hydrogen halide producing PAGs have been suggested for advantageous use in negative-working chemically amplified resists (U.S. Pat. No. 5,599,949).
U.S. Pat. No. 5,731,364 discloses that binulear sulfonium compounds having perfluoroaryl sulfonate and perfluoroalkyl sulfonate are useful for the image formation of positive-working and negative-working photoresists.
This patent, however, does not suggest specific superiority in use of sulfonium compounds of nonafluorobutane sulfonate as PAGs in combination with hydroxystyrene based resin having a protective group which can be eliminated with an acid.
Among these PAGs, those onium salts producing trifluoromethane sulfonic acids upon exposure are particularly preferred, because superior sensitivity and good ultimate resolution of the photoresist system can be obtained. In addition, these PAGs are known to reduce the formation of insolubles on the substrate or at the substrate/resist interface known as scum.
It was found, however, that minor quantities of the rather volatile trifluoromethane sulfonic acid (TFSA) produced during the irradiation process may evaporate (outgas) from the photoresist film and cause corrosion of the exposure and process equipment. The same trouble is observed when hydrogen halide producing PAGs are used. It may be anticipated that a long time exposure especially to the evaporating fumes of the volatile, aggressive TFSA may cause hazards to the health of the labor force. In addition, it is known that resist materials containing PAGs which produce TFSA tend to produce the so-called T-shaped pattern profiles, and show linewidth changes upon process delays (i.e. inadequate delay time stability) due to the high volatility and the diffusion properties of this acid. Attempts to identify an

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