Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-11-06
2002-04-16
Baxter, Janet (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
C430S281100, C430S326000, C430S914000, C430S919000, C430S920000, C430S921000, C430S923000
Reexamination Certificate
active
06372406
ABSTRACT:
BACKGROUND OF THE INVENTION
Acid-catalyzed resist compositions are widely used in photolithography applications for manufacture of integrated circuits and other devices where patterned mask layers are employed in device manufacture.
Acid-catalyzed photoresists are generally characterized by the combination of an acid-sensitive resist polymer (or in some instances an acid-sensitive monomer or oligomer) with a radiation-sensitive acid-generating compound (photosensitive acid generator or PAG). On exposure of the resist composition to a suitable radiation source, the PAC generates an acid of sufficient strength to cause a reaction with the acid-sensitive resist polymer or other acid-sensitive component. The reaction is typically catalytic in nature (i.e., the initial acid generated reacts with the acid-sensitive polymer to create additional acid which is available for further reaction). The acid-catalyzed reaction is often enhanced by baking the exposed resist composition.
In the case of positive photoresist compositions, the acid generated on exposure to radiation typically causes the exposed resist composition to exhibit increased solubility in alkaline media (and/or other property difference) compared to the unexposed resist. In negative resists, the acid generated typically causes the exposed resist composition to exhibit reduced solubility in alkaline media;(and/or other property difference) compared to the unexposed resist. Some acid-catalyzed resist compositions (hybrid resists) are capable of acting as positive or negative resists depending on the radiation exposure and post-exposure treatment.
In most applications, the acid-catalyzed resist composition is applied to a surface where a patterned (mask) layer is desired (e.g. to the surface of a semiconductor wafer) as a liquid solution. The solvent is then typically removed to form a thin solid layer on the desired surface. In many instances, the solvent removal may be assisted by a heating step. The applied resist layer is then exposed to the desired radiation. The exposure is typically done through a mask containing a pattern of openings to create a corresponding pattern of exposed areas in the resist. In some cases, such as with the use of electron beam (e-beam) radiation, a patternwise exposure may be achieved without a mask by scanning the electron-beam over the resist layer in a patterned manner.
After exposure, the pattern is developed by selective removal of the exposed or unexposed portions of the resist depending on whether the resist acting in a positive mode or a negative mode. Prior to selective removal, the exposed resist layer may be treated by application of heat to enhance the property differences created by the exposure. Once the exposed resist layer is ready for development, the selective removal is typically done by treating the resist layer with a solvent which selectively removes portions of the resist by dissolution. The patterned resist layer may then be used in whatever manner desired for the specific manufacturing objective.
In most photolithography applications, the size of detail in the exposed pattern continues to become increasingly finer. Often, there is a desire to create patterns having resolution of details in the sub-micron range. This desire is especially strong in the manufacture of integrated circuits since the reduction of detail size generally corresponds to an increase is device density that can be constructed. Similar desires for the ability to produce fine details exist in other areas such as the manufacture of micromachines, magnetic heads, magnetic/electronic storage devices, etc.
In addition to the performance pressures created by the demand for finer resolution, there are the significant demands associated with large scale commercial manufacture. For example, the photoresist composition should retain its performance capability even after storage between formulation and use. In addition, the retained performance should be predictable. Photoresist compositions having a better ability to meet these manufacturing demands will result in reduced cost of the overall manufacturing process (e.g. more consistent reproduction of patterns, greater flexibility in manufacturing process configuration, etc.).
For acid-catalyzed positive photoresists, the presence of residual acidic species in the unexposed photoresist composition often causes performance degradation due to gradual reaction of the residual acid with the acid-sensitive polymer. Since this reaction is not controlled by the radiation exposure, performance degradation such as loss of contrast, variation in dose sensitivity, etc. can result. Additionally, residual acid may cause loss of shelf life in the photoresist formulation. In some instances, shelf life up to a year may demanded of a photoresist formulation.
In the past, the problem of residual acid in positive photoresists has been addressed by addition of certain base additives to the photoresist composition to scavenge residual acid. Unfortunately, such base additives have often exhibited adverse interaction with the photosensitive acid generator in the photoresist composition.
SUMMARY OF THE INVENTION
The invention provides acid-catalyzed positive photoresist compositions which have improved shelf-life and performance consistency. The compositions of the invention are generally characterized by the presence of a deactivated aromatic amine additive.
In one aspect, the invention encompasses positive photoresist compositions comprising:
a) an acid-sensitive positive photoresist polymer component selected from the group consisting of (i) an acid-sensitive photoresist polymer, (ii) an acid-sensitive photoresist polymer with an additional acid-sensitive compound, and (iii) a non-acid-sensitive alkaline-soluble photoresist polymer with an acid-sensitive alkaline solubility inhibitor,
b) a radiation-sensitive acid-generating component, and
c) a deactivated aromatic amine.
The photoresist polymer preferably contains acid-labile groups which generate acid upon cleaving. The compositions may contain a solvent for the unexposed resist.
The invention also encompasses photoresist structures containing the photoresist compositions of the invention as well as photolithographic processes using the photoresist compositions of the invention to make photoresist structures and to transfer patterns from photoresist structures to an underlying layer of ceramic insulator, metal conductor, semiconductor or other material.
These and other aspects of the invention are discussed in further detail below.
DETAILED DESCRIPTION OF THE INVENTION
Broadly, the invention is based on the discovery that deactivated aromatic amines are especially useful as additives to improve the shelf life and performance of chemically amplified photoresist compositions, especially in comparison to other known base additives. The invention also encompasses the discovery that deactivated aromatic amines have improved compatibility with a wider range of photosensitive acid-generating components which may be used in chemically amplified positive photoresist compositions.
The chemically amplified positive photoresist compositions of the invention are generally characterized by the combination of:
a) acid-sensitive positive photoresist polymer component selected from the group consisting of (i) an acid-sensitive photoresist polymer, (ii) an acid-sensitive photoresist polymer with an additional acid-sensitive compound, and (iii) a non-acid-sensitive alkaline-soluble photoresist polymer with an acid-sensitive alkaline solubility inhibitor,
b) a radiation-sensitive acid-generating component, and
c) a deactivated aromatic amine.
The photoresist polymer component preferably contains acid-labile groups which generate acid upon cleaving. The compositions may contain a solvent for the unexposed resist as well as other auxiliary components.
The photoresist polymer used in the present invention may be any acid-sensitive positive photoresist polymer. These polymers are typically characterized by the presence of acid-labile “protecting” grou
Brunsvold William R.
Katnani Ahmad D.
Varanasi Pushkara R.
Baxter Janet
Capella Steven
International Business Machines - Corporation
Lee Sin J.
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