We have developed an advanced micro-lithographic process for producing 0.1 µm contact holes (CH). A chemical shrink technology, resolution enhancement lithography assisted by chemical shrink (RELACS) utilizes the cross-linking reaction catalyzed by the acid component existing in a predefined resist pattern. This “RELACS” process is a hole shrinking procedure that includes simple coating, baking, and rinse steps applied after conventional photolithography. We evaluated the dependency of CH shrinkage on resist formulation. Though the acetal type KrF positive resist (low activation energy system) can achieve around 0.1 µm CH after RELACS processing under the optimized condition, the acrylate type positive resist (high activation energy system) showed less shrinkage under the same process condition. The shrinkage performance of the RELACS process largely depends on the resist chemistry used as the underlying layer. The results of these studies are discussed in terms of the influence of the base polymer on shrinkage performance and tendency.

Mitsubishi Electric Corporation (MELCO) has developed an advanced microlithographic process for producing O.1.tm contact holes (CH). A chemical shrink technology, RELACSTM (Resolution Enhancement Lithography Assisted by Chemical Shrink), utilizes the crosslinking reaction catalyzed by the acid component existing in a predefined resist pattern 1,2 This "RELACSTM" process is a hole shrinking procedure that includes simple coating, baking, and rinse steps applied after conventional photolithography. This paper examines the process parameters affecting shrinkage of CH size. We subsequently evaluated the dependency of CH shrinkage on resist formulation.We conducted investigations of shrink magnitude dependency on each process parameter.. Photoresist lithography process: CH size, exposure dose, post development bake temperature . AZ® R200 (a product of Clariant (Japan) K.K.) RELACSTM process: Soft bake temperature, film thickness, mixing bake temperature (diffusion bake temperature), etc. We found that the mixing bake condition (diffusion bake temperature) is one of most critical parameters to affect the amount ofCH shrink.Additionally, the structural influence ofphotoacid generators on shrinkage performance was also investigated in both high and low activation energy resist systems. The shrinkage behavior by the photoacid generator of the resist is considered in terms ofthe structure (molecular volume) ofthe photogenerated acid and its acidity (pKa).The results of these studies are discussed in terms of base polymer influence on shrinkage performance and tendency. Process impact of the structure and acidity of the photogenerated acid is explored. Though the experimental acetal type KrF positive resist (low activation energy system) can achieve around 0. 1j.m CH after RELACSTM processing under the optimized condition, the experimental acrylate type positive resist (high activation energy system) showed less shrinkage under the same process condition. The shrinkage performance of RELACSTM process largely depends on the resist chemistry used as the underlying layer. Further, shrinkage degree can be controlled by process optimization even for the high activation energy type photoresist.

Bottom anti-reflective coatings (BARC) provide a production proven solution to improve linearity, depth-of-focus, CD control and process latitudes of photoresists. A series of BARCs compatible with chemically amplified deep ultra-violet (DUV) photoresists exhibiting different k values ranging from 0.1 to 0.6 at the DUV wavelength (248 nm) has been developed. The relationship between the k values and the etch rates of the BARC polymers with different dye concentrations in the polymer has been investigated. As a result, BARCs with targeted k values and etch rates can be provided. Formulation aspects of the BARC materials including edge bead remover (EBR) compatibility and evaluation results of these BARCs with different DUV resists are also discussed.

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In our previous paper [Jpn. J. Appl. Phys. 40 (2001) 419], we reported the development of an advanced micro-lithographic process for producing 0.1 µm contact holes by KrF excimer laser (248 nm) lithography. This chemical shrinkage technology, called resolution enhancement lithography assisted by chemical shrink (RELACS), utilizes the cross-linking reaction catalyzed by the acid component remaining in a predefined resist pattern. We report herein the results of the application of RELACS to i-line (365 nm) lithography. The properties of RELACS for i-line lithography were very different from those for KrF lithography. This is due to the difference in chemical mechanism between i-line and KrF resists. The characteristics of the application of RELACS to i-line lithography were studied by conducting basic experiments on the addition of a photo-acid generator (PAG) to an i-line resist and investigating the property of the cross-linking reactions involved in the pre-doping of various acids to RELACS film. Finally, we optimized RELACS materials to match i-line resist and realized the fabrication of contact holes less than 0.2 µm diameter by i-line lithography.