Mitsuhito Suwa

Novel high refractive index positive-tone photosensitive polyimide for microlens of image sensors

A novel high refractive index positive-tone photosensitive polyimide (posi-PSPI) has been successfully developed. The posi-PSPI has a refractive index of 1.78 at 633 nm and good transparency (> 80% at 400 nm). It is prepared from an alkali—soluble transparent polyimide precursor, a diazo-naphthoquinone-type photoactive compound, a surface-modified high refractive index nanosol, and a UV absorbent. The posi-PSPI has a round shape because of the UV absorbent. Further, it displays good sensitivity as well as a good round pattern profile after thermal curing. In addition, the 1% weight loss temperature of the posi-PSPI is 407 °C, which indicates that the posi-PSPI has excellent thermal stability.

ArF single-layer photoresists based on alkaline-developable ROMP-H resin

Novel ArF single layer photoresists, which are based on new type of alicyclic polymers prepared by ROMP (Ring Opening Metathesis Polymerization), are reported. Norbornenes with ester group were mainly used as monomers for polymerization. The prepared resins were potentially endowed with alkaline developability by hydrolyzing the ester groups. Hydrolyzed resins showed developability to conventional aqueous TMAH developer. The polymerized resins were hydrogenated onto the double bonds in the polymer main chain in order to improve the transparency of the resins at 193-nm. The hydrogenated ROMP (ROMP-H) resins showed high transparency at 193-nm and equivalently good etch resistance to that of KrF deep UV resist. The formulated resist with a ROMP-H resin and triphenyl sulfonium trifluoromethanesulfonate resolved 0.28- micrometers L/S in KrF exposure (N.A. equals 0.50) and 0.225-micrometers L/S in ArF exposure (N.A. equals 0.55).

EFFECT OF ADDITIVES IN ArF SINGLE LAYER CHEMICAL AMPLIFICATION PHOTORESIST

This paper describes a new approach to the design of positive-tone ArF single layer chemical amplification (CA) photoresist. The main issue is the effect of small molecular compounds as additives in methacrylic-based ArF CA photoresist. Three alicyclic compounds with adamantyl moiety and two aromatic compounds with naphthyl moiety were selected as additives. Their influences on the photoresist properties were examined and clarified as follows: •Transparency of the resist film at 193-nm could be controlled by the loading level and the sorts of additives. Alicyclic additives made the resist film more transparent. •Both the photospeed and the contrast of the resist were drastically influenced by the loaded additives. Enhancement of the photospeed was easily achieved. •Thermal properties of the resist film could also be affected by additives. However, the effect was generally temperate. •The loaded additives could mitigate T-top formation of resist profile due to the control of the inherent dissolution rate of the resist.Loading the additives would compensate some inherent defects of matrix acrylic polymers and consequently allow considerable latitude in resist design of ArF CA resist. A three component system comprising an acrylic polymer, a photoacid generator, and adamantanecarboxylic acid showed good imaging performance (0.26μmL/S, 35mJ/cm2) on KrF exposure.