Kaichiro Nakano

Positive chemically amplified resist for ArF excimer laser lithography composed of a novel transparent photoacid generator and an alicyclic terpolymer

A new positive chemically amplified resist which consists of a novel photoacid generator NEALS (new alkylsulfonium salt) and methacrylate terpolymer with tricyclodecanyl group (TCDA) has been developed. NEALS shows good thermal stability up to 151 degree(s)C, high transparency and high acid generation efficiency for an ArF excimer laser exposure. A new base polymer with TCDA groups demonstrated high transparency (69.3%/micrometers ), high thermal stability up to 141 degree(s)C, a good dry-etching resistance and high solubility for an aqueous base (tetramethylammonium hydroxide) developer. A 0.20 micrometers lines and spaces pattern has been resolved using an ArF excimer laser exposure system (NA equals 0.55).

Novel negative photoresist based on polar alicyclic polymers for ArF excimer laser lithography

A new polar alicyclic polymer has been developed as an ArF negative resist polymer. Poly(carboxytetracyclo[4.4.0.12,517,10] dodecyl acrylate-hydroxytricyclo[5.2.1.02,6]decyl acrylate (polyCTCDDAm-TCDAOHn)) has carboxyl and hydroxyl groups. It was founded that reactivity of the hydroxyl group was much higher than that of the carboxyl group in the acid- catalyzed crosslinking reaction. Poly(CTCDDA32-TCDAOH68) exhibits good solubility (0.5 micrometers /sec) in the standard developer (2.38% TMAH aq.), high transparency (70%/0.5 micrometers ) at 193-nm and high thermal stability (decomposition point: 230 degree(s)C). A chemically amplified negative resist composed of this polymer and 1,3,4,6- tetrakis(methoxymethyl)glicoluril (TMGU) provided a resolution of 0.18-micrometers L/S pattern with an ArF exposure system (NA equals 0.55) at a 9.2 mJ/cm2 dose.

ArF chemically amplified positive resist based on alicyclic lactone polymer

We developed alicyclic acrylates with a hydrophilic moiety for use as an ArF chemically amplified positive resist. These monomers have an alicyclic unit, a norbornyl group, and a hydrophilic group, such as a hydroxyl, ester, acetate, or γ-lactone group. The acrylate polymer having a γ-lactone unit, 5-acryloyloxy-6-hydroxynorbornane-2-carboxylic 6-lactone, exhibited high thermal stability and high hydrophilicity. A chemically amplified positive resist composed of a terpolymer using the norbornyl acrylate with a lactone structure and a photoacid generator produced a fine resolution of a 0.12 µm L/S pattern at 16.3 mJ/cm2 by ArF exposure. This resist also produced a contact hole resolution of 0.14 µm with a depth of focus of 0.5 µm and exhibited good dry-etching resistance. The oxide etching rate achieved when using the developed resist is 1.29 times that of using a novolac resist, and it produces no resist top roughness after etching.

Novel alkaline-soluble alicyclic polymer poly(TCDMACOOH) for ArF chemically amplified positive resists

We have developed a novel ArF resist polymer poly[carboxy- tricyclo(5.3.2.0)decanylmethyl methacrylate] [poly(TCDMACOOH)], which has a carboxyl substituent on the tricyclodecanyl group. This polymer exhibited good solubility (1.93 micrometer/sec) in a 2.38% TMAH solution, high transparency (70%/micrometer) at 193 nm, and a good dry-etching resistance for CF4 gas (1.2 times the etching rate of novolac resin). Furthermore, the resist composed of the partially protected copolymer poly(TCDMACOOH60-TCDMACOOtBu40) with a photoacid generator exhibits a resolution of 0.18 micrometer L/S using an ArF exposure system (NA equals 0.55).

Transparent photoacid generator (ALS) for ArF excimer laser lithography and chemically amplified resist

A novel photoacid generator, ALS (alkylsulfonium salt; cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethane- sulfonate) for ArF excimer laser ((lambda) equals193 nm) lithography and a single-layer resist have been developed. ALS shows high transparency at 193 nm and photoacid generating capability on irradiation by ArF excimer laser. A novel methacrylate terpolymer, poly(tricyclo[5.2.1.02,6]decanylmethacrylate-co-2- tetrahydropyranylmethacrylate-co-methacrylic acid), is synthesized as a base resin. The resist, consisting of ALS and the polymer, shows chemical amplification and good resolution. A 0.2-micrometers line and space negative-tone image is observed at 15 mJ/cm2 dose using an ArF excimer laser.

Adhesion characteristics of alicyclic polymers for use in ArF excimer laser lithography

We evaluate the adhesion characteristics and relationship between work of adhesion and structure of polar-alicyclic polymers we developed for use in ArF excimer laser lithography. We found that the adhesion of the polymers and resists in both the alkaline-developer and water circumstances depends on the work of adhesion in air. Stronger adhesion can be obtained with higher polarity of polymer films caused by the higher surface free energy due to hydrogen bonds. The polarity of polymers and functional groups is evaluated with their relative dielectric constants. With the standard developer (2.38% tetramethylammonium hydroxide aqueous solution), the chemically amplified resist based on poly(carboxy- tetracyclo[4.4.0.12,5.17,10]dodecylacrylate- co-hydroxy-tricyclo[5.2.1.02,6]decylacrylate) forms a 0.18-micrometers L&S pattern by the ArF excimer laser dose.

Dissolution behavior of alicyclic polymers designed for ArF excimer laser lithography

We have analyzed the dissolution rate of alicyclic polymer resists designed for ArF excimer laser lithography with an in-house laser dissolution rate monitor. The analyzed polymers were methacrylate terpolymer with a tricyclodecanyl group and carboxy-tricyclodecanylmethyl methacrylate copolymer which has a polar carboxylic acid in alicyclic groups. We found that the alicyclic polymer dissolution rate was affected very little by developing conditions such as developer concentration or kind of developer. Furthermore, when we measure the dissolution rate as a function of the polar molecule content, we found that the dissolution rate of the alicyclic polymer is similar to that of conventional polyvinylphenol (PVP) polymers. We also demonstrate that the polymer dissolution rate can be predicted from the percolation theory for both conventional PVP polymer and alicyclic polymers. Moreover, the percolation theory can be applied to chemically amplified positive resists while taking the contribution of the protective group to polarity into consideration. These findings should be very useful for theoretical resist design and material development.

Function-integrated alicyclic polymer for ArF chemically amplified resists

We have designed a function-integrated alicyclic polymer, poly[carboxy-tetracyclo(4.4.0.12,5.17,10)dodecyl methacrylate] [poly(CTCDDMA)], which has both a dry- etching resistant unit (the tetracyclododecyl group) and a carboxyl substituent, inducing alkaline-solubility. This polymer exhibits good dry-etching resistance; the etching rate for chlorine plasma is 1.2 times that for the novolac resist because it contains 100 mol% of the alicyclic groups. It also exhibits good solubility in a TMAH solution and good adhesion to the silicon substrate because of the hydrophilic carboxyl group. The chemically amplified resist composed of the ethoxyethyl-protected copolymer poly(CTCDDMA67-ECTCDDMA33) with a photoacid generator resolved a 0.15-micrometer L/S pattern at 21.8 mJ/cm2 using an ArF exposure system (NA equals 0.55).

Development of Alicyclic Polymers for Multimode Waveguide Array and its Characteristics for Use in Optical Interconnection

We have carried out elemental research and development regarding optical transmission technology to establish the petaFLOPS - (1015 floating point number operations per second) class supercomputer. We describe our development of an alicyclic polymer, waveguide arrays formed with the polymer, and their characteristics for multimode optical data transmission. We have also developed high-density optoelectronic modules with a 4.5times4.5times0.5-mm low-temperature co-fired ceramic (LTCC) substrate that transmits 12 signals, and demonstrated a 10-Gbps/ch error-free transmission with the polymeric-waveguide array. We also showed a 20-Gbps/ch optical eye as a transmitter with a 1.1-mum range InGaAs vertical-cavity surface-emitting laser (VCSEL).

Photo-acid generator having aromatic ketone structure for ArF chemically amplified resist

We designed dialkylsulfonium salts with an aromatic ketone structure (a 1-indanone, 1-tetralone, or 4-chromanone unit) as a photo-acid generator (PAG) for ArF chemically amplified resists. Their thermal stability was affected by the alkyl subsitituents; sulfonium salts with two methyl groups or a pentamethylene group exhibited a decomposition temperature of more than 200 °C. The absorption coefficients at 193 nm for the new PAGs were 1/3 to 1/4 that of the conventional triphenylsulfonium salt. The photo-acid generating efficiencies of these sulfonium salts for an ArF laser were influenced by the ketone structures. The efficiency of the sulfonium salt with the 1-tetralone group was higher than the others. A positive resist using a dimethyl(1-oxo-2-indanyl)sulfonium salt achieved a 0.13 μm L/S pattern.