Takateru Asano

New, deep UV resist (LMR) for lift‐off technique

A new, deep UV resist, LMR (low molecular weight resist) has been developed. LMR is a quinone–diazide ester of a novolak resin whose molecular weight is about 1000. It has strong absorption in the deep UV region (12 μm−1 at 250 nm). LMR is negative working upon irradiation with deep UV light and forms an overhung structure with a single development step. The sensitivity of LMR is 30 mJ/cm2 and 0.3 μm wide spaces are clearly resolved. By use of LMR, a simple and reliable lift‐off process is realized. Submicron wide metal patterns having a thickness twice that of the resist can be formed by this process.

Sub-Half-Micron i-Line Lithography by Use of LMR-UV Resist

Negative photoresist, LMR-UV, has been developed for i-line lithography. It resolves isolated 0.3 µm space and 0.35 µm hole patterns of 1.0 µm thickness by using a 0.42-numerical-aperture i-line reduction projection aligner. LMR-UV gives overhung profiles because of its large absorption coefficient of 3.8 µm-1 at the i-line. New phase-shifting mask patterns which are adapted to isolated space and hole patterns for negative resist have been developed. By use of this mask, LMR-UV clearly resolves 0.25 µm space and 0.3 µm hole patterns by using the i-line aligner. This phase-shifting mask improves both resolution and focus margin.

Application of diazonaphthoquinone compounds and a diazonium salt to contrast enhanced lithography

New photobleachable materials, two kinds of diazonaphthoquinone compounds and a diazonium salt, have been developed for contrast enhanced lithography. These materials are quite soluble in nonpolar solvents and are stable even in solution. Therefore, they can be directly coated on a bottom resist layer and removed without attacking it. Their films have strong absorption bands in the UV region involving g‐, h‐, and i‐lines. They are uniformly bleached by UV exposure. When these materials employ as contrast enhancement layers, 1.0 μm line and space patterns are clearly resolved by using a mirror projection aligner and 0.55 μm line and space patterns are clearly resolved by using an i‐line reduction projection aligner.

New trilevel and bilevel resist systems using silyl ethers of novolak and low molecular weight resist

A new intermediate layer material, silyl ether of novolak (Si–novolak), and a new Si containing resist, silyl ether of a naphthoquinone diazide ester of novolak, Si–LMR (low molecular weight resist), have been developed for trilevel and bilevel resist systems, respectively. Si–novolak has high O2‐reactive ion etching (RIE) resistivity and high solubility in nonpolar solvents, such as xylene and chlorobenzene, which cause no damage to the film of novolak. When novolak and Si–novolak are employed as the bottom and intermediate layer materials, respectively, both layers can be formed by successive coatings without baking the bottom layer. Si–novolak is easily hardened by deep UV light. Therefore, a trilevel resist can be formed by one deep UV blanket exposure and one baking step, besides coating steps. The triresist system, LMR/Si–novolak/novolak, provides 0.5 μm resist patterns with steep profiles and good line control over topography. Si–LMR is a negative deep UV resist and its sensitivity is 100 mJ/cm2. T...

Formation of thick and narrow-spacing metal patterns by lift-off technique using negative photoresists, LMR and LMR-UV

Abstract We already reported a negative resist, LMR, for deep uv (230–280 nm) lithography. It gives overhung profiles by simple development. We have further developed a new developer which enables LMR to be workable with light in a wider spectral range. 2.0 um thick Au patterns having 0.75 um metal-metal spacings are achieved by lift-off technique with this developer. LMR-UV has been developed for uv (350–450 nm) lithography. It is a negative working resist and forms overhung profiles in a similar manner to LMR.

New PCM (HR-PCM) Technique Using Novolak-Diazide Type Photoresist As A Bottom Layer

A new High dry etching Resistivity Portable Conformable Masking, HR-PCM, has been developed. HR-PCM consists of a negative working resist and an image reversal resist as upper and bottom layers, respectivery. LMR-UV (Low Molecular weight Resist for UV lithography) is used as an upper layer and AZ-5214 or MP-2400A (added amine to MP-2400) as a bottom layer. As these resists are of novolak based resin, the dry etching resistivity of HR-PCM is much higher than that of conventional PCM whose bottom layer is PMMA. LMR-UV is a negative working resist and can be coated on the bottom layer and developed without damaging it because both a coating solvent and a developer are of organic solvent having small polarity such as monochlorobenzene. The latent image of the bottom layer formed by the penetrated light through the upper layer is reversed by the post exposure baking. The bottom layer under the exposed upper layer is more resistive to an alkaline. developer than the unexposed one. Therefore, HR-PCM can reliably forms double layer resist patterns. 0.55 and 0.6 μm line and space patterns are obtained on an i- and a g-line wafer steppers, respectively.