Toshio Sakamizu

Nanometer‐scale imaging characteristics of novolak resin‐based chemical amplification negative resist systems and molecular weight distribution effects of the resin matrix

Molecular weight distribution effects of novolak resin‐based chemical amplification negative resist systems are investigated for electron‐beam lithography. The resist systems investigated consist of onium salts as an acid generator, a methoxymethyl melamine crosslinker, and a conventional/fractionated novolak resin matrix. Delineated patterns of both types of resist systems are compared to evaluate submicron‐scale resolution. The conventional novolak resin‐based system shows higher contrast than the fractionated one. High aspect ratio patterns are resolved for the conventional novolak‐based resist, whereas poor results are obtained for the fractionated resin‐based one on the submicron scale. Very thin films (30 nm) of both resist systems are delineated with a finely focused electron beam (diameter: approximately 2 nm at 5 kV) from a scanning electron microscope. Nanometer‐scale edge roughness (nanoedge roughness) is observed for the conventional novolak resin‐based resist. On the contrary, the degree of n...

Acid-Catalyzed Reactions of Tetrahydropyranyl-Protected Polyvinylphenol in a Novolak-Resin-Based Positive Resist

This paper deals with an acid-catalyzed reaction mechanism of a polymeric dissolution inhibitor of a novolak-resin-based positive chemical amplification resist system. This resist system consists of a novolak matrix resin, tri(methanesulfonyloxy)benzene as an acid generator, and tetrahydropyranyl-protected polyvinylphenol (THP-M) as a polymeric dissolution inhibitor. The acid-catalyzed deprotection products of THP-M in the resist film are detected and their subsequent acid-catalyzed reactivities are evaluated. It is found that tetrahydropyranyl group are exchanged between THP-M and the matrix to yield a strong dissolution inhibitor, causing negative tone behavior at the overexposure dose. High-resolution patterns (0.3-µm contact holes) are achieved with high sensitivity (2.4 µC/cm2 at 50 kV).

Development of positive electron‐beam resist for 50 kV electron‐beam direct‐writing lithography

A positive chemical amplification resist system has been developed for 50 kV electron‐beam direct‐writing lithography. This resist consists of a meta‐cresol/para‐cresol novolak resin, tetrahydropyranyl‐protected polyvinylphenol (THP‐M) as a polymeric dissolution inhibitor, and tri(methanesulfonyloxy)benzene (MeSB) as an acid generator. Radiation‐induced hydrolysis of MeSB in the novolak resin matrix was confirmed to yield methanesulfonic acid and phenol derivatives by using gel‐permeation and high‐performance liquid chromatography. The catalytic chain length of THP‐M deprotection was estimated to be approximately 300 in the matrix. It was found that the compatibility of a polymeric dissolution inhibitor with a novolak matrix relates to their polarity characteristics, and that the increase of para‐cresol ratio in the novolak matrix can enhance the compatibility with THP‐M and dissolution‐inhibition capability of the composition. The optimized composition and process of the resist system achieved high aspec...

Electron-beam nanolithography and line-edge roughness of acid-breakable resin-based positive resist

Abstract A positive chemical amplification resist based on acid-catalyzed fragmentation of the acetal groups in the polymer main-chain has been developed for electron-beam (EB) nanolithography. This resist consists of an acid generator, an acid-diffusion controller and an acid-breakable (AB) resin that is synthesized through a co-condensation reaction between polyphenol and aromatic multi-functional vinylether compound. Despite a large difference in the molecular weight distribution of the AB resins, the AB resin-based resists (ABRs) provide high-resolution patterns (60-nm line-and-spaces) with high sensitivity ( 2 at 30 kV). AFM analysis showed the surface roughness for ABR is less than half (RMS: ∼1 nm) compared with that for novolak resin-based resist. By using ABR, the sub-100 nm L/S patterns with line-edge roughness (3 σ ) about 5 nm are obtained.

Improvement of post-exposure delay stability of chemically amplified positive resist

We have been developing a novolak-based chemically amplified positive resist for next generation photomask (below 0.18 micrometer) fabrication. This resist prevents footing profile by use of a hydrophilic polyphenol compound. We succeeded in improving PED and PCD stability by addition of an ion- dissociative compound. We obtained vertical resist profiles on a chromium-oxide (CrOx) substrate. With the resist, we could make a well defined 0.25 micrometer line-and-space patterns on a CrOx substrate at a dose of 4.0 uC/cm2. Under the ambient air (amines concentration: 4 ppb, humidity: 45%), the line width change was less than 10 nm when the delay time between EB exposure and post-exposure-baking was from 0 to 8 hours. Under the same condition, the line width change was less than 20 nm even when the post-coating delay (PCD) time was 7 days.

Acid-Breakable Resin-Based Chemical Amplification Positive Resist for Electron-Beam Mastering: Design and Lithographic Performance

A positive chemical amplification resist based on acid-catalyzed fragmentation of acetal groups in its main chain has been developed as a means of reducing line-edge roughness. The resist consists of an acid generator, an acid-diffusion controller and an acid-breakable (AB) resin that is synthesized through a co-condensation reaction between polyphenol and aromatic multifunctional vinylether compound. The effects of the fractionation of AB resins on resin properties and line-edge roughness (LER) are evaluated. Although AB resins have wide molecular weight distributions, the density of acetal groups in this AB resin is found to be almost constant except in the lower molecular weight components. The resist with a fractionated resin from which such components are removed provides high-resolution patterns (70-nm-wide pit) with fairly low LER. AFM analysis shows that the surface roughness (SR) of the resist with the fractionated resin is smaller than that of a resist using nonfractionated AB resin, and that the SR value is not altered throughout the range of exposure doses up to just below the start of dissolution. By using the fractionated AB resin, the AB resin-based resist (ABR) is capable of forming sub-100 nm L/S patterns with less than 5 nm of LER (3σ).

Chemically amplified positive resist for next-generation photomask fabrication

We have been developing novolak-based chemically amplified positive resists for the next generation photomask fabrication. In this paper, we report two different types of EB resists: RE-5150P and RE-5160P. Our resist materials consist of four components: a novolak matrix resin, a polyphenol compound, an acid generator and a dissolution inhibitor. We applied two different types of dissolution inhibitors to our resist materials. RE-5150P and RE-5160P employed respective a high and a low activation energy type of a dissolution inhibitor. RE-5150P has high contrast and RE- 5160P has wide process window. As a result, we confirmed RE- 5150P could achieve 0.24 micrometer line-and-space vertical resist pattern profiles at 8 (mu) C/cm2 using the 50 kV EB- writer HL-800M, and RE-5160P has wide process window: post exposure delay stability is over 24 hrs. and post coating delay stability is over 30 days.

Surface and line-edge roughness in acid-breakable resin-based positive resist

A positive chemical amplification resist based on acid-catalyzed fragmentation of acetal groups in its main-chain has been developed as a means for reducing line-edge roughness. The resist consists of an acid-generator, an acid-diffusion controller and an acid-breakable (AB) resin that is synthesized through a co-condensation reaction between polyphenol and aromatic multi-functional vinylether compound. The effects of the fractionation of AB resins on resin properties and line-edge roughness (LER) are evaluated. Although AB resins have wide molecular-weight distributions, the density of acetal groups in this AB resin is found to be almost constant except in the lower molecular-weight components. The resist with a fractionated resin from which such components removed provides the high resolution of 60-nm line-and-space (L/S) patterns with fairly low LER. AFM analysis shows the surface roughness (SR) for the resist with the fractionated resin is smaller than that for a resist using non-fractionated AB resin, and that the SR value is not altered throughout the range of exposure doses up to just below the beginning of dissolution. By using the fractionated AB resin, the AB resin-based resist (ABR) is capable of forming sub-100 nm L/S patterns with less than 5 nm of LER (3σ).

Acid-breakable-resin-based chemical amplification positive resist for 0.1-μm-rule reticle fabrication: design and lithographic performance

We have designed a new chemical amplification (CA) positive resist for 0.1micrometers reticle fabrication. This positive resist consists of an acid-generator, an acid-diffusion controller, and an acid-breakable (AB) resin that can be converted to initial polyphenol units by an acid-catalyzed reaction. In the exposed region, main-chain scission of the AB resin matrix produces nearly mono-dispersed fragments (the polyphenol). This complete fragmentation results in an extremely high dissolution rate with an aqueous-base developer (tetramethylammonium hydroxide: 2.38 wt%). The AB resin-based resist enabled fabrication of scum free 0.15micrometers line-and-space patterns on a CrOx plate by using a 50-kV electron-beam reticle writer (HL series). The line- edge roughness of patterns delineated by this resist (<10 nm) was less than half that for previously developed novolak-resin-based CA resists (RE series:>30nm).

Improvement of the resolution and accuracy of chemical-amplification positive resist for 0.13-μm reticle fabrication

We have developed a novolak-based chemical-amplification resist for 0.13-micrometers or later reticle fabrication. For the 0.13-micrometers or later design-rule reticle-fabrication with OPC patterns, the resist resolution is required under 0.2-micrometers on the mask substrate. To improve the chemical-amplification resist resolution, it is necessary to control the acid- diffusion in the resist film. We have developed the technique of the acid-diffusion control with neutral-salt additives. By use of the resist with this technique, we could fabricate 0.14-micrometers 1/s patterns on a CrOx substrate at a dose of 9.3-(mu) C/cm2. The resist has a good margin of doses.