Isao Satou

High sensitive negative silylation process for 193nm lithography

We have developed a negative silylation process using a new photoacid generator, which does not easily evaporate during post-exposure-bake (PEB) and a new polymer, poly(1-ethoxyethyloxystyrene(49)-t-butyloxy-carbonyloxystyrene(48)). 0.12 @m m line-and-space patterns were fabricated with a high sensitivity of 4mJ/cm^2.

Progress of top surface imaging process

Top surface imaging (TSI) process is a very important technology to extend the photolithography down to 0.1 /spl mu/m or smaller dimension. As the silylation process, we have been evaluating a bi-layer silylation process and a silylation process applying silylation treatment after alkaline wet development (SILYAL). In this paper, we report the high performance of the silylation process for 193-nm lithography and also the high capability of this process for 157-nm lithography. For the former process, patterns are generated without using wet-development, therefore, the adhesive property and high transparency of resist material are not necessary. For the latter process, wet-development is applied to the top layer, therefore, this process is similar to bi-layer resist process using Si-containing resist.

Development of advanced silylation process for 157-nm lithography

The top surface imaging (TSI) process is a very important technology to extend photolithography down to 0.1 μm or smaller dimensions. For the TSI process, we are evaluating an advanced silylation process applying a vapor phase silylation treatment after an alkaline wet-development of the top layer (SILYAL). We could apply a very thin poly-vinyl-phenol type resist with 0.07 μm or less thickness as the top silylation layer in order to improve the optical contrast during the exposure. In this paper, we report the high capability and progress of this SILYAL process for 157-nm lithography.

Control of acidity of the substrate for precise pattern fabrication using a chemically amplified resist

The chemically amplified (CA) resist has been widely and generally used for sub-quarter micron device fabrication using a KrF excimer laser stepper. However many problems have been revealed and laborious efforts have been seriously undertaken to solve them. Among these issues, we have been examining the dependence of the resist characteristics on the substrate properties. In order to control and minimize the fluctuation of the critical dimension, we have been evaluating the relation between the cleanliness of the substrate materials and the CA resist patterning characteristics, especially, we have been focusing on the effect of a wet cleaning process-step which is a necessary and important process-step for actual device manufacturing. Among the several materials which we evaluated, we found that the characteristics of an amorphous carbon(a-C) film used as an anti-reflective coating were significantly affected and changed by the sulfuric acid and hydroperoxide mixture (SPM) cleaning. For the other materials, no characteristic changes in the cause of this SPM cleaning were observed, and this cleaning method was effective and applicable to almost materials except the a-C film. In case of the a-C film, the acidic residue remained after the cleaning, and this contamination changed the acidity of the film. The resist patterning characteristics fabricated on the contaminated film were drastically changed, and pattern collapse occurred. In order to diminish this remaining contamination and control the acidity of the contaminated substrate, we tried to apply a high temperature treatment, an alkaline treatment and a UV cure treatment.

Application of top surface imaging process to 157-nm lithography

A top surface imaging (TSI) process with a very thin imaging resist is one of the approaches for 100-nm or smaller pattern fabrication. We have been evaluating the different types of bilayer silylation processes for 193nm lithography, such as the bilayer silylation process without applying any wet-development and an improved bilayer silylation process that applies the vapor phase silylation treatment after alkaline wet-development of the top layer (SILYAL). We have been trying to apply these TSI processes to 157nm lithography and could successfully fabricate sub-100-nm fine resist patterns with high aspect ratios. We confirmed the lithographic high performance of these bilayer silylation processes and 157-nm lithography. In this paper, we describe the current status and progress in these silylation processes for 157nm lithography.

Extension of the ArF Excimer Lithography to Sub-0.10 µm Design Rule Devices Using Bi-layer Silylation Process

The device design rule has been significantly reduced, and a practical pattern fabrication technique for sub-0.10 µm or smaller dimensions is urgently required. The top surface imaging (TSI) process using an ArF excimer laser (wavelength=193 nm) is a promising approach to the realization of this demand. We have been evaluating the positive-tone silylation process as one of the TSI processes in order to extend the limit of ArF optical lithography. We found that for the positive tone silylation process, control of the silylation depth and profile is very important, and the bi-layer silylation process using a thin silylation resist as a top layer is a practical and effective process for fine pattern fabrication. In this report, we describe the high lithographic performances of this bi-layer silylation process and its application to sub-0.10 µm rule device manufacturing.

Study of bilayer negative-tone silylation process for 193-nm lithography

We have been evaluating the silylation process for 193-nm lithography as one of the Top Surface Imaging (TSI) techniques. In this paper, we describe a bi-layer negative- tone silylation process using polyvinylphenol (PVP) resin as a top layer, whose hydroxyl sites are fully protected by tertiary-butoxycarbonyl (t-BOC) and/or 1-ethoxyethyl (EOE) groups. First, we used a silylation resist fully-protected by only t-BOC. We could fabricate 0.12 micrometer L/S patterns without using any resolution enhancement techniques. In addition, there was a rectangular profile of resist patterns and no scums around the spaces after the dry development. However, the sensitivity was about 11 mJ/cm2, the LER of the 0.13 micrometer L/S patterns was about 15 nm (3(sigma) ), and also the CD fluctuated according to the PED time. In order to improve these characteristics of the silylation resist, we applied the EOE group as a protective one for practical materials which contributes to easy deprotection. When we changed the protection ratio of t-BOC to EOE, we observed that the pattern profile became worse based on the increase in the protection ratio of the EOE group. However, we could improve the pattern profile by controlling the hygroscopic characteristic of the silylation resist. In the case of the silylation resist protected by t-BOC/EOE (70/30), we could successfully obtain 0.12 micrometer L/S patterns with the high sensitivity of about 2 mJ/cm2.

Bilayer silylation process for 193-nm lithography

Top surface imaging (TSI) techniques have been studied in order to enlarge the process window for fine pattern fabrication. We have been evaluating the silylation process for 193 nm lithography as one of the TSI techniques, and in this paper, we would like to focus on the effect of the silylation resist thickness of the process window. We found that a very thin silylation resists was effective in widening the fine pattern fabricating margin, and we tried to use a thin silylation resist as the top layer of the bi- layer resist system for practical applications. In order to fully realize the ability of this bi-layer silylation process, we optimized the dry-development conditions and resist structures before evaluation of the lithographic performance. A negative tone resist was used in our bi-layer silylation process, and positive tone patterns were generated after the dry-development. In this process, the depth of the silylated area was controlled, and the excess swelling caused by too many silylation reactions was restricted. Moreover, the profile of the silylated area was formed into an almost rectangular shape which was good and appropriate for precise critical dimension control. The process window was significantly enlarged, and the 0.11 micrometers L/S patterns were successfully fabricated without using any resolution enhancement techniques. We confirmed that the bi-layer silylation process is one of the best approaches to improve the lithographic performance of the silylation process.