Noboru Moriuchi

Practical phase‐shifting mask technology for 0.3 μm large scale integrations

An i‐line phase‐shifting mask technology intended for practical use has been developed. The new technology can provide defect‐free phase‐shifting masks and can produce 0.3 μm large scale integration with large lithographic latitudes. The phase‐shifting masks manufactured here apply the following two major techniques. The first technique is to form phase‐shifting patterns on the chrome mask. This technique features single‐layer shifters using an organic spin on glass (SOG), a simple patterning process of the SOG, and a focused ion beam gas‐assisted etching repair process of shifter defects. The second technique is to create half‐micron chrome patterns using a high‐accuracy e‐beam writing system ‘‘EB‐MX’’ and high‐resolution chemically amplified e‐beam resist ‘‘PSR’’.

New process for resist removal after lithography process using adhesive tape

A novel concept for the resist removal after the photolithography in the wafer process is introduced. This new process is to peel off the resist layer with a special adhesive tape. A very little contamination on wafers is confirmed. Especially the metal contamination with this new process is very little compared with conventional O2 plasma ashing. Therefore the electrical properties of oxide layer and substrate are significantly improved. This new process should be very effective for the production of front-edge devices because of this improvement. In this paper, along with these observations, the mechanism of the removal is discussed. The monomer in the adhesive layer migrates into the resist layer and the two layers consolidated together. Very fine microanalysis technique to detect this phenomenon in situ is also explained.

Negative resists for i-line lithography utilizing acid-catalyzed intramolecular dehydration reaction

Chemical amplification negative resist system composed of a novolak resin, a carbinol and an acid generator is investigated for i-line phase-shift lithography. The reaction in this resist is based on an acid-catalyzed intramolecular dehydration reaction. The dehydration products act as aqueous-base dissolution inhibitors, and carbinol compounds in unexposed areas work as dissolution promoters. The resist composed of a novolak resin, 1,4-bis((alpha) -hydroxyisopropyl) benzene (DIOL-1) and 2- naphthoylmethyltetramethylenesulfonium triflate (PAG-2) gives the best lithographic performance in terms of sensitivity and resolution. Line-and-space patterns of 0.275 micrometers are obtained using an i-line stepper (NA:0.45) in conjunction with a phase shifting mask.

Optimized Material For Bottom Layer Of Trilevel Resist System

Requirements for the bottom layer of the trilevel resist system are examined with the aid of the SAMPLE simulator. Some conventional positive photoresists and our new bottom layer material RG-3900B are evaluated as a bottom layer. RG-3900B is a phenolic resin mixed with a novel azide compound. It is found that RG-3900B has the following excellent optical properties with relatively short baking time at about 200°C; it strongly absorbs the exposing light and is transparent at visible regions for alignment. Therefore, when applied as a bottom layer, it minimizes linewidth variations on highly reflective substrate topography without degradation of alignment accuracy. RG-3900B has been successfully applied to our various devices with multilevel metalization to obtain fine patterns.