Naohiko Oyasato

Development of comprehensive LCA database based on input-output tables

We have developed an LCA database based on the latest Input-Output (IO) tables for Japan, which were released in 2004. One of the features of this database is hybrid analysis. The ten main imported commodities have been evaluated by the process analysis method and added to environmental burdens inside Japan, calculated based on the Japanese IO tables. In this database, 30 types of inventory have been estimated, including emissions to the atmosphere and hydrosphere, as well as the amounts of resources consumed.

Chemically Amplified Resists Using 1,2‐Naphthoquinone Diazide‐4‐sulfonates as Photoacid Generators

A novel positive chemically amplified resist containing partially t-butoxycarbonylmethylated poly(4-hydroxy-styrenes)s and 1,2-naphthoquinone diazide-4-sulfonates (NQ4)s was investigated. The resists are effective for a wide region of UV lights including i-line KrF excimer laser lights. The NQ4s photodecompose to form sulfonic acids with accelerate the decomposition of t-butyl moieties of the polymers to form carboxylic acid. Only a few % of NQ4s realize the chemically amplified resists. NQ4s having electron-withdrawing groups give resists with high sensitives which provide excellent subhalf micron patterns when exposed to either i-line light or KrF excimer laser

Preparations and properties of novel positive photosensitive polyimides

Polyamic acid esters with phenol moieties (Ph-ES) were synthesized from diamines and dicarboxylic acids bonding to phenol moieties through ester linkage. To synthesize the dicarboxylic acids, 1 mol of BTDA was reacted with 2 mol of m-hydroxybenzyl alcohol in NMP. The resultant dicarboxylic acid are predominantly benzyl esters, not phenyl esters, was condensed with ODA, using DCC as condensing agent. The polyimide precursors Ph-ES was actually soluble in basic aqueous solutions. However, its dissolution rate was too low for binder resins used for resists. To increase the resist dissolution rate, polyamic acid PA, which is assumed to be more soluble in the base developer, was added to Ph-ES. The PA was synthesized from BTDA and ODA. Resists containing Ph-ES (60 wt%), PA (20 wt%) and naphthoquinone diazide (20 wt%) gave 4 micron line and space pattern with 5 micron thickness. There was no pattern deformation, even after the polyamic acid ester was heated at 320 degree(s)C to form the polyimides. The PA content was critical to the high resolution achievement. As the content of the PA to Ph-ES increases, the pattern shape of the resist deteriorated rapidly. At more than 40 wt% PA rate, patterns could not be obtained, because fine patterns peeled off form the silicon wafer substrate during the development. This proved that adjusting dissolution rates in basic aqueous solutions is one of the significant points for realizing fine resist patterns.