Hirokazu Niki

Long life sealed nickel-zinc cell using a new separator

Abstract Because of internal shorting due to zinc (Zn) dendrite formation at the Zn electrode, nickel-zinc (NiZn) secondary cell cycle life is somewhat less than the NiCd cell cycle life. To solve this problem, a new kind of separator was developed which consisted of nylon non-woven cloth coated with poly(vinyl alcohol) (PVA) containing boric acid. This separator has a high ionic conductivity, but is resistant to zincate ion penetration. A large number of additives, effective for Zn dendrite suppression, was also tested. From them, bismuth oxide (Bi 2 O 3 ) was selected and added, together with calcium hydroxide (Ca(OH) 2 ), to the Zn electrode. A charging method, applying an intermittent anodic pulse, was found to be effective to reduce the Zn electrode shape change and prolong the cycle life of this cell. By using these materials and investigating a cell construction containing an electrolytic solution and hydrogen gas absorber, sizes AA, C, and D sealed NiZn cells were developed whose charging and discharging cycle life achieved over 500 cycles, for a size C cell.

Characterization of a Newly Developed Contrast Enhancement Material for G-line Exposure

The bleaching characteristics for a contrast enhancement layer (CEL) material were succesfully described by parameters A, B and C; these were used for the modeling of a positive photoresist exposure. As a result, it was clarified that both the A and C values should be large, but the B value must be as small as possible. According to the obtained information, a new CEL material was proposed, which consists of the diazonium compound and the alkyl modified phenol resin. Using the composed CEL material, a submicron resist pattern with a steep profile was obtained. Furthermore, it was found that the development latitude increases, but that the exposure latitude does not change upon using the CEL.

Quarter- and subquarter-micron deep-UV lithography with chemically amplified positive resist

The resist performance for quarter- and sub-quarter-micron domains using partially t- butoxycarbonylmethylated poly(4-vinylphenol) (BOCM-PVP) as a polymer dissolution inhibitor is reported. This resist contains some additives to improve resolution and process stability. This resist has high resolution, with linearity down to 0.225 micrometer L & S at 38 mJ/cm2 on a KrF excimer laser stepper (NA equals 0.5, sigma equals 0.5) with a COG mask. Using a halftone phase shifting mask, 0.175 micrometer L & S patterns are resolved with a 1 micrometer depth of focus (DOF) on a KrF excimer stepper (NA equals 0.5, sigma equals 0.7, 1/2 annular illumination). The line width change vs. PEB temperature ((Delta) CD/(Delta) T) is 1.3 nm/degree. The line width shift over time between exposure and PEB is within plus or minus 0.01 micrometer even after 1 hr delay in a basic- contamination-free environment (NH3 less than 1 ppb).

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