Seigo Ohno

Near‐infrared sensitive electrophotographic photoconductors using chloroindium chlorophthalocyanine

Layered electrophotographic photoconductors using chloroindium chlorophthalocyanine have been investigated. An evaporated film of chloroindium chlorophthalocyanine has a broad and strong light absorption band in the visible to near‐infrared region and its crystal structure is very stable. The photoconductor using chloroindium chlorophthalocyanine as a carrier generation layer and polyvinylcarbazole as a carrier transport layer is highly sensitive in a wide spectral region (500–900 nm) without any special treatment during its preparation. The typical value of sensitivity is 2.5 cm2/μJ at 800–900 nm, so that this photoconductor is most suitable for a laser printer equipped with a AlGaAs laser diode.

Plasma characteristics and etch uniformity in CF4 magnetron etching using an annular permanent magnet

Etch characteristics of SiO2 and Si obtained by magnetron etching using an annular permanent magnet were analyzed. From these analyses, etch characteristics were found to be classified into three regimes. Remarkable enhancements in SiO2 etch rate, 25–40 times, were observed at constant Vrf by applying magnetic field of 150 G. Ion densities over the cathode were found to be distributed linearly along the E×B drift direction. Such an ion density distribution will be formed by the repeated process (ionization→ion bombardment→electron emission and drift→ionization). Etch distribution can be averaged and flattened to a uniformity of below ±2% by the magnetic field being rotated in 90° steps.

Characterization of SiO2/Si(100) interface structure of N2O-oxynitrided ultrathin SiO2 films

The SiO2/Si(100) interface structure of N2O-oxynitrided ultrathin SiO2 film has been investigated. The structure of the SiO2/Si interface, evaluated from the lattice image of high-resolution transmission electron microscopy (HRTEM), seems to be quite uniform, at least ordered within one or two atomic layers. The layer of the half-spacing order of the Si lattice, which consists of one or two atomic layers, is found between the Si and SiO2 layers. Nanoanalysis by transmission electron energy loss spectroscopy (EELS) indicates that nitrogen atoms bonded to Si atoms are present near the SiO2/Si interface. The EELS plasmon loss image showed the accumulation of nitrogen within 1 nm of the interface.

New, deep UV resist (LMR) for lift‐off technique

A new, deep UV resist, LMR (low molecular weight resist) has been developed. LMR is a quinone–diazide ester of a novolak resin whose molecular weight is about 1000. It has strong absorption in the deep UV region (12 μm−1 at 250 nm). LMR is negative working upon irradiation with deep UV light and forms an overhung structure with a single development step. The sensitivity of LMR is 30 mJ/cm2 and 0.3 μm wide spaces are clearly resolved. By use of LMR, a simple and reliable lift‐off process is realized. Submicron wide metal patterns having a thickness twice that of the resist can be formed by this process.

Arf Laser-Induced Chemical-Vapor Deposition of Tungsten for Gate Electrodes

The deposition of W films by ArF laser-induced chemical-vapor deposition (LCVD) was investigated as a function of incident laser power, WF 6 and H 2 partial pressures, and substrate temperature. The deposition of W films by LCVD is discussed dividing that into two parts, thermal CVD (TCVD) and photon assisted CVD (P h CVD). The rate of P h CVD has been defined as the difference between the rates with and without laser irradiation. The reaction orders for P h CVD are 1, 0 with respect to WF 6 and H 2 partial pressures, respectively, and the rate linearly increases with increase in laser repetition rate. The activation energy in P h CVD is 0.17 eV. These facts indicate that, in LCVD, P h CVD takes place independently of TCVD and that the deposition rate in P h CVD is determined by the formation of F radicals in the dissociation of WF 6 molecules by laser irradiation. MOS capacitors with LCVD-W gates were fabricated and their characteristics were compared with those with sputtered-W gates. It was shown that the level of contamination due to mobile ions in the capacitor with the LCVD-W gate was extremely low.

Application of diazonaphthoquinone compounds and a diazonium salt to contrast enhanced lithography

New photobleachable materials, two kinds of diazonaphthoquinone compounds and a diazonium salt, have been developed for contrast enhanced lithography. These materials are quite soluble in nonpolar solvents and are stable even in solution. Therefore, they can be directly coated on a bottom resist layer and removed without attacking it. Their films have strong absorption bands in the UV region involving g‐, h‐, and i‐lines. They are uniformly bleached by UV exposure. When these materials employ as contrast enhancement layers, 1.0 μm line and space patterns are clearly resolved by using a mirror projection aligner and 0.55 μm line and space patterns are clearly resolved by using an i‐line reduction projection aligner.

New trilevel and bilevel resist systems using silyl ethers of novolak and low molecular weight resist

A new intermediate layer material, silyl ether of novolak (Si–novolak), and a new Si containing resist, silyl ether of a naphthoquinone diazide ester of novolak, Si–LMR (low molecular weight resist), have been developed for trilevel and bilevel resist systems, respectively. Si–novolak has high O2‐reactive ion etching (RIE) resistivity and high solubility in nonpolar solvents, such as xylene and chlorobenzene, which cause no damage to the film of novolak. When novolak and Si–novolak are employed as the bottom and intermediate layer materials, respectively, both layers can be formed by successive coatings without baking the bottom layer. Si–novolak is easily hardened by deep UV light. Therefore, a trilevel resist can be formed by one deep UV blanket exposure and one baking step, besides coating steps. The triresist system, LMR/Si–novolak/novolak, provides 0.5 μm resist patterns with steep profiles and good line control over topography. Si–LMR is a negative deep UV resist and its sensitivity is 100 mJ/cm2. T...

Crosslinking positive resist for deep UV photolithography and its application to LSI fabrication processes

A new, crosslinking positive resist for deep‐uv photolithography has been developed. This resist, a copolymer of glycidyl methacrylate and methyl methacrylate (GCM), degrades on irradiation with light from a D2 lamp and has a sensitivity of 0.25 J/cm2. Three‐fourths μm line and space patterns are well resolved. It crosslinks at temperatures above 170°C in an inert atmosphere. This enables strengthening of the resist film by heat treatment after pattern delineation,greatly improving the adhesion and thermal properties of the resist. With these improvements, this resist can successfully be used for etching both SiO2 and phosphosilicate glass in a buffered HF solution. It can also be used for dry etching in CF4 plasma. It is preferable to use noncrosslinked GCM for CF4 plasma etching because the etching rate of noncrosslinked GCM is reduced to about one‐third that of crosslinked GCM.

Time-dependent dielectric breakbown evaluation for rapid-thermally grown SiO2 films formed on submicron-grooved Si surfaces

Abstract MOS capacitors formed on submicron-grooved (100)Si surfaces have been studied by time-dependent dielectric breakdown tests and transmission electron microscopy. Their time to breakdown depends on the number and profile of groove corners. Rounding off the convex upper corners of Si grooves by rapid thermal processing and rounding off the concave bottom corners by reactive ion etching successfully suppress electric field localization at groove corners and improve the reliability of MOS capacitors formed on grooves.

Influence of annealing ambients on ZrSi2 formation

Abstract The formation of zirconium silicide was studied in many kinds of annealing ambients, i.e., Ar-H 2 , Ar-O 2 , N 2 -O 2 , Ar-N 2 -O 2 , and Ar-air. When the ambient involves both N 2 and O 2 , such as Ar-N 2 -O 2 and N 2 -O 2 , in the range of [N 2 ]/([N 2 ] +[O 2 ])>0.9, the film resistivity becomes higher than that of the Ar-O 2 case, even at the same O 2 concentration. This is because a thick ZrO x N y layer is formed on the ZrSi 2 layer. When the ratio of [N 2 ]/([N 2 ] + [O 2 ]) in the Ar-N 2 -O 2 ambient is less than 0.9, the films are partially peeled off from the substrate. The resistivity of a film annealed in the Ar-air ambient is very high at even a few ppm O 2 . This is because the film peels off and then the oxidation of the peeled film is accelerated by a small amount of H 2 O in air.