Kozo Mochiji

Peroxypolytungstic acids: A new inorganic resist material

Recently reported amorphous polytungstic acids containing peroxo groups are found to provide a new inorganic resist. A homogeneous resist film can be formed easily with the spin coating method. This film is made insoluble in water by deep ultraviolet, x ray, and electron beam irradiation. The oxygen reactive ion etching (O2 RIE) durability is found to be high enough that a bilayer resist scheme employing this resist as a top imaging layer gives a high resolution pattern (line and space: 0.38 μm). The mechanism for the radiation induced reaction is also discussed.

Desorption induced by electronic potential energy of multiply charged ions

Abstract Particle desorption is investigated in terms of bombardment of a GaAs surface by slow multiply charged Ar ions (charge state q ⩽ 9, kinetic energy E k ⩽ 3 keV). The desorption yield of Ga and As atoms as well as H + ions drastically increased with the charge state of the incident Ar ions, but was changed little by the kinetic energy of the Ar ions. These results demonstrate that desorption reactions at the surface are greatly enhanced by the potential energy of the incident ions. From an analysis of the potential energy dependence of the desorption yield based on the Coulomb explosion model, it is found that the lifetime of multiple holes created by the multiply charged Ar ions is longer than that of a single hole by 2 to 3 orders of magnitude.

Formation of a thin SiO2 film using synchrotron radiation excited reaction

The possibility of altering an oxygen‐adsorbed Si surface to SiO2 using a synchrotron radiation (SR) excited reaction is evidenced for the first time. Oxygen gas is adsorbed on a clean Si surface, and soft x‐ray is irradiated on it by SR. As a result, H partly terminated on the oxygen‐adsorbed Si surface is eliminated and the surface becomes more SiO2‐like. This is proved by x‐ray photoelectron spectroscopy (XPS) analysis. Photostimulated desorption (PSD) of H+ ions, which are emitted from the surface, is also detected during SR irradiation. The Si—O bond formation model followed by H+ PSD explains this oxidation.

Desorption of Ga and As Atoms from GaAs Surface Induced by Slow Multiply Charged Ar Ions

A reaction on a semiconductor surface induced by the potential energy of slow multiply charged ions (MCIs) has been investigated. By using an Einzel-type ion decelerator, beams of slow MCIs (Ar q+ ; q≤10) with an ion current of several tens of nanoamperes and with the kinetic energy (E k ) of 30 x q eV were produced. Irradiating a GaAs surface with the slow Ar q+ induced the desorption of Ga and As atoms, and this desorption was almost independent of the E k but strongly dependent on the q ; that is, on the potential energy (E p ) of the Ar q+ . The effect of E p on atom desorption was analyzed quantitatively in terms of a model based on the Coulomb repulsion between holes generated on the surface through neutralization of the MCIs.

Low‐temperature synchrotron‐radiation‐excited etching of silicon dioxide with sulfur hexafluoride adsorption

Ultralarge‐scale integration circuits now require innovative microfabrication processes in order to achieve gigabit‐scale integration. One approach is to use soft x rays, because they can give excellent spatial resolution by their short wavelength and high‐reaction selectivity by core‐electron excitation. Synchrotron‐radiation (SR) ‐excited etching of SiO2 and Si is studied from the viewpoints of pattern replicability and analysis of etching selectivity between two layers. Deep‐submicron patterns of SiO2 are formed by cooling the specimen with liquid N2 and adsorbing SF6 reaction gas during SR irradiation. Photon‐stimulated desorption ions from SF6‐adsorbed SiO2 and Si surfaces are first investigated. As a result, ion species such as SiF+n and SO+n, which are etching products from the surface, are obtained only from SiO2, and this selective etching of SiO2 is also investigated by x‐ray photoelectron spectroscopy. In this selective etching mechanism, constraint of Si‐etching by passivation of photofragment...

Extraction of trapped ions from the Tokyo electron beam ion trap

A beam line for transporting highly charged ions extracted from the Tokyo Electron Beam Ion Trap is being constructed in order to study ion-surface interactions and to inject into secondary ion traps for atomic physics experiments. A basic idea for the design and a computer modeling for the extraction system are described. The results of a test experiment to detect the total number of ions extracted from the EBIT are also reported.

Photon-stimulated desorption from chemically treated Si surfaces

Abstract Experimental results are presented on the synchrotron-radiation-induced desorption of oxygen ions from HF-treated Si surfaces measured with a quadrupole mass analyzer operated in the pulse-counting mode. The effect of atomic hydrogen exposure was studied. Desorption of H + , O + and F + ions was observed from HF-treated Si surfaces. The yield of O + ions was increased more than 30-fold by exposure to atomic hydrogen.

Soft x‐ray spectroscopy of polymer resist using synchrotron radiation

Soft x‐ray absorption spectra and spectral sensitivity of x‐ray resists are studied by using synchrotron radiation. Spectral sensitivity is successfully evaluated from the fragment yield change of the decomposed resists by changing incident x‐ray wavelengths. This evaluation method is newly developed here. Using this technique, x‐ray wavelength dependency for the decomposition efficiency of polymer resists poly(2‐methylpentene‐1‐sulfone) and their decomposition characteristics are clarified. These are very important for development of more sensitive x‐ray resists.

Soft x‐ray spectral characterization of resist polymer using synchrotron radiation

Soft x‐ray absorption spectra and spectral sensitivity of x‐ray resist, poly‐2‐methylpentene‐1‐sulfone, are studied using synchrotron radiation. Shape resonance around the S2p edge and chemical shift among C1s levels are observed in the absorption spectra. The degradation efficiency of the resist is found to vary with incident photon wavelength.

0.1-micrometer scaling by 1:1 synchrotron radiation lithography

Abstract The dimensional accuracy of an X-ray mask and resolution capability of 1:1 SR (synchrotron radiation) lithography for 0.1-μm scaling are studied. The mask-to-mask overlay error is minimized below the measurement accuracy (0.04 μm, 3σ) by controlling the stress of the SiN membrane and the W absorber. 1:1 SR proximity printing is capable of 0.1-μm resolution by adjusting the exposing SR wavelength just over the Si-K edge and reducing the mask-wafer gap to 10 μm.