Kenji Gamo

Ion Beam Assisted Deposition of Metal Organic Films Using Focused Ion Beams

50 keV Ar+ or focused Au+ were irradiated in a trimethyl aluminum atmosphere to investigate characteristics of ion beam assisted deposition. About 80 nm thick films were deposited at a dose of 1×1016/cm2. The film composition and its depth dependence was measured by Auger electron spectroscopy. It was found that the film contains oxygen, carbon and aluminum, and the atomic ratio varies across the film depth. The atomic ratio was 0.8(O):1.1 (C):1.4(Al) at the surface and was 0.8(O):3.3(C):1(Al) inside. A direct maskless pattern deposition was also done using 50 keV focused ion beams.

NOVEL CLASS OF LOW MOLECULAR-WEIGHT ORGANIC RESISTS FOR NANOMETER LITHOGRAPHY

A novel class of low molecular‐weight organic resist materials for nanometer lithography, 1,3,5‐tris[4‐(4‐toluenesulfonyloxy)phenyl]benzene (TsOTPB) and 4,4′,4″‐tris(allylsuccinimido) triphenylamine (ASITPA), was designed and synthesized. TsOTPB with a glass‐transition temperature (Tg) of 64 °C and ASITPA with a Tg of 80 °C were found to function as positive and negative resists, respectively, enabling the fabrication of 150 and 70 nm line patterns on exposure to an electron beam at 50 keV.

Reordering of implanted amorphous layers in gaas

Abstract Channeling measurements have been utilized to investigate the reordering of amorphous layers produced by implantation of 100 keV Zn or 400 keV Se ions at a dose of 3 × 1013 ions/cm2 into GaAs substrates at LN2 temperatures. Annealing was carried out at temperatures between 200 and 600°C for , and oriented substrates. From the results of annealing experiments we conclude that reordering of amorphous layers is not a simple epitaxial regrowth process as is found for implanted Si and Ge. Analysis with X-ray diffraction and TEM techniques show that the reordered layer is epitaxial on the underlying substrate but appreciable disorder in the form of sub-structure is present.

Nanofabrication by FIB

Recent advanced FIB systems enable one to define patterns with a dimension around 10 nm, which is required for quantum devices operating near room temperature and is of increasing importance for nanofabrication tools. Various nanofabrication techniques using focused ion beams have been investigated including lithography, maskless ion implantation and in situ fabrication. For direct nanofabrication by FIB, generation of damage may be a problem for some applications, but previous investigations suggest that this can be minimized by using proper processing techniques.

Maskless ion beam assisted deposition of W and Ta films

Abstract Characteristics of maskless ion beam assisted deposition for W and Ta films have been investigated. For the deposition, 35keV focused Ga or 50keV broad He+, Ar+ or Xe+ ion beams were irradiated in WF6 or Ta(OC2H5)5 atmosphere at a pressure ranging from a few mTorr to 100mTorr. The deposition rate was higher for heavier ions because of the higher energy deposition rate. The deposited film composition was measured by Auger electron spectroscopy. The Auger analysis suggests that the decomposition is induced in WF6 or Ta(OC2H5)5 adsorbed on the target surface by the ion bombardment and unvolatile W and Ta are deposited. By cooling the target at 80K, 500nm thick layers were deposited at a dose of 7.5×1014/cm2.

Molecular layer etching of GaAs

Layer‐by‐layer controlled molecular layer self‐limiting etching at one molecular layer of GaAs was successfully achieved for the first time by alternatively feeding an etchant of Cl and applying a low energy Ar ion beam to the GaAs substrate. The etching rate saturates exactly at one molecular layer per cycle and is independent of etchant feeding rate and the energetic ion beam flux.

Pressure and irradiation angle dependence of maskless ion beam assisted etching of GaAs and Si

Maskless ion beam assisted etching of GaAs and Si has been investigated. Focused Ga+ ion beam was irradiated on GaAs and Si in chlorine and xenon difluoride gas atmosphere, respectively. It was found that an optimum gas pressure existed to improve the etching rate. The etching rate showed a maximum at a bombarding angle of 60°–70°. The simulation of the etching profile was in reasonable agreement with the observed profiles. It was also found that redeposition effect is absent for ion beam assisted etching.

100 keV focused ion beam system with a E×B mass filter for maskless ion implantation

Various liquid metal alloy ion sources and a 100 keV mass separated focused ion beam system have been fabricated and their basic characteristics have been measured. These are mass spectra, energy spread and angular current intensity for ion sources, and focusing characteristics of the system. It was observed that Be–Si–Au ternary alloy ion sources produce doubly charged Be and Si ions and the importance of these ion sources is demonstrated by fabricating a GaAs JFET using a maskless ion implantation technique and by PMMA resist exposure.

Surface processes in digital etching of GaAs

Abstract The self-limited etching characteristics and the surface processes in digital etching of GaAs employing a Cl radical—Ar ion system are described. In the case that the self-limiting mechanism is involved in the digital etching procedure, the etch rate saturates at the same value for both Cl2 feed time and Ar ion irradiation time. Excessive Cl accumulation at the surface is considered to prevent the surface from etching, leading to a gradual decrease in etched depth during repetition of the digital etching cycles.

Digital Etching Using KrF Excimer Laser: Approach to Atomic-Order-Controlled Etching by Photo Induced Reaction

Cl2-based digital etching of GaAs has been studied using a 248 nm KrF excimer laser, which allowed a self-limited etching reaction. A threshold fluence for etching of 13 mJ/cm2 was found, above which the etch rate abruptly increases and finally saturates at around 0.2 nm/cycle from 20 to 33 mJ/cm2. The self-limiting etching characteristics can be explained assuming the etching reaction to be limited by the amount of adsorbed Cl2. The etched depth is proportional to the number of digital etching cycles, and atomic-order-controlled etching is achieved.