J. Haga

Fabrication of three-dimensional structures of resist by proton beam writing

The fabrication of three-dimensional (3D) structures was demonstrated by proton beam writing (PBW) using a MeV light-ion microbeam system at Japan Atomic Energy Agency. The fabrication of the 3D structures was performed using PBW in a thick SU-8 layer with a thickness of up to 50μm, which is a typical negative resist. The authors exposed the negative resist on a silicon substrate to focused MeV proton beams within 1μm in diameter, using two different beam energies to obtain two different depths in the resist aiming at fabrication of 3D structures. The two different beam energies were obtained using a 75μm Kapton film as a beam energy degrader to generate 1.6MeV proton beam from 3.0MeV, or using the accelerator voltage control in order to produce beam energy of 1.2MeV. The 3D lines and space structures with the same shape were fabricated using the two different methods. An Arc de Triomphe shape was also manufactured to demonstrate the superior and unique features of the PBW as a versatile tool for deep mic...

Development of micromachining technology in ion microbeam system at TIARA, JAEA

An ion-beam-lithography technique has been progressed in the microbeam systems at Japan Atomic Energy Agency (JAEA) Takasaki. In order to obtain a high-precision measure for microbeam size estimation with a high precision, we applied this technique combined with the electroplating process to make a Ni relief pattern as a resolution standard used in secondary electron imaging. As a result, the smallest beam size could be recorded. The scattering of ions in the materials influenced the spatial resolution and this is also discussed.

Fabrication of high-aspect-ratio pillars by Proton Beam Writing and Application to DEP-devices

Scanning electron microscopy (SEM) images show that 21 mum thick SU-8 pillars on silicon develop after proton beam writing (PBW). These data demonstrate a capability of PBW to fabricate vertical pillars with a height of 21.0 mum and a width of as small as 1.1 mum with a high aspect ratio of 20, and with a uniformity over 700 mum square area. An optical microscope image shows a part of a dielectrophoretic (DEP) device, where the high-aspect-ratio SU-8 pillars with a 12 mum pitch are formed in the gap between the two surface electrodes. Preliminary investigation shows that Escherichia coli can be trapped at pillar structures under AC bias (3 volts, 100 kHz) of the two electrodes. The trapping behavior of DEP device with different structures and sizes are examined.

Lithography using focused high-energy proton beam for fabrication of high-aspect-ratio microstructures

This report demonstrates the three-dimensional fabrication capability of the proton beam writing (PBW) method. Recent activities of PBW in view of applications for MEMS and biosensors are also discussed.

Electroplating of Metal Micro-structure using a Resist Micro-machined by Proton Beam Writing

In this paper,we report the fabrication of Ni structures by electroplating a Ni layer on micro-machined PMMA, a typical resist material. This process involves following steps, (i) Spin coating a resist layer of 5 mum thick PMMA. (ii) Exposure by PBW of 1.7 MeV focused proton beam.(iii) Development of the PMMA with IPA-water (7:3) for 20 min and rinsed in deionized water [4]. (iv) Deposition of a seed layer of 40-nm thick Au by magnetron sputtering for electroplating on the surface of the micro-structure, (v) Electroplating of the micro-structure using a typical nickel sulfamate bath solution. The bath temperature was kept at 35 degC. (vi) Removal of the PMMA structure was made by immersion in acetone and the Ni structure was rinsed in ethanol. Therefore, the PBW is a promising tool for fabrication of metal components such as a stamp for imprint lithography. Imprinting using the 300-nm-thick Ni structure on PMMA was also demonstrated.