Nao Honda

Fabrication and high-speed characterization of SU-8 shrouded two-dimensional microimpellers

In this study, the performance of shrouded two-dimensional microimpellers was measured for application to a micro centrifugal pump used in a portable fuel cell system. Two types of microimpellers were designed, and fabricated by a multi-layer photolithography process using an ultrathick photoresist (SU-8 3000). Microimpellers with a diameter of 10 mm were tested using an air spindle up to maximum rotation speeds determined by the destruction of the microimpellers, which are 350 000 rpm for a purely-radial-outlet blade impeller and 450 000 rpm for a backward blade impeller. The purely-radial-outlet blade impeller showed a higher pressure rise—2.8 kPa at 150 000 rpm, 5.1 kPa at 200 000 rpm and 12.5 kPa at 300 000 rpm. The measured performance satisfies the requirement of the micro centrifugal pump. However, the measured pressure rises are roughly half of the simulated values. The influence of the radial clearance and height difference between the impeller and the diffuser was investigated using an electromagnetic motor and impellers with a diameter of 16 mm. Against expectation, a better pumping performance was obtained with a larger tip clearance, and the height difference did not affect the pumping performance. These unexpected results suggest that the tip clearance and the clearance between the impeller shroud and the stationary housing act as a diffuser.

Profile simulation of SU-8 thick film resist

XP SU-8 3000 (hereinafter referred to as “SU-8”) thick-film resist is a chemically amplified negative resist based on epoxy resin. Here, we report on the profile simulation for this resist. Profile simulation is an important technique for planning experiments. Thus, there have been many reports on simulation techniques. In particular, many studies have been conducted on chemically amplified positive resists, as they are major resist materials used in the IC industry. However, there have been few simulation studies concerning chemically amplified negative resists. Under these circumstances, we have considered performing simulations on chemically amplified negative resist. The results of the simulation and the SEM observations are in good agreement. This study demonstrates that simulation is possible for a chemically amplified negative resist (SU-8).

Study of nano-imprint for sub-100nm patterning by using SU-8 3000NIL resist

SU-8 (Kayaku Microchem Co., Ltd.) provides well-defined resist profiles with high aspect ratios, and is also suitable for use as a permanent resist. SU-8 has been widely used for many years in the MEMS (Micro Electro Mechanical System), IC package (bump, insulator, encapsulation), micro fluid (inkjet, micro reactor, biochips), and optical device (waveguide, optical switch) fields. SU-8 is a chemically amplified negative resist based on epoxy resin. This resist generates a strong acid during exposure, and PEB (Post Exposure Baking) induces the crosslinking reaction of the resin with the acid working as a catalyst to insolubilize the resist. In our study, we sought to investigate the potential application of SU-8 3000NIL, the most commonly used resist for the MEMS process, to imprint lithography. The results we obtained indicate that SU-8 3000NIL can indeed be applied to imprint lithography after optimizing process conditions for imprinting.