The etching rate profile over the 50-mm diameter single-crystalline C-face 4H-SiC wafer by ClF3 gas was numerically evaluated by means of the numerical calculation accounting for the transport phenomena. The etching rate uniformity is expected to be improved by means of adjusting the pinhole diameter and their arrangement of the gas distributor.

Widely used coating materials, such as tantalum carbide, silicon nitride and aluminum nitride, were exposed to chlorine trifluoride gas at various temperatures. The tantalum carbide powder was etched and vaporized by a quick and significant exothermic chemical reaction at temperatures higher than room temperature. The silicon nitride powder was etched that produced volatile products at temperatures higher than 250°C. An aluminum nitride plate and powder showed a slight increase in weight at temperatures higher than 500°C due to fluorination. The aluminum nitride plate thickness increased causing a surface smoothing effect without any cracking. The aluminum nitride is expected to work as the anticorrosive coating material to the chlorine fluoride gas at high temperatures, thus allowing fluorination.

A 50-mm diameter silicon carbide wafer thinning technique by means of a chemical reaction using a chlorine trifluoride (ClF3) gas was studied accounting for the gas distributor design and the total gas flow rate. The entire etching depth profile could become uniform with the increasing total gas flow rate at the fixed chlorine trifluoride gas concentration. A relationship between the pinhole arrangement of the gas distributor and the local etching rate profile was clarified by comparing the quick calculation and the measurement.

In this study, we propose an advanced architecture of a smart electrode for neural stimulation of a retinal prosthesis. A feature of the proposed architecture is embedding CMOS microchips into the core of the stimulus electrodes. Microchip integration without dead space on the array is possible. Additionally, higher durability can be expected because the microchips are protected by the stimulus electrodes like a metal casing. Dedicated circular-shaped CMOS microchips were designed and fabricated. The microchip measured 400 μm in diameter. Stimulus electrodes that had a microcavity for embedding the microchip were also fabricated. In the assembly process, the CMOS microchip was mounted on a flexible substrate, and then the stimulus electrode was mounted to cover the microchip. The microchip was completely built into the inside of the electrode. By performing an ex-vivo experiment using the extracted eyeball of a pig, stimulus function of the electrode was demonstrated successfully.

For improving the productivity of the semiconductor silicon carbide power devices, a very large diameter wafer process was studied, particularly for the non-plasma wafer etching using the chlorine trifluoride gas. Taking into account the motion of heavy gas, such as the chlorine trifluoride gas having the large molecular weight, the transport phenomena in the etching reactor were evaluated and designed using the computational fluid dynamics. The simple gas distributor design for a 200-mm-diameter wafer was evaluated in detail in order to uniformly spread the etchant gas over the wide wafer surface.