Yoshio Kawamura

Electrostatically driven gas valve with high conductance

The characteristics of a gas valve driven by electrostatic force are investigated. The gas valve consists of a pair of planar electrodes with a conductive film between them. Three valve ports pass through the electrode plates. The film is elastically bent in an S-shape in the middle and the S-bend moves back and forth as voltage is alternately applied between the film and each electrode. This valve has a high conductance achieved by large vertical film displacement. The valve is suitable for rarefied gas control systems, such as the molecular beam epitaxy (MBE) apparatus, which requires a gas flow rate on the order of 1 sccm under a low pressure of less than 100 Pa. Experimental models of the gas valve are constructed to investigate the valves operation. The maximum pressure difference the valve can handle depends on the applied voltage and the size of the port orifice. A valve with 2.0 mm inlet and outlet ports can work under the operating condition of the MBE apparatus. >

Individual and mass operation of biological cells using micromechanical silicon devices

Abstract A cell fusion technique using micromechanical silicon devices has been developed. It permits several one-to-one fusion operations between two different cell groups to be carried out simultaneously, instead of the conventional collective fusion operation. A matrix array of 1584 microchambers, each containing a single pair of cells, has been fabricated on a 3 inch silicon wafer. Fusion of the paired cells is induced by electric pulses applied between electrodes embedded in the microchambers. In order to feed a pair from two different cell groups to every microchamber, a cell carrier made of a silicon wafer has been developed. The carrier plate has the same numbers of cell absorption ports in the matrix array as the microchambers. A single cell particle is absorbed to and released from the port by applying liquid pressure from the rear side of the plate. The carrier plate is transferred over the microchamber plate and simultaneously releases cells into the microchambers. Repeating this process independently for the cell groups A and B, a single pair of AB is formed in every chamber. It is observed that pairs of lettuce cells are successfully fused in the microchambers.

A wafer-handling interface under processing ambient conditions for a single-wafer cluster tool

The pretreatment process used in semiconductor manufacturing can include over one-hundred processes, and about 90% of the wafer transfers are done between processors or process chambers that have different ambient conditions from each other; that is, between the atmosphere and a vacuum ambient or between a low and a high vacuum ambient. The throughput and yield from a semiconductor manufacturing line can be greatly improved by reducing the pumping and setting time of each process chamber ambient that is needed when transferring a wafer. We previously proposed a wafer-handling interface that operates under processing ambient conditions (the WHIPAC), with which the processing ambient conditions in the process chamber need not be changed for every wafer exchange and processing ambient fluctuations can be made smaller. We have developed a WHIPAC that allows the wafer in a process chamber under processing ambient conditions to be exchanged with a small mobile buffer chamber located in the transfer chamber at the center of a cluster tool used for single-wafer processing. This paper describes the principle of the WHIPAC for a single-wafer cluster tool and discusses the experimental results obtained from tests of a prototype system.

New selective doping technique for boron using a HBO2 source and a thin oxide mask

Selective adsorption of HBO2 on Si(100) partially covered with thin (≲1 nm) oxide is observed using a Si molecular‐beam epitaxy system. The thin oxide is formed by local oxidation by a ArF excimer laser or wet chemical treatment. A selective adsorption rate of more than 20 is observed at 700 °C. After the adsorption, the oxide can be sublimated at 800 °C annealing in ultrahigh vacuum without boron desorption. These phenomena can be applied to selective shallow doping without photoresist.

Development of one-to-one biological cell fusion technique using micromechanical devices.

A cell fusion technique using micromechanical silicon devices has been developed. It permits a number of one-to-one cell fusion operations between two different biological cell groups to be carried out simultaneously, instead of the conventional collective fusion operation. A matrix array of 1584 microchambers, each containing a single pair of cells, have been fabricated on a 3-inch silicon wafer. Fusion of the paired cells is induced by electric pulses applied between electrodes embedded in the microchambers. In order to feed a pair of cells from two different cell groups to every microchamber, a cell carrier made of a silicon wafer has been developed. A single cell particle is absorbed to and released from the port of the carrier plate. The carrier plate is transferred over the microchamber plate and simultaneously releases cells into the microchambers. Repeating this operation independently for the cell groups A and B, a single pair of AB is formed in every microchamber. It is observed that pairs of lettuce cells are successfully fused in the microchambers.

Development of noncontact positioning apparatus with large outlet pneumatic gauge for reduction projection aligner.

Reduction projection aligner needs a noncontact measurement means for the position of the wafer surface. A pneumatic gauge is suitable to detect the position of the wafer surface coated with several materials. The pneumatic gauge for this purpose has large outlet diameter which equals the reduction projection area. It must work under large operation gap and at the same time extremely low flow rate for semiconductor process. In this paper, design method and accuracy of the noncontact positioning apparatus with the large-outlet pneumatic gauge and some experimental results are described. Main results obtained are as follows: (1) Positioning accuracy depends mainly on pressure transducer accuracy. (2) Developed apparatus having a 20 mm outlet diameter, and a 90 μm gap, has achieved a positioning acuracy of 0.08 μm (3σ) under low flow rate (0.4l/min).