Yuuichi Mikata

Low Leakage Current Polysilicon Oxide Grown by Two-Step Oxidation

The decrease in polysilicon oxide leakage current was experimentally investigated in the range of the oxide thickness from 14nm to 60nm. As a result, it was concluded that the suppression of the oxidation rate at an early stage of the oxidation reduced the conductance of the polysilicon oxide.

Agile fab concepts for cost effective and QTAT mini fab

Recently SoC devices require QTAT and low cost. Also SoC device quickly change its design so that total production amount is not so many. In this situation we propose the Agile fab to solve these problems. The basic concept of the Agile fab consists of following three ideas; (i) Small size Jab supported by virtual Jab, (ii) Multi-task and multi-functional tools, (iii) Minimization and smoothing of RPT (Raw Process Time). WIP control is important for maximum production and minimized X-factor. Multi-functional and multi-task tools make it possible to reduce the excess capacity and the excess investment. Those tools are furnace, dry etching, wet cleaning, stencil ion implantation. Reduction of RPT is achieved by the sequential process, stencil mask ion implantation process, scan-coating for insulating layers and new electro-plating process. The total RPT is reduced less than a half of conventional case. The tool numbers can be reduced to about a half using the multi-functional, multi-task tools and minimization of RPT.

The Formation of Boron‐Doped Polycrystalline Si with Extremely Low Resistivities at Low Temperatures

A process consisting of the deposition of amorphous silicon at low temperatures and subsequent annealing has been proposed for fabricating a boron-doped polycrystalline silicon film with a low resistivity. This process realized large grain growth up to 3 to 5 μm, leading to a low resistivity of 1.4 mΩ.cm, which one-half to about one-third compared with that of direct deposited boron doped polysilicon. In addition to this, extremely low deposition temperature (∼350 o C) using a Si 2 H 6 /B 2 H 6 mixture attained uniform boron concentration across the wafers

Novel approach for precise control of oxide thickness

The control of gate oxide thickness has been very important for device characteristic and reliabilities in MOS transistor. The precise control of oxide thickness becomes more and more important, with continuous shrinkage of device dimension. Tighten SPC limits that mean the precise control of oxide thickness, make tool availability decrease. Because extra test run is necessary for adjustments of process time. The decrease of machines uptime will be serious problem in near future. We show the schemes for improvement of oxide thickness variation in use of multiple regression analysis and so on. Fluctuation in atmospheric pressure and process temperature, are main factors of thickness variation from process to process. New oxidation control system is fabricated to take atmospheric pressure and process temperature into account. This new system can download some process data and atmospheric data during the process. Oxidation time for target thickness is calculated in use of these data. Oxidation time is controlled from calculation value from process to process. This new system realizes precise control of oxide thickness without doing any test run.