A NOVEL USE OF SUPERCONDUCTING OXIDES IN A NONCONTACT CARRIER FOR VLSI PLANTS

A high-Tc superconductor has outstanding intergrain superconductivity and troublesome intergrain electrical conductivity at the same time. B ut once we consider to utilize the intergrain characteristic only, neg lecting the intergrain conductivity, a new world of applied supercondu ctivity is open before us. An yttrium-family superconducting oxide can be a very strong pinned second class superconductor by the processing technique by which proper sizes and delicate distribution of precipit ates are introduced in the material1). The fishing effect showing the stable floating of superconducting oxide material has its origin in th is strong pinning force. Now in an advanced Japanese VLSI plant a magn etically supported non-contact wafer-carrier is used in order to avoid the production of even traces of fine dust made by the friction of th e wheels2-3). In this system the controlled attractive force between c onventional electro-magnets and an iron guideway is used. The outstand ing fishing effect of a strong pinned yttrium-family superconducting o xide processed by the QMG method can be expected to replace electro-ma gnets. We testfabricated a magnetically suspended non-contact carrier in the same dimension as a VLSI wafer-carrier currently used, with fou r QMG processed yttrium-family bulk pellets4). The carrier runs at any controlled speed with a load of under 3 kg, with very high stability in the vertical and lateral positions. It was driven by a linear induc tion motor. The outline of this system and its carrier will be reporte d as well as the superconducting levitation performance of the carrier .