The present invention relates to a rolling bearing with solid lubricant used in a semiconductor producing apparatus.
Generally, in rolling bearings, a lubricant, such as grease, is fed between the inner and outer rings and between the rolling elements and the cage to decrease the rolling friction or sliding friction being subjected thereto so as to improve the durability of the bearing.
When a rolling bearing is to be used in vacuum requiring a high degree of cleanliness as in a semiconductor producing apparatus, the vapor of the lubricant becomes a source of contamination; thus, grease and other fluid lubricants cannot be used. Therefore, for a rolling bearing to be used in such environment, a solid lubricant having a low vapor pressure is required. At present, as to solid lubricants for rolling bearings, the laminar substance such as molybdenum disulfide, the soft metal such as gold, silver and lead, high polymer such as PTFE and polyimide are in wide use.
In recent years, in the semiconductor production field, as the degree of integration increases, the line width of electric circuits has been decreasing, and for fear that wear particles of the solid lubricant discharged from the bearing should short-circuit the electric circuit for its adhesion to the patterns, the trend is toward refraining from using solid lubricants of the soft metal type which are conductive. On the other hand, although solid lubricants, such as molybdenum disulfide and PTFE (polymer) are not conductive, they have low adherebility and low wear resistance; thus, they are inferior in durability to soft metals.
Further, in a recent semiconductor producing apparatus, not only a bearing which can be used in vacuum but also a bearing which can be used in both air and vacuum and which has a low dust producing rate and corrosion resistance has been called for. That is, it is mostly in the wafer treating process that vacuum bearings are used in the semiconductor producing process. The apparatus used in this process tends to be made in an in-line form; thus, the wafer conveyor requires a bearing to operate in both air and vacuum environments. Further, the high degree of integration of semiconductor necessarily requires suppressing the production of dust. Further, in some places where the apparatus is used, corrosion resistance and heat resistance are required.
Accordingly, an object of the present invention is to provide a rolling bearing with solid lubricant which is superior in durability when used both in air and in vacuum and which has a low dust producing rate and is suitable for use in the semiconductor producing field.