| 摘要 |
<p>APPARATUS FOR PROJECTING A SERIES OF IMAGES ONTO DIES OF A SEMICONDUCTOR WAFER A focusing system for maintaining a wafer at the focal plane of a projected image, comprising: at least three fluid probes each having a discharge orifice disposed in a plane parallel to said focal plane; means for projecting a stream of fluid through each of said orifices and against a wafer and generating a fluid back pressure signal indicative of the distance of a wafer from said focal plane; chuck means for holding a wafer; means for moving said chuck means and a wafer positioned thereon to positions parallel to said focal plane, said moving means comprising at least three fluid operated piston means, each piston means being coupled to said chuck means and in fluid communication with one of said probes for moving said chuck means in response to said back pressure developed between said one probe and said wafer.</p> |
