| 摘要 |
PURPOSE:To secure a wafer so that the plane thereof is perpendicular to light rays regardless of any possible warpage of the wafer, by employing an electrostatic wafer chuck. CONSTITUTION:An electrostatic chuck 7 secures a wafer 3 thereon by means of electrostatic force so that the plane of the wafer 3 is perpendicular to light rays 1. This is effected because the electrostatic force is sufficiently strong, and the wafer 3 can be retained in this state even if it has warpage. The wafer 3 is removed by blowing air against it through air holes 6. Since the chuck 7 reliably secures the wafer 3 so that the plane thereof is perpendicular to the light rays, there is no offset of focal point within the wafer 3, so that it is possible to increase the production yield. |
