Wafer holding mechanism
View Patent ↗A wafer holding mechanism for holding a wafer of the type used in the manufacture of semiconductor devices is herein described. The mechanism has a first plate having a number of offsets that define at least one lip that extends radially inward of the offsets. A second plate is positioned adjacent the first plate and generally between the first plate and the lip such that one or more fingers coupled to the second plate oppose the lip that depends from the first plate. When the second plate is moved to a closed position, the at least one lip and the one or more fingers cooperatively grasp an edge of a wafer therebetween. The wafer holding mechanism is coupled to a drive that rotates the wafer before an imaging mechanism for capturing images of the wafer as it rotates.
1. A method of inspecting a surface of a wafer comprising:
grasping a wafer at one or more selected regions around its periphery such that there is substantially no relative movement between a mechanism for grasping the wafer and the wafer;
characterizing a deformation of the wafer due to+a manner in which the wafer is grasped;
adjusting a focusing mechanism to ensure that images of the surface of the wafer remain substantially in-focus using data derived from the characterization of the wafer deformation;
rotating the wafer about an axis substantially normal to the surface of the wafer while maintaining the wafer generally horizontal;
capturing images of the surface of the wafer as the surface of the wafer is rotated past an imaging mechanism,
wherein characterizing a deformation of a wafer comprises:
modeling a predicted deformation of the wafer based at least in part on the physical properties of the wafer and at least one boundary conditions of a clamped grasped wafer;
measuring at least some portion of an actual wafer to obtain shape data; and
normalizing the model of the predicted deformation of the surface of the wafer using the shape data.