Patent ID: 6079256
Filing Date: 2000-06-27
Classification: G03F,H01L

Abstract:
An apparatus to determine the relative position between two layers of a device, wherein a second layer of said two layers is located above a first layer of said two layers utilizing a target including a first periodic structure on said first layer of said device and a second periodic structure that complements said first periodic structure with said second periodic structure on said second layer of said device at a location that is adjacent said first periodic structure, said apparatus comprising:a microscopic height variation detector in communication with said target on said device, said microscopic height variation detector including:a stylus having:an atomic sized tip in communication with said target on said device; anda cantilever arm having distal and proximate ends thereof with said atomic sized tip affixed to said distal end thereof; andan angular deflection detector affixed to said proximate end of said stylus to develop an electrical signal directly proportional to vertical displacement of said atomic sized tip of said stylus;a translational system coupled to said microscopic height variation detector and said device to provide movement therebetween with said atomic sized tip addressing a selected path on said device;a memory coupled to said angular deflection detector to store electrical signals therefrom as said atomic sized tip traverses said device for comparison with later received electrical signals produced when said atomic sized tip traverses a different path across said device under control of said translational system to calculate any offset between said first and second periodic structures of said target; anda computing and control system coupled to said translational system to cause said atomic sized tip to traverse across said target on said device and to sequentially vary the path of said atomic sized tip across said surface of said device in two such paths, and coupled to receive signals from said angular deflection detector and said memory to calculate any offset between said first periodic structure and said second periodic structure of said target with two electrical signals, one from each of said angular deflection detector and said memory.