Patent ID: 7425238

Claim:
A substrate holding chuck, which has protrusions for supporting a substrate, for holding the substrate by negative pressure while the substrate is being supported by said protrusions, said protrusions including: (a) a circular first peripheral wall portion disposed along an outer circumferential portion of the chuck; and (b) a plurality of pin-shaped protrusions inside said circular first peripheral wall portion, said chuck having: (i) a first area, disposed inwardly of and along said circular first peripheral wall portion, in which said pin-shaped protrusions are arrayed in one or more concentric circles having a center identical with a center of said circular first peripheral wall portion; (ii) a second area, disposed inwardly of said first area, in which said pin-shaped protrusions are arrayed in a grid-like manner; and (iii) a third area, which is disposed between said first and second areas, in which arrangement of said pin-shaped protrusions is different from the concentric circle and the grid-like manner, and said pin-shaped protrusions are arrayed to provide a substantially uniform supporting force, wherein a spacing D at which said pin-shaped protrusions are arranged in a concentric circle in said first area satisfies the relation 0.8P≦D≦1.2P, where P represents a pitch at which said pin-shaped protrusions are arrayed in the grid-like manner in said second area.