Patent ID: 7867063

Claim:
An elastic membrane for use in a substrate holding apparatus, said elastic membrane comprising: a contact portion to be brought into contact with a substrate; a first annular circumferential wall extending upwardly from said contact portion, said first annular circumferential wall being located at a circumferential edge of said contact portion and having a first stretchable and contractible portion, said first stretchable and contractible portion including a folded-back portion having an inwardly-folded portion and an outwardly-folded portion extending along a circumferential direction of said first annular circumferential wall; and a second annular circumferential wall extending upwardly from said contact portion, said second annular circumferential wall being located radially inwardly of said first annular circumferential wall and having a second stretchable and contractible portion, said second stretchable and contractible portion including an inwardly-extending portion that is folded so as to extend inwardly from said contact portion along a circumferential direction of said second annular circumferential wall, said inwardly-extending portion being positioned at a lower end of said second annular circumferential wall.