Patent ID: 6967796

Claim:
A method of manufacturing a diffractive optical element, which is used for an optical system of an exposure apparatus, said diffractive optical element comprising: (i) an effective area; (ii) a peripheral area surrounding the effective area; (iii) a light-shielding member composed of a laminated layer of Cr oxide and Cr disposed on a surface of the peripheral area; and (iv) a holding frame, wherein the laminated layer includes an alignment mark at a predetermined position with respect to the center of the effective area and in relation to the holding frame so as to center the effective area in the holding frame, said method comprising the steps of: coating a substrate with photoresist; patterning the photoresist into a pattern for making the alignment mark and a pattern for making the effective area; etching the substrate covered with the patterned resist; peeling the photoresist; forming the light-shielding member and the alignment mark by forming a laminated layer of Cr oxide and Cr on the peripheral area of the substrate; and attaching the substrate to the holding frame.