Patent ID: 9598305
Date: 2017-03-21
CPC Classifications: B82Y,C03C,G03F,Y10T

Claim:
1. A synthetic quartz glass substrate having a front surface having a 6 inch square major surface including a central surface area of 148 mm square including a central surface area (A) of 132 mm square, a surface region extending from the perimeter of the central surface area (A) of 132 mm square to the perimeter of the major surface being inclined and a back surface, wherein on the front surface, the central surface area (A) of 132 mm square has a flatness of up to 50 nm, on the front surface, a frame region (B), constituted by the central surface area of 148 mm square excluding the central surface area (A) of 132 mm square, has a flatness of up to 150 nm, the central surface area (A) of 132 mm square has an average plane and the frame region (B) has an average plane, and the average plane of the central surface area (A) of 132 mm square is higher than the average plane of the frame region (B) by 50 nm to 100 nm, and the front surface and the back surface of the substrate are designed such that a central surface area of 142 mm square of the front surface presents a flatness of up to 50 nm and a central surface area of 142 mm square of the back surface has a flatness of up to 500 nm, when the glass substrate is mounted on a stepper by suction chucking at a 3-mm region extending from 2 mm to 5 mm inward from the perimeter of the major surface of the front surface.