Patent ID: 9323158
Filing Date: 2016-04-26
CPC Classification: G02B,G03F

Claim Text:
1. A method of designing an extreme ultraviolet lithography projection objective, wherein the projection objective is disposed between a mask and a wafer plane, the objective comprising six lenses and an aperture diaphragm positioned from the mask along a beam propagation direction to the wafer plane in the order of: a first lens (M 1 ), the aperture diaphragm disposed on a second lens (M 2 ), the second lens, a third lens (M 3 ), a fourth lens (M 4 ), a fifth lens (M 5 ), and a sixth lens (M 6 ), said method comprising the steps of: determining a set of optical parameters of the projection objective comprising: object side numerical aperture (NAO), magnification of the objective (M), image side numerical aperture (NAI), object field height (YOB), image field height (YIM); and incidental angle of chief ray on object side (CA) based on NAO; determining a ratio of the object field height YOB to the distance between the mask and the first lens M determining a distance between the mask and the first lens M determining the radius of the first lens M where h z1 denotes the height of chief ray (RAY1) on the first lens M 1 , and z z1 denotes the axial distance of an incidental point of chief ray RAY1 on the first lens M 1 to the vertex of the first lens M 1 ; determining the radius of the second lens M where U a2 denotes the slope angle of an upper marginal ray (RAY2) on the first lens M 1 , h a2 denotes the height of an upper marginal ray (RAY2) on the second lens M 2 , and h b1 denotes the height of a lower marginal ray (RAY3) on the first lens M 1 ; determining the distance between the fifth lens M defining a virtual plane D where h b6 denotes the height of the lower marginal ray RAY3 on the sixth lens M 6 , h bD1 denotes the height of the lower marginal ray RAY3 on the virtual plane D 1 , z b6 denotes the axial distance between incidental point of the lower marginal ray on the sixth lens M 6 and the vertex of the sixth lens M 6 , and U′ b6 denotes the slope angle of the lower marginal ray RAY3 on the sixth lens M 6 ; determining the radius of the fifth lens M where h b5 denotes the height of lower marginal ray RAY3 on the fifth lens M 5 , h a6 denotes the height of lower marginal ray RAY3 on the sixth lens M 6 , U′ b5 denotes the slope angle of the lower marginal ray RAY3 on the fifth lens M 5 , z a6 denotes the axial distance between an incidental point of the upper marginal ray RAY2 on the sixth lens M 6 and the vertex of the sixth lens M 6 , and U′ b5 denotes the slope angle of the lower marginal ray RAY3 on the fifth lens M 5 ; and determining the radius of the third lens M