Lithography pupil shaping optical system and method for generating off-axis illumination mode
A lithography pupil shaping optical system and method for generating off-axis illumination mode. The invention is composed of illumination mode generation unit, rotatable wave plate, polarization beam splitter unit, ring I generation unit and ring II generation unit. Through selecting corresponding diffractive optical element and appropriate adjustment, this invention can generate various illumination modes including single ring illumination mode and double ring illumination mode. The intensity at pupil plane and the inner and outer diameters of the off-axis illumination mode can be adjusted continuously.
1. A lithography pupil shaping optical system comprising of illumination mode generation unit ( 1 ), rotatable wave plate ( 2 ), polarization beam splitter unit ( 3 ), ring I generation unit ( 4 ) and ring II generation unit ( 5 ), in which said illumination mode generation unit ( 1 ) is composed of diffractive optical element ( 101 ) and zoom collimating lens group ( 102 ); diffractive optical element ( 101 ) is exchangeable to achieve conventional, dipole, and quadrupole illumination modes, respectively; said ring I generation unit ( 4 ) is composed of first quarter-wave plate ( 401 ), first convex axicon ( 402 ) and first movable mirror ( 403 ); and said ring II generation unit ( 5 ) is composed of second quarter-wave plate ( 501 ), second convex axicon ( 502 ) and second movable mirror ( 503 ), the positions of the above components being as follows:
along the positive direction of z-axis, diffractive optical element ( 101 ), zoom collimating lens group ( 102 ), rotatable wave plate ( 2 ), polarization beam splitter unit ( 3 ), first quarter-wave plate ( 401 ), first convex axicon ( 402 ) and first movable mirror ( 403 ) are placed sequentially; the conical tip of said first convex axicon ( 402 ) is faced with said first movable mirror ( 403 ); said first movable mirror is coated with polarization-maintaining reflection film; and said first movable mirror possesses mechanical structures by which the distance between the conical tip of said first convex axicon and said first movable mirror can be adjusted continuously, and
the light passing through said polarization beam splitter unit ( 3 ) is split into a reflected light and a transmitted light, and along the direction of the reflected light, said second quarter-wave plate ( 501 ), said second convex axicon ( 502 ) and said second movable mirror ( 503 ) are placed sequentially; the conical tip of said second convex axicon ( 502 ) is faced with said second movable mirror ( 503 ); said second movable mirror ( 503 ) is coated with polarization-maintaining reflection film; said second movable mirror possesses mechanical structures by which the distance between the conical tip of said second convex axicon and said second movable mirror can be adjusted continuously; and the rear surface of said diffractive optical element ( 101 ) is placed at the front focal plane of said zoom collimating lens group ( 102 ).
2. A method for generating an off-axis illumination mode using the lithography pupil shaping optical system according to claim 1 , the method comprising the following steps:
{circle around (1)} according to the required illumination mode, select corresponding said diffractive optical element;
{circle around (2)} according to the required intensity distribution size of the illumination mode, adjust the focal length of said zoom collimating lens group;
{circle around (3)} according to the required energy distribution relationship of said first single ring beam to said second single ring beam, adjust the angle θ 0 between the fast axis of said rotatable wave plate and x-axis;
{circle around (4)} according to the required inner and outer diameters of said first single ring beam, determine and adjust the distance d 1 between the conical tip of said first convex axicon and said first movable mirror;
{circle around (5)} according to the required inner and outer diameters of said second single ring beam, determine and adjust the distance d 2 between the conical tip of said second convex axicon and said second movable mirror; and
{circle around (6)} when said first single ring beam in step {circle around (4)} and said single ring beam in step {circle around (5)} overlap completely or partially, or when the inner or outer diameter of said first single ring beam in step {circle around (4)} equals the outer or inner diameter of said second single ring beam in step {circle around (5)}, a single ring illumination mode is obtained; and, otherwise, a double ring illumination mode is obtained.