Apparatus and method for phase shift photomasking

A method for illuminating a phase shift photomask to reduce aberrations of an objective lens, in a photolithographic apparatus, wherein the aberrations are exaggerated by the phase shift photomask, the method comprising:

• generating light for illuminating an aperture of the objective lens;
• controlling the intensity of the light and shaping the light into a Gaussian intensity distribution pattern across the aperture to reduce exaggerations of aberrations of an objective lens by diffracting the light with a diffraction masking aperture having a half tone diffraction pattern of dithered pixels patterned for distributing the light into a Gaussian intensity distribution pattern;
• providing phase shift photomask with an object pattern in the path of the Gaussian intensity distribution pattern;
• projecting an image of the phase shift photomask object pattern through an objective lens with aberrations, whereby the Gaussian distribution pattern reduces the aberration exaggerations caused by the phase shift photomask.

A photolithographic apparatus comprising:

• a light source constructed and arranged to illuminate a projection imaging system;
• a light controller constructed and arranged to control the intensity of the light and to shape the light into a Gaussian intensity illumination distribution pattern to reduce exaggerations of aberrations of an objective lens;
• a phase shift photomask with an object pattern and disposed in the path of the Gaussian intensity distribution pattern, said phase shift photomask exaggerating aberrations in the objective lens;
• an objective lens with aberrations for receiving the projected image of the phase shift photomask object pattern, whereby the Gaussian intensity illumination distribution pattern reduces aberration exaggerations caused by the phase shift photomask.

A method for illuminating a phase shift photomask to reduce aberrations of an objective lens, in a photolithographic apparatus, wherein the aberrations are exaggerated by the phase shift photomask, the method comprising:

• generating light for illuminating an aperture of the objective lens;
• controlling the intensity of the light and shaping the light into a Gaussian-type intensity distribution pattern across the aperture to reduce exaggerations of aberrations of an objective lens;
• providing phase shift photomask with an object pattern in the path of the Gaussian intensity distribution pattern;
• and
• projecting an image of the phase shift photomask object pattern through an objective lens with aberrations, whereby the Gaussian-type distribution pattern reduces the aberration exaggerations caused by the phase shift photomask,
• wherein the light is controlled and shaped into a Gaussian intensity distribution pattern by diffracting the light through a masking aperture having a half tone diffraction pattern of dithered pixels patterned for distributing the light into a Gaussian intensity distribution pattern.

A photolithographic apparatus comprising:

• a light source constructed and arranged to illuminate a projection imaging system;
• a light controller constructed and arranged to control the intensity of the light and to shape the light into a Gaussian intensity illumination distribution pattern to reduce exaggerations of aberrations of an objective lens;
• a phase shift photomask with an object pattern and disposed in the path of the Gaussian intensity distribution pattern, said phase shift photomask exaggerating aberrations in the objective lens;
• and
• an objective lens with aberrations for receiving the projected image of the phase shift photomask object pattern, whereby the Gaussian intensity illumination distribution pattern reduces aberration exaggerations caused by the phase shift photomask,
• wherein the light controller comprises a diffraction masking aperture having a half tone diffraction pattern of dithered pixels patterned to distribute the light into a Gaussian intensity distribution pattern.

A photolithographic apparatus comprising:

• a light source constructed and arranged to illuminate a projection imaging system;
• a light controller constructed and arranged to control the intensity of the light and to shape the light into a Gaussian intensity illumination distribution pattern to reduce exaggerations of aberrations of an objective lens;
• a phase shift photomask with an object pattern and disposed in the path of the Gaussian intensity distribution pattern, said phase shift photomask exaggerating aberrations in the objective lens;
• and
• an objective lens with aberrations for receiving the projected image of the phase shift photomask object pattern, whereby the Gaussian intensity illumination distribution pattern reduces aberration exaggerations caused by the phase shift photomask,
• wherein said light controller comprises a half-tone diffraction masking aperture comprising an array of pixels, each pixel of a clear or opaque type and of the same size, said clear and opaque pixels for respectively passing and blocking incident light, wherein the number, size, and type of the pixels arc chosen in accordance with the wavelength of light used to illuminate the photomask, and the size and shape of the features of the phase shift photomask, to generate a Gaussian illumination intensity pattern on the phase shift photomask.