Systematic method for production of phase-shifting photolithographic masks

A systematic method of producing masks for use within a photolithographic illumination system characterized by a transmission function in which light is transmitted through non-opaque portions of said masks positioned in an object plane and in which an image is formed on an image plane, comprising the steps of:

• formulating a coherent approximation of said transmission function;
• defining a binary image pattern to be formed by said illumination system on said image plane;
• generating a continuous mask function of continuously-varying phase which satisfies predetermined error criteria based on said coherent approximation of said transmission function and said binary image pattern, said continuous mask function including a real part and an imaginary part;
• transforming said real part of said continuous mask function into a first two-phase mask function having two phase levels and transforming said imaginary part of said continuous mask function into a second two-phase mask function having two phase levels;
• and
• generating a first mask in accordance with said first two-phase mask function and generating a second two-phase mask in accordance with said second two-phase mask function, said first mask including a plurality of first pixel regions wherein each first pixel region has a transmittance corresponding to one of said two phase levels, said second mask including a plurality of second pixel regions wherein each second pixel region has a transmittance corresponding to one of said two phase levels.

A system for producing masks for use within a photolithographic illumination system characterized by a transmission function in which light is transmitted through non-opaque portions of said masks positioned in an object plane and in which an image is formed on an image plane, comprising the steps of:

• a computer system, including:
• a computer memory in which is stored data representing a coherent approximation of said transmission function, and data representing a binary image pattern to be formed by said illumination system on said image plane;
• a first mask generation program that generates a continuous mask function of continuously-varying phase which satisfies predetermined error criteria based on said coherent approximation of said transmission function and said binary image pattern;
• and
• a second mask generation program that transforms said mask function into a quadrature-phase mask function by dividing said continuously-varying phase into four phase levels;
• and
• mask fabrication equipment that generates said mask in accordance with said quadrature-phase mask function, said mask including a plurality of pixel regions wherein each pixel region has a transmittance corresponding to one of said four phase levels.

A system for producing masks for use within a photolithographic illumination system characterized by a transmission function in which light is transmitted through non-opaque portions of said masks positioned in an object plane and in which an image is formed on an image plane, comprising the steps of:

• a computer system, including:
• a computer memory in which is stored data representing a coherent approximation of said transmission function, and data representing a binary image pattern to be formed by said illumination system on said image plane;
• a first mask generation program that generates a continuous mask function of continuously-varying phase which satisfies predetermined error criteria based on said coherent approximation of said transmission function and said binary image pattern, said continuous mask function including a real part and an imaginary part;
• and
• a second mask generation program that transforms said real part of said continuous mask function into a first two-phase mask function having two phase levels and transforming said imaginary part of said continuous mask function into a second two-phase mask function having two phase levels;
• and
• mask fabrication equipment that generates a first mask in accordance with said first two-phase mask function and generates a second two-phase mask in accordance with said second two-phase mask function, said first mask including a plurality of first pixel regions wherein each first pixel region has a transmittance corresponding to one of said two phase levels, said second mask including a plurality of second pixel regions wherein each second pixel region has a transmittance corresponding to one of said two phase levels.

A systematic method of producing a mask for use within a photolithographic illumination system characterized by a transmission function in which light is transmitted through non-opaque portions of said mask positioned in an object plane and in which an image is formed on an image plane, comprising the steps of:

• formulating a coherent approximation of said transmission function;
• defining a binary image pattern to be formed by said illumination system on said image plane;
• generating a continuous mask function of continuously-varying phase which satisfies predetermined error criteria based on said coherent approximation of said transmission function and said binary image pattern;
• transforming said mask function into a plural-phase mask function by dividing said continuously-varying phase into a plurality of phase levels;
• generating said mask in accordance with said plural-phase mask function, said mask including a plurality of pixel regions wherein each pixel region has a transmittance corresponding to one of said plurality of phase levels.