Mask and method for focus monitoring

A focus-monitoring mask which is adapted to be employed on an occasion of transferring a pattern on a wafer by way of photolithography, said mask comprising;

• a first pattern region having at least one first monitor pattern which is constituted by a first opening surrounded by a first film or constituted by the first film surrounded by the first opening, and is capable of giving a first phase difference to an exposure light passing through said first film relative to an exposure light passing through said first opening;
• and
• a second pattern region having at least one second monitor pattern which is constituted by a second opening surrounded by a second film or constituted by the second film surrounded by the second opening, and is capable of giving a second phase difference to an exposure light passing through said second film relative to an exposure light passing through said second opening, said second phase difference being different from said first phase difference;
• wherein said first and second monitor patterns have a configuration in which both ends thereof are tapered from a central portion thereof.

A focus-monitoring mask which comprises;

• a first pattern region having at least one first tapered monitor pattern which is constituted by a first film surrounded by a first opening or constituted by the first opening surrounded by the first film;
• and
• a second pattern region having at least one second tapered monitor pattern which is constituted by a second opening surrounded by a second film or constituted by the second film surrounded by the second opening, said second tapered monitor pattern tapering in a direction which is opposite to a tapering direction of said first tapered monitor pattern;
• wherein a phase of exposure light passing through said second tapered monitor pattern differs from a phase of exposure light passing through said first tapered monitor pattern.

A method for focus monitoring which is designed to monitor a magnitude of deviation from a best focus state on an occasion of transferring a pattern on a wafer by way of photolithography, said method comprising the steps of;

• transferring a pattern on a wafer by making use of a focus-monitoring mask which comprises a first pattern region having at least one first tapered monitor pattern which is constituted by a first film surrounded by a first opening or constituted by the first opening surrounded by the first film;
• and a second pattern region having at least one second tapered monitor pattern which is constituted by a second opening surrounded by a second film or constituted by the second film surrounded by the second opening, said second tapered monitor pattern tapering in a direction which is opposite to a tapering direction of said first monitor pattern;
• wherein a phase of exposure light passing through said second monitor pattern differs from a phase of exposure light passing through said first monitor pattern;
• measuring a relative position between the first and second monitor patterns among the patterns formed on the wafer;
• and
• calculating, on the basis of the relative position measured, a deviation of the relative position of focus.

A method for focus monitoring which is designed to monitor a magnitude of deviation from an best focus state on an occasion of transferring a pattern on a wafer by way of photolithography, said method comprising the steps of;

• transferring a pattern on a wafer by making use of a focus-monitoring mask having four groups of focus monitor pattern each group of focus monitor pattern comprising a first pattern region having at least one first tapered monitor pattern which is constituted by a first film surrounded by a first opening or constituted by the first opening surrounded by the first film;
• and a second pattern region having at least one second tapered monitor pattern which is constituted by a second opening surrounded by a second film or constituted by the second film surrounded by the second opening, said second tapered monitor pattern tapering in a direction which is opposite to a tapering direction of said first tapered monitor pattern;
• wherein a phase of exposure light passing through said second tapered monitor pattern differs from a phase of exposure light passing through said first tapered monitor pattern, and said four groups of focus monitor pattern are designed such that a direction of distal end of said tapered pattern is set to an angle of 0 degree, +45 degrees, −45 degrees and 90 degrees, respectively;
• measuring a relative position between the monitor patterns of the first and second pattern regions among the patterns formed on the wafer;
• and
• correcting, on the basis of the relative position measured, a deviation of focus that is resulted from an aberration of irradiation optical lens.