Method for error reduction in lithography

A method for predicting and correcting geometrical errors in lithography using masks, including large-area photomasks or reticles, and exposure stations, including wafer steppers or projection aligners, printing the pattern of said masks on a workpiece, including a display panel or a semiconductor wafer, comprising the steps of

• providing a mask substrate,
• providing a pattern data file,
• providing a mask writer for writing said pattern onto said mask substrate,
• collecting information about at least one of the following:
• the mask substrate
• the mask writer, and
• the exposure station;
• predicting from said information distorsions that will occur in the pattern, when it is subsequently printed on the workpiece
• calculating from said prediction a correction map to diminish said predicted distorsion, and
• exposing said pattern onto said mask substrate while applying said correction map for said distorsions;
• wherein said information about the mask writer includes information relating to at least one of a mask blank clamping structure, a mask writer exposure, a mask writer process and a mask writer pellicalizing;
• wherein said information about the mask writer further includes information about at least one error source selected from a group of error sources including:
• gravity and bending errors from mask blank clamping, non-uniformity errors in the mask blank exposure, time effect errors in the mask blank exposure, stage errors in the mask blank exposure, beam and grid effect errors in the mask blank exposure, stray exposure errors, non-uniformity errors in the mask writer process, complete relief of resist stress errors, partial relief of chrome stress errors and bending errors from pellicle mount,
• wherein the collected information comprises information relating to the properties of the resist on the mask substrate, and
• wherein the information relating to the properties of the resist on the mask substrate comprises information relating to resist thickness, resist softbake variations, built-in thickness, and stress in the resist.

A method for predicting and correcting geometrical errors in lithography using masks, including large-area photomasks or reticles, and exposure stations, including wafer steppers or projection aligners, printing the pattern of said masks on a workpiece, including a display panel or a semiconductor wafer, comprising the steps of

• providing a mask substrate,
• providing a pattern data file,
• providing a mask writer for writing said pattern onto said mask substrate,
• collecting information about at least one of the following:
• the mask substrate
• the mask writer, and
• the exposure station;
• predicting from said information distorsions that will occur in the pattern, when it is subsequently printed on the workpiece
• calculating from said prediction a correction map to diminish said predicted distorsion, and
• exposing said pattern onto said mask substrate while applying said correction map for said distorsions;
• wherein said information about the mask writer includes information relating to at least one of a mask blank clamping structure, a mask writer exposure;
• a mask writer process and a mask writer pellicalizing;
• wherein said information about the mask writer further includes information about at least one error source selected from a group of error sources including:
• gravity and bending errors from mask blank clamping, non-uniformity errors in the mask blank exposure, time effect errors in the mask blank exposure, stage errors in the mask blank exposure, beam and grid effect errors in the mask blank exposure, stray exposure errors, non-uniformity errors in the mask writer process, complete relief of resist stress errors, partial relief of chrome stress errors and bending errors from pellicle mount,
• wherein the method further comprises providing a mathematical model of the mask substrate, including a finite element model, whereby the prediction of the distortions occurring in the pattern as well as the calculation of the correction is done by means of the mathematical model;
• and
• wherein said mask writer and/or said exposure station comprises a clamping structure for holding said mask substrate and/or workpiece, said information about the mask writer comprises information about geometrical properties about said clamping structure and whereby said mathematical model used in the prediction step combines said collected information with the geometrical properties of the clamping structure.

A method for predicting and correcting geometrical errors in lithography using masks, including large-area photomasks or reticles, and exposure stations, including wafer steppers or projection aligners, printing the pattern of said masks on a workpiece, including a display panel or a semiconductor wafer, comprising the steps of

• providing a mask substrate,
• providing a pattern data file,
• providing a mask writer for writing said pattern onto said mask substrate,
• collecting information about at least one of the following:
• information about the mask substrate
• information about the mask writer, and
• information about the exposure station;
• predicting from said information distorsions that will occur in the pattern, when it is subsequently printed on the workpiece
• calculating from said prediction a correction map to diminish said predicted distorsion, and
• exposing said pattern onto said mask substrate while applying said correction map for said distorsions;
• wherein said information about the mask writer includes information relating to at least one of a mask blank clamping structure, a mask writer exposure, a mask writer process and a mask writer pellicalizing;
• wherein said information about the mask writer further includes information about at least one error source selected from a group of error sources including:
• gravity and bending errors from mask blank clamping, non-uniformity errors in the mask blank exposure, time effect errors in the mask blank exposure, stage errors in the mask blank exposure, beam and grid effect errors in the mask blank exposure, stray exposure errors, non-uniformity errors in the mask writer process, complete relief of resist stress errors, partial relief of chrome stress errors and bending errors from pellicle mount,
• wherein at least a first lithographic machine is arranged to print a pattern on said mask substrate thereby producing a mask, and at least a second lithographic machine is arranged to print a pattern on said workpiece, using said mask,
• said at least first lithographic machine comprises a first clamping structure for holding said mask substrate,
• said at least second lithographic machine comprises at least a second clamping structure for holding said mask,
• wherein at least one of said clamping structures being kinematically overdetermined, comprising the additional steps of:
• providing a numerical computer model describing the geometry of said workpiece;
• further characterizing and providing data for said over-determined clamping structure and,
• using the model for said workpiece and the data for said clamping structure to compute the distortion of the pattern due to different clamping in said lithographic machines.

A pattern correction system for predicting and correcting geometrical errors in lithography using masks, including large-area photomasks or reticles, and exposure stations, including wafer steppers or projection aligners, printing the pattern of said masks on a workpiece, including a display panel or a semiconductor wafer, comprising:

• communication and storage means for retrieving and storing geometrical information about the mask writer or the mask writer and any of the mask substrate and exposure station;
• a computing unit for predicting an error map arising from the combined geometrical information using a mathematical model;
• wherein said information about the mask writer includes information relating to at least one of a mask blank clamping structure, a mask writer exposure, a mask writer process and a mask writer pellicalizing;
• wherein said geometrical information further includes information about at least one error source selected from a group of error sources including:
• gravity and bending errors from mask blank clamping, non-uniformity errors in the mask blank exposure, time effect errors in the mask blank exposure, stage errors in the mask blank exposure, beam and grid effect errors in the mask blank exposure, stray exposure errors, non-uniformity errors in the mask writer process, complete relief of resist stress errors, partial relief of chrome stress errors and bending errors from pellicle mount.

A control system for predicting and correcting placement and size errors in lithography using masks, including large-area photomasks or reticles, and exposure stations, including wafer steppers or projection aligners, printing the pattern of said masks on a workpiece, including a display panel or a semiconductor wafer, comprising:

• first computing means, and
• second computing means being connected to information-gathering means for gathering information about the mask writer or the mask writer and any of the mask substrate and exposure station;
• where said second computing means comprises a storage means for storing said information,
• means for transferring said information from said second computing means to said first computing means,
• where said first computing means comprises a mathematical error prediction model to generate an error correction map using said information, the correction being intended for controlling the mask making process;
• wherein said gathered information about the mask writer includes information relating to at least one of a mask blank clamping structure, a mask writer exposure, a mask writer process and a mask writer pellicalizing;
• wherein said information further includes information about at least one error source selected from a group of error sources including:
• gravity and bending errors from mask blank clamping, non-uniformity errors in the mask blank exposure, time effect errors in the mask blank exposure, stage errors in the mask blank exposure, beam and grid effect errors in the mask blank exposure, stray exposure errors, non-uniformity errors in the mask writer process, complete relief of resist stress errors, partial relief of chrome stress errors and bending errors from pellicle mount.