Scatterometric measurement of undercut multi-layer diffracting signatures

A method of making a simulated diffraction signal of an undercut multi-layer diffracting structure fabricated on a semiconductor substrate, the method comprising:

• specifying a first layer model structure;
• specifying at least one second layer model structure positioned on and extending beyond the first layer model structure in at least one dimension to define an undercut model pattern;
• and
• generating a simulated diffraction signal from the undercut model pattern of the diffracting structure.

A method of making a library of simulated diffraction signals of an undercut multi-layer diffracting structure fabricated on a semiconductor substrate for use in semiconductor metrology, the method comprising:

• specifying at least one first layer model structure with at least one second layer model structure positioned on the first layer model structure and extending beyond the first layer model structure in at least one dimension to define a first undercut model pattern of a diffracting structure;
• specifying at least one second undercut model pattern of a diffracting structure by varying at least one parameter associated with the first layer model structure or the second layer model structure;
• and
• generating simulated diffraction signals from members of the undercut model patterns of the multi-layer diffracting structure.

A method of making a library of simulated diffraction signals of an undercut multi-layer diffracting structure fabricated on a semiconductor substrate for use in semiconductor metrology, the method comprising:

• specifying at least one first layer model structure with at least one second layer model structure positioned thereon and extending beyond the first layer model structure in at least one dimension to define a first undercut model pattern of a diffracting structure;
• specifying at least one second undercut model pattern of a diffracting structure by varying at least one parameter associated with the first layer model structure or the second layer model structure;
• generating simulated diffraction signatures from members of the undercut model patterns of the multi-layer diffracting structure;
• obtaining a diffraction signature of the diffracting structure on a semiconductor substrate;
• and
• comparing the diffraction signature of the diffracting structure to the simulated diffraction signatures of members of the undercut multi-layer model patterns of the diffracting structure.

A method of determining at least one parameter associated with an undercut multi-layer diffracting structure fabricated on a semiconductor substrate, the method comprising:

• specifying at least one first layer model structure with at least one second layer model structure positioned thereon and extending beyond the first layer model structure in at least one dimension to define an undercut model pattern of a diffracting structure;
• generating a simulated diffraction signature from the undercut model pattern of the multi-layer diffracting structure;
• obtaining a diffraction signature of the diffracting structure on a semiconductor substrate;
• comparing the diffraction signature of the diffracting structure to the simulated diffraction signature of the undercut multi-layer model pattern of the diffracting structure;
• utilizing regression analysis to vary at least one parameter associated with the first layer model structure or the second layer model structure of the undercut multi-layer model pattern to obtain a best match model pattern.

A method of inferentially measuring at least one parameter associated with an undercut multi-layer diffracting structure fabricated on a semiconductor substrate by means of a radiation-based tool, the method comprising:

• specifying at least one first layer model structure with at least one second layer model structure positioned thereon and extending beyond the first layer model structure in at least one dimension to define a first undercut model pattern of a diffracting structure;
• specifying at least one second undercut model pattern of a diffracting structure by varying at least one parameter associated with the first layer model structure or the second layer model structure;
• generating simulated diffraction signatures from members of the undercut model patterns of the multi-layer diffracting structure;
• obtaining a diffraction signature of the multi-layer diffracting structure on a semiconductor substrate by means of a radiation-based tool;
• comparing the diffraction signature of the multi-layer diffracting structure to the simulated diffraction signatures of undercut multi-layer model patterns of the diffracting structure, and selecting a close match simulated diffraction signature;
• and
• deriving at least one parameter associated with the multi-layer diffracting structure by examination of the model pattern generating a close match simulated diffraction signature.