Model optimization for structures with additional materials

A method of modeling wafer structure profile, the method comprising:

• a) determining one or more termination criteria;
• b) determining whether the wafer structure includes a layer having three or more materials along a line with the layer;
• c) creating an optical metrology model, wherein three or more materials are incorporated in the model for the layer having three or more materials;
• d) obtaining a set of diffraction signals converted from a set of diffraction beams measured off of the wafer;
• e) simulating a set of diffraction signals using the optical metrology model;
• f) determining if the one or mom termination criteria are met by using the set of simulated diffraction signals and the set of diffraction signals converted from the set of diffraction beams measured off of the wafer;
• and
• g) if the one or more termination criteria are not met:
• modifying the optical metrology model;
• and
• iterating steps e) and f) until the one or more termination criteria are met;
• and
• h) creating a library comprising diffraction signal and profile pairs according to data generated from the optical metrology model.

A computer-readable storage medium containing computer executable code to create an optical metrology model for a wafer structure by instruction the computer to operate as follows:

• a) determining one or more termination criteria;
• b) determining whether the wafer structure includes at least one layer having three or more materials along a line within the at least one layer;
• c) creating an optical metrology model, wherein three or more materials are incorporated in the model for the at least one layer having three or more material;
• d) obtaining a set of diffraction signals converted from a set of diffraction beams measured off of the wafer;
• e) simulating a set of diffraction signals using the optical metrology model;
• f) determining if the one or more termination criteria are met by using the set of simulated diffraction signals and ate set of diffraction signals converted from the set of diffraction beams measured off of the wafer;
• and
• g) if the one or more termination criteria are not met:
• modifying the optical metrology model;
• and
• iterating steps e) and f) until the one or more termination criteria are met.

A system for creating an optical metrology model for a wafer structure, the system comprising:

• an input device configured to transmit a set of wafer composition data;
• a profile model generator configured to received the set of wafer composition data from the input device and generate a profile model of the wafer structure, wherein the profile model incorporates to presence of additional materials for a wafer comprising at least one layer having three or more materials along a line within the at least one layer;
• an optical metrology model generator coupled to the profile model generator, wherein the optical metrology model is configured to receive the profile model from the profile model generator and generate an optical metrology model according to the profile model and a set of model output data;
• a diffraction signal simulator coupled to the optical metrology model generator, wherein the diffraction signal simulator is configured to generate a set of simulated diffraction signal;
• an optical metrology device configured to measure a set of diffraction beams off the wafer structure and convert the diffraction beams into a set of diffraction signals;
• and
• a termination criteria checker coupled to the input device, the diffraction signal simulator, and the optical metrology device, wherein to termination criteria checker is configured to receive the one or more termination criteria from the input device, the set of simulated diffraction signals from the diffraction signal simulator, and the set of diffraction signals converted from the set of diffraction beams measured off the wafer structure from the optical metrology device, and wherein the termination criteria checker is configured to determine if the one or more termination criteria are met using the set of simulated diffraction signals and the set of diffraction signals measured off of the wafer.

A system for generating a diffraction signal and profile pairs library by creating an optical metrology model, the system comprising:

• an input device configured to transmit a set of wafer composition data;
• a profile model generator configured to received the set of wafer composition data from the input device and generate a profile model of the wafer structure, wherein the profile model incorporates the presence of additional materials for a layer of the wafer structure having three or materials along a line in the layer;
• an optical metrology model generator coupled to the profile model generator, wherein the optical metrology model is configured to receive the profile model from the profile model generator, generate an optical metrology model according to the profile model;
• a diffraction signal simulator coupled, to the optical metrology model generator, wherein the diffraction signal simulator is configured to generate a set of simulated diffraction signals;
• and
• a library generator coupled to the optical metrology generator, the library generator configured to generate a library of diffraction signal and profile pairs;
• an optical metrology device configured to measure a set of diffraction beams off the wafer structure and convert the set of diffraction beams into a set of diffraction signals;
• and
• a termination criteria checker coupled to the input device, the diffraction signal simulator, and the optical metrology device, wherein the termination criteria checker is configured to receive the one or more termination criteria from the input device, the set of simulated diffraction signals from the diffraction signal simulator, and the set of diffraction signals converted from the set of diffraction beams measured off the wafer structure from the optical metrology device, and wherein the termination criteria checker is configured to determine if the one or more termination criteria are met using the set of simulated diffraction signals and the set of diffraction signals measured off of the wafer.

A system for monitoring and correcting a lithographic process, the system comprising:

• an optical metrology device configured to measure diffraction beams off a wafer structure and convert them to diffraction signals;
• an optical metrology model generator configured to generate an optical metrology model;
• a diffraction signal simulator coupled to the optical metrology model generator, wherein the diffraction signal simulator is configured to generate a set of simulated diffraction signals;
• a termination criteria checker coupled to the diffraction signal simulator and the optical metrology device, and wherein the termination criteria checker is configured to determine if one or more termination criteria are met using the set of simulated diffraction signals and the set of diffraction signals converted from the set of diffraction beams measured off of the wafer;
• and
• a profile application server coupled to the optical metrology device, wherein the profile application server further comprises:
• a diffraction signal and profile pairs library, the library created with an optical metrology model, wherein the optical metrology model is created by incorporating additional materials for wafer structures having at least one layer with three or more materials along a line with the at least one layer.