METHOD AND DEVICE FOR GENERATING A REFERENCE IMAGE IN THE CHARACTERIZATION OF A MASK FOR MICROLITHOGRAPHY

• US 20180129131A1
• Filed: 11/09/2017
• Published: 05/10/2018
• Est. Priority Date: 11/09/2016
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Schmidt, Carsten, Himmelhaus, Michael
• Granted Patent: US 10,429,731 B2
• Time in Patent Office: Days
• CPC Class Codes: G03F 1/70 Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G06F 2111/06 Multi-objective optimisation, e.g. Pareto optimisation using simulated annealing [SA], ant colony algorithms or genetic algorithms [GA]
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]
• CPC Class Codes: G06F 30/398 Design verification or optimisation, e.g. using design rule check [DRC], layout versus schematics [LVS] or finite element methods [FEM] optical proximity correction [OPC] design processes G03F1/36

Abstract

The invention relates to a method and a device for generating a reference image in the characterization of a mask for microlithography, wherein the mask comprises a plurality of structures and wherein the reference image is generated by simulation of the imaging of said mask, said imaging being effected by a given optical system, both using a rigorous simulation and using a Kirchhoff simulation, wherein the method comprises the following steps: assigning each structure of said plurality of structures either to a first category or to a second category, calculating a plurality of first partial spectra for structures of the first category with implementation of rigorous simulations, calculating a second partial spectrum for structures of the second category with implementation of a Kirchhoff simulation, generating a hybrid spectrum on the basis of the first partial spectra and the second partial spectrum, and generating the reference image with implementation of an optical forward propagation of said hybrid spectrum in the optical system.

Claims

1. A method for generating a reference image in the characterization of a mask for microlithography, wherein the mask comprises a plurality of structures and wherein the reference image is generated by simulation of the imaging of said mask, said imaging being effected by a given optical system, both using a rigorous simulation and using a Kirchhoff simulation, wherein the method comprises the following steps:

a) assigning each structure of said plurality of structures either to a first category or to a second category;

b) calculating, using one or more data processors, a plurality of first partial spectra for structures of the first category with implementation of rigorous simulations;

c) calculating, using the one or more data processors, a second partial spectrum for structures of the second category with implementation of a Kirchhoff simulation;

d) generating, using the one or more data processors, a hybrid spectrum on the basis of the first partial spectra and the second partial spectrum; and

e) generating, using the one or more data processors, the reference image with implementation of an optical forward propagation of said hybrid spectrum in the optical system.

2. The method according to claim 1, in which the structures assigned to the first category in step a) comprise auxiliary structures having a structure size below the resolution limit of the optical system.

3. The method according to claim 2, in which the structures assigned to the second category in step a) comprise used structures that are intended for imaging onto a wafer in a microlithographic exposure process.

4. The method according to claim 2, in which partial spectra calculated for structures of the first category with implementation of rigorous simulations are retrieved from a database generated beforehand.

5. The method according to claim 2, in which step e) of generating the reference image is carried out repeatedly in an iterative process, wherein mask parameters, system parameters of the optical system and/or illumination parameters taken as a basis for the simulation are varied during this iteration.

6. The method according to claim 2, in which before generating a hybrid spectrum on the basis of the first partial spectra and the second partial spectrum in step d) the spectral resolution of the first partial spectra is increased.

7. The method according to claim 1, in which the structures assigned to the second category in step a) comprise used structures that are intended for imaging onto a wafer in a microlithographic exposure process.

8. The method according to claim 1, in which partial spectra calculated for structures of the first category with implementation of rigorous simulations are retrieved from a database generated beforehand.

9. The method according to claim 1, in which step e) of generating the reference image is carried out repeatedly in an iterative process, wherein mask parameters, system parameters of the optical system and/or illumination parameters taken as a basis for the simulation are varied during this iteration.

10. The method according to claim 9, in which during said iteration the mask properties to be determined in the characterization of the mask, in particular possible defect positions, remain excluded from a variation.

11. The method according to claim 1, in which before generating a hybrid spectrum on the basis of the first partial spectra and the second partial spectrum in step d) the spectral resolution of the first partial spectra is increased.

12. A device for generating a reference image in the characterization of the mask for microlithography, in which the device is configured to implement a process for generating the reference image, wherein the mask comprises a plurality of structures and wherein the reference image is generated by simulation of the imaging of said mask, said imaging being effected by a given optical system, both using a rigorous simulation and using a Kirchhoff simulation, wherein the process includes:

a) assigning each structure of said plurality of structures either to a first category or to a second category;

b) calculating, using one or more data processors, a plurality of first partial spectra for structures of the first category with implementation of rigorous simulations;

c) calculating, using the one or more data processors, a second partial spectrum for structures of the second category with implementation of a Kirchhoff simulation;

d) generating, using the one or more data processors, a hybrid spectrum on the basis of the first partial spectra and the second partial spectrum; and

e) generating, using the one or more data processors, the reference image with implementation of an optical forward propagation of said hybrid spectrum in the optical system.

13. The device of claim 12 in which the structures assigned to the first category in step a) comprise auxiliary structures having a structure size below the resolution limit of the optical system.

14. The device of claim 13 in which the structures assigned to the second category in step a) comprise used structures that are intended for imaging onto a wafer in a microlithographic exposure process.

15. The device of claim 13 in which partial spectra calculated for structures of the first category with implementation of rigorous simulations are retrieved from a database generated beforehand.

16. The device of claim 12 in which the structures assigned to the second category in step a) comprise used structures that are intended for imaging onto a wafer in a microlithographic exposure process.

17. The device of claim 12, comprising a database that stores partial spectra calculated for structures of the first category with implementation of rigorous simulations.

18. The device of claim 12 in which the device is configured to carry out step e) of generating the reference image repeatedly in an iterative process, wherein mask parameters, system parameters of the optical system and/or illumination parameters taken as a basis for the simulation are varied during this iteration.

19. The device of claim 18 in which during said iteration the mask properties to be determined in the characterization of the mask, including possible defect positions, remain excluded from a variation.

20. The device of claim 12 in which before generating a hybrid spectrum on the basis of the first partial spectra and the second partial spectrum in step d) the spectral resolution of the first partial spectra is increased.