METHODS AND SYSTEM FOR LITHOGRAPHY CALIBRATION

• US 20100119961A1
• Filed: 11/05/2009
• Published: 05/13/2010
• Est. Priority Date: 11/06/2008
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Feng, Hanying, Cao, Yu, YE, Jun
• Granted Patent: US 8,418,088 B2
• Time in Patent Office: Days
• US Class Current: 430/30
• CPC Class Codes: G03F 1/36 Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
• CPC Class Codes: G03F 1/68 Preparation processes not covered by groups G03F1/20 - G03F1/50
• CPC Class Codes: G03F 7/70433 Layout for increasing efficiency or for compensating imaging errors, e.g. layout of exposure fields for reducing focus errors; Use of mask features for increasing efficiency or for compensating imaging errors
• 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: G03F 7/70516 Calibration of components of the microlithographic apparatus, e.g. light sources, addressable masks or detectors
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]

Abstract

A method of efficient optical and resist parameters calibration based on simulating imaging performance of a lithographic process utilized to image a target design having a plurality of features. The method includes the steps of determining a function for generating a simulated image, where the function accounts for process variations associated with the lithographic process; and generating the simulated image utilizing the function, where the simulated image represents the imaging result of the target design for the lithographic process. Systems and methods for calibration of lithographic processes whereby a polynomial fit is calculated for a nominal configuration of the optical system and which can be used to estimate critical dimensions for other configurations.

Claims

1. A method of calibrating a photolithographic system, comprising:

obtaining a plurality of measured dimensions of circuit patterns generated using a configuration of a photolithographic process;

generating a plurality of estimated dimensions of the circuit patterns using a model of the configuration of the photolithographic process;

for certain of the circuit patterns, calculating a polynomial fit between the estimated dimensions and predefined parameters related to the configuration; and

calibrating the photolithographic process based on the polynomial fit, wherein calibrating the photolithographic process includes the step of minimizing differences between the estimated and measured dimensions using an optimization algorithm.

2. The method of claim 1, wherein the estimated and measured dimensions include dimensions defining contour shapes of the circuit patterns.

3. The method of claim 1, wherein the step of minimizing differences includes minimizing the sum of squared differences between the estimated and measured dimensions.

4. The method of claim 1, wherein certain of the estimated and measured dimensions relate to critical dimensions of the circuit patterns.

5. The method of claim 4, wherein calibrating the photolithographic process includes determining a linear relationship between at least one optical parameter and one or more estimated critical dimensions.

6. The method of claim 4, wherein calibrating the photolithographic process includes determining a linear relationship between at least one optical parameter and the plurality of estimated dimensions and a second or higher order relationship between at least one optical parameter and one or more estimated critical dimensions.

7. The method of claim 1, wherein calibrating the photolithographic process includes computing the estimated dimensions using a fitted polynomial of selected parameters.

8. The method of claim 7, wherein calculating the polynomial fit of selected parameters further includes using differential transmission cross coefficients.

9. The method of claim 1, wherein calculating the polynomial fit includes performing a least square approximation for each one of the plurality of estimated dimensions using polynomials of a further plurality of model parameters.

10. A computer readable medium bearing a computer program for calibrating a photolithographic system, the computer program, when executed, causing a computer to perform the method of claim 1.

11. A device manufacturing method comprising the steps of:

(a) providing a substrate that is at least partially covered by a layer of radiation-sensitive material;

(b) providing a projection beam of radiation using an imaging system and generating a mask utilized to endow the projection beam with a pattern in its cross-section;

(c) projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material, wherein, generating in step (b) comprises

obtaining a plurality of measured dimensions of circuit patterns generated using a configuration of a photolithographic process;

generating a plurality of estimated dimensions of the circuit patterns using a model of the configuration of the photolithographic process;

for certain of the circuit patterns, calculating a polynomial fit between the estimated dimensions and predefined parameters related to the configuration; and

calibrating the photolithographic process based on the polynomial fit, wherein calibrating the photolithographic process includes the step of minimizing differences between the estimated and measured dimensions using an optimizing algorithm.

12. A calibration method, comprising:

generating a model for a lithographic process, the model comprising a polynomial series expansion around a nominal value of a physical parameter of the lithographic process; and

fitting the model to measured dimensions of imaging results obtained by applying the lithographic process at a plurality of values of the physical parameter by optimizing at least one polynomial expansion coefficient.

13. The calibration method of claim 12, further comprising optimizing at least two polynomial expansion coefficients.

14. The calibration method according to claim 12, further comprising using weight factors for different values of the physical parameter.

15. The calibration method according to claim 12, further comprising generating differential transmission cross coefficients in a part of the model corresponding to an imaging process.

16. The calibration method according to claim 12, further comprising performing a further polynomial series expansion around a further nominal value of a further physical parameter of the lithographic process, and wherein the imaging results are obtained at a plurality of values of the further physical parameter and wherein fitting the model comprises optimizing at least one further polynomial expansion coefficient corresponding to the further polynomial series expansion.

17. The calibration method according to claim 16, comprising using weight factors for combinations of different values of the physical parameter and the further physical parameter.

18. The calibration method according to claim 12, further comprising:

determining a variation of a metric with variation of the parameter around the value of the nominal parameter using the model;

repeating the generating and fitting steps at a different value of the nominal parameter;

determining a further variation of a metric with variation of the parameter around the different value of the nominal parameter using the model; and

selecting a value for the physical parameter based on the variation of the value of the physical parameter and the further variation of the value of the physical parameter.