METHOD AND APPARATUS FOR CORRECTING ERRORS OF A PHOTOLITHOGRAPHIC MASK

• US 20120009511A1
• Filed: 07/11/2011
• Published: 01/12/2012
• Est. Priority Date: 07/12/2010
• Status: Active Grant

• Current Assignee: Carl Zeiss SMS Ltd. (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss SMS Ltd. (Carl-Zeiss-Stiftung)
• Inventors: Dmitriev, Vladimir
• Granted Patent: US 9,658,527 B2
• Time in Patent Office: Days
• US Class Current: 430/5
• CPC Class Codes: G03F 1/72 Repair or correction of mask defects
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G03F 7/70466 Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature stitching G03F7/70475
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness

Abstract

A method for correcting a plurality of errors of a photolithographic mask, comprising optimizing first parameters of a imaging transformation of the photolithographic mask and second parameters of a laser beam locally directed onto the photolithographic mask, and correcting the plurality of errors by applying an imaging transformation using optimized first parameters and locally directing the laser beam onto the photolithographic mask using optimized second parameters, wherein the first and the second parameters are simultaneously optimized in a joint optimization process.

Claims

1. A method for correcting a plurality of errors of a photolithographic mask;

the method comprising;

a. optimizing first parameters of an imaging transformation of the photolithographic mask and second parameters of a laser beam locally directed onto the photolithographic mask; and

b. correcting the plurality of errors by applying an imaging transformation using optimized first parameters and locally directing the laser beam onto the photolithographic mask using optimized second parameters;

c. wherein the first and the second parameters are simultaneously optimized in a joint optimization process.

2. The method according to claim 1, wherein the joint optimization process comprises:

a. setting up a target functional comprising error data, first imaging transformation parameters and second laser beam parameters; and

b. minimizing the target functional by simultaneously varying the first imaging transformation parameters and the second laser beam parameters.

3. The method according to claim 2, wherein a Lagrange variational principle is used to setup the target functional and/or the target functional minimizes a potential energy distribution introduced into the photolithographic mask by the first and the second parameters.

4. The method according to claim 1, wherein the imaging transformation comprises a linear imaging transformation and the linear imaging transformation comprises two parameters for a photolithographic mask shift, two parameters for a photolithographic mask scaling and two parameters for a generalized rotation of the photolithographic mask.

5. The method according to claim 1, wherein the second laser beam parameters comprise at least one of an energy of the laser beam, a numerical aperture, a focus size, a beam polarization, an astigmatism, a pulse length, a repetition rate, a number of pulses directed onto one location of the photolithographic mask, or a distance between two locations the laser beam is directed onto the photolithographic mask.

6. The method according to claim 1, wherein the laser beam locally modifies at least one of a density or an optical transmission distribution of the photolithographic mask, and/or wherein at least one of the locally modified density or the optical transmission of the photolithographic mask is discontinuously modified within a plurality of small volumes of the photolithographic mask, wherein each small volume is called a pixel.

7. The method according to claim 2, wherein the target functional is minimized as a mean square of residual displacements using a Tikhonov regularization.

8. The method according to claim 2, wherein the target functional comprises at least one weighting function as a constraint in at least one of an active area or a non-active area of the photolithographic mask, and/or wherein the weighting function is constructed to simultaneously correct registration errors and flatness errors of the plurality of errors.

9. The method according to claim 1, wherein the plurality of errors comprises different types of the plurality of errors and/or wherein the different types of the plurality of errors comprise at least one of registration errors, optical transmission errors, or planarity errors.

10. The method according to claim 1, wherein errors not corrected and/or introduced when locally directing the laser beam onto the substrate of the photolithographic mask generating pixels in a first layer of the substrate of the photolithographic mask for correcting the plurality of errors are corrected by again directing the laser beam onto the substrate of the photolithographic mask and generating pixels in a second layer of the substrate of the photolithographic mask.

11. The method according to claim 1, wherein at least one of the laser beam or the photolithographic mask is rotated by an angle parallel to the laser beam for a portion of a time period the laser beam is directed onto the photolithographic mask.

12. The method according to claim 1, wherein directing the laser beam onto the photolithographic mask does not introduce a variation of an optical transmission distribution for a laser beam at the exposure wavelength of the photolithographic mask.

13. The method according to claim 1, wherein directing the laser beam onto the photolithographic mask additionally introduces a predetermined variation of the optical transmission distribution across the photolithographic mask for the laser beam at the exposure wavelength of the photolithographic mask.

14. The method according to claim 1, further comprising directing the laser beam on the photolithographic mask in order to correct errors newly introduced in the photolithographic mask by correcting optical transmission distribution errors in the active area of the photolithographic mask.

15. The method according to claim 1, wherein directing the laser beam on the photolithographic mask comprises at least two sets of second laser beam parameters so that correcting of optical transmission distribution errors across the photolithographic mask does not introduce registration errors into the photolithographic mask.

16. The method according to claim 1, wherein the second parameters of the laser beam comprise a pulse energy ranging from 0.05 μ

J to 5 μ

J, a pulse length ranging from 0.05 ps to 100 ps, a repetition rate ranging from 1 kHz to 10 MHz, a pulse density ranging from 1,000 pulses per mm² to 10,000,000 pulses per mm², the NA of an objective ranging from 0.1 to 0.9 and the magnification of the objective ranging from 5×

to 40×

.

17. The method according to claim 21, wherein the first set of second laser beam parameters comprises a pulse energy of 0.45 μ

J-0.55 μ

J, pulse duration of 5-10 ps, a repetition rate of 10 kHz-100 kHz, the NA of the objective of 0.2 -0.4, a magnification of the objective of 10×

-20× and

a pulse density of 1,000-100,000 pulses per mm², and the second set of the second laser beam parameters comprises a pulse energy of 0.27 μ

J-0.37 μ

J and a pulse density of 5,000-500,000 pulses per mm².

18. The method according to claim 1, wherein directing the laser beam on the photolithographic mask using optimized second parameters comprises directing the laser beam on the photolithographic mask using at least three sets of second laser beam parameters, a first set and a second set for directing the laser beam onto the active area having different pulse energies and a third set for directing the laser beam onto the non-active area of the photolithographic mask.

19. The method according to claim 2, wherein the target functional is used in order to minimize an overlay error between at least one first photolithographic mask and at least one second photolithographic mask.

21. The method of claim 1, wherein directing the laser beam comprises directing the laser beam with a first set of second laser beam parameters onto an active area of the photolithographic mask and with a second set of second laser beam parameters onto a non-active area of the photolithographic mask.

20. An apparatus for correcting a plurality of errors of a photolithographic mask, comprising:

a. at least one computing means operable for simultaneously optimizing first parameters of an imaging transformation of the photolithographic mask and second parameters of a laser beam locally directed onto the photolithographic mask;

b. at least one laser source for generating the laser beam of light pulses according to optimized second laser beam parameters; and

c. at least one scanning means for performing an imaging transformation according to optimized first imaging parameters.