Pattern-dependent proximity matching/tuning including light manipulation by projection optics

• US 8,560,978 B2
• Filed: 11/09/2011
• Issued: 10/15/2013
• Est. Priority Date: 11/10/2010
• 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
• Primary Examiner(s): Kik, Phallaka
• Application Number:
  US13/293,113
• Publication Number:
  US 20120117521A1
• Time in Patent Office: 706 Days
• Field of Search: 716/52, 716/53, 716/54, 716/55, 716/56, 700/98, 700/110, 700/120, 700/121, 430/5, 378/35
• US Class Current: 716/52
• CPC Class Codes: G03F 1/20 Masks or mask blanks for imaging by charged particle beam [CPB] radiation, e.g. by electron beam; Preparation thereof
• CPC Class Codes: G03F 1/24 Reflection masks; Preparation thereof
• CPC Class Codes: G03F 1/26 Phase shift masks [PSM]; PSM blanks; Preparation thereof
• 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 1/38 Masks having auxiliary features, e.g. special coatings or marks for alignment or testing; Preparation thereof
• CPC Class Codes: G03F 1/50 Mask blanks not covered by G03F1/20 - G03F1/34; Preparation thereof
• CPC Class Codes: G03F 1/72 Repair or correction of mask defects
• CPC Class Codes: G03F 1/88 prepared by photographic processes for production of originals simulating relief
• CPC Class Codes: G03F 7/70141 Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system
• CPC Class Codes: G03F 7/70258 Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system
• CPC Class Codes: G03F 7/70525 Controlling normal operating mode, e.g. matching different apparatus, remote control or prediction of failure
• CPC Class Codes: G06F 17/10 Complex mathematical operations function generation by table look-up G06F1/03; evaluation of elementary functions by calculation G06F7/544
• CPC Class Codes: G06F 2119/18 Manufacturability analysis or optimisation for manufacturability
• CPC Class Codes: G06F 30/20 Design optimisation, verification or simulation optimisation, verification or simulation of circuit designs G06F30/30
• CPC Class Codes: G06F 30/333 Design for testability [DFT], e.g. scan chain or built-in self-test [BIST]
• 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
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass
• CPC Class Codes: G21K 5/00 Irradiation devices discharge tubes for irradiating H01J37/00
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

Described herein are methods for matching the characteristics of a lithographic projection apparatus to a reference lithographic projection apparatus, where the matching includes optimizing projection optics characteristics. The projection optics can be used to shape wavefront in the lithographic projection apparatus. According to the embodiments herein, the methods can be accelerated by using linear fitting algorithm or using Taylor series expansion using partial derivatives of transmission cross coefficients (TCCs).

Claims

1. A computer-implemented method for tuning a lithographic process to a reference lithographic process, the lithographic process being configured for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus comprising an illumination source and projection optics, the method comprising:

defining a multi-variable cost function of a plurality of design variables that represent characteristics of the lithographic process, wherein the cost function represents a difference in lithographic response between the lithographic process and the reference lithographic process and wherein at least some of the design variables comprise characteristics of the projection optics; and

reconfiguring, using a computer, the characteristics of the lithographic process by adjusting the design variables until a predefined termination condition is satisfied.

2. The method of claim 1, wherein the reference lithographic process represents one of the following:

a lithographic response of a reference lithographic projection apparatus;

a desired lithographic response of a virtual reference lithographic projection apparatus;

a lithographic response as measured from the portion of the design layout imaged on a reference substrate; and

a lithographic response from a lithographic projection apparatus that is physically and/or characteristically different from the lithographic projection apparatus being used to tune the lithographic process.

3. The method of claim 1, wherein the portion of the design layout comprises one or more of the following:

an entire design layout, a clip, a section of a design layout that is known to have one or more critical features, a section of the design layout where a hot spot or a warm spot has been identified from a full-chip simulation, and a section of the design layout where one or more critical features have been identified by a pattern selection method.

4. The method of claim 1, wherein the predefined termination condition includes one or more of:

minimization of the cost function;

maximization of the cost function;

reaching a preset number of iterations;

reaching a value of the cost function equal to or beyond a preset threshold value;

reaching a predefined computation time; and

, reaching a value of the cost function within an acceptable error limit.

5. The method of claim 1, wherein the method further comprises:

using values of the design variables to update the lithographic process when the predetermined termination condition is satisfied;

comparing the updated lithographic process with the reference lithographic process; and

repeating the updating step and the comparing step until an additional termination condition is satisfied.

6. The method of claim 5, wherein the additional termination condition indicates an acceptable matching between the characteristics of the lithographic process and the reference lithographic process.

7. The method of claim 1, wherein one or more of the design variables are characteristics of the illumination source.

8. The method of claim 1, wherein the reconfiguration step is performed without constraints or with constraints dictating a range of at least some of the design variables.

9. The method of claim 8, wherein at least some of the design variables are under constraints representing physical restrictions in a hardware implementation of the lithographic projection apparatus.

10. The method of claim 9, wherein the constraints include one or more of:

tuning ranges, rules governing mask manufacturability, and interdependence between the design variables.

11. The method of claim 1, wherein the cost function is a function of a difference of one or more of the following lithographic metrics:

edge placement error, critical dimension, resist contour distance, worst defect size, and best focus shift.

12. The method of claim 1, wherein the method comprises, prior to performing the steps of the optimization process, selecting a subset of target patterns that characteristically represents features of the portion of the design layout.

13. The method of claim 12, wherein identified hot spots or warm spots are converted into test patterns and are included in the subset of test patterns that are used for a current optimization process.

14. The method of claim 1, wherein optimization of various design variables are performed simultaneously until the predefined termination condition is satisfied.

15. The method of claim 1, wherein optimization of various design variables are performed alternatively, keeping at least some of the design variables fixed while the other design variables are optimized, and

repeating the alternative optimization process until the predefined termination condition is satisfied.

16. The method of claim 1, wherein the optimization process includes iteratively minimizing the cost function by calculating linear fitting coefficients within predefined relatively small neighborhoods around a starting point in each iteration.

17. The method of claim 1, wherein the cost function is minimized by solving polynomials, including higher-order polynomials of the design variables.

18. The method of claim 17, wherein the cost function is expanded in terms of fitting constant coefficients.

19. The method of claim 18, wherein the fitting constant coefficients are computed from coefficients from polynomial expansion of transmission cross coefficients (TCCs).

20. A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions when executed by a computer implementing the method of claim 1.