Lithographic system, device manufacturing method, setpoint data optimization method, and apparatus for producing optimized setpoint data

• US 20080143982A1
• Filed: 12/14/2006
• Published: 06/19/2008
• Est. Priority Date: 12/14/2006
• Status: Active Grant

• Current Assignee: ASML Holding NV, ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Holding NV, ASML Netherlands BV (ASML Holding NV)
• Inventors: Kastrup, Bernardo, Albright, Ronald P., Tinnemans, Patricius Aloysius Jacobus, Troost, Kars Zeger, Hintersteiner, Jason Douglas, Cebuhar, Wenceslao A.
• Granted Patent: US 8,259,285 B2
• Time in Patent Office: Days
• US Class Current: 355/53
• 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 7/70283 Mask effects on the imaging process
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70441 Optical proximity correction [OPC]
• 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 7/70558 Dose control, i.e. achievement of a desired dose
• CPC Class Codes: G03F 7/70791 Large workpieces, e.g. glass substrates for flat panel displays or solar panels

Abstract

An iterative method of producing optimized setpoint data for controlling the actuation of elements of an array of individually controllable elements in a maskless system and systems therefore. The optimization is based on estimation of a device structure that can utilizes one or more of the following factors: the low-pass characteristics of the projection system, the configuration of the illumination system, and the process window properties.

Claims

1. A method of producing optimized setpoint data for controlling actuation of elements of an array of individually controllable elements configured to modulate a radiation beam in a maskless lithography system, the maskless lithography system having an illumination system configured to condition the radiation beam and a projection system configured to project the modulated radiation beam onto a substrate, the method comprising:

a) obtaining starting setpoint data;

b) estimating the device structure that would result from applying the starting setpoint data to the array of individually controllable elements configured to modulate a radiation beam;

c) comparing the device structure estimated in step (b) with a target device structure to be formed on a substrate to determine a device structure error;

d) modifying the setpoint data and repeating steps (b) and (c) using the modified setpoint data instead of the starting setpoint data until the device structure error falls below a predetermined threshold; and

e) outputting the modified setpoint data for which the device structure error is below the predetermined threshold as the optimized setpoint data, whereby the array of individually controllable elements is actuated based on the modified setpoint data.

2. The method according to claim 1, wherein the estimating step (b) utilizes at least one of the following factors:

low-pass characteristics of the projection system, a configuration of the illumination system, and process window properties.

3. The method according to claim 1, wherein the starting setpoint data is obtained based on the target device structure.

4. The method according to claim 1, further comprising:

estimating the device structure expected to result from exposure of a substrate in a reference lithography device; and

using the device structure thus estimated as the target device structure.

5. The method according to claim 4, wherein the reference lithography device is a mask-based lithography device using a mask comprising optical proximity corrections.

6. The method according to claim 1, wherein step (b) comprises:

b1) estimating the radiation dose pattern that would be exposed onto the substrate as a result of applying the setpoint data to the array of individually controllable elements; and

b2) estimating the device structure that would result from a post-exposure processing of the substrate after exposure to the estimated radiation dose pattern.

7. The method according to claim 6, wherein step (b1) comprises:

using a mathematical model representing the performance of a reference array of individually controllable elements, the reference array being a mathematical construct of an idealized, error-free version of a particular design of array.

8. The method according to claim 7, wherein the mathematical model utilizes the following property of the reference array:

reflection from slits between elements, element reflectivity, polarization dependence, hinge effects, or specific angle of incidence of radiation on the reference array.

9. The method according to claim 8, wherein the mathematical model is based on calculating an at least approximate solution to Maxwell'"'"'s equations for the diffraction behavior of the reference array.

10. The method according to claim 6, wherein step (b1) comprises:

using a mathematical model representing performance of a particular instance of an array of individually controllable elements, the mathematical model utilizes deviations from the reference array due to imperfections in the particular instance.

11. The method according to claim 10, wherein the mathematical model utilizes:

element height variations, non-responsive elements, elements with limited active range, variations in element surfaces, variations in array shape, variations in element reflectivity, sharpness of the phase step, or particular dielectric properties of the material of which the element is made.

12. The method according to claim 6, wherein step (b1) comprises:

using a mathematical model representing performance of a reference projection system, the reference projection system being a mathematical construct of an idealized, error-free version of a particular design of projection system.

13. The method according to claim 12, wherein step (b1) comprises:

using a mathematical model representing the performance of a particular instance of a projection system, the mathematical model utilizes deviations from the reference projection system due to imperfections in the particular instance.

14. The method according to claim 6, wherein step (b1) comprises:

using a mathematical model representing performance of a reference illumination system, the reference illumination system being a mathematical construct of an idealized, error-free version of a particular design of illumination system.

15. The method according to claim 14, wherein step (b1) comprises:

using a mathematical model representing the performance of a particular instance of an illumination system, the mathematical model utilizes account deviations from the reference illumination system due to imperfections in the particular instance.

16. The method according to claim 6, wherein step (b2) comprises using a mathematical model of the post-exposure processing.

17. The method according to claim 16, wherein the mathematical model represents a relationship between the radiation dose pattern exposed onto the substrate and a device structure that is expected to emerge after the post-exposure processing.

18. The method according to claim 17, wherein the mathematical model utilizes the effects of post exposure bake, resist acid diffusion, development, hardbake, deposit, implant, immersion, or etching.

19. The method according to claim 1, wherein the comparison in step (c) is based on an estimated radiation dose pattern associated with the estimated device structure and an estimated radiation dose pattern associated with the target device structure.

20. The method according to claim 1, wherein in step (d) the setpoint data is modified or optimized using a merit function, a least-squares method in either the spatial domain or the frequency domain, at substrate level, at a particular focus or through a range of focus, or at a particular dose or through a range of dose.

21. A device manufacturing method comprising:

a) obtaining starting setpoint data;

b) estimating a device structure that would result from applying the starting setpoint data to an array of individually controllable elements configured to modulate a radiation beam;

c) comparing the device structure estimated in step (b) with a target device structure to be formed on a substrate to determine a device structure error;

d) modifying the setpoint data and repeating steps (b) and (c) using the modified setpoint data instead of the starting setpoint data until the device structure error falls below a predetermined threshold;

e) outputting the modified setpoint data for which the device structure error is below the predetermined threshold as the optimized setpoint data;

f) modulating the radiation beam using the array of individually controllable elements actuated using the optimized setpoint data; and

g) projecting the modulated radiation beam onto a substrate.

22. A flat panel display manufactured according to the method of claim 21.

23. An integrated circuit device manufactured according to the method of claim 21.

24. A lithographic system, comprising:

an illumination system configured to condition a radiation beam;

an array of individually controllable elements capable of modulating the radiation beam;

a setpoint data optimizer configured to produce optimized setpoint data and apply the optimized setpoint data to the array of individually controllable elements; and

a projection system configured to project the modulated radiation beam onto a substrate.

25. An apparatus for producing optimized setpoint data for controlling actuation of elements of an array of individually controllable elements configured to modulate a radiation beam in a maskless lithography system, the maskless lithography system having an illumination system configured to condition the radiation beam and a projection system configured to project the modulated radiation beam onto a substrate, the apparatus comprising:

a device structure estimating device configured to estimate the device structure that would result from applying given setpoint data to the array of individually controllable elements configured to modulate the radiation beam; and

a setpoint data optimizer arranged iteratively to estimate the device structure using the device structure estimated device and different setpoint data until a difference between the estimated device structure and a target device structure to be formed on a substrate is smaller than a predetermined threshold, thus determining optimized setpoint data.

26. A lithographic system, comprising:

an illumination system configured to condition a radiation beam;

an array of individually controllable elements capable of modulating the radiation beam;

a projection system configured to project the modulated radiation beam onto a substrate; and

an apparatus for producing optimized setpoint data comprising,

a device structure estimating device configured to estimate a device structure that would result from applying given setpoint data to the array of individually controllable elements configured to modulate the radiation beam, and

a setpoint data optimizer arranged iteratively to estimate the device structure using the device structure estimated device and different setpoint data until a difference between the estimated device structure and a target device structure to be formed on a substrate is smaller than a predetermined threshold, thus determining optimized setpoint data.