Lithographic apparatus and method

• US 20070296942A1
• Filed: 06/21/2006
• Published: 12/27/2007
• Est. Priority Date: 06/21/2006
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Tinnemans, Patricius Aloysius Jacobus
• Granted Patent: US 8,896,808 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• 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 7/70433 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 9/7026 Focusing

Abstract

A lithographic apparatus comprises an illumination system, an array of individually controllable elements, a projection system, and a control system. The illumination system conditions a radiation beam. The array of individually controllable elements modulates the cross-section of the radiation beam. The projection system projects the modulated radiation beam onto a target portion of a substrate. The control system calculates a pattern that is to be formed on the array of individually controllable elements. The calculation includes an adjustment of the pattern, such that its focal plane is shifted in response to a measured separation between the target portion of the substrate and a focal plane of the projection system.

Claims

1. A lithographic apparatus, comprising:

an illumination system configured to condition a radiation beam;

an array of individually controllable elements configured to modulate the radiation beam;

a projection system configured to project the modulated radiation beam onto a target portion of a substrate;

a measuring system configured to measure a separation between a focal plane of the projection system and the target portion of the substrate; and

a control system configured to determine a pattern to be formed by the array of individually controllable elements, the determination including an adjustment of the pattern, such that its focal plane is shifted in response to the measured separation between the target portion of the substrate and the focal plane of the projection system.

2. The lithographic apparatus of claim 1, wherein the control system is configured to determine the adjustment of the pattern, at least in part, using a fractional Fourier transform.

3. The lithographic apparatus of claim 1, wherein the control system is configured to adjust the array to thereby shift the focal plane, such that the focal plane corresponds with the target portion of the substrate.

4. The lithographic apparatus of claim 1, wherein the control system is configured to adjust the array to thereby shift the focal plane to one of a plurality of predetermined alternative focal planes.

5. The lithographic apparatus of claim 4, wherein control system is configured to adjust the array to achieve at least two alternative focal planes.

6. The lithographic apparatus of claim 5, wherein control system is configured to adjust the array to achieve at least four alternative focal planes are provided.

7. The lithographic apparatus of claim 1, further comprising:

a memory coupled to the control system, the memory being configured to store a plurality of pre-calculated adjusted patterns for retrieval when required.

8. The lithographic apparatus of claim 1, further comprising:

a plurality of the arrays of individually controllable elements.

9. A method of forming a device, comprising:

(a) measuring a separation between a target portion of a substrate and a focal plane of a projection system to generate a measured signal;

(b) determining an adjustment to pattern data based on the measured signal, such that the focal plane is shifted in response to the measured separation between the target portion of the substrate and the focal plane of the projection system;

(c) forming a pattern on a patterning device using the adjusted pattern data;

(d) patterning a beam of radiation using the patterning device; and

(e) projecting the patterned beam onto the target portion of the substrate.

10. The method of claim 9, wherein the determination in step (b) is performed at least in part using a fractional Fourier transform.

11. The method of claim 9, wherein step (b) comprises shifting the focal plane, such that it corresponds with the target portion of the substrate.

12. The method of claim 9, wherein step (b) comprises shifting the focal plan to one of a plurality of predetermined alternative focal planes.

13. The method of claim 12, wherein step (b) comprises providing at least two alternative focal planes.

14. The method of claim 13, wherein step (b) comprises providing at least four alternative focal planes.

15. The method of claim 12, wherein step (b) further comprises storing a plurality of predetermined adjusted patterns.