System and method to ensure source and image stability

Patent metadata

Field	Value
Publication number	US-9459537-B2
Application number	US-201213530065-A
Country	US
Kind code	B2
Filing date	Jun 21, 2012
Priority date	Jun 22, 2011
Publication date	Oct 4, 2016
Grant date	Oct 4, 2016

Abstract

The present invention discloses various system and process embodiments where wafer-metrology and direct measurements of the lithography apparatus characteristics are combined to achieve temporal drift reduction in a lithography apparatus/process using a simulation model. The simulation model may have sub-components. For example, a sub-model may represent a first set of optical conditions, and another sub-model may represent a second set of optical conditions. The first set of optical conditions may be a standard set of illumination conditions, and the second set may be a custom set of illumination conditions. Using the inter-relationship of the sub-models, stability control under custom illumination condition can be achieved faster without wafer metrology.

First claim

What is claimed is:

1. A method of controlling stability in a lithography process, the method comprising:
(a) defining baseline performances of a lithography apparatus for use in the lithography process in a lithography model, wherein a first sub-model of the lithography model defining a first baseline performance is obtained under a first illumination condition, and a second sub-model of the lithography model defining a second baseline performance is obtained under a second illumination condition, the lithography model comprising one or more illumination source pupil characteristics and one or more lithography process response parameters;
(b) monitoring illumination stability of the lithography apparatus under the first illumination condition by measuring a first temporal drift data of the one or more illumination source pupil characteristics and using the first measured temporal drift data to maintain the one or more illumination source pupil characteristics within or substantially close to the first baseline performance; and
(c) monitoring lithography process response stability under the second illumination condition by measuring a second temporal drift data of the one or more lithography process response parameters and using the second measured temporal drift data to maintain the lithography process response within or substantially close to the second baseline performance.

2. The method of claim 1 , wherein the first illumination condition comprises a standard illumination condition or a custom illumination condition.

3. The method of claim 1 , wherein the second illumination condition comprises a standard illumination condition, or a custom illumination condition.

4. The method of claim 2 , wherein the standard illumination condition comprises one or more standard illumination modes, and the custom illumination condition comprises one or more custom illumination modes.

5. The method of claim 1 , wherein step (b) is performed using direct measurement of the one or more illumination source pupil characteristics.

6. The method of claim 1 , wherein step (c) is performed using one or both of a wafer metrology technique, and a lithography apparatus characteristics measurement technique.

7. The method of claim 1 , wherein steps (b) and (c) include adjusting settings of the lithography apparatus used to perform the lithography process.

8. The method of claim 7 , wherein the settings of the lithography apparatus include one or more selected from: an illumination source characteristic, a projection optics characteristic, a reticle characteristic, or a wafer characteristic.

9. The method of claim 7 , wherein in step (c), the one or more lithography process response parameters comprise a parameter indicative of a response of the lithography process to variations of one or more settings of the lithography apparatus.

10. The method of claim 9 , wherein the one or more lithography process response parameters include one or more selected from: critical dimension (CD) error, overlay error, sidewall angle change, or best focus offset.

11. The method of claim 1 , wherein the one or more illumination source pupil characteristics are controlled by one or more selected from: tuning the illumination source intensity, tuning the illumination source wavelength, controlling beam pointing, or tuning the illumination source polarization.

12. The method of claim 1 , wherein projection optics characteristics are adjusted to ensure stability of a point-source transmission cross-coefficient (TCC) function that is used to define the first baseline performance of an illumination source.

13. The method of claim 1 , wherein prior to step (a), a plurality of patterns are designed or obtained, wherein a first subset of the plurality of patterns corresponds to the variation of a first lithography process parameter, and a second subset of the plurality of patterns corresponds to the variation of a second lithography process parameter.

14. The method of claim 13 , wherein the patterns comprise test patterns on a test reticle, test patterns on a target reticle, or target patterns on a target reticle.

15. The method of claim 14 , wherein test patterns on a target reticle are located on one or more selected from: scribe lines, one or more edges of a design layout, or unutilized real estate on the design layout adjacent to or interspersed with target patterns.

16. The method of claim 1 , wherein the lithography model for the baseline performance is derived by matching with or adapting to an existing reference model.

17. A method of reducing temporal drift of lithography process parameters to maintain performance stability in a lithography process, the method comprising:
(a) defining baseline performances for the lithography process in a lithography model, wherein a first sub-model of the lithography model defining a first baseline performance is obtained under a first optical condition, and a second sub-model of the lithography model defining a second baseline performance is obtained under a second optical condition;
(b) measuring a first temporal drift data of a first lithography process parameter with respect to the first baseline performance under the first optical condition;
(c) measuring a second temporal drift data of a second lithography process parameter with respect to the second baseline performance under the second optical condition; and
(d) using inter-relationship of the first and the second sub-models, and the measured first and the second temporal drift data to determine required adjustments in the first and the second lithography process parameters to maintain the lithography process within or substantially close to the defined baseline performances, wherein the inter-relationship of the first and the second sub-models comprises a mathematical function that relates a lithography process response change with a change in the optical condition in both the first and the second sub-models.

18. The method of claim 17 , wherein the first optical condition comprises a standard optical condition, or a custom optical condition.

19. A method of controlling stability in a current lithography process by matching the current lithography process with a reference lithography process, the method comprising:
(a) defining reference performances for the reference lithography process in a lithography model, wherein a first sub-model of the lithography model defining a first reference performance is obtained under a first illumination condition, and a second sub-model of the lithography model defining a second reference performance is obtained under a second illumination condition, the lithography model comprising one or more illumination source pupil characteristics and one or more lithography process response parameters;
(b) monitoring illumination stability in the current lithography process under the first illumination condition by measuring a first temporal drift data of the one or more illumination source pupil characteristics and using the first measured temporal drift data to maintain the current one or more illumination source pupil characteristics within or substantially close to the first reference performance; and
(c) monitoring lithography process response stability in the current lithography process under the second illumination condition by measuring a second temporal drift data of the one or more lithography process response parameters and using the second measured temporal drift data to maintain the current lithography process response within or substantially close to the s

Assignees

• Cao Yu
• Ye Jun
• Vellanki Venugopal
• Mulkens Johannes Catharinus Hubertus
• Asml Netherlands Bv

Inventors

• Cao Yu
• Ye Jun
• Vellanki Venugopal
• Mulkens Johannes Catharinus Hubertus

Classifications

• G03F7/70525

  Controlling normal operating mode, e.g. matching different apparatus, remote control or prediction of failure · CPC title

• G03F7/70133 Primary

  Measurement of illumination distribution, in pupil plane or field plane · CPC title

• G03F7/705

  Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions · CPC title

• G03F7/70616

  Monitoring the printed patterns · CPC title