Mr. Corey Loke Profile

Corey Loke

at ASML

SPIE Involvement:

Author

Publications (2)

This will count as one of your downloads.

You will have access to both the presentation and article (if available).

DOWNLOAD NOW

This content is available for download via your institution's subscription. To access this item, please sign in to your personal account.

Email or Username Forgot your username?

Password Forgot your password?

Show

Keep me signed in

No SPIE account? Create an account

Proceedings Article | 5 March 2021 Presentation + Paper

Frequency modulation as a tool to distinguish between particles and stray light during inspection of EUV/DUV reticles

Michal Pawlowski, Corey Loke, Aage Bendiksen, Ryan Munden, Steve Roux

Proceedings Volume 11698, 116980H (2021) https://doi.org/10.1117/12.2576450

KEYWORDS: Reticles, Stray light, Particles, Inspection, Frequency modulation, Signal detection, Imaging systems, Optical lithography, Light scattering, Sensors

Read Abstract +

A frequency modulation technique is described to distinguish between particle signals and stray light in a prototype of a photolithographic mask inspection system. Strict cleanliness requirements apply to the reticles used in photolithography, and to guarantee correct alignment and pattern reproduction both sides of a reticle (pellicle on front side and reticle back side) need to be inspected for contamination. Reticles constitute difficult inspection targets for imaging systems, because their diffractive patterns can redirect light in arbitrary directions which may potentially result in false positive detections. In this paper we introduce a frequency encoded structural illumination system which enables automatic delineation between stray light and particle signal. In our approach, a sinusoidal pattern whose temporal frequency changes with spatial coordinates is used to obliquely illuminate the surface under test. Incoherent illumination is used, and thus the signal recorded by the imaging optics positioned normal to the inspected surface is a superposition of light scattered by particles and stray light redirected by the photolithographic pattern. Because the inspected surface and reticle pattern are from the perspective of an observation system axially separated, the frequency response of each individual detector point is z position dependent. Therefore, Fourier analysis can be used to analyze the frequency content of each pixel individually and by comparing measured with expected frequencies, one can distinguish between light scattered by particles and stray light. The frequency encoding technique can be used in both imaging and scatterometry based systems. Example experimental results are presented.

Proceedings Article | 22 February 2021 Presentation + Paper

Frequency encoding scheme for reticle front and back side inspection

Michal Pawlowski, Corey Loke, Aage Bendiksen, Peter Kochersperger, Roberto Wiener, Steve Roux, Ryan Munden

Proceedings Volume 11611, 116110O (2021) https://doi.org/10.1117/12.2584772

KEYWORDS: Reticles, Particles, Inspection, Stray light, Computer programming, Signal detection, Particle systems, Imaging systems, Visualization, Superposition

Read Abstract +

EUV and DUV reticles are inspected before exposure to guarantee the quality of the lithographic process. The pellicle and the reticle back side are typically inspected for the presence of contaminants which are several micrometers in diameter. While detection of macroscopic particles is fairly straightforward, delineation between particle and stray light due to diffractive properties of reticle pattern is challenging. We present a particle detection system based on structural illumination technology capable of automatic delineation between contaminants and stray light. During measurement a series of images is acquired by a macro-imaging optical detector (e.g. camera) positioned normal in reference to the investigated sample. The surface under test is illuminated at an oblique angle by an incoherent polychromatic projection system projecting a pattern whose temporal frequency changes across the inspected surface. The signal acquired by the detector is in general an incoherent sum of light scattered by particles with stray light returned by the diffractive pattern. Temporal samples of intensity data are analyzed pixel by pixel in the Fourier domain and the particles are differentiated from the stray light by comparing the Fourier spectra of the acquired signal with the frequency a particle should generate at an analyzed pixel based on the system geometry. Thus, unwanted stray light signal contributions are separated from particle signal by performing logical operations on the signal in the Fourier domain. Experimental results from a technology demonstrator are provided to illustrate performance.

My Library

You currently do not have any folders to save your paper to! Create a new folder below.

Folder Name

Folder Description

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks. You are receiving this notice because your organization may not have SPIE eBooks access.*

*Shibboleth/Open Athens users─please sign in to access your institution's subscriptions.

To obtain this item, you may purchase the complete book in print or electronic format on SPIE.org.

ORGANIZATIONAL
Sign in with credentials provided by your organization.

Organizational Username

Organizational Password

Show/Hide Password

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available

Members:

Non-members: ADD TO CART

Keywords/Phrases

Search In:

Publication Years