Semiconductors Technology

Course 857 Optical Lithography

Dr. Uzodinma Okoroanyanwu is teaching this 4-day course on Optical Lithography. Optical lithography, also called photolithography, can be described as a printing technology that eminently illustrates the perfect marriage between chemistry and optics. This is a technology that uses photons to induce chemical reactions in photoresist films (the image recording medium) and results in the transformation of the exposed part of the photoresist film relative to the unexposed part. Light/photoresist interactions lead to photochemical reactions and photophysical processes that underlie the contrast between the exposed and unexposed region of the film, and this is manifested as the latent image. This lithographic image contrast forms the basis of the printed image and underlies the usage of optical lithographic printing in transferring to the photoresist-coated wafer surface geometric patterns representing integrated circuit (IC) design information on a photomask. Other interesting attributes of optical lithography include the potential for image reduction using projection optics, use of transmission or reflective photomasks, and extremely high capacity for image information transfer on the order of terapixels per exposure shot for the latest advanced exposure tools, which makes for high throughput and high patterning fidelity. This course examines at both introductory and advanced levels the physical and chemical basis of optical lithography.

Available course dates

This course has no planned course dates.

If you are interested in this course, contact us at cei@cei.se

TECHNOLOGY FOCUS

The IC design imperatives for high performance, low power consumption, and small form factors mandate increasing the number of metallization layers in IC devices. Some advanced IC chips today have more than 11 metallization levels that are fabricated in over 300 sequenced processing steps. At the heart of these processing steps lies semiconductor lithography (of which optical lithography is the most dominant form), for it determines and sets the design rule for each technology node. Each layer is defined by a geometric pattern representing circuit design information that must be transferred to the wafer surface to realize the integrated circuit. Semiconductor lithography is the process that transfers to the wafer surface the mask information for each layer of the IC. The optical lithographic exposure wavelengths span the range from 436 nm, 405 nm, 365 nm, 248 nm, 193 nm, to 13.5 nm (EUV). EUV lithography is the most advanced lithographic technology and is in production today at the 3 nm technology node in leading edge Fabs.

Instructor

Dr. Uzodinma Okoroanyanwu

COURSE CONTENT

This course is divided into two main sections: fundamentals of optical lithography and advanced topics in optical lithography. The fundamentals of optical lithography section is divided into six modules, including optical lithography and its role in IC manufacturing, optical lithographic image formation, optical lithographic resist materials chemistry, practical optical lithographic resist processing, reflectivity and control, and lift-off resist pattern transfer. The advanced topics of optical lithography section is in two modules and covers materials on aberrations, low-k₁ lithography, polarization and high numerical aperture effects, as well as EUV lithography. On a practical level, the course will cover exposure systems, operational principles and theories that underpin the various optical lithographic technologies; strategies, processes, and materials used in their operations; their unique features, strengths, and limitations; and specific applications to which they are targeted. Additionally, status, technical challenges, scaling, and future trends of optical lithographic technologies in general will be covered.

WHO SHOULD ATTEND

This course is intended for scientists, engineers, and technicians who wish to expand their knowledge of optical lithography.

Daily Schedule

DAY 1 – Fundamentals of optical lithography
Module 1 Optical lithography and its role in integrated circuit device manufacturing

Principles of optical projection lithography
Elements of optical lithography – exposure tools and systems (design considerations & properties), masks, resists
Optical lithography in IC device manufacture
Optical lithography roadmap and state-of-the-art today

Module 2 – Optical lithographic image formation

Definitions – resolution, depth of focus, numerical aperture (NA)
Diffraction & Huygen’s principle
Image formation in a projection system
The aerial image & its quality metrics

DAY 2 – Fundamentals of optical lithography, cont’d.
Module 3. Optical lithographic resist materials chemistry

Overview
Image recording in optical resist film
Optical lithographic imaging mechanisms
Resist materials platforms

Module 4. Practical optical lithographic resist processing

Process flow
Lithographic process control – contrast curves, focus-exposure matrix, Bossung plots
Planarization
Advanced resist processing
Select applications of optical lithographic resists

Module 5. Reflectivity and control

Overview
CD control over topography
Reflectivity control
Top surface imaging

Module 6. Lift-off Resist Pattern Transfer

Overview of lift-off pattern transfer process
Lift-off pattern transfer versus other pattern transfer approaches
Positive resist lift-off process
Negative resist lift-off process

DAY 3 – Advanced topics in optical lithography
Module 7 – Aberrations, low-k₁ lithography, polarization & high-NA effects

Optical aberrations & their effects on lithographic imaging
Low-k₁ lithography
Optical proximity effects (OPE) & optical proximity correction (OPC)
Off axis illumination (OAI)
Patterning issues & their resolutions

DAY 4 – Advanced topics in optical lithography, cont’d.
Module 8 – EUV lithography

Overview
EUVL exposure system
EUVL sources
EUVL masks
EUV resist materials and processing
EUVL patterning performance & challenges
EUV scaling and extendibility

ALL COURSE DATES FOR THE CATEGORY: Semiconductors Technology

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