Specific Process Knowledge/Lithography

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Lithography

Lithography is a technique used to transfer patterns from a physical or digital mask onto a substrate. At DTU Nanolab, four different lithography methods are available, each suited to specific applications and requirements.

UV lithography
UV lithography is a widely used technique in microfabrication for creating patterns on a substrate using ultraviolet light. It is particularly effective for producing features down to about 1 micrometer in size, making it suitable for many conventional semiconductor and microsystem applications. The process relies on transferring patterns from a mask (physical or digital) onto a photoresist-coated surface, offering a reliable and relatively cost-effective approach for medium-resolution fabrication tasks.

DUV stepper lithography
Deep ultraviolet (DUV) stepper lithography is an advanced form of optical lithography designed to achieve much smaller feature sizes, typically down to around 200 nanometers. By using shorter wavelengths and precision stepper systems, it enables high-resolution patterning across wafers with excellent alignment accuracy. This method is commonly used in modern semiconductor manufacturing, where scaling down device dimensions is critical for improving performance and integration density.

E-beam lithography
Electron-beam (e-beam) lithography is a highly precise patterning technique that uses a focused beam of electrons instead of light to define structures. It enables the fabrication of extremely small features, reaching dimensions as low as about 10 nanometers. Due to its high resolution and flexibility, it is often used for research, prototyping, and mask fabrication, although it is generally slower and more expensive than optical methods.

Nanoimprint lithography
Nanoimprint lithography is a patterning technique that relies on mechanically imprinting or stamping nanoscale features onto a surface without the need for irradiation. By pressing a mold into a resist layer, it can replicate fine structures with high fidelity and at relatively low cost. This method is particularly attractive for large-area and high-throughput applications, offering a straightforward alternative to more complex lithographic processes.

Comparing lithography methods at DTU Nanolab

	UV Lithography	DUV Stepper Lithography	E-beam Lithography	Nano Imprint Lithography
Generel description	Pattern transfer via ultraviolet light (UV)	Pattern transfer via deep ultraviolet light (DUV)	Patterning by electron beam	Pattern transfer via hot embossing (HE)
Pattern size range	~1 µm and up (resist type, thickness, and pattern dependent)	~200 nm and up (pattern type, shape and pitch dependent)	~10-1000 nm (and larger at high currents)	~20 nm and up
Standard resists	UV sensitive, positive tone: AZ 5214E AZ 4562 AZ MiR 701 UV sensitive, negative tone: AZ 5214E AZ nLOF 2020 SU-8	DUV sensitive, positive tone: JSR KRF M230Y JSR KRF M35G DUV sensitive, negative tone: UVN2300-0.8	E-beam sensitive, positive tone: AR-P 6200.xx (CSAR) ZEP 502A PMMA E-beam sensitive, negative tone: HSQ mr-EBL AR-N 7520	Imprint polymers: Topas PMMA mr-I 7030R
Resist thickness range	~0.5 µm to 200 µm	~50 nm to 2 µm	~30 nm to 1 µm	~100 nm to 2 µm
Typical exposure time	Mask aligner: 10-180 s per wafer Maskless aligner: 5-60 minutes per wafer	Process dependent: Pattern Pattern area Dose Throughput is up to 60 wafers/hour	Process dependent: Dose [µC/cm2]: $Q$ Beam current [A]: $I$ Pattern area [cm2]: $a$ Process time [s]: $t=\frac{Q\cdot a}{I}$	Process dependent, including heating/cooling rates
Substrate size	chips down to 3 mm x 3 mm 50 mm wafers 100 mm wafers 150 mm wafers 200 mm wafers	100 mm wafers 150 mm wafers 200 mm wafers	We have cassettes fitting: 4 small samples (slit openings: 20mm, 12mm, 8mm, 4mm) 6 wafers of 50 mm in size 3 wafers of 100 mm in size 1 wafer of 150 mm in size 1 wafer of 200 mm in size Only one cassette can be loaded at a time	small samples 50 mm wafers 100 mm wafers 150 mm wafers
Allowed materials	Any standard cleanroom material	Any standard cleanroom material	Any standard cleanroom material, except: Materials that will degas Graphene requires special treatment	Any standard cleanroom material

Equipment and Process Pages

Pre-lithography Getting started with UV lithography Resist User bottles in the cleanroom UV Resist DUV Resist E-beam Resist Imprint Resist Substrate Pre-treatment HMDS BHF Oven 250C

Coating & baking Automatic spin coating Spin Coater: Gamma UV Spin Coater: Süss Stepper Spin Coater: Gamma e-beam & UV Manual spin coating Spin Coater: RCD8 Spin Coater: Labspin 02/03 Spin Coater: Labspin 04 (PFL) Spray coating Spray Coater Soft & hard baking Hotplates Ovens

Exposure UV Exposure Tools Aligner: MA6-1 Aligner: MA6-2 Aligner: Maskless 01 Aligner: Maskless 02 Aligner: Maskless 03 Aligner: Maskless 04 (PFL) Mask Aligner vs Maskless Aligner Deep-UV Exposure DUV Stepper (Canon FPA-3000EX4) Electron Beam Exposure JEOL 9500 Raith Eline Nano Imprint Lithography Molecular Vapour Deposition Imprinter 01

Development Manual development Manual beaker development SU-8 development Developer: SU8 (Wetbench) Semi-automatic puddle development Developer: E-beam 02 Developer: TMAH Manual 02 Automatic puddle development Developer: TMAH UV-lithography Developer: TMAH Stepper

Post-lithography Descum Plasma Asher 3: Descum Plasma Asher 4 Plasma Asher 5 BHF Lift-off Lift-off Strip Plasma Asher 3: Descum Plasma Asher 4 Plasma Asher 5 Resist Strip

Lithography Tool Package Training

DTU Nanolab offers a Tool Package Training course for Lithography (TPT Lithography), which covers the basic theory of lithography as well as an introduction to some of the most used tools for lithographic processing.

You are required to pass this course in order to become eligible for tool training on the lithography equipment in the cleanroom facility of DTU Nanolab. The course includes theory on lithographic processes and common equipment operation and consists of lecture videos followed by a quiz for each video. Once completed successfully, you may continue to the online equipment training for the specific lithography equipment you want to use. After completing the online equipment training, you can then request hands-on training for the equipment in the cleanroom via training@nanolab.dtu.dk.

The course is available via DTU Learn. You sign up for the course by enrolling yourself in the course here

TPT lithography course contents

• Online lecture videos
• Online quiz for each lecture video

Learning objectives

• Coating
• Exposure
• Development
• Resist, substrates and pre-treatment
• Post-lithography steps

Course responsible

• Jens Hindborg Hemmingsen
• Thomas Aarøe Anhøj

If you have questions you can contact us via lithography@nanolab.dtu.dk

Knowledge and Information about Lithography

Literature Franssila, 2010, Chapter 9: Optical Lithography Franssila, 2010, Chapter 10: Advanced Lithography Handbook of Microlithography, Micromachining, and Microfabrication, Chapter 2: E-beam Lithography Stefan Landis,Lithography, Chapter 3: E-beam Lithography Application notes from MicroChemicals GmbH, e.g. Lithography Trouble-Shooter Lecture videos Lithography TPT lecture videos: Current version (6 videos, 1:28 hours:minutes in total) on YouTube Old version (7 videos, 2:41 hours in total) on YouTube A full lecture series from a UT Austin course on microfabrication by "litho guru" Chris Mack. Half of the lectures are on (projection) lithography :-)	Training videos Training Video: Automatic Spin Coater Training Video: Manual Spin Coater Labspin Training Video: UV Mask Aligner Part I (Operation) Training Video: UV Mask Aligner Part II (Alignment) Training Video: Maskless aligner Training Video Training Video: Maskless aligner Conversion Training Video: Maskless aligner Series and Navigation Training Video: Maskless aligner Alignment Training Video: Automatic Puddle Developer Training Video: Manual Puddle Developer Playlists on YouTube: Maskless aligner (MLA) training videos Lithography equipment training videos (old)	Manuals NB: Access to manuals require DTU login Automatic Spin Coater: Spin Coater: Gamma UV Manual Spin Coater: Spin Coater: Labspin 02 or Spin Coater: Labspin 03 Maskless Aligners: MLA 01 or MLA 02 or MLA 02 UV Mask Aligner: MA6-2 Automatic Puddle Developer: Developer: TMAH UV-lithography Manual Puddle Developer: Developer: TMAH Manual Manual E-beam Developer: Developer: E-beam Manual Process Flows UV resist process flows E-beam resist process flows