Specific Process Knowledge/Lithography/UVLithography
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UV Lithography uses ultraviolet light to transfer a pattern from a photo-mask or a design file to a wafer coated with photoresist. The photoresist film is spin coated onto the wafers, the design is transferred to the resist by using an aligner, and subsequently the resist pattern is developed. DTU Nanolab houses a number of automatic or manual coaters, mask or maskless aligners, as well as automatic or semi-automatic developers.
Getting started
Before you plan your UV processing and request for training on any equipment in UV lithography, please go through the following steps. Include the information in the training request.
Also, please remember that the Lithography Tool Package Training is mandatory before training in any lithography equipment.
If you are new to photolithography, you can visit this wikipedia webpage about photolithography before you start.
- Complete the TPT Lithography course: Lithography Tool Package Training.
- Prepare a process flow which describes all steps in your UV lithography process. You can find docx-templates in this table.
- Design device: Design your device and layout. A detailed instruction on how to design a layout (mask) can be found here.
- Substrate pretreatment: In many processes it is recommended to pretreat or prime your wafer before spin-coating. In some spin-coaters, these pretreatment processes are included in the spin coating of resist.
- Resist Type: Choose the type of resist you wish to use: a list of UV lithography resist types available at DTU Nanolab can be found on this page.
- Positive tone resist: Resist exposed to UV light will be dissolved in the developer. The mask openings are an exact copy of the resist pattern which is to remain on the wafer.
- Negative tone resist: Resist exposed to UV light will become polymerized and difficult to dissolve. The mask openings are an inverse copy of the resist pattern which is to remain on the wafer.
- Thickness of resist: In general, it is recommended to work at or below an aspect ratio of ~1, i.e. where the width of the pattern is larger than the thickness of the resist. Furthermore, when you decide the resist thickness, consider which transfer you need:
- For lift-off processes, we recommend resist thickness at least 5 times larger than the thickness of the metal to be lifted.
- For dry etch or wet etch processes, investigate the resist etch rate of your process as this might limit the minimum thickness of your resist.
- Spin Coater: Do you wish to use a manual spin coater or an automatic spin coater? See a list of spin coaters here.
- Exposure: Choose which aligner you wish to use, and consider the exposure dose.
- Mask: If you wish to use a mask aligner, order a photomask for your UV process. Instructions on how to order a photomask can be found here.
- Development: Choose which equipment you wish to use to develop your photoresist from this list. Remember the development process influences the exposure dose.
Resist Overview
| Resist | Polarity | Spectral sensitivity | Manufacturer | Comments | Technical reports | Spin Coating | Exposure | Developer | Rinse | Remover | Process flows (in docx-format) |
| AZ 5214E | Positive but the image can be reversed | 310 - 420 nm | Merck KGaA
Supplied by MicroChemicals GmbH |
Can be used for both positive and image reversed (negative) processes with resist thickness between 1 and 4 µm. | AZ5214E.pdf | Automatic spin coater (Gamma UV or Gamma e-beam & UV) | Mask aligner (KS or MA6 - 2) | AZ 351B developer
or |
DI water | Acetone |
Mask aligner: Process_Flow_AZ5214_pos.docx Process_Flow_AZ5214_rev.docx Maskless aligner: Process_Flow_AZ5214_MLA_pos.docx Process_Flow_AZ5214_MLA_rev.docx |
| AZ 4562 | Positive | 310 - 440 nm | Merck KGaA
Supplied by MicroChemicals GmbH |
For process with resist thickness between 6 and 25 µm. | AZ4500.pdf | Automatic spin coater (Gamma e-beam & UV) | Mask aligner (KS or MA6 - 2) | AZ 351B developer
or |
DI water | Acetone |
Mask aligner: Process_Flow_thick_AZ4562.docx Maskless aligner: Process_Flow_thick_AZ4562_MLA.docx |
| AZ MiR 701 | Positive | 310 - 445 nm | Merck KGaA
Supplied by MicroChemicals GmbH |
High selectivity for dry etch.
Resist thickness 1.5 - 4 µm. |
AZ_MiR_701.pdf | Automatic spin coater (Gamma UV or Gamma e-beam & UV) | AZ 726 MIF developer | DI water | Remover 1165 |
Mask aligner: Process_Flow_AZ_MiR701.docx Maskless aligner: Process_Flow_AZ_MiR701_MLA.docx | |
| AZ nLOF 2020 | Negative | 310 - 380 nm | Merck KGaA
Supplied by MicroChemicals GmbH |
Negative sidewalls for lift-off.
Resist thickness 1.5 - 4 µm. |
AZ_nLOF_2020.pdf | Automatic spin coater (Gamma UV) | AZ 726 MIF developer | DI water | Remover 1165 |
Mask aligner: Process_Flow_AZ_nLOF_2020.docx Maskless aligner: Process_Flow_AZ_nLOF_2020_MLA.docx | |
| SU-8 | Negative | 350 - 400 nm | Kayaku Advanced Materials, Inc.
Supplied by micro resist technology GmbH |
High aspect ratio.
Resist thickness 1 µm to several 100 µm. |
SU-8_DataSheet_2005.pdf, SU-8_DataSheet_2075.pdf | Manual spin coater (LabSpin or RCD8) | mr-Dev 600 developer (PGMEA) | IPA | Plasma ashing can remove crosslinked SU-8 | Process_Flow_SU8_70um.docx |
Other process flows:
- Process_Flow_ChipOnCarrier.docx: A procedure for UV lithography on a chip using automatic coater and developer.
Process information
Pretreatment
Coaters
UV Exposure
Information on UV Exposure Dose
Baking
Development
Descum
Stripping Resist
Lift-off
Information from our suppliers
Application notes from MicroChemicals GmbH, e.g. Lithography Trouble-Shooter