Specific Process Knowledge/Lithography/UVLithography
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UV Lithography uses ultraviolet light to transfer a pattern from a mask to a wafer coated with photoresist. The photoresist film is spin coated on the wafers and the pattern is transferred to the wafer by using a mask aligner. DTU Danchip houses a number of automatic or semi-automatic coaters and mask aligners.
Getting started
Before you plan your UV processing and request for training on any equipment in UV lithography, go through the following steps.
If you are new to photolithography, you can visit this wikipedia webpage about photolithography before you start.
- Resist Type: Choose the type of resist you wish to use:
- Positive tone resist: Resist exposed to UV light will be dissolved in the developer. The mask is an exact copy of the 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 is an inverse copy of the pattern which is to remain on the wafer.
- A list of UV lithography resist types available at DTU Danchip can be found on this page.
- Thickness of resist: In general, it is recommended to work with an aspect ratio of ~1, i.e. where the width of the pattern is of same size than the thickness of the resist. Furthermore, when you decide for the resist thickness, consider which transfer you need:
- For lift-off processes, we recommend resist thicknnesses ~5 times larger than the thickness of the metal to be lifted.
- For dry or wet etch processes, investigate the resist etch rate of your process as this might limit the minimum thickness of your resist.
- 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. If you use either the RCD8, SSE or a manual spin coater, you should add a pretreatment step prior to spin coating in your process flow.
- Mask: Design and order a photomask for your UV process. A detailed instruction on how to design and order a photomask can be found here.
- Prepare a process flow which describes all steps in your UV lithography process. You can find templates in this table.
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 | AZ Electronic Materials | Can be used for both positive and reverse processes with resist thickness between 1 and 4 µm. | AZ5214E.pdf | SSE,
KS Spinner or |
KS Aligner, | AZ 351B developer
or |
DI water | Acetone | |
| AZ 4562 | Positive | 310 - 440 nm | AZ Electronic Materials | For process with resist thickness between 6 and 25 µm. | AZ4500.pdf | SSE or | KS Aligner, | AZ 351B developer
or |
DI water | Acetone | Process_Flow_thick_AZ4562.docx |
| AZ MiR 701 | Positive | 310 - 445 nm | AZ Electronic Materials | High selectivity for dry etch.
Resist thickness 1 - 2 µm. |
AZ_MiR_701.pdf | Spin Track 1 + 2 | KS Aligner, | AZ 726 MIF developer | DI water | Remover 1165 | Process_Flow_AZ_MiR701.docx |
| AZ nLOF 2020 | Negative | 310 - 380 nm | AZ Electronic Materials | Negative sidewalls for lift-off.
Resist thickness 1.5 - 3 µm. |
AZ_nLOF_2020.pdf | Spin Track 1 + 2 | KS Aligner, | AZ 726 MIF developer | DI water | Remover 1165 | Process_Flow_AZ_nLOF_2020.docx |
| SU-8 | Negative | 350 - 400 nm | Microchem | High aspect ratio.
Resist thickness 1 µm to several 100 µm. |
SU-8_DataSheet_2005.pdf, SU-8_DataSheet_2075.pdf | KS Spinner | Aligner-6inch,
KS Aligner or |
mr-Dev 600 developer (PGMEA) | IPA | Plasma ashing can remove crosslinked SU-8 | Process_Flow_SU8_70um.docx |