Maskless Aligner (Heidelberg MLA150)
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About
The MLA150 allows for arbitrary direct-write patterning of I-Line photoresists from an uploaded CAD drawing/file (GDS, DXF, CIF etc.). The system uses a digital micromirror device ("DMD", an array of MEMS mirrors) for patterning the exposure light-field, to programmatically expose digitized patterns directly onto the sample - no glass photomasks/reticles are required.
Depending on the exposure options and write area, the MLA is able to expose a 100mm wafer in about 30min, and achieves minimum features sizes around 0.5µm, with overlay/alignment accuracy better than 200nm.
The system has a continuous, automatic autofocus, using optical and pneumatic detection of the substrate surface.
The software allows for custom drawings and alignment marks to be exposed onto any feature located on the microscope.
Greyscale lithography allows for photoresist profiles with repeatable slanted or tapered structures, via an 8-bit greyscale bitmap or layer-structured DXF file. See the Greyscale Limitations page for more info.
The high-aspect ratio (variable/long focal length) option enables vertical sidewalls on very thick (~100µm) photoresists.
Detailed Specifications
- Maximum Writeable Area: 150 x 150mm
- Substrate size: 9-inch square or 200mm round down to 5-mm pieces
- Contact staff for pieces < 5 mm.
- Wafer / substrate thickness: Max. 9mm / Min. 0.1mm
- Exposure optics:
- Digital micromirror device (DMD)
- Laser #1: 375nm
- Laser #2: 405nm
- Lens NA = 0.95
- Alignment Accuracy: Global ≤ 500nm; Local ("Field") ≤ 250nm
- Linewidth variation: ≤100nm (relevant to stitched exposure fields)
- Minimum Features: ~0.40µm line/space demonstrated with 0.5µm-thick PR. Requires additional effort. ≥1µm is relatively straightforward.
- Write Grid (Address Unit):
- High Quality Mode (std.): 40nm
- Fast Mode: 100nm
- Additional manufacturer options:
- High-resolution option (Write Mode 1)
- Extended Focus Range
- Variable Focal Depth
- Optical (laser) Autofocus in addition to std. Pneumatic Autofocus
- Greyscale Mode
- (No backside alignment)
Documentation
Operating Procedures
- MLA150 - Standard Operating Procedure - updated Oct 7th 2022
- Includes File-upload procedure, CAD Conversion, Exposure and Alignment.
- Large Image Patterning - one way to generate a GDS file out of an arbitrary image (eg. JPG, BMP, PNG etc.)
- Substrate Templates have been updated, reflecting allowed sample sizes for each focus mode.
- Focus Exposure Matrix Tips ("Series" mode) - it is normal to have to recalibrate your Dose/Focus after some time (eg. few months, or sooner if you're targeting <<2µm resolution)
Troubleshooting & Known Bugs
- See the above page for troubleshooting/recovery info and workarounds to known bugs.
- Double-side polished transparent substrates can sometimes produce difficulties, due to the exposure light reflecting from the wafer underside. Many users have found ways to make them work properly - contact staff if you need help with this.
Video Trainings
To get authorized on this tool, please study the training videos below, and when you are ready, contact the supervisor for a hands-on check-off.
Important: You must be authorized by a supervisor to use the tool! The video training is only one part of the training. Contact the Supervisor for training procedures.
- Heidelberg MLA150 Training Video
- Bookmarks in the video can point you to specific solutions/procedures.
- UPDATES to the Video Training: please review the addendums below:
- New software has been installed, the SOP shows the newer menu options.
- CRITICAL: There are now TWO locations on which you must choose "Optical Autofocus". Failure to do so can result in system damage.
- Substrate Templates have been updated, which are currently not reflected in the video.
- Numerous solved issues have been added to the Troubleshooting page.
Design Tools/Info
Recipes
- Recipes > Lithography > Maskless Aligner MLA150
- Starting recipes for various I-Line photoresists