Small & mid-size fabs / foundries
- Inline or at-line photoresist thickness checks
- Monitoring process drift without a full metrology tower
- Potential integration into existing coaters, tracks or inspection tools
Single-shot color metrology for photoresist thickness
DensPear RTG is a LUT-based optical method that estimates photoresist thickness from a single RGB or white-light image. Designed for small and mid-size fabs, metrology labs and equipment makers.
Early-stage R&D project by DensPear LLC (Georgia), focused on practical optical metrology for real-world processes.
RTG in one look
- Single-shot color measurement (RGB / white-light)
- LUT-based link between color and film thickness
- Works with standard microscope / inspection cameras
- Targets affordable metrology outside top-tier fabs
Online RTG demo: coming soon
RTG Technology
RTG (Reflective Thickness from a single image using a color LUT) is a physics-based method for estimating thin film thickness from one camera exposure. Instead of scanning wavelength or polarization, RTG uses the color response of a standard camera and a pre-computed lookup table (LUT).
How RTG works
- Optical model. We model the optical stack (substrate + layers + photoresist), illumination spectrum, numerical aperture (NA) and camera spectral sensitivity.
- LUT generation. For a range of thicknesses we simulate the reflected spectrum and convert it into camera signals (RGB channels or an effective “white” channel). The result is a LUT that maps measured color to possible thickness.
- Measurement. For a new image, the measured pixel values are matched against the LUT to estimate best-fit thickness and sensitivity.
- Modes: RGB and white. RGB mode uses three narrow bands for higher sensitivity; white mode uses broad illumination and camera sensitivity for simpler hardware.
Why single-shot color?
Traditional reflectometry and ellipsometry rely on scanning wavelength or polarization. RTG compresses spectral information into a single exposure:
- No spectrometer or moving parts in the optical path
- Potentially lower cost and smaller footprint
- Easy to integrate into existing tools (spinners, tracks, inspection)
- Physically transparent method: sensitivity and limits can be analyzed using the underlying optical model
RTG is currently at an advanced simulation and software prototype stage and is not yet an industrially qualified metrology tool.
Current status & limitations
- Simulation engine and LUT generation implemented in software
- Support for different stacks, NA and source spectra
- Real-world accuracy depends on calibration to your process, hardware and recipes
- Experimental validation on real photoresists and stacks is in progress
DensPear is looking for partners interested in joint validation, pilot deployments and OEM integration of RTG.
Use Cases & Target Partners
RTG is intended for organizations that need more metrology than a simple “black box”, but cannot or do not want to invest in the most expensive high-end tools.
Metrology labs & service providers
- Feasibility studies and process development
- Complementary measurements alongside spectral or ellipsometric tools
- Offering “single-shot thickness estimation” as an additional service
Equipment makers (OEM)
- Compact metrology modules for coaters, tracks or exposure tools
- Application-specific LUTs for OEM optical paths
- Joint development and differentiation for regional and specialty fabs
Universities & research centers
- Teaching thin-film interference and color-based metrology
- R&D on new materials and processes
- Joint publications and collaborative projects
Pilot Measurements: Send Us Your Images
Before we release an online RTG demo, DensPear offers pilot measurements as a collaborative R&D service. You send representative images and basic process information. We run our RTG prototype and return estimated thickness data and qualitative sensitivity analysis.
What you get
- Approximate thickness estimates for selected regions
- Sensitivity vs thickness for your stack and optics
- Feedback on whether RTG is a good candidate for your process and hardware
Pilot results are research-only and must not be used as a replacement for qualified production metrology.
What to send
- Bright-field images from microscope or inspection cameras
- Preferably fixed focus and fixed illumination across the field
- RAW or minimally processed images preferred (PNG/TIFF/JPEG possible)
Minimum process information
- Photoresist type and nominal thickness range
- Stack description (substrate and layers)
- Approximate NA / objective and light source type (white LED, halogen, narrow-band, etc.)
- Any available reference thickness for selected points (optional but very helpful)
How to submit images
Please send a short email to info@denspear.com with the subject line:
RTG pilot measurements – image submission
Include a brief description of your organization and use case, your preferred contact person and time zone, and a link to a secure file share containing the images.
About DensPear LLC
DensPear LLC is an independent R&D company focused on optical metrology for semiconductor and microfabrication processes. The team combines experience in lithography, thin-film physics and scientific software development.
The company is registered in Georgia and works with international partners. RTG is currently in the early-stage R&D and pilot phase. We are actively looking for:
- Pilot customers among small and mid-size fabs
- Metrology labs interested in joint validation
- Equipment makers considering integrated metrology modules
- Academic partners for teaching and research projects
Our goal is to make physically transparent, affordable metrology tools that can realistically be used outside of top-tier fabs, without sacrificing understanding of the underlying physics.
Contact & Collaboration
If you are interested in RTG, pilot measurements or joint R&D, please get in touch with us.
Contact details
- Email: info@denspear.com
- Website: denspear.com
- Company: DensPear LLC
- Location: Georgia
Preferred topics include pilot measurements based on your images, joint validation on your photoresists and stacks, OEM integration and academic collaborations.