XFAB TEXAS NXQ8008AL – Mask Aligner Qualification and Review. By Dr. Thomas Johnston
The NXQ8008AL is the next generation version of the popular full field proximity Mask Aligner. The NXQ8008AL is designed for the requirements in state of the art cleanroom environments. The system is Windows based with a touchscreen interface and easy for production operations to control. The NXQ8008AL is a fully auto align system that shows operations all puritan information at a glance. The top load mask and non-contact gap allow for high volume production while mask protection is achieved. The NXQ8008AL is capable of multi subtrate types and thickness and require little to no interruption between runs.
The tool combines the field experience of a proven exposure optics and wafer to mask alignment as well as a fully automated cassette to cassette handling system. The full field exposure and wafer handling system the NXQ8008AL offers 100+ wph first prints and 80+ wph with pilot substrates in the proximity and auto alignment mode with a moderate exposure time. The high throughput combined with the relative low investment cost made the NXQ8008AL XFAB’s preferred solution for our needs.
The NXQ first step in the alignment process is obtained with a non-contact prealigner and dual arm robot. The robot and prealigner are able to achieve a highly accurate and precise position of the wafer onto the chuck that allows the alignment targets to be correctly positioned in the NXQ’s field of view at the highest optical magnification. NXQ8008AL views two alignment targets at the same time with the dual video microscopes. This allows dual mask patterns to be viewed at the same time through a digital image recognizer and OCR registration on multi-field monitor. This control format allows for greater accuracy and reduced pattern recognition errors. The standard 5x objectives were used for all alignments and provide an excellent magnification and DOF combination. Higher Magnification objectives can easily be installed as needed depending on PR thickness, target sizes and alignment requirements.
The qualification test was performed in order to determine the NXQ capability under the current XFAB process. The coat and develop operations were performed on standard 8000 SVG systems using DOW SPR220 7.0 resist and MF26a developer. The thickness target was 6.9um on SiO2 and Nitride pilots. Multiple types of etched alignment marks were employed to determine correct pattern recognition. The NXQ8008AL was able to achieve an impressive 0.6um (3sig) on 10 wafer lot setups on 3 different runs. I would expect sub half micron 3 sigma alignment accuracy to be achieved using a 1-2um thick PR.
I want to thank NXQ for the use of their reticle system and technical expertise. I highly recommend the NXQ8000 Series Mask Aligners for the production of MEMS, SAW, Power devices, diodes and other telecom devices.