Spray Coating of Photoresist Using Ultrasonic Spray Deposition
Direct spray coating of photoresist onto MEMS wafers and other 3D microstructures has been performed for the past decade, with significant research regarding the advantages of spray deposition into deep well (high) topographies. Photoresist coating with ultrasonic spray is shown to have advantages over conventional spin coating in depositing a more uniform coating, particularly along the top section of side walls of trenches and v-grooves structures, where centrifugal spin makes it impossible to deposit a uniform film along the side wall without excessive photoresist being deposited on the bottom of the cavities.
Ultrasonic spray is a simple, economical and repeatable process for photoresist coating. Sono-Tek ultrasonic coating systems enable fine control of flow rate, coating speed, and deposition amount using simple layering techniques. Low velocity spray shaping defines the atomized spray into precise, controllable patterns, avoiding overspray while producing very thin, uniform layers. Direct spray coating using ultrasonic technology is proven to be a reliable and effective method for depositing photoresist onto 3D microstructures, resulting in reduced device failure from overexposure of the metal to etchant.
Go to http://www.sono-tek.com/wp-content/uploads/2012/01/Photoresist_Spray_Using_Ultrasonics.pdf to read a technical article describing photoresist film coverage improvement using ultrasonic spray technology.
The benefits of ultrasonic nozzles in photoresist direct spray coating processes include:
- Non-clogging atomized spray
- Ability to deposit thin nanolayers with high uniformity
- Repeatable proven spray process
The heart of all Sono-Tek spray systems is our patented ultrasonic spray nozzle, which uses high frequency sound vibrations to produce a soft mist of mathematically defined droplets. This eliminates clogging, since no pressure is used to produce the spray, and the droplets have a very narrow drop distribution size, further contributing to uniformity of the layer deposited. Go to http://www.sono-tek.com/how-ultrasonic-nozzles-work/ for more information.
Sono-Tek’s ExactaCoat system is a full coating solution, ideal for direct photoresist coating onto MEMs wafers. Using Sono-Tek’s patented ultrasonic nozzle technology, the ExactaCoat can be configured with AccuMist, Vortex, or Impact spray shaping systems. Sono-Tek’s coating experts work closely with customers to determine the best air shaping system for each application. Go to http://www.sono-tek.com/photoresist-spray-equipment/ for more information.