Spray coating technology provides several benefits and allows the ability to overcome remaining drawbacks of spin coating such as low material consumption, but more importantly can provide uniform coatings on non-planar surfaces or even inside the cavities, vias or trenches.
Although spin coating is still a preferred method of resist processing and a well-understood technology, this process has fundamental limitations with respect to device topography, material consumption, and oversized and fragile substrates. However, many applications often exhibit high topography variations. The surface planarity of the coated material significantly impacts further processes. For example, patterning on high-topography wafers, LIGA (lithography, electroforming, and molding), temporary bonding, nanoimprint lithography (NIL) and adhesive bonding rely on advanced coating capabilities and process excellence. Combining numerous requirements such as ultra-thin film thickness or flat surface – especially inside the cavities or vias – upsurges the process control complexity. Proprietary OmniSpray technology can fulfill such challenging requirements by providing excellent uniformity results. Its pressure-less ultrasonic atomization of the resist material guarantees precisely controlled droplet size and its narrow spectral distribution independent from N2 flow. Fully recipe-controlled spray nozzle parameters and x/y meander movement provide high flexibility and repeatability of the spray coating process. The optionally available heated chuck system can further extend the application range. Furthermore, NanoSpray/NanoFill technologies belong to other important advancements by EV Group. The patented multi-step NanoSpray process is a unique coating technique under vacuum conditions, enabling uniform resist coverage of a variety of via geometries and sidewalls for high aspect TSVs with ratio of up to 1:20. NanoFill technology allows complete, void-free filling of vias with flat surfaces. These novel coating processes enable applications like in-via lithography, fast and cost-efficient deposition of organic low-k dielectrics, and easy-to-remove in-via protective coatings. Moreover, EVG’s process technology excellence includes an extensive range of materials such as positive and negative resists, polyimides, double-sided coating of thin-resist layers, high-viscosity resists or resins containing nanoparticles, and is thus able to fulfill advanced process parameters challenged by current market demands.