Flow Condition in Resist Spray Coating and Patterning Performance for Three-Dimensional Photolithography over Deep Structures

Spray coating of the photoresist is an attractive technique that offers new processes for realizing three-dimensional structures in a manner compatible with well-established planar photolithography. There are, however, many hurdles to overcome for its development, including the analysis of coating mechanism. Essentially, this is because the method used is the complex gas-liquid two-phase flow. In this paper, the detailed results relating to the resist film deposition inside microstructures of the Si wafer are described, while focusing on the pinhole distribution, which is a serious drawback of the application. In addition, the performance of the pattern transfer over deep (>1 mm) structures is investigated using a projection-type aligner.