Study on volume production of uniform wafer-level micro glass cavities by a chemical foaming process (CFP)

In this paper, an improved chemical foaming process (CFP) for wafer-level glass cavities will be demonstrated for volume production in a clean room. First of all, suitable foaming agents transferring techniques are investigated to avoid powder pollution to the chips in a clean room. In addition, the precise controlling of the sizes of the glass cavities is studied theoretically and experimentally. The shapes, morphology and sizes of the glass cavities formed by the improved CFP are characterized by AFM and digital 3D microscopy. A theoretical model for precisely predicting the final shapes and sizes are established. Moreover, glass cavities with uniform structures and precisely controlled sizes at a 4-inch wafer are prepared successfully. The improved CFP will provide a novel volume-production technique for micro-machining of glass, which has many applications in MEMS and MOEMS.