Multilevel microstructure fabrication using single-step 3D photolithography and single-step electroplating

We developed a useful method to obtain multilevel microstructures simply by single-step 3D photolithography followed by single-step electroplating. By varying UV exposure depth with multiple photomasks in a single-coated conventional thick photoresist, we form multilevel photoresist molds in a single lithography step. After the 3D mold patterning, metal electroplating is performed on it until 3D metallic microstructures are obtained. The critical issue in this process, the exposure depth control, was carefully examined by observing the exposure time vs. development characteristic of the resist, in the film thickness range of 40 to approximately 90 um. We proposed a simple method to reproducibly obtain the resist thickness of each level as designed. Using the unique overplating feature in electroplating process, we demonstrated two utmost practical examples: a unified Orifice Plate Assembly (OPA), which has orifice, channel, and reservoirs in a single body, for high-resolution inkjet printhead, and an electroplated Solenoid-type Integrated Inductor (SI²). Both were fabricated using a single-coated 80 μm-thick photoresist with only two photomasks, and have many advantages in productivity and performance. This method does not stack planar layer vertically to make 3D microstructures as in the conventional ways, therefore, is a simple, low-cost, and high-yield process. And also, it is IC compatible due to its low process temperature and monolithic process.