Comparing the costs of photoresist coating using spin, spray, or electrodeposition systems

The cost of the photoresist coating process is a major component of the cost of ownership in semiconductor manufacturing. Minimizing the volume of resist used in coating applications results in lower manufacturing costs by reducing both chemical consumption and waste disposal costs. Estimating the amount of resist consumed and understanding the parameters involved in the process help fabs to calculate the coating costs. This article compares the costs of spin, spray, and electrodeposition (ED) photoresist coating methods, which are used to form the thick (3¿10-µm) resist layers that are often required to fabricate 3-D microstructures, radio-frequency MEMS devices, and advanced packaging.1,2 To evaluate the costs of photoresist consumed in such processes, a figure of merit is introduced that defines resist- coating efficiency. The efficiency values cited here were derived from tests on 100-mm silicon wafers. The article estimates resist costs only. It does not consider equipment- and maintenance-related costs.