photolithography microscope projection photolithography microscope-projection photolithography CHMO:0001416 A synthesis method that uses light to transfer a pattern to a substrate. A solution of photoresist (a polymer) is deposited on the substrate by spin coating. The photoresist-coated substrate is then heated to drive off excess solvent ('soft-baked', 'prebaked', 'post-application baked', PAB), typically at 90–100 °C. A reduced image of the desired pattern is then projected on the photoresist using a microscope and the substrate is exposed to intense (typically UV) light. A post-exposure bake (PEB) at 120–180 °C is performed before immersing the substrate in a 'developer' which removes excess photoresist. Positive photoresist becomes soluble in the developer when exposed; negative photoresist becomes insoluble in the developer. Finally the substrate is baked again ('hard-baked') to solidify the remaining photoresist. MPPL MPP