Effect of varying the composition of copolymers of glycidyl methacrylate and 3‐chlorostyrene (GMC) on electron lithographic performance

The polymerization kinetics, molecular parameters, and electron lithographic response of a series of copolymers of glycidyl methacrylate (GMA) and 3‐chlorostyrene (CLS) have been determined. The polymerization rate, molecular weight, and polydispersity decrease with increasing mole fraction of 3‐chlorostyrene ( X CLS ). Similarly, the sensitivity of this system decreases as the percentage of CLS in the copolymer increases. The value of D   g 0.5for the copolymer containing 14.3 mole percent CLS is 0.45 μ C /cm 2 increasing to 3.2 μ C /cm 2 for the 54 percent CLS copolymer of equivalent molecular weight. On the contrary the wet air and O 2 plasma etch rates decrease as X CLS increases. For example, the etch rate using wet air for PGMA is ∼ 30 percent greater than GMC ( X CLS = 0.54). The post exposure polymerization rate decreases as the CLS content increases. The extent of the post cure reaction is dose dependent being a maximum at D   g 0.6= 0.64 μ C /cm 2 for the copolymer containing 14.3 mole percent CLS.