Electron-beam writing, wafer

The nanoimprint was first developed by Chou and colleagues.Their process is called thermal nanoimprint, which is shown in Figure 4.1. The transfer layer on a Si wafer is thermal plasticity polymethylmethacrylate (PMMA) (Tg = 105°C). A mold of Si02 is produced by electron beam writing. 

Clearly, the sensitivity of a resist should be commensurate with machine design parameters to allow optimized throughput. For example, an electron beam exposure system writing at a modulation rate of 20 MHz (dwell time of 50 nsec), a beam current of 5 x 10-8 amps at 10 kV, and an address structure (spot size) of 0.25 2 would require a resist with a sensitivity of 10 6 C/cm2 (1 / 2) or better in order to write the maximum number of wafers per hour of which it is capable. The same argument also applies to other exposure tools. 

Electron beam resists to be used in direct wafer writing for submicron devices need significant improvement in sensitivity, resolution and dry etching durability. Multilayer resist (MLR) systems are now regarded as the most important technology to perform practical submicron lithography for VLSI fabrication (1-3). Many advantages in MLR compared with one layer resists (1LR) are listed here ... 

The main advantage of NIL techniques, over direct-write techniques such as electron beam lithography, is that NIL can be used for rapid replication of nanoscale features on a wafer substrate. There are several variations of NIL, developed by different manufacturers of NIL systems. The following sections give a brief overview of some of the most important concepts of NIL. 

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