Electron-beam direct-write lithography

The two principal modes of operation of electron-beam exposure systems include the maskless direct-write electron-beam machines and the mask-based electron-beam machines. Direct-write electron-beam machines operate directly from design data and are capable of extremely high resolution. Mask-based electron-beam systems utilize masks in their imaging process. The implementation of electron-beam lithography in mix-and-match mode with optical lithography in a manufacturing environment has been demonstrated. 

Of the reported materials, the only commercially available resists are one of the MMA-MAA/MMA-MACl compositions and a t-butyl methacrylate copolymer material (13). In this work, we have chosen to examine the copolymer mixture, which crosslinks at a temperature of 160°C compared to 250 C for the single copolymer. We have carried out experiments to optimize its use for direct write electron beam lithography. 

The current technological competition for practical fabrication of 0.5 - 1.0 pm feature is in between photolithography and electron beam direct writing, and between single layer and multi-level resist. For less than 0.5 pm, the use of electron beam writing with multilevel resist will be inevitable. Further developments in electron resists from the standpoint of both resist chemistry and process development will be necessary to establish the electron beam lithography. 

The major advantages of electron-beam lithography over conventional photolithography are a higher potential resolution and the possibility of direct beam writing on the resist surface. In addition to the usual requirements discussed earlier, positive or negative electron-beam resists have to possess the following properties ... 

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. 

Electron beam lithography is a direct-write method in which a focused beam of electrons is directly scanned over the resist [4,5]. No mask is required as the pattern... 

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 ... 

It is equally worthy to note that a resist based on hydrogen silesquioxanes (HSQs) and formulated in methylisobutyl ketone (MIBK) carrier solvent has recently been reported to have demonstrated pitch resolution down to 20 nm in a 30-nm-thick HSQ film with electron-beam direct-write lithography (exposure... 

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