Negative electron-beam resists

Figure 3. Size of clear and opaque 2.0 fim features as a function of exposure dose for a negative electron beam resist. The dose Dp that results in the correct feature size is denoted as the "sensitivity .

Methods 1 and 3 have been utilized in dry developed resist systems. To our knowledge, there are no resist systems commercially available that depend on post-exposure treatment other than the post-curing effect in negative electron beam resists mentioned earlier. Since such systems are still largely in the research phase we will not discuss them here but rather refer the reader to the literature for more detailed descriptions (44-50). 

A Novel Technique for Determining Radiation Chemical Yields of Negative Electron-Beam Resists... 

From this result on MRS, we expected that a combination of phenolic-resin-based resist and aqueous alkaline developer would lead to etching-type dissolution and non-swelling resist patterns. In this paper, we report on a new non-swelling negative electron beam resist consisting of an epoxy novolac, azide compound and phenolic resin matrix (EAP) and discuss the radiation chemistry of this resist. 

To achieve a manufacturable system for sub-0.5-pm patterning, extremely precise control of the molecular properties, structure, composition, and purity of the polymer is required (Table 4). Meeting these requirements provides intellectual challenges in ultrapurification reaction engineering and chemical synthesis. An illustration of the control required in this synthesis process can be found in a negative electron beam resist, GMC. 

The major reaction pathways for SNR operating as a negative electron beam resist are general known, but several problems still remain. 

Many reports have been published on negative electron-beam resists. Most of these resists utilize radiation-induced gel-formation as the insolubilzation reaction. However, a major problem with these resists, is that their resolution is limited by swelling which is induced by the developer during development. 

Poly(glycidyl methacrylate) (PGMA), a well-known negative electron beam resist first reported by Hirai et al. (55), actually functions as a positive-tone resist upon DUV exposure (Table 3.1) (56). The epoxide functionality responsible for cross-linking under electron beam exposure does not absorb in the DUV region, and the response of PGMA to DUV radiation is determined by the absorption due to the n — tt transition of the carbonyl chromo-... 

The negative electron beam resists as shown in Table VII are based on vinyl polymers —... 

Taniguchi, Y. Hatano, S. Shiraishi, S. Horigone, S. Nonogaki, and K. Naraoka, PGMA as a high resolution, high sensitivity negative electron beam resist, Jpn. J. Appl. Phys. 18, 1143 (1979). 

When some or all of the phenyl rings are substituted with halogen (Scheme 6.11), the radiation sensitivity and the cross-linking efficiency of polystyrene can be enhanced significantly. Negative electron-beam resist formulated from iodi-nated and chlorinated polystyrene and based on this approach have been reported. Sensitivity of about 2 p.C/cm and resolution of about 1-p.m features have been demonstrated with these materials. ... 

Ueno, H. Shiriashi, and S. Nonogaki, Insolubilization mechanism and lithographic character istics of a negative electron beam resist iodinated polystyrene, J. Appl. Polym. Sci. 29, 223 (1984). "ibid. 

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 ... 

Table 6.5 Some negative electron-beam resists ...

PT and 3-butylPT as electrically conductive materials are useful as electron beam resists [148]. A negative electron beam resist can be produced by an electron beam to form functionalization and cross-linking in 3-octylPT in a single step creating submicron scale polymer structures carrying functionalized groups [149, 150]. 

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