Ion projection lithography

The third way to employ ion beams in lithography is to combine the first two techniques and use an ion optical column to project the image of the pattern of a stencil mask onto a wafer. This is called ion projection lithography (IPL), which was pioneered at Ion Microfabrication Systems (IMS) of Austria in the late 1980s.Because IPL is the most technologically important of the three versions of ion-beam lithographies, we shall discuss it in much greater detail. 

Stengl, H. Loschner, and P. Wolf, Ion projection lithography machine IPLM 01 A new tool for sub 0.5 micron modification of materials, J. Vac. Set Technol. B 6, 194 (1986). 

Melngailis, Applications of ion microbeams in lithography and direct processing, Handbook of VLSI Microlithography, 2nd ed., J.N. Helbert, Ed., William Andrew Inc., pp. 790 855 (2001). 

Levinson, Principles of Lithography, 2nd ed., pp. 398 400, SPIE Press, Bellingham, WA 

The principle of maskless ion projection lithography is illustrated in Fig. 15.10. A hroad ion beam is used to illuminate a programmable aperture plate with thousands of apertures of micrometer-scale dimensions, generating up to 4000 beams. In the vicinity of the apertures are tiny deflection plates, each of which can be individually controlled with the aid of integrated CMOS electronics. The slightly deflected beams are blocked at the stopping plate, and the nondeflected 

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Figure 15.8 Schematicof three ways of employing ion beams in lithography (a) focused ion beam lithography, (b) proximity ion-beam lithography, (c) ion projection lithography.

Figure 15.10 Schematic of a maskless ion projection lithography system developed at IMS, Vienna, Austria. (Courtesy of G. Gross.)...

Kaesmaier and H. Loschner, Overview of the Ion Projection Lithography European MEDEA and International Program, Proc. SPIE 3997, 19 32 (2000). 

Figure 15.11 Resolution SEM images of features ranging in size from 22-nm half-pitch (hp) to 90 nm (1 1.5 pitch), printed with maskless ion projection lithography system on 20-nm hydrosilesquixane resist, using 10-keV argon ions at an exposure dose of...

Figure 15.12 SEM image of directly patterned 70-nm Cr on quartz mask blanks with maskless ion projection lithography system, using 10-keV argon ions at a sputtering dose of 39 xC/cm. ...

Figure 15.13 SEM image of directly patterned cone structures (formed by redeposition processes at the lens edges following prolonged sputtering GaAs substrate) with maskless Ion projection lithography system, using 250,000 parallel 10-keV argon...

Preliminary experiments with electron-beam writing and ion-beam projection lithography have demonstrated that the S-layer may also be patterned by these techniques in the sub-lOO-nm range (nnpnblished resnlts). The combination of ion-beam projection lithography and S-layers as resist might become important in the near fntnre, since ion beams allow the transfer of smaller featnres into S-layer lattices compared to optical lithography. 

Using EBL or ion beam lithography (IBL) a variation of shapes and dimensions can bee realized even down to 10 nm in size. With EBL large areas cannot be made accurately due to the problems with the long-range coherence of the e-beam writer and also the throughput is very low. But it is a very flexible method for the fabrication of nanostructures of arbitrary shapes for research [4]. Recently it has been shown that EB and IB projection methods can solve the problems with the throughput and mis-coherence... 

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