Stefan Hirscher

Large-field ion optics for projection and proximity printing and for maskless lithography (ML2)

Recent studies carried out with Infineon Technologies have shown the utility of Ion Projection Lithography (IPL) for the manufacturing of integrated circuits. In cooperation with IBM Storage Technology Division the patterning of magnetic films by resist-less Ion Projection Direct Structuring (IPDS) has been demonstrated. With masked ion beam proximity techniques unique capabilities for lithography on non-planar (curved) surfaces are outlined. Designs are presented for a masked ion beam proximity lithography (MIBPL) exposure tool with sub - 20 nm resolution capability within 88 mmo exposure fields. The possibility of extremely high reduction ratios (200:1) for high-volume ion projection mask-less lithography (IP-ML2) is discussed.

Ion projection lithography below 70 nm: tool performance and resist process

Abstract Ion projection lithography (IPL) uses electrostatic ion-optics for reduction printing of stencil mask patterns to wafer substrates. The IPL process development tool (PDT) prints field sizes of 12.5 mm×12.5 mm (wafer) at a demagnification factor of 4. First printing results demonstrating different aspects such as resolution, linearity, exposure schemes with stencil masks and image stabilization are available. As an integral part of IPL a resist process suitable for 50 nm minimum feature size has been established using the IMS 1:1 ion beam proximity exposure tool. This resist process has been transferred successfully to the PDT. Compared to previous experiments, sensitivity and contrast have been determined for a larger number of resist materials and with higher precision. Improved resist patterns, better CD linearity and higher stability with respect to pattern collapse have been achieved by optimizing the process parameters. For a Shipley resist, system input parameters for simulations have been determined. Results for the quantum efficiency obtained by Szmanda’s titration method will be presented.

Large-field particle beam optics for projection and proximity printing and for maskless lithography

Recent studies have shown the utility of ion projection lithography (IPL) for the manufacturing of integrated circuits. In addition, ion projection direct structuring (IPDS) can be used for resistless, noncontact modification of materials. In cooperation with IBM Storage Technology Division, ion projection patterning of magnetic media layers has been demonstrated. With masked ion beam proximity techniques, unique capabilities for lithography on nonplanar (curved) surfaces are outlined. Designs are presented for a masked ion beam proximity lithography (MIBL) and masked ion beam direct structuring (MIBS) tool with sub-20-nm resolution capability within 88-mm□ exposure fields. The possibility of extremely high reduction ratios (200:1) for high-volume projection maskless lithography (projection-ML2) is discussed. In the case of projection-ML2 there are advantages of using electrons instead of ions. Including gray scaling, an improved concept for a ⩽50-nm projection-ML2 system is presented with the potential to meet a throughput of 20 wafers per hour (300 mm).

Comparison of EUV mask architectures by process window analysis

Several masks have been fabricated and exposed with the small-field Micro Exposure Tool (MET) at the Advanced Light Source (ALS) synchrotron in Berkeley using EUV radiation at 13.5 nm wavelength. Investigated mask types include two different absorber masks with TaN absorber as well as an etched multilayer mask. The resulting printing performance under different illumination conditions were studied by process window analysis on wafer level. Features with resolution of 60 nm and below were resolved with all masks. The TaN absorber masks with different stack thicknesses showed a similar size of process window. The differences in process windows for line patterns were analyzed for 60 nm patterns. The implications on the choice of optimum mask architecture are discussed.

Comparative study of mask architectures for EUV lithography

Three different architectures were compared as candidates for EUV lithography masks. Binary masks were fabricated using two different stacks of absorber materials and using a selective etching process to directly pattern the multilayer of the mask blank. To compare the effects of mask architecture on resist patterning, all three masks were used to print features into photoresist on the EUV micro-exposure tool (MET) at Lawrence Berkeley National Laboratory. Process windows, depth of focus, mask contrast at EUV, and horizontal and vertical line width bias were use as metrics to compare mask architecture. From printing experiments, a mask architecture using a tantalum nitride absorber stack exhibited the greatest depth of focus and process window of the three masks. Experimental results obtained using prototype masks are discussed in relation to simulations. After accounting for CD biasing on the masks, similar performance was found for all three mask architectures.

Stability of DRAM-devices with respect to 75 keV helium ion beam irradiation as required for ion projection lithography of critical layers

Abstract Ion projection lithography (IPL) is one of the next generation lithography techniques, targeting the 50-nm node and below. During the last year tool, mask and process development have made major advances. A resolution of 50 nm has been achieved locally, 75 nm over a field size of 12.5×12.5 mm 2 . Compatibility of ion projection lithography with a standard semiconductor process has not been proven so far. Possible device damage is still seen as a critical issue. Therefore experimental investigation of the influence of ion beam irradiation on the functionality of state-of-the-art chips is necessary. We carried out the experiment with a state-of-the-art DRAM product processed at a high volume production site. The experiment demonstrates that 75 keV He + ion beam exposure with ion doses as used for ion projection lithography would cause no detrimental damage. Thus IPL is suitable for semiconductor device fabrication.

Ion projection lithography (IPL): posters presented at the 5th Intrnational SEMATECH Next-Generation Lithography (NGL) workshop

At the 5th NGL Workshop, 28-3OAug200l , the IPL team, headed by Infineon Technologies, has presented overhead foils1 providing an overview of results as achieved with the Ion Projection Lithography Process Development Tool (PDT) which has been developed and realized by IMS-Vienna as part of the 1997-2001 European MEDEA project. Furthermore concepts for a full field (25X25mm2) ion projection stepper and its wafer throughput potential have been presented.