Rainer Kaesmaier

Measuring acid generation efficiency in chemically amplified resists with all three beams

A method for measuring acid generation efficiency is presented and utilized to determine the relative efficiency of four photoacid generators (PAGs) upon radiation with photon, electron, and ion beams. In this method, chemically amplified resists are prepared with varying amounts of base, coated into thin films (1000 A), and exposed. Linear plots of the base concentration against the threshold exposure dose for each resist yield the threshold acid concentration and the acid generation rate constant for each PAG. The acid-generating efficiency of the four PAGs (ND-Tf, TPS-Tf, TBI-PFOS, and TBI-Tf) upon irradiation with DUV (248 nm), EUV (13.4 nm), x-ray (1 nm), e beam (30 and 50 keV), and He+ ions is evaluated.

Ion projection lithography: International development program

Ion projection lithography (IPL) has demonstrated not only the resolution required for next-generation lithography (50 nm resolution at >4:1 aspect ratio) [Bruenger et al., Microelectron Eng. 46, 477 (1999)] but also cost advantages with respect to other competing technologies [Gross et al., J. Vac. Sci. Technol. B 16, 3150 (1998)]. This article reports on the progress of a worldwide development program, with the target to manufacture a process development tool and create the necessary mask infrastructure to demonstrate that IPL is a viable industrial lithography technology for the future. An overview of papers, reporting on the progress in critical areas, is given and new, experimentally validated, simulations of complementary mask stitching are shown for the first time. Longitudinal and lateral offsets of up to 32 nm for 100 nm critical dimensions are possible with linewidth variations less than 11 nm. Our concept for beta tools, based on a powerful new stitcher strategy, is described. This will lead to...

Directly sputtered stress-compensated carbon protective layer for silicon stencil masks

Silicon stencil masks for ion beam projection lithography have a protective layer stopping the ions and thus preventing a change in the Si membrane stress. This is needed to maintain extremely tight pattern placement specifications even when they are irradiated with high exposure doses. The fabrication of carbon protective layers by indirect sputter coating which are suitable for helium ion beam exposure has already been reported. This article describes a method of forming very low stress carbon protective layers based on direct radio frequency sputter coating with nitrogen added to the argon sputter gas and in situ thermal treatment using commercially available equipment. The carbon layers thus produced are stable in conventional environments. The article deals also with the physical characterization of carbon layers and the protection performances of these coatings under helium ion beam exposure using accelerated lifetime testing.

p-n junction-based wafer flow process for stencil mask fabrication

The development of stencil masks is considered to be critical to the success of the new ion projection lithography technology. We present here a p-n junction wafer flow process where all fabrication steps are realized on a bulk Si wafer except the final trench etching through the 2–4-μm-thick Si membrane. Stencil masks were produced in a conventional complementary metal-oxide-semiconductor 150 mm wafer line, using an e-beam direct writing tool for patterning. The resist patterns were transferred by standard reactive ion etching (RIE) into a stress-controlled SiON hard mask layer. Subsequent to depositing an Al metal layer for contact to the n-doped wafer surface, the membrane was realized by a wet chemical etch which implemented well established reverse biased p-n junction etch stop techniques. Then, openings through the Si membrane were etched by RIE or inductively coupled plasma etching. Finally, the remaining hard mask layer was removed in BHF. The realized Si membrane diameter was 120 mm with a stenci...

Ion projection lithography: Status of the MEDEA project and United States/European cooperation

Structure and targets of the European MEDEA project on ion projection lithography as well as related U.S./European cooperation are explained. By assuming 10 μm virtual source size and 1 eV (full width half maximum) energy spread calculations for a multielectrode electrostatic ion–optical system (1.25 m between ion source and stencil mask, ≈1.8 m between mask and wafer) we realize the possibility of 100 nm resolution (line and space) over an exposure field of 22×22 mm2 even when using the MONTEC model for calculating the stochastic blur and when running 3.3 μA He+ ion beam current through the ion–optical column, thus more than twice exceeding target specifications. Thus, for 100 nm resolution and 50% pattern density the raw throughput is ≈12 cm2/s corresponding to >75 WPH (pattern within 80% of 300 mm wafer area).

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: Progress of European MEDEA & International Program

The European & International Development Program on Ion Projection Lithography is competing with several other Next Generation Lithography technologies to be implemented in future semiconductor manufacturing for structure sizes below 100nm. A recent paper [2] gives a good overview on the status of critical issues as well as a complete summary of additional papers describing the recent activities in the program. Thus, this paper concentrates on some key results within the program. A status of the tool handling system is given as well as some updated data in terms of possible ion current through future beta tool concept due to improvement in material development as well as theoretical implementations into future designs. In the mask technology part, the concept of a specially developed correction and splitting software for IPL stencil masks is described. As highlight of the IPL mask section, the first manufactured 200mm stencil mask with the SOI wafer-flow process, worldwide, could be presented. For the activities in the resist process simulations, the intention was in first hand, to show as kind of overview the two mainly separately running activities, which are in detail described elsewhere [2,18,19]. The one activity leads to a detailed understanding of ion-scattering effects and the other to an understanding of the relation between diffusion processes and line-edge roughness smoothing. Some ion specific effects like the compensation of ion scattering and energy absorption leading to possible resist profile improvements are described in more detail. In addition, this paper tries to give, for the first time, a comprehensive, complete description of the current understanding about the whole IPL resist process.

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).

Characterization of a process development tool for ion projection lithography

This article describes the performance of a process development tool for ion projection lithography (IPL), realized as part of the MEDEA program of the European Union. This system was designed for a 12.5×12.5 mm2 exposure field and 4:1 reduction ratio between the mask and the wafer. The design incorporates several novel concepts, including a negative electrostatic lens at the mask to reduce distortion and field-composable lenses to provide electronic fine alignment of the system. Continuous control of magnification, position offset, distortion, and telecentricity is provided by a real-time feedback system (pattern lock) that monitors the position of reference beamlets traveling in parallel with the integrated circuit image through the ion-optical system. After mechanically aligning the center and tilt of the lenses relative to the optical axis to within 10 μm and 50 μrad, respectively, we achieved 100 nm resolution over the full design field, with 75 nm resolution in local areas within the field. The redu...

Experimental results of the stochastic Coulomb interaction in ion projection lithography

Throughput and resolution are connected in ion and electron projection lithography (IPL and EPL) because of the space charge and Coulomb interaction between the particles in the beam. Due to the lack of experimental data it was not possible to estimate this effect accurately. Therefore an experiment setup has been developed which has the most significant parameters close to planned IPL exposure tools. These parameters are the linear particle density and the crossover shape and size. The stochastic Coulomb interaction blur, depending on the total beam current, has been measured in about 100 settings of the beam current, beam energy, and crossover shape. The results show that the stochastic Coulomb interaction blur scales to the power of 0.587±0.101 (1σ) of the linear particle density in a system with a uniform crossover of 400 μm. To decrease the current density in crossover IPL systems can have an aberrated crossover. In case of this type of crossover of 670 μm the current dependency is 0.820±0.072 (1σ). ...