Ion projection lithography: International development program

Abstract

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 a high-throughput tool for manufacturing integrated-circuit generations with minimum feature sizes of 50 nm and, possibly, below.

Fabrication of open stencil masks with asymmetric void ratio for the ion projection lithography space charge experiment

“…Since neither an established theory nor experimental data on this important effect exist in literature, experimental studies of these effects have been carried out in the frame of the IPL project. 2 The results of this experiment were already presented at EIPBN '99. 1 An essential part of these experiments was a specially designed open stencil mask, the space charge test mask ͑SCTM͒.…”

Neutral particle lithography: a simple solution to charge-related artefacts in ion beam proximity printing

“…As the pitch of the mask pattern decreases below about 250 nm, those laterally scattered particles which had previously been stopped within the mask begin to escape from adjacent open windows, resulting in an additional component of background exposure that worsens as the mask pattern density increases. In these high density applications it is necessary to build up the pattern on the wafer from the superposition of multiple exposures of one or more stencil masks [3,20]. A very useful example of multiple exposures of a single mask is aperture array lithography (AAL) [37] which uses a template mask with a sparse periodic array of stencil openings to write every unit cell in a large area array simultaneously.…”

“…NPL was originally developed, as part of a larger ion projection lithography program [3], to study the distortion of large area stencil masks during ion exposure. These masks were fabricated with a 4 × 4 cm 2 pattern area in a 3 µm thick silicon membrane, 12 cm in diameter.…”

“…This has been accomplished by relentlessly shrinking the wavelength of the exposing radiation from visible light in the early years to the deep ultra-violet photons of today. This paradigm of reducing wavelength may continue with electrons [2], light ions [3] and extreme ultraviolet [4] or it may shift to imprinting techniques [5][6][7][8]. Beyond the semiconductor roadmap [9] is the domain of nanoscale integrated systems, based perhaps on magnetic, quantum-dot, nanotube or molecular devices [10][11][12][13], that could support a new generation of information processing systems, and the expansion of global productivity [14], far beyond the semiconductor era.…”

Mechanical nanostepping for atom beam lithography

“…6 The charge of the ions, however, makes them sensitive to mask and wafer charging, inducing a component of line-edge roughness that increases with proximity gap and decreasing feature size. 4,8 One approach, aperture array lithography, 9 uses a template mask with a sparse periodic array of stencil openings to write every unit cell in a large area array simultaneously. This technology, atom beam lithography ͑ABL͒, uses energetic neutral atoms instead of ions and can resolve mask features as small as 13 nm with 2 nm pattern fidelity.…”