Peter Hahmann

Electron beam direct write: shaped beam overcomes resolution concerns

In semiconductor industry time to market is one of the key success factors. Therefore fast prototyping and low-volume production will become extremely important for developing process technologies that are well ahead of the current technological level. Electron Beam Lithography has been launched for industrial use as a direct write technology for these types of applications. However, limited throughput rates and high tool complexity have been seen as the major concerns restricting the industrial use of this technology. Nowadays this begins to change. Variable Shaped Beam (VSB) writers have been established in Electron Beam Direct Write (EBDW) on Si or GaAs. In the paper semiconductor industry requirements to EBDW will be outlined. Behind this background the Vistec SB3050 lithography system will be reviewed. The achieved resolution enhancement of the VSB system down to the 22nm node exposure capability will be discussed in detail; application examples will be given. Combining EBDW in a Mix and Match technology with optical lithography is one way to utilize the high flexibility advantage of this technology and to overcome existing throughput concerns. However, to some extend a common Single Electron Beam Technology (SBT) will always be limited in throughput. Therefore Vistecs approach of a system that is based on the massive parallelisation of beams (MBT), which was initially pursued in a European Project, will also be discussed.

Evaluation of fine pattern definition with electron-beam direct writing lithography

Electron beam (e-beam) lithography is one of the potential candidates for defining fine patterns smaller than 100 nm. To increase throughput, variably shaped beams with vector scan and cell projection techniques have been proposed on the e- beam system. In order to achieve high pattern fidelity in the e-beam lithography special care must be taken with respect to effects, that could result from shot-to-shot, subfield-to- subfield, and stripe boundaries. The key considerations on the pattern fidelity are dimension control and edge roughness. In this paper, methods to enhance pattern fidelity are proposed and discussed. A Leicas WEPRINT 200 system (Leica Microsystems Lithography GmbH), which exerts exposure while continuously moving the stage technique to increase throughput, is used for evaluating the effectiveness of these methods. For the dimension uniformity, the important task is to master shot butting, subfield and stripe stitching and counteract the proximity effects. By employing beam sizing for proximity effect correction and double-pass exposure to suppress stitching error, the dimension variation is largely eliminated. Several factors including accelerating voltage, beam size, proximity effect, beam blur due to Coulomb interaction, and process controllability are found to affect the CD accuracy. To improve the CD accuracy, pattern-bias compensation and proximity effect correction methods are employed in 0.1 micrometer range and below. Good results on dimension accuracy are obtained by properly considering the intra- and inter-proximity effects. Finally, the performance comparison between these methods is discussed.

Mix and match capability of e-beam direct-write for the 65-nm technology

An easy way to pattern 65nm CD target, when optical lithography technology is not available, is to use an Electron Beam Direct Write tool (EBDW), which is well known for its high resolution patterning potentials, with the drawback of a very low throughput. Emerging techniques of electron projection lithography also propose the same patterning capability with enhanced throughput. One of the most crucial issues, when dealing with integration, is the overlay capability of the systems. This paper exposes the studies made on the overlay capability issue of the LEICA EBDW installed in STMicroelectronics (STM) production plant in Crolles (France) and proves our tool is ready to support the 65nm node technology development.

ZBA31: an advanced mask writer meeting the demands of the 1-gigabit DRAM generation

It is now widely accepted that variable shaped beam ( VSB ) writers have some significant advantages compared to the gaussian principle systems, especially when throughput is considered. The ZBA variable shaped beam system introduced in this paper is the most advanced mask generator from Jenoptik Germany. We have utilized the VSB electron optical concept from the very beginning of designing e-beam systems of the ZBA-series more than 20 years ago. The unique combination of this longstanding experience, more than 120 systems were constructed and comissioned, with some very recent developments in the software and operation logistics of the system, allow the ZBA31H maskwriter system to provide the complete performance that is required to satisfy the demands of the 1 G-DRAM generation masks.