Hans-Joachim Döring

Multi-shaped-beam (MSB): an evolutionary approach for high throughput e-beam lithography

The development of next-generation lithography (NGL) such as EUV, NIL and maskless lithography (ML2) are driven by the half pitch reduction and increasing integration density of integrated circuits down to the 22nm node and beyond. For electron beam direct write (EBDW) several revolutionary pixel based concepts have been under development since several years. By contrast an evolutionary and full package high throughput multi electron-beam approach called Multi Shaped Beam (MSB), which is based on proven Variable Shaped Beam (VSB) technology, will be presented in this paper. In the recent decade VSB has already been applied in EBDW for device learning, early prototyping and low volume fabrication in production environments for both silicon and compound semiconductor applications. Above all the high resolution and the high flexibility due to the avoidance of expensive masks for critical layers made it an attractive solution for advanced technology nodes down to 32nm half pitch. The limitation in throughput of VSB has been mitigated in a major extension of VSB by the qualification of the cell projection (CP) technology concurrently used with VSB. With CP more pixels in complex shapes can be projected in one shot, enabling a remarkable shot count reduction for repetitive pattern. The most advanced step to extend the mature VSB technology for higher throughput is its parallelization in one column applying MEMS based multi deflection arrays. With this Vistec MSB technology, multiple shaped beamlets are generated simultaneously, each controllable individually in shape size and beam on time. Compared to pixel based ML2 approaches the MSB technology enables the maskless, variable and parallel projection of a large number of pixels per beamlet times the number of beamlets. Basic concepts, exposure examples and performance results of each of the described throughput enhancement steps will be presented.

Projection maskless lithography

Recent studies have shown the feasibility of Projection Mask-Less Lithography (PML2) for small and medium volume device production (2-5 WPH) for the 45nm technology node. This PML2 tool concept comprises a combined electrostatic-magnetic electron optical column with 200x de-magnification factor. Instead of a mask there is a programmable aperture plate enabling dynamic beam structuring. Wafer exposure is done stripe-by-stripe with a scanning 300mm wafer stage. Detailed calculations of the PML2 optical column (2-step demagnification) including Monte-Carlo simulations of Coulomb interactions are presented. The extendibility of PML2 technology for the 32nm node will be discussed.

Precisely Assembled Multi Deflection Arrays – Key Components for Multi Shaped Beam Lithography

Multi shaped beam lithography requires the precise and durable alignment and fixation of MEMS based Multi Deflection Arrays on stable ceramic system platforms using vacuum and high temperature compatible interconnection and joining technologies. Micron accuracy during assembly is accomplished by mark detection using image processing and 3DOF alignment procedures; while interconnection as well as precise fixation is carried out using a fine pitch solder bumping process. Qualification investigations using electron beam equipment show that the precisely aligned multi shaped beam arrays are able to deflect the electron beams in accordance with the simulation results.