No abstract

The calculation of the thermoelectric power of superlattices, previously carried out in a tight-binding approximation, is here extended to a general energy-momentum relation. For the Kronig-Penney potential, corrections to the thermoelectric power are obtained and are shown as a function of the Fermi level within the miniband. The corrections are shown to be appreciable for narrow barriers and/or small conduction band offsets.

Alternating Aperture Phase Shift Mask (AAPSM) is one of the most effective approaches to improve the resolution of logic gate structures for ArF lithography of the 65nm half-pitch node and beyond because AAPSM shows good performance due to the high image contrast and the small mask error enhancement factor (MEEF).For AAPSM, the issue of intensity imbalance between pi-space and zero-space is well known. In order to solve this issue, several kinds of AAPSM, such as single trench with undercut, single trench with bias are used in production application.The fabrication of single trench with bias AAPSM requires that the quartz dry etch satisfies many conditions. The etched quartz features must not only show excellent depth uniformity but also good etch depth linearity across a wide range of feature sizes. However, in defocus conditions, the through-pitch image placement error becomes worse even with good quartz etch depth linearity. The reason is that the phase error caused by mask topography is different depending on the pitch.In this work, we minimize the phase error through-pitch and through-focus by rigorous 3D mask simulations. Based on the results, we have fabricated two masks with opposite quartz depth linearity signatures to estimate the imaging impact of phase errors and used them for exposures on an ASML XT:1250Di immersion scanner. We discuss the feasibility of this method by comparison of through-focus and through-pitch image placement errors between wafer printing, AIMS, and simulation.

No abstract

While the modified illumination with various ifiumination apertures is the promising method to get fmer patterns, there are many problems in putting it into practical use. In particular, the different apertures give different effects on the lens distortion and they cause the pattern displacement. In this paper, we studied the image placement error of fme patterns under 1 im and its pattern pitch dependence using various illumination apertures. The 1st layer of O.8prn lines and spaces is patterned using conventional aperture(NA=O.57, a=O.6) and the 2nd layer is exposed on the etched patterns with various apertures such as conventional, annular and small sigma. The patterns of the 2nd layer are O.4jim lines with various spaces. Pattern displacements of the 2nd layer are measured within the lens field along the X axis. The results show that the displacements are affected by the illumination status. In addition, the displacement varies with the pattern pitch and the placements of the fine patterns are different from those of large overlay patterns such as box-in-box. These results are confirmed by the optical simulator. The simulated results correspond to the experimental results and they point out the 3rd order coma aberration most effects the pattern displacement. The pattern size and pitch dependence of the image displacement reveals that the measurement results of the conventional overlay patterns such as box-in-box with the sizes of 1O-2Ojim doesn't represent the overlay of the fine patterns of actual devices.