Junichiro Iba

Trench transformation technology using hydrogen annealing for realizing highly reliable device structure with thin dielectric films

The shape and the surface morphology of the trench structure was successfully transformed by the annealing in hydrogen ambient. The corner was rounded and the surface morphology was smoothened on the inside of the trench. Electrical characteristics of the thin oxide grown in the deep trench capacitor were drastically improved. The hydrogen annealing condition was optimized based on the transformation mechanism.

Electrical characterization of across-field lithographic performance for 256-Mbit DRAM technologies

Lithographic performance has typically been evaluated at a single point within the stepper field. However, this evaluation method does not completely provide the total lithographic performance on a chip because of variations introduced by the stepper as well as the reticle. In this paper, the evaluation method and characteristics of across-field performance are shown through the use of electrical line width measurements and exposure-defocus (ED) analysis. The across-field performance is analyzed by both the average process window and the common process window for two resolution enhanced photolithography techniques: phase-shifting mask (PSM) and off-axis illumination (OAI). The average process window corresponds to a single-point evaluation while the common process window includes all lithographic fluctuations across the field. Consequently, the common process window is much smaller than the average process window. Moreover, to consider the effect of mask critical dimension (CD) deviation on lithographic performance, a mask CD deviation enhancement factor (MEF) is introduced. By MEF correction, the contribution of mask CD deviation to common window degradation is obtained.

Viability of conventional high-NA KrF imaging for sub-0.25-um lithography

As the competitive pressures of the semiconductor industry drive to feature sizes below 250 nanometer, unconventional imaging approaches are being considered in order to preserve the cost effectiveness of optical lithography. To achieve minimum feature size with a usable process window, phase shift masks, off-axis illumination, and ArF lithography have been investigated with varying degrees of success. Unfortuanely, the maturity and flexibility of such techniques are questionable at this time. This paper investigates the extendibilty of traditional imaging approaches for use in the sub 250 nanometer regime. Aerial image simulations were used to set expectation levels by increasing lens numerical aperture versus prior state of the art exposure systems. Experimental data was then generated with an advanced 0.6 NA excimer laser based step and scan exposure system. Single point per field comparisons are made between simulations and experimental data covering linearity, depth of focus, and exposure dose window for feature sizes between 250 nanometers and 200 nanometers. In addition, data reviewing the ability to extend such performance across a 25 mm by 33 mm field size is reviewed.