Giovanni Rivera

Overlay performance on tungsten CMP layers using the ATHENA alignment system

Not Available

Optimization of partial coherence for half-micron i-line lithography

A wide range of partial coherences is explored in order to clarify their real impact on lithographic latitude of different kinds of patterns. The effects of coherence variations on process characteristics are reported in terms of exposure latitude and focus budget. It is shown that the use of a particular coherence, different from the standard one, can practically benefit the latitude of a critical layer such as the contact mask.

Direct measurement of stepper mark detection accuracy on processed wafers

A novel method to evaluate the accuracy of the stepper alignment system on processed substrates has been developed. The technique allows one to measure directly, with a limited number of wafers and high accuracy, just the contribution of the alignment system inaccuracy to final overlay. Applications of the method are under evaluation, especially in the optimization of the alignment systems of steppers. Experimental procedures and algorithms are provided and some examples of experimental results are shown.

On wafer measurement of mask-induced overlay error

In this paper we present the results of an evaluation into the effects of mask unflatness on the overlay budget. We have investigated two different situations: firstly the case of a single sided telecentric lens and secondly that of a double telecentric one. The results have been determined by measuring this effect directly on wafer.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Process-induced wafer distortion: its measurement and effects on overlay in stepper-based advanced lithography

The distortion introduced by some manufacturing steps on wafers can sometimes have a strong effect on overlay results. Thermal processes, for example, can introduce wafer distortions that cannot be completely compensated by the stepper alignment system with a consequent degradation in overlay. A new methodology which can measure the process induced distortion on wafers (exposed with a stepper system) at different steps in a standard process flow has been developed and is described in this paper. This method does not require any external metrology instruments apart from a standard precision stepper and the method is compatible with all process layers. Experimental results of application of the method on manufacturing process are presented.

Qualification of tools for overlay measurement on processed wafers

Abstract In this paper we present two new methodologies to verify the accuracy of a measurement tool. The dependence of the measurements on substrates and the correlation with the same patterns with the same misalignment is shown. Theusefulness and reliability of the methods is proved by examples on commercially available equipment.