Timothy E. Neary

MARS: Femtosecond laser mask advanced repair system in manufacturing

Presently available nanosecond laser based tools for removing Cr defects from photomasks have proven inadequate to the task due to the thermal nature of the ablation process which produces metal splatter, haze, reduced transmission, and pitting of the quartz substrate. These problems are virtually nonexistent when employing femtosecond pulses of light to ablate Cr defects in a nonthermal process. Photomasks repaired with ultrashort light pulses exhibit transmission approaching 100%, no observable glass damage, and exceptional spatial resolution. We have built a femtosecond pulsed laser mask repair system which is presently operating successfully in a manufacturing environment.

Implementation and performance of a femtosecond laser mask repair system in manufacturing

Current laser based tools for removing Cr defects are fundamentally limited due to the thermal nature of ablation carried out with nanosecond pulses. Conversely, ablation carried out with femtosecond pulses of light removes Cr in a non-thermal process. As a result, the problems of metal splatter, haze, reduced transmission and pitting of the underlying quartz common to nanosecond ablation are virtually nonexistent with femtosecond ablation of Cr. In this paper we describe a femtosecond pulsed laser mask repair system which is presently operating successfully in a manufacturing environment.

In-situ damage monitoring of composite structures

The feasibility of embedding piezoelectric transducers in composite panels for the measurement of phase velocities is presented. The theoretical dispersion curves for a composite panel are generated and the experimental measurements of phase velocities compared. In this paper the method for testing and for evaluating the experimental phase velocities is developed. The experimental methodology is validated by excellent agreement to theoretical values. This measurement methodology is used to detect holes drilled in composite plates to show the usefulness of the procedure. Signal losses of between 10% and 48% can be detected with this embedded transducer method.

Mask defect reduction through automated pellicle mounting

At IBM’s Mask House, we deigned, installed, and evaluated a fully automated pellicle mounting tool. Features include very low particulate levels, ability to mount a wide variety of pellicles, ease of operation, and pellicle and mask inspection capability. During an evaluation period, pellicles were mounted both with this fully automated tool and with a semiautomatic tool. The fully automated tool showed good reliability (>95% availability) and a 2X lower incidence of foreign material contemination as compared with the semiautomatic tool.