Masaki Suzuki

Heterodyne holographic nanometer alignment for a wafer stepper

Abstract Optical Heterodyne interferometry was applied on the Holographic Nanometer Alignment system for a wafer stepper. The total overlay accuracy for TTL off-axis HHWA and TTR HHNA were successfully obtained within 110 and 90 nm/(mean+3σ) for AL wafers, respectively. A high speed and reliable alignment system was confirmed to fabricate half-micron and future sub-half micron devices.

Interferometric Nanometer Alignment for a Wafer Stepper by Two Wave-Front Reconstruction onto Deformed Wafer Gratings

A discussion is presented on a reduction projection wafer stepper with an interferometric nanometer alignment detector by two wave-front reconstruction. The optics of the detector to form an interferometer comprises two coherent beams and a grating on a wafer. The alignment detector detects the relative position of the reticle grating to the wafer grating. It has been verified that the response sensitivity to the step movements of the wafer was 5 nanometers. The response signals received from various deformed alignment gratings indicated an ideal cosine wave form. The resultant overlay to the irregular surface gratings on an Al deposited wafer was improved to 0.1 µm/3 sigma.

Heterodyne holographic nanometer alignment for a half-micron wafer stepper

Heterodyne Holographic Nanometer Alignment system has been applied in a halfmicron wafer stepperfor mass production usage to achieve the overlay accuracy within 0. 1 micron. Resultant overlay accuracy was successfully obtained within 63nm/3sigma for die by die alignment sequence and 8Onm/3sigma for multisampling global alignment sequence. A throughput of 50 6inch wafers per one hour was achieved for multi global alignment sequence. Alignment error budget was estimated for this alignment system and it was confirmed that total overlay accuracy of all processed wafers within 0. 1 micron for halfmicron photolithography was realized using Heterodyne Holographic Nanometer Alignmnent method. In addition onaxis TTR (Through The Reticle) alignment system was investigated for a future subhalf micron wafer stepper and the resul tant overlay accuracy was improved to be 55nm/3sigma. 1 .