Enhancement of the image fidelity and pattern accuracy of a DUV laser generated photomask through next-generation hardware

Currently, the ALTA (R) 4300 generation DUV Laser system is capable of printing critical and semi-critical photomasks for the 130nm and 90nm IC technology nodes. With improved optical elements, an improved objective lens, and a higher bandwidth datapath the capability of the tool has been dramatically enhanced. Both the tool's diffractive optic element (DOE) and acousto-optic modulator (AOM) have been refined. Additionally, the tool's 33x, 0.8NA objective lens has been replaced with a 42x, 0.9NA objective lens. Finally, the tool's datapath has been enhanced to maintain the ALTA system's superior write times on the critical layers. Quantitative results of these enhancements will be detailed through reporting of critical feature resolution limits, CD uniformity control, and pattern placement accuracy. Performance will be shown from masks printed pre- and post-hardware upgrade. Experimental results will be compared with theoretical calculations that show the expected improvement for each relevant parameter.