8 October 2014 Laser-written binary OMOG photomasks for high-volume non-critical 193-nm photolithographic layers
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Abstract
Photomasks are key elements of photolithographic processes, implying that their degradation must be reliably monitored and strongly mitigated. Indeed, the photo-induced oxidation of Cr in Cr On Glass (COG) photomasks and the concomitant electrostatic-field migration present in high-volume production using 193-nm photolithographic scanners severely deteriorate the pattern transfer quality, therefore limiting the lifetime of these reticles. To moderate this effect, Opaque MoSi On Glass (OMOG) photomasks, significantly less prone to such degradation, are currently being massively used in leading-edge microfabrication flows. The type of mask fabrication process normally used involving ebeam writing is however not adapted for non-critical photolithographic layers that do not yet benefit from its inherent performances but still suffer from its high cost and its long processing time. It is therefore proposed in this work to combine the simplicity of laser writing and the resistance of MoSi to degradation by using laser-written binary OMOG photomasks for the non-critical layers (e.g. ion-implantation) of a 28-nm production flow. To evaluate one of this new reticle, its pattern transfer fidelity is compared to the one of a laser-written binary COG mask already qualified for production from a photolithographic quality perspective, both masks being treated using the same optical proximity correction (OPC) model. Dispersive and dissipative properties, critical dimension uniformity, pattern linearity and pattern proximity are directly measured on wafer level, subsequently revealing that both photomasks match in terms of OPC parameters. The utilized OPC model is moreover proven robust against the use of both types of masks, consequently making the conversion from COG to OMOG particularly simple. These experimental results therefore qualify the new mask fabrication type and pave the way for a major utilization in high-volume production.
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Rémi Rivière, Rémi Rivière, Selvi Gopalakrishnan, Selvi Gopalakrishnan, Martin Mazur, Martin Mazur, Nevzat Öner, Nevzat Öner, Sven Mühle, Sven Mühle, Rolf Seltmann, Rolf Seltmann, } "Laser-written binary OMOG photomasks for high-volume non-critical 193-nm photolithographic layers", Proc. SPIE 9235, Photomask Technology 2014, 92350S (8 October 2014); doi: 10.1117/12.2059622; https://doi.org/10.1117/12.2059622
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