Conventionally, lithography technology has contributed to the miniaturization of semiconductors by improving resolutions achieved though making wavelength shorter and shorter.
However, with the advent of immersion lithography and multiple patterning technologies, the trend of shorter wavelength has slowed down. Instead, immersion lithography technology is playing a major role to support mass production.
In the past years, lithography units have achieved further evolution enabling the contrast to be further improved by mitigating optical aberration gap. In line with this, a parameter called E95 which is for Monochromaticity for light sources has been mitigated, which made it possible to further reduce the spectrum width.Assuming that optical setting parameters NA and σ are set for the same value in a legacy lithography unit and a latest model lithography unit, there should be differences in parameters such as Iso-Dense Bias which is sensitive to contrast, due to optical differences and the difference in contrast caused by the optical differences.
For mass production sites equipped with various immersion lithography units keeping up with the times, we have studied the feasibility to compensate the CD bias differences caused by the differences in NA and σ settings, by handling the light source E95% as a variable number. We have also derived the scopes (coverages) necessary for E95% to compensate gaps between existing units or recipes, and presented optical challenges with the E95% set for what we derived.
Toshihiro Oga, Kenji Takahisa, and Takeshi Ohta, "Tailing-edge technology applications like broader E95 approach into the cutting edge DUV light source for tool matching on the ArFi lithography (Conference Presentation)," Proc. SPIE 10587, Optical Microlithography XXXI, 1058713 (Presented at SPIE Advanced Lithography: March 01, 2018; Published: 20 March 2018); https://doi.org/10.1117/12.2297523.5754403553001.
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