All chipmakers understand that variability is the adversary of any process and reduction is essential to improving yield which translates to profit. Aggressive process window and yield specifications necessitate tight inline variation requirements on the DUV light source which impact scanner imaging performance. Improvements in reducing bandwidth variation have been realized with DynaPulse™ bandwidth control technology as significant reduction in bandwidth variation translates to a reduction in CD variation for critical device structures.
Previous work on a NAND Via layer has demonstrated an improvement in process capability through improve source and mask optimization with greater ILS and reduced MEEF that improved CDU by 25%. Using this Via layer, we have developed a methodology to quantify the contribution in an overall CDU budget breakdown. Data from the light source is collected using SmartPulse™ allowing for the development of additional methodologies using predictive models to quantify CD variation from Cymer’s legacy, DynaPulse 1 and DynaPulse 2 bandwidth control technologies. CD non-uniformities due to laser bandwidth variation for lot to lot, wafer to wafer, field to field and within field is now available based on known sensitivities and modeled. This data can assist in understanding the contribution from laser bandwidth variation in global and local CDU budgets.
For 32 nm Node Logic Device, we studied the effect of laser bandwidth variation on Optical Proximity Effect (OPE) by
investigating through-pitch critical dimension (CD) performance. Our investigation evaluated CD performance with and
without the application of Sub-resolution Assist Features (SRAF). These results enabled us to determine the Iso-Dense
Bias (IDB), and sensitivity to laser bandwidth, for both SRAF and no-SRAF cases, as well as the impact on Process
Window. From the IDB results we present the required laser bandwidth stability in order to maintain OPE variation
within CD Budget tolerances. We also introduce OPE matching results between different generation Immersion
Lithography exposure tools evaluated for 45nm Node Logic Device.
For 45 nm Node logic devices, we have investigated the impact of laser bandwidth fluctuation on Optical Proximity
Effect (OPE) by evaluating variation in through-pitch critical dimension (CD) performance. In addition, from these
results we have calculated the Iso-Dense Bias (IDB), and determined the sensitivity to laser bandwidth fluctuation. These
IDB results also enable us to present the laser bandwidth stability that is required to maintain a constant OPE. And
finally, we introduce results from an investigation into OPE-matching between different generations of exposure tools,
whereby in addition to laser bandwidth control, tilt-scan methodology was employed.
The k1 factor continues to be driven downwards, even beyond its theoretical limit 0.25, in order to enable the 32 nm
feature generation and beyond. Due to the extremely small process-window that will be available for such extremely
demanding imaging challenges, it is necessary that not only each unit contributing to the imaging system be driven to its
ultimate performance capability, but also that the final integrated imaging system apply each of the different
components in an optimum way with respect to one another, and maintain that optimum performance level and
cooperation at all times. Components included in such an integrated imaging system include the projection lens,
illumination optics, light source, in-situ metrology tooling, aberration control, and dose control. In this paper we are
going to discuss the required functions of each component of the imaging system and how to optimally control each unit
in cooperation with the others in order to achieve the goal of 32 nm patterning and beyond.