Source mask optimization (SMO) emerged as powerful resolution enhancement technique (RET) for advanced technology nodes. However, there is a plethora of flow and verification metrics in the field, confounding the end user of the technique. Systemic study of different flows and the possible unification thereof is missing. This contribution is intended to reveal the pros and cons of different SMO approaches and verification metrics, understand the commonality and difference, and provide a generic guideline for RET selection via SMO. The paper discusses 3 different type of variations commonly arise in SMO, namely pattern preparation and selection, availability of relevant OPC recipe for freeform source and finally the metrics used in source verification. Several pattern selection algorithms are compared and advantages of systematic pattern selection algorithms are discussed. In the absence of a full resist model for SMO, alternative SMO flow without full resist model is reviewed. Preferred verification flow with quality metrics of DOF and MEEF is examined.
We propose a partial least squares (PLS)-preconditioned importance sampling method for yield estimation. The method
makes use of the rotating vector obtained through PLS regression, and finds the boundary point along the vector by line
search. A biased distribution is constructed around that point for subsequent importance sampling simulation. This
method is shown to be much more stable and efficient than existing approaches and is validated via an SRAM example.
Timely process characterization is crucial in Design for Manufacturing. Scatterometry as a powerful metrology tool can
be extended for optical system characterization. In this paper, we show how scatterometry can be used in conjunction
with an array of dual-pitch or dual-bar gratings to measure optical aberrations. Multiple pattern designs are presented
and compared. A linear model is used to describe the relation between aberration and measurable quantities. Firstprinciple
simulation results shows the current approach can simultaneously measure various Zernike coefficients with
accuracy ~2 mλ.
This paper proposes a new highly sensitive scatterometry based Probe-Pattern Grating Focus Monitor. The high
sensitivity is achieved by placing transparent lines spaced at the strong focus spillover distance of around 0.6λ/NA from
the centerline of a 90 degree phase-shifted probe line that functions as an interferometer detector. The monitor translates
the focus error into the probe line trench depth, which can be measured by scatterometry techniques. Simulations of
optical imaging, resist development and Optical Digital Profilometry measurements are used to evaluate the expected
practical performance. A linear model is developed to estimate focus error based on the measured probe trench depth.
The results indicate that the ODP measurement from a single wafer focus setting can detect both the defocus direction
and the defocus distance to well under 0.1 Rayleigh unit of defocus.
We present a three dimensional photonic crystal structure capable of being used as light sources in quantum information system. The band structure and defect mode properties are given. A stochastic method is employed to study the dynamics of the system. Strong Purcell effect is expected to be observed in this structure, which make it an efficient light emitter in quantum information applications.