Reinhard März

Benchmark of FEM, waveguide, and FDTD algorithms for rigorous mask simulation

An extremely fast time-harmonic finite element solver developed for the transmission analysis of photonic crystals was applied to mask simulation problems. The applicability was proven by examining a set of typical problems and by a benchmarking against two established methods (FDTD and a differential method) and an analytical example. The new finite element approach was up to 100 times faster than the competing approaches for moderate target accuracies, and it was the only method which allowed to reach high target accuracies.

Tunable distributed feedback laser with photonic crystal mirrors

We report the development of a tunable laser diode based on InP using photonic crystal mirrors. The laser consists of two longitudinally coupled ridge waveguide segments that are coupled through a photonic crystal mirror segment. A laterally defined binary superimposed grating provides a distributed feedback in each of the cavities. Quasi-continuous tuning is achieved in a 24.5 nm window with 56 channels as typically required by wavelength division multiplexing applications.

Tunable photonic crystal coupled-cavity laser

We report the development of a tunable photonic crystal coupled-cavity laser diode based on InP. The laser consists of two photonic crystal channel waveguides that are coupled through a photonic crystal mirror segment in /spl Gamma/-M direction. The cavity lengths define the respective mode spacings in the cavities. The tuning characteristics of the device are compared with results obtained from a transfer matrix model. Quasi-continuous tuning is achieved in a 29.6-nm window with 36 wavelength division multiplexing channels spaced 0.8 nm apart (ITU grid). The simplicity of fabrication and promising output characteristics should make this tunable laser design an interesting source for monolithic integration into highly integrated photonic circuits.

Rigorous Simulation of 3D Masks

We perform 3D lithography simulations by using a finite-element solver. To proof applicability to real 3D problems we investigate DUV light propagation through a structure of size 9μm x 4μm x 65nm. On this relatively large computational domain we perform rigorous computations (No Hopkins) taking into account a grid of 11 x 21 source points with two polarization directions each. We obtain well converged results with an accuracy of the diffraction orders of about 1%. The results compare well to experimental aerial imaging results. We further investigate the convergence of 3D solutions towards quasi-exact results obtained with different methods.

Litho-friendly design (LfD) methodologies applied to library cells

During the last years, various DfM (Design for Manufacturability) concepts have been proposed and discussed. Resolution enhancement technologies with the goal to provide reasonable printability over the whole lithographic process window, and the optimization of these tools and processes by print image simulation (PW-ORC) have become crucial aspects of DfM today. In addition, designers and layouters will become increasingly involved in yield discussions, as they will get tools and methods to identify and remove yield issues in the drawn layout. Such a lithography-aware design data flow, which is called LfD (Litho-friendly Design), is a very important step towards a fully developed DFM environment. Recently, the leading EDA tool vendors have provided tools for efficient process window analysis and a scoring of lithography issues in a form, which is close to productive usability. We report in this paper the implementation of LfD into the design flow of library cells for the 90 nm and the 65 nm design rule technologies. Specific aspects of such a LfD flow, like the availability of robust process models in early development stages are discussed as well as appropriate means to assess the results.

Thermooptically tunable optical phased array in SiO/sub 2/-Si

A thermooptically tunable optical phased array in the SiO/sub 2/-Si material which allows forward and backward tuning, was successfully demonstrated. By imprinting grooves into the substrate it was possible to achieve a tuning efficiency of 2 nm/W and a wavelength tuning over 6 nm.

Photonic crystal waveguides with propagation losses in the 1 dB/mm range

High-quality photonic crystal waveguides have been fabricated in the InGaAsP∕InP and GaAs∕AlGaAs material systems aimed at the communication wavelengths of 1.55 and 1.31 μm. The waveguides consist of omitted rows of holes in a triangular lattice of air holes etched into the semiconductor heterostructures by electron cyclotron resonance reactive ion etching. Efficient waveguiding has been observed in optical transmission measurements, with waveguide losses ranging from 1.5dB∕mm for a waveguide with three missing row of holes (W3) to 0.2dB∕mm for seven missing rows (W7).

Widely tunable complex-coupled distributed feedback laser with photonic Crystal mirrors and integrated optical amplifier

We report the development of a current-controlled widely tunable laser diode based on InP with photonic crystal mirrors and an integrated amplifier section for stabilized power output. The laser consists of three longitudinally coupled ridge waveguide cavities that are coupled through photonic crystal mirror segments. A laterally defined binary superimposed grating provides complex-coupled distributed feedback into two of the laser cavities. The wavelength can be switched over a range of 26 nm. Through adjustment of the current into a third amplifier section, the output power can be stabilized over the tuning range of the laser.

Rerouting and guided-repair strategies to resolve lithography hotspots

In contrast to defect limited yield loss, systematic yield detractors like lithography hotspots may cause a huge yield loss per event. For 45 nm and subsequent technology nodes, those findings are for this reason classified as DRC-like errors and need to be fixed before tape-out. In this paper, we report a comparison - from the use-model point-of-view - of two different methods for removal of lithography hotspots. First, a rip-up & re-routing and second, a guided-repair approach will be presented. This includes a discussion of the impact in the routing context, mainly radius of influence and timing closure, aspects of multiple layer involvement and the layout hierarchy, and the limitations caused by the layout grid.

Hardware verification of litho-friendly design (LfD) methodologies

With the upcoming technology generations, it will become more and more challenging to provide a good yield and a fast yield ramp. The contribution of Resolution Enhancement Technologies (RET) to Design for Manufacturability (DfM) targets is to provide a good printability over the whole process window and the control by print image simulation (PW-ORC) and to identify and remove yield issues imprinted in the drawn layout in early phases of the design flow. Such a lithography-aware design data flow, which we call LfD (Litho-friendly Design) will be a very important step towards a fully developed DfM environment. We report in this paper the application of a LfD design flow used for library cells at the MAPLE, an Infineon 65 nm design prototype fabricated by Chartered. The results of the process variability analysis are verified by experimental results (dose-focus exposure matrices).