Paul Davids

Electro-optic polymer cladding ring resonator modulators

Compact, low capacitance optical modulators are vital for efficient, high-speed chip to chip optical interconnects. Electro-optic (EO) polymer cladding micro-ring resonator modulators have been fabricated and their performance is characterized. Optical modulators with ring diameters smaller than 50 microm have been demonstrated in a silicon nitride based waveguide system on silicon oxide with a top cladding of an electro-optic polymer. Optical modulation has been observed with clock signals up to 10 GHz.

Surface plasmon polarization filtering in a single mode dielectric waveguide

We demonstrate that metallic electrodes symmetrically placed about a single mode dielectric waveguide can effectively polarize the mode by excitation of surface plasmons. The transmission through the metal electrode waveguide structure is examined as a function of mode polarization and electrode spacing. It is found that modes polarized perpendicular to the metal surface can resonantly excite surface plasmons, extinguishing the mode in the waveguide core, while modes polarized parallel to metal surface only suffer mode attenuation due to the presence of the metal. The phase matching conditions for excitation of surface plasmons are examined and the polarization and insertion loss of the transmitted mode is experimentally verified.

Challenges for on-chip optical interconnects

As integrated circuit interconnect dimensions continue to shrink and signaling frequencies increase, interconnect performance degrades. The performance degradation is due to several factors such as power consumption, cross-talk, and signal attenuation. On-chip optical interconnects are a potential solution to these scaling issues because they offer the promise of providing higher bandwidth. In this paper, progress on the major on-chip optical building blocks will be reviewed. It will be shown that significant advances have been made in the design and fabrication of waveguides, detectors, and couplers. However, major challenges in high speed electrical to optical conversion and signaling remain.

Generalized inverse problem for partially coherent projection lithography

In this paper, we will outline general mathematical techniques applied to the solution of the inverse problem for partially coherent lithographic imaging. The forward imaging problem is reviewed and its solution is discussed within the framework of 2D sampling and matrix coherence theory. The intensity distribution on the wafer is shown to be a bilinear functional in the sampled mask transmission values, and represents a continuous sparse set of variables for optimization. We review various iterative techniques to optimize the sampled mask transmission, called a tau-map. From the optimal tau-map, a procedure is required to construct a pixelated mask representation with restricted transmission values. This mask representation is not unique since the problem is ill-posed, and leads to multiple mask solutions for a single optimal tau-map. Various procedures based on spectral techniques and principle component analysis to quantize the mask are reviewed.

Physical Modeling of Layout-Dependent Transistor Performance

Design for Manufacturability (DFM) is a phrase that often accompanies discussion of layout optimization for lithography process effects, particularly Optical Proximity Correction (OPC). In an environment where process technology and circuit design are developed together, many other process-layout co-optimization strategies can be investigated. In this paper we discuss physical modeling to enable co-optimization strategies from a device performance point of view by examining layout-induced variation in front-end manufacturing processes used to engineer transistor strain and dopant diffusion/activation.

Surface plasmon induced polarization rotation and optical vorticity in a single mode waveguide.

The control and manipulation of the mode polarization state in a single mode dielectric waveguide is of considerable significance for optical information processing utilizing the polarization state to store digital information and integrated photonic devices used for high speed signaling. Here we report on an integrated on-chip mode polarization rotation based on short metal Cu electrodes placed in close proximity to the dielectric waveguide core. Polarization mode rotation with specific rotation of 10(4) degrees/mm is observed for offset metallic electrodes placed diagonally along a single mode dielectric waveguide. The mechanism for the polarization rotation is shown to be directional coupling into guided surface plasmon modes at the metal corners and coupling between the guided plasmon modes. This inter-plasmon coupling gives rise to giant polarization rotation and optical vorticity (helical power flow) in the waveguide.

Coupled eigenmode theory applied to thick mask modeling of TM polarized imaging

Coupled eigenmode (CEM) theory for TM polarized illumination is presented and applied to the 3D modeling of a linespace reticle. In this approach, the electric and magnetic field inside a line-space reticle is described in terms of an orthogonal set of eigenmodes of Maxwells equations. The diffraction of light by the reticle can then be expressed as a coherent sum of diffraction orders produced by each eigenmode independently. Fresnel transmission, overlap of eigenmodes with diffraction orders and propagation through the mask are shown to be the interactions that determine the complex amplitude of the diffraction orders produced by each mode. We further shown that only a small number of eigenmodes are needed to accurately calculate image contrast under TM polarized illumination.

Coupled eigenmode theory applied to thick mask modeling

Coupled eigenmode (CEM) theory is presented and applied to the 3D modeling of a line-space reticle. In this approach, the electric field inside a line-space reticle is described in terms of an orthogonal set of eigenmodes of Maxwells equations. The diffraction of light by the reticle can then be expressed as a coherent sum of diffraction orders produced by each eigenmode independently. Fresnel transmission, overlap of eigenmodes with diffraction orders and propagation through the mask are shown to be the interactions that determine the complex amplitude of the diffraction orders produced by each mode. CEM is then applied to the cases of a binary mask and an att-PSM under dipole illumination. It is shown that the behavior of contrast with pitch and mask bias is primarily affected by the propagation loss of the eigenmodes, which increases for smaller trench widths. In the case of the binary mask, this attenuation causes one eigenmode to become dominant and the resultant image approaches the perfect imaging of a single eigenmode. In the case of att-PSM, this attenuation causes a detuning of the transmission and phase, and thus, the image contrast is degraded.