In this paper we describe a method of fabricating a Fabry-Perot filter array consisting of four distinct wavelengths using a stopping layer, which in turn is discriminately measured. Precise control of the oxide thickness is demonstrated by using reflectance to measure center wavelengths (CWL) between 645nm-822nm with full width half maximum (FWHM) values of 15 nm. These parameters are used to confirm good narrow band filter characteristics. The physical and chemical properties of an oxide layer converted from a silicon-carbon-nitride (SiCN) etch stop layer (ESL) is reported for both as-deposited and the resultant oxidized film. The filter array can be fabricated directly on top of silicon photo diodes, to form a complete multi-wavelength sensor system. Fabricating a multi-wavelength filter array using etch-stop layers can provide better thickness control and across wafer uniformity compared to a timed-etch approach.
KEYWORDS: Etching, Polymerization, Molecules, Monte Carlo methods, Finite element methods, Lithography, Ultraviolet radiation, Molecular interactions, Scanning electron microscopy, Optical lithography
Step and Flash Imprint Lithography (SFIL) is a revolutionary next generation lithography option that has become increasingly attractive in recent years. Elimination of the costly optics of current step and scan imaging tools makes SFIL a serious candidate for large-scale commercial patterning of critical dimensions below ~50 nm. This work focuses on the kinetics of the UV curing of the liquid etch barrier and the resulting densification/contraction of the etch barrier as it solidifies during this step. Previous experimental work in our group has measured the bulk densification of several etch barrier formulations, typically about 9 % (v/v). It remains unknown, however, how much etch barrier contraction occurs during the formation of nano-scale features. Furthermore, it is of interest to examine how changes in monomer pendant group size impact imprinted feature profiles.
This work provides answers to these questions through a combination of modeling and experimental efforts. Densification due to the photopolymerization reaction and the resulting shift from Van der Waals’ to covalent interactions is modeled using Monte-Carlo techniques. The model allows for determination of extent of reaction, degree of polymerization, and local density changes as a function of the etch barrier formulation and the interaction energies between molecules (including the quartz template). Experimental efforts focus on a new technique to examine trench profiles in the quartz template using TEM characterization. Additionally, SEM images of imprinted images from various etch barrier formulations were examined to determine local contraction of the etch barrier. Over a large range of etch barrier formulations, which range from 10 - 20 % volumetric contraction as bulk materials, it was found that dense 100 nm lines printed approximately the same size and shape.
Extreme ultraviolet lithography (EUVL) is a leading next generation lithography technology. The mask blank for EUVL consists of a low thermal expansion material substrate having a square photomask form factor that is coated with Mo/Si multilayers. One of the challenges in implementing EUVL is to economically fabricate multilayer-coated mask blanks with no printable defects. The starting substrates, due to the required tight specifications of flatness and defects, might have a very high manufacturing cost and hence a method to recover these substrates for reuse without compromising the properties will enable a lower cost for the masks. This paper details a potential approach to remove the damaged multilayers from the substrates without compromising the morphology and characteristics of the starting substrate. Furthermore, the process is applicable to optical elements of the EUV projection optics system that have reflective Mo/Si mirrors of various shapes.
In this work, we report the effect of annealing temperature on the properties of epitaxial PbZr0.52Ti0.48O3 (PZT) films deposited using sol-gel techniques on (001) Si substrates with a thin, epitaxial SrTiO3 (STO) interlayer. The STO is grown on silicon using molecular beam epitaxy (MBE) and acts as the template for PZT growth. We report the values for stress, density, thickness, and refractive index vs. anneal temperatures for a thin PZT film. AFM surface roughness values of less than 0.4 nm are typical for this film. XRD patterns show the film to be c-axis orientated, with PHI scans demonstrating that the [100] PZT is orientated along the [110] Si direction. SEM cross-sections show the film morphology is free of gain boundaries and are clear of interfacial layers from the multiple spin/bake/anneal deposition technique, thereby making this material an excellent candidate for electro-optic applications.
Extreme ultraviolet lithography (EUVL) is the leading candidate for next generation lithography with the potential for extendibility beyond the 50-nm node. The three-layer absorber stack for EUVL reticles consists of an absorber, repair buffer and etch-stop layers, while a two-layer absorber stack eliminates the etch-stop layer. A portion of the mask pattern distortion can be assigned to the absorber stack's film stress. Ideally, the absorber stack films would have zero stress uniformly across the mask, which would produce zero pattern distortion when the films were removed during the pattern transfer processes. Maintaining adequate thin film stress control and uniformity relies on accurate thin film thickness measurements. The thin film deposition parameters can have a significant influence on the metrology technique's ability to measure the thin film's thickness. We have studied resistive and photonic metrology techniques for absorber stack thin film thickness measurement and stress control.
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