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Monocrystalline PLZT Curved Surface Optical And Electro-Optical Components On A Silicon Wafer

IP.com Disclosure Number: IPCOM000010099D
Original Publication Date: 2002-Oct-22
Included in the Prior Art Database: 2002-Oct-22
Document File: 2 page(s) / 26K

Publishing Venue

Motorola

Related People

Gregory J. Dunn: AUTHOR [+2]

Abstract

High quality epitaxial layers of monocrystalline materials can be grown overlying monocrystalline substrates such as large silicon wafers by forming a compliant substrate for growing the monocrystalline layers. An accommodating buffer layer comprises a layer of monocrystalline oxide spaced apart from a silicon wafer by an amorphous interface layer of silicon oxide. The amorphous interface layer dissipates strain and permits the growth of a high quality monocrystalline oxide accommodating buffer layer. Any lattice mismatch between the accommodating buffer layer and the underlying silicon substrate is taken care of by the amorphous interface layer. This epitaxial method permits the growth of high quality monocrystalline lead lanthanum zirconate titanate (PLZT) optical and electro-optical components, such as lenses, prisms, and waveguides, with curved or straight surfaces, on a strontium titanate (STO) accommodating buffer layer on a silicon wafer, offering substantial cost advantages over single crystal STO substrates of the prior art, and allowing monolithic integration with silicon and compound semiconductor electronics, lasers and light emitting diodes, and optical detectors.

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Monocrystalline PLZT Curved Surface Optical And Electro-Optical Components On A Silicon Wafer

Gregory J. Dunn and Robert T. Croswell

Abstract

High quality epitaxial layers of monocrystalline materials can be grown overlying monocrystalline substrates such as large silicon wafers by forming a compliant substrate for growing the monocrystalline layers.� An accommodating buffer layer comprises a layer of monocrystalline oxide spaced apart from a silicon wafer by an amorphous interface layer of silicon oxide.� � The amorphous interface layer dissipates strain and permits the growth of a high quality monocrystalline oxide accommodating buffer layer.� � � Any lattice mismatch between the accommodating buffer layer and the underlying silicon substrate is taken care of by the amorphous interface layer.� This epitaxial method permits the growth of high quality monocrystalline lead lanthanum zirconate titanate (PLZT) optical and electro-optical components, such as lenses, prisms, and waveguides, with curved or straight surfaces, on a strontium titanate (STO) accommodating buffer layer on a silicon wafer, offering substantial cost advantages over single crystal STO substrates of the prior art, and allowing monolithic integration with silicon and compound semiconductor electronics, lasers and light emitting diodes, and optical detectors.�

Problem

PLZT is a transparent perovskite with rapid electro-optic response.� Commercial applications of bulk PLZT have included high-speed electro-optic modulators, attenuators, switches, and polarization transformers for long haul high-speed optical networks.� In the past five years there has been significant development activity on thin film PLZT at leading optical component firms.� Thin film PLZT would allow both low operating voltages and, potentially, integration with semiconductor electronics.� Epitaxial PLZT is particularly desired to maximize the material’s anisotropic properties and to minimize loss from grain boundary scattering.� U.S. Patent 6,307,996 teaches the fabrication of optical lenses and waveguides with precision curved surfaces by patterning an amorphous PLZT film, followed by solid phase epitaxy.� Etching the PLZT in its amorphous state prevents edge roughness due to anisotropic etching of the monocrystalline material, and moreover allows etch selectivity between the amorphous PLZT film and an underlying crystalline oxide.� A significant drawback of this approach is that it depends upon a single crystal strontium titanate (STO) wafer for epitaxial formation of the PLZT films.� This limits the practical value of the technology, since S...