Epitaxial Metal Electrode Stack With Rare Earth Oxide Template
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Solution Overview
Problem
Epitaxial growth of high-quality metal layers over semiconductor materials is challenging due to issues like polycrystalline growth, defects, and grain boundaries, which affect the acoustic performance and resonant frequencies in devices such as RF filters and lead to increased resistivity.
Innovation Solution
A layered structure comprising a substrate, a rare earth oxide layer epitaxially grown over the substrate, a metal layer epitaxially grown over the rare earth oxide, and a semiconductor layer epitaxially grown over the metal layer, where the rare earth oxide layer acts as a template to prevent unwanted interdiffusion and provide a high-quality interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metal contact layers are applied to epitaxial structures with complex topography, then device functionality is achieved, but the metal layers become polycrystalline with defects and grain boundaries that increase resistivity and reduce acoustic performance
Solution Approach 1:
The patent introduces an epitaxial metal layer as an intermediary between the semiconductor layers and the underlying substrate or contact structures. This epitaxial metal layer serves as a high-quality template that prevents the formation of polycrystalline structures with grain boundaries, thereby maintaining low resistivity and high acoustic performance even in devices with complex topography
Solution Approach 2:
The patent changes the crystalline structure parameter of the metal layer from polycrystalline to epitaxial (single crystal) by controlling the growth conditions and using the semiconductor layer as a template. This parameter change eliminates grain boundaries and defects, directly improving both crystal quality and acoustic performance
2Speed
If metal layers are made thinner to access high resonant frequencies, then device performance improves, but crystal quality deteriorates due to increasing effect of defects and grain boundaries
Solution Approach 1:
The epitaxial metal layer acts as an intermediary template that enables the growth of high-quality thin metal films. By providing a single-crystal template, it allows the metal layer to be made thinner for high resonant frequencies while maintaining crystal quality, as the epitaxial growth process prevents defect formation even at reduced thicknesses
3Adaptability or versatility
If extensive etching and deposition are performed to achieve device functionality, then device complexity increases, but manufacturing complexity and process time increase
Solution Approach 1:
The epitaxial metal layer serves multiple functions simultaneously: it provides high-quality acoustic performance, acts as a template for subsequent layer growth, prevents unwanted interdiffusion, and enables device functionality. This multi-functionality reduces the need for separate processing steps and simplifies the overall manufacturing process
4Reliability
If YSZ is used to separate metal from silicon substrate to prevent siliciding, then unwanted interdiffusion is prevented, but the substrate quality deteriorates due to grain boundaries and mixed crystallinity
Solution Approach 1:
The patent uses an epitaxial rare earth oxide layer as an intermediary between the metal layer and the silicon substrate. This layer prevents unwanted interdiffusion and siliciding while maintaining high crystal quality throughout the structure, unlike YSZ which introduces grain boundaries and mixed crystallinity
Solution Approach 2:
The patent changes the material parameter from YSZ (polycrystalline, mixed crystallinity) to epitaxial rare earth oxide (single crystal, uniform crystallinity). This parameter change maintains the protective function against interdiffusion while eliminating the crystal quality deterioration caused by grain boundaries
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the growth of high-quality epitaxial metal layers with reduced defects, improving the acoustic performance and resonant frequencies by maintaining high film quality even at thinner thicknesses, and enhancing the reflectivity of epitaxial stacks in devices like VCSELs.
Implementation Method 1
a first metal layer epitaxially grown over the rare earth oxide (REO) layer
Implementation Method 2
a first metal layer epitaxially grown over the rare earth oxide (REO) layer
Implementation Method 3
a first semiconductor layer epitaxially grown over the first metal layer
Data Source
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AI summary
Systems and methods are described herein to include an epitaxial metal layer between a rare earth oxide and a semiconductor layer. Systems and methods are described to grow a layered structure, comprising a substrate, a first rare earth oxide layer epitaxially grown over the substrate, a first metal layer epitaxially grown over the rare earth oxide layer, and a first semiconductor layer epitaxially grown over the first metal layer. Specifically, the substrate may include a porous portion, which is usually aligned with the metal layer, with or without a rare earth oxide layer in between.