Lithium Niobate Mesa Epitaxy on Silicon for CMOS Phase Modulators
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge lies in producing lithium niobate layers on silicon-based substrates with high crystalline quality and controlled stoichiometry, while minimizing production costs and avoiding the complexities of transfer techniques that incur mechanical stresses and contamination risks.
Innovation Solution
A method involving the formation of a nitride-based refractory nucleation layer on a silicon substrate, followed by epitaxial growth of a lithium niobate or lithium tantalate layer portion, which allows for localized growth and reduced mechanical stresses, maintaining stoichiometry and crystalline quality, and integrating these layers directly into silicon technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transfer technique is used to produce thin LiNbO3 layer on silicon substrate, then lithium niobate layer can be formed on silicon substrate, but production cost increases significantly and thickness homogeneity deteriorates
Solution Approach 1:
The patent introduces a silicon oxide intermediate layer between the silicon substrate and the lithium niobate layer. This intermediate layer serves as a buffer that reduces thermal expansion mismatch and mechanical stress, enabling direct growth of high-quality LiNbO3 on silicon without complex transfer processes. The intermediate layer mediates the interface compatibility issues between dissimilar materials.
Solution Approach 2:
The patent replaces the mechanical transfer process (which involves bonding, etching, and thinning steps) with a direct epitaxial growth process. By using chemical vapor deposition or similar techniques to grow LiNbO3 directly on the silicon substrate with the oxide intermediate layer, the method eliminates the need for mechanical handling and transfer operations, thereby reducing complexity and cost.
2Area of stationary object
If solid plate transfer is used to form LiNbO3 layer, then entire surface coverage is achieved, but mechanical stresses from thermal dilatation difference cause formation difficulties
Solution Approach 1:
The patent applies local quality by creating a patterned structure where lithium niobate is formed only in specific regions defined by openings in a masking layer. This localized formation approach allows each region to be independently optimized and reduces the cumulative mechanical stress across the entire substrate, making the process more controllable and less prone to stress-induced defects.
3Length of moving object
If LiNbO3 layer is etched to form local portions, then local formation is achieved, but production line contamination with lithium occurs
Solution Approach 1:
The patent performs preliminary action by forming the lithium niobate layer locally from the beginning through selective epitaxial growth in openings of a masking layer, rather than forming a complete layer and then etching it. This preliminary localization prevents lithium material from being deposited in areas where it is not needed, thereby eliminating the source of contamination that would otherwise require aggressive etching processes.
4Length of stationary object
If thin LiNbO3 layer is transferred and thinned, then thickness range is achieved, but thickness homogeneity deteriorates with standard deviation around 50 nm
Solution Approach 1:
The patent replaces the mechanical transfer and thinning process with a direct controlled deposition process. By using epitaxial growth or chemical vapor deposition to form the LiNbO3 layer directly on the silicon substrate, the thickness can be precisely controlled through deposition parameters (time, temperature, precursor flow rates), achieving superior thickness uniformity without the mechanical variations inherent in transfer processes.
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 production of thin lithium niobate layers with precise thickness control and high crystalline quality, reducing production costs and integrating them seamlessly into CMOS technology, thus facilitating the development of advanced electrooptical devices like phase modulators.
Implementation Method 1
Forming, by epitaxy, a lithium niobate- or lithium tantalate-based layer portion, called LNO portion, made of mesa on the exposed part of the nucleation layer
Implementation Method 2
The principle of optical phase modulators is typically based on a local modulation of the refraction index of the material, wherein the light wave propagates. This refraction index variation can be advantageously obtained by Pockels effect
Data Source
AI summary
A device including, stacked in a vertical direction (z), a silicon-based substrate, a nucleation layer made of a nitride-based refractory material, a lithium niobate-based layer portion, called LNO portion, made of mesa on the nucleation layer, the LNO portion being bordered by a masking layer. The device further includes at least one electrode configured to apply an electric field to the LNO portion. A method for producing such a device, including a formation by localised epitaxy of the LNO portion, is also disclosed.