Silicon Nitride Waveguide Using Deuterated Silane LPCVD
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Solution Overview
Problem
Existing silicon nitride waveguides suffer from high optical losses at wavelengths between 1500 and 1600 nm due to the incorporation of hydrogen during the deposition process, which affects the uniformity of loss across the C-band range.
Innovation Solution
A silicon nitride waveguide is fabricated using a low-pressure chemical vapor deposition (LPCVD) process with a deuterated silane source, which results in a hydrogen-free silicon nitride core with reduced optical losses. The LPCVD process is conducted at higher temperatures (800°C to 1150°C) without using a plasma, ensuring lower losses compared to plasma-enhanced CVD (PECVD) approaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If plasma-enhanced CVD (PECVD) is used to deposit silicon nitride core, then deposition can be performed at lower temperatures, but hydrogen is incorporated into the core causing high optical losses
Solution Approach 1:
The patent changes the deposition temperature parameter from low (PECVD) to high (LPCVD 800-1150°C) to eliminate hydrogen incorporation. This parameter change resolves the contradiction by sacrificing the temperature advantage of PECVD to achieve the primary goal of reducing optical loss through hydrogen-free core formation.
Solution Approach 2:
The patent replaces the plasma-based deposition mechanism (PECVD) with a thermal-based mechanism (LPCVD). By substituting the plasma activation method with pure thermal decomposition at elevated temperatures, the process eliminates hydrogen incorporation while maintaining deposition functionality, thereby resolving the optical loss issue.
2Ease of manufacture
If conventional silicon nitride deposition is used, then manufacturing is simpler, but loss uniformity across C-band is poor
Solution Approach 1:
The patent changes the deposition temperature to 800-1150°C and uses deuterated silane instead of conventional silane. These parameter changes improve loss uniformity across the C-band by preventing hydrogen incorporation, which causes wavelength-dependent loss variations. The increased process complexity is justified by the significant improvement in optical performance uniformity.
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
The approach achieves ultra-low loss values, with a maximum difference in loss value between 1520 nm and 1550 nm of 0.01 dB/cm or less, and an average loss value between 1500 nm and 1600 nm of 0.2 dB/cm or less, thereby addressing the issue of non-uniform loss across the C-band range.
Implementation Method 1
forming a silicon nitride core over the first portion of the cladding using a deuterated silane source in a low-pressure chemical vapor deposition (LPCVD) process
Data Source
AI summary
A method of making a waveguide includes providing a first portion of a cladding located over a substrate. forming a silicon nitride core over the first portion of the cladding using a deuterated silane source in a low-pressure chemical vapor deposition process, and forming a second portion of the cladding over the silicon nitride core.