Polycrystalline Silicon Insulating Layer for SOI Waveguides
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is the difficulty in forming thick insulating layers, which leads to increased costs, processing complexities, and substrate distortion, resulting in propagation losses and defects in optical waveguides due to light leakage.
Innovation Solution
A semiconductor device configuration using a polycrystalline silicon layer under a thin insulating layer to reduce the thickness of the cladding layer, mitigating film stress and distortion, and employing a thin silicon oxide film to cover the optical waveguides, thereby suppressing light leakage and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick insulating layer is formed to reduce light leakage, then light leakage is reduced, but manufacturing difficulty and cost increase
Solution Approach 1:
The patent divides the insulating layer into multiple thin layers (first insulating layer and second insulating layer) instead of using a single thick layer. Each layer has a thickness of 50-200 nm, which is much thinner than the conventional single thick layer. This segmentation reduces light leakage effectively while avoiding the manufacturing difficulties associated with thick insulating layers.
Solution Approach 2:
The patent changes the thickness parameter of the insulating layer from a single thick layer (conventional approach) to multiple thin layers (50-200 nm each). This parameter change maintains the light leakage reduction benefit while significantly improving ease of manufacture, as thin layers are much easier to form uniformly and process without causing substrate distortion.
2Object-affected harmful factors
If a thick insulating layer is formed to reduce light leakage, then light leakage is reduced, but substrate distortion occurs
Solution Approach 1:
By segmenting the insulating layer into multiple thin layers (first insulating layer and second insulating layer, each 50-200 nm thick), the patent eliminates substrate distortion that would occur with a thick insulating layer, while still achieving effective light leakage reduction through the cumulative effect of multiple layers.
Solution Approach 2:
The patent changes the insulating layer thickness parameter from a single thick layer to multiple thin layers with controlled thickness (50-200 nm each). This parameter change prevents substrate distortion by keeping individual layer thicknesses below the distortion threshold, while maintaining effective light leakage suppression.
3Object-affected harmful factors
If a thick insulating layer is formed to reduce light leakage, then light leakage is reduced, but propagation loss increases due to defects
Solution Approach 1:
The patent segments the insulating layer into multiple thin layers (first and second insulating layers, each 50-200 nm), which reduces light leakage effectively without creating the defects associated with thick layers. This segmentation approach minimizes propagation loss by avoiding the formation of defects that would occur in thick insulating layers.
Solution Approach 2:
The patent optimizes the insulating layer thickness parameter by using multiple thin layers (50-200 nm each) instead of a single thick layer. This parameter optimization reduces light leakage while minimizing propagation loss, as the thin layers do not induce substrate distortion or create defects that would increase energy loss.
4Object-affected harmful factors
If a thick insulating layer is formed to reduce light leakage, then light leakage is reduced, but exposure accuracy decreases
Solution Approach 1:
The patent divides the insulating layer into multiple thin layers (first insulating layer and second insulating layer, each 50-200 nm), which maintains exposure accuracy by avoiding the substrate distortion that occurs with thick layers, while still achieving effective light leakage reduction through the multi-layer structure.
Solution Approach 2:
The patent optimizes the insulating layer thickness parameter by using multiple thin layers (50-200 nm each) instead of a single thick layer. This parameter optimization maintains exposure accuracy by preventing substrate distortion, while still achieving effective light leakage suppression through the cumulative effect of multiple layers.
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 reduces propagation losses, maintains transmission characteristics, and improves exposure accuracy, reducing the risk of substrate distortion and defects while maintaining efficient optical signal transmission.
Implementation Method 1
Through the optical waveguides made of silicon as a material, light partially leaks out to the periphery approximately in the same range as a wavelength of light during propagation through the optical waveguides. In order to reduce a propagation loss due to the leakage of light, the peripheries (left, right, top, and bottom) of the optical waveguides are covered with an insulating film made of silicon oxide.
Data Source
AI summary
An SOI substrate includes a base substrate, a polycrystalline silicon layer formed on the base substrate, an insulating layer formed on the polycrystalline silicon layer, and a semiconductor layer formed on the insulating layer, and optical waveguides are formed in the semiconductor layer of the SOI substrate. Thus, by arranging the polycrystalline silicon layer under the insulating layer, the insulating layer can be made thin. Since the polycrystalline silicon layer includes a plurality of grains (a mass of grains made of a single crystal Si), even when leakage of light is generated beyond the insulating layer, reflection (diffusion) of light can be suppressed. In addition, by arranging the polycrystalline silicon layer under the insulating layer, the insulating layer can be made thin, so that distortion of a substrate can be suppressed.