Optical Attenuator Trench Bottom Semiconductor Replacement
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Solution Overview
Problem
The fabrication of optical attenuators with ridge waveguides results in undesirably low yield due to inconsistencies in the thickness of the light-transmitting medium at the bottom of trenches, leading to devices with low performance levels and increased waste.
Innovation Solution
Replacing the light-transmitting medium at the bottom of the trenches with contact semiconductors, such as polysilicon, which are deposited uniformly, reducing non-uniformity issues and increasing fabrication yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trenches are etched into the light-transmitting medium to form doped regions, then optical attenuation can be achieved through free carrier absorption, but the thickness variation of the light-transmitting medium at the bottom of trenches causes low fabrication yield
Solution Approach 1:
The patent removes the light-transmitting medium from the bottom of the trenches and replaces it with semiconductor material. This extraction eliminates the problematic interface where thickness variations occur, while preserving the trench structure's ability to contain doped regions for carrier injection and achieve optical attenuation.
Solution Approach 2:
The patent changes the material parameter at the trench bottom from light-transmitting medium to semiconductor material. This parameter change fundamentally alters the physical properties at the critical interface, eliminating sensitivity to thickness variations while maintaining the electrical functionality for carrier injection.
2Productivity
If the light-transmitting medium thickness at trench bottom is reduced to minimize waste, then fabrication yield improves, but the original medium provides inconsistent thickness leading to low performance
Solution Approach 1:
By changing the material parameter from light-transmitting medium to semiconductor, the patent decouples the thickness control from the original medium's inconsistent properties. The semiconductor material can be deposited with controlled thickness independent of the underlying structure, enabling both high yield and consistent performance.
Solution Approach 2:
The patent creates a composite structure where semiconductor material is integrated into the trench bottom, combining the optical waveguide functionality of the light-transmitting medium with the electrical injection capability of the semiconductor. This composite approach resolves the conflict between yield and performance.
3Device complexity
If doped regions are formed directly in the light-transmitting medium at trench bottom, then device structure is simplified, but thickness variations cause large source of waste
Solution Approach 1:
The patent extracts the light-transmitting medium from the trench bottom region, creating a distinct semiconductor-containing structure. This extraction adds a material layer but eliminates the need to control thickness in the problematic region, reducing fabrication waste while maintaining structural clarity.
Solution Approach 2:
The patent segments the trench structure into distinct regions: the light-transmitting medium forms the waveguide walls while the semiconductor material occupies the bottom. This segmentation separates the optical confinement function from the electrical injection function, reducing interdependence and fabrication waste.
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 use of contact semiconductors in the trenches enhances the fabrication yield and attenuation efficiency by minimizing the impact of light-transmitting medium thickness variations, resulting in higher performing optical devices.
Implementation Method 1
contact semiconductors, such as polysilicon, which are deposited uniformly
Implementation Method 2
electrical energy is applied to doped region of the light-transmitting medium so as to inject free carriers into the waveguide
Data Source
AI summary
A method of forming an attenuator on an optical device includes forming a ridge for a waveguide. The ridge is formed in a light-transmitting medium that is positioned on a base. The ridge extends upwards from slab regions of the light-transmitting medium. The method also includes forming trenches in the slab regions of the light-transmitting medium such that the trenches extend through the light-transmitting medium to the base. The trenches are formed such that the ridge is located between the trenches. The method also includes forming a semiconductor in a bottom of each of the trenches and then doping a region of each of the semiconductors.