Ge-on-Si Photodetector Strain Uniformity via Segmented Base
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Solution Overview
Problem
Existing semiconductor fabrication methods for Ge-on-Si photodetectors result in non-uniform tensile strain profiles, leading to reduced device sensitivity and compromised high-frequency performance due to compressive strain near the side surfaces and bottom portions of the Ge strip.
Innovation Solution
A method involving a Ge-on-insulator platform where the second base portion is removed to expose the first base portion, allowing a stressor element to apply uniform tensile strain, achieved through self-aligned dry etching techniques, ensuring a more uniform strain profile and enhanced absorption coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stressor layer is deposited on the Ge strip to apply tensile strain, then the absorption coefficient is enhanced, but the strain profile becomes non-uniform with compressive strain near side surfaces and bottom portions
Solution Approach 1:
The base layer is segmented into a first base portion and a second base portion. The stressor layer is selectively deposited only on the first base portion, which has a larger area than the Ge strip. This segmentation allows the stressor layer to apply uniform tensile strain through the Ge strip without creating compressive strain zones, thereby resolving the non-uniform strain profile problem while maintaining enhanced absorption coefficient.
Solution Approach 2:
Different regions of the base layer are given different functions: the first base portion serves as the stress application region with larger area for uniform stress distribution, while the second base portion is removed to expose the Ge strip sides. This local differentiation ensures uniform tensile strain across the Ge strip thickness and sides, eliminating the compressive strain zones that would otherwise form.
2Reliability
If the Ge strip length is increased to compensate for low responsivity, then the absorption coefficient is improved, but the device capacitance increases and high frequency performance is compromised
Solution Approach 1:
The strain parameter is changed from the conventional non-uniform distribution to a uniformly enhanced tensile strain of 0.4-0.6% through the entire Ge strip. This uniform strain enhancement increases the absorption coefficient sufficiently to allow shorter device lengths while maintaining high responsivity, thereby preserving high frequency performance with reduced capacitance.
3Manufacturing precision
If deep wet etching is used to create suspended structure for uniform strain, then strain uniformity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of creating a suspended structure by removing the base layer underneath the Ge strip, the invention takes out only the second base portion that is adjacent to and larger than the Ge strip. This extraction simplifies the structure by maintaining the base layer support while achieving uniform strain through the selective stressor layer deposition on the first base portion, avoiding the complexity of suspended structures.
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 results in a significantly more uniform tensile strain profile along the depth of the semiconductor element, enhancing the absorption coefficient and extending the optical absorption edge, thereby improving photodetector sensitivity and high-frequency performance.
Implementation Method 1
a stressor element arranged on the first base portion and having a tensile stress; The stressor element applies stress to the first base portion, thereby causing the semiconductor element to experience a more uniform profile of tensile strain
Data Source
AI summary
Disclosed is a method of facilitating straining of a semiconductor element (331) for semiconductor fabrication. In a described embodiment, the method comprises: providing a base layer (320) with the semiconductor element (331) arranged on a first base portion (321) of the base layer (320), the semiconductor element (331) being subjected to a strain relating to a characteristic of the first base portion (321); and adjusting the characteristic of the first base portion (321) to facilitate straining of the semiconductor element (331).