Semiconductor Trenches for Light Absorption via Wet Etching
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Solution Overview
Problem
Silicon-based semiconductor devices face high surface reflectivity issues, leading to suboptimal quantum efficiency and photon absorption, particularly in the near-infrared region, which limits their performance and application, and existing black silicon production methods struggle with reducing critical dimensions and dark current.
Innovation Solution
A method involving a substrate with a locating notch and a patterned mask layer oriented in specific crystallographic directions, using wet etching to form trenches with decreasing cross-sectional width, which enhances light absorption and conversion efficiency while reducing critical dimensions and dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the silicon surface is left untreated, then the manufacturing process is simple, but the light reflectivity is too high (40-60%), severely limiting photon absorption and quantum efficiency
Solution Approach 1:
The patent applies curvature by forming spherical or dome-shaped silicon structures through controlled etching processes. These curved surfaces reduce light reflectivity by minimizing abrupt surface transitions and enabling gradual light penetration, thereby improving photon absorption while maintaining manufacturing feasibility
Solution Approach 2:
The patent implements local quality by creating regions with different surface properties - specifically, forming spherical structures in certain areas while maintaining flat surfaces in others. This allows selective optimization of light absorption in specific regions without compromising the entire device structure
2Loss of energy
If greater silicon thickness is used to increase photon absorption efficiency, then light absorption improves, but the semiconductor process complexity and cost increase significantly
Solution Approach 1:
The patent transitions from a two-dimensional planar structure to a three-dimensional spherical structure. This dimensional change increases the effective light absorption path length and surface area without requiring increased substrate thickness, thereby improving photon absorption efficiency while avoiding additional process complexity
Solution Approach 2:
The patent embeds spherical silicon structures within the existing substrate architecture, creating a nested configuration where the spherical structures are integrated into the planar substrate. This allows enhanced light absorption functionality to be incorporated without adding external layers or complex multi-step processes
3Loss of energy
If existing black silicon production methods are used to reduce light reflectivity, then light absorption improves, but critical dimensions cannot be further reduced and dark current remains significant
Solution Approach 1:
The patent changes the geometric parameters of the silicon structures by forming spherical or dome-shaped features with controlled radii and depths. By optimizing these geometric parameters, the patent achieves both reduced light reflectivity and improved critical dimension control, while the smooth curved surfaces minimize defect formation that would otherwise increase dark current
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 increases light absorption and conversion efficiency, reduces critical dimensions, and minimizes dark current by optimizing the substrate's surface structure through the use of wet etching, resulting in improved semiconductor device performance.
Implementation Method 1
forming a plurality of trenches by performing a wet etching process on the surface of the substrate using the patterned mask layer as a mask
Implementation Method 2
enhance the ability of a silicon surface in a device to capture incident light energy and thus reduce reflective loss of the light energy and improve the device's light absorption and conversion efficiency
Data Source
AI summary
A semiconductor device and a method of fabricating the same are disclosed. A reference direction for a substrate is parallel to a first or second crystallographic direction, and a patterned hard mask layer is distributed along the first crystallographic direction. For substrates with notches oriented in different crystallographic directions, the patterned mask layer may be used as a mask for forming trenches in the substrate surface. When viewed normal to a cross-section perpendicular to the substrate, each trench has a cross-sectional width decreasing from the substrate surface toward the inside of the substrate. This allows the semiconductor device to have increased light absorption and conversion efficiency. Forming the trenches by wet etching can avoid increased dark current due to damage to the trenches’ side surfaces that may be caused by the use of a dry etching process. Thus, an effective improvement in terms of dark current can be achieved.