Textured Silicon Imager Structure for Infrared Light Absorption
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Solution Overview
Problem
Traditional silicon-based photodetecting imagers have limited absorption and detection properties for infrared light, as silicon is an indirect bandgap semiconductor with low absorption of electromagnetic radiation with wavelengths greater than 1100 nm, requiring substantial absorption depths that are not efficiently achieved in standard silicon wafers.
Innovation Solution
The introduction of a textured region on the semiconductor substrate, which can be positioned opposite or adjacent to doped regions, enhances the absorption of infrared electromagnetic radiation by increasing the effective absorption length and includes surface features such as cones, pyramids, or microlenses, formed through processes like laser processing or chemical etching, to facilitate the detection of longer wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard silicon substrate is used for infrared detection, then the device structure is simple and manufacturing is easy, but the absorption of electromagnetic radiation with wavelengths greater than 1100 nm is very low
Solution Approach 1:
The patent applies surface texturing with curved features (pyramids, cones, or other non-planar geometries) to the silicon substrate. This curvature increases the optical path length and multiple internal reflections of infrared radiation, thereby enhancing absorption in the wavelength range greater than 1100 nm where standard flat silicon substrates have very low absorption due to silicon's indirect bandgap properties.
2Reliability
If the semiconductor substrate thickness is increased to improve infrared absorption, then the absorption depth is sufficient, but the device becomes thicker and less integrated
Solution Approach 1:
Instead of increasing substrate thickness, the patent introduces surface texturing with curved features that create multiple internal reflections and extend the optical path length within the existing substrate thickness. This allows sufficient absorption depth to be achieved while maintaining a thin, integrated device structure suitable for modern semiconductor manufacturing.
3Reliability
If a textured region is added to increase effective absorption length, then infrared detection is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent implements surface texturing using self-organizing chemical etching processes that create uniform pyramidal or conical structures through controlled silicon dissolution. This approach achieves the desired curvature-based light trapping while using well-established semiconductor manufacturing techniques, thereby limiting the increase in device complexity and manufacturing difficulty.
Solution Approach 2:
The patent optimizes the texturing parameters (etching time, chemical composition, temperature) to achieve the desired surface morphology that maximizes infrared absorption. By carefully controlling these parameters, the effective absorption length is increased while keeping the manufacturing process within reasonable complexity bounds using standard semiconductor fabrication equipment.
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 allows for increased quantum efficiency and responsivity, enabling the absorption of longer wavelengths within a thinner semiconductor material, improving the signal-to-noise ratio and response speed of the photodetectors.
Implementation Method 1
interacting with electromagnetic radiation further includes increasing the semiconductor substrate's effective absorption length as compared to a semiconductor substrate lacking a textured region
Implementation Method 2
CMOS sensors are typically manufactured from silicon and can covert visible incident light into a photocurrent
Data Source
AI summary
Photosensitive devices and associated methods are provided. In one aspect, for example, a photosensitive imager device can include a semiconductor substrate having multiple doped regions forming at least one junction, a textured region coupled to the semiconductor substrate and positioned to interact with electromagnetic radiation, and an electrical transfer element coupled to the semiconductor substrate and operable to transfer an electrical signal from the at least one junction. In one aspect, the textured region is operable to facilitate generation of an electrical signal from the detection of infrared electromagnetic radiation. In another aspect, interacting with electromagnetic radiation further includes increasing the semiconductor substrate's effective absorption wavelength as compared to a semiconductor substrate lacking a textured region.