SiGe Imaging Surface Structure for Defect-Free IR Light Capture
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Solution Overview
Problem
Current techniques face challenges in producing silicon germanium substrates without defects like dislocations or mosaic structures, which can lead to uneven structure formation issues during etching, resulting in dents or cracks in solid-state imaging devices.
Innovation Solution
A solid-state imaging device with a substrate and light incident surface layer made of a compound semiconductor containing germanium, where the germanium concentration increases towards the surface, allowing for the formation of a tapered bump structure through crystalline anisotropic and isotropic etching, enabling defect-free uneven structure formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an uneven structure is formed on a light incident surface of a substrate including silicon germanium using crystalline anisotropic etching, then the quantum efficiency in the infrared region can be increased, but there is a possibility that an etching solution enters a defect of the silicon germanium and thus the uneven structure has a dent or a crack
Solution Approach 1:
The patent applies preliminary action by forming a protective film on the light incident surface of the silicon germanium substrate before performing crystalline anisotropic etching. This protective film prevents the etching solution from entering defects such as dislocations and mosaic structures, thereby avoiding the formation of dents or cracks while still allowing the uneven structure to be formed for enhancing infrared quantum efficiency.
2Manufacturing precision
If a protective film is formed on the light incident surface before etching, then the uneven structure can be formed without dents or cracks, but the production process becomes more complex
Solution Approach 1:
The patent applies parameter changes by selecting a protective film material with specific properties (such as silicon oxide or silicon nitride) and controlling its thickness and formation conditions. By optimizing these parameters, the protective film effectively prevents etching solution penetration while minimizing the added complexity to the production process. The film is removed after etching, leaving the desired uneven structure without dents or cracks.
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 the easy formation of a tapered bump structure on the light incident surface of a silicon germanium substrate, enhancing quantum efficiency in the infrared region by increasing the optical path length and reducing defects in the imaging device.
Implementation Method 1
a substrate in which a plurality of photoelectric conversion parts is formed
Implementation Method 2
forming a groove having a lattice shape in the light incident surface layer by performing crystalline anisotropic etching on the light incident surface layer
Data Source
AI summary
A solid-state imaging device is provided with a substrate in which a plurality of photoelectric conversion parts is formed, and with a light incident surface layer formed on the light incident surface of the substrate. The substrate and the light incident surface layer include a compound semiconductor containing germanium. A concentration of the germanium in the light incident surface layer increases toward a surface side remote from the substrate. At the time of production, isotropic etching is performed after a lattice-shaped groove is formed in the light incident surface layer, so that a groove width of the lattice-shaped groove increases toward a light incident surface side of the light incident surface layer due to a difference in etching rate attributed to the concentration of the germanium, and an uneven structure having a tapered bump can thus be formed relatively easily.