Silicon Photodetection Element Back Surface Asperity
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Solution Overview
Problem
Conventional silicon photodiodes have limited spectral sensitivity in the near-infrared wavelength band and are expensive to manufacture, with complex processes involved.
Innovation Solution
A semiconductor photodetection element using a silicon substrate with a higher impurity concentration accumulation layer and an irregular asperity on the second principal surface, which increases the light travel distance and absorption, improving spectral sensitivity and reducing dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound semiconductors (InGaAsN, InGaAsNSb, InGaAsNP) are used to improve spectral sensitivity in the near-infrared wavelength band, then spectral sensitivity is improved, but manufacturing cost increases and manufacturing complexity increases
Solution Approach 1:
The invention changes the optical parameters of silicon by forming an accumulation layer with high impurity concentration on the back surface. This modifies the electrical and optical properties of the silicon substrate, enabling it to detect near-infrared light effectively without requiring expensive compound semiconductor materials. The parameter change in impurity concentration transforms silicon's inherent properties to achieve the desired spectral sensitivity.
Solution Approach 2:
The invention replaces expensive compound semiconductor materials with inexpensive silicon, which is the standard material in the semiconductor industry. By using silicon with modified properties through accumulation layer formation, the patent achieves near-infrared detection capability at much lower cost, utilizing a material that is abundant and already widely used in existing semiconductor manufacturing processes.
2Reliability
If compound semiconductors (InGaAsN, InGaAsNSb, InGaAsNP) are used to improve spectral sensitivity in the near-infrared wavelength band, then spectral sensitivity is improved, but device complexity increases
Solution Approach 1:
The invention modifies the electrical parameters of silicon by forming an accumulation layer with controlled impurity concentration. This parameter change enables the silicon substrate to function as a near-infrared photodetector without requiring complex multi-layer compound semiconductor structures. The simplified structure uses only silicon with modified properties, reducing manufacturing process complexity.
Solution Approach 2:
The invention extracts and utilizes the near-infrared detection capability from silicon itself by modifying its properties through accumulation layer formation, rather than importing this capability from compound semiconductor materials. This extraction approach simplifies the device structure by eliminating the need for complex heteroepitaxial growth processes required for InGaAsN and related materials.
3Ease of manufacture
If conventional silicon photodiodes are used, then manufacturing cost is low and ease of manufacture is high, but spectral sensitivity in the near-infrared wavelength band is insufficient
Solution Approach 1:
The invention changes the optical and electrical parameters of conventional silicon by forming an accumulation layer with high impurity concentration on the back surface. This parameter modification extends silicon's spectral response into the near-infrared region while maintaining its inherent manufacturing advantages. The accumulated carriers in the high-impurity layer enhance light absorption and carrier generation in the near-infrared wavelength range.
Solution Approach 2:
The invention introduces a new dimension to silicon photodetection by forming an accumulation layer on the back surface, creating a three-dimensional structure with varying impurity concentrations. This dimensional approach allows light incident on the back surface to interact with the accumulated carriers, enabling near-infrared detection without compromising the simplicity and low cost of silicon-based manufacturing.
4Reliability
If light travels a short distance through the silicon substrate, then manufacturing is simpler, but spectral sensitivity in the near-infrared wavelength band is insufficient
Solution Approach 1:
The invention utilizes the back surface of the silicon substrate as a new dimension for light entry, allowing light to travel through the thickness of the substrate rather than along its surface. By forming an accumulation layer on the back surface, the patent creates a path for light to interact with accumulated carriers, effectively increasing the interaction distance and enhancing near-infrared absorption without requiring a larger substrate area.
Solution Approach 2:
The invention changes the electrical parameter of the silicon substrate by forming an accumulation layer with high impurity concentration. This parameter change increases the density of free carriers that can absorb near-infrared photons, effectively increasing the absorption coefficient and allowing sufficient spectral sensitivity to be achieved with a reasonable substrate thickness, thus optimizing the light travel distance.
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 solution enhances spectral sensitivity in the near-infrared wavelength band while simplifying manufacturing and reducing costs, achieving improved photodetection sensitivity and reduced dark current.
Implementation Method 1
light incident into the semiconductor photodetection element is reflected, scattered, or diffused by the region to travel through a long distance in the silicon substrate
Implementation Method 2
light incident into the semiconductor photodetection element is reflected, scattered, or diffused by the region to travel through a long distance in the silicon substrate
Implementation Method 3
This causes the light incident into the semiconductor photodetection element to be mostly absorbed in the silicon substrate
Implementation Method 4
unwanted carriers generated independent of light on the second principal surface side recombine there, which can reduce dark current
Implementation Method 5
A semiconductor photodetection element comprising: a silicon substrate which is comprised of a semiconductor of a first conductivity type... and which has a semiconductor region of a second conductivity type formed on the first principal surface side
Data Source
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AI summary
A semiconductor photodetection element SP has a silicon substrate 21 comprised of a semiconductor of a first conductivity type, having a first principal surface 21a and a second principal surface 21b opposed to each other, and having a semiconductor layer 23 of a second conductivity type formed on the first principal surface 21a side; and charge transfer electrodes 25 provided on the first principal surface 21a and adapted to transfer generated charge. In the silicon substrate 21, an accumulation layer 31 of the first conductivity type having a higher impurity concentration than the silicon substrate 21 is formed on the second principal surface 21b side and an irregular asperity 10 is formed in a region opposed to at least the semiconductor region 23, in the second principal surface 21b. The region where the irregular asperity 10 is formed in the second principal surface 21b of the silicon substrate 21 is optically exposed.