MOS Transistor Light Sensor Bulk Region Doping
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Solution Overview
Problem
Existing light registration technologies, such as bipolar transistors used in CMOS image sensors, face issues with poorly controlled geometry, low current gain, and strong temperature dependency, leading to non-linear light intensity signal quality, particularly in integrated chip applications like chip cards.
Innovation Solution
A MOS-transistor structure with a bulk region of different doping type between source/drain regions, where charge carriers generated by light control current flow without relying on an electric field, and a high resistance connection is established to reduce leakage and temperature dependency, using a secondary MOS-transistor structure to set the bulk region at a defined potential and bypass leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bipolar transistor is used as a photo-transistor with a floating base, then light detection capability is achieved, but geometry control is poor and current gain is low
Solution Approach 1:
The patent changes the fundamental operating parameter from bipolar transistor physics to MOS transistor physics. By using a MOS transistor structure with controlled doping types (p-type source/drain regions and n-type bulk region), the invention achieves precise geometric control through standard MOS fabrication processes while maintaining light detection capability through photo-generated charge carriers in the bulk region.
2Measurement precision
If a bipolar transistor is used as a photo-transistor, then light detection capability is achieved, but temperature dependency is strong and linearity is poor
Solution Approach 1:
The patent changes the physical mechanism from bipolar transistor operation to MOS transistor operation. The MOS structure with p-type source/drain regions and n-type bulk region operates through photo-generated charge carriers controlling current flow, which exhibits significantly reduced temperature dependency compared to bipolar transistor operation, thereby improving linearity and temperature stability.
3Measurement precision
If a bipolar transistor is used as a photo-transistor, then light detection capability is achieved, but current gain is low
Solution Approach 1:
The patent transitions from bipolar transistor physics to MOS transistor physics, where the current control mechanism through photo-generated charge carriers in the bulk region provides superior current gain. The MOS structure allows for better control of current flow between source and drain regions through the bulk region, achieving higher current gain than bipolar photo-transistors.
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 improves light detection accuracy and linearity by reducing leakage current and temperature dependency, ensuring a reliable and integrated light sensing capability within a chip card, with output signals proportional to light intensity and wavelength.
Implementation Method 1
in the bulk region charge carriers are generated in dependence of light impinging on the bulk region
Data Source
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AI summary
Described is an arrangement for registering light, comprising: a MOS-transistor structure (101,201,401,501,601,701) having a first source/drain region (103), a second source/drain region (105), and a bulk region (107) at least partially between the first source/drain region and the second source/drain region, wherein the bulk region has a doping type different from another doping type of the first and the second source/drain regions, wherein in the bulk region (107) charge carriers are generated in dependence of light (111) impinging on the bulk region (107), wherein the generated charge carriers control a current flowing from the first source/drain region (103) to the second source/drain region (105) via at least a portion of the bulk region.