Radiation Image Sensor Capacitive Section Oxidation
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Solution Overview
Problem
In direct conversion radiation image sensors, it is challenging to increase capacitance per unit area due to the need for a minimum insulating film thickness to prevent short circuits, limiting the capacity of capacitive elements.
Innovation Solution
A radiation image sensor design incorporating a semiconductor substrate with a conductor layer and an insulating layer, where the insulating layer is formed by oxidation, allowing for higher quality and thinner films, and an additional impurity diffused region to manage excess charge, thereby increasing capacitance and preventing saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the insulating film thickness is reduced to increase capacitance per unit area, then the capacitance increases, but the risk of short circuit between layers increases
Solution Approach 1:
The invention changes the formation method parameter of the insulating film from CVD to oxidation, which enables achieving higher quality films with thinner thickness while maintaining reliability, thus resolving the contradiction between increasing capacitance and preventing short circuits
Solution Approach 2:
The invention replaces the CVD deposition process with an oxidation process to form the insulating film. This substitution allows for thinner film thickness with better quality control, enabling higher capacitance per unit area while maintaining adequate insulation to prevent short circuits
2Reliability
If CVD is used to deposit the insulating film, then the film can be formed with adequate thickness, but the capacitance per unit area is limited
Solution Approach 1:
The invention changes the insulating film formation parameter from CVD thickness control to oxidation thickness control, which inherently produces thinner yet higher quality films, thereby increasing capacitance per unit area while maintaining reliability through superior film quality
Solution Approach 2:
The invention substitutes the CVD deposition mechanism with an oxidation mechanism for insulating film formation. This replacement enables achieving the desired balance between thin film thickness (for higher capacitance) and film quality (for preventing short circuits)
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 design enhances capacitance per unit area, reduces the risk of capacitive section saturation and charge leakage, and simplifies the manufacturing process by integrating the capacitive section with the MOS transistor formation.
Implementation Method 1
the insulating layer can be formed by oxidation of the surface of the semiconductor substrate
Implementation Method 2
a solid-state material for directly converting radiation into charge (CdTe or the like) is provided on a circuit board accumulating and transferring charge
Data Source
Figure 1
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AI summary
A radiation image sensor 1A includes a charge generation section 4 and, a circuit board 3 accumulating and transferring charge generated in the charge generation section 4. The circuit board 3 includes a semiconductor substrate 10, a capacitive section 5 accumulating the charge generated in the charge generation section 4, and a MOS transistor 7 in the semiconductor substrate 10. The MOS transistor 7 includes one end connected to the capacitive section 5 and another end connected to a wire transferring the charge. The capacitive section 5 includes a partial region 10b of the semiconductor substrate 10, a conductor layer 31 disposed on the partial region 10b and electrically connected to the charge generation section 4, and an insulating layer 22 interposed between the partial region 10b and the conductor layer 31.