Semiconductor Sensor Backside Bias Depletion Punch-Through
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Solution Overview
Problem
Existing semiconductor sensors for detecting ionizing radiation face challenges in achieving complete depletion of the substrate without causing a punch-through effect, which limits the voltage that can be applied to the carrier collection regions connected to low-voltage front-end electronic circuits, and results in inefficient carrier collection and spatial resolution loss.
Innovation Solution
A semiconductor sensor design featuring a backside bias electrode with an intermediate semiconductor layer having a higher doping concentration than the substrate, and buried doped regions of opposite types to shield superficial regions containing readout circuits, allowing for complete depletion of the substrate to carrier collection regions with a smaller reverse bias voltage and preventing punch-through effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high reverse bias voltage is applied to completely deplete the substrate, then carrier collection efficiency is improved, but punch-through effect occurs causing carriers to flow to wrong regions
Solution Approach 1:
The patent applies different doping concentrations to different regions: the intermediate layer has higher doping concentration than the substrate, and buried doped regions have specific doping types. This creates locally optimized electrical fields that enable complete depletion at lower voltages while preventing punch-through effects at circuit interfaces.
Solution Approach 2:
The intermediate semiconductor layer acts as a mediator between the substrate and the superficial regions containing readout circuits. It provides a transition zone with higher doping concentration that enables complete substrate depletion while the buried doped regions within this intermediate layer prevent carrier flow to wrong regions, thus avoiding punch-through effects.
2Productivity
If a large collection electrode is made to divert field lines from readout circuit wells, then carrier collection is improved, but chip area is significantly lost and spatial resolution deteriorates
Solution Approach 1:
The patent changes the doping concentration parameter by introducing an intermediate layer with higher doping than the substrate. This parameter change creates more efficient field line distribution that improves carrier collection without requiring excessively large collection electrodes, thereby maintaining spatial resolution.
3Device complexity
If readout circuitry is integrated on the same chip as PIN diodes, then device complexity and parasitic capacitance are reduced, but voltage management becomes more difficult due to conflicting requirements between complete depletion and low-voltage circuit operation
Solution Approach 1:
The patent creates locally optimized doping regions: the intermediate layer with higher doping concentration and buried doped regions of specific types. These local modifications create favorable electrical conditions that enable complete substrate depletion at voltages compatible with low-voltage readout circuit operation, thus resolving the voltage management conflict.
Solution Approach 2:
By changing the doping concentration parameter in the intermediate layer and introducing buried doped regions, the patent reduces the voltage required for complete substrate depletion. This parameter change allows monolithic integration of high-performance sensors with low-voltage readout circuits without compromising either depletion efficiency or circuit operation.
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 sensor achieves efficient carrier collection and maintains high spatial resolution with a voltage difference of about 1V between carrier collection and doped regions, preventing carrier flow through the potential barrier and delaying punch-through effects until a larger voltage increment, thus enabling effective detection of ionizing radiation with reduced electronic noise.
Implementation Method 1
By applying a reverse voltage between the backside bias electrode and the collection electrodes, the bias layer depletes the substrate from the backside and the carrier collection regions deplete the portions of the intermediate layer
Implementation Method 2
carriers generated by ionizing radiation or particles that impinge on the substrate
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
This disclosure provides a semiconductor sensor of ionizing radiation and/or ionizing particles with a backside bias electrode and a backside junction for completely depleting the semiconductor substrate up to carrier collection regions each connected to a respective collection electrode of carriers generated by ionization in the substrate. Differently from prior sensors, the sensor of this disclosure has an intermediate semiconductor layer formed upon the substrate, having a greater doping concentration than the doping concentration of the substrate and a doping of a same type. In this intermediate layer, buried doped regions of opposite type one separated from the other are formed for shielding superficial regions in which readout circuits are defined.