Image Sensor Temperature Diode Isolation via P-Type Implant
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Solution Overview
Problem
The compatibility between temperature sensors and electronic shutter pulses in image sensors is compromised due to substrate punch-through, leading to corrupted temperature readings and potential damage to the reading components.
Innovation Solution
The design includes a substrate with specific conductivity type regions and dopant densities to minimize substrate punch-through, allowing the temperature sensor to operate independently of the electronic shutter pulse, with a timing generator and processor coordinating the shutter pulse application and temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a high voltage pulse is applied to the substrate for electronic shutter function, then charge is drained from photodiodes, but substrate punch-through occurs and corrupts temperature diode readings
Solution Approach 1:
A p-type implant region is introduced as an intermediary layer between the n-type substrate and the temperature diode. This intermediate region acts as a barrier that prevents the high voltage electronic shutter pulse from causing substrate punch-through that would otherwise corrupt temperature diode readings, while allowing the temperature measurement function to operate independently.
Solution Approach 2:
The patent applies a specific dopant concentration profile locally at the temperature diode region, with the p-type implant region having a higher dopant concentration than surrounding areas. This localized modification of material properties creates an electrical barrier specifically where needed to protect the temperature diode from substrate punch-through effects during electronic shutter operation.
2Productivity
If high voltage pulse is applied for electronic shutter, then global reset is achieved, but voltage increase across temperature diode damages reading component
Solution Approach 1:
The p-type implant region serves as a protective intermediary that blocks the propagation of high voltage from the substrate to the temperature diode and reading component. This prevents voltage spikes during electronic shutter operation from reaching and damaging the sensitive reading component, while still allowing the electronic shutter function to perform global reset effectively.
3Measurement precision
If temperature diode is used for temperature sensing, then temperature measurement is enabled, but substrate punch-through alters the voltage-current relationship
Solution Approach 1:
The patent modifies the local electrical properties of the substrate by introducing a p-type implant region with specific dopant concentration and depth profile. This creates a localized electrical barrier that maintains the stability of the temperature diode's voltage-current relationship by preventing substrate punch-through, while preserving the temperature sensing capability.
Solution Approach 2:
The p-type implant region acts as a sacrificial structural element that absorbs the stress of high voltage pulses, protecting the more critical temperature diode and reading component from damage. This one-way protection structure is designed to handle the transient high voltage conditions without compromising the permanent measurement functions.
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 configuration ensures accurate temperature measurements without disruption from the electronic shutter pulse, preventing damage to the reading components and maintaining sensor performance.
Implementation Method 1
The relationship between the voltage across the diode and the current through the diode is temperature dependent. In other words, at the same voltage, the current increases with the temperature. Likewise, at the same current, the absolute value of the voltage decreases with the temperature.
Implementation Method 2
a processor connected to the reading component can control a thermoelectric cooler coupled to the image sensor based on the temperature measurements
Implementation Method 3
a first well in the substrate and having an opposite conductivity type and doped with opposite conductivity type dopant at a first dosage at a first implantation energy, a second well in the first well and having the opposite conductivity type and doped with opposite conductivity type dopant at a second dosage higher than the first dosage
Data Source
AI summary
An image sensor includes a substrate having a first conductivity type. A first well in the substrate has an opposite conductivity type and is doped with opposite conductivity type dopant. A second well in the first well has the opposite conductivity type and is doped with opposite conductivity type dopant. A first region in the second well has the opposite conductivity type and is doped with opposite conductivity type dopant. A second region in the first region has the first conductivity type and is doped with first conductivity type dopant. A third region in the second well adjacent the first region is of the opposite conductivity type and is doped with opposite conductivity type dopant. A temperature sensor is disposed between, and is connected to each of, the second region and the third region.