Image Sensor Heat Treatment for White Spot Defect Reduction
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Solution Overview
Problem
CMOS image sensors experience an increase in white spot defects over time due to electron-hole pair generation in the depletion layer from cosmic rays and radiation, leading to quality degradation and reduced yield.
Innovation Solution
A method involving the manufacturing of image sensors, followed by selection for defects, and a multi-stage heat treatment process with temperature ranges from 70°C to 120°C for 30 minutes to 5 hours, and a second heat treatment at a temperature at least 50°C higher than the first, to reduce white spot defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If image sensors are manufactured and tested without heat treatment, then manufacturing process is simple and fast, but white spot defects occur over time leading to quality degradation
Solution Approach 1:
The patent applies preliminary action by performing heat treatment on image sensors immediately after manufacturing and before they are shipped to customers. This pre-treatment eliminates potential white spot defects that would otherwise develop during storage or use, thereby ensuring long-term quality without requiring complex ongoing monitoring or correction systems.
Solution Approach 2:
The patent utilizes parameter changes by applying controlled thermal energy to the image sensors during heat treatment. By changing the temperature parameter (heating to specific temperatures for predetermined periods), the patent modifies the physical state of materials within the sensor to prevent defect formation, thereby improving reliability through a relatively simple thermal process.
2Reliability
If multi-stage heat treatment is applied to reduce white spot defects, then quality and yield are improved, but manufacturing time and process complexity increase
Solution Approach 1:
The multi-stage heat treatment process is implemented as a preliminary action immediately following manufacturing. By completing all necessary thermal treatments before the sensors enter storage or distribution, the patent ensures high yield and quality without requiring additional time during later stages, thus minimizing the impact on overall manufacturing efficiency.
Solution Approach 2:
The patent employs phase transitions through controlled heating and cooling cycles in the multi-stage heat treatment process. By transitioning materials through specific thermal phases at controlled rates, the treatment effectively prevents white spot defects while maintaining a streamlined process that does not significantly extend manufacturing time.
3Reliability
If heat treatment is performed on all manufactured image sensors, then white spot defect rate is reduced, but energy consumption and processing time increase
Solution Approach 1:
The patent optimizes energy consumption by carefully selecting and controlling thermal parameters in the heat treatment process. By using the minimum necessary temperatures and durations required to prevent white spot defects, the patent achieves effective defect reduction while minimizing the energy input required, making the process efficient and scalable.
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 heat treatment process significantly reduces the white spot defect rate, thereby improving the yield and quality of image sensors by effectively addressing the issue of defect occurrence over time.
Implementation Method 1
heat-treating the selected image sensor without defects
Implementation Method 2
first heat-treating the selected image sensor without defects in a range of 70 degrees Celsius to 120 degrees Celsius for 30 minutes to 5 hours
Data Source
AI summary
A method for reducing white spots of the image sensor may include: manufacturing an image sensor; testing the manufactured image sensor to select an image sensor without defects; and heat-treating the selected image sensor without defects.