Dummy Gate Patterns for CMOS Image Sensor Thermal Uniformity
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Solution Overview
Problem
CMOS image sensors face quality degradation due to temperature irregularities in the image-sensing element region caused by heat transfer from the logic circuit region during optical annealing, resulting from differing mean pitches of circuit patterns leading to uneven light absorption and temperature distribution.
Innovation Solution
The introduction of dummy gate patterns with a constant pitch equal to that of the logic circuit region's gate patterns in the image-sensing element region to balance light absorption rates and reduce temperature irregularities, achieved through the same manufacturing process without adding new steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical annealing is performed on CMOS image sensor, then the manufacturing process is completed, but temperature irregularities occur in the image-sensing element region due to heat transfer from the logic circuit region
Solution Approach 1:
The patent applies local quality by introducing dummy gate patterns specifically in the image-sensing element region where temperature uniformity is needed. These dummy gates create localized light absorption to compensate for the heat generated in the logic circuit region, achieving non-uniform light absorption distribution that results in uniform temperature across the substrate during optical annealing.
Solution Approach 2:
The patent implements preliminary anti-action by pre-introducing dummy gate patterns into the image-sensing element region before optical annealing. This preliminary structure preparation creates anticipatory light absorption that counteracts the expected heat transfer from the logic circuit region, preventing temperature irregularities before they occur during the annealing process.
2Temperature
If dummy gate patterns are introduced in the image-sensing element region, then temperature uniformity is improved, but the device structure becomes more complex
Solution Approach 1:
The patent merges the dummy gate patterns with the existing gate conductor formation process. The dummy gates are formed using the same material and process steps as the functional gates in the logic circuit region, combining multiple functions into a single structure that simplifies manufacturing while achieving temperature uniformity.
Solution Approach 2:
The dummy gate patterns serve multiple functions: they act as structural placeholders during manufacturing, provide light absorption control during optical annealing, and maintain electrical isolation in the image-sensing element region. This multi-functionality reduces the need for separate dedicated temperature control structures.
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 approach reduces temperature variations in the image-sensing element region, enhancing product quality by maintaining uniform temperature distribution and potentially increasing photodiode sensitivity without increasing manufacturing costs or time.
Implementation Method 1
the pitch of gate conductors (GCs), which are circuit patterns of the logic circuit, is smaller than the incident wavelength and the light absorption rate becomes higher
Implementation Method 2
heat transfers from the logic circuit region to the image-sensing element region due to thermal diffusion
Data Source
AI summary
According to one embodiment, an image sensor includes an image-sensing element region formed by arranging a plurality of image-sensing elements on a semiconductor substrate, and a logic circuit region formed in a region different from the image-sensing element region on the substrate and including a plurality of gate patterns. Further, dummy gate patterns are formed with a constant pitch on the image-sensing element region.