Solid-State Imaging Device Impurity Layer Alignment
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Solution Overview
Problem
Conventional solid-state imaging devices face challenges in consistently forming gate electrodes relative to N-type impurity layers, leading to variations in the overlap area and depth of charge reservoirs, which affect residual image characteristics across different products.
Innovation Solution
The method involves forming a second impurity layer by implanting impurities obliquely with respect to the semiconductor substrate surface, ensuring precise alignment with the gate electrode, thereby controlling the overlap area and impurity concentration to achieve consistent potential depths and improved charge transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gate electrode is formed based on visual determination of the impurity layer position, then the manufacturing process is simple, but the position accuracy of the gate electrode varies greatly
Solution Approach 1:
A marker layer is introduced as an intermediary between the impurity layer and the gate electrode formation process. The marker layer contains markers that are visually detectable and serve as reference points for aligning the gate electrode with the impurity layer, thereby improving position accuracy without complicating the manufacturing process
Solution Approach 2:
The position information of the impurity layer is copied onto the marker layer through the marker formation process. This copying allows the gate electrode to be accurately positioned by referencing the markers rather than directly visualizing the impurity layer, solving the precision problem while maintaining process simplicity
2Reliability
If the N-type impurity layer protrudes from the pixel unit to form charge accumulating units, then charge transfer is enabled, but the overlap area with the gate electrode varies greatly affecting residual image characteristics
Solution Approach 1:
The marker layer acts as an intermediary that provides precise positional reference for the gate electrode relative to the protruding N-type impurity layer. This ensures consistent overlap area between the gate electrode and impurity layer across different charge accumulating units, while maintaining the necessary charge transfer function
Solution Approach 2:
The visual determination method is replaced with a marker-based alignment system. The markers provide objective, measurable reference points that eliminate the variability inherent in visual estimation, ensuring consistent overlap areas for reliable charge transfer
3Adaptability or versatility
If different residual image characteristics are required in different products, then product adaptability is improved, but the difficulty of determining precise impurity layer position increases
Solution Approach 1:
The marker layer provides a standardized intermediary system that works across different product variants. By adjusting marker positions or gate electrode patterns relative to these markers, different residual image characteristics can be achieved without increasing the difficulty of impurity layer position determination
Solution Approach 2:
The marker-based system allows easy adjustment of geometric parameters (marker positions, gate electrode dimensions, overlap areas) to achieve different residual image characteristics for different products, while the measurement and determination process remains straightforward through marker reference
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 variations in residual image characteristics and transfer efficiency between charge accumulating units, resulting in more consistent product performance by accurately positioning the second impurity layer relative to the gate electrode.
Implementation Method 1
forming a second impurity layer by implanting an impurity of a second conductivity type into the first impurity layer in an oblique direction with respect to the surface of the semiconductor substrate
Data Source
AI summary
Certain embodiments provide method for manufacturing a solid-state imaging device, including forming an electrode and forming a second impurity layer. The electrode is formed on a semiconductor substrate including a first impurity layer of a first conductivity type on a surface. The second impurity layer is a second conductivity type and is formed by implanting an impurity of a second conductivity type into the first impurity layer in an oblique direction with respect to the surface of the semiconductor substrate on the condition that the impurity penetrates an end portion of the electrode, based on a position of the electrode. The second impurity layer is bonded to the first impurity layer to constitute a photodiode, and a portion of the second impurity layer is disposed under the electrode.