Semiconductor Guard Ring with Twin Defect Layer
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Solution Overview
Problem
Existing semiconductor devices with guard rings formed by ion implantation face a tradeoff between suppressing leak current and reducing crystal defects, leading to potential pixel defects and reduced reliability in image sensors.
Innovation Solution
A semiconductor device with a current blocking region comprising an impurity diffusion layer and a defect extension preventing layer, where the defect extension preventing layer has a different crystal structure and is formed in contact with the impurity diffusion layer to prevent pixel defects from extending to the surface, while maintaining high impurity concentration for effective leak current suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the concentration of impurities in the guard ring is increased to suppress leak current, then the effect of suppressing leak current is enhanced, but crystal defects are induced leading to defective pixels
Solution Approach 1:
The guard ring structure is segmented into two distinct layers: a first guard ring layer with high impurity concentration for suppressing leak current, and a second guard ring layer with low impurity concentration for preventing crystal defects. This segmentation allows each layer to perform its specific function without the adverse effects of the other, resolving the contradiction between leak current suppression and defective pixel prevention.
Solution Approach 2:
Different regions of the guard ring are assigned different impurity concentrations based on their specific functional requirements. The first guard ring layer (deeper region) has high impurity concentration optimized for leak current suppression, while the second guard ring layer (shallower region) has low impurity concentration optimized for minimizing crystal defects. This local differentiation of quality allows simultaneous optimization of both conflicting requirements.
2Reliability
If the concentration of impurities in the guard ring is decreased to reduce crystal defects, then the possibility of defective pixels is reduced, but the effect of suppressing leak current is weakened
Solution Approach 1:
The guard ring is divided into two functional segments: the first guard ring layer positioned deeper in the substrate with high impurity concentration to suppress leak current, and the second guard ring layer positioned shallower with low impurity concentration to minimize crystal defects. This segmentation enables both functions to coexist without compromise.
Solution Approach 2:
The solution moves from a single-dimensional (single-layer) guard ring structure to a two-dimensional (multi-layer) structure with vertical differentiation. By adding the depth dimension and positioning layers at different depths, the patent achieves simultaneous optimization of leak current suppression (deeper layer) and defect reduction (shallower layer) that cannot be achieved with a uniform single-layer structure.
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 effectively suppresses both leak current between adjacent photoelectric conversion elements and pixel defects, enhancing the reliability of pixel signal detection in semiconductor devices.
Implementation Method 1
a defect extension preventing layer adapted to form a twin with the impurity diffusion layer by being in contact with the impurity diffusion layer
Implementation Method 2
A guard ring is formed, for example, by forming an impurity diffusion layer in a semiconductor substrate by ion implantation
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a photoelectric conversion element, a first isolation insulating film, and a current blocking region. The first isolation insulating film is formed around the photoelectric conversion element. The current blocking region is formed in a region between the photoelectric conversion element and the first isolation insulating film. The current blocking region includes an impurity diffusion layer, and a defect extension preventing layer disposed in contact with the impurity diffusion layer to form a twin with the impurity diffusion layer. The defect extension preventing layer has a different crystal structure from that of the impurity diffusion layer. At least a part of the current blocking region is disposed in contact with the first isolation insulating film.