Image Sensor Re-crystallization Layer Defect Removal
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Solution Overview
Problem
Existing image sensors face challenges in preventing noise due to dark current, which is caused by defects in the substrate, particularly dislocations and stacking faults, that are difficult to remove through conventional post-treatments like oxidation and hydrogen termination.
Innovation Solution
The image sensor incorporates a re-crystallization layer formed with elements different from the substrate, which is continuously applied along the substrate surfaces and trenches to remove defects, including those beneath the surface, thereby preventing dark current and noise. This is achieved through a process involving primary and secondary ion-implantation followed by annealing, with the re-crystallization layers containing metalloid or nonmetallic elements from group 14 to 18.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional post-treatments like oxidation and hydrogen termination are used, then the substrate surface is treated, but defects beneath the surface such as dislocations and stacking faults remain difficult to remove
Solution Approach 1:
The patent applies preliminary action by forming the re-crystallization layer before final substrate processing steps. The layer is introduced early to prevent defect formation rather than attempting to remove them later, addressing the limitation of conventional post-treatments that cannot reach subsurface defects
Solution Approach 2:
The re-crystallization layer acts as an intermediary substance between the substrate and the external environment. This intermediate layer with different crystal structure and composition prevents dark current generation at the substrate surface and interfaces, solving the problem of subsurface defects that conventional treatments cannot address
2Reliability
If a re-crystallization layer with different elements is formed, then defects are removed and dark current is prevented, but the manufacturing process becomes more complex
Solution Approach 1:
The patent changes material parameters by introducing elements from group 14-18 (such as Si, Ge, Sn, C, N, O) to form the re-crystallization layer. This parameter change in composition creates a layer with different crystal structure that prevents dark current while the ion-implantation and annealing processes integrate into existing fabrication workflows
Solution Approach 2:
The re-crystallization layer creates a composite structure combining the substrate material with additional elements. This composite approach allows tailoring of electrical and structural properties to prevent dark current, while the layer can be formed using modified versions of standard semiconductor processing techniques
3Manufacturing precision
If ion-implantation and annealing processes are used to form re-crystallization layers, then defects are effectively removed, but the manufacturing time and energy consumption increase
Solution Approach 1:
The patent employs periodic action through sequential ion-implantation steps followed by annealing cycles. The process alternates between introducing elements and heating to enable diffusion and re-crystallization, achieving effective defect removal through repeated cycles rather than single prolonged treatment
Solution Approach 2:
The annealing process utilizes phase transitions by heating the substrate to temperatures where the implanted elements diffuse and the amorphous or disordered regions transform into re-crystallized structures. This phase change mechanism enables effective defect removal while controlling the duration and intensity of thermal processing
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 solution effectively removes defects at and beneath the substrate surfaces, preventing dark current and noise, while improving electrical characteristics and process efficiency, allowing for high-quality image implementation.
Implementation Method 1
a re-crystallization layer formed in the substrate to be in contact with bottom and side surfaces of the trench and a surface of the substrate
Implementation Method 2
This is achieved through a process involving primary and secondary ion-implantation followed by annealing
Data Source
AI summary
An image sensor may include: a trench formed in a substrate; an impurity region formed in the substrate to be in contact with the trench; and a re-crystallization layer formed in the substrate to be in contact with bottom and side surfaces of the trench and a surface of the substrate. The re-crystallization layer may contain one or more kinds of elements different from an element constituting the substrate.