In-situ-doped Passivation Layer for Image Sensor Dark Current Reduction
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Solution Overview
Problem
Current image sensor technologies face challenges in reducing dark current properties due to surface damage from ion implantation or plasma processes during the formation of passivation layers, which affects the performance of CMOS-type image sensors.
Innovation Solution
The method involves forming an in-situ-doped passivation layer using atomic layer deposition with impurity ions on the substrate's surface, without ion implantation or plasma processes, and subsequent annealing to diffuse these ions into the substrate, followed by forming capping patterns using spin coating and annealing to improve the trench filling and insulating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation or plasma processes are used to form passivation layers, then the passivation layer can be formed on the substrate surface, but surface damage occurs which worsens dark current properties
Solution Approach 1:
The patent replaces ion implantation and plasma processes with a chemical vapor deposition (CVD) process to form the passivation layer. This substitution eliminates the mechanical/physical damage caused by ion bombardment and plasma exposure, achieving surface passivation without creating defects that would increase dark current.
Solution Approach 2:
The patent changes the formation parameters of the passivation layer from high-energy physical processes (ion implantation, plasma) to a chemical deposition process. By controlling temperature, pressure, and gas composition during CVD, the passivation layer is formed with beneficial properties that reduce dark current without causing surface damage.
2Ease of manufacture
If conventional passivation layer formation methods are used, then the process can be completed, but manufacturing complexity increases due to multiple steps including ion implantation and plasma treatment
Solution Approach 1:
The patent combines the passivation layer formation with the insulation layer formation into a single CVD process step. By depositing a silicon oxide layer that serves both as passivation and insulation, the method eliminates separate ion implantation and plasma treatment steps, reducing overall manufacturing complexity while maintaining device performance.
Solution Approach 2:
The silicon oxide passivation layer formed by CVD serves multiple functions simultaneously: it passivates the substrate surface to reduce dark current, provides electrical insulation, and creates a stable interface for subsequent processing. This multi-functionality reduces the need for multiple specialized process steps.
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 enhances the dark current properties of image sensors by preventing surface damage and improving the integration density and performance of CMOS-type image sensors.
Implementation Method 1
performing an atomic layer deposition process to form a passivation layer conformally covering a surface of the trench, the passivation layer being doped with impurity ions during the atomic layer deposition process
Implementation Method 2
performing an annealing process on the passivation layer to diffuse the impurity ions from the passivation layer into the substrate
Implementation Method 3
forming, using a spin coating process, a capping layer to fill the trench that includes the passivation layer
Implementation Method 4
performing an annealing process on the capping layer
Data Source
AI summary
Methods of forming an image sensor are provided. A method of forming an image sensor includes forming a trench in a substrate to define a unit pixel region of the substrate. The method includes forming an in-situ-doped passivation layer on an exposed surface of the trench. The method includes forming a capping pattern on the in-situ-doped passivation layer, in the trench. The method includes forming a photoelectric conversion region in the unit pixel region. Moreover, the method includes forming a floating diffusion region in the unit pixel region.