Deep Trench Isolation Pre-Cleaning for Low-Defect Pixel Passivation
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Solution Overview
Problem
Optical crosstalk occurs between adjacent pixel regions in a pixel array due to photons passing through deep trench isolation structures, leading to defects in passivation layers, increased dark current, reduced sensitivity, and decreased low-light performance.
Innovation Solution
A cyclic pre-cleaning technique is used to clean the sidewalls and bottom of recesses in deep trench isolation structures before forming passivation layers, involving deposition and etch cycles to remove oxygen and reduce carbon contamination, thereby enhancing the quality of the passivation layer and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If deep trench isolation structures are used to reduce optical crosstalk, then optical crosstalk is reduced, but defects occur in passivation layers due to high oxygen concentration on the silicon substrate
Solution Approach 1:
The patent applies preliminary action by performing a pre-cleaning process on the silicon substrate surface before depositing the passivation layer. This pre-cleaning removes oxygen and carbon contaminants from the substrate surface, preventing defects in the subsequently formed passivation layer while maintaining the optical crosstalk reduction benefits of the deep trench isolation structure.
Solution Approach 2:
The patent introduces an intermediary cleaning process between the substrate preparation and passivation layer deposition. This intermediary step uses oxygen plasma to selectively remove oxygen and carbon contaminants from the silicon substrate surface, acting as a mediator that enables both optical crosstalk reduction and high-quality passivation layer formation.
2Ease of manufacture
If passivation layers are formed over deep trench isolation structures without pre-cleaning, then the deep trench isolation structure is formed, but defects occur including increased dark current and reduced sensitivity
Solution Approach 1:
The pre-cleaning process is performed as a preliminary action before passivation layer deposition to remove surface contaminants. This preliminary cleaning step ensures that the passivation layer can be formed with high uniformity and without defects, while the deep trench isolation structure is already in place, thus maintaining ease of manufacture.
Solution Approach 2:
The patent changes the surface parameters of the silicon substrate by removing oxygen and carbon contaminants through oxygen plasma treatment. This parameter change in surface cleanliness enables the formation of uniform passivation layers with improved manufacturing precision, while the overall manufacturing process remains straightforward.
3Ease of manufacture
If oxygen concentration is high on the silicon substrate, then the deep trench isolation structure can be formed, but carbon concentration increases in the passivation layer and dislocation occurs
Solution Approach 1:
An oxygen plasma cleaning step is introduced as an intermediary process between trench formation and passivation layer deposition. This intermediary cleaning removes excess oxygen and carbon from the substrate surface, preventing carbon incorporation and dislocation in the passivation layer while maintaining ease of trench filling.
Solution Approach 2:
The patent extracts harmful oxygen and carbon contaminants from the silicon substrate surface using oxygen plasma before passivation layer deposition. This extraction process removes the source of carbon concentration increase and dislocation, ensuring passivation layer integrity while keeping the manufacturing process simple.
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 pre-cleaning technique improves the crosstalk mitigation performance of deep trench isolation structures, increasing the overall performance of the image sensor by reducing defects and enhancing sensitivity and low-light performance.
Implementation Method 1
A cyclic pre-cleaning technique is used to clean the sidewalls and bottom of recesses in deep trench isolation structures before forming passivation layers, involving deposition and etch cycles to remove oxygen and reduce carbon contamination
Data Source
AI summary
A cyclic pre-cleaning technique may be used to clean the surfaces of a recess in which a deep trench isolation (DTI) structure is to be formed. The cyclic pre-cleaning technique may include performing one or more deposition and etch cycles to remove oxygen from the surfaces of the recess to reduce the oxygen concentration in the surfaces of the recess. A passivation layer may be formed in the recess after the cyclic pre-cleaning technique is used to clean the surfaces. The cyclic pre-cleaning technique may include the use of germanium (Ge) to bond with oxygen in the surfaces of the recess, which results in the formation of germanium oxide (GeO). The germanium oxide is removed, resulting in reduced oxygen concentration in the surfaces of the recess. The reduced oxygen concentration increases the quality of epitaxial growth of the passivation layer in the recess.