CMOS Image Sensor Fabrication Step Height for Uniform Color Filters
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Solution Overview
Problem
The existing methods for fabricating CMOS image sensors suffer from striation issues during the formation of color filters, which affect the uniformity of the color filter layer thickness and subsequently impact pixel performance due to the presence of notches or recesses where the color filter layer accumulates during the spin coating process.
Innovation Solution
The method involves forming a step height instead of a notch or recess at the contact pad location, preventing the color filter layer from accumulating and ensuring accurate alignment for the optical shielding layer, thereby preventing striation and improving pixel performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a notch or recess is formed at the contact pad location, then the color filter layer can be deposited, but the color filter layer accumulates in the notch/recess causing striation and non-uniform thickness
Solution Approach 1:
Instead of forming a notch or recess at the contact pad location (conventional approach), the invention inverts the approach by forming a protrusion or raised structure. This protrusion prevents the color filter layer from accumulating during spin coating, thereby eliminating striation and achieving uniform thickness without the harmful effects of notches.
2Manufacturing precision
If the contact pad is exposed during spin coating, then the color filter layer can be formed, but alignment accuracy for the optical shielding layer is compromised
Solution Approach 1:
The invention performs preliminary action by forming the protrusion structure at the contact pad location before the spin coating process. This pre-formed structure serves as an alignment reference that guides the subsequent optical shielding layer formation, ensuring high alignment accuracy while simplifying the overall fabrication process.
3Productivity
If spin coating is used to form the color filter layer, then the process is simple and fast, but striation occurs due to accumulation in notches/recesses
Solution Approach 1:
The invention applies preliminary anti-action by creating a protrusion structure that pre-prevents the accumulation of color filter layer material during spin coating. This proactive measure counteracts the inherent tendency of material to accumulate in notches or recesses, thereby maintaining both high productivity through spin coating and uniformity of the color filter layer.
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 prevents striation and enhances the alignment accuracy, leading to improved yield and performance of the CMOS image sensor by ensuring uniform color filter layer thickness and accurate optical shielding layer formation.
Implementation Method 1
The color filter layer is formed on the substrate by a spin coating step
Implementation Method 2
performing a first etching process to remove a portion of the first dielectric layer for exposing the contact pad and forming a step height
Data Source
AI summary
A method for fabricating a CMOS image sensor includes providing a substrate having a sensor array region and a peripheral region defined thereon, forming at least a contact pad on the substrate of the peripheral region, forming a first dielectric layer covering the contact pad on the substrate, performing a first etching process to expose the contact pad and to form a step height, forming an optical shielding layer on the first dielectric layer, forming a plurality of color filters on the first dielectric layer, sequentially forming a planarizing layer and a plurality of micro-lenses on the first dielectric layer.