Inorganic Microlens Fabrication for High-Temperature CMOS Sensors
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Solution Overview
Problem
Current microlens fabrication methods for CMOS image sensors are limited by the use of organic materials that degrade at high temperatures and require additional passivation layers, leading to increased costs and potential issues with oblique light beams due to the distance between the microlens and photodiode.
Innovation Solution
A method involving the formation of micro bumps using inorganic dielectric materials through etching processes, followed by the deposition of an optical film using CVD, which allows the microlens to operate in high-temperature environments without fracturing and eliminates the need for additional passivation layers, while enabling the use of R/G/B filter layers directly over the photodiode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic materials are used for microlens fabrication, then the fabrication process is simpler, but the microlens degrades at high temperatures and requires additional passivation layers
Solution Approach 1:
The patent changes the material parameter from organic resin to inorganic dielectric material (such as silicon oxide, silicon nitride, or silicon oxynitride). This material substitution enables the microlens to withstand high temperatures (above 400°C) without degradation, eliminating the need for additional passivation layers while maintaining fabrication feasibility through standard semiconductor processes
Solution Approach 2:
The patent employs inorganic dielectric materials that combine the optical properties needed for microlens function with high-temperature stability. These materials form a composite structure with the substrate that provides both optical performance and thermal resistance, resolving the contradiction between ease of manufacture and high-temperature reliability
2Reliability
If additional passivation layers are added to protect microlens, then microlens reliability improves, but manufacturing cost and process complexity increase
Solution Approach 1:
The inorganic dielectric material serves multiple functions simultaneously: it forms the optical microlens structure, provides mechanical support, and acts as a passivation layer protecting against environmental degradation. This multi-functionality eliminates the need for separate protective layers, reducing device complexity while maintaining reliability
3Ease of manufacture
If microlens is positioned farther from photodiode, then fabrication ease improves, but oblique light beam performance deteriorates
Solution Approach 1:
The patent changes the mechanical properties of the microlens material to enable direct bonding to the substrate at close proximity. The inorganic dielectric material allows for precise positioning and strong adhesion, enabling the microlens to be placed immediately over the photodiode aperture without the distance constraints that affect organic materials, thereby eliminating oblique light beam scattering
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 enables microlenses to function effectively in high-temperature environments like laser reading and writing devices without fracturing, reduces costs by eliminating the need for additional passivation layers, and minimizes issues with oblique light beams by reducing the distance between the microlens and photodiode.
Implementation Method 1
etching the first thin film to form at least a micro bump
Implementation Method 2
the deposition of an optical film using CVD
Data Source
AI summary
The present invention provides a method of fabricating a microlens, comprising providing a substrate with at least a dielectric layer thereon, forming a first thin film on the dielectric layer surface, etching the first thin film to form at least a micro bump, and forming a second thin film on the micro bump surface and dielectric layer surface, wherein the second thin film and the micro bump form the microlens. The present invention microlens can be applied in the environment with high temperature, and a passivation layer is not required for the present invention microlens.