Transient Index Layer for CMOS Imager Photon Reflection
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Solution Overview
Problem
Conventional CMOS imager designs suffer from significant photon reflection at the junction of different refractive index media, leading to light loss and crosstalk between pixels, which hinders the efficient reception and propagation of light in solid state imaging and display devices.
Innovation Solution
The introduction of an intermediate transient index layer with a gradual refractive index transition between the silicon and silicon dioxide layers in CMOS imager pixel cells, formed through methods like silicon quantum dot formation or reactive PVD/CVD deposition, reduces reflection by smoothing the refractive index change, thereby enhancing light transmission and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an intermediate transient index layer is introduced to reduce photon reflection, then light transmission to photosensors is improved, but device structure and fabrication complexity increase
Solution Approach 1:
An intermediate layer with transient refractive index (gradually transitioning from silicon to silicon dioxide) is introduced between the silicon photodiode and the silicon dioxide protective layer. This intermediary layer reduces the abrupt refractive index change, thereby minimizing photon reflection and improving light transmission to the photosensor.
Solution Approach 2:
The refractive index parameter is gradually changed through the intermediate layer, transitioning from the high refractive index of silicon to the low refractive index of silicon dioxide. This gradual parameter change reduces reflection by avoiding abrupt transitions, directly addressing the photon reflection loss problem.
2Ease of manufacture
If conventional silicon-silicon dioxide stack is used, then manufacturing is simplified, but significant photon reflection occurs at the junction
Solution Approach 1:
The intermediate transient index layer serves as a mediator between silicon and silicon dioxide, maintaining compatibility with conventional CMOS fabrication processes while reducing photon reflection. The layer can be formed using standard deposition techniques, balancing manufacturing ease with optical performance improvement.
Solution Approach 2:
The optical stack becomes a composite structure combining silicon, intermediate transient index material, and silicon dioxide. This composite approach allows optimization of optical properties while maintaining compatibility with conventional manufacturing processes.
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 significantly minimizes photon reflection and crosstalk, allowing more photons to reach the photosensors or photoemitters, thereby improving the optical characteristics and efficiency of both imaging and display devices.
Implementation Method 1
A significant source of photon reflection can occur at the junction of different media, each having a different refractive index. Photon reflection between two different media can be expressed by the following formula: R = ((n1 - n2) / (n1 + n2))^2 where n1 and n2 are the refractive indices of the two media and R is the percentage of photons reflected at the junction of the two media.
Implementation Method 2
A significant source of photon reflection can occur at the junction of different media, each having a different refractive index. Photon reflection between two different media can be expressed by the following formula: R = ((n1 - n2) / (n1 + n2))^2 where n1 and n2 are the refractive indices of the two media and R is the percentage of photons reflected at the junction of the two media.
Data Source
AI summary
A transient index stack having an intermediate transient index layer, for use in an imaging device or a display device, that reduces reflection between layers having different refractive indexes by making a gradual transition from one refractive index to another. Other embodiments include a pixel array in an imaging or display device, an imager system having improved optical characteristics for reception of light by photosensors and a display system having improved optical characteristics for transmission of light by photoemitters. Enhanced reception of light is achieved by reducing reflection between a photolayer, for example, a photosensor or photoemitter, and surrounding media by introducing an intermediate layer with a transient refractive index between the photolayer and surrounding media such that more photons reach the photolayer. The surrounding media can include a protective layer of optically transparent media.