Planar Spectral Filter Cavities for Compact Image Sensors
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Solution Overview
Problem
Conventional image sensors using spectral filters are bulky and heavy, hindering miniaturization efforts, as they integrate optical elements and circuits on a single semiconductor chip.
Innovation Solution
A spectral filter design featuring a plurality of reflective layers with cavities of varying thicknesses, including etch stop layers and dielectric layers, arranged in a two-dimensional manner to selectively transmit light of specific wavelengths, allowing for miniaturization while maintaining optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional spectral filters are used to achieve spectral filtering capability, then optical performance is maintained, but the image sensor becomes bulky and heavy
Solution Approach 1:
The spectral filter is divided into multiple discrete layers including reflective layers, cavities, etch stop layers, and dielectric layers. Each layer performs a specific function in the spectral filtering process, allowing the overall filtering capability to be maintained while reducing the total volume compared to conventional monolithic filters.
Solution Approach 2:
The patent transitions from conventional three-dimensional bulky filters to a planar, two-dimensional layered structure that can be integrated directly onto the semiconductor chip. This dimensional change enables spectral filtering functionality to be embedded within the chip plane rather than adding vertical bulk.
2Measurement precision
If the number of layers in the spectral filter is increased to improve spectral selectivity, then filtering precision is improved, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes specific parameters of each layer including thickness, refractive index, and material composition to achieve the desired spectral selectivity. By carefully controlling these parameters, high spectral precision is obtained without requiring an excessive number of layers, thus managing manufacturing complexity.
Solution Approach 2:
The spectral filter employs composite structures combining different materials with complementary properties - metallic reflective layers for high reflectivity, dielectric layers for specific wavelength selection, and etch stop layers for manufacturing control. This composite approach achieves superior spectral selectivity while maintaining a manageable layer count.
3Ease of manufacture
If etch stop layers with high etch selectivity are used to facilitate cavity formation, then manufacturing ease is improved, but refractive index mismatch may occur
Solution Approach 1:
The etch stop layers are strategically positioned only where needed during the fabrication process to define cavity boundaries, rather than being present throughout the entire structure. This localized application provides manufacturing ease during cavity formation while minimizing the impact of refractive index mismatch on overall optical performance in the final device.
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 the creation of compact image sensors with improved transmittance and spectral filtering capabilities, facilitating the integration of optical and electronic components on a single chip, thus addressing the challenge of miniaturization.
Implementation Method 1
a plurality of first reflective layers spaced apart from each other and facing each other; and at least a first cavity and a second cavity provided between the plurality of first reflective layers
Implementation Method 2
first reflective layers includes a metal reflective layer... The spectral filter may have the first reflective layers include a Bragg reflective layer
Implementation Method 3
The spectral filter may have a difference between a refractive index of a material included in the one or more dielectric layers and refractive indices of materials included in the etch stop layers
Data Source
AI summary
Provided are a spectral filter, a method of manufacturing the same, and an image sensor and an electronic device each including the spectral filter. The spectral filter includes a plurality of first reflective layers provided spaced apart from each other, and a plurality of cavities provided between the plurality of first reflective layers. The cavities have different thicknesses according to a center wavelength. Each of the cavities includes a plurality of etch stop layers having a constant total thickness according to the center wavelength, and at least one dielectric layer having a total thickness which changes according to the center wavelength, wherein the etch stop layers include materials having etch selectivities different than that of the dielectric layer.