Copper Optical Filter Stack with Silicon Nitride Adhesion Layer
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Solution Overview
Problem
Existing optical filters used in imaging devices, particularly those colored by pigments, are not robust enough and degrade at temperatures above 200° C, and alternative metal layer filters face delamination issues during heat treatments.
Innovation Solution
A stack comprising layers of copper on hydrogenated silicon nitride with specific formation parameters, including a low silicon-to-nitrogen ratio and compressive mechanical stresses, and a silicon oxide layer to promote copper adherence, eliminating the need for tantalum or tantalum nitride barrier layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic filters colored by pigments are used, then the filters can be manufactured with existing processes, but the filters are not robust and degrade at temperatures above 200° C
Solution Approach 1:
The patent changes the material parameters by replacing organic pigment-based filters with inorganic metal layers (silver, aluminum, gold) having different thermal and mechanical properties. This material substitution fundamentally alters the thermal stability parameter, enabling operation at temperatures above 200° C while maintaining structural integrity.
Solution Approach 2:
The patent creates a composite structure by combining metal layers with dielectric materials (such as silicon nitride, silicon oxide, or titanium oxide) to form resonant optical filters. This composite approach provides both the optical filtering functionality and the thermal-mechanical robustness required for high-temperature operation.
2Reliability
If metal layers are used to form optical filters, then the filters are more robust and thermally stable, but delamination occurs during heat treatments
Solution Approach 1:
The patent introduces dielectric layers (silicon nitride, silicon oxide, or titanium oxide) as intermediary layers between the metal layers and the substrate. These intermediary layers act as adhesion promoters and stress buffers, preventing delamination during heat treatments while maintaining the thermal stability benefits of metal-based filters.
Solution Approach 2:
The patent applies different dielectric materials at different locations within the filter structure. For example, silicon nitride may be used as the primary dielectric layer, with silicon oxide or titanium oxide applied in specific regions or as additional layers, optimizing both adhesion and optical performance in different parts of the device.
3Stability of the object's composition
If barrier layers comprising tantalum or tantalum nitride are deposited to ensure copper adherence, then the adhesion is improved, but interference occurs in multi-layer optical filters
Solution Approach 1:
The patent extracts or removes the tantalum/tantalum nitride barrier layers from the structure, replacing them with dielectric materials that do not cause optical interference. This extraction eliminates the harmful optical effects while maintaining adequate adhesion through the dielectric layer design.
Solution Approach 2:
The patent uses thin dielectric layers (silicon oxide, silicon nitride) that serve the adhesion function temporarily during manufacturing but do not interfere with the final optical performance. These layers are designed to be thin enough to minimize optical interference while providing sufficient adhesion support.
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 resulting stack is more robust and resistant to thermal stress, enabling the formation of durable optical filters suitable for integrated circuits that withstand temperature increases without delamination.
Implementation Method 1
formation of a layer of silicon oxide on the layer of hydrogenated silicon nitride
Implementation Method 2
a layer of hydrogenated silicon nitride having, in the vicinity of its upper side, for example in a thickness of about 50 nanometers, a ratio of the number of silicon atoms per cubic centimeter to the number of nitrogen atoms per cubic centimeter lower than 0.8
Data Source
AI summary
A stack of layers defines a filter and is formed by copper on hydrogenated silicon nitride supported by a carrier. The filter includes a layer of hydrogenated silicon nitride, a layer of silicon oxide on the layer of hydrogenated silicon nitride and a layer of copper on the layer of silicon oxide. The layer of hydrogenated silicon nitride may have, in a vicinity of its upper side, a ratio of a number of silicon atoms per cubic centimeter to a number of nitrogen atoms per cubic centimeter lower than 0.8 (or even lower than 0.6), with a number of silicon-hydrogen bonds smaller than or equal to 6×1021 bonds per cubic centimeter (or even smaller than 0.5×1021 bonds per cubic centimeter). The filter further includes an additional layer of copper between the layer of hydrogenated silicon nitride and the carrier.