Multispectral Filter Manufacturing via 3D Structured Resist
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Solution Overview
Problem
Existing methods for manufacturing multispectral filters, such as those using Fabry-Perot cavities, face challenges in achieving precise control over dielectric layer thicknesses, especially for wavelengths below 40 nm, due to limitations in grayscale lithography and reflection phenomena at the metal-resist interface.
Innovation Solution
A method involving three-dimensional structuring of a layer of material on a substrate with photoelectric transducers, followed by conformal deposition of reflective and dielectric layers, allowing for precise control of Fabry-Perot cavity thicknesses through planarization and additional dielectric layer deposition, enabling thicknesses below 40 nm without the limitations of grayscale lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If grayscale lithography is used to structure the resist layer after depositing the first metal layer, then the Fabry-Perot cavity can be formed, but the reflection phenomenon at the metal-resist interface greatly affects control on the resist thickness
Solution Approach 1:
The patent applies preliminary action by performing the grayscale lithography structuring step on the resist layer BEFORE depositing the first metal layer. This reverses the conventional sequence where lithography is performed after metal deposition. By structuring the resist first, the harmful reflection phenomenon at the metal-resist interface during lithography is eliminated, allowing precise control of resist thickness without interference from subsequent metal layer reflections.
2Manufacturing precision
If grayscale lithography is used to obtain resist pattern thicknesses of 40 or 50 nm, then the visible range filtering is sufficient, but such thicknesses are difficult to obtain for wavelengths below 40 nm
Solution Approach 1:
The patent performs the grayscale lithography structuring step before metal layer deposition, enabling much thinner dielectric layers (below 40 nm) to be achieved. By eliminating the reflection interference that occurs when lithography is performed after metal deposition, the process can accurately create the ultra-thin resist patterns required for filtering lower wavelengths, which were previously difficult to obtain with conventional sequences.
Solution Approach 2:
The patent inverts the conventional manufacturing sequence by performing grayscale lithography on the resist layer before depositing metal layers, rather than after. This inversion removes the harmful reflection effect that limits thickness control, thereby enabling the production of ultra-thin dielectric layers (below 40 nm) necessary for extending filtering capability to lower wavelengths.
3Adaptability or versatility
If conventional semiconductor manufacturing techniques with masking and etching are used to form dielectric cavities with three different values, then RGB filters can be obtained, but significant technological restrictions and process complexity arise
Solution Approach 1:
The patent employs parameter changes by utilizing grayscale lithography to directly vary the resist layer thickness across different regions, creating dielectric cavities with different thickness values (including three different values for RGB filters) in a single process step. This eliminates the need for multiple masking and etching operations, significantly reducing process complexity while maintaining the ability to produce multiple color filter types.
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 allows for the production of multispectral filters with improved thickness control and reduced crosstalk between pixels, enhancing the efficiency and resolution of imaging devices by achieving thinner dielectric layers and better optical isolation.
Implementation Method 1
Metal/dielectric colour filters made from a Fabry-Perot cavity are especially known. These filters comprise one or more dielectric (or possibly semiconducting) cavities formed between two thin metal films having a metal mirror function so as to form a Fabry-Perot cavity.
Implementation Method 2
The transmission of the filter is set by adjusting the thickness of the cavity. Thus, in operation, part of the incident light corresponding to the wavelength of the filter is transmitted through it in the form of a coloured beam, while the rest of the incident light is reflected.
Data Source
AI summary
A method for manufacturing a multispectral filter for electromagnetic radiation including at least two filters, each filter including a first reflective layer, a second reflective layer, a Fabry-Perot cavity dielectric layer, the method including depositing a layer of structuring material onto a carrier substrate including at least two photoelectric transducers; 3D structuring the layer of structuring material to obtain at least two patterns of different heights, one of the patterns having a maximum reference height relative to the carrier substrate; conformally depositing a first reflective layer; depositing a layer of the dielectric material intended to form the dielectric patterns of the Fabry-Perot cavities; planarising the dielectric material by removal with a selective stop at the top of the highest structuring material pattern, depositing a layer made of the same dielectric material so as to complete formation of the Fabry-Perot cavities and a second reflective layer onto the two Fabry-Perot cavities.