Variable Wavelength Interference Filter Diaphragm Dry Etching
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Solution Overview
Problem
Existing variable wavelength interference filters face challenges in reducing the size of the movable unit due to the formation of sloped sections during wet etching, and they struggle with controlling film thickness and adjusting etching amounts, leading to yield deterioration and increased processing load.
Innovation Solution
The proposed variable wavelength interference filter utilizes a special SOI substrate with a BOX layer only at predetermined locations, allowing for dry etching to form a diaphragm unit with a uniform thickness and reducing side etching, thereby minimizing filter size and maximizing filter region diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If wet etching is used to form the diaphragm unit, then the diaphragm unit includes sloped sections that reduce the size of the movable unit, but it becomes difficult to adjust the etching amount and control film thickness uniformly
Solution Approach 1:
The patent changes the etching method from wet etching to dry etching. This parameter change enables precise control of etching depth and maintains uniform film thickness without forming sloped sections, while still achieving size reduction through selective removal of the lower cladding layer.
Solution Approach 2:
The patent segments the cladding layer into two distinct layers: an upper cladding layer and a lower cladding layer. This segmentation allows selective removal of only the lower cladding layer through dry etching, enabling precise control over the diaphragm structure and maintaining uniform thickness while reducing movable unit size.
2Volume of moving object
If wet etching is used to form the diaphragm unit, then sloped sections are formed that reduce movable unit size, but the processing load increases and yield deteriorates
Solution Approach 1:
The patent changes the etching method from wet etching to dry etching. This parameter change eliminates the need for complex etching amount adjustments and provides better control over the etching process, thereby reducing processing load and improving manufacturing yield while achieving size reduction.
Solution Approach 2:
The patent introduces a sacrificial lower cladding layer as an intermediary structure that facilitates precise diaphragm formation. This layer acts as a placeholder that can be selectively removed through dry etching, enabling controlled size reduction without the complications of wet etching and improving overall process reliability.
3Volume of moving object
If the diaphragm unit is formed with non-flat surfaces due to wet etching, then the movable unit size is reduced, but the movable unit may tilt during displacement
Solution Approach 1:
The patent changes the etching method from wet etching to dry etching. This parameter change produces flat surfaces on the diaphragm unit by preventing the formation of sloped sections, ensuring uniform thickness and maintaining stability during movable unit displacement while still achieving size reduction through selective layer removal.
Solution Approach 2:
The patent segments the cladding layer into upper and lower layers, allowing selective removal of the lower layer. This segmentation enables precise control over the diaphragm structure, maintaining flat surfaces and uniform thickness that prevent tilting during operation.
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 configuration enables a more compact variable wavelength interference filter with improved yield and reduced processing complexity, while ensuring a uniform thickness and preventing tilting of the movable unit during displacement.
Implementation Method 1
Variable wavelength interference filter
Implementation Method 2
first substrate provided with a first reflective film, and a second substrate provided with a second reflective film that is opposed to the first reflective film
Data Source
AI summary
A variable wavelength interference filter includes: a first substrate provided with a first reflective film; and a second substrate provided with a second reflective film that is opposed to the first reflective film with a gap being interposed between the first reflective film and the second reflective film, in which the first substrate includes an SOI substrate in which a first layer, a second layer, and a third layer are layered in this order along a thickness direction, the first substrate includes: a movable unit provided with the first reflective film; a diaphragm unit configured to surround the movable unit; and a base section configured to support the movable unit through the diaphragm unit so as to be able to advance and retreat along the thickness direction, the diaphragm unit is a portion having a thickness in the thickness direction smaller than the base section due to a groove opening in a surface of the first substrate that is at an opposite side from the second substrate, and includes the second layer and the third layer, and at least surfaces, at the second substrate side, of the base section and the diaphragm unit of the first substrate are flat when the movable unit is not displaced.