Monocrystalline Silicon Membrane for MEMS Display Pixels
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Solution Overview
Problem
Conventional microelectromechanical systems (MEMS) used in displays face challenges such as integration difficulties, quality issues in sacrificial layer etching, and high complexity and cost, particularly in forming moveable membranes and sealing liquid crystals in display technologies like DLP and LCOS.
Innovation Solution
A MEMS device comprising a semiconductor substrate with a monocrystalline semiconductor membrane and anchor structures, where the gap distance between the membrane and substrate changes to control light reflection or transmission, enabling the formation of pixels in display devices through a method involving a sacrificial layer and etching aperture process at controlled temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional MEMS techniques use etching of sacrificial silicon oxide layers to form moveable membranes, then membranes can be released and flex in operation, but integration with other systems and manufacturing processes becomes difficult
Solution Approach 1:
The patent changes the material parameter from conventional silicon oxide to silicon-germanium alloy, and changes the etching temperature parameter to a range of 500-800°C. This enables selective etching of the sacrificial layer while maintaining compatibility with standard semiconductor manufacturing processes, thereby improving ease of manufacture and integration while managing process complexity
Solution Approach 2:
The patent introduces an intermediary sacrificial layer made of silicon-germanium material that can be selectively removed through etching apertures. This intermediary layer enables membrane release without requiring complex integration processes, as it can be etched away through predefined apertures using temperature-controlled selective etching
2Manufacturing precision
If conventional techniques etch sacrificial silicon oxide layers to release membranes, then moveable membranes can be formed, but the achievable quality and selectivity of the etching is insufficient
Solution Approach 1:
The patent achieves high etching quality and selectivity by changing the temperature parameter to a specific range of 500-800°C. At these temperatures, the etching process selectively removes silicon-germanium material while preserving other layers, thereby improving manufacturing precision without significantly complicating the manufacturing process
Solution Approach 2:
The patent applies local quality by creating etching apertures at specific locations where selective etching is needed. The sacrificial layer is removed only in these localized regions, allowing precise control over where membranes are released while maintaining the integrity of other structures
3Device complexity
If DLP techniques use arrays of tiny mirrors with additional lenses and light absorbers, then light can be directed and images can be formed, but the device complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into the membrane structure itself. The movable membrane acts as both a structural element and an optical element that directly modulates light transmission by varying the gap distance. This eliminates the need for separate lenses and light absorbers, thereby reducing device complexity and manufacturing cost
Solution Approach 2:
The membrane structure serves multiple functions: it provides mechanical support, enables light modulation through gap variation, and acts as a reflective or transmissive optical element. This multi-functionality reduces the overall component count and simplifies the display device structure compared to conventional DLP techniques
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 improved integration, reduced complexity, and lower costs in manufacturing MEMS-based display technologies by enabling precise control over pixel color and brightness through varying the gap distance between the membrane and substrate, facilitating the creation of efficient and cost-effective display devices.
Implementation Method 1
a portion of a light beam incident on the membrane is reflected or transmitted by the MEMS device dependent on the gap distance
Implementation Method 2
a portion of a light beam incident on the membrane is reflected or transmitted by the MEMS device dependent on the gap distance
Implementation Method 3
The moveable membranes are formed by etching or otherwise removing a sacrificial layer of covered silicon oxide from the structure, thereby forming a cavity and releasing at least a portion of the membrane from the underlying substrate so that the membrane can move and flex in operation
Data Source
AI summary
Embodiments relate to microelectromechanical systems (MEMS) and more particularly to membrane structures comprising pixels for use in, e.g., display devices. In embodiments, a membrane structure comprises a monocrystalline silicon membrane above a cavity formed over a silicon substrate. The membrane structure can comprise a light interference structure that, depending upon a variable distance between the membrane and the substrate, transmits or reflects different wavelengths of light. Related devices, systems and methods are also disclosed.