MEMS Micro-Lens Curvature Control With Reduced Optical Aberration
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Solution Overview
Problem
The manufacturing process for MEMS optical devices with reconfigurable focus is complex and costly, and the square shape of the supporting element within the cavity leads to undesirable optical aberrations due to lack of circular symmetry.
Innovation Solution
A manufacturing process that forms a MEMS optical device with a cylindrical micro-lens and supporting element, where the micro-lens is created within cavities of varying shapes, allowing for independent geometry of the main cavity and supporting elements, eliminating the need for backend operations and reducing optical aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the supporting element is housed in the cavity with a square shape, then the overall dimensions are reduced, but optical aberrations increase due to lack of circular symmetry
Solution Approach 1:
The invention separates the cavity shape from the supporting element shape. The cavity maintains a circular cross-section to ensure optical symmetry, while the supporting element ( deposited as a separate layer) can have a square footprint. This segmentation allows each component to optimize its shape independently, resolving the contradiction between compact dimensions and optical quality.
Solution Approach 2:
The invention resolves the shape conflict by transitioning to a multi-layered structure where the supporting element is deposited as a separate layer on the membrane rather than being integrated within the cavity volume. This dimensional separation allows the supporting element to have a square planar footprint while the cavity maintains its circular cross-section, eliminating optical aberrations while preserving compact overall dimensions.
2Ease of manufacture
If the micro-lens is formed by depositing polymeric material on the back of the wafer within the cavity, then the micro-lens can be integrated, but the manufacturing process becomes complex and costly
Solution Approach 1:
Instead of depositing the polymeric micro-lens material on the back of the wafer within the cavity (complex backend operation), the invention inverts the approach by forming the micro-lens from the front side. The polymeric material is deposited on the front surface of the wafer, allowing the micro-lens to be formed during standard frontend processing rather than requiring complex backend operations.
Solution Approach 2:
The micro-lens is formed preliminarily during the frontend wafer processing stage rather than as a subsequent backend operation. By depositing and shaping the polymeric material on the front surface early in the manufacturing process, the lens formation is integrated into the standard CMOS fabrication flow, eliminating the need for complex backend operations and reducing overall manufacturing complexity.
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 process simplifies the manufacturing of MEMS optical devices, reduces costs, and minimizes optical aberrations by allowing for a more symmetrical and efficient design, enabling precise control of the micro-lens curvature for autofocus applications.
Implementation Method 1
The piezoelectric actuator 6 comprises a piezoelectric layer, made, for example, of lead zirconate titanate (PZT). The piezoelectric actuator 6 can be governed so as to deform the membrane 4, as well as the micro-lens 8, in order to vary the position of focus of the micro-lens 8 itself.
Implementation Method 2
the focusing process is controlled by the curvature that the deformation of the membrane 4, caused by the piezoelectric actuator 6, induces on a top surface 8′ of the micro-lens 8
Data Source
AI summary
A MEMS optical device including: a semiconductor body; a main cavity, which extends within the semiconductor body; a membrane suspended over the main cavity; a piezoelectric actuator, which is mechanically coupled to the membrane and can be electronically controlled so as to deform the membrane; a micro-lens, mechanically coupled to the membrane so as to undergo deformation following the deformation of the membrane; and a rigid optical element, which contacts the micro-lens and is arranged so that the micro-lens is interposed between the rigid optical element and the membrane. The micro-lens and the main cavity are arranged on opposite sides of the membrane.