Structured Membrane Fabrication Using Acetone-Dissolvable Wax Handles
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Solution Overview
Problem
Conventional structured membrane fabrication techniques using dry etching and wet etching face issues with carcinogenic temporary bonding materials and aggressive etch stop processes that can damage the final device, and require 'hard' masks that compromise mechanical or electrical properties.
Innovation Solution
A method involving a membrane wafer with a thin-film on a substrate, where an inert protectant is applied to exposed portions, and a wax handle is used to support the substrate, allowing selective etching without exposing the thin-film until the substrate's backside is processed, using acetone to dissolve the wax and reveal the etching regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dry etching and wet etching techniques are used with temporary bonding materials, then the wafer can be temporarily supported during processing, but the bonding materials are carcinogenic and require aggressive removal processes that can damage the final device
Solution Approach 1:
The patent removes the temporary bonding material entirely from the process. Instead of bonding the wafer to a handle with carcinogenic materials and then removing them, the method uses a protectant layer that remains in place throughout processing, eliminating the need for temporary bonding and its harmful removal processes
Solution Approach 2:
The patent introduces a protectant layer as an intermediary between the wafer and the etching process. This protectant serves the function of protecting exposed portions during substrate etching without requiring temporary bonding materials, thereby eliminating carcinogenic substances while maintaining device support during processing
2Manufacturing precision
If 'hard' metal or oxide masks are used for etching, then the mask provides sufficient protection during aggressive etching processes, but the mask removal processes compromise the mechanical or electrical properties of the ultimate device
Solution Approach 1:
The patent changes the material parameter of the protective layer from hard metal/oxide masks to a softer protectant material that can be applied as a thin film. This protectant provides sufficient protection during etching through its chemical inertness and adhesion properties, yet can be removed without aggressive processes that would damage the device's mechanical or electrical properties
Solution Approach 2:
The patent applies the protectant selectively to exposed portions of the wafer where protection is needed, while leaving other areas unprotected for subsequent etching. This localized application provides precise protection where required without requiring aggressive mask removal processes
3Manufacturing precision
If photoresist is used as an imaging layer with thin-film material, then the wafer can be etched to define cuts and holes, but the process requires temporary bonding to handle that compromises the final device
Solution Approach 1:
The patent combines the functions of the imaging layer and protective layer into a single protectant layer. This protectant serves both as the pattern definition medium and as the protective coating during substrate etching, eliminating the need for separate temporary bonding and handle structures, thereby reducing process complexity while maintaining pattern definition precision
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 method preserves the integrity of the device, avoids the use of harmful materials, and enables precise cut openings in the membrane without compromising mechanical or electrical properties, adaptable to various micromachining applications.
Implementation Method 1
The wax is exposed to acetone so that it dissolves thereby also uncoupling the handle from the protectant
Data Source
AI summary
A structured membrane fabrication method begins with a membrane wafer on a substrate and at least one thin-film on the membrane wafer such that portions of the membrane wafer are exposed. The exposed portions of the membrane wafer and each thin-film are covered with an acetone-inert protectant. Portions of the protectant are etched through to the membrane wafer while each thin-film remains fully covered by the protectant. A handle is coupled to the protectant with a wax that dissolves in acetone. Portions of the substrate are then removed to define and expose a contiguous region of the membrane wafer adjacent to each thin-film and the portions of the protectant so-etched. The wax is exposed to acetone so that it dissolves. The contiguous region of the membrane wafer is then etched through at the portions of the protectant so-etched. The protectant is then removed.