Shadow Mask Carrier Substrate Alignment for MEMS
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Solution Overview
Problem
Shadow mask patterning in microfabrication faces challenges such as alignment precision limitations, which restrict miniaturization and require large, heavy fixtures unsuitable for rotating wafer holders, affecting the uniformity and precision of the deposition process.
Innovation Solution
A method involving a shadow mask adhered to a carrier substrate with different adhesive layers, allowing precise alignment and separation for accurate deposition on a semiconductor substrate, enabling the use of rotating wafer holders and improving miniaturization capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shadow mask patterning is used to fabricate fragile microstructures, then photoresist-related mechanical damage is avoided and processing steps are reduced, but alignment precision is limited and miniaturization is restricted
Solution Approach 1:
The patent introduces a carrier substrate as an intermediary between the shadow mask and the deposition system. The shadow mask is bonded to the carrier substrate, which provides mechanical support and enables precise positioning without directly handling the fragile mask. This intermediary structure allows the use of rotating wafer holders and precision alignment systems that would be incompatible with direct mask-to-substrate approaches.
Solution Approach 2:
The system is segmented into distinct functional components: the shadow mask (for pattern definition), the carrier substrate (for mechanical support and positioning), and the semiconductor substrate (for deposition). This segmentation allows each component to be optimized independently - the mask for pattern precision, the carrier for mechanical stability and alignment, and the substrate for device fabrication.
2Manufacturing precision
If a fixture is used to hold the shadow mask and wafer at aligned positions, then alignment precision is maintained, but the fixture becomes large and heavy making it unsuitable for rotating wafer holders
Solution Approach 1:
The patent extracts the alignment and positioning function from a traditional heavy fixture and transfers it to the carrier substrate. The carrier substrate, which must already be precisely positioned for wafer processing, serves dual purposes: mechanical support for the shadow mask and alignment reference for the deposition process. This eliminates the need for separate heavy alignment fixtures.
Solution Approach 2:
The carrier substrate performs multiple functions simultaneously: it provides mechanical support for the shadow mask, serves as an alignment reference through alignment marks, and is compatible with rotating wafer holder systems. This multi-functionality replaces what would traditionally require multiple separate components including heavy fixtures.
3Device complexity
If the shadow mask is directly handled without a carrier substrate, then the system is simpler, but alignment precision deteriorates and miniaturization capabilities are lost
Solution Approach 1:
The carrier substrate acts as a necessary intermediary that enables precise alignment and positioning. While it adds a component to the system, it provides critical functions that cannot be achieved with direct mask handling: mechanical stability, precise positioning through alignment marks, and compatibility with automated deposition systems. The added complexity is justified by the substantial improvement in alignment 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
Enhances alignment precision, allows for the fabrication of smaller components with lower tolerances for errors, and improves the uniformity of the deposition process, enabling the production of high-resolution MEMS devices without the need for bulky fixtures.
Implementation Method 1
adhering a first surface of a mask to a carrier substrate via a first adhesive layer
Implementation Method 2
forming a second adhesive layer on at least one of a second surface of the mask or a third surface of a wafer
Implementation Method 3
the second surface and the third surface being kept parallel with each other by a plurality of proximity flags
Implementation Method 4
depositing material via the pattern of openings of the mask to form a pattern of material on the third surface of the wafer
Data Source
AI summary
A method comprising: adhering a first surface of a mask to a carrier substrate via a first adhesive layer; forming a second adhesive layer on at least one of a second surface of the mask or a third surface of a wafer having a second alignment mark; bringing the carrier substrate and the wafer towards each other along a vertical axis such that the second surface of the mask and the third surface of the wafer is separated by an alignment gap based on a thickness of the second adhesive layer; performing an alignment operation based on imaging the first alignment mark and the second alignment mark; configuring the second surface of the mask to adhere to the third surface of the wafer via the second adhesive; and disconnecting the carrier substrate from the mask.