Surface Layer Transfer to Cavity Substrates via Temporary Pillars
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Solution Overview
Problem
Manufacturing substrates with a surface layer over a plurality of cavities, especially with low thickness on large cavities, is complex due to the need for precise geometry and distribution configurations, which existing methods struggle to achieve effectively.
Innovation Solution
A method involving a donor substrate and a support substrate with cavities, where temporary pillars are created and used for molecular adhesion, followed by thinning of the donor substrate to form a surface layer, and subsequent removal of the pillars through etching, allowing for the transfer of a high-quality surface layer onto the support substrate with cavities of varying geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to manufacture substrates with surface layer over cavities, then manufacturing process is simpler, but manufacturing precision and quality of surface layer on large cavities deteriorates
Solution Approach 1:
The method segments the manufacturing process into distinct stages: forming pillars in cavities, assembling donor substrate, selective thinning to create surface layer, and pillar removal. This segmentation enables precise control of surface layer quality on large cavities by treating different regions (cavity areas vs. non-cavity areas) differently during thinning.
Solution Approach 2:
Pillars are created in advance within the cavities before the surface layer is formed. This preliminary action provides a structural framework that guides the subsequent thinning process, ensuring that the surface layer is selectively removed only over cavity regions while maintaining integrity elsewhere.
2Manufacturing precision
If surface layer is thinned to low thickness over large cavities, then membrane uniformity improves, but structural stability during manufacturing deteriorates
Solution Approach 1:
Pillars are positioned within cavities before thinning to provide mechanical support and prevent excessive thinning or collapse of the surface layer over large cavity areas. These pillars act as cushions that maintain structural stability during the thinning process while allowing the surface layer to achieve the desired low thickness and uniformity.
Solution Approach 2:
The thinning process creates different local qualities: the surface layer is thinned to low thickness over cavity regions (where pillars provide support) while maintaining greater thickness in non-cavity regions. This local differentiation achieves membrane uniformity over cavities without compromising overall structural stability.
3Strength
If temporary pillars are added to support surface layer, then structural stability improves, but device complexity and manufacturing steps increase
Solution Approach 1:
Pillars are introduced as temporary support structures during manufacturing and then completely removed after serving their purpose. This discarding of temporary elements enables the achievement of structural stability during manufacturing without leaving residual complexity in the final device, as the pillars are eliminated in a subsequent removal step.
Solution Approach 2:
Pillars serve as intermediary elements that facilitate the manufacturing process by providing temporary support during critical stages. They mediate between the conflicting requirements of structural stability and surface layer thinning, enabling the process to proceed successfully before being removed to leave the final clean structure.
4Manufacturing precision
If conventional thinning methods are used, then manufacturing process is simpler, but crystalline quality and thickness control of surface layer deteriorates
Solution Approach 1:
The thinning process is segmented to occur selectively in different regions: aggressive thinning over cavity areas (guided by pillars) and controlled thinning in non-cavity areas. This segmentation preserves crystalline quality by avoiding excessive thinning in regions where it is not needed while achieving the required thickness uniformity over cavities.
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
Enables the transfer of a high-quality surface layer with controlled thickness onto substrates with cavities of any geometry, including large dimensions, ensuring compliance with MEMS device specifications and improving the crystalline quality and uniformity of the membrane.
Implementation Method 1
the implantation of light species in said donor substrate, so as to form a buried fragile zone extending between a first part of the donor substrate, intended to form the surface layer, and a second part of the donor substrate intended to form the remainder of the donor substrate
Implementation Method 2
the assembly includes molecular adhesion between, on the one hand, the donor substrate, and on the other hand, the first face of the supporting substrate and the upper surface of at least one pillar
Implementation Method 3
the removal of the pillar includes local etching of the surface layer to form an opening through said surface layer, and chemical etching of the pillar via said opening
Data Source
Figure 1~2b
Figure 2c~2e
Figure 2f~2g
AI summary
The invention relates to a method for transferring a surface layer (10) to a carrier substrate (20) having cavities (23), the method comprising: - providing a donor substrate, - providing the carrier substrate (20) having a first face and comprising cavities (23), each cavity opening at said first face and having a bottom and peripheral walls, - creating at least one temporary pillar (30) in at least one of the cavities (23), the pillar (30) having an upper surface that is coplanar with the first face of the carrier substrate (20), - joining the donor substrate and the carrier substrate (20) at the first face of the carrier substrate, - thinning the donor substrate so as to form the surface layer (10), - removing the at least one temporary pillar (30).