Soft Metal Layer Surface Roughness Reduction via Compression
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Solution Overview
Problem
Existing methods for bonding micro devices to substrates face challenges in achieving a low average surface roughness of soft metal layers, which is crucial for effective interstitial diffusion and bonding quality, as conventional deposition methods often result in surface roughness greater than 80 nm, hindering efficient micro-bonding processes.
Innovation Solution
A method involving the formation of an epitaxial layer, a soft metal layer with a specific thickness, and a glue layer on a carrier substrate, followed by the application of external pressure to reduce the surface roughness of the soft metal layer from an initial value greater than 80 nm to less than 80 nm, utilizing techniques like electron gun deposition and sputtering for the soft metal layer and ultraviolet glue layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition methods are used to form soft metal layer, then the deposition process is simple and fast, but the average surface roughness is greater than 80 nm which hinders bonding quality
Solution Approach 1:
The patent applies preliminary action by forming an epitaxial layer with a specific crystal structure before depositing the soft metal layer. This pre-prepared substrate structure promotes smoother metal deposition and reduces surface roughness to below 80 nm, addressing the bonding quality requirement before the actual metal layer formation occurs.
Solution Approach 2:
The patent changes physical and chemical parameters including deposition temperature, deposition rate, and soft metal layer thickness (50-200 nm) to optimize surface roughness. By controlling these parameters during deposition, the method achieves smooth surfaces suitable for bonding while maintaining process feasibility.
2Strength
If soft metal layer thickness is increased to improve bonding force, then bonding strength is enhanced, but surface roughness increases making bonding more difficult
Solution Approach 1:
The patent optimizes the soft metal layer thickness to a specific range of 50-200 nm, which is thinner than conventional layers. This parameter optimization ensures sufficient bonding force through enhanced interstitial diffusion while maintaining low surface roughness below 80 nm, resolving the contradiction between strength and precision.
Solution Approach 2:
The patent creates a composite structure consisting of an epitaxial layer with specific crystal orientation and a soft metal layer. This composite material system leverages the epitaxial layer's smooth surface to reduce overall surface roughness while the soft metal layer provides necessary bonding force through controlled diffusion.
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 method effectively reduces the average surface roughness of the soft metal layer to less than 80 nm, enhancing the bonding interface for micro-bonding processes by improving the contact area and bonding force through interstitial diffusion and liquid-assisted binding, making it suitable for mass production manufacturing.
Implementation Method 1
forming an epitaxial layer on a growth substrate
Implementation Method 2
utilizing techniques like electron gun deposition and sputtering for the soft metal layer
Implementation Method 3
utilizing techniques like electron gun deposition and sputtering for the soft metal layer
Implementation Method 4
applying an external pressure to compress the glue layer and the soft metal layer such that the average surface roughness of the bonding surface of the soft metal layer is reduced from the first value to a second value
Implementation Method 5
forming a glue layer on a carrier substrate
Data Source
AI summary
A method for minimizing an average surface includes: forming an epitaxial layer on a growth substrate; forming the soft metal layer on the epitaxial layer in which the average surface roughness of a bonding surface of the soft metal layer is greater than a first value; forming a glue layer on a carrier substrate; placing a combination of the glue layer and the carrier substrate on the bonding surface in which the glue layer being in contact with the bonding surface of the soft metal layer; and applying an external pressure to compress the glue layer and the soft metal layer such that the average surface roughness of the bonding surface of the soft metal layer is reduced from the first value to a second value, wherein the second value is less than 80 nm.