Copper-Copper Bonding via Oxygen-Enriched Crystalline Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current copper-copper bonding methods require ultra-high vacuum, high temperature, or specific atmospheres, which can damage MEMS and complicate the process, and often necessitate pressure that affects alignment.
Innovation Solution
A method involving the formation of a crystalline oxygen-enriched copper layer on copper surfaces, polished to less than 1 nm RMS roughness, allowing for bonding at room temperature and atmospheric pressure without pressure or annealing, enabling alignment and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermocompression or ultra-high vacuum methods are used for copper-copper bonding, then good bonding results are obtained, but the process requires ultra-high vacuum, high temperature, or specific atmosphere which can damage MEMS and complicate the process
Solution Approach 1:
The invention changes the bonding parameters from ultra-high vacuum and high temperature conditions to ambient temperature and atmospheric pressure conditions. The surface is modified by forming a crystalline oxygen-enriched copper layer through controlled oxidation, which enables bonding under simple ambient conditions without requiring complex vacuum systems or high temperature equipment, thus resolving the contradiction between bonding quality and process complexity
Solution Approach 2:
The invention introduces an intermediary substance - a crystalline oxygen-enriched copper layer - that mediates the bonding process. This intermediate layer forms on the copper surface through controlled oxidation and enables direct bonding under ambient conditions, acting as a bridge that allows bonding without requiring ultra-high vacuum or high temperature, thus simplifying the process while maintaining bonding reliability
2Reliability
If pressure is applied during copper-copper bonding, then bonding is achieved, but alignment between plates is damaged
Solution Approach 1:
The invention replaces the mechanical bonding system (requiring applied pressure) with a chemical-surface system. The crystalline oxygen-enriched copper layer formed on the surfaces enables bonding through surface chemistry and molecular interaction rather than mechanical compression, eliminating the need for applied pressure during bonding and thus preserving alignment precision while achieving bonding strength
3Reliability
If high temperature is used for copper-copper bonding, then bonding is achieved, but MEMS components are damaged
Solution Approach 1:
The invention fundamentally changes the temperature parameter from high temperature to ambient temperature. The formation of the crystalline oxygen-enriched copper layer through controlled oxidation at ambient conditions enables bonding without requiring high temperature processing, thus eliminating thermal damage to sensitive MEMS components while maintaining bonding quality
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 achieves strong, electrically conductive copper-copper bonding with improved alignment and mechanical strength, suitable for microelectronic devices, particularly in three-dimensional integration and MEMS encapsulation, without damaging sensitive components.
Implementation Method 1
forming a crystalline layer of oxygen-enriched copper on each of the surfaces
Implementation Method 2
polishing the surfaces so as to obtain a roughness of less than 1 nm RMS, and hydrophilic surfaces
Data Source
Figure 1A~1D
Figure 1E~2
Figure 3~4
AI summary
The invention relates to a method for adhering a first copper element to a second copper element, comprising a step of forming a crystalline layer of oxygen-enriched copper on each of the surfaces of each of the first and second elements, by means of which the elements will be in contact, the total thickness of the two layers being less than 6 nm, said step including: a) at least one step of polishing the surfaces so as to obtain a roughness of less than 1 nm RMS and hydrophilic surfaces; b) at least one step of cleaning said surfaces in order to remove any particles from the polishing process and the majority of corrosion inhibitors; and c) a step of contacting the two crystalline layers of oxygen-enriched copper.