Copper Direct Bonding via (220) Orientation at Room Temperature
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Solution Overview
Problem
Current direct bonding techniques for copper in microelectronics require high temperatures or ultra-high vacuum environments, which are incompatible with certain structures, and result in low fracture energy, making long-term storage necessary, which is impractical for industrial use.
Innovation Solution
A method involving physical vapor deposition to form a copper layer with preferential crystallinity on a TiN or TaN growth layer, allowing direct bonding at room temperature without pressure, promoting faster reinforcement of fracture energy through controlled crystallographic orientation and surface preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermocompression bonding is used to achieve high mechanical strength, then bonding strength is improved, but high temperature above 250°C is required which may be incompatible with certain assembled structures
Solution Approach 1:
The invention changes the bonding parameters from high temperature (above 250°C) to room temperature by modifying the copper surface properties through controlled oxidation and organic contaminant removal, enabling strong bonding without thermal damage to sensitive structures
Solution Approach 2:
The invention replaces the thermal-mechanical bonding mechanism (thermocompression requiring heat and pressure) with a chemical-surface mechanism involving oxide layer formation and organic contaminant removal, allowing bonding at room temperature while maintaining strength
2Temperature
If ultra-high vacuum bonding is used to achieve room temperature bonding, then bonding temperature is reduced, but ultra-high vacuum environment is required which is difficult to use in industry
Solution Approach 1:
The invention enables the copper surfaces to self-prepare for bonding through controlled oxidation and organic contaminant removal in ambient conditions, eliminating the need for ultra-high vacuum equipment and complex manufacturing environments
Solution Approach 2:
The invention changes the environmental parameters from ultra-high vacuum to ambient atmosphere by controlling the chemical state of the copper surface, making the process industrially feasible while maintaining room temperature bonding
3Ease of manufacture
If direct bonding is performed without surface activation to simplify the process, then manufacturing complexity is reduced, but fracture energy is low requiring long-term storage
Solution Approach 1:
The invention performs preliminary surface preparation by controlling oxidation and removing organic contaminants before bonding, which enhances fracture energy and eliminates the need for long-term storage while keeping the process simple
Solution Approach 2:
The invention changes the surface chemical parameters through controlled oxidation and contaminant removal, transforming the copper surface to achieve high fracture energy without complex processing or extended storage requirements
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 rapid and robust reinforcement of fracture energy at room temperature, enabling quicker and more efficient bonding with improved mechanical strength, compatible with industrial processes and reducing storage time.
Implementation Method 1
deposition on a semiconductor substrate of at least a portion of a given material by physical vapor deposition forming a growth portion, the given material being chosen from TiN x and TaN x, deposition on the portion of given material of at least a portion of copper
Implementation Method 2
polishing the surfaces of the elements containing the copper portion so that they have a roughness of less than 1 nm RMS and hydrophilic properties
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3~4
AI summary
Process for producing a structure by direct adhesive bonding of two elements comprising the production of the elements to be assembled and the assembly of said elements, in which the production of the elements to be assembled comprises the steps: - deposition on a substrate of a TiN or TaN layer by physical vapour deposition, - deposition of a copper layer on the TiN or TaN layer, the conditions under which the TinN or TaN layer is deposited by physical vapour deposition being such that the copper layer has a mainly crystallographic orientation (220), and in which the assembly of said elements comprises the steps: - polishing the surfaces of the copper layers intended to come into contact so that they have a roughness of less than 1 nm RMS and hydrophilic properties, - bringing said surfaces into contact, - storing said structure at atmospheric pressure and at ambient temperature.