Diffusion Barrier for Low-Temperature Semiconductor Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices face challenges in fusion-bonding at low temperatures with thin metal bonding films, as high-temperature heat treatment can adversely affect device characteristics due to the easy diffusion of bump materials like Au or Cu, leading to instability and potential damage.
Innovation Solution
Incorporating a diffusion prevention film of a third metal material with a lower diffusion coefficient, such as TiW, between the bump and the bonding film of a second metal material with a lower melting point, like Sn or In, allows for low-temperature fusion bonding while preventing mutual diffusion and maintaining bonding film integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of metal bonding films is reduced to minimize volume expansion and diffusion, then bonding stability improves, but the melting point increases due to alloy formation requiring high-temperature heat treatment
Solution Approach 1:
A diffusion prevention film made of a third metal material (e.g., Ti, W, Ta, Mo, or their alloys) is introduced as an intermediary layer between the bump (first metal material) and the bonding film (second metal material). This mediator prevents mutual diffusion between Au and Sn, allowing the bonding film to remain in elemental state with lower melting point, thus enabling low-temperature fusion bonding while maintaining bonding stability.
Solution Approach 2:
The invention creates a composite structure consisting of three metal materials: the bump material (Au or Cu), the diffusion prevention film (Ti, W, Ta, Mo or their alloys), and the bonding film (Sn, In, or Sn-In alloy). This composite structure leverages the low diffusion coefficient of the third metal to prevent alloying, thereby maintaining the low melting point of the bonding film while ensuring bonding reliability.
2Strength
If high-temperature heat treatment is applied to fuse alloyed bonding films, then bonding strength is achieved, but adverse effects on semiconductor chip characteristics occur
Solution Approach 1:
The diffusion prevention film acts as a protective intermediary that blocks the diffusion path between the bump material and bonding film material. By preventing alloy formation, it maintains the bonding film in its elemental state with lower melting point, enabling fusion bonding at temperatures that do not adversely affect semiconductor chip characteristics while still achieving sufficient bonding strength.
Solution Approach 2:
The invention changes the chemical composition parameter of the bonding interface by introducing a diffusion barrier, which fundamentally alters the phase transition temperature of the bonding film from alloy state (high melting point) to elemental state (low melting point). This parameter change enables low-temperature processing that protects semiconductor characteristics while maintaining bonding strength.
3Stability of the object's composition
If the thickness of metal bonding films is increased to eliminate concerns about diffusion, then diffusion stability improves, but volume expansion and fusion diffusion occur due to heat generation during use
Solution Approach 1:
The diffusion prevention film serves as a permanent intermediary barrier that prevents mutual diffusion between the bump and bonding film regardless of bonding film thickness. This allows the use of thin bonding films (0.1-5 μm) while maintaining diffusion stability, thereby minimizing volume expansion and heat-affected zone during device operation.
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
This approach enables low-temperature fusion bonding with sufficient strength by keeping the bonding film in an elemental state, reducing thermal stress on semiconductor devices and maintaining their characteristics, while ensuring stable bonding between the semiconductor chip and substrate.
Implementation Method 1
a diffusion prevention film of a third metal material (e.g., TiW) provided between the top surface of the bump and the bonding film as covering at least part of the top surface of the bump, the third metal material having a lower diffusion coefficient than the second metal material with respect to the first metal material
Implementation Method 2
the second metal material having a lower melting point in an elemental state than an alloy of the first metal material and the second metal material
Data Source
AI summary
An inventive electronic device includes a substrate, a bump of a first metal material provided on a surface of the substrate, a bonding film of a second metal material provided on a top surface of the bump for bonding the electronic device to an electrical connection portion of a second device, the second metal material having a lower melting point in an elemental state than an alloy of the first metal material and the second metal material, and a diffusion prevention film of a third metal material provided between the top surface of the bump and the bonding film as covering at least part of the top surface of the bump, the third metal material having a lower diffusion coefficient than the second metal material with respect to the first metal material.