Semiconductor Bonding Pad Alloy Region for Thermal Stress
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Solution Overview
Problem
The ultrasonic bonding method for metal wiring on semiconductor devices experiences stress due to thermal expansion differences between semiconductor chips and metal wires, leading to uneven bonding strength and potential separation under temperature changes, limiting the number of temperature cycles before disconnection.
Innovation Solution
A semiconductor device configuration with a metal layer of a different alloy than the metal electrode, forming a harder alloy region at the bonding interface, which enhances bonding strength and stability by increasing the hardness of the bonding part, allowing for more temperature cycles before disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ultrasonic bonding method is used to bond metal wiring to metal electrode, then bonding can be achieved in a simple manner, but bonding strength becomes uneven and separation occurs under temperature changes
Solution Approach 1:
A metal layer is introduced as an intermediary between the metal electrode and metal wiring. This intermediate metal layer facilitates uniform bonding by mediating the interaction between the two metals, preventing direct bonding issues and ensuring consistent bonding strength across the bonding surface.
Solution Approach 2:
The bonding structure is designed as a composite system consisting of metal electrode + metal layer + metal wiring. This composite structure combines the advantages of different materials to achieve both ease of manufacture and reliable, uniform bonding strength under temperature variations.
2Device complexity
If conventional bonding structure is used, then manufacturing is simple, but the number of temperature cycles before disconnection is limited
Solution Approach 1:
The metal layer serves as a mediator that absorbs and distributes thermal stress uniformly during temperature cycles. This intermediate layer prevents stress concentration at the bonding interface, thereby extending the number of temperature cycles the bonding can withstand before disconnection occurs.
Solution Approach 2:
By changing the material parameter (introducing a different metal layer with appropriate thermal and mechanical properties), the bonding structure's endurance to temperature cycles is significantly improved while maintaining relatively simple manufacturing processes.
3Reliability
If metal layer with different alloy than metal electrode is used, then bonding part hardness increases and bonding becomes more stable, but material selection and process complexity increase
Solution Approach 1:
The metal layer is applied locally at the bonding interface rather than throughout the entire structure. This localized application provides the necessary hardness and stability improvements only where needed for bonding, while keeping the rest of the structure simple and maintaining ease of manufacturing.
Solution Approach 2:
The bonding interface is designed as a composite structure with specific material composition (metal electrode + metal layer with different alloy + metal wiring). This composite approach enhances bonding stability through controlled material combination while managing complexity through systematic material selection.
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 solution provides stable and firm bonding between semiconductor chips and metal wiring, maintaining connection reliability even under broad temperature changes, as demonstrated by improved shear strength tests and alloying reactions that enhance thermal stress tolerance.
Implementation Method 1
the bonding part has an alloy region harder than the metal wiring
Implementation Method 2
vibrating a metal wire at a predetermined ultrasonic frequency
Implementation Method 3
generate local frictional heat in the contacting part in a short time and to melt the metals
Implementation Method 4
stress is generated in a bonding part using ultrasonic bonding method due to a difference between coefficient of thermal expansion of a semiconductor chip and that of a metal wire
Data Source
AI summary
An object of the present invention is to stabilize and strengthen the strength of a bonding part between a metal electrode on a semiconductor chip and metal wiring connected thereto using a simple structure.Provided is a semiconductor device including a metal layer 130 on a surface of a metal electrode 120 formed on a semiconductor chip 110, the metal layer 130 consisting of a metal or an alloy different from a constituent metal of the metal electrode 120, metal wiring 140 is connected to the metal layer 130 via a bonding part 150, wherein the constituent metal of the metal layer 130 is a metal or an alloy different from the constituent metal of the metal electrode 120, and the bonding part 150 has an alloy region harder than the metal wiring 140.