Semiconductor Pad Electrode Resistance Reduction via Alloy Formation
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Solution Overview
Problem
Conventional semiconductor device manufacturing methods face challenges in reducing the resistance value of pad electrodes due to the formation of oxide films on the current path, which hinders efficient current flow.
Innovation Solution
A semiconductor device structure is developed with a pad electrode, insulating layers, and a metal layer with concave portions, where a plating metal layer is formed with uneven thickness, allowing for alloy formation between the metal and electrode metals, thereby reducing resistance through step coverage in the concave portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation film (silicon nitride) is formed on the Al electrode pad and an opening is made to form a barrier metal film, then the Al electrode pad is protected from oxidation, but an oxide film is formed on the exposed Al electrode pad surface, increasing resistance
Solution Approach 1:
A metal layer is formed on the Al electrode pad surface before the passivation film is deposited. This preliminary metal layer serves as a base that prevents oxide film formation on the Al electrode pad when the opening is later created, while still allowing the passivation film to protect the pad from oxidation.
Solution Approach 2:
The patent uses a composite structure consisting of the Al electrode pad, a preliminary metal layer, and a passivation film. This composite structure allows the metal layer to prevent oxidation while the passivation film provides protection, solving the contradiction between protection and low resistance.
2Reliability
If a barrier metal film is formed on the exposed Al electrode pad, then the pad is protected from further oxidation, but the oxide film already formed on the pad surface increases the resistance value
Solution Approach 1:
The metal layer is deposited on the Al electrode pad before the passivation film is formed and before the opening is created. This preliminary action ensures that when the opening is made, the metal layer (not oxide) is exposed, preventing the formation of high-resistance oxide films while still allowing subsequent barrier metal formation for oxidation protection.
3Ease of manufacture
If the metal layer is formed with uniform thickness, then the structure is simple to manufacture, but no alloy layer is formed and resistance cannot be reduced
Solution Approach 1:
The metal layer is formed with non-uniform thickness, being thinner at the bottom of the opening region and thicker at the periphery. This local variation in thickness allows the plating metal layer to contact the Al electrode pad directly at the bottom, forming alloy layers that reduce resistance, while maintaining ease of manufacture through standard deposition processes.
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 structure significantly reduces the resistance value between the pad electrode and the plating metal layer, enhancing current path efficiency and performance.
Implementation Method 1
an alloy layer including at least a metal included in the metal layer and a metal included in the electrode is generated
Implementation Method 2
a metal layer which is formed on a surface of the insulating layer as well as in the opening regions, is connected to the pad electrode
Data Source
AI summary
In a semiconductor device according to the present invention, a plurality of opening regions 5 to 8 are formed in an insulating film on a pad electrode 3. A metal layer 9 formed on the pad electrode 3 has a plurality of concave portions 10 to 13 formed therein by covering the opening regions 5 to 8. Moreover, in a peripheral portion at a bottom of each of the concave portions 10 to 13 in the metal layer 9, the metal layer 9 and a Cu plating layer 19 react with each other. By use of this structure, the metal reaction area serves as a current path on the pad electrode 3. Thus, a resistance value on the pad electrode 3 is reduced.