Semiconductor Redistribution Layer with Silver Film and Polyimide Gutter
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Solution Overview
Problem
Current semiconductor devices with redistribution layers face challenges in reducing manufacturing costs and improving reliability, particularly due to the use of copper wires, which require additional gold pads and photolithography processes, leading to increased costs and reduced withstand voltage between adjacent layers.
Innovation Solution
A semiconductor device structure featuring a protective insulating film with a redistribution layer gutter and a single-layer polyimide resin film, where a barrier film and silver film are formed to prevent copper migration and enhance adhesiveness, allowing direct coupling of copper wires without the need for gold pads or extensive photolithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If copper wire is used instead of gold wire, then manufacturing cost is reduced, but adhesiveness between the wire and pad is insufficient
Solution Approach 1:
The patent employs a composite pad structure consisting of a copper pad, a nickel undercoat layer, and a gold upper layer. This multi-material composition leverages the low cost and high conductivity of copper, the adhesion properties of nickel, and the oxidation resistance and weldability of gold, thereby achieving both cost reduction and reliable copper wire bonding.
Solution Approach 2:
The nickel undercoat layer serves as an intermediary between the copper pad and the gold upper layer, as well as between the copper pad and the copper wire. This intermediate layer facilitates adhesion and prevents direct contact between incompatible materials, solving the adhesiveness problem while maintaining cost efficiency.
2Reliability
If a gold pad is formed to enable copper wire coupling, then adhesiveness is improved, but manufacturing cost increases
Solution Approach 1:
The gold layer is applied only to the specific region where wire bonding is required, rather than covering the entire pad area. This localized application reduces gold consumption and manufacturing cost while maintaining the necessary adhesiveness and wire bonding capability at the critical interface.
Solution Approach 2:
The composite pad structure with copper, nickel, and gold layers optimizes material usage by assigning each material to its most effective function, reducing overall material cost while maintaining performance.
3Manufacturing precision
If multiple photolithography processes are used to form the redistribution layer, then manufacturing precision is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines the formation of the redistribution layer pattern and the pad structure into a single photolithography process. By using a lift-off technique with a strategically designed mask pattern, multiple structural elements are created simultaneously, reducing the total number of photolithography steps while maintaining manufacturing precision.
Solution Approach 2:
The photolithography mask is designed in advance to include all necessary pattern features (redistribution layer and pad contours) in a single exposure step. This preliminary planning allows complex structures to be formed without requiring multiple sequential lithography processes.
4Device complexity
If copper migration is not prevented, then manufacturing process is simplified, but reliability in high voltage operation deteriorates
Solution Approach 1:
The nickel undercoat layer acts as a diffusion barrier and intermediary between copper layers, preventing copper migration while maintaining structural integrity. This intermediate barrier enables high voltage operation reliability without significantly complicating the manufacturing process.
Solution Approach 2:
The multi-layer composite structure with nickel and gold over the copper pad provides inherent protection against copper migration. The nickel layer specifically serves as a diffusion barrier, while the gold layer provides oxidation resistance, together ensuring reliability in high voltage applications.
Data Source
AI summary
A semiconductor device includes an opening and a redistribution layer gutter which are formed integrally in a polyimide resin film of a single layer. A redistribution layer is formed in the polyimide resin film of a single layer. A wiring material (silver) including the redistribution layer can be inhibited from migrating.