Copper Wire Adhesion via Aluminum Covering Film
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Solution Overview
Problem
Semiconductor devices with copper (Cu) uppermost wires face issues such as passivation film separation, copper diffusion into interlayer dielectric films, alignment mark recognition accuracy, and stress-induced cracking, particularly due to the inferior adhesiveness of Cu to insulating materials and high ionization rates.
Innovation Solution
Employing a semiconductor device structure with a copper uppermost wire covered by an aluminum wire covering film, which enhances adhesion to both the wire and the passivation film, and using tungsten vias to prevent copper diffusion, along with specific geometries to disperse stress and reduce alignment mark thickness for improved recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Cu is used as the uppermost wire material to reduce wire resistance, then electrical conductivity is improved, but adhesion to the passivation film deteriorates causing separation
Solution Approach 1:
An Al wire covering film is introduced as an intermediary layer between the Cu uppermost wire and the SiN passivation film. The Al layer provides excellent adhesion to both Cu and SiN, preventing passivation film separation while maintaining the low resistance benefit of Cu wires. This mediator resolves the adhesion problem without sacrificing electrical conductivity.
Solution Approach 2:
The uppermost wire structure is designed as a composite with multiple layers including Cu core and Al covering film. This composite structure combines the high conductivity of Cu with the excellent adhesion properties of Al, achieving both electrical performance and mechanical reliability simultaneously.
2Use of energy by moving object
If Cu is used as wire material, then electrical conductivity is improved, but Cu diffusion into the interlayer dielectric film increases
Solution Approach 1:
A barrier film is introduced as an intermediary between the Cu wire and the interlayer dielectric film to prevent Cu diffusion. This barrier layer blocks the harmful diffusion of Cu ions into the dielectric while allowing the Cu wire to maintain its excellent electrical conductivity for signal transmission.
3Measurement precision
If alignment mark thickness is reduced for better recognition, then measurement precision is improved, but structural strength deteriorates
Solution Approach 1:
The alignment mark is constructed as a composite structure combining Cu and Al layers. The Cu layer provides visibility for optical recognition, while the Al layer reinforces structural strength. This composite design allows the alignment mark to be thin enough for precise recognition while maintaining sufficient mechanical strength.
4Ease of manufacture
If passivation film is formed directly on Cu wire, then manufacturing process is simplified, but stress concentration and cracking occur
Solution Approach 1:
The Al wire covering film serves as a mediator between the Cu wire and the SiN passivation film. This intermediate Al layer has appropriate mechanical properties that reduce stress concentration during passivation film formation, preventing cracking while adding only one additional thin layer that does not significantly complicate the manufacturing process.
Data Source
AI summary
A semiconductor device includes an interlayer dielectric film, a passivation film, made of an insulating material, formed on the interlayer dielectric film, an uppermost wire, made of a material mainly composed of copper, formed between the surface of the interlayer dielectric film and the passivation film, and a wire covering film, made of a material mainly composed of aluminum, interposed between the passivation film and the surface of the uppermost wire for covering the surface of the uppermost wire.