Copper-Aluminum Interconnect Structure With Graded Work Functions
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Solution Overview
Problem
Semiconductor devices face high resistance in interconnections due to the use of metals, which slows down electrical signals and increases the RC constant in circuits as they shrink in size.
Innovation Solution
A conductive structure comprising an aluminum wire covered by a dielectric layer, with a contact hole filled by a copper wire surrounded by a diffusion block layer, and a conductive material layer with specific work functions to reduce resistance, including multiple conductive layers with work functions between 4.1 and 4.6, and a dual damascene structure formed by copper wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metals are used in interconnections, then electrical connectivity is achieved, but resistance increases and signal speed decreases
Solution Approach 1:
The patent uses a composite material structure consisting of multiple conductive layers with different work functions (aluminum, titanium, copper, tungsten, molybdenum, platinum, palladium, rhodium, iridium, silver, gold) stacked together. This composite structure combines the advantages of different metals to achieve both low resistance and good electrical connectivity, resolving the contradiction between connectivity reliability and signal speed.
Solution Approach 2:
The patent changes the work function parameter of the conductive layers by selecting materials with progressively different work functions (ranging from 4.1 to 5.6 eV). This parameter optimization allows for reduced contact resistance and improved electron transport, thereby enhancing signal speed while maintaining connectivity.
2Length of moving object
If interconnection size is reduced, then device scaling is achieved, but resistance increases and RC constant increases
Solution Approach 1:
The multi-layer composite conductive structure maintains low resistance even in scaled-down dimensions by combining materials with complementary properties. The layered structure provides multiple conduction paths and reduces contact resistance, compensating for the increased resistance that occurs with smaller interconnection sizes.
Solution Approach 2:
The patent applies different material properties to different regions of the interconnection structure. Each layer is positioned strategically based on its work function, creating local optimization of electrical properties throughout the interconnection path, which helps maintain low resistance in miniaturized structures.
3Ease of manufacture
If single metal layers are used, then manufacturing is simple, but resistance is high and performance is limited
Solution Approach 1:
While the structure is more complex than single-layer designs, the patent employs standard semiconductor manufacturing techniques (physical vapor deposition, chemical vapor deposition, atomic layer deposition) to create the multi-layer composite structure. The systematic layering approach, guided by work function gradients, optimizes resistance performance while remaining compatible with existing manufacturing 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 solution effectively reduces interconnection resistance, enhancing signal speed and reducing the RC constant in semiconductor circuits.
Implementation Method 1
the conductive material layer includes numerous conductive layers, work functions of all of the conductive layers are between 4.1 and 4.6, the conductive layer with the smallest work function among all the conductive layers is disposed closest to the aluminum wire, and the conductive layer with the largest work function among all the conductive layers is disposed closest to the first diffusion block layer
Data Source
AI summary
A conductive structure of copper and aluminum includes an aluminum wire. A first dielectric layer covers the aluminum wire. A contact hole penetrates the first dielectric layer, and a first diffusion block layer fills the contact hole and contacts the sidewall of the contact hole. A first copper wire fills the contact hole. The first diffusion block layer contacts and surrounds the first copper wire. A conductive material layer covers and contacts the aluminum wire and the first diffusion block layer. The conductive material layer includes numerous conductive layers. The work functions of all conductive layers are between 4.1 and 4.6. The conductive layer with the smallest work function among all the conductive layers is closest to the aluminum wire, and the conductive layer with the largest work function among all the conductive layers is closest to the first diffusion block layer.