Segmented Copper Interconnect Barrier for Low Resistance
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Solution Overview
Problem
Current diffusion barrier layers in copper interconnects, such as refractory metals like tantalum and titanium, have high resistance, leading to increased RC delay and adhesion issues, especially in small features, and existing deposition methods like PVD and ALD face challenges in scalability and throughput.
Innovation Solution
A method involving the deposition of a first oxygen-containing dielectric barrier layer and a self-aligned metal oxide layer formed during annealing, which complements or enhances the barrier capabilities, improving adhesion and preventing copper diffusion, thereby reducing resistance and peeling issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refractory metals (Ta, Ti) or nitride compounds are used as diffusion barrier layers, then copper diffusion prevention is improved, but resistance increases and adhesion deteriorates
Solution Approach 1:
The barrier layer is segmented into multiple functional layers: a first barrier layer (refractory metal or nitride) for copper diffusion prevention, and a second barrier layer (oxygen-containing dielectric material) for adhesion enhancement and resistance reduction. Each layer performs its specific function independently, resolving the contradiction between diffusion prevention and adhesion quality.
Solution Approach 2:
The barrier structure uses composite materials combining refractory metals/nitrides with oxygen-containing dielectric materials. This composite approach allows the structure to simultaneously achieve copper diffusion prevention (from the refractory layer) and improved adhesion with low-k dielectric (from the oxygen-containing dielectric layer), while reducing overall resistance.
2Reliability
If refractory metals are used as diffusion barrier layers, then copper diffusion is prevented, but RC delay increases due to high resistance
Solution Approach 1:
The barrier function is segmented between two layers: the first barrier layer (refractory metal/nitride) provides diffusion prevention, while the second barrier layer (oxygen-containing dielectric) provides low-resistance electrical contact. This segmentation allows copper diffusion prevention without the high resistance penalty, reducing RC delay.
Solution Approach 2:
The oxygen-containing dielectric material acts as an intermediary layer between the refractory metal barrier and the copper fill. It mediates the electrical connection, providing both adhesion and lower resistance compared to pure refractory metals, thereby reducing RC delay while maintaining diffusion prevention.
3Length of stationary object
If PVD process is used for depositing thin TaN/Ta barrier layer, then barrier thickness is reduced, but adhesion between barrier layer and IMD layer cannot be achieved
Solution Approach 1:
The barrier structure is segmented into two layers with distinct functions: the first barrier layer (thin TaN/Ta) provides copper diffusion prevention, while the second barrier layer (oxygen-containing dielectric) provides adhesion to the IMD layer. This segmentation allows thin barrier thickness without compromising adhesion, as the adhesion function is assigned to the second layer.
Solution Approach 2:
The barrier structure uses composite materials where the oxygen-containing dielectric layer complements the thin refractory metal layer. The composite structure achieves both thin thickness (from the thin TaN/Ta layer) and good adhesion (from the oxygen-containing dielectric layer bonding to IMD), resolving the contradiction.
4Manufacturing precision
If ALD process is used for depositing very thin diffusion barrier layer, then uniform coverage is improved, but deposition rate decreases and throughput deteriorates
Solution Approach 1:
The barrier function is segmented into two layers deposited by different processes. The first barrier layer can be deposited by ALD for uniform coverage, while the second barrier layer provides adhesion and resistance benefits. This segmentation allows using ALD's uniform coverage advantage without requiring the entire barrier structure to be deposited by ALD, improving throughput.
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 lowers resistance, enhances adhesion, and prevents copper peeling, improving the yield and performance of copper interconnects by forming a robust barrier structure between copper and low-k dielectric materials.
Implementation Method 1
a first barrier layer between the first portion of the copper-containing layer and the dielectric layer
Implementation Method 2
a self-aligned metal oxide layer formed during annealing, which complements or enhances the barrier capabilities
Implementation Method 3
a self-aligned metal oxide layer formed during annealing
Implementation Method 4
these metallic films have high resistance, thereby causing increased resistance in the copper lines
Data Source
AI summary
A method of making a semiconductor device includes forming a dielectric layer over a semiconductor substrate. The method further includes forming a copper-containing layer in the dielectric layer, wherein the copper-containing layer has a first portion and a second portion. The method further includes forming a first barrier layer between the first portion of the copper-containing layer and the dielectric layer. The method further includes forming a second barrier layer at a boundary between the second portion of the copper-containing layer and the dielectric layer wherein the second barrier layer is adjacent to an exposed portion of the dielectric layer. The first barrier layer is a dielectric layer, and the second barrier layer is a metal oxide layer, and a boundary between a sidewall of the copper-containing layer and the first barrier layer is free of the second barrier layer.