Cu Interconnect Barrier Stack Using Ta/Ti Layers to Limit Migration
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Solution Overview
Problem
Semiconductor devices with Cu wiring face reliability issues due to the oxidation of Ti-based barrier metal films during high-temperature processing, leading to increased resistance, while Ta-based films fail to suppress Cu migration effectively.
Innovation Solution
A semiconductor device configuration featuring a first barrier metal film with Ta and a second barrier metal film with Ti, where Ti diffuses into the conductive film, suppressing Cu migration and oxidation, thereby improving reliability and reducing wiring resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ti is used as the barrier metal film material, then cost is reduced and Cu migration is suppressed, but wiring resistance increases due to oxidation during high-temperature processing
Solution Approach 1:
The barrier metal film is divided into two separate layers: a lower Ti layer (5-20 nm thick) that provides Cu migration suppression through diffusion, and an upper Ta layer (10-50 nm thick) that prevents oxidation. This segmentation allows each material to perform its optimal function without the drawbacks of using either material alone.
Solution Approach 2:
The invention uses a composite barrier metal film structure combining Ti and Ta layers. The Ti layer provides diffusion barrier functionality while the Ta layer provides oxidation resistance. This composite structure leverages the complementary properties of both materials to achieve both Cu migration suppression and low wiring resistance.
2Ease of manufacture
If Ti barrier metal film is used, then cost is reduced, but wiring resistance increases due to oxidation during high-temperature processing
Solution Approach 1:
The barrier metal film is divided into two separate layers: a lower Ti layer (5-20 nm thick) that provides Cu migration suppression through diffusion, and an upper Ta layer (10-50 nm thick) that prevents oxidation. This segmentation allows each material to perform its optimal function without the drawbacks of using either material alone.
Solution Approach 2:
Different portions of the barrier metal film have different material compositions optimized for their specific functions. The lower layer uses Ti for cost-effectiveness and diffusion barrier properties, while the upper layer uses Ta for oxidation resistance. This local differentiation of material quality achieves both cost reduction and performance improvement.
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 described configuration effectively suppresses Cu migration and oxidation, enhancing the reliability of semiconductor devices while maintaining low wiring resistance by using a Ta-based first barrier metal film and a Ti-based second barrier metal film with controlled thicknesses.
Implementation Method 1
high reliability can be obtained by diffusion of the barrier metal film material itself into the Cu wiring
Data Source
AI summary
A semiconductor device according to the embodiment includes: a first interlayer insulating film; a lower wiring layer provided in the first interlayer insulating film; a second interlayer insulating film provided on the first interlayer insulating film and having a first trench provided therein; and an upper wiring layer provided in the first trench of the second interlayer insulating film and electrically connected to the lower wiring layer, wherein the upper wiring layer includes: a first barrier metal film provided in the first trench, and mainly composed of Ta; a second barrier metal film provided in the first trench via the first barrier metal film, and mainly composed of Ti; and a first conductive film provided in the first trench via the first barrier metal film and the second barrier metal film, and mainly composed of a first metal.