Multi-Deck Conductive Feature for FinFET Interconnects
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Solution Overview
Problem
The semiconductor industry faces challenges in scaling planar devices, particularly with non-planar transistors like FinFETs, due to issues such as short-channel effects, current leakage, and interconnect structure resistance, especially in metal filling and contact resistance, which conventional conductive features struggle to address effectively.
Innovation Solution
A semiconductor device structure and method that includes a multi-deck conductive feature with a bottom metal feature of cobalt and a top metal feature of copper, separated by a barrier layer and a liner, which enhances adhesion, barrier effects, and gap filling, reducing resistance and improving conductivity in the interconnect structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-deck conductive features are used, then the structure is simple, but the resistance is high and gap filling is poor
Solution Approach 1:
The conductive feature is divided into multiple decks (first deck, second deck, third deck) with different metal materials. Each deck can be independently optimized for specific functions: lower decks use metals with good gap filling (e.g., cobalt), upper decks use metals with low resistance (e.g., copper). This segmentation resolves the contradiction by allowing complex multi-material structure to achieve better conductivity and gap filling performance.
Solution Approach 2:
The patent employs composite metal structures where different metal materials are combined in a multi-deck configuration. Each deck uses metals selected based on their specific properties: some metals provide excellent gap filling capability while others provide low resistance. This composite approach allows the conductive feature to simultaneously achieve good gap filling and low resistance, resolving the technical contradiction between reliability and structural complexity.
2Productivity
If contact hole dimensions are reduced, then the interconnect density increases, but the contact resistance increases
Solution Approach 1:
Different metal materials are assigned to different decks based on their local functional requirements. Lower decks that interface with contact holes use metals with superior gap filling properties to ensure complete filling of reduced-dimension holes, while upper decks use low-resistance metals to minimize overall resistance. This local optimization resolves the contradiction between increased interconnect density and maintained contact resistance.
3Length of stationary object
If barrier layer dimensions are reduced, then the contact hole size decreases, but the metal filling becomes more difficult
Solution Approach 1:
The conductive feature is segmented into multiple decks where lower decks use metals specifically selected for their gap filling capability to fill the contact holes formed by reduced barrier layers. This segmentation allows the manufacturing process to overcome the difficulty of filling small contact holes by using materials with appropriate wetting and filling properties in the lower decks, while upper decks use low-resistance metals.
Data Source
AI summary
The present disclosure provides a semiconductor device structure that includes: a fin active region extruded above a semiconductor substrate; a gate stack disposed on the fin active region, wherein the gate stack includes a gate dielectric layer and a gate electrode; source/drain (S/D) features formed on the fin active region and interposed by the gate stack; and a conductive feature electrically connected to the gate electrode or the S/D features. The conductive feature includes a bottom metal feature of a first metal; a top metal feature of a second metal over the bottom metal feature, wherein the second metal is different from the first metal in composition; a barrier layer surrounding both the top metal feature and the bottom metal feature; and a liner surrounding both the top metal feature and separating the top metal feature from the bottom metal feature and the barrier layer.