Gate-to-Source/Drain Butted Contact With Sidewall Extension
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Solution Overview
Problem
Conventional gate-to-source/drain connections in multi-gate devices, such as FinFETs and MBC transistors, suffer from limited contact surfaces and high contact resistance due to butted contacts, which are not self-aligned and require high overlay accuracy, increasing manufacturing costs.
Innovation Solution
A butted contact structure with an extending portion that laterally extends between the gate structure and source/drain contact, providing additional sidewall contact surfaces to reduce resistance and improve alignment, thereby enhancing the connection between gate and source/drain features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a butted contact structure is used to connect gate and source/drain features, then the device can be manufactured with conventional processes, but the contact surface area is limited and contact resistance is high
Solution Approach 1:
The contact structure extends vertically into the trench to create additional contact surfaces. The first contact portion contacts the gate electrode while the second contact portion contacts the source/drain feature, with the conductive material extending downward to provide multiple contact interfaces, effectively moving from a single-plane contact to a three-dimensional contact structure.
Solution Approach 2:
The contact structure is formed within a trench that is etched into the substrate. The conductive material is deposited within this trench structure, nesting the contact portions within the trench boundaries while extending vertically to contact both the gate electrode and source/drain feature at different depths.
2Ease of manufacture
If a butted contact is used for gate-to-source/drain connection, then the structure is simple, but the alignment accuracy requirement is high and manufacturing cost increases
Solution Approach 1:
The trench structure serves multiple functions: it provides the containment boundary for the conductive material, defines the vertical extent of the contact, and positions the contact portions relative to the gate and source/drain features. The trench acts as a self-aligning structure that guides the conductive material formation process.
Solution Approach 2:
The trench is etched into the substrate before the conductive material is deposited. This preliminary formation of the trench structure establishes the geometric constraints and alignment references needed for subsequent conductive material deposition, ensuring proper positioning of the contact portions.
Data Source
AI summary
A method according to the present disclosure includes forming a fin-shaped structure protruding from a substrate, forming a gate structure intersecting the fin-shaped structure, forming a gate spacer on a sidewall of the gate structure, and forming a conductive feature above the fin-shaped structure. The gate spacer is laterally between the gate structure and the conductive feature. The method also includes depositing a dielectric layer over the gate structure and the conductive feature, performing an etching process, thereby forming an opening through the dielectric layer and exposing top surfaces of the conductive feature and the gate structure, recessing the gate spacers through the opening, thereby exposing the sidewall of the gate structure, and forming a contact feature in the opening, wherein the contact feature is in contact with the conductive feature and has a bottom portion protruding downward to be in contact with the sidewall of the gate structure.