Source/Drain Contact Structure for Void-Free Metal Filling
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Solution Overview
Problem
As semiconductor device sizes shrink, conventional methods for forming source/drain contacts often result in voids or bubbles, leading to increased parasitic resistance and degraded device performance.
Innovation Solution
A novel fabrication process flow that includes etching a source/drain contact opening through an interlayer dielectric, forming a silicide layer with a concave upper surface, and using a two-step deposition process involving physical vapor deposition for a tungsten capping layer and chemical vapor deposition for a molybdenum conductive material, reducing the likelihood of void formation and enhancing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication processes are used to form source/drain contacts, then the manufacturing process is simple, but voids or bubbles are trapped in the contacts increasing parasitic resistance
Solution Approach 1:
The fabrication process is divided into distinct segments: forming a mandrel structure, depositing first and second conductive materials in sequence, and selective removal steps. This segmentation allows each layer to be deposited under optimized conditions, preventing void formation while maintaining process control
Solution Approach 2:
A mandrel structure is formed in advance before depositing the conductive materials. This preliminary action creates a template that guides the subsequent deposition process, ensuring proper material placement and preventing voids from forming during filling
2Productivity
If device size is scaled down to increase functional density, then production efficiency increases and costs decrease, but void formation in contacts becomes more difficult to avoid
Solution Approach 1:
The deposition parameters are optimized for each conductive material layer, with different deposition conditions used for the first and second conductive materials. This allows precise control over material properties and interface quality even at scaled dimensions
Solution Approach 2:
The contact structure uses composite materials with different properties - a first conductive material for the lower portion and a second conductive material for the upper portion. This composite approach optimizes electrical properties and prevents void formation at interfaces while maintaining small device dimensions
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 process results in source/drain contacts that are substantially void-free, reducing parasitic resistance and improving device performance by enabling faster speed and lower power consumption, while also increasing yield.
Implementation Method 1
depositing a first conductive material, such as tungsten, with a physical vapor deposition (PVD) process to form a capping layer
Implementation Method 2
depositing a second conductive material, such as molybdenum, with a chemical vapor deposition (CVD) process to form a conductive material
Data Source
AI summary
A source/drain component is disposed over an active region and surrounded by a dielectric material. A source/drain contact is disposed over the source/drain component. The source/drain contact includes a conductive capping layer and a conductive material having a different material composition than the conductive capping layer. The conductive material has a recessed bottom surface that is in direct contact with the conductive capping layer. A source/drain via is disposed over the source/drain contact. The source/drain via and the conductive material have different material compositions. The conductive capping layer contains tungsten, the conductive material contains molybdenum, and the source/drain via contains tungsten.