Semiconductor Contact Structure With Selective Barrier Thickness
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Solution Overview
Problem
As semiconductor process nodes advance to smaller feature sizes, contact resistance issues arise due to reduced areas for contact plugs and the use of advanced materials, necessitating improved methods to reduce resistance and enhance adhesion between tungsten plugs and conductive plugs.
Innovation Solution
A method involving the formation of a blocking layer on the tungsten plug by electrostatic adsorption, followed by selective growth of a sidewall barrier on the trench and a thin bottom barrier on the plug, using a chemical composition of solvent, surfactant, and pH buffer to enhance adhesion and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the area for contact plugs is reduced to accommodate smaller feature sizes, then manufacturing precision is improved, but contact resistance increases
Solution Approach 1:
The patent applies different materials with different properties to different locations: a first barrier material (e.g., titanium nitride) is deposited on the sidewall of the trench, while a second barrier material (e.g., cobalt) is deposited on the bottom surface of the trench. This local differentiation allows optimization of each region's function - the sidewall material provides diffusion barrier properties, while the bottom material provides low contact resistance and good adhesion to the conductive plug.
Solution Approach 2:
The contact structure uses a composite barrier system combining two different barrier materials instead of a single uniform material. This composite approach leverages the complementary properties of different materials to simultaneously achieve low contact resistance, good adhesion, and effective diffusion barrier function in the constrained contact plug area.
2Productivity
If advanced materials are used in contact plugs, then productivity is improved, but adhesion between tungsten plug and conductive plug deteriorates
Solution Approach 1:
The patent introduces barrier materials as intermediary layers between the tungsten plug and the conductive plug (such as copper). The first barrier material on the sidewall and the second barrier material on the bottom act as mediators that provide both diffusion barrier function and adhesion promotion, enabling good bonding between the tungsten plug and the conductive plug while preventing interdiffusion of atoms.
3Reliability
If a thick barrier layer is formed to reduce contact resistance, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The barrier layer is segmented into two distinct parts: a first barrier material layer on the sidewall and a second barrier material layer on the bottom surface. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall structural simplicity and manufacturability through sequential deposition processes.
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 method achieves reduced contact resistance and improved adhesion between tungsten and conductive plugs, ensuring stability during thermal processes, while preventing defects and oxidation, and maintaining thermal stability of the blocking layer.
Implementation Method 1
forming a blocking layer on the tungsten plug by electrostatic adsorption
Data Source
AI summary
A semiconductor structure includes a semiconductor substrate, a dielectric layer, a tungsten plug, a conductive plug, and a contact barrier. The dielectric layer is over a semiconductor substrate. The tungsten plug is in the dielectric layer. The conductive plug is on the tungsten plug. The contact barrier includes a sidewall barrier on a sidewall of the conductive plug and a bottom barrier between the conductive plug and the tungsten plug. A thickness of the sidewall barrier is greater than a thickness of the bottom barrier.