Copper Interconnect Structure with Gradient Seed Layers
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Solution Overview
Problem
As semiconductor devices shrink, seams or cracks develop at the junction between copper interconnects and diffusion barrier layers, leading to electromigration and stress migration, which degrade the reliability of copper interconnect structures.
Innovation Solution
The implementation of multiple Advanced Gradient Seed (AGS) layers, comprising alternating barrier and seed layers, is used to reduce the occurrence of seams and cracks between copper and diffusion barrier layers, enhancing adhesion and reducing electromigration and stress migration effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single barrier layer is used to prevent copper diffusion, then copper diffusion is blocked, but seams or cracks develop at the joinder between copper and barrier layer leading to electromigration and stress migration
Solution Approach 1:
The single barrier layer is segmented into multiple alternating barrier and seed layers. This segmentation creates a gradient structure that reduces the abrupt interface between copper and barrier material, thereby minimizing seam and crack formation while maintaining diffusion barrier functionality.
Solution Approach 2:
The interconnect structure uses a composite multi-layer configuration combining barrier materials (e.g., tantalum, tungsten) and seed materials (e.g., copper, copper alloys) in alternating layers. This composite structure provides both diffusion barrier properties and mechanical integrity, eliminating the harmful effects of single-layer interfaces.
2Productivity
If copper is deposited in high-density interconnect openings, then interconnect density increases, but voids form at the bottom of openings due to line-of-sight deposition limitations
Solution Approach 1:
Seed layers are deposited preliminarily on the barrier layers before copper fill. These seed layers provide a conformal coating that ensures complete coverage of the opening surfaces, including bottom and sidewalls, preparing the structure for subsequent copper deposition and preventing void formation.
Solution Approach 2:
Different materials with specific properties are used at different locations: barrier materials at the interface with dielectric for diffusion prevention, and copper/copper-alloy seed layers for conductive fill. This local material optimization ensures both density and fill uniformity in high-density interconnects.
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
This approach significantly improves the reliability of copper interconnect structures by reducing seams and cracks, thereby enhancing the structural integrity and performance of copper interconnects, especially in advanced node devices.
Implementation Method 1
copper diffuses through dielectric materials, so the copper interconnect structures must be encapsulated by a diffusion barrier layer
Implementation Method 2
enhancing adhesion and reducing electromigration and stress migration effects
Implementation Method 3
copper is deposited within the opening, and then a polishing/planarization process is used to remove copper from over the dielectric layer, leaving copper inlaid within the opening
Data Source
AI summary
A copper interconnect structure in a semiconductor device including an opening formed in a dielectric layer of the semiconductor device, the opening having sidewalls and a bottom. A first barrier layer is conformally deposited on the sidewalls and the bottom of the opening. A first seed layer is conformally deposited on the first barrier layer. A second barrier layer is conformally deposited on the first seed layer. A second seed layer is conformally deposited on the second barrier layer and a conductive plug is deposited in the opening of the dielectric layer.