Cobalt Interconnect Resistance Recovery via Hydrogen Anneal
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Solution Overview
Problem
The challenge is to remove Cobalt oxide layers from interconnects in CMOS structures without increasing the line resistance, as existing methods like ammonia plasma treatment can cause nitridation and silicidation, leading to resistance increases in Cobalt interconnects.
Innovation Solution
A method involving the use of a Nitrogen-containing gas plasma or Hydrogen plasma to remove Nitrogen from Cobalt interconnects, followed by depositing a thin dielectric or etch stop layer that is later thickened, using Hydrogen treatments to prevent nitridation and silicidation, and ensuring the layers are thin enough to allow Nitrogen removal without increasing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ammonia plasma treatment is used to remove Cobalt oxide layer, then oxide removal is effective, but line resistance increases due to nitridation
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma treatment from ammonia-based (nitrogen-containing) to hydrogen-based or fluorocarbon-based, fundamentally altering the chemical environment to prevent nitridation while maintaining oxide removal capability. This parameter change resolves the contradiction by eliminating the source of nitrogen that causes resistance increase.
Solution Approach 2:
The patent introduces a thin dielectric barrier layer (20-50 Angstroms) that serves as a temporary protective barrier during plasma treatment. This thin layer is deliberately designed to be permeable to oxygen for oxide removal but blocking to nitrogen, allowing selective removal of harmful nitrogen while permitting oxide removal. The layer is later removed or integrated, serving its purpose temporarily.
2Manufacturing precision
If thin dielectric barrier layer is deposited to prevent nitridation, then resistance control is improved, but Nitrogen removal becomes difficult
Solution Approach 1:
The patent changes the thickness parameter of the dielectric barrier layer to a specific range (20-50 Angstroms) that creates optimal permeability characteristics. This thinness allows hydrogen to diffuse through and remove nitrogen while maintaining the barrier's protective function against nitridation. The parameter optimization resolves the contradiction by making the layer thin enough for nitrogen removal but thick enough to provide protection.
Solution Approach 2:
The thin dielectric barrier layer acts as an intermediary that mediates between the plasma environment and the Cobalt interconnect. It selectively permits hydrogen to pass through for nitrogen removal while blocking nitrogen from causing nitridation. This intermediary function resolves the contradiction by enabling controlled nitrogen removal while maintaining protection.
3Manufacturing precision
If Hydrogen plasma or thermal anneal is used to remove Nitrogen, then resistance is reduced, but process complexity increases
Solution Approach 1:
The patent combines multiple functions into the thin dielectric barrier layer: it serves as a nitrogen barrier, a hydrogen permeation membrane, and a protective layer during subsequent processing. By merging these functions into a single thin layer, the patent reduces overall process complexity while achieving nitrogen removal and resistance control.
Solution Approach 2:
The patent performs preliminary removal of nitrogen through the thin dielectric barrier layer before subsequent thickening of the barrier layer. This preliminary action eliminates nitrogen while the layer is still thin and permeable, preventing future nitridation issues. The preliminary nitrogen removal step simplifies later processing by preventing the need for additional nitrogen removal steps.
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 effectively reduces the electrical resistance of Cobalt interconnects by removing Nitrogen through thin dielectric or etch stop layers, preventing nitridation and silicidation, and allowing for the subsequent thickening of these layers without further resistance increases.
Implementation Method 1
removing Nitrogen from the interlayer interconnect through the dielectric barrier layer and increasing thickness of the dielectric barrier layer above the threshold thickness. In one embodiment, the removing Nitrogen from the interlayer interconnect comprises exposing the workpiece to a Hydrogen plasma
Implementation Method 2
the removing Nitrogen from the interlayer interconnect comprises exposing the workpiece to a Hydrogen plasma, radicals or Hydrogen thermal anneal
Implementation Method 3
removing oxide from an exposed surface of the interlayer interconnect by treating the workpiece in a plasma formed of a Nitrogen-containing gas
Data Source
AI summary
Resistance increase in Cobalt interconnects due to nitridation occurring during removal of surface oxide from Cobalt interconnects and deposition of Nitrogen-containing film on Cobalt interconnects is solved by a Hydrogen thermal anneal or plasma treatment. Removal of the Nitrogen is through a thin overlying layer which may be a dielectric barrier layer or an etch stop layer.