Cobalt Contact Stress Control Layer Annealing
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Solution Overview
Problem
The integration of cobalt in semiconductor device structures is challenging due to defect formation and voids created during the annealing process, which can result in high contact resistance and electrical shorts, especially in advanced design rules for silicide formation and grain size increase.
Innovation Solution
A method involving the deposition of a stress control layer on cobalt-filled structures before annealing to prevent diffusion and subsequent removal, which includes forming a patterned substrate with cobalt fillings, depositing a metal liner layer, and using a stress control layer to prevent cobalt diffusion, followed by annealing and removal of the stress control layer and overburden.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If annealing is performed to increase grain size of cobalt, then grain size increases and silicide formation is enabled, but voids and defects form causing high contact resistance and electrical shorts
Solution Approach 1:
A stress control layer is deposited on the cobalt structure before annealing to preemptively prevent void formation and cobalt bridging during the thermal process. This preliminary protective action allows the annealing to proceed successfully for grain growth while maintaining contact integrity
Solution Approach 2:
The stress control layer acts as an intermediary between the cobalt and the environment, mediating the stress effects during annealing. This intermediate layer prevents direct interaction that would cause harmful void formation while allowing the desired grain growth to occur
2Ease of manufacture
If cobalt is deposited to fill trenches and vias, then contact structures are formed, but cobalt diffusion into surrounding layers occurs causing defects
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the cobalt fill and the surrounding dielectric/trench structures. This intermediate layer prevents cobalt atoms from diffusing into adjacent regions while allowing the cobalt to maintain its contact-filling function
Solution Approach 2:
Different layers are assigned different functional qualities: the cobalt provides conductive filling, the diffusion barrier prevents atomic migration, and the stress control layer manages thermal stress. Each layer has a specialized local function that addresses specific problems
3Object-generated harmful factors
If stress control layer is deposited to prevent cobalt diffusion, then diffusion is prevented, but process complexity increases due to additional deposition and removal steps
Solution Approach 1:
The stress control layer is designed to perform multiple functions simultaneously: it serves as a diffusion barrier, a stress management layer, and a process integration element. This multi-functionality reduces the need for separate dedicated layers for each function
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 prevents void formation and cobalt bridging, ensuring reliable contact structures with reduced contact resistance and enabling effective grain size increase and silicide formation.
Implementation Method 1
The patterned substrate is annealed to increase grain size of the cobalt
Implementation Method 2
the stress control layer is configured to prevent diffusion of the cobalt into the stress control layer
Data Source
AI summary
Methods and structures for forming cobalt contact and/or cobalt interconnects includes depositing a stress control layer onto the cobalt layer prior to annealing after which the stress control layer can be removed. The stress control layer prevents formation of defects that can occur in the absence of the stress control layer.