Cobalt Silicide Layer Stack for Defect-Free IC Manufacturing
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Solution Overview
Problem
Existing methods for producing integrated circuits often result in defects and dislocations, particularly at the silicon level, which can compromise the quality of electrical connections and lead to delamination issues during the stacking of layers.
Innovation Solution
A method involving the deposition of a metallic layer, a protective titanium nitride layer, and an additional layer to balance stress between layers, followed by heat treatments to form cobalt silicide, with the additional layer being removed to prevent defects and dislocations, ensuring a defect-free integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer of titanium nitride is deposited on the cobalt layer, then diffusion barrier protection is improved, but stress imbalance causes defects and dislocations in the network
Solution Approach 1:
An additional layer is deposited on the protective layer to modify the stress parameters of the stack. This additional layer has different mechanical properties that balance the stress distribution, preventing the network defects caused by the original titanium nitride protective layer while maintaining its diffusion barrier function.
Solution Approach 2:
The solution uses a composite structure with multiple layers (cobalt layer, titanium nitride protective layer, and additional balancing layer). This composite material approach allows combining the diffusion barrier properties of titanium nitride with the stress-balancing properties of the additional layer, resolving both protection and defect-free requirements simultaneously.
2Reliability
If heat treatment is applied to form cobalt silicide, then electrical conductivity is improved, but defects and dislocations occur during the process
Solution Approach 1:
The additional layer is deposited before the heat treatment process to preemptively balance the stress that will occur during silicide formation. This preliminary action prevents defects from forming during the heat treatment, allowing the electrical conductivity improvement to occur without network damage.
Solution Approach 2:
The additional layer acts as a cushioning element that absorbs and balances the stress generated during heat treatment. This beforehand cushioning prevents the stress from causing defects and dislocations, enabling safe heat treatment to improve electrical connection quality.
3Stability of the object's composition
If layers are stacked to avoid holes at interfaces, then delamination risk is reduced, but stress accumulation causes defects in the network
Solution Approach 1:
The additional layer changes the stress distribution parameters within the stack, balancing the internal stresses that would otherwise cause network defects. This parameter modification allows maintaining stable layer bonding while preventing defect formation.
Solution Approach 2:
The additional layer is strategically positioned and designed with specific local properties to address stress concentration issues at critical interfaces. This local quality adjustment balances stress where needed without compromising the overall layer bonding stability.
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 effectively prevents defects and dislocations, ensuring high-quality electrical connections and maintaining the integrity of the integrated circuit without visible evidence of the defect-prevention process.
Implementation Method 1
a protective layer 3 is deposited, for example a layer of titanium nitride (TiN), which acts as a diffusion barrier
Implementation Method 2
a heat treatment operation (heating) is carried out, which is the RTA1 step. This heat treatment operation can be of the order of 500°C, but at least 350°C to modify at least the first layer, here of cobalt, to pass from cobalt to cobalt silicide
Implementation Method 3
a portion of silicon is taken for the production of this cobalt silicide
Implementation Method 4
the titanium nitride protective layer is removed by a wet etching operation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The process enables the fabrication of a defect-free or dislocation-free integrated circuit at the end of the process. A first layer (2) of a metallic chemical compound is initially deposited on a silicon substrate (1). A protective layer (3) is then deposited on top of this first layer, consisting of a main chemical compound different from the main chemical compound of the first layer. An additional layer (4) is then deposited on top of the protective layer. This additional layer comprises a main chemical compound that is different from, equivalent to, or of equivalent dimensions to the main chemical compound of the first layer. In a subsequent step of the process, a heat treatment operation is carried out at a defined first temperature to generate a silicide (2', 2") consisting of the main compound of the first layer and silicon in a first stoichiometry.In a subsequent step of the process, the additional layer and the protective layer are removed by a wet etching operation. In a final step, another heat treatment operation is carried out at a defined temperature higher than the first temperature in order to change the stoichiometry of the previously created silicide.