Silicide Formation via Selective Epitaxial Growth
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Solution Overview
Problem
As semiconductor device dimensions decrease, the source/drain sheet resistance increases, becoming a significant portion of the series resistance, and existing methods for forming silicide layers consume the silicon substrate, thereby increasing this resistance.
Innovation Solution
The method involves growing a silicide in a nitrogen-contained environment using selective epitaxial growth (SEG) technique, which forms a silicide without consuming the silicon substrate, thereby maintaining the junction depth and reducing source/drain sheet resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If device dimensions are reduced, then device density increases, but source/drain sheet resistance becomes a larger portion of series resistance
Solution Approach 1:
The invention extracts the problematic substrate consumption effect from the silicide formation process by introducing a nitrogen barrier. This separation allows silicide formation to proceed without the harmful side effect of excessive substrate consumption, maintaining low source/drain sheet resistance even as device dimensions shrink
Solution Approach 2:
A nitrogen-containing inert atmosphere is used during silicide formation to prevent unwanted reactions and control the reaction kinetics. This inert environment prevents the metal from directly consuming the substrate, maintaining source/drain region integrity during scaling
2Reliability
If Ti metal layer reacts with nitrogen gas to form TiN barrier layer, then volcano effect is prevented, but processing complexity increases
Solution Approach 1:
The TiN barrier layer formation is merged with the existing silicide formation process by using the same nitrogen-containing atmosphere. This combination eliminates the need for separate barrier layer deposition steps, maintaining reliability while avoiding increased processing complexity
Solution Approach 2:
The nitrogen-containing atmosphere serves multiple functions: it forms the TiN barrier layer to prevent the volcano effect, controls the silicide formation kinetics, and maintains source/drain region integrity. This multi-functionality reduces the need for additional processing 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 lowers the source/drain sheet resistance, improves adhesion between copper wires and the dielectric layer, and reduces processing time while maintaining the well implant engineering.
Implementation Method 1
Through the SEG technique, a silicide is grown in a nitrogen-contained environment, so as to lower the source/drain sheet resistance
Data Source
AI summary
A method for fabricating a semiconductor device to lower source/drain sheet resistance is provided. A dielectric layer with a plurality of contact windows is formed on a semiconductor device. Next, selective epitaxial growth (SEG) is implemented, and then a metal layer is sputtered. After that, a silicide is formed by heat treatment. In another embodiment, selective epitaxial growth is implemented first, and then a dielectric layer with a plurality of contact windows is formed. Then, a metal layer is sputtered, and a silicide is then formed by heat treatment. Since the silicide is formed by way of SEG, the silicon substrate will not be consumed during the process of forming the silicide, and the depth of the junction region is maintained, and the source/drain sheet resistance is lowered.