SRAM Contact Plug Barrier Layer Gradient Composition
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Solution Overview
Problem
Current SRAM architecture faces challenges in producing desirable patterns as the pitch of the exposure process decreases, leading to difficulties in enhancing exposure quality.
Innovation Solution
The method involves forming a gate structure on a substrate, creating an epitaxial layer, and fabricating contact plugs with a barrier layer having a gradient concentration of titanium and nitrogen, where the bottom portion is titanium-rich and the top portion is nitrogen-rich, to improve the SRAM architecture's exposure quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch of the exposure process is decreased to increase integration density, then productivity is improved, but manufacturing precision deteriorates making it difficult to produce desirable patterns
Solution Approach 1:
The barrier layer is designed with gradient composition where the bottom portion is titanium-rich and the top portion is nitrogen-rich. This local variation in material properties optimizes adhesion at the interface with the substrate while maintaining appropriate barrier properties at the top, enabling successful patterning at reduced pitch
Solution Approach 2:
The barrier layer's chemical composition is changed by creating a gradient structure with varying titanium and nitrogen concentrations. This parameter change in material composition improves the adhesion and patterning quality, allowing the exposure process to achieve desirable patterns at smaller pitch dimensions
2Ease of manufacture
If a uniform barrier layer is used in the contact hole, then ease of manufacture is improved, but adhesion and metal loss control deteriorate
Solution Approach 1:
The barrier layer transitions from a uniform structure to a gradient structure where composition varies through the thickness. The bottom portion is titanium-rich for optimal adhesion to the substrate, while the top portion is nitrogen-rich for better metal layer compatibility, resolving the adhesion and metal loss issues without significantly complicating the fabrication process
3Reliability
If the barrier layer composition is optimized for adhesion, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The barrier layer composition is optimized by creating a gradient structure with continuous variation in titanium and nitrogen concentrations. This parameter optimization improves adhesion and reduces metal loss, while the gradient nature allows for a single-step or few-step deposition process rather than requiring multiple discrete layers, thus limiting the increase in manufacturing complexity
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 enhances the SRAM architecture's ability to produce high-quality patterns by optimizing the barrier layer's composition, reducing metal loss and improving adhesion, thereby addressing the challenges posed by decreasing pitch in the exposure process.
Implementation Method 1
improving adhesion
Data Source
AI summary
A method for fabricating a static random access memory (SRAM) includes the steps of: forming a gate structure on a substrate; forming an epitaxial layer adjacent to the gate structure; forming a first interlayer dielectric (ILD) layer around the gate structure; transforming the gate structure into a metal gate; forming a contact hole exposing the epitaxial layer, forming a barrier layer in the contact hole, forming a metal layer on the barrier layer, and then planarizing the metal layer and the barrier layer to form a contact plug. Preferably, a bottom portion of the barrier layer includes a titanium rich portion and a top portion of the barrier layer includes a nitrogen rich portion.