Source/Drain Protection Layer for Reliable FinFET Contact Etching
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Solution Overview
Problem
As semiconductor devices undergo manufacturing processes, the reduction in minimum feature sizes leads to challenges such as damage and oxidation of source/drain regions, which affect the reproducibility and reliability of contact formation, particularly during the formation of interlayer dielectric layers.
Innovation Solution
A protection layer, such as silicon oxynitride, is formed over the source/drain regions, and an annealing process is used to reduce its nitrogen content, allowing for easier etching and preventing oxidation, enabling the use of a thinner contact etch stop layer without increasing the risk of damage, thus improving the formation of source/drain contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection layer is formed over source/drain regions to prevent damage and oxidation, then reliability of contact formation is improved, but device complexity increases due to additional processing steps
Solution Approach 1:
A protection layer is formed over the source/drain regions before subsequent processing steps to prevent damage and oxidation during manufacturing. This preliminary protective measure ensures the integrity of the source/drain regions throughout the fabrication process, directly improving contact formation reliability.
Solution Approach 2:
The protection layer undergoes an annealing process that changes its chemical composition by reducing nitrogen content. This parameter change transforms the layer from a high-nitrogen state (providing protection) to a low-nitrogen state (easier to etch), resolving the contradiction between protection effectiveness and ease of removal.
2Manufacturing precision
If the contact etch stop layer is made thinner to improve contact formation precision, then manufacturing precision is improved, but source/drain regions become more vulnerable to damage
Solution Approach 1:
The protection layer is deposited beforehand to cushion and protect the source/drain regions from potential damage during processing. This allows the contact etch stop layer to be made thinner for improved precision, while the protection layer compensates for the increased vulnerability by absorbing harmful effects during fabrication.
3Strength
If a protection layer with high nitrogen content is used to maximize protective effect, then strength of protection is improved, but etching difficulty increases
Solution Approach 1:
The protection layer's properties are made dynamic through the annealing process. Initially, the layer has high nitrogen content providing strong protection during critical processing steps. After serving its protective function, the annealing process reduces nitrogen content, making the layer easier to etch away. This dynamic transformation resolves the contradiction between protection strength and etching ease.
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 protection layer effectively reduces damage to source/drain regions during subsequent processing steps, allows for a thinner etch stop layer, and enhances the reproducibility of contact formation, while the annealing process facilitates easier etching and reduces nitrogen content, maintaining the benefits of a thin contact etch stop layer.
Implementation Method 1
an annealing process is used to reduce its nitrogen content, allowing for easier etching
Data Source
AI summary
A method includes forming a fin extending from a substrate; forming an first isolation region along opposing sidewalls of the fin; forming a gate structure over the fin; forming an epitaxial source/drain region in the fin adjacent the gate structure; forming an etch stop layer over the epitaxial source/drain region and over the gate structure; forming a protection layer over the etch stop layer, the protection layer including silicon oxynitride; and forming a second isolation material over the protection layer, wherein forming the second isolation material reduces a nitrogen concentration of the protection layer.