Source/Drain Contact Openings With Protective Layer Against FinFET Shorting
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Solution Overview
Problem
As semiconductor devices continue to shrink in feature size, challenges arise in maintaining integration density and preventing shorting of adjacent source/drain regions during the manufacturing process, particularly in the formation of contact openings in FinFETs.
Innovation Solution
The process involves initially forming contact openings to a smaller width and then expanding them to a larger width using a controlled etching process, and applying a protective layer to prevent shorting and protect surrounding features during the formation of metal-semiconductor alloy regions on the source/drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact openings are formed directly to the required width, then manufacturing process is simpler, but adjacent source/drain regions may short
Solution Approach 1:
The contact opening formation process is divided into two separate etching steps: first forming initial contact openings through the interlayer dielectric, then forming contact holes through the mandrel and into the source/drain regions. This segmentation allows each step to be optimized independently, preventing shorting while maintaining process control.
Solution Approach 2:
A mandrel structure is formed beforehand and used as a template to guide the formation of contact holes. The mandrel is positioned between adjacent source/drain regions and serves as a physical barrier during etching, preventing the etch from creating direct pathways between adjacent regions. This preliminary structure enables reliable contact formation without risk of shorting.
2Productivity
If feature size is reduced to increase integration density, then more components fit in given area, but manufacturing precision becomes harder to maintain
Solution Approach 1:
The mandrel structure serves multiple functions automatically: it defines the contact hole position, controls the contact hole width, and prevents etching into adjacent source/drain regions. The self-aligned nature of the mandrel eliminates the need for separate alignment steps, maintaining precision even as feature sizes are reduced to increase integration density.
3Reliability
If protective layer is applied during metal-semiconductor alloy formation, then surrounding features are protected from etching, but process steps increase
Solution Approach 1:
The mandrel structure serves multiple purposes throughout the process: it acts as a spacer during contact opening formation, provides a template for contact hole positioning, and serves as a protective barrier during metal-semiconductor alloy formation. By making the mandrel multi-functional, additional protective measures are unnecessary, avoiding increases in process complexity while maintaining reliability.
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 improves manufacturing yield by avoiding shorting of adjacent source/drain regions and enhances device performance by ensuring accurate contact formation with highly doped regions of the epitaxial source/drain regions.
Implementation Method 1
the protective layer covering the gate mask during the cleaning process
Implementation Method 2
annealing the metal to form a metal-semiconductor alloy region on the source/drain region
Implementation Method 3
etching an opening through the protective layer, the opening exposing the source/drain region
Data Source
AI summary
In an embodiment, a method includes: depositing a protective layer on a source/drain region and a gate mask, the gate mask disposed on a gate structure, the gate structure disposed on a channel region of a substrate, the channel region adjoining the source/drain region; etching an opening through the protective layer, the opening exposing the source/drain region; depositing a metal in the opening and on the protective layer; annealing the metal to form a metal-semiconductor alloy region on the source/drain region; and removing residue of the metal from the opening with a cleaning process, the protective layer covering the gate mask during the cleaning process.