Self-Aligned Contacts for Field Effect Transistors
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Solution Overview
Problem
The fabrication of metallic contacts in semiconductor field effect transistors often results in shorts due to misalignment during the manufacturing process.
Innovation Solution
The design includes a gate stack with strategically positioned contact portions, where the distance between the first and second contact portions is greater than their width, and additional contact portions in the source and drain regions, reducing the likelihood of shorts by offsetting the gate region contacts from the source and drain region contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If metallic contacts are positioned close together to reduce device area, then device integration density is improved, but misalignment during fabrication causes shorts between contacts
Solution Approach 1:
The patent introduces a third dimensional offset between gate region contacts and source/drain region contacts, in addition to the planar spacing. This vertical/staggered arrangement in multiple dimensions allows contacts to be positioned closer in the device plane while maintaining sufficient separation to prevent shorts during fabrication alignment variations.
Solution Approach 2:
The contact structure is segmented into distinct gate region contacts and source/drain region contacts, with each serving separate functions. This segmentation allows independent positioning and spacing optimization, enabling the gate contacts to be offset from source/drain contacts, thereby reducing short risks while maintaining compact overall device area.
2Reliability
If spacing between contacts is increased to prevent shorts, then manufacturing reliability is improved, but device area increases
Solution Approach 1:
Instead of increasing planar spacing between all contacts, the patent utilizes vertical offset and staggered positioning in the third dimension. This allows maintaining minimal planar spacing for compact device area while achieving effective separation for short prevention through multi-dimensional contact arrangement.
Solution Approach 2:
The patent applies different spacing and positioning strategies to different contact regions locally. Gate region contacts are offset from source/drain region contacts by specific distances (e.g., 0.5-2 micrometers), creating localized separation zones where needed for short prevention without uniformly increasing overall device area.
3Manufacturing precision
If self-aligned fabrication is used to improve alignment precision, then manufacturing complexity increases
Solution Approach 1:
The patent designs contact regions and spacing to be established in advance during earlier fabrication steps, such as defining contact holes through photolithography patterns before metal deposition. This preliminary positioning of contact regions enables subsequent self-aligned processes to maintain precision without requiring complex real-time alignment adjustments.
Solution Approach 2:
The patent introduces intermediate spacer structures and sacrificial layers that mediate the alignment between gate contacts and source/drain contacts. These intermediary elements are formed through standard self-aligned processes, providing physical references that guide subsequent contact formation steps and reduce the need for complex direct alignment procedures.
Data Source
AI summary
A field effect transistor device includes a gate stack disposed on a substrate a first contact portion disposed on a first distal end of the gate stack, a second contact portion disposed on a second distal end of the gate stack, the first contact portion disposed a distance (d) from the second contact portion, and a third contact portion having a width (w) disposed in a source region of the device, the distance (d) is greater than the width (w).