Inclined Source/Drain Contact Surface for Semiconductor Devices
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Solution Overview
Problem
As semiconductor devices are designed with smaller feature sizes, the contact resistance between contacts and source/drain regions increases, limiting further performance improvements, despite existing methods to reduce this resistance.
Innovation Solution
A semiconductor device with inclined upper contact surfaces on the source and drain regions, formed using an additional self-limiting etching step, which increases the contact area by at least 50% and includes a gate structure with sidewall spacers and raised source and drain regions, along with epitaxial layers and silicide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If contacts are made smaller to accommodate smaller feature sizes, then device integration density is improved, but contact resistance increases
Solution Approach 1:
The patent transitions from a traditional flat contact surface to an inclined contact surface that extends laterally beneath the gate structure. This dimensional change allows the contact to access the source/drain region through the sidewall spacer area, effectively increasing the contact area without increasing the vertical footprint, thereby reducing contact resistance while maintaining small feature sizes
Solution Approach 2:
The contact surface is formed with a specific inclination angle (30-45 degrees) rather than being flat or vertical. This angled geometry optimizes the contact area by creating a sloped interface between the contact and the source/drain region, improving electrical connection while accommodating the reduced contact dimensions
2Reliability
If an inclined contact surface is formed to increase contact area, then contact resistance is reduced, but device complexity increases
Solution Approach 1:
The inclined contact surface is formed through a self-aligned process where the contact etch automatically follows the sidewall spacer profile. By preparing the sidewall spacers first and using them as self-aligned masks, the complex inclined geometry is achieved without requiring additional alignment steps or complex lithography, thereby reducing manufacturing complexity
Solution Approach 2:
The sidewall spacers serve dual functions: they define the gate structure boundaries and simultaneously serve as self-aligned masks for forming the inclined contact surfaces. The contact etch process automatically conforms to the sidewall spacer geometry, eliminating the need for separate mask alignment and pattern definition steps, thereby simplifying the overall manufacturing process
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having a channel region therein, a gate structure above the channel region, and source and drain regions on opposite sides of the gate structure. A respective contact is on each of the source and drain regions. At least one of the source and drain regions has an inclined upper contact surface with the respective contact. The inclined upper contact surface has at least a 50% greater area than would a corresponding flat contact surface.