Embedded Source Drain Stressor Recess Profile Uniformity
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Solution Overview
Problem
Field effect transistors (FETs) with embedded stressor regions for enhanced carrier mobility face non-uniformity in device performance due to varying recess profiles caused by loading effects during the formation of stressor material, affecting the proximity and volume of source and drain regions to the channel region.
Innovation Solution
The solution involves forming a source or drain region with distinct laterally extended epitaxially grown stressor material, where a first region is embedded under a spacer by a gate structure and a second region extends the vertical depth of the first region, optimizing the recess formation processes separately to enhance proximity and volume, thereby stabilizing the mechanical stress applied to the channel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If recesses are formed in the body of the FET for embedding stressor material, then mechanical stress can be applied to enhance carrier mobility, but the profiles of the recesses become non-uniform due to loading effects of neighboring geometry
Solution Approach 1:
The patent divides the source/drain region formation into two separate stages: first forming a shallow recess to a first depth, then forming a deeper recess to a second depth. This segmentation allows each recess formation step to be optimized independently, reducing the impact of loading effects from neighboring geometry on the overall profile uniformity.
Solution Approach 2:
The patent performs preliminary actions by forming the first recess and filling it with stressor material before forming the second recess. This preliminary action establishes a foundation that reduces the sensitivity of the final structure to loading effects, ensuring more uniform stress distribution.
2Reliability
If the volume of embedded stressor regions is increased to enhance mechanical stress, then carrier mobility improves, but the proximity control to the channel region becomes less precise
Solution Approach 1:
The patent segments the stressor material volume into two distinct components: stressor material in the first recess and stressor material in the second recess. This allows independent optimization of each component's volume and position, enabling precise control over the overall proximity to the channel region while maintaining sufficient total volume for effective stress application.
Solution Approach 2:
The patent applies local quality by creating different stressor material configurations at different depths. The first recess provides stressor material closer to the channel for precise proximity control, while the second recess extends the volume deeper into the body for enhanced total stress, with each region optimized for its specific function.
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 the uniformity and stability of the mechanical stress applied to the channel region, leading to enhanced carrier mobility and device performance by optimizing the proximity and volume of the source and drain regions independently.
Implementation Method 1
Lattice mismatch between the material of a channel region and the material of the embedded stressor regions causes mechanical stress applied to the channel region.
Data Source
AI summary
In some embodiments, in a method, a body structure with a gate structure configured thereon is provided. The gate structure comprises a gate side wall traversing the body structure. A spacer is formed over the gate side wall. A first recess is formed in the body structure. The first recess is formed beside the spacer and extending laterally under the spacer. A recess extension is formed under the first recess to extend a vertical depth of the first recess. Stressor material with a lattice constant different from that of the body structure is grown such that the extended first recess is filled.