Epitaxial Stress-Inducing Source and Drain Regions for MOS Devices
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Solution Overview
Problem
As semiconductor devices shrink in size, the thickness of stress-inducing films decreases, reducing performance benefits and increasing the likelihood of channel contamination from ion implantation, necessitating new methods for fabricating epitaxially-grown, stress-inducing source and drain regions with fewer process steps and without ion implantation.
Innovation Solution
A method involving a single etch step to form self-aligned source and drain recesses in both NMOS and PMOS devices, filling them with a first epitaxial monocrystalline material for stress-inducing properties, and replacing it with a second material having opposite stress-inducing properties, while in situ-doping during epitaxial growth to enhance performance and reduce process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stress-inducing films are used to enhance carrier mobility, then transistor performance is improved, but the stress benefit declines as film thickness decreases with device pitch scaling
Solution Approach 1:
The patent changes the physical state and formation method of stress-inducing regions from thin deposited films to epitaxially grown source and drain regions. This parameter change allows stress to be induced through the epitaxial growth process itself rather than relying on thin film thickness, maintaining stress effectiveness even as device dimensions scale down.
Solution Approach 2:
The patent replaces the mechanical stress application method (thin stress-inducing films) with an epitaxial growth-based stress induction method. The stress is induced through the epitaxial growth process and in-situ doping, substituting the need for separate thin stress films with integrated stress-inducing source and drain regions.
2Quantity of substance
If ion implantation is used for doping source and drain regions, then doping is achieved, but channel contamination by impurity dopants increases
Solution Approach 1:
The patent replaces ion implantation with epitaxial growth for doping source and drain regions. The in-situ doping during epitaxial growth achieves the required dopant concentration without the high-energy ion bombardment that causes channel contamination, eliminating the harmful effect while maintaining the doping function.
Solution Approach 2:
The patent uses epitaxial growth as an intermediary process to introduce dopants into source and drain regions. This intermediary method allows controlled dopant incorporation during the growth of monocrystalline material, avoiding direct ion implantation into the channel region and thus preventing contamination.
3Manufacturing precision
If multiple process steps are used to fabricate stress-inducing regions, then precise control is achieved, but process complexity increases
Solution Approach 1:
The patent merges multiple functions into the epitaxial growth process: stress induction, doping, and source/drain region formation are all achieved in a single epitaxial growth step. This consolidation reduces process complexity while maintaining precise control over stress characteristics through in-situ doping and controlled growth conditions.
Solution Approach 2:
The epitaxial growth process is designed to perform multiple functions simultaneously: it forms the source and drain regions, induces stress through the growth process itself, and incorporates dopants in-situ. This multi-functionality reduces the number of separate process steps needed while maintaining manufacturing precision.
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 simplifies the processing sequence, reduces lithography and etch steps, and eliminates the need for ion implantation, enabling performance-enhancing stress-inducing regions for advanced semiconductor devices without channel contamination risks.
Implementation Method 1
epitaxially growing a first stress-inducing monocrystalline material in the first and second recesses
Implementation Method 2
epitaxially growing an in situ-doped compressive stress-inducing monocrystalline material
Data Source
AI summary
Methods of fabricating a semiconductor device on and in a semiconductor substrate having a first region and a second region are provided. In accordance with an exemplary embodiment of the invention, a method comprises forming a first gate stack overlying the first region and a second gate stack overlying the second region, etching into the substrate first recesses and second recesses, the first recesses aligned at least to the first gate stack in the first region, and the second recesses aligned at least to the second gate stack in the second region, epitaxially growing a first stress-inducing monocrystalline material in the first and second recesses, removing the first stress-inducing monocrystalline material from the first recesses, and epitaxially growing a second stress-inducing monocrystalline material in the first recesses, wherein the second stress-inducing monocrystalline material has a composition different from the first stress-inducing monocrystalline material.