Ga-doped SiGe Layer Formation via Segregated Deposition
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Solution Overview
Problem
Existing methods for forming Ga-doped SiGe layers, such as epitaxial growth of SiGe:B followed by Ga implantation and anneal, disrupt the lattice and are not compatible with all semiconductor structures, and there is a need for improved methods to achieve low contact and bulk resistivity with reduced carbon contamination.
Innovation Solution
A method involving the co-deposition of Si, Ge, and Ga, with a C-containing Ga precursor in the first portion and subsequent deposition without the precursor in the second portion, allowing Ga to segregate and restrict carbon to the first portion, resulting in uniformly distributed dopants and reduced resistivity in the SiGe:Ga and SiGe:B:Ga layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ga implantation and anneal are used to form Ga-doped SiGe layers, then Ga doping is achieved, but lattice disruption and damage occur
Solution Approach 1:
Ga is pre-mixed with Si and Ge precursors before deposition, allowing Ga to be incorporated into the SiGe lattice during epitaxial growth without requiring subsequent implantation steps. This preliminary incorporation prevents lattice disruption while achieving the desired Ga doping concentration.
Solution Approach 2:
The epitaxial growth process acts as an intermediary mechanism that facilitates Ga incorporation into SiGe without direct implantation. The controlled chemical vapor deposition environment allows Ga atoms to be seamlessly integrated into the growing crystal lattice, avoiding the mechanical damage associated with ion implantation.
2Reliability
If post-implantation anneal is performed, then Ga activation is achieved, but compatibility with other semiconductor structures is reduced
Solution Approach 1:
The epitaxial growth process continuously incorporates Ga into the SiGe lattice in its activated state, eliminating the need for separate annealing steps. This continuous incorporation ensures Ga activation while maintaining compatibility with existing semiconductor structures that cannot withstand high-temperature annealing.
Solution Approach 2:
The epitaxial growth process itself serves the dual function of both depositing SiGe material and simultaneously incorporating activated Ga dopants. This self-service approach eliminates the need for additional processing steps, making the method compatible with a broader range of semiconductor structures.
3Quantity of substance
If C-containing Ga precursor is used throughout deposition, then Ga incorporation is maintained, but carbon contamination increases
Solution Approach 1:
The deposition process is segmented into distinct stages: an initial stage using C-containing Ga precursor to establish Ga incorporation, followed by a subsequent stage using non-carbon-containing precursor to maintain Ga doping while reducing carbon contamination. This segmentation allows optimization of both Ga incorporation and carbon control.
Solution Approach 2:
A thin initial layer is deposited using the C-containing Ga precursor to establish sufficient Ga incorporation, after which the precursor is switched to a non-carbon-containing version. This preliminary action ensures Ga is properly incorporated before carbon contamination becomes a concern in thicker layers.
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 achieves low contact and bulk resistivity with improved electrical properties and reduced carbon contamination, enabling the formation of SiGe:Ga and SiGe:B:Ga layers suitable for semiconductor devices with enhanced reliability and efficiency.
Implementation Method 1
allowing Ga to segregate and restrict carbon to the first portion
Implementation Method 2
depositing, in the presence of a C-containing Ga precursor, SiGe:Ga on a substrate
Data Source
AI summary
A method for forming a Ga-doped SiGe layer comprises depositing, in the presence of a C-containing Ga precursor, Ga-doped SiGe on a substrate, thereby forming a first portion of the Ga-doped SiGe layer. The method further comprises depositing, in the absence of the C-containing Ga precursor, SiGe on the first portion, thereby forming a second portion of the Ga-doped SiGe layer.