Shallow Heavily Doped Semiconductor Layer via Cyclic Selective Epitaxy
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Solution Overview
Problem
Current methods for achieving high active dopant concentration in semiconductor layers face challenges such as dopant diffusion and integration difficulties, particularly in CMOS processes, where selective epitaxial growth and ionic implantation methods struggle to maintain a sharp dopant profile and high concentration.
Innovation Solution
A cyclic selective deposition method involving a substrate with mono-crystalline and insulating zones, where a doping atmosphere with gaseous dopant precursors is followed by a deposition atmosphere with silicon or germanium precursors, and then an etching atmosphere to selectively grow a mono-crystalline semiconductor layer with high dopant concentration, while maintaining a different texture over insulating zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ionic implantation is used to achieve high dopant concentration, then carrier concentration in source and drain regions is improved, but parasitic resistance cannot be sufficiently reduced and dopant profile sharpness is compromised
Solution Approach 1:
The invention changes the fundamental parameter of dopant introduction from post-growth implantation to in-situ doping during epitaxial growth. This allows dopant concentration to be controlled at the molecular level during deposition, achieving higher concentrations with sharper profiles and reduced parasitic resistance by forming highly doped regions directly during the growth process rather than through subsequent implantation and annealing
2Quantity of substance
If high temperature annealing is performed to increase active dopant concentration, then dopant activation is improved, but dopant diffusion increases and profile sharpness is lost
Solution Approach 1:
The invention performs doping action preliminarily during the epitaxial growth process itself, incorporating dopants into the crystal lattice as the material is being formed. This eliminates the need for subsequent high-temperature annealing to activate dopants, as they are already in their active positions within the lattice during growth, thereby avoiding dopant diffusion and maintaining profile sharpness
Solution Approach 2:
The invention extracts the doping function from the separate post-growth implantation and annealing process and integrates it directly into the epitaxial growth process. By taking out the doping step and combining it with growth, the method achieves dopant activation without the harmful thermal diffusion that occurs in conventional separate annealing processes
3Stability of the object's composition
If selective epitaxial growth is used to form monocrystalline layers, then crystal quality is improved, but achieving high dopant concentration with sharp profiles becomes difficult
Solution Approach 1:
The invention merges two previously separate processes - selective epitaxial growth and in-situ doping - into a single integrated process. By combining crystal growth with dopant incorporation during the same epitaxial deposition step, the method simultaneously achieves high monocrystalline quality and sharp dopant profiles with high concentration, eliminating the trade-off that existed when these functions were performed separately
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 method allows for a high active dopant concentration with reduced dopant diffusion and integration difficulties, achieving a sharp dopant profile and improved semiconductor film quality compared to conventional techniques.
Implementation Method 1
submitting the substrate to a doping atmosphere comprising gaseous dopant precursors
Implementation Method 2
submitting the substrate to a deposition atmosphere comprising gaseous silicon or germanium precursors under conditions causing depositing of a semiconductor layer with a mono-crystalline portion over the first zone
Implementation Method 3
submitting the substrate to a deposition atmosphere comprising gaseous silicon or germanium precursors
Implementation Method 4
submitting the substrate to an etching atmosphere comprising a gaseous chloride precursor for removing the semiconductor layer over the second zone
Data Source
AI summary
The deposition method comprises providing a substrate with a first mono-crystalline zone made of a semiconductor material and a second zone made of an insulating material. During a passivation step, a passivation atmosphere is applied on the substrate so as to cover the first zone with doping impurities. During a deposition step, gaseous silicon and/or germanium precursors are introduced and a doped semiconductor film is formed. The semiconductor film is mono-crystalline over the first zone and has a different texture over the second zone. During an etching step, a chloride gaseous precursor is applied on the substrate so as to remove the semiconductor layer over the second zone.