Selective Silicon Carbon Epitaxy via Low Temperature Deposition
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Solution Overview
Problem
Current selective epitaxy processes for forming silicon-carbon epitaxial layers in semiconductor devices face challenges such as the need for high temperatures, unpredictable dopant incorporation, and difficulty in achieving high substitutional carbon levels, which can lead to increased series resistance and reduced selectivity, especially when trying to form heavily n-doped Si:C epitaxy.
Innovation Solution
A method involving the epitaxial formation of a silicon-carbon film on a substrate using deposition gases with a silicon source, a carbon source, and an n-type dopant at temperatures below 600°C, followed by exposure to hydrogen chloride as an etching gas at elevated temperatures and pressures, to achieve selective deposition of heavily doped n-type epitaxy on monocrystalline surfaces while minimizing polycrystalline growth on secondary surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperatures are used in selective epitaxy processes, then deposition rate is improved, but uncontrolled nitridation and reduced selectivity occur
Solution Approach 1:
The patent changes the temperature parameter from conventional high temperatures (800-1000°C) to low temperatures (500-650°C) to suppress nitridation while maintaining deposition through modified gas chemistry and pressure conditions
Solution Approach 2:
The patent uses an inert or reducing atmosphere with specific gas compositions (silane, hydrogen, nitrogen) to prevent unwanted nitridation reactions while enabling controlled epitaxial deposition at lower temperatures
2Productivity
If high temperatures are used in selective epitaxy processes, then deposition rate is improved, but selectivity deteriorates
Solution Approach 1:
The patent modifies multiple parameters simultaneously - lowering temperature to 500-650°C, adjusting pressure to 20-100 Torr, and optimizing gas flow rates - to achieve both acceptable deposition rates and high selectivity (>10:1)
3Manufacturing precision
If low temperatures are used for epitaxial deposition, then substitutional carbon levels are improved, but deposition rate decreases
Solution Approach 1:
The patent optimizes the combination of temperature (500-650°C), pressure (20-100 Torr), and gas composition (silane flow rates, carbon source concentrations) to achieve high substitutional carbon incorporation while maintaining practical deposition rates
4Reliability
If heavily n-doped Si:C epitaxy is formed, then series resistance is reduced, but selectivity and carbon level control become difficult
Solution Approach 1:
The patent uses low temperature (500-650°C) combined with specific doping gas concentrations and pressure conditions to achieve heavy n-type doping (10^19-10^20 atoms/cm³) while maintaining selectivity and controlling carbon incorporation
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 allows for the formation of heavily doped n-type epitaxy with high substitutional carbon levels, reducing series resistance and improving selectivity, while maintaining lower processing temperatures to prevent uncontrolled nitridation and enhance dopant incorporation, thus facilitating the manufacture of high-quality transistor devices.
Implementation Method 1
exposing the substrate to deposition gases comprising a silicon source, a carbon source and an n-type dopant at a temperature of less than about 600° C. and a deposition pressure
Implementation Method 2
A method for epitaxially forming a silicon-carbon film on a substrate surface, comprises placing a substrate including a monocrystalline surface and secondary surfaces into a process chamber; exposing the substrate to deposition gases
Implementation Method 3
exposing the substrate to an etching gas comprising hydrogen chloride at a temperature exceeding about 600° C. and at a pressure at least about 10 times the pressure during exposure to the deposition gas
Data Source
AI summary
Methods for formation of epitaxial layers containing n-doped silicon are disclosed, including methods for the formation and treatment of epitaxial layers in semiconductor devices, for example, Metal Oxide Semiconductor Field Effect Transistor (MOSFET) devices. Formation of the n-doped epitaxial layer involves exposing a substrate in a process chamber to deposition gases including a silicon source, a carbon source and an n-dopant source at a first temperature and pressure and then exposing the substrate to an etchant at a second higher temperature and a higher pressure than during deposition.