High-Mobility Substrate Passivation via Nitrogen-Hydrogen Plasma
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Solution Overview
Problem
The development of metal-oxide semiconductor field-effect transistors with high-mobility channels, such as InGaAs, is hindered by the high density of traps at the gate dielectric/III-V semiconductor interface, and achieving a pristine passivated surface without damaging the bulk film is challenging, especially due to the formation of low-quality native oxides which complicates integration and increases resistivity.
Innovation Solution
A method involving alternating pulses of a metal precursor and a nitrogen-hydrogen plasma is used to form a passivation layer on high-mobility substrates, reducing the density of interface traps and enabling in-situ cleaning and dielectric gate stack deposition, thereby improving transfer characteristics and reducing resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet chemistry is used to clean the substrate surface, then the native oxide is removed, but the cleaning is insufficient and requires additional processing steps
Solution Approach 1:
The patent replaces wet chemical cleaning with plasma-based cleaning. The plasma process uses reactive species to chemically etch and remove native oxides and contaminants from the substrate surface, providing superior cleaning effectiveness without requiring multiple wet chemistry steps. This substitution of cleaning mechanisms resolves the contradiction by achieving thorough surface preparation in a single, more effective process step.
Solution Approach 2:
The patent employs plasma parameters (power, pressure, gas composition, treatment time) to optimize the cleaning process. By adjusting these parameters, the plasma can effectively remove native oxides and contaminants while controlling the etch rate to prevent substrate damage. This parameter optimization enables single-step plasma cleaning to replace multi-step wet chemistry processes, resolving the contradiction between cleaning effectiveness and process complexity.
2Manufacturing precision
If air exposure time is extended to allow complete oxide removal, then the substrate is thoroughly cleaned, but the interface quality degrades due to re-oxidation
Solution Approach 1:
The patent performs plasma cleaning immediately before dielectric deposition without breaking vacuum or exposing the substrate to air. This preliminary plasma treatment removes native oxides and prepares the surface in-situ, creating a pristine interface that is immediately covered by the deposited dielectric layer. This eliminates the queue time and re-oxidation risk associated with air exposure, resolving the contradiction between thorough cleaning and interface quality preservation.
Solution Approach 2:
The patent maintains an inert vacuum environment throughout the plasma cleaning and subsequent dielectric deposition processes. This inert atmosphere prevents re-oxidation of the substrate surface during the cleaning process and between steps, allowing thorough native oxide removal while preserving interface quality. The continuous vacuum environment eliminates air exposure time, resolving the contradiction between cleaning completeness and interface degradation.
3Productivity
If plasma power is increased to enhance cleaning effectiveness, then the native oxide is removed more efficiently, but the bulk film is damaged
Solution Approach 1:
The patent uses controlled plasma exposure with optimized power levels and treatment durations to achieve sufficient native oxide removal without excessive energy input that would damage the substrate. The plasma cleaning is applied with just enough intensity and duration to remove the native oxide layer and prepare the surface, avoiding the bulk damage that would result from higher power or longer exposure. This partial action approach resolves the contradiction between cleaning efficiency and film integrity.
Solution Approach 2:
The patent employs pulsed plasma treatment rather than continuous high-power plasma exposure. The periodic application of plasma allows for controlled removal of native oxides while providing intervals that prevent excessive heating and damage to the bulk film. This periodic action enables efficient cleaning while preserving substrate integrity, resolving the contradiction between cleaning effectiveness and bulk film damage.
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 effectively minimizes the sub-threshold slope, lowers leakage, and enhances capacitance scaling, leading to improved electrostatic control and reliability of semiconductor devices.
Implementation Method 1
The method includes applying to the high-mobility substrate alternating pulses of a metal precursor and exposure to a plasma of a gas or gas mixture. The gas or gas mixture contains both nitrogen and hydrogen.
Implementation Method 2
exposing the interface layer to a plasma of a gas or a gas mixture, thereby cleaning the interface layer
Implementation Method 3
forming a passivation layer on the high-mobility substrate by application of the alternating pulses of the metal precursor and plasma exposure
Implementation Method 4
forming the interface layer on the substrate, and converting the interface layer into a metal oxide by applying alternating pulses of a metal precursor and exposure to a plasma of a gas or gas mixture
Data Source
AI summary
A technique relates to in-situ cleaning of a high-mobility substrate. Alternating pulses of a metal precursor and exposure to a plasma of a gas or gas mixture are applied. The gas or gas mixture contains both nitrogen and hydrogen (e.g., NH3). A passivation layer is formed on the high-mobility substrate by alternating pulses of the metal precursor and exposure to the plasma of a gas, or gas mixture, containing both nitrogen and hydrogen.