Room-Temperature NbN Thin Films With Controlled Internal Stress
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Solution Overview
Problem
Existing NbN superconducting thin films face challenges with high internal stress, which affects their stability and reliability, particularly due to high deposition temperatures and thermal expansion coefficient differences between the film and substrate, making them unsuitable for low-cost, high-frequency terahertz applications.
Innovation Solution
A method for depositing low-stress NbN superconducting thin films at room temperature using Si-based substrates, adjusting the N2/Ar mass flow ratio, sputtering power, and deposition pressure to control internal stress within a range of -500 MPa to 500 MPa, thereby regulating the phase formation and crystal nucleation mode during growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high vacuum magnetron sputtering technology is used with substrate temperature ranging from 450°C to 850°C, then NbN thin films can be deposited, but the high deposition temperature limits the preparation process compatibility and introduces additional thermal stress
Solution Approach 1:
The patent changes the deposition temperature parameter from high temperature (450-850°C) to room temperature, which resolves the contradiction by enabling process compatibility with lift-off and other semiconductor fabrication techniques while maintaining film quality through optimized sputtering power (50-800 W) and deposition pressure (1.0-10.0 mTorr) parameters
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for thermal stress through room temperature deposition, preventing the thermal expansion mismatch stress that would otherwise occur during cooling from high deposition temperatures, thereby avoiding film cracking and delamination
2Productivity
If high vacuum magnetron sputtering with rapid crystal nuclei growth is used, then NbN thin films can be formed, but the high deposition temperature and rapid growth affect the density of the thin film
Solution Approach 1:
The patent optimizes the sputtering power parameter range (50-800 W) and deposition pressure (1.0-10.0 mTorr) to achieve balanced film density and deposition efficiency at room temperature, replacing the traditional high temperature process that caused rapid but poor-quality crystal growth
3Manufacturing precision
If single crystal substrates such as MgO or buffer layers on Si substrates are used, then NbN thin films can be grown, but the process becomes complex and costly
Solution Approach 1:
The patent extracts and eliminates the complex buffer layer preparation steps (GaN, TiN, or Nb5N6) and expensive single crystal MgO substrate requirements, achieving high-quality NbN film growth directly on simple Si-based substrates through room temperature sputtering with optimized parameters
Solution Approach 2:
The patent replaces expensive single crystal MgO substrates with inexpensive Si-based substrates, significantly reducing material costs while achieving comparable or superior film quality through the room temperature deposition process
4Adaptability or versatility
If room temperature deposition is used on Si-based substrates, then process compatibility and cost are improved, but controlling internal stress becomes challenging
Solution Approach 1:
The patent systematically optimizes three key parameters - sputtering power (50-800 W), deposition pressure (1.0-10.0 mTorr), and N2/Ar mass flow ratio (5%-50%) - to achieve precise control of internal stress within -500 MPa to 500 MPa, demonstrating that room temperature deposition can effectively control stress through parameter optimization
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 efficient and cost-effective preparation of low-stress NbN thin films compatible with mature semiconductor processes, suitable for terahertz superconducting dynamic inductance thermal detectors, with stress levels meeting the requirements for mass industrial production.
Implementation Method 1
NbN superconducting thin films are deposited on Si substrate by adjusting the N2/Ar mass flow ratio to 5%-50%, the sputtering power to 50-800 W and the deposition pressure to 1.0-10.0 mTorr
Data Source
AI summary
The present invention discloses the low-stress niobium nitride (NbN) superconducting thin film and preparation method and application thereof. The preparation method includes the following steps: providing the metal Nb target and the Si-based substrates, fixing the Si-based substrate at room temperature, adjusting the mass flow ratio of N2/Ar to 20%-50%, the sputtering power to 50-400 W and the deposition pressure to 3.0-10.0 mTorr, NbN superconducting thin films with a stress range of-500 MPa˜500 MPa and a thickness of 70-150 nm were deposited on Si-based substrates. By synergistically controlling the mass flow rate ratio of N2/Ar, sputtering power, and deposition pressure, low stress NbN superconducting thin films can be easily and efficiently prepared. The stress range of the prepared NbN superconducting thin films meets the preparation requirements of superconducting dynamic inductance detectors, and can be mass-produced.