Nanocrystalline Diamond Film Deposition at Low Temperatures
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for depositing nanocrystalline diamond films require high temperatures (700-900°C), which is incompatible with the thermal budget constraints of microelectromechanical systems (MEMS) and CMOS integrated circuit electronics, and result in inferior diamond-like carbon films when deposited at lower temperatures.
Innovation Solution
A method involving the use of nanocrystalline diamond powder to seed the substrate, fine control of plasma power and pressure, and active temperature control using a water-cooled sample holder with continuous rotation to deposit phase-pure nanocrystalline diamond films at low temperatures (<500°C) with high deposition rates, ensuring the films are continuous, pinhole-free, and fully dense.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature deposition (700-900°C) is used to grow nanocrystalline diamond films, then film quality and density are improved, but thermal budget constraints of MEMS and CMOS devices are violated
Solution Approach 1:
The substrate surface is pre-seeded with nanocrystalline diamond powder before the actual film deposition. This preliminary action provides nucleation sites that enable high-quality diamond film growth at lower temperatures, resolving the contradiction between film quality and deposition temperature by preparing the surface in advance to facilitate low-temperature crystallization
Solution Approach 2:
The patent changes the plasma chemistry parameters by using a hydrogen-rich plasma environment with specific gas flow ratios and microwave power settings. This parameter change enables the plasma to provide both the energy needed for diamond formation and the hydrogen atoms that promote low-temperature growth, allowing high-quality films to be deposited below 700°C
2Temperature
If low temperature deposition is used to meet thermal budget constraints, then device compatibility is improved, but film quality deteriorates to inferior diamond-like carbon
Solution Approach 1:
Nanocrystalline diamond powder is introduced as an intermediary material that seeds the substrate surface. This intermediary provides pre-formed diamond crystallites that act as templates for further growth, enabling the deposition of high-quality diamond films at low temperatures by mediating between the plasma and the substrate
Solution Approach 2:
The plasma parameters are optimized with specific microwave power (300-700W), pressure (20-100 mTorr), and gas composition (CH4-H2-He mixture) to create a hydrogen-rich environment that enables low-temperature diamond growth. These parameter changes maintain film quality by controlling the plasma chemistry to favor diamond formation over amorphous carbon deposition
3Productivity
If high deposition rates are achieved to reduce processing time, then productivity is improved, but film uniformity and continuity may be compromised
Solution Approach 1:
The substrate is rotated during deposition to dynamically redistribute the incoming plasma flux across the substrate surface. This dynamic motion ensures uniform film thickness and composition across large areas while maintaining high deposition rates, as the rotation continuously exposes different regions to the plasma for equal durations
Solution Approach 2:
The deposition process operates in continuous mode with sustained plasma generation and continuous substrate rotation. This continuity ensures that diamond film growth proceeds uniformly across the entire substrate surface without interruption, maintaining both high deposition rates and film uniformity throughout the process
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
The method achieves nanocrystalline diamond films with average grain sizes up to 20 nm, suitable for applications in MEMS and bio-MEMS devices, maintaining the properties of natural diamond while adhering to the thermal budget constraints, with deposition rates sufficient for practical use as antistiction coatings and electrochemical electrodes.
Implementation Method 1
the use of nanocrystalline diamond powder, preferably of average grain size less than about 30 nm, to seed the substrate surface prior to growth
Implementation Method 2
Fine control of plasma power and pressure during the growth process to control and minimize plasma heating of the substrate
Implementation Method 3
plasma power and pressure during the growth process to control and minimize plasma heating of the substrate
Implementation Method 4
Use of a water-cooled sample holder which incorporates both active heating and cooling to control the temperature of the substrate in the range of 200-500° C.
Implementation Method 5
Continuous rotation of the sample to enhance uniformity of the temperature of the sample during growth
Implementation Method 6
Major techniques for depositing diamond-like films onto substrates involve using hydrogen-rich plasma chemistries via plasma enhanced chemical vapor deposition (PECVD)
Data Source
AI summary
A method of depositing nanocrystalline diamond film on a substrate at a rate of not less than about 0.2 microns/hour at a substrate temperature less than about 500° C. The method includes seeding the substrate surface with nanocrystalline diamond powder to an areal density of not less than about 1010sites/cm2, and contacting the seeded substrate surface with a gas of about 99% by volume of an inert gas other than helium and about 1% by volume of methane or hydrogen and one or more of acetylene, fullerene and anthracene in the presence of a microwave induced plasma while maintaining the substrate temperature less than about 500° C. to deposit nanocrystalline diamond on the seeded substrate surface at a rate not less than about 0.2 microns/hour. Coatings of nanocrystalline diamond with average particle diameters of less than about 20 nanometers can be deposited with thermal budgets of 500° C.-4 hours or less onto a variety of substrates such as MEMS devices.