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ThinSonic Pulsed CVD Systems
How Pulsed CVD Works
The ThinSonic™ chemical vapor deposition system operates on a unique but simple principle developed by researchers at Cornell University. In essence, the system relies on the introduction of a small amount of precursor liquid (approximately 100 µl) into an ultrasonic atomizing spray nozzle. The nozzle produces a soft, unpressurized spray of small drops (mean drop size of approximately 15 µm) as a short pulse into the top of an evacuated quartz chamber.
The spray vaporizes almost immediately and is drawn onto a heated substrate at the bottom of a chamber, creating a micro-layer deposition. The efficiency of the pulsed ultrasonic deposition is nearly 100%.
This process is repeated when the chamber is drawn down again to a suitable vacuum of approximately 1 torr. Cycle time is about 10 seconds.
The thickness of the deposition is determined by the number of pulses and the amount of precursor injected per pulse. The unique method of liquid delivery results in each pulse delivering a precisely defined and repeatable quantity of precursor.
A precise amount of liquid is transferred first from the piston pump, through a zero-dead volume valve, into a short length of tubing referred to as the "calibrated dispense volume." Once entrained in the tubing, the volume valve, along with another valve located between the pressurized argon gas source and the sample, are turned so that the entire sample is forced through the ultrasonic nozzle, where it is atomized.
The system has proven successful in a variety of Metallic Organic CVD applications, as well as in CVD applications using polymers. Standard ThinSonic CVD Features:
- Fully automated operation using a PC interface including system controls, outputs, and data logging functions
- Sono-Tek ultrasonic nozzle -- 120 kHz operating frequency
- 3" diameter quartz reaction chamber (14" long)
- Monel susceptor plate (2" diameter) uniformly heated by a 1000 watt ceramic plate heater
- Water-cooled base plate
- Thermocouple sensing and control assembly
- Control module containing Broadband Ultrasonic Generator, temperature controller, vacuum gage, manual override switches, and system power supply
- Precision, valveless piston metering pump with ceramic piston and liner
- Precursor, purging solvent, and waste collection containers
- Argon gas pressure regulator
- NESLAB chiller; Model CFT-33M; cooling capacity 650 W @ 5º C
- 2-stage vacuum pump; capacity -- 25 l/min
ThinSonic CVD Applications
- Electronic coatings on semiconductor wafers, solar cells, fuel cells, sensors
- Hardness coatings for wear resistance
- Biological coatings for heart valves, hip and knee joints, and dental implants
Click to view printable PDF file
Reprinted from Acta Materialia, Vol 49, Krumdieck, S.,"Kinetic Model of Low Pressure Film Deposition from Single Precursor Vapor in a Well-Mixed Cold-Wall Reactor," 2001, with permission from Elsevier Science.
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"Growth rate and morphology for ceramic films by pulsed-MOCVD," Department of Mechanical Engineering, University of Colorado at Boulder.
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"Conversion Efficiency of Alkoxide Precursor to Oxide Films Crown by an Ultrasoinc-Assisted Pulsed Liquid Injection, Metalorganic Chemical Vapor Deposition (Pulsed-CVD) Process," Department of Mechanical Engineering, University of Colorado at Boulder.
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"Chemical Vapor Deposition by Pulsed Ultrasonic Direct Injection," Mark Leiby, Applications Engineer, Sono-Tek Corporation.
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