PECVD 1 (PlasmaTherm 790)
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About
Films: This is a Plasma-Therm model 790 plasma enhanced chemical vapor deposition system for depositing SiO2, Si3N4, or SiOxNy dielectric films.
Hardware: The system uses a capacitively-coupled 13.56 MHz source excitation to produce the plasma between two parallel aluminum plates. The gas is injected over the sample through a 6” diameter showerhead. The samples are placed on the system anode (to minimize ion damage) which is heated to 250-350°C (250°C is standard).
Gases:
SiH4 (Silane) is the Silicon precursor gas. It is diluted with He down to 2% Silane for safety.
N2O is the Oxygen precursor gas, for producing SiO2.
NH4 is the Nitrogen precursor gas, for producing Si3N4.
CF4 & O2 are used for plasma-cleaning the chamber, by etching off deposited SiO2/Si3N4 films from the chamber walls (in addition to wet-cleaning the chamber walls).
N2 is available as a purging gas or carrier gas. A very low percentage of N2 is expected to "crack" at the low RF powers used on this system.
Film Properties:
SiO2 is produced from SiH4/He 2%/98% and N2O at 250°C. The typical deposition rate is 400 Å/min at 300 mT pressure. The typical BOE etch rate of this oxide is about 400 nm/min.
Si3N4 is produced from SiH4/He 2%/98% and NH3 at 250°C or 350°C. The more dense films are produced at 350°C. The stress of the nitride can be altered by adjusting the N2:He ratio of the deposition.
Applications: These films are typically used for reactive ion etching masks, electrical insulators, chemical passivation layers, optical anti-reflective coatings and capacitor dielectrics. The system is fully programmable with windows-based software.
Usage: Users type in a deposition time for each recipe, using the published (or user-measured) deposition rates. Current dep rates for standard films can be found on the PECVD#1 process control data charts.
Custom programs for dielectric stacks or different process parameters or SiOxNy films can be written and saved.
Detailed Specifications
- Gases available: NH3, N2O, 2%SiH4/He, N2,CF4 and O2
- ~10mT base chamber pressure
- 13.56 MHz excitation freq.
- Automatic tuning network
- RF Power control
- Sample size: pieces to 6” wafers
- Full computer operation
- Standard recipes with deposition variable time
Documentation
- Operating Instructions
- Wafer Coating Process Traveler
- For particle counting method, see the Surfscan Scanning Procedure
Recipes & Data
- Standard Recipes: Recipes > Deposition > PECVD#1
- Process Control Charts: Process Control > PECVD#1