SACVD stands for Sub-Atmospheric Pressure Chemical Vapor Deposition.
SACVD is a type of chemical vapor deposition (CVD) process performed at a pressure lower than atmospheric pressure. It's primarily used for depositing thin films, particularly silicon dioxide (SiO2), often using Tetraethyl orthosilicate (TEOS) and ozone (O3) as precursors. This TEOS/O3 process is favored because it reduces the time materials need to be at high temperatures, which is crucial for manufacturing Ultra Large Scale Integration (ULSI) circuits.
Here's a more detailed breakdown:
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Chemical Vapor Deposition (CVD): A process where gaseous precursors react chemically on a substrate to produce a thin solid film.
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Sub-Atmospheric Pressure: Refers to a pressure below standard atmospheric pressure (around 100 kPa or 760 Torr). SACVD typically operates in the range of 100 Pa to 10 kPa.
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TEOS/Ozone Silicon Dioxide CVD: This is a common application of SACVD. TEOS (Tetraethyl orthosilicate) is a silicon alkoxide source, and ozone (O3) acts as an oxidizing agent. Together, they react on the substrate surface to form a high-quality SiO2 film.
Key Advantages of SACVD (particularly TEOS/O3 SACVD):
- Improved Film Uniformity: Lower pressure can lead to more uniform film deposition across the substrate.
- Enhanced Step Coverage: SACVD provides better coverage of complex surface features, such as trenches and vias, which are crucial in microelectronics manufacturing.
- Reduced Time-at-Temperature: TEOS/O3 SACVD minimizes the time the wafer spends at elevated temperatures, preventing unwanted diffusion and degradation in underlying layers. This is particularly beneficial for advanced ULSI manufacturing where thermal budgets are tightly constrained.
- Lower Contamination: Reduced pressure can minimize the incorporation of contaminants into the deposited film.
Applications of SACVD:
- Interlayer Dielectric (ILD) Deposition: Laying down insulating layers between conducting layers in integrated circuits. This is where the TEOS/O3 process is predominantly used.
- Passivation Layers: Creating protective layers on semiconductor devices.
- Diffusion Barriers: Depositing thin films that prevent unwanted diffusion of materials.
In summary, SACVD is a valuable technique for depositing thin films with excellent properties, particularly in microelectronics, due to its ability to provide good film quality, conformity, and reduced thermal budget requirements.
