TEOS is an abbreviation of Tetraethyl orthosilicate with its molecular formula, Si(OCH2CH3)4. A TEOS molecule takes a tetrahedral structure. TEOS is a colorless liquid at room temperature with an alcohol like odour. It starts boiling at 169 °C but starts evaporating at 45 °C (called flash point). Its vapor pressure is about 1.5 Torr at room temperature. TEOS is flammable under a fire conditions. Inhalation of TEOS vapor is harmful to humans. It's irritating to the eyes and skins. Ingestion of it may cause dizziness, vomiting, headache, diarrhea and nausea. Chronic exposure can damage internal organs such as liver, blood, kidneys and lungs.

For TEOS LPCVD process, the vapor may be brought to the reaction chamber using either a bubbler or a liquid injector. In either case, the liquid is slightly heated to a temperature above the room temperature for enhanced partial pressure. The vapor to be delivered to the process chamber should be free of water moisture to avoid formation of polymers. TEOS interaction with the moisture produces polymerized products and reduces TEOS partial pressure gradually over time, which would then alter the film characteristics (called drift).

In a TEOS oxide CVD process, TEOS is delivered mostly using an inert carrier gas to a reaction chamber heated to a temperature between 650 and 850 °C. TEOS molecules are dissociated and adsorbed onto the wafer surface. The neighboring ethyl alkyl groups then interact with each other to form stable products, which then detach from the surface and behind a -O-Si-O- link to the surface. Although TEOS is an excellent source of oxygen atoms by itself, adding O2 gas increases the deposition rate. N2 is the most popular choice for the carrier gas.

This single-precursor LPCVD oxide process holds several advantages over LTO: more conformal step coverage and better quality, purity, reflow properties, and thermal stability. A disadvantage is that it runs at a higher temperature (625-725 °C) than aluminium can tolerate.

  • Typical film thickness: 0.05 - 3 µm
  • Batch Size: 50 (18" flat zone) or 100 (34" flat zone)
  • Refractive index at 550 nm / 1.41 - 1.46
  • Deposition rate: 15 - 25 nm/min. (150 - 250 µm/min.)
  • Gases: TEOS (99.9999%)/O2
  • Uniformity: < 5% for 8"
  • Typical TEOS Temp: 35 - 50 °C
  • Typical Deposition Temperature: 625 - 725 °C Gradient
  • Typical Deposition Pressure: a few Torr or lower
  • Typical Gas Flow Rate: Consult Tystar engineers
  • Substrate Materials: Silicon, Silicon Nitride, III-V semiconductors, and etc.

TEOS LPCVD is used to deposit oxide for dielectric materials, isolation layers, hard mask materials, and optical waveguides. For further details of TEOS/O2 process, contact Tystar Corporation at (310) 781-9219 or sales@tystar.com

LPCVD Processes