Specific Process Knowledge/Thin film deposition/Deposition of Silicon Oxide/Deposition of Silicon Oxide using LPCVD TEOS: Difference between revisions
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==LPCVD TEOS Furnace (B3)== | ==LPCVD TEOS Furnace (B3)== | ||
[[Image:teos1.jpg|300x300px|thumb|Figure 1: TEOS structure]] | [[Image:teos1.jpg|300x300px|thumb|Figure 1: TEOS molecule structure]] | ||
[[Image: | [[Image:TEOS.jpg|300x300px|thumb|Figure 2: LPCVD TEOS oxide deposited on Si trenches]] | ||
TEOS is Tetra-Ethyl-Ortho-Silicate, | DTU Nanolab has one furnace for deposition of LPCVD TEOS oxide. The furnace was installed in the cleanroom in 1995. | ||
In the furnace LPCVD oxide can be deposited on 4" wafers. It is not possible to deposit LPCVD TEOS oxide on 6" wafers in he cleanroom. | |||
TEOS is is Tetra-Ethyl-Ortho-Silicate, sometimes also referred to as Tetra-Ethoxy-Silane, and it has the chemical formula Si(C<sub>2</sub>H<sub>5</sub>O)<sub>4</sub>. It is a liquid that is stored in a bubbler. When a deposition is started, the bubbler is heated to 75 C, and TEOS is then vaporized and introduced into the furnace. | |||
In the furnace, TEOS is thermally decomposed on the sample surface, so that a layer of silicon oxide (SiO<sub>2</sub>) is deposited on the wafer surface: | |||
Si(C<sub>2</sub>H<sub>5</sub>O)<sub>4</sub> ''(l)'' → SiO<sub>2</sub> ''(s)'' + 4 CH<sub>2</sub>H<sub>4</sub> ''(g)'' + 2 H<sub>2</sub>O ''(g)'' | |||
Carbon can be incorporated in the film, but this can be reduced by an annealing. | |||
The difference between TEOS and silane (used for deposition of silicon nitrid) is essentially that in TEOS the silicon atom is already oxidized. Therefore the conversion of TEOS to silicon dioxide is a rearrangement rather than an oxidation. As can be seen from figure 1 what is basically required to deposit silicon dioxide is a removal of two oxygen atoms for that a relative high temperature of 725 <sup>o</sup>C. | |||
There one standard process for deposition on the LPCVD TEOS furnace called TEOS. Anyway there are two standby recipe, which used for load and unload the wafers : one called "Standby" for standard process and other one called "Stb-slw" which is for unloading thicker oxides. And on this recipe the furnace will be opened significantly slower than normal standby recipe. Thick TEOS layers have a tendency to form cracks when they are moved to fast out from the furnace. | There one standard process for deposition on the LPCVD TEOS furnace called TEOS. Anyway there are two standby recipe, which used for load and unload the wafers : one called "Standby" for standard process and other one called "Stb-slw" which is for unloading thicker oxides. And on this recipe the furnace will be opened significantly slower than normal standby recipe. Thick TEOS layers have a tendency to form cracks when they are moved to fast out from the furnace. | ||