Specific Process Knowledge/Wafer cleaning/RCA: Difference between revisions
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==RCA cleaning== | ==RCA cleaning== | ||
[[Image:RCA-bænk_RR2_0.JPG|300x300px|thumb|RCA bench: positioned in cleanroom B1. <br /> RCA1 - RCA2 - HF - BHF(pre-dep wafers)]] | [[Image:RCA-bænk_RR2_0.JPG|300x300px|thumb|RCA bench: positioned in cleanroom B1. <br /> RCA1 - RCA2 - HF - BHF(pre-dep wafers)]] | ||
The RCA cleaning procedure was originally developed by the Radio Corporation of America (RCA) as part of manufacturing electron tube components. This process has since been adapted to silicon semiconductor processing. RCA is a two-step process (RCA1 and RCA2), and RCA1 should always be made before RCA2 because removing organic contaminants is a requirement before metallic contaminants can be removed effectively.<br> | |||
RCA1 is a powerful oxidizer and will thus remove organic contaminants. The ammonium hydroxide in RCA1 also has good solvating power as it can complex metals such as Cu, Ag, Ni, Co and Cd into solution. RCA2 forms soluble complexes with heavy metals and also shows cleaning action similar to that of piranha solutions. Furthermore, solutions of hydrochloric acid, which is a major constituent of RCA2, has proven effective at removing alkali metal ions. It is important that the chemicals used are very clean. RCA mixtures are therefore only used for up to a few batches (boats) of wafers and once an RCA mixture has cooled down it should not be reheated/reused. A new mixture should be made instead. Since RCA1 and RCA2 can oxidize silicon to silicon dioxide, an HF dip can be used to remove the thin oxide formed during RCA clean.<br \> | |||
The RCA clean is used for cleaning wafers before taking them into the furnaces and a few other equipments (check the cross contamination sheet). | The RCA clean is used for cleaning wafers before taking them into the furnaces and a few other equipments (check the cross contamination sheet). | ||
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*RCA1 contains: H<sub>2</sub>O, NH<sub>4</sub>OH and H<sub>2</sub>O<sub>2</sub> (5:1:1). It is used for removal of light organics, particles and metals.<br> | *RCA1 contains: H<sub>2</sub>O, NH<sub>4</sub>OH and H<sub>2</sub>O<sub>2</sub> (5:1:1). It is used for removal of light organics, particles and metals.<br> | ||
*RCA2 contains: H<sub>2</sub>O, HCl and H<sub>2</sub>O<sub>2</sub> (5:1:1). It is used for removal of | *RCA2 contains: H<sub>2</sub>O, HCl and H<sub>2</sub>O<sub>2</sub> (5:1:1). It is used for removal of heavy metals, metal hydroxides, and residual metals including alkali metals.<br> | ||
You can find the APV for the RCA bench [http://labmanager.dtu.dk/d4Show.php?id=1916&mach=243 here] | You can find the APV for the RCA bench [http://labmanager.dtu.dk/d4Show.php?id=1916&mach=243 here] | ||