Specific Process Knowledge/Wafer cleaning/RCA: Difference between revisions
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[[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 | 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 metal 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 \> | 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 \> | ||