Chamber matching is closely related to chamber conditioning. Plasma parameters can vary significantly within a wet clean cycle, sometimes by a factor of two.
The range of plasma parameters within a wet clean cycle with device parameters still in spec provides also the range of harmless deviations between different chambers.
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The
diagram shows
the collision
rate of mainframe with four chambers over a period of 4 months (about
70.000 wafers). Short-term variations are due to chamber
conditioning after wet
clean (see arrows). The long-term driftsindicate chamber aging Chamber C exhibits a higher electron collision rate and differs from the other chambers.
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The diagram shows the electron density of the mainframe as above and indicates good chamber matching. Whereas the electron density of the chambers A, B, and D show a small decreasing trend, chamber C exhibits a long-term increase. After a maintenance measure (wet clean) on Nov. 20th, Chamber C, including the exchange of many square parts, again matches the other chambers. Note: Date are shown as dd.mm. |