Electrolyte concentration control system for high rate electroplating

An electroplating apparatus for depositing a metal on a semiconductor substrate having one or more recessed features, the apparatus comprising:

• (a) a vessel configured to maintain a concentrated electroplating solution at a temperature of at least about 40° C., wherein said solution would have formed a precipitate at 20° C.;
• (b) an electroplating cell configured for bringing the concentrated electrolyte in contact with the semiconductor substrate at a temperature of at least about 40° C., wherein the vessel is in fluidic communication with the electroplating cell or wherein the vessel is the electroplating cell;
• (c) one or more sensors, configured to monitor one or more properties of the electroplating solution related to precipitation of a salt from the electroplating solution in the vessel, wherein the one or more sensors comprise a sensor selected from the group consisting of a temperature sensor and an optical concentration sensor, and are in communication with an apparatus controller;
• and
• (d) the apparatus controller comprising program instructions for:
• (i) receiving readings provided by at least one of the temperature sensor and the optical concentration sensor;
• (ii) causing a generation of a signal if temperature drops below a pre-determined value or if a concentration of the metal salt determined by the optical concentration sensor rises above a pre-determined value, wherein said pre-determined values are indicative of a risk of metal salt precipitation and are pre-set in the controller;
• and
• (iii) causing an addition of a predetermined amount of a diluent to the concentrated electroplating solution in the vessel in response to the signal to avoid precipitation of the salt from the concentrated electroplating solution in the vessel.