Summary:During electroplating, the amount of current flowing to the metal surface can be controlled by hardware that is part of the electroplating equipment. The hardware may include a movable anode chamber, a movable shield, conductive elements and auxiliar......
During electroplating, the amount of current flowing to the metal surface can be controlled by hardware that is part of the electroplating equipment. The hardware may include a movable anode chamber, a movable shield, conductive elements and auxiliary cathodes. The auxiliary cathode can be dynamically controlled during the process to adjust the amount of current flowing to the wafer. A secondary auxiliary cathode may also be used in some applications. The auxiliary cathode can help explain the rapid changes in metal sheet resistance that occur during metal deposition.
An auxiliary cathode may be located between the anode and the ion permeable element in the plating chamber. This auxiliary cathode can be controlled by controller 378 . This controller can be connected to power sources 380 and 370 . Controllers can also be used to independently control the potentials. The controller can also be used to control the current flow to the wafer. The current density of the auxiliary cathode can decrease with the increase of coating thickness. In some cases, the current density of the auxiliary cathode is higher in the early stages of the electroplating process than in the later stages. This is because the auxiliary cathode can receive a high level of current.
During the first six seconds of the electroplating process, the movable shield can be fixed. The shield can move at about 6 to 8 millimeters per second. The movable shield may be configured to move in an upward direction toward the anode when electroplating copper, and may be configured to move in an upward direction away from the anode when electroplating other metals. The distance between the movable shield and the anode may be greater than twenty millimeters. In some embodiments of the invention, the auxiliary cathode is located near the bottom surface of the HRVA. The auxiliary cathode can be configured to reduce the magnitude of the current density vector by diverting the current to the EIRIS. Auxiliary cathodes can also be configured to reduce the current density vector by diverting the current to other chambers.
Auxiliary cathodes can also be configured to minimize terminal effects that may occur during plating. Auxiliary cathodes provide initial high current densities that can be used to speed up the plating process. This can be used to speed up the electroplating process by diverting the current to the EIRIS. During electroplating, the auxiliary cathode can also be gradually lowered as the sheet metal resistance begins to decrease. This is because the auxiliary cathode is connected to a power supply and can be used to quickly control the amount of current flowing to the wafer. The auxiliary cathode may not be used in the early stages of the electroplating process because the current density of the auxiliary cathode will not be very high. After a few seconds, the auxiliary cathode may even be disabled.
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