Microdevices are manufactured by depositing and working several layers of materials on a single substrate to produce a large number of individual devices. For example, layers of photoresist, conductive materials, and dielectric materials are deposited, patterned, developed, etched, planarized, and otherwise manipulated to form features in and/or on a substrate. The features are arranged to form integrated circuits, micro-fluidic systems, and other structures.
Wet chemical processes are commonly used to form features on microfeature workpieces. Wet chemical processes are generally performed in wet chemical processing tools that have a plurality of individual processing chambers for cleaning, etching, electrochemically depositing materials, or performing combinations of these processes. Each chamber typically includes a vessel in which wet processing fluids are received, and a workpiece support (e.g., a lift-rotate unit) that holds the workpiece in the vessel during processing. A robot moves the workpiece into and out of the chambers.
One concern with integrated wet chemical processing tools is that the processing chambers must be maintained and/or repaired periodically. In electrochemical deposition chambers, for example, consumable electrodes degrade over time because the reaction between the electrodes and the electrolytic solution decomposes the electrodes. The shapes of the consumable electrodes accordingly change, causing variations in the electrical field. As a result, consumable electrodes must be replaced periodically to maintain the desired deposition parameters across the workpiece. The electrical contacts that contact the workpiece also may need to be cleaned or replaced periodically. To maintain or repair electrochemical deposition chambers, they are typically removed from the tool and replaced with an extra chamber.
One problem with repairing or maintaining existing wet chemical processing chambers is that the tool must be taken offline for an extended period of time to remove and replace the processing chamber. When the processing chamber is removed from the tool, a pre-maintained processing chamber is mounted in its place. The robot and the lift-rotate unit are then recalibrated to operate with the new processing chamber. Recalibrating the robot and the lift-rotate unit is a time-consuming process that increases the downtime for repairing or maintaining processing chambers. As a result, when only one processing chamber of the tool does not meet specifications, it is often more efficient to continue operating the tool without stopping to repair the one processing chamber until more processing chambers do not meet the performance specifications. The loss of throughput of a single processing chamber, therefore, is not as severe as the loss of throughput caused by taking the tool offline to repair or maintain a single one of the processing chambers.
The practice of operating the tool until at least two processing chambers do not meet specifications severely impacts the throughput of the tool. For example, if the tool is not repaired or maintained until at least two or three processing chambers are out of specification, then the tool operates at only a fraction of its full capacity for a period of time before it is taken offline for maintenance. This increases the operating costs of the tool because the throughput not only suffers while the tool is offline to replace the wet processing chambers and recalibrate the robot, but the throughput is also reduced while the tool is online because it operates at only a fraction of its full capacity. Moreover, as the feature sizes of the processed workpiece decrease, the electrochemical deposition chambers must consistently meet much higher performance specifications. This causes the processing chambers to fall out of specification sooner, which results in shutting down the tool more frequently. Therefore, the downtime associated with repairing and/or maintaining electrochemical deposition chambers and other types of wet chemical processing chambers is significantly increasing the cost of operating wet chemical processing tools.
The electrochemical deposition chambers housed in the tool may also suffer from several drawbacks. For example, during electrolytic processing in these chambers, a diffusion layer develops at the surface of the workpiece in contact with an electrolytic liquid. The concentration of the material applied to or removed from the workpiece varies over the thickness of the diffusion layer. In many cases, it is desirable to reduce the thickness of the diffusion layer so as to allow an increase in the speed with which material is added to or removed from the workpiece. In other cases, it is desirable to otherwise control the material transfer at the surface of the workpiece, for example, to control the composition of an alloy deposited on the surface, or to more uniformly deposit materials in surface recesses having different aspect ratios.
One approach to reducing the diffusion layer thickness is to increase the flow velocity of the electrolyte at the surface of the workpiece. For example, some vessels include paddles that translate or rotate adjacent to the workpiece to create a high speed, agitated flow at the surface of the workpiece. In one particular arrangement, the workpiece is spaced apart from an anode by a first distance along a first axis (generally normal to the surface of the workpiece) during processing. A paddle having a height of about 25% of the first distance along the first axis oscillates between the workpiece in the anode along a second axis transverse to the first axis. In other arrangements, the paddle rotates relative to the workpiece. In still further arrangements, fluid jets are directed at the workpiece to agitate the flow at the workpiece surface.
The foregoing arrangements suffer from several drawbacks. For example, it is often difficult even with one or more paddles or fluid jets, to achieve the flow velocities necessary to significantly reduce the diffusion layer thickness at the surface of the workpiece. Furthermore, when a paddle is used to agitate the flow adjacent to the microfeature workpiece, it can create “shadows” in the electrical field within the electrolyte, causing undesirable nonuniformities in the deposition or removal of material from the microfeature workpiece. Still further, a potential drawback associated with rotating paddles is that they may be unable to accurately control radial variations in the material application/removal process, because the speed of the paddle relative to the workpiece varies as a function of the radius and has a singularity at the center of the workpiece.
The reactors in which such paddles are positioned may also suffer from several drawbacks. For example, the electrode in the reactor may not apply or remove material from the workpiece in a spatially uniform manner, causing some areas of the workpiece to gain or lose material at a greater rate than others. Existing devices are also not configured to transfer material to and/or from different types of workpieces without requiring lengthy, unproductive time intervals between processing periods, during which the devices must be reconfigured (for example, by moving the electrode and/or a shield to adjust the electric field within the electrolyte). Another drawback is that the paddles can disturb the uniformity of the electric field created by the electrode, which further affects the uniformity with which material is applied to or removed from the workpiece. Still another drawback with the foregoing arrangements is that the vessel may also include a magnet positioned proximate to the workpiece to control the magnetic orientation of material applied to the workpiece. When the electrode is removed from the vessel for servicing or replacement, it has been difficult to do so without interfering with and/or damaging the magnet.