Inert anode electroplating processor and replenisher

An electroplating processor has a vessel holding an electrolyte. An inert anode in the vessel has an anode wire within an anode membrane tube. A head for holds a wafer in contact with the electrolyte in the vessel. The wafer is connected to a cathode. A catholyte replenisher is connected to the vessel. The catholyte replenisher adds metal ions into the catholyte by moving ions of a bulk metal through a catholyte membrane in the catholyte replenisher.

BACKGROUND OF THE INVENTION

Manufacture of semiconductor integrated circuits and other micro-scale devices typically requires formation of multiple metal layers on a wafer or other substrate. By electroplating metals layers in combination with other steps, patterned metal layers forming the micro-scale devices are created.

Electroplating is performed in an electroplating processor with the device side of the wafer in a bath of liquid electrolyte, and with electrical contacts on a contact ring touching a conductive layer on the wafer surface. Electrical current is passed through the electrolyte and the conductive layer. Metal ions in the electrolyte plate out onto the wafer, creating a metal layer on the wafer.

Electroplating processors typically have consumable anodes, which are beneficial for bath stability and cost of ownership. For example, it is common to use copper consumable anodes when plating copper. The copper ions taken out of the plating bath are replenished by the copper coming off of the anodes, thus maintaining the metal concentration in the plating bath. This is a very cost effective way to maintain the metal ions in the bath compared to replacing the electrolyte bath in a bleed and feed scheme. However, using consumable anodes requires a relatively complex and costly design to allow the consumable anodes to be replaced. Even more complexity is added when consumable anodes are combined with a membrane (for example a cation membrane) to avoid degrading the electrolyte, or oxidizing the consumable anodes during idle state operation, and for other reasons.

Such systems require many mechanical parts for seals and membrane supports. Electroplating processors using inert anodes have been proposed as an alternative to using a consumable anode. An inert anode reactor holds promise to reduce chamber complexity, cost, and maintenance. However, use of inert anodes has led to other disadvantages, especially related to maintaining the metal ion concentration in a cost effective manner compared to consumable anodes and the generation of gas at the inert anode which can cause defects on the workpiece. Accordingly, engineering challenges remain to providing an inert anode electroplating processor.

SUMMARY OF THE INVENTION

In one aspect, an electroplating processor has a vessel holding a vessel-catholyte (electrolyte liquid). An inert anode in the vessel has an anode wire within an anode membrane tube. A head holds a wafer in contact with the vessel-catholyte. The wafer is connected to a cathode. A vessel-catholyte replenisher is connected via return and supply lines to the vessel to circulate vessel-catholyte through the vessel and the vessel-catholyte replenisher. The vessel-catholyte replenisher adds metal ions into the vessel-catholyte by moving ions of a bulk metal through a catholyte membrane in the vessel-catholyte replenisher. Alternatively, the vessel-catholyte replenisher may add metal ions directly into the vessel-catholyte, without using a catholyte membrane.

DETAILED DESCRIPTION OF THE DRAWINGS

InFIG. 1, an electroplating processor20has a rotor24in a head22for holding a wafer50. The rotor24has a contact ring30which may move vertically to engage contact fingers35on the contact ring30onto the down facing surface of a wafer50. The contact fingers35are connected to a negative voltage source during electroplating. A bellows32may be used to seal internal components of the head22. A motor28in the head rotates the wafer50held in the contact ring30during electroplating. The processor20may alternatively have various other types of head22. For example the head22may operate with a wafer50held in a chuck rather than handling the wafer50directly, or the rotor and motor may be omitted with the wafer held stationery during electroplating. A seal on the contact ring seals against the wafer to seal the contact fingers35away from the catholyte during processing.

The head22is positioned over an electroplating vessel38of the electroplating processor20. One or more inert anodes are provided in the vessel38. In the example shown, the electroplating processor20has an inner anode40and an outer anode42. Multiple electroplating processors20may be provided in columns within an electroplating system, with one or more robots moving wafers in the system.

InFIG. 2the anodes40and42have a wire45within a membrane tube47. The membrane tube47may have an outer protective sleeve or covering49. The membrane tube47(including the electrode wire) may be circular, or optionally formed into a spiral, or linear arrays, or take another form appropriate to create the electric field adapted for the workpiece being processed. The wire45may be a 0.5 to 2 mm diameter platinum wire within a 2-3 mm inside diameter membrane tube47. The wire45may also be a platinum clad wire with an interior core of another metal such as niobium, nickel, or copper. A resistive diffuser may be provided in the vessel above the inert anodes.

A flow space51is provided around the wire45within the membrane tube47. Although the wire45may be nominally centered within the membrane tube47, in practice the position of the wire within the membrane tube will vary, to the extent that the wire may be touching the inside wall of the membrane tube, at some locations. No spacers or other techniques to center the wire within the membrane tube are needed.

Referring toFIG. 3, in a three-compartment replenisher70, during electroplating, process anolyte is pumped through a process anolyte loop152which includes the anode membrane tubes47and a process anolyte chamber150which is a process anolyte source to the anodes40and42. The membrane tubes forming the anodes40and42may be formed into a ring or circle, contained within a circular slot41in an anode plate43of the vessel38, as shown inFIG. 1, i.e., with the membrane tubes resting on the floor of the vessel38. The replenisher70is external to the processor20in that it is a separate unit which may be located remote from the processor, within a processing system.

The wire45of each anode40,42is electrically connected to a positive voltage source (relative to the voltage applied to the wafer) to create an electric field within the vessel. Each of the inert anodes may be connected to one electrical power supply channel, or they may be connected to separate electrical power supply channels, via an electrical connector60on the vessel38. One to four inert anodes may typically be used. The anolyte flow through the membrane tubes carries the gas out of the vessel. In use, the voltage source induces an electric current flow causing conversion of water at the inert anode into oxygen gas and hydrogen ions and the deposition of copper ions from the vessel-catholyte onto the wafer.

The wire45in the anodes40and42is inert and does not react chemically with the anolyte. The wafer50, or a conductive seed layer on the wafer50, is connected to a negative voltage source. During electroplating, the electric field within the vessel38causes metal ions in the vessel-catholyte to deposit onto the wafer50, creating a metal layer on the wafer50.

FIG. 1shows a design having an inner anode40surrounded by a single outer anode42, although a single anode, or multiple concentric outer anodes may be used. An electric field shaping unit44made of a di-electric material may be positioned in the vessel38to shape the electric field in the vessel38. Other designs, such as shown in U.S. Pat. Nos. 8,496,790; 7,857,958 and 6,228,232 may also be used.

Turning now also toFIG. 3, the metal layer plated onto the wafer50is formed from metal ions in the vessel-catholyte which move through the vessel-catholyte to the wafer surface due to the electric field in the vessel38. A vessel-catholyte replenishing system70is connected to the vessel38to supply metal ions into the vessel-catholyte. The vessel-catholyte replenishing system70has a vessel-catholyte return line (a tube or pipe) and a vessel-catholyte supply line78connecting a replenisher74in a catholyte circulation loop, generally indicated at80inFIG. 3. Typically, a vessel-catholyte tank76is included in the catholyte circulation loop80, with the vessel-catholyte tank76supplying vessel-catholyte to multiple electroplating processors20within a processing system. The catholyte circulation loop80includes at least one pump, and may also include other components such as heaters, filters, valves, etc. The replenisher74may be in line with the catholyte return, or it may alternatively be connected in a separate flow loop out of and back to the catholyte tank.

FIG. 4shows an enlarged schematic view of the replenisher74. A replenisher anolyte circulates within the replenisher74through a replenisher anolyte loop91including a replenisher anolyte chamber98and optionally a replenisher anolyte tank96. The replenisher anolyte may be a copper sulfate electrolyte with no acid. The anolyte replenisher within the replenisher74does not require a recirculation loop and may just consist of an anolyte chamber98. A gas sparger, for example, nitrogen gas sparger can provide agitation for the replenisher without the complication of a recirculation loop requiring plumbing and a pump. If a low acid electrolyte or anolyte is used, when current is passed across the replenisher, Cu++ ions transport or move across the membrane into the catholyte, rather than protons. Gas sparging may reduce oxidation of bulk copper material.

A de-ionized water supply line124supplies make-up de-ionized water into the replenisher anolyte tank96or the chamber98. Bulk plating material92, such as copper pellets, are provided in the replenisher anolyte chamber98and provide the material which is plated onto the wafer50. A pump circulates replenisher anolyte through the replenisher anolyte chamber98. The replenisher anolyte is entirely separate from the anolyte provided to the anodes40and/or42.

In an alternative design, an anolyte chamber98is used without any replenisher anolyte loop91. A gas sparger, for example, N2 sparge can provide agitation for the anolyte chamber98without using a replenisher anolyte loop. A low acid anolyte insures that when current is passed across the replenisher that Cu++ ions are transported across the membrane into the catholyte rather than protons.

Within the replenisher74, a first cation membrane104is positioned between the replenisher anolyte in the replenisher anolyte chamber98and catholyte in a catholyte chamber106, to separate the replenisher anolyte from the catholyte. The catholyte return line72is connected to one side of the catholyte chamber106and the vessel-catholyte supply line78is connected to the other side of the catholyte chamber106, to circulate vessel-catholyte from the vessel38through the catholyte chamber. Alternately, the catholyte flow loop through the replenisher74can be a separate low circuit with the catholyte tank.

The first cation membrane104allows metal ions and water to pass through the replenisher anolyte chamber98into the catholyte in the catholyte chamber, while otherwise providing a barrier between the replenisher anolyte and the catholyte. Deionized water may added to the vessel-catholyte to replenish water lost to evaporation, but more commonly water evaporation can be enhanced to evaporate the water entering into the vessel-catholyte through electro-osmosis from the anolyte replenisher. An evaporator may be provided for this purpose. The flow of metal ions into the vessel-catholyte replenishes the concentration of metal ions in the vessel-catholyte.

As metal ions in the vessel-catholyte are deposited onto the wafer50to form the metal layer on the wafer50, they are replaced with metal ions originating from the bulk plating material92moving through the replenisher anolyte and the first membrane104into the catholyte flowing through the catholyte chamber106of the replenisher74. In the example shown the metal ions are copper ions (Cu++) and the vessel-catholyte is a high acid copper electrolyte.

An inert cathode114is located in the replenisher chamber112opposite from the second cation membrane108. The negative or cathode of a DC power supply130is electrically connected to the inert cathode114. The positive or anode of the DC power supply130is electrically connected to the bulk plating material92or metal in the replenisher anolyte chamber98applying or creating a voltage differential across the replenisher74. Replenisher electrolyte in the replenisher chamber112may optionally circulate through a replenisher tank118, with de-ionized water and sulfuric acid added to the replenisher electrolyte via an inlet122. The replenisher chamber112electrolyte may comprise de-ionized water with 1-10% sulfuric acid. The inert cathode114may be a platinum or platinum-clad wire or plate. The second ionic membrane108helps to retain copper ions in the first compartment.

Referring toFIGS. 1 and 2, the processor20may optionally include an electric current thief electrode46in the vessel38, although in many cases no electric current thief is necessary. In this case, the electric current thief electrode46may also have an electric current thief wire within an electric current thief membrane tube, similar to the anode40or42described above. If a thief electrode is used, reconditioning electrolyte may be pumped through the electric current thief membrane tube. The electric current thief wire is generally connected to a negative voltage source which is controlled independently of the negative voltage source connected to the wafer50via the contact ring30.

The electric current thief membrane tube may be connected to a replenisher chamber112in the replenisher74via a replenisher circulation loop, generally indicated at82, via a replenisher electrolyte return line84and a replenisher electrolyte supply line86. If used, the high acid catholyte bath in catholyte chamber106insures that a high portion of the current crossing membrane108is protons rather than metal ions. In this way, the current within the replenisher74replenishes the copper within the vessel-catholyte while preventing it from being lost through the membrane.

A second cation membrane108is positioned between the catholyte in the catholyte chamber106and the replenisher electrolyte in the replenisher chamber112. The second cation membrane108allows protons and small amounts of source metal to pass through from the catholyte in the catholyte chamber106into the replenisher electrolyte in the replenisher chamber112. The primary function of replenisher chamber112is to complete the electrical circuit for the replenisher chamber in a way that does not plate metal out onto the inert cathode114. The replenisher chamber112may be used with or without an extra tank or circulation loop.

The high acid electrolyte or catholyte bath in catholyte chamber106insures that a high portion of the current crossing membrane108is protons rather than metal ions, so that the cathode reaction on the inert cathode114is mostly hydrogen evolution. In this way, the current within the replenisher74replenishes the copper within the catholyte while preventing it from being lost through membrane108. This avoids metal build up and electrode maintenance.

In the replenisher, the chamber112may be provided without an extra tank or recirculation loop. In the anolyte, nitrogen sparging may be sufficient keeping the plumbing and pumping requirements more simple.

In operation, metal ions in the vessel-catholyte in the vessel deposit onto the wafer50to form a metal layer on the wafer50, via the conducting of electric current from the anodes40and42to the wafer50. Vessel-catholyte flows from the vessel into the catholyte chamber106in the replenisher74, where metal ions are added back into the vessel-catholyte, which then returns to the vessel, typically with the catholyte continuously flowing through the catholyte circulation loop80. The replenisher anolyte also generally flows continuously in the replenisher anolyte loop91. De-ionized water is added into the replenisher anolyte to make up for water losses in the electro-osmosis of water through the first cation membrane104. Protons and small amounts of metal ions pass through the second cation membrane108into the replenisher electrolyte in the replenisher chamber112. The vessel-catholyte may be a high-acid wafer level packaging plating electrolyte with additives, as is well known in electroplating technology.

During electroplating, a chemical reaction takes place on the wire surface which converts water into oxygen gas and hydrogen ions (H+). The hydrogen ions which pass through the membrane tube wall and into the chamber catholyte. These ions then become part of the vessel-catholyte that flows to the catholyte chamber106. The majority of these ions carry current through the membrane108, where hydrogen ions are removed from the chamber catholyte.

The oxygen gas is exhausted from the membrane tubes via vacuum or venting, or by sparging with nitrogen gas. The process anolyte itself is not otherwise chemically changed during electroplating.

FIG. 5shows an alternative replenisher140having a process anolyte chamber142connected with the anode membrane tubes of the anodes in an process anolyte flow loop152. The process anolyte in the process anolyte chamber142is separated from the catholyte by the second cation membrane108on one side, and by a third cation membrane154on the other side of the process anolyte chamber142. In this design protons and a small amount of metal ions pass through the second cation membrane108, and protons and a much smaller amount of metal ions pass through the third cation membrane154.

The extra replenisher anolyte between the high Cu++ catholyte bath in catholyte chamber106and the inert cathode114further reduces the amount of metal that may reach the inert cathode114and plate out on the electrode and require maintenance. It also allows for flowing the anolyte through the replenisher in chamber142to use the small amount of copper than may enter the anolyte though membrane108and then pass this copper back into the chamber catholyte through the anode tubes. The third cation membrane154or the membrane108may be replaced with a anion membrane. The extra flowing anolyte through the chamber142also allows for a balance in proton exchange between the catholyte and the anolyte. Protons leave the anolyte as current pass through the anode, membrane tubes within the plating chamber, and the protons are replaced across the membrane108in the replenishment cell. The copper can pass back into the chamber catholyte through the membrane tubes as current forces cations (i.e. H+ and Cu++) from the anolyte into the chamber catholyte. The embodiment ofFIG. 5may also be designed with the membrane104omitted. In this case, an inline replenishment cell has no membrane104, and the bulk copper is exposed to the chamber catholyte.

During idle state operation, the system is ready but not in actual use. In the idle state, when the replenisher is not in use, the system170stops the flow of catholyte over the bulk plating material92which forms the consumable anode. Idle state operation avoids osmosis of water across the membrane. Idle state operation also allows for easy access to the consumable anode for maintenance, for example to replace copper pellets as they are consumed. Idle state can be accomplished by stopping flow to the relatively small volume of chamber-catholyte present in the replenisher compared to the large volume of a vessel-catholyte tank of a processing system supplying multiple processors20. This protects the additives in the vessel-catholyte tank from the exposed metal during long idle times.

In a modified design ofFIG. 4, the inert cathode114may be placed within a filter, bag or enclosure within the catholyte or replenisher chamber, to reduce mass transfer to the anode and metal plating onto the inert cathode114. Optionally a resistive screen may be provided on the inert cathode114to limit metal plating onto the inert cathode114. In addition, to prevent metal from depositing onto the inert cathode114, replenisher electrolyte may be removed and replaced on a schedule. Metal may also be removed from the inert cathode by periodically running the replenisher in reverse (by switching the polarity of the power supply130) to de-plate the inert cathode, or by using chemical etching.

The membranes108and/or154may be replaced by an anion membrane to prevent any copper ions moving from the catholyte into the replenisher electrolyte. To operate the replenisher74without excessive electrical loading, the chambers98,106and112may be narrow, for example with the chambers106,112and142(if used) having a width of 3-8 or 4-6 millimeters, and with the chamber98having a width of 8-12 millimeters. Chambers having these widths, and a length and a height of about 266 milliliters are calculated to have sufficient capacity for operating a processor electroplating copper onto a 300 millimeter diameter wafer. The chambers may also be cylindrical in a co-axial arrangement. One or two replenishments cells, each with about the area of a 300 mm wafer, are calculated to have sufficient capacity to operate a processing system having with 4-12 electroplating processors20.

The narrow chamber gaps are helpful to reduce the replenisher voltage and, thus, power supply wattage requirement. The metal pellets in the anolyte chamber98can completely fill the chamber and rest against the membrane74. This keeps the voltage need to flow current to a minimum by limiting the distance from the anode to the membrane. The anolyte bath conductivity is the lowest of all the baths in the system, so there is the most benefit in power supply voltage by minimizing the distance in the current must travel in the anolyte.

Vessel-catholyte as referred to here is the copper (or other metal ion) containing electrolyte. The replenisher anolyte and the replenisher electrolyte may all be the same electrolyte so tanks, plumbing, etc. can be combined in various ways. The process anolyte, replenisher electrolyte, and thiefolyte (if any) may all be the same electrolyte. Also, the process anolyte, replenisher electrolyte, and thiefolyte (if any) may all be all be mixtures of deionized water and sulfuric acid, which are relatively inexpensive.

In the embodiments ofFIG. 3-5, an alternative replenisher90is presented as a separate device in line with the plating chamber plumping system. The plumbing to the replenisher can optionally be arranged so that the process anolyte also flows through it (i.e.152onFIG. 5). However, in other embodiments, the replenisher can be integrated into the vessel-catholyte tank (76inFIG. 3). Constructing the replenisher in this manner can simplify the system and allow the metal replenishment to be applied directly to the large volume of vessel-catholyte in the main system vessel-catholyte tank. As one specific embodiment, one of the side walls in the vessel-catholyte tank may connect directly to another smaller tank comprising the replenisher anolyte chamber98. Similarly, the other chambers of the replenisher can be adjacent tanks with common walls including the membranes built into the walls.

The replenisher may be operated to increase the metal concentration in the vessel-catholyte to levels higher than available with consumable anode processors. This operation allows for higher plating rates. This electrochemical method may increase metal concentration to supersaturated levels, further increasing the plating rate and feature morphology. Generally, the replenisher should run at least at the same number of amp-minutes as the plating chamber(s) to insure that the metal concentration in the bath is maintained. However, it is likely than the replenisher amp-minutes may run slightly higher to make up for losses of metal through membrane108in the replenisher, or for any other loss than may occur in the system. The replenisher also allows the metal concentration to be increased as already described.

An additional advantage of the replenisher approach is that the consumable anode replenishment is centralized to one location (i.e. the replenisher(s)) rather than at each chamber separately.

Therefore, the invention allows simplified chambers with inert anodes with the same low cost of ownership. Copper replenishment is centralized and can be done without ever taking the tool down for maintenance. This feature results in an increase in uptime.

The terms anode wire, current thief wire, anode membrane tube, current thief membrane tube, catholyte membrane and replenisher electrolyte membrane are descriptors used in the claims only to distinguish the claimed elements from each other, and are not characteristics or material properties of the claimed elements. Indeed, the same wire, membrane tubes, and membranes may be used for these elements. The term wire means an elongated metal element, typically round like a wire, but also including other shapes such as a flat ribbon and plated on, or braided elements.

The operation of the replenisher74largely maintains the stability of the vessel-catholyte. Removal and replacement of vessel-catholyte, other than via the catholyte circulation loop, is minimal, as the vessel-catholyte remains stable, except potentially for additive replenishment and limiting the buildup of additive by-products.

Turning toFIG. 6, an alternative system170is similar to the system ofFIG. 5without the anolyte membrane. The vertical orientation of the replenisher catholyte helps to release gas generated during operation. In addition, use of the tanks172and174with the tank membrane174between them avoids the need for extra plumbing as needed in an in-line replenisher. A replenisher membrane178separates the process anolyte in the second tank176from the replenisher catholyte which is optionally in a third tank182within the second tank176. A gas sparge outlet180may release a gas, such as nitrogen, into the third tank182.

The system ofFIG. 6may increase consumption of vessel-catholyte additives because additives in the vessel-catholyte are able come in contact with the consumable anode. To reduce additive consumption, an idle state operation may minimize the surface area of the consumable anode. In one method of operation, the replenisher is held in idle state until the copper (or other anode material) in the vessel-catholyte reaches the lower limit of the copper concentration control limit. The replenisher then is put in operation at a higher rate than what the system is consuming to replenish the copper in the vessel-catholyte. When the upper control limit of copper is reached, the replenisher190may be turned off and put back into idle state operation.

FIG. 7shows a system which may be the same asFIG. 6, but further including a divider membrane for the anode, and having a common catholyte. In the idle state when the replenisher is not operating, the recirculation from the vessel-catholyte tank to the anode section can be turned off. When the recirculation is on, the electrolyte bath makeup on both sides of the192membrane is kept uniform and water build-up may be avoided.

FIG. 8shows a system200having a vessel-catholyte tank202which holds vessel-catholyte for use by multiple electroplating processors20. A mesh anode support204is positioned under the copper anode. A mesh contact206is electrically connected to the mesh anode support and connects to the power supply130. The copper anode and the mesh anode support204are held within a holder214in the vessel-catholyte tank202. A contact membrane208separates the electrolyte around the copper anode from the chamber catholyte. Anolyte flow within the tank202is separated from the chamber catholyte in the tank202via an upper membrane210and a lower membrane212. The membranes208,210and212may be horizontal, or within 10 degrees of horizontal.

Current flow in the replenisher causes erosion of the consumable anode material or the bulk copper material. Using a near horizontal orientation may reduce erosion of the consumable anode material, e.g., copper. The anolyte compartment is on the top and gravity keeps the copper material at the same distance from the membrane at all times as the copper erodes. The anode compartment may be completely open to atmosphere for easy access. Positioning the replenisher within the system vessel-catholyte tank202reduces plumping connections and components.FIGS. 8-10generally show a first tank in, or submerged within an internal tank or second tank. Where these designs are used, plumbing may be provided to allow mixing of the of the contents of the first tank and the second tank, and independent draining of the first compartment for idle state operation, to lessen consumption of additives. Erosion of the consumable anode is associated with a flow of hydrogen ions across the second membrane to retain copper ions in the first compartment and reduce copper ion transport into the second compartment, and the flow hydrogen ions cross the second membrane reduces the transport of copper ions into the third compartment, to reduce copper deposition onto the inert cathode.

FIG. 9shows a system220similar toFIG. 8but with a holder222modified to create a flow path224which allows electrolyte around the copper anode to flow up and out of the holder and into the chamber catholyte in the tank202. In this system, the flow into the replenisher containing the anode can be stopped to put the replenisher into the idle state. The first compartment, or others, may have independent draining for idle state operation, to lessen consumption of additives.

FIG. 10shows a system230similar toFIGS. 8 and 9and having a holder232which is open to the chamber catholyte in the tank202, and using the third tank182and the replenisher membrane178as shown inFIGS. 6 and 7. A three compartment system may be designed as inFIG. 5, but without the membrane74(and without the optional replenisher anolyte tank96) allowing the copper pellets to contact the chamber catholyte and avoid water osmosis. An in-line system likeFIG. 5, but without the membrane74can be placed in idle state by stopping flow of the chamber catholyte through the in-line replenisher. This would protect the additives in the large chamber catholyte tank from the bulk anode material or bulk copper.

The systems described above may have only have three compartments. For example, the replenisher anolyte/chamber catholyte membrane may be omitted. This avoids water accumulation in the vessel-catholyte which is a very challenging problem for high amp-min processes. An isolyte section may also be omitted, with anolyte flow to the process chambers in a completely separate tank/flow path. The effects of more Cu++ ions getting to the replenisher cathode may be reduced by cathode maintenance and/or bleed and feed.

As described, the replenisher may be placed in the vessel-catholyte tank for the tool. This avoids pumping/plumbing vessel-catholyte to the replenisher. In this design the replenisher may have a first section or frame comprising the replenisher anode compartment. The second section or frame holds the anolyte and replenisher catholyte. Placed adjacent to each other with a gap allowing the vessel-catholyte to pass between completes the replenisher and refreshes the copper in the tank. If there is no anolyte membrane in the replenisher, then copper can be placed directly into the system vessel-catholyte tank adjacent to the half-replenisher comprised of the anolyte/catholyte compartments. When using copper pellets as the anode, the pellets may entirely fill the compartment, and even touch the membrane, to minimize the replenisher voltage drop, and simplify the restocking of the consumable anode material.

The systems described may also be designed with the wafer held vertically rather than horizontally. The membranes are ionic membranes.

The current flow across the cationic membrane is carried by the positive ions in the bath on the upstream (with respect to the ionic current flow) side of the membrane. In copper acid baths, these are copper ions and hydrogen ions. The total current is the sum of the partial current carried by the copper ions and the partial current carried by the hydrogen ions. A low acid bath has very few hydrogen ions and so the copper ion partial current is very high (e.g., in the first compartment). A high acid bath contains a high concentration of hydrogen ions. As these ions are much more mobile than the copper ions, the hydrogen ion partial current is very high. The hydrogen ion partial current may be greater than 90% of the total current across the membrane. Correspondingly, the copper ion partial current may be less than 10% of the total current flow across the membrane. Ideally, the current across the second membrane is all hydrogen ions so that are copper replenishment efficiency is 100%. However, if this is not the case, then the replenishment cell current might need to be increased or bleed and feed might be needed in order to compensate for the lower copper replenishment efficiency. A pumped or forced flow through the different compartments may be used in addition to or instead of the use of gas sparging, as at high currents, Joule heating may require forced flow through the compartments avoid temperature increases.

Thus, novel apparatus and methods have been shown and described. Various changes and substitutions may of course be made without departing from the spirit and scope of the invention. The invention, therefore, should not be limited except by the following claims and their equivalents.