US20240287702A1

US20240287702A1 - Methods of reducing or eliminating deposits in an electroplating system

Info

Publication number: US20240287702A1
Application number: US18/173,683
Authority: US
Inventors: Adam Marc McClure
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2023-02-23
Filing date: 2023-02-23
Publication date: 2024-08-29
Also published as: WO2024177881A1

Abstract

The present technology includes methods for reducing the formation of insoluble deposits in a plating system or a surface thereof. The methods include reducing a volume of a plating solution having a first pH in a plating bath from a first volume to a second volume, adding a replenishment agent to the plating solution to increase the volume of the plating solution from the second volume to the first volume. The replenishment agent is characterized by a second pH, where the second pH varies from the first pH by less than or about 5.

Description

TECHNICAL FIELD

The present technology relates to methods for reducing or eliminating precipitates or deposits before, during, and after electrochemical plating. More specifically, the present technology relates to methods for reducing insoluble deposits, such as plate-up or precipitates, on various surfaces of a plating system or in the electroplating bath by utilizing a replenishment agent having a predetermined pH.

BACKGROUND

Integrated circuits are made possible by processes that produce intricately patterned material layers on substrate surfaces. After formation, etching, and other processing on a substrate, metal or other conductive materials are often deposited or formed to provide the electrical connections between components. Because this metallization may be performed after many manufacturing operations, problems caused during the metallization may create expensive waste substrates or wafers.
The metal layers are often applied to the wafers via electrochemical plating in a plating chamber, such as an electroplating chamber. A typical plating chamber includes a vessel for holding an electrolyte or plating solution, one or more anodes in the vessel in contact with the plating solution, and a head having a contact ring with multiple electrical contact fingers that touch the substrate. The electrically conductive surface of the workpiece is immersed in the plating solution such as a bath of liquid electrolyte and an electrical contact causes metal ions in the plating solution to plate out onto the substrate, forming a metal layer or film. Generally multiple plating processors are provided within an enclosure, along with other types of processors, to form a plating system, such as a plating system.
Insoluble deposits forming plate-up on bath components and/or electrical contacts on a contact ring require frequent maintenance for cleaning and/or deplating. In addition, build up within the bath or on bath components often reaches a point where the insoluble deposits are so significant that the bath itself must be replaced.
Thus, there is a need for a method for preventing insoluble deposits in the bath itself or on plating bath surfaces and components. These and other needs are addressed by the present technology.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present technology include methods for reducing the formation of precipitates in an electroplating bath, or insoluble deposits in a plating system or a surface thereof. Embodiments of the method include reducing a volume of a plating solution having a first pH in a plating bath from a first volume to a second volume. Embodiments including adding a replenishment agent to the plating solution to increase the volume of the plating solution from the second volume to the first volume. In embodiments, the replenishment agent is characterized by a second pH, where the second pH varies from the first pH by less than or about 5.
In embodiments, the plating solution is characterized by a change in the first pH subsequent the replenishment of less than or about 3. In further embodiments, the plating solution further includes metal ions, organometallic particle, organic particles, or a combination thereof. In more embodiments, less than about 10 wt. % of the metal ions, organometallic particles, organic particles, or a combination thereof precipitate from the plating solution subsequent the replenishment. In further embodiments, the reduction in volume includes evaporating a portion of the plating solution. Embodiments include where the plating solution has a first electrolyte concentration and a second electrolyte concentration subsequent the replenishment, where the first electrolyte concentration varies from the second electrolyte concentration by 10 wt. % or less.
Additionally, or alternatively, embodiments include where the first pH is from about 0 to about 5 and the second pH is from about 0 to about 5. Further embodiments include where the first pH is from about 8 to about 12 and the second pH is from about 8 to about 12. In embodiments, the second pH varies from the first pH by less than or about 1.5. In more embodiments, the second pH value varies from the first pH by less than or about 3.
In embodiments, the replenishment agent is a mineral acid, a carbonic acid, cathode water, anode water, or a combination thereof. In more embodiments, the replenishment agent is methane sulfonic acid, carbonic acid, cathode water, anode water, or a combination thereof. Embodiments include where the replenishment agent is characterized by a pH of less than 3.
Embodiments of the present technology include a method for reducing the formation of insoluble deposits in a plating system or a surface thereof. Embodiments include reducing a volume of plating solution having a first pH in a plating bath. Embodiments include conditioning a replenishment agent to a second pH, where the second pH is characterized by varying from the first pH by less than or about 3. In embodiments, the replenishment agent includes carbonic acid, electrolyzed water, or a combination thereof. In embodiments, the replenishment agent is generally free of mineral acids.
Embodiments of the present technology include a method for reducing the formation of insoluble deposits in a plating system or a surface thereof. Embodiments include a plating system that includes a plating bath containing a plating solution, a head comprising a seal, a substrate coupled with the seal, and a bath supply. Embodiments include moving the head from a first position to a second position, where the seal and the substrate are disposed in the plating solution in the second position. Embodiments include contacting the substrate with one or more insoluble ions. Embodiments include adding a replenishment agent to the plating solution. In embodiments, the replenishment agent is characterized by a second pH, where the second pH varies from the first pH by less than or about 5.
In embodiments, the plating system also includes a plating bath conditioning system. In more embodiments, the method includes conditioning the replenishment agent to the second pH. In further embodiments, the conditioning includes selecting an acid, adjusting an acid concentration, adding an acidifying agent, adding an alkalization agent, or a combination thereof.
Such technology may provide numerous benefits over conventional techniques. For example, embodiments of the present technology reduce or even eliminate plate-up on plating system surfaces or components therein. In addition, the present technology can utilize replenishment agents that do not alter concentrations of existing bath solutes. The present technology may therefore provide methods for reducing or eliminating insoluble build up so as to greatly extend the life span of plating systems. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 shows a schematic perspective view of a plating system according to embodiments of the present technology.

FIG. 2 shows a partial cross-sectional view of a plating system according to embodiments of the present technology.

FIG. 3 shows a schematic diagram of a plating solution conditioning system according to embodiments of the present technology.

FIG. 4 shows exemplary operations in a method of reducing the formation of insoluble deposits in a plating system.

Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations and may include exaggerated material for illustrative purposes.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.

DETAILED DESCRIPTION OF THE INVENTION

Existing plating systems exhibit plating solution liquid volume loss, such as due to evaporation, spillage, and the like. Conventional systems utilize deionized water to maintain plating solution volume. However, deionized water problematically leads to the formation of insoluble contaminants, such as organometallics, metallics, and the like in the bath, that precipitate, plate-up, or form scale within the bath or upon bath surfaces and components, including seals utilized to separate components from intake and outtake lines, and substrate support heads, and to keep the plating solution away from electrical contacts. The precipitates that can form precipitates include insoluble solids and/or precursors thereof that may deposit as scale on processing equipment. For instance, the plate-up can be formed from various metals and organic precursors in the plating solution. Plate-up on system components also problematically leads to formation of a conductive path between the component(s) and contacts resulting in the plating of the contacts over desired substrate plating, as well as seal and contact failure.
Conventional methods for removing insoluble deposits, such as plate-up, have focused on removal chemistries or physical mechanisms targeted at removing insoluble deposits formed on the plating system surfaces and components thereon. For instance, physical mechanisms can include using a brush, polymer pad, or similar device to physically contact the system or component thereof to remove some amount of contamination. Alternatively, removal chemistries can include cleaning agents such as nitric acid, other acids, sodium hydroxide, potassium hydroxide or another strong base. Unfortunately, such physical and chemical conventional mechanisms require removal or disassembly of the bath, or removal of the plating solution, and can often fail to remove all plate-up present. Such inefficient removal leads to frequent replacement, as any remaining insoluble deposit can increase the speed and amount of future deposits when back in use.
The present technology has found that by utilizing a replenishment agent having a predetermined pH, insoluble deposits can be reduced, or even prevented from forming, eliminating the necessity of extensive cleaning processes. Without wishing to be bound by theory, the present technology has found that a large differential in the bath pH to the replenishment agent pH increases the deposition of insoluble materials on plating system components or surfaces thereof. Namely, organic particles, metal particles and ions, and organometallic particles that were soluble in the pH of the plating solution prior to dilution, can be forced to precipitate from solution due to the change in pH from the introduction of the replenishment agent, and adhere to whatever surface is available. On a single occurrence, insoluble deposits are virtually negligible. But on surfaces which are repeatedly cycled through the sequence of low bath volume followed by a replenishment agent having a higher or lower pH, each cycle can create insoluble deposits which will build up as cycling progresses. Eventually the deposits can form a conductive or semi-conductive film which acts as a precursor to plate-up. Once a conductive path is established between an electron source, such as a power supply, and the precursor film, plate-up can occur. Thus, the present technology has found that by carefully controlling the pH of the replenishment agent, plate-up can be reduced or eliminated by preventing the initial precipitation and deposit of insoluble materials, even, in embodiments, in the absence of cleaning.
The present disclosure has observed that avoiding deposits or plate-up advantageously maintains the life of the plating equipment including contacts or seals while eliminating scheduled downtime for cleaning. For example, maintenance for cleaning and/or deplating on the seal and/or electrical contacts on a contact ring may be avoided by providing a replenishment agent having a predetermined pH that varies from the plating solution pH by less than or about 5. By avoiding or reducing the need to remove insoluble deposits by preventing formation of the deposit, the throughput or use efficiency of the plating system is increased, as the plating system does not have to idle during cleaning procedures. The present disclosure has observed that by providing a replenishment agent with a pH similar to the pH of the plating solution or electrolyte, precipitation of contaminants or problematic species that accumulate or promote insoluble deposits on surfaces within the plating system is avoided or reduced as the contaminants or problematic species remain soluble instead of precipitating from solution. For instance, as the insoluble material remains a solute or soluble material in solution, the insoluble material can then be easily removed from the equipment or processing system, by filtration or separation processes.
For instance, in embodiments, less than or about 20 wt. % of metal ions, metal particles, organometallic particles, organic particles, or a combination thereof, precipitate from the plating solution subsequent addition of a replenishment agent discussed herein, based upon the weight of the metal ions, metal particles, organometallic particles, organic particles, or a combination thereof present in the plating solution prior to addition of the replenishment agent, such as less than or about 15 wt. %, such as less than or about 10 wt. %, such as less than or about 7.5 wt. %, such as less than or about 5 wt. %, such as less than or about 2.5 wt. %, such as less than or about 1 wt. % or any ranges or values therebetween, per rinse/replenish cycle, or over a lifetime of a bath.
Nonetheless, FIG. 1 shows a schematic perspective view of a plating system 100 that can perform plating methods according to embodiments of the present technology. Plating system 100 is operable to perform both electroplating operations and electroless plating operations. In electroplating operations, the plating system 100 delivers an electric current to a substrate so that ions in an electroplating bath in contact with the substrate may be reduced and plated on the substrate. In electroless plating operations, the plating system 100 does not deliver an electric current to the substrate. Instead, the plating relies on the spontaneous reduction of ions in the plating bath when they contact surfaces of the substrate that include a material that has a lower standard electrode potential (E°) than the ions. Plating system 100 illustrates an exemplary plating system, including a system head 110 and a bowl 115. During plating operations, a substrate may be clamped to the system head 110, inverted, and extended into bowl 115 to perform a plating operation. Plating system 100 may include a head lifter 120, which may be configured to both raise and rotate the head 110, or otherwise position the head within the system, including tilting operations. The head and bowl may be attached to a deck plate 125 or other structure that may be part of a larger system incorporating multiple plating systems 100, and which may share electrolyte and other materials. A rotor may allow a substrate clamped to the head to be rotated within the bowl or outside the bowl in different operations. The rotor may include a contact ring, which may provide the conductive contact with the substrate. A seal 130 discussed further below may be connected with the head. Seal 130 may include a chucked wafer to be processed.
FIG. 1 illustrates a plating system 100 that may include components to be cleaned directly on the platform. In embodiments, the plating system 100 further includes an in situ rinse system 135 for component cleaning. In additional embodiments (not shown) a plating system may be configured with a platform on which the head may be moved to an additional module where a seal or other component cleaning is performed.
FIG. 2 shows a partial cross-sectional view of a plating chamber that includes a plating apparatus 200 according to some embodiments of the present technology. The plating apparatus 200 may be incorporated with a plating system, including system 100 described above. As illustrated in FIG. 2 , a plating bath 205 of a plating system containing a plating solution 207, such as a bath of liquid electrolyte, is shown along with a head 210 having a substrate 215 coupled with the head. An inlet supply 212 (shown more clearly in FIG. 3, 312 ) can supply an electrolyte and a source of metal ion(s) to be deposited on the surface of a substrate, as well as a replenishment agent as discussed herein. The metal or metals to be plated onto the substrate are present in a plating solution as species of metal ions to be deposited onto the substrate. In embodiments, the metal ions are deposited under process conditions that preferentially deposit metal ions into recessed features as opposed to the surrounding field surfaces. In embodiments, head 210 is movable to position a wafer substrate 215 into contact with the plating solution 207 such as a bath of liquid electrolyte in plating bath 205. The plating apparatus also includes a bath return line 214.
In the illustrated embodiment, a substrate is coupled with a seal 216 incorporated on the head 210. A rinsing frame 220 may be coupled above the plating bath 205 and may be configured to receive the head 210 into the vessel during plating. Rinsing frame 220 may include a rim 225 extending circumferentially about an upper surface of the plating bath 205. A rinsing channel 227 may be defined between the rim 225 and an upper surface of the plating bath 205. For example, rim 225 may include interior sidewalls 230 characterized by a sloping profile. As described above, rinse fluid slung off a substrate may contact the sidewalls 230 and may be received in a plenum 235 extending about the rim for collection of the rinse fluid from the plating apparatus 200.
In embodiments, plating apparatus 200 may additionally include one or more cleaning components. The cleaning components may include one or more nozzles used to deliver fluids to or towards the substrate 215 or the head 210. FIG. 2 illustrates one of a variety of embodiments in which improved rinse assemblies may be used to protect the bath and substrate during rinsing operations. In additional embodiments, a side clean nozzle 250 may extend through the rim 225 of the rinsing frame 220 and be directed to rinse seal 216, along with aspects of substrate 215.
FIG. 3 is a schematic diagram of a plating solution conditioning system 300. The plating solution conditioning system 300 provides the electrolyte and constituent generated during the plating process, referred to herein as the constituent, as well as the replenishment agent, to the plating system(s) for the plating process. The plating solution conditioning system 300 generally includes a supply tank 302, a conditioning module 303, a filtration module 305, a chemical analyzer module 316, and a bath waste disposal system 322 connected to the analyzing module 316 by a waste drain 321. One or more controllers 310, 311, and 319 control the composition of the electrolyte and the constituent in the supply tank 302 and the operation of the plating solution conditioning system 300. Preferably, the controllers are independently operable but integrated with the control system 318 of the plating system 100.
The supply tank 302 provides a reservoir for electrolyte and constituent which includes a supply line 312 that is connected to each of the plating process cells through one or more fluid pumps 308 and valves 307. A heat exchanger 324 or a heater/chiller disposed in thermal connection with the supply tank 302 controls the temperature of the electrolyte and constituent stored in the supply tank 302. The heat exchanger 324 is connected to and operated by the controller 310.
The conditioning module 303 is connected to the supply tank 302 by a supply line and includes a plurality of source tanks 306, 330, or feed bottles, a plurality of valves 309, 307, and a controller 311. The source tanks 306 contain the chemicals needed for composing the electrolyte and constituent, and typically include a deionized water source tank and copper sulfate (CuSO₄) source tank for composing the electrolyte. Source tank 330 contains the replenishment agent and may therefore be referred to as replenishment agent tank 330. The replenishment agent tank 330 of the conditioning module 303 is preferably regulated by valve 331 and controlled by controller 311. Other source tanks 306 may contain hydrogen sulfate (H2_SO₄), hydrogen chloride (HCl) and various additives such as glycol, or carbon dioxide.
The valves 309 and 331 associated with each source tank 306, 330 regulate the flow of chemicals to the supply tank 302 and may be any of numerous commercially available valves such as butterfly valves, throttle valves and the like. Activation of the valves 309 and 331 is accomplished by the controller 311, which is preferably connected to the system control 318 to receive signals therefrom. The filtration module 305 includes a plurality of filter tanks 304. A return line 314 is connected between each of the process cells and one or more filter tanks 304. The filter tanks 304 remove the undesired contents in the used plating solution before returning the plating solution to the supply tank 302 for re-use.
The supply tank 302 is also connected to the filter tanks 304 to facilitate re-circulation and filtration of the electrolyte and constituent in the supply tank 302. By re-circulating the plating solution from the supply tank 302 through the filter tanks 304, the undesired contents in the plating solution are continuously removed by the filter tanks 304 to maintain a consistent level of purity. Additionally, re-circulating the plating solution between the supply tank 302 and the filtration module 305 allows the various chemicals in the plating solution to be thoroughly mixed.
The conditioning system 300 also includes a chemical analyzer module 316 that provides real-time chemical analysis of the chemical composition of the electrolyte and constituent. The analyzer module 316 is fluidly coupled to the supply tank 302 by a sample line 313 and to the waste disposal system 322 by an outlet line 321. The analyzer module 316 generally includes at least one analyzer and a controller to operate the analyzer.
The number of analyzers required for a particular processing tool depends on the composition of the plating solution. For example, while a first analyzer may be used to monitor the concentrations of organic substances, a second analyzer is needed for determination of the pH of a plating solution and/or replenishment agent. Additional analyzers may be used to monitor specific constituents to be added to the plating solution, preferably a constituent whose concentration can influence the pH of the replenishment agent.
In the specific embodiment shown in FIG. 3 the chemical analyzer module 316 includes an auto titration analyzer 315 and a pH measurement system 317. Both analyzers are commercially available from various suppliers. The auto titration analyzer 315 determines the concentrations of inorganic substances such as copper chloride and acid for a copper deposition. The pH measurement system 317 determines the pH of the plating solution 207 and replenishment agent 330, which are returned to the supply tank 302 from the process cells. The analyzer module shown FIG. 3 is merely illustrative. In another embodiment each analyzer may be coupled to the supply tank by a separate supply line and be operated by separate controllers. The controller 319 initiates command signals to operate the analyzers 315, 317 in order to generate data.
The information from the chemical analyzers 315, 317 is then communicated to the control system 318. The control system 318 processes the information and transmits signals that include user-defined chemical dosage parameters to the conditioning controller 311. The received information is used to provide real-time adjustments to the source chemical conditioning rates by operating one or more of the valves 309 and 331 thereby maintaining a desired, and preferably constant, chemical composition of the electrolyte and constituent throughout the plating process. The waste from the analyzer module is then flowed to the waste disposal system 322 via the outlet line 321.
Nonetheless, as discussed above, addition of a replenishment agent 330 continuously or periodically during the deposition process can also be initiated by the control system 318 via the controller 311. Once in supply tank 302, replenishment agent 330 is analyzed for pH. The pH is then adjusted to vary from the plating solution pH by less than or about 5, such as less than or about 4.5, such as less than about 4.25, such as less than or about 4, such as less than or about 3.75, such as less than or about 3.5, such as less than or about 3.25, such as less than or about 3, such as less than or about 2.75, such as less than or about 2.5, such as less than or about 2.25, such as less than or about 2, such as less than or about 1.75, such as less than or about 1.5, such as less than or about 1.25, such as less than or about 1, such as less than or about 0.75, such as less than or about 0.5, such as less than or about 0.25, or any ranges or values therebetween. Thus, in embodiments, the pH of the plating solution and the pH of the replenishment agent may be substantially the same.
Stated differently, in embodiments, the pH of the replenishment agent may be selected such that, subsequent replenishment, the plating solution is characterized by a change of pH of less than or about 20%, such as less than or about 15%, such as less than or about 12.5%, such as less than or about 10%, such as less than or about 7.5%, such as less than or about 5%, such as less than or about 2.5%, such as less than or about 1%, or any ranges or values therebetween. For instance, in embodiments, subsequent replenishment, the plating solution is characterized by a change of pH of less than or about 4, such as less than or about 3.5, such as less than or about 3, such as less than or about 2.75, such as less than or about 2.5, such as less than or about 2.25, such as less than or about 2, such as less than or about 1.75, such as less than or about 1.5, such as less than or about 1.25, such as less than or about 1, such as less than or about 0.75, such as less than or about 0.5, such as less than or about 0.25, or any ranges or values therebetween.
In embodiments, the pH of the plating solution may vary from the pH of the replenishment agent by a pH value of about 2 or less, such as about 1.5 or less, such as about 1 or less, such as about 0.5 or less, such as about 0.2 or less, or any ranges or values therebetween. For instance, in embodiments, when the plating solution pH is from about 0 to about 5, such as about 0.5 to about 4.5, such as about 1 to about 4, or any ranges or values therebetween, the replenishment agent pH is also from about 0 to about 5, such as about 0.5 to about 4.5, such as about 1 to about 4, or any ranges or values therebetween. Additionally, or alternatively, when the first pH is from about 8 to about 12, such as about 8 to about 11, such as about 8.5 to about 10, or any ranges or values therebetween, the second pH is from about 8 to about 12, such as about 8 to about 11, such as about 8.5 to about 10, or any ranges or values therebetween.
Namely, as discussed above, by using a replenishment agent with a preselected pH, a rapid change in the plating solution pH can be avoided, and insoluble materials maintained in solution. The pH of the plating solution can be measured according to known techniques, such as use of a pH meter in a 20 degree Celsius solution, to obtain a plating solution pH value, and the pH of the replenishment agent may be predetermined or corrected as discussed, to obtain a second pH value, which may be the same as the first pH value or different, according to the above values. In embodiments, the pH meter is calibrated as known in the art. In some embodiments, the pH of the plating solution and/or replenishment agent may be less than or about 6, such as less than or about 5, such as less than or about 4.5, such as less than or about 4, such as less than or about 3.5, such as less than or about 3, such as less than or about 2.5, such as less than or about 2, such as less than or about 1.5, such as less than or about 1, or any ranges or values therebetween. Additionally, or alternatively, in embodiments, the pH of the plating solution and/or replenishment agent may be greater than about 7, such as greater than or about 8, such as greater than or about 8.5, such as greater than about 9, such as greater than or about 9.5, such as greater than or about 10, such as greater than or about 10.5, or any ranges or values therebetween.
In embodiments, the pH of the plating solution, replenishment agent, or a combination thereof, may be selected based upon the precursor particles in solution. Namely, as known in the art, some plating materials, such as tin silver (SnAg) have increased likelihood of plate-up of insoluble particles and may therefore require a very low pH (such as less than or about 3) of the plating bath solution, replenishment agent, or both, to increase solubility and prevent insoluble deposits. Nonetheless, as would be understood by one having skill in the art, non-limiting metals (or ions thereof) that may be included in the plating solutions include copper, tin, gold, nickel, silver, palladium, platinum, and rhodium, and alloys such as noble metal alloys, tin-copper, tin-silver, tin-silver-copper, tin-bismuth, permalloy and other nickel alloys, lead-tin alloys, and other lead-free alloys, and can be utilized in a plating system having any one or more of the above pH values or ranges.
Moreover, in embodiments, the replenishment agent may contain the replenishment agent in a solvent. In embodiments, the solvent may be the same solvent contained in the plating bath electrolyte, such as water (deionized water), in some embodiments. Selecting a pH of the replenishment agent may include selecting a type of replenishment agent. In embodiments, the replenishment agent is a mineral acid, such as an acid derived from an inorganic compound. Non-limiting examples of suitable mineral acids include hydrogen bromide (BrH), hydrogen iodide (HI), hydrochloric acid (HCl), nitric acid (HNO₃), nitrous acid (HNO₂), phosphoric acid (H₃PO₄), sulfuric acid (H₂SO₄), boric acid (H₃BO₃), hydrofluoric acid (HF), hydrobromic acid (HBr), perchloric acid (HClO₄), hydroiodic acid (HI), and combinations thereof. In embodiments, organic acids such as alkylsulfonic acids, e.g., methane sulfonic acid (MSA) is a suitable replenishment agent in accordance with the present disclosure. In embodiments, organic acids provide pH control as described herein, but also act as chelating agents sufficient for bonding with species in solution which, if not chelated, may promote the formation of plate-up films. In some embodiments, MSA may include 1M MSA, and may be diluted in water 50:1. In some embodiments suitable methane sulfonic acid for use herein includes methane sulfonic acid having a molar concentration in the range of 0.02 M to about 1 M, such as about 0.03 M to about 0.75 M, such as about 0.4 M to about 0.5 M, or any ranges or values therebetween, and a pH in the range of 1 to 6, such as 2 to 5, such as 2.5 to 4.5.
In embodiments, the replenishment agent includes methane sulfonic acid alone, or in combination with one or more pH adjusting agents. For example, methane sulfonic acid (pH of about 2 and a concentration of approximately 20 g/L methane sulfonic acid (MSA) in water) may provide the replenishment agent with a pH sufficient to prevent or eliminate formation of a precursor layer and/or subsequent plate-up. In one embodiment, methane sulfonic acid is a suitable rinse agent for use in accordance with the present disclosure, wherein the methane sulfonic acid has a concentration of at least 3.6 g/L and solution thereof has a pH of about 3.
However, in embodiments, the present disclosure has found that by utilizing a mineral acid in the replenishment agent, the total concentration of mineral acids in the plating bath may be increased over time. Thus, in embodiments, the replenishment agent is an acid solution comprising carbonic acid (H₂CO₃). In embodiments, a carbonic acid replenishment agent is formed by dissolving carbon dioxide in water and under pressure to achieve the desired pH. In embodiments, carbon dioxide may also be injected directly in water to form carbonic acid or may be pressurized on one side of a permeable membrane with water on the other side of the membrane. Such systems are commercially available and are often known as gas contactors. Gas diffuses through the barrier and dissolves in the water, thereby forming carbonic acid. In embodiments, carbonic acid is provided in amounts sufficient and under conditions suitable for preventing the formation of insoluble deposits.
Additionally, or alternatively, in embodiments, the replenishment agent is electrolyzed water such as cathode water having a pH according to any one or more of the ranges set forth above. By using the cathode water as a replenishment agent, constituents of the plating solution and/or plating bath remain in solution and do not form precipitates in the bath or deposit on the surfaces, creating the plate-up precursor film and eventual plate-up. In embodiments, such as where an alkali plating solution or bath, anode water may be used in a similar manner.
Thus, in embodiments, the replenishment agent can be a mineral acid, carbonic acid, electrolyzed water, include cathode and/or anode water, or a combination thereof. In further embodiments, the replenishment agent can be methane sulfonic acid, carbonic acid, electrolyzed water, or a combination thereof.
Furthermore, in embodiments, the plating solution contains a first electrolyte concentration prior to addition of a replenishment agent, and a second electrolyte concentration subsequent the addition. In embodiments, the first electrolyte concentration may vary from the second electrolyte concentration by less than or about 10 wt. % based upon the weight of electrolyte in the plating solution, such as less than or about 9 wt. %, such as less than or about 8 wt. %, such as less than or about 7 wt. %, such as less than or about 6 wt. %, such as less than or about 5 wt. %, such as less than or about 4 wt. %, such as less than or about 3 wt. %, such as less than or about 2 wt. %, such as less than or about 1 wt. %, or any ranges or values therebetween. In some embodiments, the replenishment agent may therefore be generally free of mineral acids to avoid an increase in electrolyte concentration.
Nonetheless, in embodiments, a pH adjusting agent may also be included to obtain a preselected pH of a replenishment agent. In embodiments, pH adjusting agents may be provided in any amount necessary to obtain a desired pH value in the final composition of the replenishment agent. Acidic pH adjusting agents can be organic acids, including amino acids, and inorganic mineral acids. Non-limiting examples of acidic pH adjusting agents include acetic acid, citric acid, fumaric acid, glutamic acid, glycolic acid, hydrochloric acid, lactic acid, nitric acid, phosphoric acid, sodium bisulfate, sulfuric acid, and the like, and combinations thereof. In embodiments, all organic acids are contemplated for use as pH adjusting agents. Non-limiting examples of alkaline pH adjusting agents include alkali metal hydroxides, such as sodium hydroxide, and potassium hydroxide; ammonium hydroxide; organic bases; and alkali metal salts of inorganic acids, such as sodium borate (borax), sodium phosphate, sodium pyrophosphate, and the like, and mixtures thereof.
As may be clear from the above, conditioning of the replenishment agent may include one or more operations 410 that will be discussed in greater detail in regards to FIG. 4 . For instance, in embodiments, conditioning of the replenishment agent includes altering the native pH of the replenishment agent to a second pH. In embodiments, as discussed above, the conditioning can include selecting a replenishment agent that exhibits the desired pH. In such an embodiment, the native pH may be generally equal to the second pH. Additionally, or alternatively, the conditioning can include changing a concentration of the acid in solution of the replenishment agent, adding a pH adjusting agent, such as an acidifying agent or an alkalization agent, or a combination thereof.
Nonetheless, after the replenishment agent 330 has been conditioned to the desired pH, the replenishment agent may be transferred to the plating bath 205 to replace any lost plating solution volume. In embodiments, the replenishment agent 330 may be supplied continuously, or may be added after one or more plating cycles. Additionally, or alternatively, the replenishment agent 330 may be added to the plating bath 205 anytime the plating bath 205 registers a decrease in volume of the plating solution. of greater than or about 1 vol % based upon the volume of the plating bath solution, such as greater than or about 2.5 vol %, such as greater than or about 5 vol. %, such as greater than or about 7.5 vol. %, such as greater than or about 10 vol. %, or any ranges or values therebetween. For instance, in embodiments, the bath may have an operating volume, and a replenishment agent is added to the bath anytime the fluid drops below the operating level until the operating level is re-achieved.
Although the above discussed embodiments utilize real-time monitoring and adjustments of the replenishment agent, various alternatives may be employed according to the technology described herein. For example, the conditioning module 303 may be controlled manually by an operator observing the output values provided by the chemical analyzer module 316. For instance, the system software allows for both an automatic real-time adjustment mode as well as an operator (manual) mode. Further, although multiple controllers are shown in FIG. 3 , a single controller may be used to operate various constituents of the system such as the chemical analyzer module 316, the conditioning module 303, and the heat exchanger 324. Other embodiments will be apparent to those skilled in the art.
Nonetheless, it should be understood that, in embodiments, the method according to the present disclosure includes a non-transitory computer readable medium having instructions stored thereon that, when executed, cause a method for reducing or eliminating the formation of conductive deposits on surfaces in a plating system. For instance, in embodiments, a non-transitory computer readable medium may execute any one or more operations of the method, such as executing measurement of pH, comparing pH, conditioning the pH of the replenishment agent, and/or replenishing the bath.
The plating solution conditioning system 300 also includes a waste drain 320 connected to a waste disposal system 322 for safe disposal of used electrolytes, constituents, chemicals and other fluids used in the plating system. Preferably, the plating cells include a direct line connection to the waste drain 320 or the waste disposal system 322 to drain the plating cells without returning the plating solution through the plating solution conditioning system 300. The plating solution conditioning system 300 preferably also includes a bleed off connection to bleed off excess electrolyte and constituent to the waste drain 320.
Although not shown in FIG. 3 , the plating solution conditioning system 300 may include a number of other constituents. For example, the plating solution conditioning system 300 preferably also includes one or more additional tanks for storage of chemicals for a substrate cleaning system. Double-contained piping for hazardous material connections may also be employed to provide safe transport of the chemicals throughout the system. Optionally, the plating solution conditioning system 300 includes connections to additional or external processing system to provide additional supplies to the plating system.
Embodiments of the above-described systems and chambers may be present in a plating chamber that exhibits reduced or eliminated precipitates or plate-up as discussed herein. FIG. 4 shows exemplary operations in a method 400 of replenishing a plating bath according to embodiments of the present technology. The method 400 may also include one or more operations prior to the initiation of the method, including filing, plating, solute adjustment, or any other operations that may be performed prior to the described operations. The method may further include a number of optional operations, which may or may not be specifically associated with some embodiments of methods according to the present technology. For example, many of the operations are described in order to provide a broader scope of the processes performed but are not critical to the technology or may be performed by alternative methodology, as will be discussed further below.
Method 400 may include operations described schematically in regards to FIGS. 1 to 3 , as discussed above, for reducing the formation of insoluble deposits in semiconductor plating systems or a surface thereof during plating. For instance, method 400 includes an operation 402 that includes providing a plating system 100. As discussed above, the plating system 100 may include a movable head that is capable of moving from a first position to a second position in order to dispose substrate 215 and/or seal 130 within contact of plating solution 207, in optional operation 404. After disposing the substrate 215 and/or seal 130 within contact of plating solution 207, the method may include optional operation 406 of plating substrate 215 as discussed above.
At operation 408, the plating solution volume may be reduced. In embodiments, the reduction in volume may be due to evaporation, spillage, transfer, or the like. Nonetheless, in embodiments, the volume of the plating solution is reduced from a first volume to a second volume.
Operation 410 includes the step of optionally conditioning the replenishment agent. As discussed above, in some embodiments, the replenishment agent may already be characterized by a suitable pH, and no conditioning is necessary. Nonetheless, a replenishment agent may be provided at operation 410, that has a pH that varies from the pH of the plating solution by less than or about 40%. As discussed above, the replenishment agent may naturally have the required pH, or may be conditioned at operation 410 to include one or more additional pH adjusting agents.
Nonetheless, in embodiments, the method includes, as shown in operation 412, replenishing the plating bath solution having a first pH (the detected pH) to volume greater than the second volume, which may, in embodiments, be equal to the first volume, with the replenishment agent. Furthermore, as discussed above, it should be understood that method 400 does not require removal of any components from the plating bath, or disassembly of the bath itself. Instead, by carefully tailoring the composition of the replenishment agent, the insoluble materials that contribute to bath precipitates or plate up may be maintained in solution and removed utilizing any of the filter processes discussed in regards to FIG. 3 . Thus, the present technology prevents plate-up from occurring without requiring down-time of the plating bath, eliminating the need for disruptive cleaning processes. Furthermore, the present technology has found that by utilizing a replenishment agent as discussed herein, the initial precipitation of insoluble particles or ions due to rapid changes in pH upon introduction of a diluent having a disparate pH can be avoided. Thus, the formation of bath precipitates or an initial layer of insoluble material, and plate-up caused therefrom can be greatly reduced or completely avoided. This effect can be particularly pronounced in portion of bath 205 adjacent to inlet supply 212, such as any seals, valves, or components (not shown) located adjacent to the inlet supply 212, as well as any seals or locations particularly susceptible to insoluble deposits.
Furthermore, it should be understood that the original volume can also be referred to as a first volume. Thus, in some aspects, operation 412 may occur when a second volume, which is less than the first volume, is detected in the plating system 100. The decrease in plating solution volume can be according to any one or more of the above discussed values or ranges.
In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details. For example, other bath or plating apparatus that may benefit from the plate-up or residue prevention techniques described may also be used with the present technology.
Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology.
Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. Where multiple values are provided in a list, any range encompassing or based on any of those values is similarly specifically disclosed.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a replenishment agent” includes a plurality of such replenishment agents, and reference to “the volume” includes reference to one or more volumes and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.

Claims

What is claimed is:

1. A method of reducing formation of insoluble deposits in a plating system or a surface thereof, the method comprising:

reducing a volume of a plating solution having a first pH in a plating bath from a first volume to a second volume; and

adding a replenishment agent to the plating solution to increase the volume of the plating solution from the second volume to the first volume, wherein the replenishment agent is characterized by a second pH, wherein the second pH varies from the first pH by less than or about 5.

2. The method of claim 1, wherein the plating solution is characterized by a change in pH subsequent the addition of less than or about 3.

3. The method of claim 1, wherein the plating solution further comprises metal ions, metal particles, organometallic particles, organic particles, or a combination thereof.

4. The method of claim 3, wherein less than about 10 wt. % of the metal ions, metal particles, organometallic particles, organic particles, or a combination thereof precipitate from the plating solution subsequent the replenishment, based upon the weight of the metal ions, metal particles, organometallic particles, organic particles, or a combination thereof in the plating solution prior to addition.

5. The method of claim 1, wherein the first pH is from about 0 to about 5, and wherein the second pH is from about 0 to about 5.

6. The method of claim 1, wherein the first pH is from about 8 to about 12, and wherein the second pH is from about 8 to about 12.

7. The method of claim 1, wherein the second pH varies from the first pH by less than or about 1.5.

8. The method of claim 7, wherein the second pH varies from the first pH by less than or about 3.

9. The method of claim 1, wherein the replenishment agent comprises a mineral acid, carbonic acid, cathode water, anode water, or a combination thereof.

10. The method of claim 9, wherein the replenishment agent comprises methane sulfonic acid, carbonic acid, cathode water, anode water, or a combination thereof.

11. The method of claim 10, wherein the replenishment agent is characterized by a pH of less than 3.

12. The method of claim 1, wherein the reduction in volume includes evaporating a portion of the plating solution.

13. The method of claim 1, wherein the plating solution comprises a first electrolyte concentration, and a second electrolyte concentration subsequent the addition, wherein the first electrolyte concentration varies from the second electrolyte concentration by less than or about 10 wt. % based upon a weight of electrolyte in the plating solution.

14. A method of reducing formation of insoluble deposits in a plating system or a surface thereof, the method comprising:

reducing a volume of a plating solution having a first pH in a plating bath;

conditioning a replenishment agent to a second pH, wherein the second pH is characterized by varying from the first pH by less than or about 3, wherein the replenishment agent comprises carbonic acid, electrolyzed water, or a combination thereof; and

adding the replenishment agent to the plating solution to increase the volume of the plating solution.

15. The method of claim 14, wherein the replenishment agent is generally free of mineral acids.

16. A method of reducing formation of insoluble deposits in a plating system or a surface thereof,

the plating system comprising a plating bath containing a plating solution, a head comprising a seal, a substrate coupled with the seal, and a bath supply, the plating solution being characterized by a first pH;

the method comprising:

moving the head from a first position to a second position, wherein the seal and the substrate are disposed in the plating solution in the second position,

contacting the substrate with one or more insoluble ions; and

adding a replenishment agent to the plating solution, wherein the replenishment agent is characterized by a second pH, wherein the second pH varies from the first pH by less than or about 5.

17. The method of claim 16, wherein the plating system further comprises a plating solution conditioning system.

18. The method of claim 17, further comprising conditioning the replenishment agent to the second pH.

19. The method of claim 18, wherein the conditioning comprises selecting an acid, adjusting an acid concentration, adding an acidifying agent, adding an alkalization agent, or a combination thereof.

20. The method of claim 19, wherein the acidifying agent and/or the alkalization agent includes electrolysis.