60/135,267, filed on May 21,1999, the disclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION This invention relates to methods for wet processing electronic components having surfaces containing copper. The methods of the present invention are particularly useful for cleaning such copper containing electronic components.

BACKGROUND OF THE INVENTION Wet processing of electronic components, such as semiconductor wafers, flat panels, and other electronic component precursors is used extensively during the manufacture of integrated circuits. Preferably, wet processing is carried out to prepare the electronic component for processing steps such as diffusion, ion implantation, epitaxial growth, chemical vapor deposition, and hemispherical silicon grain growth, or combinations thereof. During wet processing, the electronic components are contacted with a series of processing solutions.

The processing solutions may be used, for example, to etch, to remove photoresist, to clean, or to rinse the electronic components. See, e. g., U. S. Patent Nos. 4,577,650; 4,740,249; 4,738,272; 4,856,544; 4,633,893; 4,778,532; 4,917,123; and EP 0 233 184, assigned to a common assignee, and Burkman et al., Wet Chemical Processes-Aqueous CleaningProcesses, pg 111-151 in Handbook of Semiconductor Wafer Cleaning Technology (edited by Werner Kern, Published by Noyes Publication Parkridge, New Jersey 1993), the disclosures of which are herein incorporated by reference in their entirety.

There are various types of systems available for wet processing. For example, the electronic components may be processed in a single vessel system closed to the environment (such as a Full-FlowTM system supplied by CFMT Technologies), a single vessel system open to the environment, or a multiple open bath system (e. g., wet bench) having a plurality of baths open to the atmosphere.

Following processing, the electronic components are typically dried. Drying of the semiconductor substrates can be done using various methods, with the goal being to ensure that there is no contamination created during the drying process. Methods of drying include evaporation, centrifugal force in a spin-rinser-dryer, steam or chemical drying of wafers, including the method and apparatus disclosed in, for example, U. S. Pat. Nos.

4,778,532 and 4,911,761.

With respect to wet process methods used for cleaning electronic components, much effort has been devoted to finding suitable cleaning processes for electronic components made of predominantly silicon and minor amounts of other components such as aluminum, silicon oxide, silicon nitride, titanium or titanium containing compounds such as titanium nitride, or titanium silicide, tungsten or tungsten containing compounds such as tungsten silicide, cobalt silicide, or combinations thereof. By"cleaning"it is meant a process that removes contaminants such as particles, organics such as waxes, residual polish, or grease, or other contaminants such as oxide layers that are adhered to the surfaces of the electronic components.

For silicon containing electronic components, prior to any metallization step where metals are applied to the electronic component, it has been found that contacting the electronic components with an"SC1 Solution,"and subsequently contacting the electronic components with an"SC2 Solution"is very effective in cleaning silicon containing electronic components. Additionally, cleaning may be enhanced by contacting the silicon containing electronic components with an aqueous solution containing hydrofluoric acid prior to contact with the SC1 Solution.

The SC1 solution is an aqueous solution containing hydrogen peroxide and ammonium hydroxide with concentrations typically ranging from about 5: 1: 1 to about 200: 1: 1 partsbyvolume H2O : H202 : NH40H. The SC1 solution is believed to clean through a surface oxidation/etching mechanism. For example, it is believed that the hydrogen peroxide grows an oxide layer on the surfaces of the silicon containing electronic component, while the ammonium hydroxide simultaneously etches or removes the resulting oxide from the surfaces.

Eventually, a steady state is reached where a relatively thin (e. g., about 1 nm) layer of oxide is simultaneously grown and etched on the surfaces. This oxide growth and etching causes adhered particles and other contaminants to be loosened. Once loosened, the particles and other contaminants can be rinsed away from the surfaces of the electronic components.

The SC2 solution, which is contacted with the silicon containing electronic components after contact with the SC 1 solution contains hydrogen peroxide, hydrochloric acid and water. Typical concentrations for S C2 solutions range from about 5: 1: 1 to about 1000: 0: 1 parts by volume H2O: H202 : HC1. The SC2 solution is used to remove any metal deposition (such as the deposition of iron, aluminum, and copper) that occurs during contacting the electronic components with the SC1 solution. Because the purity of chemicals in the SC1 solution have improved, metal deposition is not as much of a problem today, and frequently the SC2 treatment step is eliminated.

If the surfaces of the electronic components have been treated to contain metals, such as aluminum, the use of aqueous wet processing solutions is greatly reduced. For example, many metals, such as aluminum, are severely corroded when contacted with aqueous solutions. As a result, wet processing of metal containing electronic components, is typically carried out with solvents instead of aqueous solutions. However, the use of solvents is not as desirable because of environmental concerns such as the disposal or recycling of the solvents, and increased safety risks, such as flammability hazards.

Recently, electronic component manufacturers have begun to use copper to replace aluminum in electronic components. The desire to replace aluminum with copper has been primarily due to copper's lower resistivity. Copper also has the advantage of having improved corrosion resistance. However, not much is known about cleaning electronic components containing copper with aqueous solutions.

U. S. Patent No. 4,714,517 et al., to Malladi (hereinafter"Malladi") discloses an approach for cleaning copper parts used for tape automated bonding of semiconductor devices. The Malladi process includes immersing the copper part in a caustic bath and subjecting the copper part to a weak organic acid such as citric acid, tartaric acid, etc. to passivate the surface. However, Malladi does not provide a method for controlling copper etching during cleaning.

The present invention provides additional methods for wet processing electronic components having copper containing surfaces. The wet processing methods of the present invention preferably use conventional solutions typically used for wet processing silicon electronic components. The methods of the present invention are particularly useful for removing particulate contamination from the surfaces of copper containing electronic

components while controlling the amount of etching of the copper on the electronic components.

SUMMARY OF THE INVENTION The present invention provides methods of wet processing electronic components having copper containing surfaces. The methods of the present invention include: contacting the surfaces of the electronic components with a copper oxidizing solution for a first contact time; and subsequently contacting the surfaces of the electronic components with an etching solution for a second contact time. The etching solution is maintained at an aqueous pH of 5 or lower and contains an etching agent and less than 5,000 ppb dissolved or suspended oxygen. The contacting of the surfaces of the electronic components with the copper oxidizing solution and the etching solution removes contaminants from the surfaces of the electronic components. The use of the aforementioned two steps provides control of metallic removal and/or corrosion during wet processing of electronic components containing copper.

In a preferred embodiment, the present invention provides a method of wet processing electronic components having surfaces containing copper that includes placing one or more electronic components in a single vessel; filling the vessel with a copper oxidizing solution comprising an oxidizing agent; contacting the electronic components with the copper oxidizing solution for a first contact time and removing the copper oxidizing solution from the vessel. The method also includes subsequently filling the vessel with a hydrofluoric acid containing solution having a pH of 5 or lower and having less than 5000 ppb dissolved or suspended oxygen; contacting the electronic components with the hydrofluoric acid containing solution for a second contact time and removing the hydrofluoric acid containing solution from the vessel, where the contacting of the surfaces of the electronic components with the copper oxidizing solution and the hydrofluoric acid containing solution removes contaminants from the surfaces of the electronic components.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a bar graph showing the percent particle removal for electronic components having copper containing surfaces treated in accordance with the processes of Comparative Examples 1 through 4, and Example 5.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides methods for wet processing electronic components having surfaces containing copper. The methods of the present invention are particularly useful for cleaning such electronic components, for example to remove contaminants such as particles, organic compounds, polish, grease, or oxide layers, adhered to the surfaces of the electronic components.

The methods of the present invention are useful in any wet processing procedure where it is desired to clean electronic components having copper containing surfaces. By"wet processing"it is meant that the electronic components are contacted with one or more liquids (hereinafter referred to as"process liquids") to process the electronic components in a desired manner. For example, it may be desired to treat the electronic components to clean, etch, or remove photoresist from the surfaces of the electronic components. It may also be desired to rinse the electronic components between such treatment steps. Wet processing may also include steps where the electronic components are contacted with other fluids, such as a gas, a vapor, or a liquid mixed with a vapor or gas, or combinations thereof. As used herein, the term"fluid"includes liquids, gases, liquids in their vapor phases, or combinations thereof. Typically, such wet processing is carried out to prepare the electronic components with copper for processing steps such as dielectric chemical vapor deposition, plasma etch, or reactive ion etching, or combinations thereof.

There are various types of process fluids used during wet processing.

Generally, the most common types of process fluids used during wet processing are chemical treatment liquids or fluids, and rinsing liquids or fluids. As used herein a"chemical treatment liquid"or"chemical treatment fluid"is any liquid or fluid that reacts in some manner with the surfaces of the electronic components to alter the surface composition of the electronic component. For example, the chemical treatment liquid or fluid may have activity in removing contamination adhered or chemically bound to the surfaces of the electronic components, such as particulate, metallic, photoresist, or organic materials, or activity in etching the surfaces of the electronic component, or activity in growing an oxide layer on the surface of the electronic component. The chemical treatment fluids useful in the present invention contain one or more chemically reactive agents to achieve the desired surface treatment. Preferably, the concentration of such chemically reactive agents will be greater than 1000 ppm and more preferably greater than 10,000 ppm, based on the weight of the chemical treatment fluid. It is

also possible for the chemical treatment fluid to contain 100 % of one or more chemically reactive agents. Examples of chemical treatment fluids useful in the methods of the present invention are described in more detail hereinafter.

As used herein,"rinsing liquid"or"rinsing fluid"refers to DI water or some other liquid or fluid that removes from the electronic components and/or vessel residual chemical treatment fluids, reaction by-products, and/or particles or other contaminants freed or loosened by the chemical treatment step. The rinsing liquids or fluids may also be used to prevent redeposition of loosened particles or contaminants onto the electronic components or vessel. Examples of rinsing fluids useful in the methods of the present invention are described in more detail hereinafter.

As used herein,"chemical treatment step"or"wet processing step"refers to contacting the electronic components with a chemical treatment fluid or process fluid respectively.

By"electronic components having copper containing surfaces"it is meant that the electronic components preferably have surfaces that are at least about 0.1 percent covered with copper based on the total surface area of the electronic components. The thickness of copper on the surfaces is preferably at least about 0.1 microns and more preferably from about 0.5 microns to about 5 microns. Thus, the electronic components are at least partially covered with copper. In the case of partial coverage, the electronic components can be covered with copper in a patterned fashioned. Examples of electronic components that have surfaces containing copper include electronic component precursors such as semiconductor wafers, flat panels, and other components used in the manufacture of electronic components (i. e., integrated circuits); CD ROM disks; hard drive memory disks; or multichip modules.

In the wet processing methods of the present invention, electronic components having copper containing surfaces are contacted with a copper oxidizing solution and subsequently contacted with an etching solution containing less than 5000 ppb of dissolved or suspended oxygen. Although in no way intending to be bound by theory, it is believed that the copper oxidizing solution oxidizes the copper containing surfaces (e. g., from Cu°+ to Cu2+) to form a thin (e. g., less than about 1.0 nm) layer of a copper oxide or combinations of different copper oxides. The etching solution is believed to etch this layer of copper oxide at a controlled rate.

The copper oxidizing solution that the electronic components are contacted with is any liquid that is capable of oxidizing the copper located on the surfaces of the electronic components. The copper oxidizing solution should also preferably not contain agents that lead to etching of the copper. The copper oxidizing solution is preferably maintained at a pH of at least about 7 or greater, and more preferably at least about 8 or greater to inhibit etching of the copper. To maintain the copper oxidizing solution at such a pH, preferably the copper oxidizing solution does not contain acids (e. g., HC1, HF, nitric acid) in an amount to lower the pH below 7.

Suitable copper oxidizing solutions include for example solutions containing oxidizing agents such as hydrogen peroxide, ozone, iron cyanide, or combinations thereof.

Preferably, the oxidizing agent is hydrogen peroxide. These oxidizing agents are preferably dissolved or dispersed in any compatible liquid, for example, water, basic aqueous solutions, or non-oxidizable organic solvents such as fluorinated hydrocarbons, or combinations thereof.

It is also possible that the oxidizing agent could be a liquid so that it would not be necessary to dissolve the oxidizing agent in a liquid. Preferably, the oxidizing agent is dissolved or dispersed in water.

The concentration of the oxidizing agent in the copper oxidizing solution will depend on the oxidizing agent chosen. Generally, however, the copper oxidizing solution preferably contains from about 0.1 volume percent to 100 volume percent and more preferably from about 10 volume percent to about 70 volume percent oxidizing agent based on the total volume of the solution. In the case of hydrogen peroxide, preferably the concentration of hydrogen peroxide in the copper oxidizing solution is from about 0.1 volume percent to about 10 volume percent, and more preferably from about 0.2 volume percent to about 1.0 volume percent, based on the total volume of the copper oxidizing solution. In the case of ozone, preferably the concentration of ozone in the copper oxidizing solution is from about 10 ppm to about 50 ppm and more preferably from about 10 ppm to about 40 ppm.

In a preferred embodiment of the present invention, the copper oxidizing solution is an SC 1 solution preferably having a ratio, based on volume, of H2O: H202: NH40H of from about 5: 1: 1 to about 200: 1: 1, more preferably from about 50: 1: 1 to about 150: 1: 1 and most preferably from about 90: 1: 1 to about 110: 1: 1.

The copper oxidizing solution may also contain other additives in addition to the oxidizing agent to enhance wet processing. For example, the copper oxidizing solution may also contain surfactants, anti-corrosion agents, or any other conventional additive typically added to wet processing liquids used for cleaning. Preferably, these other additives are present in the copper oxidizing solution in an amount of less than about 5.0 percent by volume and more preferably from about 0.01 percent by volume to about 1.0 percent by volume.

If it is desired to include surfactants in the copper oxidizing solution, preferably, the surfactants are present in an amount of less than about 1 percent by volume, and more preferably less than about 0.5 percent by volume, based on the total volume of the copper oxidizing solution. Examples of surfactants that may be used include anionic, nonionic, cationic and amphoteric surfactants disclosed in for example Kirk-Othmer Concise Encyclopedia of Chemical Technology, published by John Wiley & Sons, NY, 1985, pages 1142 tol 144 and McCutcheon's Detergents and Emulsifiers, 1981 North American Edition, MC Publishing Company, Glen Rock, N. J. 1981, which are hereby incorporated by reference in their entireties. Preferred surfactants for use in the present invention include alkaline surfactants and VALTRON surfactants such as VALTRON'SP2275, and SP2220 supplied by Valtech Corporation of Pughtown, PA, NCW601A supplied by Wako Company.

If it is desired to include anti-corrosion agents in the copper oxidizing solution, preferably, the anti-corrosion agents are present in the copper oxidizing solution in an amount of from about 0.1 weight percent to about 1.0 weight percent based on the total weight of the copper oxidizing solution. Examples of anti-corrosion agents that may be used include for example benzotriazole.

The electronic components are preferably contacted with the copper oxidizing solution for a contact time sufficient to assure that a uniform layer of copper oxide forms across the wafer, and so that some particle removal occurs due to oxidation of the copper and dissolution of the copper oxide. By"contact time,"as used herein, it is meant the time an electronic component is exposed to a process liquid. For example, the contact time will include the time an electronic component is exposed to the process liquid during filling a vessel with the process liquid or immersing the electronic component in the process liquid; the time the electronic component is soaked in the process liquid; and the time the electronic component is exposed to the process liquid while the process liquid or electronic component is being

removed from the vessel. The actual contact time chosen will depend on such factors as the oxidizing agents present in the copper oxidizing solution, the concentration of the oxidizing agent, and the temperature of the copper oxidizing solution. Preferably, however, the contact time will be for at least 30 seconds and no more than 10 minutes.

The temperature of the copper oxidizing solution during contacting is such that decomposition of the oxidizing agent in the copper oxidizing solution is inhibited. Preferably the temperature of the copper oxidizing solution is less than 60 °C and more preferably from about 20 °C to about 40 °C.

The contacting of the electronic components with the copper oxidizing solution may be carried out by any known wet processing technique and will depend largely upon the wet processing system chosen. For example, one or more electronic components may be immersed and withdrawn in a bath containing the copper oxidizing solution. Alternatively, the electronic components may be placed in a vessel and the copper oxidizing solution may be directed through the vessel to fill the vessel full with the solution to achieve contacting.

Contacting can be carried out under dynamic conditions (e. g., directing the solution through a vessel containing the electronic components continuously), under static conditions (e. g., soaking the electronic components in the solution) or a combination of both (e. g., directing the solution through the vessel for a period of time, and then allowing the electronic components to soak in the solution for another period of time). Suitable wet processing systems for contacting the electronic components are described in more detail hereinafter.

Subsequent to contacting the electronic components with the copper oxidizing solution, the electronic components are contacted with an etching solution. The etching solution is any liquid containing an etching agent capable of etching the oxidized copper.

Preferably, the etching solution contains one or more non-oxidizing acids (e. g., acids that will not oxidize the copper) that maintain the etching solution at a pH of about 5 or lower. The amount of etching agent present in the etching solution is preferably an amount to maintain the pH of the etching solution at about 5 or lower, more preferably at about 4 or lower and most preferably at about 3 or lower. Examples of non-oxidizing acids useful in the present invention include hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, organic acids such as acetic acid, citric acid, or tartaric acid, or combinations thereof. The liquid solution in which

the etching agent is dissolved or dispersed in is preferably water, but may also be an organic solvent such as ethylene glycol, propylene carbonate, or methanol, or combinations thereof.

In a preferred embodiment of the present invention, the etching solution is a hydrofluoric acid containing solution. The hydrofluoric acid containing solution may contain hydrofluoric acid, buffered hydrofluoric acid, ammonium fluoride, or any other substances which generates hydrofluoric acid in solution, or combinations thereof. The hydrofluoric acid is preferably present in the hydrofluoric acid solution in a volume ratio of H20: HF of from about 5: 1 to about 1000: 1, more preferably from about 100: 1 to about 800: 1, and most preferably from about 200: 1 to about 600: 1.

It has been found in the present invention, that it is preferable to maintain the etching solution at conditions to promote a slow and controlled etching rate (e. g., less than about 10 nm per minute of copper and more preferably less than about 1 nm per minute). It is preferable to have a slow and controlled etching rate of copper so that no more than the minimal amount of copper needed to clean the electronic components is removed. Factors that affect the copper etching rate include the concentration of etching agent in the etching solution, the pH of the etching solution, the amount of dissolved or suspended oxygen or other oxidizing agents in the etching solution, and the temperature of the etching solution. For example, the etching rate of copper is reduced by decreasing the concentrations of etching agent, dissolved or suspended oxygen, and other copper oxidizing agents in the etching solution, increasing the pH, and decreasing the temperature of the solution. Of the aforementioned factors affecting the copper etching rate, the amount of dissolved or suspended oxygen or other copper oxidizing agents in the etching solution has probably the greatest impact on the copper etching rate. This is because oxygen or other copper oxidizing agents react with copper to form copper oxide and the copper oxide is easily etched at pHs of the etching solution.

The dissolved or suspended oxygen in the etching solution is preferably maintained at a concentration of less than 5000 ppb, more preferably less than 100 ppb, and most preferably kept as low as possible, based on the total weight of the etching solution.

Also, it is preferable to maintain other copper oxidizing agents (such as those useful in the copper oxidizing solution, e. g., H202) at concentrations of less than 5000 ppb, more preferably less than 100 ppb, and most preferably kept as low as possible. As discussed previously, maintaining the dissolved or suspended oxygen or other copper oxidizing agents at such low

levels reduces the etching rate of the copper so that etching is controlled.

As previously mentioned, the etching solution is preferably maintained at apH of equal to or less than 5, more preferably at a pH of equal to or less than about 4, and most preferably at a pH of equal to or less than about 3. In addition to the etching agent, buffering agents may be added to the etching solution to aid in maintaining the pH within the aforementioned ranges. The buffering agent is preferably added in an amount sufficient to maintain the pH within the above preferred range. Preferably, the buffering agent is present in the etching solution in an amount of from about 0.01 weight percent to about 5.0 weight percent, and more preferably from about 0.05 weight percent to about 0.5 weight percent, based on the total weight of the etching solution.

In a preferred embodiment of the present invention, the etching solution contains hydrofluoric acid and hydrochloric acid. The hydrochloric acid is desirable because it aids in lowering the pH and assures that the zeta potential of the surfaces is positive so that particles are repelled. Preferably the hydrochloric acid is present in the etching solution in a volume ratio of H2O : HC1, per 1 part by volume of hydrofluoric acid, of from about 50: 1 to about 1000: 1, more preferably from about 500: 1 to about 500: 10, and more preferably from about 500: 3 to about 500: 7.

The etching solution may also contain other additives in addition to the etching agent to enhance wet processing. For example, the etching solution may also contain surfactants, anti-corrosion agents, or any other conventional additive typically added to wet processing liquids used for cleaning. Preferably, these other additives are present in the etching solution in amounts previously described for the copper oxidizing solution.

The electronic components are preferably contacted with the etching solution for a contact time sufficient to remove the oxide formed during contacting of the electronic components with the copper oxidizing solution. The actual contact time chosen will depend on such factors as the concentrations of etching agent and dissolved or suspended oxygen in the etching solution, the pH and temperature of the etching solution and the type of etching agent used. Preferably, however, the contact time will be for at least 30 seconds and no more than two minutes.

The temperature of the etching solution during contacting is such that etching is controlled, and a slow etching rate is achieved (e. g., about 10 nm per minute or less).

Preferably the temperature of the etching solution is less than 50 °C and more preferably from about 20 °C to about 30 °C.

The contacting of the electronic components with the etching solution may be carried out by any wet processing technique previously described for contacting the electronic components with the copper oxidizing solution. For example, one or more electronic components may be immersed and withdrawn in a bath containing the etching solution.

Alternatively, the electronic components may be placed in a vessel and the etching solution may be directed through the vessel to fill the vessel full with the solution to achieve contacting.

Additionally, contacting can be carried out under dynamic conditions, under static conditions, or a combination of both.

In a preferred embodiment of the present invention, in an effort to minimize the concentration of dissolved or suspended oxygen, contacting of the electronic components with the etching solution is performed in an environment where the electronic components and the etching solution are isolated from sources of oxygen, such as from the atmosphere. This isolation may be carried out by wet processing in a system that is closable to the environment (described in more detail hereinafter) or in a system that is blanketed by an inert gas such as nitrogen or a noble gas such as argon.

Additionally, because copper is susceptible to reoxidation after treatment with the etching solution, preferably any fluids (whether chemical treatment or rinsing) contacted with the electronic components, after contacting the electronic components with the etching solution, should contain low levels of dissolved or suspended oxygen or other copper oxidizing agents (e. g., those useful in the copper oxidizing solution). Preferably, such fluids will contain less than about 500 ppb, more preferably less than 50 ppb, and most preferably levels as low as possible of dissolved or suspended oxygen based on the total weight of the fluid. Preferably such fluids will also contain less than about 500 ppb, more preferably less than 50 ppb and most preferably no other copper oxidizing agent. By having low levels of dissolved or suspended oxygen and low levels of copper oxidizing agents in these fluids, the risk of reoxidizing the surfaces of the electronic components after treatment with the etching solution is significantly reduced.

In addition to contacting the electronic components with the copper oxidizing solution and the etching solution, the electronic components may be contacted with any number

of other chemical treatment fluids (e. g., gas, liquid, vapor or any combination thereof) to achieve the desired result. For example, the electronic components may be contacted with chemical treatment fluids used to etch (hereinafter referred to as etching fluids), grow an oxide layer (hereinafter referred to as oxide growing fluids), to remove photoresist (hereinafter referred to as photoresist removal fluids), to enhance cleaning (hereinafter referred to as cleaning fluids), or combinations thereof. The electronic components may also be rinsed with a rinsing fluid at any time during the wet processing method. Preferably, the chemical treatment fluids and rinsing fluids are liquids.

One skilled in the art will recognize that there are various process fluids that can be used during wet processing. Other examples of process fluids that can be used during wet processing are disclosed in"Chemical Etching"by Werner Kern et al., in Thin Film Processes, edited by John L. Vosser et al., published by Academic Press, NY 1978, pages 401- 496, which is incorporated by reference in its entirety.

In addition to contacting the electronic components with chemical treatment fluids, the electronic components may also be contacted with rinsing fluids. As previously described, rinsing fluids are used to remove from the electronic components and/or vessel residual chemical treatment fluids, reaction by-products, and/or particles or other contaminants freed or loosened by a chemical treatment step. The rinsing fluids may also be used to prevent redeposition of loosened particles or contaminants onto the electronic components or vessel.

Any rinsing fluid may be chosen that is effective in achieving the effects described above. In selecting a rinsing fluid, such factors as the nature of the surfaces of the electronic components to be rinsed, the nature of contaminants dissolved in the chemical treatment fluid, and the nature of the chemical treatment fluid to be rinsed should be considered. Also, the proposed rinsing fluid should be compatible (i. e., relatively nonreactive) with the materials of construction in contact with the fluid. Rinsing fluids which may be used include for example water, organic solvents, mixtures of organic solvents, or combinations thereof. Preferred organic solvents include those organic compounds useful as drying solutions disclosed hereinafter such as Cl to C, o alcohols, and preferably Cl to C6 alcohols. Preferably the rinsing fluid is a liquid and contains low levels of oxygen (e. g,. preferably less than 5000 ppb, more preferably less than 500 ppb, and most preferably less than 100 ppb). In a most preferred embodiment the rinsing fluid is deionized water.

Rinsing fluids may also optionally contain low levels of chemically reactive agents to enhance rinsing. For example, surfactants, and/or anti-corrosion agents may be used in rinsing fluids. The concentration of such additives in the rinsing fluid is minute. For example, the concentration is preferably not greater than about 1000 ppm by weight and more preferably not greater than 100 ppm by weight based on the total weight of the rinsing fluid.

One skilled in the art will recognize that the selection of chemical treatment fluids and the sequence of chemical treatment fluids and rinsing fluids will depend upon the desired wet processing results. For example, the electronic components could be contacted with a rinsing fluid before or after one or more chemical treatment steps. Alternatively, it may be desired in some wet processing methods to have one chemical treatment step directly follow another chemical treatment step, without contacting the electronic components with a rinsing fluid between two chemical treatment steps (i. e., no intervening rinse). Such sequential wet processing, with no intervening rinse, is described in, for example, U. S. application Serial No.

08/684,543 filed July 19,1996, which is hereby incorporated by reference in its entirety.

Also, for example, in one embodiment of the present invention, it is preferred, prior to contacting the electronic components with the copper oxidizing solution, to contact the electronic components with a rinsing fluid such as deionized water to wet the surfaces of the electronic components. Preferably, in such a wet processing step, the rinsing fluid is at a temperature of from about 20 °C to about 60 °C and more preferably from about 20 °C to about 40 °C. It may also be desirable to add a surfactant to such a rinsing fluid, preferably at the levels previously described for the copper oxidizing solution.

In another embodiment of the present invention, the electronic components are contacted with a rinsing fluid after contacting the electronic components with the copper oxidizing solution, but before contacting the electronic components with the etching solution.

The rinsing fluid is preferably deionized water at a temperature of from about 20 °C to about 60 °C. Preferably, the rinsing fluid also has low levels of oxygen as previously described herein. The electronic components are preferably contacted with the rinsing fluid for a contact time sufficient to remove residual chemicals, reaction by-products, and/or particles or other contaminants loosened from treatment with the copper oxidizing solution. It is also possible, however, to contact the electronic components with the copper oxidizing solution, directly

followed by contacting the electronic components with the etching solution with no intervening rinse between these two chemical treatment steps.

Following contact of the electronic components with the etching solution, it is preferred in the present invention, that the electronic components are contacted with a rinsing fluid of deionized water having a temperature of from about 20 °C to about 60 °C. This rinsing step is preferably carried out to remove residual chemicals, reaction-by products, and loosened particles or other contaminants remaining in the vessel or on the surfaces of the electronic components after contacting the electronic components with the etching solution. The rinsing fluid in such a step preferably contains low levels of dissolved or suspended oxygen (as described previously) to minimize the risk of reoxidation of the copper.

As mentioned previously, it may be desirable to add surfactant to process liquids used in the present invention. The presence of one or more surfactants in a process liquid (including the copper oxidizing solution, etching solution or rinsing liquid) is especially preferred where the electronic components will be exposed to a gas-liquid interface. For example, an electronic component may be exposed to a gas-liquid interface during immersion or withdrawal of the electronic component in a process liquid. The electronic components may also be exposed to a gas-liquid interface during the filling of a vessel with a process liquid. It has been found that surfactants aid in reducing particle deposition or adhesion in several ways.

For example, a surfactant will collect in the liquid at the gas-liquid interface (i. e., liquid surface), thereby displacing any particles at the liquid surface. Minimizing the amount of particles at the liquid surface reduces the likelihood of a particle at the liquid surface coming into contact with the electronic component. Also, the surfactant provides an electrochemical barrier to prevent further particulate adhesion. For example, the surfactant will gather at a liquid surface, a solid surface or any other surface that will help to lower its overall energy, including particles and electronic components. Since the electronic components and particles are surrounded on all sides by surfactant, the overall charge of the particle/surfactant and semiconductor substrate/surfactant may be approximated as the charge of the surfactant. Since the particles and semiconductor substrate have the same charge of the surfactant, they will not be attracted to each other as opposite charges are, thereby preventing additional particle adhesion during immersion. The selection of a surfactant will depend on the wet processing step. For example, the pH of the surfactant should be compatible with the pH of the chemical

treatment solution (e. g., preferably an alkaline surfactant is used with the copper oxidizing solution and preferably an acidic, nonoxidizing surfactant is used with the etching solution).

In a most preferred embodiment of the present invention, the electronic components are contacted with a copper oxidizing solution that is an SC1 solution having a temperature of about 25 °C for a contact time of about 3 minutes or less. The SC1 solution preferably contains water, ammonium hydroxide, and hydrogen peroxide in a volume ratio of about 100: 1: 1 respectively, and a surfactant in an amount of less than 1 percent by volume based on the volume of the copper oxidizing solution. The electronic components are then preferably rinsed with deionized water at a temperature of about 25 °C for a contact time of about 5 minutes. Following the rinse, the electronic components are then preferably contacted with a hydrofluoric acid containing solution having a temperature of about 25 °C for a contact time of about less than 2 minutes. The hydrofluoric acid containing solution preferably contains water, hydrofluoric acid, and hydrochloric acid in a volume ratio of about 500: 1: 5 respectively. The electronic components are again rinsed with deionized water having a temperature of about 25 °C for about five minutes, and then dried with isopropanol at a temperature of 45 °C for about one minute.

In another preferred embodiment of the present invention, the wet processing is carried out according to the most preferred embodiment described above, except that the copper oxidizing solution contains water and hydrogen peroxide in a volume ratio of about 100: 1 respectively. The copper oxidizing solution also preferably contains a surfactant at the levels described above, but contains no ammonium hydroxide.

Thus there are various types of ways in which the electronic components can be wet processed in accordance with the method of the present invention. For example, wet processing can be carried out using sonic energy (such as in the megasonic energy range, e. g. from about 500 kHz to about 1 MHz) during the contacting of the electronic components with a process liquid to enhance cleaning. Additionally, methods may include wet processing techniques disclosed in for example U. S. Patent No. 5,383,484; U. S. Patent Application Ser.

Nos. 08/684,543, July 19,1996; 09/209,101, filed December 10,1998; and 09/253,157, filed February 19,1999; and U. S. Provisional Patent Application Ser. Nos. 60/087,758 filed June 2,1998; and 60/111,350 filed December 8,1998, the disclosures of which are all hereby incorporated by reference in their entireties.

The methods of the invention may be carried out in generally any wet processing equipment including for example multiple bath systems (e. g., wet bench), and single vessel systems (open or closable to the environment). See, e. g., Chapter 1: Overview and Evolution of Semiconductor Wafer Contamination and Cleaning Technology by Werner Kern and Chapter 3: Aqueous Cleaning Processes by Don C. Burkman, Donald Deal, Donald C.

Grant, and Charlie A. Peterson in Handbook of Semiconductor Wafer Cleaning Technology (edited by Werner Kern, Published by Noyes Publication Parkridge, New Jersey 1993), and Wet Etch Cleaning by Hiroyuki Horiki and Takao Nakazawa in Ultraclean Technology Handbook, Volume 1, (edited by Tadahiro Ohmi published by Marcel Dekker), the disclosures of which are herein incorporated by reference in their entirety.

In a preferred embodiment of the invention, the electronic components are housed in a single vessel system. Preferably single vessel systems such as those disclosed in U. S. PatentNos. 4,778,532,4,917,123,4,911,761,4,795,497,4,899,767,4,984,597, 4,633,893, 4,917,123,4,738,272,4,577,650,5,571,337 and 5,569,330, the disclosures ofwhich are herein incorporated by reference in their entirety, are used. Preferred commercially available single vessel systems are Full-FIowTM vessels such as those manufactured by CFM Technologies, Poseidon manufactured by Steag, and FL820L manufactured by Dainippon Screen. Such systems are preferred because the oxygen levels can be more readily controlled.

In a most preferred embodiment of the present invention, the electronic components are wet processed in an enclosable wet processing system to reduce the exposure of the electronic components to oxygen, thus minimizing the risk of reoxidation once the surfaces of the electronic components are cleaned. The enclosable wet processing system is also preferably capable of receiving different process fluids in various sequences. A preferred method of delivering process fluids to the vessel is by direct displacement of one fluid with another. The Full Flow wet processing system manufactured by CFM Technologies, Inc is an example of a system capable of delivering fluids by direct displacement.

In a preferred method of the present invention using a single, enclosable vessel, one or more electronic components are placed in a process vessel and closed to the environment. Prior to contacting the electronic components with the copper oxidizing solution, the electronic components may optionally be contacted with a rinsing fluid or any other desired process fluid for pretreatment of the electronic component. Such contacting can be

accomplished through directing the fluid into the process vessel to fill the process vessel full with the fluid so that gases from the atmosphere or residual fluid from a previous step are not significantly trapped within the vessel. The fluid can be continuously directed through the vessel once the vessel is full of fluid, or the flow of fluid can be stopped to soak the electronic components for a desired time. Following such pretreatment steps, the fluid currently in the vessel is removed from the vessel, and the copper oxidizing solution can be directed into the vessel to contact the electronic components with the copper oxidizing solution. Following contact with the copper oxidizing solution, the electronic components may be optionally rinsed, and then contacted with the etching solution, such as a hydrofluoric acid containing solution.

After contact with the etching solution the electronic components can optionally be rinsed or treated in any other desired manner.

The removal of one process fluid with another process fluid in the enclosable single vessel can be accomplished in several ways. For example, the process fluid in the process vessel can be completely removed (i. e., drained), and then the next process fluid can be directed into the vessel during or after draining. In another embodiment, the process fluid present in the vessel can be directly displaced by the next desired process fluid as described for example in U. S. Patent No. 4,778,532.

Following wet processing with chemical treatment or rinsing fluids, the electronic components are preferably dried. By"dry"or"drying"it is meant that the electronic components are preferably made substantially free of liquid droplets. By removing liquid droplets during drying, impurities present in the liquid droplets do not remain on the surfaces of the semiconductor substrates when the liquid droplets evaporate. Such impurities undesirably leave marks (e. g., watermarks) or other residues on the surfaces of the semiconductor substrates. However, it is also contemplated that drying may simply involve removing a treating, or rinsing fluid, for example with the aid of a drying fluid stream, or by other means known to those skilled in the art.

Any method or system of drying may be used. Suitable methods of drying include for example evaporation, centrifugal force in a spin-rinser-dryer, steam or chemical drying, or combinations thereof.

A preferred method of drying uses a drying fluid stream to directly displace the last processing solution that the electronic components are contacted with prior to drying

(hereinafter referred to as"direct displace drying"). Suitable methods and systems for direct displace drying are disclosed in for example U. S. Patent Nos. 4,778,532,4,795,497,4,911,761, 4,984,597,5,571,337, and 5,569,330. Other direct displace dryers that can be used include Marangoni type dryers supplied by manufacturers such as Steag, Dainippon, and YieldUp.

Most preferably, the system and method of U. S. Patent No. 4,7911,761 is used for drying the electronic components.

Preferably, the drying fluid stream is formed from a partially or completely vaporized drying solution. The drying fluid stream may be for example superheated, a mixture of vapor and liquid, saturated vapor or a mixture of vapor and a noncondensible gas.

The drying solution chosen to form the drying fluid stream is preferably miscible with the last process fluid in the vessel and non-reactive with the surfaces of the electronic components. The drying solution also preferably has a relatively low boiling point to facilitate drying. For example, the drying solution is preferably selected from organic compounds having a boiling point of less than about 140 degrees centigrade at atmospheric pressure. Examples of drying solutions which may be employed are steam, alcohols such as methanol, ethanol, 1-propanol, isopropanol, n-butanol, secbutanol, tertbutanol, or tert-amyl alcohol, acetone, acetonitrile, hexafluoroacetone, nitromethane, acetic acid, propionic acid, ethylene glycol mono-methyl ether, difluoroethane, ethyl acetate, isopropyl acetate, 1,1,2-trichloro-1,2,2- trifluoroethane, 1,2-dichloroethane, trichloroethane, perfluoro-2-butyltetrahydrofuran, perfluoro-1,4-dimethylcyclohexane or combinations thereof.

Preferably, the drying solution is a C, to C6 alcohol, such as for example methanol, ethanol, 1-propanol, isopropanol, n-butanol, secbutanol, tertbutanol, tert-amyl alcohol, pentanol, hexanol or combinations thereof.

In a preferred embodiment of the present invention a drying solution is selected which is miscible with the processing solution present in the process vessel immediately before drying and forms a minimum-boiling azeotrope with the processing solution. Since water is the most convenient and commonly used solvent for chemical treatment or rinsing fluids, a drying solution which forms a minimum-boiling azeotrope with water is especially preferred.

Preferably, to reduce the risk ofreoxidation and contamination ofthe electronic components the wet processing and drying is performed in a single vessel without removing the electronic components from the vessel. Suitable wet processing systems for carrying out

both wet processing and drying in a single vessel include for example Full Flow wet processing systems manufactured by CFM technologies, Poseidon manufactured by Steag, and FL820L manufactured by Dainippon Screen.

Following drying, the electronic components may be removed from the drying vessel and further processed in any desired manner.

The electronic components obtained using the methods of the present invention preferably are substantially free of particle contamination. By"substantially free"it is meant that the semiconductor substrates contain preferably less than 0.05 particles per cm2, and more preferably less than 0.016 particles per cm2. The particle size of particles remaining on the semiconductor substrate is preferably equal to or less than 0.3 llm and more preferably less than 0.12 pm in diameter as measured by KLA Tencor SP1 particle scanning equipment.

Preferably all particles greater than 0.3 llm are removed using the methods of the present invention.

The methods of the present invention are particularly useful for removing non- metallic particles from the surfaces of the electronic components. Examples of non-metallic particles include SiO2, Si3N4, organic material, or combinations thereof.

EXAMPLES The methods of the present invention were used to wet process semiconductor wafers having copper containing surfaces. The copper containing wafers in all examples were made of silicon and silicon oxide, and were completely coated with 400 nm layer of copper.

After wet processing, selected wafers were then analyzed for particles using a Tencor SP1 particle scanning equipment available from KLA Tencor.

Comparative Examples 1-3 A Full-FlowTM 8100 Wet Processing System manufactured by CFM Technologies, Inc. was fully loaded with copper containing wafers. The vessel was filled with the chemical treatment solution shown for Comparative 1 in Table 1 at a rate of 12 gallons per minute for a total injection time of 120 seconds. The temperature of the chemical treatment solutions was 30 °C. After the vessel was filled, the wafers were soaked in the chemical treatment solution for an additional 120 seconds. During contacting of the wafers with the chemical treatment solution, the wafers were exposed to megasonic energy at a frequency of about 650 kHz for about 1 minute.

The chemical treatment solution was then directly displaced with a rinsing solution of deionized water having a temperature of 30 °C and less than about 100 ppb of oxygen. The deionized water was introduced into the process vessel at a flow rate of 24 gpm for 60 seconds and then cycled to a flow rate of 12 gpm for 60 seconds. This cycling was repeated until the deionized water exiting the process vessel had a resistivity of 5 mega-ohms.

After reaching this resistivity, the flow of deionized water continued to be cycled through the process vessel for an additional minute. The total rinsing time was greater than 3 minutes and the wafers were exposed to megasonic energy during the rinsing.

Following the rinse, the wafers were dried with a drying fluid stream of isopropanol vapor. The isopropanol vapor was directed through the process vessel at a pressure of 1.5 psig, 45 °C for 9 minutes.

Two more batches of wafers were processed in the manner described above for a total of three runs.

Three wafers from each batch of wafers were then analyzed for particle contamination for particles ranging in size from 18 microns to 400 microns with a 6 mm edge exclusion. The average results are shown in Table 2.

The above process was repeated for each of the comparative chemical treatment solutions shown in Table 1. For each comparative example, procedures were the same as above, except that for Comparative 3, the vessel was filled with the chemical treatment solution at a rate of 18 gpm, and the electronic components were soaked, after completing the fill, for one minute with no megasonic energy. Additionally, the electronic components in Comparative 3 were rinsed according to the procedure used for Comparative 1, except that the temperature of the rinse solution was at 45 °C and the total rinsing time was about 2 minutes.

Table 1: Compositions of Chemical Treatment Solution

Example Composition of Chemical Treatment Solution (in parts by volume) H2O H202 NH40H HF HC1 Surf.' Comparative 1 100 1.3 2.2 0.0 0.0 0.6 (treatment with copper oxidizing solution only) Comparative 22 100 0.0 2.2 0.0 0.0 0.6 (treatment with only an NH40H solution containing no oxidizing agent or HF) Comparative3 100 0.0 0.0 0.2 1.0 0.0 (treatment with HF containing solution only) 'Surfactant, VALTRON SP2200, supplied by Valtech Corporation 2 Contained less than about 100 ppb of oxygen Comparative Example 4--Treatment with NH40H solution having no oxidizing agent followed by treatment with HF containing solution The Full Flow vessel used for Comparative Examples 1-3 was fully loaded with copper containing wafers. The vessel was filled with a first chemical treatment solution having a composition of 100: 2.2: 0.6 H20: NH40H: surfactant in parts by volume, less than about 100 ppb oxygen, and a temperature of 30 °C. The first chemical treatment solution was directed in the vessel at a rate of 12 gpm for a total injection time of 120 seconds. After the vessel was filled, the wafers were soaked in the first chemical treatment solution for an additional 120 seconds. During contacting of the wafers with the first chemical treatment solution the wafers were also exposed to megasonic energy at a frequency of about 650 kHz.

The first chemical treatment solution was then directly displaced with a rinsing solution of deionized water (having less than about 100 ppb oxygen) in accordance with the procedure used for Comparative Example 1. The rinse was then directly displaced with a second chemical treatment solution having a composition of 100: 0.2: 1 H2O: HF: HC1 in parts by volume, less than about 100 ppb of oxygen, and a temperature of 30 °C. The second chemical treatment solution was directed in the vessel at a rate of 18 gpm for a total injection

time of 120 seconds. After the vessel was filled, the wafers were soaked in the second chemical treatment solution for an additional 120 seconds (without megasonic energy).

The second chemical treatment solution was then directly displaced with a rinsing solution of deionized water having less than about 100 ppb oxygen in accordance with the procedure used for Comparative Example 3. Following rinsing the wafers were dried in accordance with the procedure used for Comparative Examples 1 to 3.

Two more batches of wafers were processed in the manner described above for a total of three runs.

Three wafers from each batch of wafers were then analyzed for particle contamination for particles ranging in size from 18 microns to 400 microns with a 6 mm edge exclusion. The average results are shown in Table 2.

Example 5--Treatment with copper oxidizing solution followed by treatment with HF containing solution The procedure of Comparative Example 4 was repeated except that the first chemical treatment solution contained H2O : H2O2 : NH40H : surfactant in parts by volume, 100: 2.2: 1.3: 0.25, respectively.

Two more batches of wafers were processed in the manner described above for a total of three runs.

Three wafers from each batch of wafers were then analyzed for particle contamination for particles ranging in size from 18 microns to 400 microns with a 6 mm edge exclusion. The average results are shown in Table 2.

Table 2: Particles Removed Avg. LPD Count' Example Pre Post Delta % Removed | Comparative1 11841 1984-9857 83 Comparative 2 10002 1951-8051 80 Comparative 3 2115 291-1824 86 Comparative4 10002 1943-8059 81 Example5 5334 3-5331 99.9 1 'Average Light Point Defect Count

The data in Table 2 reports the average number of particles per wafer detected on the three wafers. The"Pre"column reports the average number particles per wafer prior to wet processing, the"Post"column reports the average number of particles after wet processing, and the"Delta"column reports the average change in particles per wafer between"Pre"and "Post"wet processing. A negative"Delta"means that particles were removed during wet processing. The"% Removal"column reports the average percentage of particles removed based on the number of particles present on the wafer prior to wet processing.

The data in Table 2 demonstrates that the methods of the present invention are effective in reducing particle contamination during wet processing of copper containing electronic components. For example, in Example 5, by contacting the copper containing wafers with an SC 1 solution, and subsequently contacting the wafers with a solution containing hydrofluoric acid and hydrochloric acid, 99.9 % of the particles were removed. These results are surprising and unexpected when considering the Comparative Examples. For example, when contacting the copper containing wafers with an SC 1 solution (Comparative Example 1), an ammonium hydroxide solution (Comparative Example 2), a hydrofluoric acid/hydrochloric acid solution (Comparative Example 3) or the combination of an ammonium hydroxide solution followed by a hydrofluoric acid/hydrochloric acid solution (Comparative 4) the % particle removal was no higher than 86%. These results are shown schematically in Figure 1.

Figure 1 is a bar graph showing the % particle removal for Comparative Examples 1 to 4 and Example 5. As can be seen in Figure 1, copper containing wafers processed in accordance with the method of the present invention performed unexpectedly better than Comparative Examples 1 to 4.

Although the present invention has been described above with respect to particular preferred embodiments, it will be apparent to those skilled in the art that numerous modifications and variations can be made to those designs. The descriptions provided are for illustrative purposes and are not intended to limit the invention.