KR20130142197A - Cleaning lead-frames to improve wirebonding process - Google Patents

Abstract

The present invention is a method of treating a semiconductor substrate to remove undesired material from the semiconductor substrate or to prepare the surface of the semiconductor substrate for subsequent bonding, the substrate comprising a leadframe comprising a die, bonding pads, contacts and wires. And contacting the substrate with the liquid cleaning composition, and a composition useful in the present method.

Description

CLEANING LEAD-FRAMES TO IMPROVE WIREBONDING PROCESS to Improve Wirebonding Process

This application claims priority to US Provisional Application No. 61 / 478,582, filed April 25, 2011, which is incorporated by reference in its entirety.

The present invention relates to a method of cleaning metal surfaces on semiconductor chips and leadframes to improve wirebonding processes. In particular, the present invention relates to a method comprising exposing a metal surface to an aqueous cleaning solution to remove metal oxides, contaminants, and other residues from metal surfaces on chips and leadframes.

During the production of semiconductor devices, leadframes are traditionally used as a cost-effective way to simultaneously mount and process a plurality of semiconductor dies or chips. Each leadframe typically has a plurality of die pads for mounting the chip. The leadframe also acts as a means for electrically connecting the chip to an external device through the lead of the leadframe. Bonding wires are connected to the electrical contacts found on the leads and chips of the leadframe in a process known as wire bonding. The bond pad typically comprises Al, but it may also be Cu. The other end of the wire is attached to a contact lead (which may be Ag, Au, etc.) on the leadframe.

In related aspects, a conventional conventional process for manufacturing a die package is shown in FIG. 1. First, in step 10, the die is cut or sawed from the wafer on which the die is formed. After the die is cut from the wafer, the backside of the die is firmly attached to the carrier or leadframe in die bonding or die attach step 12. Typically, in die bonding step 12, the die is attached to the leadframe using an organic adhesive, for example epoxy, which is then cured by baking. Immediately after the epoxy has cured, in step 14, the die is bonded to the leadframe.

The above-described process of joining metal wires to bonding pads and contacts is called "wirebonding". One problem that can occur during wirebonding is that the metal wire is not sticky to the bond pads and / or contacts. Poor adhesion between the wire and the bond pad / contact can have several reasons, for example, the metal surface is oxidized and contaminants are present on the metal surface. Poor adhesion between metal wire and bond pads / contacts results in no stick on pads (NSOP), non stick on leads (NSOL), short tails, lifted ball defects, poor intermetallic compound uniformity, Such mechanisms, such as bond pad cratering, voiding, and the like, can cause process failures directly or indirectly. These not only result in insufficient bonding process, but can also result in poor device reliability. In order to improve the adhesion, the metal surface must be cleaned before wirebonding.

Conventionally, before the wire bonding step 14, the front face of the die is cleaned by, for example, treating the leadframe and attached die with an argon plasma. However, this argon plasma process has several disadvantages. For example, the argon plasma process does not completely clean residues and particulates on Cu and Al bond pads. In addition, the argon plasma process does not efficiently remove copper or aluminum oxide from the bond pads. As a final example, the argon plasma process does not efficiently remove other contaminants such as fluorine from the Al bond pads without damaging the components being processed. Accordingly, there is a need for a method of cleaning the metal surfaces involved in a wirebonding process, such as, for example, wires, bond pads, and leadframe contacts, which does not exhibit the disadvantages described above.

The present invention is a method of treating a leadframe assembly to remove undesired material from the leadframe assembly or to prepare the surface of the leadframe assembly for subsequent bonding, wherein the leadframe assembly includes a leadframe, a die, and a bond pad thereon. A composition comprising one or more of a portion or parts that are bearing dies, contacts, contact leads, and wires, wherein at least a portion of the leadframe assembly or parts of the leadframe assembly comprises water and at least one acid or at least one salt By providing a method comprising the step of contacting with the above, this need is met. The composition used in the contacting step may comprise from 0.003 to about 25 weight percent of one or more carboxylic acids.

The present invention relates to a method for processing a leadframe assembly or substrate comprising at least one of a leadframe and a die, a bond pad, a die-attach material, a mold compound, a list of parts or parts that are contacts and wires. As an example, a leadframe assembly (semiconductor substrate) or a portion thereof may be selected from an acid selected from a carboxylic acid or a polybasic acid and a salt of an acid (e.g., an ammonium salt) and an acid to salt (e.g., Acid buffer solution with a molar ratio of ammonium salt); And optionally, an organic polar solvent which may be miscible in water at all rates; And optionally contacting a composition comprising, consisting essentially of, or consisting of fluoride, and water, in some embodiments, wherein the composition has a pH in the range of about 3 to about 7 May comprise aluminum metal on at least one surface; It provides a method that may include the additional step of drying the semiconductor substrate.

In another aspect, the invention processes a semiconductor substrate or leadframe assembly or substrate to remove undesired material from the semiconductor substrate or leadframe assembly or substrate or to prepare the surface of the leadframe assembly or substrate for subsequent bonding. The method of claim 1, wherein the leadframe assembly comprises a leadframe comprising at least one of a die, a bond pad, a die-attach material, a mold compound, a parts list of contacts and wires, wherein the leadframe or portion of the leadframe is approximately 0.005. To about 16% by weight of at least one carboxylic acid, salts thereof, or mixtures thereof, or amine group-containing carboxylic acids, salts thereof, or mixtures thereof; From about 0.003 to about 4 weight percent of at least one hydroxyl carboxylic acid, salts thereof, or mixtures thereof or amine group-containing hydroxyl carboxylic acid, salts thereof, or mixtures thereof; And contacting a composition comprising, consisting essentially of, or consisting essentially of the remainder of water, wherein the semiconductor substrate comprises copper metal on at least one surface. step; And drying the semiconductor substrate. In some embodiments, dicarboxylic acids are preferred.

In another aspect, the invention is a method of processing a leadframe assembly comprising a leadframe, wherein the one or more individual dies are attached to a leadframe comprising contact leads (eg, aluminum, copper, Ni, Pd, Au, Ag and Mg) forming an assembly having a metal surface; An acid buffer having a leadframe assembly having a carboxylic acid or polybasic acid and a salt of an acid (eg, ammonium salt) in a molar ratio of acid to salt (eg, ammonium salt) ranging from 10: 1 to 1:10; And optionally organic polar solvents (ie solvents miscible in water in all proportions); And optionally contacting a composition comprising, consisting essentially of, or consisting of fluoride, and water, wherein the composition can have a pH in the range of about 3 to about 7; Drying the substrate; Performing a wirebonding step comprising attaching a wire between the bond pad on the die and the contact lead on the leadframe to form the die and leadframe assembly; And forming a mold over the die and leadframe assembly to form a packaged circuit.

In another aspect, the invention provides a method of processing a microelectronic device substrate comprising a leadframe, comprising: attaching individual dies to a leadframe comprising a contact lead to form a substrate having an exposed aluminum metal surface; The semiconductor substrate may comprise about 0.005 to about 16 weight percent of at least one dicarboxylic acid, salts thereof, or mixtures thereof; From about 0.003 to about 4 weight percent of at least one hydroxyl carboxylic acid, salts thereof, or mixtures thereof or amine group-containing acid, salts thereof, or mixtures thereof; And contacting with the composition substantially comprising, consisting essentially of, or consisting of, water having a pH of about 1 to about 4; Drying the substrate; Performing a wirebonding step comprising attaching a wire between the bond pad on the die and the contact lead on the leadframe to form the die and leadframe assembly; And forming a mold over the die and leadframe assembly to form a packaged circuit.

Other aspects, features and embodiments of the invention will become more fully apparent from the following description and the appended claims. All weight percents described herein are based on the total weight of the composition, unless stated otherwise. “Consisting essentially of” refers to the removal of metal oxides from the bond pads of a leadframe assembly when these compositions are added to the same claimed cleaning composition when these unclaimed components are used in the same cleaning process. It means that it may contain ingredients that are not claimed so long as they do not substantially affect it. The removal rate of the metal oxide from the leadframe assembly is preferably about 2 dB / min or more. The oxide removal rate is not intended to indicate a limitation of the leadframe cleaning process. For example, in a batch cleaning process, several leadframes can be immersed in a cleaning batch containing the cleaning solution described herein that provides an oxide removal rate of 1 to 2 kPa / min for a long time, for example 100 minutes. You can still get a clean leadframe.

The invention also provides a leadframe cleaning composition useful in the methods described herein.

The foregoing summary, as well as the following detailed description of the preferred embodiments of the invention, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, presently preferred embodiments are shown in the drawings. However, it is to be understood that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings,
1 is a block diagram illustrating typical steps involved in the manufacture of an integrated circuit device.
2 is a block diagram illustrating the steps of the method of the present invention.
3 is a graph illustrating the aluminum surface treatment performance of one embodiment of the present invention.
4 is a graph illustrating the performance of one embodiment of the present invention.
5 is a graph illustrating the performance of one embodiment of the present invention.
6 is a graph illustrating the performance in terms of copper oxide removal and re-growth for one embodiment of the present invention.
7 is a graph illustrating the performance in terms of copper oxide removal and re-growth for one embodiment of the present invention.

The present invention relates to a composition for processing a microelectronic device substrate and package comprising a composition useful for the preparation of a metal surface during a process of connecting metal wires from a bond pad to a leadframe during a wirebonding process. The term "leadframe" may be used, but is not intended to be limited to, and includes all types of semiconductor packaging substrates, such as plated or unplated BGA and organic substrates and leadframes. The invention also relates to a method of treating a leadframe assembly or semiconductor substrate to remove undesired material from the leadframe assembly or semiconductor substrate or to prepare the surface of the leadframe assembly or semiconductor substrate for subsequent bonding. The term "leadframe assembly" or "leadframe substrate" shall include other components that are part of at least one die joined and attached thereto, eg, bonded or soldered thereto. It may be used to mean any type of leadframe that may be, but is not intended to be limited thereto.

For ease of reference, “microelectronic devices” correspond to semiconductor substrates and packages, flat panel displays, and micromechanical systems (MEMS), fabricated for use in microelectronic, integrated circuit, or computer chip applications. The term “microelectronic device” is not intended to be limiting in any way, and will be understood to include any substrate that eventually becomes a microelectronic device or a microelectronic assembly. Preferably, the microelectronic device comprises a leadframe assembly or a semiconductor substrate.

As used herein, "carboxylic acid" refers to an amine group containing mono-, di- or poly-carboxylic acid, salts thereof or mixtures thereof, hydroxy group containing mono-, di- or (unless otherwise defined or apparent from the context). Mono-, di- or poly-carboxylic acids, including poly-carboxylic acids, salts thereof or mixtures thereof and / or other group-containing mono-, di- or poly-carboxylic acids.

The term "semiconductor substrate" as used herein includes any substrate or partially formed package that eventually becomes a microelectronic device or microelectronic assembly. Preferably, the semiconductor substrate comprises a leadframe assembly comprising a die attached to the leadframe.

As used herein, “about” is intended to correspond to ± 5% of the stated values.

As used herein, “suitability” for cleaning contaminants from a microelectronic device having the contaminants thereon (including metal oxides) thereon refers to a microelectronic device, more specifically a leadframe assembly or a leadframe assembly. Corresponds to the removal of at least some of the residues / contaminants from the component, for example a die or a bonding pad on the die. Preferably, at least 90% of the residues / contaminates are removed from the microelectronic device, more particularly the leadframe assembly or parts of the leadframe assembly, for example a die or bonding pads on the die, using the compositions and methods of the present invention. More preferably, at least 99% of the residues / contaminants are removed.

Due to advantages in electrical performance and cost, fabricating integrated circuits using copper or aluminum wiring metallization techniques has become popular. To prevent the intermetallic phase, the IC is provided with copper or aluminum pads. Typically, wire bonding of ICs and chip carriers or leadframes is performed using gold and copper wire materials, but aluminum and silver have also been used. Bonding these wires to different pad materials forms different metallurgical systems. In recent years, there is a tendency to move from gold to copper wire mainly due to reasonably low cost reasons.

Unfortunately, both copper and aluminum oxidize very quickly, making it more difficult to achieve reliable wire bonds. Accordingly, to ensure the bondability and reliability of the wire bond, one of the important conditions is that there should be no or substantially no contaminants including oxides on the bond surface. Typically, multiple circuits are formed in one place on a single wafer, after which the wafer is moved elsewhere, where the die is cut from the wafer and packaged. Since significant time may elapse between the wafer fabrication and packaging process, oxidation of the copper or aluminum bond pads on the die may occur during this time. Accordingly, the present invention provides for effective cleaning of copper and aluminum pads of integrated circuits after fabricating the circuit on the wafer, but before the die is encapsulated or fully packaged.

With reference to FIG. 2, a method of manufacturing a semiconductor wafer having a plurality of integrated circuits formed thereon is provided. The integrated circuit may have a bonding pad formed of copper or aluminum. Methods of forming circuits with such pads on silicon wafers are known and detailed discussion thereof is not required for the understanding of the present invention. It is understood that the processes of the present invention are performed after the integrated circuit (s) are formed on the wafer. Generally, this is after all layers have been applied to the wafer, the wafer is rinsed in deionized water and the backside of the wafer is ground to remove unwanted material. Subsequently, the wafer is processed in a test / assembly / packaging facility where a test of each chip or die is performed as a wafer, and in this step known as wafer level testing, a good die is identified. Thereafter, the wafer is diced or singulated by a dicing process. Each resulting chip or die ("known good die") determined to have passed the wafer level test applies epoxy, solder paste or other adhesive material to the leadframe and / or the surface, which may be the back side of the die or dies, and The die may be attached to the leadframe by a die attach process step or steps comprising attaching the die or dies to the die. The leadframe may have solder bumps or stud bumps or similar attachment parts formed thereon to receive the die, on which epoxy, solder paste or other adhesive material is applied or received. Typically, the leadframe may be in the form of a strip or continuous tape / reel, which contains a number of attached dies that are subsequently formed into a package. Where epoxy is applied, the leadframe or substrate may then be epoxy-cured in a high temperature process to ensure proper adhesion of the die to the substrate. If solder paste is used, this will be done after the soldering step. The wire is then connected between the bond pad on the die and the contacts on the leadframe. Such a leadframe or leadframe assembly will be singulated to form individual packages that are molded and encapsulated (hereinafter). FIELD OF THE INVENTION The present invention relates to cleaning performed on leadframe assemblies that may occur after high temperature epoxy curing or other die attach steps and prior to wire bonding, to remove oxides and other contaminants from metal bond pads and leadframe or substrate contacts and surfaces. Is provided for.

Referring to FIG. 2, a method of manufacturing a semiconductor wafer having a plurality of integrated circuits formed thereon is described. The integrated circuit may have a bonding pad formed of copper or aluminum. Methods of forming circuits with such pads on silicon wafers are known and detailed discussion thereof is not required for the understanding of the present invention. It is understood that the method of the present invention is performed after the integrated circuit (s) are formed on the wafer. Generally, this occurs after all the layers have been applied to the wafer, the wafer is rinsed in deionized water and the backside of the wafer is ground to remove unwanted material, and further preferably, after the test of each chip or die is performed. Typically, after the test and before dicing is performed, the wafer is cleaned again using solvents such as deionized water, isopropyl alcohol, acetone and methanol. The present invention relates to cleaning performed after the wafer is typically tested, and either before or after formation of the leadframe assembly, and provides for attaching the leadwire to the bond pad after removing oxide from the metal bond pad. . After these steps, the step of molding the packing for the leadframe assembly may typically follow under vacuum. Although not shown in FIG. 2, the method of the present invention leads to a bond pad immediately before or after formation of the leadframe assembly, after formation of the leadframe assembly (ie, after attaching the die (s) to the leadframe). After the attachment of the wire, a method of performing a cleaning step is included.

More specifically, starting from step 20 divided into steps 20A and 20B, the wafer, and in particular the metal bond pads of each die, are represented by either of two cleaning compositions, Composition A or Composition B. In contact with the cleaning compositions, such compositions will be described in more detail below (the method in FIG. 2 can be represented by a single cleaning step). Preferably, the cleaning step of the method of the present invention comprises a leadframe assembly, or at least a portion of the leadframe assembly, for example a die or a bond pad on the die, which may already be attached to the leadframe, using composition A (preferably Al— Adhering to either the containing substrate) or Composition B (preferably, to an Al-containing or Cu-containing substrate). At least a portion of the leadframe assembly preferably contains from about 1 minute to about 40 minutes, preferably from about 5 minutes to about 30 minutes, and more preferably from about 20 to about 30 minutes, at room temperature or at an elevated temperature in a batch comprising the composition. Dip or immerse for hours.

The composition used to clean the bond pad of the leadframe assembly comprises an aqueous solution comprising an acid or salt or a mixture of acids and salts. The composition used to clean the bond pad of the leadframe assembly comprises an aqueous solution comprising an acid, preferably at least one carboxylic acid or polybasic acid. The composition may comprise water and about 0.003% to about 25% by weight of one or more acids. Some embodiments of the composition may have a pH of 1 to 7. In some embodiments, the composition comprises an acid buffer and the acid is part of the acid buffer. In other embodiments, the composition comprises one or more carboxylic acids. The composition may comprise one or more acids and / or one or more solvents and / or one or more fluorides (also referred to as fluoride containing compounds) and / or one or more additives. The additives may include surfactants and / or corrosion inhibitors. For example, some embodiments of the compositions useful in the methods of the present invention include citric acid, and optionally surfactants. Some embodiments of the composition include, in addition to one or more acids, 0 weight percent or 30 weight percent to 90 weight percent organic polar solvent; 0.0005% to 20% by weight of fluoride; 0.5% to 40% by weight of water; Up to 15% by weight of optional corrosion inhibitors and / or surfactants. Examples of some compositions useful in the method of the present invention include water, acetic acid or citric acid, ammonium fluoride and dimethylacetamide and optionally propylene glycol and optionally corrosion inhibitors.

Composition A will be used to refer to a composition useful in the method of the present invention for cleaning a leadframe assembly comprising an acid buffer. Composition B will be referred to as a composition useful in the method of the present invention for cleaning a leadframe assembly that does not include an acid buffer.

Composition A

In one embodiment of the invention, the cleaning composition is composition A. Composition A is a cleaning composition comprising an acid buffer and water, and may also comprise a polar solvent (ie preferably miscible in water in all proportions), and / or fluoride. In certain embodiments, the composition is adjusted to a pH in the range of about 3 to about 7 and optionally comprises corrosion inhibitors and / or other additives. Some embodiments of composition A may be corrosion inhibitor-free and / or additive-free and / or surfactant-free and / or solvent free. The acid that is part of the acid buffer preferably comprises carboxylic acid and / or polybasic acid.

Preferably, Composition A comprises an amount of acid buffer required to obtain a composition having a pH in the range of 3-7; 0% to 90% by weight or 30% to 90% by weight of organic polar solvent miscible in water in all proportions; 0.001% to 20% by weight of fluoride; 0.5 wt% to 40 wt% water; And up to 15% by weight of a corrosion inhibitor (and / or other additives). In alternative embodiments, the composition may comprise up to 90% or more than 90% by weight of water.

As mentioned above, Composition A described herein comprises an acid buffer. Acid buffers, when added to the compositions described herein, provide a buffered composition with a pH adjusted to minimize corrosion of sensitive metals such as aluminum, copper, titanium, and the like. Acid buffer is added in an amount necessary to obtain the desired pH range for the composition. As used herein, the term “acid buffer” is a solution that resists changes in pH as a result of small additions of acids or bases to the composition. The addition of acid buffers to the compositions described herein prevents pH swings due to dilution with water or contamination with bases or acids.

To provide such a buffering effect in the composition, the molar ratio of acid to its conjugate base in acid buffer ranges from 10: 1 to 1:10, or substantially 1: 1, or 1: 1, which is Substantially means ± 2% by weight of the same molar concentration. Buffers are commonly thought of as weak acids and the widest buffer range for either acid or base is about 1 pH unit for each side of pK _a of weak acid groups. The setting of the pH for the buffer may be a conjugate base (or in certain embodiments, an acid and an acid of 10: 1 to 1:10, or substantially 1: 1, with an appropriate pK _a for the desired pH range. Protonated base) in the molar ratio of acid to base.

In addition, certain salts having _a pK _a of less than about 6 when dissolved in water can be used with or without acid when dissolved in water to prepare the cleaning composition.

In certain preferred embodiments, the acid buffer contains an ammonium salt of carboxylic acid or polybasic acid, for example phosphoric acid. Exemplary acid buffers include acetic acid / acetate salts (eg, ammonium salts, amine salts, etc.), benzoic acid / benzoate salts (eg, ammonium salts, amine salts, etc.), and phenolic acid / phenolate salts. (Eg, ammonium salts, amine salts, and the like). Examples of ammonium salts are the ammonium salts of acetic acid or phosphoric acid. In one embodiment, the acid buffer is an aqueous solution of ammonium acetate and acetic acid. In another embodiment, the acid buffer is benzoic acid and ammonium benzoate.

The composition may comprise 0.003 to 30% by weight, or 0.5 to 25% by weight, or 0.5 to 20% by weight, or 0.5 to 15% by weight acid, ie the acid used in the buffer. In certain embodiments, the acid buffer may contain a weak acid such as trihydroxybenzene, dihydroxybenzene, and / or salicylic hydroxamic acid. In such embodiments, the amount of weak acid added may range from 0.003 to 30 weight percent, or from 0.5 to 25 weight percent, or from 0.5 to 20 weight percent, or from 0.5 to 3 weight percent. The amount of conjugate base depends on the amount of acid added to the composition to provide a buffer solution to the composition.

Although the pH of the composition according to the invention may be from 1 to 11, in certain embodiments, the pH in the range of about 3 to about 9 or in the range of about 3 to about 7, or in the range of about 3 to about 6 is the most sensitive metal. May be passivated with minimal corrosion. Preferably, the pH ranges from about 3 to about 7.

One or more organic polar solvents that may be added to the compositions described herein are solvents miscible with water. These solvents may be used alone or in any combination. One or more solvents may be present in the composition and may include about 0% to about 90% by weight, or 30% to about 90% by weight, or about 30% to about 70% by weight, and all proportions in water It may be an organic polar solvent miscible with. Examples of organic polar solvents include dimethylacetamide (DMAC), monoethanolamine, n-methylethanolamine, formamide, n-methyl formamide, gamma-butyrolactone, N-methylpyrrolidone, and the like. It is not limited to this. Still other solvents include dihydric and polyhydric alcohols such as diols and polyols such as (C ₂ -C ₂₀ ) alkane diols and (C ₃ -C ₂₀ ) alkane triols, cyclic alcohols and substituted alcohols. Other solvents include urea such as dimethyl urea, tetramethyl urea and the like. Specific examples of such organic polar solvents are propylene glycol, tetrahydrofurfuryl alcohol (THFA), diacetone alcohol and 1,4-cyclohexanedimethanol. Preferred solvents include one or more of dimethylacetamide, dimethyl urea, propylene glycol, which are used alone or in combination with one another or with other solvents.

In certain embodiments, the organic polar solvent can be one or more glycol ethers. Glycol ethers are typically water miscible and are glycol mono (C ₁ -C ₆ ) alkyl ethers and glycol di (C ₁ -C ₆ ) alkyl ethers, such as (C ₁ -C ₂₀ ) alkane diols, (C _1- C ₆ ) alkyl ethers, and (C ₁ -C ₂₀ ) alkane diol di (C ₁ -C ₆ ) alkyl ethers, but are not limited thereto. Examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene Glycol monopropyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monobenzyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene Glycol monomethyl ether, triethylene glycol dimethyl ether, polyethylene glycol monomethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, ethylene glycol monomethyl ether acetate, ethylene Recall monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether , Dipropylene monobutyl ether, dipropylene glycol isopropyl ether, tripropylene glycol monomethyl ether, 1-methoxy-2-butanol, 2-methoxy-1-butanol, 2-methoxy-2-methylbutanol, 1 , 1-dimethoxyethane and 2- (2-butoxyethoxy) ethanol. More common examples of glycol ethers are propylene glycol monomethyl ether, propylene glycol monopropyl ether, tri (propylene glycol) monomethyl ether and 2- (2-butoxyethoxy) ethanol. One example is dipropylene glycol monomethyl ether used alone or in combination with other solvents in the compositions used in the present invention.

Fluoride is preferably present in the composition of Composition A described herein. Fluoride, also referred to as a fluoride-containing compound, has the general formula R ₁ R ₂ R ₃ R ₄ NF, wherein R ₁ , R ₂ , R ₃ , and R ₄ are independently hydrogen, alcohol groups, alkoxy groups, alkyl Groups or mixtures thereof). Examples of such compounds are ammonium fluoride (NH ₄ F), tetramethyl ammonium fluoride, tetraethyl ammonium fluoride, tetrabutyl ammonium fluoride and choline fluoride. Another example of fluoride-containing compounds includes fluorinated boric acid and hydrofluoric acid. The fluoride is preferably present in an amount of 0.0005 or 0.001% to 20% by weight, or 0.1% to 10% by weight. Ammonium fluoride is preferred. In such embodiments, ammonium fluoride may be commercially available as a 40% aqueous solution.

Water is present as an element of the compositions of the present invention and compositions used in the methods of the present invention. It may be present simultaneously as a component of the other components of the invention, for example as an aqueous solution of ammonium fluoride or as an aqueous solution of acid buffer, or may be added separately. Preferably the water is present in an amount from 0.5% to 40% by weight. In certain embodiments, the presence of water can improve the solubility of ammonium fluoride in the compositions of the present invention and aid in the removal of contaminants.

Corrosion inhibitors in amounts up to 20% by weight may be added to the compositions of the present invention. Preferably, the inhibitor concentration is about 0.5% to 8% by weight. For similar applications any corrosion inhibitors known in the art can be used, for example the corrosion inhibitors described in US Pat. No. 5,417,877, which is incorporated herein by reference. In certain embodiments, it has been found that inhibitor compositions having _a pK _a greater than 6, as well as inhibitor compositions having _a pK _a less than about 6, do not work in a system having a pH range of about 3 to about 6. Accordingly, preferred inhibitor compositions are inhibitor compositions having _a pK _a of about 6 or less. For lower pH cleaning solutions, a pK _a of less than about 4 may be desirable. Corrosion inhibitors can be organic acids, organic acid salts, phenols, triazoles, or hydroxylamines. Examples of preferred inhibitor compositions include anthranilic acid, salicylic acid, gallic acid, benzoic acid, isophthalic acid, maleic acid, fumaric acid, D, L-malic acid, malonic acid, phthalic acid, maleic anhydride, phthalic anhydride, carboxybenzotriazole, diethyl hydroxyl Amines and lactic acid and citric acid salts thereof and the like. Further examples of corrosion inhibitors that may be used include catechol, tert-butyl catechol, pyrogallol, and esters of gallic acid, or esters of catechol, salicylic acid, pyrogallol, and gallic acid.

The composition may also include one or more of the following optional additives: surfactants, chelating agents, chemical modifiers, dyes, biocides, and other additives. The additive (s) may be added to such an extent that does not adversely affect the pH range of the composition. Some examples of illustrative additives include acetylenic alcohols and derivatives thereof, acetylenic diols (nonionic alkoxylated and / or self-emulsifiable acetylenic diol surfactants) and derivatives thereof, alcohols, quaternary amines and di Amines, amides (including aprotic solvents such as dimethyl formamide and dimethylacetamide), alkyl alkanolamines (eg diethanolethylamine), and chelating agents such as beta-dike Tones, beta-ketoimines, carboxylic acids, malic acid and tartaric acid based esters and diesters and derivatives thereof, and tertiary amines, diamines and triamines. Also included herein are surfactants and other additives, which are described below in the amounts described for surfactants for Composition B. In certain embodiments, carboxylic acids that may be added to the composition in acid buffer may also be provided as chelating agents.

Formulations suitable for use as Composition A in the present invention are described in US Pat. No. 6,828,289 and US Pat. No. 7,361,631, the contents of which are incorporated herein by reference in their entirety.

Composition B

Composition B will refer to a composition useful in the method of the present invention for cleaning a leadframe assembly that includes one or more acids but no acid buffer.

Composition B is a fluoride-free or fluoride containing aqueous composition. The term “fluoride-free” refers to at least substantially fluoride-free (eg, containing up to about 100 ppb of fluoride). Composition B may comprise from about 0.003 to about 25 weight percent acid, preferably one or more carboxylic acids and water (in aqueous solution). In some embodiments, the composition may comprise about 0.003 to about 25 weight percent acid, water, and up to 20 weight percent of one or more surfactants and / or one or more corrosion inhibitors. In some embodiments, the surfactant comprises one or more sulfonic acid surfactants.

In some embodiments, Composition B comprises from 0.005 to about 16 weight percent of at least one carboxylic acid, salts thereof, or mixtures thereof, which may be amine group-containing carboxylic acids, salts thereof, or mixtures thereof; And / or from about 0.003 to about 4 weight percent of at least one hydroxyl carboxylic acid, salts thereof or mixtures thereof or amine group-containing carboxylic acid, salts thereof or mixtures thereof, and substantially the balance of water. And a pH of about 1 to about 4.

In another embodiment, Composition B comprises from 0.005 to about 16 weight percent of at least one dicarboxylic acid, salts or mixtures thereof, from about 0.003 to about 4 weight percent of at least one hydroxy carboxylic acid, salts thereof or mixture; Or an amine group-containing carboxylic acid, salts thereof, or mixtures thereof, and substantially the remainder of water, and having a pH of about 1 to about 4.

Typical carboxylic acids include dicarboxylic acids including carboxylic acids having 2 to 6 carbon atoms and include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid. Preferred acids are citric acid. Suitable salts include alkali metal and ammonium salts. Mixtures comprising citric acid and oxalic acid and optionally malonic acid can be used in composition B. Examples of amine group containing dicarboxylic acids include glutamic acid and aspartic acid.

Examples of hydroxycarboxylic acids include malic acid, tartaric acid and citric acid. Preferred hydroxycarboxylic acids are citric acid. Suitable salts include alkali metals, and ammonium salts.

Preferred salts of hydrocarboxylic acids are ammonium citrate.

The amine containing carboxylic acid may be glycine, valine, alanine, phenylalanine and the like.

Preferred mono-carboxylic acids include formic acid, acetic acid and propionic acid.

In certain embodiments, composition B may further comprise at least one solvent, preferably an organic solvent or an organic polar solvent, preferably an organic solvent or organic polar solvent miscible with water. These solvents may be used alone or in combination. All solvents described above as useful in Composition A are useful in any of the compositions of the present invention. Preferred solvents for use in Composition B include dimethylacetamide (DMAC), monoethanolamine, n-methylethanolamine, formamide, n-methyl formamide, gamma-butyrolactone, and N-methylpyrrolidone, and the like. Dihydric and polyhydric alcohols such as diols and polyols such as (C ₂ -C ₂₀ ) alkane diols and (C ₃ -C ₂₀ ) alkane triols, cyclic alcohols and substituted alcohol ureas such as dimethyl urea and Tetramethyl urea and the like, but are not limited thereto. Specific examples of such organic polar solvents are propylene glycol, tetrahydrofurfuryl alcohol (THFA), diacetone alcohol and 1,4-cyclohexanedimethanol and propylene glycol monomethyl ether. The solvent, if present, is preferably present in an amount of 0% to 60%, or 0% to 40%, or 10% to 40% by weight.

Composition B may further comprise one or more fluorides (ie, fluoride containing compounds) described above for composition A. Examples of such compounds are ammonium fluoride, tetramethyl ammonium fluoride, tetraethyl ammonium fluoride, tetrabutyl ammonium fluoride and choline fluoride. Another example of fluoride containing compounds includes hydrofluoric acid. The fluoride containing compound, if present, is preferably 0.0005% to 20% or 0.001% to 20% or 0.1% to 10% or 0.001% to 5% or 0.001% to 2 Present in weight percent. Ammonium fluoride is preferred. In some embodiments, ammonium fluoride may be commercially available as a 40% aqueous solution. In compositions comprising fluorides, it is preferred that an organic solvent is also present in this composition, but also embodiments of Composition B with fluoride and no organic solvent, and other organic solvents with no fluoride in the composition Embodiments exist.

In addition to water, preferably deionized water, composition B may comprise one or more of the following optional additives: surfactants, biocides, corrosion inhibitors, chelating agents, chemical modifiers, dyes, and other additives. One example of an additive includes up to about 0.002% by weight of the active portion of the biocide. A common biocide is Katan. Catan

1.2% 5-chloro-2-methyl-4-isothiazolin-3-one

0.4% 2-methyl-4-isothiazolin-3-one

1.1% MgCl ₂

1.75% Mg (NO ₃ ) ₂

0.16% Copper Nitrate Trihydrate

Contains 95.85% of water. Biocides can be used in any of the compositions of the present invention.

The additive (s) may be added in a range that does not adversely affect the desired pH range of the composition. Some examples of illustrative additives include surfactants such as acetylenic alcohols and derivatives thereof, acetylenic diols (nonionic alkoxylated and / or self-emulsifiable acetylenic diol surfactants) and derivatives thereof, sulfols Phonic acid surfactants such as linear alkylbenzenesulfonates (LAS), straight chain fatty acids and / or salts thereof, coconut oil fatty acid derivatives, tall oil acid derivatives, sarcosides, acetylated polypeptides, secondary alkylbenzenesulfonates, lignin Sulfonates, N-acyl-n-alkyltaurates, fatty alcohol sulfates (FAS), crude sulfonates, secondary alkanesulfonates (SAS), paraffin sulfonates, fatty alcohol ether sulfates (FAES), α-olefin sulfonates , Sulfosuccinate esters, alkylnaphthalenesulfonates, isethionates, sulfate esters, sulfated linear primary alcohols, sulfated polyoxy Tyleneated straight chain alcohols, sulfated triglyceride oils, phosphoric and polyphosphoric esters and perfluorinated anions and mixtures of these and any of the surfactants and other known surfactants described herein, alcohols, quaternary amines and Di-amines, amides (aprotic solvents such as dimethyl formamide and dimethyl acetamide), alkyl alkanolamines (eg diethanolethylamine), and chelating agents such as beta-diketones, Beta-ketoimines, carboxylic acids, malic acid and tartaric acid based esters and diesters and derivatives thereof, and tertiary amines, diamines and triamines. In certain embodiments, carboxylic acids that may be added to the composition may also be provided as chelating agents. The additives may be commercially available in relatively pure form or as diluted components in water or other solvents. For example, SAS-10 is available as SAS at a concentration of 10% by weight in water. The additive may also include a corrosion inhibitor, preferred corrosion inhibitors are described above for composition A. However, in certain embodiments, the inhibitor composition having a pK _a of greater than about 4, as well as inhibitor compositions having a pK _a of less than about 4 does not function in a system with a pH range of from about 1 to about 4. The total amount of the additive, when present, is typically about 0.001 to about 10, or about 0.005 to about 5, or about 0.01 to about 1 weight percent. Preferred additives are one or more surfactants and / or corrosion inhibitors. In embodiments involving carboxylic acids, surfactants and water, preferred surfactants are one or more sulfonic acid surfactants.

One preferred embodiment includes one or more acids, one or more fluorides, one or more organic solvents and one or more surfactants in the weight ranges defined herein for Composition B. Another preferred embodiment is a composition comprising one or more acids, one or more fluorides, one or more organic solvents, and one or more corrosion inhibitors in the weight ranges defined herein for Composition B. Other compositions include water and acids, and each of the fluorides, solvents and additives is an optional component.

Composition B typically comprises more than 35% by weight of water. In solvent-free embodiments, Composition B typically comprises more than about 50, or more than about 75, or more than about 90, or more than about 95.5, or more than about 98 weight percent water. When composition B comprises one or more solvents, composition B typically comprises 35 to 95 wt% water or 40 to 90 wt% water or 45 to 85 wt% water.

The carboxylic acid or dicarboxylic acid and / or salt is typically present in an amount of about 0.005 to about 16 weight percent, more typically about 0.1 to about 3 weight percent and preferably about 0.3 to about 0.5 weight percent. When a mixture of acids is used, for example oxalic acid and malonic acid, or a mixture of citric acid and oxalic acid, each of these is typically from about 0.003 to about 8 weight percent, more typically from about 0.05 to about 1.5 weight percent, and preferably It is present in an amount of about 0.1 to about 0.3% by weight.

The hydroxycarboxylic acid, when present in the composition, is typically in an amount of about 0.003% to about 8% by weight, more typically about 0.05 to about 1.5% by weight, and preferably about 0.1% to about 0.3% by weight. Present in the composition.

When used, amino-group containing acids, such as glycine, when present in a composition, are typically from about 0.003 to about 4 weight percent, more typically from about 0.005 to about 1.5 weight percent, and preferably from about 0.005 to about Used in amounts of 0.05% by weight.

Although the pH of the composition according to the invention may be between 1 and 11, for composition B, the pH is preferably between about 1 and about 4, and more preferably between about 1 and about 3, with a specific example being about 2. . pH is typically measured using pH paper or a suitable pH reference electrode. According to the present invention, pH was found to be important for achieving the objects of the present invention. In particular, the compositions include metallic and non-metallic particulate oxides, as well as silicon dioxide; Metal ion contaminants such as K, Ca, Ti, Cr, Mn, Fe, Ni, Cu and Zn; Various sulfur and chloride impurities adsorbed on various surface materials present on the die or substrate can be removed.

Another feature of the invention is that the composition is relatively stable even in concentrated form. For example, about 0.1 to about 16 weight percent, and preferably about 6 to about 10 weight percent dicarboxylic acid, about 0.05 to about 8 weight percent, and preferably about 3 to about 5 weight percent A concentrate of a composition comprising a dihydroxy carboxylic acid or amino acid of and substantially the remainder of the water may be provided and delivered to an end user, who then subsequently removes it from the process tool for about 19: 1 for convenience and economics. It can be diluted by weight dilution.

Formulations suitable for use as Composition B in the present invention are described in US Pat. No. 6,627,546 and US Pat. No. 7,524,801, the contents of which are incorporated herein by reference in their entirety.

The cleaning method according to the invention leaves the metal surface cleaner clean and thus provides good adhesion between the metal wire and the joining pads on the die and leadframe contacts.

Referring back to FIG. 2, in either step 20A or 20B, after exposing (contacting) a portion of the substrate or leadframe cleaning assembly to the cleaning composition, the substrate is dried and a wirebonding step 14 is performed. The substrate can be actively or passively dried using either ambient or warm air that can be moved relative to the leadframe assembly, for example by a commercial blow dryer or by moving the leadframe assembly. Alternatively, the substrate can be dried using compressed air or a gas such as nitrogen. The drying time can vary from a few seconds to a few minutes. However, since the metal pad can be oxidized, it is desirable that the substrate is not exposed to ambient air for an extended time.

The rinsing step with deionized water can be carried out after the washing step and before the drying step.

Immediately after the wirebonding is completed, the substrate is molded in step 16. Preferably, the substrate is vacuum packed in step 16. Vacuum packing can be carried out using generally known commercially available vacuum packing equipment. Preferably, the substrate is packed in a shock proof container made of non-reactive material.

As will be evident, the present invention relates to a die having a metal pad, such that when the die on the wafer is ready to be packaged, the metal pad has less oxidation and other contaminants and thus wire bonding of the pad forms a more reliable bond. It provides a method of manufacturing. The invention also provides a method of making a die with metal bond pads during a die packaging process that reduces oxidation and other contaminants on the metal bond pads so that wire bonding of the pads can form more reliable bonds. As will be appreciated, the present invention relates to a method of manufacturing metal bond pads, such as, for example, copper and aluminum pads for wirebonding. The present invention is not limited to the use of copper wire for wirebonding as other wires, for example gold or aluminum, can be used. In addition, although the present invention is carried out using ball bonding, it is not limited to ball bonding, but may be implemented by wedge bonding.

Although the present invention has been described primarily in connection with cleaning semiconductor substrates, the cleaning compositions of the present invention can be used to clean any substrate, including organic and inorganic residues.

Example

The following example illustrates that cleaning solutions A1, A2, B1, and B2 remove metal oxides on the bond pads and contacts. This cleaning solution will also remove contaminants, fluorine, and other residues on the bond pads and contacts. This cleaning solution will remain on the metal surface in the detergent state, so that the metal wire will have good adhesion during wirebonding. Cleaning solutions A1 and A2 correspond to composition A, which will remove metal oxides from the Al bond pads. Cleaning solutions B1 and B2 correspond to composition B, which will remove metal oxides from the Cu bond pad. The compositions evaluated are as follows:

Washing solution A1 : dimethylacetamide (57.5%); DI water (13.9%); Ammonium acetate (15.6%); Acetic acid (12.0%); Ammonium fluoride (1.0%).

Washing solution A2 : N-methyl-2-pyrrolidone (63.9%); DI water (30.0%); Ammonium acetate (2.6%); Acetic acid (2.0%); Ammonium fluoride (0.50%); Carboxy benzotriazole (1.0%).

Washing solution B1 : DI water (98.333%); Citric acid (0.667%); Malonic acid (0.333%); Oxalic acid (0.667%).

Washing solution B2 : DI water (98.27%); Citric acid (0.667%); Malonic acid (0.333%); Oxalic acid (0.667%); SAS-10 (0.063%).

The process for cleaning the leadframe (die attached) in the cleaning solutions A1, A2, B1, and B2 is as follows. The cleaning solution was applied to the leadframe after the die attach curing step and before the wirebonding step. The cleaning solution was applied to the leadframe in any such way: 1) the leadframe was immersed in a tank of cleaning solution, 2) the cleaning solution was sprayed onto the leadframe. The optimum temperature of the cleaning solution is in the range of 25 ° C to 50 ° C. The optimal exposure time for the cleaning solution ranges from 5 minutes to 30 minutes. After exposure to the cleaning solution, the leadframe was rinsed with deionized water. The optimal temperature for DI water rinse is 25 ° C (room temperature). The optimal time for DI water rinse is in the range of 30 seconds to 3 minutes. After rinsing the leadframe in DI water, the leadframe was dried. Immediately after drying the leadframe, this leadframe can be sent to a wirebonding step.

Of composition A Al Oxide  Ability to remove

The following shows the data collected using X-ray photoelectron spectroscopy (XPS). This data was collected on Al bond pads on the die over the entire wafer. Prior to exposure to cleaning solution A, the thickness of the Al oxide layer on the Al bond pad is about 70-85 mm 3. After exposure to the cleaning solutions A1 and A2, the thickness of the Al oxide was reduced to about 30-40 kPa, which is the typical thickness of the native oxide layer naturally formed on the Al surface. These data show that the cleaning solutions A1 and A2 removed Al oxide, after which the natural layer of Al oxide was grown again. The overall reduction in Al oxide thickness after exposure to cleaning solutions A1 and A2 is large and will improve the adhesion between the metal wire and the Al bond pads during wirebonding.

Table 1 : XPS data for Al oxide thickness / patterned Al bond pad wafer

With reference to FIG. 3, additional data is shown that the cleaning solution A1 removes Al oxide. This data was collected using Auger depth profiling. Prior to exposure to cleaning solution A1, oxygen is present in the Al metal up to a depth of about 100 kPa. Thus, this is a measure of the thickness of the Al oxide layer. After exposure to the cleaning solution A1, oxygen only penetrates to Al to a depth of about 35 kPa. Al oxide thickness was substantially reduced. This is after placing the Al bond pads exposed in air for 3 days. Further data is also shown after the Al bond pads are placed in air for 14 days. In addition, the penetration depth of the oxygen level is much lower than before exposure to the cleaning solution A1.

Ability to remove fluorine on Al bond pads of composition A

Another contaminant on the Al bond pads that can cause poor adhesion is embedded fluorine (F). F can be obtained on the Al bond pad, for example, during a plasma etch process used to etch through the passivation layer and expose the Al bond pad. The plasma is typically CF ₄ based, whereby F from the plasma can be obtained on the Al surface. F can react with moisture in the air to cause corrosion on the Al bond pads. This corrosion will continue as long as F is still present on the Al. Thus, removing this F will minimize the corrosion that occurs when the Al bond pads are placed in air. If less corrosion occurs, the Al surface will be cleaned better and the metal wire will have better adhesion to the bond pads. 4 and 5 illustrate the ability of cleaning solution A1 to remove F from Al bond pads.

Composition A is lower Al Protect

Cleaning solutions A1 and A2 are very effective for removing Al oxide, but such cleaning solutions also need to have very small etch rates for the underlying Al metal phase. If this cleaning solution removes Al oxide and severely etches the underlying Al metal, the wirebonding performance may not be improved. The data in Table 2 below show that the cleaning solutions A1 and A2 have very low etch rates on Al.

Table 2 : Al etching rate

Of composition B Cu Oxide  Remove and re- Growth rate  Ability to minimize

The data illustrated by FIGS. 6 and 7 were collected using ellipsometry. The initial thickness of Cu oxide on the blanket wafer of Cu was measured prior to exposure to cleaning solutions. The data indicate that this initial thickness of Cu oxide (shown at time = −1 day in the graph) is about 25-30 μs thick. After exposure to the cleaning solutions B1 and B2, the thickness of the Cu oxide was reduced to about 5-10 kPa. These data indicate that cleaning solutions B1 and B2 removed most of the Cu oxides. Cu will of course passivate and form a native oxide layer. The thickness of the Cu oxide layer was measured again every other day until 14 days. During these 14 days, the Cu wafers were exposed to ambient air. The data indicate that re-growth of Cu oxide over 14 days is slow. Since cleaning solutions B1 and B2 do not remove only Cu oxide, this cleaning solution minimizes the re-growth rate of Cu oxide.

Composition B is lower Cu Protect

Cleaning solutions B1 and B2 are very effective in providing Cu oxides, but such cleaning solutions also need to have very small etch rates on the underlying Cu metal. If this cleaning solution removes the Cu oxide and severely etches the underlying Cu metal, the wirebonding performance may not be improved. The data in Table 3 below show that the cleaning solutions B1 and B2 have very low etch rates on Cu.

Table 3 : Cu Etch Rate

Further examples of cleaning solution A

The following experiments were performed using a beaker with a stir bar to simulate the leadframe cleaning process.

Wash solution A1 (as described above) was prepared as follows: 575 gm of dimethylacetamide (DMAc), 139 gm of deionized water (DIW), 156 gm in a 1 liter HDPE poly-bottle Ammonium acetate, 120 gm of acetic acid, and 10 gm of ammonium fluoride were added. The bottle was capped and shaken. A 5% solution was prepared by diluting a sample of Cleaning Solution A1 with DIW and the solution pH was determined to be 4.9.

Al or Al ₂ O ₃ wafers tested in this experiment are blanket wafers. Wafer immersion in the beaker was set for at least 90 minutes.

Al (0.5% Cu) metal on a titanium nitride (TiN) substrate having a resistivity of 338.24 ohms-kW / Sq was obtained from SVMI and has a nominal 8000 kW thickness of Al. During storage, the Al substrate can grow up to 150 kPa of oxide layers. Accordingly, before the etch rate measurement, 2 "x2" Al piece was pre-treated with Al substrate by dipping for 2 minutes in an aqueous solution of 25 ℃ to 42.5 wt.% H ₃ PO ₄ in deionized water of. After soaking for 2 minutes, the Al pieces were rinsed with deionized water for 3 minutes, dried with N ₂ gun for 30 seconds, and then the Al film thickness was measured. Al pieces pretreated in this manner were used directly in the etch rate measurements performed.

Al or Al ₂ O ₃ removal tests were performed as follows. Each 2 "x2" piece of Al or Al ₂ O ₃ substrate in a 500 ml glass beaker was immersed in 330 ml of cleaning solution A1 and the solution was stirred at 300 rpm on a stir plate. The temperature was recorded as 25 ° C. Thickness measurements in mm were performed three times after 0, 20, 40, 60, and 90 minutes.

All thickness measurements were performed using the ResMap Four Point probe. Film thickness versus time data was then recorded. For the cleaning solution A1, the etching rate was determined to be 1.8 dl / min for Al.

Elliptical tests were performed to determine the Al ₂ O ₃ oxide thickness using a FilmTek SCI ellipsometer. Thereafter, film thickness versus time data was recorded. For the cleaning solution A1, the etching rate was determined to be 10.1 dl / min for Al ₂ O ₃ .

Further cleaning solutions A94B, A94E, A97E, A97F, and A97G were prepared as A1 except varying the concentration of the components. In this solution, DI water makes up the remainder of the composition to make 100% by weight. These solution compositions, their pH measurements, and their etch rate results are summarized in Table I. The etch rate of the Al and Al ₂ O ₃ are different relative etch rates of the Al and Al ₂ O ₃ appears to be obtainable by a variety of component concentrations. The A1 solution exhibits a higher Al ₂ O ₃ etch rate than the Al etch rate.

Table I

Cleaning solution A96G was prepared as cleaning solution A1 except replacing DMAC with propylene glycol (PG). The composition, its pH measurement and etch rate results are summarized in Table II and compared to the cleaning solution A1.

Table II

Wash solutions A94A, A94D, A96A and A96B were prepared as A1 except replacing DMAC with PG. In this solution, DI water makes up the remainder of the composition to make 100% by weight. These solution compositions, their pH measurements, and their etch rate results are summarized in Table III. This example shows that the relative etch rates for Al and Al ₂ O ₃ can be altered by changing the component and buffer concentrations to achieve the desired cleaning performance.

Table III

Cleaning solutions A96E and A96F were prepared as A1 except replacing DMAC with PG. In this solution, DI water makes up the remainder of the composition to make 100% by weight. These solution compositions, their pH measurements and their etch rate results are summarized in Table IV and compared to A96A and A97E. Since aqueous formulations at lower solvent concentrations may sometimes be desirable, lesser amounts of solvent have been used. The best cleaning for a particular application will be provided by the relative amount of solvent to water, the amount of fluoride and the solution pH. The solvent type may also fine tune the cleaning results.

Table IV

Washing solutions A96C, A96D, A97B, and A97D were prepared as A1 except using a dimethyl urea (DMU) solvent and showing the effect of adding a dipropylene glycol monomethyl ether (DPM) cosolvent to PG. In this solution, DI water makes up the remainder of the composition to make 100% by weight. These solution compositions, their pH measurements and their etch rate results are summarized in Table V and compared with A96A and A96B.

Table V

Addition of Cleaning Solution B Example

Cleaning solutions B91A, B92A, B92D, B92E and B92F were prepared and tested as A1 except using the matrix of components described in Table VI. In this solution, DI water makes up the remainder of the composition to make 100% by weight. Using 0.45 wt% citric acid and 0.0017 wt% NH ₄ F plus water matrix, the etch rates were measured for 0, 10, 30 and 40 wt% PG formulations.

Table VI

Cleaning solutions B92F, B92H, B92I, and B92J were prepared and tested as A1 except using the matrix of components described in Table VII. In this solution, DI water makes up the remainder of the composition to make 100% by weight.

Table VII

Further tests were performed using different corrosion inhibitor molecules for the B1 cleaning solution at B100A, B100B, B100C, B100D and B101A. Citric acid was 0.45 wt% (wt% absolute).

* AKYPO LF surfactant is a glycol ether carboxylic acid surfactant.

** HEDTA is hydroxyethylenediamine triacetic acid.

The description of the above embodiments and preferred embodiments is considered to be illustrative, and should be considered as limiting the invention as defined by the claims. As will be readily appreciated, various modifications and combinations of the features and components in the above-described compositions can be used without departing from the invention described in the claims. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims. All components described herein may be combined in any of the ranges described. Compositions A and B components may be exchanged in any of the above compositions in the ranges described for any of these. All comprising languages include consisting essentially of and consisting of.

Claims (23)

A method of treating a leadframe assembly to remove undesired material from the leadframe assembly or to prepare the surface of the leadframe assembly for subsequent bonding, wherein the leadframe assembly is a leadframe, die , A die with a bond pad thereon, one or more of the parts of a contact, a contact lead, and a wire,
Contacting some or all of the leadframe assembly or one or more components of the leadframe assembly with a composition comprising water and one or more acids, or one or more salts. The method of claim 1 wherein the method is
Drying the leadframe assembly or one or more components of the leadframe assembly; And
And performing a wirebonding step comprising attaching the wire between the bond pad on the die and the contact lead on the leadframe. 3. The method of claim 1 or 2, further comprising forming a mold over the leadframe assembly to form a packaged circuit. 4. The method of any one of claims 1 to 3, wherein attaching the one or more dies to the leadframe before or after the contacting step, wherein the leadframe includes the contact lead with an exposed metal surface. And further comprising said composition used in said contacting step having a pH of about 1 to about 7. The method of claim 1, wherein the composition used in the contacting step comprises from 0.003 to about 25 weight percent of one or more carboxylic acids. The composition according to any one of claims 1 to 5, wherein the composition used in the contacting step comprises an acid buffer, the acid of the acid buffer is selected from carboxylic or polybasic acids, and the acid buffer is 10 Further comprising a salt of the acid in a molar ratio of acid to salt in the range of from 1 to 1:10. The method of claim 6, wherein the acid buffer in the composition used in the contacting step comprises one or more of acetic acid / acetate salts, benzoic acid / benzoate salts, and phenolic acid / phenolate salts. 8. The composition of claim 1, wherein the composition used in the contacting step comprises from about 0.003 to about 4 weight percent of one or more hydroxyl carboxylic acids, salts thereof, or mixtures thereof, or an amine group-containing. 9. Carboxylic acids, salts thereof, or mixtures thereof. 9. The composition according to claim 1, wherein the composition used in the contacting step is citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic and fumaric acid, and salts thereof At least one carboxylic acid, salts thereof, or mixtures thereof selected from the group consisting of a mixture of; 10. The process according to any one of claims 1 to 9, wherein said composition used in the contacting step comprises citric acid. The composition according to any one of the preceding claims, wherein the composition used in the contacting step is
About 0.005 to about 16 weight percent of one or more carboxylic acids, salts thereof, or mixtures thereof; And
From about 0.003 to about 4 weight percent of one or more hydroxyl carboxylic acids, salts thereof, or mixtures thereof, or amine group-containing acids, salts thereof, or mixtures thereof,
The balance is substantially water. The composition according to claim 1, wherein the composition used in the contacting step is citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic and fumaric acid, and salts thereof And at least two carboxylic acids, salts or mixtures thereof selected from the group consisting of mixtures of, and further comprising at least one solvent, at least one fluoride, and optionally at least one surfactant. The composition of claim 1, wherein the composition used in the contacting step is of the formula R ₁ R ₂ R ₃ R ₄ NF (wherein R ₁ , R ₂ , R ₃ , and R ₄ Is independently a fluoride selected from the group consisting of hydrogen, an alcohol group, an alkoxy group, an alkyl group or a mixture thereof. The method of claim 1, wherein the composition used in the contacting step further comprises one or more components selected from the group consisting of organic polar solvents, fluorides, surfactants and corrosion inhibitors. The method of claim 1, wherein the composition used in the contacting step further comprises an organic polar solvent and fluoride. 16. The composition according to any one of claims 1 to 15, wherein the composition used in the contacting step is dimethylacetamide (DMAC), monoethanolamine, n-methylethanolamine, formamide, n-methyl formamide, gamma. -Butyrolactone, N-methylpyrrolidone, dihydric alcohols, polyhydric alcohols, diols and polyols such as (C ₂ -C ₂₀ ) alkane diols and (C ₃ -C ₂₀ ) alkane triols, cyclic alcohols and substitutions And alcohol selected from the group consisting of glycols, glycol ethers, tetrahydrofurfuryl alcohol (THFA), diacetone alcohol, 1,4-cyclohexanedimethanol, and urea and mixtures thereof. The method of claim 1, wherein the composition used in the contacting step comprises 30% to 90% by weight of an organic polar solvent; 0.0005% to 20% by weight of fluoride; 0.5% to 40% by weight of water; And up to 15 weight percent of an optional corrosion inhibitor. 18. The composition of any one of claims 1 to 17, wherein the composition used in the contacting step has a pH in the range of 3 to 7, the composition comprising 30% to 90% by weight of the organic polar solvent; 0.001% to 20% by weight of the fluoride; 15 wt% or less of an optional surfactant, further wherein the water is present at 0.5 wt% to 40 wt%. The method of claim 1, wherein the composition used in the contacting step comprises an ammonium salt. The method of claim 1, wherein the composition used in the contacting step comprises propylene glycol or dimethylacetamide, or mixtures thereof. The method of claim 1, wherein the composition used in the contacting step further comprises one or more surfactants. 22. The composition of any one of the preceding claims wherein the composition used in the contacting step is
About 0.1 to about 3 weight percent of one or more dicarboxylic acids, salts thereof, or mixtures thereof; And
From about 0.05 to about 1.5 weight percent of one or more hydroxyl carboxylic acids, salts thereof, or mixtures thereof,
The balance is substantially water,
And the composition has a pH of about 1 to about 4. 23. A composition used for cleaning a leadframe assembly or parts of a leadframe assembly used in the contacting step of any of claims 1-22.

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