KR101729203B1 - Cleaning lead-frames to improve wirebonding process - Google Patents

Abstract

The present invention is directed to a method of processing a semiconductor substrate to remove a material not desired from the semiconductor substrate or to prepare a surface of the semiconductor substrate for subsequent bonding, the substrate comprising a lead frame comprising a die, a bond pad, And contacting the substrate with a liquid cleaning composition, and to compositions useful in the method.

Description

CLEANING LEAD-FRAMES TO IMPROVE WIREBONDING PROCESS FOR IMPROVED WIRE BONDING PROCESS [0002]

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

The present invention relates to a method of cleaning a metal surface on a semiconductor chip and a lead frame to improve a wire bonding process. In particular, the invention relates to a method comprising exposing a metal surface to an aqueous cleaning solution to remove metal oxides, contaminants, and other residues from the metal surface on the chip and leadframe.

During the production of a semiconductor device, a leadframe is traditionally used as a cost-effective way to simultaneously mount and process a plurality of semiconductor dies or chips. Each lead frame typically has a plurality of die pads for mounting chips. The lead frame also acts as a means for electrically connecting the chip to the external device through the lead of the lead frame. The bonding wire is connected to an electrical contact found on the leads of the lead frame and on the chip in a known process as wire bonding. The bonding 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 lead frame.

In the relevant part, a conventional conventional process for making a die package is shown in Fig. 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 a die bonding or die attach step (12). Typically, in the die bonding step 12, the die is attached to the lead frame using an organic adhesive, such as epoxy, and then cured by baking. Immediately after the epoxy is cured, in step 14, the die is bonded to the lead frame.

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

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

A method of processing a leadframe assembly to remove a material not desired from the leadframe assembly or to prepare a surface of the leadframe assembly for subsequent bonding, the leadframe assembly comprising a leadframe, a die, Wherein at least a portion of the components of the lead frame assembly or lead frame assembly comprises at least one of water and at least one acid or at least one salt, wherein the composition comprises at least one of a die, a contact, a contact lead, And contacting the substrate with the substrate. The composition used in the contacting step may comprise from 0.003% to about 25% by weight of one or more carboxylic acids.

The present invention provides a method of processing a substrate comprising at least one of a lead frame assembly or a list of parts or parts that are a lead frame and a die, a bond pad, a die attach material, a mold compound, a contact and a wire (Semiconductor substrate), or a portion thereof, with an acid selected from a carboxylic acid or a salt of a polybasic acid and an acid (for example, an ammonium salt) in an acid to salt ratio of from 10: 1 to 1:10, Ammonium salt) in a molar ratio of acid buffer solution; And optionally, an organic polar solvent which may be miscible in all ratios in water; And optionally, a fluoride, and water, and in some embodiments, the composition has a pH in the range of about 3 to about 7, and in some embodiments, the leadframe May comprise an aluminum metal on at least one surface; The method provides a method that can include an additional step of drying the semiconductor substrate.

In another aspect, the present invention provides a method of processing a semiconductor substrate or a lead frame assembly or substrate to remove a material not desired from the semiconductor substrate or lead frame assembly or substrate, or to prepare the surface of the lead frame assembly or substrate for subsequent bonding Wherein the lead frame assembly comprises a lead frame comprising at least one of a die, a bond pad, a die-attached material, a moiety compound, a list of parts of a contact and a wire, and wherein the lead frame or portion of the lead frame is about 0.005 To about 16% by weight of at least one carboxylic acid, a salt or a mixture thereof, or an amine group-containing carboxylic acid, a salt or a mixture thereof; From about 0.003 to about 4 weight percent of at least one hydroxyl carboxylic acid, a salt or a mixture thereof, or an amine group-containing hydroxyl carboxylic acid, a salt thereof, or a mixture thereof; Contacting a substrate with a composition comprising, consisting essentially of, consisting essentially of, and consisting essentially of the balance of water and having a pH of from about 1 to about 4, wherein the semiconductor substrate comprises a copper metal on at least one surface step; And drying the semiconductor substrate. In some embodiments, a dicarboxylic acid is preferred.

In another aspect, the present invention provides a method of processing a leadframe assembly including a leadframe, the method comprising: attaching one or more individual dies to a leadframe comprising a contact lead to expose the exposed (e.g., aluminum, Pd, Au, Ag, and Mg) metal surfaces; An acid buffer solution having a molar ratio of carboxylic acid or polybasic acid and a salt of an acid (e.g., ammonium salt) in the range of 10: 1 to 1:10 acid to salt (e.g., ammonium salt); And optionally an organic polar solvent (i. E., A solvent that is miscible in all ratios in water); Contacting the composition with a composition comprising, consisting essentially of, or consisting of fluoride and water, wherein the composition can have a pH in the range of from about 3 to about 7; Drying the substrate; Performing a wire bonding step comprising attaching a wire between a bond pad on the die and a contact lead on the lead frame to form a die and a lead frame assembly; And forming a mold over the die and lead frame assembly to form a packaged circuit.

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

Other aspects, features and embodiments of the present invention will become more fully apparent from the following description and appended claims. All weight percentages described herein are based on the total weight of the composition, unless otherwise stated. "Consisting essentially of" means that when the composition is otherwise added to the same claimed cleaning composition, removal of the metal oxide from the bonding pad of the lead frame assembly when these uncharged components are used in the same cleaning process ≪ RTI ID = 0.0 > and / or < / RTI > does not substantially affect the properties of the composition. The removal rate of the metal oxide from the lead frame assembly is preferably about 2 A / min or more. The oxide removal rate is not intended to indicate the limit of the lead frame cleaning process. For example, in a batch cleaning process, several leadframes may be exposed to a cleaning bath containing the cleaning solution described herein to provide an oxide removal rate of 1-2 A / min over a long period of time, It is possible to obtain a lead frame which can be dipped and still clean.

The present invention also provides lead frame cleaning compositions useful in the methods described herein.

The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings presently preferred embodiments. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings,
Figure 1 is a block diagram illustrating typical steps involved in the manufacture of an integrated circuit device.
Figure 2 is a block diagram illustrating the steps of the method of the present invention.
3 is a graph illustrating aluminum surface treatment performance in one embodiment of the present invention.
4 is a graph illustrating performance of one embodiment of the present invention.
5 is a graph illustrating performance of one embodiment of the present invention.
Figure 6 is a graph illustrating performance in terms of copper oxide removal and re-growth for one embodiment of the present invention.
Figure 7 is a graph illustrating 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 treating microelectronic device substrates and packages comprising a composition useful for preparing a metal surface during a process of connecting metal wires from a bond pad to a lead frame during a wire bonding process. The term "leadframe" may be used, but is not intended to be limited to, and includes all types of semiconductor packaging substrates, for example, a plated or unplated BGA, and an organic substrate and leadframe. The present invention also relates to a method of processing a lead frame assembly or semiconductor substrate to remove a material not desired from the lead frame assembly or semiconductor substrate or to prepare a lead frame assembly or a surface of the semiconductor substrate for subsequent bonding. The term "leadframe assembly" or "leadframe substrate" includes at least one die coupled to and further attached to, e.g., But is not intended to be limited thereto. ≪ RTI ID = 0.0 > [0031] < / RTI >

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

As used herein, "carboxylic acid" refers to an amine-containing mono-, di- or poly-carboxylic acid, salts thereof or mixtures thereof, (unless otherwise specified or apparent from the context) Refers to mono-, di- or poly-carboxylic acids comprising 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 will eventually become a microelectronic device or microelectronic assembly. Preferably, the semiconductor substrate includes a lead frame assembly including a die attached to the lead frame.

As used herein, "about" is intended to represent +/- 5% of the stated value.

As used herein, "suitability " for cleaning contaminants from microelectronic devices having such contaminants (including metal oxides) thereon is referred to in the context of microelectronic devices, more particularly leadframe assemblies or leadframe assemblies This corresponds to the removal of at least a portion of the residue / contaminant from the bonding pad on the part, for example a die or die. Preferably, at least 90% of the residues / contaminants are removed from the bond pad on the part of the microelectronic device, more specifically the leadframe assembly or leadframe assembly, e.g., die or die, using the compositions and methods of the present invention. More preferably, at least 99% of the residue / contaminant is removed.

Because of its advantages in electrical performance and cost, it has become popular to fabricate integrated circuits using copper or aluminum wiring metallization techniques. To prevent intermetallic phases, ICs are provided with copper or aluminum pads. Typically, wire bonding of ICs and chip carriers or lead frames is performed using gold and copper wire materials, but aluminum and silver have also been used. The bonding of these wires to different pad materials creates a different metallurgical system. Recently, there is a tendency to migrate from gold to copper wire, mainly synchronized due to reasonably low cost reasons.

Unfortunately, both copper and aluminum are oxidized very quickly, making it more difficult to achieve reliable wire bonding. Thus, in order to ensure the bonding ability and reliability of the wire bonding, one of the important conditions is that there should be no or substantially no contaminants containing oxides at the bonding 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 and packaged from the wafer. Oxidation of the copper or aluminum bond pads on the die may occur during this time, as considerable time may elapse between wafer fabrication and packaging processes. Thus, the present invention provides for effectively cleaning the copper and aluminum pads of an integrated circuit after the circuits have been fabricated on the wafer, but before the die is encapsulated or fully packaged.

Referring to FIG. 2, there is provided a method of manufacturing a semiconductor wafer on which a plurality of integrated circuits are formed. The integrated circuit may have a bond pad formed of copper or aluminum. Methods of forming circuits with such pads on silicon wafers are known, and a detailed discussion thereof is not required for an 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 are applied to the wafer, the wafer is rinsed in deionized water, and the backside of the wafer is ground to remove unwanted material. Thereafter, the wafers are processed in a test / assembly / packaging facility where testing of each chip or die is performed as a wafer, and at this stage, 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 an epoxy, solder paste, or other adhesive material to the leadframe and / To the lead frame by die attach process steps or steps that include attaching the die or dies to the lead frame. The leadframe may have a solder bump or stud bump or similar attachment parts formed thereon for receiving 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 then contains a plurality of attached die formed into a package. If an epoxy is applied, the lead frame or substrate may then be epoxy-cured in a high temperature process to ensure proper adhesion of the die to the substrate. If a solder paste is used, this will be done after the soldering step. Thereafter, the wire is connected between the bond pads on the die and the contacts on the lead frame. Such leadframe or leadframe assemblies will be singulated to form individual packages that are then molded and encapsulated (see below). The present invention relates to cleaning performed on lead frame assemblies that can occur after high temperature epoxy curing or other die attach steps and prior to wire bonding and is useful for removing oxides and other contaminants from metal bond pads and lead frame or substrate contacts and surfaces Lt; / RTI >

2, a method of manufacturing a semiconductor wafer having a plurality of integrated circuits formed thereon is described. The integrated circuit may have a bond pad formed of copper or aluminum. Methods for forming circuits with such pads on silicon wafers are well known and a detailed discussion thereof is not required for an 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 layers are applied to the wafer and the wafer is rinsed in deionized water and the backside of the wafer is ground to remove unwanted material, and additionally, preferably after testing of each chip or die. Typically, after the test and before dicing is performed, the wafer is again cleaned using solvents such as deionized water, isopropyl alcohol, acetone and methanol. The present invention relates to cleaning performed on a wafer either before, after, or after dicing, and before or after the formation of a leadframe assembly, and after attaching a lead wire to the bonding pad after removing the oxide from the metal bonding pad ≪ / RTI > After these steps, the step of modifying the packing for the lead frame assembly may typically be followed under vacuum. Although not shown in FIG. 2, the method of the present invention can be applied to the leadframe just before or after the formation of the leadframe assembly, after formation of the leadframe assembly (i.e., after attaching the die (s) to the leadframe) After the attachment of the wire, a method of performing the cleaning step is included.

More specifically, starting with step 20, which is divided into steps 20A and 20B, the wafers, and in particular the metal bonding pads of each die, are shown as either of the two cleaning compositions Composition A or Composition B Are contacted with the same cleaning composition, each of which will be described in more detail below (the method in Figure 2 can be represented by a single cleaning step). Preferably, the cleaning step of the method of the present invention is carried out using a lead frame assembly, or at least a portion of the lead frame assembly, for example a bond pad on a die or die that may already be attached to the lead frame, Containing substrate) or composition B (preferably for an Al-containing or Cu-containing substrate). At least a portion of the lead frame assembly is preferably applied in a bath containing the composition at room or elevated temperature for about 1 minute to about 40 minutes, preferably about 5 minutes to about 30 minutes, and more preferably about 20 to about 30 minutes ≪ / RTI > for a period of time.

Compositions used to clean bond pads of lead frame assemblies include an aqueous solution comprising an acid or a salt or a mixture of an acid and a salt. Compositions used to clean bond pads of lead frame assemblies include aqueous solutions comprising acids, preferably one or more carboxylic acids or polybasic acids. The composition may comprise water and from about 0.003% to about 25% by weight of one or more acids. Some embodiments of the composition may have a pH of from 1 to 7. In some embodiments, the composition comprises an acid buffer solution, wherein the acid is part of an acid buffer solution. In another embodiment, the composition comprises at least one carboxylic acid. 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 additive may comprise a surfactant and / or a corrosion inhibitor. For example, some embodiments of compositions useful in the methods of the present invention include citric acid, and optionally, a surfactant. Some embodiments of the composition include, in addition to one or more acids, 0 wt.% Or 30 wt.% To 90 wt.% Of an organic polar solvent; From 0.0005% to 20% by weight of fluoride; From 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 process 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 compositions useful in the method of the present invention for cleaning lead frame assemblies, including acid buffer solutions. Composition B will be referred to as a composition useful in the method of the present invention for cleaning a lead frame assembly that does not include an acid buffer solution.

Composition A

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

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

As mentioned above, the composition A described herein comprises an acid buffer solution. An acid buffer solution, when added to the composition described herein, provides a buffered composition having a pH adjusted to minimize corrosion of sensitive metals such as aluminum, copper, titanium, and the like. The acid buffer solution is added in an amount essential to obtain the desired pH range for the composition. As used herein, the term "acid buffer solution" is a solution that inhibits a change in pH as a result of the addition of a small amount of acid or base to the composition. The addition of acid buffer solution to the compositions described herein prevents pH swing due to dilution with water or contamination with base or acid.

The molar ratio of the acid to the conjugate base in acid buffer to provide such buffering effect in the composition is in the range of from 10: 1 to 1:10, or substantially 1: 1, or 1: 1, Practically means ± 2% by weight of the same molar concentration. Buffering agents are commonly referred to as weak acids and the broadest buffer range for either acid or base is about 1 pH unit for each side of the pK _a of the weak acid group. The setting of the pH for the buffer may be carried out with a suitable pK _a for the desired pH range, in the range of 10: 1 to 1:10, or substantially 1: 1 of the acid and acid for the conjugate base (or, in certain embodiments, Lt; / RTI > acid) to the < RTI ID = 0.0 > base < / RTI >

In addition, certain salts having _a pK _a less than about 6 when dissolved in water may be used with or without acid when dissolved in water to make a cleaning composition.

In certain preferred embodiments, the acid buffer solution contains a carboxylic acid or a polybasic acid, for example, an ammonium salt of phosphoric acid. Exemplary acid buffer solutions include acetic acid / acetate salts (e.g., ammonium salts, amine salts, etc.), benzoic acid / benzoate salts (e.g., ammonium salts, amine salts, etc.), and phenolic acid / (E. G., Ammonium salts, amine salts, etc.). Examples of ammonium salts are acetic acid or ammonium salts of phosphoric acid. In one embodiment, the acid buffer solution is an aqueous solution of ammonium acetate and acetic acid. In another embodiment, the acid buffer solution is benzoic acid and ammonium benzoate.

The composition may comprise from 0.003 to 30 wt.%, Alternatively from 0.5 to 25 wt.%, Alternatively from 0.5 to 20 wt.%, Alternatively from 0.5 to 15 wt.% Acid, i.e. an acid used in the buffer. In certain embodiments, the acid buffer solution may contain a weak acid such as trihydroxybenzene, dihydroxybenzene, and / or salicylhydroxamic acid. In such embodiments, the amount of weak acid added may range from 0.003 to 30 wt%, alternatively from 0.5 to 25 wt%, alternatively from 0.5 to 20 wt%, alternatively from 0.5 to 3 wt%. The amount of the conjugate base will depend on the amount of acid added to the composition to provide a buffer solution in the composition.

The pH of the composition according to the present invention may be from 1 to 11, but in certain embodiments, a pH in the range of from about 3 to about 9, or in the range of from about 3 to about 7, or in the range of from about 3 to about 6, To the minimum corrosion. Preferably, the pH range is from about 3 to about 7.

The one or more organic polar solvents that may be added to the compositions described herein are water miscible solvents. These solvents may be used alone or in any combination. One or more solvents may be present in the composition and may include from about 0 wt% to about 90 wt%, or from 30 wt% to about 90 wt%, or from about 30 wt% to about 70 wt% Can be mixed with organic polar solvents for daily use. Examples of organic polar solvents include dimethylacetamide (DMAC), monoethanolamine, n-methylethanolamine, formamide, n-methylformamide, gamma-butyrolactone, But is not limited thereto. Other solvents include bivalent and polyhydric alcohols, such as diols and polyols, such as (C ₂ -C ₂₀ ) alkane diols and (C ₃ -C ₂₀ ) alkanetriols, cyclic alcohols, and substituted alcohols. Other solvents include urea, such as dimethyl urea, and tetramethylurea, and the like. Specific examples of such organic polar solvents include propylene glycol, tetrahydrofurfuryl alcohol (THFA), diacetone alcohol and 1,4-cyclohexanedimethanol. Preferred solvents include at least one of dimethylacetamide, dimethylurea, propylene glycol, which are used alone or in combination with each other or with other solvents.

In certain embodiments, the organic polar solvent may be one or more glycol ethers. Glycol ethers are typically water miscible glycol mono (C ₁ -C ₆₎ alkyl ethers and glycol di (C ₁ -C ₆₎ alkyl ethers such as (C ₁ -C ₂₀₎ alkanediols, (C ₁ - (C ₁ -C ₆ ) alkyl ether, and (C ₁ -C ₂₀ ) alkane diol di (C ₁ -C ₆ ) alkyl ether. 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 Propylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, , Dipropylene monobutyl ether, dipropylene glycol isopropyl ether, tripropylene glycol monomethyl ether, 1-methoxy-2-butanol, 2-methoxy-1-butanol, 2-methoxy- , 1-dimethoxyethane and 2- (2-butoxyethoxy) ethanol. More typical examples of glycol ethers include 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.

The fluoride is preferably present in the composition of composition A described herein. Fluoride, also referred to as a fluoride-containing compound, is a compound of 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, an alcohol group, Or a mixture thereof. Examples of such compounds, there are ammonium fluoride (NH ₄ F), tetramethylammonium fluoride, tetraethylammonium fluoride, tetrabutylammonium fluoride and choline fluoride. Other examples of fluoride-containing compounds include fluoroboric acid and hydrofluoric acid. The fluoride is preferably present in an amount of from 0.0005 or 0.001 wt% to 20 wt%, or from 0.1 wt% to 10 wt%. Ammonium fluoride is preferred. In these embodiments, ammonium fluoride may be commercially available as a 40% aqueous solution.

Water exists as a component of the composition of the present invention and the composition used in the method of the present invention. Which may be present at the same time as the components of the other components of the invention, for example as an aqueous solution of ammonium fluoride or as an aqueous acid buffer solution, or may be added separately. Preferably, water is present in an amount of 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.

A corrosion inhibitor amounting up to 20% by weight can be added to the composition of the present invention. Preferably, the inhibitor concentration is from about 0.5% to 8% by weight. Any corrosion inhibitor known in the art for similar applications, such as the corrosion inhibitors described in U.S. Patent No. 5,417,877, which is incorporated herein by reference, may be used. 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 systems having a pH range from about 3 to about 6. Thus, 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 preferred. The corrosion inhibitor may be an organic acid, an organic acid salt, a phenol, a triazole, or a hydroxylamine. Examples of preferred inhibitor compositions include, but are not limited to, 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, Amines and lactic acid and their citrates and the like. Additional examples of corrosion inhibitors that may be used include esters of catechol, tertiary-butyl catechol, pyrogallol, and 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 an extent that does not adversely affect the pH range of the composition. Some examples of exemplary 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 dimethylformamide and dimethylacetamide), alkylalkanolamines (e.g. diethanolethylamine), and chelating agents such as beta-diketones Ton, beta-ketoimine, carboxylic acid, malic and tartaric acid based esters and diesters and derivatives thereof, and tertiary amines, diamines and triamines. Also included herein are surfactants and other additives described in the amounts described for surfactants for composition B below. In certain embodiments, the carboxylic acid that may be added to the composition in the acid buffer solution may also be provided as a chelating agent.

Formulations suitable for use as composition A in the present invention are described in U.S. Patent No. 6,828,289 and U.S. Patent 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 lead frame assembly, including one or more acids but not an acid buffer solution.

Composition B is a fluoride-free or fluoride-containing aqueous composition. The term "fluoride-free" refers to at least a substantially fluoride-free (e.g., containing up to about 100 ppb fluoride). Composition B may comprise from about 0.003 to about 25 weight percent acid, preferably at least one carboxylic acid and water (in aqueous solution). In some embodiments, the composition may comprise from 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 at least one sulfonic acid surfactant.

In some embodiments, the composition B comprises 0.005 to about 16% by weight of at least one carboxylic acid, a salt or a mixture thereof, which may be an amine group-containing carboxylic acid, a salt thereof or a mixture thereof; And / or from about 0.003 to about 4% by weight of at least one hydroxyl carboxylic acid, a salt or mixture thereof, or an amine group-containing carboxylic acid, a salt thereof or a mixture thereof, And has a pH of from about 1 to about 4.

In another embodiment, the composition B comprises from 0.005 to about 16% by weight of at least one dicarboxylic acid, their salts or mixtures thereof, from about 0.003 to about 4% by weight of at least one hydroxycarboxylic acid, mixture; Or amine group-containing carboxylic acids, salts thereof, or mixtures thereof, and substantially residual water, and has a pH of from about 1 to about 4.

Typical carboxylic acids include dicarboxylic acids containing carboxylic acids having two to six carbon atoms and include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid. The preferred acid is citric acid. Suitable salts include alkali metal and ammonium salts. A mixture comprising citric acid and oxalic acid and optionally malonic acid may 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. The preferred hydroxycarboxylic acid is citric acid. Suitable salts include alkali metal, and ammonium salts.

A preferred salt of the hydrocarboxylic acid is ammonium citrate.

Amine-containing carboxylic acids may be glycine, valine, alanine, phenylalanine, and the like.

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

In certain embodiments, the composition B may further comprise at least one solvent, preferably an organic solvent or an organic polar solvent, preferably an organic solvent miscible with water or an organic polar solvent. These solvents may be used alone or in combination. All solvents mentioned above as being useful in Composition A are useful in any of the compositions of the present invention. Preferred solvents for use in Composition B include solvents such as dimethylacetamide (DMAC), monoethanolamine, n-methylethanolamine, formamide, n-methylformamide, gamma-butyrolactone, Di- and polyhydric alcohols such as diols and polyols such as (C ₂ -C ₂₀ ) alkanediol and (C ₃ -C ₂₀ ) alkanetriols, cyclic alcohols and substituted alcohol ureas such as dimethylurea and Tetramethylurea, 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 from 0 wt% to 60 wt%, or from 0 wt% to 40 wt%, or from 10 wt% to 40 wt%.

Composition B may further comprise one or more of the fluorides described above for composition A (i.e., the fluoride containing compound). Examples of such compounds include ammonium fluoride, tetramethylammonium fluoride, tetraethylammonium fluoride, tetrabutylammonium fluoride and choline fluoride. Another example of fluoride containing compounds includes hydrofluoric acid. Fluoride containing compounds, if present, preferably contain from 0.0005% to 20%, or from 0.001% to 20%, or from 0.1% to 10%, or from 0.001% to 5%, or from 0.001% to 2% By weight. Ammonium fluoride is preferred. In some embodiments, ammonium fluoride may be commercially available as a 40% aqueous solution. In compositions comprising fluoride, it is preferred that an organic solvent also be present in such a composition, but also embodiments of composition B that have fluoride and do not have an organic solvent, and other embodiments that have an organic solvent and do not have fluoride in the composition Specific examples 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. An example of an additive comprises up to about 0.002% by weight of the active portion of the biocide. A common biocide is Kathan. Katan

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

And 95.85% of water. Biocides may be used in any composition of the present invention.

The additive (s) may be added to the extent that they do not adversely affect the desired pH range of the composition. Some examples of exemplary additives include surfactants, for example, acetylenic alcohols and derivatives thereof, acetylenic diols (nonionic alkoxylated and / or self-emulsifiable acetylenic diol surfactants) and derivatives thereof, (LAS), linear fatty acids and / or salts thereof, coconut oil fatty acid derivatives, tall oil acid derivatives, sarcosides, acetylated polypeptides, secondary alkyl benzene sulfonates, lignin (FAS), crude sulphonate, secondary alkane sulphonate (SAS), paraffin sulphonate, fatty alcohol ether sulphate (FAES), alpha -olefin sulphonate , Sulfosuccinate esters, alkyl naphthalene sulfonates, isethionates, sulfuric acid esters, sulfated linear primary alcohols, sulfated polyoxy Sulfurized straight chain alcohols, sulfated triglyceride oils, phosphoric and polyphosphoric acid esters and perfluorinated anions and mixtures of these and any of the surfactants described herein and other known surfactants, alcohols, quaternary amines and Such as di-amines, amides (aprotic solvents such as dimethylformamide and dimethylacetamide), alkylalkanolamines (e.g. diethanolethylamine), and chelating agents such as beta-diketones, Beta-ketoimine, carboxylic acid, malic and tartaric acid based esters and diesters and derivatives thereof, and tertiary amines, diamines and triamines. In certain embodiments, the carboxylic acid that may be added to the composition may also be provided as a chelating agent. The additive 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, and a preferred corrosion inhibitor is 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 additive, if present, is typically from about 0.001 to about 10, or from about 0.005 to about 5, or from 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 at least one acid, at least one fluoride, at least one organic solvent, and at least one surfactant in the weight ranges specified herein for composition B. Another preferred embodiment is a composition comprising at least one acid, at least one fluoride, at least one organic solvent, and at least one corrosion inhibitor in the weight ranges specified herein for composition B. Other compositions include water and acid, and each of the fluoride, solvent, and additive is an optional component.

Composition B typically comprises greater than 35% water by weight. In solventless embodiments, composition B typically comprises greater than about 50, or greater than about 75, or greater than about 90, or greater than about 95.5, or greater than about 98 weight percent water. When composition B comprises at least one solvent, 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 usually present in an amount of from about 0.005 to about 16% by weight, more usually from about 0.1 to about 3% by weight, and preferably from about 0.3 to about 0.5% by weight. When a mixture of acids, for example, oxalic acid and malonic acid, or a mixture of citric acid and oxalic acid is used, each of these is typically present in an amount of from about 0.003 to about 8 wt%, more typically from about 0.05 to about 1.5 wt% Is present in an amount of about 0.1 to about 0.3 weight percent.

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

When used, the amino-group containing acid, such as glycine, when present in the composition, will typically contain from about 0.003 to about 4% by weight, more usually from about 0.005 to about 1.5% by weight, and preferably from about 0.005 to about 0.5% 0.05% by weight.

The pH of the composition according to the invention may be from 1 to 11, but for composition B the pH is preferably from about 1 to about 4, and more preferably from about 1 to about 3, with specific examples being about 2 . The pH is typically measured using a pH paper or a suitable pH reference electrode. According to the present invention, it has been found that pH is 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 the various surface materials present on the die or substrate can be removed.

Another feature of the present invention is that the composition is relatively stable even in concentrated form. From about 0.1 to about 16 weight percent, and preferably from about 6 to about 10 weight percent dicarboxylic acid, from about 0.05 weight percent to about 8 weight percent, and preferably from about 3 weight percent to about 5 weight percent, Of a dihydroxycarboxylic acid or amino acid and substantially residual water can be provided and delivered to the end user and the user will then be able to dispense it from the processing tool for convenient and economical reasons at a ratio of about 19: It can be diluted by weight-based dilution.

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

The cleaning process according to the present invention leaves a metal surface cleaner and thus provides good adhesion between the metal wires and the bonding pad on the die and lead frame contacts.

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

The rinsing step with deionized water can be performed after the cleaning step and before the drying step.

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

As will become evident, the present invention provides 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 the wire bonding of the pad forms a more reliable bond. ≪ / RTI > The present invention also provides a method of fabricating a die having a metal bond pad during a die packaging process to reduce oxidation and other contaminants on the metal bond pad, so that wire bonding of the pad can form a more reliable bond. As will be appreciated, the present invention is directed to a method of making metal bond pads, such as, for example, copper and aluminum pads for wire bonding. The present invention is not limited to the use of copper wire for wire bonding, as other wires, for example gold or aluminum may be used. Further, although the present invention is carried out using ball bonding, it is not limited to ball bonding, and can be performed by wedge bonding.

While the present invention has been described primarily with reference to a cleaning semiconductor substrate, the cleaning composition of the present invention can be used to clean any substrate including organic and inorganic residues.

Example

The following examples illustrate that the cleaning solutions A1, A2, B1 and B2 remove metal oxides on the bonding pads and contacts. This cleaning solution will also remove contaminants, fluorine, and other residues on the bonding pads and contacts. This cleaning solution will remain on the metal surface as a detergent and the metal wire will have good adhesion during wire bonding. The cleaning solutions A1 and A2 correspond to the above composition A, which will remove the metal oxides from the Al bonding pads. The cleaning solutions B1 and B2 correspond to the above composition B, which will remove the metal oxides from the Cu bonding pads. The compositions to be evaluated are as follows:

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

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

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

Cleaning 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 lead frame (with the die attached) in the cleaning solutions A1, A2, B1, and B2 is as follows. The cleaning solution was applied to the lead frame after the die attach hardening step and before the wire bonding step. The cleaning solution was applied to the lead frame in any such manner: 1) immersing the lead frame in the tank of the cleaning solution, and 2) spraying the cleaning solution onto the lead frame. The optimum temperature of the cleaning solution is in the range of 25 캜 to 50 캜. The optimum exposure time for the cleaning solution is in the range of 5 minutes to 30 minutes. After exposure to the cleaning solution, the lead frame was rinsed with deionized water. The optimum temperature of the DI water rinse is 25 DEG C (room temperature). The optimal time for DI rinse is in the range of 30 seconds to 3 minutes. After rinsing the lead frame in DI water, the lead frame was dried. Immediately after the lead frame is dried, such a lead frame can be sent to the wire bonding step.

Composition A Al Oxide  Ability to remove

The data collected using X-ray photoelectron spectroscopy (XPS) are shown below. This data is collected on the Al junction pad on the die on the entire wafer. Prior to exposure to cleaning solution A, the thickness of the Al oxide layer on the Al junction pad is about 70 to 85 ANGSTROM. After exposure to cleaning solutions Al and A2, the thickness of the Al oxide was reduced to about 30 to 40 angstroms, which is a typical thickness of the native oxide layer that is naturally formed on the Al surface. This data indicates that the cleaning solutions A1 and A2 removed the Al oxide and then the natural layer of the Al oxide was re-grown. 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 bonding pads during wire bonding.

Table 1 : Al oxide thickness / XPS data for patterned Al junction pad wafers

Referring to Fig. 3, additional data showing that cleaning solution A1 removes Al oxide is presented. These data were collected using Auger depth profiling. Prior to exposure to cleaning solution Al, oxygen is present in the Al metal to a depth of about 100 angstroms. Thus, this is a measure of the thickness of the Al oxide layer. After exposure to the cleaning solution A1, oxygen penetrates into the Al to a depth of only about 35 Angstroms. Al oxide thickness was substantially reduced. This is after placing the Al bonding pads exposed for 3 days in air. In addition, additional data is shown after placing the Al bonding pads in the air for 14 days. In addition, the depth of penetration of the oxygen level is much lower than before exposure to the cleaning solution A1.

The ability to remove fluorine on the Al bonding pad of Composition A

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

Composition A contains Al Protect

The cleaning solutions A1 and A2 are very effective at removing Al oxide, but such a cleaning solution also needs to have a very low etching rate for the underlying Al metal phase. If such cleaning solution removes the Al oxide and severely etches the underlying Al metal, the wire bonding performance may not be improved. The data in Table 2 below shows that the cleaning solutions A1 and A2 have a very low etch rate on the Al phase.

Table 2 : Al etch rate

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

The data exemplified by Figs. 6 and 7 are 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 show that this initial thickness of Cu oxide (shown at time = -1 day in the graph) is about 25 to 30 Angstroms thick. After exposure to the cleaning solutions B1 and B2, the thickness of the Cu oxide was reduced to about 5 to 10 angstroms. This data indicates that the cleaning solutions B1 and B2 removed most of the Cu oxide. Cu will of course passivate and form a natural oxide layer. The thickness of the Cu oxide layer was again measured every other day up to 14 days. During these 14 days, Cu wafers were exposed to ambient air. The data indicate that re-growth of Cu oxide over 14 days is slow. Since the cleaning solutions B1 and B2 do not remove only the Cu oxide, this cleaning solution minimizes the re-growth rate of the Cu oxide.

Composition B is the lower Cu Protect

Although the cleaning solutions B1 and B2 are very effective in providing Cu oxide, this cleaning solution also needs to have a very low etching rate on the underlying Cu metal. If such cleaning solution removes Cu oxide and severely etches the underlying Cu metal, wire bonding performance may not be improved. The data in Table 3 below shows that cleaning solutions B1 and B2 have a very low etch rate on Cu.

Table 3 : Cu etch rate

Additional Example of Cleaning Solution A

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

A 1 liter HDPE poly-bottle was charged with 575 gm of dimethylacetamide (DMAc), 139 gm deionized water (DIW), 156 gm < RTI ID = 0.0 > Of ammonium acetate, 120 gm of acetic acid, and 10 gm of ammonium fluoride. The bottle was capped and shaken. A sample of cleaning solution A1 was diluted with DIW to make a 5% solution, and the solution pH was measured to be 4.9.

The Al or Al ₂ O ₃ wafers tested in this experiment are blanket wafers. The wafer immersion in the beaker was set up to 90 minutes.

Al (0.5% Cu) metal on a titanium nitride (TiN) substrate with a resistivity of 338.24 ohms-A / Sq was obtained from SVMI and has a nominal thickness of 8000 A of Al. During storage, the Al substrate can grow an oxide layer up to 150 ANGSTROM. Thus, prior to measuring the etch rate, the Al substrate was pretreated by immersing 2 "x 2" pieces of Al in an aqueous solution of 42.5 wt% H ₃ PO ₄ in deionized water at 25 ° C for 2 minutes. After soaking for 2 minutes, the Al pieces were rinsed with deionized water for 3 minutes and dried in N ₂ gun for 30 seconds, after which the Al film thickness was measured. In this way, pretreated Al pieces were used directly in the etch rate measurements performed.

The Al or Al ₂ O ₃ removal test was carried out as follows. In a 500 ml glass beaker, each 2 "x 2" piece of Al or Al ₂ O ₃ substrate was immersed in 330 ml of cleaning solution A1 and the solution was stirred at 300 rpm on a stirring plate. The temperature was reported to be 25 ° C. A thickness measurement was performed three times after 0, 20, 40, 60, and 90 minutes.

All thickness measurements were performed using the ResMap Four Point probe. The film thickness versus time data was subsequently recorded. For the cleaning solution A1, the etching rate was measured to be 1.8 ANGSTROM / min for Al.

An elliptic test was performed to determine the Al ₂ O ₃ oxide thickness using a FilmTek SCI ellipsometer. Then, the film thickness versus time data was recorded. With respect to the cleaning solution A1, the etching rate was determined to be 10.1 Å / min for the Al ₂ O _3.

Additional cleaning solutions A94B, A94E, A97E, A97F, and A97G were prepared as in A1 except that the concentrations of the components varied. In this solution, the DI water occupies the balance 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 shows an Al ₂ O ₃ etching rate higher than the Al etching rate.

Table I

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

Table II

Cleaning solutions A94A, A94D, A96A and A96B were prepared as in A1 except that DMAC was replaced by PG. In this solution, the DI water occupies the balance 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 concentration to achieve the desired cleaning performance.

Table III

Cleaning solutions A96E and A96F were prepared as in A1 except that DMAC was replaced with PG. In this solution, the DI water occupies the balance 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 with A96A and A97E. Since aqueous formulations at lower solvent concentrations may sometimes be desirable, less solvent is used. The best rinsing 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 be able to finely adjust the cleaning result.

Table IV

Cleaning solutions A96C, A96D, A97B, and A97D were prepared as in A1 except that dimethyl urea (DMU) solvent was used and the effect of adding a dipropylene glycol monomethyl ether (DPM) co-solvent to PG. In this solution, the DI water occupies the balance 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 in A1 except that the matrix of ingredients described in Table VI was used. In this solution, the DI water occupies the balance of the composition to make 100% by weight. Etch rates were determined for 0, 10, 30 and 40 wt% PG formulations using 0.45 wt% citric acid and 0.0017 wt% NH ₄ F plus water matrix.

TABLE VI

Cleaning solutions B92F, B92H, B92I, and B92J were prepared and tested as in A1 except that a matrix of the ingredients described in Table VII was used. In this solution, the DI water occupies the balance of the composition to make 100% by weight.

TABLE VII

Additional 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 hydroxyethylenediaminetriacetic acid.

The description of the above embodiments and preferred embodiments is to be considered as illustrative and limits the invention as defined by the claims. As will be readily appreciated, many variations and combinations of features and components in the above-described compositions may be utilized without departing from the invention as 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 of the ingredients described herein may be combined in any range as described. Compositions A and B components may be exchanged for any of the above compositions in the ranges described for any of these. The word " comprising " encompasses essentially consisting of and consisting of.

Claims (25)

CLAIMS What is claimed is: 1. A method of processing a leadframe assembly to remove unwanted material from a leadframe assembly or to prepare a surface of the leadframe assembly for subsequent bonding,
The lead frame assembly includes at least one of a lead frame, a die, a die having a bond pad thereon, a contact, a contact lead, and parts of a wire ,
Attaching at least one die having a bond pad thereon to a leadframe to form a leadframe assembly, the leadframe comprising a contact lead having an exposed metal surface;
Contacting the contact pad with a composition comprising (a) water, and (b) at least one acid, at least one salt or a mixture thereof, to remove the metal oxide from the bond pad and the contact lead Wherein the composition comprises from 0.003 to 25% by weight of at least one carboxylic acid;
Drying the lead frame assembly;
Performing a wirebonding step comprising attaching a wire between a bond pad on one or more dies and a contact lead on the leadframe; And
Forming a mold over the lead frame assembly to form a packaged circuit. ≪ RTI ID = 0.0 > 11. < / RTI > delete delete The method of claim 1, wherein the composition used in the contacting step has a pH of from 1 to 7. delete 2. The method of claim 1, wherein the composition used in the contacting step comprises an acid buffer solution, wherein the acid of the acid buffer solution is selected from a carboxylic acid or a polybasic acid, Lt; RTI ID = 0.0 > acid-to-salt < / RTI > salt. 7. The method of claim 6, wherein the acid buffer solution in the composition used in the contacting step comprises at least one of a mixture of acetic acid and acetate salts, a mixture of benzoic acid and benzoate salt, and a mixture of phenolic acid and phenolate salt. The composition of claim 1, wherein the composition used in the contacting step comprises from 0.003 to 4% by weight of at least one hydroxyl carboxylic acid, a salt thereof or a mixture thereof, or an amine group-containing carboxylic acid, Methods of inclusion. The composition of claim 8, wherein the composition used in the contacting step is selected from the group consisting of citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid, Or more carboxylic acid, a salt thereof, or a mixture thereof. 10. The method of claim 9, wherein the composition used in the contacting step comprises citric acid. The method of claim 1, wherein the composition used in the contacting step comprises
From 0.005 to 16% by weight of one or more carboxylic acids, their salts or mixtures thereof;
From 0.003 to 4% by weight of one or more hydroxyl carboxylic acids, salts thereof or mixtures thereof, or amine group-containing acids, salts thereof or mixtures thereof; And
Including water. The composition of claim 11, wherein the composition used in the contacting step is selected from the group consisting of citric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid and fumaric acid, At least one carboxylic acid, salt or mixture thereof, and at least one solvent, and at least one fluoride. 8. The method of claim 7, wherein the composition used in the contacting step is a compound of 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, An alkoxy group, an alkyl group or a mixture thereof). 8. The method of claim 7, 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. 8. The method of claim 7, wherein the composition used in the contacting step further comprises an organic polar solvent and fluoride. 16. The method of claim 15, wherein the composition used in the contacting step is selected from the group consisting of dimethylacetamide (DMAC), monoethanolamine, n-methylethanolamine, formamide, n-methylformamide, gamma-butyrolactone, Cyclohexanedimethanol, and urea, such as pyrrolidone, dihydric alcohol, polyhydric alcohol, diols and polyols, cyclic alcohols and substituted alcohols and glycols, glycol ethers, tetrahydrofurfuryl alcohol (THFA), diacetone alcohols, ≪ / RTI > and mixtures thereof. 17. The method of claim 16, wherein the composition used in the contacting step comprises from 30% to 90% by weight of an organic polar solvent; From 0.0005% to 20% by weight of fluoride; And from 0.5% to 40% by weight of water. The method of claim 1, wherein the composition used in the contacting step has a pH in the range of 3 to 7, the composition comprises 30% to 90% by weight of an organic polar solvent; And from 0.001% to 20% by weight of fluoride, and wherein said water is present in an amount of from 0.5% to 40% by weight. 7. The method of claim 6, 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 a mixture thereof. 13. The method of claim 12, wherein the composition used in the contacting step further comprises at least one surfactant. The method of claim 1, wherein the composition used in the contacting step
0.1 to 3% by weight of one or more dicarboxylic acids, their salts or mixtures thereof;
From 0.05 to 1.5% by weight of at least one hydroxyl carboxylic acid, their salts or mixtures thereof; And
Water,
RTI ID = 0.0 > 1 < / RTI > delete 18. The method of claim 17, wherein the composition used in the contacting step further comprises 0.5 to 15 weight percent corrosion inhibitor. 19. The method of claim 18, wherein the composition used in the contacting step further comprises from 0.001 to 15% by weight of a surfactant.

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