JP2011233769A - Method for forming copper wiring pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a copper wiring pattern, which can easily form the copper wiring pattern having a satisfactory cross-sectional shape.SOLUTION: The method for forming a copper wiring pattern (4), which uses an etching liquid containing a cupric ion source, acid, a side etching inhibitor and water, includes: a first etching step of etching an article to be etched with the etching liquid so that an etching amount (T) in a depth direction becomes 50-90% of a copper thickness (T) at the start of etching; and a second etching step of etching the article to be etched subsequently after the first etching step until the end of the etching process with the etching liquid. When an etching rate in the first etching step is R1 and an etching rate in the second etching step is R2, a value of R2/R1 is 0.40-0.85.

Description

  The present invention relates to a method for forming a copper wiring pattern using an etchant containing a cupric ion source, an acid, a side etching inhibitor and water.

  In the production of a printed wiring board, when a copper wiring pattern is formed by a photoetching method, an iron chloride etching solution, a copper chloride etching solution, an alkaline etching solution or the like is used as an etching solution. However, these etching solutions have a problem that the copper under the etching resist is dissolved from the side surface. That is, a portion that is originally desired not to be removed by etching by being coated with an etching resist (that is, a copper wiring portion) is removed by side etching, and the width becomes narrower from the bottom to the top of the copper wiring. The phenomenon occurred. In particular, when forming a fine copper wiring pattern of line / space = 25 μm / 25 μm (the width of the line is 25 μm and the gap between the lines is 25 μm), the top of the copper wiring must be made as thin as possible. Don't be.

  Conventionally, an etching solution that can suppress the thinning of the top of the copper wiring has been studied. For example, Patent Document 1 below discloses a pattern forming etching solution that can prevent the top of a copper wiring from being thinned by blending a specific azole as a side etching inhibitor. In Patent Document 1, the azole is bonded to cuprous ions in the liquid near the side surface from the top of the copper wiring pattern, and a protective film is formed from the top of the copper wiring pattern to the side surface. It is thought that thinning is suppressed.

  According to the etching solution of Patent Document 1, although excessive progress of etching can be suppressed by the protective film at the pattern top, etching sometimes proceeds excessively at the pattern bottom. If the etching of the pattern bottom proceeds excessively, the adhesion between the pattern and the substrate may be reduced, and the pattern may peel off. In addition, when the quality inspection is performed due to excessive etching of the pattern bottom, the pattern bottom may not be confirmed from above the pattern.

  On the other hand, Patent Document 2 below proposes a method of forming a copper wiring pattern having a good cross-sectional shape by using an etching solution containing a side etching inhibitor in the latter half of the etching process. In Patent Document 2, first, etching is performed halfway with a first etching solution that does not include a side etching inhibitor, then the second etching solution that includes a side etching inhibitor is changed, and etching is subsequently performed to obtain a copper wiring pattern. Is forming.

JP-A-2005-330572 JP 2007-180172 A

  However, in the method for forming a copper wiring pattern described in Patent Document 2, either one of the pattern top and bottom may be excessively etched depending on the timing of changing the etching solution. Further, since the etching is performed with two kinds of etching solutions having different compositions, the solution management is complicated.

  The present invention provides a method for forming a copper wiring pattern, which can easily form a copper wiring pattern having a good cross-sectional shape.

  The method for forming a copper wiring pattern according to the present invention is a method for forming a copper wiring pattern using an etchant containing a cupric ion source, an acid, a side etching inhibitor, and water. A first etching step of etching with the etching solution until the copper thickness reaches 50 to 90%, and a second etching step of etching with the etching solution until the end of etching following the first etching step, When the etching rate in the first etching step is R1, and the etching rate in the second etching step is R2, the value of R2 / R1 is 0.40 to 0.85.

  The “copper” in the present invention may be made of copper or a copper alloy. Further, in this specification, “copper” refers to copper or a copper alloy.

  In the method for forming a copper wiring pattern of the present invention, etching is performed under conditions where the etching progresses fast until the etching amount in the depth direction reaches 50 to 90% of the copper thickness at the start of etching, and then the etching proceeds. By performing etching under slow conditions, a copper wiring pattern having a good cross-sectional shape can be easily formed.

AC is sectional drawing according to process for demonstrating one Embodiment of the formation method of the copper wiring pattern of this invention.

  The method for forming a copper wiring pattern according to the present invention includes a first etching step in which etching is performed under a condition that the etching progresses rapidly until the etching amount in the depth direction becomes 50 to 90% of the copper thickness at the start of etching. And a second etching step of etching under the condition that the etching progresses slowly until the end of the etching using the etching solution having the same composition following the one etching step. When the etching rate in the first etching step is R1, and the etching rate in the second etching step is R2, the value of R2 / R1 is 0.40 to 0.85. The “etching amount in the depth direction” is a value obtained by subtracting the copper thickness at the etching location from the copper thickness at the start of etching.

  In the present invention, in the first etching step with a relatively high etching rate, after etching while suppressing excessive etching of the pattern top by the side etching inhibitor, the etching rate is decreased within a predetermined range, and then the second etching step is continued. In the etching process, etching is performed while suppressing excessive etching at the bottom of the pattern. Thereby, a copper wiring pattern having a good cross-sectional shape can be formed. In addition, since the first etching step and the second etching step are performed using the etching solution having the same composition, the liquid management becomes easy. Therefore, according to the present invention, a copper wiring pattern having a good cross-sectional shape can be easily formed. In the first and second etching steps, etching may be performed in the same etching tank or in different etching tanks. When etching is performed in a separate etching tank, the substrate transport time from the etching tank in the first etching process to the etching tank in the second etching process may be about 1 to 5 seconds. Moreover, unless the effect of this invention is inhibited, you may provide processes, such as an acid cleaning process, between a 1st etching process and a 2nd etching process, for example.

  In the first etching step, etching is performed until the etching amount in the depth direction becomes 50 to 90% of the copper thickness at the start of etching. In order to form a copper wiring pattern having a better cross-sectional shape, it is preferable to etch until the etching amount in the depth direction is 60 to 90% of the copper thickness at the start of etching in the first etching step. If the etching rate is reduced before the etching amount in the depth direction reaches 50% of the copper thickness at the start of etching, there is a possibility that an unetched portion remains. On the other hand, if the etching rate is decreased after the etching amount in the depth direction exceeds 90% of the copper thickness at the start of etching, the pattern bottom may be excessively etched.

  In the present invention, the ratio (R2 / R1) of the etching rate (R1) in the first etching step and the etching rate (R2) in the second etching step is 0.40 to 0.85. In order to form a copper wiring pattern having a better cross-sectional shape, R2 / R1 is preferably 0.50 to 0.70. If R2 / R1 is less than 0.40, an unetched portion may remain. On the other hand, if R2 / R1 exceeds 0.85, the pattern bottom may be excessively etched. In the present invention, the etching rate is the copper thickness (μm) etched per unit time (1 minute), and the weight loss (μm) of copper before and after etching is divided by the etching time (minutes). Calculated.

  The etching method in the first and second etching steps is not particularly limited. For example, a method of spraying an etching solution onto a portion of an insulating substrate that is not covered with an etching resist of a copper layer, a method of applying an etching solution to the etching target in a liquid film state, or an etching target in the etching solution And the like. Among these, an etching method using a spray is preferable because the etching rate can be easily controlled.

  When etching is performed using a spray, the etching rate may be controlled by selecting the spray nozzle, adjusting the spray pressure, adjusting the distance between the spray nozzle and the etching target, and the like. In order to form a copper wiring pattern having a better cross-sectional shape, when the spray pressure in the first etching step is P1, and the spray pressure in the second etching step is P2, the value of P2 / P1 is 0.24. It is preferable to adjust so that it may become -0.60, and it is more preferable to adjust so that it may become 0.30-0.50. Here, the “spray pressure” refers to the spray pressure immediately after spraying from the spray nozzle. Usually, the spray pressure is in the range of 0.03 to 0.3 MPa. The etching rate can also be controlled by adjusting the temperature of the etching solution within a range of 20 to 50 ° C., for example. Control of the etching rate by adjusting the temperature of the etching solution is effective even when etching is performed by a method other than spraying.

  When the etching rate is controlled by adjusting the spray pressure, the etching rate when etching a general electrolytic copper foil at a spray pressure of 0.12 MPa and an etching solution temperature of 35 ° C. is in the range of 1 to 35 μm / min. Is preferably used, more preferably an etchant in the range of 5 to 30 μm / min, and still more preferably an etchant in the range of 10 to 25 μm / min.

  In the present invention, in order to effectively suppress excessive etching at the bottom of the pattern, the etching rate in the first etching step is preferably 35 μm / min or less, more preferably 30 μm / min or less, and 25 μm / min More preferably, it is less than or equal to minutes. Further, from the viewpoint of shortening the etching time, the etching rate in the first etching step is preferably 1 μm / min or more, and more preferably 2 μm / min or more.

  The method for forming a copper wiring pattern of the present invention can be used for various pattern formations, but includes a first pattern region and a second pattern region having a second pattern region having an interval narrower than the interval between the wirings of the first pattern region. This is useful as a method for forming a wiring pattern. When forming the copper wiring pattern including the first and second pattern regions by the conventional etching method, the etching time is shorter in the second pattern region where the spacing between the wirings is narrower than in the first pattern region where the spacing between the wirings is wide. Becomes longer. Therefore, when the etching of the second pattern region is completed, the copper layer of the first pattern region may be excessively etched, and the pattern bottom may be thinned. In the present invention, as described above, since the etching rate is reduced from the first etching step to the second etching step, excessive etching of the copper layer in the first pattern region can be suppressed. In particular, the present invention relates to a copper wiring pattern in which a value obtained by subtracting D2 from D1 is 7 μm or more, where D1 is an interval between wirings in the first pattern region and D2 is an interval between wirings in the second pattern region. It is useful for the method of forming.

  Next, components of the etching solution that can be used in the present invention will be described.

(Cupric ion source)
The cupric ion source is a component added as an oxidizing agent that oxidizes metallic copper. Examples of the cupric ion source include cupric chloride, cupric sulfate, cupric bromide, cupric salts of organic acids, cupric hydroxide, and the like. Among these, cupric chloride is particularly preferable because of its high solubility and high etching rate.

  The concentration range of the cupric ion source is preferably a copper ion concentration of 14 to 155 g / L, particularly preferably 33 to 122 g / L. If it exists in this range, the fall of an etching rate can be prevented, and since the solubility of a cupric ion becomes favorable, an etching rate can be maintained stably. In addition, when using cupric chloride which is a preferable cupric ion source, the concentration of cupric chloride is preferably in the range of 30 to 330 g / L, more preferably 70 to 260 g / L.

(acid)
An acid is a component added in order to melt | dissolve the metal copper oxidized with the cupric ion. Examples of the acid used include at least one selected from inorganic acids and organic acids.

  Examples of the inorganic acid include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and the like. Examples of the organic acid include formic acid, acetic acid, oxalic acid, maleic acid, benzoic acid, glycolic acid and the like. Among these, hydrochloric acid is preferable as a particularly preferable acid from the viewpoint of etching rate stability and copper dissolution stability (high ability to retain cuprous ions and cupric ions in the etching solution). .

  The acid concentration is preferably 7 to 180 g / L, more preferably 18 to 110 g / L, and still more preferably 18 to 80 g / L. When the acid concentration is 7 g / L or more, a stable etching rate can be obtained, and a decrease in dissolution stability of copper can be prevented. On the other hand, when the acid concentration is 180 g / L or less, the etching solution can be prevented from eroding between the etching resist and copper, and reoxidation of the copper surface can be prevented.

(Side etching inhibitor)
A side etching inhibitor is added to the etching solution that can be used in the present invention in order to suppress excessive etching at the top of the pattern. The side etching inhibitor may be any compound that can form a hardly soluble protective film on the copper surface by forming a coordination bond with copper ions. For example, an azole compound, a nitrogen-containing polymer, or a compound having at least one group selected from an amino group, an imino group, a carboxyl group, a carbonyl group, and a hydroxyl group, and a sulfur atom, and having 7 or less carbon atoms (Hereinafter simply referred to as “sulfur-containing compound”).

  Among the side etching inhibitors listed above, an azole compound is preferable, and an azole having only a nitrogen atom as a hetero atom in the ring (hereinafter also simply referred to as “azole”) is preferable.

  The azole may be a monocyclic compound or a compound having condensed rings. In particular, imidazole compounds, triazole compounds, and tetrazole compounds are preferable, and two or more of these azoles may be used in combination.

  Examples of the imidazole compound include imidazoles such as imidazole, 2-methylimidazole, 2-undecyl-4-methylimidazole, 2-phenylimidazole, benzimidazole, 2-methylbenzimidazole, and 2-undecylbenzo. Benzimidazoles such as imidazole, 2-phenylbenzimidazole, 2-mercaptobenzimidazole and the like can be mentioned.

  Examples of the triazole-based compound include, for example, 1,2,3-triazole, 1,2,4-triazole, 5-phenyl-1,2,4-triazole, and 5-amino-1,2,4-triazole. , Benzotriazole, 1-methyl-benzotriazole, tolyltriazole and the like.

  Examples of the tetrazole compounds include 1H-tetrazole, 5-amino-1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-mercapto-1H-tetrazole, and 1-phenyl. -5-mercapto-1H-tetrazole, 1-cyclohexyl-5-mercapto-1H-tetrazole, 5,5'-bi-1H-tetrazole, and their ammonium or Na salts, Zn salts, Ca salts, K salts, etc. And metal salts thereof.

  Examples of the nitrogen-containing polymer include polyethyleneimine, polyallylamine, polydiallylamine, polyamine sulfone, and polyacrylamide. Nitrogen-containing copolymers may also be used. Examples of the nitrogen-containing copolymer include a copolymer containing at least two selected from primary to tertiary amines, primary to tertiary amine salts, quaternary ammonium salts, acrylamide and sulfur dioxide in the monomer.

  Specific examples of the sulfur-containing compound having an amino group include thiourea, thiourea dioxide, N-methylthiourea, 1,3-dimethylthiourea, and 1,3-diethylthiourea. Specific examples of the sulfur-containing compound having the imino group include ethylenethiourea. Specific examples of the sulfur-containing compound having a carboxyl group include thioglycolic acid, α-mercaptopropionic acid, 3-mercaptopropionic acid, 2,2′-thiodiglycolic acid, thiomalic acid, mercaptosuccinic acid, L- Examples include cysteine and L (-)-cystine. Specific examples of the sulfur-containing compound having a carbonyl group include 2-thiobarbituric acid. Specific examples of the sulfur-containing compound having a hydroxyl group include thioglycol.

  The concentration of the side etching inhibitor is preferably 0.01 to 50 g / L, more preferably 0.01 to 15 g / L, and still more preferably 0.02 to 10 g / L. If the concentration of the side etching inhibitor is 0.01 g / L or more, excessive etching of the pattern top can be reliably suppressed. On the other hand, when the concentration of the side etching inhibitor is 50 g / L or less, it is possible to prevent the etching rate from decreasing and to reliably etch the portion to be etched, thus preventing the occurrence of short circuit (insulation failure). Can do.

(Other additives)
The etching solution that can be used in the present invention is at least selected from a cationic surfactant, glycol, and glycol ether in order to increase the stability of the solution, perform uniform etching, and make the surface shape after etching uniform. Various additives such as alcohols, amides, anionic surfactants, solvents, nonionic surfactants, amphoteric surfactants, and cationic polymers may be blended as necessary. Specific examples of these additives are shown below.

Cationic surfactants: alkyl type quaternary ammonium salts such as benzalkonium chloride, alkyltrimethylammonium chloride, etc. Glycol: ethylene glycol, diethylene glycol, propylene glycol, polyalkylene glycol (alkylene group having about 4 to 500 carbon atoms), etc. Glycol ether: Propylene glycol monoethyl ether, ethylene glycol monobutyl ether, dipropylene glycol methyl ether, diethylene glycol butyl ether, etc. Alcohols: methanol, ethanol, 1-propanol, 2-propanol, butanol, benzyl alcohol, 2-phenoxyethanol, etc. Amides: N, N-dimethylformamide, dimethylimidazolidinone, N-methyl-2-pyrrolidone, etc. Anionic surfactant: Fatty acid salt, alkyl sulfate ester salt, alkyl phosphate ester salt, etc. Solvent: Sulfoxides such as dimethyl sulfoxide Nonionic surfactant: Polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene and polyoxyethylene Block polymers with oxypropylene, etc. Amphoteric surfactants: Betaine such as lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, laurylhydroxysulfobetaine, lauryldimethylamine oxide, aminocarboxylic acid, etc.

  Further, the cationic polymer is preferably a polymer compound that is soluble in water and exhibits a cationic behavior and has a molecular weight of 1,000 or more, more preferably a molecular weight of several thousand to several million. Specific examples include polyethyleneimine, polyalkylene polyamine, quaternary ammonium salt type styrene polymer, quaternary ammonium salt type aminoalkyl (meth) acrylate polymer, quaternary ammonium salt type diallylamine polymer, A copolymer of quaternary ammonium salt type diallylamine and acrylamide, a polymer of a salt of aminoalkylacrylamide, a cationic cellulose derivative and the like can be mentioned. Examples of the salt include hydrochloride. Among the cationic polymers, polyethyleneimine and polyalkylenepolyamine are preferable. In addition, the said cationic polymer may use 2 or more types together. As the cationic polymer, those commercially available as an antistatic agent for resins and fibers, a polymer flocculant for wastewater treatment, a hair rinse conditioning component, and the like may be used.

  In addition, the etching solution that can be used in the present invention includes oxidation of hydrogen peroxide or the like in order to oxidize cuprous ions generated in the solution by copper etching and return them to cupric ions to restore the etching ability. An agent may be blended.

  The etching solution can be easily prepared by dissolving the above-described components in water. The water is preferably water from which ionic substances and impurities such as ion-exchanged water, pure water, and ultrapure water have been removed.

  Next, an embodiment of a method for forming a copper wiring pattern of the present invention will be described with reference to the drawings. 1A to 1C to be referred to are cross-sectional views by process for explaining an embodiment of a method for forming a copper wiring pattern of the present invention.

  First, as shown in FIG. 1A, an etching resist pattern 3 is formed on a copper layer 2 provided on an insulating substrate 1. The insulating substrate 1 includes a so-called glass epoxy base material in which a glass fiber fabric is impregnated with an epoxy resin, a so-called phenol paper base material in which paper is impregnated with a phenol resin, and a so-called aramid epoxy group in which an aramid fiber nonwoven fabric is impregnated with an epoxy resin. A substrate (electrically insulating substrate) such as a material, a polyimide film, or a ceramic substrate can be used.

Next, as shown in FIG. 1B, until the etching amount T ₁ of the depth direction is 50 to 90% copper thickness T ₀ at the start of etching, it is etched by the above etching solution (first etching step). The etching amount T ₁ of the depth direction refers to the etching amount of the most deeply etched portions of the etching portion 2a.

Then, as shown in FIG. 1C, following the first etching step, etching is performed with the etching solution until the end of etching (second etching step). At this time, when the etching rate in the first etching step is R1, and the etching rate in the second etching step is R2, the etching rate is adjusted so that the value of R2 / R1 is 0.40 to 0.85. To do. Next, the etching resist pattern 3 is peeled off (not shown), and the copper wiring pattern 4 is obtained. As described above, according to the present invention, excessive etching of the top and bottom of the copper wiring pattern 4 can be suppressed, so that the width W ₁ of the top of the copper wiring pattern 4 and the width W ₂ of the bottom of the copper wiring pattern 4 are. (W ₂ −W ₁ ) can be reduced.

  Hereinafter, in order to facilitate understanding of the present invention, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

  The components shown in Table 1 and Table 2 were dissolved in ion-exchanged water to prepare etching solutions for Examples 1 to 10 and Comparative Examples 1 to 10. In addition, the density | concentration of hydrochloric acid shown in Table 1 and Table 2 is a density | concentration as hydrogen chloride.

  On the other hand, a copper-clad laminate (substrate for printed wiring board) in which a 12 μm thick copper foil is attached to a glass epoxy substrate (manufactured by Hitachi Chemical Co., Ltd., GEA-67N) is prepared. A dry film resist (SUNFORT SPG-152, manufactured by Asahi Kasei Co., Ltd.) is pasted, and a resist pattern in which a 50 μm pitch pattern area of line / space = 25 μm / 25 μm and a 100 μm pitch pattern area of line / space = 50 μm / 50 μm is mixed. Formed.

  Next, using the etching solutions of Examples 1 to 10 and Comparative Examples 1 to 10 (both liquid temperatures are 35 ° C.), the spray device having a capacity of 1 L is used in Table 1 (Examples) and Table 2 (Comparative Examples). The copper foil not coated with the resist pattern was etched by spraying under the conditions shown. In addition, as for the nozzle of the said spray apparatus, all used the fan-shaped nozzle (the product made by Ikeuchi company, VP9020TPVDF). Moreover, about the space | interval of a nozzle and copper foil, all were 70 mm. After etching, a 3 wt% aqueous sodium hydroxide solution was sprayed to peel off the resist pattern to obtain a copper wiring pattern. In addition, about the comparative example 10, after etching with the etching solution which dissolved ferric chloride (400g / L) and hydrochloric acid (30g / L) in ion-exchange water as a 1st etching process, as a 2nd etching process Etching was performed with an etching solution having the composition shown in Comparative Example 10 in Table 2.

The obtained substrate was cut, the cross-sectional shape of the formed copper wiring pattern was observed, and the difference (W ₂ −W ₁ ) between the width (W ₂ ) and the top width (W ₁ ) of the copper wiring pattern was measured. did. Further, the amount of pattern thinning (25−W ₁ ) with respect to the resist pattern width in the 50 μm pitch pattern region was calculated from the measured value of the top width (W ₁ ). The results are shown in Table 1 (Examples) and Table 2 (Comparative Examples).

As shown in Table 1 and Table 2, in Examples 1 to 10, the value of (W ₂ −W ₁ ) was small and the pattern thinning amount was small. On the other hand, in Comparative Examples 1 to 10, at least one of the value of (W ₂ −W ₁ ) and the pattern thinning amount showed a large value (large absolute value). In addition, about the copper wiring pattern of 50 micrometers pitch of the comparative example 2, since the contact | adherence area of a resist pattern and a copper layer decreased by side etching, the resist pattern disappeared and a copper wiring pattern was not able to be formed. Moreover, about the 50 micrometer pitch copper wiring pattern of the comparative examples 5, 7, and 8, since the unetched location remained, the copper wiring pattern was not able to be formed.

1 of the bottom of the width W ₂ of copper wiring pattern on the top of the etching amount W ₁ copper wiring pattern of the insulating substrate 2 copper layer 2a etching portions 3 etching resist pattern 4 copper wiring pattern T ₀ etching starting copper thickness T ₁ the depth direction width

Claims (7)

In the method of forming a copper wiring pattern using an etchant containing a cupric ion source, acid, side etching inhibitor and water,
A first etching step of etching with the etching solution until the etching amount in the depth direction is 50 to 90% of the copper thickness at the start of etching;
A second etching step of etching with the etchant until the end of etching following the first etching step,
The copper wiring pattern, wherein R1 / R1 is 0.40 to 0.85, where R1 is an etching rate in the first etching step and R2 is an etching rate in the second etching step. Forming method.   2. The method for forming a copper wiring pattern according to claim 1, wherein each of the first and second etching steps is a step of etching by spraying.   3. The copper wiring according to claim 2, wherein the value of P2 / P1 is 0.24 to 0.60 when the spray pressure in the first etching step is P1 and the spray pressure in the second etching step is P2. Pattern formation method.   The copper wiring pattern according to any one of claims 1 to 3, wherein the copper wiring pattern includes a first pattern region and a second pattern region having an interval narrower than an interval between the wirings of the first pattern region. Pattern formation method.   5. The value obtained by subtracting D <b> 2 from D <b> 1 is 7 μm or more, where D <b> 1 is an interval between wirings in the first pattern region and D <b> 2 is an interval between wirings in the second pattern region. Of forming a copper wiring pattern.   The method for forming a copper wiring pattern according to claim 1, wherein an etching rate in the first etching step is 35 μm / min or less.   The method for forming a copper wiring pattern according to claim 1, wherein the side etching inhibitor is an azole having only a nitrogen atom as a different atom in the ring.

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