Gold etching solution, its use and method for etching wafer plated gold-silver alloy

Abstract

The application relates to the field of advanced packaging semiconductor driving chips, and discloses a gold etching solution, application of the gold etching solution and a method for etching a wafer electroplated gold-silver alloy. The gold etching solution comprises a complexing agent, an oxidizing agent, an aluminum protective agent and a solvent; wherein the complexing agent comprises a main complexing agent and an auxiliary complexing agent; the main complexing agent is selected from thiourea and / or a thiourea derivative; the auxiliary complexing agent is selected from at least one of butyl xanthate, isoamyl xanthate, thiuram disulfide and diethyl phosphonate; and the weight ratio of the complexing agent: the oxidizing agent: the aluminum protective agent: the solvent is 1:(0.2-1.5):(0.2-1.5):(20-30). The gold etching solution has mild oxidizing property, can selectively etch a PVD gold seed layer, avoids etching the gold-silver alloy bump itself, does not cause the gold-silver alloy bump to appear serious deformation, avoids damage to aluminum lines in the wafer caused by etching, and has mild etching conditions and adjustable gold etching rate.

Description

Technical Field

[0001] This invention relates to the field of advanced packaged semiconductor driver chips, specifically to a gold etching solution and its application, and a method for etching wafers to electroplat gold and silver alloys. Background Technology

[0002] In the fabrication of liquid crystal driver chips, gold accounts for 70%-90% of the cost of packaging materials. Finding a material to replace gold has become imperative. Considering that silver belongs to the same group as metals and that the price of silver is much lower than that of gold, gold-silver alloy electroplating has a significant cost advantage. Moreover, silver has better electrical and thermal conductivity than gold, making it the most promising alternative for industrial mass production.

[0003] In the packaging process of liquid crystal driver chips, after the gold bumps are prepared, the gold seed layer and adhesion layer need to be removed to achieve circuit isolation between the gold bumps. CN116406431A discloses an etching solution for gold or gold alloys, containing iodine, potassium iodide, an organic solvent, and water. Using this iodine- and potassium iodide-containing etching solution to etch a gold film, the main reaction in the etching process involves the oxidation of gold by iodine to form gold ions (Au). + ) and iodide ions (I - ) and gold ions (Au) + The interaction of these components forms a stable complex. Etching solutions with iodine and potassium iodide as the main components are already in mass production and use in industry, and their advantage is that they can efficiently etch gold.

[0004] However, the iodine / potassium iodide etching solution has too large a selectivity for gold and silver etching, and the silver etching rate is significantly faster than that of gold. After the gold seed layer is etched, it will cause severe deformation of the gold and silver bumps, making it unsuitable for etching gold and silver alloys and unable to be applied to the etching of gold and silver alloys on wafers.

[0005] Therefore, there is an urgent need to provide a new gold etching solution to solve the problem of severe deformation of gold-silver alloy bumps while etching the gold seed layer. Summary of the Invention

[0006] This invention addresses the problem of severe deformation of gold-silver alloy bumps after etching with existing iodine / potassium iodide etching solutions. It provides a gold etching solution, its application, and a method for etching gold-silver alloy plated wafers. This gold etching solution can efficiently etch the gold seed layer of gold-silver alloy bumps while preventing significant bump deformation.

[0007] To achieve the above objectives, the present invention provides a gold etching solution in a first aspect, the gold etching solution comprising: a complexing agent, an oxidizing agent, an aluminum protectant, and a solvent;

[0008] The complexing agent comprises a primary complexing agent and a secondary complexing agent; the primary complexing agent is selected from thiourea and / or thiourea derivatives; the secondary complexing agent is selected from at least one of butyl xanthate, isopentyl xanthate, thiouron, and diethyl phosphonate.

[0009] The weight ratio of the complexing agent, oxidizing agent, aluminum protectant, and solvent is 1:(0.2-1.5):(0.2-1.5):(20-30).

[0010] The present invention provides, in a second aspect, the application of the gold etching solution described in the first aspect in the etching of gold and silver alloys for wafer electroplating in semiconductor manufacturing.

[0011] The present invention provides a method for etching a wafer to electroplat gold and silver alloy, the method comprising: contacting the wafer to electroplat gold and silver alloy with the gold etching solution described in the first aspect above, and etching away the gold seed layer on the surface of the wafer to electroplat gold and silver alloy.

[0012] Through the above technical solution, the gold etching solution provided by this invention can selectively etch the PVD gold seed layer, avoiding etching the gold-silver alloy bumps themselves, preventing severe deformation of the gold-silver alloy bumps, and avoiding damage to the aluminum circuitry in the wafer during etching. This etching solution has mild oxidizing properties, mild etching conditions, and an adjustable gold etching rate. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0014] Figure 1 This is an image of the unetched wafer.

[0015] Figure 2 This is a wafer image after etching with the etching solution in Example 1 of the present invention.

[0016] Figure 3 This is a wafer image after etching with the etching solution of Comparative Example 5 of the present invention. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention. Any equivalent changes or modifications made in accordance with the spirit and essence of the present invention should fall within the protection scope of the present invention.

[0018] The present invention provides a gold etching solution in a first aspect, the gold etching solution comprising: a complexing agent, an oxidizing agent, an aluminum protectant, and a solvent;

[0019] The complexing agent comprises a primary complexing agent and a secondary complexing agent; the primary complexing agent is selected from thiourea and / or thiourea derivatives; the secondary complexing agent is selected from at least one of butyl xanthate, isopentyl xanthate, thiouron, and diethyl phosphonate.

[0020] The weight ratio of the complexing agent, oxidizing agent, aluminum protectant, and solvent is 1:(0.2-1.5):(0.2-1.5):(20-30).

[0021] Existing halogen-containing etching solutions (e.g., those containing iodine and potassium iodide) are unsuitable for gold-silver alloys. This is because iodine and potassium iodide etch silver too quickly, causing deformation of the alloy bumps. Furthermore, the silver iodide produced during etching is insoluble and easily adheres to the product surface, causing defects. The inventors of this invention have discovered that using a gold etching solution containing the aforementioned specific primary and secondary complexing agents allows for highly efficient etching of gold while exhibiting relatively weak etching of silver. When this etching solution is used to etch gold-silver alloys plated on semiconductor wafers, it selectively etches the PVD gold seed layer on the wafer. Compared to conventional etching solutions, this significantly reduces damage to the gold-silver alloy bumps, thus preventing severe deformation of the bumps.

[0022] According to the present invention, the components in the gold etching solution, while satisfying the above-mentioned proportional relationship, preferably have a weight ratio of complexing agent: oxidant: aluminum protectant: solvent of 1:(0.2-1):(0.2-1):(20-30), which can make the gold etching solution have better selective etching performance.

[0023] According to the present invention, in the gold etching solution, the weight ratio of the main complexing agent to the auxiliary complexing agent can be 1:(0.5-2), which is beneficial for protecting the shape and appearance of the gold-silver alloy. Preferably, the weight ratio of the main complexing agent to the auxiliary complexing agent is 1:(1-1.5).

[0024] According to the present invention, in the gold etching solution, the main complexing agent is selected from thiourea and / or thiourea derivatives, which can more effectively undergo a complexation reaction with gold.

[0025] In this invention, the thiourea derivative may be selected from at least one of amidothiourea, N-methylthiourea and N-ethylthiourea.

[0026] In this invention, the primary complexing agent may be selected from at least one of thiourea, amidothiourea, N-methylthiourea, and N-ethylthiourea.

[0027] Preferably, the primary complexing agent is further selected from thiourea and / or amidothiourea.

[0028] According to a more preferred embodiment of the present invention, the main complexing agent is thiourea.

[0029] According to the present invention, in the gold etching solution, the auxiliary complexing agent can selectively adsorb onto the surface of the gold-silver alloy to form a hydrophobic film, thereby improving etching efficiency. The presence of both the primary and auxiliary complexing agents significantly enhances selective etching performance and etching rate.

[0030] In this invention, preferably, the co-complexing agent may be selected from butyl xanthate and / or isopentyl xanthate.

[0031] According to a more preferred embodiment of the present invention, the co-complexing agent is butyl xanthate.

[0032] According to the present invention, in the gold etching solution, the oxidant can enhance the complexing ability of the complexing agent on gold. The selection of the oxidant is not particularly limited in the present invention, and conventional oxidants used in gold etching solutions in the art can be used. Preferably, the oxidant can be selected from at least one of ferric nitrate, sodium m-nitrotoluenesulfonate, hydrogen peroxide, sodium bismuthate, and manganese sulfate (Mn2(SO4)3), with sodium m-nitrotoluenesulfonate being preferred, as it helps to improve etching efficiency and save reaction time.

[0033] According to a preferred embodiment of the present invention, the oxidant is sodium m-nitrotoluenesulfonate.

[0034] According to the present invention, in the gold etching solution, the aluminum protective agent can be adsorbed onto the aluminum metal to form a protective film, thereby protecting the aluminum circuitry. Preferably, the aluminum protective agent can be selected from at least one of potassium citrate, sodium ethylenediaminediacetate, hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, glycine, imidazole, benzoimidazole, 2-ethylimidazole, benzotriazole, 1-propylimidazole, triethanolamine, and 2-mercaptobenzothiazole. The above-mentioned protective agents can form a protective film on the aluminum metal, preventing the aluminum metal from reacting under alkaline conditions.

[0035] According to a preferred embodiment of the present invention, the aluminum protectant is selected from hydroxyethylidene diphosphonic acid and / or sodium ethylenediamine diacetate.

[0036] According to the present invention, the selection of the solvent in the gold etching solution is not particularly limited, and solvents conventionally used for gold etching solutions in the art can be used. Preferably, the solvent can be selected from at least one of water, isopropanol, and ethanol.

[0037] According to a preferred embodiment of the present invention, the solvent is water.

[0038] According to the present invention, in addition to the components described above, the gold etching solution may also include a pH buffer and / or a surfactant.

[0039] In this invention, the selection of the pH buffer in the gold etching solution is not particularly limited, and conventional pH buffers used in gold etching solutions in the art can be used. Preferably, the pH buffer can be selected from at least one of sodium acetate-acetic acid buffer, sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, and sodium nitrite-sodium nitrate buffer, which is more conducive to stabilizing the pH value of the etching solution.

[0040] According to a preferred embodiment of the present invention, the pH buffer is sodium acetate-acetic acid buffer salt.

[0041] According to the present invention, in the gold etching solution, preferably, the weight ratio of the complexing agent to the pH buffer is 1:(0.5-2), which can better stabilize the pH value of the etching solution over a long period of time.

[0042] In this invention, the selection of the surfactant in the gold etching solution is not particularly limited, and conventional surfactants used in gold etching solutions in the art can be used. Preferably, the surfactant can be selected from at least one of PEG-7, PEG-10, PEG-800, PEG-2000, sodium dodecylbenzenesulfonate, dodecylphenol polyoxyethylene ether, polyethylene glycol p-isooctylphenyl ether, dodecyl alcohol polyoxyethylene ether, tallow alcohol polyether-4, dodecyl alcohol ether, lauryl alcohol ether, N-methylpyrrolidone, and glycerol, and is more preferably N-methylpyrrolidone and / or glycerol, which helps to reduce the surface tension of the etching solution and improve the etching ability of the etching solution in the gaps.

[0043] According to a preferred embodiment of the present invention, the surfactant is N-methylpyrrolidone.

[0044] According to the present invention, in the gold etching solution, preferably, the weight ratio of the complexing agent to the surfactant is 1:(0.0001-0.1), which can better etch the gold seed layer in the gaps of the solution.

[0045] According to the present invention, the gold etching solution is weakly alkaline. Preferably, the pH value of the gold etching solution is 8-11, more preferably 9-10.

[0046] The gold etching solution provided by this invention has mild oxidizing properties, enabling efficient gold etching. The gold etching rate is controllable and easily adjustable, while its etching effect on silver is relatively weak. This etching solution is used to etch gold-silver alloys plated on semiconductor wafers. While etching away the gold seed layer, it prevents significant deformation of the gold-silver alloy bumps and avoids damage to the aluminum circuitry on the wafer. This etching solution is also environmentally friendly and safe.

[0047] According to a preferred embodiment of the present invention, the gold etching solution comprises a complexing agent (thiourea and butyl xanthate in a weight ratio of 1:1-1.2), an oxidizing agent (sodium m-nitrotoluenesulfonate), an aluminum protectant (hydroxyethylidene diphosphonic acid and / or sodium ethylenediamine diacetate), a pH buffer (sodium acetate-acetic acid buffer), a surfactant (N-methylpyrrolidone and / or glycerol), and a solvent (water), wherein the weight ratio of complexing agent: oxidizing agent: aluminum protectant: pH buffer: surfactant: solvent is 1:(0.2-0.5):(0.2-0.5):(1-2):(0.0001-0.1):(20-25), which enables the gold etching solution to have further improved high-efficiency gold etching, minimal damage to gold-silver alloy bumps, and avoidance of damage to aluminum circuitry on the wafer.

[0048] In this invention, the gold etching solution can be prepared by mixing its components.

[0049] According to a preferred embodiment of the present invention, it can be prepared by the following steps:

[0050] (1) The complexing agent, oxidizing agent and first portion of solvent are mixed in the above proportions to obtain a first liquid phase product;

[0051] (2) The first liquid phase product is mixed with the pH buffer, surfactant and second solvent to obtain a second liquid phase product;

[0052] (3) The second liquid phase product is mixed with the aluminum protective agent and the third solvent to obtain the gold etching solution.

[0053] Using the above preparation steps makes it easier to prepare a gold etching solution with uniformly mixed components.

[0054] According to the present invention, in the above preparation steps, the proportions of the first solvent, the second solvent, and the third solvent are not particularly limited, as long as each step can obtain a liquid phase product in which the components are fully dissolved and homogeneous.

[0055] The present invention provides, in a second aspect, the application of the gold etching solution described in the first aspect in the etching of gold and silver alloys for wafer electroplating in semiconductor manufacturing.

[0056] The gold etching solution provided by the present invention has the effects described in the first aspect above. The gold etching solution is used to etch gold and silver alloys plated on wafers in semiconductor manufacturing. It can peel off the gold film without causing significant deformation of the gold and silver alloy bumps, and can avoid damaging the aluminum lines on the wafer. It can well meet the production process requirements of gold and silver alloys plated on wafers.

[0057] The present invention provides a method for etching a wafer to electroplat gold and silver alloy, the method comprising: contacting the wafer to electroplat gold and silver alloy with the gold etching solution described in the first aspect above, and etching away the gold seed layer on the surface of the wafer to electroplat gold and silver alloy.

[0058] According to the present invention, in the method of etching a wafer to electroplate a gold-silver alloy, the contact is preferably carried out by completely immersing the object to be etched in the gold etching solution.

[0059] According to the present invention, in the method of etching wafers for electroplating gold and silver alloys, the contact conditions include: a contact temperature of 40-65°C, preferably 50-60°C; and a contact time of 2-5 minutes.

[0060] According to the present invention, in the method of etching a wafer to electroplate a gold-silver alloy, preferably, the contact temperature can be obtained by preheating the gold etching solution before the contact occurs.

[0061] According to the present invention, in the method for etching a wafer to electroplate a gold-silver alloy, the contact is preferably carried out under stirring conditions, which is more conducive to improving the uniformity of etching. Preferably, the stirring rate is 100-500 rpm.

[0062] According to the present invention, the method for etching wafers to electroplate gold and silver alloys further includes washing the etched object with a conventional cleaning agent (e.g., water) to remove the etching solution after etching is completed, followed by drying.

[0063] The present invention will be described in detail below through examples. Unless otherwise specified, the following examples and comparative examples are all conventional methods; the reagents and materials mentioned are commercially available unless otherwise specified.

[0064] Example 1

[0065] This example illustrates the preparation of gold etching solution.

[0066] (1) According to the ratio, the complexing agent (thiourea: butyl xanthate in a weight ratio of 1:1), the oxidizing agent (sodium m-nitrotoluenesulfonate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0067] (2) The first liquid phase product is mixed with pH buffer (sodium acetate-acetic acid buffer salt, wherein acetic acid is added in the form of 10% by weight acetic acid solution, and the weight ratio of sodium acetate to acetic acid solution is 5:1), surfactant (glycerol), and second part of water. After complete dissolution, the second liquid phase product is obtained.

[0068] (3) Mix all of the above second liquid phase products with aluminum protective agent (hydroxyethylidene diphosphonic acid) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L1) is obtained.

[0069] In the prepared gold etching solution L1, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.25:1.25:0.0025:22.25. The pH value of L1 is 9.

[0070] Example 2

[0071] This example illustrates the preparation of gold etching solution.

[0072] (1) According to the ratio, the complexing agent (thiourea:isoamyl xanthate in a weight ratio of 1:1), the oxidizing agent (sodium m-nitrotoluenesulfonate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0073] (2) The first liquid phase product is mixed with pH buffer (sodium acetate-acetic acid buffer salt, wherein acetic acid is added in the form of 10% by weight acetic acid solution, and the weight ratio of sodium acetate to acetic acid solution is 5:1), surfactant (N-methylpyrrolidone), and second part of water. After dissolution, the second liquid phase product is obtained.

[0074] (3) Mix all of the above second liquid phase products with aluminum protective agent (sodium ethylenediamine diacetate) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L2) is obtained.

[0075] In the prepared gold etching solution L2, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent was 1:0.25:0.25:0.875:0.005:22.625. The pH value of L2 was 9.2.

[0076] Example 3

[0077] This example illustrates the preparation of gold etching solution.

[0078] (1) According to the proportion, the complexing agent (thiourea: isoamyl xanthate in a weight ratio of 1:1), the oxidizing agent (ferric nitrate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0079] (2) The first liquid phase product is mixed with pH buffer (sodium acetate-acetic acid buffer salt, wherein acetic acid is added in the form of 10% by weight acetic acid solution, and the weight ratio of sodium acetate to acetic acid solution is 5:1), surfactant (PEG-800), and second part of water. After dissolution, the second liquid phase product is obtained.

[0080] (3) Mix all of the above second liquid phase products with aluminum protective agent (potassium citrate) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L3) is obtained.

[0081] In the prepared gold etching solution L3, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent was 1:0.25:0.5:1:0.0125:22.25. The pH value of L3 was 9.2.

[0082] Example 4

[0083] This example illustrates the preparation of gold etching solution.

[0084] (1) According to the ratio, the complexing agent (thiourea: butyl xanthate in a weight ratio of 1:1), the oxidizing agent (sodium m-nitrotoluenesulfonate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0085] (2) The first liquid phase product is mixed with pH buffer (sodium acetate-acetic acid buffer salt, wherein acetic acid is added in the form of 10% by weight acetic acid solution, and the weight ratio of sodium acetate to acetic acid solution is 5:1), surfactant (dodecyl alcohol polyoxyethylene ether), and second part of water. After dissolution, the second liquid phase product is obtained.

[0086] (3) Mix all of the above second liquid phase products with aluminum protective agent (2-ethylimidazole) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L4) is obtained.

[0087] In the prepared gold etching solution L4, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent was 1:0.25:0.25:1:0.00125:22.5. The pH value of L4 was 9.3.

[0088] Example 5

[0089] This example illustrates the preparation of gold etching solution.

[0090] (1) According to the ratio, the complexing agent (thiourea:thiouric acid ester weight ratio is 1:1), the oxidizing agent (ferric nitrate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0091] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-10:dodecyl ether in a weight ratio of 1:1), and the second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0092] (3) Mix all of the above second liquid phase products with aluminum protective agent (imidazolium) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L5) is obtained.

[0093] In the prepared gold etching solution L5, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.5:1.25:0.00522:22. The pH value of L5 is 9.2.

[0094] Example 6

[0095] This example illustrates the preparation of gold etching solution.

[0096] (1) According to the ratio, the complexing agent (thiourea: isoamyl xanthate in a weight ratio of 1:1), the oxidizing agent (sodium bismuthate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0097] (2) Mix all of the above first liquid phase products with pH buffer (sodium dihydrogen phosphate-disodium hydrogen phosphate buffer salt, the weight ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate is 1:2.5), surfactant (sodium dodecylbenzene sulfonate), and the second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0098] (3) Mix all of the above second liquid phase products with aluminum protective agent (glycine) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L6) is obtained.

[0099] In the prepared gold etching solution L6, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.25:0.875:0.0005:22.625. The pH value of L6 is 9.

[0100] Example 7

[0101] This example illustrates the preparation of gold etching solution.

[0102] (1) According to the ratio, the complexing agent (thiourea: diethyl phosphonate in a weight ratio of 1:1), the oxidizing agent (sodium m-nitrotoluenesulfonate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0103] (2) Mix all of the above first liquid phase products with pH buffer (sodium dihydrogen phosphate-disodium hydrogen phosphate buffer salt, the weight ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate is 1:8), surfactant (glycerol), and second part of water in a second mixture. After complete dissolution, the second liquid phase product is obtained.

[0104] (3) Mix all of the above second liquid phase products with aluminum protective agent (hydroxyethylidene diphosphonic acid) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L7) is obtained.

[0105] In the prepared gold etching solution L7, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.75:1.125:0.00125:22. The pH value of L7 is 9.

[0106] Example 8

[0107] This example illustrates the preparation of gold etching solution.

[0108] (1) According to the proportion, the complexing agent (amidinethiourea: butyl xanthate in a weight ratio of 1:1), the oxidizing agent (hydrogen peroxide aqueous solution with a concentration of 30% by weight) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0109] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-2000), and second part of water in a second mixture. After complete dissolution, the second liquid phase product is obtained.

[0110] (3) Mix all of the above second liquid phase products with aluminum protective agent (benzotriazole) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L8) is obtained.

[0111] In the prepared gold etching solution L8, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent was 1:0.5:0.25:1.25:0.0013:22. The pH value of L8 was 9.5.

[0112] Example 9

[0113] This example illustrates the preparation of gold etching solution.

[0114] (1) According to the proportion, the complexing agent (the weight ratio of amidothiourea to butyl xanthate is 1:2.3), the oxidizing agent (hydrogen peroxide aqueous solution with a concentration of 30% by weight) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0115] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-2000), and second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0116] (3) Mix all of the above second liquid phase products with aluminum protective agent (benzotriazole) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as L9) is obtained.

[0117] In the prepared gold etching solution L9, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.4:0.2:1:0.001:20.4. The pH value of L9 is 9.5.

[0118] Comparative Example 1

[0119] This example illustrates the preparation of gold etching solution.

[0120] (1) According to the proportion, the complexing agent (thiouric acid ester), oxidizing agent (ferric nitrate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0121] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-10:dodecyl ether in a weight ratio of 1:1), and the second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0122] (3) Mix all of the above second liquid phase products with aluminum protective agent (imidazolium) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as DL1) is obtained.

[0123] In the prepared gold etching solution DL1, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.5:1.25:0.00522:22. The pH value of DL1 is 9.2.

[0124] Comparative Example 2

[0125] This example illustrates the preparation of gold etching solution.

[0126] (1) According to the proportion, the complexing agent (thiourea), oxidizing agent (ferric nitrate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0127] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-10:dodecyl ether in a weight ratio of 1:1), and the second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0128] (3) Mix all of the above second liquid phase products with aluminum protective agent (imidazolium) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as DL2) is obtained.

[0129] In the prepared gold etching solution DL2, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.5:1.25:0.00522:22. The pH value of DL2 is 9.2.

[0130] Comparative Example 3

[0131] This example illustrates the preparation of gold etching solution.

[0132] (1) According to the ratio, the complexing agent (1,3-dihydroxymethyl-5,5-dimethylhydantoin:thiocarbamate in a weight ratio of 1:1), the oxidizing agent (ferric nitrate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0133] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-10:dodecyl ether in a weight ratio of 1:1), and the second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0134] (3) Mix all of the above second liquid phase products with aluminum protectant (imidazolium) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as DL3) is obtained.

[0135] In the prepared gold etching solution DL3, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.5:1.25:0.00522:22. The pH value of DL3 is 9.2.

[0136] Comparative Example 4

[0137] This example illustrates the preparation of gold etching solution.

[0138] (1) According to the ratio, the complexing agent (thiourea:urea weight ratio of 1:1), oxidant (ferric nitrate) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0139] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-10:dodecyl ether in a weight ratio of 1:1), and the second part of water in a second mixing process. After complete dissolution, the second liquid phase product is obtained.

[0140] (3) Mix all of the above second liquid phase products with aluminum protective agent (imidazolium) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as DL4) is obtained.

[0141] In the prepared gold etching solution DL4, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:0.25:0.5:1.25:0.00522:22. The pH value of DL4 is 9.

[0142] Comparative Example 5

[0143] The gold etching solution (denoted as DL5) was prepared according to the method in Example 1 of CN114351144B.

[0144] Comparative Example 6

[0145] This example illustrates the preparation of gold etching solution.

[0146] (1) According to the proportion, the complexing agent (amidinethiourea: butyl xanthate in a weight ratio of 1:1), the oxidizing agent (hydrogen peroxide aqueous solution with a concentration of 30% by weight) and the first part of water are combined and dissolved to obtain the first liquid phase product;

[0147] (2) Mix all of the above first liquid phase products with pH buffer (sodium nitrite-sodium nitrate buffer salt, the weight ratio of sodium nitrite to sodium nitrate is 1.5:1), surfactant (PEG-2000), and second part of water in a second mixture. After complete dissolution, the second liquid phase product is obtained.

[0148] (3) Mix all of the above second liquid phase products with aluminum protective agent (benzotriazole) and third part water in a third mixture. After complete dissolution, a clear gold etching solution (denoted as DL6) is obtained.

[0149] In the prepared gold etching solution DL6, the weight ratio of complexing agent: oxidant: aluminum protectant: pH buffer: surfactant: solvent is 1:2.5:0.25:1.25:0.0025:30. The pH value of DL6 is 9.

[0150] Test case

[0151] Etching tests were conducted on the gold etching solutions L1-L9 and DL1-DL6 prepared in Examples 1-9 and Comparative Examples 1-6, respectively. Specifically, under certain temperature conditions, wafers with a gold film deposited on a silicon substrate were etched using an immersion etching method (stirring rate of 150 rpm). The wafers were completely immersed in the gold etching solution until the PVD gold film on the wafers was completely removed. After etching, the wafers were taken out, rinsed with pure water, and dried with cold air. The test results are shown in Table 1.

[0152] Table 1

[0153]

[0154] Note: In Table 1, " / " indicates no etching effect. The X-axis difference represents the change in the short side length of the gold-silver alloy bump, the Y-axis difference represents the change in the long side length of the gold-silver alloy bump, and the Z-axis difference represents the change in the height of the gold-silver alloy bump. The gold-silver alloy bumps using DL5 etching solution showed deformation.

[0155] As shown in Table 1, etching solutions L1-L9 can etch the gold seed layer on the gold-silver alloy plated on the wafer at a relatively fast etching rate, and can completely etch the gold seed layer, while causing minimal damage to the aluminum metal (very low etching rate for aluminum). Etching solutions DL1-DL4 have virtually no etching ability on the gold seed layer on the gold-silver alloy plated on the wafer, and the gold etching rate of etching solution DL6 is too low. Etching solution DL5 uses an iodine / potassium iodide system, which will cause significant damage to the gold-silver alloy bumps (excessively high X-axis, Y-axis, and Z-axis differences). Furthermore, Figure 1 This is an image of the unetched wafer. Figure 2 This is a wafer image after etching using the etching solution from Example 1 in this test. Figure 3 The image shows the wafer after etching with the etching solution of Comparative Example 5 in this test. It can be seen that after etching with the etching solution of Example 1, the bumps did not deform significantly, while after etching with the etching solution of Example 5, the bumps were severely deformed.

[0156] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A gold etching liquid, characterized by, The gold etching solution includes: a complexing agent, an oxidizing agent, an aluminum protectant, and a solvent; The complexing agent comprises a primary complexing agent and a secondary complexing agent; the primary complexing agent is selected from thiourea and / or thiourea derivatives; the secondary complexing agent is selected from at least one of butyl xanthate, isopentyl xanthate, thiouron, and diethyl phosphonate. The weight ratio of the complexing agent, oxidizing agent, aluminum protectant, and solvent is 1:(0.2-1.5):(0.2-1.5):(20-30). The weight ratio of the primary complexing agent to the secondary complexing agent is 1:(0.5-2).

2. The gold etching liquid according to claim 1, wherein The weight ratio of the complexing agent, oxidizing agent, aluminum protectant, and solvent is 1:(0.2-1):(0.2-1):(20-30).

3. The gold etching solution of claim 1, wherein The weight ratio of the primary complexing agent to the secondary complexing agent is 1:(1-1.5).

4. The gold etching liquid according to claim 1 or 2, characterized by, The main complexing agent is selected from at least one of thiourea, amidothiourea, N-methylthiourea and N-ethylthiourea; And / or, the co-complexing agent is selected from butyl xanthate and / or isopentyl xanthate.

5. The gold etching liquid according to claim 1 or 2, characterized by, The oxidant is selected from at least one of ferric nitrate, sodium m-nitrotoluenesulfonate, hydrogen peroxide, sodium bismuthate, and manganese sulfate; And / or, the aluminum protectant is selected from at least one of potassium citrate, sodium ethylenediamine diacetate, hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, glycine, imidazole, benzoimidazole, 2-ethylimidazole, benzotriazole, 1-propylimidazole, triethanolamine and 2-mercaptobenzothiazole; And / or, the solvent is selected from at least one of water, isopropanol, and ethanol; And / or, the gold etching solution further includes a pH buffer and / or a surfactant.

6. The gold etching solution according to claim 5, wherein The oxidant is sodium m-nitrotoluenesulfonate; And / or, the aluminum protectant is hydroxyethylidene diphosphonic acid and / or sodium ethylenediamine diacetate; And / or, the solvent is water.

7. The gold etching solution according to claim 5, wherein The pH buffer is selected from at least one of sodium acetate-acetic acid buffer, sodium dihydrogen phosphate-disodium hydrogen phosphate buffer, and sodium nitrite-sodium nitrate buffer. And / or, the surfactant is selected from at least one of PEG-7, PEG-10, PEG-800, PEG-2000, sodium dodecylbenzenesulfonate, dodecylphenol polyoxyethylene ether, polyethylene glycol p-isooctylphenyl ether, dodecyl alcohol polyoxyethylene ether, tallow alcohol polyether-4, dodecyl alcohol ether, lauryl alcohol ether, N-methylpyrrolidone and glycerol.

8. The gold etching solution according to claim 7, wherein The pH buffer is sodium acetate-acetic acid buffer salt; And / or, the surfactant is N-methylpyrrolidone and / or glycerol.

9. The gold etching liquid according to claim 1 or 2, wherein The weight ratio of the complexing agent to the pH buffer is 1:(0.5-2). And / or, the weight ratio of the complexing agent to the surfactant is 1:(0.0001-0.1). And / or, the pH value of the gold etching solution is 8-11.

10. The application of the gold etching solution according to any one of claims 1-9 in the etching of gold and silver alloys on wafers in semiconductor manufacturing.

11. A method of etching a gold-silver alloy plated wafer, characterized by, The method includes: contacting a wafer electroplated with a gold-silver alloy with the gold etching solution described in any one of claims 1-9 to etch away the gold seed layer on the surface of the wafer electroplated with the gold-silver alloy.

12. The method according to claim 11, characterized in that, The contact conditions include: a contact temperature of 40-65℃ and a contact time of 2-5 minutes.

Images