An etching solution for selectively etching AlCu layer relative to laminated metal and preparation method thereof

Abstract

The present invention belongs to the field of integrated circuit electronic chemicals, and specifically relates to an etching solution for selectively etching an AlCu layer relative to a laminated metal and a preparation method thereof. The etching solution is mainly used for selectively etching an AlCu alloy layer relative to a laminated metal (composed of a photoresist, an AlCu alloy layer, a W layer, a TiN layer and a Ti layer from top to bottom), and its composition includes an oxidant, a corrosive agent, an additive, a complexing agent, a leveling agent and ultrapure water. The present invention provides an etching solution for selectively etching an AlCu layer relative to a laminated metal and a preparation method thereof. The use of the etching solution according to the method can not only effectively control the etching of the AlCu layer in the laminated metal while other metal layers are not etched, but also has high etching accuracy and good etching morphology, and has no damage to the electrochemical properties of the substrate.

Description

Technical Field

[0001] The invention belongs to the field of electronic chemicals, and in particular relates to an etching solution for selectively etching an AlCu layer relative to a laminated metal and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of the field of microelectronic device manufacturing, people's requirements for electronic equipment are more miniaturized, highly functional, and thinner, that is, the printed circuit boards in integrated circuits are required to be more and more miniaturized and integrated. Among the many printed circuit board materials, AlCu alloys are widely used in metal wiring of semiconductor devices due to their excellent properties, such as higher conductivity and ductility, good adhesion to the underlying substrate or dielectric layer, high mechanical strength and good heat dissipation performance. Therefore, the fine etching of AlCu alloy is one of the key processes in the manufacturing process of printed circuit boards. Metal wiring is a structure that interconnects different devices. It is usually formed by dry etching or wet etching. Due to the high adaptability and high selectivity of wet etching, as well as the advantages of low cost and large-scale processing, it has long been preferred in the industry.

[0003] When AlCu alloy is used as metal wiring, there are also some problems of its own. When AlCu alloy is used as gate metal wiring, its adhesion with substrate (such as glass, etc.) is poor; when it is used as source and drain wiring, it may diffuse to the substrate of AlCu, that is, silicon semiconductor film. In order to prevent or reduce the occurrence of the above situation, researchers try to add one or more metal film layers that can achieve metal barrier between the configuration line and the substrate such as glass, such as W, Ti and Mo metal film layers, so as to construct a laminated metal structure and improve the wide application of AlCu alloy in the field of microelectronic devices. Due to the different composition of metals between different film layers, there are great differences in chemical and electrochemical properties. At the same time, electrochemical reactions are prone to occur between different metal film layers during the etching process, resulting in cracks and subsequent process disconnection, thereby reducing the yield of electronic products. Therefore, it is an ideal etching process to effectively etch different metal layers separately, but this poses a great challenge to the development of etching solution formula.

[0004] To solve the above problems, the present invention provides an etching solution for selectively etching an AlCu layer relative to a laminated metal and a preparation method thereof. The etching solution used according to the method can not only effectively control the etching of the AlCu layer in the laminated metal while other metal layers are not etched, but also has high etching accuracy and good etching morphology, and has no damage to the electrochemical properties of the substrate. Summary of the invention

[0005] The present invention aims to provide an etching solution and a preparation method thereof for selectively etching the AlCu layer in the laminated metal in the existing semiconductor integrated circuit process, in order to solve the problem that the selective etching of the AlCu layer in the laminated metal is difficult to control.

[0006] The etching solution uses an oxidant to oxidize AlCu to form oxides; the oxides of AlCu are removed by dissolving in contact with a corrosive agent, thereby increasing the etching rate; the etching rate of AlCu is adjusted by an additive, so that the etching solution has a faster etching rate for the AlCu layer relative to other metal stacks, that is, has a higher selectivity for the AlCu layer; the addition of an etching stabilizer ensures good etching performance, stabilizes the etching rate and the side etching rate; the addition of a complexing agent can protect other metal layers, while controlling the etching selectivity and the etching rate.

[0007] To achieve the purpose of the invention, the raw materials of the invention include: 2-4wt% oxidant, 70-75wt% corrosive agent, 10-15wt% additive, 0.5-5wt% complexing agent and 0.1-1wt% etching stabilizer, and the rest is water.

[0008] In the implementation case, the oxidant is nitric acid; the corrosive agent is phosphoric acid or polyphosphoric acid; and the additive is acetic acid.

[0009] In the implementation case, the complexing agent is at least one of N-methylpiperidine, N-acylamino acid, 4-sulfonaminopyridine, 4-(3,5-dimethylphenyl)-2,6-di-p-tolylpyridine, 4-chloro-3-pyridinesulfonamide, 4-methylbenzenesulfonate pyridine, tetrakis(4-aminophenyl)porphyrin, tetrahydropyrrolodihydrochlorin and tetraphenylporphyrin, 5,10,15,20-tetraaminophenylporphyrin, 5,10,15,20-tetracarboxyphenylporphyrin, β-mercaptoethylamine, 4-aminopyridine-2,6-dicarboxylic acid dimethyl ester and 2,6-pyridinedicarboxylic acid monomethyl ester.

[0010] In the implementation case, the etching stabilizer is at least one of modified alkyl diethanolamide, sodium α-olefin sulfonate, diethylene glycol monobutyl ether, stearic acid diethanolamide, stearic acid monoethanolamide, dodecyl phosphate, didodecyl hydrogen phosphate, N,N-bis(2-acrylamidoethyl)acrylamide and alkyl monoethanolamide.

[0011] In the implementation case, the modified alkyl diethanolamide is prepared by introducing a polysuccinimide polymer into the alkyl diethanolamide chain.

[0012] In the implementation case, the method for preparing an etching solution for selectively etching the AlCu layer relative to the laminated metal is: weighing the oxidant, corrosive agent, additive, chelating agent, etching stabilizer and ultrapure water respectively in proportion, configuring them in the order of water, corrosive agent, oxidant, additive, chelating agent and etching stabilizer, and cooling them to room temperature after mixing them evenly.

[0013] In the implementation case, the etching temperature is 40-50° C., the etching method is immersion etching, and the etching time is 12.5 min.

[0014] The etching method described herein is characterized in that: after removing the exposed AlCu film layer, the ratio of the lateral etching depth of the AlCu film layer covered by the photoresist to the longitudinal etching depth of the exposed AlCu film layer is less than 3, or less than 2, or less than 1.5. Further, for the preferred composition, the ratio range is less than about 1.35 and the etching effect is highly stable; the lateral etching depth of the AlCu layer covered by the photoresist is the lateral etching amount, and the lateral etching amount ranges from 5.8 μm to 6.8 μm.

[0015] Advantages and beneficial effects of the present invention:

[0016] 1) The invention has a simple formula and simple preparation steps, but can achieve the purpose of etching only the AlCu layer without etching other metal layers, and effectively avoid electrochemical reactions between metal layers; wet etching is performed at a higher temperature for a longer time, and the results show that the etching solution formula does not damage or dissolve the photoresist layer.

[0017] 2) The etching solution composition according to each example listed in the present invention may not include hydrogen peroxide, thereby preventing the exothermic decomposition of hydrogen peroxide from generating gas and causing the etching effect to be unstable.

[0018] 3) Introducing corrosive phosphoric acid or polyphosphoric acid on the basis of nitric acid improves the etching rate of the AlCu alloy, and the etching rate of the etching solution can be controlled by adjusting the ratio of nitric acid or phosphoric acid and polyphosphoric acid.

[0019] 4) H2 will be produced during the etching reaction. The existence and production rate of H2 bubbles will directly affect the surface tension of the solution. The introduction of acetic acid as an additive can reduce the surface tension of the solution, increase the wetting effect, and improve the etching uniformity. Acetic acid also acts as a buffer. Acetic acid can adjust the oxidation rate of nitric acid. By adjusting the ratio of acetic acid, the etching rate can be controlled.

[0020] 5) The introduction of complexing agents such as N-methylpiperidine, N-acylamino acid and 4-sulfonaminopyridine can form metal chelates with the free trivalent aluminum ions and divalent copper ions produced by the etching reaction, thereby reducing the concentration of metal ions in the solution, preventing or alleviating the decomposition of nitric acid catalyzed by divalent copper ions, ensuring the stability of the etching effect, extending the life of the etching solution, and improving the utilization rate of the etching solution.

[0021] 6) The introduction of etching stabilizers such as modified alkyl diethanolamide, sodium α-olefin sulfonate, diethylene glycol monobutyl ether and stearic acid diethanolamide can effectively control the etching rate and etching morphology, and improve the stability of the etching effect and the etching accuracy.

[0022] 7) Aiming at the needs in semiconductor technology, the present invention can effectively protect the silicon substrate; by regulating the content of each component in the etching solution, it is beneficial to realize the preparation or patterning design of AlCu nanowires; and effectively avoid the residual AlCu layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the test piece microstructure, A is the schematic diagram before etching, and B is the schematic diagram after etching.

[0024] Figure 2 SEM image of the multilayer metal structure before etching.

[0025] Figure 3 SEM image of the W layer after etching of the multilayer metal structure sheet.

[0026] Figure 4 This is the SEM slice test image of Comparative Example 1.

[0027] Figure 5 SEM slice test image of Example 2.

[0028] Figure 6 SEM slice test image of Example 3.

[0029] Figure 7 SEM slice test image of Example 4.

[0030] Figure 8 SEM slice test image of Example 5.

[0031] Fig. 9 SEM slice test image of Example 6.

[0032] Fig.10 SEM slice test image of Example 7.

[0033] Fig.11 SEM slice test image of Example 8.

[0034] Fig.12 SEM slice test image of Example 9.

[0035] Fig.13 SEM slice test image of Example 10.

[0036] Fig.14 SEM slice test image of Example 11.

[0037] Fig.15 SEM slice test image of Example 12.

[0038] Fig.16 SEM slice test image of Example 13.

[0039] Fig.17 SEM slice test image of Example 14.

[0040] Fig.18 SEM slice test image of Example 15.

[0041] Fig.19 SEM slice test image of Example 16. DETAILED DESCRIPTION

[0042] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with embodiments, but the content of the present invention is not limited to the following examples.

[0043] Comparative Example 1

[0044] In Comparative Example 1, a conventional hydrogen peroxide / sulfuric acid solution is used, and the components and contents of the solution are shown in Table 1. The etching solution is prepared according to the components and contents listed in Table 1. Figure 1 , 2 The semiconductor device shown is etched. Figure 1 This is a schematic diagram of the microstructure of a semiconductor device with multiple metal film layers exposed on a silicon substrate partially covered with photoresist according to the present invention. The thickness of the AlCu layer in the semiconductor device is about 5.2μm, the etching temperature is 45°C, and the etching time is 12.5min. After etching, the multi-layer metal structure sheet is cleaned and dried and subjected to SEM slice testing. The SEM picture is as follows Figure 4 The etching effects are summarized in Table 2. In the comparative example, the exposed AlCu film layer was not completely etched, the side etching amount of the AlCu layer under the photoresist was about 4.9 μm, the etching effect was general, the etching rate was slow, and there was no peeling of the photoresist.

[0045] Table 1 Comparative Examples Components and Contents

[0046]

[0047] Table 2 Etching effect of comparative examples

[0048]

[0049] Example 1

[0050] An etching solution for selectively etching an AlCu layer relative to a laminated metal, the components of which are shown in Table 3:

[0051] Table 3 Components and contents of Example 1

[0052]

[0053]

[0054] Prepare the etching solution according to the components and contents listed in Table 3. Figure 1 , 2 The semiconductor device shown in the figure is etched, the etching solution temperature is controlled at 45°C, and the etching time is 12.5 minutes. After etching, the multilayer metal structure is cleaned and dried and SEM sliced ​​for testing. The SEM picture is shown in Figure 5 The etching effects are summarized in Table 4.

[0055] Figure 1 The microstructure diagram of the semiconductor device with multiple metal film layers exposed on the silicon substrate partially covered with photoresist, wherein the AlCu layer is about 5.2μm, and the exposed AlCu film layer is etched and or removed therefrom by the etching solution and etching method of the present invention. After etching the structure sheet using the formula of the present patent, the metal W layer is not etched and the TiN and Ti layers are not etched after 12.5 minutes. Figure 2 This is the SEM test picture of the semiconductor device before etching. Figure 3 This is the state of the W metal layer after etching. The thickness of the W layer does not change before and after etching, and is about 400nm.

[0056] During the etching process, the exposed AlCu film layer needs to be completely etched. During this process, the etching solution will laterally etch the AlCu film layer under the photoresist. After etching, cleaning and drying, the semiconductor device is subjected to SEM sectioning test. The SEM picture is as follows: Figure 5 The etching effect is shown in Table 4. In Example 1, the exposed AlCu film layer is completely etched, the side etching amount of the AlCu layer under the photoresist is about 6.2 μm, the ratio of the side etching amount to the AlCu layer thickness is about 1.19, and the photoresist is not stripped, that is, the etching effect is excellent.

[0057] Example 2

[0058] Same as Example 1, the complexing agent is adjusted to 1.0% N-acylglycine, 0.6% 4-sulfaminopyridine and 0.5% 4-(3,5-dimethylphenyl)-2,6-di-p-tolylpyridine, the etching stabilizer is adjusted to 0.2% dodecyl phosphate and 0.2% didodecyl hydrogen phosphate, and the contents of other components remain unchanged, set to Example 2, the semiconductor device etching steps and testing methods are the same as Example 1.

[0059] SEM test results are shown in Figure 6 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 6.8 μm, but the etching effect is still better, the ratio of the side etching amount to the AlCu layer thickness is about 1.31, and the photoresist is not stripped.

[0060] Example 3

[0061] The same as in Example 1, the oxidizing agent nitric acid is adjusted from 2.5% to 2.1%, the complexing agent is adjusted to 2.1% of 4-chloro-3-pyridinesulfonamide, the etching stabilizer is adjusted to 0.8% of diethylene glycol monobutyl ether and 0.1% of sodium α-olefin sulfonate, the contents of other components remain unchanged, set to Example 3, the semiconductor device etching steps and testing methods are the same as in Example 1.

[0062] SEM test results are shown in Figure 7 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is reduced by about 5.8 μm, the etching effect is excellent, the ratio of the side etching amount to the AlCu layer thickness is about 1.06, and the photoresist is not stripped.

[0063] Example 4

[0064] Same as Example 1, only the oxidizing agent nitric acid is adjusted from 2.5% to 1.8%, and the contents of other components remain unchanged, which is set as Example 4. The semiconductor device etching steps and testing methods are the same as Example 1.

[0065] SEM test results are shown in Figure 8 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is reduced by about 5.3 μm, but the exposed AlCu film layer is not completely etched. The side etching rate of this formula is too slow and the photoresist is not stripped.

[0066] Example 5

[0067] The same as Example 1, only the etchant phosphoric acid is adjusted from 71% to 74%, the complexing agent is adjusted to 1.3% of 5,10,15,20-tetraaminophenylporphyrin and 0.9% of 5,10,15,20-tetracarboxylphenylporphyrin, the leveling agent is adjusted to 0.6% of stearic acid monoethanolamide, and the contents of other components remain unchanged, set to Example 5, the semiconductor device etching steps and testing methods are the same as Example 1.

[0068] SEM test results are shown in Fig. 9 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 6.4 μm, but the etching effect is still good, the ratio of the side etching amount to the AlCu layer thickness is about 1.23, and the photoresist is not stripped.

[0069] Example 6

[0070] Same as Example 1, only the etchant phosphoric acid is adjusted from 71% to 78.5%, and the contents of other components remain unchanged, which is set as Example 6. The semiconductor device etching steps and testing methods are the same as Example 1.

[0071] SEM test results are shown in Fig.10The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 7.4 μm, but the etching effect is general. The side etching rate of this formula is too fast, resulting in poor side etching effect.

[0072] It is easy to control and has low consumables. The ratio of side etching to AlCu layer thickness is about 1.42, and the photoresist is not stripped.

[0073] Example 7

[0074] Same as in Example 1, the etchant phosphoric acid is adjusted from 71% to 70.6%, the complexing agent is adjusted to 1.0% of 4-methylbenzenesulfonate pyridine, the leveling agent is adjusted to 0.7% of stearic acid diethanolamide, and the contents of other components remain unchanged, set to Example 7, the semiconductor device etching steps and testing methods are the same as in Example 1.

[0075] SEM test results are shown in Fig.11 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is reduced by about 6.3 μm, the etching effect is still good, the ratio of the side etching amount to the AlCu layer thickness is about 1.21, and the photoresist is not stripped.

[0076] Example 8

[0077] Same as Example 1, only the etchant phosphoric acid is adjusted from 71% to 68%, and the contents of other components remain unchanged, which is set as Example 8. The semiconductor device etching steps and testing methods are the same as Example 1.

[0078] SEM test results are shown in Fig.12 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is reduced by about 4.3 μm, but the etching effect is general, the etching rate is too slow, and the photoresist is not stripped.

[0079] Example 9

[0080] The same as Example 1, except that the additives are not added and the contents of other components remain unchanged, is set as Example 9, and the semiconductor device etching steps and testing methods are the same as Example 1.

[0081] SEM test results are shown in Fig.13 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 6.9 μm, but the etching effect is general, the side etching data is unstable, the ratio of the side etching amount to the AlCu layer thickness is about 1.33, and the photoresist is not stripped.

[0082] Example 10

[0083] The same as Example 1, except that the complexing agent is not added and the contents of other components remain unchanged, is set as Example 10, and the semiconductor device etching steps and testing methods are the same as Example 1.

[0084] SEM test results are shown in Fig.14 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 7.4 μm, but the side etching data is unstable, the etching effect is general, the ratio of the side etching amount to the AlCu layer thickness is about 1.42, and the photoresist is not stripped.

[0085] Embodiment 11

[0086] Same as in Example 1, the complexing agent is adjusted to 1.2% of 4-aminopyridine-2,6-dicarboxylic acid dimethyl ester and 1.3% of 2,6-pyridinedicarboxylic acid monomethyl ester, the etching stabilizer is adjusted to 0.8% of N,N-bis(2-acrylamideethyl)acrylamide, and the contents of other components remain unchanged. It is set to Example 11, and the semiconductor device etching steps and testing methods are the same as in Example 1.

[0087] SEM test results are shown in Fig.15 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is reduced by about 5.9 μm, the etching effect is excellent, the ratio of the side etching amount to the thickness of the etched AlCu layer is about 1.13, and the photoresist is not stripped.

[0088] Example 12

[0089] The same as Example 1, except that the etching stabilizer is not added and the contents of other components remain unchanged, is set as Example 12, and the semiconductor device etching steps and testing methods are the same as Example 1.

[0090] SEM test results are shown in Fig.16 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is increased by about 7.2 μm, the etching effect is general, the side etching rate is fast and difficult to control, the ratio of the side etching amount to the thickness of the etched AlCu layer is about 1.38, and the photoresist is not stripped.

[0091] Example 13

[0092] Same as Example 1, only the etching temperature is set to 42° C., and the contents of other components remain unchanged, which is set to Example 11. The etching steps and testing methods of the semiconductor device are the same as those in Example 1.

[0093] SEM test results are shown in Fig.17 The etching effect is shown in Table 4. Compared with Example 13, the side etching amount of this embodiment is reduced by about 5.9 μm, the etching effect is excellent, the ratio of the side etching amount to the thickness of the etched AlCu layer is about 1.13, and the photoresist is not stripped.

[0094] Embodiment 14

[0095] Same as Example 1, only the etching temperature is set to 35° C., and the contents of other components remain unchanged, which is set to Example 14. The etching steps and testing methods of the semiconductor device are the same as those in Example 1.

[0096] SEM test results are shown in Fig.18 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount of this embodiment is reduced by about 4.0 μm, the AlCu layer is not completely etched, the etching effect is general, the side etching rate is slow, and the photoresist is not stripped.

[0097] Embodiment 15

[0098] Same as Example 1, only the etching temperature is set to 55° C., and the contents of other components remain unchanged, which is set to Example 15. The etching steps and testing methods of the semiconductor device are the same as those in Example 1.

[0099] SEM test results are shown in Fig.19 The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 13.9 μm, the etching effect is general, the side etching is fast and energy-consuming, the ratio of the side etching amount to the thickness of the etched AlCu layer is about 2.67, and the photoresist is not stripped.

[0100] Example 16

[0101] Same as Example 1, the complexing agent is changed to 0.8% of tetrakis(4-aminophenyl)porphyrin, 0.5% of tetraphenylporphyrin and 1.5% of tetrahydropyrrolodihydrochlorin, the etching stabilizer is adjusted to 0.75% of alkyl monoethanolamide, and the contents of other components remain unchanged, set to Example 16, the semiconductor device etching steps and testing methods are the same as Example 1.

[0102] The etching effect is shown in Table 4. Compared with Example 1, the side etching amount in this embodiment is increased by about 6.5 μm, the etching effect is better, the ratio of the side etching amount to the thickness of the etched AlCu layer is about 1.25, and the photoresist is not stripped.

[0103] Table 4 Etching effect of each embodiment

[0104]

[0105]

[0106] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the invention.

Claims

1. An etching solution for selectively etching an AlCu layer relative to a laminated metal, characterized in that: The etching solution comprises 2-4 wt% of an oxidant, 70-75 wt% of a corrosive agent, 10-15 wt% of acetic acid, 0.5-5 wt% of a complexing agent and 0.1-1 wt% of an etching stabilizer, and the rest is water; the complexing agent is N-methylpiperidine, N-acylamino acid, 4-sulfonaminopyridine, 4-(3,5-dimethylphenyl)-2,6-di-p-tolylpyridine, 4-chloro-3-pyridinesulfonamide, 4-methylbenzenesulfonate pyridine, tetrakis(4-aminophenyl)porphyrin, tetrahydropyrrolodihydrochlorin and tetraphenylporphyrin, 5,10,15,20-tetraaminophenylporphyrin, 5,10,15,20-tetracarboxyphenylporphyrin, β-mercaptoethylamine, 4-aminopyridine -2,6-dicarboxylic acid dimethyl ester and 2,6-pyridine dicarboxylic acid monomethyl ester; the etching stabilizer is at least one of modified alkyl diethanolamide, sodium α-olefin sulfonate, diethylene glycol monobutyl ether, stearic acid diethanolamide, stearic acid monoethanolamide, dodecyl phosphate, didodecyl hydrogen phosphate, N,N-bis(2-acrylamidoethyl)acrylamide and alkyl monoethanolamide; the modified alkyl diethanolamide is prepared by introducing a polysuccinimide polymer into the alkyl diethanolamide chain.

2. The etching solution for selectively etching the AlCu layer relative to the laminated metal according to claim 1, characterized in that: The oxidant is nitric acid; the corrosive agent is phosphoric acid or polyphosphoric acid.

3. The method for preparing an etching solution for selectively etching an AlCu layer relative to a laminated metal according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: weighing an oxidant, a corrosive agent, acetic acid, a complexing agent, an etching stabilizer and ultrapure water respectively according to a certain proportion, preparing the mixture in the order of water, the corrosive agent, the oxidant, acetic acid, the complexing agent and the etching stabilizer, mixing the mixture evenly and cooling the mixture to room temperature.

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