BOE etching solution

Abstract

In order to solve the problem that an existing BOE etching solution cannot consider the etching rate, the etching uniformity and the service life of the etching solution at the same time, the invention provides a BOE etching solution which comprises the following components: hydrogen fluoride, ammonium fluoride and a corrosion inhibitor, the corrosion inhibitor comprises a compound shown as a structural formula 1: # imgabs0 # structural formula 1, R1 is selected from substituted or unsubstituted C2-C6 alkyl, and R2 is selected from substituted or unsubstituted C2-C6 ether-containing alkyl. The BOE etching solution provided by the invention has a relatively high silicon oxide / silicon nitride and Si etching selection ratio, can effectively improve the etching uniformity, is beneficial to reducing surface defects, and ensures the flatness and smoothness of an etched surface. In addition, the BOE etching liquid is stable in chemical composition and long in service life.

Description

Technical Field

[0001] The invention belongs to the technical field of etching solutions, and in particular relates to a BOE etching solution. Background Art

[0002] BOE (Buffered Oxide Etch) is composed of hydrofluoric acid, ammonium fluoride, additives and water, and is mainly used for etching silicon oxide, silicon nitride, etc. in the integrated circuit process. In practical applications, the etching rate, etching uniformity and silicon oxide and Si etching selectivity of buffered oxide etchant for silicon oxide, silicon nitride, etc. need to be considered. If the etching rate is too low, the survival efficiency will be reduced, and insufficient etching uniformity or too low silicon oxide and Si etching selectivity will increase the roughness of the substrate surface after etching, and there will be problems with silicon oxide residue.

[0003] At the same time, the life of the etching solution (i.e., the length of use, which affects the manufacturing efficiency and manufacturing cost of the product) is also an issue that needs attention. The existing solution can achieve different etching rates of silicon oxide and silicon nitride by adjusting the content of hydrofluoric acid and ammonium fluoride, and can achieve etching uniformity of silicon oxide and the etching selectivity of silicon oxide / silicon nitride and Si by adjusting surfactants and additives. However, the above solution cannot take into account the etching rate, etching uniformity and life of the etching solution (i.e., the length of use, which affects the manufacturing efficiency and manufacturing cost of the product) at the same time. Summary of the invention

[0004] Aiming at the problem that the existing BOE etching solution cannot take into account the etching rate, etching uniformity and life of the etching solution at the same time, the present invention provides a BOE etching solution.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: The present invention provides a BOE etching solution, comprising the following components: Hydrogen fluoride, ammonium fluoride, and corrosion inhibitors; The corrosion inhibitor includes a compound shown in structural formula 1: Structural formula 1 Wherein, R1 is selected from substituted or unsubstituted C2~C6 hydrocarbon groups, and R2 is selected from substituted or unsubstituted C2~C6 ether-containing hydrocarbon groups.

[0006] Optionally, R1 is selected from a C2-C6 alkenyl group, and R2 is selected from a group shown in Structural Formula 2: Structural formula 2 Wherein, R3 and R4 are each independently selected from a hydrocarbon group of C1 to C5, and the total number of carbon atoms of R3 and R4 is C2 to C6.

[0007] Optionally, the compound represented by structural formula 1 includes one or more of N-ethoxymethyl acrylamide, N-(N-butoxymethyl) acrylamide, and N-(butoxymethyl)-2-methyl-2-acrylamide.

[0008] Optionally, based on the total mass of the BOE etching solution being 100%, the mass percentage of the corrosion inhibitor is 0.01% to 0.5%.

[0009] Optionally, based on the total mass of the BOE etching solution being 100%, the mass percentage of the hydrogen fluoride is 0.1%-10.0%, and the mass percentage of the ammonium fluoride is 1.0%-20.0%.

[0010] Optionally, the BOE etching solution further includes a fluorine-containing surfactant, and the fluorine-containing surfactant includes a compound shown in Structural Formula 3: Structural formula 3 wherein R5, R6, and R8 are each independently selected from a C1-C4 hydrocarbon group partially substituted or fully substituted with F, R7 is selected from a F atom or a C1-C4 hydrocarbon group partially substituted or fully substituted with F, and R9 is selected from a sulfonic acid group and its ammonium salt or a carboxylic acid group and its ammonium salt; Fluorination rate = total number of F atoms in R5, R6, R7, and R8 / (2*(total number of carbon atoms in R5, R6, R7, and R8)+1)>80%.

[0011] Optionally, based on the total mass of the BOE etching solution being 100%, the mass percentage of the fluorinated surfactant is 0.01%-0.10%.

[0012] Optionally, in the BOE etching solution, the mass ratio of ammonium ions to fluorine-containing surfactant is (500~5000):1.

[0013] Optionally, the BOE etching solution also includes a solvent.

[0014] Optionally, the BOE etching solution further includes an etching rate regulator, and the etching rate regulator includes one or more of an organic acid and an organic base; The organic acid comprises one or more of succinic acid, lactic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, and triethyl propionic acid; The organic base includes one or more of ethanolamine, triethanolamine, heptylamine, decylamine, undecylamine and dodecylamine; Taking the total mass of the BOE etching solution as 100%, the mass percentage of the etching rate regulator is 0.001%-0.50%.

[0015] According to the BOE etching solution provided by the present invention, the compound shown in structural formula 1 is used as a corrosion inhibitor. The compound shown in structural formula 1 can form a protective layer on the silicon substrate, so that the silicon material is protected during the etching process, ensuring that only the target material (silicon oxide, silicon nitride) is etched, improving the silicon oxide / silicon nitride and Si etching selectivity, and avoiding unnecessary damage. In particular, the ether group in the compound shown in structural formula 1 can enhance its wettability with silicon oxide, thereby helping to reduce the edge effect during the etching process, improve etching uniformity, help reduce surface defects, and ensure the flatness and smoothness of the etched surface. Furthermore, the compound shown in structural formula 1 is helpful in helping to stabilize the chemical composition of the etching solution, preventing premature failure, and thus extending the service life of the etching solution. DETAILED DESCRIPTION

[0016] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] In the description of the present invention, the term "ether-containing hydrocarbon group" refers to a hydrocarbon group containing an ether group, and specifically, it can be understood as a group in which one or more carbon atoms in the hydrocarbon group are replaced by oxygen.

[0018] In the description of the present invention, the term "substituted hydrocarbon group" refers to a group in which a single or multiple hydrogen atoms in a hydrocarbon group are replaced by a substituent containing a heteroatom (oxygen, nitrogen, sulfur), and specifically, the substituent is a hydroxyl group or an amine group.

[0019] An embodiment of the present invention provides a BOE etching solution, comprising the following components: Hydrogen fluoride, ammonium fluoride, and corrosion inhibitors; The corrosion inhibitor includes a compound shown in structural formula 1: Structural formula 1 Wherein, R1 is selected from substituted or unsubstituted C2~C6 hydrocarbon groups, and R2 is selected from substituted or unsubstituted C2~C6 ether-containing hydrocarbon groups.

[0020] Among them, the compound shown in structural formula 1 can form a protective layer on the silicon substrate, so that the silicon material is protected during the etching process, ensuring that only the target material (silicon oxide, silicon nitride) is etched, improving the silicon oxide / silicon nitride and Si etching selectivity, and avoiding unnecessary damage. In particular, the ether group in the compound shown in structural formula 1 can enhance its wettability with silicon oxide, thereby helping to reduce the edge effect during the etching process, improve etching uniformity, help reduce surface defects, and ensure the flatness and smoothness of the etched surface. Furthermore, the compound shown in structural formula 1 is helpful in helping to stabilize the chemical composition of the etching solution, preventing premature failure, and thus extending the service life of the etching solution.

[0021] In some embodiments, R1 is selected from a C2-C6 alkenyl group, and R2 is selected from a group shown in Structural Formula 2: Structural formula 2 Wherein, R3 and R4 are each independently selected from a hydrocarbon group of C1 to C5, and the total number of carbon atoms of R3 and R4 is C2 to C6.

[0022] In the compound shown in Structural Formula 1, if the number of carbon atoms of R1 is too small, the steric hindrance effect of the compound shown in Structural Formula 1 is weak, affecting the etching protection effect; if the number of carbon atoms of R2 is too high, it will affect the solubility of the compound shown in Structural Formula 1, affect the amount of the compound shown in Structural Formula 1 added in the BOE etching solution, and further affect the etching effect.

[0023] Compared with R1 being selected from an alkyl group, when R1 is selected from an unsaturated alkenyl group, it can better cooperate with other components in the etching solution, such as an organic acid and an organic base, to improve the etching uniformity.

[0024] In a preferred embodiment, the R1 is selected from vinyl.

[0025] In some embodiments, the compound represented by structural formula 1 includes one or more of N-ethoxymethyl acrylamide, N-(N-butoxymethyl) acrylamide, and N-(butoxymethyl)-2-methyl-2-acrylamide.

[0026] In some embodiments, based on the total mass of the BOE etching solution being 100%, the mass percentage of the corrosion inhibitor is 0.01% to 0.5%.

[0027] In a specific embodiment, based on the total mass of the BOE etching solution as 100%, the mass percentage of the corrosion inhibitor can be 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0028] The corrosion inhibitor has the function of controlling etching efficiency and etching selectivity, which is beneficial to reducing surface defects and improving surface quality; if the amount of the corrosion inhibitor added is too low, it is difficult to play a protective role on the silicon substrate, which may easily lead to increased roughness of the etched surface; if the amount of the corrosion inhibitor added is too high, it will affect the etching efficiency, making the etching process slow, resulting in reduced production efficiency.

[0029] In some embodiments, based on the total mass of the BOE etching solution being 100%, the mass percentage of the hydrogen fluoride is 0.1% to 10.0%, and the mass percentage of the ammonium fluoride is 1.0% to 20.0%.

[0030] In a specific embodiment, based on the total mass of the BOE etching solution as 100%, the mass percentage of the hydrogen fluoride may be 0.01%, 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5% or 10%; the mass percentage of the ammonium fluoride may be 1%, 1.5%, 2%, 2.2%, 2.8%, 3%, 4%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0031] In BOE etching solution, hydrogen fluoride (HF) is the main etchant. Compared with other etchants, HF has a faster etching rate and can effectively etch silicon oxide. If the amount of hydrogen fluoride added is too low, it is difficult to obtain a good etching efficiency. If the amount of hydrogen fluoride added is too high, it will cause too fast etching, and then lead to etching of other forms of silicon, such as polycrystalline silicon or single crystal silicon, and thus damage the substrate.

[0032] In the BOE etching solution, ammonium fluoride and hydrogen fluoride are used as a buffer, which can provide fluoride ions required for etching on the one hand, and can adjust the pH value of the BOE etching solution on the other hand to avoid the pH value being too low, so as to adjust the etching rate; if the amount of ammonium fluoride added is too low, the pH value of the BOE etching solution will fluctuate too much during the etching process, and the etching efficiency will be too fast; if the amount of ammonium fluoride added is too high, the etching efficiency will be reduced.

[0033] In some embodiments, the BOE etching solution further includes a fluorine-containing surfactant, and the fluorine-containing surfactant includes a compound shown in Structural Formula 3: Structural formula 3 wherein R5, R6, and R8 are each independently selected from a C1-C4 hydrocarbon group partially substituted or fully substituted with F, R7 is selected from a F atom or a C1-C4 hydrocarbon group partially substituted or fully substituted with F, and R9 is selected from a sulfonic acid group and its ammonium salt or a carboxylic acid group and its ammonium salt; Fluorination rate = total number of F atoms in R5, R6, R7, and R8 / (2*(total number of carbon atoms in R5, R6, R7, and R8)+1)>80%.

[0034] By adding a fluorinated surfactant to the BOE etching solution, the wettability of the BOE etching solution to the surface to be etched can be improved, ensuring that the BOE etching solution can be evenly spread on the surface to be etched, while reducing bubble formation, promoting the detachment of particles from the surface to be etched, and improving etching uniformity.

[0035] The inventors studied the structure of fluorinated surfactants and found that when the fluorinated surfactant satisfies the structural formula 3, its fluorination rate has a great influence on its service life and the smoothness of the etched surface. When the fluorination rate meets the above conditions, it can form a repulsive force with the surface of the filter element material (PTFE, etc.) in water, reduce the adsorption of the fluorinated surfactant in the BOE etching solution on its surface, and thus maintain a relatively stable BOE etching solution component and extend the service life of the line.

[0036] In some embodiments, based on the total mass of the BOE etching solution being 100%, the mass percentage of the fluorinated surfactant is 0.01%-0.10%.

[0037] In a specific embodiment, based on the total mass of the BOE etching solution as 100%, the mass percentage of the fluorinated surfactant may be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%.

[0038] If the amount of the fluorinated surfactant added is too low, the improvement in the smoothness of the etched surface is not obvious; if the amount of the fluorinated surfactant added is too high, it will have a greater impact on the chemical properties of the etching solution, which is also not conducive to improving the etching uniformity, and at the same time increases the risk of residual fluorinated surfactant after etching.

[0039] In some embodiments, in the BOE etching solution, the mass ratio of ammonium ions to fluorine-containing surfactant is (500~5000):1.

[0040] In a specific embodiment, in the BOE etching solution, the mass ratio of ammonium ions to fluorine-containing surfactant can be 500:1, 600:1, 800:1, 1000:1, 1200:1, 1500:1, 1800:1, 2000:1, 2500:1, 3000:1, 3500:1, 4000:1, 4500:1 or 5000:1.

[0041] The concentration of ammonium ions in the BOE etching solution is related to the ionization effect of the fluorinated surfactant. If the mass ratio of ammonium ions to fluorinated surfactant is too low, the fluorinated surfactant in the BOE etching solution is not easy to ionize and cannot effectively reduce the surface tension of the solution. If C>5000, the pH and buffering capacity of the system are prone to large fluctuations during the etching process, resulting in problems such as etching rate and etching stability.

[0042] In some embodiments, the BOE etching solution further includes a solvent.

[0043] In a preferred embodiment, the solvent is selected from water.

[0044] In some embodiments, the BOE etching solution further includes an etching rate regulator, and the etching rate regulator includes one or more of an organic acid and an organic base.

[0045] The etching rate regulator has a similar function to the ammonium fluoride and is used to adjust the etching rate. Different organic acids and organic bases can be selected to be added alone or in combination according to different etching rate requirements.

[0046] In some embodiments, the organic acid comprises one or more of succinic acid, lactic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, and triethylpropionic acid.

[0047] In some embodiments, the organic base comprises one or more of ethanolamine, triethanolamine, heptylamine, decylamine, undecylamine, and dodecylamine.

[0048] In some embodiments, based on the total mass of the BOE etching solution being 100%, the mass percentage of the etching rate regulator is 0.001%-0.50%.

[0049] In a specific embodiment, based on the total mass of the BOE etching solution as 100%, the mass percentage of the etching rate regulator can be 0.001%, 0.003%, 0.005%, 0.008%, 0.01%, 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45% or 0.5%.

[0050] Another embodiment of the present invention provides a method for preparing the BOE etching solution as described above, comprising the following steps: According to the mass ratio, 0.1% to 10.0% of hydrogen fluoride, 1.0% to 20.0% of ammonium fluoride, 0.01% to 0.5% of corrosion inhibitor and the remaining amount of solvent are uniformly mixed to obtain a BOE etching solution.

[0051] In some embodiments, the mixed raw material further comprises 0.01%-0.10% fluorinated surfactant.

[0052] In some embodiments, the mixed feedstock further includes 0.001%-0.50% of an etch rate modifier.

[0053] The present invention is further described below by way of examples.

[0054] Table 1 Embodiments 1 to 8 Examples 1 to 8 are used to illustrate the preparation method of the BOE etching solution disclosed in the present invention, which includes the following steps: According to the material selection and mass percentage of Examples 1 to 8 in Table 1, hydrogen fluoride, ammonium fluoride, corrosion inhibitor, fluorine-containing surfactant, etching rate regulator and the remaining amount of solvent are mixed uniformly to obtain a BOE etching solution.

[0055] Comparative Examples 1 to 5 Comparative Examples 1 to 5 are used to illustrate the preparation method of the BOE etching solution disclosed in the present invention, which includes the following steps: According to the material selection and mass percentage of Comparative Examples 1 to 5 in Table 1, hydrogen fluoride, ammonium fluoride, corrosion inhibitor, fluorine-containing surfactant, etching rate regulator and the remaining amount of solvent are mixed uniformly to obtain a BOE etching solution.

[0056] Performance Testing The BOE etching solution prepared above was subjected to the following performance tests: In the silicon oxide layer etching process, the wafer is etched with BOE etching solution at 22-24°C for 1-2 minutes. After etching, it is cleaned and blown dry. The performance of the solution is evaluated by surface tension and substrate roughness; After the BOE etching solution was applied to the silicon oxide layer etching process and recycled for 7 days, the above operation was repeated to test the surface tension and substrate roughness.

[0057] The test results obtained are entered in Table 2.

[0058] Table 2 It can be seen from the test results in Table 2 that by adding the compound shown in structural formula 1 as a corrosion inhibitor to the BOE etching solution, the edge effect during the etching process can be effectively reduced, the etching uniformity can be improved, and the surface defects after etching can be reduced, thereby reducing the surface roughness.

[0059] By comparing the test results of Examples 1 to 6 with those of Examples 7 and 8, it can be seen that when the fluorination rate of the fluorinated surfactant is greater than 80%, on the one hand, it is beneficial to reduce the surface tension to improve the wettability of the surface to be etched and improve the etching uniformity. On the other hand, it is also beneficial to maintain a relatively stable BOE etching solution component and extend the service life of the line.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A BOE etching solution, characterized in that: Includes the following components: Hydrogen fluoride, ammonium fluoride, and corrosion inhibitors; The corrosion inhibitor includes a compound shown in structural formula 1: Structural formula 1 Wherein, R1 is selected from substituted or unsubstituted C2~C6 hydrocarbon groups, and R2 is selected from substituted or unsubstituted C2~C6 ether-containing hydrocarbon groups.

2. The BOE etching solution according to claim 1, characterized in that R1 is selected from a C2-C6 alkenyl group, and R2 is selected from a group shown in structural formula 2: Structural formula 2 Wherein, R3 and R4 are each independently selected from a hydrocarbon group of C1 to C5, and the total number of carbon atoms of R3 and R4 is C2 to C6.

3. The BOE etching solution according to claim 2, characterized in that The compound represented by the structural formula 1 includes one or more of N-ethoxymethyl acrylamide, N-(N-butoxymethyl) acrylamide, and N-(butoxymethyl)-2-methyl-2-acrylamide.

4. The BOE etching solution according to claim 1, characterized in that Taking the total mass of the BOE etching solution as 100%, the mass percentage of the corrosion inhibitor is 0.01% to 0.5%.

5. The BOE etching solution according to claim 1, characterized in that Taking the total mass of the BOE etching solution as 100%, the mass percentage of the hydrogen fluoride is 0.1%-10.0%, and the mass percentage of the ammonium fluoride is 1.0%-20.0%.

6. The BOE etching solution according to claim 1, characterized in that The BOE etching solution further includes a fluorine-containing surfactant, and the fluorine-containing surfactant includes a compound shown in structural formula 3: Structural formula 3 wherein R5, R6, and R8 are each independently selected from a C1-C4 hydrocarbon group partially substituted or fully substituted with F, R7 is selected from a F atom or a C1-C4 hydrocarbon group partially substituted or fully substituted with F, and R9 is selected from a sulfonic acid group and its ammonium salt or a carboxylic acid group and its ammonium salt; Fluorination rate = total number of F atoms in R5, R6, R7, and R8 / (2*(total number of carbon atoms in R5, R6, R7, and R8)+1)>80%.

7. The BOE etching solution according to claim 6, characterized in that: Taking the total mass of the BOE etching solution as 100%, the mass percentage of the fluorine-containing surfactant is 0.01%-0.10%.

8. The BOE etching solution according to claim 1, characterized in that In the BOE etching solution, the mass ratio of ammonium ions to fluorine-containing surfactant is (500-5000):

1.

9. The BOE etching solution according to claim 1, characterized in that: The BOE etching solution also includes a solvent.

10. The BOE etching solution according to claim 1, characterized in that: The BOE etching solution also includes an etching rate regulator, and the etching rate regulator includes one or more of an organic acid and an organic base; The organic acid comprises one or more of succinic acid, lactic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, and triethyl propionic acid; The organic base includes one or more of ethanolamine, triethanolamine, heptylamine, decylamine, undecylamine and dodecylamine; Taking the total mass of the BOE etching solution as 100%, the mass percentage of the etching rate regulator is 0.001%-0.50%.

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