Etching solution for nanometer-sized silicon oxide layer and method for preparing the same

Abstract

The present application relates to a kind of etching solution for nanometer size silicon oxide layer, including the following components according to weight parts:49% of hydrofluoric acid 5-30 parts;40% of ammonium fluoride 5-50 parts;Composite modifier 0.5-10 parts;Wetting and leveling agent 0.1-1 part;Deionized water 20-60 parts.Composite modifier is the complex of anion-cation surfactant;Wetting and leveling agent is fluorine-modified organosilicon polymer.The present application provides a method for etching silicon dioxide structure piece using the above etching solution.The present application uses composite modifier, which can not only improve surface activity and reduce surface tension, but also improve the adsorption amount of each component on the surface of substrate, and the molecular arrangement of surface adsorption layer is more compact.Composite modifier and wetting and leveling agent can reduce the surface tension of solution system on the one hand;On the other hand, it can reduce the etching angle, and the pore structure is controllable.The introduction of fluorine can significantly reduce the surface tension of etching solution, improve the wettability of substrate, and the overall composite leveling, wetting and defoaming function.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor manufacturing process, and particularly relates to an etching solution for a nanometer-sized silicon oxide layer and a preparation method thereof. BACKGROUND

[0002] When the feature size of a semiconductor process is reduced to below deep submicron, the size width of the transistor source and drain active region is continuously reduced, which leads to the continuous increase of the active region series resistance of the device. In addition, the size of the back-end interconnection contact hole is also continuously reduced, and with the continuous reduction of the size of the contact hole, the contact resistance of a single contact hole is also continuously increased.

[0003] The requirements for the corresponding electronic chemicals are greatly improved for the contact hole of the 0.25μm process technology platform, and not only good wetting performance is required, but also a higher requirement for the etching angle is required to ensure that the contact resistance is within an effective range.

[0004] Some silicon oxide etching solutions are disclosed in the prior art, for example:

[0005] Reference Document 1 discloses an etching solution for a silicon dioxide film, and the main components include hydrofluoric acid, ammonium fluoride, an additive, a surfactant, and ultrapure water. The hydrofluoric acid in the etching solution is used for etching the silicon dioxide film; the ammonium fluoride is used to provide fluoride ions to stabilize the etching rate of the etching solution; the additive is used to reduce the surface tension of the etching solution, improve the surface morphology after etching, and make the wafer surface after etching more flat and uniform; and the surfactant is used to improve the dispersing ability of the additive in the etching solution, so that the etching solution is in a uniform state.

[0006] Reference Document 2 discloses a high-selectivity buffered oxide etching solution and a preparation method thereof. The main components of the etching solution are hydrofluoric acid, ammonium fluoride, a modified surfactant, an additive, and ultrapure water. The etching solution is used for high-selectivity etching of a silicon dioxide film, and has excellent inhibition effect on etching of a silicon nitride film. The additive has excellent solubility and dispersibility in the hydrogen fluoride solution system, avoids the defect that the additive will precipitate at low temperature, and can reduce the surface tension of the etching solution and improve the flatness of the wafer surface after etching.

[0007] The wetting performance and etching angle of the silicon oxide etching solution in the prior art still have room for improvement. Therefore, it is necessary to develop a silicon oxide layer etching solution that completely wets the silicon oxide and has a small etching angle.

[0008] Reference Documents:

[0009] Reference Document 1: CN111471463B.

[0010] Reference Document 2: CN114891509A. SUMMARY

[0011] The application designs an etching solution for nanometer-sized silicon oxide layer and a preparation method thereof, and solves the technical problem of providing an etching solution for etching nanometer-sized silicon oxide layer, which has high wettability and can be applied to the field of deep submicron semiconductor manufacturing process to achieve the effect of etching nanometer-sized micropores.

[0012] In order to solve the above-mentioned technical problems, the application adopts the following scheme:

[0013] An etching solution for nanometer-sized silicon oxide layer, characterized by comprising the following components in terms of weight parts:

[0014] Hydrofluoric acid with a mass concentration of 49%: 5-30 parts;

[0015] Ammonium fluoride with a mass concentration of 40%: 5-50 parts;

[0016] Composite modifier: 0.5-10 parts;

[0017] Wetting leveling agent: 0.1-1 part;

[0018] Deionized water: 20-60 parts;

[0019] The composite modifier is a complex of cationic surfactant and anionic surfactant.

[0020] The cationic surfactant is an ammonium salt type cationic surfactant, and the anionic surfactant is a sulfate anionic surfactant.

[0021] The wetting leveling agent is a fluorine-modified organic silicon polymer.

[0022] Further, the etching solution for nanometer-sized silicon oxide layer comprises the following components in terms of weight parts:

[0023] Hydrofluoric acid with a mass concentration of 49%: 5-20 parts;

[0024] Ammonium fluoride with a mass concentration of 40%: 10-30 parts;

[0025] Composite modifier: 1-5 parts;

[0026] Wetting leveling agent: 0.1-0.5 part;

[0027] Deionized water: 30-50 parts;

[0028] The composite modifier is a complex of cationic surfactant and anionic surfactant, and the mass ratio of the cationic surfactant to the anionic surfactant is 1:1-10.

[0029] The wetting and leveling agent is a fluorine-substituted polyether modified silicone oil.

[0030] Further, the ammonium salt type cationic surfactant is a double long chain quaternary ammonium salt; and is selected from one or more of cetyl dimethyl benzyl ammonium chloride, cetyl dimethyl benzyl ammonium bromide, cetyl dimethyl benzyl ammonium methyl bromide.

[0031] Further, the sulfate anionic surfactant is a sulfate ester salt with a C atom number of 8-16; and is selected from one or more of sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium octyl sulfate, sodium dodecyl polyoxyethylene ether sulfate.

[0032] Further, the ammonium salt type cationic surfactant is cetyl dimethyl benzyl ammonium chloride; and the sulfate anionic surfactant is ammonium dodecyl sulfate.

[0033] The mass ratio of the cetyl dimethyl benzyl ammonium chloride to the ammonium dodecyl sulfate is 1:1-5.

[0034] Further, the wetting and leveling agent is a fluorine-substituted polyether modified silicone oil, and a preparation method thereof is as follows:

[0035] Step 1: under nitrogen protection, polyether modified silicone oil is added into a reaction kettle, and the reaction kettle is heated to 25-60℃;

[0036] Step 2: a tetrahydrofuran (THF) suspension containing NaH and a fluorination reagent are added into the reaction kettle, and the reaction is stirred at a speed of 100 r / min for 24-48 h, so that the fluorine-substituted polyether modified silicone oil is prepared;

[0037] The specific reaction is as follows:

[0038]

[0039] Further, the mass ratio of the polyether modified silicone oil, the tetrahydrofuran (THF) suspension containing NaH and the fluorination reagent in step 1 and step 2 is 100:(5-20):(20-50).

[0040] In the tetrahydrofuran (THF) suspension containing NaH, NaH accounts for 25-50 wt%.

[0041] The application further discloses a preparation method of an etching solution for a nanometer-sized silicon oxide layer, and the preparation method comprises the following steps:

[0042] Step 1: each component is weighed according to a proportion respectively;

[0043] Step 2: the composite modifier is added into deionized water, and stirred at a speed of 60-120 r / min for 2-4 h, so that reagent A is obtained.

[0044] Step 3: Add the weighed ammonium fluoride and hydrofluoric acid to reagent A obtained in step 2, stir at 80 r / min for 5 min, add wetting and leveling agent, and continue stirring for 15 min to obtain etching solution for nano-sized silicon oxide layer.

[0045] This invention also discloses an etching method for a nano-sized silicon dioxide layer, characterized by comprising the following specific steps:

[0046] Step 1: Place the etching solution for nano-sized silicon oxide layers in a 40L chemical bath, maintain the temperature between 20℃ and 25℃, circulate the etching solution at a rate of 4-5L / min, and place the wafer vertically in the slot.

[0047] Step 2: After the etching in Step 1 is completed, place the wafer in a chemical bath filled with ultrapure water. The ultrapure water in the chemical bath is circulated at a rate of 4-5 L / min. After 5-10 minutes, remove the wafer.

[0048] Step 3: Purge the wafer surface with high-purity nitrogen gas at a flow rate of 100L / min for 1-3 minutes to complete the etching process of the silicon oxide layer on the wafer surface.

[0049] The present invention also discloses the use of an etchant for etching nanoscale silicon oxide layers in etching nanoscale silicon oxide layers.

[0050] In this invention, more preferably, the mass ratio of the cationic surfactant hexadecyl dimethyl benzyl ammonium chloride to the anionic surfactant dodecyl ammonium sulfate is 1:1-3.

[0051] The most preferred mass ratio of the cationic surfactant hexadecyl dimethyl benzyl ammonium chloride to the anionic surfactant dodecyl ammonium sulfate is 1:2.

[0052] The etching solution and its preparation method for nano-sized silicon oxide layers of the present invention have the following beneficial effects:

[0053] (1) The present invention prepares a fluorine-substituted polyether modified silicone oil. The introduction of fluorine can significantly reduce the surface tension of the etching solution and improve the wettability of the substrate. In addition, the original silicone oil structure has good leveling performance, thus combining leveling, wetting and defoaming functions.

[0054] (2) In this invention, the composite modifier and wetting and leveling agent can reduce the surface tension of the solution system to below 20mN / m, which can effectively wet the 0.25μm pore structure; on the other hand, they can reduce the etching angle and make the pore structure controllable.

[0055] (3) The present invention uses both ammonium salt cationic surfactant and sulfate anionic surfactant. The combination of anionic and cationic surfactants can not only improve surface activity and reduce surface tension, but also increase the adsorption amount of each component on the substrate surface, making the surface adsorption layer molecules more compact.

[0056] (4) The preparation method in this invention is scientific and effective, highly operable, and suitable for large-scale production. Attached Figure Description

[0057] Figure 1 : An optical microscope image magnified 1870 times for the silica pore structure wetted in Example 1;

[0058] Figure 2 : An optical microscope image magnified 1870 times using the wetted silica pore structure of Comparative Example 1;

[0059] Figure 3 : A SEM image magnified 100k times for the etched silica pore structure using Example 1;

[0060] Figure 4 : This is a SEM image magnified 100k times for the etched silica pore structure using Comparative Example 1. Detailed Implementation

[0061] The following describes specific embodiments and appendices. Figure 1 To be continued Figure 4 The present invention will be further described as follows:

[0062] Table 1 Examples 1-12

[0063]

[0064]

[0065] The preparation method of the etching solution in the present application is as follows :

[0066] The method for preparing the etching solution for nano-sized silicon oxide layers in this invention includes the following steps:

[0067] Step 1: Weigh each component according to the proportions;

[0068] Step 2: Add the composite modifier to deionized water and stir at 80 r / min for 3 h to obtain reagent A;

[0069] Step 3: Add the weighed ammonium fluoride and hydrofluoric acid to reagent A obtained in step 2, stir at 80 r / min for 5 min, add wetting and leveling agent, and continue stirring for 15 min to obtain etching solution for nano-sized silicon oxide layer.

[0070] The preparation method of the wetting and leveling agent fluorine-substituted polyether modified silicone oil of the present application is as follows :

[0071] Step 1: Under nitrogen protection, add polyether-modified silicone oil to the reactor and heat the reactor to 50°C;

[0072] Step 2: Add a tetrahydrofuran (THF) suspension containing NaH and a fluorinating agent to the reaction vessel, and stir the reaction at 100 r / min for 36 h to obtain fluorinated polyether modified silicone oil.

[0073] In steps 1 and 2, the mass ratio of polyether-modified silicone oil, tetrahydrofuran (THF) suspension containing NaH, and fluorinating agent is 100:15:30.

[0074] In the tetrahydrofuran (THF) suspension containing NaH, NaH accounts for 40 wt%.

[0075] In this invention, the polyether-modified silicone oil is generally a substance with CAS number 67674-67-3.

[0076] The fluorinating reagent used in this invention can generally be any commercially available fluorinating reagent.

[0077] The specific reactions are as follows:

[0078]

[0079] The etching solution in the present application is used for the etching method of the nanometer-sized silicon dioxide layer, which comprises the following specific steps :

[0080] Step 1: Place the etching solution for nano-sized silicon oxide layers in a 40L chemical bath, maintain the temperature at 25℃, circulate the etching solution at a rate of 4.5L / min, and place the wafer vertically in the slot.

[0081] Step 2: After the etching in Step 1 is completed, place the wafer in a chemical bath filled with ultrapure water. The ultrapure water in the chemical bath is circulated at a rate of 4.5 L / min. After 10 minutes, remove the wafer.

[0082] Step 3: Purge the wafer surface with high-purity nitrogen at a flow rate of 100 L / min for 2 minutes to complete the etching process of the silicon oxide layer on the wafer surface.

[0083] Table 2 Comparative Examples 1-5

[0084]

[0085]

[0086] Table 3 Test Results

[0087]

[0088]

[0089] Analysis of the test results of Table 3

[0090] To investigate the effect of the composite modifier in this invention on the etching performance of the etching solution, the following technical means were adopted:

[0091] 1. Prepare the etching solutions for nano-sized silicon oxide layers according to the specified proportions.

[0092] 2. Test its surface tension and conduct etching experiments;

[0093] 3. Then observe the wettability under an optical microscope;

[0094] 4. Observe the etching angle of the cross section under SEM.

[0095] Performance Test 1: Wettability: The morphology is observed under an optical microscope. The wettability is judged by the morphology after etching. If the wettability is good, there is no SiO2 residue in the pores; otherwise, there is serious residue.

[0096] Performance Test 2: Etching Angle: SEM observation of the cross-sectional etching angle.

[0097] Performance Test 3: Surface Tension: Surface tension data was measured using a surface tension meter.

[0098] Analysis of the test results of Table 3 :

[0099] By comparing specific embodiments 1-12 of the present invention with comparative examples 1-5 and the specific test results, it can be seen that the wetting performance in embodiments 1-12 of the present invention can all achieve complete wetting, proving that its wetting performance is excellent.

[0100] In embodiments 1-12 of this invention, the etching angles are all within the range of 40-50°, which is beneficial for better control of the hole structure.

[0101] Meanwhile, the products in Examples 1-12 of this invention can reduce the surface tension of the solution system to below 20 mN / m, and can effectively wet a pore structure of 0.25 μm.

[0102] Comparative Examples 1-5 all exhibit smaller etching angles, greater surface tension, and are unable to achieve complete wetting.

[0103] The above test results demonstrate that the product of the present invention has better wetting properties, a larger etching angle, and lower surface tension, and can better adapt to the new chemical production requirements in the field of semiconductor manufacturing processes.

[0104] The above-described performance tests were performed on Example 1 and Comparative Example 1 respectively:

[0105] Figure 1 This is an optical microscope image magnified 1870x for the silica pore structure wetted using Example 1. From... Figure 1 It can be seen that Example 1 has better wetting properties and can better wet the porous structure of silica.

[0106] Figure 2 Optical microscope image magnified 1870x using the wetted silica pore structure of Comparative Example 1. From Figure 2 It can be seen that Comparative Example 1 cannot completely wet the silica pore structure; some pores can be wetted, while others cannot.

[0107] Figure 3 This is a 100kx magnified SEM image of the etched silica pore structure used in Example 1. From... Figure 3 It can be seen that the etching angle of Example 1 is larger, which can better preserve the hole structure.

[0108] Figure 4 This is a 100kx magnified SEM image of the etched silica pore structure used in Comparative Example 1. From... Figure 4 It can be seen that the etching angle of Comparative Example 1 is too small to maintain the hole structure.

[0109] Meanwhile, the test data in the table also shows that the surface tension of the solution system in Example 1 is 12 mN / m, while the surface tension in Comparative Example 1 is 33 mN / m. It can be seen that the etching solution of the present invention can greatly reduce the surface tension of the solution system, which is more conducive to improving surface activity and strengthening the control of pore structure.

[0110] The data from each set of performance tests show that the etching solution of this invention for nano-sized silicon oxide layers has unique performance advantages.

[0111] The etching solution and its preparation method for nano-sized silicon oxide layers of the present invention have the following beneficial effects:

[0112] (1) The present invention prepares a fluorine-substituted polyether modified silicone oil. The introduction of fluorine can significantly reduce the surface tension of the etching solution and improve the wettability of the substrate. In addition, the original silicone oil structure has good leveling performance, thus combining leveling, wetting and defoaming functions.

[0113] (2) In this invention, the composite modifier and wetting and leveling agent can reduce the surface tension of the solution system to below 20mN / m, which can effectively wet the 0.25μm pore structure; on the other hand, they can reduce the etching angle and make the pore structure controllable.

[0114] (3) The present invention uses both ammonium salt cationic surfactant and sulfate anionic surfactant. The two work together. The combination of cationic and anionic surfactants can not only improve surface activity and reduce surface tension, but also increase the adsorption amount of each component on the substrate surface, making the surface adsorption layer molecules more compact.

[0115] (4) The preparation method in this invention is scientific and effective, highly operable, and suitable for large-scale production.

[0116] The present invention has been described above by way of example with reference to the embodiments and accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. An etching solution for nanoscale silicon oxide layers, characterized in that, Based on parts by weight, it includes the following components: 5-30 parts of hydrofluoric acid with a mass concentration of 49%; 5-50 parts of ammonium fluoride with a mass concentration of 40%; 0.5-10 parts of composite modifier; 0.1-1 part wetting and leveling agent; 20-60 parts deionized water; The composite modifier is a mixture of cationic and anionic surfactants. The cationic surfactant is selected from one or more of hexadecyl dimethyl benzyl ammonium chloride, hexadecyl dimethyl benzyl ammonium bromide, and hexadecyl dimethyl benzyl methyl ammonium bromide; The anionic surfactant is a sulfate salt with 8-16 carbon atoms; The wetting and leveling agent is a fluorinated polyether modified silicone oil, and its preparation method is as follows: Step 1: Under nitrogen protection, add polyether-modified silicone oil to the reactor and heat the reactor to 25-60℃; Step 2: Add a tetrahydrofuran (THF) suspension containing NaH and a fluorinating agent to the reaction vessel, and stir the reaction at 100 r / min for 24-48 h to obtain fluorinated polyether modified silicone oil. The specific reactions are as follows: 。 2. The etching solution for nano-sized silicon oxide layers according to claim 1, characterized in that, Based on parts by weight, it includes the following components: 5-20 parts of hydrofluoric acid with a mass concentration of 49%; 10-30 parts of ammonium fluoride with a mass concentration of 40%; 1-5 parts of composite modifier; 0.1-0.5 parts of wetting and leveling agent; 30-50 parts deionized water; The mass ratio of the cationic surfactant to the anionic surfactant is 1:1-10.

3. The etching solution for nanoscale silicon oxide layers according to claim 1, characterized in that: The anionic surfactant is selected from one or more of sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium octyl sulfate, and sodium dodecyl polyoxyethylene ether sulfate.

4. The etching solution for nanoscale silicon oxide layers according to any one of claims 1-3, characterized in that: The cationic surfactant is hexadecyl dimethyl benzyl ammonium chloride; the anionic surfactant is dodecyl ammonium sulfate. The mass ratio of hexadecyl dimethyl benzyl ammonium chloride to dodecyl ammonium sulfate is 1:1-5.

5. The etching solution for nanoscale silicon oxide layers according to claim 1, characterized in that: The mass ratio of the polyether-modified silicone oil, the tetrahydrofuran (THF) suspension containing NaH, and the fluorinating agent mentioned in steps 1 and 2 is 100:(5-20):(20-50). In the tetrahydrofuran (THF) suspension containing NaH, NaH accounts for 25-50 wt%.

6. A method for preparing an etching solution for nano-sized silicon oxide layers according to any one of claims 1-5, characterized in that... Includes the following steps: Step 1: Weigh each component according to the proportions; Step 2: Add the composite modifier to deionized water and stir at 60-120 r / min for 2-4 h to obtain reagent A; Step 3: Add the weighed ammonium fluoride and hydrofluoric acid to reagent A obtained in step 2, stir at 80 r / min for 5 min, add wetting and leveling agent, and continue stirring for 15 min to obtain etching solution for nano-sized silicon oxide layer.

7. A method for etching a nano-sized silicon dioxide layer using the etching solution according to any one of claims 1-5, characterized in that... It includes the following specific steps: Step 1: Place the etching solution for nano-sized silicon oxide layers in a 40L chemical bath, maintain the temperature between 20℃ and 25℃, circulate the etching solution at a rate of 4-5L / min, and place the wafer vertically in the slot. Step 2: After the etching in Step 1 is completed, place the wafer in a chemical bath filled with ultrapure water. The ultrapure water in the chemical bath is circulated at a rate of 4-5 L / min. After 5-10 minutes, remove the wafer. Step 3: Purge the wafer surface with high-purity nitrogen gas at a flow rate of 100L / min for 1-3 minutes to complete the etching process of the silicon oxide layer on the wafer surface.

8. Use of the etching solution for nanoscale silicon oxide layers according to any one of claims 1-5 in etching nanoscale silicon oxide layers.

Images