High-selection-ratio semiconductor buffer oxide etching solution as well as preparation method and application thereof

Abstract

The invention relates to a high-selection-ratio semiconductor buffer oxide etching solution as well as a preparation method and application thereof. The high-selection-ratio semiconductor buffer oxide etching solution comprises the following components in parts by weight: 0.1-0.5 part of a functional agent; 1-5 parts of a solubilizer; 5-20 parts of hydrogen fluoride; 20 to 35 parts of ammonium fluoride; and 20-40 parts of ultrapure water. The functional agent is added into the high-selection-ratio semiconductor buffer oxide etching solution, new organic molecules and hydrochloric acid or hydrobromic acid existing in the form of ions can be dissociated, the pH value of the etching solution is dynamically adjusted through acid radicals existing in the form of ions, the etching rate of the etching solution is guaranteed, damage to Si in the SiO2 etching process is avoided, and the etching efficiency is improved. The selection ratio of the etching liquid is improved, Si damage after etching is reduced, the surface tension can be reduced through the functional agent, and the wettability of the system is improved.

Description

Technical Field

[0001] The invention belongs to the field of etching solutions, and in particular relates to a semiconductor buffered oxide etching solution with a high selectivity ratio, and a preparation method and application thereof. Background Art

[0002] Buffered oxide etchant (BOE) achieves the purpose of etching by removing or thinning the oxide layer of the semiconductor silicon wafer film that is not covered by photoresist. It is often used in microstructure production and silicon-based light-emitting devices.

[0003] BOE etching solution usually uses ultrapure water as solvent, and a certain concentration of HF and NH4F are mixed in a certain proportion to obtain the BOE etching solution of the required ratio. The etching selectivity refers to the ratio of the etching rates of two materials during the etching process. By adjusting the formula of BOE, the etching selectivity of silicon (Si) and silicon dioxide (SiO2) can be affected, thereby achieving the control of fine structures, such as the size of channels and circuits. If the silicon is damaged too much during the etching process, it may cause the silicon surface roughness to increase or form tiny defects, and residual silicon or silicides to remain on the surface of the device, which may affect the electrical characteristics of the device or introduce adverse effects, affecting the performance and long-term reliability of the device.

[0004] Reducing silicon damage can help maintain the integrity and accuracy of the device structure, avoid performance degradation or functional failure caused by damage, and help maintain the good quality of the silicon surface, thereby optimizing the electrical properties of the device. Therefore, improving the etching selectivity of BOE etching solution, reducing silicon damage, and improving the etching selectivity of silicon dioxide and silicon are crucial to semiconductor processing and manufacturing. Summary of the invention

[0005] The technical problem solved by the present invention is that the current BOE etching solution causes excessive damage to silicon during the etching process, which may increase the roughness of the silicon surface or form tiny defects, affecting the performance and long-term reliability of the device.

[0006] In view of the technical problems existing in the prior art, the present invention designs a semiconductor buffered oxide etching solution with high selectivity and its preparation method and application. The etching solution is simple and efficient, has good wettability, has a high etching selectivity for SiO2 and Si, can be used in the field of semiconductor processing and manufacturing, and is used to solve the problem that BOE etching solution causes damage to Si during the etching process.

[0007] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0008] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0009] A high selectivity semiconductor buffered oxide etching solution comprises the following components in parts by weight:

[0010]

[0011] Wherein, the functional agent is 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt.

[0012] Furthermore, the functional agent is 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrochloride (CAS No.: 90210-36-9) or 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrobromide (CAS No.: 91998-52-6).

[0013] Furthermore, the functional agent is 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrochloride.

[0014] Furthermore, the solubilizing agent is one or more of acetonitrile, methanol, acetone and isopropanol.

[0015] The present invention also discloses a method for preparing the above-mentioned high selectivity semiconductor buffered oxide etching solution, comprising the following steps:

[0016] Step 1: Weigh each component in its respective amount;

[0017] Step 2: Add the weighed hydrogen fluoride to ultrapure water, stir at 60-120 r / min for 40-60 min, add ammonium fluoride, and continue stirring for 40-60 min to obtain reagent A;

[0018] Step 3: dissolve the functional agent in the weighed solubilizer, and stir at a rate of 60-120 r / min for 30-60 min to obtain reagent B;

[0019] Step 4: Add reagent B to reagent A obtained in step 2, and continue stirring for 30 minutes to obtain a buffered oxide etching solution with a high selectivity.

[0020] The present invention also discloses an etching method of the above-mentioned high selectivity semiconductor buffered oxide etching solution, comprising the following steps:

[0021] Step 1: Place the wafer vertically in a container filled with a 25±0.5℃ high selectivity buffered oxide etchant and etch for 1-5 minutes;

[0022] Step 2: After the etching in step 1 is completed, the wafer is placed in ultrapure water, acetone and ultrapure water for cleaning in sequence, and each time it is placed for 1-3 minutes before being taken out;

[0023] Step 3: Purge the wafer surface with high-purity nitrogen for 1-3 minutes to complete the etching of the silicon oxide layer on the wafer surface.

[0024] Furthermore, the high selectivity buffered oxide etching solution in step 1 is circulated at a speed of 4-5 L / min.

[0025] Furthermore, the ultrapure water and acetone in step 2 are circulated at a speed of 4-5 L / min.

[0026] The invention also discloses a use of the semiconductor buffered oxide etching solution with a high selectivity ratio in etching a silicon oxide layer on the surface of a semiconductor wafer.

[0027] In the present invention, in order to further improve the effect of the etching solution, the components can be further preferably: 0.1-0.3 parts of functional agent; 2-4 parts of solubilizer; 12-20 parts of hydrogen fluoride; 25-30 parts of ammonium fluoride; 30-40 parts of ultrapure water.

[0028] In the present invention, the solubilizing agent is preferably methanol.

[0029] In the present invention, the functional agent can dissociate into 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole organic molecules and hydrochloric acid or hydrobromic acid in the form of ions in the etching solution.

[0030] Ionic hydrochloric acid or hydrobromic acid can dynamically adjust the pH value of the etching solution, while improving the material transfer rate in the etching solution, ensuring that the reactants are fully contacted and react quickly, accelerating the etching rate and improving the etching selectivity.

[0031] The triethoxysilyl group in 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt is siliphilic and can chemically bond with the silicon surface to form Si-O bonds with the silicon surface. This siliphilic property makes it have a strong adsorption ability on the silicon surface.

[0032] In contrast, the SiO2 surface is usually composed of silicon-oxygen bonds and hydroxyl groups, which may be less silicon-philic than the bare silicon surface.

[0033] At the same time, there are a large number of hydrogen ions (H + ) and fluoride ion (F - ), these ions will affect the charge distribution and structure of the SiO2 surface, weakening the adsorption capacity of 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt on SiO2.

[0034] At the same time, the thiol (-SH) in the organic molecule may be partially protonated into thiol in a strong acid environment, which can form an S-Si bond with the silicon surface through sulfur. This bond and mode can stably chemically adsorb the thiol group on the Si surface.

[0035] Imidazole has good water solubility and surface activity, which can reduce surface tension and improve the wettability of etching solution. While the uniform arrangement of organic molecules provides a physical barrier for Si, the imidazole group, as the terminal group of the monolayer, can adsorb F through hydrogen bonding or electrostatic interaction. - Or HF molecules, further protecting the underlying Si substrate, making it easier for 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole organic molecules to form a stable and orderly monolayer on the Si surface, protecting the Si surface during the etching process, improving the etching selectivity of the etching solution to SiO2 and Si, and reducing Si damage after etching.

[0036] The present invention provides a preparation method and application of a semiconductor buffered oxide etching solution with a high selectivity ratio, which has the following beneficial effects:

[0037] 1. In the high selectivity buffered oxide etching solution of the present invention, 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt is added to dissociate 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole organic molecules and hydrochloric acid or hydrobromic acid in the form of ions are released, and the pH value of the etching solution is dynamically adjusted by acid radicals in the form of ions to ensure the etching rate of the etching solution. A monomolecular layer is formed on the Si surface by the 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole organic molecules, so that damage to Si is avoided during SiO2 etching, the selectivity of the etching solution is improved, and the damage to Si after etching is reduced.

[0038] 2. The 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt of the present invention can also reduce surface tension and improve wettability of etching solution.

[0039] 3. The preparation method of the high selectivity buffered oxide etching solution of the present invention is simple and convenient, has strong operability, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 : This is an atomic force microscope (AFM) surface roughness display of the wafer obtained after etching for 1 hour using the etching solution of Example 1 of the present invention;

[0041] Figure 2: This is an atomic force microscope (AFM) surface roughness display diagram of the wafer obtained after etching for 1 hour using the etching solution of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

[0043] Table 1 Examples 1-5

[0044]

[0045]

[0046] Table 2 Comparative Examples 1-3

[0047]

[0048] Table 3 Test data

[0049]

[0050] About the preparation method of the etching solution of the present invention:

[0051] In the present invention, the preparation methods of etching solutions of multiple groups of embodiments and comparative examples are all prepared according to the following method:

[0052] Step 1: Weigh each component in its respective amount;

[0053] Step 2: Add the weighed hydrogen fluoride into ultrapure water, stir at 120 r / min for 60 min, add ammonium fluoride, and continue stirring for 60 min to obtain reagent A;

[0054] Step 3: dissolve the functional agent in the weighed solubilizer, and stir at a rate of 120 r / min for 60 min to obtain reagent B;

[0055] Step 4: Add reagent B to reagent A obtained in step 2, and continue stirring for 30 minutes to obtain a buffered oxide etching solution with a high selectivity.

[0056] Regarding the etching method of the present invention:

[0057] Step 1: Place the wafer vertically in a container filled with 25±0.5℃ high selectivity buffered oxide etchant and etch for 2 minutes;

[0058] Step 2: After the etching in step 1 is completed, the wafer is placed in ultrapure water, acetone and ultrapure water for cleaning in sequence, and taken out after each placement for 2 minutes;

[0059] Step 3: Purge the wafer surface with high-purity nitrogen for 2 minutes to complete the etching process of the silicon oxide layer on the wafer surface.

[0060] In step 1, the high selectivity buffered oxide etching solution is circulated at a speed of 4 L / min. In step 2, ultrapure water and acetone are circulated at a speed of 4 L / min.

[0061] About performance testing and description:

[0062] To compare the etching rate, etching selectivity and silicon surface roughness of the etching solution on the SiO2 layer and the Si layer, the following tests were conducted:

[0063] Performance test 1 Etching rate determination method:

[0064] A 4 cm × 4 cm silicon oxide layer wafer (silicon oxide layer thickness is ) and a bare silicon wafer with the silicon oxide layer completely removed from the surface are respectively immersed in the etching solution (100 mL) of the embodiment or the comparative example, and the etching endpoint of the silicon oxide wafer is determined based on the conversion of the hydrophilic property of the silicon oxide layer on the wafer surface into the hydrophobic property of the silicon layer.

[0065] Then take out the wafer, rinse it with pure water, and dry it with high-purity nitrogen.

[0066] Then the etching rate is calculated by the formula: silicon oxide layer or silicon layer thickness / immersion time, etching selectivity=silicon oxide layer etching rate / metal silicide layer etching rate.

[0067] Performance Test 2 Silicon Surface Roughness Method:

[0068] After the bare silicon wafer is immersed in the etching solution of the embodiment or the comparative example for 1 hour, the surface roughness test of the obtained etched bare silicon wafer is performed using an atomic force microscope. This test method is a conventional surface test method, and the specific operation and details will not be described in detail here.

[0069] Analysis of the test results:

[0070] Based on Table 3, it can be seen that the 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt functional agent in the etching solution of the present invention can increase the etching selectivity of SiO2 / Si to greater than 2500, and the roughness after etching is less than 0.40 nm, thereby reducing the degree of damage to silicon.

[0071] Comparative Example 1 uses γ-aminopropyltriethoxysilane as a functional agent, which cannot dissociate hydrochloric acid or hydrobromic acid in the form of ions. The etching selectivity ratio of SiO2 / Si can only reach about 2193, and the roughness after etching is 1.02nm.

[0072] Comparative Example 2 uses N,N'-thiocarbonyldiimidazole as a functional agent, does not contain a triethoxysilyl group, and the etching selectivity ratio of SiO2 / Si can only reach about 2302, resulting in large roughness after etching.

[0073] Comparative Example 3 does not contain the functional agent 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrochloride, and the etching selectivity ratio of SiO2 / Si can only reach about 1707, and the roughness after etching is large.

[0074] Further comparison is made through the attached drawings in the specification:

[0075] Figure 1 This is an atomic force microscope (AFM) surface roughness display of a wafer obtained after etching for 1 hour using the etching solution of Example 1 of the present invention;

[0076] Figure 2 This is an atomic force microscope (AFM) surface roughness display of a wafer obtained after etching for 1 hour using the etching solution of Comparative Example 3 of the present invention.

[0077] from Figure 1-2 It can be seen that the roughness of the substrate is reduced after etching using Example 1 of the present invention.

[0078] The functional agent is added to the semiconductor buffered oxide etching solution with high selectivity, which can dissociate 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole organic molecules and hydrochloric acid or hydrobromic acid in the form of ions. The pH value of the etching solution is dynamically adjusted by the acid radicals in the form of ions to ensure the etching rate of the etching solution, avoid damage to Si during SiO2 etching, improve the selectivity of the etching solution, and reduce Si damage after etching. The functional agent can also reduce surface tension and improve the wettability of the system.

[0079] The present invention is described exemplarily above in conjunction with the embodiments and drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned methods. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A high selectivity semiconductor buffered oxide etching solution, characterized in that: According to parts by weight, it includes the following components: Wherein, the functional agent is 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole salt.

2. The high selectivity semiconductor buffered oxide etching solution according to claim 1, characterized in that: The functional agent is 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrochloride or 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrobromide.

3. The high selectivity semiconductor buffered oxide etching solution according to claim 2, characterized in that: The functional agent is 4,5-dihydro-2-[[3-(triethoxysilyl)propyl]thio]-1H-imidazole hydrochloride.

4. The high selectivity semiconductor buffered oxide etching solution according to claim 1, characterized in that: The solubilizing agent is one or more of acetonitrile, methanol, acetone and isopropanol.

5. A method for preparing a semiconductor buffered oxide etching solution with high selectivity according to any one of claims 1 to 4, characterized in that The following steps are involved: Step 1: Weigh the respective amounts of each component; Step 2: Add the weighed hydrogen fluoride to ultrapure water, stir at 60-120 r / min for 40-60 min, add ammonium fluoride, and continue stirring for 40-60 min to obtain reagent A; Step 3: dissolve the functional agent in the weighed solubilizer, and stir at a rate of 60-120 r / min for 30-60 min to obtain reagent B; Step 4: Add reagent B to reagent A obtained in step 2, and continue stirring for 30 minutes to obtain a buffered oxide etching solution with a high selectivity.

6. An etching method for a semiconductor buffered oxide etching solution with a high selectivity ratio according to any one of claims 1 to 4, characterized in that The following steps are involved: Step 1: Place the wafer vertically in a container filled with a 25±0.5℃ high selectivity buffered oxide etchant and etch for 1-5 minutes; Step 2: After the etching in step 1 is completed, the wafer is placed in ultrapure water, acetone and ultrapure water for cleaning in sequence, and each time it is placed for 1-3 minutes before being taken out; Step 3: Purge the wafer surface with high-purity nitrogen for 1-3 minutes to complete the etching of the silicon oxide layer on the wafer surface.

7. The etching method of the semiconductor buffered oxide etching solution with high selectivity according to claim 6, characterized in that: The high selectivity buffered oxide etching solution in step 1 is circulated at a speed of 4-5 L / min.

8. The etching method of the semiconductor buffered oxide etching solution with high selectivity according to claim 6, characterized in that: The ultrapure water and acetone described in step 2 are circulated at a speed of 4-5 L / min.

9. Use of the high selectivity semiconductor buffered oxide etching solution according to any one of claims 1 to 4 in etching a silicon oxide layer on the surface of a semiconductor wafer.

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