Semiconductor BOE etching solution as well as preparation method and application thereof
By adding compounds of formula I and amide sulfonates of specific structures to the BOE etching solution, the complex coated silica is formed, and the problem of excessively fast and uneven etching rate of the existing BOE etching solution is solved, and the More stable and uniform etching effect.
Patent Information
- Application Number
- CN202411534245.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-02-14
AI Technical Summary
The existing BOE etching solution has a large contact angle to the silicon wafer, a too fast etching rate, and a problem that etching is uneven.
A semiconductor BOE etching solution is used, in which the compound of formula I structure and amide sulfonate with a specific structure is added to the etching solution, and complex is generated by N-S coordination, and coated on silicon oxide, thereby reducing the etching rate and Surface tension.
The etching rate, surface tension and contact angle are significantly reduced, and the etching uniformity is improved, ensuring that the etched silicon wafer is clean and free of impurities.
Smart Images
Figure CN119432384A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to etching liquid technology, in particular to a semiconductor BOE etching liquid, a preparation method and application thereof. Background Art
[0002] Buffered oxide etchant (BOE) achieves the purpose of etching by removing the oxide layer portion of the semiconductor silicon wafer film that is not covered by the photoresist. It has been widely used in the production of microstructures and silicon-based light-emitting devices.
[0003] The preparation method of BOE etching solution generally uses ultrapure water as solvent, mixes a certain concentration of hydrofluoric acid and ammonium fluoride in a certain proportion, and obtains a BOE etching solution of the required proportion. However, the surface tension of the BOE etching solution obtained by the above preparation method is very large, and the etching rate is very fast, resulting in poor etching uniformity. In order to reduce the surface tension of the BOE etching solution and the etching rate of silicon oxide, a surfactant needs to be added during the preparation process of the BOE etching solution.
[0004] However, the BOE etching solution containing surfactants has a large contact angle with the silicon wafer and a poor ability to penetrate complex microscopic surfaces, which cannot ensure the uniformity of the etching pattern, resulting in a very fast etching rate of the etching solution and uneven etching. Summary of the invention
[0005] The purpose of the present invention is to provide a semiconductor BOE etching solution to solve the problems that the existing BOE etching solution has a large contact angle with the silicon wafer, an excessively fast etching rate, and uneven etching. The etching solution has a small contact angle with the silicon wafer, a stable and slow etching rate, and the etched silicon wafer is clean, uniform, and free of impurities.
[0006] 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", etc. and similar meanings, as well as closed-ended "composed of", "composed of", etc. and similar meanings.
[0007] To achieve the above object, the technical solution adopted by the present invention is: a semiconductor BOE etching solution, comprising the following components in weight proportions:
[0008]
[0009] The additive includes a compound of formula I and / or an amide sulfonate;
[0010]
[0011] Furthermore, when the additive comprises a compound of formula I and an amide sulfonate, the mass ratio of the compound of formula I to the amide sulfonate is 7:0.5-2.
[0012] Furthermore, the mass ratio of the compound of formula I to the amide sulfonate is preferably 7:0.5.
[0013] Furthermore, the amide sulfonate is selected from sodium N-oleoyl-N-methyltaurate (CasNo: 137-20-2) and / or sodium 2-acrylamido-2-methylpropanesulfonate (CasNo: 5165-97-9).
[0014] Furthermore, the amide sulfonate is preferably sodium N-oleoyl-N-methyltaurate.
[0015] Furthermore, the additive is 4-8 parts.
[0016] Furthermore, the hydrofluoric acid is 5-8 parts.
[0017] Furthermore, the ammonium fluoride is 18-20 parts.
[0018] Furthermore, the compound of formula I is synthesized by the following method:
[0019] Step 1, add sulfuric acid dropwise to 4-(2,2-diphenylethylidene)-N,N-di(p-tolyl)aniline, control the temperature at 2-5°C, stir for 2.5-3 hours, add nitric acid dropwise while stirring, control the temperature at 2-5°C, continue stirring for 2.5-3 hours, extract with trialkylmethylamine after the reaction is completed, dry and remove the solvent to obtain a nitration product, wherein the solvent is all liquid except the nitration product (solid);
[0020] Step 2: Nitroation product, perfluorooctane sulfonic acid amine and AlCl 3 Dissolve in an organic solvent and mix evenly, react at 35°C-50°C for 5.5-6 hours, stand to separate into layers, collect the upper layer of liquid, and recrystallize to obtain a compound of formula I.
[0021] The reaction formula involved in step 1 is:
[0022]
[0023] The reaction formula involved in step 2 is:
[0024]
[0025] Further, in step 2, the organic solvent is nitrobenzene, and the amount of nitrobenzene is such that it can dissolve the substances (nitration product, perfluorooctane sulfonic acid amine and AlCl 3) is used as the reference, and the specific dosage is not limited.
[0026] Furthermore, the amount of 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline used is 2-5 parts.
[0027] Furthermore, the amount of 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline used is preferably 3 parts.
[0028] Furthermore, the amount of nitric acid used is 1-3 parts.
[0029] Furthermore, the amount of nitric acid used is preferably 2 parts.
[0030] Furthermore, the amount of sulfuric acid used is 1-5 parts.
[0031] Furthermore, the amount of sulfuric acid used is preferably 4 parts.
[0032] Furthermore, the amount of the perfluorooctane sulfonic acid amine is 2-7 parts.
[0033] Furthermore, the amount of the perfluorooctane sulfonic acid amine used is preferably 5 parts.
[0034] Furthermore, the AlCl 3 The dosage is 0.01-0.05 parts.
[0035] Furthermore, the AlCl 3 The amount used is preferably 0.02 parts.
[0036] Furthermore, the mass ratio of the 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline to nitric acid is 3:2-5:1.
[0037] Furthermore, the mass ratio of the 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline to nitric acid is preferably 3:2-2:1.
[0038] Another object of the present invention is to disclose a method for preparing a semiconductor BOE etching solution, comprising the following steps: mixing ultrapure water, hydrofluoric acid and ammonium fluoride, and stirring at room temperature for 25-30 minutes; adding additives while stirring, and mixing to obtain a semiconductor BOE etching solution.
[0039] Another object of the present invention is to disclose an application of a semiconductor BOE etching solution in the field of etching silicon wafers.
[0040] Further, the method of etching a silicon wafer using the BOE etching solution is as follows:
[0041] Step 1: Put the semiconductor BOE etching solution into a container, disturb the silicon wafer at 20-25°C for 5-10 minutes to obtain the etched silicon wafer;
[0042] Step 2: Place the etched silicon wafer in ultrapure water and purge it with nitrogen to complete the etching.
[0043] The semiconductor BOE etching solution, preparation method and application thereof of the present invention have the following advantages compared with the prior art:
[0044] 1) The present invention nitrates 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline. 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline contains a methyl group, which is an electron-repelling group. When the electron-repelling inductive effect of the methyl group is transmitted along the benzene ring, a positive and negative alternation phenomenon occurs on the benzene ring. The electron cloud density of the ortho position of the methyl group is higher, while the electron cloud density of the meta position is lower. Therefore, when the electrophilic reagent attacks toluene, the newly introduced group always enters the ortho position with high electron cloud density, and the introduced nitro group just has an electron-withdrawing inductive effect. From the perspective of the conjugation effect, the nitro group has an electron-withdrawing conjugation effect. Therefore, the electronic effect of the nitro group reduces the electron cloud density on the benzene ring, has a meta-positioning effect, and makes the nitro group connected to the meta position of the benzene ring; then perfluorooctanesulfonic acid amine is reacted with AlCl 3 An electrophilic carbon cation is generated under the catalyst, and then attacks the benzene ring with a methyl group to form a new carbon cation complex, and finally deprotonates to obtain a compound of formula I with a specific structure, wherein the compound of formula I has symmetry.
[0045] 2) The semiconductor BOE etching solution of the present invention contains a compound of formula I having a specific structure, which is combined with an amide sulfonate. The compound of formula I can undergo NS coordination with the amide sulfonate to form a complex, which is coated on silicon oxide, thereby reducing the etching rate of the BOE etching solution; at the same time, the compound of formula I also contains a sulfonamide group, which can increase the solubility of the amide sulfonate in the etching solution, thereby generating more coordination and further inhibiting the etching rate. BRIEF DESCRIPTION OF THE DRAWINGS
[0046] Attached Figure 1 is the infrared spectrum of the compound of formula I;
[0047] Attached Figure 2 This is a SEM image after etching with the etching solution of Example 1, with a magnification of 600 times;
[0048] Attached Figure 3 This is the SEM image of the comparative example 1 after etching with the etching solution, with a magnification of 600 times. DETAILED DESCRIPTION
[0049] The present invention is further described below with reference to the examples. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:
[0050] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.
[0051] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints A and B.
[0052] In the present specification, a numerical range expressed using "above" or "below" means a numerical range including the number.
[0053] In this specification, the word "may" includes both performing a certain process and not performing a certain process.
[0054] In this specification, the use of "optional" or "optional" indicates that certain substances, components, execution steps, application conditions and other factors are used or not used.
[0055] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 15-25°C.
[0056] In this manual, the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.
[0057] Examples 1-5
[0058] Examples 1-5 disclose a variety of semiconductor BOE etching solutions, including components and weight ratios as shown in Table 1.
[0059] The preparation method of semiconductor BOE etching solution comprises the following steps:
[0060] S1: Weigh water, hydrofluoric acid and ammonium fluoride solution and stir at room temperature;
[0061] S2: After stirring for 30 minutes, additives are added under stirring, and after mixing evenly, a semiconductor BOE etching solution is obtained.
[0062] Table 1 Components and weight ratios of semiconductor BOE etching solutions in Examples 1-5
[0063]
[0064] Note: The compound of formula I is referred to as compound.
[0065] Comparative Examples 1-4
[0066] Comparative Examples 1-4 disclose a variety of etching solutions, the components and weight ratios of which are shown in Table 2, and the preparation methods thereof are the same as those of Example 1.
[0067] Table 2 Components and weight ratios of etching solutions in comparative examples 1-4
[0068]
[0069] The components and weight ratios of the compounds of formula I involved in the above Examples 1-5 and Comparative Examples 1-4 are shown in Table 3.
[0070] The compound of formula I is prepared by the following preparation method:
[0071] Step 1: Pour 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline into a glass reaction cup, control the temperature below 5°C, slowly add sulfuric acid, stir for 3 hours, then add nitric acid dropwise while stirring, and continue stirring for 3 hours. During this period, the temperature is always controlled below 5°C. After the reaction is completed, extract, dry, and remove the solvent to obtain the nitration product.
[0072] Step 2: The nitration product obtained in step 1, perfluorooctane sulfonic acid amine and AlCl 3 The mixture was dissolved in nitrobenzene organic solvent and mixed evenly, and reacted at 42°C for 6 hours. The mixture was allowed to stand and stratified, and the upper liquid was collected. The mixture was recrystallized to obtain a compound of formula I.
[0073] Table 3 Components and weight ratios of compounds 1-3 of formula I
[0074]
[0075]
[0076] Attached Figure 1 is the infrared spectrum of the compound of formula I; Figure 1 It can be seen that at 1607cm -1 The bending vibration peak of NH appears at 2918 cm-1, which also belongs to the bending vibration peak of CN. The stretching vibration of the CH bond of the benzene ring appears at 2918 cm-1. -1 Nearby, at 1169cm -1 The peak of the sulfonic acid group appears at 1234 cm -1 、1230cm -1 、1083cm -1 All the peaks that appear belong to the FC bond and the two peaks of the nitro bond, which are at 1607cm -1 and 1396cm -1The above data prove that compound 1 of formula I was successfully prepared.
[0077] The etching solutions of Examples 1-5 and Comparative Examples 1-4 were tested respectively, and the test methods and test results are as follows:
[0078] About performance testing and description:
[0079] Performance 1BOE etching solution wettability test
[0080] The contact angle of the etching solution was tested at room temperature using a contact angle meter to characterize its wettability. The test results are shown in Table 4.
[0081] Performance 2BOE etching solution etching rate test
[0082] Using a silicon dioxide substrate as the base, after the etching solution is prepared, a circulating water bath is used to maintain the temperature of the etching solution at 25°C during the test.
[0083] The etching process is to cut a 12-inch thermally oxidized silicon dioxide chip with a structure into a size of 2cm×2cm, etch it for 5 minutes under disturbance conditions, and use a film thickness meter to detect the thickness of silicon dioxide before and after etching. The etching rate of silicon dioxide is calculated based on the thickness difference before and after etching / etching time. The test results are shown in Table 4.
[0084] Performance 3BOE etching solution surface tension test
[0085] The surface tension of the etching solution was measured at room temperature using a surface tension tester. The test results are shown in Table 4.
[0086] Table 4 Test data
[0087]
[0088]
[0089] Based on Table 4, it can be seen that the embodiments of the present invention significantly reduce the etching rate, surface tension and contact angle compared to the comparative example.
[0090] Comparative Example 1 does not add the compound of Formula I, and Comparative Example 2 does not add sodium N-oleoyl-N-methyltaurate, both of which result in a larger contact angle of the etching solution to the silicon wafer, and a very fast etching rate of the etching solution, resulting in uneven etching. This proves that the combination of the compound of Formula I and sodium N-oleoyl-N-methyltaurate can significantly reduce the etching rate, surface tension and contact angle, and improve the uniformity of etching.
[0091] Comparative Example 3 uses a combination of perfluorooctane sulfonic acid amine and sodium N-oleoyl-N-methyl taurate. The generated complex is limited, resulting in a larger contact angle of the etching solution to the silicon wafer and a very fast etching rate of the etching solution.
[0092] Comparative Example 4 uses a combination of 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline and sodium N-oleoyl-N-methyltaurate, which has poor solubility in the etching solution, resulting in a large contact angle of the etching solution to the silicon wafer and a fast etching rate of the etching solution.
[0093] Attached Figure 2 The SEM image after etching by the etching solution of Example 1 is magnified 600 times; Figure 2 It can be seen that the silicon wafer after etching with the etching solution is very clean, the etching is relatively uniform, and no impurities appear. Figure 3 This is the SEM image of the etching solution after etching in Comparative Example 1, with a magnification of 600 times. Figure 3 It can be seen that there are obvious impurities in the silicon wafer after etching and the etching is uneven.
[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A semiconductor BOE etching solution, characterized in that: The composition includes the following components in weight ratio: The additive includes a compound of formula I and / or an amide sulfonate; 2. The semiconductor BOE etching solution according to claim 1, characterized in that: When the additive comprises a compound of formula I and amide sulfonate, the mass ratio of the compound of formula I to amide sulfonate is 7:0.5-2.
3. The semiconductor BOE etching solution according to claim 1, characterized in that: The amide sulfonate is selected from sodium N-oleoyl-N-methyl taurate and / or sodium 2-acrylamido-2-methylpropane sulfonate.
4. The semiconductor BOE etching solution according to claim 1, characterized in that: The compound of formula I is synthesized by the following method: Step 1, add sulfuric acid dropwise to 4-(2,2-diphenylethylene)-N,N-di(p-tolyl)aniline, control the temperature at 2-5°C, stir for 2.5-3 hours, add nitric acid dropwise while stirring, control the temperature at 2-5°C, continue stirring for 2.5-3 hours, extract after the reaction is completed, and dry to remove the solvent to obtain a nitroation product; Step 2: Add the nitration product, perfluorooctanesulfonic acid amine and AlCl3 into an organic solvent and mix evenly, react at 35°C-50°C for 5.5-6 hours, stand to separate layers, collect the upper layer of liquid, and recrystallize to obtain a compound of formula I.
5. The semiconductor BOE etching solution according to claim 1, characterized in that: In the synthesis method of the compound of formula I, the weight ratio of each component is as follows:
6. The semiconductor BOE etching solution according to claim 1, characterized in that: The mass ratio of the 4-(2,2-diphenylvinyl)-N,N-di-p-tolylaniline to nitric acid is 3:2-5:
1.
7. A method for preparing a semiconductor BOE etching solution according to any one of claims 1 to 6, comprising the following steps: Water, hydrofluoric acid and ammonium fluoride are mixed, and stirred at room temperature for 25-30 minutes; additives are added under stirring, and the mixture is mixed to obtain a semiconductor BOE etching solution.
8. Use of the semiconductor BOE etching solution according to any one of claims 1 to 6 in the field of etching silicon wafers.
9. The use according to claim 8, characterized in that: The method for etching a silicon wafer using the BOE etching solution is as follows: Step 1: Put the semiconductor BOE etching solution into a container, disturb the silicon wafer at 20-25°C for 5-10 minutes to obtain the etched silicon wafer; Step 2: Place the etched silicon wafer in ultrapure water and purge it with nitrogen to complete the etching.