A low surface tension silicon dioxide etching solution and its preparation method and application

Abstract

The invention discloses a low surface tension silicon dioxide etching liquid, which includes hydrofluoric acid, ammonium fluoride, deionized water and an additive; the additive is first obtained by copolymerization of maleic anhydride, polyol diene ether and acryloxytrimethoxysilane, and then hydrolyzed under acidic conditions. The low surface tension silicon dioxide etching liquid of the invention solves the problems of low etching selectivity, poor etching uniformity, severe corrosion to silicon substrate and easy defects in the semiconductor manufacturing process of traditional etching liquids; the etching liquid of the invention can not only effectively reduce the surface tension and improve the affinity of the etching liquid to the silicon substrate, but also enhance the selective etching ability of silicon dioxide during the etching process, reduce the corrosion of the silicon substrate, achieve a more uniform and precise etching effect, and thus improve the production quality and yield of semiconductor chips. The invention also discloses a preparation method and application of a low surface tension silicon dioxide etching liquid.

Description

Technical Field

[0001] The invention relates to the technical field of etching liquid, and in particular to a low surface tension silicon dioxide etching liquid and a preparation method and application thereof. Background Art

[0002] In the semiconductor manufacturing process, etching is a crucial step for accurately removing excess material on silicon wafers to form circuit patterns. Traditional silicon dioxide etching solutions usually contain ingredients such as hydrofluoric acid (HF), ammonium fluoride (NH4F) and deionized water, which can effectively etch silicon dioxide materials to a certain extent.

[0003] However, as the feature size of integrated circuits continues to shrink, higher requirements are placed on the etching process. While traditional etching solutions can achieve high-precision etching, they are often accompanied by some problems, such as low etching selectivity, easy defects on the surface of the etched silicon wafer, and corrosion of the silicon wafer substrate. These problems not only affect the performance and yield of the device, but also increase production costs.

[0004] In addition, traditional etching solutions may produce some by-products during the etching process, such as SiF4 gas, which, if not controlled, may pollute the environment and affect the health of operators. Therefore, developing a new type of silicon dioxide etching solution that can not only meet the needs of high-precision etching but also reduce damage to the silicon wafer substrate and environmental pollution has become an important research direction in the field of semiconductor manufacturing. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned technologies, the present invention provides a low surface tension silicon dioxide etching solution, which aims to solve the problems of low etching selectivity, poor etching uniformity, severe corrosion to silicon substrate and easy defects in the etching process existing in traditional etching solutions.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A low surface tension silicon dioxide etching solution, the etching solution comprising hydrofluoric acid, ammonium fluoride, deionized water and an additive shown in structural formula I;

[0008] (I),

[0009] In the formula, R1 and R2 are independently selected from alkane groups of 2 or 3 carbon atoms, R3 is H or methyl, R4 is an alkane group of 1 to 3 carbon atoms, m:n:p is 1 to 5:1 to 5:1 to 5, It is the hydrolysis product of trimethoxysilane.

[0010] As a preferred technical solution, the mass ratio of the hydrofluoric acid, ammonium fluoride, deionized water and additive is 1.5-15:3-30:50-80:0.1-0.5.

[0011] As a preferred technical solution, the additive is firstly obtained by copolymerization of maleic anhydride, polyol diene ether and acryloxytrimethoxysilane, and then by hydrolysis under acidic conditions.

[0012] As a preferred technical solution, the polyol diene ether is at least one of di(2-allyloxyethyl) ether, diethylene glycol divinyl ether and triethylene glycol divinyl ether.

[0013] As a preferred technical solution, the acryloxytrimethoxysilane is at least one of acryloxymethyltrimethoxysilane, 3-(methacryloxy)propyltrimethoxysilane, (3-acryloxypropyl)trimethoxysilane, and methacryloxymethyltrimethoxysilane.

[0014] As a preferred technical solution, the molar ratio of maleic anhydride, polyol diene ether and acryloxytrimethoxysilane is 1-5:1-5:1-5.

[0015] Another aspect of the present invention is to provide a method for preparing the above-mentioned low surface tension silicon dioxide etching solution, the preparation method comprising the following steps:

[0016] S1: adding maleic anhydride, polyol diene ether and acryloyloxytrimethoxysilane into a reactor containing a solvent, stirring and mixing evenly, adding a catalytic amount of an initiator, heating and performing a copolymerization reaction to obtain a maleic anhydride / diene ether / acrylate silane copolymer;

[0017] S2: dissolving the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 in a suitable solvent, then adjusting the pH value to acidic, and performing a hydrolysis reaction to obtain the desired additive;

[0018] S3: The additive obtained in step S2 is stirred and mixed evenly with hydrofluoric acid, ammonium fluoride and deionized water to obtain the low surface tension silicon dioxide etching solution.

[0019] As a preferred technical solution, in step S1, the copolymerization reaction is carried out at an operating temperature of 60 to 80°C.

[0020] As a preferred technical solution, in step S2, the pH value is 4.8-5.2.

[0021] The third aspect of the present invention is to provide an application of the low surface tension silica etching solution as described above, wherein the etching solution is applied to the etching of semiconductor chips through the following steps: immersing the semiconductor chip in the etching solution, ultrasonically vibrating for 1 to 5 minutes to complete the etching operation, then washing with ultrapure water and anhydrous ethanol alternately at least twice, and finally blowing with high-purity nitrogen to complete the drying treatment of the semiconductor chip.

[0022] The hydrofluoric acid in the etching solution of the present invention mainly plays an etching role, and can react with silicon dioxide (SiO2) to form a soluble silicon fluoride complex SiF4 gas, which effectively removes the oxide layer. In addition, ammonium fluoride plays a role as a buffer, which helps to maintain the pH value of the etching solution, and it also forms a complex fluoride with silicon, promoting a more controllable etching process.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The low surface tension silicon dioxide etching liquid of the present invention is compounded with an additive of an innovative molecular structure, which is hydrolyzed by maleic anhydride so that the etching liquid of the present invention contains an appropriate amount of carboxyl polar functional groups, and interacts with SiF4 gas and ammonia molecules through hydrogen bonding and its acidic characteristics, promoting the adsorption and removal of gas molecules in the liquid phase, which not only enhances the wettability and etching ability of the etching liquid to silicon dioxide, but also improves the selectivity and uniformity of etching; at the same time, the additive carries a hydrolyzate of trimethoxysilane, which not only improves the stability of the etching liquid and the protective effect on the substrate, ensuring that the corrosion of the silicon substrate during the etching process is extremely small, and due to its low surface tension characteristics, it helps the etching liquid to spread on the surface of the silicon substrate, reducing the problem of uneven surface tension during the etching process; in addition, the main chain of the additive of the present invention also has abundant ether functional group substances, which further reduces the surface tension of the etching liquid. In general, the etching liquid compounded with the additive of the present invention, hydrofluoric acid and ammonium fluoride has high selectivity and controlled etching characteristics for silicon dioxide during the etching process, and will not form defects on the surface of the silicon substrate. DETAILED DESCRIPTION

[0025] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0026] The etching solution prepared by the preparation method of the present application is used in the etching process of semiconductor chips, and the following performance tests are mainly carried out, including etching residue verification, film uniformity test, silicon damage verification, defoaming time verification and etching rate stability verification.

[0027] Performance Test 1: Etching Residue Verification

[0028] In the etching residue verification test, a 12-inch SiO2 Pattern Wafer was immersed for 60 seconds in a 23°C water bath to simulate the actual etching environment. After the test, a scanning electron microscope (SEM) was used to carefully observe the surface of the silicon wafer to evaluate whether there was any residue after etching.

[0029] Performance Test 2: Film Uniformity Test (TTV)

[0030] The film uniformity test is conducted by measuring the thickness variation of the film on a 12-inch SiO2 Dummy Wafer. A 60-second immersion test is conducted at 23°C, and 49 test points are evenly selected on the surface of the silicon wafer for measurement using a film thickness meter. The etching uniformity is evaluated by calculating the difference between the maximum and minimum film thickness values ​​(TTV) at these test points.

[0031] Performance Test 3: Silicon Damage Verification

[0032] The silicon damage verification test is conducted by measuring the film thickness change of a 2cm*2cm silicon sample before and after etching. The immersion test is conducted at 23°C for 300 seconds, and the film thickness of the silicon sample is measured using a film thickness meter. The silicon damage rate is calculated using the formula (film thickness before value - film thickness after value) / time.

[0033] Performance Test 4: Defoaming Time Verification

[0034] The defoaming time verification test is completed by shaking and bubbling experiment. At 23℃, 20mL of etching solution is shaken for 10 seconds and then left to stand, and the time for the foam on the surface of the etching solution to disappear is recorded by visual observation.

[0035] Performance Test 5: Etching Rate Stability Verification

[0036] The etching rate stability test was completed by soaking the 2cm*2cm SiO2Dummy Wafer at different time points (12 hours, 24 hours, 48 ​​hours, and 72 hours) and measuring the etching rate using a film thickness meter. Each soaking was 60 seconds at 23°C, and the fluctuation of the etching rate was evaluated by calculating the difference between the maximum rate and the minimum rate. Example 1

[0037] The method for preparing the low surface tension silicon dioxide etching solution of this embodiment comprises the following steps:

[0038] S1: 0.05 mol of maleic anhydride, 0.05 mol of triethylene glycol divinyl ether and 0.05 mol of acryloxymethyltrimethoxysilane are added to a reactor containing 250 mL of dimethyl sulfoxide solvent, stirred and mixed uniformly, and then a catalytic amount of initiator benzoyl peroxide is added. After heating, a copolymerization reaction is carried out at an operating temperature of 80° C. to obtain a maleic anhydride / diolefin ether / acrylate silane copolymer;

[0039] S2: 8 g of the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 was dissolved in 100 mL of a solvent (composed of deionized water and propylene carbonate in a volume ratio of 1:1), and then the pH value was adjusted to acidic, the pH value being 4.8, and a hydrolysis reaction was performed. After reacting for 2 hours, the desired additive was obtained;

[0040] S3: 0.1 g of the additive obtained in step S2 is stirred and mixed with 1.5 g of hydrofluoric acid, 3 g of ammonium fluoride and 50 g of deionized water to obtain the low surface tension silicon dioxide etching solution. The surface tension of the silicon dioxide etching solution of this embodiment is measured using a surface tension meter and a maximum bubble pressure method; the result shows that the surface tension value is 10 mN / m.

[0041] The etching solution prepared by the preparation method of this embodiment is applied to the etching of semiconductor chips through the following steps: the semiconductor chip is immersed in the etching solution, ultrasonically vibrated for 5 minutes to complete the etching operation, then alternately cleaned with ultrapure water and anhydrous ethanol at least twice, and finally purged with high-purity nitrogen to complete the drying process of the semiconductor chip.

[0042] The test results show that: there is no residue on the surface of the semiconductor chip after etching in this embodiment, the etching rate fluctuation value is 0.262 angstroms per second, the silicon damage verification value is 0.326 angstroms per minute, the etching film uniformity test result is 1.151 angstroms, and the defoaming time is 5.2 seconds. Example 2

[0043] The method for preparing the low surface tension silicon dioxide etching solution of this embodiment comprises the following steps:

[0044] S1: 0.02 mol of maleic anhydride, 0.05 mol of diethylene glycol divinyl ether and 0.03 mol of 3-(methacryloyloxy)propyltrimethoxysilane are added to a reactor containing 250 mL of dimethyl sulfoxide solvent, stirred and mixed uniformly, and then a catalytic amount of initiator benzoyl peroxide is added. After heating, a copolymerization reaction is carried out at an operating temperature of 80° C. to obtain a maleic anhydride / diolefin ether / acrylate silane copolymer;

[0045] S2: dissolving 10 g of the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 in 100 mL of a solvent (composed of deionized water and propylene carbonate in a volume ratio of 1:1), adjusting the pH value to an acidic pH value of 5.2, and performing a hydrolysis reaction. After reacting for 2 hours, the desired additive is obtained;

[0046] S3: 0.2 g of the additive obtained in step S2 is stirred and mixed with 3 g of hydrofluoric acid, 6 g of ammonium fluoride and 60 g of deionized water to obtain the low surface tension silicon dioxide etching solution. The surface tension of the silicon dioxide etching solution of this embodiment is measured using a surface tension meter and a maximum bubble pressure method; the result shows that the surface tension value is 9.8 mN / m.

[0047] The etching solution prepared by the preparation method of this embodiment is applied to the etching of semiconductor chips through the following steps: the semiconductor chip is immersed in the etching solution, ultrasonically vibrated for 5 minutes to complete the etching operation, then alternately cleaned with ultrapure water and anhydrous ethanol at least twice, and finally purged with high-purity nitrogen to complete the drying process of the semiconductor chip.

[0048] The test results show that: there is no residue on the surface of the semiconductor chip in this embodiment after etching, the etching rate fluctuation value is 0.284 angstroms per second, the silicon damage verification value is 0.366 angstroms per minute, the etching film uniformity test result is 1.058 angstroms, and the defoaming time is 5.9 seconds. Example 3

[0049] The method for preparing the low surface tension silicon dioxide etching solution of this embodiment comprises the following steps:

[0050] S1: 0.05 mol of maleic anhydride, 0.1 mol of di(2-allyloxyethyl) ether and 0.05 mol of (3-acryloxypropyl) trimethoxysilane are added into a reactor containing 250 mL of dimethyl sulfoxide solvent, stirred and mixed uniformly, and then a catalytic amount of initiator benzoyl peroxide is added. After heating, a copolymerization reaction is carried out at an operating temperature of 60° C. to obtain a maleic anhydride / diolefin ether / acrylate silane copolymer;

[0051] S2: 12 g of the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 was dissolved in 100 mL of a solvent (composed of deionized water and propylene carbonate in a volume ratio of 1:1), and then the pH value was adjusted to acidic, the pH value being 5.0, and a hydrolysis reaction was performed. After reacting for 2 hours, the desired additive was obtained;

[0052] S3: 0.3 g of the additive obtained in step S2 is stirred and mixed with 10 g of hydrofluoric acid, 15 g of ammonium fluoride and 60 g of deionized water to obtain the low surface tension silicon dioxide etching solution. The surface tension of the silicon dioxide etching solution of this embodiment is measured using a surface tension meter and a maximum bubble pressure method; the result shows that the surface tension value is 10.2 mN / m.

[0053] The etching solution prepared by the preparation method of this embodiment is applied to the etching of semiconductor chips through the following steps: the semiconductor chip is immersed in the etching solution, ultrasonically vibrated for 5 minutes to complete the etching operation, then alternately cleaned with ultrapure water and anhydrous ethanol at least twice, and finally purged with high-purity nitrogen to complete the drying process of the semiconductor chip.

[0054] The test results show that: there is no residue on the surface of the semiconductor chip in this embodiment after etching, the etching rate fluctuation value is 0.301 angstroms per second, the silicon damage verification value is 0.348 angstroms per minute, the etching film uniformity test result is 1.255 angstroms, and the defoaming time is 6.3 seconds. Example 4

[0055] The method for preparing the low surface tension silicon dioxide etching solution of this embodiment comprises the following steps:

[0056] S1: 0.03 mol of maleic anhydride, 0.05 mol of triethylene glycol divinyl ether and 0.02 mol of methacryloyloxymethyltrimethoxysilane are added to a reactor containing 250 mL of dimethyl sulfoxide solvent, stirred and mixed uniformly, and then a catalytic amount of initiator benzoyl peroxide is added. After heating, a copolymerization reaction is carried out at an operating temperature of 60° C. to obtain a maleic anhydride / diolefin ether / acrylate silane copolymer;

[0057] S2: 8 g of the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 was dissolved in 100 mL of a solvent (composed of deionized water and propylene carbonate in a volume ratio of 1:1), and then the pH value was adjusted to acidic, the pH value being 4.8, and a hydrolysis reaction was performed. After reacting for 2 hours, the desired additive was obtained;

[0058] S3: 0.4 g of the additive obtained in step S2 is stirred and mixed with 12 g of hydrofluoric acid, 24 g of ammonium fluoride and 70 g of deionized water to obtain the low surface tension silicon dioxide etching solution. The surface tension of the silicon dioxide etching solution of this embodiment is measured using a surface tension meter and a maximum bubble pressure method; the result shows that the surface tension value is 9.9 mN / m.

[0059] The etching solution prepared by the preparation method of this embodiment is applied to the etching of semiconductor chips through the following steps: the semiconductor chip is immersed in the etching solution, ultrasonically vibrated for 5 minutes to complete the etching operation, then alternately cleaned with ultrapure water and anhydrous ethanol at least twice, and finally purged with high-purity nitrogen to complete the drying process of the semiconductor chip.

[0060] The test results show that: there is no residue on the surface of the semiconductor chip in this embodiment after etching, the etching rate fluctuation value is 0.295 angstroms per second, the silicon damage verification value is 0.315 angstroms per minute, the etching film uniformity test result is 1.256 angstroms, and the defoaming time is 6.7 seconds. Example 5

[0061] The method for preparing the low surface tension silicon dioxide etching solution of this embodiment comprises the following steps:

[0062] S1: 0.1 mol of maleic anhydride, 0.1 mol of diethylene glycol divinyl ether and 0.1 mol of 3-(methacryloyloxy)propyltrimethoxysilane are added to a reactor containing 250 mL of dimethyl sulfoxide solvent, stirred and mixed uniformly, and then a catalytic amount of initiator benzoyl peroxide is added. After heating, a copolymerization reaction is carried out at an operating temperature of 80° C. to obtain a maleic anhydride / diolefin ether / acrylate silane copolymer;

[0063] S2: dissolving 10 g of the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 in 100 mL of a solvent (composed of deionized water and propylene carbonate in a volume ratio of 1:1), adjusting the pH value to an acidic pH value of 5.2, and performing a hydrolysis reaction. After reacting for 2 hours, the desired additive is obtained;

[0064] S3: 0.5 g of the additive obtained in step S2 is stirred and mixed with 15 g of hydrofluoric acid, 30 g of ammonium fluoride and 80 g of deionized water to obtain the low surface tension silicon dioxide etching solution. The surface tension of the silicon dioxide etching solution of this embodiment is measured by using a surface tension meter and a maximum bubble pressure method; the result shows that the surface tension value is 9.7 mN / m.

[0065] The etching solution prepared by the preparation method of this embodiment is applied to the etching of semiconductor chips through the following steps: the semiconductor chip is immersed in the etching solution, ultrasonically vibrated for 5 minutes to complete the etching operation, then alternately cleaned with ultrapure water and anhydrous ethanol at least twice, and finally purged with high-purity nitrogen to complete the drying process of the semiconductor chip.

[0066] The test results show that: there is no residue on the surface of the semiconductor chip after etching in this embodiment, the etching rate fluctuation value is 0.324 angstroms per second, the silicon damage verification value is 0.313 angstroms per minute, the etching film uniformity test result is 1.152 angstroms, and the defoaming time is 6.8 seconds.

[0067] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A low surface tension silicon dioxide etching solution, characterized in that: The etching solution comprises hydrofluoric acid, ammonium fluoride, deionized water and an additive shown in structural formula I; In the formula, R1 and R2 are independently selected from alkane groups of 2 or 3 carbon atoms, R3 is H or methyl, R4 is an alkane group of 1 to 3 carbon atoms, m:n:p is 1 to 5:1 to 5:1 to 5, It is a hydrolysis product of trimethoxysilane; the mass ratio of the hydrofluoric acid, ammonium fluoride, deionized water and additive is 1.5-15:3-30:50-80:0.1-0.

5.

2. The low surface tension silicon dioxide etching solution according to claim 1, characterized in that: The additive is firstly obtained by copolymerization of maleic anhydride, polyol diene ether and acryloxy trimethoxy silane, and then hydrolyzed under acidic conditions.

3. The low surface tension silicon dioxide etching solution as claimed in claim 2, characterized in that: The polyol diene ether is at least one of di(2-allyloxyethyl) ether, diethylene glycol divinyl ether and triethylene glycol divinyl ether.

4. The low surface tension silicon dioxide etching solution as claimed in claim 2, characterized in that: The acryloxytrimethoxysilane is at least one of acryloxymethyltrimethoxysilane, 3-(methacryloxy)propyltrimethoxysilane, (3-acryloxypropyl)trimethoxysilane and methacryloxymethyltrimethoxysilane.

5. The low surface tension silicon dioxide etching solution as claimed in claim 2, characterized in that: The molar ratio of maleic anhydride, polyol diene ether and acryloxytrimethoxysilane is 1-5:1-5:1-5.

6. A method for preparing a low surface tension silicon dioxide etching solution as claimed in any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1: adding maleic anhydride, polyol diene ether and acryloyloxytrimethoxysilane into a reactor containing a solvent, stirring and mixing evenly, adding a catalytic amount of an initiator, heating and performing a copolymerization reaction to obtain a maleic anhydride / diene ether / acrylate silane copolymer; S2: dissolving the maleic anhydride / diolefin ether / acrylate silane copolymer obtained in step S1 in a suitable solvent, then adjusting the pH value to acidic, and performing a hydrolysis reaction to obtain the desired additive; S3: stirring and mixing the additive obtained in step S2 with hydrofluoric acid, ammonium fluoride and deionized water to obtain the low surface tension silicon dioxide etching solution.

7. A method for preparing a low surface tension silicon dioxide etching solution as claimed in claim 6, characterized in that: In step S1, the copolymerization reaction is carried out at an operating temperature of 60-80°C.

8. A method for preparing a low surface tension silicon dioxide etching solution as claimed in claim 6, characterized in that: In step S2, the pH value is 4.8-5.

2.

9. Use of the low surface tension silicon dioxide etching solution according to any one of claims 1 to 5, characterized in that: The etching solution is applied to the etching of semiconductor chips through the following steps: immersing the semiconductor chip in the etching solution, ultrasonically vibrating for 1 to 5 minutes to complete the etching operation, then washing with ultrapure water and anhydrous ethanol alternately at least twice, and finally purging with high-purity nitrogen to complete the drying process of the semiconductor chip.

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