KR100796194B1 - Etching Solution for Silicon Oxide Layers - Google Patents

Abstract

The present invention relates to an etching method of silicon oxide film, as ammonium fluoroalkylsulfonamide series (S1), perfluoroalkylsulfonate series (S2) as surfactants in conventional BOE (Buffered Oxide Etchant: HF-NH4F-H2O) ), By adding polyethylene glycol series (S3) in various compositions and concentrations, 1) lowering the segregation temperature and 2) improving affinity with the wafer surface (hydrophilic or hydrophobic) to improve etching uniformity, and 3) lowering the etching uniformity. Anti-foaming agent (antifoaming agent) was added to suppress foaming, which is the cause of 4), and the method of preparing an etchant having controllable etching profile by varying the composition of the surfactant.

Hydrogen fluoride, ammonium fluoride, etching, surfactant, etching composition

Description

Method for manufacturing silicon oxide etching solution {Etching Solution for Silicon Oxide Layers}

Figure 1

Contact angle measurement (Measurement method: Sessile Drop method)

Figure 2

Top left: Silicon thermal oxide electron microscope (SEM) images patterned with positive photoresist before etching

Idol: Silicon thermal oxide electron microscope (SEM) photo patterned with positive photoresist after etching

Lower left: Silicon thermal oxide electron micrograph (SEM) patterned with negative photoresist before etching

Lower Right: Silicon Thermal Oxide Electron Microscopy (SEM) Patterned with Negative Photoresist after Etching

Figure 3

Etch Type Angle and Etching Amount

  Etch type: angle with photoresist (PR) contact surface

  Etching amount (Å / min): h (Å) / hour (min)

Figure 4a

Various etching forms according to the etchant: Etching angle (20 ~ 25 degrees)

Figure 4b

Various etching forms according to the etchant: Etching angle (35 ~ 40 degrees)

Figure 4c

Various etching forms according to the etchant: Etching angle (80 ~ 85 degrees)

Figure 4d

Various etching forms according to the etchant: Etching angle (45 ~ 40 degrees)

4A-4D illustrate some examples of silicon thermal oxide film (SiO 2) etch patterns patterned with negative photoresist and in the invention the etch angles range from approximately 10 to 130 degrees depending on the etchant.

Figure 5

Top left: Silicon filtrate (hydrophobic) affinity "surface" photo of filtrate during affinity evaluation

Idol: "Normal" photograph of surface filtrate during evaluation of silicon film hydrophobic affinity

Lower left: Surface filtrate "is" photo during evaluation of silicon film hydrophobic affinity

Lower Right: Surface Filtration "Many" Photographs during Evaluation of Silicone Membrane Affinity

The present invention relates to a silicon oxide film etching method, and more particularly, to a silicon oxide film etching method using a wet etchant to which anionic and nonionic surfactants are added.

In the process of manufacturing a semiconductor device, a silicon oxide film is used for electrical insulation between conductive layers.

This silicon oxide film is formed by a deposition or growth method and is removed by a dry or wet method.

Dilute hydrofluoric acid (DHF) and Buffered Oxide Etchant (BOE) are widely used as wet etchants for wet etching silicon oxide films. The BOE solution is a mixture of hydrogen fluoride (HF) and ammonium fluoride (NH 4 F), and NH 4 HF 2 coexists by mixing HF, NH 4 F and DI water. In the case of using the BOE solution, the etching rate is controlled by the composition ratio of HF and NH 4 F. At this time, the weight ratio of NH 4 F is 15 ~ in order to prevent the crystallization (Solide Phase Segregation) of NH 4 HF 2 and NH 4 F. Should be limited to 17%.

Crystallization of NH4F and NH4 HF2 is directly related to the stability and particle contamination of the etchant, so that the temperature above the crystallization temperature should be maintained when the etchant is moved, stored or used.

Looking at the surfactant (Surfactant) added to the BOE solution cited in the existing patent, aliphatic carboxylic acid, salts of aliphatic carboxylic acid, aliphatic amine and aliphatic alcohol in the application No. 1987-0010754, the application number 10-1996-0023653 Dimethylsulfoxide, acetonitrile [CH3CN], cyanobenzene [C6H6CN], application no. 10-1997-0081149, dimethylformamide (N, N-Dimethylformamide), application no. R-OSOHA, R-PO4 (HA) 2, R2-PO4HA, R-SO3HA in 10-2004-0034566 (R is a C4-C22 hydrocarbon group having a straight chain or side chain, A Ammonia or amine) and the like are listed as additive surfactants. Surfactants should increase the affinity with the silicon wafer to ensure that the surface of the wafer is smooth and that the etchant has a reduced film quality and contact angle. However, the BOE added with the above-mentioned surfactant has limitations in the main components of the etchant at a certain concentration or in a specific process, and also generates bubbles, which causes problems in the etching uniformity. There is a limit that cannot solve various problems at the same time.

Therefore, the present invention is described above by using a wet etching agent in which ammonium fluoroalkylsulfonamide series (S1), perfluoroalkylsulfonate series (S2), and polyethylene glycol series (S3) are added in various compositions and concentrations as surfactants. To solve the shortcomings and further to the etching profile (Etchprofile) controllable silicon oxide etching method manufacturing method.

In the silicon oxide film etching method according to the present invention, the silicon oxide film formed on the wafer is etched using a wet etchant including a surfactant, and a BOE solution is used as the wet etchant.

Next, the present invention will be described in detail with reference to the accompanying drawings.

The BOE solution is a mixture of HF and NH4 F, and NH4 HF2 is present together by mixing HF and NH4 F. After etching the oxide layer, (NH 4) 2 SiF 6 is present in the BOE solution as a reaction product. Therefore, since these materials exist in the salt and ion states of the salts in the aqueous solution, the surfactant must be able to maintain or increase the solubility of these materials.

That is, the surfactant preferably satisfies the following conditions.

1) It should not affect the etching cost.

2) Due to the low surface tension, the affinity with the film surface (hydrophilic or hydrophobic) should be improved.

3) Particle contamination should not be generated by maintaining or improving the solubility of salts, salt ions and reaction products in the BOE solution.

4) The etching uniformity due to foaming should not be reduced.

5) Particles should not be attached to the wafer surface.

6) The etching selectivity for silicon and silicon oxide should be high.

7) Must not react with BOE solution.

In particular, the present invention has a function of controlling the etching form by adjusting the surfactant composition and concentration.

The present invention is a silicon oxide film etchant that satisfies the above conditions by combining at least two anionic and nonionic surfactants in the BOE.

As surfactant, ammonium fluoroalkyl sulfonamide series (S1), perfluoroalkyl sulfonate series (S2), and polyethylene glycol series (S3) were used. S1 is a factor that controls the surface tension of the etchant, the affinity with the silicon film and the etching form by the combination with S2, S2 allows the etchant to be controlled by affecting the affinity with the oxide film and the etching form, and S3 serves as an antifoam At the same time, S2 acts in the opposite direction, which affects the etching pattern, thereby making it possible to control the etching pattern.

The etchant of the present invention is a BOE solution containing 0.001 to 0.5% of the surfactant as weight percent (percentage (%) means weight percent unless otherwise specified).

In the present invention, 243 types of etching solutions were prepared at the minimum, middle and maximum concentrations of the compositions (HF, NH4F, S1, S2 and S3), and the surface correlation and the affinity with the membrane surface were evaluated to evaluate the functional affinity of each concentration. The basic evaluation was to derive the relationship.

In the present invention, after fixing the HF and NH4F to a specific concentration based on the above basic evaluation results, the following conclusions were drawn by clarifying the correlation between the surface tension, the etching form and the antifoaming force while further changing the surfactant composition.

In other words, S1 used in the present invention decreases the surface tension with increasing concentration. Above a certain concentration, S1 converges to a certain surface tension, fixes the concentration of S1, and increases the concentration of S2. The increase and decrease and the etching pattern have no effect on the angle with the positive photoresist (p-PR) contact surface but decrease the angle with the negative photoresist (n-PR) contact surface (see FIGS. 3 and 4). Increasing S3 after fixing the composition of S1 and S2 decreases the amount of foaming and then converges above a certain concentration and the etch form affects the angle with the p-PR contact surface but the angle with the n-PR contact surface increases. Converges above a certain concentration. The main function of the surfactant described above does not change depending on the HF and NH4F concentrations, but the concentration of the surfactant may be adjusted to exhibit similar etching liquid properties.

In the following, specific examples of preparing an etchant according to the present invention will be described. The following examples are only illustrative of the present invention in more detail, and are only a few of the evaluations for the present invention. That is, the present invention is not limited by the examples below.

Example 1

It consists of 14 etchant mixed with surfactant (wt%) and deionized water as fixed by weight of 5.5% HF and 20% NH4F as weight%.

Etchant Ammonium Flor Butylsulfonamide Perfluorobutyl sulfonate Polyethyllan glycol Surface tension (dyne / cm) Contact angle (degrees) Etch type (degrees) p-PR n-PR Comparative example LAL1000 30 46 80 45 H0 87 65 75 80 H1 0.01 26 50 80 77 H2 0.03 24 47 80 74 H3 0.05 20 46 80 70 H4 0.1 19 45 80 70 H5 0.05 0.001 20 47 78 60 H6 0.05 0.002 20 46 78 45 H7 0.05 0.005 20 43 78 35 H8 0.05 0.01 19 40 78 45 H9 0.05 0.005 0.001 23 47 79 55 H10 0.05 0.005 0.002 27 48 79 60 H11 0.05 0.005 0.005 32 50 80 70 H12 0.05 0.005 0.01 40 55 81 80

Etchant (NH4) 2SiF6 Solubility (g) Silicone membrane affinity Bubble Removal Time (sec) Foam Crystallization temperature Departure time Surface filtrate Comparative example 4.2 5 have 65 5 -7 ~ -6 H0 3.4 One none - One 7-8 H1 4.0 3 Few 5 or less 3 -7 ~ -6 H2 4.0 4 Few 5 or less 3 -7 ~ -6 H3 4.0 4 Few 5 or less 3 -7 ~ -6 H4 4.0 5 Few 5 or less 3 -8 ~ -7 H5 4.3 5 usually 5 or less 3 -8 ~ -7 H6 4.3 5 usually 5 or less 3 -8 ~ -7 H7 4.3 5 many 35 4 -8 ~ -7 H8 4.3 5 have 57 5 -9 ~ -8 H9 4.1 5 have 15 4 -9 to -8 H10 4.1 4 usually 5 or less 3 -9 to -8 H11 4.1 3 none 5 or less 2 -8 ~ -7 H12 4.1 2 none 5 or less 2 -8 ~ -7

It consists of 14 etching liquids fixed by HF 1.75% and NH4F 17% by weight and mixed with surfactant (wt%) and deionized water as shown below. Recipe Ammonium Flor Butylsulfonamide Perfluorobutyl sulfonate Polyethyllan glycol Surface tension (dyne / cm) Contact angle (degrees) Etch type (degrees) SiO2 film quality p-PR n-PR Comparative example LAL400 28 45 78 50 L0 90 78 72 80 L1 0.01 23 47 75 74 L2 0.03 21 46 75 70 L3 0.05 18 43 77 65 L4 0.1 18 43 77 65 L5 0.05 0.001 18 43 78 60 L6 0.05 0.002 18 41 78 55 L7 0.05 0.005 18 38 78 45 L8 0.05 0.01 18 38 78 50 L9 0.05 0.005 0.001 21 47 79 50 L10 0.05 0.005 0.002 25 47 79 60 L11 0.05 0.005 0.005 30 50 80 70 L12 0.05 0.005 0.01 39 53 80 80

Recipe (NH4) 2SiF6 Solubility Silicone membrane affinity Bubble Removal Time (sec) Foam Crystallization temperature Departure time Surface filtrate Comparative example 4.3 5 have 65 5 -8 ~ -7 L0 3.8 One none - One 7-8 L1 4.4 3 Few 5 or less 3 -9 to -8 L2 4.4 4 Few 5 or less 3 -9 to -8 L3 4.4 4 Few 5 or less 3 -9 to -8 L4 4.4 5 Few 5 or less 3 -10 ~ -9 L5 4.3 5 usually 5 or less 3 -10 ~ -9 L6 4.3 5 usually 5 or less 3 -10 ~ -9 L7 4.3 5 many 35 4 -10 ~ -9 L8 4.3 5 have 57 5 -11 to -10 L9 4.2 5 have 15 4 -11 to -10 L10 4.2 4 usually 5 or less 3 -11 to -10 L11 4.2 3 none 5 or less 2 -11 to -10 L12 4.2 2 none 5 or less 2 -11 to -10

As shown in Table 1 and Table 2, an etching solution added with a surfactant was prepared and evaluated using the following evaluation method.

Pendent drop method (25 ° C.): Measurements are shown in Tables 1 and 2 using a surface tension meter.

Sessile Drop Method: Measurements on silicon film quality using a contact angle meter are shown in Tables 1 and 2.

Silicone membrane affinity evaluation (25 degreeC): Fill 80 ml of etching liquids in a 100 ml beaker, soak a silicone membrane (7x10cm) for 30 second, and take out,

A. Etch solution departure time measurement

    Observe the removal time of the etching solution on the silicon film, and in 1: 1 or less, 2: 1 to 5 seconds 3: 5 to 30 seconds, 4:30 to 300 seconds, 5: 5 minutes or more. Indicated.

B.surface filtrate measurement

   After 5 minutes, check the surface film camera. After dividing the film surface into 5 parts, observe the remaining portion of the etching solution (surface filtrate).

   5/5: Many, less than 5/5-more than 4/5: Yes, less than 4/5-more than 2/5: Usually, less than 2/5-more than 1/5: Almost none, less than 1/5: No It is shown in Table 1 and Table 2.

Foam amount evaluation (25 degrees Celsius)

 : Fill 100ml Teflon bottle with 50ml of etchant and shake for 30 seconds

 A. Foam measurement

    By dividing the empty space of Teflon disease by 5

    More than 4/5: Many, 4 / 5-3 / 5: Yes, 3 / 5-2 / 5: Usually, 2 / 5-1 / 5: Almost none, Less than 1/5: No

    Table 1 and Table 2 are shown.

 N. Debubbling time measurement

     The removal time of the bubbles observed on the surface of the etching solution was measured and shown in Tables 1 and 2.

Etch type evaluation (25 ℃)

     : For etching pattern evaluation, a specimen in which SiO 2 (thermal oxide film) was formed on a silicon wafer and a pattern was formed thereon with a negative photoresist and a positive photoresist was prepared.

     Fill 80 ml of the etchant in a 100 ml beaker and pattern with n-PR or p-PR prepared by the above method.

     After dipping SiO2 film (20000Å, 2x4cm) for 30 minutes (time determined according to HF and NH4F content of etching solution), take out, wash with deionized water (3 minutes) and dry with nitrogen gas, and then analyze by SEM (SEM). The angles were measured and shown in Tables 1 and 2.

Evaluation of etching amount per minute by silicon oxide film quality (25 ℃)

     : Fill 100ml beaker with 80ml of etchant and dip film of p-PR patterned SiO2, TEOS, PEOXD, PSG, BPSG, UDO, LTO, HTO and so on as shown in Table 3, then remove and remove deionized water (3 minutes) and nitrogen After drying with a gas (SEM, Scanning Electron Microscope) photographing the etching amount (unit: Å / min) was measured and the results are shown in Table 3.

(NH4) 2SiF6 Solubility Evaluation (25 ℃)

      : After the etching solution was prepared with the compositions shown in Tables 1 and 2, the amount of (NH 4) 2 SiF 6 dissolved in 100 g of the etching solution was evaluated and shown in Tables 1 and 2.

Membrane Si02 BPSG PSG HTO LTO TEOS PEOXD UDO Dip Time (sec) 360 120 10 60 30 180 120 30 Comparative Example <LAL1000> 1027 3050 20160 2785 7470 2378 5876 21688 H0 1038 3073 20216 2775 7480 2390 5809 21690 H12 1016 3065 20211 2750 7410 2360 5822 21671 H0-1 1025 3058 20174 2754 7455 2339 5854 21651 H0-2 1037 3069 20248 2783 7432 2396 5876 21713 H0-3 1013 3077 20168 2743 7461 2347 5724 21639 Membrane Si02 BPSG PSG HTO LTO TEOS PEOXD UDO Dip Time (sec) 600 360 30 180 60 420 420 60 Comparative Example <LAL400> 401 1234 5102 880 1698 859 1783 5480 L0 395 1209 5127 875 1693 849 1776 5441 L12 397 1194 5138 890 1675 863 1751 5430 L0-1 386 1205 5116 893 1708 855 1790 5452 L0-2 392 1191 5083 862 1683 839 1747 5471 L0-3 413 1128 5098 884 1704 861 1756 5432

In Table 3, H0-1, H0-2, and H0-3 are 0.1% mixed with surfactant ammonium fluorobutyl sulfonamide (S1), perfluorobutyl sulfonate (S2), and polyethylene glycol (S3) in H0 etchant composition. One of the etchant, L0-1, L0-2, L0-3 is an etchant obtained by mixing 0.1% of surfactant ammonium fluoro butyl sulfonamide, perfluoro butyl sulfonate and polyethylene glycol in the composition of the L0 etchant. It was confirmed that the etching amount according to the etching solution of Table 3 was not significantly different, and the surfactants used in the present invention had no effect on the silicon oxide film etching amount within the concentration range (total amount 0.002 to 0.5% by weight).

As described above, the surface tension, silicon film affinity, etching form, and etching amount were evaluated, and the following conclusions were drawn.

That is, the surfactant used in the present invention has no effect on the silicon oxide film etching amount, 1) surfactant, S1, decreases the surface tension according to the increase of the silver concentration convergence to a certain surface tension above a certain concentration, 2) S1 By increasing the concentration of surfactant and increasing the concentration of surfactant, S2, the affinity of silicon film (hydrophobic) and affinity are increased and decreased.In addition, the etching pattern does not affect the angle with the p-PR contact surface, but with the n-PR contact surface. Reduce the angle. 3) After fixing the composition of S1 and S2, increasing surfactant, S3, decreases the amount of foaming. Concentration of foaming occurs above a certain concentration, and the etch type has a slight effect on the angle with the p-PR contact surface. The angle with the n-PR contact surface increases and converges above a certain concentration. Some examples of etching forms are shown in FIG. 4. At a certain concentration of BOE (extremely high or low HF and NH4F), the ammonium butyl butylsulfonamide (S1) content is less than 0.001%, which increases the surface tension and decreases the affinity with silicon film. When mixed with butyl sulfonate (S2) and polyethylene glycol (S3), the viscosity increases and particle adsorption problems may occur after etching. If the content of perfluorobutyl sulfonate (S2) is less than 0.001%, the affinity with the silicon film is sharply dropped, causing problems such as lowering of the etching uniformity, and higher than 0.125%, such as high viscosity and excessive foaming. Polyethylene glycol (S3) is less than 0.001% is not preferable because the ability to remove the foam is less than 0.125% may cause problems of crystallization in the etching solution. In addition, if the content of the total surfactant is less than 0.002%, the affinity with the silicon film and the solubility of the etching product may be lowered, and at 0.5% or more, problems such as particle generation and high viscosity may cause problems such as lowering of etching uniformity.

The etchant according to the present invention is composed of HF, NH4F, deionized water, and a surfactant, and improves affinity with a film surface (hydrophilicity or hydrophobicity) and bubbles to prevent oxide film etching uniformity due to high integration of devices and miniaturization of pattern size. In order to prevent particle contamination, the solubility of salts, salt ions and reaction products (NH4) 2SiF6 in BOE solution was improved to prevent particle contamination. The control room for defect generation according to the etching type has been expanded.

The spirit and scope of the present invention described above is not limited by the embodiments and the accompanying drawings as described, since the substitution, modification and modification can be made by those skilled in the art.

Claims (7)

delete Ammonium Floralkylsulfonamide as HF, NH4F, Deionized Water and Surfactant             Series (S1), perfluoroalkylsulfonate series (S2), polyethylene glycol             Silicon oxide film selected by mixing at least two or more of the series (S3)             Etching solution. The solution of claim 1, wherein the ammonium fluoroalkylsulfonamide-based surfactant (S1) has a carbon number in the range of 1-10. The silicon oxide film etching solution of claim 2, wherein the perfluoroalkyl sulfonate-based surfactant (S2) has a carbon number in the range of 1-10. The solution of claim 3, wherein the polyethylene glycol-based surfactant (S3) has a molecular weight in the range of 100 to 20000 g / mole. The weight percent of the composition according to claim 2 containing 0.001-0.25% of ammonium fluoroalkylsulfonamide series (S1), 0.001-0.125% of perfluoroalkylsulfonate series (S2), and 0.001-0.125% polyethylene glycol series (S3). Silicon oxide film etching solution, characterized in that. delete

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