JP2852355B2 - Fine processing surface treatment agent - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a microfabricated surface treating agent composition, and more particularly, to a wet etching method for microfabricating a silicon oxide film at the time of manufacturing a semiconductor device, The present invention relates to a finely processed surface treatment agent which is extremely effective when used for cleaning a surface or a finely processed semiconductor element surface.

[Conventional technology]

2. Description of the Related Art In a wet process for a semiconductor integrated circuit, there is an increasing need for cleaning, etching, and cleaning, refinement, and enhancement of patterning and cleaning of a wafer surface and a microfabricated surface with the progress of integration. Hydrofluoric acid and a mixed solution of hydrogen fluoride and ammonium fluoride, so-called buffered hydrofluoric acid, are both used as cleaning / etching and patterning purposes as fine processing surface treatment agents that are indispensable for this process. For ultra-micron integration, higher performance and higher functionality are required.

Buffered hydrofluoric acid is usually a mixture of 40% ammonium fluoride solution and 50% hydrofluoric acid in various ratios, for example, in the range of 100: 1 to 6: 1, the silicon oxide film etching rate is reduced from about 90Å / min. It is used for etching while controlling at about 1200 ° / min. In this case, the chemical composition of buffered hydrofluoric acid is about 35 to 40% for ammonium fluoride and about 0.5 to 7% for hydrogen fluoride. Is thought to be necessary for buffering chemistry.

In recent years, various methods have been developed to improve the wettability of this buffered hydrofluoric acid on wafer surface components, for example, US
In P.4,795,582 and JP-A-63-283028, an aliphatic carboxylic acid, a salt of an aliphatic carboxylic acid, an aliphatic amine and an aliphatic alcohol are blended as a hydrocarbon surfactant to impart wettability. By doing so, the uniformity of fine etching and the particle adhesion are improved. It is also known that the chemical composition of this buffered hydrofluoric acid has a drawback that crystals are precipitated during storage in the cold season due to the high concentration of ammonium fluoride. Also USP 3,650,960 and JP-A-58-932
No. 38 is proposed. However, when the etching action of buffered hydrofluoric acid is pursued in detail from the viewpoint of the ion chemical reaction mechanism, not only the chemical composition conventionally used widely is not stoichiometrically inappropriate, but rather the normal etching An essential deficiency has been identified that impairs the response signal. The problems of the conventional chemical composition are summarized as follows.

(1) To generate HF ₂ ^- ions necessary for etching the SiO ₂ film, HF requires an equimolar amount of NH ₄ F, but an excessive NH ₄ F concentration does not contribute to the etching reaction. .

Therefore, increasing the mixing ratio of 40% ammonium fluoride to 50% hydrofluoric acid for a low etching rate requires:
The unnecessary excess of NH ₄ F concentration is to be increased further.

(2) The solubility of ammonium silicofluoride (NH ₄ ) ₂ SiF ₆ generated by the reaction between the SiO ₂ film and HF ₂ ⁻ ions in buffered hydrofluoric acid solutions was measured for various buffered hydrofluoric acid compositions. The solubility of the product is NH
It was found that the concentration was significantly reduced by increasing the ₄ F concentration.

Therefore, an unnecessary excess of the NH ₄ F concentration significantly impairs the temporal linearity of the fine pattern etching reaction and the uniformity of the patterning.

(3) The leakage of buffered hydrofluoric acid can be improved by blending an aliphatic hydrocarbon-based surfactant, but there is a narrow optimum range in the relationship between the surfactant concentration and the surfactant activity, Its concentration control is an important management factor.

This optimum range is narrower as the NH ₄ F concentration is higher.

Next, with respect to dilute hydrofluoric acid as a cleaning agent for the wafer surface and the microfabricated surface, the cleaning function is expected to be dramatically improved by imparting wettability. Surfactants satisfying the functionality have not been developed.

Cleaning using dilute hydrofluoric acid is used as an important step, but the smoothness of the cleaning surface is noted as a very important factor in submicron devices. Although the buffered hydrofluoric acid etching surface of silicon wafers becomes rough, a technique for normalizing by adding an appropriate surfactant is described in, for example,
Developed by 63-283028. Examination of the cleaning surface of the silicon wafer with dilute hydrofluoric acid revealed that its smoothness was damaged. Such surface defects are a serious obstacle to the formation of, for example, shallow junctions in highly integrated circuits. Therefore,
It is considered that the development of a means for obtaining surface smoothness by imparting leakage even in dilute hydrofluoric acid cleaning is an inevitable technology in the future.

[Problems to be solved by the invention]

It is an object of the present invention to enhance the chemical composition of buffered hydrofluoric acid as an etching agent, the essential mechanism of the etching chemical reaction works normally, the chemical protection of the photoresist is ensured, and the functional area of imparting wettability is extended. In other words, the purpose is to provide wettability to dilute hydrofluoric acid as a cleaning agent and to improve the direction in which the smoothness of the cleaning surface is exhibited.

[Means for solving the problem]

By lowering the NH ₄ F concentration of the buffered hydrofluoric acid to less than 15% and preparing the HF concentration within a range of less than 8%, while maintaining the etching ability and the resist protecting ability up to the SiO ₂ film etching rate of about 1500Å / min, The uniformity and completeness of submicron pattern etching can be expressed, and at this NH ₄ F concentration, the range of the number of carbon atoms that can be used is increased due to the expansion of the compounding area of the hydrocarbon-based surfactant, It has been found that the functional area of the activator can be extended to improve the cleanliness of the etched surface. In addition, it was confirmed that by adding an appropriate amount of ammonium fluoride to dilute hydrofluoric acid, the hydrocarbon-based surfactant exhibited a wettability function, and it was found that smoothness of the cleaning surface could be obtained. The invention has been completed.

[Configuration and operation of the invention]

The microfabricated surface treatment agent of the present invention comprises: (1) a mixed solution of hydrofluoric acid, an ammonium fluoride solution and water, wherein hydrogen fluoride is contained in an amount of 0.01 to less than 8% by weight and ammonium fluoride is contained in an amount of 0.01 to 15% by weight. An aqueous solution containing less than 10% by weight of at least one selected from the group of surfactants consisting of aliphatic carboxylic acids and salts thereof, aliphatic amines and aliphatic alcohols, and
The fatty acid carboxylic acid is represented by the general formula C _n H _{2n + 1} COOH (n is an integer of 25 or less), and the aliphatic amine is represented by the general formula C _m H
_{2m + 1} NH ₂ (m represents an integer of 25 or less), and the aliphatic alcohol is represented by the general formula C _n H _{2n + 1} OH (n represents an integer of 25 or less). Fine processing surface treatment agent. (2) In an aqueous solution containing 0.01 to less than 8% by weight of hydrogen fluoride and 0.01 to less than 15% by weight of ammonium fluoride,
The finely-processed surface treatment agent according to claim 1, further comprising an aliphatic amine and at least one of an aliphatic carboxylic acid and a salt thereof and an aliphatic alcohol.

(3) The treating agent according to (1) or (2), wherein the finely processed surface treatment is an etching agent for a silicon oxide film.

(4) The fine processing surface treatment is a cleaning agent for a silicon surface and a semiconductor element surface.
The processing agent according to any one of the above.

Consists of

In the low concentration range of the ammonium fluoride of the present invention, the functionality of the surfactant is better exhibited. In the region where the concentration of ammonium fluoride was high, the effect was exhibited only when the number of carbon atoms of the surfactant was 12 or less. Investigating the effective range by adding a surfactant to buffered hydrofluoric acid with a low concentration of ammonium fluoride, a surfactant with a higher carbon number also exerts an effect in the region with an ammonium fluoride concentration of less than 15% I found to do. In other words, by controlling the ammonium fluoride concentration to less than 15%, good results were also obtained in wettability control.

Aliphatic amines reduce the contact angle of the treating agent and improve the wettability, but have a large foaming power and, as such, adversely affect the semiconductor manufacturing process. By adding an aliphatic carboxylic acid or an aliphatic alcohol having a defoaming power in order to suppress the foaming power, the foaming power was reduced and the functionality of the treating agent was completed. Furthermore, aliphatic carboxylic acids and alcohols showed only the defoaming effect in the region of high ammonium fluoride concentration, but in the ammonium fluoride concentration region of less than 15%, not only the defoaming effect but also the improvement of wettability were improved. recognized.

One serving aliphatic amine surfactants for use in the present invention has the general formula C _m H _{2m + 1} NH ₂ [m is an integer of 25 or less. And a secondary or tertiary amine. An example is as follows.

C ₇ H ₁₅ NH ₂ , C ₈ H ₁₇ NH ₂ , C ₉ H ₁₉ NH ₂ , C ₁₀ H ₂₁ NH ₂ , C ₁₂ H ₂₅ NH ₂ , C ₁₄ H ₂₉ NH ₂ , C ₁₆ H ₃₃ NH ₂ , C _{18 H 37 NH 2, C 20} H 41 NH 2, 2- (C 2 H 5) -C 7 H 14 NH 2,
(C ₅ H ₁₁ ) ₂ NH, (C ₁₀ H ₂₁ ) ₂ NH, (CH ₃ ) ₂ (C ₁₀ H ₂₁ ) N
(C ₈ H ₁₇ ) ₃ N aliphatic carboxylic acid has the general formula C _n H _{2n + 1} COOH [n is 25
Represents the following integers. ] The compound shown by these. An example is as follows.

_{C 5 H 11 COOH, C 6} H 13 COOH, C 7 H 13 COOH, C 8 H 17 COOH, C 9 H 19 COOH, C 10 H 21 COOH, C 12 H 25 COOH, C 14 H 29 COOH, C 16 H ₃₃ COOH, C ₁₈ H ₃₇ COOH and the aliphatic carboxylate are represented by the general formula C _n H _{2n + 1} COONH ₃ R
[R represents a hydrogen atom or an alkyl group. n represents an integer of 25 or less. ] It is a salt shown. An example is as follows.

_{C 5 H 11 COONH 4, C} 7 H 15 COONH 3 (H 15 C 7), C 8 H 17 COONH 3 (H 17 C 8), C 7 H 15 COONH 3 (H 15 C 7), C 7 H 15 COONH ₄ , C ₈ H ₁₇ COONH ₄ , C ₁₄ H ₂₉ NH ₃ OOCC ₁₄ H ₂₅ Aliphatic alcohol is represented by the general formula C _n H _{2n + 1} OH [n represents an integer of 25 or less. ] The compound shown by these. For example, C ₆ H ₁₃ OH, C ₇ H ₁₅ OH, C ₈ H ₁₇ OH, C ₉ H ₁₉ OH, C ₁₀ H ₂₁ OH, C ₁₂ H ₂₅ OH, C ₁₈ H ₃₅ OH, C ₁₈ H ₃₇ OH, C ₂₀ H ₄₁ OH These surfactants are used in one kind or in a mixture of two or more kinds, and may be in a solid form or a liquid form. The addition amount is about 10 to 10,000 ppm, preferably about 50 to 1000 ppm, based on the total composition. 10p surfactant added
When the amount is less than pm, the effect of the addition is hardly recognized, while
Even if it is added more than 0 ppm, the effect corresponding thereto cannot be obtained.

It was recognized that the treating agent of the present invention exhibited a sufficient effect of relaxing the resist.

Hereinafter, the results of experiments performed by the present inventors on which the present invention is based will be described.

To generate 1.SiO ₂ film etching rate and BHF composition fluorosilicate ion SiF ₆ ^-2 by dissolving SiO ₂ is, HF ₂ ^- is the required presence of ions. Using HF solution
The reaction for dissolving SiO ₂ proceeds according to (3) via dissociation formulas (1) and (2), and the dissolution rate is based on dissociation formulas (1) and (2).
Depends on the equilibrium constant of.

_{HF + H 2 = H 3 O} + + F - (1) HF + H 3 O + + F - = H 3 O + + HF 2 - (2) SiO 2 + 4HF 2 - = SiF 6 2- + 2F - + 2H 2 O (3) NH 4 HF _The reaction for dissolving SiO ₂ using the _two solutions proceeds according to (3) via the dissociation formula (4), and the dissolution rate depends only on the equilibrium constant of the dissociation formula (4).

^{_{NH 4 HF 2 = NH 4 +}} + HF 2 - (4) in a stoichiometric ratio, each relative to SiO ₂ 1 mol s HF8 mol and NH
₄ HF ₂ 4 mol is equivalent, but since the dissociation degree of (1) and (2) is much smaller than that of (4), in order to obtain the same etching rate, HF is higher than NH ₄ HF _2. The need for a much higher concentration is apparent from the following liquid composition and etching rate.

Therefore, formulated with NH ₄ F than HF alone, but better to use a so-called buffered BHF hydrofluoric acid it is clear that it is effective, even when blended with NH ₄ F or the equivalent with respect to HF dissolution Conventionally, there is no recognition that it does not contribute to the reaction.
The composition containing NH ₄ F in excess with respect to the composition shown in Table 1 has a higher HF content due to the suppression of dissociation in equation (4) due to the increase in NH ₄ F concentration.
It shows a decrease in the etching rate regardless of the same concentration.

FIG. 1 shows the results of a detailed study of the relationship between the SiO ₂ film etching rate and the BHF composition. Also, A, B,
A show that the C and respectively following: 500Å / min B: 1000Å / min C: 1200Å / min D: NH 4 HF 2 Table 2 fixes the HF concentration of 4%, the etching by changing the NH ₄ F concentration It is a rate.

Similarly, HF concentration of 0.5 wt%, 1 wt%, 2 wt%, 6 wt%, 8 wt%
%, The etching rate was determined. A BHF composition of 15% or less with respect to the NH ₄ F concentration is sufficient for obtaining an etching rate of 90 to 1500 ° / min which is generally required, and the concentration currently used as a mainstream is 30 to 40%.
Has no meaning at all from the necessity of the etching rate.

2. (NH ₄ ) ₂ SiF ₆ Solubility and NH ₄ F Concentration (NH ₄ ) ₂ SiF ₆ solubility for various BHF composition solutions was measured and is shown in FIG. (NH ₄ ) ₂ SiF ₆ Solubility is NH ₄ F
It was found that it decreased significantly with the concentration. However, E, F, G and H in FIG. 2 represent the following, respectively. HF 0%, HF
0.5%, HF2.4%, HF6.0%.

3.SiO ₂ film in the pattern etching of (NH _{4) 2} SiF ₆ BHF during the etching of the saturation effect SiO ₂ film (NH _{4) 2} SiF ₆ concentration increases and reaches a saturation concentration, (NH ₄₎ Etching stops due to ₂ SiF ₆ crystal precipitation. (NH ₄₎ in the etching point using the solubility data of ₂ SiF ₆ (NH ₄₎ it is possible to simulate a ₂ SiF ₆ saturated region. Since it is difficult to idealize changes in [SiF ₆ ^2- ion diffusion rate / SiO ₂ etching rate] due to various conditions such as concentration and temperature and changes in the liquid composition due to the reaction, the simulation is performed using the SiF ₆ generated by the reaction.
^The calculation was made as a model in which the liquid phase portion where the ^2- ions reached the saturation concentration in the initial composition of BHF expanded in a hemispherical shape around the etching point, and this is shown in FIG. For contact hole size 10μm and 0.5μm, depth 1μ
m, the (NH ₄ ) ₂ SiF ₆ solubility is 1: 5
(NH ₄ ) ₂ SiF ₆ saturated region of BHF solution which differs by
BHF with a higher NH ₄ F concentration is (NH ₄ )
It is evident that ₂ SiF ₆ is greatly affected by saturated precipitation. The first point to be noted is the relationship with the contact hole size. The (NH ₄ ) ₂ SiF ₆ saturated region is proportional to the square of the hole size and is larger as the hole size is larger. The relationship between the size of the hole size and the etching unevenness was investigated, and this is shown in Table 2. 1μm for 10μm hole
Compared with the following holes, the degree of etching defects is significantly higher than that of the following holes, and clearly shows the effect of (NH ₄ ) ₂ SiF ₆ saturation.

The second point to be noted is the relationship with the aspect ratio of the hole. As shown in FIG. 3, the aspect ratio of a hole that can be etched in the same saturated region is (NH ₄ ) ₂ SiF ₆
Inversely proportional to solubility. This effect is more remarkable as the hole size becomes smaller, and as shown in Table 3, in the submicron size etching, the etching aspect ratio of BHF having a high NH ₄ F concentration is suppressed to a small value.

From the above simulation and etching data, it was clarified how an excessive NH ₄ F concentration causes an obstacle to etching. FIGS. 3A and 3B show the following cases, respectively.

(A): NH ₄ F 38.1% HF 2.4% SpGr 1.114 (NH ₄ ) ₂ The solubility of SiF ₆ is 1.9 / 100 g BHF (20 ° C.) (B): NH ₄ F 15.1% HF 2.4% SpGr 1.114 (NH ₄ ) ₂ The solubility of SiF ₆ is 9.4 / 100 g BHF (20 ° C.). The third point to note further is the effect of (NH ₄ ) ₂ SiF saturation on the etching rate persistence. As shown in FIG. ₄ , the etching rate of BHF having a large NH ₄ F concentration is reduced earlier because the solubility of (NH ₄ ) ₂ SiF ₆ is small.
However, Fig. 4 shows a square hole of 10 μm at HF 2.4% at 25 ° C.
In the figure, the amount of etching was measured.
Represents the following, respectively.

A: NH ₄ F 38.1% B: NH ₄ F 15.0% or more from analysis data 1 to 3 for cleaning silicon oxide film and fine pattern etching using etchin composition consisting of hydrogen fluoride and ammonium fluoride In the conventional ammonium fluoride concentration 15 ~ 40
%, And most commonly 30 to 40%, has a decrease in the etching rate and a decrease in the solubility and solubility of the formed ammonium silicofluoride. It was clarified to be the root cause of various defects. Etching rate required for thermal oxide film etching 800-1500Å / min 25 ° C
It is clear from the analysis data of FIG. 1 and the dissociation formulas (1) to (4) that the NH ₄ F concentration necessary for obtaining the concentration is preferably 15% or less, preferably 10% or less.

4. Surfactant functional area and NH ₄ F concentration By mixing a hydrocarbon surfactant with buffered hydrofluoric acid, the contact angle can be reduced and the wettability to the wafer surface can be improved, and the surface activity can be improved. Filtration and cleaning of fine particles in buffered hydrofluoric acid can be performed in a specific concentration range of the agent. Such a surfactant concentration region is called a functional concentration region, and it has been clarified that this functional concentration region depends on the NH ₄ F concentration in the buffered hydrofluoric acid, and this is shown in FIG.

As the surfactant is added, the contact angle decreases, but becomes constant at a certain concentration. This concentration point is called the critical micelle concentration (CMC) point. When the NH ₄ F concentration is high, the curve reaching the CMC point is steep and the width of the functional concentration region of the surfactant having a small number of particles is narrow. If a surfactant is added slightly beyond this control width, spots due to micelles may be detected during etching of the silicon oxide film. On the other hand, it was found that when the NH ₄ F concentration was less than 15%, the gradient of CMC reached was gentle and the functional concentration range of the surfactant having a small number of particles was wide. In the low NH ₄ F concentration region, no stain was observed during the etching of the silicon oxide film. As a result, in buffered hydrofluoric acid with an NH ₄ F concentration of less than 15%, the functional concentration range of the surfactant is expanded, so that buffered hydrofluoric acid with excellent wettability and cleanliness can be adjusted with a sufficiently wide control range. It has become possible. The fifth
Figures (a), (b) and (c) represent the following, respectively. FIG. 5 shows the contact angle A and the number of particles in FIGS.

5.Crystallization temperature In high NH ₄ F concentration range, buffered hydrofluoric acid
Crystal precipitation of NH ₄ HF ₂ occurs, causing a change in the etching rate in the wet etching process and causing trouble. It has been found that when the NH ₄ F concentration is changed, two relational lines exist for the precipitation of crystals. One is the freezing point depression curve and the other is the crystallization curve. In the region where the NH ₄ F concentration is low, the freezing point decreases as NH ₄ F increases. The solid phase deposited in this region is ice. It shows the lowest point at about 15%, after which it becomes a crystallization region and the crystal deposition temperature rises. The solid phase deposited in this region is NH ₄ HF ₂ . These results are shown in FIG. By reducing the NH ₄ F concentration to less than 15%, the precipitation of NH ₄ HF ₂ crystals can be prevented to a considerably low temperature. Also, even if icing occurs, there is no effect on the etching rate because it is easily dissolved by increasing the temperature.

 However, the symbols in FIG. 6 indicate the following, respectively.

6. Smoothness of Cleaning Surface Generally, a dilute solution of hydrofluoric acid is used to clean a silicon surface or a microfabricated semiconductor element surface. However, it was recognized that cleaning with dilute hydrofluoric acid gave roughness to the cleaning surface. In order to prevent roughening, it is necessary to add a surfactant. However, no suitable surfactant has been found in which dilute hydrofluoric acid gives functions such as wettability and low particle properties. However, it was recognized that the addition of a small amount of NH ₄ F to dilute hydrofluoric acid made it possible to add a surfactant exhibiting various functions.
It has been found that when ammonium fluoride and the surfactant of the present invention are added so as to have the same etching rate as dilute hydrofluoric acid, the wettability is improved and the roughness of the cleaning surface is prevented. The results are shown in Table 14. The smoothing of the cleaning surface facilitated the formation of shallow junctions.

In particular, it is preferable to use a surfactant in combination for cleaning properties, and it is particularly preferable to use an aliphatic amine in combination with at least one of aliphatic carboxylic acids and aliphatic alcohols.

〔The invention's effect〕

It has been clarified that by lowering the concentration of ammonium fluoride, the solubility of ammonium silicofluoride is increased and the defect rate of pattern etching is eliminated, and at the same time, it is effective for etching with a high aspect ratio. Since the concentration of ammonium fluoride is lower than that of conventional buffered hydrofluoric acid, hydrocarbon surfactants with a larger carbon number can be used, and the functions of wettability and cleanliness are well exhibited, and the amount of addition is reduced. The width can be widened and the management becomes easy. It is also recognized that even low ammonium fluoride concentration can sufficiently alleviate the chemical action on the resist, and it is also effective for cleaning highly integrated semiconductor elements or silicon wafers and finely processed surfaces, and has a shallow junction. During formation, the surface can be smoothed and conventional obstacles can be removed.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Reference Example 1 A 10 μm contact hole was etched using a composition having a predetermined HF concentration and an NH ₄ F concentration of 9.9% shown in Table 3. The defective rate at that time was measured with an optical microscope. Table 3 shows the results.

Comparative Example 1 The same treatment as in Reference Example 1 was performed using the predetermined composition liquid shown in Table 4. Table 4 shows the results.

Reference Example 2 Contact holes of various sizes were etched using the predetermined composition liquids shown in Table 5. The defective rate at this time was measured with an optical microscope. Table 5 shows the results.

COMPARATIVE EXAMPLE Contact holes of various sizes were etched by using a predetermined composition shown in Table 6. The defective rate at this time was measured with an optical microscope. The results are shown in Table 6.

Reference Example 3 After a contact hole of 0.7 μm was etched with a composition solution having a HF concentration of 0.5% and an NH ₄ F concentration of 9.9% for a certain period of time, the depth of the cross section was measured by an electron microscope, and the aspect ratio at that time was measured. (Opening width / depth). The results are shown in Table 7.

Comparative Example 3 In Reference Example 3, the NH ₄ F concentration was changed to 39.6%, and all other treatments were the same. The results are shown in Table 8.

Reference Example 4 A 10 μm contact hole was etched with a composition solution having a HF concentration of 2.4% and an NH ₄ F concentration of 9.9% by using a step gauge. The results are shown in Table 9.

The results are shown in FIG. The etching rate line is a straight line passing through the origin, and the etching rate is constant.

Comparative Example 4 In Reference Example 4, the NH ₄ F concentration was changed to 38.1%, and all other treatments were the same. The results are shown in Table 10.

As shown in FIG. 4, it does not pass through the origin of the etching rate line, that is, the start of etching is slow, and the etching rate decreases with the etching time.

Reference Example 5 A 10 μm contact hole was etched with a solution obtained by adding HF having a predetermined concentration shown in Table 11 to an NH ₄ F concentration of 5%, and the result was measured with an optical microscope. Table 11 shows the results.

Reference Example 6 A prescribed amount of a prescribed surfactant shown in Table 12 below was added to a composition solution having an NH ₄ F concentration of 9.9% and a HF concentration of 0.5%, and the composition was added at 10 μm and 1.
A 0 μm contact hole was etched. The defective rate at this time was measured by observation with an optical microscope. This result
Also shown in Table 12.

Example 1 A solution obtained by adding 800 ppm of C ₁₄ H ₂₅ NH ₂ and 400 ppm of C ₈ H ₁₇ COOH to an aqueous solution containing 14% of ammonium fluoride and 2.4% of hydrofluoric acid was subjected to etching of SiO ₂ on a silicon wafer, and the silicon wafer was etched. Examination of the above with a microscope revealed no spots. The results are shown in Table 13.

Comparative Example 5 Results of etching SiO ₂ on a silicon wafer with a solution obtained by adding 100 ppm of C ₁₄ H ₂₉ NH ₂ and 60 ppm of C ₈ H ₁₇ COOH to an aqueous solution containing 38.1% of ammonium fluoride and 2.4% of hydrofluoric acid A spot has occurred. The results are shown in Table 13.

However, the occurrence of the stains in Example 1 and Comparative Example 5 indicates that the SiO ₂ was not etched uniformly but remained in a stained state. Further, as is apparent from Comparative Row 5, when a surfactant is added, a high content of ammonium fluoride causes stains, so that a large amount of surfactant cannot be added.

It also shows that good results cannot be obtained if the concentration of ammonium fluoride is high even when a surfactant is used in combination.

Example 2 A P-type silicon wafer manufactured by the CZ method was NH ₄ F 5.0
%, HF 1.7%, cleaning with an aqueous solution containing 80 ppm of C ₁₄ H ₂₇ NH ₂ and 40 ppm of C ₈ H ₁₇ COOH and microscopic inspection, the surface of the wafer was smooth. The results are shown in Table 14.

Comparative Example 6 As a result of cleaning a P-type silicon wafer manufactured by the CZ method using a 4.9% HF aqueous solution having the same etching rate as in Example 2, the surface was found to be rough. The results are shown in Table 14.

Example 3 Using the treatment agent of the present invention, a film thickness of 13 was formed on a silicon wafer.
A 000 mm resist (OFPR-800) was applied, a contact hole of 10 μm was opened, and etching was performed. Microscopic examination revealed no abnormality in the resist. The results are shown in Table 15.

Example 4 A surfactant was added to an aqueous solution containing 10% of NH ₄ F and 1% of HF, and its foaming was examined.

The measurement of foaming was performed by placing 10 ml of the treating agent in a plastic container having an inner diameter of 30 mm and a height of 70 mm, shaking for 10 seconds, and then determining the time until defoaming.

In each of the experimental examples, the wettability to silicon was good, and it was indicated by the contact angle. The results are shown in Table 16.

[Brief description of the drawings]

FIG. 1 is a drawing showing the relationship between the etching rate of the SiO ₂ film and the BHF composition at 25 ° C. FIG. 2 is a graph showing the solubility of (NH ₄ ) ₂ SiF ₄ at 25 ° C. for various BHF compositions. Fig. 3 shows BHF in contact hole etching
Simulation of (NH ₄ ) ₂ SiF ₆ saturated region of solution (SiO ₂
FIG. ₄ is an explanatory diagram showing + BHF → (NH ₄ ) ₂ SiF ₆ ). FIG. 4 is a drawing showing the effect of suppressing the etching rate by (NH ₄ ) ₂ SiF ₆ generation. FIG. 5 is an explanatory diagram showing a functional concentration region of a surfactant. FIG. 6 is a graph showing the crystallization concentration. FIG. 7 is a simulated diagram of a micrograph of the wafer surface.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-93238 (JP, A) JP-A-50-73574 (JP, A) JP-A-61-207586 (JP, A) JP-A-59-73586 31029 (JP, A) JP 3-17372 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/306 H01L 21/308 C09K 13/08 C23F 1/24

Claims (4)

(57) [Claims] 1. A mixed solution comprising hydrofluoric acid, an ammonium fluoride solution and water, wherein hydrogen fluoride is contained in an amount of 0.01 to 8% by weight.
And an aqueous solution containing 0.01 to less than 15% by weight of ammonium fluoride, at least one selected from the group consisting of aliphatic carboxylic acids and salts thereof, and surfactants consisting of aliphatic amines and aliphatic alcohols. And
The aliphatic carboxylic acid has the general formula C _n H _{2n + 1} COOH (n is 25
Wherein the aliphatic amine is represented by the general formula C _m
A microfabricated surface treatment represented by H _{2m + 1} NH ₂ (m represents an integer of 25 or less), and an aliphatic alcohol represented by the general formula C _n H _{2n + 1} OH (n represents an integer of 25 or less) Agent. 2. An aqueous solution containing 0.01 to less than 8% by weight of hydrogen fluoride and 0.01 to less than 15% by weight of ammonium fluoride, containing an aliphatic amine, an aliphatic carboxylic acid, a salt thereof and an aliphatic carboxylic acid. The finely-processed surface treatment agent according to claim 1, further comprising at least one of alcohols. 3. The processing agent according to claim 1, wherein the finely processed surface treatment is an etching agent for a silicon oxide film. 4. The treatment agent according to claim 1, wherein the surface treatment for fine processing is a cleaning agent for a silicon surface and a semiconductor element surface.