KR950014734B1 - Surface treatment agent for fine surface treatment - Google Patents

Abstract

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Description

Micro Surface Treatment

1 shows the relationship between the etching rate of SiO ₂ film and the composition of BHF at 25 ° C.

2 is a graph showing the dissolution of (NH ₄ ) ₂ SiF ₆ at 25 ° C. for various BHF compositions.

3A and 3B are explanatory diagrams showing a simulation (SiO ₂ + BHF → (NH ₄ ) ₂ SiF ₆ ) of a (Nh ₄ ) ₂ SiF ₆ saturation region of a BHF solution when etching a hole in contact.

4 is a graph showing the effect of suppressing the etching rate by (NH ₄ ) ₂ SiF ₆ production.

5a and 5b are graphs showing the functional concentration region of the surface active agent.

6 is a graph showing the crystallization concentration.

7a and 7b show a simulation of a water surface micrograph.

8 to 10 show results of etching rates measured in various oxide films.

The present invention relates to a composition of microfabricated surface treatment agent.

More specifically, the present invention relates to a micro-processing surface treatment agent which is extremely effective when wet etching for the fine processing of silicon oxide film in the semiconductor device manufacturing process and for the purpose of washing the semiconductor device to be microfabricated.

In recent years, in the wet process of semiconductor integrated circuits, the cleaning of the wafer surface and the microfabricated surface, the cleaning, the etching, the refinement, and the advancement of the etching have increased with the progress of the integration degree.

So-called buffered hydrofluoric acid, such as hydrofluoric acid and a mixed solution of hydrofluoric acid and ammonium fluoride, is used as a microfinishing surface treatment agent for cleaning, etching and patterning purposes and for buffered hydrogen fluoride for submicron ultra-high integration. High performance and high functionality has been highly demanded.

Buffered hydrofluoric acid is usually prepared by mixing 40% ammonium fluoride solution and 50% hydrofluoric acid in various ratios. For example, the etching rate of the silicon oxide film in the range of 100: 1-6: 1 is about 90 kPa / min. It is used for etching by adjusting to -1200mW / min.

In this case, the chemical composition of the buffered hydrofluoric acid is approximately 35-40% for ammonium fluoride and approximately 0.5-7% for hydrofluoric acid.

Ammonium fluoride is considered to be necessary for controlling the etching rate and for completing the chemical action of the photoresist.

Recently, several methods have been proposed to improve the wettability of buffered hydrofluoric acid on wafer surface structures.

For example, in U.S. Patent No. 3,650,960 and Japanese Patent Laid-Open No. 63-283028, aliphatic carboxylic acids, salts of aliphatic carboxylic acids, aliphatic amines and aliphatic alcohols are added to give wettability to homogeneity of microetching and adhesion of particles. Sex is improved.

However, since the chemical composition of the buffered hydrofluoric acid has a high ammonium fluoride concentration, it is known that crystals precipitate during storage in winter.

In order to overcome such a problem, U.S. Patent No. 3,650,960 and Japanese Patent Laid-Open No. 63-283028 also disclose proposals using other compositions with reduced concentrations of ammonium fluoride.

If the etching action of buffered hydrofluoric acid is permanent in detail from the point of view of the ion chemical reaction mechanism, it is found that there are intrinsic crystals that are inadequate to the conventional chemical composition stoichiometry and further impede the progress of the normal etching reaction. .

The problems of conventional chemical composition are summarized below.

이온의 생성에는 HF에 동등한 몰의 NH₄F가 필요하고, 이들 이상 과잉의 NH₄F 농도는 에칭반응에 어떠한 기여도 못한다.(1) required to etch SiO ₂ film

The formation of ions requires moles of NH ₄ F equivalent to HF, and these excess NH ₄ F concentrations do not contribute to the etching reaction.

Therefore, increasing the mixing ratio of 40% ammonium fluoride to 50% hydrofluoric acid for low etching rate is gradually increasing the unnecessary excess of NH ₄ F concentration.

이온의 반응에 따라 생성되는 암모늄헥사플루오로실리케이트((NH₄)₂SiF₆)의 완충플루오르화수소산용액에 대한 용해도를, 각종의 완충플루오르화수소산조성에 의해 측정한 결과, 이 생성물의 용해도는 NH₄F의 농도증가 때문에 현저하게 감소된다는 것이 밝혀졌다.(2) SiO ₂ film

The solubility of the ammonium hexafluorosilicate ((NH ₄ ) ₂ SiF ₆ ) produced by the reaction of the ions in the buffered hydrofluoric acid solution was measured by various buffered hydrofluoric acid compositions. It was found that due to the increase in concentration of NH ₄ F is significantly reduced.

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

(3) The wettability of buffered hydrofluoric acid can be improved by mixing aliphatic hydrocarbon surfactant.

However, there is a narrow optimal range in the relationship between surfactant concentration and its function.

Control of the concentration is an important control factor.

As the concentration of NH ₄ F increases, the optimum region described above becomes narrower.

Even in dilute hydrofluoric acid as a cleaning agent for the wafer surface and the microfabricated surface, it was expected that the cleaning function would be remarkably improved by imparting wettability.

However, at present, no surfactant has been developed that satisfies the freshness, stability and functionality.

Detergents using dilute hydrofluoric acid are used as an important process, and the smoothness of the wash surface is an important factor in submicron devices.

Rough surfaces occur on the buffered hydrofluoric acid etching surface of the silicon wafer.

According to Japanese Patent Laid-Open No. 63-283028, the rough surface can be normalized by mixing an appropriate surfactant.

However, as a result of analyzing the washing surface of the silicon wafer by dilute hydrofluoric acid, it was found that the smoothness of the washing surface was impaired.

Such damage is, for example, an increased obstacle to the formation of shallow junctions.

Therefore, development of a means for providing wettability even in dilute hydrofluoric acid washing and obtaining surface smoothness is considered an indispensable technique.

It is an object of the present invention to ensure that the chemical composition of buffered hydrofluoric acid used as an etchant ensures the normal mechanism of the etching chemical reaction, ensures chemical protection of the photoresist and expands the functional area of imparting wettability. have.

It is another object of the present invention to improve the functionality by providing wettability to dilute hydrofluoric acid used as a cleaning agent to soften the cleaning surface.

As a result of repeated studies, the present inventors firstly reduced the NF ₄ F concentration of the chlorophyll hydrofluoric acid to less than 15%, and prepared the HF concentration in the range of less than 8% to the etching rate of SiO0 _{9 to} about 1500 Pa / min. By maintaining the etching ability and the protection of the resist, the uniformity and completeness of the submicron pattern etching could be shown.

Secondly, the present inventors can increase the range of carbon number available by expanding the mixing region of the hydrocarbon surfactant in the above-described NH ₄ F concentration, and the functional region of the surfactant can be expanded to improve the washability of the etching surface. I knew that.

Third, the present inventors have completed the present invention by knowing that a hydrocarbon surfactant exhibits wettability by mixing an appropriate amount of ammonium fluoride with dilute hydrofluoric acid, and that the wash surface smoothness is obtained using such wettability.

The microfabricated surface treating agent of the present invention comprises (1) a microfabricated surface treating agent containing a mixed solution consisting of hydrofluoric acid, ammonium fluoride and water, wherein the mixed solution contains less than 0.01-8% by weight of hydrofluoric acid and fluorinated Micromachined surface treatment agent containing less than 0.01-15% by weight of ammonium

(2) A microfabricated surface treatment agent comprising an aqueous solution containing less than 0.01-8% by weight of hydrofluoric acid and less than 0.01-15% by weight of ammonium fluoride, wherein the aqueous solution is an aliphatic carboxylic acid and its salts, aliphatic amines and aliphatic compounds. Surface treatment agent containing at least one selected from the group of each surfactant consisting of alcohol

(3) A microfabricated surface treatment agent consisting of an aqueous solution containing less than 0.01-8% by weight of hydrofluoric acid and less than 0.01-15% by weight of ammonium fluoride, wherein the aqueous solution also contains an aliphatic amine, an aliphatic carboxylic acid and Surface treatment agent containing at least one selected from the group consisting of salts and aliphatic alcohols thereof

(4) The microfabrication surface treatment agent according to (1), wherein the micromachining surface treatment agent is an etching agent of a silicon oxide film.

(5) The microfabrication surface treatment agent according to (2), wherein the micromachining surface treatment agent is an etching agent of a silicon oxide film.

(6) The microfabricated surface treatment agent according to (3), wherein the microfabricated surface treatment agent is an etchant for a silicon oxide film.

(7) The microfabricated surface treatment agent according to (1), wherein the microfabricated surface treatment agent is a cleaning agent for the silicon surface and the semiconductor element surface.

(8) The microfabricated surface treatment agent according to (2), wherein the microfabricated surface treatment agent is a cleaning agent for the silicon surface and the semiconductor element surface.

(9) The microfabricated surface treatment agent according to (3), which contains any of the microfabricated surface treatment agent which is a cleaning agent for the silicon surface and the semiconductor element surface.

The ammonium fluoride of the present invention exhibited better functionality of the surfactant in the low concentration region.

On the other hand, in the high concentration region of ammonium fluoride, the functionality of the surfactant appeared only when the carbon number of the surfactant was 12 or less.

As a result of investigating the effective area by mixing the surfactant with the buffered hydrofluoric acid of low concentration ammonium fluoride, it was found that the surfactant having a larger carbon number was effective even when the concentration of ammonium fluoride was less than 15%.

In other words, by making the ammonium fluoride concentration less than 15% gave good results in controlling the wettability.

Aliphatic amines lowered the contact angle of the treatment agent to improve wettability.

However, the foaming power of aliphatic amine becomes large, and using it adversely affects a semiconductor manufacturing process.

In order to suppress such a foaming force, an antifoaming aliphatic carboxylic acid or an aliphatic alcohol was added to capture the foaming force and a satisfactory functional treatment agent was prepared.

Although aliphatic carboxylic acid and aliphatic alcohol showed defoaming power only in the region of high ammonium fluoride concentration, they were found to improve not only the defoaming power but also wettability in the ammonium fluoride concentration range of less than 15%.

The aliphatic amines of one kind of surfactant used in the present invention include compounds represented by the general formula (C _m H _2m-1 NH ₂ (m is an integer of 25 or less)) and secondary or tertiary amines. .

For example:

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 is a formula (the compound (n is an integer of not more than 25 represented by _{C n H 2n + 1 COOH)} , for example, as it follows.

C ₅ H ₁₁ COOH, C ₆ H ₁₃ COOH, C ₇ H ₁₅ 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.

The aliphatic carboxylate is a compound represented by the general formula C _n H _{2n + 1} COONH ₃ R (R is a hydrogen atom or an alkyl group, n is an integer of 25 or less), for example.

C ₅ H ₁₁ COONH ₃ , C ₇ H ₁₅ COONH ₃ (H ₁₅ C ₇ ), C ₈ H ₁₇ COONH ₃ (H ₁₇ C ₃ ), 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 OCC ₁₄ H ₂₅ .

Aliphatic alcohol is a compound represented by the general formula _{C n H 2n + 1 OH (} n is an integer of 25 or less), for example, as it follows.

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 ₁₇ H ₃₅ OH, C ₁₈ H ₃₇ OH, C ₂₀ H ₄₁ OH.

The above-mentioned surfactants are used in one kind or in a mixture of two or more kinds, and are also used as a solid or a liquid thereof.

The amount added is in the range of 10-10000 ppm with respect to the total composition, preferably in the range of 50-1000 ppm.

If the addition amount is less than 10 ppm, the addition effect hardly appears.

It was confirmed that the treatment agent of the present invention exhibited sufficient relaxation.

On the other hand, when it exceeds 1000 ppm, the effect corresponding to the excess amount cannot be obtained.

It was confirmed that the treatment agent of the present invention exhibited sufficient relaxation.

Hereinafter, the experimental result by the present inventor which became the basis of this invention is demonstrated.

1. Etching Rate of SiO ₂ Film and Composition of BHF

Dissolution of SiO ₂ to produce SiF ₆ ^-2 requires the presence of ions.

The reaction for dissolving SiO ₂ using HF solution proceeds to (3) via dissociation equation (1) (2) and the dissolution rate depends on the equilibrium constant of dissociation equation (1) (2).

_{HF + H 2 O = H 3} O + F - (1)

^{_{HF + H 3 O + F -}} = H 3 O + + HF 2 - (2)

^{_{SiO 2 + 4HF 2 - = SiF}} 6 2- + 2F 2 + 2H 2 O (3)

The reaction of dissolving SiO ₂ using NH ₄ HF ₂ solution proceeds through dissociation equation (4) to (3), and the dissolution rate depends on the equilibrium constant of dissociation equation (4).

^{_{NH 4 HF 2 = NH 4 +}} + HF 2 - (4)

According to the stoichiometric ratio, 8 moles of HF and 4 molar equivalents of NH ₄ HF ₂ are used with respect to SiO ₂ / mol.

(1) Since the dissociation degree of (2) is smaller than (4), it is evident from the etching rates of the liquid compositions (1) and (2) shown in Table 1 that HF requires a high concentration compared to NH ₄ NF ₂ .

TABLE 1

BHF Composition and SiO ₂ Film Etching Rate

Therefore, it is clear that it is more effective to use buffered hydrofluoric acid mixed with so-called NH ₄ F than to use HF alone.

However, there has been no conventional recognition that adding more than equivalents of NH ₄ F to HF makes no contribution to the dissolution reaction.

The composition ③, in which excess NH ₄ was mixed in comparison with the composition ②, shows that the etching rate decreases despite the same HF concentration because of the inhibition of dissociation of the formula (4) due to the increase in the NH ₄ F concentration.

FIG. 1 shows the relationship between the etching rate of the SiO ₂ film and the BHF composition as described above, and A, B, C and D are as follows.

A: 500 s / min

B: 1000 mW / min

C: 1200 cc / min

D: NH ₄ HF ₂

Table 2 shows the etch rates obtained by fixing the HF concentration to 4% and varying the concentration of NH ₄ F.

TABLE 2

In the same manner, the etching rate was also determined for each of the HF concentrations of 0.5%, 1%, 2%, 6% and 8% by weight.

Because of this result, the BHF composition is generally sufficient when the NH ₄ F concentration is less than 15% to obtain the required etching rate of 90-1500 mW / min, and the currently used concentration of 30-40% has no meaning in terms of etching rate. It turns out that

2. Solubility of (NH ₄ ) ₂ SiF ₆ and Concentration of NH ₄ F

2 shows the results of solubility measurement of (NH ₄ ) ₂ SiF ₆ for various BHF compositions.

It was found from FIG. 2 that the (NH ₄ ) ₂ SiF ₆ solubility significantly decreased with decreasing NH ₄ F concentration.

In Figure 2, the symbols E, F, G and H represent HF = 0%, HF = 0.5%, HF = 2.4% and HF = 6.0%, respectively.

3. (NH ₄ ) ₂ SiF ₆ Saturation Effects on the Etching of SiO ₂ Films

When the concentration of (NH ₄ ) ₂ SiF _{6 in} BHF increases due to etching of the SiO ₂ film and reaches the saturation concentration, the etching is stopped by crystallization of (NH ₄ ) ₂ SiF ₆ .

(NH _{4) 2} using the solubility data (data) of SiF ₆ in the etching point (NH _{4) 2} SiF ₆ can be simulated in the saturation region.

Since it is difficult to idealize the change of the solution composition due to the concentration and temperature of the "SiF ₆ ^2- ion diffusion rate / SiO ₂ etching rate" and the temperature, it is difficult to idealize the model in the simulation. _The liquid phase at which ₆ ^2- ions reached the saturation concentration of BHF in the initial composition of BHF was made in such a way that it extends semicircularly from the etching point and the necessary calculations were made with such a model.

The simulation is shown in FIG.

Referring to FIG. 3, when the contact hole sizes are 10 µm and 5 µm, respectively, when (NH ₄ ) ₂ SiF ₆ solubility is different from the ratio of 1: 5 when etching at a depth of 1 µm, the (NH ₄ ) Since the ₂ SiF ₆ saturation region is also different from the ratio of 1: 5, it is evident that the larger NH ₄ F concentration is more affected by the precipitation of saturated (NH ₄ ) ₂ SiF ₆ .

Several points were noted from this point of view.

The first point observed is related to the size of the contact hole.

The saturation region of (NH ₄ ) ₂ SiF ₆ increases as the hole size increases, that is, proportional to the square of the hole size.

Table 2 shows the relationship between the etching spots of the hole sizes.

10㎛ hole as compared with the hole of less 1㎛, notably high etching coupling, (NH _{4) 2} SiF ₆ are shown to clarify the influence of the saturation.

The second point watched relates to the aspect ratio of the holes.

As shown in Fig. 3, the aspect ratio of the pores obtained by etching the same saturated region is inversely proportional to the solubility of (NH ₄ ) ₂ SiF ₆ .

This effect becomes remarkable when the hole size becomes small.

Third, as shown in Fig., NH ₄ F concentration of the aspect ratio of the etching with BHF large in the sub-micron etching is suppressed.

From the above simulation and etching data, it became clear by the inventors how the excess concentration of NH ₄ F interferes with etching.

3A and 3B show the following compositions, respectively.

(a) NH ₄ F 38.1%

HF 2.4%

SpGr 1.114

(NH ₄ ) ₂ SiF ₆ Solubility: 1.9 / 100g BHF (20 ℃)

(b) NH ₄ F 15.1%

HF 2.4%

SpGr 1.114

(NH ₄ ) ₂ SiF ₆ Solubility: 9.4 / 100g BHF (20 ℃)

A third note again is the saturation effect of (NH ₄ ) ₂ SiF ₆ on the continuity of etch rate.

As shown in FIG. 4, NH ₄ F concentration is smaller, because the solubility of (NH _{4) 2} SiF ₆ for high BHF, faster more and a reduction in etch rate.

From this point of view, FIG. 4 shows that the etching amount of a square hole of 10 mu m was measured at 25 ° C with 2.4% HF, and symbols A and B in the figure are as follows.

A: NH ₄ F is 38.1%

B: NH ₄ F is 15.0%

Based on the above 1-3 data, the ammonium fluoride concentration of 15-40%, more generally, is used for cleaning and fine pattern etching of the silicon oxide film using an etchant composed of hydrofluoric acid and ammonium fluoride. 30-40% is not only lowering the etching rate but also lowering the solubility of the ammonium hexafluorosilicate, and it is explained that the root cause is a serious defect in the increase in the defective rate due to the etching stain and the failure of the etching aspect ratio.

In addition, the dissociation equations (1) to (4) described above indicate that an appropriate concentration of NH ₄ F required to obtain an etching rate of 800-1500 kPa / min for etching the thermal oxide film is 15% or less, preferably 10% or less. I could understand from.

4. Surfactant Functional Area and NH ₄ F Concentration

By mixing the hydrocarbon surfactant with the buffered hydrofluoric acid, the contact angle can be reduced to improve the wettability on the wafer surface, and the fine particles in the buffered hydrofluoric acid can be over-purified in a specific concentration region of the surfactant.

Such a surfactant specific concentration region is called a functional concentration region.

5 clearly shows that such a range of functional concentrations depends on the NH ₄ F concentration of buffered hydrofluoric acid.

The contact angle decreases with the addition of surfactant, but at some concentration the contact angle becomes constant.

This concentration point is called "critical micelle concentration" (CMC).

In the case where the concentration of NH ₄ F is high, the curve reaching the CMC point is sharp, and at the same time, the width of the functional concentration region of the surfactant having a small number of particles decreases.

If the surfactant is added slightly beyond the management area or width, rust is found due to the micelles during the etching of the silicon oxide film.

On the other hand, when the concentration of NH ₄ F is less than 15%, the curve reaching the CMC point is smooth and the functional concentration range of the surfactant having a small number of particles is widened.

When etching silicon oxide, no rust was found.

As a result, in the buffered hydrofluoric acid having a NH ₄ F concentration of less than 15%, since the functional concentration region of the surfactant is extended, it is possible to control the buffered hydrofluoric acid excellent in wettability and cleanness to a sufficiently wide management region.

In Figures 5a, b, and c, the marks o and o are as follows.

In addition, symbol A represents a contact angle, and symbol B represents a particle number.

5. Crystallization Temperature

In the region of high NH ₄ F concentration, buffered hydrofluoric acid causes crystal precipitation of NH ₄ HF ₂ .

Such crystal precipitation shows a drawback in changing the etching rate in the wet etching process.

In this respect, the present inventors found that there exist two relational curves in the crystallization according to the change of the NH ₄ F concentration.

One is a point drop curve and a crystallization curve.

In the low NH ₄ F concentration region, the freezing point becomes lower with increasing NH ₄ F.

The solid phase that precipitates in this region is ice.

The lowest point is at about 15%, which increases the crystallization temperature as the crystallization zone moves.

The solid phase which precipitates in this area is NH ₄ HF ₂ .

6 shows their results.

It can be seen from FIG. 6 that the precipitation of NH ₄ HF ₂ can be suppressed in a wide range by reducing the NH ₄ F concentration to less than 15%.

In addition, when freezing occurs, the ice melts easily as the temperature increases, and thus does not affect the etching rate.

In Fig. 6, each symbol represents the following.

6. Smoothness on cleaning surface

To wash the silicon surface or the surface of the microfabricated semiconductor device, a dilute solution of hydrofluoric acid is generally used.

However, the cleaning of hydrofluoric acid has the drawback of spotting on the surface of the skin.

In order to avoid the occurrence of such stains, the addition of surfactants was necessary.

Indeed, no suitable surfactant has been found that imparts wettability and low particleability of dilute hydrofluoric acid.

In view of this, the present inventors have found that when a small amount of NH ₄ F is added to dilute hydrofluoric acid, the addition of a surfactant may exhibit the wettability and other functionalities described above.

Accordingly, it was found that the wettability was improved and at the same time, staining was prevented from occurring on the cleaning surface. Such results are shown in Table 14.

Formation of shallow bonds is facilitated by smoothing the cleaning surface.

In improving washability, it is preferable to use surfactant together, It is especially preferable to use together with at least 1 sort (s) of aliphatic amine, aliphatic carboxylic acid, or aliphatic alcohol.

7. Suntec etching

By reducing the concentration of ammonium fluoride, the etching rate for PSG film, BPSG film and thermal oxide film can be changed.

The results of measuring the etching rates of various oxide films are shown in FIGS. 8 to 10.

When buffered hydrofluoric acid having a hydrofluoric acid concentration of 5.05 and an ammonium fluoride concentration of 4.6% was used, the etching rate of the thermal oxide film was 772 dl / min.

On the other hand, the etching rate of the PSG film was 33700 kV / min, the BPSG film (not heat treated) was 6370 kPa / min, and the BPSG film (heat treated) was 2614 kPa / min.

The etching rate of these PSG and BPSG films means that the thermal oxide film is 43.7 times, 8.25 times and 3.4 times faster than the etching rate.

Therefore, using this difference in etching speed, for example, when the thermal oxide film and the PSG film coexist, the PSG film is etched, and the thermal oxide film is not etched.

In this manner, selective etching can be performed.

As described above, it has been found by the present invention to reduce the concentration of ammonium fluoride, thereby increasing the solubility of (NH ₄ ) ₂ SiF ₆ to eliminate the defective rate of pattern etching and to exhibit high aspect ratio etching.

Since the concentration of ammonium fluoride is lower than that of the conventional buffered hydrofluoric acid, a hydrocarbon surfactant having a larger carbon number is used, and functionalities such as wettability and cleanliness can be exerted well.

Moreover, it was easy to manage because the width of the addition amount was wide.

The low concentration of ammonium fluoride makes it possible to sufficiently mitigate the chemistry of the resist in accordance with the present invention.

The present invention has the advantage that the surface has smoothness when forming shallow junctions, as well as cleaning of highly integrated semiconductor devices, silicon wafers or micromachined surfaces, eliminating the drawbacks of the prior art.

EXAMPLE

Embodiments of the present invention will now be described in detail.

Example 1

The contact holes having a diameter of 10 mu m were etched using the respective solutions having a predetermined concentration of HF shown in Table 3 and having a concentration of NH ₄ F of 99%.

At this time, the contact hole measured the defective rate by the optical microscope. The results are shown in Table 3.

TABLE 3

Comparative Example 1

The same treatment as in Example 1 was performed using each solution having the composition shown in Table 4. The results are shown in Table 4.

TABLE 4

Example 2

Various contact holes were etched using the respective solutions having the concentrations shown in Table 5.

The defective rate of contact hole was measured with the optical microscope. The results are shown in Table 5.

TABLE 5

Comparative Example 2

Various contact holes were etched using the respective solutions having the concentrations shown in Table 6.

The defective rate of a contact hole was measured with the optical microscope. The results are shown in Table 6.

TABLE 6

Example 3

After etching a contact hole of 0.7 µm for a predetermined time using a solution composed of 0.5% HF and 9.9% NH ₄ F, the etching depth was measured by an electron microscope to obtain an aspect ratio (opening width / depth). The results are shown in Table 7.

TABLE 7

Comparative Example 3

In Example 3, etching was carried out in the same manner as in Example 3 except that the concentration of NH ₄ F was 39.6%. The results are shown in Table 8.

TABLE 8

Example 4

After etching a contact hole of 10 μm using a solution composed of 2.4% HF and 9.9% NH ₄ F, the etching depth was measured by a step gauge. The results are shown in Table 9.

TABLE 9

The results are also shown in FIG.

It can be seen that the etching rate is constant because the etching rate is represented by a straight line passing through the origin.

[Comparative Example 4]

In Example 4, etching was carried out in the same manner as in Example 4 except that the concentration of NH ₄ F was 38.1%. The results are shown in Table 10.

TABLE 10

As shown in FIG. 4, the etching rate curve does not pass through the origin.

That is, the onset of etching is delayed and the etching rate is lowered.

Example 5

A contact hole having a diameter of 10 µm was etched using a solution prepared by adding HF at the concentration shown in Table 11 of NH ₄ F at 5%.

Next, the result was measured with the optical microscope. The results are shown in Table 11.

TABLE 11

Example 6

A contact hole having a diameter of 10 μm was etched using a solution prepared by adding a predetermined amount of the surfactant shown in Table 12 to a solution of 9.9% NH ₄ F and 0.5% HF, followed by an optical microscope. The defective rate of was measured. The results are shown in Table 12.

TABLE 12

Example 7

SiO ₂ on the silicon wafer was etched using a solution prepared by adding 800 ppm C ₁₄ H ₂₉ NH ₂ and 400 ppm C ₈ H ₁₇ COOH to a solution containing 14% ammonium fluoride and 2.4% hydrofluoric acid, and then microscopically Examination of the silicon wafer revealed no rust. The results are shown in Table 13.

[Comparative Example 5]

SiO ₂ on the silicon wafer was etched using a solution prepared by adding 100 ppm C ₁₄ H ₂₉ NH ₂ and 60 ppm C ₈ H ₁₇ COOH to a solution containing 14% ammonium fluoride and 2.4% hydrofluoric acid, followed by a microscope After inspecting the silicon wafer, rust was found. The results are shown in Table 13.

TABLE 13

In view of this, the generation of rust in Example 7 and Comparative Example 5 described above means that SiO ₂ is not etched uniformly but remains in the form of rust.

As apparent from Comparative Example 5, it can be seen from the table that the addition of a large amount of surfactant is not good because rust appears at a high content of ammonium fluoride when the surfactant is added.

In addition, it can be seen from the table that a high concentration of ammonium fluoride when using a surfactant together does not yield good results.

Example 8

The P-type silicon wafer prepared by the CZ method was washed with a solution containing NH ₄ F 5%, HF 1.7%, C ₁₄ H ₂₇ NH ₂ 80 ppm and C ₈ H ₁₇ COOH 40 ppm, and then the wafer was cleaned with a microscope. As a result of the inspection, the surface of the washed wafer was found to have smoothness. The results are shown in Table 14.

Comparative Example 6

As a result of washing the P-type silicon wafer produced by the CZ method using a 4.9% HF solution having the same etching rate as in Example 8, the surface was found to be rough. The results are shown in Table 14.

TABLE 14

Example 9

Using the treatment agent of the present invention, a resist film (OFPR-800) having a film thickness of 13000 kPa was applied onto a silicon wafer, and a contact hole of 10 mu m was etched.

As a result of the examination of the microscope, no abnormality was observed in the resist. The results are shown in Table 15.

TABLE 15

Example 10

Surfactant was added to the aqueous solution containing 10% of NH ₄ F and 1% of HF, and the foaming was investigated.

For foaming measurement, 10 ml of the treatment agent was put into a plastic container having an inner diameter of 30 mm and a height of 70 mm, and then the container was shaken for 10 seconds.

The time taken for the foaming diary to stop (parcel time) was obtained. The results are shown in Table 16.

TABLE 16

Claims (9)

A micro-processing surface treatment agent containing a mixed solution of hydrofluoric acid, ammonium fluoride, and water, wherein the mixed solution contains less than 0.01-8% by weight of hydrofluoric acid and less than 0.01-15% by weight of ammonium fluoride. Surface finishes. The group of surfactants according to claim 1, comprising an aliphatic carboxylic acid and salts thereof, aliphatic amines and aliphatic alcohols in an aqueous solution containing less than 0.01-8% by weight of hydrofluoric acid and less than 0.01-15% by weight of fluorinated hammonium. Micro-processing surface treatment agent containing at least one selected from. The aliphatic carboxylic acid, salts and aliphatic alcohols of claim 1, while containing an aliphatic amine in an aqueous solution containing less than 0.01-8% by weight of hydrofluoric acid and less than 0.01-15% by weight of ammonium fluoride. Micro-processing surface treatment agent which contained at least any 1 type. The microfabricated surface treating agent according to claim 1, wherein the surface treating agent is an etching agent of a silicon oxide film. 3. The microfabricated surface treating agent according to claim 2, wherein the surface treating agent is an etching agent of a silicon oxide film. 4. The microfabricated surface treatment agent according to claim 3, wherein the surface treatment agent is an etchant for a silicon oxide film. The microfabricated surface treating agent according to claim 1, wherein the surface treating agent is a cleaning agent for the silicon surface and the semiconductor device surface. 3. The microfabricated surface treating agent according to claim 2, wherein the surface treating agent is a cleaning agent for silicon surfaces and semiconductor device surfaces. 4. The microfabricated surface treatment agent according to claim 3, wherein the microfabricated surface treatment agent is a cleaning agent for the silicon surface and the semiconductor element surface.

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