JPS59219472A - Etching solution for interface protecting film - Google Patents

Abstract

PURPOSE:To obtain an etching soln. for an interface protecting film preventing the sticking of contaminants to the surface of a body to be treated by mixing a buffer soln. contg. ammonium fluoride and hydrofluoric acid with a surfactant contg. fluorine, acetic acid, nitric acid and alcohol. CONSTITUTION:About 80-95vol% buffer soln. contg. ammonium fluoride and hydrofluoric acid is mixed with about 0.01-5% surfactant contg. fluorine, proper amounts of acetic acid and nitric acid, and about 2-15% alcohol inhibiting the conversion of the surfactant into micelle such as isopropyl alcohol to obtain an etching soln. for an interface protecting film such as a silicon oxide film. When an interface protecting film is etched with the etching soln., the sticking of contaminants to the surface of the body to be treated can be prevented. Deterioration in the characteristics of the body is also prevented, and the rate of restoration of cleanliness after treatment can be increased.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a corrosive solution for interfacial protection films.

[Technical background of the invention and its problems]

Conventionally, as a corrosive solution for a so-called interface protection film such as a silicon oxide film, fluoride water and acid alone have been used, or hydrofluoric acid and 7. A so-called slow bath solution containing ammonium chloride is used.

Such corrosive liquids are used in the pre-process of oxidation treatment and diffusion treatment in the manufacturing process of semiconductor devices. When the silicon substrate is taken out of the retentate during these treatments, the surface of the silicon substrate is directly exposed to air due to its water-repellent nature. Therefore, dirt and other contaminants trapped in the gas-liquid phase (atmosphere/corrosive liquid) easily adhere to the surface of the silicon substrate. Furthermore, these contaminants adhere to the surface of the silicon substrate with great adhesion force due to direct reaction with the surface of the silicon substrate. As a result, there was a problem in that even if a cleaning step was performed after removing the material from the corrosive solution, contaminants and the like could not be easily removed.

In order to solve this problem, the etching solution for silicon and silicon oxide films must be a mixed solution containing at least hydrofluoric acid and a surfactant, and if necessary, either acetic acid, nitric acid, or A product containing both has been developed.

However, such corrosive liquids have the following problems.

■If acetic acid is used, it will solidify at low temperatures and cannot be used.

2) Recovery to a clean state after washing with deionized water after eating algae is slow h0. 3. If a P-N junction element is formed on a silicon substrate, it may lead to poor voltage resistance and the current amplification factor of the transistor. Significantly, the surfactant separates into the liquid and deposits fibrous foreign matter on the surface after feeding. This foreign material enters the P-N junction,
A leakage current of several to several microamperes occurs.

This can be conveniently used in the production of hand conductor devices using silicon substrates.7! i: '-''r 6 Note that this foreign material is a small one with a length of about 0.3 to 0.5 μ.

[Purpose of the invention]

The present invention provides an interface protection film that prevents contaminants from adhering between the surfaces of the object to be treated, prevents deterioration of the characteristics of the object, and improves the cleanliness recovery rate after treatment. Its purpose is to provide a rotting liquid of

[Summary of the invention]

The present invention prevents contaminants from adhering to the surface of the object to be treated, and prevents contaminants from adhering to the surface of the object to be treated. This is a corrosive solution for the interfacial protective film that prevents the deterioration of body properties and improves the cleanliness recovery rate after treatment.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

This interfacial protective film corrosive solution contains a fluorine-based surfactant,
It is a mixture of acetic acid, nitric acid and alcohol.

Here, the mixing ratio of each component is 80 to 95%
VoL%, fluorine surfactant is 0.01-5 Vot
%, alcohol is 2-i 5 Votφ.

The alcohol used is one that can be used to form micelles of the fluorosurfactant, for example, isopropyl alcohol.

The buffer used is, for example, 49% hydrofluoric acid diluted with deionized water as necessary or a buffer containing an appropriate amount of ammonium fluoride.

Acetic acid works in synergy with the surface tension lowering effect of the surfactant to quickly separate fine particles such as dust generated during the etching process from the object to be processed.

Nitric acid exhibits an etching effect when the object to be processed is a silicon substrate.

The operating temperature of this interfacial protective film is i.

It is set appropriately in the range of ~30°C.

In addition, if the mixing ratio of alcohol is less than 2Vo1%, the effect of preventing micelle formation will not be sufficiently obtained;
If the Vo exceeds 1%, sufficient corrosive (etching) action as a corrosive liquid cannot be obtained.

When we investigated the surface tension of the corrosion a() of the interfacial insulation membrane constructed in this way while changing the 0 degrees of the corrosive liquid, we found that the first
The results shown by characteristic line (1) in the figure were obtained. In order to compare with this, the surface tension of a conventional corrosive liquid made of 49% fluorinated acid at 9 degrees Celsius was plotted four times, and the result was obtained as shown by the characteristic line ω) in the same figure.

As is clear from the figure, the corrosive liquid of the present invention, shown by characteristic line (1), exhibits a much smaller surface tension than the conventional one, and is suitable for etching objects. It can quickly remove contaminants such as dust that accumulate on the surface.

Next, examples of the present invention will be described. A 10% diluted solution of the interfacial protective film etchant of the present invention having the following composition is formed on a silicon substrate, and the surface thereof is coated with an interfacial protective film consisting of a silicon oxide film. The object to be treated is soaked in water for about 10 seconds, and then the object to be treated is taken out from the corrosive solution, washed with deionized water, and dried in a dryer to remove any residual residue on the surface of the interfacial protective film. When we investigated the relationship between the number of deposited particles and the particle diameter, we found that the line of property σn is shown in Figure 2.
) The results shown in (fr) were obtained. Furthermore, the surface of the interfacial protective film after the treatment was extremely bright and delicious, and was patterned into a predetermined 79 turns.

For comparison, a treatment similar to that described above was applied to the object using a conventional corrosive solution consisting of 49% hydrofluoric acid, and the dust particles remaining on the surface of the interface preservation film were removed. When we investigated the relationship between the number and particle diameter, we obtained the results shown in Figure 2 as a characteristic line.

As is clear from the results shown in FIG. 2, on the surface of the object treated with the corrosive solution of the example, there were almost no dust particles remaining in the particle diameter range of 0 to 40μ.
It can be seen that in the comparative example, a large number of dust particles with a diameter of 0 to 10 μm remain. Furthermore, in order to confirm the effect of removing dust particles, the relationship between deionized water resistance and deionized water washing time was investigated, and as shown by the characteristic line (V) in FIG. It can be seen that the deionized water resistance value is larger than that of the conventional corrosive liquid shown by the characteristic line (b) in the figure, and the cleaning effect is superior. In addition, when we investigated the leakage current characteristics of the treated object after treatment, we found that in the example, part of the surfactant did not separate from the melt during treatment, preventing the generation of leakage current. As shown by the characteristic line (■) in Figure 4,
A large leakage current is already generated from the low Du<;Y bias voltage value indicated by 75 (and 011 in the figure for the comparative example) showing excellent characteristics.

Further, the current increase Q''Z4 rate (β) (I.=1rnA) of the object to be treated treated with the corrosive liquid of the example is about 150
On the other hand, it was found that the ldi current increase rate (β) (lc=1rnA) of the sample treated with the corrosive liquid of the above comparative example was 50-70.

〔Effect of the invention〕

As explained above, according to the corrosive liquid for the interfacial retention film according to the present invention, the surface of the object to be treated can be contaminated! It has remarkable effects such as being able to prevent the adhesion of 1"/lJ quality, prevent deterioration of the characteristics of the object to be treated, and improve the cleanliness recovery rate after treatment.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between surface tension and fake liquid concentration;
Figure 2 is a characteristic diagram showing the relationship between the number of dust particles and particle diameter, and Figure 3 is a characteristic color diagram showing the relationship between deionized water specific resistance and deionized water cleaning time. It is a graph showing the relationship between leak 11 flow and 12 bias evening pressure.

Claims (2)

[Claims] (1) Into a buffer solution containing ammonium fluoride and fluorinated water, add a predetermined amount of fluorine fiber surfactant, acetic acid, nitric acid,
and alcohol. (2) The corrosive solution for an interfacial protective film according to claim 1, wherein the alcohol is inglobil alcohol which completely prevents the surfactant from forming micelles.