JP2576409B2 - Method and apparatus for removing metal impurities - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for removing metal impurities in a chemical solution, and more particularly to a method for removing metal impurities in a hydrofluoric acid-based solution using particles containing silicon as a main component as an adsorbent. A method and an apparatus therefor.

[0002]

2. Description of the Related Art Hydrofluoric acid chemicals are mainly used for etching a silicon oxide film in a semiconductor manufacturing process, and include an HF solution, an HF / NH ₄ F mixed solution and the like. This etching process is usually performed by immersing the silicon substrate in a chemical solution or spraying the silicon substrate with the chemical solution.

The life of the chemical is logically determined by the deterioration of the etching rate. However, in practice, metal and dust are accumulated in the chemical due to repeated processing, and this effect is more significant. If metal or dust in the chemical liquid adheres to the silicon substrate, it causes deterioration of the dielectric strength of the oxide film and poor formation of a fine pattern, which significantly deteriorates the performance of the semiconductor element. Therefore, the exchange of the chemical is performed at a cycle much shorter than the original life determined by the etching rate.

[0004] In order to solve the above-mentioned problem, a means for removing metals and dusts by adsorption and filtration while circulating a hydrofluoric acid-based chemical solution is employed. Thus, dust is relatively easily removed by this type of means, but there are many problems with metal removal. FIG. 5 shows a cross-sectional view of a conventional metal impurity removing apparatus of this type. As shown in FIG. 1, a resin container 2 is filled with silicon particles 4 as an adsorbent.
By circulating the hydrofluoric acid-based chemical solution 3 through the filter, metal impurities in the chemical solution are selectively removed.

[0005] Silicon particles, which are adsorbents, are contaminated by removing metal impurities in a chemical solution. Conventionally, they have been regenerated and reused by washing with ammonia water or hydrogen peroxide water. Therefore, in the conventional silicon particles, the silicon on the surface is terminated with oxygen or hydrogen (hereinafter, referred to as a first conventional example). Since there is no nucleus for adsorbing metal impurities in such particles having silicon terminated with oxygen or hydrogen, there is a drawback that the adsorption efficiency is low and the adsorption capacity is rapidly lowered.

[0006] In view of this, several proposals have been made to form an adsorption nucleus on the particle surface in order to cope with this point. JP 4
Japanese Patent Publication No. -286328 proposes that silicon particles are irradiated with accelerated rare gas ions such as Ar ions to form defects on the particle surfaces, thereby efficiently adsorbing metal (Cu) ions. (Hereinafter, referred to as a second conventional example). Japanese Patent Application No. 4-157199 proposes that Au is precipitated on silicon particles and used as an adsorption nucleus (hereinafter, referred to as a third conventional example).

[0007]

In the first conventional example described above, the surface of the silicon particles is terminated with oxygen or hydrogen, and there is no metal that acts as an adsorption nucleus of the metal, so that the metal removing ability is small. Further, in the second conventional example of irradiating accelerated Ar ions or the like, since the surface of the particles becomes physically weak, the etching of the silicon particles is facilitated by hydrofluoric acid, and the silicon concentration in the chemical solution is increased. This is likely to cause an increase in dust, such as the generation of external particles, which increase the particle size. Further, in the third conventional example in which precipitated Au is used as an adsorption nucleus, there is a possibility that this Au may peel off from the particle surface or dissolve in the solution during use, and these may adhere to the wafer to be processed and cause defects. Cause. The present invention has been made to address the above-mentioned problems, and an object of the present invention is to provide a method and an apparatus capable of dramatically improving the ability to remove metal impurities without giving new contaminants. To provide.

[0008]

According to the present invention, in order to achieve the above object, (1) a step of exposing particles containing silicon as a main component to a fluid containing chlorine to terminate silicon on the surface of the particles with chlorine. And (2) passing a hydrofluoric acid-based chemical solution into a container filled with particles whose surface silicon is terminated with chlorine to adsorb metal impurities in the chemical solution to the particles. A removal method is provided.

According to the present invention, metal impurities in a hydrofluoric acid-based chemical solution in which particles containing silicon as a main component are filled as an adsorbent in a container having an inlet and an outlet for the chemical solution are removed. In the above apparatus, there is provided a metal impurity removing apparatus, wherein silicon on the surface of the particles is terminated with chlorine.

[0010]

When the silicon particles are exposed to a fluid containing chlorine, oxygen and hydrogen terminating the silicon are replaced by chlorine. Chlorine which has terminated the surface of silicon particles acts as a metal impurity adsorption nucleus which is much stronger than oxygen and hydrogen which are similar termination groups. The adsorption of metal impurities is limited by the generated metal impurity adsorption nuclei. Therefore, metal impurities contained in the hydrofluoric acid-based chemical solution are quickly and abundantly adsorbed on the silicon particle surface. The silicon particles terminated with chlorine do not increase the silicon concentration or the gold concentration in the chemical solution and do not generate particles, so that a semiconductor device can be manufactured with a high yield.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a metal impurity removing apparatus used in an embodiment of the present invention. Silicon particles 1 with chlorine-terminated silicon on the surface
And the hydrofluoric acid chemical solution 3 is circulated. Metal impurities such as Cu contained in the hydrofluoric acid-based chemical are easily captured by chlorine nuclei formed on the surface of the silicon particles and removed from the liquid.

FIG. 2 is a flowchart showing a method for removing metal impurities in a chemical solution according to a first embodiment of the present invention. First, the silicon particles 1 and the resin container 2 contaminated by metal impurities and dust are cleaned by a normal cleaning method using aqueous ammonia and hydrogen peroxide to remove contaminants. Next, by immersing the silicon particles in hydrochloric acid, the silicon on the surface is terminated with chlorine which is an adsorption nucleus of a metal impurity. By filling the silicon particles 1 whose surfaces have been terminated with chlorine into a cleaned resin container 2, the metal impurity removing apparatus shown in FIG. 1 is produced or reproduced. The metal impurity is removed by passing a hydrofluoric acid-based chemical solution through the metal impurity removing device.

FIG. 3 is a flowchart showing a method for removing metal impurities in a chemical solution according to a second embodiment of the present invention. First, dust and metal impurities are removed from the silicon particles and the resin container by ordinary washing. Next, the silicon film is immersed in hydrofluoric acid to remove the oxide film on the particle surface. Subsequently, the silicon particles are treated with hydrochloric acid to terminate the silicon on the surface with chlorine which is an adsorption nucleus of a metal impurity.
By filling silicon particles whose surface is terminated with chlorine into a resin container, a metal impurity removing device is produced.
The metal impurity is removed by passing a hydrofluoric acid-based chemical solution through the metal impurity removing device. In the method of the present embodiment, the extremely active surface from which the oxide film has been completely removed is subjected to the chlorine termination treatment, so that a stronger metal impurity removing ability is exhibited.

FIG. 4 shows the change over time of various impurity concentrations in hydrofluoric acid when 1 ppm of copper is added to hydrofluoric acid and this chemical is circulated through the metal impurity removing apparatus of each of the conventional example and the present invention. FIG. In the case of using silicon particles having no nucleus and terminated with oxygen or hydrogen as the adsorbent [(a) First Conventional Example], the copper removal rate was lower than that of the method of the embodiment of the present invention. Is low.

In the case of forming a physical defect serving as an adsorption nucleus on the silicon particle surface by irradiation of rare gas ions [(b) second conventional example], silicon is eluted vigorously, and the copper removal rate is low at the initial stage. Although good, it deteriorated with the increase of silicon elution. In the case of depositing gold as adsorption nuclei on the surface of silicon particles [(c) Third Conventional Example],
Large gold elution is observed. Gold adhering to the substrate surface causes a leakage current, and gold taken into the crystal forms a deep level in silicon, which significantly degrades device characteristics.

In the first embodiment ((d)) of the present invention in which the surface of the silicon particles is terminated with chlorine, the copper removal rate is almost the same as that of the third embodiment using gold as a deposition nucleus. The silicon concentration and its change with time are the least. Further, in the second embodiment [(e)] in which the oxide film was removed, in addition to the effect of the first embodiment, the removal of copper was more quickly achieved.

While the preferred embodiment has been described above,
The present invention is not limited to these embodiments, and various changes can be made without departing from the gist of the present invention. For example, the terminal treatment with chlorine can be performed by a treatment in a chlorine atmosphere, a treatment in a hydrogen chloride atmosphere, a treatment in a plasma atmosphere containing chlorine, or the like, instead of the method of immersion in hydrochloric acid. In addition, silicon particles serving as an adsorbent may be any of single crystal, polycrystal, and amorphous.

[0018]

As described above, in the method for removing metal impurities in a chemical solution according to the present invention, the surface of silicon particles used as an adsorbent is terminated with chlorine acting as a strong metal impurity adsorption nucleus. Since the hydrofluoric acid-based chemical solution is filtered by the manufactured metal impurity removal device, the concentration of metal impurities in the chemical solution can be sufficiently increased without increasing the concentration of gold or silicon or increasing the number of particles. Can be reduced. Therefore, according to the present invention, a semiconductor device having stable characteristics can be manufactured with a high yield.

[Brief description of the drawings]

FIG. 1 is a sectional view of a metal impurity removing apparatus used in an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a first embodiment of the present invention.

FIG. 3 is a flowchart for explaining a second embodiment of the present invention.

FIG. 4 is a graph showing the concentration of various materials in a chemical solution in each of the conventional examples and the examples of the present invention.

FIG. 5 is a cross-sectional view of a conventional metal impurity removing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon particle whose surface was terminated by chlorine 2 Resin container 3 Hydrofluoric acid chemical solution 4 Silicon particle whose surface was terminated by oxygen or hydrogen

Claims (4)

(57) [Claims] 1. A step of (1) exposing particles containing silicon as a main component to a fluid containing chlorine to terminate silicon on the surface of the particles with chlorine; Passing a hydrofluoric acid-based chemical solution through a filled container to adsorb metal impurities in the chemical solution to the particles. 2. The method according to claim 1, wherein a step of removing a silicon oxide film on the surface of the particles is added prior to the step (1). 3. The method according to claim 1, wherein the fluid containing chlorine in the step (1) is hydrochloric acid. 4. An apparatus for removing metal impurities in a hydrofluoric acid-based chemical solution in which particles mainly composed of silicon are filled as an adsorbent in a container provided with an inlet and an outlet for the chemical solution. A metal impurity removing apparatus, wherein silicon on the surface is terminated with chlorine.