TWI615896B - 矽 Wafer manufacturing method - Google Patents

Description

矽 Wafer manufacturing method

The present invention relates to a method for manufacturing a tantalum wafer, and more particularly to a method for reducing the amount of fluorine remaining on the surface of a tantalum wafer when a tantalum wafer is manufactured by a cleaning step including HF cleaning.矽 Wafer manufacturing method.

The manufacturing process of the wafer usually includes the following steps: cutting the wafer (slice) from the twin ingot; surface treatment such as grinding, etching, etc.; cleaning step; and further performing the subsequent steps as needed in response to the use of the wafer (annealing, epitaxial layer formation, etc.).

The washing step is usually performed by SC-1 washing, SC-2 washing, or the like, and is also washed with hydrofluoric acid (hereinafter, also referred to as "HF washing") (for example, refer to the patent). Document 1).

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Publication No. 2009-506538

In recent years, in order to achieve a high degree of cleansing of the surface of the tantalum wafer in the cleaning step of the tantalum wafer, hydrofluoric acid (HF washing) is applied to the final cleaning treatment. However, fluorine is usually left on the surface of the germanium wafer after HF washing. Ion (F-). When a semiconductor device is manufactured using a germanium wafer having fluorine ions remaining on its surface, there is a possibility that an abnormality in the formation of an oxide film (a decrease in film thickness) may occur during the formation of a gate oxide film which is performed at the initial stage of the manufacturing process. Therefore, there is a case where it is required to reduce the amount of residual fluorine ions in the germanium wafer subjected to HF cleaning.

Accordingly, it is an object of the present invention to provide a method for producing a tantalum wafer comprising a ruthenium wafer which is washed with HF and which has little residual fluoride ion.

In order to achieve the above object, the present inventors have focused on the results of the research, and it has been found that by washing (cleaning) with an aqueous solution containing hydrochloric acid as a wet treatment in the next step after HF washing, HF can be washed and dried. Fluoride ions remaining on the surface of the wafer are highly removed. In view of this point, the inventors presumed the following.

Fluoride ion F ^- is the most electron-negative ion, which forms a strong ionic bond on the surface of the ruthenium wafer and stays on the surface of the wafer. By using an aqueous solution containing hydrochloric acid, it can suppress the presence of F ^- and stay in the crystal. The fluorine on the round surface is removed in the neutral state of HF. However, as a result of the study by the inventors, it is clear that the treatment other than washing with an aqueous solution containing hydrochloric acid is a wet treatment in the next step of HF washing, for example, when washing with water and washing with another chemical liquid, it is difficult to Fluoride ions are highly removed from the surface of the germanium wafer. The present invention has been completed based on the above knowledge.

That is, the above object is achieved by a method for manufacturing a germanium wafer, comprising the steps of: manufacturing a wafer: a step of preparing a germanium wafer; and a step of washing the surface of the germanium wafer; The washing step includes: washing with hydrofluoric acid; and It is washed with an aqueous solution containing hydrochloric acid as a wet treatment for the next step of washing with hydrofluoric acid.

In one aspect, the aqueous solution containing hydrochloric acid contains only an aqueous solution containing hydrochloric acid as an acid component.

In one aspect, the aqueous solution containing hydrochloric acid contains 0.01 ppm or more of hydrochloric acid on a mass basis.

In one aspect, the aqueous solution containing hydrochloric acid contains 1000 ppm or less of hydrochloric acid on a mass basis.

In one aspect, the above-described washing time using the aqueous solution containing hydrochloric acid is 5 minutes or shorter.

In one aspect, prior to washing with hydrofluoric acid, one or more washes selected from the group consisting of SC-1 washing and water washing are performed.

In one aspect, after washing with the aqueous solution containing hydrochloric acid as described above, one or more kinds of washings selected from the group consisting of washing with water and washing with ozone water are carried out.

According to the present invention, it is possible to provide a tantalum wafer having less residual fluorine ions despite HF cleaning.

Form for implementing the invention

The present invention relates to a method for fabricating a germanium wafer comprising the steps of: preparing a germanium wafer; and washing the surface of the germanium wafer Step. In the method for producing a tantalum wafer of the present invention, the washing step includes: washing with hydrofluoric acid (HF washing); and washing with an aqueous solution containing hydrochloric acid as a step of washing with hydrofluoric acid. Wet treatment.

Hereinafter, the method of manufacturing the tantalum wafer of the present invention will be described in further detail.

Steps to prepare the wafer

The wafer to be subjected to the cleaning step can be prepared using a conventional method. For example, a wafer can be sliced from a twin ingot grown by a CZ method or the like, and a surface treatment such as lapping, etching, polishing, or the like of the obtained tantalum wafer can be prepared. Perform a cleaning step on the wafer. However, the invention is not particularly limited by the methods described above. Further, obtaining a commercially available tantalum wafer is also included in the aspect of the present invention as a step of preparing a tantalum wafer.

Washing step

The cleaning step of the method for producing a tantalum wafer according to the present invention includes at least: HF washing; and a wet treatment in which the aqueous solution containing hydrochloric acid is washed as a lower step of HF washing. Here, the wet treatment including washing with an aqueous solution containing hydrochloric acid as a step of washing with hydrofluoric acid (HF washing) means not performing water, washing liquid, etc. after HF washing. The liquid is contacted with the surface of the HF-treated wafer wafer, and washed with an aqueous solution containing hydrochloric acid. By performing the wet treatment using the aqueous solution containing hydrochloric acid as the next step after the HF washing, the fluorine ions remaining on the surface of the tantalum wafer after the HF treatment can be highly removed.

(i) HF washing

The HF cleaning system can be carried out in the same manner as the HF cleaning which is usually performed on a silicon wafer. For example, by hydrofluoric acid (HF aqueous solution) having a hydrofluoric acid concentration of about 0.01 to 5% by mass in contact with the surface of the ruthenium wafer, the surface of the ruthenium wafer can be washed with hydrofluoric acid. The contact of the surface of the wafer with hydrofluoric acid can be performed, for example, by immersing the tantalum wafer in a liquid bath containing hydrofluoric acid. The hydrofluoric acid at the time of washing may be heated or cooled at normal temperature, and the liquid temperature is not particularly limited. Further, the term "normal temperature" refers to a temperature in a state where temperature control (heating or cooling) is not performed. The contact time (washing time) of the germanium wafer and the hydrofluoric acid is also not particularly limited, and may be, for example, about 0.5 to 10 minutes as an example. Further, by using HF cleaning, the natural oxide film (SiO ₂ film) on the surface layer of the tantalum wafer can be completely removed, or a part of it can remain. When the natural oxide film is completely removed, LPD (Light Point Defect) quality is lowered due to water mark or the like. Therefore, a small amount of natural oxide film remains after HF cleaning (for example, a film thickness of 0.5 nm or less) In the case where it is preferable, the present invention is not particularly limited. Since the surface of the wafer in which the natural oxide film remains is highly hydrophilic, the fluorine ions tend to remain more likely to remain, but in this case, according to the present invention, washing with an aqueous solution containing hydrochloric acid described later will be used. The removal of fluoride ions provides a silicon wafer with less residual fluoride ions.

(ii) Washing with an aqueous solution containing hydrochloric acid

In the method for producing a tantalum wafer according to the present invention, the tantalum wafer subjected to the HF washing is subjected to a wet treatment in which one step of HF washing is performed by washing with an aqueous solution containing hydrochloric acid. Thereby, the fluorine ions remaining on the surface of the germanium wafer after the HF cleaning can be highly removed, and a germanium wafer having a small amount of residual fluorine ions can be provided.

The hydrochloric acid-containing aqueous solution used for the above-described cleaning has a concentration of hydrochloric acid HCl of 0.001 ppm or more on a mass basis, and from the viewpoint of more efficiently removing fluorine ions from the surface of the ruthenium wafer. More preferably 0.01 ppm or more. From the viewpoint of efficient removal of fluoride ions, the concentration of HCl is higher the better, but the higher the concentration of hydrochloric acid, since the Cl ^- ion and lines formed in the metal ion attached to the surface of the wafer and the metal ions contained in an aqueous solution Salt causes the frequency of particles on the surface of the wafer to increase. In general, when the chloride ion concentration is 1 × 10 ¹¹ atoms/cm ² or more, the frequency of generation of fine particles is increased. Therefore, the concentration of hydrochloric acid is set so that the concentration of chloride ions in the system is not 1 × 10 ¹¹ atoms/cm ² or more. good. In this regard, the hydrochloric acid concentration of the aqueous solution containing hydrochloric acid is preferably 1000 ppm or less on a mass basis. However, when the amount of metal ions in the system can be reduced by means of removing the metal ions by using a chelating agent, an aqueous solution containing hydrochloric acid having a hydrochloric acid concentration of more than 1000 ppm can also be used. In this regard, the hydrochloric acid concentration of the aqueous solution containing hydrochloric acid may be, for example, 3,000 ppm or less, or may be 2,000 ppm or less.

The aqueous solution containing hydrochloric acid may coexist with an acid component other than hydrochloric acid and may not coexist. When coexisting an acid component other than hydrochloric acid, there is a possibility that the following phenomenon occurs: While the fluoride ions remaining on the surface of the wafer and the acid contained in the acidic solution generate HF, the coexisting acid etches the surface of the germanium wafer and roughens the surface; The coexisting acid is firmly attached to the surface of the wafer; When the coexisting acid system has a strong oxidizing power, it causes corrosion of piping components and the like. On the other hand, when an acidic aqueous solution containing only hydrochloric acid as an acid component is produced, the fluorine ions remaining on the surface of the tantalum wafer after HF washing can be removed without causing the above phenomenon. Therefore, the aqueous solution containing hydrochloric acid is preferably an acidic aqueous solution containing only hydrochloric acid as an acid component. Further, the aqueous solution containing hydrochloric acid may also contain an acid. Ingredients other than ingredients. As such a component, for example, a component which does not inhibit the HF formation reaction of hydrochloric acid and fluoride ions, such as a nonionic surfactant or a thickener (water-soluble polymer), is preferable.

As with HF washing, the above is washed with an aqueous solution containing hydrochloric acid. For example, it can be carried out by bringing the aqueous solution containing hydrochloric acid into contact with the surface of the crucible wafer. The contact of the surface of the crucible wafer with the aqueous solution containing hydrochloric acid can be carried out, for example, by immersing the crucible wafer in a liquid bath containing the aqueous solution containing hydrochloric acid. The aqueous solution containing hydrochloric acid at the time of washing may be heated or cooled at normal temperature, and the liquid temperature is not particularly limited. The contact time (washing time) of the ruthenium wafer with the aqueous solution containing hydrochloric acid is preferably 5 minutes or less, and preferably 2 minutes or more from the viewpoint of efficiently removing fluorine ions.

(iii) Any cleaning

The cleaning step of the ruthenium wafer of the present invention includes a wet treatment which is washed by the above-mentioned HF and washed with an aqueous solution containing hydrochloric acid as a step of HF washing, as a necessary washing treatment method. However, other washing treatments may be performed before or after such necessary washing treatments. In the other cleaning treatment, one or more kinds of cleaning treatments which are conventionally used for the cleaning treatment of the semiconductor substrate, for example, SC-1 washing, ozone water washing, and water washing can be performed. Here, the "SC-1 washing" refers to a washing treatment of an SC1 liquid obtained by mixing ammonia water/H ₂ O ₂ /H ₂ O. The SC1 liquid system can be heated or cooled at normal temperature. Moreover, it is preferable that the ozone concentration of the ozone water used for washing is about 2 to 20 ppm on a mass basis. The water and ozone water used in the water washing can be heated or cooled at normal temperature. The processing time is not particularly limited. It is preferable to wash the arbitrarily washed water after washing with an aqueous solution containing hydrochloric acid, and to wash it with either or both of water washing and ozone water washing. Further, as the washing treatment which is arbitrarily performed before the HF washing, it is preferable to remove either or both of the SC-1 washing and the washing with respect to the particulate component present on the surface.

The ruthenium wafer after the rinsing treatment can be subjected to post-treatment such as drying arbitrarily, and the subsequent steps such as annealing can be performed as needed.

According to the method for producing a tantalum wafer of the present invention described above, it is possible to provide a tantalum wafer having a small amount of residual fluorine ions after HF cleaning.

[Examples]

Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited by the aspects shown in the examples. In addition, any of "ppm" and "%" described below is based on mass. Further, unless otherwise specified, each operation system was carried out at room temperature (about 25 ° C) without controlling the temperature. The so-called normal temperature described below means that it is left at room temperature. Further, as the aqueous solution containing hydrochloric acid described below, an aqueous solution in which only hydrochloric acid is added as an acid component is used.

[Example 1]

1. The first stage (SC-1 wash)

Prepare a silicon wafer (diameter: 300 mm) after finishing and polishing. The prepared tantalum wafer was washed with a solution prepared by mixing 29% by mass of ammonia water at 60 ° C: 30% by mass of H ₂ O ₂ : H ₂ O = 0.5:1:10 (volume ratio) for 4 minutes.

2. The second stage (washing)

The wafer after the first stage of treatment was subjected to rinsing treatment for 4 minutes using continuous water injection using ultrapure water at normal temperature.

3. The third stage (HF washing)

The wafer after the second-stage treatment was immersed in a 0.05 mass% HF solution (hydrofluoric acid) at normal temperature for 4 minutes and washed with HF.

4. The fourth stage (washing with an aqueous solution containing hydrochloric acid)

The ruthenium wafer subjected to the third-stage treatment was immediately immersed for 4 minutes at a normal temperature hydrochloric acid-containing aqueous solution having a hydrochloric acid concentration of 0.005 ppm on a mass basis without performing another wet treatment, and was subjected to a washing treatment.

5. The fifth stage (washing)

The wafer after the fourth-stage treatment was subjected to rinsing treatment at room temperature for ultra-pure water and continuous water injection for 4 minutes.

[Embodiment 2]

The same treatment as in Example 1 was carried out except that the aqueous solution containing hydrochloric acid used in the fourth stage was changed to an aqueous solution containing hydrochloric acid having a hydrochloric acid concentration of 0.01 ppm.

[Example 3]

The same treatment as in Example 1 was carried out except that the aqueous solution containing hydrochloric acid used in the fourth stage was changed to an aqueous solution containing hydrochloric acid having a hydrochloric acid concentration of 1 ppm.

[Example 4]

The same treatment as in Example 1 was carried out except that the aqueous solution containing hydrochloric acid used in the fourth stage was changed to an aqueous solution containing hydrochloric acid having a hydrochloric acid concentration of 1000 ppm.

[Example 5]

In addition to the aqueous solution containing hydrochloric acid used in the fourth stage, it is changed to hydrochloric acid. The same treatment as in Example 1 was carried out except for an aqueous solution containing hydrochloric acid having a concentration of 2000 ppm.

[Comparative Example 1]

The same treatment as in Example 1 was carried out except that the aqueous solution containing hydrochloric acid was not used in the fourth stage.

[Comparative Example 2]

The same treatment as in Example 1 was carried out except that the aqueous solution containing hydrochloric acid in the fourth stage was washed and changed to ozone water having an ozone concentration of 10 ppm and washed continuously for 4 minutes.

[Comparative Example 3]

Except for the HF washing in the third stage and the washing with the aqueous solution containing hydrochloric acid in the fourth stage, the rinsing treatment was carried out by using ultrapure water at normal temperature and continuously supplying for 4 minutes. The same processing.

[Comparative Example 4]

Except for the HF washing in the third stage and the washing with the aqueous solution containing hydrochloric acid in the fourth stage, the ozone water having an ozone concentration of 10 ppm is used for washing for 4 minutes, and is carried out and implemented. Example 1 was treated in the same manner.

<Evaluation method>

1. Determination of fluoride ion (F ^- ) concentration and chloride ion (Cl ^- ) concentration

The concentration of fluoride ions and the concentration of chloride ions present on the surface of the cleaned germanium wafer were measured by ion chromatography.

2. Determination of haze value

The haze value was measured by using a particle counter (SP-2 manufactured by KLA. Tencor Co., Ltd.) and the surface of the cleaned wafer was confirmed by the value obtained in the DWO mode.

The above results are shown in Table 1.

As shown in Table 1, it is dissolved in water without using hydrochloric acid. The liquid was washed as Comparative Example 1 of the wet treatment in the next step after the HF washing, and the examples 1 to 5 which were subjected to the wet treatment of the next step after the HF washing using the aqueous solution containing hydrochloric acid were carried out. Can reduce the fluoride ion concentration.

In addition, Comparative Example 2 in which ozone water was not used for washing, and ozone water washing was used instead of washing with an aqueous solution containing hydrochloric acid after HF washing, was confirmed to have a high fluoride ion concentration.

On the other hand, in Comparative Example 3 and 4 in which another wet treatment was performed between HF washing and washing with an aqueous solution containing hydrochloric acid (Comparative Example 3: water washing, Comparative Example 4: washing with ozone water) was used. Fluoride ions could not be removed from the surface of the germanium wafer as in Examples 1 to 5.

From the above results, it was confirmed that the wet treatment using the aqueous solution containing hydrochloric acid as the next step of HF washing can highly remove the fluorine ions remaining on the surface of the tantalum wafer after the HF treatment.

In addition, since the atomization values of Examples 1 to 5 are equal to or less than the comparative examples, it is also possible to confirm that fluorine can remain on the surface of the crucible wafer after the HF treatment without causing a large roughening of the surface. The ions are removed efficiently.

Further, from the viewpoint of comparison between the examples and from the viewpoint of more efficiently removing fluorine ions, it is preferred to use an aqueous solution containing hydrochloric acid containing 0.01 ppm or more of hydrochloric acid on a mass basis (Examples 2 to 5). It is also preferable to use an aqueous solution containing hydrochloric acid containing 1000 ppm or less of hydrochloric acid on a mass basis from the viewpoint of reducing residual chlorine ions on the surface of the wafer (Examples 1 to 4).

Industrial availability

The present invention is useful in the field of manufacturing semiconductor substrates.

Claims (4)

A method for manufacturing a germanium wafer includes the following steps: a method of manufacturing a wafer: a step of preparing a germanium wafer; and a step of washing the surface of the germanium wafer; the washing step includes: using hydrogen fluoride Acid washing; and washing with an aqueous solution containing hydrochloric acid as a wet treatment using a step of washing with hydrofluoric acid, wherein the aqueous solution containing hydrochloric acid contains 0.01 ppm to 1 ppm of hydrochloric acid on a mass basis, wherein After the hydrofluoric acid is washed, the fluoride ion of the hydrofluoric acid remains on the surface of the tantalum wafer, and the aqueous solution containing hydrochloric acid is washed to remove the fluorine ions remaining on the surface of the tantalum wafer, and the hydrochloric acid-containing The aqueous solution is an aqueous solution containing only hydrochloric acid as an acid component. The method for producing a tantalum wafer according to the first aspect of the invention, wherein the washing time using the aqueous solution containing hydrochloric acid is 5 minutes or shorter. The method for producing a tantalum wafer according to claim 1, wherein before the washing with hydrofluoric acid, one or more types of cleaning selected from the group consisting of washing and washing with SC-1 are performed. The method for producing a tantalum wafer according to the first aspect of the invention, wherein after washing with the aqueous solution containing hydrochloric acid, one or more kinds of washings selected from the group consisting of washing with water and washing with ozone water are carried out.