TWI506690B - Silicon 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 residual fluorine on the surface of a tantalum wafer when a tantalum wafer is manufactured by a cleaning step including HF cleaning.制造 Wafer manufacturing method.

The manufacturing process of the germanium wafer generally includes the steps of: cutting a wafer (slice) from a twin ingot; surface treatment such as polishing, etching, etc.; washing step; and further performing the subsequent steps as necessary according 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 Patent Document 1).

Prior technical literature

Patent literature

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

In recent years, in order to achieve high-definition clarity of the surface of the tantalum wafer, the method of using the hydrofluoric acid (HF washing) is applied to the final cleaning treatment. However, fluorine ions (F ^- ) are usually left on the surface of the germanium wafer after HF washing. 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 (lower film thickness) may occur during the gate oxide film formation treatment 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 the HF wafer washed by HF can be washed (cleaned) by using a predetermined concentration of aqueous ammonia or an aqueous solution containing an ammonium salt, and the HF can be washed. Fluoride ions remaining on the surface of the wafer are removed. In view of this point, the inventors presumed the following.

It is considered that the fluorine ions remaining on the surface of the germanium wafer after HF washing are present on the surface of the wafer by fluoroantimonic acid (H ₂ SiF ₆ ). On the other hand, aqueous ammonia and an aqueous solution containing an ammonium salt contain an ammonium ion NH4 ⁺ . When ammonium ion NH4 ⁺ is in contact with the surface of the germanium wafer in which fluoroantimonic acid (H ₂ SiF ₆ ) is present, ammonium fluoroantimonate ((NH ₄ ) ₂ SiF ₆ ) is formed on the surface of the germanium wafer. Since this ammonium fluoroantimonate is a water-soluble component, it is dissolved in an aqueous solution. As a result, the inventors presumed that fluorine ions can be removed from the surface of the germanium wafer. Here, by using an aqueous solution containing 0.01 ppm or more of ammonia or an ammonium salt (hereinafter also referred to as "ammonia") on a mass basis, it is possible to effectively remove fluorine ions from the surface of the tantalum wafer. However, when the concentration of the ammonia is more than 3 ppm, the surface of the surface of the tantalum wafer is greatly roughened (atomization is caused) by the cleaning, and it is difficult to provide a tantalum wafer having high flatness. On the other hand, the ruthenium wafer after the HF cleaning treatment is washed with an aqueous solution containing ammonia at a concentration of 0.01 ppm or more and 3 ppm or less, thereby providing a small amount of residual fluorine ions and suppressing generation of atomization. High quality silicon wafers.

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 is characterized in that the washing step comprises: washing with hydrofluoric acid; and after washing with hydrofluoric acid, washing with an ammonia-based washing liquid; the ammonia-based washing liquid, the ammonia concentration thereof It is an aqueous solution of 0.01 ppm or more and 3 ppm or less of the ammonia water based on the mass basis, or an ammonium salt-containing aqueous solution having an ammonium salt concentration of 0.01 ppm or more and 3 ppm or less on a mass basis.

In one aspect, the above ammonium salt is a (hydrogen) carbonate. Here, the carbonic acid (hydrogen) salt is used in the sense of containing a carbonate and a hydrogencarbonate.

In one aspect, the washing time used in the ammonia-based cleaning solution is 5 minutes or shorter.

In one aspect, between the washing with the hydrofluoric acid and the washing with the ammonia-based cleaning solution, one or more types of washing selected from the group consisting of washing with water and washing with ozone water are carried out.

In one aspect, one or more kinds of washings selected from the group consisting of washing and washing with SC-1 are performed before washing with the above hydrofluoric acid.

According to the present invention, it is possible to provide fluorine separation despite being washed by HF. The sub-residue is low and suppresses the generation of atomized high-quality germanium wafers.

Fig. 1 is a graph showing the effect of ammonia concentration and washing time of ammonia water on the effect of removing fluoride ions.

Fig. 2 is a graph showing the effect of ammonia concentration and washing time of ammonia on atomization (face roughening).

Form for implementing the invention

The present invention relates to a method of manufacturing a wafer comprising the steps of: preparing a wafer: and washing the surface of the wafer. In the method for producing a tantalum wafer according to the present invention, the washing step includes: washing with hydrofluoric acid (HF washing); and washing with hydrofluoric acid, using an ammonia-based washing liquid. Wash. In addition, the ammonia-based cleaning liquid has an ammonia concentration of 0.01 ppm or more and 3 ppm or less of ammonia water based on mass, or an ammonium salt concentration of 0.01 ppm or more and 3 ppm or less of ammonium salt based on mass. Aqueous solution.

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, the wafer can be prepared by cutting the wafer from a twin ingot grown by the CZ method or the like, and by subjecting the obtained tantalum wafer to a surface treatment such as lapping, etching, polishing, or the like. The step of the wafer. However, the invention is not particularly limited by the methods described above. Also, obtain a commercially available silicon wafer, It is also included in the present invention as an aspect of the step of preparing a wafer.

Washing step

The cleaning step of the method for producing a tantalum wafer of the present invention includes at least HF washing; and washing with an ammonia-based cleaning liquid after HF washing. The concentration of the ammonia contained in the ammonia-based cleaning liquid used herein is 0.01 ppm or more and 3 ppm or less on a mass basis. As described above, by washing with the ammonia-based cleaning solution after HF washing, large roughening is not caused, and fluoride ions remaining on the surface of the ruthenium wafer after HF washing can be 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. However, in this case, according to the present invention, the cleaning of the ammonia-based cleaning liquid described later is used. The removal of fluorine ions provides a germanium wafer with less residual fluorine ions.

(ii) Washing with ammonia-based cleaning solution

In the method for producing a wafer according to the present invention, the HF-cleaned wafer is subjected to cleaning using an ammonia-based cleaning solution containing 0.01 ppm by mass. Above and below 3 ppm of ammonia. As a result, as described above, it is possible to remove the fluorine ions remaining on the surface of the germanium wafer after the HF washing without causing a large roughening of the surface, and it is possible to provide a germanium wafer having a small amount of residual fluorine ions.

The ammonia-based cleaning liquid used in the above washing is an aqueous solution of ammonia or an ammonium salt. Aqueous solution of NH ₃ of ammonia-based aqueous ammonia, which is generated by ionization of NH4 ^+. On the other hand, the ammonium salt contained in the aqueous solution containing an ammonium salt may be used as a supply source of ammonium ions (NH4 ⁺ ), and the relative ion (anion) type is not limited. The ammonium salt may be an inorganic salt or an organic salt, and an inorganic salt is preferred from the viewpoint of preventing the organic substance from adhering to the surface of the ruthenium wafer. Examples of the inorganic ammonium salt include ammonium carbonate, ammonium hydrogencarbonate, ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium disulfide, ammonium nitrite, ammonium sulfite, and the like. From the viewpoints of solubility in water, ease of availability, ease of preparation of an aqueous solution, and the like, ammonium (hydrogen)carbonate is preferred.

The higher the ammonia concentration of the ammonia-based cleaning liquid, the higher the removal efficiency of fluorine ions, which is preferable. From the viewpoint of efficiently removing fluorine ions, the ammonium concentration is set to 0.01 ppm or more on a mass basis. Preferably, the ammonia concentration is 1 ppm or more. On the other hand, from the viewpoint of preventing surface roughening of the surface of the tantalum wafer, the ammonia concentration is set to 3 ppm or less. Moreover, the above aqueous solution can also be The components other than the ammonia coexist, but the coexisting component is preferably a component that does not interfere with the reaction between the fluoride ion and the ammonium ion. Examples of such a component include a nonionic surfactant, a tackifier (water-soluble polymer), and the like. Further, in ammonia water, ammonia is partially ionized and exists as ammonium ions, and the concentration of ammonia in the present invention means the concentration of ammonia (ammonia or ammonium salt) mixed with water at the time of preparation of an aqueous solution, that is, addition. the amount.

Similarly to the HF washing, the cleaning can be performed, for example, by bringing the ammonia-based cleaning liquid into contact with the surface of the crucible wafer. The contact of the surface of the crucible with the ammonia-based cleaning solution can be performed, for example, by immersing the crucible wafer in a liquid bath containing an ammonia-based cleaning liquid. The ammonia-based cleaning liquid 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 and the ammonia-based cleaning liquid is preferably 5 minutes or less from the viewpoint of preventing surface roughening of the ruthenium wafer, and from the viewpoint of efficiently removing fluorine ions. It is better to use more than 2 minutes.

(iii) Any cleaning

The cleaning step of the tantalum wafer of the present invention includes the above-described HF washing and the use of the ammonia-based cleaning liquid after the HF washing, in a necessary washing treatment, but it may be These other washing treatments are performed before or after the necessary washing treatment. As the other cleaning treatment, one or more kinds of various cleaning treatments, such as SC-1 washing, ozone water washing, and water washing, which are conventionally used as the cleaning treatment of the semiconductor substrate, 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. From the viewpoint of efficiently removing fluorine ions, it is preferred to continuously perform HF washing and washing with an ammonia-based cleaning liquid, and no other chemical liquid treatment is performed between the washings. However, washing with water and ozone water is carried out between the HF washing and the washing with the ammonia-based cleaning solution, so that the efficiency of removing the fluoride ions by washing with the ammonia-based cleaning solution is not lowered. . Therefore, between HF washing and washing with an ammonia-based cleaning solution, it is preferable to wash both water and ozone water. 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 arbitrarily delivered to a post-treatment such as drying, or a step subsequent to the use of annealing or the like can be delivered as necessary.

According to the method for producing a tantalum wafer of the present invention described above, it is possible to provide a tantalum wafer which does not cause large surface roughening and which has a small amount of residual fluorine ions after HF washing.

[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 a quality standard. 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.

A. Examples of using ammonia water. Comparative example

[Example 1]

1. The first stage (SC-1 wash)

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

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 ammonia)

The ruthenium wafer after the third-stage treatment was immersed in a normal-temperature ammonia water having an ammonia concentration of 0.01 ppm on a mass basis for 4 minutes to carry out 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 ammonia water used in the fourth stage was changed to ammonia water having an ammonia concentration of 1 ppm.

[Example 3]

The same treatment as in Example 1 was carried out except that the ammonia water used in the fourth stage was changed to ammonia water having an ammonia concentration of 3 ppm.

[Comparative Example 1]

Implementation and implementation except for the use of ammonia washing in the fourth stage Example 1 was treated in the same manner.

[Comparative Example 2]

The same treatment as in Example 1 was carried out except that the ammonia water used in the fourth stage was changed to ammonia water having an ammonia concentration of 0.005 ppm.

[Comparative Example 3]

The same treatment as in Example 1 was carried out except that the ammonia water used in the fourth stage was changed to ammonia water having an ammonia concentration of 5 ppm.

[Comparative Example 4]

The same treatment as in Example 1 was carried out except that the ammonia water used in the fourth stage was washed and washed with ozone water having an ozone concentration of 10 ppm.

[Example 4]

1. The first stage (SC-1 wash)

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

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)

The wafer after the third-stage treatment was subjected to rinsing treatment for 4 minutes using continuous water injection using ultra-pure water at normal temperature.

5. The fifth stage (washing with ammonia)

The silicon wafer after the fourth-stage treatment was immersed in a normal-temperature ammonia water having an ammonia concentration of 0.01 ppm on a mass basis for 4 minutes to carry out a washing treatment.

6. The sixth stage (washing)

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

[Example 5]

1. The first stage (SC-1 wash)

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

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 ozone water)

The wafer after the third-stage treatment was subjected to a cleaning treatment for 4 minutes using a continuous supply method using ozone water having an ozone concentration of 10 ppm.

5. The fifth stage (washing with ammonia)

The silicon wafer after the fourth-stage treatment was immersed in a normal-temperature ammonia water having an ammonia concentration of 0.01 ppm on a mass basis for 4 minutes to carry out a washing treatment.

6. The sixth stage (washing)

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

B. Examples and Comparative Examples Using an Aqueous Solution Containing Ammonium Bicarbonate

[Examples 6 to 8, Comparative Examples 5 and 6]

The same treatment as in Example 1 was carried out except that the aqueous ammonia used in the fourth stage was changed to an aqueous solution containing ammonium hydrogencarbonate at the concentration shown in Table 2.

<Evaluation method>

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

The concentration of fluoride ions present on the surface of the cleaned germanium wafer was 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 Tables 1 and 2.

As shown in Table 1, Comparative Example 1 which was washed without using an ammonia-based cleaning solution after HF treatment was washed with an ammonia-based cleaning solution having a concentration of 0.01 ppm or more and 3 ppm or less after HF washing. The net examples 1 to 8 are capable of reducing the fluoride ion concentration. Further, the atomization is less and the surface of the tantalum wafer has high flatness.

On the other hand, in Comparative Example 1 in which the ammonia-based cleaning solution was not washed after the HF treatment, Comparative Example 2 in which the ammonia-based cleaning solution having a concentration of less than 0.01 ppm was washed after HF washing was used. 5, can not reduce the fluoride ion concentration.

On the other hand, in Comparative Examples 3 and 6 which were washed with an ammonia-based cleaning solution having a concentration of more than 3 ppm after HF washing, the atomization was remarkably generated as compared with the examples.

Further, after washing with HF water after washing with HF, instead of Comparative Example 4, which was washed with an ammonia-based cleaning solution, Comparative Example 1 which was washed without using ozone water was able to confirm a high fluoride ion. concentration.

From the above results, it was confirmed that after the HF washing, the ammonia-based cleaning liquid having a concentration of 0.01 ppm or more and 3 ppm or less was used for cleaning, and the surface was not roughened and the HF was efficiently obtained. The fluoride ions remaining on the surface of the germanium wafer are removed after the treatment.

C. Washing time and fluoride ion removal effect using ammonia-based cleaning solution And confirmation of the effects of atomization,

The ruthenium wafer was subjected to the same treatment as in Example 1 except that the ammonia water containing the ammonia shown in Table 3 was used and washed at the time indicated in Table 3, and the fluorine was evaluated by the above method. Ion concentration and atomization. The results are shown in Table 3. Further, from the results shown in Table 3, a graph showing the influence of the ammonia concentration and the washing time on the concentration of the fluoride ion, and a graph showing the influence on the atomization (surface roughening) were produced and displayed in the first Figure 2.

Evaluation results

As shown in Fig. 1, by using ammonia water having an ammonia concentration of 0.01 ppm or more, it is possible to confirm that the washing time is increased, and as the ammonia concentration is increased, the fluoride ion concentration can be reduced.

On the other hand, when the haze value measured by the above-described method is more than 0.180 ppm for fogging, noise due to surface roughness (atomization) is generated, so that the particle counter cannot be used for accurate measurement of particles or the like. The possibility of causing obstacles such as evaluation of actual manufacturing steps. As shown in Fig. 2, for the atomization, if the ammonia concentration is 3 ppm or less and the haze value is 0.180 ppm or less, it is possible to confirm the use for washing after HF washing. The concentration of the ammonia-based cleaning solution should be set to 0.01 ppm or more and 3 ppm or less to reduce the concentration of the fluoride ion and suppress the generation of atomization.

Industrial availability

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

Claims (9)

A method for manufacturing a tantalum wafer, comprising the steps of: preparing a wafer: a step of preparing a wafer; and washing the surface of the tantalum wafer; and the washing step comprises: using hydrogen fluoride After washing with hydrofluoric acid, the ammonia-based cleaning solution is washed with hydrofluoric acid, and the ammonia-based cleaning solution has an ammonia concentration of 0.01 ppm or more and 3 ppm or less on a mass basis. The ammonia water or the ammonium salt concentration thereof is an aqueous solution containing an ammonium salt of 0.01 ppm or more and 3 ppm or less on a mass basis. The method for producing a tantalum wafer according to the first aspect of the invention, wherein the ammonium salt is a (hydrogen)carbonate. The method for producing a tantalum wafer according to the first or second aspect of the invention, wherein the washing time used in the ammonia-based cleaning liquid is 5 minutes or shorter. The method for producing a tantalum wafer according to the first or second aspect of the invention, wherein the washing with the hydrofluoric acid and the washing with the ammonia-based cleaning solution are performed by washing with water and using ozone water. Washing one or more of the groups consisting of washing. The method for producing a tantalum wafer according to the third aspect of the invention, wherein the washing with the hydrofluoric acid and the washing with the ammonia-based cleaning solution are performed by washing with water and washing with ozone water. Washing one or more of the group. The method for producing a tantalum wafer according to claim 1 or 2, wherein before the washing with the hydrofluoric acid, one or more types selected from the group consisting of SC-1 washing and water washing are performed. net. The method for producing a tantalum wafer according to the third aspect of the invention, wherein before the washing with the hydrofluoric acid, one or more types of cleaning selected from the group consisting of washing with SC-1 and washing with water are performed. The method for producing a tantalum wafer according to the fourth aspect of the invention, wherein before the washing with the hydrofluoric acid, one or more types of cleaning selected from the group consisting of washing with SC-1 and washing with water are performed. The method for producing a tantalum wafer according to the fifth aspect of the invention, wherein before the washing with the hydrofluoric acid, one or more types of cleaning selected from the group consisting of washing with SC-1 and washing with water are performed.