JP2000169233A - Wet cleaning of silicon carbide sintered product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and easily remove organic impurities and inorganic ones both existing on the surface of and near the surface of a silicon carbide sintered product by washing it through the sequential immersion treatment of the sintered product in a quasi-aqueous organic solvent, an aqueous ammonium solution, an aqueous inorganic acid solution and deionized water. SOLUTION: This method for the wet cleaning of a silicon carbide sintered product is to sequentially subject the sintered product to the following treatment so as to wash it and to make the washing degree on its surface become the level of <1×1011 atoms/cm2: (1) removing organic impurities adhered to the surface of and near the surface of the sintered product by soaking it in a quasi-aqueous organic solution for 2-60 min; (2) soaking it in an aqueous ammonium solution having 25-35 dynes/cm surface tension for 5-120 min; (3) removing metallic impurities on its surface of and near its surface by soaking it in an aqueous inorganic acid solution having 0. 3-68 wt.% concentration for 5-120 min; (4) soaking it in deionized water having <=100 ppt impurity and 16-18 MΩ resistivity for 2-60 min in an overflowing state. At least one of the processes preferably is conducted in a state that ultrasonic vibration is applied to the aqueous solution and the aqueous solution of at least one of the processes preferably shows >=30 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for wet-cleaning a silicon carbide sintered body for various semiconductor members and electronic parts. Specifically, dummy wafers that require high purity,
The present invention relates to a method for removing organic substance contamination, metal element contamination, and particle contamination of a silicon carbide sintered body for use in semiconductor production with respect to a target, a heating element, and the like.

[0002]

2. Description of the Related Art Silicon carbide is a substance having a strong covalent bond and has higher strength at high temperatures than before. Heat resistance, wear resistance. It has been used in many applications by taking advantage of its excellent properties such as chemical resistance. These advantages have attracted attention, and application to the fields of electronics, information, and semiconductors has recently been expected.

As semiconductor silicon integrated circuits become more highly integrated and thinner, the various semiconductor members and electronic components used in these fields are required to have higher purity and higher density. A hot press sintering method and a reaction sintering method using a metal-based sintering agent have been studied intensively. However, the silicon carbide sintered body obtained by these sintering methods has high purity and high density, but contaminates the surface and the vicinity of the surface during the pre- and post-production processes (sintering, processing, handling, etc.). It is the current situation.

[0004] Therefore, in order to apply the silicon carbide sintered body to various semiconductor members and electronic components, that is, to prevent contamination and particles from contaminating, it is necessary to achieve a surface purity equivalent to that of a silicon wafer by surface cleaning. Indispensable.

As a report on a method for cleaning a silicon carbide sintered body, (1) Registration No. 181841 discloses that after acid cleaning,
The method of oxidizing at a temperature of 1200 ° C. or more and then performing a surface treatment in a nitrogen atmosphere is described in (2) Japanese Patent Application Laid-Open No. 5-17229: a method of blast cleaning with silica abrasive grains and then wet cleaning with a mixed acid of hydrofluoric acid and nitric acid. However, (3) JP-A-6-77
In No. 310, after rinsing and washing in hydrofluoric acid aqueous solution, rinsing with ultrapure water and further dry-cleaning with oxygen and halogen gas,
The method of oxygen treatment is as follows: (4) Since it is very difficult to achieve high purity after sintering, once the porous silicon carbide is subjected to a hydrogen halide gas and inorganic acid cleaning treatment at the time of high purity purification, Secondary sintering method (JP-A-55-158622,
JP-A-60-138913, JP-A-64-72964
No.) have been reported.

The above method requires not only simple wet cleaning, but also oxidation, blast cleaning, secondary sintering and the like, which complicates the process, and cannot be said to be an excellent cleaning method.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned facts, and an object of the present invention is to provide a method for manufacturing a surface of a silicon carbide sintered body so as to be used for various semiconductor members and electronic components. An object of the present invention is to provide a wet cleaning method for a silicon carbide sintered body that can easily remove organic and inorganic impurities present in the vicinity of a surface by cleaning.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that even high-density, high-purity silicon carbide sintered bodies applicable to various semiconductor members and electronic components are subject to process contamination and the like. Focusing on the fact that the concentration of organic and inorganic impurities on the surface and in the vicinity of the surface is remarkably increased and it is difficult to apply it to various semiconductor members and electronic components, a method for easily removing organic and inorganic impurities by washing has been found. That is, the present invention

<1> A silicon carbide sintered body characterized by sequentially treating a silicon carbide sintered body in a step of dipping in a semi-aqueous organic solvent, a step of dipping in an inorganic acid aqueous solution, and a step of dipping in pure water. A wet cleaning method for the aggregate.

<2> The silicon carbide sintered body is sequentially treated in a step of dipping in a semi-aqueous organic solvent, a step of dipping in an ammonium aqueous solution, a step of dipping in an inorganic acid aqueous solution, and a step of dipping in pure water. A wet cleaning method for a silicon carbide sintered body, characterized in that:

<3> The silicon carbide sintered body is sequentially treated in a step of dipping in a semi-aqueous organic solvent, a step of dipping in an aqueous solution of inorganic acid, a step of dipping in an aqueous solution of ammonium, and a step of dipping in pure water. A wet cleaning method for a silicon carbide sintered body, characterized in that:

<4> At least one step is performed while applying ultrasonic vibration to the liquid.
The wet cleaning method for a silicon carbide sintered body according to any one of <3>.

<5> The temperature of the liquid in at least one of the steps is at least 30 ° C.
4) The wet cleaning method for a silicon carbide sintered body according to any one of the above items.

<6> The quasi-aqueous organic solvent is a petroleum hydrocarbon, an organic acid ester, a glycol ether, a mixed solvent thereof, or a mixture of these solvents or a mixed solvent and a surfactant. <1> to <5 above
> The wet cleaning method for a silicon carbide sintered body according to any one of the above items.

<7> The above-mentioned <1> to <1>, wherein the inorganic acid aqueous solution is a hydrofluoric acid aqueous solution, a nitric acid aqueous solution, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, a hydrogen peroxide solution, an ozone water, or a mixed acid aqueous solution thereof. <6> The wet cleaning method for a silicon carbide sintered body according to any one of <6>.

<8> The above-mentioned <2> to <2>, wherein the aqueous ammonium solution is an aqueous solution of a tetraalkylammonium halide, an aqueous solution of a tetraalkylammonium perchlorate, aqueous ammonia, or a mixed aqueous solution of these and aqueous hydrogen peroxide. The wet cleaning method for a silicon carbide sintered body according to any one of <7>.

According to the wet cleaning method for a silicon carbide sintered body of the present invention, the silicon carbide sintered body can be applied to various semiconductor members and electronic parts.
It can be up to a level of less than ¹¹ atoms / cm ² .

In the wet cleaning method for a silicon carbide sintered body according to the present invention, the entire cleaning liquid is constituted by a chemical solution that is soluble or rinsable in water, and a drying process or the like is not required during the cleaning step. There is an advantage that the entire process can be simplified.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The wet cleaning method of a silicon carbide sintered body of the present invention comprises the steps of immersing a silicon carbide sintered body (hereinafter, sometimes referred to as a body to be cleaned) in a semi-aqueous organic solvent.
This is a method of sequentially performing a process of immersing in an inorganic acid aqueous solution and a process of immersing in pure water. By performing these steps in this order, first, organic substances (eg, oil films, fingerprints, and waxes) on the surface are removed by the quasi-aqueous organic solvent, and then the metal elements on the surface and near the surface by the aqueous inorganic acid solution are removed. It becomes possible. In addition, it is preferable that the step of immersing in an aqueous ammonium solution is performed between the above steps, and that the used organic solvent and particles are more easily removed.

The step of immersing in the semi-aqueous organic solvent is a step of removing organic substances adhering to the surface and near the surface of the silicon carbide sintered body.

The quasi-aqueous organic solvent refers to an organic solvent soluble in water and a solvent which is insoluble in water but can be easily removed by washing with water. That is, in the present invention, the quasi-aqueous organic solvent includes those which are soluble in water, those in which a hydrophilic group is partially introduced into a water-insoluble solvent, and those in which a surfactant is added in advance. Specific examples of the quasi-aqueous organic solvent include petroleum hydrocarbons, organic acid esters, glycol ethers, mixed solvents thereof, and mixtures of these solvents or mixed solvents with surfactants. As the mixed solvent and the mixture, a mixed solvent of a petroleum hydrocarbon and an organic acid ester or glycol ether, a mixture of a petroleum hydrocarbon and an organic acid ester or glycol ether and a surfactant, a petroleum hydrocarbon and a surfactant And a mixture of an organic ester and a surfactant.

Examples of the petroleum hydrocarbon include aliphatic hydrocarbons represented by naphthene and hexane.

Examples of the organic acid esters include fatty acid esters (for example, fatty acid methyl esters), glycerin esters, sorbitan esters and the like.

Examples of the glycol ether include propylene glycol ether, propylene glycol methyl ether, diethylene glycol dimethyl ether and the like.

The surfactant is not particularly limited as long as it fulfills the desired purpose, but may be polyoxyethylene fatty acid methyl, alkylamine oxide, polyoxyalkylene glycol, ethylene oxide or propylene oxide adduct of alkylamine. And the like are preferable.

In the step of immersing in the semi-aqueous organic solvent, the time for immersing the silicon carbide sintered body depends on the amount and type of the organic substances adhered thereto, but is preferably 2 minutes to 60 minutes, preferably 10 minutes to 10 minutes. 30 minutes is more preferable, and 10 minutes to 15 minutes is still more preferable.

In the step of immersion in the quasi-aqueous organic solvent, it is effective to heat to 50 to 70 ° C. from the viewpoint of increasing the dissolving power of the attached organic substance.

The step of immersing in the inorganic acid aqueous solution is a step of removing metal impurities on and near the surface of the silicon carbide sintered body.

Examples of the inorganic acid aqueous solution include a hydrofluoric acid aqueous solution, a nitric acid aqueous solution, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, a hydrogen peroxide solution, an ozone water, and a mixed acid aqueous solution thereof. Examples of the mixed acid aqueous solution include a hydrofluoric nitric acid aqueous solution, a mixed acid aqueous solution of hydrofluoric nitric acid and sulfuric acid, and a mixed acid aqueous solution of hydrofluoric acid and hydrochloric acid.

The concentration of the aqueous inorganic acid solution is 0.3
The content is preferably from 68 to 68% by weight, more preferably from 1 to 40% by weight, still more preferably from 5 to 10% by weight. This concentration is 0.
If it is less than 3% by weight, the effect of removing metal impurities may be insufficient. If it exceeds 68% by weight, the roughness of the surface of the object to be cleaned may be reduced.

A nonionic surfactant may be added to the inorganic acid aqueous solution in order to prevent reattachment of the metal ions once eluted. As the nonionic surfactant,
The same is as described above.

In the step of dipping in the inorganic acid aqueous solution, the time for dipping the silicon carbide sintered body is from 5 minutes to 120 minutes.
Minutes, more preferably 10 minutes to 60 minutes, even more preferably 20 minutes to 30 minutes.

The step of immersing in the pure water is a step of removing residual components adhered to the surface and the vicinity of the surface of the silicon carbide sintered body by using the solvent and the aqueous solution used in each step.

The pure water preferably has a purity of 100 ppt or less and a specific resistance of 16 to 18 MΩ, and more preferably has a purity of less than 10 ppt.

It is preferable that the step of immersing in the pure water is performed by an overflow method so that the step is always washed with a new solution.

In the step of immersing in the ammonium aqueous solution, the organic solvent in the preceding step, which is presumed to be attached in a minute amount on the surface of the silicon carbide sintered body and in the vicinity of the surface, is removed by a surface active effect, and particles are removed. This is the step of removing.

Examples of the aqueous ammonium solution include aqueous solutions of ethylene oxide or propylene oxide addition polymers such as alkylamine oxides and alkylamines, tetraalkylammonium halides (eg, tetramethylammonium halide) and tetraalkylammonium perchlorates. An aqueous solution of a quaternary ammonium salt of
Ammonia water, and a mixed aqueous solution of these and hydrogen peroxide water, and the like can be given. Of these, aqueous quaternary ammonium salts such as tetraalkylammonium halides and tetraalkylammonium perchlorates, and aqueous ammonia are preferred.

The aqueous ammonium solution varies depending on the type and the like, but usually has a surface tension of 25 to 35 dyne / c.
It is preferable to use m.

The aqueous ammonium solution may be used alone or in combination of two or more.

In the step of dipping in the aqueous ammonium solution, the time for dipping the silicon carbide sintered body is from 5 minutes to 1 minute.
20 minutes are preferable, 10 minutes to 60 minutes are more preferable, and 2 minutes
0 to 30 minutes is more preferable.

In the wet cleaning method of the silicon carbide sintered body according to the present invention, from the viewpoint that impurities present on the surface and near the surface are more easily dissolved by applying physical vibration to the object to be cleaned, Preferably, at least one step of is performed while irradiating the aqueous solution with ultrasonic vibrations,
The cleaning may be performed while vibrating the object to be cleaned or sweeping the ultrasonic frequency. This is particularly effective when performed in a step of dipping in an aqueous solution of an inorganic acid.

In the wet cleaning method of the silicon carbide sintered body of the present invention, the temperature of the solvent or the aqueous solution in at least one of the above steps is preferably set to 30 ° C. in order to improve the dissolving ability of various impurities and deposits. Above, more preferably 40 ° C
As described above, it is particularly preferable to carry out the reaction at 50 ° C. or higher. The upper limit of this temperature is equal to or lower than the boiling point of the solvent or aqueous solution used. This is particularly effective when performed in a step of immersion in a quasi-aqueous organic solvent.

In the wet cleaning method of the silicon carbide sintered body of the present invention, a step of immersing the silicon carbide sintered body in cleaning water may be performed between the above steps. When the step of immersing in the washing water is performed, for example, after the step of immersing in the quasi-aqueous organic solvent, the solvent attached to the object to be cleaned can be easily washed off, so that the aqueous solution in the next step is contaminated. It becomes difficult.

As the washing water, pure water, distilled water,
Ion-exchanged water and the like can be mentioned, but from the viewpoint of preventing reverse contamination of the object to be cleaned in the step of immersing in cleaning water, the pure water is preferable.

In the step of dipping in the washing water, the time for dipping the silicon carbide sintered body is preferably 2 minutes to 60 minutes, more preferably 5 minutes to 30 minutes, and further preferably 10 minutes to 20 minutes.

The step of dipping in the washing water may be performed by an overflow method so that the washing is always performed with a new solution.

In the wet cleaning method of the silicon carbide sintered body of the present invention, the silicon carbide sintered body as the body to be cleaned is of high density and high purity which can be used for various semiconductor members and electronic parts. Although not particularly limited, for example, a silicon carbide sintered body obtained by hot press sintering using a non-metallic auxiliary agent, a silicon carbide sintered body described in Japanese Patent Application No. 10-67565 previously filed by the present applicant, etc. Is mentioned.

As a device and a tool used in the wet cleaning method of the silicon carbide sintered body of the present invention, polyvinyl chloride (PVC) having excellent chemical resistance is preferable, and highly purified PVC is particularly preferable. It is. The ultrasonic generator, the heater, and the like are preferably those whose surfaces are subjected to Teflon processing.

The silicon carbide sintered body obtained by the wet cleaning method of the silicon carbide sintered body of the present invention can be suitably used for various semiconductor members and electronic parts. , A heater, a plasma etching electrode, an ion implantation target, etc., for which high purity and particle free are desired.

[0050]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. (Cleaning object) The cleaning object (silicon carbide sintered body) used in the following Examples and Examples was evaluated using the same sample. The object to be cleaned is a lithographic plate of 40 × 40 × 2t. This lithographic plate has one surface rough-polished and the other surface a mirror surface. The surface cleanliness (impurity adhesion amount) before cleaning is 1 × 10 ¹³ to 1 × 10 ^{16 at.}
ms / cm ² .

(Measurement of Surface Cleanliness (Amount of Impurity)) The measurement of surface cleanliness (amount of impurities) was carried out using light elements (B, N).
a, Al) is obtained by rinsing the surface of an object to be cleaned by using an aqueous solution containing 1% each of hydrofluoric nitric acid and nitric acid to extract impurities, and extracting the aqueous solution by ICP-MS (“Inductively C”).
coupledPlasma Mass Spectro
meter (inductively coupled plasma mass spectrometer) "). Other elements are immersed in a pure water solution and dried, and then subjected to TXRF (“Total Reflection”).
X-Ray Fluorescence meter (total reflection X-ray fluorescence spectrometer) "). Note that TXR
When analyzing in F, the relative sensitivity coefficient in silicon was used. In addition, the fact that the ICP-MS analysis value and the TXRF analysis value are substantially equal indicates that K, Cr, Fe, Ni, Cu, Zn
Confirmed by the analysis value.

Example 1 An object to be cleaned was placed in a stock solution of a quasi-aqueous organic solvent (a mixed solvent of petroleum hydrocarbons, organic acid esters and nonionic surfactants) at 50 ° C. with ultrasonic waves (100
(V-26 ± 2 kHz) for 15 minutes, rinsing with water, and then hydrofluoric / nitric acid aqueous solution (38% hydrofluoric acid: 68%).
% Nitric acid: water = 1: 1: 20) for 30 minutes, and further immersed in pure water, and then the surface cleanliness was measured. The surface cleanliness of the object to be cleaned is 8 × 10 ⁹ to 1 × 10 ¹¹ atoms / s.
cm ² , and details are shown in Table 1. In addition, each of the above treatments was carried out at a normal temperature of the aqueous solution except for the treatment of immersion in the semi-aqueous organic solvent.

Example 2 A body to be cleaned was immersed in glycol ether for 20 minutes, and immersed in a quaternary ammonium salt aqueous solution for 30 minutes.
After immersion in a hydrofluoric / nitric acid aqueous solution (38% hydrofluoric acid: 68% nitric acid: water = 1: 1: 20) for 30 minutes, and further immersion in pure water, the surface cleanliness was measured. The surface cleanliness of the object to be cleaned is 8 × 10 ^{9 to} 9 × 10 ¹⁰ atoms / cm.
² and details are shown in Table 1. In addition, each of the above processes
The temperature of the solvent and the aqueous solution was set to normal temperature.

Example 3 The procedure of Example 1 was repeated, except that ultrasonic waves (100 V-26 ± 2 kHz) were used for each treatment, and the surface cleanliness was measured. The surface cleanliness of the object to be cleaned is 8 × 10 ^{9 to} 9 × 10
^{It is 10} atoms / cm ² , and details are shown in Table 1.

Example 4 Example 1 was repeated except that the temperature of the solvent and the aqueous solution was changed to 70 ° C. in each treatment.
After the same treatment, the surface cleanliness was measured. The surface cleanliness of the object to be cleaned is 8 × 10 ⁹ to 1 × 10 ¹¹ atoms.
/ Cm ² , and details are shown in Table 1.

Example 5 An object to be cleaned was placed in a stock solution of a quasi-aqueous organic solvent (mixed solvent of petroleum hydrocarbon, organic acid ester and nonionic surfactant) at 50 ° C. with ultrasonic waves (100
V-26 ± 2 kHz) for 15 minutes while irradiating
Immersion for 30 minutes in aqueous solution of quaternary ammonium salt, immersion for 30 minutes in aqueous solution of hydrofluoric acid / nitric acid / sulfuric acid (38% hydrofluoric acid: 68% nitric acid: 98% sulfuric acid: water = 1: 1: 1: 20), and further pure water After immersion, the surface cleanliness was measured. The surface cleanliness of the object to be cleaned is 4 × 10 ^{9 to} 9 × 10 ¹⁰ atoms /
cm ² , and the analysis values of Zn and Cr obtained here are the detection lower limit of TXRF. Details are shown in Table 1. In addition, each of the above treatments was carried out at a normal temperature of the aqueous solution except for the treatment of immersion in the semi-aqueous organic solvent.

Comparative Example 1 The procedure of Example 1 was repeated, except that the sample was not immersed in an aqueous solution of hydrofluoric / nitric acid. The surface cleanliness of the object to be cleaned is less than 1 × 10 ¹¹ to 1 × 10 ¹⁵ atoms / cm ² , and details are shown in Table 1.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the substrate was not immersed in a quasi-aqueous organic solvent, and the surface cleanness was measured. The surface cleanliness of the object to be cleaned is less than 1 × 10 ¹⁰ to 1 × 10 ¹⁴ atoms / cm ² , and details are shown in Table 1.

[0059]

[Table 1]

From Table 1, it can be seen that the silicon carbide sintered body of the present invention subjected to the wet cleaning treatment has a surface cleaning level of less than 1 × 10 ¹¹ atoms / cm ² applicable to various semiconductor members and electronic members. It turns out that it is a degree. In particular, Example 5 using sulfuric acid was particularly effective for removing Al.

[0061]

As described above, the present invention provides a method for wet-cleaning a silicon carbide sintered body which can easily clean and remove organic and inorganic impurities existing on and near the surface of the silicon carbide sintered body. can do.

Claims (8)

[Claims] 1. A method of sintering a silicon carbide sintered body in a step of dipping in a semi-aqueous organic solvent, a step of dipping in an inorganic acid aqueous solution, and a step of dipping in pure water. How to wet clean the body. 2. a step of immersing the silicon carbide sintered body in a quasi-aqueous organic solvent, a step of immersing it in an aqueous ammonium solution, a step of immersing it in an aqueous inorganic acid solution, and a step of immersing it in pure water.
Wet cleaning method for a silicon carbide sintered body, characterized by sequentially treating the silicon carbide sintered body. 3. A process of immersing a silicon carbide sintered body in a quasi-aqueous organic solvent, a step of immersing in an inorganic acid aqueous solution, a step of immersing in an ammonium aqueous solution, and a step of immersing in pure water sequentially. A wet cleaning method for a silicon carbide sintered body. 4. The wet cleaning method for a silicon carbide sintered body according to claim 1, wherein at least one step is performed while applying ultrasonic vibration to the liquid. 5. The method according to claim 1, wherein the temperature of the liquid in at least one step is 3
The method for wet-cleaning a silicon carbide sintered body according to claim 1, wherein the temperature is 0 ° C. or higher. 6. The quasi-aqueous organic solvent is a petroleum hydrocarbon, an organic acid ester, a glycol ether, a mixed solvent thereof, or a mixture of these solvents or a mixed solvent and a surfactant. Item 6. The wet cleaning method for a silicon carbide sintered body according to any one of Items 1 to 5. 7. The method according to claim 1, wherein the inorganic acid aqueous solution is a hydrofluoric acid aqueous solution, a nitric acid aqueous solution, a sulfuric acid aqueous solution, a hydrochloric acid, a hydrogen peroxide solution, an ozone water, or a mixed acid aqueous solution thereof. A wet cleaning method for a silicon carbide sintered body according to any one of the above. 8. The method according to claim 2, wherein the aqueous ammonium solution is an aqueous solution of a tetraalkylammonium halide, an aqueous solution of a tetraalkylammonium perchlorate, aqueous ammonia, or a mixed aqueous solution of these and an aqueous solution of hydrogen peroxide. The wet cleaning method for a silicon carbide sintered body according to any one of the above.