JP2008208000A - Corrosion resistant member and gas nozzle using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosion resistant member such as a gas nozzle causing little occurrence of particles. <P>SOLUTION: The corrosion resistant member comprises a plurality of columnar aluminum nitride crystal grains forming a part of a substrate surface composed of an aluminum nitride sintered compact, and has a region where the maximum height difference between the peak of each columnar aluminum nitride crystal grain and the peak of each aluminum nitride crystal grain with a shape other than a columnar shape in all the directions of 20 μm with the above peak as the center is ≥4 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a corrosion-resistant member made of an aluminum nitride sintered body and a gas nozzle using the same.

  The aluminum nitride sintered body is used for a corrosion resistant member such as a gas nozzle for supplying a reactive gas to a thin film forming apparatus such as a chemical vapor deposition (CVD) apparatus, or a base of a corrosion resistant member.

In Patent Document 1, a molded body containing an aluminum nitride powder and a sintering aid is fired, and the obtained aluminum nitride-based sintered body is polished and then heat-treated at a temperature lower by 50 ° C. than the firing temperature. The resulting aluminum nitride sintered body is described. By this heat treatment, it is said that the liquid phase of the sintering aid is filled in the microcracks (fine cracks) generated during the polishing process, and the strength can be improved.
JP 2001-102476 A

  However, the aluminum nitride sintered body of Patent Document 1 has a problem that the corrosion resistance is deteriorated because a large amount of a sintering aid having a lower corrosion resistance than aluminum nitride is formed on the surface.

  For example, a corrosive gas such as silane gas reacts with oxygen to form silicon oxide in plasma and reacts with nitrogen to form silicon nitride. These oxides and nitrides react with the corrosion-resistant surface 10. Is deposited and deposited. This deposition of the reaction product occurs on the outer wall surface of a gas nozzle for supplying a corrosive gas in a film formation process on a silicon wafer in a semiconductor manufacturing process. The deposited reactant may be partly peeled off due to mechanical vibrations generated in the semiconductor manufacturing equipment, the flow of corrosive gas, heating by plasma heat, etc. In addition, pinholes and protrusions occur in silicon oxides and nitrides deposited on silicon wafers, reducing the quality of the silicon wafer, so that the reactants are peeled off even if the reactants are deposited thick on the corrosion-resistant member. It needs to be difficult.

  In view of this problem, an object of the present invention is to provide a corrosion-resistant member that is excellent in corrosion resistance and hardly generates particles from the surface. Furthermore, it aims at providing a corrosion-resistant member with high heat conductivity.

  In view of the above, the present invention has a plurality of columnar aluminum nitride crystal particles forming a part of the surface of a substrate made of an aluminum nitride-based sintered body, and the apexes of the columnar aluminum nitride crystal particles and the apexes It has a region having a maximum height difference of 4 μm or more from the apex of aluminum nitride crystal grains other than the columnar shape in the center of 20 μm square.

  Further, the substrate has one or more columnar aluminum nitride crystal particles in a surface of 200 μm square.

  Furthermore, the oxygen content in the aluminum nitride sintered body is 1% by mass or less.

  And it is applicable to the gas nozzle which consists of the said corrosion-resistant member, Furthermore, the said corrosion-resistant member forms the inner surface, It is characterized by the above-mentioned.

  According to the present invention, it is possible to remarkably suppress the reaction product from peeling and forming particles, to reduce particles generated from the corrosion-resistant surface, and to provide a corrosion-resistant member that is not easily corroded by corrosive gas. At the same time, the thermal conductivity of the corrosion-resistant member can be increased.

  The best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic view of a photograph of the corrosion resistant surface of the corrosion resistant member of the present invention taken obliquely from above (an angle of about 30 ° with respect to the corrosion resistant surface) using a scanning electron microscope (SEM).

  The corrosion-resistant member 20 has a corrosion-resistant surface 10 that is exposed to a corrosive gas such as silane gas, and is a corrosion-resistant member 20 made of an aluminum nitride-based sintered body. It has crystal grains 12 made of a plurality of columnar aluminum nitrides that protrude. Here, FIG. 1 shows that the end 16 in the longitudinal direction of the crystal particle 12 protrudes from the corrosion-resistant surface 10.

  In the corrosion-resistant member 20 of the present invention, the plurality of columnar crystal particles 12 projecting from the surface serve to suppress the separation of the corrosive gas reactant deposited on the corrosion-resistant surface 10. It can suppress that it peels and becomes a particle, and can reduce the particle which generate | occur | produces from the corrosion-resistant surface 10. FIG.

  The columnar crystal particles 12 are columnar crystal particles having an L / W value of 1.5 or more shown in FIG. 2 when the crystal particles 12 protruding from the corrosion-resistant surface 10 are observed. This means that one end 16 of the direction exists away from the corrosion-resistant surface 10. It can be confirmed by observing the corrosion-resistant surface 10 using a scanning electron microscope (SEM) that the crystal particles 12 are columnar.

  Here, the corrosion-resistant surface 10 includes crystal particles 14 that do not protrude from the corrosion-resistant surface 10, and the crystal particles 14 are not columnar. For example, the surface shape is a low-profile mountain shape, and thus a plurality of crystal particles 14. The unevenness of the corrosion-resistant surface 10 formed by has almost no effect of suppressing the peeling of the reactant.

  Furthermore, the average protrusion height H of the columnar crystal particles 12 is preferably 4 μm or more. The protrusion height H of each crystal particle 12 can be measured by observing the corrosion-resistant surface 10 with an SEM. An SEM photograph including the corrosion-resistant surface 10 and the crystal particles 12 is taken from a direction perpendicular to the longitudinal direction of the crystal particles 12 with an angle of 20 ° or less with respect to the corrosion-resistant surface 10, and the protrusion height H can be obtained. The average value of the projecting heights of the crystal grains 12 is determined by measuring the projecting heights H of at least 10 crystal grains 12 and setting the average value of these projecting heights H. Here, if the angle is within 20 ° with respect to the corrosion-resistant surface 10, there is a case where the protruding height in a strict sense is different, but in the present invention, the protruding height H of the crystal grain 12 is measured in this way. .

  Further, the L / W of the crystal particles 12 is preferably 2 or more. As a result, even when the reactant becomes thick, the reactant can be firmly fixed by the action of the anchor effect by the columnar crystals, and the reactant becomes more difficult to peel off, so that the generation of particles can be further reduced. The L / W of the crystal particles 12 can be confirmed by observing the corrosion-resistant surface 10 using a scanning electron microscope. FIG. 2 is a schematic diagram showing a method for observing the crystal particles 12 with a scanning electron microscope and obtaining the L / W. The length L of the crystal particles is defined as the length (long diameter) in the longitudinal direction of the crystal particles, and the width W (short diameter) of the crystal particles 12 is defined as a width at half the length L, thereby obtaining L / W Can be sought. When measuring L / W, the crystal particles 12 are observed from a direction substantially perpendicular to the longitudinal direction of the crystal particles 12.

  Further, the average size of the crystal grains 12 is preferably such that W is 1 μm or more and L is 3 μm or more. As a result, the mechanical strength of the crystal particles 12 is increased, so that even if the crystal particles 12 are stressed by the reactant, the crystal particles 12 are not broken or cracked, and the generation of particles is particularly suppressed. Can do.

  Furthermore, the average protrusion angle α of the columnar crystal particles 12 is preferably 30 ° or more on average. Thereby, since the reactant is more firmly fixed by increasing the anchor effect, the generation of particles can be minimized.

  The average protrusion angle α of the crystal particles 12 can be measured as follows. In a state where the crystal particles 12 are obliquely above the corrosion resistant surface 10 within an angle of 20 ° and observed from the direction perpendicular to the longitudinal direction of the crystal particles 12, the corrosion resistant surface 10 and the crystal particles 12 are A SEM photograph including the image is taken, and the protrusion angle α is measured from this photograph. The average value of the protrusion angles α of the crystal grains 12 is an average value of ten protrusion angles α. Here, if the angle is within 20 ° with respect to the corrosion-resistant surface 10, there is a case where the protruding angle in a strict sense is different, but in the present invention, the protruding angle α of the crystal grain 12 is measured in this way.

  Further, it is more preferable that the aluminum nitride sintered body constituting the corrosion resistant member 20 is substantially made of only aluminum nitride. In this case, both of the crystal grains 12 and 14 are made of aluminum nitride crystal grains. As a result, the entire corrosion-resistant surface 10 can be covered with an aluminum nitride crystal having excellent corrosion resistance, so that the corrosion-resistant member 20 that is not particularly corroded by the corrosive gas can be obtained.

  It can be confirmed that the corrosion-resistant member 20 is substantially made only of aluminum nitride by measuring the corrosion-resistant member by an X-ray diffraction method using Cu-Kα rays and the crystal phase is made only of aluminum nitride.

  Furthermore, it is particularly preferable that the aluminum nitride sintered body constituting the corrosion-resistant member 20 is substantially made only of aluminum nitride and has an oxygen content of 1% by mass or less. Thereby, the thermal conductivity of the corrosion-resistant member 20 can be increased. When the thermal conductivity of the corrosion-resistant member 20 is high, when a corrosive gas is supplied from a gas nozzle for supplying a corrosive gas used in a film forming apparatus or the like on a silicon wafer, heating and cooling of the gas nozzle should be accelerated. Therefore, the film thickness formed on the silicon wafer can be made uniform. For example, the thermal conductivity of the corrosion-resistant member 20 is preferably 60 W / m · K or more.

  The thermal conductivity can be obtained by obtaining a thermal diffusivity using a laser flash method and multiplying the thermal diffusivity, specific gravity, and specific heat capacity.

  The oxygen content of the aluminum nitride sintered body constituting the corrosion-resistant member 20 is determined by infrared absorption of oxygen generated when the aluminum nitride sintered body is heated and decomposed using a molten metal of nickel and tin as a combusting agent. This is possible by quantitative analysis.

  The gas nozzle of the present invention is used to supply a corrosive gas such as silane gas into the processing chamber, and is composed of a corrosion-resistant member 20. Thereby, since it can be set as a gas nozzle with few generation | occurrence | production of a particle, it can be set as the gas nozzle which can suppress that a particle accumulates on to-be-processed objects, such as a silicon wafer. When the object to be processed is a silicon wafer, when forming a thin film on the silicon wafer by the CVD method, it is difficult for particles to be generated from the gas nozzle. Can be reduced.

  FIG. 4 shows a cross-sectional view of the gas nozzle of the present invention.

  In general, a gas nozzle has an injection hole 22 that is an outlet for ejecting gas, an inner wall surface 24 thereof, and a supply hole 26 for supplying gas.

  Since the gas nozzle of the present invention can reduce the separation of reactants, the amount of particles into the gas discharged from the gas nozzle can also be reduced. Thus, for example, when the gas nozzle of the present invention is used as a gas nozzle for a CVD apparatus for forming a thin film on a wafer, a wafer on which a high-quality thin film with fewer pinholes can be produced.

  The manufacturing method of the corrosion-resistant member 20 is as follows, for example. The case where the shape of the corrosion-resistant member 20 is a cylindrical sintered body (gas nozzle) having ejection holes will be described as an example.

99 to 99.99 mass% of aluminum nitride powder and ytterbium oxide (Yb ₂ O ₃ ), dysprosium oxide (Dy ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), and erbium oxide (Er) as sintering aids ₂ O ₃ ) A powder comprising at least one oxide selected from 0.01 to 1% by mass is used as a starting material, and an organic binder and ethanol are added to and mixed with this mixed powder to produce a slurry. . The obtained slurry is spray-dried, the obtained granule is CIP-molded (cold isostatic pressing), and the obtained molded body is cut to produce a cylindrical molded body. This cylindrical shaped body is heat treated in nitrogen gas at 400 to 800 ° C. for 0.5 to 12 hours to degrease the organic binder, and then molded into a firing container made of a high-purity dense aluminum nitride sintered body. The body is placed and subjected to primary firing in nitrogen gas at 1850 ° C. or more and less than 2000 ° C. for 1 to 25 hours, so that the density is 3.22 g / cm ³ or more, and aluminum nitride having coarse holes of gas nozzle injection holes A quality cylindrical primary sintered body (example: outer diameter 12 mm, length 45 mm) is produced.

  Next, in order to finish the hole diameter of the coarse hole with high accuracy, after cooling to room temperature after firing, diamond abrasive grains having an average particle diameter of 1 μm are applied to a tungsten wire (eg, wire diameter φ0.398 mm), and the injection hole The inner wall surface 24 of the injection hole 22 is polished with a wire such that the inner diameter of the injection hole 22 becomes 0.4 ± 0.0004 mm. After the wire polishing, the wire-polished one is placed in a firing container made of a high-purity dense aluminum nitride sintered body, and secondary firing is performed at a temperature higher than the primary firing in nitrogen gas. Thereby, the corrosion-resistant member 20 which consists of an aluminum nitride sintered body is obtained.

  The corrosion-resistant member 20 manufactured in this way has a plurality of crystal grains 12 made of aluminum nitride that protrude on the surface side from the other crystal grains 14 on the surface side. The cause of this is not clear, but the aluminum nitride crystal particles on the surface of the sintered body after the primary firing repeatedly sublimate from solid to gas and from gas to solid during the secondary firing. It is considered that the crystal particles 12 protrude from the surface.

  In order to make the crystal particles 12 into columnar particles, in the manufacturing method described above, a powder consisting only of an aluminum nitride powder is used instead of the mixed powder, and the temperature of the primary firing is 1900 ° C. or higher and lower than 1950 ° C. Is made 1950 or more and 2050 ° C. or less, and the temperature of secondary baking is higher than the temperature of primary baking. In order to set the L / W of the crystal particles 12 to 2 or more, the primary firing temperature is set to 1950 ° C. or more and less than 2000 ° C., and the secondary firing temperature is set to 2000 ° C. or more and 2050 ° C. or less. Moreover, the corrosion-resistant member which consists only of aluminum nitride can be manufactured by these manufacturing methods.

  Furthermore, in order to set the oxygen content of the corrosion-resistant member 20 to 1% by mass or less, an aluminum nitride powder having an oxygen content of 1% by mass or less is used.

  When manufacturing a gas nozzle, it is preferable to make the temperature of secondary baking 20 degreeC or more higher than the temperature of primary baking. Thereby, since fine cracks generated when the rough holes of the gas nozzle are polished can be eliminated in the secondary firing, the crystal particles 14 are less likely to be degranulated starting from the cracks. This is because there is no risk of becoming.

  The sample of the Example of this invention was created in the following ways.

A mixed powder composed of an aluminum nitride powder having an average particle size of 1.5 μm and a powder of yttrium oxide (Y ₂ O ₃ ) or erbium oxide (Er ₂ O ₃ ), or only aluminum nitride powder as a starting material. An organic binder and ethanol were added to and mixed with each other to prepare a slurry. The obtained slurry was spray-dried, the obtained granule was CIP-molded (cold isostatic pressing), and the resulting molded product was cut to produce a plurality of cylindrical molded products. The obtained cylindrical molded body was degreased by heat treatment in nitrogen gas at 700 ° C. for 5 hours, and then the molded body was placed in a firing container made of a high-purity dense aluminum nitride sintered body. A primary sintered body made of aluminum nitride having a density of 3.22 g / cm ³ or more and rough holes of gas nozzle injection holes by primary firing in gas (eg, 12 mm in outer diameter, 45 mm in length) Was made. In addition, when the oxide that is a sintering aid is used as a starting material, the proportion of the aluminum nitride powder in the mixed powder is 100% minus the proportion (%) of the oxide that is a sintering aid. It is.

  Next, in order to finish the hole diameter of the rough hole with high accuracy, after cooling to room temperature after firing, diamond abrasive grains having an average particle diameter of 1 μm are applied to a tungsten wire having a wire diameter of 0.398 mm, and the hole diameter of the injection holes 22 The inner wall surface 24 of the injection hole 22 was polished with a wire so that the inner diameter became 0.4 ± 0.0004 mm. After the wire polishing, the wire-polished one was placed in a firing container made of a high-purity dense aluminum nitride sintered body, and was secondarily fired in nitrogen gas to produce a gas nozzle that was a sample of the present invention. . Other conditions were as shown in Table 1.

  The obtained sample of the present invention was evaluated as follows. As a result of analyzing the rare earth element contained in the sample by ICP emission spectroscopic analysis, it was the same as the content of the rare earth element in the starting material. It was confirmed by measuring by microscopic X-ray diffraction that the crystal grains 12 were aluminum nitride. The presence of a plurality of protruding columnar crystal particles was confirmed by observing the outer wall surface 28 of the sample with a scanning electron microscope (SEM). The L / W of the crystal particles 12 was determined by selecting 10 crystal particles, calculating the average value of the major axis L and the average value of the minor axis W, and dividing the average value of L by the average value of W. The average value of the protrusion height H of the crystal particles 12 included in the sample was obtained from the SEM photograph. The oxygen content of the sample was measured using a TC-600 type analyzer manufactured by LECO Corporation. A sample was cut out to obtain the thermal diffusivity using a laser flash method, and the thermal conductivity was obtained from the product of the thermal diffusivity, specific gravity and specific heat capacity.

Next, when forming a film with the gas nozzle of the present invention, the sample (gas nozzle) of the present invention and pure water are placed in a cleaning chamber of 28 kHz and 1200 W in a clean room higher than class 1000, and divided into rough cleaning and finish cleaning. In turn, each was subjected to ultrasonic cleaning for 5 minutes and dried. Eight dried samples were mounted in a CVD apparatus container, a dummy silicon wafer having a diameter of 300 mm was fixed in the chamber, and a silicon oxide film was formed on the wafer as follows. A silicon wafer is placed in a container of a CVD apparatus maintained at a high vacuum, silane gas (SiH ₄ gas) is introduced at a flow rate of 150 SCCM (standard cubic centimeter per minute), and oxygen gas is introduced at a flow rate of 900 SCCM, and the pressure in the container is reduced to 0. The wafer temperature was kept at 370 ° C. In this state, a high frequency of 2.45 GHz and 1.8 kW was introduced into the container using a high frequency power source to generate plasma of silane gas and oxygen gas and held for 300 seconds. As a result, a silicon oxide film was formed on the silicon wafer. Thereafter, supply of silane gas and oxygen gas was stopped to stop plasma generation.

The sample gas nozzle was removed, and the amount of particles generated was measured as follows. First, the sample of the present invention and pure water were placed in a 28 kHz, 1200 W cleaning bowl in a clean room of a higher level than class 1000, and ultrasonic cleaning was performed for 5 minutes each in order, divided into rough cleaning and finishing cleaning. Pour 3 L of pure water sufficiently degassed through a 0.1 μm filter into the bathtub of an ultrasonic cleaner (Honda Electronics W-113), and hang the sample after finishing cleaning with a resin fishing line. Soaked in pure water so as not to touch. In the soaked state, ultrasonic waves were applied at a frequency of 45 kHz for 30 seconds. Pure water containing particles in the bath was sampled after application of ultrasonic waves. The number of particles contained in the sampled water was measured using an in-liquid particle measuring device (PARTICLE MEASURING SYSTEMS CLS-700). In this measurement, the number of each particle having a particle size of 0.2 μm or more and 1.0 μm or more was measured. The measured number of particles was converted to the number of particles generated per 1 cm ^{2 of the} surface area of the sample, and the amount of particles generated (number / cm ² ) was used.

The results are shown in Table 1.

  Sample No. of the present invention. In Nos. 1 to 12, a plurality of protruding crystal particles 12 were observed, and the generation of particles was small. Among these, the sample No. 1 in which the crystal particles 12 are columnar particles is used. No. 5 to 12 had fewer particles. In particular, sample No. with L / W of 2 or more. 7 to 12 had particularly few particles. Sample No. having an oxygen content of 0.3 mass% or less. 3-8 had a thermal conductivity of 68 to 91 W / m · K, and the thermal conductivity of the sample of the present invention was high.

  Next, as a comparative example, a sample No. outside the scope of the present invention was used. In Nos. 13 to 16, very many particles were generated as compared with the sample of the example.

It is the surface schematic diagram which expanded the surface of the corrosion-resistant surface of the corrosion-resistant member of this invention seeing from diagonally upward. It is a schematic cross section which shows the method of calculating | requiring L / W of the columnar crystal grain in the corrosion-resistant surface of the corrosion-resistant member of this invention. It is a schematic diagram which shows the relationship between L and W. It is sectional drawing to which the site | part containing the ejection hole of the gas nozzle of this invention was expanded.

Explanation of symbols

10: Corrosion resistant surface 12, 14: Crystal particle 16: End portion 20: Corrosion resistant member 22: Injection hole 24: Inner wall surface 26: Supply hole H: Projection height L: Length W: Width

Claims (5)

A plurality of columnar aluminum nitride crystal particles forming a part of the surface of a substrate made of an aluminum nitride sintered body, and having a vertex other than the columnar shape in a 20 μm square centering on the vertex of the columnar aluminum nitride crystal particle A corrosion-resistant member having a region where the maximum height difference from the apex of the aluminum nitride crystal particles is 4 μm or more. 2. The corrosion-resistant member according to claim 1, comprising one or more columnar aluminum nitride crystal particles in a surface of 200 μm square of the base. The corrosion-resistant member according to claim 1 or 2, wherein an oxygen content in the aluminum nitride sintered body is 1% by mass or less. A gas nozzle comprising the corrosion-resistant member according to claim 1. The gas nozzle according to claim 4, wherein the corrosion-resistant member forms an inner surface.

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