JP5869437B2 - Method for joining SiC sintered bodies - Google Patents

Description

The present invention relates to a bonding how the SiC sintered body.

  Since the SiC sintered body has high strength and high rigidity, it is widely used as a fixing jig for fixing a wafer, a drawing mask, etc. during various processes in the semiconductor manufacturing process. Such a fixing jig is provided with a groove through which a heat medium for temperature adjustment flows. In order to provide a groove inside, it is necessary to join a SiC sintered body having a groove formed on the joint surface.

  The SiC sintered body may be joined by sandwiching Si in powder form or plate-like shape between the SiC sintered bodies and heat-treating at a melting point of Si or higher. Since Si is heated to a melting point or higher during bonding and becomes liquid, when it has grooves, Si often oozes into the grooves. Thus, Patent Document 1 discloses that C-surface processing is performed on the end portion of the joint surface to capture the exuded Si and prevent the exudation of Si into the groove.

  However, since it is difficult to control the flow of molten Si, it is very difficult to make the thickness and width of the bonding layer constant. As a result, the cross-sectional area of the groove is not constant in each part, and it is difficult to completely control the flow rate at each place when a heat medium is passed through the groove, and it is difficult to perform precise temperature adjustment. Therefore, there has been a demand for a bonding method in which there is no variation in the thickness and width of the bonding layer, and as a result, a structure having a uniform cross-sectional area of the groove can be obtained.

  Therefore, the SiC sintered body may be joined by heating and pressing in a state where the joining surfaces of the SiC sintered body are in direct contact with each other without using a joining material such as Si.

Japanese Patent Laid-Open No. 2001-261459

  However, when joining by heating and pressing in a state where the joint surfaces of the SiC sintered bodies are in direct contact with each other, there is a possibility that voids are generated on the joint surface and the joint cannot be performed satisfactorily. If there is a gap in the joint surface, the heat medium that has flowed into the groove leaks out.

The present invention has been made in view of these problems, to provide a bonding how the bonding interface can be well bonded to SiC sintered body without causing a gap to a SiC sintered body Objective.

  The SiC sintered body joining method of the present invention includes the steps of preparing two SiC sintered bodies, and assuming that the longest dimension of the joining surface of the SiC sintered body is L (mm). Polishing the bonded surfaces of the bonded bodies so that the flatness a (μm) satisfies a ≦ L / 60 and a convex shape toward the center, and bonding of the two SiC sintered bodies And a step of processing at 1500 ° C. or higher for 10 minutes or longer while pressing the joint surfaces with a pressure of 0.1 MPa or higher.

  According to the bonding method of the SiC sintered body of the present invention, the bonding surface is convex toward the central portion, so that the central portion of the bonding surface is in reliable contact during heat treatment, and there is a gap in the central portion of the bonding interface. Is less likely to occur. If the flatness a (μm) satisfies a ≦ L / 60 so that the convex shape is not too high, as will be described later in the section of the embodiment for carrying out the invention, the end of the joint interface is also formed. It was found that voids were not easily generated. Therefore, it is possible to obtain a SiC bonded body having no voids at the bonding interface with a high yield.

  By the way, when the thickness of the SiC sintered body is too thick, there is a possibility that voids are generated at the end of the bonding interface without deformation of the bonding surface during heat treatment.

Therefore, in the method for joining SiC sintered bodies according to the present invention, when the thickness of the SiC sintered body is t (mm), the flatness a (μm) satisfies a ≦ 50 / t. polished intends line.

  In this case, as will be described later in the column of the embodiment for carrying out the invention, it has been found that no void is generated at the end of the bonding interface.

  Moreover, in the joining method of the SiC sintered compact of this invention, it is preferable to perform the said process below 1500 degreeC or more below the sintering temperature of the said SiC sintered compact.

  In this case, grain growth at the bonding interface is suppressed, and a decrease in bonding strength can be prevented. And it becomes possible to also suppress the deformation | transformation at the time of joining by this.

  Moreover, in the joining method of the SiC sintered compact of this invention, it is preferable to provide the process of forming a groove | channel in the joining surface of at least one SiC sintered compact of said 2 SiC sintered compact.

  In this case, a SiC joined body having a groove inside can be obtained. The inner groove may be a groove forming a closed space or a groove communicating with the outside.

(A), (b) is a schematic sectional drawing explaining the joining method of a SiC sintered compact in order. The table | surface which put together the result of the Example. The table | surface which put together the result of the comparative example.

  The joining method of the SiC sintered compact concerning the embodiment of the present invention is explained.

  Here, as shown in FIG. 1A, a case where two flat SiC sintered bodies 11 and 12 are joined will be described.

The SiC sintered bodies 11 and 12 can be manufactured by a known manufacturing process by adding known additives, sintering aids and the like to the SiC raw material powder as necessary. For example, B ₄ C, C or the like can be used as a sintering aid.

  It is preferable that SiC sintered bodies 11 and 12 are sufficiently densified. This is because if the densification is insufficient, the SiC sintered bodies 11 and 12 are deformed, and the shape accuracy of the internal groove 13 after joining is lowered. Specifically, the SiC sintered bodies 11 and 12 preferably have a relative density of 95% or more.

  A groove 12b is formed in the joint surface 12a of one SiC sintered body 12. Thereby, the SiC joined body 10 which has the internal groove | channel 13 can be obtained by joining the joining surfaces of the SiC sintered compacts 11 and 12. FIG.

  In addition, although the case where the groove | channel 12b was formed in the joining surface 12a of one SiC sintered body 12 was shown here, it is not limited to this, The joining surface 11a of the other SiC sintered body 11 is also shown. A groove may be formed. Further, the number and shape of the grooves formed in the SiC sintered bodies 11 and 12 are not limited. Furthermore, it is not necessary to form a groove in any of the SiC sintered bodies 11 and 12.

  Both the joining surfaces 11a and 12a of the SiC sintered bodies 11 and 12 are polished into a smooth convex shape from the periphery toward the center, except for the grooves 12b formed on the joining surface 12a. In the drawings, the thickness direction is enlarged with respect to the width direction, and the convex shapes of the joint surfaces 11a and 12a are emphasized. Since the joint surface has a smooth convex shape toward the central portion, the flatness a substantially means the height of the convex shape.

Both the joining surfaces 11a and 12a satisfy the relationship of the formula (1) between the flatness a (μm) and the longest dimension L (mm).
a ≦ L / 60 (1)

  The longest part is, for example, a diameter when the joint surface is circular, and a diagonal line when the joint surface is rectangular. The SiC sintered bodies 11 and 12 are not limited to circular plates and rectangular plates, and may be plates having various shapes such as polygonal plates.

Furthermore, it is preferable that the flatness a (μm) of the joining surfaces 11 a and 12 a satisfy the relationship of the formula (2) with the thickness t (mm) of the SiC sintered body 12.
a ≦ 50 / t (2)

  The polishing of the joint surfaces 11a and 12a may be performed, for example, by lapping. The groove 12b is processed before or after the polishing process. The SiC sintered body 12 may be roughly processed before sintering, and the precision processing may be performed on the groove 12b after sintering. The groove 12b may be formed by, for example, milling using an end mill or the like, or processing using a machining center.

  In the joining process, the joining surfaces 11a and 12a are combined and heat-treated at 1500 ° C. or more for 10 minutes or more while pressing with a pressure of 0.1 MPa or more from a direction perpendicular to the joining surfaces 11a and 12a. Note that after the heat treatment, an annealing treatment may be performed in order to remove the residual stress.

  The pressurization is performed, for example, by placing a weight on the upper surface of the stacked SiC sintered bodies 11 and 12 or using a hot press furnace so that a pressure of 0.1 MPa or more is uniformly applied to the joint surfaces 11a and 12a. Press. The direction perpendicular to the joining surfaces 11a and 12a may be a direction perpendicular to the joining surfaces 11a and 12a as a substantially flat surface. When the applied pressure is less than 0.1 MPa, contact between the joining surfaces 11a and 12a becomes insufficient during heat treatment, and a gap of 1 to several μm is generated at the joining interface, which is not preferable.

  The heat treatment temperature is preferably 1500 ° C. or more, particularly preferably in the range of 1500 ° C. to 2000 ° C. If the heat treatment temperature exceeds 2000 ° C., the SiC sintered bodies 11 and 12 may be softened and the shape of the groove 12b may change, so that the cross-sectional area accuracy of the internal groove 13 may not be ensured satisfactorily. There is.

  The heat treatment temperature is preferably lower than the firing temperature of the SiC sintered bodies 11 and 12. This is to suppress the grain growth and prevent the bonding strength from decreasing. Thereby, the deformation | transformation at the time of joining can also be suppressed and it becomes possible to make constant the cross-sectional area for every location of the internal groove | channel 13. FIG.

  On the other hand, when the heat treatment temperature is less than 1500 ° C., mass transfer does not occur at the contact portions of the bonding surfaces 11a and 12a, and a gap of 1 to several μm may be generated at the bonding interface.

  The treatment time is preferably 10 minutes or more, particularly 10 to 240 minutes. When the processing time is less than 10 minutes, the entire SiC sintered bodies 11 and 12 are not uniformly heated, and there is a possibility that voids are locally generated at the bonding interface. On the other hand, when the treatment time exceeds 240 minutes, the effect on the integration reaction is not changed, which is economically disadvantageous.

  When the bonding surfaces 11a and 12a are concave or flat toward the center, a gap is likely to be generated particularly at the center of the bonding interface during heat treatment. On the other hand, if the joint surfaces 11a and 12a are convex toward the central portion, the central portions of the joint surfaces 11a and 12a come into contact with each other during heat treatment, so that it is difficult for a gap to be formed in the central portion of the joint interface. However, if the convex shapes of the joint surfaces 11a and 12a are too high, voids are likely to be generated at the ends of the joint interface.

  Therefore, as will be described later in Examples and Conventional Examples, it is understood that if the flatness a of the joining surfaces 11a and 12a satisfies the relationship of the above formula (1), no gap is generated at the end of the joining interface. It was.

  Furthermore, if the thickness t of the SiC sintered bodies 11 and 12 is too thick, the bonding surfaces 11a and 12a are not deformed during the heat treatment, and there is a possibility that voids are generated at the ends of the bonding interface.

  However, as will be described later in Examples and Conventional Examples, it is found that if the flatness a of the joining surfaces 11a and 12a satisfies the relationship of the above formula (2), no gap is generated at the end of the joining interface. It was.

  As shown in FIG. 1B, the SiC joined body 10 in which the SiC sintered bodies 11 and 12 are joined has an internal groove 13. And since the deformation | transformation which arises at the time of joining is very few, the cross-sectional area for every location of the internal groove 13 becomes fixed, and it becomes possible to suppress the dispersion | variation in the flowing water resistance of the heat medium which flows through the internal groove 13. Therefore, when the SiC joined body 10 is used as a jig for fixing an object to be processed such as a wafer or a drawing mask in a semiconductor manufacturing process, by flowing a heat medium for temperature adjustment through the internal groove 13, It becomes possible to perform temperature adjustment uniformly with high accuracy.

Examples and comparative examples
Hereinafter, the present invention will be described in detail with specific examples and comparative examples of the present invention.

Two SiC sintered bodies 11 and 12 were produced by a known process. Specifically, SiC powder having an average particle size of 1 μm or less, 0.1 to 0.5% by mass of B ₄ C and 2 to 4% by mass of C (carbon black) as a sintering aid, a molding aid As a raw material powder, a binder such as PVA was added. Next, this raw material powder was granulated with a spray dryer or the like and then CIP-molded. And after forming the groove | channel 12b by roughing, the SiC sintered compacts 11 and 12 were obtained by baking at 2000 degreeC-2200 degreeC in argon atmosphere. The relative density of the SiC sintered bodies 11 and 12 was 99.0%.

  The SiC sintered bodies 11 and 12 are discs having the same shape except for the presence or absence of the groove 12a. The diameter L and thickness t of the SiC sintered bodies 11 and 12 are shown in the respective columns of FIGS. Since SiC sintered bodies 11 and 12 have a disk shape, diameter L is the longest dimension of the joint surface.

  The joining surfaces 11a and 12a of the SiC sintered bodies 11 and 12 were lapped to make the joining surfaces 11a and 12a smooth and convex toward the center. And flatness a was measured using the laser interference type shape measuring machine.

  A groove 12b having a depth of 2 mm and a width of 2 mm traversing through the central portion was formed on the joining surface 12a of the SiC sintered body 12 by precision machining using a machining center. The dimension of the groove 12b was measured accurately.

  The dimensions of the groove 12b were measured at a total of five locations in the cross sections S1 to S5 every 15 mm along the longitudinal direction of the groove 12b with the cross section S3 at the center of the groove 12b as the center. It described in each column of 3. The product of the depth and width of the groove 12b, that is, the variation in cross-sectional area was 0.2% or less. The variation was calculated by dividing the difference between the maximum value and the minimum value of the five cross-sectional areas calculated from the measured values in the cross sections S1 to S5 by the average value of the calculated five cross-sectional areas.

  The two SiC sintered bodies were subjected to heat treatment in a state in which the bonding surfaces were put together in a hot press furnace and pressed from a direction perpendicular to the bonding surfaces and heated to obtain a SiC bonded body.

  The dimension of the internal groove 13 was measured at a total of five locations in the cross sections S1 to S5 every 15 mm along the longitudinal direction of the internal groove 13 with the cross section S3 at the center of the internal groove 13 as the center. The measured values at each of the cross sections S1 to S5 are shown in the respective columns of FIGS. And the dispersion | variation was computed by dividing the difference of the maximum value of five cross-sectional areas calculated from the measured value in each cross section S1-S5 with the minimum value by the average value of five calculated cross-sectional areas.

〔Example〕
As shown in FIG. 2, in all Examples 1-10, the said Formula (1) and Formula (2) were satisfy | filled. Moreover, all the processing conditions at the time of heat processing were a processing pressure of 0.1 MPa or more, a heating temperature of 1500 ° C. or more, and a processing time of 10 minutes to 240 minutes.

  In all Examples 1 to 10, no voids could be observed at the bonding interface of the SiC bonded body 10.

  Moreover, about the particle size of the SiC joined body 10, the average particle diameter before and behind joining was measured by SEM observation of the cross section, and it was investigated whether the grain was growing. When the average particle diameter was measured by the line intercept method, no grain growth was observed in all of Examples 1 to 10.

  Moreover, in all Examples 1-10, the dispersion | variation in the cross-sectional area of the internal groove 13 was smaller than 1%, and it turned out that the shape precision of the internal groove 13 is very high.

[Comparative Example]
As shown in FIG. 3, in Comparative Example 1, the flatness a (μm) of the joint surfaces 11a and 12a was both greater than L / 60 (mm). In Comparative Example 1, voids were observed in the cross sections S1 and S5 near the end of the bonding interface.

  In Comparative Example 2, the flatness a (μm) of the joint surfaces 11a and 12a was both greater than 50 / t. In Comparative Example 2, voids were observed in the cross sections S1 and S5 near the end of the bonding interface.

  In Comparative Example 3, the treatment temperature during the heat treatment was 1400 ° C., which was lower than 1500 ° C. In Comparative Example 3, voids were observed in all the cross sections S1 to S5, and bonding was not possible.

  In Comparative Example 4, the treatment time during the heat treatment was 5 minutes, which was shorter than 10 minutes. In Comparative Example 4, voids were observed in the cross sections S1 and S5 near the end of the bonding interface.

  In Comparative Example 5, the applied pressure during the heat treatment was 0.05 MPa, which was smaller than 0.1 MPa. In Comparative Example 5, voids were observed in the cross sections S1 and S5 near the end of the bonding interface.

  In Comparative Example 6, the flatness a (μm) of the joint surfaces 11a and 12a was both greater than L / 60 (mm) and greater than 50 / t (mm). In Comparative Example 6, voids were observed in all the cross sections S1 to S5.

  In Comparative Example 7, the heat treatment temperature exceeded the sintering temperature of the SiC sintered body. In Comparative Example 7, the variation in the cross-sectional area of the internal groove 13 was greater than 1%, and the shape accuracy of the internal groove 13 was poor.

  DESCRIPTION OF SYMBOLS 10 ... SiC joined body, 11, 12 ... SiC sintered compact, 11a, 12a ... Joining surface, 12b ... Groove, 13 ... Internal groove.

Claims (3)

Preparing two SiC sintered bodies;
When the longest dimension of the bonded surface of the SiC sintered body is L (mm), the flatness a (μm) of the bonded surfaces of the two SiC sintered bodies satisfies a ≦ L / 60, and the center A process of polishing so as to be convex toward the part;
A process of combining the joining surfaces of the two SiC sintered bodies and treating the joining surfaces at a pressure of 0.1 MPa or more and at 1500 ° C. or more for 10 minutes or more ,
When the thickness of the SiC sintered body is t (mm), the polishing is performed so that the flatness a (μm) satisfies a ≦ 50 / t . Joining method. Method of joining SiC sintered body according to claim 1, characterized in that performing the processing at a sintering temperature below 1500 ° C. or more of the SiC sintered body. The method for joining SiC sintered bodies according to claim 1, further comprising a step of forming a groove in a joining surface of at least one of the two SiC sintered bodies.

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