JP4885165B2 - Vacuum adsorption device - Google Patents

Description

The present invention relates to a vacuum suction apparatus that holds, for example, a semiconductor wafer or a glass substrate by suction.

Conventionally, when a substrate such as a semiconductor wafer is transported, processed, or inspected in a manufacturing process of a semiconductor device, for example, a vacuum suction device using a vacuum pressure has been used. A vacuum suction device in which a surface to be placed is formed of a porous body is used. For example, a mounting portion 11 made of a disk-shaped porous body as shown in FIG. 1 is joined to a support portion 13 made of a vessel-like dense body with an adhesive such as resin or glass, and It has been proposed that the substrate W is adsorbed on the placement surface of the placement portion by vacuum suction from the suction hole 14.

In the method of bonding the mounting portion and the support portion using such an adhesive, it is necessary to grind the bottom surface and side surface of the mounting portion, which becomes the bonding surface, and the inner surface of the support portion. There was a problem of becoming. In addition, even when the joint surface between the support part and the mounting part is processed, when the mounting part and the support part are joined, a part of the resin, glass, etc. used as an adhesive penetrates the porous body. As a result, poor adhesion occurs and bonding strength decreases, so that there is a problem that the mounting portion is detached from the support portion and the device is damaged.

Also, in vacuum suction devices used in processing equipment, grinding dust is sucked into the porous body, causing clogging, resulting in non-uniform suction, or grinding dust moving to the back of the substrate and contaminating the substrate. Therefore, it is necessary to remove clogged grinding debris. However, if there is a gap between the mounting part and the support part, even when trying to clean the porous body by injecting the cleaning liquid from the back side of the mounting part, the majority of the cleaning liquid passes through this gap, There was a problem that the porous body could not be sufficiently cleaned.

Therefore, the applicant of the present invention is a vacuum adsorption device including a mounting portion made of a porous body and a support portion made of a dense body, wherein the bonding interface between the mounting portion and the support portion is substantially A vacuum suction device that is integrally fired without a gap has been proposed (Patent Document 1). This vacuum adsorption device fills the concave part where the mounting part of the support part is formed with the slurry obtained by adding alcohol etc. to the ceramic powder and glass powder, and fires it at a temperature above the softening point of the glass It is produced by doing. According to such a method, the mounting portion and the support portion can be joined at a low cost, and the problem of the gap can be solved.
JP 2005-22027 A

However, when the substrate is processed, the grinding liquid is sucked from a slight gap between the support portion surface 13a and the substrate, and the placement portion is contaminated. In addition, since the outer peripheral portion of the mounting portion is intensively contaminated, there is a problem that it cannot be removed even after cleaning for a long time. Normally, such a vacuum suction device is used for a long period of time while the surface becomes dirty or worn to form a new mounting surface by grinding the surface. Since it cannot be used, it has been desired to prevent clogging inside the mounting portion.

On the other hand, in recent years, the processing accuracy required as the substrate has become larger and thinner has become more sophisticated, and even if the surface is clogged slightly, the adsorption force becomes non-uniform and may cause inaccuracy. Clogging of the surface as well as the inside has become a problem.

The present invention has been made in view of such circumstances, and it is an object of the present invention to prevent clogging of the porous body of the mounting portion, to exhibit a uniform adsorption force, and to extend the life of the apparatus. And

In order to solve the above-described problems, the present invention provides a mounting portion made of a ceramic porous body for adsorbing and holding a substrate;
A concave suction portion made of a ceramic porous body surrounding the mounting portion;
A suction hole communicating with the pores of the concave suction part, and a support part for supporting the concave suction part;
A vacuum adsorption device comprising:
The placing portion and the supporting portion are directly joined to the concave suction portion substantially without a gap,
The vacuum suction device is characterized in that an average pore diameter of the concave suction portion is larger than an average pore diameter of the mounting portion.

In the present invention, since the concave suction portion is provided, clogging of the placement portion can be prevented. Moreover, since the concave suction part is formed so as to surround the placing part, it is possible to prevent grinding waste from entering the placing part. Moreover, since the average pore diameter of the concave suction portion is larger than the average pore diameter of the mounting portion, the grinding dust is selectively taken into the concave suction portion and can be easily removed.

The open porosity of the mounting portion is desirably 20% to 50%, and the average pore diameter is desirably 10 μm to 50 μm. With such a porosity and an average pore diameter, the substrate can be placed with sufficient adsorption power with sufficient strength to be applied to the placement portion.

The open porosity of the concave suction part is preferably 20 to 50%, and the average pore diameter is preferably 50 μm to 200 μm. About the open porosity, the said range is suitable from an intensity | strength surface similarly to a mounting part. Since a part of the substrate is also placed on the concave suction part, a predetermined strength is required. When the open porosity is larger than 50%, the strength is weakened, and the surface accuracy of itself and the processing accuracy of the substrate are lowered. Conversely, if the open porosity is less than 20%, clogging is likely to occur when grinding waste is taken in, which is not preferable.

In addition, since the support portion of the dense body has a higher strength than the placement portion of the porous body, the portion placed on the support portion and the placement portion when the substrate is placed and processed are placed on the placement portion. There may be a step in the substrate shape after processing. In order to prevent this, a significant step can be mitigated by making the strength of the concave suction portion larger than the placement portion and smaller than the support portion. Specifically, the ceramic powder having an average particle size larger than that of the ceramic powder used also as the raw material for the mounting portion is used as the raw material for the concave suction portion to form the above-mentioned predetermined porosity so as to obtain an appropriate strength. it can.

Furthermore, the placement surface of the porous body is deformed by the placement surface being pushed by atmospheric pressure through the substrate when the substrate is sucked and placed. At this time, since the concave suction portion having higher strength than the placement portion is formed surrounding the placement portion, the deformation due to the atmospheric pressure can be suppressed.

If the average pore diameter of the concave suction portion is smaller than 50 μm, clogging of grinding dust tends to occur. On the other hand, if it is larger than 200 μm, the substrate may follow the pores when the substrate is adsorbed, which may cause a processing defect.

The concave suction part can remove grinding dust generated when the substrate is ground after being taken into the concave suction part. The grinding scraps are taken in when the substrate is placed and sucked, and the grinding scraps may be removed simultaneously with the suction or separately during the cleaning.

As described above, according to the vacuum suction device of the present invention, by preventing clogging of the porous body of the mounting portion, a uniform suction force can be exhibited and the life of the device can be extended.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a silicon substrate will be taken up for explanation.

FIG. 2 is a schematic sectional view of the vacuum suction device 20 of the present invention. The vacuum suction device 20 includes a disk-shaped mounting portion 21, a concave suction portion 22 provided so as to surround the entire mounting surface 21 a of the mounting portion 21, and the mounting portion 21 and the concave suction portion 22. And a vessel-like support portion 23 for supporting the above. As shown in FIG. 2, the silicon substrate W is sucked and held by the vacuum suction device 20 so as to cover the placement surface 21a, the annularly exposed concave suction portion surface 22a, and a part of the support portion surface 23a.

The open porosity of the mounting portion 21 is preferably 20% or more and 50% or less, and the average pore diameter is preferably 10 μm or more and 50 μm or less. The reason why the open porosity of the mounting portion 21 is in such a range is that if it is within the above range, the pressure loss becomes large and it becomes difficult to obtain sufficient adsorption force, or sufficient mechanical strength is obtained. This is because it cannot be obtained or the flatness of the mounting surface 21a is not lowered. In addition, the average pore diameter is set in the above range. If the average pore diameter is less than 10 μm, the pressure loss may increase and the adsorption force may be weakened. Conversely, if the average pore diameter exceeds 50 μm, the surface accuracy of the mounting surface 21a may be deteriorated. Because there is.

The mounting part 21 and the concave suction part are made of a ceramic porous body. These are composed of a predetermined ceramic powder and a glass of a binder, and have a porous structure having open pores communicating therewith. For the ceramic powder, for example, alumina, zirconia, silicon carbide, silicon nitride or the like can be used.

The softening point of the glass used for the mounting part 21 is preferably equal to or lower than the softening point of the glass used for the concave suction part 22. Since the concave suction part 22 is formed first, the glass contained in the concave suction part is remarkably softened and melted during firing for forming the placement part 21 so as not to be deformed or contracted. is there. For example, an aluminosilicate glass having a softening point near 1000 ° C. can be selected as the glass of the concave suction section, and a borosilicate glass having a softening point of 900 ° C. or less can be selected as the glass of the placement section. Further, the same ceramic powder as the placement portion 21 can be used for the ceramic powder of the concave suction portion 22.

It is desirable that the Young's modulus of the concave suction part 22 is larger than the Young's modulus of the placement part 21 and smaller than the Young's modulus of the support part 23. With such a configuration, it is possible to relieve a step generated in the processed substrate shape between a portion placed on the support portion and a portion placed on the placement portion when the substrate is processed. Specifically, the ceramic powder having an average particle size larger than that of the ceramic powder used also as the raw material for the mounting portion is used as the raw material for the concave suction portion to form the above-mentioned predetermined porosity so as to obtain an appropriate strength. it can.

The width of the concave suction part surface 22a is 4 mm or more and 2 to 25%, more preferably 10 to 18% of the substrate radius. If this width is too large, the surface accuracy is lowered, and if it is too small, grinding scraps easily enter the mounting portion, so that the removal function is lowered. If it is in such a range, there will be almost no fall of surface accuracy, and since grinding waste can also be removed, it will become possible to use it for a long time. The thickness of the concave suction part facing the suction hole side is desirably 5 mm or more for the same reason. About the thickness of the mounting part, it is used while grinding the mounting surface, so if it is thick, it can be used for a long time, but if it is too thick, deformation due to atmospheric pressure becomes large and undesirable, so it should be within 20 mm Is preferred.

As the ceramic powder of the mounting portion 21, a powder of 30 to 180 μm can be used, and as the ceramic powder of the concave suction portion, a powder of 180 to 1000 μm can be used. In order to make the average pore diameter of the concave suction part larger than the average pore diameter of the mounting part, it is preferable to use a material ceramic powder larger than the mounting part.

The material of the support portion 23 is not particularly limited, and ceramics such as alumina, zirconia, silicon carbide, and silicon nitride are used. However, from the viewpoint of thermal expansion, it is preferable to use the same ceramic powder as the placement portion.

A suction hole 24 is provided in the support portion 23. The suction hole can be used for injecting the cleaning liquid into the porous body in addition to the function of vacuum suction by connecting to a vacuum source such as a vacuum pump. In addition, since the grinding fluid containing grinding scraps is also sucked in during vacuum suction, a trap or the like may be provided between the vacuum source and these may be removed. As a matter of course, a suction hole, a cleaning liquid injection hole, and a hole for removing grinding dust may be provided separately. The arrangement of the suction holes is not particularly limited as long as a sufficient and uniform vacuum suction force can be obtained. The same applies to the case of forming suction grooves in addition to the suction holes, and various shapes such as concentric circles arranged at predetermined intervals, those arranged radially, and combinations of circular grooves and radial grooves can be adopted. .

Next, the manufacturing method of the vacuum suction apparatus 20 of this invention is demonstrated.
First, water or alcohol is added to and mixed with ceramic powder and glass powder, which are raw materials for the ceramic porous body forming the concave suction portion 22, to prepare a slurry. For mixing the raw materials, a known method such as a ball mill or a mixer can be applied. Here, the amount of water or alcohol is not particularly limited, but the amount of water or alcohol added is adjusted so that desired fluidity can be obtained in consideration of the particle size of the ceramic powder and the amount of glass powder added. The amount of the ceramic powder and the glass powder is adjusted in consideration of the target open porosity, the particle size of the ceramic powder, the firing temperature, the glass viscosity, and the like. It is desirable to add in the range of 30 parts by mass.

Next, the concave suction portion of the ceramic support portion 23 produced by a known molding method such as CIP molding or cast molding, a known firing method such as electric furnace firing or hot press, and a known grinding method using a diamond grindstone or the like. The slurry is filled in a recess (not shown) in which is formed. At this time, it is preferable to apply vacuum defoaming for removing coarse bubbles in the slurry and vibration for enhancing the filling as necessary. In addition, the suction hole 24 is closed by a burned-out member such as wax or resin before pouring the mixture serving as the placement portion. The support portion may be provided with a suction groove so that vacuum suction can be performed smoothly.

After the slurry is filled in the concave portion of the support portion and sufficiently dried, it is fired at a temperature equal to or higher than the softening point of the glass. At this time, if the firing temperature is lower than the softening point of the glass, the glass does not melt and the ceramic powder cannot be bonded. Conversely, if the firing temperature is too high, deformation or shrinkage occurs. Thus, it is desirable to fire at as low a temperature as possible.

Next, a counterbore process for forming the placement portion 21 is performed. A known method using a machining center or the like can be applied to the counterboring process.

The mounting part 21 is produced by filling a slurry of ceramic powder and glass powder in the same manner as the concave suction part 22. At this time, by filling the pores of the concave suction portion with a disappearing member such as a resin, it is possible to prevent a problem that the ceramic powder and the glass powder of the mounting portion enter the pores.

After the mounting portion is fired at a temperature equal to or lower than the firing temperature of the concave suction portion, the mounting surface 21a, the concave suction portion surface 22a, and the support portion surface 23a are ground so as to be substantially flush with each other. Processing. Grinding can be performed by a commonly used grinding method such as a diamond grindstone.

A vacuum suction apparatus was produced by the above-described manufacturing method. The produced vacuum suction device has a mounting portion diameter of 250 mm, a thickness of 5 mm, a concave suction portion diameter of 298 mm, a concave suction portion surface 22 a width of 24 mm, a concave suction portion thickness facing the suction hole side of 15 mm, The overall diameter is 350 mm and the thickness is 25 mm. Alumina sintered body (Young's modulus 390 GPa) is used as the support, and alumina powder (average particle size 125 to 2000 μm) and glass powder (aluminosilicate glass, average particle size 5 to 20 μm, softening point 950 ° C.) After forming the concave suction part made of the material, counterbore processing is performed, and the placing part is similarly alumina powder (average particle size 40 to 180 μm) and glass powder (borosilicate glass, average particle size: 2 to 10 μm, Softening point 650 ° C.). The average particle size of the ceramic powder is based on laser diffraction particle size distribution measurement.

Table 1 shows the average pore diameter of each mounting part and the concave suction part, the open porosity, and the results of evaluating the silicon substrate by vacuum adsorption for each of the produced vacuum adsorption apparatuses. For the open porosity, five samples of about 10 × 10 × 10 mm were cut out from each part and measured by Archimedes method, and the average pore diameter was measured by mercury intrusion method using the same sample.

The evaluation of the grinding results was performed by grinding a silicon substrate (diameter 300 mm, thickness 800 μm) vacuum-adsorbed at a vacuum degree (gauge pressure) of −50 kPa using a 800-th diamond grinding stone, and then the outer peripheral edge of the substrate The difference in thickness between the center part and the central part was 1 μm or less. In the grinding scrap removal test, after a grinding liquid containing grinding scraps was allowed to flow for 10 minutes from above the adsorbed substrate, the process of flowing the cleaning liquid from the suction hole side to the porous body was repeated 10 times, and then the vacuum suction device was After slicing and observing the cross section, good (◯) and bad (×) were relatively evaluated according to the degree of clogging.

Good results were obtained for production Nos. 1 to 5 within the scope of the present invention.

On the other hand, in Production No. 6, which is outside the scope of the present invention, the same porous material was used for the placement portion and the concave suction portion, so that grinding dust was not removed and no improvement in processing accuracy was observed. In Production No. 7 having a low porosity of the concave suction portion, although the grinding accuracy was good, the contamination with grinding dust was remarkable. In the case of such an apparatus, even if the accuracy at the beginning of grinding is good, it cannot be applied because the accuracy decreases as the usage time elapses. In Production No. 8 in which the pore diameter of the concave suction portion was large, the substrate portion on the concave suction portion followed the pores, resulting in poor grinding, resulting in poor processing accuracy. Further, along with this, a gap on the surface of the support portion was increased, so that a large amount of grinding fluid flowed in and the grinding dust was significantly contaminated. In production No. 9 where the porosity of the concave suction part is large and the Young's modulus is low, the step formed near the boundary between the concave suction part and the support part is large. And the mounting part was contaminated.

The schematic sectional drawing of the conventional vacuum suction apparatus. The schematic sectional drawing of the vacuum suction apparatus of this invention.

Explanation of symbols

20: Vacuum suction device 21: Placement part 21a: Placement surface 22: Recessed suction part 22a: Recessed suction part surface 23: Support part 23a: Support part surface 24: Suction hole W: Silicon substrate

Claims (4)

A mounting portion made of a ceramic porous body for adsorbing and holding a substrate;
A concave suction portion made of a ceramic porous body surrounding the mounting portion;
A suction hole communicating with the pores of the concave suction part, and a support part for supporting the concave suction part;
A vacuum adsorption device comprising:
The placing portion and the supporting portion are directly joined to the concave suction portion substantially without a gap,
A vacuum suction device, wherein an average pore diameter of the front concave suction portion is larger than an average pore diameter of the placement portion. 2. The vacuum adsorption device according to claim 1, wherein the placement portion has an open porosity of 20% to 50% and an average pore diameter of 10 μm to 50 μm. The vacuum suction device according to claim 1 or 2, wherein the concave suction portion has an open porosity of 20 to 50% and an average pore diameter of 50 µm to 200 µm. The method of using the vacuum suction device according to claim 1, wherein grinding scrap generated when the substrate is ground is removed after being taken into the concave suction portion.

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