JP4718397B2 - Manufacturing method of vacuum suction device - Google Patents

Description

The present invention relates to a vacuum suction device for sucking and holding a semiconductor wafer or the like when grinding a semiconductor wafer or a glass substrate for liquid crystal.

When a semiconductor wafer is transported, processed, or inspected, a vacuum suction device using a vacuum pressure is used. In order to perform uniform suction, a vacuum suction device that sucks and holds the entire surface of the semiconductor wafer with a porous body is used. It is being considered. For example, the adsorption portion of the placement portion described above is formed by joining the placement portion made of a porous body to the support portion made of a dense body with an adhesive such as resin or glass, and vacuuming from the lower suction hole. A device for fixing a semiconductor wafer is proposed (for example, Patent Document 1). In such a manufacturing method in which the mounting portion and the support portion are bonded with an adhesive, it is impossible to completely match the bonding surfaces, and the adhesive soaks into the mounting portion that is a porous body. A gap is inevitably generated in the part. For this reason, particularly when used for wafer grinding / polishing, there is a problem that the mounting deformation of the mounting portion occurs in the gap due to the pressing of the grindstone, and the processing accuracy of the semiconductor wafer deteriorates. Therefore, the present applicant completely brought the porous body and the dense body into close contact by a manufacturing method in which a porous body raw material composed of ceramic powder and glass powder of a binder material is poured into a concave support portion and molded and fired. A vacuum suction device was developed to solve the problem of gaps observed in the manufacturing method in which bonding is performed with an adhesive (Patent Document 2).

JP-A-53-090871 Japanese Patent Laid-Open No. 2005-22027

However, although the problem of the porous body and the gap has been solved, the deformation of the mounting portion made of the porous body cannot be completely eliminated. This is because the mounting portion made of a porous body has low strength, and when the vacuum in the mounting portion is increased by vacuum suction of the semiconductor wafer, the mounting surface is pushed by atmospheric pressure through the semiconductor wafer, This is because the mounting surface is deformed to sink into the concave shape. Due to this deformation, there has been a problem that the grinding accuracy of the wafer is lowered.

In addition, the wafer grinding accuracy can be improved by adjusting the axis of the wafer grinding wheel against the deformation of the mounting surface, but this operation needs to be adjusted little by little while actually grinding the wafer. For this reason, there is a problem that it is very time-consuming.

The present invention has been found to solve the above problems, and by forming the mounting surface in anticipation of deformation during vacuum suction, without complicated work such as precise adjustment of the grinding wheel shaft. This makes it possible to grind an object to be adsorbed such as a wafer with high accuracy.

A vacuum suction device manufactured by the method of the present invention has a mounting portion made of a ceramic porous body for adsorbing and holding an object to be adsorbed on a mounting surface, and an intake hole communicating with the pores of the mounting portion. and a support portion made of dense ceramic, a porous structure of the mounting section has a structure with no continuous gap to the boundary surface between the supporting portion, the mounting surface is an apex substantially at the center Convex type.

The reason why the mounting surface of the vacuum suction device of the present invention is a convex type having the approximate center as the apex is to flatten the object to be adsorbed such as a wafer by vacuum suction. That is, the deformation of the mounting surface during vacuum suction shows the largest sinking at the approximate center, and can be flattened by making the mounting surface convex in advance. The reason why the deformation of the mounting surface is larger at the center than at the outer peripheral portion is that the outer peripheral portion of the mounting portion is in close contact with the support portion made of a dense body that is not exposed to atmospheric pressure, and the wafer is mounted. It is considered that the vacuum level in the vicinity of the outer peripheral end portion is lower than that in the central portion because outside air is sucked from the outer peripheral end portion when placed on the surface and vacuum-adsorbed. Accordingly, when the wafer is actually ground and polished by making the mounting surface convex, the mounting surface becomes flat and high-precision processing of the wafer becomes easy. In addition, the precision adjustment of the grindstone shaft is almost unnecessary, and the operation can be greatly simplified. Furthermore, since the flatness of the mounting surface at the time of vacuum suction is high, the processing accuracy of an object to be sucked such as a wafer can be dramatically improved.

Moreover, the support surface surrounding the mounting surface and the mounting surface at the time of vacuum suction of the target object may be substantially flush.

In the present invention, the mounting surface and the support surface that surrounds the outer periphery of the mounting surface are generally processed, but in the present invention, when the object to be adsorbed is not vacuum-adsorbed, the mounting surface and the support portion The surface is not substantially the same surface, and the mounting surface is convex, whereas the support surface is a flat surface. Conventionally, the mounting surface and the support surface have been processed to be substantially the same surface, so that only the mounting surface is deformed during vacuum suction, resulting in a difference in the grinding amount between the outer peripheral edge and the center of the wafer. However, according to the present invention, the mounting surface and the support surface are substantially flush with each other at the time of vacuum suction, so that such a problem does not occur. The substantially identical planes here do not strictly require flatness, but in order to improve the grinding accuracy of the wafer, as high flatness as possible is preferable, at least the mounting surface and the outer peripheral edge of the wafer. It is desirable that the flatness of the planar adsorbent consisting of the surface of the support portion on which the portion is placed is 1 μm or less.

The present invention is a method of manufacturing the vacuum suction device, wherein the suction target is adsorbed on the surface of the mounting part at a degree of vacuum such that the target object is in close contact with the surface of the mounting part. The difference between the height of the surface of the mounting portion and the height of the surface of the mounting portion when the adsorbed body is adsorbed to the surface of the mounting portion at a vacuum level higher than the vacuum level in a plurality of points. By measuring, the step of measuring a sinking amount distribution representing a change mode of the difference according to the difference in the position of the surface of the mounting portion in the use vacuum degree, and the concave shape obtained from the sinking amount distribution is inverted. And a step of processing the surface of the mounting portion into a convex shape to form a mounting surface.

The flatness of the mounting surface under the specified conditions can be improved by measuring the deformation amount under the use conditions in advance and processing into a shape corresponding to the deformation amount. Although the amount of deformation can be predicted to some extent from the physical property value of the mounting portion, the amount of deformation may be different even if the shape is actually the same. This is because, as described above, the sinking deformation of the mounting surface is due to factors such as adhesion to the supporting portion of the outer peripheral portion of the mounting portion and airtightness when the wafer is mounted.

Further, the vacuum suction device of the present invention processes the surface of the mounting unit while maintaining the inside of the mounting unit at a use vacuum degree, and a step of infiltrating and solidifying the liquid into the surface layer of the mounting unit to make it airtight. It can also be obtained by a manufacturing method including a step of setting a mounting surface and a step of removing the liquid.

According to this manufacturing method, since the mounting surface can be formed under the same conditions as when the wafer is vacuum-sucked, the flatness of the wafer can be further increased. Here, various liquids such as a thermosetting resin such as an acrylic resin, a thermoplastic resin such as an epoxy resin, wax, wax, and water can be used as the liquid to be infiltrated into the surface layer of the mounting portion. The viscosity of the liquid is adjusted by increasing the solid content or using a thickener or the like so as to remain on the surface layer of the mounting portion. The thickness of the surface layer into which the liquid permeates and solidifies is preferably as thin as possible within a range where the surface of the mounting portion can be hermetically sealed. This is because if the thickness is too thick, the sinking deformation of the mounting portion becomes small, which is not preferable. Therefore, the thickness of the surface layer is desirably 20% or less of the placement portion thickness. When water is used, it is good to grind while cooling so that the ice does not melt when grinding the mounting surface. As a method of removing the liquid solidified on the surface layer, a method of dissolving in a solvent or vaporizing by heating can be employed.

Furthermore, the vacuum suction device of the present invention includes a slurry adjustment step of adjusting slurry by adding water or alcohol to ceramic powder and glass powder, and a support provided with a recess in which the slurry is placed. It is preferable to produce by a manufacturing method including a slurry filling step for filling the concave portion of the portion and a firing step for firing the support portion filled with the slurry in the concave portion at a temperature equal to or higher than the softening point of the glass.

According to this manufacturing method, since a local gap does not occur between the mounting portion and the support portion, the deformation of the mounting surface during vacuum suction is constant. Moreover, the amount of sink deformation at the center of the mounting surface does not exceed 5 μm at a vacuum pressure (gauge pressure) of about −50 to −100 kPa when the wafer is normally vacuum-adsorbed. On the other hand, the deformation due to the gap in the vacuum suction device obtained by joining the conventional porous mounting part to the dense support part is not constant because the position of the gap is irregular, and the deformation amount is several tens of μm. Therefore, it cannot respond by processing the mounting surface. Therefore, in order to obtain the vacuum suction device of the present invention, it is preferable to use the present manufacturing method in which no gap is generated between the mounting portion and the support portion, and the deformation due to sinking can be suppressed to 5 μm or less. The height of the convex shape of the surface is preferably 5 μm or less. In addition, since the adhesion between the placement portion and the support portion is also good, the deformation of the placement surface during vacuum suction is the most sunk deformation at the central portion, and the reproducibility is good.

As described above, according to the present invention, the mounting surface is formed in anticipation of deformation during vacuum suction, thereby simplifying complicated operations such as precise adjustment of the grinding wheel shaft during wafer grinding, and high-precision wafer fabrication. Enables grinding.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing a schematic configuration of a vacuum suction device 1 according to an embodiment of the present invention. The vacuum suction device 1 includes a mounting part 2 made of a porous body, a support part 3 made of a dense body that supports the mounting part, and a suction part 4 formed on the support part. An intake groove 5 is provided for suctioning the entire mounting surface, and a semiconductor wafer, for example, is mounted on the mounting surface 2a as the adsorbed member W (FIG. 2). The suction hole 4 is provided on the back side of the mounting portion so as to penetrate the support portion 3 and is placed on the placement surface 2 a by being sucked by a vacuum pump (not shown) through the suction hole 4. A semiconductor wafer or the like, which is an object to be adsorbed, is adsorbed by vacuum. There is no gap that exceeds the pore diameter of the mounting portion at the bonding interface between the mounting portion 2 and the supporting portion 3, and the porous structure has a continuous structure up to the boundary surface with the supporting portion.

The mounting surface 2a has a convex shape with the approximate center 2b as an apex, and its height h is 5 μm or less. As shown in the schematic diagram (FIG. 2) in which the wafer W is placed on the placement surface 2a of the vacuum suction apparatus of the present invention by vacuum suction, the placement surface 2a is deformed by pressing by atmospheric pressure when the wafer is placed. And become flat. At this time, the mounting surface 2a and the support portion surface 3a are flush with each other, and a highly flat process is possible on the entire surface including the outer peripheral portion of the wafer.

Examples of ceramics used for the dense support portion 3 of the vacuum suction device include alumina, silicon nitride, silicon carbide, and zirconia. The mounting portion 2 is made of a composite material of ceramic powder and glass powder, and the ceramic powder is preferably the same as the ceramic used for the dense support portion from the viewpoint of thermal expansion. The thermal expansion as a whole is not limited to this as long as it is equivalent to that of the support portion.

Here, the pores of the mounting portion 2 made of a porous body communicate with each other, and the average pore diameter is 10 to 150 μm and the porosity is 20 to 50% from the viewpoint of vacuum adsorption force and surface accuracy of the mounting surface 2a. In order to obtain such a pore diameter and porosity, it is preferable to use a ceramic powder having an average particle diameter of 30 μm to 150 μm as a constituent material of the mounting portion.

Next, it is preferable to use a glass whose thermal expansion coefficient is smaller than that of the ceramics which are the other constituent components of the supporting portion and the mounting portion. The reason for this is that by using low thermal expansion glass, it is possible to eliminate the gap at the interface between the porous body after sintering and the support member, and to the glass having a role as a binder in the porous body. This is because a state where compressive stress is applied is desirable.

In the present invention, it is preferable that the average particle diameter of the glass powder as the constituent material of the placement portion is smaller than the average particle diameter of the ceramic powder as the other constituent material of the placement portion. The reason is that if the average particle size of the glass powder is larger than that of the ceramic powder, filling of the ceramic powder is hindered, and thus firing shrinkage occurs when sintering at a glass softening point or higher. The average particle size of the glass is preferably 1/3 or less, more preferably 1/5 or less, of the average particle size of the ceramic powder.

The amount of the glass powder to be added is not particularly limited, but a small amount is desirable because when it is added in a large amount as in the case where the particle size of the glass powder is large, filling of the ceramic powder is inhibited and firing shrinkage occurs. However, if the amount is too small, the bonding strength of the ceramic powder is lowered, and problems such as degranulation and chipping occur, so an amount that exhibits the bonding strength is required. Specifically, it is adjusted in consideration of the target porosity, the particle size of the ceramic powder, the firing temperature, the glass viscosity, etc., but it is generally desirable to add and mix about 5% to 30% by mass with respect to the ceramic powder. .

Next, the manufacturing method of the vacuum suction apparatus 1 of this invention is demonstrated. First, water or alcohol is added to and mixed with alumina powder and glass powder, or silicon carbide powder and glass powder, which are raw material powders of the porous body forming the mounting portion 2, 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. In consideration of the particle size of the ceramic powder and the addition amount of the glass powder, the addition amount of water or alcohol is adjusted so as to obtain a desired fluidity.

Next, mounting of the ceramic support 3 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 the placement portion is formed. At this time, it is advisable to apply vacuum defoaming for removing residual bubbles and vibration for enhancing filling as necessary. Moreover, the suction part 4 and the space | gap 5 are obstruct | occluded by burning-off members, such as a wax and resin, before pouring the mixture used as a mounting part.

Next, after fully drying the support part which filled the slurry with the recessed part, it baked at the temperature more than the softening point of glass. At this time, if the firing temperature is lower than the softening point of the glass, sufficient integration cannot be achieved. On the other hand, if the firing temperature is too high, deformation or shrinkage occurs.

After firing the mounting part, the above-mentioned surface of the mounting part and the surface of the support part are subjected to surface grinding and measurement of the sinking amount distribution. For the grinding of the surface of the mounting portion and the surface of the support portion, a commonly used method such as a diamond grindstone can be adopted. The amount of sinking distribution is measured using an adsorbent such as a semiconductor wafer, a ceramic dummy wafer, a metal sheet, or a resin sheet that follows the deformation of the surface of the mounting part using the surface of the mounting part subjected to planar processing. The height of the surface of the mounting portion when the wafer is adsorbed at a degree of vacuum (e.g., -5 kPa; gauge pressure) such that the object to be adsorbed is in close contact with the mounting surface, and the degree of vacuum used during wafer grinding (e.g.,- The difference from the height of the surface of the mounting portion when adsorbed at 100 kPa) can be performed by measuring an arbitrary number of points with an electric micrometer.

Next, the measured deformation amount is mapped, and the surface of the mounting portion is ground and polished by a known method such as surface grinding or lapping to obtain a mounting surface 2a. At this time, the mapping data may be smoothed so that the surface of the mounting portion can be easily processed.

In addition, as described above, the surface of the mounting unit is infiltrated and solidified by liquid, and then the mounting unit surface is ground and the mounting surface is ground while keeping the inside of the mounting unit at a use vacuum degree. It can also be produced by removing the solidified liquid by solvent or heating.

Hereinafter, the present invention will be described in detail by way of examples and comparative examples of the present invention.
(Example 1) Alumina powder (average particle size 125 μm), glass powder (borosilicate glass, average particle size: 20 μm, thermal expansion coefficient 40 × 10 ⁻⁷ / ° C., softening point 800 ° C.) and distilled water 100: 20 After mixing at a mass ratio of 20 and kneading using a mixer, the slurry was 350 mm in outer diameter and 20.5 mm in height (recess inner diameter 298 mm, depth 5.5 mm; cutting allowance approximately 0.5 mm, intake hole diameter and After casting on a dense alumina support (thermal expansion coefficient: 8.0 × 10 ⁻⁶ / ° C.) having a suction groove width of 2 mm, vacuum defoaming was performed, and vibration was applied for sedimentation. After drying at 100 ° C., firing was performed at 1000 ° C. Next, the surface was ground with a diamond grindstone to obtain a placement portion surface. The amount of sinking distribution is measured when the wafer (diameter 300 mm, thickness 800 μm) is brought into close contact with the surface of the mounting part at a vacuum level of −5 kPa and when the wafer is adsorbed at a vacuum degree of −100 kPa in the thickness direction of the mounting part. The quantity was measured at an arbitrary 100 points with an electric micrometer and mapped. The sinking amount at the approximate center of the surface of the mounting portion was 4.8 μm, the sinking amount decreased toward the outer periphery, and no sinking was observed at the outer peripheral end. Based on the mapping, surface grinding was performed using a # 800 diamond grindstone to obtain a convex mounting surface having a height of approximately 4.8 μm at the center and a flat support surface. A wafer grinding test was conducted using the obtained vacuum suction device. A semiconductor wafer (diameter: 300 mm, thickness: 800 μm) vacuum-adsorbed at a vacuum level of −100 kPa (diameter: 300 mm, thickness: 800 μm) is ground by 100 μm using a # 800 diamond grindstone, and then the wafer interference is measured using a laser interference type shape measuring instrument. The flatness was measured. 30 sheets were ground and the flatness was 1.0 μm or less. Adjustment of the grindstone shaft was very easy compared to the prior art.

(Example 2) In the same manner as in Example 1, after placing the raw material for the placement portion into the concave portion of the dense alumina support portion having the same shape and firing, the surface of the placement portion was formed by grinding. Next, a room temperature curable epoxy resin was applied to the surface layer of the mounting portion and allowed to solidify. The surface of the mounting portion was flattened using a # 800 diamond grindstone while vacuuming the inside of the mounting portion to maintain a vacuum degree of −100 kPa, and then the epoxy resin was dissolved and removed using acetone. The shape of the obtained mounting surface was a convex shape having a height of 4.7 μm with the approximate center as the apex. When a wafer grinding test was performed in the same manner as in Example 1, 30 wafers were ground, and the flatness was 1.0 μm or less. Adjustment of the grindstone shaft was very easy compared to the prior art.

(Comparative Example) A vacuum suction device having the same shape as the example except for the mounting surface was produced. The mounting surface was not convex, and the surface of the mounting portion and the surface of the supporting portion were subjected to surface grinding using a # 800 diamond grindstone to obtain flat mounting surfaces and the surface of the supporting portion. When a wafer grinding test was performed under the same conditions as in the example, 30 wafers were ground, and the flatness was all greater than 1.0 μm. Compared to the embodiment, the axis adjustment took much time and the wafer grinding accuracy was also poor.

It is a schematic cross section which shows schematic structure of the vacuum suction apparatus of this invention. It is a schematic cross section which shows schematic structure at the time of semiconductor wafer mounting of the vacuum suction apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Vacuum suction apparatus 2; Mounting part 2a; Mounting surface 3; Support part 3a; Support part surface 4; Intake hole 5; Intake groove 2b; W: Adsorbent

Claims (2)

The mounting portion includes a mounting portion made of a ceramic porous body for adsorbing and holding an object to be adsorbed on the mounting surface, and a support portion made of dense ceramic having an intake hole communicating with the pores of the mounting portion. The manufacturing method of the vacuum suction device, wherein the porous structure of the mounting portion has a structure without a continuous gap to the boundary surface with the support portion, and the mounting surface is a convex shape having the approximate center at the top. ,
When the adsorbent is adsorbed on the surface of the mounting part at a degree of vacuum such that the adsorbent adheres to the surface of the mounting part, the height of the mounting part surface is higher than the vacuum level. the difference between the height of the mounting table surface when said adsorbed on the mounting table surface the attracted body at a vacuum degree, by measuring at a plurality of points, part surface before described in the use vacuum Measuring a sinking amount distribution representing a change mode of the difference according to a difference in position of
And a step of processing the surface of the mounting portion into a convex shape obtained by inverting the concave shape obtained from the sink amount distribution to form a mounting surface. The method of claim 1, wherein
A step of infiltrating and solidifying the liquid on the surface layer of the mounting portion to make it airtight; a step of processing the surface of the mounting portion to form a mounting surface while maintaining the inside of the mounting portion at a use vacuum level; Removing the liquid solidified on the surface layer of the part.

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