JP2008028170A - Vacuum suction device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum suction device capable of grinding a wafer into a very flat surface. <P>SOLUTION: The device is provided with a placing section 2 for sucking and holding a workpiece to be sucked and made of a ceramic porous body, and a supporting section 3 made of dense ceramic and having air inlet ports 4 and/or air inlet trenches 5 communicating to air pores of the placing section. The placing section has a thickness t of 2 mm-6 mm. Further, the diameter of each air inlet port 4 and the width of each air inlet trench 5 are smaller than the thickness t of the placing section, the sinking quantity of the placing section in sucking and holding the workpiece W to be sucked is not more than 3 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

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, see Patent Document 1).

JP-A-53-090871

In bonding with an adhesive such as glass, the bonding surface cannot be completely adhered, and there is inevitably a gap. Therefore, when processing an object to be adsorbed such as a wafer, a mounting made of a porous material is used. The portion is bent and deformed in the gap portion, and the processing accuracy of the wafer or the like is lowered. Such bending deformation becomes prominent when the thickness of the porous body is reduced, so that the mounting portion is inevitably thick.

However, if the thickness of the porous body of the mounting section is large, even if the bonding state between the support section and the mounting section is good, the atmospheric pressure applied to the mounting surface during vacuum suction of the target object such as a wafer In addition, since the compression deformation occurs due to the pressing of the grindstone at the time of grinding the adsorbent, the grinding accuracy cannot be increased.

The present invention has been found to solve the above-described problems, and an object of the present invention is to provide a vacuum suction device capable of reducing the deformation of the mounting portion and grinding an object to be adsorbed such as a wafer with high accuracy. And

That is, the vacuum suction device of the present invention has a dense portion having a placement portion made of a ceramic porous body for adsorbing and holding an object to be adsorbed, and an intake hole and / or an intake groove communicating with the pores of the placement portion. A vacuum suction device including a supporting portion made of ceramics, wherein the mounting portion has a thickness of 2 mm or more and 6 mm or less.

Thereby, the atmospheric pressure at the time of vacuum suction and the compression deformation due to the pressing of the grinding wheel can be reduced, and the grinding accuracy of the adherend such as a wafer can be dramatically increased. The reason why the thickness of the mounting portion is 2 mm or more is that if it is smaller than 2 mm, local deflection occurs in the intake holes and the groove portions. The reason why the thickness of the mounting portion is set to 6 mm or less is that when the thickness is larger than 6 mm, the compressive deformation increases as described above.

Further, the present invention is characterized in that the diameter of the intake hole communicating with the support portion and the groove width of the intake groove are smaller than the mounting portion thickness.

Since the mounting portion in the vacuum suction device of the present invention is small in thickness, it tends to bend and deform locally locally at the portion communicating with the suction hole and the suction groove of the support portion. By making the groove width smaller than the placement portion thickness, the bending deformation can be suppressed to a slight amount. Therefore, it is desirable to reduce the hole diameter of the intake hole and the width of the intake groove within a range where a desired vacuum suction force can be obtained, but considering the ease of processing and strength of the support portion, the diameter of the intake hole and the width of the intake groove are 0.3 mm or more is preferable. This is because processing to be smaller than 0.3 mm is difficult and a crack may occur in the support portion. The intake hole is essential for vacuum suction, but the intake groove can be eliminated as necessary. That is, as long as a sufficient and uniform vacuum suction force can be obtained, only the intake holes may be used. The arrangement of the intake holes is not particularly limited as long as a sufficient and uniform vacuum suction force can be obtained. The same applies to the shape of the intake groove, and various shapes such as a concentric circle arranged at a predetermined interval, a lattice arranged, and a combination of a circle and a cross can be adopted.

In addition, the vacuum suction device of the present invention is characterized in that the sinking amount of the mounting portion when the object to be adsorbed is held by suction is 3 μm or less.

By reducing the thickness of the mounting portion and suppressing the influence of bending deformation caused by the intake holes and the intake grooves, the amount of sinking of the mounting portion can be reduced. The sinking amount of the mounting portion of the present invention can be set to 3 μm or less, and as a result, the processing accuracy of a wafer or the like can be increased.

In addition, the vacuum suction device according to the present invention includes a slurry adjustment step of adjusting slurry by adding water or alcohol to ceramic powder and glass powder, and a recess in which the slurry is placed. It is obtained by a manufacturing method comprising: a slurry filling step for filling the concave portion of the support 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. .

In the conventional manufacturing method in which the support portion and the placement portion are joined with an adhesive such as glass, a gap is inevitably formed, and the placement portion is deformed flexibly. Moreover, in order to suppress the bending deformation, the thickness of the mounting portion has to be increased. However, in the present invention, since the raw material slurry is directly filled into the concave portion where the mounting portion of the support portion is formed, no gap is generated at the bonding interface between the support portion and the mounting portion. Therefore, the thickness of the mounting portion can be reduced, and the grinding accuracy of the wafer or the like can be dramatically increased.

As described above, according to the present invention, it is possible to reduce the atmospheric pressure when the object to be adsorbed such as the wafer is vacuum-adsorbed and the deformation of the mounting portion due to the pressing of the grindstone during the grinding of the object to be adsorbed. It becomes possible to dramatically improve the grinding accuracy.

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 portion 2 made of a porous body, a support portion 3 made of a dense body that supports the mounting portion, and an intake hole 4 formed in the support portion. An air intake groove 5 is provided to suck the entire surface of the mounting portion, and a semiconductor wafer, for example, is mounted on the mounting surface 2a as the adherend W. 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.

Next, the placement surface 2a is formed by grinding together with the placement portion 2 and the support surface 3a around the placement portion. 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 vacuum-adsorbed.

Examples of the ceramic used for the dense support portion include alumina, silicon nitride, silicon carbide, zirconia and the like. The mounting part 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 part from the viewpoint of thermal expansion. However, the thermal expansion is not limited to this as long as it is equivalent to that of the support portion.

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

Next, it is preferable to use a glass having a thermal expansion coefficient smaller than that of the ceramic which is the other constituent component of the supporting portion and the mounting portion described above. 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 open porosity, the particle size of the ceramic powder, the firing temperature, the glass viscosity, and the like. desirable.

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 ceramic 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 support portion 3 of the dense ceramic 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. In addition, the air intake holes 4 and the air intake grooves 5 are closed by a burned-out member such as wax or resin before pouring the mixture that becomes the mounting portion.

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 portion, grinding is performed so that the mounting surface 2a and the support portion surface 3a are substantially in the same plane. At this time, the thickness t of the placement portion is adjusted to be 2 mm or more and 6 mm or less. The mounting surface 2a and the support portion surface 3a can be ground by a commonly used grinding method such as a diamond grindstone.

According to such a manufacturing method, since the mounting portion and the support portion are sufficiently in close contact with each other, even if the porous body of the mounting portion is thin, the porous body does not bend and deform due to the gap. . Furthermore, since processing for matching the joint surfaces of the mounting portion and the support portion is unnecessary, the dense sintered body serving as the support portion can be used as it is without being processed. Therefore, not only the wafer processing accuracy is improved, but also the manufacturing cost of the vacuum suction device can be greatly reduced.

Hereinafter, the present invention will be described in detail by way of examples and comparative examples of the present invention.
Examples 1 to 3 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 After mixing with a mass ratio of 20:20 and kneading using a mixer, the slurry was outer diameter 350 mm, height 20.5 mm (recess inner diameter 298 mm, depth 2.5, 4.5, 6.5 mm, Cast into a dense alumina support (heat expansion coefficient 8.0 × 10-6 / ° C.) with a suction hole diameter and suction groove width of 1.5 mm, vacuum degassing, and then add vibration to settle and fill. It was. After drying at 100 ° C., firing was performed at 1000 ° C. Next, the mounting surface of the vacuum suction device was obtained by grinding the surface with a diamond grindstone. The amount of grinding was adjusted so that the thickness t of the mounting portion was 2, 4, and 6 mm, respectively. Using the obtained vacuum suction device, a semiconductor wafer (diameter 300 mm, thickness 800 μm) was brought into close contact with the mounting surface by applying a negative pressure (gauge pressure) of −5 kPa, and −50 kPa (gauge pressure). The amount of displacement (sink amount) in the thickness direction of the placement portion when vacuum-adsorbed in was measured at an arbitrary 73 points on the semiconductor wafer with an electric micrometer to obtain the maximum value. In each of Examples 1, 2, and 3 (respective mounting portion thicknesses 2, 4, and 6 mm), the maximum value of the sinking amount was 3 μm or less.

(Comparative example 1) After processing the alumina porous body equivalent to an Example into a predetermined shape and setting it as a mounting part (diameter 298 mm), the mounting part is an alumina support part (outer diameter 350 mm, height 20.5 mm, A glass powder (borosilicate glass) having a softening point lower than that of the porous glass powder is inserted into a concave inner diameter of 298 mm, a depth of 4.5 mm, an intake hole diameter and an intake groove width of 1.5 mm). And an average particle diameter of 20 μm, a thermal expansion coefficient of 50 × 10 −7 / ° C., and a softening point of 650 ° C.) were glass-bonded at 800 ° C., and a mounting surface was obtained by surface polishing in the same manner as in the examples. The amount of grinding was adjusted so that the thickness of the mounting portion was 4 mm. When the semiconductor wafer was vacuum-sucked and the amount of displacement was examined in the same manner as in the above example, a sinking portion larger than 3 μm was found. When the joint between the support portion and the placement portion where the sinking amount is large was cut and observed, a gap was observed.

(Comparative Examples 2 to 4) By a method similar to that of the example, vacuum suction devices having a mounting portion thickness of 1 mm and 7 mm (Comparative Examples 2 and 3; other shapes are the same as those of Examples 1 to 3, respectively) A vacuum suction device (Comparative Example 4; other shapes are the same as those in Examples 1 to 3) having a mounting portion thickness of 4 mm and a suction hole and suction groove width of 5 mm was prepared and evaluated in the same manner. In Comparative Example 2 and Comparative Example 4 in which the intake hole and the intake groove width are larger than the mounting portion thickness, a sink larger than 3 μm was observed in a portion where the intake groove was present. In Comparative Example 3 having a mounting portion thickness of 7 mm, the amount of sinking was greater than 3 μm over most of the mounting surface.

It is a schematic cross section which shows schematic structure 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 W: Adsorbed object t;

Claims (4)

Vacuum adsorption comprising a mounting portion made of a ceramic porous body for adsorbing and holding an object to be adsorbed, and a support portion made of a dense ceramic having suction holes and / or suction grooves communicating with the pores of the mounting portion It is an apparatus, Comprising: The vacuum suction apparatus characterized by the thickness of the said mounting part being 2 mm or more and 6 mm or less. The vacuum suction device according to claim 1, wherein a hole diameter of the intake hole and a groove width of the intake groove are smaller than a mounting portion thickness. The vacuum suction device according to claim 1 or 2, wherein a sinking amount of the mounting portion when the object to be adsorbed is held by suction is 3 µm or less. A slurry adjustment step of adjusting the slurry by adding water or alcohol to ceramic powder and glass powder and mixing the slurry, and a slurry filling step of filling the slurry into the concave portion of the support portion provided with the concave portion in which the placement portion is formed And a baking step of baking the support portion in which the concave portion is filled with the slurry at a temperature equal to or higher than the softening point of the glass.

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