JPS594045A - Vacuum attracting and fixing means - Google Patents

Abstract

PURPOSE:To prevent wearness and missing of chuck table by closely attaching the circumferential part consisting of a material which does not allow the air to pass through to the chuck table. CONSTITUTION:The circumferential part of chuck table 21 formed with a porous material is surrounded by the circumferential part 20 consisting of a material which is sufficiently dense and does not allow the air to pass through. The circumferential part 20 is so formed that it is closely attached to the table 21. Since such a circumferential part 20 is provided, the table 21 is attracted by a vacuum chamber 19 at the time when air is exhausted from an exhaustion duct 15 and a wafer 12 is attracted and fixed to the table 21. In such a structure, the grinding liquid penetrates into the table 12 with a reduced degree and since the external edge of wafer 12 is placed on the surface of circumferential part 20, wearness and missing of table 21 is little generated. Accordingly, the wafer 12 is not broken or does not generate missing of a part thereof.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to a vacuum suction and fixing device, and more particularly to a chuck table for suctioning and fixing a thin substrate such as a semiconductor wafer in a process of cutting it under vacuum.

(2) Background of the technology In the manufacturing process of semiconductor devices, wafers with a thickness of, for example, about 625 μm are subjected to wafer processes such as exposure, heat treatment (1), vapor deposition, and chemical vapor deposition (CVD).
e.g. 490 μm before final assembly.
The cutting is performed on the back side of the various devices opposite the surface on which they are made.

A vacuum suction and fixing device for cutting a wafer will be explained with reference to the schematic cross-sectional view of Fig. 1.
2 is a wafer to be cut, which is placed with its back side up on a chuck table 11 made of porous material of a vacuum suction fixing device IO, and the device 10 is mounted on a rotating turntable 1. . Cup wheel for cutting (
A grindstone 6 is placed above the turntable 1 and rotates at high speed in the direction shown by the arrow. In the figure, 3 is a motor, 2 is a spindle, 4 is a driving means for moving the spindle 2 up and down, and 5 is a stand. Motor 3 is inside spindle 2.
A mechanism for transmitting the rotation to the cup wheel 6 is built-in. Note that the dashed-dotted line in the figure indicates the center line of the turntable l.

(2) The turntable 1 has a structure as shown in the schematic plan view of FIG.
The turntable 1 and the cup wheel 6 rotate in the directions shown by the arrows. Note that in FIG. 2 and subsequent figures, the same parts as those already shown are designated by the same reference numerals.

The vacuum suction fixing device 10 has the configuration shown in the cross-sectional view of FIG. 3, and consists of a lower table 16 and an upper table 18 that are integrally fixed by a fixing means 17, and a porous chuck table is placed on the upper table 18. The wafer 12 is suctioned and fixed onto the chuck table 11 by evacuating the vacuum chamber 19 by evacuating the exhaust duct 15 in the direction shown by the arrow in the figure. In order to maintain a vacuum, the outer periphery of the chuck table 11 is coated with a plastic wall 13, and in addition, a sealing plastic 14 is impregnated along the outer edge of the chuck table 11.

(3) Prior Art and Problems Wafer cutting in the prior art will be explained with reference to the cross-sectional view in Fig. 4.As seen in the figure, (3) the top surface of the wafer 12 is the back surface to be cut, and it is indicated by the arrow. When the cup wheel 6 is moved in the direction shown, the tooth tip 7 of the cup wheel 6 picks up the wafer, e.g.
Cut approximately 00μm. At this time, 12' of the wafer 12
The portion indicated by is fractured, and the surface 12 is formed flat to a degree close to mirror finish. Note that the portion indicated by 8 in the figure is a cup that holds the tooth tips 7, and the cup wheel 6 is connected to the spindle 2 via a shaft 9. The one-dot chain line indicates the center line of the cup wheel. Returning to FIG. 1, when the force ``■'' acts in the direction of the arrow due to evacuation, the force ``■'' is decomposed into a lateral (horizontal) force F2, an upward force Fl, and -. In experiments using the illustrated apparatus, it has been confirmed that F2>Fl, and since such a force relationship holds, it is possible to cut a wafer as shown in FIG. 4.

When the above-mentioned cup wheel is used for a long period of time (wafer cutting), the polishing liquid used for cutting may seep into the chuck table 11, and the wafer 12
The outer edge of the chuck table 11 may be worn out or fall off due to contact between the chuck table 11 and the chuck table 11, which may cause the outer circumference of the pull 11 to deform and crack or chip the wafer. Even though the outer edge of the chuck table was impregnated with plastic, there was a vacuum leak, which resulted in insufficient wafer suction.

Among these failures, if the wafer is cracked or chipped, the loss is significant because the wafer process has already been completed for the wafer.

(4) Purpose of the Invention In view of the above-mentioned conventional problems, the present invention provides a vacuum suction system that has a chuck table that has sufficient suction force to the wafer, does not damage the wafer, and does not wear out or break itself. To provide a fixation device.

(5) Structure and object of the invention According to the present invention, a chuck table is provided whose periphery is closely surrounded by an outer periphery of a high-strength metal or ceramic material that does not allow air to pass through. This is accomplished by providing a vacuum suction (5) means configured to engage the upper table of the device.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 5 shows a vacuum suction fixing device according to the present invention in cross section, and this device 30 has the following features except for the chuck table 21 (the other parts are similar to the conventional device shown in FIG. 3).
The same parts as those already shown are designated by the same reference numerals, and since the configuration and function of each part are exactly the same as in the conventional device, detailed explanation thereof will be omitted.

In the illustrated embodiment, the periphery of the chuck table 21, which is made of porous material (e.g. ceramic), is surrounded by an outer periphery 20 made of a strong, sufficiently dense and airtight metal. The outer peripheral portion 20 is formed so as to adjoin the chuck table 21 very closely. The material for the outer peripheral portion 20 may be any material that satisfies the above conditions, and ceramics that do not allow air to pass through may also be used. As can be understood from the figure, in order to maintain closeness between the chuck table 21 and the outer circumference 20, the lower part of the outer circumference 20 is connected to the upper table 20.
8 and (6) engage with each other, and the central portion thereof forms a step inward, and this step portion engages with the lower portion of the two-chuck table 21. Further, the dimensions of the outer periphery of the wafer placed on the chuck table 21 are set so that the outer periphery of the wafer rests on approximately the center of the upper surface of the outer periphery 20.

By providing the outer peripheral portion 20 as described above, when exhausting from the exhaust duct 15, the chuck table 21 is attracted by the vacuum chamber 19, and since the chuck table 21 is porous, the wafer 12 is not directed toward the chuck table 21. It is absorbed and fixed. The above-described configuration of the wafer 12, chuck table 21, and outer circumferential portion 20 reduces the possibility of polishing liquid seeping into the chuck table, and since the outer edge of the wafer rests on the hard surface of the outer circumferential portion 20, wear of the chuck table is reduced. , almost no shedding occurs,
The wafer is always placed flat on the flat chuck table 21, and the suction force acts uniformly on the entire wafer, thereby significantly reducing the risk of cracking or chipping the wafer.

Furthermore, since the structure of the outer periphery consists of only two steps (7) and the material is metal or ceramic, there are no particularly difficult problems in manufacturing compared to the case of the prior art.

(7) Effects of the Invention As explained in detail above, in the vacuum suction fixing device according to the present invention, abrasion of the chuck table is prevented by surrounding the chuck table with an outer peripheral part made of metal or ceramic that is in close contact with the chuck table. In addition, since the chamfer and two-cut chip are always kept flat and perfect, damage such as cracking of the wafer is avoided, which is highly effective in improving the manufacturing yield of semiconductor devices. Note that although the above description has been made using cutting of a wafer as an example, the scope of application of the present invention is not limited thereto, and extends to apparatuses used for processing substrates other than wafers.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a wafer cutting device, and Figure 2 is a schematic cross-sectional view of a wafer cutting device.
FIG. 3 is a schematic sectional view of a conventional vacuum suction and fixing device (8), FIG. 4 is a schematic sectional view showing wafer cutting, and FIG. 5 is a plan view of a turntable used with the device shown in the figure. FIG. 3 is a sectional view of such a vacuum suction fixing means. 1-turntable, 2-spindle, 3-motor, 4
・-・Drive means, 5 one unit, 6-cup wheel, 7-tooth tips, 8-cups, 9-shafts, 10.30-・vacuum suction fixing device, 1
1.21--Chuck table, 12--Wafer,
13--Plastic cover, 14--Sealing plastic, 15--Exhaust duct, 16-Lower table, 1
7-Fixing means, 18--Upper table, 19--Vacuum chamber, 20-Outer peripheral part 201 Fig. 1 Fig. 2 Fig. 3

Claims (1)

[Claims] A vacuum suction and fixing means configured to evacuate a vacuum chamber formed on the upper table by an upper table and a lower table fixed together, and for suctioning and fixing a substrate to be processed on a porous chuck table provided on the upper table, The outer periphery of the chuck table is surrounded by an outer periphery that is made of a material that does not easily allow air to pass through, engages with the chuck table and the upper table, and is provided closely to the chuck table. Device.