JPH11156712A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of efficiently carrying out flatening and purifying highly accurately by means of a compact device. SOLUTION: In this polishing device where the surface to be polished of a material to be polished and the polishing surface of a polishing table are mutually pressed to each other so as to perform polishing, while the circular shaped material to be polished and the polishing table are kept rotating, the device is provided with a primary polishing table, and the radius of the polishing table is set to be larger than the diameter of the surface to be polished, and with a secondary polishing table 42 where the radius R of a polishing surface is set to be smaller than the diameter 2r of a surface to be polished, but to be larger than its radius (r).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polishing apparatus,
In particular, the present invention relates to a polishing apparatus for polishing a material to be polished such as a semiconductor wafer into a flat and mirror-like surface.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has increased, circuit wiring has become finer, and the distance between wirings has become smaller. Accordingly, when a circuit is formed by optical lithography or the like, the depth of focus becomes shallow, so that a higher flatness of the imaging surface of the stepper is required. As a means for flattening the surface of a semiconductor wafer, a chemical-mechanical method for polishing a semiconductor wafer held by a carrier against a polishing cloth while supplying a polishing liquid containing abrasive grains to a polishing cloth stuck on a rotating polishing table. Polishing has been performed.

As a conventional polishing apparatus, as shown in FIG. 10, a turntable 112 having a cloth (polishing cloth) 111 adhered to an upper surface thereof, and a top ring 113 which presses the semiconductor wafer W against the turntable 112 while holding the semiconductor wafer W. Some have. Thus, the polishing cloth 11 on the upper surface of the turntable 112 rotating the semiconductor wafer W
1 is pressed by the top ring 113. On the other hand, by flowing the polishing abrasive Q from the polishing abrasive nozzle 114, the polishing abrasive Q is held by the polishing cloth 111, and the polishing abrasive Q is provided between the polishing surface (the lower surface) of the semiconductor wafer W and the polishing cloth 111. Polishing is performed in the presence of Q.

In this apparatus, the turntable 112 and the top ring 113 rotate at independent rotation speeds. The top ring 113 is formed such that the edge of the wafer W is separated from the center and the edge of the turntable 112 by a predetermined distance a, b to hold the wafer W at a position separated by b.
The entire surface of the wafer W is polished uniformly and at a high speed. Therefore, the diameter D of the turntable 112 is set to be at least twice the diameter d of the wafer W as shown in the following equation. D = 2 (d + a + b)

The polished wafer W is stored in a wafer transport cassette after one or several cleaning steps and a drying step in a cleaning apparatus. As a method for cleaning the wafer W, scrub cleaning in which the surface is rubbed with a brush such as nylon or mohair or a PVA (polyvinyl alcohol) sponge is performed.

[0006]

In the conventional polishing apparatus as described above, the relative displacement between the turntable 112 and the top ring 113 is large, and the relative speed thereof is large, so that efficient polishing is performed, Although a sufficient degree can be obtained, micro scratches are formed on the wafer surface by the abrasive grains.

In order to prevent this, it is conceivable that two turntables 112 are installed and polishing is performed by changing the material and hardness of the polishing pad 111, the rotation speed of the turntable 112, and the polishing liquid. However, as described above, the diameter of the turntable 112 is twice as large as that of the wafer W, occupying a large area, and increasing the apparatus cost. This disadvantage becomes more remarkable as the diameter of the semiconductor wafer increases.

On the other hand, with one turntable, for example,
It is conceivable to perform polishing by changing the polishing liquid or reducing the rotation speed. However, the performance is deteriorated by mixing different polishing liquids, and the efficiency is lowered by prolonging the polishing time.

As for the cleaning, when scrub cleaning is performed after polishing using an abrasive as described above, it is difficult to remove submicron-level particles or when the bonding force between the wafer and the particles is strong. However, there is a problem that the cleaning effect does not appear.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a polishing apparatus capable of efficiently performing advanced flattening and cleaning with a compact apparatus.

[0011]

According to a first aspect of the present invention, a surface to be polished of a material to be polished and a polishing surface of a polishing table are pressed against each other while rotating a circular object to be polished and a polishing table, respectively. In a polishing apparatus that performs polishing by
1 where the radius of the polished surface is set to be larger than the diameter of the polished surface
A polishing apparatus comprising: a next polishing table; and a secondary polishing table in which the radius of the polishing surface is set to be smaller than the diameter of the surface to be polished and larger than the radius.

In the polishing apparatus configured as described above, unnecessary portions are ground and the surface is flattened at the same high polishing rate by the primary polishing table as in the prior art, and micro-scratch removal and the like are performed by the secondary polishing table. Perform pre-cleaning. In the secondary polishing table, part of the material to be polished comes to the center of the polished surface or comes out of the polished surface.
At a certain point in time, the entire surface of the material to be polished is not polished at the same time. However, since the material to be polished is rotating, the amount of polishing at each point can be averaged. The axis of the polished material is preferably always on the polished surface so that the polished surface of the polished material does not tilt. The dimensions of the secondary polishing table are
The primary polishing table is at least twice the diameter of the workpiece and the area is 4
While it is more than doubled, it is greatly reduced.

According to a second aspect of the present invention, the holding means for holding the material to be polished can transfer the material to be polished to both the primary polishing table and the secondary polishing table. Item 4. A polishing apparatus according to Item 1. Normally, the holding means swings around a predetermined axis and moves between the polishing table and the workpiece transfer position. Therefore, the secondary polishing table is arranged on the swing locus.

According to a third aspect of the present invention, there is provided a polishing apparatus for performing polishing by pressing a polished surface of a polished material and a polishing surface of a polishing table against each other while rotating a circular polished material and a polishing table, respectively. In, the radius of the polished surface is set smaller than the diameter of the polished surface and larger than the radius, the axis of the polished surface is on the polished surface, and the axis of the polished surface and the A polishing apparatus characterized in that a distance between the polished surface and an edge is smaller than a radius of the polished surface.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the polishing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a view for explaining a first embodiment of a polishing apparatus according to the present invention. This apparatus is installed in a space on an installation floor F which is entirely rectangular.
The components are arranged symmetrically with respect to the center line C of the installation floor. That is, a pair of polishing units 10a and 10b are arranged on one end of the installation floor so as to face left and right, and the other end of the polishing unit 10a
a and 12b are placed, and a pair of secondary washing machines 14a and 14b are arranged between the load and unload units in this order from the load and unload unit side.
A pair of reversing machines 16a, 16b, a pair of primary cleaning machines 18
a, 18b, and one temporary placing table 20 is provided. 1
Paired primary and secondary washers 14a, 14b, 18a, 18
b, the reversing machines 16a and 16b are arranged to face each other with a center line interposed therebetween, and fixed robots 22 and 24 having arms connected by joints are arranged at positions on the center line therebetween. A pair of fixed robots 26a and 26b are provided on the left and right sides of the temporary placing table 20, respectively.

As shown in FIGS. 2 and 3, each of the polishing units 10a and 10b has a pusher 3 for transferring a workpiece W.
0, a top ring device 36 having two top rings 32 and 34, a turntable (primary polishing table) 38 having a polishing tool surface on its surface, and a dresser 40 for sharpening the polishing tool surface. It is arranged parallel to the center line. In this example, a polishing table (secondary polishing table) 42 for performing buff polishing (secondary polishing) is provided beside the top ring device 36.

The top ring device 36 includes a vertically extending column 50 rotatably supported by a base 48 attached to a bracket 46 projecting laterally from the base 44 of the turntable 38, and a tip of the column 50. And a pair of top rings 32 and 34 respectively attached to the ends of the turning arm 52. Top ring 3
Reference numerals 2 and 34 each have a function of adsorbing the material to be polished on the lower surface thereof, and are independently rotatable in a horizontal plane by a drive motor 56 and vertically movable by an air cylinder 58.

The turntable 38 is basically the same as the conventional one shown in FIG. 10, and is a rotatable table having a polishing cloth forming a polishing surface adhered on the upper surface thereof, and stably supports the polishing table. A support portion and a rotation driving device for rotating at high speed are provided, and an abrasive liquid supply nozzle is provided at an upper portion thereof with an opening at a predetermined position.

As shown in FIGS. 4 and 5, the buffing table 42 has a small diameter that can rotate and has a polishing cloth 80 on the upper surface thereof, which is basically a buffing surface, similar to the turntable 38. The table 82 is driven to rotate by a drive mechanism 86 provided in a housing 84. In the vicinity, a dresser 94 having an elevating mechanism 92 having a rotation mechanism 88, a swing mechanism 90, and an air cylinder 93 is installed. The dimensions of the buffing table 42 are such that the radius R of the polishing surface is smaller than the diameter 2r of the material to be polished and larger than the radius r.

In the buffing table 42, the wafer W on which the primary polishing has been performed by the turntable 38
Next, polishing is performed. This is finish polishing using an abrasive liquid containing abrasive grains or water polishing (secondary polishing) using pure water. Here, the finish polishing and cleaning are performed such that the axis of the material to be polished is located inside the outer edge of the polishing surface by a predetermined distance e. This e is a value sufficiently smaller than the radius r of the material to be polished. Therefore, as shown in FIG. 6, the surface to be polished is exposed outside the polishing table in a crescent shape having the maximum width (r−e). .

In this case, a portion having a large polishing force in the polishing surface is a portion on the outer peripheral side (effective polishing band Ep) having a high rotation speed and a large sliding distance with respect to the surface to be polished, The polishing power is reduced. On the other hand, since the material to be polished is also rotating, each part of the surface to be polished comes into contact with the effective polishing band Ep sequentially, and as a result, the polishing amount of each part of the surface to be polished is averaged.

Of course, in order to further improve the accuracy of averaging,
The distance e may be appropriately set, and the rotation speed, the polishing time, and the like of the polishing table and the workpiece may be appropriately controlled. Further, during the step of polishing one workpiece W, the correction polishing may be performed by swinging the arm 52 of the top rings 32 and 34 to adjust the distance e.

The pusher 30 is located on the side opposite to the turntable 38 with respect to the support column 50. When one of the top rings 32 (34) is at the polishing position on the turntable 38, the other top ring 34 ( 32) is located immediately above the pusher 30. Pusher 30
Is provided with a work table 60 that can be moved up and down, and assists in transferring the work between the top rings 32 and 34 and the robots 26a and 26b. A support column 64 of the dresser 40 is rotatably supported by a bracket 62 projecting from the base 44 of the turntable 38 on the side opposite to the top ring device 36.

As shown in FIG. 7, the temporary placing table 20
The upper part is a dry station 20A for placing a dry material to be polished, and the lower part is a wet station 20B for placing a wet polished material while preventing it from drying. The dry station 20A is open, but the wet station 20B is a closed type covered with a box 68 because it has the spray nozzles 66 arranged above and below the material to be polished. The material to be polished W is taken in and out.

Although the type of the washing machines 14a, 14b, 18a, 18b is arbitrary, for example, the polishing units 10a, 1
The primary cleaning machines 18a and 18b on the 0b side wipe the front and back surfaces of the semiconductor wafers with sponge-mounted rollers, and the secondary cleaning machines 14a and 14b on the cassettes 12a and 12b grip the edges of the semiconductor wafers so as to be in a horizontal plane. The cleaning liquid is supplied while rotating. The latter also has a function as a dryer for drying by centrifugal dehydration.

In this embodiment, the reversing machines 16a and 16b are necessary in relation to the storage system of the cassettes 12a and 12b and the gripping mechanism of the robot. However, the reversing machines 16a and 16b are always transferred with the polished surface of the semiconductor wafer facing downward. It is not necessary in such cases. Further, a structure in which the robot has a reversing function is not necessary. In this embodiment, the two reversing machines 16a and 16b are selectively used for handling a dry semiconductor wafer and for handling a wet semiconductor wafer.

The robots 22, 24, 26a, 26b
In this embodiment, four units are provided, each of which is of a fixed type and has a movable joint arm having a hand at the tip. The first robot 22 includes a pair of cassettes, secondary cleaning machines 14a and 14b, and reversing machines 16a and 16b.
The material to be polished is conveyed between them. Second robot 24
Transmits and receives the material to be polished between the pair of reversing machines 16a and 16b, the primary cleaning machines 18a and 18b, and the temporary placing table 20, respectively. Further, the third and fourth robots 26a, 26a, 2
6b is a temporary placing table 20, one of the primary washing machines 18a,
18b, a material to be polished is exchanged between any of the pushers 30.

In the polishing apparatus having such a configuration, both series processing and parallel processing are performed. FIG. 1 shows the flow of semiconductor wafers when parallel processing is performed using one cassette in the load / unload unit. In this description, as for a pair of elements provided with the center line C interposed therebetween, those located on the upper side in FIG. 1 are described as right and those located on the lower side as left.

The flow of the material to be polished (semiconductor wafer) in the parallel processing on the right polishing processing line is as follows. Right cassette 12a → first robot 22 → dry reversing machine 16a → second robot 24 → dry station 20A → third robot 26a → right polishing unit 10a
Pusher 30 → top ring 32 or 34 → polishing at turntable 38 → buff polishing at buff polishing table 42 → pusher 30 → third robot 26a → primary washing machine 18a → second robot 24 → wet reversing machine 16b →
First robot 22 → secondary washer 14a, 14b → right cassette 12a

The processing flow in each of the polishing units 10a and 10b will be described with reference to FIG. The pusher 30 already has the third robot 26a (or the fourth robot 26).
According to b), a new unpolished wafer is prepared. As shown in FIG. 2A, the polishing is performed while holding the wafer with the top ring 32, and during the polishing, the other top ring 3 is used.
Numeral 4 denotes an unprocessed wafer on the pusher 30
Receive from When the main polishing process is completed on the turntable 38, the top ring 32 is moved as shown in FIG.
The swivel of the swivel arm 52 moves the buffing table 42 onto the buffing table 42, where water polishing for finish polishing and cleaning can be performed. Of course, it is also possible to transfer it to the pusher 30 immediately after the main polishing process.

When the water polishing is completed, the top ring device 36 operates to turn the turning arm 52 to move the top ring 32 directly above the pusher 30, as shown in FIG. Then, the top ring 32 is lowered or the pusher 30 is raised to transfer the polished wafer to the pusher 30. The polished wafer is replaced with a new unpolished wafer by the third robot 26a (or the fourth robot 26b). During this time, the other top ring 34 moves to the polishing position on the turntable 38, and polishing is performed by the turntable 38, and as shown in FIG. Then, water polishing for finish polishing and cleaning is performed, and the process returns to the step of FIG.

In this step, the polishing units 10a,
Since the robots 26a and 26b for loading and unloading the material to be polished into and out of 10b are provided for each polishing processing line, the processed material to be polished by the pusher 30 is quickly replaced with an unprocessed material to be polished. Therefore, the top rings 32, 34
Does not need to wait for the arrival of the next material to be polished, and the idle time during which the turntable 38 is not polishing is reduced.

Also, in this embodiment, since each top ring device 36 has two top rings 32, 34 mounted on both ends of the turning arm 52, the other top ring 32 during the polishing process. , 34 are replaced with untreated ones, so that the top rings 32, 3 are removed.
There is no idle time for attaching the material to be polished to the workpiece 4. Therefore, parallel processing with high operation efficiency of the turntable 38 and high throughput can be performed.

FIG. 9 illustrates the flow of the material to be polished when two-stage polishing is performed using the polishing apparatus according to the above-described embodiment, that is, when a series process is performed. The outline of the flow is as follows. Right cassette 12a → first robot 22 → dry reversing machine 16a → second robot 24 → dry station 20A → third robot 26a → first
Polishing unit 10a → third robot 26a → right primary cleaner 18a → second robot 24 → wet station 20B → third robot 26b → secondary polishing unit 1
0b → third robot 26b → left primary cleaning machine 18b → second robot 24 → wet reversing machine 16b → first robot 22 → left secondary cleaning machine 14b → first robot 22 →
Right cassette 12a

In this series processing, since a wet wafer is supplied to the polishing unit 10b, the dry station 20A and the wet station 20B are selectively used. Wet station 20B
In the example, a rinsing liquid is supplied from the nozzle 66 to the upper and lower surfaces of the workpiece W to prevent the workpiece from drying.
Although the dry station 20A and the wet station 20B are separately shown in FIG. 9 for the sake of convenience, they actually overlap one another as described with reference to FIG.

[0036]

As described above, according to the present invention,
As in the prior art, unnecessary portions are ground and the surface is flattened at a high polishing rate by the primary polishing table, and the micro-scratch and the attached fine particles are removed by the secondary polishing table. Polishing with high finishing accuracy can be performed without lowering polishing efficiency as compared with the case of performing various types of polishing. The dimensions of the secondary polishing table can be set to the same degree as the dimensions of the material to be polished, and are greatly reduced as compared with the primary polishing table. Can be maintained, and the compactness of the device can be maintained.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a polishing apparatus of the present invention and a flow of a material to be polished.

FIG. 2 is a front view showing a polishing unit of the polishing apparatus of the present invention.

FIG. 3 is a plan view showing a polishing unit.

4A is an elevation view of a buffing table, and FIG. 4B is an elevation view of a dresser elevating mechanism.

FIG. 5A is a plan view showing a configuration of a buffing table,
(B) It is a side view.

FIG. 6 is a plan view schematically showing a positional relationship between a buff polishing table and a material to be polished.

FIG. 7 is a cross-sectional view illustrating a configuration of a temporary placing table.

FIG. 8 is a plan view showing the operation of the polishing unit.

FIG. 9 is a plan view schematically showing a flow of another embodiment of a material to be polished in the polishing apparatus of the present invention.

FIG. 10 is a plan view schematically showing a conventional polishing apparatus.

[Explanation of symbols]

 10a, 10b Polishing unit 12a, 12b Storage unit 14a, 14b, 18a, 18b Cleaning unit 20 Temporary placing table 26a, 26b Robot means 30 Pusher 32, 34 Top ring 36 Top ring device 38 Turntable (primary polishing table) 42 Buff Polishing table (secondary polishing table) 52 Swivel arm W Workpiece

Claims (3)

[Claims] 1. A polishing apparatus for performing polishing by pressing a surface to be polished of a material to be polished and a polishing surface of a polishing table while rotating a circular material to be polished and a polishing table, respectively, wherein a radius of the surface to be polished is 1 set larger than the diameter of the surface to be polished
A polishing apparatus comprising: a secondary polishing table; and a secondary polishing table in which a radius of a polishing surface is set smaller than a diameter of a surface to be polished and larger than the radius. 2. A holding means for holding an object to be polished, wherein:
2. The polishing apparatus according to claim 1, wherein the material to be polished can be transported to both the secondary polishing table and the secondary polishing table. 3. A polishing apparatus for performing polishing by pressing a polished surface of a polished material and a polished surface of a polishing table against each other while rotating a circular polished material and a polishing table, respectively, wherein the radius of the polished surface is Is set smaller than the diameter of the surface to be polished and larger than the radius thereof, the axis of the surface to be polished is on the polishing surface, and the distance between the axis of the surface to be polished and the edge of the polishing surface. Is smaller than the radius of the surface to be polished.