JP3257304B2 - Polishing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus, and more particularly to a polishing apparatus for polishing a surface of a semiconductor wafer or the like forming an integrated circuit.

[0002]

2. Description of the Related Art In recent years, semiconductor wafers for manufacturing integrated circuits such as LSIs (hereinafter simply referred to as wafers).
With the miniaturization of devices, it has been required to polish them to have a highly accurate and defect-free surface. The polishing mechanism is based on a mechano-chemical polishing method in which a mechanical element made of fine-particle silica or the like and an etching element made of an alkaline solution are combined.

[0003] Therefore, since the properties of the polishing agent and the polishing cloth are the main factors that determine the surface condition of the wafer, many improvements have been made in the past. However, the importance of the polishing apparatus itself is increasing with respect to recent demands for improving the accuracy of the wafer, particularly, the flatness.

Conventionally, as this type of polishing apparatus, for example, there is one having a structure disclosed in Japanese Patent Application Laid-Open No. 2-243263. The polishing apparatus includes a head that holds the wafer 3 and a platen (polishing disk) that slides a polishing surface on the wafer supported by the head.

[0005] The head has a carrier at a lower portion thereof for sucking and supporting the head. The carrier includes an elastic film having holes formed therein, and a ring for supporting the wafer from the outside in the radial direction.The holes are provided with a pure water supply unit, a vacuum source unit, and A pipeline pressure control device is connected.

According to this polishing apparatus, pure water is supplied to the elastic film by the operation of the pure water supply unit, and the wafer is adsorbed on the elastic film and peeled from the elastic film by the operation of the vacuum source unit. By the operation of the road pressure control device, the pressure in the pipeline during polishing is controlled to be constant.

[0007]

In the polishing apparatus constructed as described above, air pressure is supplied from a vacuum source unit to a group of holes provided in the elastic film.
The attachment / detachment of the wafer to / from the head is to be implemented.
In this case, the wafer once adsorbed on the head by the operation of the vacuum source unit becomes an elastic film impregnated with pure water,
There is a problem that it is difficult to separate the wafer from the elastic film simply by blowing out high-pressure air from the vacuum source unit in order to maintain the close contact with pure water.

That is, if the pressure of the high-pressure air is considerably increased, the wafer is separated from the elastic film, but in this case, excessive stress is generated in the wafer and the integrity of the wafer is impaired. In addition, the shape accuracy of the product, such as the flatness of the polished surface of the polished wafer, cannot be maintained.

[0009] In order to solve such a problem, it has been conventionally proposed to arrange a group of holes for detachment unequally with respect to a wafer. That is, when the wafer is separated from the elastic film, by separating one end side of the wafer from the elastic film, air can flow between the wafer and the elastic film to break the connection by pure water. And
The wafer and the elastic film are instantaneously separated by relatively low air pressure, so that problems such as the separation by high-pressure air are effectively solved.

However, in the case where the holes are unevenly distributed with respect to the wafer as described above, the following new problem occurs. First, there is a problem that the contact area between the wafer and the elastic film adhered to the back surface of the wafer, that is, the surface opposite to the surface to be polished becomes uneven. That is, the contact area between the wafer and the elastic film is reduced by the opening area of the hole.

For this reason, when the wafer is pressed against the polished surface of the platen, the wafer is pressed against the elastic film by the reaction force. However, since the contact area is uneven, the pressing pressure against the elastic film is reduced. Are unevenly distributed. Therefore, the elastic film is locally compressed in the region where the hole group is provided, and local elastic deformation of the wafer is allowed. In this case, the elastic deformation that has occurred on the wafer is restored by being separated from the elastic film after the polishing is completed, and the flatness of the polished surface is deteriorated.

The attachment and detachment of the wafer to and from the head by adjusting the air pressure of the holes is intended to automate the polishing operation of the wafer. In the case of a method in which the wafer is separated from the film, the separated wafer is separated from the head in an inclined state. For this reason, it becomes difficult to position the wafer after detachment, which hinders automation.

The present invention has been made in view of the above-mentioned circumstances, and has a head capable of easily and reliably attaching and detaching a polishing work such as a wafer, and a polishing apparatus capable of easily automating a polishing operation. It is intended to provide a device.

[0014]

In order to achieve the above object, the present invention provides a head for supporting a disk-shaped polishing work and a polishing disk having a polishing surface relatively moved between the head and the head. A polishing apparatus for polishing one surface of a polishing work by sliding the polishing work and the polishing surface while the polishing work is pressed against the polishing surface,
The head is composed of an adsorbent made of an elastic material adhered over the entire back surface of the polishing work, a holding carrier supporting the back surface of the adsorbent, and an outer peripheral edge of the polishing work adhered to the adsorbent. A support ring for supporting from outside in the radial direction, and a plurality of pressure adjusting holes which are opened through the adsorbent and the holding carrier and are opened on the adsorbing surface of the adsorbent and closed by the polishing work. In the vicinity of the peripheral edge are arranged evenly in the circumferential direction, and in the pressure adjusting hole,
The case where the polishing work is adsorbed to the head and the case where the polishing work is released
Over-polishing, and under-polishing near the outer periphery
In each case, the pressure in the pressure adjustment hole is changed.
Has proposed a polishing apparatus to which a pressure adjusting means is connected .

In the above polishing apparatus, the pressure adjusting hole is
It is effective if it is provided within a range of 25 mm inward in the radial direction from the outer peripheral edge of the polishing work adhered to the adsorbent, and the pressure adjusting hole of The diameter may be 0.5 mm to 2 mm.

[0016]

According to the polishing apparatus of the present invention, the back of the polishing work is brought into close contact with the adsorbent by setting the pressure in the pressure adjusting hole to a negative pressure state by the operation of the pressure adjusting means. Since the adsorbent is made of an elastic material, it absorbs some irregularities on the back surface of the polishing work and comes into close contact with the polishing work.

The back surface of the adsorbent is supported by the holding carrier. Thus, the polishing work is stably supported by the head. Also, since the support ring provided on the head supports the outer peripheral edge of the polishing work from the outside in the radial direction, it opposes the radial external force acting on the polishing work by the sliding operation with the polishing surface of the polishing machine,
The polishing work is supported so as not to be displaced with respect to the adsorbent.

The polishing work thus supported by the head is slid when being relatively moved between the polishing work and the polishing surface of the polishing machine, and one surface thereof is polished. In this case, since the pressure adjusting holes formed in the adsorbent are uniformly arranged in the circumferential direction, the distribution of the pressing pressure received from the polishing surface of the polishing machine is made uniform over the entire polishing work. In addition, the flatness of the surface to be polished after polishing is improved.

Further, since the pressure adjusting hole is provided near the outer peripheral edge of the polishing work, if the inside of the polishing work is slightly pressurized by the operation of the pressure adjusting means, the outer peripheral edge of the polishing work becomes the adsorbent. The workpiece is immediately displaced in a direction away from the workpiece, the close contact between the polishing work and the adsorbent is released, and the polishing work is separated from the adsorbent. Also in this case, since the pressure adjustment holes are evenly arranged in the circumferential direction, peeling of the polishing work and the adsorbent is simultaneously performed over the entire circumference, and when the polishing work is detached from the head. It is held so that no tilt occurs.

Further, if the pressure adjusting hole is provided within a range of 25 mm inward in the radial direction from the outer peripheral edge of the polishing work brought into close contact with the adsorbent, the pressure for peeling the polishing work from the adsorbent is provided. Can be reliably peeled in a short time while keeping the temperature low.

Further, if the diameter of the pressure adjusting holes opened on the adsorbing surface of the adsorbent is set to 0.5 mm to 2 mm, local deformation of the adsorbent near each pressure adjusting hole can be reliably prevented. It is possible to improve the shape accuracy of the polishing work.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a polishing apparatus according to the present invention will be described below with reference to FIGS. The polishing apparatus 1 of the present embodiment is also a polishing apparatus 1 for a wafer 2 and includes a head 3 for supporting the wafer 2 and a polishing table 4 having a polishing surface 4a that can be relatively moved with respect to the head 3. The basic configuration is common to the conventional example.

However, the polishing apparatus 1 of the present embodiment is different from the conventional example in the structure of the head 3. As shown in FIG. 1, the head 3 of the polishing apparatus 1 of this embodiment includes a housing 6 attached to a lower end of a rotating shaft 5,
A diaphragm 8 defining a pressure chamber 7 therein, and a disc-shaped holding carrier 9 attached to the diaphragm 8
And a retainer ring 10 disposed radially outward of the holding carrier 9 over the entire circumference, and an insert 11 (adsorbent) made of an elastic material such as polyurethane and adhered to the lower surface of the holding carrier 9. are doing.

The insert 11 is formed in the shape of a flat plate that is adhered over substantially the entire surface of the holding carrier 9, and the back surface 11 a of the insert 11 is attached to the holding carrier 9 by being attached.
Is supported stably. The suction surface 11b provided on the lower surface of the insert 11 is disposed slightly above the lower surface 10a of the retainer ring 10.

As a result, when the wafer 2 is attracted to the attracting surface 11b, the outer peripheral edge 2a of the wafer 2 is supported by the inner peripheral surface 10b of the retainer ring 10 from the outside in the radial direction. Directional movement is suppressed.

As shown in FIG. 2, the insert 11 is provided with eight pressure adjusting holes 12 near the outer peripheral edge 11c at equal intervals in the circumferential direction. In the present embodiment, as shown by a chain line in FIG. 2, a wafer 2 having an outer diameter of 6 inches, that is, 150 mm is polished, and the pressure adjustment hole 12 is formed in a radially inward direction from an outer peripheral edge 2a of the wafer 2. Is provided at a position of about 7.5 mm. The reason why the pressure adjusting hole 12 is provided at this position is to avoid the notch 2 c formed to indicate the directionality of the wafer 2 and to make the pressure adjusting hole 12 as large as possible on the outer peripheral edge 2 of the wafer 2.
This is in order to approach a.

In this embodiment, the pressure adjusting hole 12 is
The diameter is 1.0 mm. The reason why such a small configuration is adopted is that the insert 11 is
This is to avoid inconveniences such as formation of dimples by minimizing the area that does not adhere to the back surface 2d.

The holding carrier 9 is provided with conduits 13 (pressure regulating holes) communicating with the pressure regulating holes 12 of the insert 11, respectively.
Numeral 3 is connected to a manifold 14 which penetrates through the diaphragm 8 and is disposed above the diaphragm 8. Further, an air pressure source 16 and a pressure adjusting device 17 (pressure adjusting means) are connected to the manifold 14 via an air tube 15. In the drawing, reference numeral 18 denotes a groove for distributing air pressure to each pipeline 13.

The pressure adjusting device 17 is operated when the wafer 2 is attached to or detached from the head 6 and when the wafer 2 is polished. When the wafer 2 is attracted to the head 3, the pressure in the pressure adjusting hole 12 is reduced. When the wafer 2 is detached from the head 3, the inside of the pressure adjusting hole 12 is set to a relatively high pressure state.
The pressure from the air pressure source 16 is adjusted so that the inside of the chamber 2 is slightly pressurized.

The operation of the polishing apparatus 1 according to the present embodiment thus configured will be described below. First, in order for the head 3 to support the wafer 2, the back surface 2 d of the wafer 2 is arranged in contact with the suction surface 11 b of the insert 11 provided on the lower end surface of the head 3, and the pressure adjusting device 17 is operated to operate the pressure adjusting device 17. The pressure in the adjustment hole 12 is set to a negative pressure state. Thus, the rear surface 2 d of the wafer 2 is brought into close contact with the suction surface 11 b of the insert 11, and the wafer 2 is stably held by the head 3 by arranging the outer peripheral edge 2 a on the inner peripheral surface 10 b of the retainer ring 10. Will be.

At this time, since the insert 11 is made of an elastic material, the insert 11
Elastically deformed following the slight irregularities of the back 2d of
It will be brought into close contact with the back surface 11a of the insert 11.

Next, when polishing the wafer 2 held on the head 3 by the polishing apparatus 1, the polishing plate 4 is operated to horizontally turn the polishing surface 4a, and at the same time, the head 3 is rotated around the rotating shaft 5. To make it approach the polishing surface 4a of the polishing board 4 and rotate relative to each other. Then, the polished surface 2b of the wafer 2 held by the head 3 is brought into contact with the polished surface 4a of the polishing plate 4, and the pressure in the pressure chamber 7 is increased, so that the wafer 2 is slid while being pressed against the polished surface 4a. Then, the polished surface 2b is polished. At this time, the inside of the pressure adjusting hole 12 is set to a slightly high pressure state by the operation of the pressure adjusting device 17.

In this case, the polishing apparatus 1 of the present embodiment
Since the pressure adjusting holes 12 for attracting the wafer 2 to the insert 11 are provided at equal intervals around the outer periphery 2a of the wafer 2, the wafer 2 is
A uniform pressure distribution is achieved on the surface of the insert 11 by being pressed against a. In actual polishing, differences in the type of polishing cloth (differences in lamination structure, compression ratio, etc.)
This causes a difference in the polishing shape of the outer peripheral edge of the wafer.
For example, when a hard single-layer polishing cloth is used, the vicinity of the outer peripheral edge is underpolished and has a two-layer structure (hard surface, soft lower surface).
When a polishing cloth is used, overpolishing, that is, so-called dripping occurs near the outer peripheral edge. However, according to the polishing apparatus 1 of the present embodiment, a slightly high air pressure is supplied in the case of underpolishing, and a low pressure or negative pressure is supplied in the pressure adjusting hole 12 in the case of overpolishing, whereby the external pressure is reduced. By adjusting the pressure distribution in the vicinity of the peripheral edge, polishing with higher precision can be realized.

Then, the wafer 2 polished in this manner is supplied to the pressure adjusting hole 1 by the operation of the pressure adjusting device 17.
By setting the pressure in 2 to a high pressure state, it is separated from insert 11 and separated from head 1. In this case, the suction surface 11b of the insert 11
Since the pressure adjusting hole 12 which is opened in the vicinity of the outer peripheral edge 2a of the wafer 2 is arranged only in a slightly high pressure state, the outer peripheral edge 2a of the wafer 2 is immediately displaced in a direction away from the insert 11. Then, the suction state between the wafer 2 and the insert 11 is released.

Therefore, as compared with the conventional case where the pressure adjusting hole 12 is disposed at the radially inner position and supplied by a considerable amount of high-pressure air, the pressure adjusting hole 12 is first separated.
The stress generated on the wafer 2 as a product is small,
The wafer 2 is maintained in a healthy state, and does not adversely affect shape accuracy such as flatness.

Also, since the pressurized air is evenly distributed to the plurality of pressure adjusting holes 12 provided at equal intervals in the circumferential direction, the separation between the wafer 2 and the insert 11 is performed over the entire circumference. Thus, the wafer 2 is separated and dropped from the head 3 while maintaining the horizontal state. Therefore, the wafer 2 after being separated is
Since the wafer 2 is stably arranged at a fixed position without using a special positioning device, handling of the wafer 2 in a subsequent process can be facilitated. As a result, it is possible to easily automate the polishing operation including the suction, polishing, separation, and transfer of the wafer 2.

Next, the results of polishing by the polishing apparatus 1 of the above embodiment are shown in FIGS. 3 to 5 in comparison with a conventional polishing apparatus. These polishing operations are performed under the following conditions. Wafer: 6-inch silicon wafer subjected to thermal oxidation treatment Polishing pressure: 0.5 kgf / cm ² Polishing allowance: 5000 mm

FIG. 3 shows an example of a polishing result by the polishing apparatus 1 of the above embodiment. FIG. 4 shows an example of a polishing result by a conventional polishing apparatus. According to this, in the polishing apparatus 1 of the present embodiment, few contour lines appear, and it can be said that the surface of the wafer 2 is formed extremely flat. On the other hand, in the result of polishing by the conventional polishing apparatus, the contour lines are extremely dense, and the wafer 2
The surface has considerable irregularities. In the example of FIG.
The polishing accuracy 1σ is 4.5%, and in the example of FIG. 4, the polishing accuracy 1σ is 8.4%. In FIGS. 4 and 5, the sign indicates the level from the average allowance.

FIG. 5 is a diagram comparing the polishing accuracy when the above polishing is performed five times each.
According to this, it can be seen that the polishing accuracy of the surface of the wafer 2 by the polishing apparatus 1 of the present example is excellent in all the results of the experiment.

In this embodiment, the pressure adjusting holes 1
Although the number of 2 is set to 8 and arranged at equal intervals in the circumferential direction, an arbitrary number of 3 or more pressure adjusting holes 12 may be provided instead. Further, instead of disposing the pressure adjusting holes 12 at equal intervals as in the above embodiment, a hole group having two or more pressure adjusting holes 12 disposed close to each other is equally spaced apart in the circumferential direction. The same effect as described above can be achieved by the arrangement method.

Further, the pressure adjusting hole 12 is provided at a position about 7.5 mm radially inward of the outer peripheral edge 2a of the wafer 2, but at a position closed by the back surface 2d of the wafer 2, and , It may be arranged near the outer peripheral edge, for example, outside of 半径 of the radius of the wafer 2.

FIG. 6 shows a desirable range for the arrangement of the pressure adjusting holes 12. FIG. 6 is a view similar to FIG.
This is a case where eight pressure adjustment holes 12 are provided for the inch-sized wafer 2, wherein the air pressure supplied into the pressure adjustment holes 12 is used as a parameter with respect to the radial distance from the outer peripheral edge 2 a of the wafer 2. It is a figure showing the time required for peeling.

According to FIG. 6, as the position of the pressure adjusting hole 12 shifts inward in the radial direction, the time required for peeling increases, and the air pressure supplied to the pressure adjusting hole 12 is increased. It can be seen that the required peeling time decreases as the distance increases. Here, for example, the supply air pressure is 4 kg / cm
² assuming, if allowing approximately 5 seconds as release duration, position of the pressure adjusting hole is allowed from the outer peripheral edge 2a of the wafer 2 to about 25 mm.

Therefore, the position of the pressure adjusting hole 12 is desirably within a range from the outer peripheral edge 2a of the wafer 2 to about 25 mm. More preferably, the pressure adjusting hole 12 is formed in a range from the outer peripheral edge 2a of the wafer 2 to about 10 mm.
Is preferably arranged. Further, in the present embodiment, the diameter of the pressure adjusting hole 12 is set to 1.0 mm. However, the present invention is not limited to this, and a diameter of about 2 mm or less can be adopted. However, since it is used for attaching and detaching, the pressure adjusting hole 1 having an extremely small diameter is used.
2 is inappropriate, so it is necessary that the diameter be at least 0.5 mm or more.

The hatched portion in FIG. 6, that is, a range of 7 mm inward in the radial direction from the outer peripheral edge of the wafer, corresponds to the notch 2 provided at one end of the wafer 2 as described above.
pressure adjustment hole 1 in an area where wafer 2 does not exist
2 shows an area for avoiding overlapping, and the notch 2
It is desired to dispose the pressure adjusting hole 12 radially inward of the end edge of c.

However, this is because it is difficult at present to match the phases of the head 3 and the wafer 2. Therefore, the notch 2 of the wafer 2 is located at the position of the pressure adjusting hole 12.
If the phase of the wafer 2 can be adjusted so that c does not match, the pressure adjusting hole 12 can be arranged radially outward from the edge of the notch 2c, which also enables the above-described implementation. The same effect as in the example can be obtained.

In this embodiment, the insert 1
Although 1 is made of polyurethane, the present invention is not limited to this, and another elastic material such as silicone rubber may be used. Further, the present invention is not limited to the case where the silicon wafer 2 is polished, but can be applied as a polishing apparatus 11 for polishing the surface of a similar thin disk-shaped polishing work such as an aluminum substrate for a hard disk.

[0048]

As described in detail above, in the polishing apparatus according to the present invention, the head has an adsorbent made of an elastic material adhered over the entire back surface of the polishing work, and the holding carrier supporting the back surface. And a support ring for supporting the outer peripheral edge of the polishing work from the outside in the radial direction. A plurality of pressure adjusting holes that are opened through the adsorbent and the holding carrier and are opened on the suction surface and closed by the polishing work are provided. It is arranged evenly in the circumferential direction near the outer peripheral edge of the work, and its pressure adjusting hole has
When the abrasive work is adsorbed to the head and when it is released,
And under and over polishing near the outer edge
In this case, since the pressure adjusting means for changing the pressure in the pressure adjusting hole is connected, when polishing the polishing work, the polishing pressure is applied uniformly over the entire surface of the adsorbent to reduce the flatness of the surface to be polished. The effect that it can improve is produced.

Further, since the polishing work is separated from the adsorbent by increasing the pressure in the pressure adjusting holes uniformly distributed in the circumferential direction near the outer peripheral edge of the polishing work, excessive stress is generated in the polishing work. The peeling can be carried out quickly without any problem. In addition, since the peeling is performed simultaneously by the pressure adjusting holes evenly arranged, the posture of the polishing work at the time of separation can be kept constant, and the positioning operation to the subsequent transporting step can be unnecessary. Therefore, it is possible to easily automate the entire polishing operation from the suction of the polishing work by the head to the conveyance of the polishing work after the polishing is completed.

In the above-mentioned polishing apparatus, if the pressure adjusting hole is provided within a range of 25 mm inward in the radial direction from the outer peripheral edge of the polishing work brought into close contact with the adsorbent,
The polishing work can be separated from the head within 5 seconds even with a factory air pressure of about 4 kgf / cm ² .
Further, when the diameter of the pressure adjusting hole opened on the suction surface of the adsorbent is set to 0.5 mm to 2 mm, local deformation near the pressure adjusting hole of the adsorbent during polishing is prevented, and the product accuracy of the polishing work is reduced. Is achieved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the vicinity of a head showing one embodiment of a polishing apparatus according to the present invention.

FIG. 2 is a plan view of the head of the polishing apparatus of FIG. 1 as viewed from a suction surface side.

FIG. 3 is a view showing a surface polishing accuracy of a polishing work polished by the polishing apparatus of FIG. 1;

FIG. 4 is a diagram showing the surface polishing accuracy of a polishing work by a conventional polishing apparatus compared with FIG. 3;

FIG. 5 is a diagram showing a result of performing the polishing accuracy measurement of FIGS. 3 and 4 a plurality of times.

FIG. 6 is a view showing a desirable range of arrangement of pressure adjusting holes in the polishing apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Wafer (polishing work) 3 Head 4 Polishing machine 4a Polishing surface 9 Holding carrier 10 Retainer ring (support ring) 11 Insert (adsorbent) 12 ・ 13 Pressure adjusting hole 17 Pressure adjusting means

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01L 21/304 622 H01L 21/304 622L 622R (56) References Japanese Utility Model Sho 61-31656 (JP, U) Japanese Utility Model Sho 59- 39159 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B24B 37/00 B24B 37/04 H01L 21/304 621 H01L 21/304 622

Claims (3)

(57) [Claims] 1. A head for supporting a disk-shaped polishing work, and a polishing disk having a polishing surface relatively moved between the head and the head, wherein the polishing work is pressed against the polishing surface, A polishing apparatus for polishing one surface of a polishing work by sliding the polishing work and a polishing surface, wherein the head comprises an adsorbent made of an elastic material which is brought into close contact with the entire back surface of the polishing work. A holding carrier that supports the back surface of the adsorbent, and a support ring that supports the outer peripheral edge of the polishing work adhered to the adsorbent from outside in the radial direction, and penetrates the adsorbent and the holding carrier. a plurality of pressure adjusting hole is closed by the opening and polishing work on the attracting surface of the adsorbent Te is evenly disposed near the outer periphery of the polishing work in the circumferential direction, the pressure adjusting hole is before the polishing work Absorption in the head
In the case of wearing, removing, and near the outer peripheral edge
In each case of low polishing and overpolishing, the pressure adjustment
Pressure adjusting means for changing the pressure in the hole is connected
A polishing apparatus characterized by the above-mentioned. 2. The polishing apparatus according to claim 1, wherein the pressure adjusting hole is provided within a range of 25 mm inward in a radial direction from an outer peripheral edge of the polishing work brought into close contact with the adsorbent. 3. The polishing apparatus according to claim 1, wherein the diameter of the pressure adjusting hole opened on the adsorption surface of the adsorber is 0.5 mm to 2 mm.