JP2003163193A - Method for polishing wafer and polishing head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for polishing a wafer and a head for polishing the wafer in which planarization can be carried out with higher accuracy on the premise that a waxless mount system is employed. <P>SOLUTION: The method for polishing the single side of a wafer W is applicable to a wafer polishing head 101 (1, 100) employing a waxless mount system. In that method, a region PZ for arranging the wafer W is set on the side of surface 2p of a flexible film 2 coming into contact with the wafer W which is applied with pressure required for polishing from a rear surface 2q side. An annular dummy plate 10 is arranged in surface-contact with the flexible film 2 to surround the arranging region PZ, and the wafer W arranged on the inside of the dummy plate 10 is subjected to single side polishing by imparting hydraulic pressure thereto. In order to implement this inventive method, the dummy plate 10 is stuck to the flexible film 2 of the wafer polishing head 101 (1, 100) to the integrated with the film. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for single-side polishing a silicon wafer, for example, and a wafer polishing head for implementing the method.

[0002]

2. Description of the Related Art In recent years, with the high integration of semiconductor devices, the flatness required for semiconductor wafers has become more and more severe. On the other hand, since the diameter of the wafer used for the device is increasing, it is becoming difficult to improve the flatness of the wafer, which is an important issue.

To improve the microroughness of the wafer,
In other words, one of the technologies to achieve flatness at the atomic level,
Chemical-mechanical polishing method (CMP method: Chemical-Mechanical)
Polishing Method). The polishing of the wafer by the CMP method is performed by supplying a polishing agent (slurry) and applying a constant load and relative speed between the wafer and the polishing cloth. In the case of single-side polishing, the wafer is attached to the attachment block, and the load and the rotational force during polishing are applied through the attachment block by the pressure mechanism (polishing head) provided in the polishing apparatus.

As a method of mounting the wafer on the sticking block, a method of applying liquid wax to the wafer in advance by a method such as spin coating and then mounting it on the sticking block is general. After the polishing process is completed, the wafer is demounted (peeled) from the attachment block.

However, in recent years, the wafer polishing system announced by Applied Materials, Inc., located in California, USA, is surprisingly a wafer polishing head adopting a waxless mounting method which has been said to be a dream mounting method for a long time. Was equipped with. This great work has completely eliminated the process of mounting / demounting wafers on the attachment block. The wafer polishing head 100 developed by Applied Materials, Inc. is as follows.

As shown in FIG. 6, a wafer polishing head 100 manufactured by Applied Materials Co., Ltd. has a housing 50.
And a frame 52 connected to the housing 50 via a diaphragm 51. A retainer ring 53 having substantially the same diameter as the frame 52 is provided on the lower surface side of the frame 52.
Is attached, and an inner tube 54 is arranged in a space that extends inside the retainer ring 53. A holder (also referred to as a membrane support) 56 having a large number of through holes Q penetrating in the thickness direction is arranged below the inner tube 54 via a rubber flexor 55. A flexible film (also referred to as a membrane) 57 is attached to the membrane support 56, and the side opposite to the side in contact with the membrane support 56 is the wafer suction surface.

The pressure adjustment line is divided into the following three independent systems. a) Housing 50, diaphragm 51
And a line L1 for pressurizing / depressurizing the space S1 formed by the frame 52. b) A line L2 for pressurizing / depressurizing the space S2 formed by the frame 52, the inner tube 54 and the membrane support 56.
c) A line L3 that pressurizes the inside of the inner tube 54. To adsorb the wafer W, first, the inner tube 54
Is swelled toward the side of the membrane support 56, and the inner tube 54 is brought into close contact with the flexor 55. Then, the membrane support 56 is pressed and the membrane 5
Stick to 7.

Next, the space S2 is decompressed. Then, a part of the membrane 57 bends and enters the through hole Q of the membrane support 56. As a result, an airtight pocket is generated between the wafer W and the membrane 57, and the wafer W is adsorbed to the membrane 57. It is just like a suction cup sucking the wafer W. Further, when the space S1 is pressurized or depressurized, the entire lower part moves up and down from the frame 52 including the retainer ring 53. In this way, a mechanism for vacuum chucking the wafer W, which is said to be difficult to apply to the wafer polishing head, is realized.

The wafer W transferred to the transfer station of the system is chucked by the wafer polishing head 100 and transferred onto the platen. During polishing, the pressure in the spaces S1, S2 and the inner tube 54 is adjusted, and a load is applied to the wafer W and the retainer ring 53. After the polishing is completed, the wafer W is chucked again and returned to the transfer station.

[0010]

However, the dream mounting method still has some problems to be solved. One of the problems is that it is difficult to uniformly apply pressure to the wafer during polishing. The wafer to be polished must be given a rotational force while applying pressure in the thickness direction. This is one of the factors that cause the variation of the load in the radial direction, and in fact, it is clear that the thickness of the polished wafer is examined. It is also known that the variation in the polishing amount is particularly remarkable in the peripheral portion of the wafer, which often causes a problem as polishing sag in the peripheral portion of the wafer.

The wafer polishing head developed by Applied Materials Co., Ltd. is recognized for its achievement of the dream waxless mounting method and the substantial reduction in the number of steps, but the wafer flatness is further improved. From the viewpoint of making it possible, there is still a problem.
The problem regarding the flatness of the wafer is a problem that is routinely discussed in the field of polishing, and is not limited to the wafer polishing head developed by Applied Materials Co., Ltd. described above. However, with the emergence of the waxless mount method, it is important to find a new polishing method for improving the flatness of the wafer in accordance with the method, and it is an urgent task.

Therefore, the present invention provides a wafer polishing method capable of performing a highly precise flattening process, and a wafer polishing head for carrying out the method, on the premise that a waxless mount system is adopted. Is an issue.

[0013]

Means for Solving the Problems and Actions / Effects In order to solve the above problems, a wafer polishing method of the present invention is a method for polishing a single surface of a wafer, wherein the front surface forms a contact surface with the wafer and the back surface. For the flexible film that transmits the pressure required for polishing to the wafer from the side, while defining the placement area of the wafer on the surface side of the flexible film, ring-shaped so as to surround the placement area by making surface contact with the surface of the flexible film. One feature is that a dummy plate is arranged, and one-side polishing is performed so that a fluid pressure is applied to a wafer arranged inside the dummy plate.

The above-mentioned method of the present invention is intended to give the pressure during polishing to the entire wafer extremely uniformly, and the wafer to be polished is arranged so as to fit inside the ring-shaped dummy plate. To be done. With this configuration, by appropriately adjusting the degree of overlap between the flexible film and the dummy plate, it is possible to transmit the pressure to the wafer only in the portion excluding the outer peripheral portion of the flexible film.
In other words, a dummy plate is placed in contact with the outer peripheral portion of the flexible film, which is likely to cause variations in the pressure for urging the wafer, instead of the wafer, and is arranged such that the favorite wafer is in contact with the wafer as much as possible. Moreover, with respect to the wafer being polished, the dummy plate becomes an obstacle even if it is attempted to shift to the outside. Therefore, the problem that the wafer extends radially outward of the flexible film does not occur. In this way, the dummy plate has both a function as a wafer dummy and a function as a carrier.

Further, the wafer polishing head for realizing the above-mentioned method of the present invention is characterized in that a dummy plate is attached to a flexible film, and the flexible film and the dummy plate are integrated. . By doing so, it is easy to adapt the method of the present invention to an automated polishing apparatus. Further, since it is not necessary to change the structure of the polishing head itself, the cost required for designing and manufacturing can be suppressed.

[0016]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. The wafer polishing method of the present invention is a method applicable to a chemical-mechanical polishing method (so-called CMP method). The CMP method is a polishing method applied when manufacturing a semiconductor wafer. An example of the wafer manufacturing process until the polishing process is performed will be briefly described. First,
A silicon single crystal ingot manufactured by a known method such as the FZ method or the CZ method is sliced to obtain a silicon single crystal wafer. After chamfering this silicon single crystal wafer, mechanical polishing (lapping) using free abrasive grains is performed. After the lapping is completed, it is immersed in an etching solution to be subjected to a chemical etching treatment.

After the chemical etching is finished, the step of mirror-finishing the surface of the wafer is the polishing step by the CMP method. For example, when an SOI wafer having a silicon single crystal thin film formed on an insulator is manufactured by a wafer bonding method using a known ion implantation separation method (also called smart cut method), the bonded wafer is separated. After that, touch polishing (polishing with a very small stock removal) is performed by the CMP method. The polishing method of the present invention can be suitably adopted for the polishing step by the CMP method.

Now, FIG. 1 is a schematic view showing an outline of the wafer polishing method and polishing head of the present invention. As shown in FIG. 1, the present invention is a single-wafer polishing method in which the wafer W is polished on one side and at the same time, the wafers W are processed one by one. The front surface 2p of the wafer W to be polished forms a contact surface with the wafer W, and is arranged in a surface contact form with respect to the flexible film 2 that transmits the pressure required for polishing to the wafer W from the back surface 2q side. It
The flexible film 2 has an arrangement area P of the wafer W on the surface 2p side.
Z is defined. On the other hand, the ring-shaped dummy plate 10 is arranged so as to make surface contact with the surface 2p of the flexible film 2 and surround the arrangement region PZ. Then, a fluid pressure is applied to the wafer W arranged inside the dummy plate 10 through the flexible film 2. The arrangement region PZ can be regarded as a shallow recess formed by the flexible film 2 and the dummy plate 10.

A chamber 60 for applying a fluid pressure, which is an internal space of the wafer polishing head 101 in which the flexible film 2 is to be provided, may be formed behind the flexible film 2. The wafer W to which the pressure is applied is urged by the polishing cloth 34. The polishing cloth 34 is a servo motor M.
It is attached to a platen 33 that is connected to and configured to be rotatable. During the polishing, a slurry such as colloidal silica is supplied from the supply arm 36.

The fluid contained in the chamber 60 is preferably gas (air). That is, the flexible film 2 is pressurized with gas from the back surface side of the flexible film 2 to apply pressure to the wafer. Although liquids such as water and alcohol can be used, they have inferior properties as elastic fluids as compared with gases such as air.

Now, the method of the present invention can be further developed as follows. That is, as shown in the schematic view of FIG. 2, a disk-shaped holder 56 having a through hole Q in the thickness direction is arranged on the back surface 2q side of the flexible film 2, and the holder 56 can be attached to the peripheral portion thereof. The flexible film 2 is held by connecting the peripheral portions of the flexible film 2 to each other. Then, the dummy plate 10 is arranged so as to overlap the holder 56 in the thickness direction of the wafer W to be polished. With this configuration, when the back of the flexible film 2 is depressurized, the flexible film 2 comes into close contact with the holder 56, and a part of the flexible film 2 bends into the through hole Q and enters into the through hole Q to be airtight. A pocket is formed on the wafer W
Can be adsorbed on the flexible film 2. Therefore, the wafer W and the flexible film 2 can be transported integrally with the holder 56, and it is not necessary to attach the wafer W to the flexible film 2 with wax.

As a method of connecting the flexible film 2 to the holder 56, as shown in FIG.
6, the fastener 6 such as a clamp 61 may be used, and the wraparound portion may be locked to the holder 56. The through hole Q of the holder 56 may have a structure communicating with the chamber 60.

Further, the dummy plate 10 has a positional relationship in which it overlaps with the holder 56 in the thickness direction of the flexible film 2. The peripheral edge of the flexible film 2 is a disc-shaped holder 5
It is in the form of being locked at 6. Therefore, the pressure applied to the wafer W easily varies between the central portion and the peripheral portion of the flexible film 2. However, according to the method of the present invention, by disposing the dummy plate 10,
The variation is reduced. At the same time, the variation in pressure caused by the holder 56 pressing the flexible membrane 2 is also reduced.

Further, the dummy plate 1 is so arranged that the dummy plate 10 is thinner than the wafer W to be polished.
It is advisable to perform the thickness adjustment of 0 in advance. By doing so, it is possible to prevent the problem that the dummy plate 10 becomes an obstacle and a sufficient pressure cannot be applied to the wafer W.

Specifically, as shown in FIG. 3, the thickness of the wafer W to be polished and the polishing allowance d of the wafer W are used as a reference so that the wafer W has a thickness almost equal to that of the wafer W after polishing. Then, the thickness of the dummy plate 10 may be adjusted in advance. For example, if the thickness of the dummy plate 10 is made thinner than necessary, there will be a difference in the thickness between the wafer W and the dummy plate 10 even after the polishing of the wafer W is completed. In such a case, the effect of suppressing the variation in the pressure applied to the wafer W may not be sufficiently exerted. In FIG. 3, the difference in thickness is exaggerated for the sake of understanding. For example, in the touch polishing process described above, the polishing amount d of the wafer W is 100 n
It may be about m or less. In comparison,
Since the thickness of the wafer W is generally about 700 to 800 μm, the dummy plate 10 and the wafer W before polishing are polished.
The difference d in the thickness between and cannot be visually confirmed.

As a material for the dummy plate 10, a resin plate containing glass fibers, which is formed by impregnating glass fibers with a resin and molded into a plate shape, is recommended. Specifically, for example, one or more resins selected from phenol resins, polyesters, epoxy resins, melamine resins, silicone resins and the like can be used. Above all, a silicon resin (so-called silicone) is preferable because the object to be polished is represented by a silicon single crystal or a silicon oxide film. When the main body of the dummy plate 10 is silicon resin, even if the dummy plate 10 itself is ground, there is little concern that impurities will be taken into the wafer W. Also, a resin plate containing glass fibers (so-called FRP)
Since the rigidity can be improved by setting the above, distortion occurring during polishing can be suppressed. Therefore, the dummy plate 10 maintains a good contact state between the wafer W and the flexible film 2 and contributes to stable polishing. Needless to say, a laminated resin plate obtained by laminating and adhering a plurality of the glass fiber-containing resin plates may be used.

By the way, it is well known that the wafer W to be polished is thin. When the fluid pressure applied from the back of the flexible membrane 2 is not so large, it is sufficient to use the laminated resin plate containing glass fiber as described above. However, the stronger the fluid pressure is, the more the rigidity of the dummy plate is increased. Is emerging. That is, as shown in FIG.
As the friction load increases, the dummy plate 10 may be strongly pressed against the polishing cloth 34 together with the wafer W, and buckling may occur. In some cases, there is a risk of destruction. In that case, it is not desirable to apply a uniform polishing pressure to the wafer W. When there is such a possibility, polishing can be performed by the following method.

The method illustrated in FIG. 3 is applied to the dummy plate 1
It was a method of making 0 thinner than the wafer W before polishing. On the other hand, as shown in FIG.
A method of polishing with a thickness greater than that of the wafer W before polishing can also be adopted as the polishing method of the present invention. As shown in FIG. 5, the dummy plate 10 is formed thicker than the wafer W to be polished. Then, the difference in thickness between the dummy plate 10 and the wafer W caused thereby is
By using the flexible film 2 having the wafer supporting portion 2w formed to be thicker than the connecting portion with the dummy plate 10, it is possible to offset and perform polishing. According to this method, even if the dummy plate 10 is thicker than the wafer W, polishing can be reliably performed. Since the possibility that buckling deformation of the dummy plate 10 will occur is lessened, more uniform polishing pressure is applied to the wafer W.

At the time of polishing, the wafer supporting portion 2w becomes convex below the upper surface 10p of the dummy plate 10,
A polishing pressure is applied to the wafer W. Therefore, the wafer supporting portion 2w has a diameter larger than that of the wafer W, and is adjusted so as to fit within the arrangement region PZ of the wafer W. By doing so, the difference in thickness between the wafer W and the dummy plate 10 can be directly reduced, and the flexible film 2 is unnecessary.
You do not have to increase the thickness. In order to improve the flexibility of the flexible film 2, it is advantageous that its thickness is thin. If the flexibility is good, the fluid pressure can be uniformly transmitted to the wafer. In addition, ensuring good flexibility is also convenient when adopting a configuration in which the holder 56 is arranged behind the flexible film 2 and the wafer W is sucked, as illustrated in FIG. is there.

Specifically, as shown in FIG. 5, the wafer supporting portion 2w has a plate-like shape. Then, the wafer W adheres to the upper surface of the plateau (which is a part of the front surface 2p of the flexible film 2), and polishing pressure is applied from the back surface 2q side of the flexible film 2. Therefore, after the polishing is completed, the sum of the plateau height (thickness) of the wafer supporting portion 2w and the thickness of the wafer W may be substantially equal to the thickness of the dummy plate 10. Such a flexible film 2 may be formed by stacking a plurality of flexible films only on the wafer supporting portion 2w and bonding them with an adhesive, or may be integrally molded in advance.
As a material, a soft rubber material is recommended as much as possible.

On the other hand, as the material of the dummy plate 10, a laminated resin plate containing glass fiber is a suitable example in the form shown in FIG. Above all, from the viewpoint of sufficiently ensuring the rigidity of the dummy plate 10, it is preferable to use epoxy resin containing glass fiber.

The contact form of the dummy plate 10 with the flexible film 2 can be as follows. That is, as shown in FIG. 2, it is advisable to adjust all the one main surfaces of the dummy plate 10 so as to make surface contact with the flexible film 2. In this way, the flexible film 2 and the dummy plate 1
The contact area with 0 can be earned most effectively. Therefore, the effect of alleviating the variation in pressure applied to the wafer W can be most expected. The dummy plate 10 is preferably arranged so as to be attached to the flexible film 2. Then, the dummy plate 10 can be easily positioned on the flexible film 2. Of course, this method can also be adopted in the method shown in FIG. 5 in which the dummy plate 10 is made thicker than the wafer W. Then, in the following embodiments, both the method of making the flexible film 2 thinner than the wafer W before polishing and the method of making the flexible film 2 thicker than the wafer W before polishing are applicable. It is possible.

The wafer polishing head 1 shown in FIG.
In the wafer polishing head 100 illustrated in FIG. 6, reference numeral 01 is the one in which the dummy plate 10 is attached to the membrane 57 (corresponding to the flexible film 2) to integrally configure the membrane 57 and the dummy plate 10. With this configuration,
The method of the invention is now ready for implementation.

The wafer polishing head 100 shown in FIG.
Frame 52, flexor 55, inner tube 54
Also, the pressure of the fluid filling the space S2 formed by the flexible film 2 and the pressure of the fluid filling the inner tube 54 can be individually adjusted, and the action of adsorbing the wafer W on the flexible film 2 is performed. It was configured to freely apply the pressure to W. In addition to this, the dummy plate 1
By arranging 0, the problem that the pressure applied to the wafer W varies can be suppressed.

Now, the specific constitution for carrying out the method of the present invention will be described below. First, FIG. 7 is a schematic diagram showing a CMP apparatus 200 that can employ the method of the present invention. Figure 8
FIG. 8 is a top view of a polishing station 201 in the CMP apparatus 200 of FIG.

As shown in FIGS. 7 and 8, the CMP apparatus 200 is constructed as a single-wafer polishing apparatus for processing the wafer W one by one. In the polishing station 201, a plurality of platens 33 having polishing cloths 34 adhered on the upper surface are arranged. Each platen 33, 33 is independently driven to rotate by a servo motor (not shown). As shown in FIG. 8, the polishing slurry sent from the slurry mixing unit 30 is supplied onto the polishing cloth 34 by a supply arm 36 provided in a shape corresponding to each polishing cloth 34. The supply arm 36 is also used as a supply source of various chemicals and rinses. The polishing cloth adjusting device 37 is
The surface condition of the polishing cloth 34 is kept good. The wafer W prepared in the transfer station 202 is transferred to the wafer standby position 35 by a transfer robot (not shown).
Reprinted in. After that, the wafer is chucked by the wafer polishing head 1 and carried to the polishing position. When the polishing is completed and the wafer is collected, it is also carried out of the polishing station 201 from the wafer standby position 35.

CMP apparatus 20 for polishing one side of wafer W
The wafer polishing head 1 (101) for 0 is the wafer W
It is configured as a polishing head that adopts a waxless mount method of directly chucking and carrying / polishing. The wafer polishing head 1 (101) has a head driving mechanism 39.
Mounted on the vertical drive unit 31 connected to the platen 3
3 or up / down approach to wafer standby position 35 /
Separation is performed. The vertical drive unit 31 includes a shaft for driving the wafer polishing head 1 (101) to rotate, and fluid passages 11 and 12 for filling a chamber formed inside the wafer polishing head 1 (101). The fluid that fills the inside of the wafer polishing head 1 is usually air, but liquids such as water and alcohol are not impossible. The flow paths 11 and 12 extending from the inside of the wafer polishing head 1 are connected to a pressure adjusting device 400 including a vacuum pump 40, a compressor 41, an electromagnetic valve 25 and the like (see FIG. 9). Four vertical drive units 31 are connected to the head drive mechanism 39. The head drive mechanism 39 is
The vertical drive unit 31 equipped with the wafer polishing head 1 (101) is horizontally driven to move the platens 33, 33,
33 and the wafer standby position 35, respectively. As a result, the wafer W is transported from the wafer standby position 35 to the polishing position. That is,
The wafer polishing head 1 (101) has a function as a carrier for the wafer W.

The wafer polishing head 1 is constructed for the purpose of carrying out the wafer polishing method of the present invention. That is, it is a preferred example of a wafer polishing head in which the flexible film 2 and the dummy plate 10 are integrally configured. This will be described below.

As shown in FIG. 9, the wafer polishing head 1
Is a flexible film 2 whose one main surface serves as a suction surface for the wafer W.
And the flexible film 2 is disposed on the side opposite to the suction surface of the flexible film 2.
A disk-shaped holder 3 having a suction concave portion 3s on the contact surface side thereof and a frame 4 for forming a variable volume raising / lowering chamber 5 separated from the suction concave portion 3s directly above the holder 3 are provided. ing. The flexible film 2 is made of a soft rubber material. The holder 3 is made of a harder plastic material,
For example, polypropylene resin, ABS resin, or metal member can be used. The frame 4 is the CMP device 2
00 is a metal member having high rigidity attached to the vertical drive unit 31.

As described above, by the action of the pressure adjusting device 400 connected to the flow paths 11 and 12 of the wafer polishing head 1, the fluid filling the suction concave portion 3s and the fluid filling the lifting chamber 5 are respectively formed. It can be sucked and compressed independently. In the best mode, the fluid is air. For example, the electromagnetic valve 25, the vacuum pump 40, and the compressor 41 are controlled based on the computer device and the sequence program stored therein, and the suction recess 3 is formed.
s and the inside of the raising / lowering chamber 5 are adjusted to any pressure state of pressurization, depressurization, and opening to the atmosphere.

When the wafer W is suction-held, the air filling the suction recess 3s of the holder 3 is sucked to reduce the pressure in the suction recess 3s and suck the wafer W onto the flexible film 2. Then, from this state, the inside of the raising / lowering chamber 5 is depressurized to reduce the volume of the raising / lowering chamber 5, and the wafer is floated integrally with the holder 3. That is, the wafer polishing head 1 includes a suction path for sucking the wafer W, a suction path for vertically lifting the wafer W, the flexible film 2 that sucks the wafer W, and the holder 3 integrally in the vertical direction. , And two suction paths (distribution paths 11 and 12) of completely different systems. With this configuration, the suction force of the wafer W is increased and the suction force is always kept constant. Therefore, each platen 33, 3
It is extremely unlikely that a transport error will occur when the wafer W is transferred between the platen 33 and the platen 33 or between the platen 33 and the wafer standby position 35. Moreover, the head structure itself is simplified by using two suction paths, which contributes to the reduction of the number of parts.

In the preferred embodiment shown in FIG. 9, when the suction recess 3s is depressurized while maintaining the state where the flexible film 2 and the wafer W are in close contact with each other, the suction recess 3s is flexible. The wafer W is attracted to the flexible film 2 when the film 2 is pulled in. This situation can be explained using FIG. 11. FIG. 11 is a schematic view showing how the flexible film 2 is sucked and the wafer W is chucked. The wafer polishing head 1 itself is brought close to the wafer W so that an excessive pressure is not applied to the wafer W.
The pressure in the elevating chamber 5 is adjusted so that the bank portion 3k and the flexible film 2 are in close contact with each other as much as possible. Then, the wafer W is easily attracted to the flexible film 2. When the vacuum pump 40 is operated to discharge the air in the suction concave portion 3s, the portion of the flexible film 2 that is not in contact with the bank portion 3k is bent and the suction concave portion 3s.
Be drawn in. As a result, the airtight pocket 26 is formed between the wafer W and the flexible film 2, and the wafer W is
Adsorb to. Note that this mechanism is the same for the wafer polishing heads 100 and 101 having the configurations shown in FIGS. 2 and 6.

Further, as shown in FIG. 14, it is also possible to adopt a mode in which the flexible film 2 is formed with a through hole 2s penetrating in the thickness direction. The through hole 2s is provided in a shape corresponding to each of the suction concave portions 3s formed in the holder 3. Thus, even if a hole (passage 2s) is formed in the flexible film 2, the flexible film 2 and the wafer W are in close contact with each other and the suction recess 3 is formed.
If the airtightness of s is maintained, the wafer W can be chucked and separated from the polishing cloth 34. If the flexible film 2 and the peripheral edge Wk of the wafer W can be kept airtight, the pressure in the suction recess 3s can be maintained at the pressure necessary for polishing even during polishing. When the method shown in FIG. 5 is adopted, the through hole 2s is formed so as to penetrate the wafer supporting portion 2w.

Now, the detailed structure of the wafer polishing apparatus 1 will be described. First, between the holder 3 and the flexible film 2,
Each member can be arranged so that the polishing chamber 6 in which the suction recess 3s is opened is formed. Suction recess 3
When the polishing chamber 6 connected to s is formed between the flexible film 2 and the holder 3, it is possible to prevent the holder 3 and the flexible film 2 from contacting each other. That is, since the weight of the holder 3 does not reach the flexible film 2, it is possible to prevent the pressure when the wafer W is biased from being varied and to make the polishing amount uniform. Such an operation is based on the pressure adjustment of the suction concave portion 3s and the lifting chamber 5. Although details will be described later, in the embodiment shown in FIG. 9, a structure is devised in which the flexible film 2 and the holder 3 are not directly connected.

Here, FIG. 10A shows a bottom view of the holder 3, and FIG. 10B shows a sectional view thereof. As shown in (a), a plurality of suction concave portions 3s are formed in a dispersed form on the side of the holder 3 facing the flexible film 2. Further, a groove 3t that connects the plurality of suction concave portions 3s to each other is provided. Even after the flexible film 2 covers the suction concave portion 3s,
In order to continue sucking the flexible film 2, each suction recess 3
It is necessary to apply suction force to s. Therefore, as described above, the groove 3t is provided so that air can flow in and out of the suction recesses 3s, 3s. Then, since all the suction concave portions 3s are spatially connected, the pressure / suction paths can be integrated into one, the structure of the wafer polishing head 1 can be simplified, and the pressure can be easily adjusted.

As shown in FIG. 9, the pressure in the lifting chamber 5 is adjusted through the flow passage 11. The pressure in the suction concave portion 3s is adjusted through the flow path 12. Further, in the present embodiment, a through hole 22 penetrating the holder 3 toward the elevating chamber 5 side is formed in any one suction recess 3 s, and the through hole 22 is sealed. One end of the flow pipe 27 is connected via the member 28. The other end of the distribution pipe 27 is connected to the distribution path 12. The flow pipe 27 is made of a member that can expand and contract as the holder 3 moves up and down.

As shown in FIG. 10 (a), the groove 3t formed in the holder 3 has a suction concave portion 3 provided in a dispersed form.
It has a mesh structure that connects each s. Also, (b)
As shown in, the depth of the groove 3t is preferably approximately the same as the depth of the suction recess 3s. By doing so, it is possible to prevent the problem that the groove 3t is closed when the flexible film 2 is adsorbed and a sufficient adsorption force cannot be obtained.

Now, returning to FIG. 9, description will be made. Holder 3
Is connected to the frame 4 via a first airtight member 7 that allows the volume of the lifting chamber 5 to change, and is configured to be movable up and down with the frame 4 as a fulcrum. That is,
By holding the distance between the frame 4 and the polishing cloth 34 and changing the volume of the lifting chamber 5, the holder 3
The distance between the polishing cloth 34 and the polishing cloth 34, and hence the distance between the wafer W and the polishing cloth 34, can be adjusted. Even when the chucked wafer W is separated from the polishing cloth 34, it is not necessary to change the position of the frame 4.

More specifically, the frame 4 includes the holder 3
And the recesses 20 and 21 that form the lift chamber 5, and the first airtight member 7 closes the gap between the inner portions of the recesses 20 and 21 and the outer peripheral portion 14 of the holder 3 to lift the lift chamber. 5 creates a sealed state. At the same time, the holding member 3 moves up and down inside the frame 4 by the action of the first airtight member 7 to cause a change in the volume of the lifting chamber 5. Thus, the first airtight member 7
Not only maintains the airtight state of the lifting chamber 5, but also serves as a lifting mechanism for the holder 3, which contributes to a reduction in the number of parts. The vertical direction in this specification means a direction parallel to the rotation axis O of the wafer polishing head 1, and the side holding the wafer W is the downward direction and the opposite side is the upward direction.

For the first hermetic member 7, a flexible resin sealing material can be preferably used. Furthermore, a rubber material having excellent adhesion to other members is preferable. Then, the first airtight member 7 functions as a diaphragm, and the lifting mechanism described above can be easily embodied. In addition, the resin sealing material is also excellent in that it is easy to maintain airtightness. In addition,
The outer peripheral portion 14 of the holder 3 to which the first airtight member 7 is connected is
It is a ring-shaped portion integrally formed with the holder 3 in the circumferential direction and extends upward. That is,
The first airtight member 7 itself attached to the ring-shaped portion (the outer peripheral portion 14 of the holder 3) is also a ring-shaped member. If the first airtight member 7 lacks in rigidity,
A rubber material reinforced with glass fiber can also be used.

On the other hand, regarding the method of fixing the flexible film 2, in this embodiment, it is as follows. That is,
A retainer ring 9 that surrounds the flexible film 2 in the circumferential direction and is connected to the flexible film 2 directly or through another member is provided with a frame 4 through a second hermetic member 8 that allows the volume change of the polishing chamber 6. Attached to. Then, the suction recess 3s
The flexible film 2 connected to the retainer ring 9 is configured to urge the wafer W by adjusting the internal air pressure. That is, the polishing chamber 6 includes at least the flexible film 2, the holder 3, the retainer ring 9, and the frame 4.
Thus, the airtightness is secured, and the approach / separation between the flexible film 2 and the holder 3 can be controlled based on the volume change of the polishing chamber 6.

When the wafer W is polished, the second airtight member 8 is mounted on the retainer ring 9 and the frame 4 so that the second airtight member 8 is inclined so that the second airtight member 8 is inclined downward as it approaches the rotation axis O of the wafer polishing head 1. The position, flexibility, etc. are adjusted. Specifically, as shown in the schematic view of FIG. 16, the extension line of the inclination in the cross section parallel to the axis O is made to overlap the center A of the polishing surface of the wafer W.
By doing so, it is possible to prevent the rotational moment from acting on the retainer ring 9, and thus the flexible film 2. Therefore, a uniform polishing pressure can be applied to the entire wafer W. A more complete description is disclosed in Japanese Patent No. 2770730 (the title of the invention "wafer polishing apparatus", assigned to the assignee of the present invention) by K. Tanaka et al., The entire contents of which can be incorporated into the present invention.

When the wafer W is attracted to the flexible film 2, the flexible film 2 and the holder 3 are brought into close contact with each other (see FIG. 13). On the contrary, when polishing the wafer W, it is preferable that the flexible film 2 is not in contact with the holder 3. According to the present invention, the contact / non-contact state between the flexible film 2 and the holder 3 can be easily created based on the pressure adjustment of the elevating chamber 5 and the suction recess 3s (and thus the polishing chamber 6). it can. The second airtight member 8 may be made of a flexible resin sealing material like the first airtight member 7. Then, the same effect as the case where the first airtight member 7 is used for connecting the holder 3 and the frame 4 can be obtained.

When a resin sealing material is used for the first airtight member 7 and the second airtight member 8, the connection between the airtight members 7, 8 and other members (the holder 3, the frame 4 and the retainer ring 9) is As shown in FIG. 12, it can be realized by bolt fastening. FIG. 12 is an exploded view showing a method of connecting the second airtight member 8 and the retainer ring 9. The second airtight member 8, which is a ring-shaped flat rubber member, has through holes 8a penetrating in the thickness direction (corresponding to the vertical direction of the wafer polishing head 1) in its inner portion at a plurality of circumferential positions at substantially equal angular intervals. It is provided. Similarly, a through hole 8b is formed in the outer portion. Similarly, the clamp 15 is also formed with a through hole 15a. A female screw 9a is formed on the upper end surface 9p of the retainer ring 9. When fastening each member, the bolt VO is inserted through the hole 15a and the hole 8a in this order and screwed into the female screw 9a. The through hole 8b of the second airtight member 8 is for locking the outer peripheral portion of the second airtight member 8 to the frame 4 (see FIG. 9). As can be seen from FIG. 9, the above-mentioned fastening method, that is, the clamp 13,
Using 15, 16 and 17 and the bolt VO, the airtight members 7 and 8 are connected to other members (the holder 3, the frame 4 and the retainer ring 9) to keep the airtightness.

Further, the recesses of the frame 4 are stepped recesses 20 and 21 having wide mouths on the lower side. Utilizing the stepped shape, the first airtight member 7 and the second airtight member 8 having a larger diameter than the first airtight member 7 are attached to the frame 4, respectively. In this way, the holder 3 and the retainer ring 9 are brought into contact with each other in the vertical direction, and there is no fear that the smooth operation of the wafer polishing head 1, that is, the lifting operation of the holder 3 is disturbed. As a result, it is less likely that the suction force of the wafer W will be reduced. Specifically, as shown in FIG. 9, the recess 2 having the widest opening in the frame 4 is formed.
1 and the lower end surface 4r adjacent to 1 and the upper end surface 9 of the retainer ring 9.
The second airtight member 8 is arranged in a positional relationship extending over q. Similarly, the stepped recesses 20 and 21 form the frame 4
The first airtight member is arranged in a positional relationship that spans the stepped surface 4q formed on the outer peripheral portion upper end surface 14r of the holder 3. In this way, the holder 3 moves up and down inside the retainer ring 9.

FIG. 15 shows another embodiment in which a sliding member such as an O-ring capable of sealing a gap between members is adopted instead of adopting a flexible sealing material as each airtight member 7, 8. Show. In the wafer polishing head 1a shown in FIG. 15, the O ring 281 is a substitute for the first airtight member 7 and the O ring 282 is a substitute for the second airtight member 8. Alternatively, it goes without saying that the O-ring may be applied to only one of the first airtight member 7 and the second airtight member 8. As shown in FIG. 15, inside the frame 4 having a concave shape, the holder 3 is slidably held by the O-ring 281. Similarly, the retainer ring 9 is slidably held by the O-ring 282 on the outer peripheral surface of the frame 4. Although a fall prevention pin 27 is attached to the retainer ring 9, the retainer ring 9 is adjusted so that the vertical relative movement of the retainer ring 9 with respect to the frame 4 is appropriately permitted.

Returning to the preferred embodiment of FIG. 9, description will be made. The method of connecting the flexible film 2 and the retainer ring 9 can be as follows. That is, in the wafer polishing head 1, the dummy plate 10 that spans the retainer ring 9 and the flexible film 2 over the entire circumferential direction is provided on the lower end surface 9r of the retainer ring 9 and the suction surface side of the flexible film 2. There is. Then, the dummy plate 10
The wafer W in the shallow recess formed by the flexible film 2 and the flexible film 2.
Are placed and polishing is performed. Thus, the flexible film 2 is not directly connected to the retainer ring 9 and the dummy plate 10 is not connected.
By interposing, the pressure is applied to the wafer W from a portion excluding the peripheral portion of the flexible film 2, that is, from the center of the disk-shaped flexible film 2 as much as possible. That is,
During the polishing, the wafer W receives the pressure from the flexible film 2 more uniformly, so that the problem that the polishing amount varies due to the uneven pressure is effectively suppressed. The method of the present invention described above is also applied here.

The thickness of the dummy plate 10 is preferably set to be approximately the same as that of the wafer W that has been polished. That is, the wafer W and the dummy plate 1 before polishing
The difference d in thickness from 0 is the target polishing amount. This is as shown in FIG.

As shown in FIGS. 9 and 13, the peripheral edge of the flexible film 2 and the peripheral edge of the holder 3 are adjusted so as to overlap each other in the vertical movement direction of the holder 3. Therefore, based on the adjustment of the pressure and / or the amount of air that fills the suction recess 3 s and the lifting chamber 5, the peripheral edge of the holder 3 is supported by the dummy plate 10 and the flexible film 2 is formed. It is supposed to be in close contact. If the holder 3 and the flexible film 2 can be brought into close contact with each other, it becomes easy to create a trigger for the wafer W to be attracted to the flexible film 2. As a result, the wafer W becomes the flexible film 2
Will be smoothly absorbed into.

Now, the operation of polishing the wafer W using the wafer polishing head 1 of the present invention described above will be described. Steps 1 to 14 shown in FIGS. 17 and 18 show a series of operations of the wafer polishing head 1.

(Operation for Transporting Wafer W from Wafer Standby Position 35 onto Polishing Cloth 34) Standby State: Polishing chamber 6, suction recess 3s and lifting chamber 5 are open to the atmosphere. Note that FIG.
The downward arrow shown in 18 means that compressed air is sent to pressurize above atmospheric pressure. The upward arrow means that suction is performed and the pressure is reduced below atmospheric pressure. The broken line + outline arrow means opening to the atmosphere. Step 1: While the pressure of the suction concave portion 3s is maintained at the atmospheric pressure, the inside of the lifting chamber 5 is depressurized and the volume of the lifting chamber 5 is reduced. At the same time, the holder 3 moves upward relative to the frame 4. Step 2: The wafer polishing head 1 is aligned with the wafer W prepared at the wafer standby position 35 by the head drive mechanism 39 while maintaining the state of Step 1. The position of the wafer polishing head 1 may be adjusted by the head driving mechanism 39 before Step 1. At this time, the pressure in the suction recess 3s may be adjusted so that the holder 3 and the flexible film 2 come into close contact with the flexible film 2 and the wafer W, respectively. Step 3: The inside of the lifting chamber 5 is pressurized. Then, the suction recess 3s and the polishing chamber 6 are decompressed, the flexible film 2 is drawn into the suction recess 3s, and the wafer W is chucked. At this time, the wafer W is still in contact with the wafer standby position 35. Step 4: The inside of the elevating chamber 5 is depressurized while the state of Step 3 in which the wafer W is chucked is maintained. Then, the wafer W, the flexible film 2 chucking the wafer W, and the holder 3 are integrally lifted, and the wafer W is separated from the wafer standby position 35. Step 5: The head drive mechanism 39 transfers the wafer W from the wafer standby position 35 onto the polishing cloth 34.

(Operation for Polishing Wafer W) Step 6: The head drive mechanism 39 causes the wafer polishing head 1 to approach the polishing cloth 34. Step 7: The inside of the raising / lowering chamber 5 is pressurized, the volume of the raising / lowering chamber 5 is increased, and the wafer W, the flexible film 2 and the holder 3 are integrally lowered. At this time, the suction concave portion 3s is maintained in a reduced pressure state. Step 8: The inside of the suction recess 3s is pressurized. Step 9: The pressure in the lifting chamber 5 is reduced. Then, the holder 3 moves up. This state is maintained and the wafer W is polished. The pressure in the suction recess 3s and the polishing chamber 6 is adjusted to a predetermined polishing pressure.

(Operation of Returning Polished Wafer W to Wafer Standby Position 35) Step 10: While the inside of the raising / lowering chamber 5 is pressurized, the holder 3 is placed on the flexible film 2 and the flexible film 2 is placed on the wafer W. The pressure in the suction concave portion 3s is adjusted so as to be in close contact. Step 11: Suction recess 3s and polishing chamber 6
Is depressurized and the wafer W is chucked. At this time, the wafer W is still in contact with the polishing cloth 34. Step 12: Step 1 in which the wafer W is chucked
The inside of the elevating chamber 5 is depressurized while the state of 1 is maintained. Then, the wafer W, the flexible film 2 chucking the wafer W, and the holder 3 are integrally lifted, and the wafer W is separated from the polishing cloth 34. Step 13: The head drive mechanism 39 moves the wafer polishing head 1 itself away from the polishing cloth 34. Step 14: The head drive mechanism 39 transfers the wafer W chucked by the wafer polishing head to the wafer standby position 35. After that, the inside of the suction concave portion 3s is opened to the atmosphere and the wafer W is dechucked.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of a wafer polishing method and a polishing head of the present invention.

FIG. 2 is a schematic diagram following FIG.

FIG. 3 is a schematic diagram showing an example of adjusting the thickness of a dummy plate.

FIG. 4 is a schematic diagram showing a state when buckling deformation occurs in a dummy plate.

FIG. 5 is a schematic diagram showing a polishing method in the case where the dummy plate is made thicker than the wafer.

FIG. 6 is a conventional wafer polishing head adopting a waxless mount system.

FIG. 7 is a schematic view showing an example of a CMP apparatus in which a wafer polishing head is mounted.

FIG. 8 is a top view of the CMP apparatus subsequent to FIG.

FIG. 9 is a vertical cross-sectional view of the wafer polishing head of the present invention.

10 is a bottom view and a cross-sectional view of a holder included in the wafer polishing head of FIG.

FIG. 11 is a schematic view showing a state in which a flexible film is sucked and a wafer is chucked.

FIG. 12 is an exploded view showing a method of connecting the airtight member and the retainer ring.

13 is a schematic diagram illustrating the positional relationship between a flexible film and a holder in the wafer polishing head of FIG.

FIG. 14 is a schematic cross-sectional view of a flexible film in which a through hole that opens to the back surface side of the wafer and the suction recess is formed.

FIG. 15 is a vertical cross-sectional view showing another example of the connection form of the frame, the holder and the retainer ring.

FIG. 16 is a schematic diagram illustrating a connection positional relationship between a second airtight member, a frame, and a retainer ring.

FIG. 17 is a process explanatory view for explaining the operation of transferring and polishing a wafer from the wafer standby position to the polishing cloth.

FIG. 18 is a process explanatory view explaining the operation of separating the wafer from the polishing cloth and transferring the wafer to the wafer standby position, following FIG. 17;

[Explanation of symbols]

1,101 Wafer polishing head 2 Flexible membrane 2w wafer support 2p flexible membrane surface 2q Flexible membrane back side 3,56 Holder 10 Dummy plate Top of 10p dummy plate W wafer PZ placement area d Polishing allowance Q through hole

Claims (10)

[Claims] 1. A method for polishing a wafer on one side, wherein a front surface forms a contact surface with the wafer and a flexible film for transmitting a pressure necessary for polishing to the wafer from the back surface side,
A ring-shaped dummy plate is arranged so as to surround the arrangement area by making surface contact with the surface of the flexible film while defining the wafer arrangement area on the surface side, and the wafer arranged inside the dummy plate. A method for polishing a wafer, wherein single-side polishing is performed so that a fluid pressure is applied to the surface. 2. A disk-shaped holder having a through hole in the thickness direction is arranged on the back surface side of the flexible film, and the peripheral edge of the flexible film is fixed to the peripheral edge of the holder. 2. The wafer polishing method according to claim 1, wherein the dummy plate is arranged so as to hold the flexible film and overlap the holder in the thickness direction of the wafer to be polished. 3. The wafer polishing method according to claim 1, wherein the thickness of the dummy plate is adjusted in advance so that the thickness of the dummy plate is thinner than that of the wafer to be polished. 4. The thickness of the dummy plate is adjusted in advance on the basis of the thickness of the wafer to be polished and the polishing allowance of the wafer so that the wafer has a thickness almost equal to that of the wafer after polishing. 4. The method according to claim 1, wherein
The method for polishing a wafer according to any one of 1. 5. The dummy plate is formed to be thicker than a wafer to be polished, and a difference in thickness between the dummy plate and the wafer, which is caused thereby, is larger than a connecting portion with the dummy plate. Offset by using the flexible film with the wafer support formed in the flesh,
The wafer polishing method according to claim 1, wherein polishing is performed. 6. The wafer polishing method according to claim 5, wherein the wafer supporting portion is convex below the upper surface of the dummy plate to apply a polishing pressure to the wafer. 7. The wafer polishing method according to claim 1, wherein the entire one main surface of the dummy plate is brought into surface contact with the flexible film. 8. The resin plate containing glass fibers, wherein the dummy plate is formed into a plate shape by impregnating glass fibers with a resin.
The method for polishing a wafer according to item. 9. The wafer polishing according to claim 1, wherein the flexible film is pressurized by gas from the back surface side of the flexible film to apply pressure to the wafer. Method. 10. A wafer polishing head for realizing the method according to claim 1, wherein the dummy plate is attached to the flexible film to form the flexible film. A wafer polishing head characterized by being integrated with the dummy plate.