JP2000271860A - Wafer polishing device and wafer manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the load torque threshold value of a diaphragm without damaging the following characteristics of wafer in the perpendicular direction to the surface and improve polishing efficiency and uniformity of the polishing surface by setting it freely slidable in the head axial direction and restricting the displacement in the tangential direction of a circle with its center set to the head axis. SOLUTION: A guide member 50 is fitted to the upper face of a carrier 30 by a bolt 50b and a guide member 51 paired with the guide member 50 is fitted to a top plate part of a head body 33 by a bolt 51b. The interval between the opposed guide surfaces of the guide member 50 is set a little larger than the board thickness of the guide member 51. The paired guide members 50, 51 thus form an engagement state with each other with a slight clearance. This constitution does not restrict the displacement in the axis Q direction of the carrier 30 but restrict the displacement about the axis Q. This constitution can reduce the time for replacing the diaphragm and reduce the cost of the diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer polishing apparatus and a wafer manufacturing method, and more particularly, to a polishing surface uniformity in a wafer polishing apparatus which holds a wafer to be polished in a floating state and is suitable for CMP (chemical mechanical polishing) or the like. Improvement and productivity improvement.

[0002]

2. Description of the Related Art With the increasing integration of semiconductor integrated circuits and the resulting finer patterns, the demand for improved surface accuracy of wafers serving as substrates has been increasing more and more in recent years. As a wafer polishing apparatus that meets such demands, a disk-shaped platen having a polishing pad attached to the surface, and a plurality of wafer holding devices that hold one surface of a wafer to be polished and abut the other surface of the wafer on the polishing pad. 2. Description of the Related Art There is known an apparatus which includes a head and a head drive mechanism for rotating these wafer holding heads relative to a platen, and performs polishing by supplying a slurry containing abrasive grains between a polishing pad and a wafer. .

[0003] As an improvement of this type of polishing apparatus,
U.S. Pat. No. 5,205,082 discloses a wafer holding head as shown in FIG. This wafer holding head has a hollow head main body 1, a diaphragm 2 stretched horizontally in the head main body 1, and a carrier 4 fixed to the lower surface of the diaphragm 2. The retainer ring 1 has a small gap concentrically around the outer periphery of the carrier 4.
2, and the retainer ring 12 is also fixed to the diaphragm 2. Further, a stopper portion 3 of the head main body 1 is disposed concentrically with a small gap around the outer periphery of the retainer ring 12. Thus, the carrier 4 and the retainer ring 12 are floatingly supported by the head main body 1. On the upper side of the diaphragm 2, an air chamber 6 is formed by the head body 1 and the diaphragm 2.
Is formed, in which pressurized air can be supplied from a pressurized air source 10 through the inside of the shaft 8.

[0006] The polishing operation is performed by bringing the wafer W adhered and fixed to the carrier 4 via the insert S into contact with the polishing pad 14. This contact pressure can be adjusted by changing the pressure of the air supplied to the air chamber 6.
As described above, the conventional wafer polishing apparatus has an advantage that the contact pressure of the wafer W can be made uniform and the uniformity of the polished surface of the wafer can be improved. In addition,
The diaphragm 2 used here is usually formed of an elastic material such as a rubber material or an ultrathin metal plate, and has a plane rigidity that does not hinder the movement of the carrier 4 in the axial direction.

[0005]

Incidentally, a frictional force is always generated between the wafer W and the polishing pad 14 during the polishing operation. Thus, the horizontal force and torque acting on the carrier 4 and the retainer ring 12 are supported by the retainer ring 12, the flange portion 3 of the head main body 1, and the diaphragm 2 in the above-described conventional wafer polishing apparatus. The carrier 4 and the retainer ring 12 and the retainer ring 12 and the flange 3 each have a circular contour and are in a fitting relationship with a slight gap as described above. Therefore, the horizontal force acting on the carrier 4 and the retainer ring 12 can be supported by the contact between the respective side walls, but the torque around the axis is supported only by the diaphragm 2.

[0006] The torque acting on the diaphragm 2 during the polishing operation is unstable due to frictional force, and sometimes exceeds the strength limit of the diaphragm 2 and the thin-walled diaphragm 2 may be damaged. Was. Since the frictional force due to polishing and the torque acting on the diaphragm 2 increase in accordance with the force pressing the wafer W against the polishing pad 14 and the polishing speed, the pressing force is required to prevent the diaphragm 2 from being damaged. In addition, the polishing rate is limited. The limitations on the polishing conditions determine the polishing efficiency (the number of polishings per time), the surface accuracy of the polished surface, and the uniformity limit.

As a countermeasure against the above-mentioned problem, it is conceivable to increase the strength of the diaphragm 2 by increasing the thickness thereof. However, in this case, the in-plane rigidity inevitably increases, and the carrier 4 follows the carrier 4 in the axial direction. This deteriorates the flatness and uniformity of the polished surface.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and increases the load torque limit value of the diaphragm without impairing the followability of the wafer in the direction perpendicular to the surface, thereby improving the polishing efficiency and improving the uniformity of the polished surface. It is an object of the present invention to provide a wafer polishing apparatus capable of improving the performance and a wafer manufacturing method using the same in a polishing process.

[0009]

According to the present invention, there is provided an apparatus for polishing a semiconductor wafer, comprising: a platen having a polishing pad attached to a surface thereof; and a wafer to be polished. A wafer holding head that holds one surface of the wafer and abuts the other surface of the wafer on the polishing pad; and a head driving mechanism that drives the wafer holding head to polish the other surface of the wafer. A head body, a diaphragm stretched in the head body perpendicular to the head axis, a fluid chamber formed between the diaphragm and the head body, and a fluid pressure filled in the fluid chamber. A pressure adjusting mechanism for adjusting, and a circle fixed to the diaphragm, displaced in the head axis direction together with the diaphragm, and holding one surface of a wafer to be polished. And Jo carrier, arranged concentrically on the outer circumference of the carrier, is secured to the diaphragm is displaced to the head axis direction together with the diaphragm,
A polishing apparatus comprising: a retainer ring that abuts on a polishing pad during polishing; and at least one pair of guide members, one of which is fixed to the head body and the other is fixed to at least one of the carrier and the retainer ring. Is characterized by being slidable in the direction of the head axis at the meshing portion and restricting displacement in the tangential direction of a circle centered on the head axis.

According to this structure, when a torque around the axis acts on the carrier due to the abrasive frictional force, the paired guide members bear this torque, so that the shear stress of the diaphragm is greatly reduced and the diaphragm is thin. Even damage can be prevented. Further, since the paired guide members are slidable in the head axis direction, the followability of the carrier in the axis direction is not impaired.

According to a second aspect of the present invention, in the wafer polishing apparatus according to the first aspect, instead of the pair of guide members, the wafer polisher meshes with each other slidably in the axial direction of the carrier. The guide portion is formed on at least one of an outer peripheral portion of the carrier, an inner peripheral portion of the retainer ring, and an outer peripheral portion of the retainer ring and the head main body in the vicinity thereof.

According to this structure, even when the space above the carrier or the retainer ring is narrow and it is difficult to mount the guide member, the guide portion is provided on the carrier, the retainer ring, or the head main body. The same diaphragm protection effect as the first aspect of the invention can be obtained.

According to a third aspect of the present invention, there is provided a method of manufacturing a wafer, wherein the wafer polishing step uses the wafer polishing apparatus according to the first or second aspect,
The wafer is polished while adjusting the pressure in the fluid chamber, the rotation speed of the platen, and the operation speed of the head drive mechanism.

According to this wafer manufacturing method, in the polishing step, it is possible to perform polishing under a wafer pressing condition or a polishing rate which could not be used conventionally to prevent the breakage of the diaphragm, thereby improving the polishing efficiency. , And the uniformity of the polished surface of the wafer can be improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of a wafer polishing apparatus according to the present invention. First, the overall configuration will be described with reference to FIG.
Reference numeral 1 denotes a base, and a disk-shaped platen 22 is horizontally installed at the center of the base 21. The platen 22 is driven by a platen drive mechanism provided in the base 21 so that the axis P
, And a polishing pad 23 is attached to the entire upper surface thereof.

A plurality of columns 24 are installed on the upper surface of the base 21, and an upper mounting plate 25 is arranged along the columns 24 so as to be able to move up and down while keeping the horizontal. The upper mounting plate 25 is raised when mounting and removing the wafer W, and lowered during the polishing operation. On the lower surface of the upper mounting plate 25,
A disk-shaped carousel (head driving mechanism) 26 is arranged, and the carousel 26 is connected to a driving device 28 and is driven to rotate about an axis P. This rotary drive shaft is
It may be arranged off-axis from the axis P and non-coaxially with the platen 22, so that the polishing pad 23 can be used more widely. The carousel 26 is provided with a total of six wafer holding heads 27 facing the platen 22. Each wafer holding head 27
It has an axis Q as its center of rotation, and these axes Q
They are arranged every 60 ° on the circumference of a circle R centered on the top. FIG. 4 shows an arrangement relationship between the polishing pad 23 and the wafer holding head 27. Then, each wafer holding head 27
Performs a revolving motion around the axis P due to the rotation of the carousel 26 and a rotating motion around the axis Q by the gear mechanism inside the carousel 26. In the present embodiment, the number of the wafer holding heads 27 is six, but the number is not limited thereto.

Next, a wafer holding head 27 according to the present embodiment will be described with reference to FIG. The wafer holding head 27 includes a hollow head main body 33 arranged perpendicular to the axis Q and having a lower end opened, a diaphragm 29 stretched inside the head main body 33, and a carrier 30 fixed to a lower surface of the diaphragm 29. , And a retainer ring 41 concentrically disposed outside the carrier 30.

The head main body 33 has a disc-shaped top plate 31,
A cylindrical peripheral wall portion 32 connected to the outer periphery of the top plate portion 31
The top plate 31 is connected to a spindle of the carousel 26 via a shaft 34. Surrounding wall 3
2 has a diaphragm-shaped diaphragm mounting portion 32a protruding radially inward over the entire circumference near the lower end thereof, and further has a stopper portion 32b protruding radially inward below the shelf mounting portion 32a. The peripheral portion of the annular diaphragm 29 is placed on the diaphragm mounting portion 32a, and is fixed by the fixing ring 42. The diaphragm 29 is formed of an elastic material such as various types of rubber or a thin metal plate.

Although the diaphragm 29 of this embodiment is annular, the center portion is closed by attaching the carrier 30 to the lower surface thereof, and the fluid chamber 36 is formed by combining the top plate portion 31 and the peripheral wall portion 32. You. On the other hand, a flow passage 35 communicating with the fluid chamber 36 is formed inside the shaft 34, and is connected to a pressure adjusting mechanism 37. Then, by changing the fluid pressure in the fluid chamber 36 by the pressure adjusting mechanism 37, the pressing force of the carrier 30 against the polishing pad 23 can be adjusted via the diaphragm 29. As the fluid, it is generally sufficient to use air, but other types of gas or liquid may be used as needed.

The retainer ring 4 has a slight gap on the inner side of the inner peripheral surface of the stopper 32b at the lower end of the peripheral wall 32.
1 is arranged. The retainer ring 41 has an annular shape,
It is fixed to the diaphragm 29 using a fixing ring 43. With this configuration, the retainer ring 41 can be displaced in the direction of the axis Q with respect to the head main body 33. The carrier 30 is arranged with a slight gap inside the inner peripheral surface 41b at the lower end of the retainer ring 41. Further, a flange portion 41a protruding outward in the radial direction is formed on a peripheral edge portion of the retainer ring 41. When the wafer holding head 27 is pulled up from the platen 22 together with the carousel 26, the flange portion 41a becomes a peripheral wall portion. 32 is held by a stopper portion 32b formed at the lower end.

The carrier 30 is made of a material having high rigidity, such as ceramics, and is formed in a disk shape and has a constant thickness. The carrier 30 includes the retainer ring 4 as described above.
After being arranged radially inward of one, it is fixed to the diaphragm 29 with a plurality of bolts using a carrier fixing ring 44. With this configuration, the carrier 30 can be displaced in the direction of the axis Q independently of the retainer ring 41. An outwardly extending flange portion 44a is formed at the upper end of the carrier fixing ring 44. When the head is raised, the flange portion 44a is held by the stopper portion 45a of the stopper bolt 45, so that the weight of the carrier 30 is supported. I have. The stopper bolt 4
The length of 5 is adjustable by a spacer 46 and a double nut 47.

In this embodiment, on the upper surface of the carrier 30,
The guide member 50 is attached by bolts 50b, and a guide member 51 that makes a pair with the guide member 50 is attached to the top plate 31 of the head main body 33 by bolts 51b. The detailed shapes of the pair of guide members 50 and 51 are shown in cross section in FIG. In the guide member 50,
Two planes facing the “U-shaped” portion are the guide surfaces 50a. On the other hand, in the guide member 51, both surfaces of the flat plate-shaped portion are guide surfaces 51a. The distance D between the facing guide surfaces 50a of the guide member 50 is the guide member 51.
Is set to be slightly larger than the plate thickness T. Therefore, the pair of guide members 50 and 51 form a meshing state with a slight gap. With this configuration, the displacement of the carrier 30 in the direction of the axis Q is not restricted, but the rotation about the axis Q is restricted.

Since the guide members 50 and 51 slide relative to each other, a hard material such as a metal is suitable as the material, and the guide surfaces 50a and 51a are polished as necessary to reduce friction. It is desirable to do. Further, a lubricant may be applied to the guide surfaces 50a and 51a.

The guide member 50 is attached to the carrier 30 by inserting two bolts 50b into the guide member 50,
This is performed by screwing this into the carrier 30. The mounting of the guide member 51 to the top plate portion 31 of the head main body 33 is the same, and is performed by screwing two bolts 51b. By the way, in order for the guide members 50 and 51 to have the guide function which is the original purpose, it is important that the directions of the respective guide surfaces 50a and 51a are aligned in the mounted state. As in the present embodiment, if the guide members 50 and 51 are fixed with two bolts, respectively, it is possible to roughly align the directions. This can be achieved by interposing a knock pin between the carrier member 30 and the guide member 51 and the top plate 31.

FIG. 5 shows a mounting state in which the upper guide member is a guide member 54 having a female screw. Here, the top plate portion 31 is provided with two bolt insertion holes 31a, and the guide member 54 is fixed by screwing two bolts 54b from above the top plate portion 31. In this case, in order to maintain the airtightness of the fluid chamber 36, necessary airtight treatment is performed around the bolt insertion hole 31a or the bolt 54b.

Next, the operation of assembling the wafer holding head 27 having such guide members 50 and 51 will be described. First, regarding the peripheral wall portion 32 side, the guide member 50
Is mounted on the upper surface of the carrier 30 with the two bolts 50b as described above. On the other hand, the retainer ring 41 is inserted from above the peripheral wall portion 32, and the flange portion 41a is placed on the stopper portion 32b. In this state, the diaphragm 29 is fixed by the fixing ring 42 to the diaphragm attaching portion 32a of the peripheral wall portion 32.
Attach to Subsequently, the retainer ring 41 is lifted and attached to the diaphragm 29 by the fixing ring 43. Further, the carrier 30 on which the guide member 50 is mounted in advance.
Into the retainer ring 41 from below, and
9, and is fixed by the carrier fixing ring 44. On the top plate 31 side, the guide member 51 is attached to the lower surface of the top plate 31 with two bolts 51b, and the shaft 34, the stopper bolt 45 and the like are further attached. After assembling the peripheral wall portion 32 side and the top plate portion 31 side in this way, the peripheral wall portion 32 is fitted from below the top plate portion 31. The fitting operation is performed while paying attention to whether the guide members 50 and 51 are engaged. At the time of complete fitting, fixing is performed by the connection screw 38, and the assembling work is completed.

Next, the polishing operation using the polishing apparatus, the behavior around each wafer holding head, and the operation of the guide member will be described. To perform the polishing, first, the carrier 30
The wafer W is attached and fixed to the lower surface of the wafer through an insert S. The insert S is formed of a material having water absorbency, and absorbs the wafer W by surface tension when absorbing moisture. Urethane foam or the like is given as a specific material of the insert S, and its preferable thickness is 0.6 mm or more.
0.8 mm. However, the present invention does not necessarily require the use of the insert S. For example, a configuration may be employed in which the wax is interposed on the lower surface of the carrier 30 to attach the wafer W, or another attaching means may be used.

Subsequently, the upper mounting plate 25 is lowered to bring the polished surface of the wafer W into contact with the polishing pad 23. Here, the pressure in the fluid chamber 36 is adjusted by the pressure adjusting device 37,
Thereby, the pressing force of the wafer W is set to a predetermined value. Then, the polishing proceeds by driving the carousel 26 and the platen 22 while supplying the polishing slurry to the surface of the polishing pad 23.

While polishing is in progress, the diaphragm 29 has a function of floatingly supporting the carrier 30 and the retainer ring 41 so as to keep the pressing force of the wafer W against the polishing pad 23 always appropriate. Further, frictional force always acts on the polished surface. Due to the horizontal input to the carrier 30 and the retainer ring 41 due to the frictional force, a shear stress is generated in the flexible portions 29a and 29b of the diaphragm 29. The components of the shear stress are roughly classified into two types, one is due to the friction torque accompanying the rotation of the wafer holding head 27 around the axis Q, the other is the revolving motion around the axis P of the wafer holding head 27 and This is due to frictional force accompanying the rotation of the platen 22 about the axis P.

As described above, the carrier 30 and the retainer ring 41, and the retainer ring 41 and the head body 3
The third stopper portions 32b are in a fitting relationship with a slight gap. Carrier 30 and retainer ring 41
In the meantime, the relative displacement in the horizontal direction between the retainer ring 41 and the peripheral wall portion 32 is very small. Therefore, of the above-mentioned shear stress, the shear stress generated in the flexible portions 29a and 29b by the frictional force is very small. is there.

The problem is the former shear stress due to the friction torque around the axis Q. In the conventional head structure,
Since there is nothing to restrict the rotation of the carrier 30 and the retainer ring 41 about the axis Q, and the diaphragm 29 receives all the torque input about the axis Q, the flexible portions 29a, 29b
In some cases, excessive shear stress was generated. But,
In the present embodiment, torque input to the carrier 30 around the axis Q is transmitted to the guide members 50 and 51 meshing with each other.
, The shear stress of the flexible portions 29a and 29b can be greatly reduced. In FIG. 1, the guide member is a pair, but strictly, in this case, not only the guide members 50 and 51 receive the torque but also the side walls of the carrier 30, the retainer ring 41, and the stopper portion 32b. .

The guide members are not limited to a pair as shown in FIG. 1, but a plurality of guide members may be provided. For example, if two pairs of guide members are provided, the torque component can be supported only by the guide members, which may be advantageous from the viewpoint of reducing the sliding friction in the head axis direction.

FIG. 6 shows another embodiment relating to how to attach the guide member. In the present embodiment, one guide member 52
Are mounted on the retainer ring 41, and the other guide member 53, which meshes slidably in pairs, is mounted on the top plate 31 of the head main body. In this mounting method, the diaphragm 29
Although the shear stress of the flexible portion 29a is not reduced, this embodiment may be selected, for example, when the space above the carrier 41 is limited and a guide member cannot be attached.

In addition, a guide member may be provided on both the carrier 30 and the retainer ring 41 by combining the embodiments of FIGS. With such a configuration,
For example, in the embodiment of FIG. 1, the shear stress generated in the flexible portion 29b due to the torque input to the retainer ring 41 can be reduced.

FIGS. 7 and 8 show still another embodiment.
Serrations 30 s are provided on the entire outer periphery of carrier 30, serrations 41 s meshing therewith are provided on the entire inner periphery of retainer ring 41, and serrations 41 t are provided on retainer ring 41.
The serrations 32s meshing with the serrations are provided on the entire inner periphery of the lower end of the peripheral wall portion 32 of the head main body 33.
FIG. 8 shows the serration shape in detail by partially enlarging a cross section taken along line BB in FIG. These serrations may not be arranged over the entire circumference, but may be partially arranged on the circumference. In any case, the torque input to the carrier 30 is transmitted to the peripheral wall portion 32 of the head main body 33 via the retainer ring 41, so that the diaphragm 29
Flexible portions 29a and 29b can be protected.

[0036]

As described above, according to the first aspect of the present invention, it is possible to prevent the diaphragm from being damaged by the shearing force during polishing, thereby reducing the time required for replacing the diaphragm and reducing the cost of the diaphragm itself. be able to. In addition, the limit value of the wafer pressing pressure and the limit value of the polishing movement speed, which are conventionally determined from the viewpoint of protecting the diaphragm, can be increased, and the uniformity of the polished surface and the polishing efficiency can be improved.

According to the second aspect of the present invention, even when the space above the carrier or the retainer ring is narrow and it is difficult to attach the guide member, the guide portion is provided on the carrier, the retainer ring or the head body. By providing the same, it is possible to obtain the same diaphragm protection effect as the first aspect of the present invention.

According to the third aspect of the present invention, in the polishing process in the wafer manufacturing process, it is possible to perform polishing under a wafer pressing condition or a polishing speed which could not be conventionally used for preventing the breakage of the diaphragm, and the polishing efficiency is improved. , The wafer production efficiency thereby, and the uniformity of the polished surface of the wafer can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a head body of a wafer polishing apparatus according to a first embodiment of the present invention.

FIG. 2A shows a detailed shape of a guide member in FIG.
FIG.

FIG. 3 is a front view showing a main part of the wafer polishing apparatus according to the present invention.

FIG. 4 is a plan view showing an arrangement state of a wafer holding head and a platen of the apparatus.

FIG. 5 is a cross-sectional view of a head main body showing another embodiment relating to attachment of a guide member to a top plate portion.

FIG. 6 is a sectional view of a head main body in another embodiment relating to a mounting position of a guide member.

FIG. 7 is a sectional view of a wafer holding head main body of an embodiment in which serrations are provided on a carrier, a retainer ring, and a head main body.

FIG. 8 is a partially enlarged view of a cross section taken along line BB in FIG. 7, showing serrations provided on a carrier, a retainer ring, and a head main body.

FIG. 9 is a cross-sectional view of a head body of a conventional polishing apparatus that holds a carrier in a floating state.

[Explanation of symbols]

 22 Platen 23 Polishing Pad 26 Carousel 27 Wafer Holding Head 29 Diaphragm 30 Carrier 31 Top Plate 32 Peripheral Wall 41 Retainer Ring 50, 51 Guide Member S Insert W Wafer

Claims (3)

[Claims] 1. A platen having a polishing pad attached to a surface thereof, a wafer holding head for holding one surface of a wafer to be polished and bringing the other surface of the wafer into contact with the polishing pad, and driving the wafer holding head. A head drive mechanism for polishing the other surface of the wafer by performing the above, the wafer holding head, a head body, a diaphragm stretched in the head body perpendicular to the head axis, and the diaphragm and the head body A fluid chamber formed between the fluid chamber and a pressure adjusting mechanism for adjusting a fluid pressure filled in the fluid chamber; fixed to the diaphragm, displaced in the head axis direction together with the diaphragm, and holds one surface of a wafer to be polished. A disc-shaped carrier, which is arranged concentrically around the outer periphery of the carrier, and is fixed to the diaphragm, and A retainer ring that is displaced in the head axis direction together with the head, and abuts against a polishing pad during polishing; and at least one pair of guides, one of which is fixed to the head body and the other is fixed to at least one of the carrier and the retainer ring and meshes with each other. A wafer polishing apparatus, comprising: a guide member slidable in a direction of a head axis at a meshing portion of the guide member; and a displacement control in a tangential direction of a circle centered on the head axis. 2. The wafer polishing apparatus according to claim 1, wherein, instead of the pair of guide members, a guide portion that slidably engages with the carrier in an axial direction of the carrier and an outer peripheral portion of the carrier. A wafer polishing apparatus formed on at least one of the inner peripheral portion of the retainer ring and the outer peripheral portion of the retainer ring and the head main body in the vicinity thereof. 3. A wafer manufacturing method, wherein in the wafer polishing step, the wafer polishing apparatus according to claim 1 is used, the pressure in the fluid chamber, the rotation speed of the platen, and the head. A wafer manufacturing method, wherein a wafer is polished while adjusting an operation speed of a drive mechanism.