JPH11333712A - Polishing head and polishing device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain heat generation caused by the contact of a retainer ring and a polishing pad by providing a groove structure on contact surfaces of the retainer ring and a polishing member. SOLUTION: In a retainer ring 1, a plurality of concentric grooves 3a are formed on a surface 3 to be brought into contact with a polishing pad. Moreover, a curvature part or a chamfer part 2 is formed on the outermost periphery of the contact surface of the retainer ring 1 to the polishing pad to enable abrasives to easily enter a wafer polishing surface. The groove pitch is about 6 mm, the groove width is about 3 mm, and the depth is about 1 mm. Such a groove 2 is provided to reduce the contact area to the polishing pad. Therefore, heat is not generated caused by polishing, the polishing rate can be keep constant, and stable polishing can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a polishing head suitable for use in flattening and polishing a semiconductor device, which is carried out in a process of manufacturing a semiconductor such as ULSI, and a polishing apparatus using the same.

[0002]

2. Description of the Related Art Densification of semiconductor devices has been progressing without limitation and some of various obstacles accompanying the densification are being overcome by various techniques and methods. One of the major challenges is the flattening of global (relatively large) device surfaces. As the degree of integration of devices increases, further lamination of electrodes and the like is inevitable. In view of the reduction in the depth of focus during exposure accompanying the shortening of the wavelength of lithography, there is a great demand for accurately flattening the interlayer layer at least in the range of the exposure area. In addition, there is a high demand for so-called inlay (plug, damascene) in which the metal electrode layer is embedded, and in this case, removal and flattening of an extra metal layer after lamination are required as essential.

Conventionally, many methods for locally planarizing an interlayer layer by improving a film forming method or the like have been proposed and implemented. However, efficient planarization in a larger area which will be further required in the future is proposed. CMP is attracting attention as an advanced technology
(Chemical Mechanical Polishingma or Planarizat
This is a polishing process called ion). CMP is a process for removing the surface unevenness of a wafer by using a chemical action (dissolution with an abrasive or a solution) in combination with physical polishing, and is a leading candidate for a global planarization technique. Specifically, abrasive grains (silica, alkali, cerium oxide, etc. are common) in a soluble solvent of the abrasive such as acid or alkali
Using a polishing agent called a slurry in which is dispersed, the surface of the wafer is pressed with an appropriate polishing cloth and rubbed by relative motion to advance polishing. By making the pressure and the relative movement speed uniform over the entire surface of the wafer, it is possible to uniformly polish the surface.

FIG. 6A is a schematic side view of a CMP polishing apparatus, and FIG. 6B is a schematic top view. Reference numeral 100 denotes a platen (platen) which is driven to rotate by a platen rotation driving device; 101, a polishing pad as a "polishing member";
2 is an object to be polished (wafer), 103 is a polishing head (holder) rotated and oscillated by a polishing head driving device, 10
Reference numeral 4 denotes an abrasive (slurry) supply unit, and reference numeral 105 denotes an abrasive (slurry).

In this polishing apparatus, a polishing pad 101 as a "polishing member" is provided on a surface plate 100 which is rotationally driven by a surface plate driving device, while a wafer 102 which is an "object to be polished" is held on a polishing head 103. This wafer 1
02 is in contact with the polishing pad 101. In this state, the platen 100 is driven to rotate, a load is applied to the polishing head 103 from above, and the platen 100 is oscillated in the radial direction while rotating.

[0006] Along with this operation, the abrasive supply section 104
To discharge the polishing agent 105 onto the polishing pad 101,
This polishing agent 105 is supplied to the polishing surface of the wafer 102,
The outermost surface of the wafer 102 is polished flat. Abrasive 1
05 is diffused by the polishing pad 101 and the polishing pad 101
And the polishing pad 101 with the relative movement of the wafer 102.
And the surface of the wafer 102 is polished.

Mechanical polishing by the relative movement of the polishing pad 101 and the wafer 102 performed through the polishing agent 105;
The chemical action of the polishing agent 105 using an acid or an alkali as a solvent acts synergistically to perform good polishing, and the pressure and the relative movement speed are made uniform over the entire surface of the wafer, so that the surface is made uniform. It becomes possible to polish. The polishing head 103 includes various methods such as a backing film chuck method and a vacuum chuck method, and generally includes a wafer attaching / detaching mechanism, a pressing mechanism, and a retainer ring for preventing the wafer from jumping out.

[0008]

However, with the recent improvement in the CMP technology, the role of the retainer ring is not limited to the role of simply preventing the wafer from popping out, but the role of the polishing pad distorted due to the pressure applied to the wafer during polishing. It also plays a role in pressing the polished surface widely along the wafer surface.

That is, since the pressure on the wafer during polishing is large, the polishing surface of the polishing pad is distorted. As a result, the periphery of the wafer is not uniformly polished. The width of the retainer ring was increased (about 25 mm to 30 mm) to appropriately correct the polishing pad surface. However, by increasing the width of the retainer ring, the above-mentioned problem is solved, but another problem as described below occurs.

That is, as the width of the retainer ring increases,
There is a problem that the contact area with the polishing member (polishing pad) increases, and the heat generated by the friction increases. If the heat generation is large, the polishing rate is improved, but it is difficult to control the polishing uniformity. For the purpose of avoiding such heat generation, it is conceivable to use a ceramic or the like as the retainer ring material in order to reduce the contact resistance, but it is not suitable for a consumable retainer ring because it is expensive in price.

When the polishing pad is hard, the contact between the convex portion of the groove structure formed on the polishing pad and the end face of the retainer ring is too good, so that the polishing agent is not effectively supplied to the wafer polishing surface. And the removal of SiO ₂ and metal from the polished surface of the wafer by polishing,
So-called polishing debris, such as polishing pad debris (the polishing pad itself is also worn away by polishing) are efficiently removed from the polishing surface of the wafer without being discharged, and the accumulated polishing agent and polishing debris are aggregated into large lump. However, there is a problem that the polishing surface of the wafer is scratched.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polishing head having a retainer ring for suppressing heat generation due to contact between a retainer ring and a polishing pad, and a polishing apparatus using the same. And It is still another object of the present invention to provide a polishing head having a retainer ring for efficiently supplying an abrasive to a wafer polishing surface and efficiently discharging polishing debris generated by polishing, and a polishing apparatus using the same.

[0013]

According to the present invention, there is provided a retainer ring for holding an object to be polished and pressing the object to be polished against a polishing member for preventing the object to be polished from jumping out. In a polishing head, a groove structure is provided on a contact surface of the retainer ring with the polishing member.

[0014] The present invention also provides a second aspect of the invention wherein "a groove formed in the retainer ring is provided so that when the polishing head and the polishing pad are relatively moved, the polishing agent is applied to the polishing surface of the object to be polished. A polishing head (Claim 2) according to Claim 1 characterized by being formed so as to be wound up. In addition, the present invention is a third aspect of the present invention, `` by moving the polishing member and the polishing head relative to each other in a state where the polishing agent is interposed between the polishing member and the polishing object held by the polishing head, In a polishing apparatus for polishing an object to be polished, the polishing head is the polishing head according to claim 1 or 2, wherein a polishing apparatus (claim 3) is provided.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A retainer ring according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 (a)
1 is a schematic sectional view of a retainer ring according to an embodiment of the present invention, and (b) is a schematic bottom view thereof. In the retainer ring 1 according to the first embodiment of the present invention, a plurality of concentric grooves 3a are formed on a surface 3 that contacts a polishing pad.

A curved portion or a chamfered portion 2 is formed at the outermost peripheral portion of the contact surface of the retainer ring with the polishing pad,
The abrasive is easily introduced into the polishing surface of the wafer. The groove pitch is about 6 mm, the groove width is about 3 mm, and the depth is about 1 mm. By providing such a groove 2, the contact area with the polishing pad can be reduced.

FIG. 2A is a schematic sectional view of a retainer ring according to an embodiment of the present invention, and FIG. 2B is a schematic bottom view thereof. In the retainer ring 11 according to the second embodiment of the present invention, a groove 4a composed of a plurality of concentric grooves and a groove radiating from the center is formed on the surface 4 that contacts the polishing pad.

The concentric groove pitch is about 6 mm, the groove width is about 3 mm, the radial grooves are about 30 mm apart, and the groove width is about 10 mm.
The depth is about 1 mm. By providing the radial grooves, the contact area with the polishing pad can be further reduced, and the supply of the abrasive and the discharge of the polishing waste can be facilitated. That is, by rotation and swing of the polishing pad,
While the abrasive is mainly supplied from the radial grooves so as to be rolled into the wafer polishing surface, the polishing waste is discharged along the grooves.

FIG. 3A is a schematic sectional view of a retainer ring according to an embodiment of the present invention, and FIG. 3B is a schematic bottom view thereof. The retainer ring 21 according to the third embodiment of the present invention is configured such that the surface 5 that contacts the polishing pad is substantially tangent to the wafer (assuming that it is installed on the polishing head) from the outermost position of the end surface. Twelve grooves 5a are formed at 30 ° intervals in the pulling direction.

That is, since the abrasive tends to flow radially outward of the polishing pad due to centrifugal force caused by the rotation of the polishing pad, the groove formed in the retainer ring is formed by the rotation of the polishing pad and the rotation of the polishing head. The abrasive is supplied to the polishing surface of the wafer when the relative movement is performed by rotation and swing. Groove width is about 10mm, length is about 4
5 mm and depth is about 1 mm.

The polishing agent is supplied so as to be wound around the wafer polishing surface along the groove 5a.
is discharged along a. FIG. 4A is a schematic sectional view of a retainer ring according to the embodiment of the present invention, and FIG.
Is a schematic bottom view thereof. The retainer ring 31 according to the fourth embodiment of the present invention includes the groove 5a of the third embodiment and the other part (the contact surface with the polishing pad) 5.
Is reversed.

The contact surface 6 with the polishing pad serves as a trigger for the flow of the abrasive, and the abrasive is supplied from the groove 6a so as to be drawn into the wafer polishing surface. As the material of the retainer ring according to the first to fourth embodiments, acrylic resin, AB
S resin, epoxy resin, polyurethane, Teflon, etc. are used. The groove structure of the groove pitch, the groove width, and the groove depth is not limited to the example of the embodiment, and is variously changed depending on polishing conditions. Example 1 The 6-inch silicon wafer on which a thermal oxide film having a thickness of 10,000 mm was formed by applying the retainer ring of the third embodiment to a polishing head of a backing film chuck type as shown in FIG. Using the polishing apparatus shown in FIG. 6, polishing was performed under the following processing conditions.

The polishing head of the backing film chuck type is composed of a back plate 1 provided on a housing 12.
A retainer ring 21 is provided around the periphery of 3, and the retainer ring 21 is fixed to the back plate 13 by a set screw 14. Also, the back plate 13
A backing film 15 is adhered to the center of the wafer, and a wafer 16 is adhered to the backing film 15 with water.

In the polishing pad, a lattice-shaped groove having a pitch of 0.5 mm and a depth of 0.2 mm is formed on a hard polishing pad having a diameter of 600 mm and a thickness of 2 mm made mainly of epoxy resin. Processing conditions Polishing pad rotation speed: 50 rpm Polishing head rotation speed: 50 rpm Swing distance: 60 mm Swing speed: 600 mm / min Load applied to the polishing head: 400 g / cm ² Abrasive: SiO ₂ alkaline aqueous solution Polishing When polishing is performed at a polishing agent supply rate of 100 ml / min and a polishing time of 3 minutes, about 500 nm of SiO ₂ is removed, and the temperature of the polishing agent on the polishing pad after polishing rises by about 3 ° C. from the initial temperature of about 25 ° C. It was about 28 ° C. For example, a method of measuring the temperature of the abrasive using a thermocouple or a method of taking an image of the surface of the abrasive using an infrared camera and measuring the temperature by image processing is used.

When polishing is performed at a polishing agent supply rate of 50 ml / min and a polishing time of 2.5 minutes, about 500 nm of SiO ₂ is removed, and the temperature of the polishing agent on the polishing pad after polishing is about 25% of the initial temperature. The temperature had risen by about 7 ° C. to about 32 ° C. During the wafer replacement time of 30 seconds, the temperature on the polishing pad returned to its original value, and the temperature cycle was the same even when repeated. Polishing uniformity was good at about ± 4%. [Comparative Example 1] Instead of the retainer ring 21 of Example 1, a polishing head to which a conventional retainer ring was applied was used to supply about 500 nm of SiO ₂ at a polishing agent supply rate of 100 ml / min and a polishing time of 2.5 minutes. After removal, the temperature of the abrasive on the polishing pad after polishing increased to about 40 ° C. from about 25 ° C. of the initial temperature by about 15 ° C.

When the polishing was repeatedly performed with a wafer exchange time of 30 seconds, the temperature of the polishing agent gradually increased, and reached 50 ° C. when 25 wafers were polished. As the temperature increased, the polishing rate increased. This increase in the polishing rate affects the polishing uniformity, and the polishing uniformity is about ± 1.
It was 0%. The retainer rings of the first to fourth embodiments are not limited to the backing film chuck type polishing head applied in Example 1, but also the vacuum chuck type,
The present invention can be applied to other polishing heads such as a hydro chuck system and an air bag system.

The groove structure formed in the polishing pad is not limited to the lattice-shaped groove shown in the second embodiment, but may be a radial groove, a distorted radial groove, a spiral groove, or the like. In particular, when a radial groove or a distorted radial groove is formed in the polishing pad, it initially flows radially outward due to centrifugal force, but then has a function of penetrating along the groove. When used in combination with the retainer rings according to the second to fourth embodiments, there is a synergistic effect in that the supply and discharge of the abrasive are efficiently performed and polishing uniformity is improved. .

[0028]

As described above, in the retainer ring according to the present invention, since the groove structure is formed on the surface in contact with the polishing pad, the contact area with the polishing pad is reduced, so that heat is not generated due to friction, and the polishing rate is reduced. Can be kept constant, and stable polishing can be performed.

Since the problem of heat generation was solved by providing a groove on the contact surface of the retainer ring with the polishing pad, the range of material selection for the retainer ring was widened and an inexpensive material such as acrylic resin could be selected. The running cost can be reduced as compared with the case where expensive materials such as ceramics are selected. Further, the retainer rings of the second to fourth embodiments can improve the flow of the polishing agent (supply and discharge to and from the polishing surface), so that the wafer can be efficiently polished with a small amount of the polishing agent.

[Brief description of the drawings]

FIG. 1A is a schematic sectional view of a retainer ring according to a first embodiment of the present invention, and FIG. 1B is a schematic bottom view thereof.

FIG. 2A is a schematic sectional view of a retainer ring according to a second embodiment of the present invention, and FIG. 2B is a schematic bottom view thereof.

FIG. 3A is a schematic sectional view of a retainer ring according to a third embodiment of the present invention, and FIG. 3B is a schematic bottom view thereof.

FIG. 4A is a schematic sectional view of a retainer ring according to a fourth embodiment of the present invention, and FIG. 4B is a schematic bottom view thereof.

FIG. 5 is a schematic sectional view of a backing chuck type polishing head to which the retainer ring of the third embodiment is applied in Example 1.

FIG. 6 is a view showing the concept of a CMP polishing apparatus.

[Explanation of symbols]

1, 11, 21, 31... Retainer ring 2. Curvature portion or chamfered portion 3a, 4a, 5a, 6a... Grooves 3, 4, 5 formed on the contact surface of polishing retainer ring with polishing pad , 6 ... Contact surface of the retainer ring with the polishing pad 12 ... Housing 13 ... Backing plate 14 ... Set screw 15 ... Backing film 100 ... Surface plate 101 ... Polishing member ( Polishing pad) 16, 102: polishing object (wafer) 103: polishing head 104: abrasive supply unit 105: abrasive (slurry)

Continued on front page (72) Inventor Akira Miyachi 3-2-2-3 Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation

Claims (3)

[Claims] 1. A polishing head provided with a retainer ring for holding an object to be polished and pressing the object to be polished against a polishing member, for preventing the object to be polished from jumping out, wherein the polishing member of the retainer ring is provided. A polishing head characterized in that a groove structure is provided on a contact surface with the polishing head. 2. The groove formed in the retainer ring is formed such that when the polishing head and the polishing pad are relatively moved, the polishing agent is wound around the polishing surface of the object to be polished. The polishing head according to claim 1, wherein: 3. The object to be polished is moved relatively by moving the polishing member and the polishing head relative to each other with an abrasive interposed between the polishing member and the object to be polished held by the polishing head. A polishing apparatus for polishing, wherein the polishing head is the polishing head according to claim 1 or 2.