JP4409539B2 - Polishing apparatus and polishing member - Google Patents

Description

The present invention relates to a polishing apparatus , a polishing tool, and a polishing member , and more particularly to a polishing apparatus , a polishing tool, and a polishing member that are used to polish a material to be polished such as a semiconductor wafer, metal, ceramics, etc. to a flat and mirror surface. .

  In recent years, as semiconductor devices are highly integrated, circuit wiring is becoming finer and the distance between wirings is becoming narrower. Along with this, the depth of focus becomes shallow when circuit formation is performed by optical lithography or the like, so that a higher flatness of the imaging surface of the stepper is required. As a means for flattening the surface of the semiconductor wafer, as shown in FIG. 5, the turntable 12 having a polishing cloth (polishing cloth) 10 attached to the upper surface and the turntable 12 while holding the substrate (semiconductor wafer) W are provided. A chemical / mechanical polishing apparatus (CMP) having a top ring 14 to be pressed is used.

  In the polishing apparatus having such a configuration, the substrate W is held on the lower surface of the top ring 14, and the substrate W is pressed against the polishing cloth 10 on the upper surface of the turntable 12 rotating by the lifting cylinder. On the other hand, by flowing the polishing abrasive liquid Q from the polishing abrasive liquid nozzle 16, the polishing abrasive liquid Q is held on the polishing cloth 10, and the polishing abrasive liquid Q is interposed between the surface (lower surface) of the substrate W to be polished and the polishing cloth 10. Polishing is performed in the presence of. As a slurry, for example, when a silicon wafer is polished, a slurry in which fine particles of silica are dispersed in a chemical solution whose pH is adjusted with KOH or the like is used.

  However, the above-described conventional techniques have problems such as sufficient post-cleaning of the polished wafer, and a large load for slurry or cleaning liquid drainage.

An object of the present invention is to provide a polishing apparatus , a polishing tool, and a polishing member that reduce the load of cleaning and draining a wafer after polishing while suppressing the use of chemicals, and efficiently polishing. To do.

The polishing apparatus of the present invention form a top ring for holding the object to be polished, a polishing member having an ion exchanger, and the ultra-pure water supply means for supplying ultra-pure water, the electric field in ultra-pure water Have a power supply for.

Another polishing apparatus of the present invention includes a polishing member having an ion exchanger, a surface plate to which the polishing member is attached, a material to be polished, a sliding movement of the material to be polished against the polishing member, and relative movement Supplying a top ring for polishing the material to be polished, a power source connected to the surface plate and the top ring, and ultrapure water to apply a voltage between the surface plate and the top ring. A means for supplying ultrapure water .

The use of ultra-pure water, ultrapure water OH ^- ions or H ⁺ ions is localized near the surface to be polished, it is possible without using a chemical, a chemical-mechanical polishing.

You may make it form at least one part of an abrasive | polishing member with the raw material which contains an ion exchanger or consists of an ion exchanger which has water permeability. For example, the polishing member may be composed of an ion exchange membrane and a normal polishing pad, or may be formed of a material containing an ion exchanger such as an ion exchanger nonwoven fabric or a material made of an ion exchanger, or An ion exchanger non-woven fabric may be attached on the ion exchange membrane to further promote the ion uneven distribution action of the ion exchange membrane. Since such a material increases the mobility of ions in the polishing member, the voltage required for the movement of ions can be greatly reduced. Since the ion exchanger non-woven fabric itself has a function of holding OH ⁻ ions or H ⁺ ions, it has the effect of increasing the treatment speed by maintaining ions unevenly distributed near the surface of the material to be polished.
As such a material, for example, an ion exchanger nonwoven fabric produced in a fibrous form by a method such as graft polymerization or radiation graft polymerization is preferably used.
The polishing member of the present invention is a polishing member that polishes a material to be polished by contacting the material to be polished during polishing, and at least a part of the polishing member contains an ion exchanger or is made of an ion exchanger. It is formed with the material which has.
Another polishing member of the present invention is a polishing member for polishing a material to be polished, and the polishing member is formed by laminating a material including an ion exchanger and an ion exchange membrane.

  According to the present invention, chemical / mechanical polishing can be performed without using chemicals. Therefore, while suppressing the use of chemicals, it is possible to reduce the load of cleaning and draining the wafer after polishing, and perform polishing efficiently.

  Hereinafter, an embodiment of a polishing apparatus according to the present invention will be described with reference to FIGS. This polishing apparatus is similar to the conventional polishing apparatus shown in FIG. 5 in that it has a turntable 12 having a polishing cloth 10 affixed to its surface and a top ring (substrate gripping apparatus) 14 disposed opposite thereto. It is.

  The turntable 12 and the top ring 14 are provided with a driving device for rotating them around the respective shafts in a horizontal plane. The top ring 14 has a holding mechanism for holding the substrate on the lower surface by a method such as vacuum suction, and a polishing target. A pressing mechanism for pressing the lower surface to be polished of the substrate W, which is a material, onto the surface of the polishing cloth 10 of the turntable 12 is provided.

  Between the turntable 12 and the top ring 14, there is provided a DC power source 20 for applying a predetermined voltage with the top ring 14 side being positive. Wiring from the power source 20 is connected to a surface plate 22 that forms a substrate mounting surface of the top ring 14 and a tool mounting surface of the turntable 12 via sliding terminals and internal wiring, respectively. An ion exchange membrane 24 is attached to the tool mounting surface of the surface plate 22 as a catalyst for promoting the dissociation of water, and the polishing cloth 10 is further attached to the upper surface thereof. The ion exchange membrane 24 and the polishing cloth 10 constitute a polishing member.

  As the ion exchange membrane 24, either a cation exchange membrane or an anion exchange membrane can be used. Any known material can be used as the material, but it is desirable to set characteristics such as thickness, porosity, strength, and elasticity so as to be suitable for the rear surface of the polishing cloth 10.

Unlike the one shown in FIG. 5, this polishing apparatus adopts an internal water supply method in which ultrapure water is supplied between the polishing cloth 10 and the substrate W from the inside of the turntable 12. That is, the surface plate 22 is provided with a plurality of water supply grooves (or holes) 26 and drainage grooves (or holes) 28, and the back surface of the surface plate 22 is supplied with water supply or drainage grooves (or holes). A drainage manifold 30 is formed. The water supply / drainage manifold 30 is connected to an external water supply / drainage pipe via internal flow paths 32, 34 penetrating the shaft 12a and a fluid coupling.

Hereinafter, the polishing process by the polishing apparatus of this embodiment will be described. From the water supply pipe, by supplying ultrapure water to a manifold 30 of the Turn-down table 12, the ultrapure water, as shown in FIG. 2, is supplied from the water supply groove 26 of the platen 22 to the ion exchange membrane 24, water permeability Is supplied between the polishing cloth 10 and the surface to be polished of the substrate W via the polishing cloth 10.

Here, when a predetermined voltage is applied to the top ring 14 is positive between the top ring 14 and the turntable 12 are electric field is formed in the ultra-pure water, whereby the ultra-pure water H ⁺ ions and OH ^- ions Move. As a result, as shown in FIG. 2, OH ⁻ ions are concentrated near the substrate W surface, and H ⁺ ions are concentrated near the surface plate 22. The concentration of OH ⁻ ions in the vicinity of the substrate W is appropriately selected depending on the material of the substrate W and other polishing conditions, and the concentration is adjusted by controlling the power supply voltage.

Such ion separation is facilitated by the presence of a cation exchange membrane or an anion exchange membrane. That is, as shown in FIG. 3A, when a cation exchange membrane is used, the ionization of water is promoted, and only H ⁺ ions on the substrate W side move to the surface plate 22 side, and FIG. As shown in b), when an anion exchange membrane is used, only the OH ⁻ ions on the surface plate 22 side move to the substrate W side, and the OH ⁻ ions are likely to be localized in the vicinity of the substrate W, respectively. An example of a strongly acidic ion exchange membrane is Nafion 117 (Dupont).

  FIG. 4 shows the ion uneven distribution effect when a predetermined voltage is applied using an ion exchange membrane in pure water as compared with the case where it is not used. In FIG. 4, platinum (Pt) is used for each of the sample and the electrode, and Nafion 117 (manufactured by Dupont) having a thickness of 200 μm is used for the ion exchange membrane. As can be seen from FIG. 4, it can be seen that more current flows, that is, more water dissociates when the ion exchange membrane is used. It has also been found that when an ion exchange fiber is used in addition to the ion exchange membrane, more current flows.

  Table 1 shows the results of uneven distribution of ions by applying a predetermined voltage using an ion exchange membrane in ultrapure water, thereby processing the surface of the metal (copper) plate. Here, a platinum electrode plate serving as a cathode and a copper sample serving as an anode are immersed in ultrapure water filled in a container while maintaining a certain gap, and a cation exchange membrane (Nafion 117 is interposed between both electrodes). ), The entire container is housed in an airtight container, and the inside is purged with Ar gas. Thereby, it turns out that a process is possible by making ion unevenly distributed using an ion exchange membrane in ultrapure water.

In the state shown in FIG. 2, the top ring 14 and the turntable 12 are each rotated in a horizontal plane while the substrate W is pressed onto the surface of the polishing cloth 10 by the top ring 14, and polishing is performed. Since OH ⁻ ions are concentrated at a predetermined concentration in the vicinity of the substrate W, dissolution of silicon and silicon oxide film on the substrate W is promoted, and chemical / mechanical polishing without chemical pH adjustment. Can be achieved.

Most of the ultrapure water supplied from the water supply groove 26 is supplied to the surface of the polishing cloth 10 as described above, and is accompanied by polishing debris by the centrifugal force accompanying the rotation of the turntable 12 after performing the polishing action. However, it flows to the peripheral side of the polishing cloth 10 and scatters from the edge. Although H ⁺ ions are concentrated in the ultrapure water on the back surface side of the ion exchange membrane 24, this is discharged from the drain grooves 28 arranged alternately with the water supply grooves 26.

The ultrapure water in which H ⁺ ions are concentrated is neutralized with the OH ⁻ ions contained in the ultrapure water scattered from the turntable 12, so that no special treatment is required. As described above, in this chemical / mechanical polishing step, no chemical for pH adjustment is used, so that the labor of cleaning the substrate W after polishing and processing of the waste liquid containing the chemical can be reduced.

The polishing cloth 10 may be a conventional polishing cloth that has been used conventionally, but in the present embodiment, the polishing cloth 10 is formed of a material including an ion exchanger such as an ion exchange nonwoven fabric or a material made of an ion exchanger. is doing. Thereby, the ion uneven distribution effect of the ion exchange membrane 24 can be further promoted, and it has a role as a catalyst for promoting the dissociation of water. An ion exchanger nonwoven fabric is a fiber containing an ion exchanger having a strongly basic functional group such as —N (CH ₃ ) ₃ OH, and is produced by a graft polymerization method or a radiation graft polymerization method. Since such a material increases the mobility of ions in the polishing member, the voltage required for the movement of ions can be greatly reduced. Further, since the ion exchanger nonwoven fabric itself has a function of holding OH ⁻ ions or H ⁺ ions, it also has an effect of increasing the processing speed by maintaining ions unevenly distributed in the vicinity of the surface to be polished of the substrate W.

  In the above description, the polishing cloth 10 and the ion exchange membrane 24 are separated, but they may be formed integrally. As a result, a more specialized polishing cloth having high functionality as a polishing member can be provided, and it is not necessary to form a two-layer structure in the field, so that workability is good. Moreover, you may comprise an abrasive member only with an ion exchanger nonwoven fabric, without using an ion exchange membrane.

Further, in the above, an internal water supply method for supplying ultrapure water from the turntable 12 side is adopted and abrasive grains are not used, but an external water supply method from the polishing abrasive liquid nozzle 16 as shown in FIG. 5 is also polished. It can employ | adopt according to conditions, In this case, you may use an abrasive grain. Even when using the abrasive grains, without the conventional KOH-based slurry such as, used as suspension of abrasive particles such as SiO ₂ particles in ultrapure water. By interposing the abrasive grains, the mechanical action is promoted and the polishing rate is increased.

In this case, the ultrapure water enriched with H ⁺ ions may be drained by providing a drain groove 28 on the surface plate 22 as in the previous embodiment, or the edge of the surface plate 22 by centrifugal force. You may make it discharge from a part. In the latter case, a drainage promotion groove from the center of the surface plate 22 toward the edge may be formed. Moreover, you may use together an internal water supply system and an external water supply system.

In the above description, an example in which OH ⁻ ions are concentrated on the substrate side has been described. However, when metal such as copper wiring is polished, electrodes and negative electrodes are concentrated so that H ⁺ ions are concentrated on the substrate side. An ion exchange membrane is placed.

It is sectional drawing which shows the structure of the grinding | polishing apparatus of one embodiment of this invention. It is a figure which expands and shows the principal part of FIG. It is a schematic diagram explaining the effect | action of the grinding | polishing apparatus of FIG. It is a figure which shows the ion uneven distribution effect at the time of using an ion exchange membrane compared with the case where it is not used. It is a figure which shows the structure of the conventional grinding | polishing apparatus.

Explanation of symbols

10 Polishing cloth 12 Turntable 14 Top ring 20 Power supply 22 Surface plate 24 Ion exchange membrane 26 Water supply groove 28 Drainage groove 30 Manifold W Substrate (semiconductor wafer)

Claims (8)

A top ring that holds the material to be polished;
A polishing member having an ion exchanger;
And ultra pure water supply means for supplying ultrapure water,
Polishing apparatus characterized by having a power supply for generating an electric field in ultra-pure water.   The polishing apparatus according to claim 1, wherein the top ring and the power source are connected. The polishing apparatus comprises:
A turntable on which the polishing member is disposed;
The polishing apparatus according to claim 1, wherein the turntable and the power source are connected. The ultrapure water supply means, a polishing apparatus according to claim 3 Symbol mounting and having a water supply groove and the drain groove provided on the turntable. The polishing apparatus according to claim 4 , wherein the ultrapure water supply means includes a manifold communicating with the water supply groove and a water supply pipe communicating with the manifold. A polishing member having an ion exchanger;
A surface plate to which the polishing member is attached;
A top ring for holding the material to be polished, bringing the material to be slid into sliding contact with the polishing member, and polishing the material to be polished by relative movement;
A power source connected to the platen and the top ring to apply a voltage between the platen and the top ring;
Polishing apparatus characterized by having an ultra pure water supply means for supplying ultra-pure water.   A polishing member for polishing a material to be polished by contact with the material to be polished during polishing, wherein at least a part of the polishing member includes an ion exchanger or is formed of a material having water permeability made of an ion exchanger. A polishing member characterized by comprising:   A polishing member for polishing a material to be polished, wherein the polishing member is configured by laminating a material including an ion exchanger and an ion exchange membrane.

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