JPH09216128A - Polishing method and polishing apparatus - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To polish an object to be polished with high accuracy and at high speed to flatten it. A conductive processing liquid containing abrasive particles S that can be charged positively or negatively is applied to a processing surface of a wafer 9 and a conductive film 3.
4 is supplied to the surface of the polishing tool, and polishing is performed while applying a bias voltage 10 between the processing surface and the surface of the polishing tool. The bias voltage is applied by alternating current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method and a polishing apparatus for mirror-finishing or flattening the surface of a hard and brittle material, for example.

[0002]

2. Description of the Related Art In recent years, as electronic home appliances have become smaller and lighter and have higher functions, demands for higher performance and higher density of electronic parts to support them have been increasing more and more. Is required to produce small-sized, high-precision electronic parts at low cost by utilizing new materials such as fine ceramics, amorphous alloys, various composite materials, and crystalline materials that are being put to practical use.

Many of these new materials are extremely hard, brittle, and have unique thermal properties, and the deterioration of properties due to processing is an important issue. Further, the required processing precision such as surface roughness, flatness, and dimensional precision is becoming more severe. As a method of flattening and polishing such a hard and brittle material, CMP (Chemical Mechanical) using a mirror polishing technique for a silicon wafer has been conventionally used.
Polishing: chemical mechanical polishing) is known. The CMP method is not a mechanical precision transfer like the conventional polishing, but a polishing method using free abrasive grains, and has recently attracted attention as a global flattening technique for wafers.

[0004]

However, in the conventional CMP method, in order to maintain the processing accuracy, it is greatly influenced by the processing conditions such as polishing pad modification, dressing / truing, etc. It was the actual situation to rely on. Further, since it is free-abrasive polishing, there are problems that the processing efficiency (throughput) is low and that the polishing rate fluctuates greatly due to clogging of the polishing pad.

On the other hand, as a flattening polishing method, a method by grinding / cutting has been conventionally known, but there is a problem that the surface roughness does not reach the polishing level, and in some cases, S
High-precision polishing such as PDT (Single Point Diamont Turning) is also known, but this method has a short tool life,
There is a problem that it is not suitable for mass production of general hard and brittle materials because it is disadvantageous in terms of cost.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a polishing method and a polishing apparatus capable of polishing an object to be polished with high accuracy and high speed to flatten it. And

[0007]

In order to achieve the above object, the polishing method of the present invention comprises a conductive working fluid containing abrasive particles capable of being positively or negatively charged between a working surface and a polishing tool surface. It is characterized in that the work surface is polished while being supplied and applying a bias voltage between the work surface and the polishing tool surface.

In order to achieve the above object, the polishing apparatus of the present invention has a holding means for holding an object to be polished and a polishing tool surface which rotates relative to the object to be polished. Means, a working liquid supply means for supplying a conductive working liquid containing positively or negatively chargeable polishing particles between the working surface of the object to be polished and the polishing tool surface, the working surface and the polishing It is characterized by comprising a power source for applying a bias voltage between the tool surface and a conductive film provided on the polishing tool surface.

In the polishing method and polishing apparatus of the present invention, a conductive processing liquid containing abrasive particles capable of being positively or negatively charged is used as a polishing liquid, which is supplied between the processing surface and the polishing tool surface, and Since the polishing surface is polished while applying a bias voltage between the processing surface and the polishing tool surface, the electrophoretic phenomenon of the polishing particles occurs when the applied polarity is taken into consideration, and the polishing particles are electrically transferred to the polishing tool surface. Is sucked into. The abrasive particles sucked toward the surface of the polishing tool are adsorbed to the surface of the polishing tool to form a polishing particle layer, and polishing is performed in this state.

As a result, flattening polishing by a so-called semi-fixed abrasive grain polishing method, which is neither a free-abrasive grain polishing method nor a fixed abrasive grain polishing method, is realized. Due to the synergistic effect with the dynamic polishing, the polishing surface can be flattened with high accuracy without being affected by skilled work such as polishing pad correction and dress / truing. Further, since it is the semi-fixed abrasive grain polishing method, the throughput is higher than that of the free abrasive grain polishing method.

In the polishing method of the present invention, it is more preferable to apply the bias voltage by alternating current. In the polishing method of the present invention, by changing the bias voltage to alternating current,
Abrasive particles and debris adsorbed on the surface of the polishing tool can be temporarily repelled. As a result, the deteriorated polishing particles and polishing debris are discharged, and when the original bias voltage is applied next, the polishing particles adsorbed on the polishing tool surface are not deteriorated.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic view showing a polishing apparatus according to an embodiment, FIG. 2 is a perspective view showing the appearance of the polishing apparatus, FIG. 3 is a vertical sectional view showing the same rotary table, and FIG. 4 is a vertical sectional view showing the same spindle. 5 and 5 are sectional views for explaining the principle of the present invention.

As shown in FIGS. 1 and 2, the polishing apparatus according to the present embodiment mainly comprises a main spindle 20 and a rotary table 21. As shown in FIG. 3, in the rotary table 20, the rotational force from the motor 17 is transmitted via the pulley 15 and the flat belt 16 to the pulley 18.
Is transmitted to the joint 23, and the joint 23 rotates in conjunction with the rotation of the pulley 18. The joint 23 is bearing-supported by bearings 14 and 22, and a table 24 is provided on the surface thereof. The table 24 is formed in a disk shape having a diameter of about 200 mm, and the wafer suction film 12 made of urethane rubber or the like is attached to the surface thereof. In the present embodiment, the wafer suction film 12 with respect to the rotating shaft 8
Highly rigid members are used for the joint 23 and the bearings 14 and 22 in order to stabilize the rotation of the.

A vacuum suction pipe 25 reaching the surface of the wafer suction film 12 is housed in a hollow portion provided at the center of rotation of the joint 23 and the table 24, and one end of the vacuum suction pipe 25 is not shown. It is connected to a suction device, whereby the wafer 9 is vacuum-sucked.

As shown in FIG. 2, this rotary table 20 is fixed to the surface of a slider 6 which is provided along a rail 26 so as to be movable in the X-axis direction. It is possible to move to.
On the other hand, the main spindle 21 is fixed to a slider (not shown) movably provided along the rail in the Z-axis direction. In this spindle spindle 21, as shown in FIG. 4, the tool base 2 is detachably attached to the spindle spindle shaft 4 rotated by a spindle motor (not shown) via a mounting flange 31. A urethane rubber 1 (also referred to as a polishing pad 1), which is electrically insulated from the main spindle shaft 4 by an insulating material 32 and is formed in a disk shape having a diameter of about 220 mm, is attached to the base 2. further,
A conductive film 34 is attached to the urethane rubber 1 by a film holder 33, and the urethane rubber 1 applies tension and polishing processing pressure to the conductive film 34.

The tool portion consisting of the conductive film 34, the urethane rubber 1 and the film holder 33 can be made of a metal plate such as a copper plate, but damage such as scratches remains depending on the object to be polished. Since it may be easy, in this embodiment, a soft viscoelastic system is used. Further, in this embodiment, in order to stabilize the rotation of the conductive film 34 and the urethane rubber 1 with respect to the rotating shaft 5, a high rigidity member is used for the tool base 2, the mounting flange 31, the main spindle shaft 4, and the like. .

On the other hand, a hollow portion is formed at the center of the main spindle shaft 4 and the mounting flange 31, and a nozzle 40 made of a conductive material is provided therein. A slurry (polishing agent) is supplied to the nozzle 40 from a slurry supply device (not shown), and the slurry from the nozzle 40 is substantially radially sprayed between the conductive film 34 and the wafer 9 to be polished. It

As the polishing agent used in this embodiment, in addition to colloidal dispersion of ultrafine silica particles having a diameter of about 10 nm in an alkaline solution such as potassium hydroxide,
It is possible to use a dispersion of fine particles such as SiC or SeO in an alkaline solution. Particularly, in the polishing apparatus according to the present embodiment, an AC voltage of about several tens of volts and about 60 Hz is applied from the power source 10 to the conductive film 34 via the electrode brush 35 provided on the film holder 33,
The same AC voltage is also applied to the nozzle 40.

Next, the operation will be described. First, when the suction device of the rotary table 20 starts suction, a suction force is generated on the surface of the wafer suction film 12. In this state, as shown in FIG. 2, the wafer 9 is placed on the surface of the wafer suction film 12 with the polishing surface facing upward in the figure, and the wafer 9 is sucked onto the wafer suction film 12.

Then, the spindle motor is driven to rotate the polishing pad 1 at a rotation speed of about 1500 to 3000 rpm, and the motor 17 shown in FIG. 3 is driven to rotate the wafer suction film 12 at a rotation speed of about 30 to 50 rpm.
Rotate at 0 rpm. Further, the slider 6 is moved along the rail 26 in the X-axis direction so that the polishing pad 1 is located above the wafer 9.

Next, the slurry is supplied from the slurry supply device to the nozzle 40, and is sprayed radially between the polishing pad 1 and the wafer 9 from the nozzle 40. Before or after this, an AC voltage is applied to the conductive film 34 and the nozzle 40. When the main spindle 21 is lowered in the Z-axis direction and the polishing pad 1 is pressed against the polishing surface of the wafer 9 with a predetermined polishing pressure, the following phenomenon occurs due to the AC voltage applied to the conductive film 34 and the nozzle 40.

That is, since the polishing liquid used in the present embodiment is, for example, potassium hydroxide in which ultrafine silica particles are dispersed, the silica particles S have silanol groups and are therefore negatively charged. (See FIG. 5 (A)). This suppresses the agglomeration of the silica particles S, but in this embodiment, the charging is utilized to perform polishing. That is, when an electric field is applied to the polishing liquid containing the silica particles S, the silica particles S
And the silica particles S are electrically attracted to the conductive film 34 serving as an anode. The silica particles S sucked toward the conductive film 34 are adsorbed on the surface of the conductive film 34 to form a silica particle layer, and polishing is performed in this state (see FIG. 5 (B)). . As a result, a so-called semi-fixed abrasive grain polishing method, which is neither a free-abrasive grain polishing method nor a fixed-abrasive grain polishing method, is used to realize flattening polishing. By the synergistic effect of, the polishing surface of the wafer 9 can be flattened with high accuracy without being affected by skilled work such as polishing pad correction and dress / truing. Further, since it is the semi-fixed abrasive grain polishing method, the throughput is higher than that of the free abrasive grain polishing method.

Further, in the present embodiment, since the AC voltage is applied, the silica particles S and polishing dust adsorbed on the conductive film 34 can be temporarily repelled (FIG. 5).
(D)). That is, as the processing progresses, deteriorated silica particles, wafer debris, and the like remain adsorbed on the surface of the conductive film 34, which may cause clogging and reduce the processing efficiency (FIG. 5 (C)). )reference)). However, if the bias voltage 10 is changed to an alternating current as in the present embodiment, the deteriorated silica particles and polishing debris of the wafer are discharged, and when the original bias voltage is applied next, the surface of the conductive film 34 is The adsorbed silica particles S are not deteriorated.

The polishing method and polishing apparatus of the present invention as described above are used for the flattening process (conventional CMP polishing) of the interlayer insulating film 60 of the silicon wafer shown in FIG. 6A, and the video head shown in FIG. 6B. , Flattening processing of a magnetic head substrate 61 such as a hard disk head (conventional grinding and lapping), optical crystal processing of a micro prism 62 shown in FIG. 6C (conventional grinding and lapping), FIG.
It can be widely applied to the processing of the crystal unit 63 shown in FIG. 1 (conventionally lapping), the texturing of a hard disk (conventionally tape wrapping), and the mirror-finishing of the optical disk substrate 64 shown in FIG. it can. In this case, it is possible to perform the polishing in the wafer state W as shown in FIG. 7A or in the chip state C as shown in FIG. 7B.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention.

[0026]

As described above, according to the polishing method and the polishing apparatus of the present invention, the polishing pad can be corrected or dressed.
The polished surface can be flattened with high accuracy without being affected by skilled work such as truing. Further, since it is the semi-fixed abrasive grain polishing method, the throughput is higher than that of the free abrasive grain polishing method.

Further, according to the polishing method of the present invention, by applying a bias voltage with an alternating current, the polishing particles and polishing debris adsorbed on the polishing tool surface can be temporarily repelled. As a result, deteriorated abrasive particles and debris are discharged,
Next, when the original bias voltage is applied, the polishing particles adsorbed on the surface of the polishing tool are not deteriorated, so that not only clogging can be prevented but also the polishing rate can be maintained constant.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the external appearance of a polishing apparatus that is an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the rotary table of FIG.

4 is a cross-sectional view showing the main spindle of FIG.

FIG. 5 is a sectional view for explaining the principle of the present invention.

FIG. 6 is a cross-sectional view showing an application example of the present invention.

FIG. 7 is a perspective view showing an application example of the present invention.

[Explanation of symbols]

 1 ... Polishing pad (polishing tool surface) 9 ... Wafer (polishing object) 10 ... AC power source 20 ... Rotary table 21 ... Spindle spindle 34 ... Conductive film 40 ... Nozzle S ... Silica particles

Claims (3)

[Claims] 1. A conductive machining liquid containing positively or negatively chargeable abrasive particles is supplied between a machining surface and a polishing tool surface, and a bias voltage is applied between the machining surface and the polishing tool surface. While polishing the processed surface, a polishing method is provided. 2. The polishing method according to claim 1, wherein the bias voltage is applied by alternating current. 3. A holding means for holding an object to be polished, a polishing means having a polishing tool surface which rotates relative to the object to be polished, a processing surface of the object to be polished and the polishing tool surface. A machining liquid supply means for supplying a conductive machining liquid containing positively or negatively chargeable abrasive particles, and a power supply for applying a bias voltage between the machining surface and the polishing tool surface, And a conductive film provided on the surface of the polishing tool.