JPH10277927A - Flat surface polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve flatness after polishing by positively retaining a sucked state exerted by the polishing head of a material to be polished in polishing the flat plate-like material to be polished such as a semiconductor wafer. SOLUTION: Polishing cloth is stuck to the upper surface of a turntable 1. Rotary driving is applied to the turntable 1. A polishing head is interposed by facing the turntable 1, and is rotated and driven to suck a material to be polished from its bottom surface. Its top surface is pressed against the polishing cloth. In the polishing cloth 3, upwardly, downwardly penetrated holes 11 are formed in the entire surface of the polishing cloth. Many air-discharging holes 12 are provided in the upper surface of the turntable 1. A cavity part 13 is formed on the top surface of the turntable 1. The discharging holes 12 are penetrated as deep as the cavity part 13. A through hole 14 is formed at the central part of the turntable 1 to supply air to the cavity part 13 from a supply source interposed at the lower part of the turntable 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat-surface polishing apparatus used for flatly polishing the surface of a flat object to be polished such as a semiconductor wafer, and more particularly to an apparatus for polishing an object to be polished by a polishing head. The improvement to ensure that the state is maintained.

[0002]

2. Description of the Related Art FIG. 4 shows an outline of a conventional planar polishing apparatus. The turntable 1 is driven by a rotary drive device 2, and a polishing cloth 3 is attached to the upper surface of the turntable 1 by bonding or the like. On the other hand, a polishing head 4 is disposed above the turntable 1 so as to face the upper surface of the turntable 1. The polishing head 4 includes a top ring 5, a retainer ring 8, a main shaft 9, a pressing mechanism 6, a rotation driving mechanism (not shown), and the like.

The wafer 10 is mounted on the lower surface of the top ring 5 by vacuum suction via a backing pad 7. The backing pad 7 is an elastic body having a large number of small through holes. The backing pad 7 is vacuum-adsorbed from the lower surface of the top ring 5 in a state where the backing pad 7 is pressed against the back surface of the wafer 10. The wafer 10 is fixed to 4. The pressing mechanism 6 presses the top ring 5 downward via the main shaft 9 and presses the surface of the wafer 10 against the polishing cloth 3. A retainer ring 8 is attached to the lower surface of the top ring 5 along the outer periphery of the backing pad 7 to prevent the wafer 10 from jumping out in the circumferential direction when the holding force decreases during polishing.

In polishing the wafer 10, the turntable 1 and the polishing head 4 are driven at a predetermined number of rotations, and an abrasive in which abrasive grains are suspended is supplied from an abrasive supply nozzle 19 to the surface of the polishing pad 3. While pressing, the surface of the wafer 10 is pressed against the polishing cloth 3.

(Problems of Conventional Planar Polishing Apparatus) When the surface of the wafer 10 is polished by using the conventional planar polishing apparatus as described above, as the polishing of the wafer 10 progresses and the flatness of the surface increases. The suction force between the surface of the wafer 10 and the surface of the polishing pad 3 increases, and the suction force gradually approaches the suction force between the back surface of the wafer 10 and the backing pad 7. As a result, it is difficult to completely fix the wafer 10 by the suction force of the backing pad 7, and the wafer 10 may start to move during the polishing process. In such a case, since the wafer 10 is restrained from the surroundings by the retainer ring 8, it does not jump out of the holding head 4, but the rotational driving force from the holding head 4 is not accurately transmitted to the wafer 10, The flatness of the wafer 10 will be impaired.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional planar polishing apparatus, and an object of the present invention is to provide a polishing method for a flat object to be polished such as a semiconductor wafer. It is an object of the present invention to provide a planar polishing apparatus in which a state in which an object to be polished is adsorbed by a polishing head is reliably maintained and the flatness after polishing is excellent.

[0007]

According to the present invention, there is provided a flat-surface polishing apparatus comprising: a turntable having a polishing cloth adhered to an upper surface thereof and being driven to rotate;
A polishing head that is driven to rotate and adsorbs the object to be polished from the back surface and presses the surface against the polishing cloth; and wherein the surface of the object to be polished contacts the polishing cloth. The surface is provided with a means for blowing air or an inert gas.

According to the planar polishing apparatus of the present invention, the surface of the object to be polished is polished by blowing an inert gas such as air or nitrogen into the contact surface between the object to be polished and the polishing cloth through the means. Since the phenomenon of being adsorbed to the cloth is prevented, the state of adsorption of the object to be polished by the polishing head on the back side is reliably maintained, and as a result, a polished surface having high flatness is obtained.

Preferably, air or an inert gas is blown into the contact surface between the surface of the object to be polished and the polishing cloth.
A plurality of small holes from which these gases are discharged are formed on the upper surface of the turntable, and a polishing pad having a plurality of small holes functioning as a passage for these gases is used. Instead of this method, a means for blowing air or an inert gas from around the object to be polished may be provided on the polishing head side.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) FIG. 1 shows an example of a planar polishing apparatus according to the present invention. For configurations other than the turntable section,
Since it is common with the conventional planar polishing apparatus shown in FIG. 4, only the portions of the turntable 1 and the polishing cloth 3 are shown, (a) is a top view of the turntable portion, and (b) is an axial sectional view of the turntable portion. It is.

The polishing cloth 3 has a small hole 11 having a diameter of 1 mm penetrating vertically and formed on the entire surface of the polishing cloth. On the upper surface of the turntable 1, a number of air discharge holes 12 are provided. A hollow portion 13 is formed below the surface of the turntable 1, and the discharge hole 12 penetrates to the hollow portion 13, and a central portion of the turntable 1 has a supply portion disposed below the turntable 1. A through hole 14 for supplying air from a source (not shown) to the cavity 13 is formed.

Next, the result of polishing using the turntable shown in FIG. 1 will be described. As an object to be polished, an 8-inch silicon wafer on which a 1 μm thermal oxide film is formed is used, and this silicon wafer is adsorbed on a top ring (FIG. 4) using a backing pad 7 (FIG. 4) to perform polishing. After that, the in-plane distribution of the thermal oxide film was measured to evaluate the uniformity of the polishing amount. The polishing conditions were as follows: a pressure of 500 g / cm ² , a polishing head 5
The rotational speed of FIG. 4 was 100 rpm, the rotational speed of the turntable 1 was 100 rpm, and a slurry in which colloidal silica particles were suspended was used as an abrasive. Under these conditions,
Air was supplied from the lower part of the turntable 1 to the discharge holes 12 at a flow rate of 1 liter / minute, and polishing was performed for 3 minutes.

As a result, 5% was obtained as the value of the unprocessed film uniformity U defined by the following equation, and no movement of the wafer during polishing was observed. U = 100 × (Tmax−Tmin) / Tav [%] Here, Tmax: the maximum value of the remaining film, Tmin: the minimum value of the remaining film, and Tav: the average value of the remaining film.

For comparison, when a conventional 8-inch silicon wafer was polished under the same conditions using a conventional polishing apparatus, the value of the unprocessed film uniformity U defined by the above equation was obtained. Was 10%.

(Example 2) FIG. 2 shows another example of the planar polishing apparatus according to the present invention. Since the configuration other than the polishing head is the same as that of the conventional planar polishing apparatus shown in FIG. 4, only a sectional view of the polishing head is shown.

The top ring 5 is attached to a lower end of the main shaft 9. The wafer 10 is attached to the lower surface of the top ring 5 by vacuum suction via the backing pad 7. The backing pad 7 is an elastic body having a large number of small through holes 21 formed therein. These through holes 21 are formed by a suction hole 22 penetrating a top ring, a connection pipe 23, and a path formed inside a main shaft. 24 are sequentially connected to a vacuum pump (not shown).

On the lower surface of the top ring 5, a backing
A retainer ring 8 is attached along the outer periphery of the pad 7. A discharge port 25 for discharging air is opened on the lower surface of the retainer ring 8. The air introduced into the retainer ring 8 via the passage 27 and the connection pipe 26 formed inside the main shaft 9 is blown downward from the discharge port 25, and the surface of the wafer 10 and the polishing cloth 3 (FIG. 4) Invade between. Thus, the surface of the wafer 10 is prevented from being attracted to the polishing cloth 3, and the attracted state between the back side of the wafer 10 and the polishing head 4 is reliably maintained.

(Example 3) FIG. 3 shows another example of the planar polishing apparatus according to the present invention. In this example, a nozzle 31 for blowing air is provided outside the polishing head 4 along the outer periphery of the retainer ring 8. Also according to the configuration shown in this example, the surface of the wafer 10 is prevented from being attracted to the polishing pad 3, and the attracted state between the back side of the wafer 10 and the polishing head is reliably maintained.

[0019]

According to the planar polishing apparatus according to the present invention,
Since the phenomenon that the front side of the object to be polished is attracted to the polishing cloth is prevented, the state of adsorption between the back side of the object to be polished and the polishing head is reliably maintained, and as a result, polishing processing having high flatness The surface is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a planar polishing apparatus according to the present invention, (a).
Represents a top view of the turntable, and (b) represents a cross-sectional view of AA section.

FIG. 2 is a sectional view of a polishing head showing another example of the planar polishing apparatus of the present invention.

FIG. 3 is a view showing another example of the planar polishing apparatus of the present invention;
(A) is a top view, and (b) is a cross-sectional view taken along the line BB.

FIG. 4 is a diagram showing an outline of a conventional planar polishing apparatus.

[Explanation of symbols]

1. Turntable 2. Rotation drive mechanism 3.
..Polishing cloth, 4 polishing head, 5 top ring, 6 pressure mechanism, 7 backing pad,
8: retainer ring, 9: spindle, 10: semiconductor wafer, 11: small hole, 12: discharge hole, 13
... Cavity, 14 ... Through hole, 19 ... Abrasive supply nozzle, 21 ... Through hole, 22 ... Suction hole, 23
... Connection pipe, 24 ... Path, 25 ... Discharge port,
26 connection pipe, 27 path, 31 nozzle.

Claims (3)

[Claims] 1. A turntable having an upper surface on which a polishing cloth is adhered and driven to rotate, disposed opposite to the turntable, driven to rotate, and adsorbs an object to be polished from the back surface to polish the surface. A polishing head for pressing against a cloth, comprising: means for blowing air or an inert gas to a contact surface between the surface of the object to be polished and the polishing cloth. Flat polishing machine. 2. The surface polishing apparatus according to claim 1, wherein the turntable has a plurality of small holes formed on an upper surface thereof, and air or an inert gas is discharged through the small holes. apparatus. 3. The polishing head further comprises means for blowing air or inert gas from around the object to be polished to a contact surface between the surface of the object to be polished and the polishing cloth. The planar polishing apparatus according to claim 1.