JP2002270552A - Polishing head and polishing apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing head that can increase the degree of planarization on a wafer surface after a wafer is polished, and to provide a polishing apparatus using the polishing head. SOLUTION: The polishing head has a chuck plate 5 that allows a semiconductor wafer W to be subjected to vacuum suction for pressure-welding onto polishing cloth 56. The chuck plate 5 is formed by a ceramics plate made of silicon carbide. In the silicon carbide, a coefficient of thermal expansion αand thermal conductivity β are equal to α<=4.5×10<-6> /K and β>=170 W/m.K, respectively.

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 manufacturing semiconductor devices and the like and a polishing apparatus using the same.

[0002]

2. Description of the Related Art In recent years, with the increasing integration and density of semiconductor devices, there has been a demand for a technique for flattening the surface of a semiconductor wafer with high precision by lapping or the like.
Conventionally, a polishing apparatus as shown in FIG. 3 has been employed for this type of semiconductor wafer lapping processing (single-side polishing of a single wafer). This polishing apparatus will be described with reference to FIG.
In the figure, a polishing apparatus denoted by reference numeral 51 is an upper surface plate 5.
2 and a lower surface plate 53.

The upper surface plate 52 is composed of a polishing head having a head body 54, and is attached to a vertical shaft 55. And it is comprised so that it can rotate in the direction shown by the arrow about the said vertical axis 55 as a pivot. On the lower surface of the head main body 54, a semiconductor wafer W is mounted by a wafer holder 60 such as a wax or a backing material. On the other hand, the lower platen 53 is made of a platen for attaching a polishing cloth holding a polishing cloth 56 for polishing the semiconductor wafer W, and is rotatably arranged below the upper platen 52. Above the lower platen 53, the polishing surface 5 of the polishing pad 56 is located on the side of the upper platen 52.
A nozzle (not shown) for supplying a chemical polishing liquid such as a colloidal silica-based polishing agent is arranged on 6a.

In order to mirror-polish a semiconductor wafer W using such a polishing apparatus 51, a semiconductor wafer W is mounted on an upper surface plate 52 and a polishing cloth 56 is mounted on a lower surface plate 53.
After attaching the upper and lower platens 5 in the directions indicated by arrows in FIG.
This is performed by pressing the semiconductor wafer W onto the polishing surface 56a of the polishing cloth 56 while rotating the wafers 2 and 53 at a predetermined speed. At this time, the chemical polishing liquid is supplied between the polishing surface 56a of the polishing pad 56 and the surface of the semiconductor wafer W (the surface to be polished). The waste is discharged along with the polishing surface 56a of the polishing cloth 56 together with the debris.

By the way, in recent polishing apparatuses, since the holding ability for the semiconductor wafer W is relatively high,
There is also employed one provided with a polishing head having a chuck plate made of a ceramic material for vacuum-sucking (hard chucking) the semiconductor wafer W. In this case, the chuck plate is usually made of alumina (Al ₂ O ₃ ).
Is used.

[0006]

However, the polishing head of this type of polishing apparatus has the following problems because a ceramic plate made of alumina is used as a chuck plate. That is,
During wafer polishing, heat generated by friction between the semiconductor wafer W and the polishing cloth 56 causes a temperature difference between the upper and lower surfaces of the chuck plate, and the chuck plate undergoes thermal deformation (normal deformation in which the wafer pressing surface is convex downward). Was awake. As a result, the polishing pressure from the peripheral portion of the chuck plate is not sufficiently transmitted to the pressed surface of the semiconductor wafer W as compared with the polishing pressure from the central portion thereof, and the polishing pressure on the semiconductor wafer W becomes non-uniform. Therefore, there is a problem that the flatness (wafer shape accuracy) of the wafer surface after the wafer polishing is reduced.

FIG. 4 is a diagram showing the relationship between the wafer radial position and the polishing thickness when the semiconductor wafer W is polished on one side using a ceramic plate made of alumina as a chuck plate. In the figure,
There is a region with a small polishing amount (poor polishing) on the outer peripheral portion of the semiconductor wafer W.

The present invention has been made in view of the above circumstances, and it is possible to transmit a polishing pressure from the wafer pressing surface of a chuck plate to the entire surface to be pressed of a semiconductor wafer during wafer polishing. It is an object of the present invention to provide a polishing head capable of improving the flatness of a wafer surface later and a polishing apparatus using the same.

[0009]

A polishing head according to the present invention, which has been made to achieve the above object, is a polishing head having a chuck plate for vacuum-sucking a semiconductor wafer and pressing the semiconductor wafer against a polishing cloth. The chuck plate is formed of a ceramic plate made of silicon carbide having a thermal expansion coefficient α of α ≦ 4.5 × 10 ⁻⁶ / K and a thermal conductivity β of β ≧ 170 W / m · K. Features.

With this configuration, even if the chuck plate generates heat due to friction between the semiconductor wafer and the polishing pad, thermal deformation of the chuck plate is suppressed as compared with the case where the chuck plate is made of alumina. You. Therefore, when polishing the wafer, the polishing pressure can be transmitted from the wafer pressing surface of the chuck plate to the pressed surface of the semiconductor wafer over the entire surface, and the polishing pressure on the semiconductor wafer becomes uniform, and the flatness of the wafer surface after the wafer polishing is reduced. Can be enhanced.

On the other hand, a polishing apparatus according to the present invention comprises a polishing table for holding a polishing cloth for polishing a semiconductor wafer, a polishing head disposed above the polishing table and capable of pressing the semiconductor wafer on the polishing cloth. A polishing apparatus that presses and polishes a semiconductor wafer on the polishing cloth while relatively moving the polishing head and the surface plate, wherein the polishing head comprises:
A polishing head having the chuck plate according to claim 1.

With this configuration, even if the chuck plate generates heat due to friction between the semiconductor wafer and the polishing pad, the deformation of the chuck plate during wafer polishing is smaller than that of the chuck plate made of alumina. Is suppressed. Therefore, when polishing the wafer, the polishing pressure can be transmitted from the wafer pressing surface of the chuck plate to the pressed surface of the semiconductor wafer over the entire surface, and the polishing pressure on the semiconductor wafer becomes uniform, and the flatness of the wafer surface after the wafer polishing is reduced. It is possible to obtain a polishing apparatus that can be increased.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a polishing head according to the present invention and a polishing apparatus using the same will be described based on an embodiment shown in the drawings. FIG. 1 is a sectional view showing a use state of a polishing head according to an embodiment of the present invention. In this figure, the same reference numerals are given to the lower platen and the polishing cloth shown in FIG. As shown in FIG. 1, the polishing apparatus denoted by reference numeral 1 includes an upper surface plate 2 and a lower surface plate 53. The upper surface plate 2 is composed of a polishing head having a retainer ring 4 and a chuck plate 5, and is attached to a vertical shaft (not shown). And it is comprised so that rotation is possible about a vertical axis as a pivot.

The retainer ring 4 is formed by a ring that opens in the vertical direction. The retainer ring 4 is provided with a space 4a for holding the semiconductor wafer W inside. Thereby, the viscoelasticity of the polishing pad 56 can be prevented from adversely affecting the shape of the outer peripheral portion of the wafer during polishing of the wafer (so-called outer periphery drooping can be prevented).

The chuck plate 5 is attached to a part of the retainer ring 4, and is formed entirely of a ceramic plate made of silicon carbide (SiC) or the like. The chuck plate 5 has a thermal expansion coefficient α of α = 4.5 × 10 ⁻⁶ / K and a thermal conductivity β
Is formed by a ceramic plate made of silicon carbide with β = 170 W / m · K. The chuck plate 5 is in close contact with the entire pressed surface of the semiconductor wafer W in the wafer polishing state, and
A wafer pressing surface (smooth surface) 5a parallel to the polishing surface 56a is formed.

The chuck plate 5 has a chamber 5 communicating with a tube (not shown) for connecting a suction device.
b and a number of flow passages 5c communicating with the chamber 5b
Is provided. Thereby, the semiconductor wafer W is vacuum-adsorbed during wafer polishing, and the polishing surface 56a of the polishing cloth 56 is polished.
It is configured such that the semiconductor wafer W can be pressed against it with a pressing force P (p, p,...).

With the above configuration, mirror polishing of the semiconductor wafer W using the polishing apparatus 1 is performed in the same manner as in the prior art. That is, the semiconductor wafer W is mounted (vacuum suction) on the upper surface plate 2 and the polishing pad 56 is mounted on the lower surface plate 53.
Then, the semiconductor wafer W is pressed onto the polishing surface 56a of the polishing pad 56 while rotating the upper and lower platens 2 and 53 at a predetermined speed in a predetermined direction. At this time, the chemical polishing liquid is supplied between the polishing surface 56a of the polishing pad 56 and the surface (the surface to be polished) of the semiconductor wafer W. The paper is discharged along the polishing surface 56a of the cloth 56.

Here, as the chuck plate 5, Table 1
A ceramic plate made of a material of alumina (Al ₂ O ₃ ) and silicon carbide (SiC) having physical properties as shown in FIG. The results of the measurement (displacement of the chuck plate 5) shown in Table 2 were obtained when a comparison was made in the case of performing a thermal deformation analysis by giving a temperature difference of ° C.

[0019]

[Table 1]

[0020]

[Table 2]

That is, when a temperature difference of 5 ° C. is applied to the upper and lower surfaces of the plate, the displacement of about 10 μm when the material of chuck plate 5 is alumina, and the displacement of about 6 μm when the material is silicon carbide. Also in the case of (1), a displacement that is convex downward) occurs in each chuck plate 5.
On the other hand, when a temperature difference of 2 ° C. is applied to the upper and lower surfaces of the plate, a displacement of about 4 μm is obtained when the material of chuck plate 5 is alumina, and about 2 μm when the material is silicon carbide.
displacement of m (displacement that is convex downward in any case)
Is generated on each chuck plate 5. Thus, it can be seen that the displacement of chuck plate 5 made of silicon carbide is smaller than the displacement of chuck plate 5 made of alumina at any temperature difference.

Next, as the chuck plate 5, a ceramic plate made of a material of alumina (Al ₂ O ₃ ) and silicon carbide (SiC) having physical properties as shown in Table 1 is used, and the polishing pressure is set to 150 gf / cm ^2. And 300gf / c
When the semiconductor wafer W was polished as m ² , the wafer polishing accuracy was measured. FIG. 2 shows the measurement results. The vertical and horizontal axes in the figure indicate the wafer polishing accuracy (the amount of displacement of the concave portion) and the polishing pressure, respectively. Thus, the concave displacement amount when the chuck plate 5 is made of alumina is larger than the concave displacement amount when silicon carbide is used, and the higher the polishing pressure (the higher the temperature), the larger the concave displacement amount. It can be seen that the difference is significant.

Therefore, in the present embodiment, even if the chuck plate 5 generates heat due to friction between the semiconductor wafer W and the polishing pad 56, thermal deformation of the chuck plate 5 (deformation that becomes convex downward). Therefore, the polishing pressure can be transmitted from the wafer pressing surface 5a of the chuck plate 5 to the entire pressed surface of the semiconductor wafer W during the polishing of the wafer, and the polishing pressure on the semiconductor wafer W becomes uniform, so that the polishing pressure after the wafer polishing is reduced. The flatness of the wafer surface can be increased.

In this embodiment, the case where the chuck plate 5 is mounted in the retainer ring 4 has been described. However, the present invention is not limited to this, and the chuck plate 5 (the outer peripheral edge of the wafer pressing surface 5a). The retainer ring 4 can be attached to the. Further, in the present embodiment, the case where the retainer ring 4 is used has been described. However, the present invention is not limited to this. Of course.

Further, the material of the chuck plate (ceramic plate) 5 in the present embodiment has a thermal expansion coefficient α of α = 4.5 × 10 ⁻⁶ / K and a thermal conductivity β of β = 170 W / m. The case where silicon carbide is used as K has been described, but the present invention is not limited to this, and other physical properties (α <4.5 × 10 ⁻⁶ / K, β> 170 W / m · K)
May be used.

[0026]

As apparent from the above description, according to the polishing head and the polishing apparatus using the same according to the present invention,
The polishing pressure on the semiconductor wafer becomes uniform, and the flatness of the wafer surface after wafer polishing can be increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a use state of a polishing head (polishing apparatus) according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a polishing pressure and a wafer polishing accuracy (shape accuracy) when alumina and silicon carbide are used as materials for a chuck plate in a polishing head (polishing apparatus) according to an embodiment of the present invention. .

FIG. 3 is a front view showing a conventional polishing apparatus.

FIG. 4 is a diagram showing the relationship between the wafer radial position and the polishing thickness when a semiconductor wafer is polished on one side using a ceramic plate made of alumina as a chuck plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polishing apparatus 2 Upper surface plate (polishing head) 4 Retainer ring 5 Chuck plate 5a Wafer pressing surface 5b Chamber 5c Flow path 53 Lower surface plate 55 Vertical axis 56 Polishing cloth 56a Polishing surface W Semiconductor wafer

Claims (2)

[Claims] 1. A polishing head having a chuck plate for vacuum-sucking a semiconductor wafer and pressing against a polishing cloth, wherein the chuck plate has a coefficient of thermal expansion α ≦ 4.5 ×.
A polishing head formed of a ceramics plate made of silicon carbide and having a thermal conductivity β of 10 ⁻⁶ / K and β ≧ 170 W / m · K. 2. A polishing table, comprising: a platen for holding a polishing cloth for polishing a semiconductor wafer; and a polishing head disposed above the platen and capable of pressing the semiconductor wafer on the polishing cloth. While relatively moving the surface plate,
A polishing apparatus for pressing and polishing a semiconductor wafer on the polishing cloth, wherein the polishing head is a polishing head having the chuck plate according to claim 1.