JPH1148133A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect a polishing end point. SOLUTION: A polishing device 11 furnished with at least a surface plate and a polishing pad to polish a surface of an article to be polished provided on the surface plate is furnished with at least one through hole formed on the polishing pad, a liquid supply mechanism having a liquid supply pipe 19 communicated to the through hole and a polishing monitor system 18 to detect a polishing end point by measuring reflectance of a surface of the article to be polished through the through hole with liquid supply pipe 19 and liquid filled in the liquid supply pipe 19 as part of an optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polishing apparatus,
For example, the present invention relates to a polishing apparatus suitable for use in flattening (polishing irregularities) the surface of an insulating film or a metal film deposited on a semiconductor wafer in a process of manufacturing a high-density semiconductor integrated circuit device (ULSI) or the like.

[0002]

2. Description of the Related Art In semiconductor manufacturing, as the line width of fine processing becomes narrower, the light source wavelength of optical lithography becomes shorter,
The numerical aperture, so-called NA, is also increasing. Also,
The number of processes has also increased and the semiconductor manufacturing process has become more complicated, and the surface shape of the semiconductor device has not always been flat.

The presence of a step on the surface causes disconnection of the wiring, an increase in the local resistance value, and the like, resulting in disconnection and a reduction in current capacity, and also in the insulating film, deterioration in breakdown voltage and generation of leakage. Further, the presence of such a step indicates that the depth of focus of the semiconductor exposure apparatus has become substantially shallower. In other words, it has become necessary to flatten the surface of the semiconductor device in order to improve the yield and reliability and to increase the depth of focus margin for higher resolution.

Therefore, a polishing apparatus as shown in FIG. 2 has been proposed. This is a chemical mechanical polishing (Chemic
al Mechanical Polishing or ChemicalMechanical Plan
arization (hereinafter referred to as CMP) technology, which has been developed based on a mirror polishing method for a silicon wafer. In the conventional polishing apparatus, a polishing pad 2 is provided on a rotating platen 1, while a polishing head 3 holds a wafer 4, and the wafer 4 is in contact with the polishing pad 2. In this state, the platen 1 is rotationally driven, a load is applied to the polishing head 3 from above, and the polishing head 3 is caused to swing in the radial direction of the platen 1 while rotating.

In addition to the above operation, the polishing liquid supply nozzle 5
Then, the polishing liquid 6 is discharged onto the polishing pad 2 and the polishing liquid 6 is supplied to the polishing surface of the wafer 4 to polish the outermost surface of the wafer 4 flat. The wafer 4 is polished to a polishing end point obtained by a method described later. A method for calculating the polishing time until the polishing end point will be briefly described.

First, the initial film thickness of a sample wafer is measured in advance, and the polishing rate is calculated from the remaining film thickness after polishing, the initial film thickness, and the polishing time. In the subsequent polishing of the wafer, polishing is performed for a time calculated to obtain a desired film thickness based on the polishing rate. However, the polishing rate varies depending on the surface condition of the polishing pad.

[0007] Therefore, when a large number of wafers are polished for the time calculated by the above-described method, there is a problem that a variation in the polishing rate causes a variation in the remaining film thickness. In order to minimize such variations, it is necessary to review the setting of the polishing time every time several wafers are polished. This review work requires a great deal of time and effort, and causes a decrease in the throughput of the apparatus.

As a method for solving such a problem, an optical window is provided in the polishing pad, and through the window during polishing, an optical means is used to measure the film thickness or reflectance of the wafer polishing surface from the back side of the polishing pad. And a method of measuring the polishing end point on the spot in real time has been proposed. (Japanese Patent Laid-Open No. 7
-235520)

[0009]

However, since the polishing liquid always stays on the optical window provided on the polishing pad, the light irradiated toward the optical window and the light from the polished surface of the wafer are not polished. The reflected light is scattered by the polishing liquid or the abrasive grains in the polishing liquid, and the transmittance is remarkably reduced, or the scattered light becomes reflected light from the polished surface, and the measurement accuracy (S
/ N ratio).

Accordingly, the present invention has been made in view of such a problem, and an object of the present invention is to provide a polishing apparatus capable of accurately detecting a polishing end point.

[0011]

According to the present invention, there is provided a polishing apparatus having at least a platen and a polishing pad provided on the platen for polishing a surface of an object to be polished. At least one through hole formed in the polishing pad;
A liquid supply mechanism having a liquid supply pipe communicating with the through hole; and a liquid supply pipe and a liquid filled in the liquid supply pipe serving as a part of an optical path, and the reflectance of the surface of the object to be polished is reduced through the through hole. The present invention provides a polishing apparatus (claim 1) provided with a polishing monitor system that detects a polishing end point by measuring.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polishing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a polishing apparatus 11 according to the first embodiment includes a flat surface having an area having a diameter of about twice or more the diameter of a wafer, and a surface plate 12 rotated around a rotation axis 20 by a motor. Has a polishing pad 13 as a "polishing member".

The polishing pad 13 has a single-layer structure of a Rodel Nitta polishing pad IC1000 (polyurethane foam) or a two-layer structure composed of IC1000 and Suba400, or carbon fiber or the like added to an epoxy resin and cured. (Hereinafter referred to as CEP (carbon epoxy polisher)). When the polishing pad 13 is CEP, the grooves through which the polishing liquid passes are formed in a lattice, radial, spiral, or other shape.

A polishing head 14 is provided opposite to the polishing pad 13 for pressing the held wafer 15 against the polishing pad 13. Polishing head 1
4, for example, presses a wafer 15 as an object to be polished to a polishing pad 13 via a backing pad, and is capable of rotating and swinging by a polishing head supporting arm and a driving device (not shown). Has become.

The wafer 15 is pressed against the polishing pad 13 by the polishing head 14 with a predetermined polishing load.
4 and the polishing pad 13 are relatively moved by the rotation and swing of the platen 4 and the rotation of the platen 12. In addition to the method of holding a wafer with a backing pad, a vacuum suction method, a hydro chuck method (JP-A-8-55826), an airbag method or a diaphragm method (JP-A-7-17175)
No. 7, JP-A-7-112364) and the like.

The vacuum suction method is characterized in that polishing can be performed with reference to the back surface of the wafer. In addition, the hydro chuck method and the air bag method have a feature that uniform pressing can be performed by hydrostatic pressure because they are pressed through a fluid. Along with this operation, the polishing liquid 17 is discharged from the polishing liquid supply nozzle 16 onto the polishing pad 13, and the polishing liquid 17 is supplied to the polishing surface of the wafer 15, and
Is polished flat.

In the polishing apparatus of the present invention, the liquid 21 is supplied to a part of the polishing pad 13 and the through-hole 1 through which light passes is provided.
3a is provided. The diameter of the through hole 13a is 1 to 5
0 mm, and the most preferable diameter is 10 mm.
３０30 mm. Further, a liquid supply pipe 19 communicating with the through hole 13a is provided, and a supply pump and a liquid supply source (not shown) are provided in the liquid supply pipe 19.

Since the liquid 21 is always supplied from the through hole 13a, the polishing liquid 17 does not enter the through hole 13a, or is immediately discharged again even if it enters. The liquid 21 supplied from the through-hole 13a includes pure water, but is not limited to this as long as the liquid 21 does not affect the polishing even when mixed with the polishing liquid. Furthermore, the through hole 1
3a, that is, the platen 12 via the liquid supply pipe 19
On the lower side, a polishing monitor system 18 is provided.

Therefore, a part of the liquid supply pipe 19 and a part of the liquid 21 form a part of an optical path of the polishing monitor system 18. Therefore, the liquid supply pipe 19 or a part thereof (a part where light passes through the liquid supply pipe) 19a is used to check the polishing state of the wafer 15 or to check the polishing end point.
It is necessary that the transparent material be capable of transmitting light emitted from the light source 8 and light reflected from the polished surface of the wafer 15. Examples of the transparent material include optical glass and synthetic quartz glass, but are not limited thereto.

The surface plate 12 made of an opaque material includes:
An opening 12a is formed so that light emitted from the light source of the polishing monitor system 18 can reach a part 19a of the liquid supply pipe. Further, the platen 12 may be made of a transparent material. In that case, the opening 12a may not be formed in the platen 12.

The polishing monitor system 18 includes the liquid supply pipe 1
A light source for irradiating light toward the through-hole 13a via the liquid 9 and the liquid 21, a light receiving unit for detecting reflected light from the polishing surface of the wafer 15 taken out via the liquid 21 and the liquid supply pipe 19, and a light receiving unit Is provided with a polishing monitor for checking the polishing state of the polishing surface of the wafer 15 based on the change in the reflected light detected by the method, or detecting the polishing end point.

When the polishing end point is detected, the material of the polishing liquid supply pipe 19 and the refractive index of the liquid 21 and the reflection and absorption generated when light passes through the polishing liquid supply pipe 19 and the liquid 21 are determined in advance. Need to be considered. During polishing of the wafer 15, the liquid 21 is constantly supplied from the through-hole 13 a, so that when the wafer 15 passes through the through-hole 13 a, the polished surface is cleaned by the liquid 21.

Therefore, the light emitted from the light source of the polishing monitor system 18 irradiates the cleaned polishing surface, so that the scattered light generated by the abrasive grains (for example, colloidal silica) in the polishing liquid 17 is generated. There is no influence, and the measurement accuracy (S / N ratio of signal light) can be improved. Further, the light emitted from the light source of the polishing monitor system 18 does not attenuate because there is almost no abrasive grains on the polishing surface, and there is no need to increase the light amount of the light source in anticipation of the attenuation (light amount of the light source). Can be reduced).

[0024]

As described above, in the polishing apparatus according to the present invention, the polishing pad is provided with the through-hole, and the liquid is always supplied from the through-hole from the liquid supply mechanism having the liquid supply pipe communicating with the through-hole. Since it is supplied to the polishing pad,
The polished surface of the wafer passing through the through hole is clean. Therefore, the liquid supply pipe and a part of the liquid as a part of the optical path,
The light emitted from the polishing monitor system that measures the reflectance of the surface of the object to be polished through the through-hole and detects the polishing end point,
Irradiation is performed on the cleaned polishing surface, so that there is no influence of scattered light generated by polishing abrasive grains (eg, colloidal silica) in the polishing liquid, and measurement accuracy (S / N ratio of signal light) is improved. Can be.

The light emitted from the light source of the polishing monitor system has almost no abrasive grains on the polished surface.
There is no attenuation, and it is not necessary to increase the light amount of the light source in anticipation of the attenuation (the light amount of the light source can be reduced).

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a polishing apparatus according to the present invention.

FIG. 2 is a schematic perspective view of a conventional polishing apparatus.

[Explanation of symbols]

 11 Polishing device 1, 12 Platen 2, 13 Polishing member (polishing pad) 3, 14 Polishing head 4, 15 ... Polishing object (wafer) 5, 16 ..Polishing liquid supply nozzles 6, 17: Polishing liquid 18: Polishing monitor system 19: Fluid supply pipe 20: Rotating shaft 21: Liquid

Claims (1)

[Claims] 1. A polishing apparatus having at least a surface plate and a polishing pad provided on the surface plate for polishing a surface of an object to be polished, wherein at least one through hole formed in the polishing pad. A liquid supply mechanism having a liquid supply pipe communicating with the through hole; and a reflectance of a surface of the object to be polished through the through hole, wherein the liquid supply pipe and the liquid filled in the liquid supply pipe are part of an optical path. A polishing monitor system that detects the polishing end point by measuring the polishing end point.