JPH10209091A - End point detection in polishing apparatus and polishing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make improvement of the polishing object itself unnecessary, assure higher end point detecting accuracy, realize end point detection over a wider range and moreover execute end point detection with a comparatively low cost apparatus. SOLUTION: In this method, a polishing pad 14 as a 'polishing member' and a wafer 17 as a 'polishing object' are placed in contact with each other for relative movement, and a polishing agent is provided between these elements to detect the end point of the polishing condition in the polishing apparatus 11 to polish the wafer 17. In this case, substances which can be identified are equally mixed to this polishing agent, polishing is conducted using slurry 20 which is a mixing agent, and the polishing end point can be detected by observing the distributing condition of above substance at the polishing surface of the wafer 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an end point of a polishing state in a polishing apparatus for polishing an object to be polished, and a polishing apparatus having an end point detecting function.

[0002]

2. Description of the Related Art As the line width of fine processing in semiconductor manufacturing becomes narrower, the light source wavelength of optical lithography becomes shorter, and the numerical aperture, that is, the NA, also becomes larger. In addition, the number of steps in the semiconductor manufacturing process is increasing and becoming more complicated, and the surface shape of the semiconductor device is not necessarily flat.

[0003] The presence of a step on the surface indicates a disconnection in the wiring,
This causes a local increase in the resistance value, which leads to disconnection, a reduction in current capacity, and the like, and also leads to deterioration in breakdown voltage and generation of leakage in the insulating film. 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. 3 has been proposed. This is a chemical mechanical polishing (Chemical M
echanical Polishing or Chemical Mechanical Planari
zation) (hereinafter referred to as “CMP”) technology, which has been developed based on a mirror polishing method for a silicon wafer. That is, the polishing pad 2 is stuck on the rotating platen 1, while the holder 3 holds the wafer 4 as the “object to be polished”, and the wafer 4 is in contact with the polishing pad 2. In this state, the platen 1 is driven to rotate, and at the same time, the holder 3 is rotated while applying a load from above, and is simultaneously moved in the horizontal direction. Along with this operation, the abrasive 6 is discharged from the abrasive discharge nozzle 5 onto the polishing pad 2, and the abrasive 6 is discharged.
Is supplied to the polishing surface, and the wafer 4 held by the holder 3 is supplied.
Is polished flat.

In such a polishing apparatus, it is necessary to detect the end point of polishing. In general, a monitor wafer is used, the relationship between the amount of polishing of the monitor wafer and the polishing time is determined off-line, and the polishing time at which a desired polishing state is obtained is determined. ing.

Recently, various methods for in-line end point detection have been proposed to improve throughput and reduce costs. As a method of polishing, since the torque of the motor for rotating the wafer carrier fluctuates due to the flattening of the polishing or the exposure of the underground layer accompanying the polishing, a method of monitoring this and detecting the polishing end point, Since the frequency component of the vibration of the wafer carrier fluctuates with the polishing, a method of monitoring this to detect the polishing end point, and the capacitance between the surface plate and the wafer changes with the polishing, which is A method of monitoring and detecting a polishing end point, a method of irradiating light from the polishing surface side to the polishing surface and monitoring a scattering state of light on the polishing surface to detect a polishing end point, and a method of emitting light from the polishing surface side to the polishing surface. The method of measuring the film thickness of the transparent insulating layer to be irradiated and polished by using interference, the method of irradiating infrared light from the surface opposite to the polished surface and measuring the film pressure of the insulating film by using interference, etc. is there.

[0007]

However, in such a conventional method, a method using torque fluctuation, vibration, and capacitance requires formation of an unnecessary stop layer and wiring which are originally unnecessary. There is a problem that it is necessary to improve itself, and at the same time, the accuracy of end point detection is not sufficient. In addition, in the optical measurement method, the detection range is spot-like, cannot be performed in a wide range, and the measurement apparatus itself such as an interferometer becomes expensive.

Therefore, the present invention does not require improvement of the object to be polished, has good end point detection accuracy, can perform a wide range of end point detection, and can perform end point detection with a relatively inexpensive device. It is an object to provide a method and a polishing apparatus.

[0009]

In order to attain the object, the invention according to claim 1 makes a polishing member and an object to be polished come into contact with each other and moves relative to each other, and an abrasive is applied between the two. In the method of detecting the end point of the polishing state in the polishing apparatus for polishing the polishing object by interposing,
In the abrasive, a substance whose existence can be confirmed is evenly mixed, polishing is performed using the mixture, and an end point is detected by observing a distribution state of the substance on a polished surface of the object to be polished. An end point detection method is used.

According to a second aspect of the present invention, in addition to the first aspect, the substance whose existence can be confirmed is a dye or a fluorescent substance.

[0011] The invention described in claim 3 is the invention according to claim 1 or 2.
In addition to the above configuration, the end point is detected by observing the distribution state of the substance on the polished surface of the object to be polished from the polished surface side.

According to a fourth aspect of the present invention, the polishing member and the object to be polished are brought into contact with each other and moved relative to each other, and the polishing object supplied from the abrasive supply device is interposed between the two. In a polishing apparatus for polishing an object and detecting an end point of a polishing state at the time of the polishing, the abrasive supply device supplies a mixture in which a substance whose presence can be confirmed is uniformly mixed with the abrasive. On the other hand, the present invention is characterized in that the polishing apparatus has an observation device that detects an end point by observing a distribution state of the substance on a polishing surface of the object to be polished during polishing.

According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect, the observation device is provided on a polishing surface side of the object to be polished, and the observation device is provided on the polishing surface of the object to be polished. The end point is detected by observing the distribution state from the polished surface side.

[0014]

Embodiments of the present invention will be described below.

[First Embodiment of the Invention] FIG. 1 shows a first embodiment of the present invention.

First, the structure will be described. Reference numeral 11 in FIG. 1 denotes a polishing apparatus using a chemical mechanical polishing (CMP) technique. The polishing apparatus 11 is driven to rotate around a rotating shaft 12. A polishing pad 14 as a “polishing member” is provided on 13, while a holder 17 holds a wafer 17 that is a “polishing target”.

The holder 16 is supported by a holder support arm (not shown) and is connected to a holder driving device, whereby the wafer 17 held by the holder 16 is rotated and driven by the holder driving device. It is set to be able to move in parallel.

On the polishing pad 14, an abrasive supply device 19 for discharging the abrasive is provided. From the polishing agent supply device 19, a slurry 20 as a “mixture” in which a dye or a fluorescent substance is mixed with a polishing agent and a pH adjusting agent is supplied onto the polishing pad 14. As the dye or the fluorescent substance, a substance which is uniformly mixed when mixed with the abrasive and does not adversely affect the wafer 17 is selected.

Further, the platen 13 and the polishing pad 14
Are formed with through-holes 13a and 14a penetrating in the up-down direction.
1 is provided.

A camera 23 as an "observing device" is provided below the transparent body 21.
Thereby, light from the dye or the fluorescent substance is detected. If the amount of detected light is insufficient, a light source is provided on the camera 23 side, and light having a wavelength at which the dye or fluorescent substance reacts is irradiated onto the polished surface of the wafer 17 through the transparent body 21. good.

Next, the operation will be described.

First, the wafer 17 is brought into contact with the polishing pad 14 by transporting the wafer 17 while holding the wafer 17 in the holder 16. In this state, while rotating the platen 13 and applying a load to the holder 16 from above, the holder 16 is rotated by the holder driving device and simultaneously moved in the lateral direction. Along with this operation, the polishing layer of the wafer 17 is polished by discharging the slurry 20 from the polishing agent supply device 19 onto the polishing pad 14.

During the polishing, since the surface of the polishing layer of the wafer 17 has irregularities, the slurry 20 mainly accumulates in the concave portions, and the dye or the fluorescent substance also has a pattern corresponding to the concave portions. Then, when the polishing proceeds and the polishing layer is flattened, there is no unevenness, so that the slurry 20 is substantially uniformly distributed over the entire polishing layer surface (polishing surface). Thereby, the slurry 2
Dyes or fluorescent substances evenly mixed into 0 are distributed almost uniformly over the entire surface (polishing surface) of the polishing layer.

By detecting the state of the distribution of the dye or the fluorescent substance with the camera 23, if the distribution of the dye or the fluorescent substance is along the pattern corresponding to the concave portion, it is determined that polishing is in progress. If the distribution is uniform over the entire surface, the planarization is completed, and it can be detected that the polishing is at the end point.

Therefore, unlike the conventional method using torque fluctuation, vibration, and capacitance, it is not necessary to form a stop layer on the wafer 17 and to provide wiring. Since the polishing state can be grasped more quickly, the end point detection accuracy is better as compared with the conventional case where the end point is detected by torque fluctuation. Further, when compared with a conventional optical measurement method such as film thickness measurement utilizing interference, the measurement range such as film thickness measurement is spot-like, whereas in the present invention, the distribution state of dyes and the like is Since the method is to observe the camera 23 over a wide range, the end point detection range can be widened. Further, since the camera 23 used in this embodiment only needs to be capable of observing the distribution state of the dye or the like, the camera 23 is inexpensive as compared with a conventional film thickness measuring apparatus utilizing interference. .

Since the polishing layer of the wafer 17 is generally an insulating film layer or a metal wiring layer, when the film thickness measurement is used as the end point detection, the film thickness measurement is not performed at the metal wiring layer. In contrast to this, in the method of detecting the end point based on the distribution state of the dye or fluorescent substance on the polished surface as in the present invention, the polishing layer can be accurately formed regardless of whether the polishing layer is an insulating film layer or a metal wiring layer. Endpoint detection can be performed.

[Second Embodiment of the Invention] FIG. 2 shows a second embodiment of the present invention.

The second embodiment differs from the first embodiment in that an infrared camera 25 is provided above the holder 16 and the holder 16 is formed of, for example, quartz glass that transmits infrared light. I have.

In this way, the infrared light from the dye or the fluorescent substance on the polished surface is transferred to the holder 16 and the wafer 1.
7 and enter the infrared camera 25, the infrared camera 25 can detect the distribution state of the dye or the like on the polished surface and detect the end point.

Therefore, unlike the first embodiment, it is not necessary to form the through hole 14a in the polishing pad 14, and there is no possibility that the polishing pad will be adversely affected. Of course, also in the first embodiment,
If the polishing pad 14 and the surface plate 13 are formed of a material that transmits light, it is not necessary to form the through holes 14a.

In each of the above embodiments, the dye or the fluorescent substance is used by being mixed in the abrasive. However, the present invention is not limited to this. Of course, other substances may be used as long as they are mixed and do not adversely affect the object to be polished.

[0032]

As described above, according to the invention described in each claim, a substance whose presence can be confirmed is mixed with an abrasive, and the distribution state of the substance on the polished surface of the object to be polished is determined. Because the end point is detected by observing, there is no need to form a stop layer or wiring on the object to be polished as in the conventional method using torque fluctuation, vibration, and capacitance, and Since the polishing state can be directly grasped from the distribution state of the dye or the like, the end point detection accuracy is better than in the conventional case where the end point is detected by torque fluctuation. Further, when compared with a conventional optical measurement method such as film thickness measurement utilizing interference, the measurement range such as film thickness measurement is spot-like, whereas in the present invention, the distribution state of dyes and the like is Since the observation is performed over a wide range, the end point detection range can be widened.
Further, since it is only necessary to be able to observe the distribution state of the dye or the like, the end point can be detected with an inexpensive device as compared with a conventional film thickness measuring device utilizing interference or the like.

According to the third or fifth aspect of the present invention, the distribution of the substance whose presence can be confirmed on the polished surface is observed from the polished surface side. Regardless of the film layer or the metal wiring layer,
The end point can be detected accurately.

[Brief description of the drawings]

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

FIG. 2 is a schematic front view of a polishing apparatus according to Embodiment 2 of the present invention.

FIG. 3 is a schematic perspective view showing a conventional example.

[Explanation of symbols]

 11 Polishing device 13 Surface plate 14 Polishing pad (polishing member) 16 Holder 17 Wafer (object to be polished) 19 Abrasive supply device 20 Slurry (mixture) 23 Camera (observation device) 25 Infrared camera (observation device)

Claims (5)

[Claims] 1. An end point of the polishing state is detected in a polishing apparatus which makes a polishing member and a polishing object come into contact with each other and moves relative to each other, and interposes an abrasive between the polishing member and the polishing object to polish the polishing object. In the method, the abrasive is mixed uniformly with a substance whose presence can be confirmed, polishing is performed using the mixture, and the distribution state of the substance on the polished surface of the object to be polished is observed. An end point detecting method in a polishing apparatus, wherein an end point is detected. 2. The method according to claim 1, wherein the substance whose presence can be confirmed is a dye or a fluorescent substance. 3. An end point detecting method in a polishing apparatus according to claim 1, wherein an end point is detected by observing a distribution state of the substance on a polished surface of the object to be polished from a polished surface side. . 4. A polishing member and an object to be polished are brought into contact with each other and relatively moved, and the object to be polished is polished by interposing an abrasive supplied from an abrasive supply device between the two. A polishing apparatus for detecting an end point of a polishing state at the time of polishing, wherein the polishing agent supply device is set so as to supply a mixture in which a substance whose presence can be confirmed is uniformly mixed with the polishing agent; A polishing apparatus comprising an observation device for detecting an end point by observing a distribution state of the substance on a polishing surface of the object to be polished. 5. The observation device is provided on a polishing surface side of the object to be polished, and detects an end point by observing a distribution state of the substance on a polishing surface of the object to be polished from the polishing surface side. The polishing apparatus according to claim 4, wherein: