Polishing apparatus

Abstract

A polishing apparatus is used for polishing a substrate such as a semiconductor wafer to a flat finish. The polishing apparatus includes a polishing tool having a polishing surface, a substrate holder configured to hold a substrate, a monitoring device configured to monitor a polishing state of the surface of the substrate being polished, and a controlling device configured to change a polishing condition on the basis of the polishing state of the surface of the substrate being polished detected by the monitoring device.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a polishing apparatus for polishing a substrate such as a semiconductor wafer to a flat finish. [0003] 2. Description of the Related Art [0004] As telecommunication means such as Internet and high-speed large-capacity communication network have been remarkably developed, there has been an increasing demand for miniaturization and high integration in a semiconductor integrated circuit technology which supports the telecommunication means. [0005] However, as a semiconductor device has become smaller in size and more highly integrated, an electric signal delay in the semiconductor device, i.e., RC delay has become a large problem. The RC delay is determined by the product of interconnect resistance R and interconnect capacitance C. Therefore, a countermeasure for preventing such RC delay is to use a combination of an interconnect metal having a low electric resistance and an interlayer ...

AI Technical Summary

Benefits of technology

[0014] The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a polishing apparatus which can prevent a film formed on a substrate from being separated during a polishing process and can eliminate a need for selecting a process condition which may increase a process time in a polishing process.

[0016] According to the present invention, during polishing of the substrate, the polishing state of the surface of the substrate being polished is monitored by the monitoring device, and the polishing condition can be changed on the basis of the polishing state of the surface being polished which has been detected by the monitoring device. Therefore, even if a film composed of a material having a weak adhesion such as a low dielectric constant material is formed on the substrate, the polishing condition is changed by detecting the polishing state having a possibility of peeling-off of the film during polishing of the substrate, thus preventing the film from being peeled off.

[0018] According to the present invention, as a preset condition related to peeling-off of a film, for example, a threshold value of a frictional force acting on the polishing interface is set, and when the frictional force which is being monitored during the polishing process exceeds the threshold value, operational commands are sent from the monitoring device to the controlling device, and then the process condition is controlled so that the frictional force is lowered by the controlling device. Thus, the film formed on the substrate can be prevented from being peeled off. Further, since the threshold value at which peeling-off of the film does not occur is determined in advance, and polishing of the substrate can be performed in such a condition that the frictional force approaches the threshold value as close as possible, the excessively safe process which takes long time to polish the substrate in order to prevent the film from being peeled off is not required to be selected.

[0032] According to the present invention, even if a material having a weak adhesion such as a low dielectric constant material is used for a film of a semiconductor device, the film formed on the substrate can be prevented from being peeled off during polishing of the substrate. Further, it is not necessary to select the excessively safe process which takes long time to polish the substrate in order to prevent the film from being peeled off. Thus, the process margin can be broadened.

Problems solved by technology

However, as a semiconductor device has become smaller in size and more highly integrated, an electric signal delay in the semiconductor device, i.e., RC delay has become a large problem.

Further, as a semiconductor device has become smaller in size and more highly integrated, structures of semiconductor elements have become more complicated.

Accordingly, irregularities on a surface of a semiconductor device become increased, and hence step heights on the surface of the semiconductor device tend to be larger.

Further, an open circuit is caused by disconnection of interconnects, or a short circuit is caused by insufficient insulation between interconnect layers.

As a result, good products cannot be obtained, and the yield tends to be reduced.

Furthermore, even if a semiconductor device initially works normally, reliability of the semiconductor device is lowered after a long-term use.

Therefore, if the irregularities of the surface of the semiconductor device are increased, then it becomes difficult to form a fine pattern on the semiconductor device.

Therefore, in a case where the low dielectric constant material is used for the interlayer dielectric / intermetal dielectric, the following problems may arise in a polishing process: (1) Separation (peeling-off) occurs at an interface between the interlayer dielectric / intermetal dielectric and a metal film or other films, resulting in failure of a fabrication process of a semiconductor device.

(2) In order to prevent such separation of the interlayer dielectric / intermetal dielectric, an excessively low polishing pressure is required in the polishing process, thus increasing a process time in a polishing process.

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