Plasma processing apparatus and plasma processing method

Abstract

In a plasma processing apparatus which includes a chamber (1) equipped with a wafer stage (3) for mounting thereon a substrate (2) to be processed, and which processes the substrate (2) by exposure to a plasma (4), a photon detection sensor (5) for measuring an ultraviolet-light-induced current is placed on a circumferential portion of a substrate mounting surface (3a) of the wafer stage (3) so that the occurrence of an abnormal discharge can be detected, in real time, from a change in the output of the photon detection sensor (5).

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority of Japanese Patent Application No. 2004-159531, filed on May 28, 2004. FIELD OF THE INVENTION [0002] The present invention relates to a plasma processing apparatus, and to a plasma processing method, for processing a semiconductor wafer or the like and, more particularly, to a plasma processing apparatus and to a plasma processing method capable of monitoring, in real time, an abnormal discharge phenomenon that can occur during plasma processing. BACKGROUND OF THE INVENTION [0003] Plasma processes such as etching, thin-film deposition, etc. are indispensable for achieving high-quality, high-functionality semiconductor devices. However, one problem involved with such plasma processes is that an abnormal discharge can occur abruptly during processing in a plasma processing apparatus. If an abnormal discharge occurs, etching and thin-film deposition conditions change and, as a result, the characteristics of ...

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Benefits of technology

[0006] In view of the above situation, it is an object of the present invention to provide a plasma processing apparatus and plasma processing method that can monitor the plasma state in real time during processing and, more particularly, can monitor in real time the occurrence of an abnormal discharge.

[0009] When an abnormal discharge occurs in the plasma chamber, the plasma density appreciably drops at that instant because of the discharge, and the generation of ions, neutral particles, electrons, and ultraviolet light by the plasma decreases. When the photon detection sensor is installed, during the generation of the plasma a certain amount of current induced by the ultraviolet light generated from the plasma is observed in a steady-state condition; however, when the plasma density drops due to an abnormal discharge, and the amount of ultraviolet light generation decreases, then a spike-like current drop is observed. Accordingly, by installing the photon detection sensor on the wafer stage in the plasma processing apparatus, and by monitoring the sensor output in real time, the occurrence of an abnormal discharge manifesting itself as a spike-like current drop can be detected in real time. As a result, quick and appropriate action can be taken to deal with the abnormal discharge.

[0010] The photon detection sensor further comprises a second electrode formed on the insulating film. With the provision of this electrode, the influence of only the ultraviolet light can be observed by eliminating the influence of particles other than the vacuum ultraviolet light, such as ions and electrons. This serves to enhance the accuracy in detecting the occurrence of an abnormal discharge.

[0011] Further, a plurality of sensors, each identical to the above-described photon detection sensor, are arranged spaced apart from each other on the wafer stage. With this arrangement, it becomes possible to know the spatial distribution indicating the extent to which the effect of the abnormal discharge has spread, thus making it easier to determine, for example, which devices on the semiconductor wafer are affected.

[0014] According to the above method, the current induced by the ultraviolet light generated from the plasma is detected by the photon detection sensor mounted on the wafer stage while the plasma processing of the substrate is being performed; in this way, any abnormal discharge occurring in the plasma chamber can be detected in real time in the form of a change in current value. Accordingly, quick action can be taken to deal with the abnormality, offering the effect of enhancing the reliability and productivity of semiconductor devices.

Problems solved by technology

However, one problem involved with such plasma processes is that an abnormal discharge can occur abruptly during processing in a plasma processing apparatus.

In the worst case, the processing-apparatus may be damaged.

An abnormal discharge occurs when the large electric charge accumulated on the inside wall of the plasma chamber, etc. either exceeds a limit or is discharged for some reason during plasma processing.

As such discharge occurs in an unpredictable manner, and as there are no effective sensing methods for detecting the occurrence, with a prior known plasma processing apparatus, it has not been possible to take appropriate action by detecting the occurrence of such an abnormal discharge in real time, and this has led to the degradation of the productivity, as well as the reliability, of the produced semiconductor device.

This system is one that monitors the energy distribution, ion current, etc., for example, of the ions, electrons, and other particles generated by the plasma, but, as these changes manifest themselves relatively slowly on the semiconductor wafer in contrast with an instantaneous change in the plasma state such as an abnormal discharge, the proposed system is not suitable for real-time monitoring of an abnormal discharge.

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