Plasma processing apparatus and method for controlling the same

Abstract

The invention provides a plasma processing apparatus that realizes a most suitable inner environment of a vacuum vessel for each process. A plasma processing apparatus comprises a vacuum vessel 1, a first RF power supply 4, a second RF power supply 21, a third RF power supply 25, a first electrode 2 disposed within the vacuum vessel to which is supplied a mixture of a first RF voltage from the first RF power supply and a third RF voltage from the third RF power supply, a second electrode 14 disposed within the vacuum vessel to which is supplied a second RF voltage from the second RF power supply and having an upper surface mounting a sample 12, and a phase control unit 26 for controlling the phase difference of the second and third RF voltages, wherein the second and third RF voltages are of equal frequency, and the apparatus further comprises a first phase detecting means 32 for detecting the phase of the third RF voltage of the first electrode and a second phase detecting means 31 for detecting the phase of the second RF voltage of the second electrode, and based on the output of the first and second phase detecting means, controls the phase difference of the second and third RF voltages.

Description

[0001] The present application is based on and claims priority of Japanese patent application No. 2004-341723 filed on Nov. 26, 2004, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an art for manufacturing semiconductor devices. Specifically, the present invention relates to a plasma processing apparatus and a method for controlling the plasma processing apparatus suitable for carrying out a plasma processing of a semiconductor wafer using plasma. [0004] 2. Description of the Related Art [0005] Along with the recent trend of large-scale integration of semiconductor devices, the circuit patterns have become finer and finer, and the demands for accurate dimension processing have become very strict. Further, the wafer diameter has become as large as 300 mm with the aim to reduce manufacturing costs of the semiconductor devices, so there are also demands for uniformiz...

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Benefits of technology

[0019] In view of the problems mentioned above, the first object of the present invention is to provide a plasma processing apparatus and a method for controlling the plasma processing apparatus equipped with a function to utilize a most suitable signal for phase control, thereby solving drawbacks one through three mentioned above.

[0020] The second object of the present invention is to provide a plasma processing apparatus and a method for controlling the plasma processing apparatus equipped with the above function, that can be applied to a plasma source such as an inductively coupled plasma source having no two independent electrodes that are capacitively coupled with plasma, thereby solving the fourth drawback mentioned above.

[0022] Moreover, as a second actual example, with the object of suppressing sputtering and damage of the vacuum vessel wall and reducing the amount of contaminants caused thereby, a voltage probe is disposed around the target vacuum vessel to extract the RF signals transmitted from the upper and lower electrodes through plasma, and phase control is performed so as to minimize the voltage or to set the voltage to an appropriate value.

[0034] According to the present invention, upon performing phase control of the voltage waveforms of the third RF power and the second RF power supplying bias to the processing substrate, the phase difference at each electrode radiating power to the plasma can be controlled with high accuracy, and as a result of controlling the ion energy colliding against the wall and the interaction between ion and wall, the amount of substance generated from the wall can be controlled from minimum to maximum. As a result, it becomes possible to provide a most suitable in-vessel environment for each process performed in the apparatus for processing a processing substrate via plasma. Moreover, this function can be realized in all types of apparatuses that generate plasma, not only in those utilizing a parallel plate plasma source.

Problems solved by technology

However, according to the prior art, there are a means for detecting and a means for adjusting the phase difference of the RF between upper and lower biases, and though it is stated that the phase difference should preferably be controlled to 180 degrees, there is no disclosure on how to guarantee the achievement of the object by phase control.

The second drawback of the prior art is that even if the prior art method can be adopted to control the phase difference to 180 degrees, for example, it is not capable of guaranteeing that the phase difference of the voltages actually appearing at the upper and lower electrodes is 180 degrees.

Therefore, even if phase data is taken at each matching network of the upper and lower electrodes, the RF transmission paths that lead to the electrodes from the matching network vary, so there is no guarantee that the phase difference of the voltages generated at the electrodes is as controlled.

Another fact that influences the present problem is that the impedance of the RF transmission path leading to the earth seen from the upper electrode and the impedance of the RF transmission path leading to the earth seen from the lower electrode are not equal.

Further, since wafer processing is progressed near the lower electrode, the large amount of reaction products generated from the wafer causes the status of plasma near the lower electrode to change drastically.

What is concluded from the above is that the phase difference of voltages generated at upper and lower electrodes is determined by the overall circuits of RF passing the electrodes and the frequency of the RF, and therefore, it is not possible according to the prior-art monitoring method to accurately control the phase difference during wafer processing.

The third drawback of the conventional method results from the fact that the voltage waveform of RF biases generated at upper and lower electrodes is not a sine wave, and the conventional methods were incapable of performing optimum value control.

The cause of this displacement is that the phase difference of the electrodes are not performed accurately since the impedances of the RF transmission paths differ, and since the current / voltage waveform of the electrodes are deformed due to harmonics.

The fourth drawback of the conventional art is that the apparatus for improving wafer processing via phase control is restricted to a parallel plate plasma source equipped with upper and lower electrodes.

Various type of plasma sources are used in the industry such as an inductively coupled plasma source or an ECR plasma source, but the methods disclosed in the prior art cannot be applied to these plasma sources since they do not have two independent electrodes that are capacitively coupled with plasma.

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