Source: http://www.google.com/patents/US5332880?ie=ISO-8859-1
Timestamp: 2014-03-16 15:40:29
Document Index: 563572836

Matched Legal Cases: ['art 21', 'art 21', 'art 21', 'art 21', 'art 21', 'art 21']

Patent US5332880 - Method and apparatus for generating highly dense uniform plasma by use of a ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAt lateral sides of a plasma generating part under a vacuum, first to fourth lateral electrodes are so disposed as to surround the plasma generating part. High frequency electric power is supplied to the first lateral electrode from a first high frequency power supply, high frequency electric power is...http://www.google.com/patents/US5332880?utm_source=gb-gplus-sharePatent US5332880 - Method and apparatus for generating highly dense uniform plasma by use of a high frequency rotating electric fieldAdvanced Patent SearchPublication numberUS5332880 APublication typeGrantApplication numberUS 08/040,348Publication dateJul 26, 1994Filing dateMar 30, 1993Priority dateMar 31, 1992Fee statusLapsedPublication number040348, 08040348, US 5332880 A, US 5332880A, US-A-5332880, US5332880 A, US5332880AInventorsKenji Harafuji, Masafumi Kubota, Ichiro Nakayama, Noboru Nomura, Mitsuhiro Ohkuni, Tokuhiko TamakiOriginal AssigneeMatsushita Electric Industrial Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (7), Referenced by (27), Classifications (27), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetMethod and apparatus for generating highly dense uniform plasma by use of a high frequency rotating electric fieldUS 5332880 AAbstract At lateral sides of a plasma generating part under a vacuum, first to fourth lateral electrodes are so disposed as to surround the plasma generating part. High frequency electric power is supplied to the first lateral electrode from a first high frequency power supply, high frequency electric power is supplied to the second lateral electrode from the first high frequency power supply through a first delay circuit, high frequency electric power is supplied to the third lateral electrode from the first high frequency power supply through the first delay circuit and through a second delay circuit, and high frequency electric power is supplied to the fourth lateral electrode from the first high frequency power supply through the first and second delay circuits and through a third delay circuit. Accordingly, there are respectively applied, to the first to fourth lateral electrodes, the high frequency electric powers of which frequencies are equal to one another and of which phases are successively different from one another, and there is excited, in the plasma generating part, a rotational electric field to cause electrons in the plasma generating part to present rotational motions.
What is claimed is: 1. A plasma generating method comprising the steps of:disposing three or more lateral electrodes at lateral sides of a plasma generating part in a vacuum chamber such that said three or more lateral electrodes surround said plasma generating part, and further disposing a sample stage at a lower part of said plasma generating part; supplying a first high frequency electric power from a high frequency power supply to one of said three or more lateral electrodes; respectively supplying, to other lateral electrodes of said three or more lateral electrodes, high frequency electric powers which are supplied from said high frequency power supply through delay means, of which frequencies are the same as the frequency of said first-mentioned high frequency electric power and of which respective phases are successively different from the phase of said first-mentioned high frequency electric power; and supplying, to said sample stage, second high frequency electric power of a second frequency which is lower than said first frequency; whereby there is excited, in said plasma generating part, a rotational electric field to cause electrons therein to present rotational motions. 2. The plasma generating method of claim 1 wherein said delay means comprises a delay circuit group.
17. The plasma etching method according to claim 15, wherein said layer-to-be-etched is an oxide layer, and said etching gas includes CHF.sub.3 or CF.sub.4.
18. The plasma etching method according to claim 15, wherein said layer-to-be-etched is a polysilicon layer, and said etching gas includes Cl.sub.2 and O.sub.2.
BACKGROUND OF THE INVENTION The present invention relates to a plasma generating method and apparatus.
Disposed at the lateral sides of the chamber 81 are two pairs of AC electromagnets 88 of which phases are shifted by 90 electromagnets 88 of each pair being opposite to each other. By the two pairs of AC electromagnets 88, a rotational magnetic field is applied into the chamber 81 to facilitate discharge under a high vacuum. With such an arrangement, the rotational magnetic field causes electrons to present cycloid motions. This lengthens the motional passages of the electrons to increase the efficiency of ionization.
SUMMARY OF THE INVENTION To achieve the object above-mentioned, a first plasma generating method according to the present invention comprises the steps of: disposing a pair of lateral electrodes opposite to each other through a plasma generating part in a vacuum chamber; supplying high frequency electric power from a high frequency power supply to one of the pair of lateral electrodes; and supplying, to the other of the pair of lateral electrodes, high frequency electric power which is supplied from the high frequency power supply through a delay circuit, of which frequency is the same as that of the first-mentioned high frequency electric power and of which phase is different from that of the first-mentioned high frequency electric power; whereby there is excited, in the plasma generating part, a high frequency electric field to cause electrons therein to present oscillating motions.
DETAILED DESCRIPTION OF THE INVENTION The following description will discuss a dry etching apparatus to which applied is the plasma generating method according to a first embodiment of the present invention.
A first delay circuit 11 is disposed between the first lateral electrode 5 and the second lateral electrode 6. The first delay circuit 11 causes the high frequency electric power applied to the second lateral electrode 6 to present a difference in phase of about 90 electric power applied to the first lateral electrode 5. A second delay circuit 12 is disposed between the second lateral electrode 6 and the third lateral electrode 7. The second delay circuit 12 causes the high frequency electric power applied to the third lateral electrode 7 to present a difference in phase of about 90 electric power applied to the second lateral electrode 6. A third delay circuit 13 is disposed between the third lateral electrode 7 and the fourth lateral electrode 8. The third delay circuit 13 causes the high frequency electric power applied to the fourth lateral electrode 8 to present a difference in phase of about 90 electric power applied to the third lateral electrode 7.
Although not shown, only the first lateral electrode 5 and the third lateral electrode 7 may be disposed through the plasma generating part 21, or only the second lateral electrode 6 and the fourth lateral electrode 8 may be disposed through the plasma generating part 21, and there may be applied, to such a pair of opposite lateral electrodes, high frequency electric powers which are supplied from the same high frequency power supply, which have the same frequency, and of which phases are made different by 180 an arrangement, the electrons in the plasma generating part 21 advance as arranged in the direction of the kinetic energy inherent therein, while being subjected to oscillating motions by a high frequency electric field applied to the plasma generating part 21.
FIG. 11 (a) schematically shows an example of etching boron phosphorus glass with a dry etching apparatus to which the plasma generating method of the present invention is applied. With this dry etching apparatus, a substantially uniform plasma is generated as mentioned earlier. Accordingly, an ion flux II or etching reaction product incident upon the surface of the Si substrate 30 is uniform as shown in FIG. 11 (a). Further, the etch rate is also highly uniform as shown in FIG. 11 (b). Further, since the plasma is uniform, electric charges are hardly unevenly distributed so that damages to the devices due to the charge-build-up are considerably small. In this example, as the gas to be introduced into the chamber 1, there was used gas made based on fluorocarbon gas such as CHF.sub.3 +O.sub.2, CF.sub.4 +CH.sub.2 F.sub.2 or the like, and the gas pressure was set to 0.1 to 10 Pa. The etching rate was in the range from 100 to 350 nm/min.
According to the present embodiment discussed in the foregoing, there are applied, to the first to fourth lateral electrode 5 to 8 surrounding the plasma generating part 21, the high frequency electric powers of which frequencies are the same as one another and of which phases are respectively different by 90 electrons e in the plasma generating part 21 under a vacuum present rotational motions, thus generating a highly dense plasma excellent in uniformity inspire of a high vacuum.
The present embodiment is arranged such that each of the differences in phase among the high frequency electric powers is set to 90 is because, when each of the differences in phase is set to 90 the efficiency of supplying the electric powers to the plasma is good. However, even if each of the differences in phase is set to other than 90 obtained. Further, the phases of the high frequency electric powers applied to the first to fourth lateral electrodes 5 to 8 can be changed in terms of function of time.
From test results, it is found that the present invention produces a greater effect when there is used, as the etching gas, electronegative gas such as SF.sub.6, oxygen, chlorine, iodine or the like. This would be explained in the following manner. In a plasma of electronegative gas, the electron density is low and the resistance is high so that the potential gradient in the plasma is greater as compared with the case using electropositive gas.
In the CVD apparatus, 15 sccm of N.sub.2 gas and 15 sccm of SiH.sub.4 gas are introduced into the chamber 1. Preferably, the pressures of these gases are set to 0.07 Pa and the temperature of the sample stage 2 is set to 400 FIG. 15 shows a section of a semiconductor chip prepared by the CVD apparatus . An oxide layer 41 is formed on a Si substrate 40. Aluminum 42 deposited in a thickness of 0.8 μm by sputtering, is made in the form of a line having a width of 0.8 μm by photolithography and dry etching. On the aluminum 42, a SiN layer 43 is deposited by the CVD apparatus.
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