Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-09-20
2001-04-17
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230MW, C118S715000
Reexamination Certificate
active
06217704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a plasma processing apparatus and a processing method making use of the same. More particularly, it relates to a plasma processing apparatus by which negative ions can be generated in a large quantity and also the negative ions can be made incident on an article to be processed to etch or clean the article to remove unwanted matter therefrom, and a processing method making use of the same. This plasma processing apparatus is preferably used in processes for producing semiconductor devices such as LSIs, optical devices such as optical disks and waveguides, and magnetic devices such as magnetic disks.
2. Related Background Art
In general, it is said to be important to lower a plasma temperature in order to form negative ions in a plasma processing apparatus. The relationship between the plasma temperature and the negative ion formation can be known from the probability of attachment of electrons to particles with respect to electronic energy, which is described in, e.g., Basic Data of Plasma Physics (Sanborn C. Brown, AIP press, 1993). It is seen from this publication that the cross section in which the attachment of electrons to, e.g., chlorine-type gas molecules and dissociation thereof has a peak at about 1 eV. Meanwhile, plasma used in usual semiconductor production processes has an electron temperature of 2 to 5 eV. Accordingly, in order to efficiently form negative ions, it is considered necessary to lower the electron temperature to a suitable temperature.
For example, the following two can be given as typical examples of plasma processing apparatuses that utilize negative ions.
(1) Method making use of time afterglow of plasma:
An apparatus disclosed in Japanese Patent Laid-open Application No. 8-181125 can be given as one example of an apparatus utilizing this method. In
FIG. 5A
, reference numeral
501
denotes a microwave power source;
502
, a magnetic-filled coil;
503
, a waveguide;
510
, an article to be processed;
512
, a stand for supporting the article to be processed (hereinafter referred to as “article supporting stand”);
514
, a plasma;
531
, a vacuum vessel; and
532
, a high-frequency power source. In this method, the plasma
514
, which is formed by pulse-modulating microwaves generated from the microwave power source
501
at a cycle of 10 to 100 microseconds, is made ON/OFF, and, in the period of plasma-OFF, the plasma temperature is lowered to form negative ions. Also, a high-frequency bias is applied from the high-frequency power source
532
to the supporting stand
512
of the article
510
in synchronization with the pulse modulation of the plasma
514
to alternately draw out positive
egative ions into the article
510
to be processed as shown in
FIG. 5B
, thus the article
510
is processed.
(2) Method making use of space afterglow to spatially guide plasma downstream:
Not shown in the drawing, this method is a method which comprises placing the article to be processed downstream by tens of centimeters from the region of plasma formation and utilizing negative ions formed while being diffused downstream and cooled gradually.
The above two methods, however, have had the following problems.
i) In the method making use of pulse-modified plasma, positive ions are formed in the remaining half period where plasma is an ON state, and hence a high efficiency is promised for an etching apparatus of positive
egative-ion alternating irradiation. However, in the case of etching carried out by predominantly using negative ions, it is difficult to attain a high efficiency because the negative ions are formed only in the half of the processing time.
ii) In the method where plasma is guided spatially downstream to lower a plasma temperature to form negative ions, the recombination of plasma at vacuum vessel walls causes an abrupt decrease in plasma density itself, and hence the plasma formed in a high density can not efficiently be converted into negative ions.
Thus, in these conventional methods, there has been room for improvement in respect of large-quantity formation of negative ions and effective processing.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a plasma processing apparatus by which negative ions can be continuously formed in a high density and also the negative ions can be made incident on an article to be processed to conduct ashing, etching or cleaning of the article to remove unnecessary matters therefrom, so that a high processing rate and less charge-up damage can be achieved; and to provide a processing method making use of such apparatus.
The plasma processing apparatus according to the present invention comprises:
a vacuum vessel;
supporting means for supporting an article to be processed in the vacuum vessel;
means for introducing a first gas into a plasma generating space;
means for feeding electric energy to the first gas in the plasma generating space to generate a plasma;
means for mixing a second gas into the plasma which has been introduced into a negative ion forming space communicating with the plasma generating space, thereby forming negative ions; and
means for drawing out the negative ions and feeding the negative ions to the article.
REFERENCES:
patent: 4158589 (1979-06-01), Keller et al.
patent: 5102496 (1992-04-01), Savas
patent: 5942042 (1999-08-01), Gogh
patent: 5942075 (1999-08-01), Nagahata et al.
patent: 8-181125 (1996-07-01), None
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hassanzadeh P.
Mills Gregory
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