Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With plasma generation means remote from processing chamber
Reexamination Certificate
2001-05-31
2004-03-23
Norton, Nadine G. (Department: 1765)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With plasma generation means remote from processing chamber
C156S345390, C156S345420, C156S345460, C156S345480, C156S345490
Reexamination Certificate
active
06709546
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device and a method for etching a substrate by using an inductively coupled plasma.
BACKGROUND INFORMATION
A device and a method for etching a substrate by using an inductively coupled plasma (ICP), with some areas of the reactor being surrounded by a magnetic field coil for generating a static or time-variable magnetic field in the reactor, is discussed in German Published Patent Application No. 199 33 841. In addition, in an etching method performed using this device, a magnetic field may be generated whose direction may be at least approximately or predominately parallel to a direction defined by the tie line connecting the substrate and the inductively coupled plasma.
SUMMARY OF THE INVENTION
An object of an exemplary embodiment and exemplary method of the present invention is to provide a device and a method with which higher etching rates and an improvement in etching profiles can be achieved.
It is believed that the exemplary device and the exemplary method according to the present invention for etching a substrate have the advantage that much higher or at least higher etching rates can be achieved in anisotropic etching methods for silicon such as those patented in German Patent No. 42 41 045 and German Published Patent Application No. 197 06 682 while achieving the same or even improved quality of the etching results, in particular with regard to the profile shape achieved over the substrate surface.
Using at least two, which may be exactly two or an even number of magnetic field coils arranged one above the other, which may be with electric currents flowing through each pair in opposite directions, is believed to have the advantage that the remote effects of the component magnetic fields thus produced are reduced, and there is a weaker resulting magnetic field at the site of the inductive plasma production and at the site of the substrate than in the case of using just one magnetic field coil. Furthermore, in this way, the component magnetic fields enclosing the plasma may be adjusted in an advantageous manner and thus also to set the resulting total magnetic field to be stronger in the area of the reactor wall.
In particular, the oppositely directed component magnetic fields are produced due to the magnetic field coils with electric current flowing through each pair in opposite directions, which results in that in the proximity of the windings of the magnetic field coils in the interior of the reactor, i.e., in the proximity of the reactor wall, the resulting magnetic field intensity is high and is almost completely unaffected by adjacent coils, while the component magnetic fields generated by the individual magnetic field coils in the interior or in the center of the reactor, in particular in the area of the center of the coil, partially cancel each other out, so that the resulting magnetic field prevailing there is believed to be reduced significantly in comparison with that of just one magnetic field coil.
In addition, it is also believed that the arrangement of such magnetic field coils with current flowing through each pair in opposite directions may advantageously produce the modification of a magnetic lens effect and the development of an almost field-free drift zone in the interior of the reactor between these successive magnetic field coils, i.e., in the vicinity of the connecting plane of adjacent magnetic field coils, so that inhomogeneities from the plasma source area are not reproduced directly on the substrate. Instead, due to the modified lens effect of the coil pairs, this yields the result that the energy input from the plasma is homogenized over the surface of the substrate and an increased energy input can be established at the center of the substrate in comparison with respect the edge of the substrate.
In addition, it is also believed that due to the use of at least two magnetic coils, the magnetic field prevailing at the site of the substrate to be etched can be greatly reduced (or at least reduced) or the magnetic field intensity in the edge area of the interior of the reactor surrounding the substrate can be increased without any (or substantially without any) interference effects.
Due to the arrangement of at least two magnetic field coils according to an exemplary embodiment or exemplary method of the present invention, in particular with current flowing through them in opposite directions, the advantageous effects of a magnetic field with regard to more efficient plasma excitation may be combined with the advantages achieved due to the fact that a weaker and at the same time more homogeneous magnetic field prevails at the site of plasma generation and/or at the site of the substrate to be etched in comparison with the reactor wall and the edge areas than in the case when just one magnetic field coil is used. Furthermore, by using magnetic coils with electric current flowing through them in opposite directions, a device that is continuously adjustable via the coil current is provided, for allowing homogenizing or even “inverting” the energy input from the plasma into a wafer surface. That is, energy input from edge areas of a wafer may be focused into the center of the wafer.
It is also believed to be advantageous if an even number of magnetic field coils are used with current flowing through them in alternating current directions so that the directions of the component magnetic fields generated by the magnetic field coils change from one coil to the next. On the whole, due to the arrangement of the magnetic field coils of the exemplary embodiment or exemplary method of the present invention, this yields first a concentration of the magnetic field on the wall area of the interior of the reactor, i.e., on the inside wall of the spacers, the area of the substrate and the area of the inductively coupled plasma source.
There is also an optimum intensity in the resulting magnetic field intensity in the interior of the reactor, in particular at the center of the magnetic field coils with regard to the increase in plasma efficiency and the etching rates that can be achieved, which is to be determined in each individual case and is in the range of a few milli-Teslas, so it is now possible due to the arrangement of at least two magnetic field coils of the exemplary embodiment or exemplary method of the present invention to optimize the resulting magnetic field intensity in the interior of the reactor, in particular in the drift zone in this regard and at the same time also keep the resulting magnetic field intensity as high as possible or at least relatively high in the area of the reactor wall to ensure “high charge carrier reflection” and good magnetic containment of the plasma.
This may be because oppositely directed component magnetic fields, which may be of equal strength with regard to amplitude at equivalent or corresponding sites are generated by the different magnetic field coils, and the resulting magnetic field decreases with an arrangement of two coils in comparison with just one coil and may actually diminish to zero at the plane of symmetry between the coils. That is, an almost field-free interior area or drift zone over which the plasma can propagate almost without interference is formed between the two magnetic field coils, and at the same time the resulting magnetic field intensity in the vicinity of the reactor wall remains relatively high, so that it effectively prevents electron losses and ion losses in the manner of a magnetic cylinder.
The resulting magnetic field intensity in the interior of the coil is further reduced in this way, namely to a greater extent, the closer one approaches the plane of symmetry between the two magnetic field coils, for example. On the other hand, the resulting magnetic field intensity decreases rapidly at a certain distance from the individual magnetic field coils, i.e., the magnetic field is concentrated at the openings in the coils facing away from one another and on the walls of the reactor, which leads to the above-mentioned magnetic cy
Becker Volker
Breitschwerdt Klaus
Laermer Franz
Schilp Andrea
Kenyon & Kenyon
Norton Nadine G.
Tran Binh X.
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