Structuring device for processing a substrate

Details Structuring device for processing a substrate Structuring device for processing a substrate

1999-09-17

2002-07-16

Lund, Jeffrie R. (Department: 1763)

Coating apparatus

Gas or vapor deposition

Having means to expose a portion of a substrate to coating...

C118S715000, C118S7230AN, C118S7230ER, C118S7230IR, C118S7230ER, C118S7230MR, C118S500000, C118S504000, C156S345420

Reexamination Certificate

active

06419752

ABSTRACT:

FIELD OF THE INVENTION AND DESCRIPTION OF PRIOR ART
This invention refers to plasma structuring of a substrate surface.
To be more specific, this invention relates to a structuring device for processing a surface of a substrate, comprising a substrate chamber for mounting the substrate and a reaction chamber enabling a gas reaction at a given operating pressure, the reaction chamber having at least one gas inlet for a reaction gas and at least one injection outlet leading into the substrate chamber.
A plasma etching device of this type was proposed by Larson et al. in J. Vac. Sci. Technol. B, Vol. 10 (1992), p. 27. In this device, a glass tube widens to an expansion serving as plasma chamber, tapers back and then performs a V-shaped bend. The etchant gases enter the etching device by way of the inlet of the tube, flow through the larger plasma chamber where a radio-frequency plasma discharge is maintained, continue downstream past the vertex of the V, and are pumped off through the outlet of the tube. At the vertex an aperture is made in the thinned tubing wall. Below the aperture the substrate is positioned on a base which, in the embodiment used by Larson et al., is the upper face of a waveguide used for monitoring and which, together with the tubing wall around the aperture and vacuum-sealed by means of an O-ring, forms an etching chamber enclosing the substrate. By this etching method, it is possible to achieve a spatially confined etch process as defined by the shape of the perimeter of the etching chamber. However, this approach does not allow for high-resolution etching or simultaneous imaging during the etch. The shaping of the etching chamber defines the smallest size of the features which can be fabricated using this method. Since the size of the chamber cannot be easily made small, this method is not well suited for making structures in the micrometer and submicrometer-size range.
Structuring of features in the micrometer range and below, so-called microfabrication, is used in various fields of technology such as electronics, sensorics, integrated optics, micro-actuators, and micro-acoustic devices. Structuring here means the creating of a desired spatial pattern on the substrate surface, and comprises material processing such as removing, e.g. etching; growing, e.g. deposition; and other ways of treatment of material, e.g. doping or chemical transformation.
With regard to etching at present time, dry etching in a weakly ionized high-density plasma is most commonly used; plasma methods are also applicable for deposition processes. The benefit of plasma etching is that it allows for anisotropy, i.e. a high directionality where the material is removed preferentially along a certain crystallographic direction on the substrate. The material to be etched is chemically converted into a volatile phase which is pumped off. It is to be noted that by changing the gas composition, it is possible to switch from etching to deposition of new material straightaway.
At present, commercial microfabrication requires a combination of different methods for deposition of photo-resist, writing the required micro-patterns in the resist, and transferring the pattern from the resist into the substrate by etching of the resist and subsequent processing of the substrate. Lithographic methods are, for instance, discussed in ‘semiconductor Fabtech’, ed. M. J. Osborne, 7
th
edition, 1998, ICG Publishing Ltd., London. The lithographic methods are indirect in a sense that the desired structures are first defined in a layer deposited only temporarily and then transferred from this layer to the substrate. Therefore, microfabrication by lithographic procedure involves a plurality of steps making the complete process complex and expensive. Features as small as 200 nm can be fabricated using optical lithography, and structures with features down to 100 nm can be fabricated using particle-beam or X-ray lithography. As the size of the features continues to shrink, the equipment required for microfabrication rapidly becomes more and more expensive with respect to cost of ownership and maintenance of the complex line.
Alternative methods to lithography use direct structuring of the substrate. One direct etching arrangement for high-resolution microfabrication is the focused ion beam (FIB) technique which allows microfabrication by vector scan of the ion beam. The FIB technique, however, is very cost intensive. Also known is the combination of FIB microfabrication and in-situ analysis by scanning electron microcopy (SEM). This combination technology proved highly valuable for failure analysis and prototype development; however, its high cost and complexity are prohibitive for most commercial applications. Instead of ions, electrons can also be used for electron-beam structuring methods. It is to be noted that these structuring methods involve using a particle-beam rather than a plasma gas. One well-known complication of using particle beams is defects introduced into the substrate by the impact and/or implantation of high-energy particles.
Also known is a flow injection system for delivering a liquid etchant onto a surface and monitoring the chemical processes by means of scanning tunneling microscopy using the delivering syringe as scanning probe, as disclosed by Noll et al., in Rev. Sci. Instrum. Vol. 66 (1995), p. 4150. This system, however, relates to the investigation of chemical and electrochemical processes; due to the surface tension, the etchant liquid will spread over a large area on the substrate and prevent successful manufacturing of small-size structures.
Another method of structuring, called “hot-jet etching” is described by Geis et al., in J. Vac. Sci. Technol. B 4, 315-317 and J. Vac. Sci. Technol. B 5, 363-365. There, a stream of reactive gas is produced by means of a heated jet nozzle and directed toward a substrate. The reactive gas species of the stream are generated by thermal dissociation. The distance between the nozzle outlet and the substrate is chosen so that the entire substrate area is covered by the gas stream. In the setup of Geis et al., this distance is approximately 10 cm, which corresponds to the dimension of the wafer used as substrate. In order to achieve a structuring of the etching process, Geis et al. mainly use photoresist masks, but also propose to employ stencil masks positioned above the surface of the substrate to be processed. Thus, the production of the reactive gas stream and determination of the etch pattern are determined by separate devices, and thus the hot-jet etching method employs indirect structuring as well, like indirect lithography. Therefore, it requires pre-structuring of the mask layer or the stencil mask and brings about the disadvantages as discussed above.
SUMMARY OF THE INVENTION
It is an aim of this invention to develop a novel, inexpensive technology for direct microfabrication by etching of the substrate surface in the micrometer range and below, based on direct structuring of surfaces using plasma. As a further aim, the technology should allow for local growth and chemical modifying of material on the surfaces. Moreover, structuring shall be possible without introducing damages from the particles applied. It is a further aim of the invention to allow for simultaneous microfabrication and imaging.
These aims are achieved by a structuring device as mentioned at the beginning wherein (see, e.g.,
FIG. 11
) the substrate chamber VC is provided with a pumping system PP for maintaining a vacuum within the substrate chamber at a pressure not above the operating pressure of the gas reaction in the reaction chamber GC, the injection outlet JL is provided with at least one injection pipe ending into an injection opening OP of given width d
1
, the injection pipe having a length s
1
not smaller than the width d
1
of the injection opening, the injection pipe forming the gas particles originating from the gas reaction into a gas jet streaming out of the injection opening OP, and the injection outlet JL and/or the substrate SB are provided with a p

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