Coating processes – Immersion or partial immersion
Patent
1995-10-02
1998-12-01
Beck, Shrive
Coating processes
Immersion or partial immersion
4273722, 427600, 118429, B05D 302, B06B 100, B05C 300
Patent
active
058435352
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to arrangements in which a layer of material is formed on a surface, and then that material is introduced into holes or trenches in the surface. It is particularly, but not exclusively, concerned with arrangements in which that surface is a surface of a semiconductor wafer (or substrate use for integrated circuits).
There are a number of situations during the formation of a semiconductor device in a semiconductor wafer where it is necessary to deposit a layer onto the wafer. One such situation arises when conductive or semiconductive tracks are to be formed over the wafer, so that those tracks may make contact with active regions of the device or circuit. Normally, such tracks must then extend through an insulating layer on the surface of the wafer so as to make contact with active regions below that insulating layer, or with further conductive tracks below that insulating layer (when the holes are usually called "vias"). Where the track extends through a hole in this way, it is important that the amount of material e.g. metal filling that hole is sufficient to ensure good electrical contact.
Another situation is when an electrically insulating layer is to be formed over the wafer, in order to isolate active regions and/or conductive tracks from each other, or to form a protective covering known as a passivation layer. Such a layer is often required to cover conductive tracks or other structures on the wafer, and these structures may be close to each other so that the gaps between them form narrow trenches. It is important that the insulating material covers all the surface with sufficient thickness to provide good electrical insulation, and that the top surface of the insulating layer is sufficiently smooth for the next stage of wafer processing.
In our European Patent Application No. EP-A-0516344 we proposed that a layer was formed on the surface of an article, in which surface there was a recess such as a hole or trench. Then, it was proposed that the article, including the layer, was subjected to elevated pressure and elevated temperature sufficient to cause the layer to deform. By suitable control of the temperature and pressure, the layer deformed sufficiently to cause the material of the layer to enter the recess to fill it.
It was thought that the primary factor causing the deformation was plastic flow by dislocation slips, activated by the elevated pressure and temperature. Surface diffusion, grain boundary diffusion and lattice diffusion were also thought to have an effect, activated by the elevated temperature. In our International Application No. PCT/GB93/02359 we discussed the possibility of the same effect being achieved by elevated pressures, without the need for elevation of temperature. We also disclosed in that specification the possibility of achieving the elevated pressure by use of a liquid in contact with the wafer.
The present invention develops that latter idea, by proposing that the elevated pressure is achieved by a pressure pulse within the liquid, rather than a static pressure change. It has been found that it is relatively straightforward to create pressure pulses in liquids which are sufficient to cause the article to be subject to pressures which are sufficient to deform the layer.
Thus from one aspect the invention includes apparatus for applying elevated pressure to the surface of a workpiece comprising a chamber, means for supporting a workpiece within the chamber, means for flooding the chamber with liquid to immerse the workpiece support and means for applying a pulse of elevated pressure to the liquid, and hence the workpiece support, when the chamber is flooded.
Preferably, as in EP-A-0516344, elevated temperatures are used. Since the present invention makes use of a pressure pulse, it also preferably makes use of a heating pulse which is transmitted from suitable heating means to the wafer by thermal transport through the liquid. This has the advantage of reducing the overall heating of the liquid and thus less heating power is needed tha
REFERENCES:
patent: 5279316 (1994-01-01), Miranda
patent: 5308792 (1994-05-01), Okabayashi et al.
Beck Shrive
Chen Bret
Trikon Technologies Limited
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