Coating apparatus – Immersion or work-confined pool type – Work extending through pool-confining wall area
Patent
1985-11-01
1986-10-14
McIntosh, John P.
Coating apparatus
Immersion or work-confined pool type
Work extending through pool-confining wall area
118419, B05C 3172
Patent
active
046165959
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for depositing a layer of silicon on a carbon tape, said device being of a type comprising:
a receptacle provided with a horizontal bottom having a slot passing therethrough, the horizontal profile of the slot comprising two parallel and facing straight segments, said segments delimiting a rectangular area whose length corresponds to the segments, the tape passing through the slot in such a manner that the width of the tape is parallel to the segments,
means for disposing a bath of liquid silicon in the receptacle, and
means for vertically drawing the tape upwardly and lengthwise in such a manner as to deposit said layer, the width of the said rectangular area being sufficiently small for the silicon meniscus connecting the tape to the walls of the slot to be stable.
A known device of this type is described in French patent specification No. 2 386 359. In this device, the slot has a rectangular horizontal section whose length is slightly greater than the width of the tape, and whose width is slightly greater than the thickness of the tape. By way of indication, for a tape which is 50 mm wide and 0.3 mm thick, the rectangular section of the slot is 50.4 mm long and 0.6 mm wide.
Such a device has a drawback. In order to avoid the tape jamming and jerking in the slot while it is being drawn therethrough, it is necessary to provide very close tolerances on the width and the alignment of the tape and also on the direction in which it is drawn. Further, it should be observed that the tape generally includes a thin protective layer of pyrocarbon: if this covering is torn off, the core of ordinary carbon in the tape is highly reactive with liquid silicon.
The aim of the present invention is to mitigate this drawback.
The present invention provides a device for depositing a layer of silicon on a carbon tape, of the above-mentioned type, characterized in that:
the wall of the slot flares outwardly at the bottom face of the bottom;
the length of the segments is equal to the width of the tape; and
the horizontal profile of the slot further includes two circular curves delimiting two circular areas disposed at respective ends of the said rectangular area, each of said circular areas being centered on the longitudinal axis of the rectangular area, the circular curves connecting with the ends of the segments in such a manner that the circular areas are in communication with the rectangular area, the diameter of the circular areas being greater than the width of the said rectangular area and less than a predetermined limit value.
A particular implementation of the present invention is described below by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a diagram of a device in accordance with the invention for depositing a layer of silicon on a carbon tape,
FIG. 2 is a vertical section view on a larger scale of a slot provided in the bottom of a receptacle constituting a part of the device shown in FIG. 1; and
FIG. 3 is a horizontal section view of the slot shown in FIG. 2.
FIG. 1 is a vertical section through a quartz receptacle 1 whose walls are surrounded by an electric oven 2. The resistances 3 of the oven 2 are connected to a source of electric current 4. The receptacle 1 contains a bath 5 of liquid silicon, said bath being fed with pellets of solid silicon from a tank 6 provided with dispensing means.
The horizontal bottom 15 of the receptacle 1 includes a slot 7, and the bottom of the oven 2 is provided with an opening 8 facing the slot 7. A carbon tape 9 is slid through the slot 7 and the opening 8 so as to pass vertically through the bath of silicon 5. The figure shows the receptacle 1 in a section on a plane perpendicular to the tape 6 and substantially through the middle of the length of the slot 7. Rolls such 10 and 11 serve to draw the tape upwardly and lengthwise in the direction of arrow 12. After passing through the bath 5, the two faces of the carbon tape 9 are covered with respective layers of silicon 13 and 14. These layers may be
REFERENCES:
patent: 3429734 (1969-02-01), Coad
patent: 4505221 (1985-03-01), Falckenberg et al.
patent: 4520752 (1985-06-01), Belouet
Compagnie Generale D'Electricite
McIntosh John P.
Societe Nationale Elf Aquitaine
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