Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a reaction vessel or depositing semi-con-
ductor material from the gaseous phase.
~ ccording to the invention there is provided a reaction vessel for
depositing semi-conductor material, especially silicon, onto heated carrier
elements, from an appropriate reaction gas flowing through the said reaction
vessel, the reaction vessel being comprised of a sheet or plate shaped base
- having the nozzles necessary for the supply and removal of the reaction gases,
and holders for the said carrier elements, together with a quartz or glass bell
sealed gas-tightly to the said base. This arrangement is characterized in
that the quartz or glass bell is pressed against the base by means of compress-
ed gas acting directly upon the outside thereof, and thus producing a gas-
tlght loint with the support. The base, and the bell located thereon are pre
Eerabl~ arranged wlthin a compressed-gas container. The compressed gas used
is an inert gas, i.e. nitrogen or a rare gas.
The inventive apparatus obviates having to clamp the bell, which
is normally necessary in order to secure it to the base and obtain a gas-tight
joint. Moreover, the envelope of compressed gas protects the enviror~ent
against an explosion of the bell which, in view of the reaction gases involved,
and the products arising from the reaction, is well within the bounds of possi-
bility.
If the bell fails or the ~oint between it and the base leaks, largequantities of compressed gas enter the reaction vessel, thus equalizing the
pressure between the outside and the inside of the bell. This may damage the
carriers, if the latter happen to be in the heated state. It is therefore
desirable that the current heating the said carriers and the supply of reaction
gas be cut off immediately. The invention preferably provides means for doing
this. Such means preferably comprises a device coupled to the reaction vessel,
which dev$ce in the event of a drop in pressure of the compressed gas below a
predetermined minimal value9 performs at least one of the functions of shutting
off the heating of the carrier
elements~ cutting off the supply of fresh reaction gas, and actuating a wa~n-
ing system, said device responding to either a fall in pressure of the com-
pressed gas beyond a predetermined lower limit, a rise in pressure of the
gases in the reaction vessel beyond a predetermined upper limit or a differ-
ence in said pressures beyond a predetermined limit.
Embodimenks of the invention will now be described, by way of
example, with reference to the accompanying drawings, in which:-
Figure 1 is a part-sectional, part-diagrclmmatic view of a system
embodying the present invention;
Figure 2 is a similar view of an alternative system embodying the
invention; and
Figure 3 is a fragmentary view showing a third possible embodiment
of the invention.
A sheet or plate-shaped base 1, preferably made of silver,has cen-
trally disposed thereof a nozzle 2 for the supply of fresh reaction gas and
an aperture 3 for the used gas, wikh provision for maintaining gas-tight
joints. The carrier elements are held by electrodes 4 which are insulated
from each other and are sealed gas-tightly where they pass through base 1.
Carrier elements 5 are in the form of two or more thin, vertical silicon rods
of the same length, the lower end of each of each holder being held in the
vertical position in each electrode and making good electrical contact there-
with, whereas the upper ends of the said holders are conductively connected
through a bridge 6 made of a conducting inert materialJ e.g. graphite or
silicon. The elec~rodes are connected to a source of power 10, through
electrical leads with switching means, the said source supplying khe electrical
current required to heat the carrier elements. The reaction chamber is sealed
gas-tight by a bell 7 made of quartz~ glass, or similar material and placed
on base 1.
When the device is in operation~ carrier elements 5 are heated, in
an atmosphere of hydrogen gas, by the heating current supplied by power source
.
10, to the high temperature necessary to deposit silicon from a reaction gas
such as SiHC13 and SiCl~ diluted with H2, or Si~l~, the said reaction gas
being supplied to the glowing carrier elements.
In the interests of safetyg and in order to obtain a gas-tight joint
between bell 7 and base 1, reaction vessel 1,7 is placed in an autoclave or
pressure vessel 8,9 which is filled with compressed gas while the device is
in operation The pressure vessel may consist, for e~ample of a steel box 8
with an apertured bottom, the said box being sealed partly by base 1 and
partly by a cover 9. The compressed gas is introduced into the said pressure
vessel through a valved line 11.
The embodiment of the invention shown in Figure 1 al.;o includes
two pressure gauges 12,13 which are in the form of electrical contacts.
Pressure gauge 12 monitors the pressure in autoclave 8,9, while pressure
gauge 13 monitors the pressure in the interior of reaction vessel 1,7.
Pressure gauge 12 is designed in a manner such that if the pressure in the
compressed gas drops below the admissible minimal value, the said gauge closes
an electrical circuit to a control unit 14. The said control unit may, how-
ever, also be activated by pressure gauge 13, as soon as the pressure of the
reaction gas in the reaction chamber exceeds a predetermined maximal value.
Activation of control unit }4 results in:
a) disconnecting power source 10 from carrier elements 5 by opening a
switch 15 in the operating circuit;
b) shutting off the supply of fresh reaction gas by actuating valve 16,
e.g. a magnetic valve;
c) actuating an optical and/or acoustical warning system 17.
It i9 also possible, according to the invention, to use an electri-
cal contact-differential-pressure gauge which is acted upon by the gas pres-
sure in reaction vessel 1,7 and that in the compressed gas. This arrc~ngement
is shown in Figure 2. To this end, the reaction chamber is connected through
a bridging tube 18 ~o the compressed-air chamber ou~side bell 7~ Tube 18 is
sealed gas-tight by means of a diaphragm 19. ~hen the pressllre in the com-
pressed gas drops below a predetermined minimaL value, resilient diaphragm 19
presses so hard against a pressure-sensitive electronic element 20, more par-
ticularly a semi-conductor component with a pn-junction, that the latter pro-
vides an adequate electrical current to activate control unit 14. This in- ~-
creases the supply of compressed gas by a motorized pressure regulator M.
In this embodiment of the invention, therefore, control unit 14 is
; activated as soon as the pressure difference between the compressed gas and
the reaction gas drops below a predetermined minimal value.
According to still another configuration of the invention ~Figure 3),
provision is made for a capillary connection 2~ and a sensitive flowmeter 25
which monitors the flow through the said capillary, this unit being located
between the interior of reaction vessel 1,7 and the chan1ber fi:Lled with com-
pressed gas. ~gain, flowmeter 25 is in the form of an electrical contactor,
and it activates control unit 14 whenever the flow velocity through the
capillary tube exceeds a predetermined absolute value. Since the flow veloc-
ity through the said capillary tube is determined by the pressure difference
to be monitored, this variant of the invention is easily understood. It
should be noted in this connection that the opening of the capillary tube into
the reaction chamber proper is located preferably in or near gas-outlet tu~e
3, so that the compressed gas, consisting more particularly o~ nitrogen, can-
not in any way impair the semi-conductor material deposited. The bore of
capillary tube 24 is so small that, on the one hand, a sensitive ~lowmeter 25
may be controlled by the leakage flow therethrough, while, on the other hand~
the loss of compressed gas or reaction gas through the said capillary tube is
as small as possible. The indicators used may also be in the form of sensitive
thyristors or cold-controlled elements which heat up automatically to a degree
which depends upon the i`low of gas. In this case, it is desirable that the
loss of compressed gas due to leakage through the capillary tube be compensa-
ted for from time to time.
