Note: Descriptions are shown in the official language in which they were submitted.
1
Method for fragmenting a rod-like material,
in particular made of polycrystalline silicon
Technical Field
The invention relates to a method for fragmenting a
rod-like material, in particular made of polycrystalline silicon,
an equipment for performing the method and a use of the equipment.
Background Art
For producing ultrapure polysilicon as a base material
for the crystal growing of polycrystalline or monocrystalline
substrates for the solar or electronic industry, the Siemens
method is mainly used. By this method, polycrystalline silicon
rods with thicknesses in the range between 100 mm and 150 mm
are produced, which have to be broken into small pieces for the
use in crystal ovens.
Thereby, it has to be considered that the pieces should
preferably have a size between 10 mm and 30 mm, must not be
smaller than 2 mm and additionally should not be spicular,
because this has a negative effect on the flow characteristics.
Due to the special crystalline structure of silicon, the
breaking of silicon rods intosuch a fraction with preferably
even sizes and shapes is very difficult.
Further it has to be considered that the ultrapure base
material must not be contaminated by the contact with extraneous
material during breaking. A contamination of the material with
extraneous material, in particular with metals, is critical and
should lie below 5 ppb, better even below 2 ppb.
DaiOkKg
7¨ate Received 2020-05-08
2
Different methods for breaking silicon rods
are known from the state of the art, at which the rods
are broken by mechanical or thermal impact, or by a com-
bination of mechanical and thermal impact. It is also
known to break the rods by shock waves.
But all these known methods have substantial
disadvantages regarding to the operation- or the equip-
ment costs, respectively, the energy input, the grain
size distribution and/or the contamination of the mate-
rial.
Disclosure of the Invention
Therefore, it is an object to provide methods and
devices which do not have these disadvantages of the state
of the art or at least partly avoid them.
Accordingly, a first aspect of the invention
relates to a method for fragmenting a rod-like material,
preferably of a semiconductor material, like polycrystal-
line silicon for example.
Thereby, an electrode arrangement with two or
more electrodes is arranged in the region of a section of
the rod-like material to be fragmented, immersed in a
process fluid, preferably water, such that the electrodes
are immersed in the process fluid and are at a distance
from one another and are each at a distance from the rod-
like material.
These distances are chosen such that in the
region of these electrodes high voltage breakdowns
through the rod-like material and/or along the surface of
the rod-like material can be generated by applying high
voltage impulses to the electrode arrangement. The size
of these distances depends on the conductivity of the
process fluid, on the conductivity of the rod-like mate-
rial and on the height of the high voltage pulses. Appro-
priate distances for the particular operation situation
DaiOHNA
7¨ate Received 2020-05-08
CA 02943892 2016-09-26
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can be determined by the person skilled in the art by
simple trial and error.
High voltage pulses are applied to the elec-
trode arrangement such that high voltage breakdowns
through the rod-like material and/or along the surface of
the rod-like material in the region of the electrodes are
generated. During the generation of the high voltage
breakdowns, a relative movement in longitudinal direction
of the rod-like material is generated between the elec-
trode arrangement and the rod-like material whereby the
location of the high voltage breakdowns through the rod-
like material and/or along the surface of the rod-like
material progressively changes in longitudinal direction
of the rod-like material.
By the inventive method, e.g. it is possible
to break rod-like semiconductor material and in particu-
lar silicon rods into a fraction with relatively equal
size and shape with a comparatively small energy input,
which fraction ideally suits for the further processing
in crystal ovens. Also the contamination with extraneous
material can be kept extremely small with this method.
In a preferred embodiment of the method, the
rod-like material is completely immersed in the process
fluid during fragmentation. Advantageously, it thereby
has an essentially horizontal position.
Thereby, it is further preferred that the
rod-like material during fragmentation is received in a
container, which is open to the top and which is tub-like
or shell-like, and that the fragments arising from the
fragmentation are collected in this container and are
transported away with this container after the complete
fragmentation.
Thereby, the method can be performed in the
industrial batch mode with relatively simple equipment
without a costly transport equipment.
In another preferred embodiment of the
method, the rod-like material is immersed with one end in
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the process fluid during fragmentation and thereby pref-
erably has an inclined position at which the lower end of
the rod-like material is immersed in the process fluid.
Hereby, the method can be realized in a simple way in a
quasi-continuous operation by a constant supply of rod-
like material in the fragmentation zone flooded with pro-
cess fluid.
Advantageously, the relative movement between
the electrode arrangement and the rod-like material is
generated at least partly by moving the rod-like material
in its longitudinal direction.
Alternatively or additionally, it is envis-
aged that the electrode arrangement is moved in longitu-
dinal direction of the rod-like material for the genera-
tion of the relative movement between the electrode ar-
rangement and the rod-like material.
Depending on the equipment concept, one or
the other variant or a combination of both variants is
particularly preferred.
Thereby, it is preferred in the last men-
tioned variant that the electrode arrangement is moved in
longitudinal direction of the rod-like material together
with a high voltage generator generating the high voltage
pulses. Hereby, a costly movable coupling of the elec-
trode arrangement to the high voltage generator is not
necessary.
If the rod-like material has an inclined or
preferably a horizontal position during fragmentation and
the electrodes of the electrode arrangement are arranged
above the rod-like material, with advantage essentially
centred with respect to the longitudinal axis of the rod-
like material, then a particular constant fragmentation
result can be reached.
The electrodes of the electrode arrangement
are preferably arranged such that the distance of the re-
spective electrodes to the surface of the rod-like mate-
rial in each case lies in the range between 2 mm to 40 mm
CA 02943892 2016-09-26
and the distance between the electrodes lies in the range
between 40 mm and 100 mm. Distances in these ranges have
proved to be particularly appropriate.
For generating the high voltage breakdowns
5 through the rod-like material and/or along the surface of
the rod-like material, the electrode arrangement is pref-
erably charged with high voltage pulses in the range be-
tween 100 KV and 300 KV, in particular in the range be-
tween 150 KV and 200 KV.
The high voltage pulses preferably have a
power per pulse between 300 Joule and 1000 Joule, in par-
ticular between 500 Joule and 750 Joule.
These voltage and power ranges have proved to
be particularly appropriate.
The application of high voltage pulses to the
electrode arrangement for generating the high voltage
breakdowns through the rod-like material and/or along the
surface of the rod-like material is preferably performed
with pulse frequencies in the range between 0.5 Hz and 40
Hz, in particular in the range between 1 Hz and 5 Hz.
The relative movement between the electrode
arrangement and the rod-like material and/or the applica-
tion of the high voltage pulses to the electrode arrange-
ment is preferably performed such that 0.5 until 1.0
pulses, in particular 0.1 until 2.0 pulses, are applied
to the electrode arrangement per millimetre relative
movement.
Such pulse frequencies and pulse applications
per millimetre relative movement proved to be particu-
larly appropriate.
The region between the electrodes of the
electrode arrangement and the rod-like material, which is
flooded with process fluid, is preferably flushed with
process liquid. In this way the fine material can be re-
moved from the process zone and a consistent quality of
the process fluid available in the process zone can be
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ensured, what can be beneficial for a stable process con-
trol.
In a preferred embodiment of the method, high
voltage pulses are applied to a first of the at least two
electrodes of the electrode arrangement for generating
the high voltage breakdowns through the rod-like material
and/or along the surface of the rod-like material while a
second of these two electrodes lies on a fixed potential,
in particular on ground potential.
In another preferred embodiment of the
method, pulses with different potential unequal to the
ground potential are simultaneously applied to the at
least two electrodes of the electrode arrangement for
generating the high voltage breakdowns through the rod-
like material and/or along the surface of the rod-like
material.
Depending on the type and the composition of
the used high voltage pulse source, the one or the other
variant can be more preferred.
A second aspect of the invention relates to
an equipment for performing the method according to the
first aspect of the invention. The equipment comprises a
process room, which can be filled with a process fluid,
particularly with water, and in which the rod-like mate-
rial or a section of this can be arranged such that the
rod-like material or the section of the rod-like material
is surrounded by process fluid when the process room is
filled with process fluid.
Furthermore, the equipment comprises an elec-
trode arrangement with at least two electrodes, which,
when the process room is filled with process fluid and as
intended receives the rod-like material or the section of
the rod-like material, can be arranged in the region of
the rod-like material or of this section of the rod-like
material such that the electrodes are immersed in the
process fluid and thereby are at a distance from one an-
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other and each are at a distance from the rod-like mate-
rial, which distances allow to generate high voltage
breakdowns through the rod-like material and/or along the
surface of the rod-like material in the region of these
electrodes in the intended operation by applying high
voltage pulses to the electrode arrangement.
As already mentioned, these distances depend
on the conductivity of the process fluid, on the conduc-
tivity of the rod-like material and on the height of the
high voltage pulses. Appropriate distances for the re-
spective operation situation can be determined by the
person skilled in the art by simple trial and error.
Furthermore, the equipment comprises means
for applying high voltage pulses to the electrode ar-
rangement for generating the high voltage breakdowns
through the rod-like material and/or along the surface of
the rod-like material, and means for generating a rela-
tive movement in longitudinal direction of the rod-like
material between the electrode arrangement and the rod-
like material during the generation of the high voltage
breakdowns during the intended operation such that the
location of the high voltage breakdowns through the rod-
like material and/or along the surface of the rod-like
material in longitudinal direction of this material is
progressively changed, wherein the rod-like material is
surrounded by process fluid at this location respectively
and the electrodes are immersed in the process fluid at
this location.
The method according to the first aspect of
the invention can easily be performed by the equipment
according to the invention.
In a preferred embodiment, the equipment has
a device for receiving the rod-like material, preferably
a container, which is open to the top and which is tub-
like or shell-like, for receiving the rod-like material.
With this container, the rod-like material during the in-
tended operation can be kept fully surrounded by process
CA 02943892 2016-09-26
fluid in the process room, and indeed preferably in a
horizontal position.
The equipment is preferably constructed such
that this tub-like or shell-like container after the in-
tended fragmentation operation can be taken from the
equipment together with the fragments of the rod-like ma-
terial arranged therein, which have emerged from the
fragmentation.
By this, a relatively simple equipment can be
provided for the industrial batch operation without
costly transport equipment.
In another preferred embodiment, the equip-
ment has a device for receiving the rod-like material, by
means of which the rod-like is hold such that it is im-
mersed in the process fluid in the process room with one
end, particularly such that it thereby has an inclined
position and the lower end is immersed in the process
fluid in the process room. Through this, a quasi-continu-
ous equipment can be realized in a simple way, at which
rod-like material is continuously supplied into the frag-
mentation zone flooded with process fluid, particularly
by gravity transportation, and fragmented therein.
The means for generating a relative movement
between the electrode arrangement and the rod-like mate-
rial are constructed for moving the rod-like material
along its longitudinal axis in a preferred embodiment.
Alternatively or additionally, these means
are constructed for moving the electrode arrangement
along the longitudinal axis of the rod.
Depending on the equipment concept the one or
the other variant or a combination of both variants are
particularly preferred.
Thereby, it is preferred in the last men-
tioned variant that the means for applying high voltage
pulses to the electrode arrangement comprise a high volt-
age generator and that the means for generating a rela-
tive movement between the electrode arrangement and the
CA 02943892 201.6.6
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rod-like material are constructed for moving the elec-
trode arrangement together with the high voltage genera-
tor along the longitudinal axis of the rod-like material.
Through this, a costly movable coupling of the electrode
arrangement to the high voltage generator is not neces-
sary.
Preferably, the equipment is constructed such
that the at least two electrodes of the electrode ar-
rangement can be arranged above the rod-like material in
an intended way, with advantage essentially centred with
respect to the longitudinal axis of the rod-like mate-
rial. A particular even fragmentation result can be
reached with such equipment.
The electrodes of the electrode arrangement
can preferably be arranged such that the distance of the
electrodes to the surface of the rod-like material in
each case lies in the range between 2 mm and 40 mm and
the distance between the electrodes lies in the range be-
tween 40 mm and 100 mm. Such distances proved to be par-
ticularly appropriate.
Furthermore, it is preferred that the equip-
ment has means for a particular automated setting of the
respective distance of the electrodes to the rod-like ma-
terial, preferably for the setting of the respective dis-
tance during the intended operation of the equipment.
The means for applying high voltage pulses to
the electrode arrangement are preferably constructed for
applying high voltage pulses to the electrode arrangement
in the range between 100 KV and 300 KV, in particular in
the range between 150 KV and 200 KV, with a power per
pulse in the range between 300 Joule and 1000 Joule, in
particular between 500 Joule and 750 Joule and with a
pulse frequency in the range between 0.5 Hz and 40 Hz, in
particular between 1 Hz and 5 Hz.
Such parameter ranges proved to be particu-
larly appropriate.
CA 02943892 2016-09-26
Furthermore, it is preferred that the means
for generating a relative movement in longitudinal direc-
tion of the rod-like material between the electrode ar-
rangement and the rod-like material or the means for ap-
5 plying high voltage pulses to the electrode arrangement,
respectively, are constructed such that 0.5 until 1.0
pulses, particularly 0.1 until 2.0 pulses, per millimetre
relative movement are applied to the electrode arrange-
ment in the fragmentation operation. Such pulse rates per
lo mm relative movement proved to be particularly appropri-
ate.
In a further preferred embodiment, the equip-
ment comprises means for flushing the region between the
electrodes of the electrode arrangement and the rod-like
material with process fluid during the fragmentation op-
eration. Such means comprise one or several supplying
nozzles, via which fresh or prepared process liquid can
be injected into the region between the electrodes and
the rod-like material, for example. Through this, it is
possible to remove fine particles from this region and to
keep the electrical conductivity of the process liquid
constant in this region, which favours a stabile process
control.
In an even further preferred embodiment of
the equipment, high voltage pulses can be applied to a
first of the at least two electrodes of the electrode ar-
rangement for generating the high voltage breakdowns
through the rod-like material and/or along the surface of
the rod-like material, while another of the at least two
electrodes lies on a fixed potential, particularly on
ground potential.
In another preferred embodiment of the equip-
ment, pulses with different potentials unequal to the
ground potential can simultaneously be applied to the at
least two electrodes of the electrode arrangement for
generating the high voltage breakdowns through the rod-
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like material and/or along the surface of the rod-like
material.
The one or the other embodiment can be more
preferred depending on the electrode arrangement and on
the used high voltage pulse generator.
Furthermore, it is preferred that the equip-
ment according to the invention has an equipment control,
by means of which the energy of the high voltage pulses,
the frequency of the high voltage pulses, the relative
speed between the electrode arrangement and the rod-like
material, the distance between the electrodes and the
rod-like material and/or specific equipment parameters
can be set and controlled, preferably during the fragmen-
tation operation, preferably automated, preferably in de-
pendence on equipment and/or process parameters deter-
mined during the intended operation.
A third aspect of the invention concerns the
use of the equipment according to the second aspect of
the invention for fragmenting rods made of semiconductor
material, preferably made of polycrystalline silicon. The
advantages of the invention particularly become apparent
in such a use of the equipment.
Brief Description of the Drawing
Further embodiments, advantages and applica-
tions of the invention result from the dependent claims
and from the now following description by means of Fig.
1. This shows a sectional view through a part of an
equipment according to the invention.
Modes for Carrying Out the Invention
Fig. 1 shows a part of an equipment according
to the invention for fragmenting polycrystalline silicon
rods 1 according to the method according to the first as-
pect of the invention in a sectional view crosswise to
the longitudinal direction of a silicon rod 1 to be frag-
mented arranged therein.
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As can be seen, the equipment has a basin 9
extending in the longitudinal direction of the silicon
rod 1, which builds a process room 8 according to the
claim, which is filled with process fluid 2, in the pre-
sent case water 2.
The silicon rod 1 to be fragmented is ar-
ranged in the process room 8 in a tub-like container 7,
the inside walls of which are built by a polyurethane mat
10, which is supported downwards by an underlayment 11
made of PE. Thereby, it has a horizontal position and is
completely surrounded by process fluid 2. The tub-like
container 7 is built and arranged in the process room 8
such that that it can be taken from the process room 8
after the complete fragmentation of the silicon rod 1 to-
gether with the fragments of the silicon rod 1 that have
emerged therefrom, which then are loosely arranged
therein.
Furthermore, the equipment comprises an elec-
trode arrangement 4 with two electrodes 5, 6, which are
arranged centred with respect to the longitudinal axis of
the silicon rod 1 above it. Both electrodes 5, 6 are im-
mersed in the process fluid 2 and high voltage pulses are
applied to the left electrode 5 by a high voltage genera-
tor (not shown) also part of the equipment during the
fragmentation operation, while the right electrode 6 is
grounded. Both electrodes 5, 6 have a clearly bigger dis-
tance to each other than each to the silicon rod 1. These
distances are chosen such that, in the region of these
electrodes 5, 6, high voltage breakdowns through the sil-
icon rod 1 and/or along the surface of the silicon rod 1,
which lead to the fragmentation of the silicon rod 1, are
generated at the application of high voltage pulses to
the left electrode 5 by the high voltage generator. In
the present case, the diameter of the silicon rod 1 is
about 120 mm, its length is about 2 m. The distances of
the electrodes 5, 6 to the surface of the silicon rod I
are about 8 mm. The distance of the electrodes 5, 6 to
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each other are about 60 mm. The high voltage pulses pro-
ducible by the high voltage pulse generator have a volt-
age of about 200 KV and are generated at a pulse fre-
quency of 5 Hz. The power per pulse is about 700 Joule.
Thereby, the electrode arrangement 4 is mova-
ble together with the high voltage pulse generator on a
(not shown) moving carrier plate in longitudinal direc-
tion of the silicon rod 1 along it during the generation
of the high voltage breakdowns such that the location of
the high voltage breakdowns through the silicon rod 1 or
along the surface of the silicon rod 1, respectively,
progressively changes in longitudinal direction of it
without thereby essentially changing the distances of the
electrodes 5, 6 to the silicon rod 1. The electrode ar-
rangement 4 moves with a speed in the range between 6 mm
and 10 mm per second along the silicon rod 1 during the
intended operation.
The equipment additionally comprises an
equipment control, by means of which the distance between
the electrodes 5, 6 and the silicon rod 1 and the moving
speed of the electrode arrangement 4 can be set during
the fragmentation operation.
While preferred embodiments of the invention
have been described in this application, it is clearly
noted that the invention is not restricted to them and
may be carried out in other ways within the scope of the
now following claims.
