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Patent 2315019 Summary

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(12) Patent: (11) CA 2315019
(54) English Title: METHOD AND INSTALLATION FOR REFINING SILICON
(54) French Title: PROCEDE ET INSTALLATION D'AFFINAGE DU SILICIUM
Status: Expired
Bibliographic Data
(51) International Patent Classification (IPC):
  • C01B 33/037 (2006.01)
(72) Inventors :
  • GARNIER, MARCEL (France)
  • TRASSY, CHRISTIAN (France)
(73) Owners :
  • CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE (France)
(71) Applicants :
  • CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE (France)
(74) Agent: NORTON ROSE FULBRIGHT CANADA LLP/S.E.N.C.R.L., S.R.L.
(74) Associate agent:
(45) Issued: 2008-02-26
(86) PCT Filing Date: 1998-12-17
(87) Open to Public Inspection: 1999-07-01
Examination requested: 2003-11-20
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/FR1998/002765
(87) International Publication Number: WO1999/032402
(85) National Entry: 2000-06-15

(30) Application Priority Data:
Application No. Country/Territory Date
97/16544 France 1997-12-19

Abstracts

English Abstract




The invention concerns a method for refining silicon, consisting
in filling a cold induction crucible (1) with solid silicon; liquefying the
crucible content; carrying out, using the induction crucible, a turbulent
mixing of the silicon bath (b) by bringing up the liquid from the bottom
of the crucible towards the free surface along the crucible central axis;
directing a plasma (f) generated by an induction plasma torch (2)
towards the bath surface for a time interval enabling the elimination
of impurities for which the plasma reactive gas (g r) is adapted.


French Abstract

L'invention concerne un procédé d'affinage du silicium, consistant à remplir un creuset froid inductif (1) de silicium solide; à liquéfier le contenu du creuset; à organiser, au moyen du creuset inductif, un brassage turbulent du bain de silicium (b) en amenant le liquide depuis le fond du creuset vers la surface libre en remontant le long de l'axe central du creuset; et à diriger un plasma (f) produit par une torche à plasma inductive (2) vers la surface du bain pendant une durée permettant l'élimination d'impuretés pour lesquelles le gaz réactif (gr) du plasma est adapté.

Claims

Note: Claims are shown in the official language in which they were submitted.




14
CLAIMS:


1. A silicon refining method comprising:
filling a cold inductive crucible with solid silicon;
melting the content of the crucible;
creating, by means of the inductive crucible, a turbulent stirring of
the silicon melt by bringing the liquid from the bottom of the crucible to a
melt
surface by ascending along the central axis of the crucible; and
directing a plasma generated by an inductive plasma torch towards
the melt surface for a duration enabling elimination of impurities for which
at least
one reactive gas of the plasma is adapted.

2. The method of claim 1, wherein the intensity of the turbulent
stirring is a function of the frequency of an electromagnetic field created by
the
crucible.

3. The method of claim 1 or 2, comprising sequentially using
several reactive gases.

4. The method of claim 3, wherein the reactive gases are selected
from the group consisting of chlorine, oxygen, hydrogen, and water vapor.

5. The method of any one of claims 1 to 4, further comprising, after
purification of the silica melt:
inverting the melt stirring direction; and
injecting, as one of the at least one reactive gas of the plasma, an
element enabling doping of the silicon.

6. The method of claim 5, wherein the reactive gas injected to dope
the silicon is hydrogen.

7. The method of any one of claims 1 to 6, wherein the silicon is
processed by batches of a volume substantially corresponding to a volume of
the
crucible, part of the silicon remaining in the crucible at an end of the
processing of
a current batch to form a liquid seed furthering the melting during a next
batch.


15
8. The method of any one of claims 1 to 7, wherein during an initial
starting phase, the plasma is used without any reactive gas to heat up a
surface of
the silicon contained in the crucible, until the silicon reaches a temperature

sufficient to make it conductive, the continuation of the silicon heating and
its
maintaining at a desired temperature being afterwards ensured by a magnetic
field
of the inductive crucible.

9. A silicon refining installation comprising:
a cold inductive crucible adapted to receive the silicon;
an inductive plasma torch directed towards a free surface of the
silicon contained in the crucible; and
a removable magnetic yoke between the plasma torch and the
crucible, the yoke being ring-shaped to enable the passing of the plasma
flame.

10. The installation of claim 9, wherein the crucible includes, at its
bottom, an aperture having its opening controlled by an electromagnetic valve.

Description

Note: Descriptions are shown in the official language in which they were submitted.



CA 02315019 2007-04-10

1
METHOD AND INSTALLATION FOR REFINING SILICON

The present invention relates to the manufacturing of
silicon to form photovoltaic cells for electric power generation.
Silicon intended for photovoltaic techniques is presently
essentially formed from the rejects of microelectronics industry,
since the silicon used for photovoltaic applications can contain a
proportion of impurities (on the order of 10-6) that is less
critical than the level of impurities (10-9) generally required in
microelectronics.
It would be desirable to have another silicon source to
produce silicon adapted to photovoltaic products. In particular,
the rejects of microelectronics industry risk becoming rapidly
insufficient to satisfy the needs of photovoltaic techniques.
It is currently attempted to refine the silicon manu-
factured for metallurgic applications to obtain silicon having a
purity adapted to photovoltaic techniques. The silicon used in
metallurgy can contain several percents of impurities such as iron,
titanium, boron, phosphorus, etc.
A method of silicon purification is known (for example,
fran European patent application 0,459,421), which consists of
directing an arc plasma towards the surface of a silicon melt. The
high speed of the plasma sets the melt in motion, the intensity of


CA 02315019 2006-10-20

2
which depends on the plasma power. The silicon is contained in a hot cruci-
ble with silica walls (Si02).
Such a method has several disadvantages. In particular, the use
of an arc plasma requires electrodes that are a source of contamination for
the silicon to be purified. Further, the oxygen in the silica wall is a source
of
contamination for the melt silicon.
The present invention aims at providing a novel method of sili-
con refining enabling reaching a high degree of purity, which is particularly
well adapted to the refining of large quantities of silicon, and thus adapted
to to an industrial method for making silicon having a sufficient degree of
purity for photovoltaic techniques.
The present invention aims, in particular, at overcoming the
disadvantages of known methods.
The present invention also aims at providing a refining method
that can be implemented from beginning to end in a same refining installa-
tion. In particular, the present invention aims at minimizing the use of
refining means that are mechanically different from one another and at
eliminating impurities of different natures within a same equipment.
The present invention further aims at having this same equip-
ment usable to "dope" the silicon once refined.
To achieve these objects, the present invention provides a sili-
con refining method comprising the steps of filling a cold inductive crucible
with solid silicon, melting the content of the crucible, creating, by means of
the inductive crucible, a turbulent stirring of the silicon melt by bringing
the
liquid from the bottom of the crucible to a melt surface by ascending along
the central axis of the crucible, and directing a plasma generated by an
inductive plasma torch towards the melt surface for a duration enabling
elimination of impurities for which at least one reactive gas of the plasma is
adapted.
According to an embodiment of the present invention, the inten-
sity of the turbulent stirring is a function of the frequency of an electro-
magnetic field created by the crucible.


CA 02315019 2000-06-15

3
According to an embodiment of-the present invention, the
method cansists of sequentially using several reactive gases.
According to an embodiment of the present inventicn, the
reactive gases are selected frcan the group including chlorine,
oxygen, hydrogen, and water vapor.
According to an enbodiment of the present invention, the
niethod further consists of, after purification of the silicon melt,
inverting the melt stirring direction and injecting, as a reactive
gas of the plasma, a silicon doping element.
According to an embodiment of the present invention, the
reactive gas injected to dope the silicon is hydrogen.
According to an embodiment of the present invention, the
silicon is processed by batches of a volunie substantially
corresponding to the volume that can be contained in the crucible,
the crucible not being integrally emptied at the end of the
processing of a current batch to form a liquid seed furthering the
melting during the next batch.
According to an embodiment of the present invention,
during an initial starting phase of the installation, the plasma is
used without any reactive gas to heat up the surface of the silicon
load contained in the crucible, until this load reaches a
temperature sufficient to make it conductive, the continuation of
the load heating and its maintaining at the desired temperature
being afterwards ensured by the magnetic field of the inductive
crucible.
The present invention further provides a silicon refining
installation including a cold inductive crucible adapted to
receiving the silicon, an inductive plasma torch directed towards
the free surface of the silicon load contai.ned in the crucible, and
a removable magnetic yoke between the plasma torch and the
crucible, the yoke being ring-shaped to enable the passing of the
plasma flame.
According to an embodiment of the present invention, the
crucible includes, at its bottom, an aperture having its opening
ccntrolled by an electromagnetic valve.


CA 02315019 2000-06-15
4

The foregoing objects, features and advantages of the
present invention will be discussed in detail in the following non-
limiting description of specific embodiments in connection with the
accompanying drawings, wherein:
Fig. 1 very schematically shows a refining installation
according to the present invention during a silicon purification
phase; and
Fig. 2 shows the installation of Fig. 1 during a silicon
doping phase according to the present invention.
The same elements have been designated by the same
reference in the different drawings. For clarity, only those
elements of the installation that are necessary to the under-
standing of the present invention have been shown in the drawings
and will be described hereafter.
According to the present invention, a silicon refining
installation essentially includes a cold crucible 1 heated by
induction (coil 12), intended for containing a silicon melt b, and
an inductive plasma torch 2 directed for "flame" f to sweep the
free surface of melt b.
The function of the plasma is to create a plasma medium
formed of the free radicals and of the ions of the plasmid gas(es)
in the vicinity of the free surface of silicon melt b. The
atmosphere thus created at the free surface of the melt is
extremely reactive and the impurities present at the melt surface
combine with the reactive gas of the plasma and become volatile
(or, conversely, solid) at the melt surface temperature. The entire
installation is maintained under a controlled atmosphere, which
enables evacuating the volatile molecules containing impurities as
the process goes along.
The choice of an inductive plasma torch has, in
particular as ccxnpared to the use of a plasma arc torch, the
advantage of not contaminating the melt by the consumption of the
electrode necessary to generate the plasma.
Another advantage of the use of a plasma torch, as
ccmpared to the use of an electron beam to focus significant power
densities favorable to the direct vaporizing of the species at the


CA 02315019 2000-06-15

surface of a melt, is that, in the case of an inductive plasma, a
system close to equilibrium is obtained, and advantage can thus be
taken of the volatility differences between the elements or the
cccnpounds thereof. For example, the silicon can avoid being
5 vaporized.
Another advantage is that the chemical action of the
plasma at the liquid-plasma interface is distributed over the
entire melt surface due to the plasma gas flow provided by the
torch.
The use of a cold inductive crucible has several
purposes. First, this has the advantage of not contaminating the
liquid silicon, which is maintained in a skull, that is, a solid
silicon skin (not shown) coats the inside of the crucible and
contains the liquid silicon. Thus, the liquid silicon does not risk
being contaminated by the material constitutive of walls 11 of the
actual crucible, or of an intermediary wall as in known methods.
Another advantage of using a cold inductive crucible is
that this enables creating a turbulent stirring in the silicon melt
to further the purification. Indeed, in the absence of any stirring
of the silicon melt, the diffusion times of the impurities that
must migrate fran the inside of the melted mass to the liquid-
plasma interface to be canbined, then vaporized, are inconpatible
with a method economically viable fran an industrial point of view.
A feature of the present invention is that the magnetic
field of the cold inductive crucible is, preferably, an A.C.
single-phase field, that is, coil 12 of cold crucible 1 is supplied
by an A.C. single-phase voltage. The choice of 'such a magnetic
field has the advantage of causing the heating up of the silicon
melt at the same time as it causes its motion.
Indeed, by submitting the silicon to an A.C. magnetic
field by means of coil 12 of the czucible, flow variations are
caused in the silicon that result in inducted currents located at
the periphery of the material (in the electrcmagnetic skin).
The induced currents have thermal effects enabling
heating (and thus melting) of the material, and mechanical effects
(magnetic pressure and turbulent stirring) resulting fran the


CA 02315019 2000-06-15

6
interaction between the currents and the applied magnetic field.
When the material becomes liquid, the non-rotational part of the
forces induces a magnetic pressure in the material, the free
surface of which then beccxnes dane-shaped (Fig. 1). The rotational
part of the forces induces driving torques within the liquid and
sets it in motion in an electromagnetic stirring. This stirring is
said to be turbulent since it causes not only high speed large
scale recirculation (at the melt scale) to constantly and rapidly
renew the free surface of the melt and bring the free species to be
eliminated near the reactive surface, but also a small scale
turbulence in the vicinity of the free surface to bring all the
substances to be eliminated to the surface and thus increase
reactional kinetics. All stirring scales are directly submitted to
an injection of kinetic energy from the magnetic energy.
Conversely, a flow by hydraulic friction as used in known
methods (EP-A-0,459,421) creates a large scale stirring and the
motion is only transmitted by degradation and power transfer to
smaller scales. In addition to the disadvantage of a large power
loss to achieve small scale turbulence, such a method does not
enable controlling the motion otherwise than by acting upon the arc
plasma generating the motion.
According to the present invention, the selecticn of the
frequency of the A.C. magnetic field enables setting the parameters
(thermal effect, magnetic pressure, electromagnetic stirring) of
the melt and, in particular, favoring one of the parameters.
According to the present invention, the frequency of coil
12 of crucible 1, powered by a generator 13, is chosen to further a
turbulent stirring of silicon melt b that, in purification steps of
the method of the present invention, is performed in the direction
symbolized by the arrows in Fig. 1, that is, the liquid is brought
fran the bottom of the crucible to the free surface by ascending
along the axis, the descent to the crucible bottan occurring at the
periphery thereof.
Whether the stirring is turbulent or not depends cn the
current frequency, on the crucible size, and on the typical value
of the magnetic field. The Reynolds number (Re) enables determining


CA 02315019 2000-06-15
7

the nature of the flow. The screen parameter (Ro)) is a function of
the crucible diameter, of the electric conductivity of the melt,
and of the frequency (Rr,D = 9aR2, where designates the
permeability of vacuum,, cD designates the pulse, a designates the
electric conductivity of the liquid material, and R designates the
crucible radius). The screen parameter characterizes the larger or
smaller penetration of the field into the melt. If the field only
very superficially penetrates (high frequencies), the Laplace
forces will only act upon the peripheral portion of the melt and
the stirring will be reduced. Similarly, if the field totally
penetrates (zero frequency), there will be no stirring. For the
stirring to be maximum, the screen parameter must have a value an
the order of 40. It should be noted that this screen parameter is
adjustable by the operator.
Such a stirring has several advantages in purification
phases.
First, the fluid of the lower part of the crucible is
rapidly brought up to the free reactive surface and the impurities
can then be ccmbined, then vaporized by the plasma to be evacuated.
it should be noted that the species formed by reaction of the
plasma with the impurities contained in the silicon are
continuously eliminated in the installation and, accordingly, the
interface reactivity is constant and does not saturate.
Another advantage of the circulation provided in Fig. 1
is that if solid particles (often lighter oxides), also resulting
fran the chemical reaction of impurities with the plasma, fozm on
the melt surface, said particles are driven towards wall 11 of
crucible 1, that is, towards the solid silicon crust where they are
trapped, thus increasing the purificaticn efficiency.
The choice of the crucible coil supply frequencies
depends on the size and shape of the crucible. For example, with a
crucible having a diameter on the order of 60 cm that can contain a
silicon load on the order of 200 kg, a frequency on the order of 50
or 60 Hz, and thus the frequency of the industrial electric system,
may be used for the crucible coil.


CA 02315019 2000-06-15
8

An advantage of the present invention is that it is now
possible to simultaneously or successively inject, with no other
manipulation than the opening of gas supply valves (not shown),
several reactive gases, gr into the plasma and to control the
concentration thereof with respect to the plasmid gases. In a torch
2 such as illustrated in Fig. 1, reactive gas gr is brought to the
center of the torch, and an auxiliary gas ga, for example, argon,
is conveyed concentrically to the reactive gases. A plasma gas gp,
for example, also argon, is further conveyed concentrically to the
auxiliary gas. An inductive coil 21 surrounds the free end of torch
2 to create the inductive plasma. The torch coil is generally
driven by an A.C. current at a frequency on the order of one NEz by
a generator 22.
According to the present invention, different reactive
gases may be injected into the plasma, either simultaneously or
successively, for their selective action upon undesirable elements.
As an ex-ample of reactive gases, oxygen, hydrogen, chlorine, or
water vapor can be mentioned. The gas selection is determined by
the chemical and thernmdynamic properties of the impurity to be
eliminated. The use of chlorine in the plasma enables forming
volatile chlorides with impurities such as boron, antimony, or
arsenic, which are among the most frequent impurities in the case
of silicon caming fran microelectronics industry rejects. Silicon
also combines with chlorine to form a volatile chloride. The
evaporation of impurities is furthered by the controlling of the
renewal of the atmosphere above the silicon melt (a lower vapor
pressure for impurity chlorides makes them more volatile).
Oxygen enables eliminating carbon traces (silicon is
obtained by the reduction of sand (silica) by carbon in an arc
furnace). It should be noted that the injection of a reactive gas
such as oxygen is perfectly controllable, conversely to an oxygen
release by a silica wall as in known methods.
Oxygen, or more efficiently water vapor, or the oxygen-
hydrogen combination, enables making boron volatile as B3H306,
which is gaseous.


CA 02315019 2000-06-15
9

Practically, for obvious security and saving reasons,
water or oxygen are preferred each time this is possible.
Preferably, the refining installation further includes a
removable magnetic yoke 3 (Fig. 2), the function of which is to
invert the flow direction in the silicon melt. The stirring speed
being proportional to the typical value of the magnetic field, the
presence or not of the magnetic yoke enables modifying this field
and provides the flow speed and the fact that it is or not
turbulent, without having to modify the frequency, which would
create serious technological and fundamental difficulties. The
function of magnetic yoke 3 will be better understood hereafter.
The present invention will now be described in relation
with a preferred example of implementation of the silicon refining
method in an installation such as described hereabove.
To begin with, cold crucible 1 is filled with silicon
powders, chips, or scraps caning, for example, from a container 4.
Since silicon is a semiccnductor, it must be preheated before
becoming progressively conductive (around 8000C) and then being
likely to be heated up by induction by means of coil 12 of crucible
1.
According to the present invention, plasma torch 2' is
first aperated to preheat the solid silicon load and bring it to
the temperature enabling obtaining a coupling with the low
frequency field created by coil 12 of crucible 1. The gas used in
the preheating phase preferably is argon. Hydrogen may be intro-
duced as a reactive gas to increase the thermal conductivity of the
plasma and thus accelerate the preheating of the silicon load.
An advantage of performing a preheating by means of the
plasma torch as campared to the conventional use of a susceptor is
that any contamination of the silicon that would otherwise be
brought by the susceptor material (generally carbon or iron) is
thus avoided.
At the end of this starting phase, the silicon has
entirely melted down and the power required to maintain this melted
state is essentially provided by the coil of crucible 1.


CA 02315019 2000-06-15

In a second purification phase, a turbulent stirring of
the silicon melt in the arrow direction in Fig. 1 is furthered, and
one or several reactive gases adapted to eliminating impurities
which, by canbining with a reactive gas at the surface of melt b,
5 form volatile species that are vaporized, are simultaneously or
successively introduced into the plasma. It should be noted that
the traces of oxygen (or of other impurities) contained in the
powders and chips introduced by solid silicon dispenser 4 in the
preceding step cause the forming of a gangue at the melt surface.
10 This gangue, formed of axides and suboxides lighter then the rest
of the melt, is rejected at the periphery of crucible 1 by the
turbulent stirring in the arrow direction in Fig. 1. A clear
surface is thus guaranteed at the liquid-plasma interface.
The purification phase may include several steps corre-
sponding to the use of different reactive gases depending on the
elements to be eliminated fran the liquid melt.
Another feature of the present invention applied to the
obtaining of silicon for photovoltaic applications is to provide a
third "daping" phase of the purified silicon, by elements
furthering the photovoltaic power of polysilicon by the passivating
of defects, for example, hydrogen.
According to the present invention, once the silicon has
been purified, a dapant is introduced into the plasma as a reactive
gas, for example, hydrogen. To imprave the inclusian of hydrogen
atans in the silicon, the turbulent stirring motions are preferably
inverted in the liquid melt. For this purpose, according to the
present invention, magnetic yoke 3, which has a ring shape crossed
by the plasma at its center, is positioned. Although it is possible
to use a ring-shaped magnetic yoke in the form of a coil controlled
by an A.C. drive, it will be preferred according to the present
inventian to use a magnetic yoke formed of a permanent magnet, for
example, in the form of two half-rings brought around plasma flame
f when the direction of the turbulent stirring is desired to be
inverted in the melt. Since this inversion of the turbulent
stirring directicn by the plasma results, as illustrated in Fig. 2,
in driving the liquid to the bottan of the crucible by descending


CA 02315019 2000-06-15
11

along the axis and having it rise back up to the free surface along
the crucible wall, it furthers the inclusion of hydrogen atans in
the nmelt.
Preferably, to avoid for the stirring inversion to cause
a return to the center of the melt of the gangues and slag rejected
at the periphery during the preceding phase, the heating power of
crucible 1 is first decreased, to increase the thickness of the
solid external layer of the melt, and thus congeal the solid
species containing impurities.
In a fourth phase, once the refined and doped silicon is
ready, it is cast in the form of ingots adapted to being sawn to
obtain solar cells. This casting may, according to an embodiment
not shown, be obtained by tilting of the crucible.
According to the embodiment shown in Figs. 1 and 2, the
casting is obtained by operating an electromagnetic valve 5 for
closing an aperture 14 at the bottcm of crucible 1.
For example, an electrcmagnetic valve may be used with
the purpose of melting down a solid silicon plug that abturates the
bottom of the crucible. This plug is maintained, during the other
phases, in the solid state by cooling down of the wall of aperture
14. A coil 51 surrounding the output aperture is then used. Coil 51
is imbricated in the low portion of the crucible with coil 12 of
the actual crucible. The frequency of the current supplying valve
coil 51 by means of a generator 52 is adapted to the size of
aperture 14 and is thus much higher than the frequency of the
current supplying coil 12 of the crucible. Too high a-coupling
between the two coils is thus avoided. In the covering area of
coils 12 and 51, none of these two frequencies is, of course,
optimal. in the absence of a current in coil 51, the crucible
material at this height is warm, and thus conductive, but solid.
When a current is applied to coil 51 of valve 5, the additional
heating causes the melting down of this area. This melting
progressively propagates downwards, thus opening the valve by
melting of the solid silicon plug. The closing of the valve is
obtai.ned by cutting off the current in coil 51.


CA 02315019 2000-06-15
12

As an alternative embodiment, a small inductive plasma
torch placed under the crucible emptying aperture may be used. This
torch is then remaved at the time when the coupling temperature is
reached (this coupling, temperature is, in the case of silicon,
smaller than the melting temperature).
To process a next load (or batch) of silicon to be
refined, a liquid quantity of the preceding phase is preferably
left to remain, to avoid a new first starting phase.
It should be noted that the inversion of the stirring
direction provided in the third doping phase may also preferen-
tially be provided in the initial starting phase, to improve the
niixing of the silicon powders and chips to be melted down by
driving them to the center of the crucible and avoiding an inane-
diate trapping by the cold walls.
An advantage of the present invention is that by means of
a single installaticn, coupling an inductive plasma and a cold
inductive crucible, a refining of the silicon with respect to all
its impurities is obtained. Accordingly, this refining can be
obtained in advantageous eccnomical conditions.
Another advantage of the present invention is that it
maintains, during purification and doping phases, the silicon in a
liquid state by means of a non-contaminating inductive heating
means. This heating means is external to the crucible and leaves
the,melt surface campletely free.
Another advantage of the use of a cold inductive crucible
is that the liquid silicon is stirred with a high turbulence
intensity that furthers matter transfers in the melt. The turbu-
lence induced in the vicinity of the interface accelerates matter
transfers between the two phases above and under the free surface
and increases reactional kinetics.
Another advantage of the present invention is that the
use of a magnetic yoke between the torch and the crucible makes an
inversion of the stirring direction possible and, accordingly, the
melting of anew silicon load can be furthered and/or the
purification can be improved and/or the dopirng of a refined silicon
can be improved.


CA 02315019 2000-06-15

13
Of course, the present invention is likely to have
various alterations, modifications and improvements which will
readily occur to those skilled in the art. In particular, the gases
used in the plasma will,be chosen according to the impurities to be
eliminated fran the melt. Further, the practical making of a
refining installation enabling implementation of the method of the
present invention is within the abilities of those skilled in the
art based on the functional indications given hereabove. It will be
ascertained to respect the coupling between the plasma and the cold
crucible that enables the seeding, without any contamination, of
the melting by induction of a semiconductor material, and the use
of a ring-shaped magnetic yoke enabling forcing the convection
direction in the melt.

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date 2008-02-26
(86) PCT Filing Date 1998-12-17
(87) PCT Publication Date 1999-07-01
(85) National Entry 2000-06-15
Examination Requested 2003-11-20
(45) Issued 2008-02-26
Expired 2018-12-17

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $300.00 2000-06-15
Maintenance Fee - Application - New Act 2 2000-12-18 $100.00 2000-06-15
Registration of a document - section 124 $100.00 2000-10-30
Maintenance Fee - Application - New Act 3 2001-12-17 $100.00 2001-11-26
Maintenance Fee - Application - New Act 4 2002-12-17 $100.00 2002-11-22
Request for Examination $400.00 2003-11-20
Maintenance Fee - Application - New Act 5 2003-12-17 $150.00 2003-11-24
Maintenance Fee - Application - New Act 6 2004-12-17 $200.00 2004-11-23
Maintenance Fee - Application - New Act 7 2005-12-19 $200.00 2005-11-29
Maintenance Fee - Application - New Act 8 2006-12-18 $200.00 2006-11-23
Maintenance Fee - Application - New Act 9 2007-12-17 $200.00 2007-11-28
Final Fee $300.00 2007-12-05
Maintenance Fee - Patent - New Act 10 2008-12-17 $250.00 2008-11-26
Maintenance Fee - Patent - New Act 11 2009-12-17 $250.00 2009-11-24
Maintenance Fee - Patent - New Act 12 2010-12-17 $250.00 2010-11-24
Maintenance Fee - Patent - New Act 13 2011-12-19 $250.00 2011-11-24
Maintenance Fee - Patent - New Act 14 2012-12-17 $250.00 2012-11-26
Maintenance Fee - Patent - New Act 15 2013-12-17 $450.00 2013-11-25
Maintenance Fee - Patent - New Act 16 2014-12-17 $450.00 2014-11-24
Maintenance Fee - Patent - New Act 17 2015-12-17 $450.00 2015-11-25
Maintenance Fee - Patent - New Act 18 2016-12-19 $450.00 2016-11-22
Maintenance Fee - Patent - New Act 19 2017-12-18 $450.00 2017-11-23
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Past Owners on Record
GARNIER, MARCEL
TRASSY, CHRISTIAN
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Description 2000-06-15 13 754
Representative Drawing 2000-09-27 1 9
Abstract 2000-06-15 1 66
Claims 2000-06-15 2 85
Drawings 2000-06-15 2 41
Cover Page 2000-09-27 1 44
Description 2006-10-20 13 743
Claims 2006-10-20 2 61
Representative Drawing 2006-11-23 1 9
Description 2007-04-10 13 740
Cover Page 2008-02-05 2 43
Correspondence 2007-01-10 1 20
Prosecution-Amendment 2006-05-08 2 81
Correspondence 2000-08-28 1 25
Assignment 2000-06-15 4 146
PCT 2000-06-15 16 628
Assignment 2000-10-30 2 97
Prosecution-Amendment 2003-11-20 1 34
Prosecution-Amendment 2006-10-20 6 205
Correspondence 2007-04-10 2 71
Correspondence 2007-12-05 1 39