U.S. patent application number 10/477345 was filed with the patent office on 2006-11-02 for method, apparatus and system for electro-deposition of a plurality of thin layers on a substrate.
This patent application is currently assigned to Universite Catholique de Louvain. Invention is credited to Stefan Matefi-Tempfli, Luc Piraux.
Application Number | 20060243597 10/477345 |
Document ID | / |
Family ID | 8177352 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060243597 |
Kind Code |
A1 |
Matefi-Tempfli; Stefan ; et
al. |
November 2, 2006 |
Method, apparatus and system for electro-deposition of a plurality
of thin layers on a substrate
Abstract
A method, apparatus and system for fabricating nanometer range,
thin multilayers, multilayered nanowires and nonocomposites by
multiple bath electro-deposition of a plurality of thin lazers on a
substrate, with the purpose to complete the actually developing
nanotechnologies, are described. A closed electrochemical system
with multiple baths, protected by inert gas, where the chemical
solutions are transferred there and back between different chemical
tanks and an electrochemical cell, are used to produce thin, in
nanometerrange, multiple layer depositions on a substrate which
stays on a fix position for all the deposition cycles inside the
electrochemical cell. The transfer method protects the system
against the cross contamination between different chemical
solutions and the risk of contamination of the chemical solutions
on their way to and from the chemical tanks. The cleaning method
protects the deposited layers aginst undersirable surface
reactions.
Inventors: |
Matefi-Tempfli; Stefan;
(Louvain-La-Neuve, BE) ; Piraux; Luc; (Louvain-La
Neuve, BE) |
Correspondence
Address: |
Stephen M De Klerk;Blakely Sokoloff Taylor & Zafman
12400 Wilshire Boulevard
7th Floor
Los Angeles
CA
90025
US
|
Assignee: |
Universite Catholique de
Louvain
Louvain-La-Neuve
BE
1348
|
Family ID: |
8177352 |
Appl. No.: |
10/477345 |
Filed: |
May 3, 2002 |
PCT Filed: |
May 3, 2002 |
PCT NO: |
PCT/EP02/04888 |
371 Date: |
January 26, 2006 |
Current U.S.
Class: |
205/170 ;
204/242 |
Current CPC
Class: |
C25D 17/00 20130101;
C25D 5/10 20130101 |
Class at
Publication: |
205/170 ;
204/242 |
International
Class: |
C25D 5/10 20060101
C25D005/10; C25B 9/00 20060101 C25B009/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2001 |
EP |
01111055.8 |
Claims
1. A method for fabricating nanometer range, thin multilayers,
multilayered nanowires and nanocomposites by electro-deposition of
a plurality of thin layers on a substrate, wherein the
electro-deposition is carried out inside a closed electrochemical
cell while the substrate is positioned, for all the deposition
steps, in the electrochemical cell, and wherein multiple chemical
solutions stored in respective tanks are transferred back and forth
between the tanks and the electrochemical cell.
2. The method of claim 1 wherein the chemical solutions transfer
process is realized using pressure differences between the chemical
tank and the electrochemical cell.
3. The method according to claim 2 wherein the pressure differences
are realized applying a pressure between 1 to 1000 mbar to the
chemical tank and to the electrochemical cell.
4. The method of claim 2 wherein the chemical solution is
transferred between the chemical tank and the electrochemical cell
through a separation chamber.
5. The method of claim 1, wherein the electrochemical cell and the
tanks are part of a closed electrochemical system.
6. The method of claim 1, wherein the closed electrochemical system
is protected by inert gas.
7. The method of claim 1, wherein the cleaning process is performed
using ultra pure water.
8. The method of claim 1, wherein the cleaning process is performed
by letting the ultra pure water flow through the electrochemical
cell and by transferring the water after cleaning from the
electrochemical cell to the wastewater tank.
9. The method of claim 1, wherein a) the substrate is placed and
fixed to the working electrode inside the electrochemical cell; b)
the chemical solution is transferred from the a respective tank to
the electrochemical cell; c) a computer controlled
electro-deposition process is carried out on the substrate; d) the
chemical solution is transferred back from the electrochemical cell
to the chemical tank for future reuse; e) the electrochemical cell
is cleaned by ultra pure water; f) steps b) to e) are repeated
until all the desired layers are deposited; g) the substrate is
removed from the electrochemical cell.
10. The method of claim 1, wherein an in automatic mode of the
entire electro-deposition cycle is provided under the control of a
computer.
11. A apparatus for fabricating nanometer range, thin multilayers,
multilayered nanowires and nanocomposites by multiple bath
electro-deposition of a plurality of thin layers on a substrate,
comprising a closed system of an electrochemical deposition system
and a multiple transfer system, the electrochemical deposition
system comprising an electrochemical cell adapted to receive the
substrate for all the deposition steps.
12. The apparatus of claim 11, wherein the electrochemical cell
includes working-, counter-and reference-electrodes such as to
enable an electrochemical process on the working electrode on a the
substrate and access means for transferring fluids to and from the
electrochemical cell.
13. The apparatus of claim 11, wherein the substrate is attached to
the working electrode to be supported on the same place in the
electrochemical cell.
14. The apparatus of claim 11, wherein the transfer system includes
a chemical solution tank; a separation chamber; means to transfer
the solution through the separation chamber between the chemical
tank and the electrochemical cell.
15. The apparatus of claim 11, comprising a cleaning system,
wherein the cleaning system comprises one of the transfer
subsystems where the tank is used as wastewater tank; an evacuation
chamber; means to allow the access of pure water to the
electrochemical cell; and means to evacuate different fluids from
the electrochemical cell.
16. The apparatus of claim 11 wherein means to transfer the
solution comprise transfer pipes between the chemical tank and the
separation chamber; transfer pipes between the separation chamber
and the electrochemical cell, gas-in and vacuum-out pipes and
electrovalves on them connected to the chemical tank to control the
transfer process.
17. The apparatus of claim 11, wherein the means to transfer the
solution comprise a gas- in pipe and an electrovalve on it
connected to the separation chamber.
18. The apparatus of claim 11, wherein the evacuation chamber
comprises a separation vessel between the electrochemical cell and
an evacuation duct, permitting to keep the electro- deposition
system under inert gas protection for all the deposition steps.
19. The apparatus of claim 11, wherein it is designed in the manner
such that it permits only one direction of flow of different kinds
of fluids from the electrochemical cell to the evacuation duct.
20. The apparatus of claim 11, wherein means to allow the access of
pure water to the electrochemical cell and means to evacuate
different fluids from the electrochemical cell comprise pipes and
an electrovalve to control the cleaning process.
21. The apparatus of claim 11, comprising a computer controlling
the apparatus to perform an in automatic mode of the entire
electro-deposition cycle.
22. The apparatus of claim 11, comprising a computer controlling
the apparatus to perform an in automatic mode of the entire
electro-deposition cycle.
23. A modular multiple bath electro-deposition system for
fabricating nanometer range, thin multilayers, multilayered
nanowires and nanocomposites by electro-deposition of a plurality
of thin layers on a substrate, in particular a variety of
multilayered nanostructures, comprising at least one
electrochemical subsystem, at least one transfer subsystem and at
least one cleaning subsystem as claimed in claim 1, wherein the
subsystems are integrated to form a closed electro-deposition
system.
24. The system of claim 23, wherein the system is protected by
inert gas.
25. The system of claim 23, comprising a computer controlling the
apparatus to perform an in automatic mode of the entire
electro-deposition cycle.
Description
[0001] The invention relates generally to a method, an apparatus
and a system for fabricating nanometer range, thin multilayers,
multilayered nanowires and nanocomposites by electro-deposition of
a plurality of thin layers on a substrate, in particular for the
fabrication of nanostructures with the purpose to complete the
actually developing nanotechnologies.
[0002] As known in the state of the art, an atomistic deposition
process represents an essential requirement for producing
multilayered structures with the individual layers a few nanometers
in thickness. Several techniques, such as molecular beam epitaxy
and sputter deposition satisfy quite well this requirement. Some
disadvantage of these techniques, such as cost, low deposition
rates or diffusion problems between the deposited layers due to
relatively high temperature of these processes, limits their
applicability. In the last few years an alternative atomistic
deposition and cost saving technique was developed for producing
thin multilayers, namely the single bath electro-deposition
technique. The electrochemical deposition of thin multilayers opens
a new way to realise compositionally modulated nanowires in
nanoporous materials like polymer and alumina membranes, which was
nearly impossible to do previously.
[0003] The single bath electro-deposition technique makes it
possible to fabricate periodic stacking of metal and alloy layers.
For this technique, the electrochemical bath contains ions of two
or more metals separable in two groups, more noble (more electro
positive) and less noble metal ions. Deposition in the controlled
way of the more noble group (metal or alloy) or of the less noble
group alloy are realized usually by varying the deposition
potential or current. The concentration of the nobler ions in the
bath usually is much lower than the concentration of the less noble
ions, to reduce undesirable co deposition effect. This single bath
technique permit to realize up to thousands of above mentioned
double layers with thickness down to a few nanometers. The main
inconvenience of this single bath technique are the impossibility
to deposit two different metals for which the electrochemical
reduction potentials are too close to each other and also the fact
that the less noble deposited metal or alloy always contains a
definite amount of nobler metal due to co deposition.
[0004] In contrast, the multiple bath electro-deposition technique
does not suffer from these limitations as to the deposited
materials. It permits to stack different types of metals,
semimetals, alloys, semiconductors, and thin oxide layers. This
technique requires the use of a different bath for each layer to be
deposited. The inconveniences, like much longer processing time due
to cleaning and transfer between baths after each deposit, limit
the maximal number of the deposited layers to a few hundreds. This
technique is widely used in industrial processes, for deposition of
thick (micrometer-range) layers. Unfortunately undesirable surface
reactions appear during the cleaning and transfer of the substrate
between the different baths, which are unacceptable for
nanometer-range thin layer deposition. The attempts to solve these
problems were unsuccessful.
[0005] It is an object of the invention to provide a method,
apparatus and system for fabricating nanometer range, thin
multilayers, multilayered nanowires and nanocomposites by multiple
bath electro-deposition which is improved with respect to the
above-mentioned problems in particular by reducing contamination of
the chemical solutions during the deposition process, by reducing
the undesirable surface reactions during electro-deposition, and
enabling sensible handling of the substrate throughout the
electro-deposition process.
[0006] According to the invention, a method for electro-deposition
of a plurality of thin layers on a substrate is provided, wherein
the electro-deposition is carried out inside a closed
electrochemical cell while the substrate is positioned, for all the
deposition steps, in the electrochemical cell, and wherein multiple
chemical solutions stored in respective tanks are transferred back
and forth between the tanks and the electrochemical cell.
[0007] In method of the invention, electro-deposition takes place
inside on a closed electrochemical cell to eliminate the
undesirable surface reactions, while the substrate stays in the
electrochemical cell for all the deposition steps the safeguard the
substrate taking into account the mechanical sensibility of the
nanostructures. In this case the substrate is not transferred
between different baths, it rest in the electrochemical cell, and
different solutions are transferred, from different chemical tanks
to the electrochemical cell.
[0008] In a preferred embodiment of the method of the invention,
the chemical solutions transfer process is realized using pressure
differences between the chemical tank and the electrochemical cell.
In particular, the pressure differences are realized applying a
pressure between 1 to 1000 mbar to the chemical tank and to the
electrochemical cell. This substantially reduces the risk of
contamination of the chemical solutions which are transferred
Multiple times to and from the electromechanical cell during the
deposition process as the solutions are not flowing through pumps
and are not passing sealing device, valves and the like.
Furthermore, the transfer process is simplified and the lifetime of
the equipment is increased.
[0009] In a further preferred embodiment of the method of the
invention, the chemical solution is transferred between the
chemical tank and the electrochemical cell through a separation
chamber. The cross contamination between different chemical
solutions are solved using these separation chambers.
[0010] In a further preferred embodiment of the method of the
invention, the elctrochemical cell and the tanks are part of a
closed electrochemical system in order to avoid contamination from
the environment.
[0011] In a further preferred embodiment of the method of the
invention, the closed electrochemical system is protected by inert
gas to further reduce contamination of the system.
[0012] In a further preferred embodiment of the method of the
invention, the cleaning process is performed using ultra pure
water. The cleaning procedure between two consecutive
electro-depositions is made using ultra pure water including no
dissolved oxygen or other chemically active gas, in order to
eliminate the undesirable surface reactions.
[0013] In a further preferred embodiment of the method of the
invention, the cleaning process is performed by letting the ultra
pure water flow through the electrochemical cell and by
transferring the water after cleaning from the electrochemical cell
to the wastewater tank. During this step, the substrate remains
also in the cell and the entire cell is cleaned with ultra pure
water. The cleaning process is performed allowing the ultra pure
water to flow through the electrochemical cell, flowing out to
evacuation. At the end, the water is removed from the cell, using
one of the same transfer subsystems, dedicated for cleaning
process, transferring the water from the cell to the wastewater
tank.
[0014] In a further preferred embodiment of the method of the
invention, a) the substrate is placed and fixed to the working
electrode inside the electrochemical cell; b) the chemical solution
is transferred from the a respective tank to the electrochemical
cell; c) a computer controlled electro-deposition process is
carried out on the substrate; d) the chemical solution is
transferred back from the electrochemical cell to the chemical tank
for future reuse; e) the electrochemical cell is cleaned by ultra
pure water; f) steps b) to e) are repeated until all the desired
layers are deposited; g) the substrate is removed from the
electrochemical cell.
[0015] In a further preferred embodiment of the method of the
invention an automatic mode of the entire electro-deposition cycle
is provided under the control of a computer. Due to the computer
control in automatic mode of the entire electro-deposition cycle,
the method is easy to use. The computer control allows also to
precisely control the thickness parameters of the deposited
layers.
[0016] A multiple bath electro-deposition apparatus of the
invention for fabrication of a plurality of thin layers on a
substrate, comprises a closed system of an electrochemical
deposition system and a multiple transfer system, the
electrochemical deposition system comprising an electrochemical
cell adapted to receive the substrate for all the deposition
steps.
[0017] The substrate reside for all the deposition steps attached
to the working electrode inside the electrochemical cell, which is
closed and the deposited layers are protected from the undesirable
surface reactions which can occur during the transfer process of
different chemical solutions. The volume of the electrochemical
cell is minimized given to the small quantity of chemical solution
needed to deposit thin layers.
[0018] According to a preferred embodiment the invention provides
an apparatus wherein the electrochemical cell includes working-,
counter- and reference-electrodes such as to enable an
electrochemical process on the working electrode on a the substrate
and access means for transferring fluids to and from the
electrochemical cell.
[0019] According to a further preferred embodiment the invention
provides an apparatus wherein the substrate is attached to the
working electrode to be supported on the same place in the
electrochemical cell.
[0020] According to a further preferred embodiment the invention
provides an apparatus wherein the transfer system includes a
chemical solution tank; a separation chamber; means to transfer the
solution through the separation chamber between the chemical tank
and the electrochemical cell.
[0021] According to a further preferred embodiment the invention
provides an apparatus comprising a cleaning system, wherein the
cleaning system comprises one of the transfer subsystems where the
tank is used as wastewater tank; an evacuation chamber; means to
allow the access of pure water to the electrochemical cell; and
means to evacuate different fluids from the electrochemical
cell.
[0022] According to a further preferred embodiment the invention
provides an apparatus wherein means to transfer the solution
comprise transfer pipes between the chemical tank and the
separation chamber; transfer pipes between the separation chamber
and the electrochemical cell, gas-in and vacuum-out pipes and
electrovalves on them connected to the chemical tank to control the
transfer process.
[0023] According to a further preferred embodiment the invention
provides an apparatus wherein the means to transfer the solution
comprise a gas-in pipe and an electrovalve on it connected to the
separation chamber.
[0024] According to a further preferred embodiment the invention
provides an apparatus wherein the evacuation chamber comprises a
separation vessel between the electrochemical cell and an
evacuation duct, permitting to keep the electro-deposition system
under inert gas protection for all the deposition steps.
[0025] The cleaning process is performed allowing the introduction
of pure water into the electrochemical cell through a pipe and an
electrovalve. The water flowing through the cell is evacuated
through pipes and an evacuation chamber. This evacuation chamber
represent a separation vessel between the electrochemical cell and
an evacuation duct, permitting to keep the electro-deposition
system for all the deposition steps under inert gas protection,
designed in the manner such that it permits only one direction of
flowing through of different kind of fluids, from the
electrochemical cell to the evacuation duct. After that the
electrovalve is closed, the remaining water on the electrochemical
cell is transferred to the wastewater tank by the dedicated
transfer subsystem for cleaning.
[0026] According to a further preferred embodiment the invention
provides an apparatus wherein it is designed in the manner such
that it permits only one direction of flow of different kinds of
fluids from the electrochemical cell to the evacuation duct.
[0027] According to a further preferred embodiment the invention
provides an apparatus wherein means to allow the access of pure
water to the electrochemical cell and means to evacuate different
fluids from the electrochemical cell comprise pipes and an
electrovalve to control the cleaning process.
[0028] According to a further preferred embodiment the invention
provides an apparatus comprises a computer controlling the
apparatus to perform an in automatic mode of the entire
electro-deposition cycle. Due to the computer control the apparatus
is easy to use even if it seems to be complex.
[0029] The invention furthermore provides a modular multiple bath
electro-deposition system for fabrication of a plurality of thin
layers on a substrate, in particular a variety of multilayered
nanostructures, comprising at least one electrochemical subsystem
as claimed in claims, at least one transfer subsystem as claimed in
claims and at least one cleaning subsystem as claimed in claims,
wherein the subsystems are integrated to form a closed
electro-deposition system. Preferably, the system is protected by
inert gas. Further perferred is a system comprising a computer
controlling the apparatus to perform an in automatic mode of the
entire electro-deposition cycle.
[0030] According to the invention a modular designed multiple bath
electro-deposition system for fabrication of multiple different
thin layers on a substrate, comprise: an electrochemical subsystem,
multiple transfer subsystems and a cleaning subsystem, everything
controlled by computer. The electrochemical subsystem includes: an
electrochemical cell; working, counter and reference electrodes
such as to enable an electrochemical process on the working
electrode on a substrate; access for different fluids therein to.
One of the transfer subsystems (each the same) includes: a chemical
solution tank; a separation chamber; means to transfer the solution
there and back, through the separation chamber, between the
chemical tank and the electrochemical cell. The cleaning subsystem
is composed by: one of the transfer subsystems where the tank is
used as wastewater tank; an evacuation chamber; means to allow the
access of pure water to the electrochemical cell; and means to
evacuate different fluids from the electrochemical cell.
[0031] In the preferred embodiments of the invention, the fixed
position on the electrochemical cell for the substrate for all the
electro-deposition steps allows the possibility of fabrication of
multilayered nanostructures and nanowires using the multiple bath
technique, solving the mechanical sensibility problems of this
structures. Due to ultra pure water use, without any dissolved
oxygen or other chemically active gas; the undesirable surface
reactions are eliminated during the cleaning process. Small volume
for the electrochemical cell allows small quantity of wastewater
production and better cleaning due to use for each cleaning step
pure water. The inert gas protection in the closed electrochemical
system of the substrate also eliminates undesirable surface
reactions during transfer process of different chemical
solutions.
[0032] The method and apparatus of the present invention provide a
large improvement in electro-deposition process of the
nanometer-range multilayers. One of the most important improvement
is the reduction of the undesirable surface reactions during
cleaning and transfer between different baths. Another important
improvement is he reduction of cross contamination between baths
and the quantity of wastewater. A further important improvement
resides in that no delicate manipulation of the substrate during
transfer between baths is necessary taking in consideration the
sensibility of the nanostructures and nanowires to eventually
mechanical shocks. Due to the modularity of the system, to the low
quantity of wastewater production and other previously presented
advantages are suitable for industrial application.
[0033] The preferred embodiments of the method, the apparatus and
the system for fabricating nanometer range, thin multilayers,
multilayered nanowires and nanocomposites by multiple bath
electro-deposition of a plurality of thin layers on a substrate,
with the purpose to complete the actually developing
nanotechnologies, comprise a closed electrochemical system with
multiple baths, protected by inert gas, where the chemical
solutions are transferred there and back between different chemical
tanks and an electrochemical cell. Multiple layer depositions in
nanometer-range, are produced on a substrate which stays on a fix
position for all the deposition cycles inside the electrochemical
cell. The transfer method protects the system against the cross
contamination between different chemical solutions and the risk of
contamination of the chemical solutions on their way to and from
the chemical tanks. The cleaning method protects the deposited
layers against undesirable surface reactions.
[0034] In order that the present invention may be more fully
understood, it will now be described by way of example and with
reference to the accompanying drawings in which:
[0035] FIG. 1 shows a block diagram of the modular designed
multiple bath electro-deposition system;
[0036] FIG. 2 shows a schematic diagram of the system in which are
showed only two of the transfer subsystems to be easily
understandable; FIG. 3 shows a schematic diagram of the cleaning
part of the system.
[0037] FIG. 1 illustrates different functional blocks of the
multiple bath electro-deposition apparatus according to the present
invention. The computer 9 using the electrochemical process control
equipment 8, for example a potentiostat and/or galvanostat,
controls the electrochemical deposition process. The future role of
the computer 9 is to control the different steps of the multilayer
electro-deposition. The main parts of the system are the
electrochemical subsystem 7 and the transfer subsystems 1, 2, 3
etc. The electro-deposition of the thin multilayers on a substrate
takes place in the electrochemical subsystem 7. The number of the
transfer subsystems is not limited, such that the system is
modular. Their number is a function of the number of different
types of desired layers in the multilayer structure. After each
deposited layer, the electrochemical subsystem is cleaned and
rinsed with ultra pure water using the cleaning part of the system
composed by evacuation and cleaning part 6 and one of the transfer
subsystems for instance 3, which has the role to remove the water
from the electrochemical cell.
[0038] The operation sequences for one electro-deposition cycle
consist on the following steps: the chemical solution is
transferred from the desired chemical tank to the electrochemical
cell; then, the electro-deposition process takes place controlled
by computer; next, the solution from the electrochemical cell is
transferred back to the chemical tank for future reuse; next, the
cleaning process of the electrochemical cell is carried out. The
multilayer-electro-deposition consists of several cycles, as
described above, the cycles being controlled in an automatic mode
by computer.
[0039] The principle of the transfer operation is illustrated in
FIG. 2 which shows only two of the transfer subsystems 1, 2 and the
electrochemical subsystem 7. For example the transfer sequence from
the chemical tank 10 to the electrochemical cell 70 consist in
starting to increase the inert gas pressure in the chemical tank
10, opening a gas-in electrovalve 12 whereupon a chemical solution
starts to flow through the transfer pipe 18 first to the separation
chamber 15 than when it is filed, through the next pipe 19 to the
electrochemical cell 70; next, when the level of the liquid is
sufficient in the electrochemical cell 70, the gas-in electrovalve
12 is closed; next, opening the gas-in electro valve 17 of the
separation chamber 15 and the vacuum-out electro-valve 14 of the
chemical tank 10 the solution from the separation chamber 15 is
transferred back to the chemical tank 10 and in parallel the
transfer pipe 19 between the separation chamber 15 and the
electrochemical cell 70 it becomes empty. During the transfer from
the chemical tank 10 to the electrochemical cell 70, in all the
rest of the transfer subsystems the gas-in electrovalves for the
separation chambers are opened for instance the electrovalve 27, 37
respectively FIGS. 2,3. The inert gas flowing through the transfer
pipe 29, 39 respectively (FIGS. 2,3) on the electrochemical cell 70
keeps the purity of the different chemical solutions preventing the
cross contamination between the newly transferred solution on the
electrochemical cell 70 and the solutions in different chemical
tanks for instance 20, 30 respectively (FIGS. 2,3). The excess
inert gas from the electrochemical cell 70 flows out through the
evacuation pipe 63, the evacuation chamber 60 and the evacuation
duct 64. The role of the evacuation chamber 60 is to keep the
electrochemical system closed and under protective inert gas. When
this transfer operation is finished, one step of the
electro-deposition process can take place.
[0040] A step of the electro-deposition process consists in
deposition of one layer on the substrate using normal
electro-deposition technique or multiple layers using the single
bath electro-deposition technique. By carrying out both techniques
in the same electrochemical system, the possibilities to realize
different kinds of multi layered structures become virtually
unlimited.
[0041] When the electro-deposition step is finished, the chemical
solution is transferred from the electrochemical cell 70 back to
the chemical tank 10 for future reuse. The transfer sequence
consist in keeping an inert gas overpressure in the electrochemical
cell 70 in all the. transfer subsystems, except this one, opening
the gas-in electrovalves for the separation chambers, for instance
the electro valve 27, 37 respectively in FIGS. 2,3; then opening
the vacuum-out electrovalve 14 whereby the solution starts to flow
through the transfer pipe 19 at first to the separation chamber 15
and then through the next pipe 18 to the chemical tank 10; next,
when the electrochemical cell 70 is empty, closing the vacuum-out
electrovalve 14 and also closing, in all the rest of the transfer
subsystems, the gas-in electrovalves for the separation chambers,
for instance closing the electro valve 27, 37 respectively in FIGS.
2,3.
[0042] The transfer procedures on all other transfer subsystems
between different chemical tanks and the electrochemical cell 70
follow the same above described sequences. When the transfer is
finished and the electrochemical cell is empty, the next step is
the cleaning procedure. This step is illustrated in FIG. 3 and
starts with opening the electrovalve 62 whereby the ultra pure
water starts to flow through pipe 61 filing the electrochemical
cell 70 and; in parallel, the previously used water from the waste
water tank 30 is transferred also to the electrochemical cell 70
using the previously described transfer sequences. The excess water
from the electrochemical cell 70 flows out through the evacuation
pipe 63, the evacuation chamber 60 and the evacuation duct 64;
where the duration of flowing the pure water is in agreement to the
volume of the electrochemical cell 70. After a certain time, the
electrovalve 62 is closed and the water from the electrochemical
cell 70 is transferred to the wastewater tank 30 using the
previously described transfer sequences. In order to increase the
efficiency of the cleaning process some of above described cleaning
sequences can be repeated. When the cleaning process is finished,
the next electro-deposition cycle can follow.
* * * * *