The invention relates to system for organic devices fabrication under oxygen free
ambience.
FIELD OF INVENTION:
The invention particularly relates to chemical or polymer chemistry. Particularly,
it relates to spin coating or deposition of contact layer of devices such as Organic
LEDs and Organic solar cells in oxygen free ambience. More particularly it relates
to contact layer deposition without taking the device out and then placing it inside
a vacuum chamber for deposition of different layers. The device of the present
invention involves integration of oxygen free chamber and thermal evaporation
system and employing a unique transfer mechanism.
BACKGROUND OF THE INVENTION:
The oxygen free glove box is important equipment for chemical and polymer
processing in order to avoid any deleterious effects of oxygen. This is also true for
making devices like Organic LEDs and Organic Solar Cells in order to make
stable and high efficiency devices. Most of the devices require the preparation of
an organic layer and contacts ( transparent conducting oxide and metal layers).
The contact layer deposition is often done by taking the device out and then
placing it inside a vacuum chamber for deposition of different layers as required
to make a good low work function contacts. In order to prevent the oxygen
exposure during this process, it has been a normal practice to enclose the vacuum
system for deposition inside another oxygen free glove box , with an
interconnectivity between the two glove boxes so as to ensure that the device
remains under oxygen free ambience throughout the fabrication. However, this
means use of two oxygen free glove boxes with added cost of equipment5 as well
cost of operation and maintenance of the glove boxes.
It was identified that it is a normal practice in vacuum technology to have a cluster
of thin film deposition systems with a facility to transfer the substrates from one
vacuum chamber to the other without causing breakage in the vacuum except for a
short time during the transfer.
The prior art known to the best of the knowledge of the inventors include US
2005 0252455 ('455) A1 published on November 17, 2005. '455 discloses a
substrate transfer mechanism for transferring a substrate includes a mounting table
on which the substrate is mounted; an arm member connected to the mounting
table and moving it. The substrate transfer mechanism further includes a
temperature control unit for controlling temperature of the mounting table,
wherein the temperature control unit forms a temperature gradient in the mounting
table. The ternpemture control unit includes a detector for detecting temperature in
an environment or a chamber in which the substrate transfer mechanism is
installed a heater for heating the mounting table and a controller for controlling an
operation of the heater based on the temperature in the environment or the
chamber detected by the detector. According to '455 conventionally, as a substrate
processing system for performing various plasma processing, such as an ion
doping process, a film forming process and an etching process, on a substrate,
there has been known a cluster type substrate processing system wherein plural
processing apparatuses are disposed radially around a common substrate transfer
chamber. The draw back of this system as highlighted in the said patent
application is: "However, in case the substrate is continuously processed by using
the aforementioned cluster type substrate processing system, when the handling
unit 157 transfers the substrate, particles transferred into the substrate transfer
chamber 154 by the handling unit 157 together with the substrate and/or
particles, cut powder, produced upon the operation of the handling unit 157 are
attached to the substrate. As a result, for example, in an etching process, the
attached particles serve as a mask to cause an etching deficiency. Further, in a
film forming process, the attached particles serve as a core to grow, resulting in
deterioration in quality offilm. "
OBJECTIVES:
The main objective of this invention is to provide a system for organic devices
fabrication under oxygen free ambience and a process for fabrication using the
said system substantially obviating if not totally eliminating the drawbacks of the
existing devices and system.
It mainly includes oxygen free glove box, thermal evaporation system and a
transfer mechanism for transfer of devicelsubstrate intended to be coated under
oxygen free ambience between an oxygen free chamber and a thermal evaporation
system for thin film coating. The oxygen free chamber i.e. glove box and a
vacuum chamber used as thermal evaporation system are integrated with each
other that enables the transfer mechanism to transferring substrate in forward and
reverse directions without getting exposed to the atmosphere containing oxygen.
The other objective is to eliminating engaging two oxygen free glove boxes.
Another objective is to provide a transfer mechanism for transferring
device/substrate intended to be coated without taking the device out of glove box
and then placing it inside a vacuum chamber for deposition of different layers.
Yet other objective is to provide a system wherein the use of second oxygen free
glove box to house the vacuum chamber is eliminated. The glove box and vacuum
chambers are placed adjacent to each other and connected with the mechanical
arm of the present invention.
DESCRIPTION OF THE FIGURES
FIG. 1. depicts the block diagram of the entire system comprising (i) oxygen free
glove box, (ii) thermal evaporation system /vacuum chamber, and (iii) transfer
mechanism.
STATEMENT OF INVENTION:
Accordingly the present invention provides a system for organic devices
fabrication under oxygen-free ambience comprising:
(i) oxygen fiee glove box,
(ii) thermal evaporation system, and
(iii) transfer mechanism
-wherein the oxygen free glove box and a thermal evaporation system are
integrated with each other, and
-where in the transfer mechanism is capable of inducing bidirectional
movement.
According to one of the inention, the oxygen free glove box comprises (a) anti
chambers A1 and A2, (b) PLC control-P, (c) quartz window -w, and (d) spin
coater S.
According to the other embodiment of the system, the thermal evaporation system
comprises (i) vacuum chamber, (ii) electrodes for thermal evaporation-
ElE2,(iii)penniug gauge-PG, (iv) cold cathode-CC, (v) viewing window W2, (vi)
substrate receiver-SR (vii) valve V1 for gas (02, N2 etc.) ingress, (viii) vacuum
valve- Vac and (ix) closed port G2 for possible extension to the system.
According to the yet other embodiment of the system, the transfer mechanism
comprises: (i) gate valve G1 for integrating oxygen free glove box and a thermal
evaporation system while keeping them in isolation, (ii) substrate holder SHY (iii)
stepper motors Mland M2, (iv) supporting rods Rland R2, (v) crown pinion gear
and holding arm A.
The invention also provides a process for organic devices fabrication under
oxygen-free ambience using the said innovative system comprising steps :
a. subjecting pre-cleaned substrate, intended to be coated, to oxygen plasma
treatment in vacuum chamber,
b. coating the plasma treated substrate with a hole transport layer followed by
subsequent annealing outside the system as claimed in claim 1
c. transferring the substrate to oxygen free glove box for absorber layer
deposition and subsequent annealing
d. spin coating the absorber layer on the substrate coated with the hole
transport layer and then annealing ,
e. transferring the substrate to vacuum chamber for metal(s) deposition for
contact making in oxygen free ambience engaging transfer mechanism,
f. bringing back the substrate in oxygen free ambience engaging transfer
mechanism to glove box for characterization.
The process as disclosed herein above provides bidirectional transferring of
substrate in oxygen free ambience by forward and backward movement of
sample holder using stepper motors, supporting rods and crown pinion gear and
coordinating opening of gate valve.
DETAILED DESCRIPTION OF THE INVENTION.
As hereinbefore disclosed, the currently employed vacuum technology for coating
thin film requires transfer of substrateldevice from one vacuum chamber to glove
box or vice-a versa thereby causing breakage in the vacuum at least for short time.
Also it may be worthwhile to point out that though the vacuum chamber is housed
in a second oxygen free glove box, the device has to be transferred mechanically
from one glove box to other. As such the exposure of the device to the
environment where the process of coating is performed can only be minimized but
can not be avoided.
Therefore, it was proposed to integrate the oxygen free glove box with the thermal
evaporation system wherein thin film deposition is carried out, using a suitable
transfer mechanism. The substrate after fabrication in the oxygen free ambient is
put on the transfer mechanism to be transported to the vacuum system thereby
preventing exposure of substrate to oxygen containing ambiance at the same time
avoiding engaging additional glove box. Appropriate pressure balance between
the two sides is achieved using any conventional means including PLC so as the
transfer takes place in either direction only when the gate valve is opened.
This strategy has the advantage of using a 'passive' transfer mechanism to achieve
the interconnection and avoid the use of another oxygen free glove box. The
transfer mechanism requires suitable motor drive for making the transfer which
does not require any extensive maintenance. The gate valve ensures that the two
chambers are isolated for normal independent operation and the transfer from one
to the other takes place in either direction as and when required.
The inventors have designed the noel system by integrating two units and transfer
mechanism and the complete system got fabricated (the oxygen free glove box,
the thermal evaporation system and the transfer assembly ) from MIS MILMAN
THIN FILM SYSTEMS PVT. LTD.,Vishwachhaya Industry Road, Gat No.
322lAI1 & 2, Pirangut, Tal. Mulshi, PUNE 412 11 1. {Contact Person - Dr. Milind
Acharya. The equipment has been tested for fabrication of organic solar cells and
the results are encouraging.
The invention thus provides a system employing new technological method for
doing the transfer between an oxygen free glove box and a vacuum
chamberlthermal evaporation system for complete device fabrication without
taking out of the glove box and exposing to the atmosphere containing oxygen.
The device can then be brought back into the oxygen free chamber for
characterization. The equipment has a quartz window for making the light from
solar simulator incident on the organic solar cell, e.g., packaging and stability
studies in totally oxygen free ambient. The packaged device can also be
transported to the vacuum system for degradation studies under different
illumination, temperature and ambient gas conditions. All these studies can be
conducted with ease since the transfer does not involve another oxygen free
chamber.
Therefore, the design of our equipment has salient features of compactness,
flexibility and expandability.
As can be seen from the block diagram depicted in figure 1, the system comprises
of three units (i) A- glove box (ii) B- thermal evaporation system and (iii)
Transfer mechanism. The glove box comprises anti chambers A1 and A2, spin
coater S, quartz window W1 and PLC control P for controlled operations of A, By
and transfer mechanism.
Thermal evaporation System consists of vacuum chamber equipped with of SRsubstrate
receiver, CC- Cold cathode, PG- Penning Gauge, Vac- Vacuum valve,
V1- Purge valve for N2 ingress, W2- Viewing Port, El, E2- Electrodes for
thermal evaporation and G2- valve for possible extension on other side.
The Transfer Mechanism comprises mechanical arm Al, GI- Gate valve for
integration of glove box and vacuum chamberlthermal evaporation system,
R1 ,R2- Motor Shafts and supporting rods, MI, M2- Stepper motors, CP- Gear
arrangement for linear substrate motion, SH- substrate holder.
Thus, the mechanical arm consists of (i) a substrate holder (single or multiple
substrates covering 10 cm x 10 cm) supported on two rods mounted inside the
oxygen free chamber. A movement arm to drive the substrate(s) is carried out
using two motors mounted outside the chamber on the top engaging rods Rl,R2,
PLC and a gate valve which allows the transfer after the pressure equalization by
means of a control valve for leaking appropriate amount of Nitrogen. A substrate
support is provided inside the vacuum system so as to place the transferred
organic layer coated substrate(s) correctly above the thermal evaporation source(s)
for making the contact coating(s) and (v) a PLC controller which ensures that the
transfer mechanism work perfectly in order to prevent any oxygen exposure and
also there is no damage to the transfer mechanism or gate valve or the oxygen
free chamber or the vacuum system in case of any untoward incident (power
failure, e.g.).
The mechanical arm is supported in the oxygen free chamber with supporting rods
having proper sealing in order to prevent air ingress. The motor shafts provide bidirectional
movement of substrate. The motor movement is translated into a linear
motion to transfer the substrate from the oxygen free chamber to the vacuum
system and to transfer the substrate from the thermal evaporation vacuum system
B to the oxygen free chamber i.e. glove box A and there is also a small up/ down
movement for the substrate holder. The up / down movement is used to deposit
the substrates inside the thermal evaporation vacuum system for contact formation
(the arm is withdrawn so as to create the required vacuum conditions for metal
etc. evaporation) and later to lift the substrates back on the transfer arm (the arm is
brought into the thermal evaporation/vacuum system after the deposition is
completed) for bringing it back to the oxygen free chamber for further device
processing and characterization. It may also be possible that for certain treatment
first done inside the vacuum system ,the transfer arm first takes the substrate in
the reverse direction, then after coating the organic layer (by spin coating e.g.) , it
can be moved in the forward direction and brought back into the vacuum chamber
for contact formation. The next reverse direction can be for moving the device
inside the oxygen free chamber for characterization. Some of the devices may be
kept inside the oxygen free chamber for degradation studies and some can be
taken back into the vacuum chamber (Forward transfer) for encapsulation coating
or degradation study under vacuum or other ambient conditions. This way,
forward and reverse motion can be repeatedly done after suitable time intervals
needed for device processing. Since the transfer is done without involving a
second oxygen free chamber , the repeated transfer does not cause any difficulty
and additional maintenance issues involved in an oxygen free chamber.
Since there is dealing with two different pressure situations with the oxygen free
chamber at nearly atmospheric pressure and the thermal evaporation system under
vacuum, the transfer has to be done carellly so as to achieve oxygen free ambient
condition during the transfers. The equalization of the pressures in the two
chambers requires controlled admission of nitrogen in the vacuum chamber till the
gate valve can be opened. The PLC ensures that the transfer takes place when the
gate valve is l l l y opened by actuating the motors to move the transfer assembly
towards the vacuum system for metal contact deposition, for example and towards
the oxygen free chamber for device characterization, for example. In either case
the gate valve is kept opened till the transfer assembly has deposited the
substrate(s) at the desired place and withdrawn inside the oxygen free chamber. In
order to ensure the assembly does not get stuck during transfer and the gate valve
closes (which will damage the system), the operation is done using online UPS to
avoid such a situation during power failure. The speed of operation is controlled
by varying the motor speed and the transfer results in lowering the sample at the
deposition area for contact formation within a short time. Then the transfer
mechanism is withdrawn and the vacuum system is operated to achieve the
conditions required for substrate treatment , contact(s) deposition etc. Once this
process is completed, the transfer process is initiated by flooding the vacuum
chamber with Nz to achieve the gate valve opening and letting the transfer
assembly lift the substrate and bring it back to the oxygen free chamber. Clearly
the two side s of the transfer assembly is maintained under oxygen free condition
without having to place it inside oxygen free chamber as is normally done.
Therefore, our system achieves the stated purpose of keeping the organic device
under all the processes needed for device fabrication, characterization and
packaging etc. The automatic control under PLC control ensures that the proper
condition is maintained under transfer and also keeps the system safe to avoid any
untoward incident cause by power failure.
As can be seen from the foregoing the unique features of the system are as
follows:
1. It is made of two independent units viz (1) a glove box and (2) a vacuum
system. The two are integrated together to achieve sequential operation of spin
coating and thin film deposition repeatedly, if needed.
This offers comfortable flexibility of operation.
2. This configuration differs from the conventional systems wherein the
vacuum system is placed inside the glove box. This restricts the flexibility of
operation
3. In our design the sample can be transported back and forth for spin coating,
thin film deposition, patterning, making contacts, protective coating etc.
4. The unique transfer mechanism can lift the sample from the glove box,
transport it to the vacuum system and bring back to the glove box as and when
required and this operation can be repeated as many times as needed.
5. Our system provides operational independence. The optical properties and
the solar cell characteristics can be measured in the glove box. The electrical and
optical properties can be measured in the vacuum system in situ.
6. The vacuum system can be easily isolated, opened to atmosphere, cleaned
up, fixtures can be changed, samples and other evaporating materials can be
loaded without disturbing the glove box.
7. The vacuum system can be Mher expanded with the help of a gate valve
for additional operations.
ADVANTAGES:
1. It offers comfortable flexibility of operation as is made of two independent
units viz (1) a glove box and (2) a vacuum system. The two are integrated together
to achieve sequential operation of spin coating and thin film deposition
repeatedly, if needed.
2. Is cost effective and provides flexibility of operation
3. Facilitates multiple transactions in both directions from glove box to vacuum
chamber while maintaining Oxygen free ambience
4. The optical properties and the solar cell characteristics can be measured in the
glove box. The electrical and optical properties can be measured in the vacuum
system in situ.

WE CLAIM:
1. A system for organic devices fabrication under oxygen-fiee ambience
comprising:
(i) oxygen fiee glove box,
(ii) thermal evaporation system, and
(iii) transfer mechanism
-wherein the oxygen free glove box and a thermal evaporation system are
integrated with each other, and
-where in the transfer mechanism is capable of inducing bidirectional
movement.
2. The system as claimed in claim 1, wherein the oxygen free glove box comprises
(a) anti chambers A1 and A2, (b) PLC control-P, (c) quartz window -w, and (d)
spin coater S.
3. The system as claimed in claim 1, wherein the thermal evaporation system
comprises (i) vacuum chamber, (ii) electrodes for thermal evaporation-
ElE2,(iii)penning gauge-PG, (iv) cold cathode-CC, (v) viewing window W2, (vi)
substrate receiver-SR (vii) valve V1 for gas (02, N2 etc.) ingress, (viii) vacuum
valve- Vac and (ix) closed port G2 for possible extension to the system.
4. The system as claimed in claim 1, wherein the transfer mechanism comprises:
(i) gate valve G1 for integrating oxygen fiee glove box and a thermal evaporation
system while keeping them in isolation, (ii) substrate holder SH, (iii) stepper
motors Mland M2, (iv) supporting rods Rland R2, (v) crown pinion gear and
holding arm A.
5. A process for organic devices fabrication under oxygen-free ambience
comprising:
a. subjecting pre-cleaned substrate, intended to be coated, to oxygen 2 0 DEC 20'3
plasma treatment in vacuum chamber, * --;.,\ BL
b. coating the plasma treated substrate with a hole transport layer followed, ,, 3 8 "' '
by subsequent annealing outside the system as claimed in claim 1
c. transferring the substrate to oxygen free glove box for absorber layer
deposition and subsequent annealing
d. spin coating the absorber layer on the substrate coated with the hole
transport layer and then annealing ,
e. transferring the substrate to vacuum chamber for metal(s) deposition
for contact making in oxygen free ambience engaging transfer
mechanism,
f. bringing back the substrate in oxygen free ambience engaging transfer
mechanism to glove box for characterization.
6. The process as claimed in claim 5, wherein the bidirectional transferring of
substrate in oxygen free ambience is carried out by forward and backward
movement of sample holder using stepper motors, supporting rods and crown
pinion gear and coordinating opening of gate valve.
Dated this &* day of December 20 13.
Mrs. L. Balasubrahrnanyam
Applicant's Authorized Agent