FIELD OF INVENTION
The present invention relates to a carrier device to safely hold wafer during
cleaning in a hot and cold liquid medium.
BACKGROUND OF THE INVENTION
Fresh Si wafers need to be cleaned in chemicals for further processes for
converting them into solar cells. The conventional process, where diffusion
furnace is used for making a pn junction, requires these fresh wafers to be
chemically cleaned and textured using alkaline solutions. Commercially available
wafers carrier are good for carrying out these processes. For hetero junction

solar cells, the cleaning/polishing method is different and requires wafers to be
cleaned and polished chemically using hot and cold acids. This method of surface
preparation technique for hetero junction solar cells is under development and is
not known to many. Use of commercially available wafer carrier, which are used
for diffused junction process, posed number of design problems and Si wafers of
125 mm Sq. could not be cleaned and polished properly for hetero junction solar
cell chemical process. After understanding the specific requirement of the
process, a new carrier device has been made where care has been taken to hold
the carrier safely without touching any active surface of the wafer during
chemical processes. New wafer carrier device have been developed and used
successfully to carry out chemical processes for developing heterojunction solar
cells.

OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose a carrier device to
safely hold wafer for cleaning in a liquid medium which eliminates the
disadvantages of the existing state of Arts.
A further object of the present invention is to propose a carrier device to safely
hold wafer for cleaning in a liquid medium which holds a number of wafers to
clean in liquid medium at a time.
A further object of the present invention is to propose a carrier device to safely
hold wafers for cleaning in a liquid medium which saves the consumption of
liquid cleaning medium.

An yet object of the present invention is to propose a carrier device to safely
hold wafers for cleaning in a liquid medium which saves cost of cleaning of
wafers.
SUMMAARY OF THE INVENTION
The present invention is provided with carrier device to safely hold wafer during
cleaning in liquid medium comprises an 'L' shaped main frame having a movable
rectangular shaped retainer attachment mounted on the long arm of 'L' shaped
and a stationary rectangular shaped side member mounted on the long arm of'L'
shaped frame disposed in between the wafer retainer and the short arm of 'L'
shaped frame and the short arm of 'L' shaped frame is provided a plurality of
slots disposed side by side having a equidistance gap between the slots and the
parallel short arms of the stationary rectangular shaped side numbers are
provided with a plurality of slots disposed side by side having a equidistance gap

between the slots; and the wafers are placed through the side member's slot and
rest on the slots of short arm of 'L' shaped frame.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Fig.l - shows a schematic isometric view of carrier device of wafers.
Fig.2 - Shows a schematic isometric view of carrier device holding two
wafers.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in Fig.l - The carrier device comprises oblique 'L' shaped main frame
(1) having a movable rectangular shaped wafer retainer attached on the top of

the Long Vertical arm (4) and a stationary rectangular shaped side member (3)
disposed in the middle of wafer retainer (2) and short arm (5) of oblique
'L' shape main frame (1). The short arm is provided with ten slots (8)
disposed side by side maintaining an equal gap between the two slots
wherein the wafers are resting. Each slot (8) having a size of 10 mm X 3
mm X* 6 mm. The parallel two small arms (6, 7) of the stationary
rectangular side member (3) are provided with the inside ten slots
disposed side by side to accommodate wafers which prevents any
slippage or disorder. After placing ten wafers on the carrier, the top
movable wafer retainer is placed on the top to protect from any disorder.
The side member (3) is disposed at a height of 80 mm from the bottom.
The carrier device holding all the wafers are immersed in a liquid cleaning
medium. The cleaning is done by a flow of chemical cleaning agent and
texturing is done in an acid solutions. The carrier device is made of non-
reactive material like Polytetrafluoroethylene (PTFE) commonly known as
Teflon.

Silicon wafers received from the manufacturers are as cut wafers and are not
ready for further processes for making a solar cells. For developing hetero
junction solar cells, the fresh Si wafers need to be cleaned in hot and cold acids
and need a special shape of carrier which does not leave any stain on the wafer
after the process is over. After understanding the specific requirement of the
process, a new shape of the carrier has been made. Schematic of the
configuration is shown in Fig. 1. The wafers are fragile and process has
contradicting requirements for securing wafers during chemical
cleaning/polishing cycle. On the one hand the wafers need to be held loosely in
the carrier so that the chemicals reach all the surfaces uniformly and on the
other hand the wafers have to be held sufficiently firmly so that they do not fly
off due to gases generated during chemical reaction which stick to silicon wafers.
The specific shape of the carrier takes care of both the requirements. The slots
have been kept 3mm wide to allow sufficient easy passage of chemicals. A space
of about 1mm is always available on either side of the wafer for easy flow of

chemicals. The depth of the slots has been kept as 6mm which allows sufficient
movement space for the wafers and still does not allow wafers to slip out of slot.
The height of the side member, as shown in the Figures, is such that the wafers
do not touch each other even if they are inclined towards each other and hold
the wafer at a suitable height to secure them safely in vertical position by
providing sufficient support so that these wafers do not break due to the liquid
currents, generated during chemical reactions. Hundreds of hetero junction cells
have been fabricated using these wafer carriers with almost 100% yield for the
chemical process.
Fig.2 shows the carrier device carrying two such wafers (9,10) inside the device.

WE CLAIM
1. A carrier device to protect wafer during cleaning in liquid medium
comprises:
- an 'L' shaped main frame having a movable rectangular shaped
retainer attachment mounted on the long arm of 'L' shaped and a
stationary rectangular shaped side member mounted on the long
arm of 'L' shaped frame disposed in between the wafer frame and
the short arm of 'L' shaped frame;
- the short arm of 'L' shaped frame is provided a plurality of slots
disposed side by side having a equidistance gap between the slots;
- the parallel short arms of the stationary rectangular shaped side
numbers are provided with a plurality of slots disposed side by side
having a equidistance gap between the slots; and

-the wafers are placed through the side member's slot and rest on
the slots of short arm of 'L' shaped frame.
2. The carrier device as claimed in claim 1 wherein the device is made of
non-reactive material Polytetrafluoroethylene.
3. The carrier device as claimed in claim 1 wherein the carrier works on both
acidic and alkaline medium.
4. The carriers device as claimed in claim 1 wherein the slots size is 10mm x
3mm x 6mm and having a gap of 4mm between the two slots.
5. The carrier device to safely hold wafer during cleaning in liquid medium as
substantially described and illustrated herein along with accompany
drawings.

ABSTRACT

The present invention is provided with a carrier device to safely hold wafer
during cleaning in liquid medium comprises an 'L' shaped main frame having a
movable rectangular shaped retainer attachment mounted on the long arm of 'L'
shaped and a stationary rectangular shaped side member mounted on the long
arm of 'L' shaped frame disposed in between the wafer frame and the short arm
of 'L' shaped frame and the short arm of 'L' shaped frame is provided a plurality
of slots disposed side by side having a equidistance gap between the slots and
the parallel short arms of the stationary rectangular shaped side numbers are
provided with a plurality of slots disposed side by side having a equidistance gap
between the slots; and the wafers are placed through the side member's slot and
rest on the slots of short arm of 'L' shaped frame.