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Indirect Sputtering deposition device
A device that allows to replace the large evaporative cells with sputtering sources for application of CIGS deposition.
The device allows working in conditions similar to the deposition with evaporative sources, but with a greater simplicity of design, control and dimensional flexibility.
A device, according to the present description, with three magnetrons with target of pure metals (Ga target has a high efficiency cooling system), is currently used by the research team of P rof. Acciarri (firstname.lastname@example.org) , at the CIGS Laboratory of Materials Science Department at the University of Milano Bicocca to make CIGS films on rigid and flexible substrates.
The device is the subject of a European patent entitled: “Equipment and process for the production of a semiconductor film”, with registration number 13425019.0 .
Advantages of the Indirect Sputtering Device:
– Deposition of the CIGS film under the same deposition conditions by evaporative sources.
– Freedom to make the same recipes achievable with evaporative sources.
– Possibility of designing sources with large dimensions at low cost.
– Ability to work with high partial pressures of Se in the area close to the substrate.
– Low Selenium leakage from the deposition area and high utilization efficiency of Selenium.
– Metals control by sputtering deposition.
– High uniformity of the flow from the source
– Metals deposition by DC sputtering in a non-reactive atmosphere.
– Option of using either planar magnetron or rotating magnetron.
Operating principle description
The following picture shows a principle diagram of indirect deposition.
In a deposition chamber is housed one or more rotating devices (1), said "Transfer Devices" and depicted in the figure by a cylinder. At this device are associated on a portion of their periphery one or more magnetrons (3), the remaining portion of the Transfer Device faces a second zone (2), separated from the zone of the magnetron through a series of warm walls (7) suitable to confine the flow of Selenium outgoing from the cell (5) and to contain the substrate (6).
The material deposited on the transfer devices by the magnetron (3) is re-evaporated by means of a heater (4) able to focus the heat flux on a generatrix of the transfer device cylinder facing the substrate.
Transfer Device embodiment
The embodiment of the transfer device has been done as shown in the following figure.
The Transfer Device cylinder (1) is constituted by a plurality of graphite ribbons (2) of about 15 mm width separated by a gap of about 0.5 mm and kept in tension between the terminal (3) provided with tension springs and the electrically insulated terminal block (4).
The useful area of deposition for sputtering devices is represented by the arc "A", the flow of the metals from sputtering devices is confined within the area bounded by the screens (9).
The evaporation from the ribbon in position (B) takes place by direct heating.
An electric current flows through the ribbon in position (B) using the moving contact (5), the pneumatic piston (7) and the power supply electrode (6) and a collector (not pictured) plased outside on the shaft.
The movement of the Transfer Device is performed step by step by means of the servomotor (8).
Using a direct heating evaporation takes place only from the ribbon which is located facing the substrate and with the minimum of the required electrical power.
The following diagram represents:
(A) speed of rotation of the transfer device
(B) angular position of the device
(C) power supply to the ribbon
The cycle time is between 10 and 15 seconds and the time for moving the transfer device and the movement of the electrical contact is less than 0.5 s.
The temperatures reached by the ribbon are of about 1450 ° K for the evaporation of In and Ga and 1900 ° K for the evaporation of Cu.
The following picture represents an integration of Transfer Devices in a roll to roll equipment for CIGS deposition.
The following picture is related to the device being tested
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