F R A U N H O F E R C E N T E R F O R S I L I C O N P H O T O V O LTA I C S C S P
WAFERING PERFORMANCE OF STRUCTURED WIRE IN CORRELATION TO THE WIRE GEOMETRY Ringo Koepge1, Kjell Buehler1, Felix Kaule1, Stephan Schoenfelder1,3, Oliver Anspach2 1Fraunhofer 2PV
Center for Silicon Photovoltaics CSP | Otto-Eissfeldt-Strasse 12 | 06120 Halle (Saale) | Germany
Crystalox Solar Silicon GmbH | Gustav-Tauschek-Strasse 2 | 99099 Erfurt | Germany
3Leipzig
University of Applied Sciences | Karl-Liebknecht-Strasse 134 | 04277 Leipzig | Germany
Telefon +49 (0) 345 5589-5311 |
[email protected]
MOTIVATION
RESULTS
Thus, there is a high potential of improvement for the use of structure wire and consumables [1, 2] Increase process efficiency by prediction of better wire geometry for higher throughput and unchanged wafer geometry Decreased consumables (wire and slurry) by efficient relation between wire geometry to slurry composition
Wire Diameter Class [µm]
Silicon carbide particle size
SiC Structured Wire S lurry Particle S ize
F1000
F800
F600
101 µm
Run #1
Run #4
Run #7
105 µm
Run #2
Run #5
Run #8
115 µm
Run #3
Run #6
Run #9
Performance ratio indicates the best wafering performance 105µm, 115µm at F800 show best performance
𝑐𝑝 𝑟𝑝 = 𝑠𝑡ℎ𝑘
rp Performance ratio cp Preston coefficient sthk Deviation of wafer thickness
High Performance Process
Performance Ratio [µm² N-1 / µm]
Performing a set of experiments for a slurry based structured wire wafering process, varying Silicon Table speed
S tructured Wire Core Diam eter
Wire Diameter Class [µm]
F600 F800 F1000 Average
Design of Experiment
Wire core diameter
Wafer Thickness Deviation [µm]
Moreover, slurry processes are the state of the art in manufacturing of semiconductor wafers
Quantification of wafering performance by the cutting efficiency (Preston coefficient) and the wafer geometry (wafer thickness deviation) Preston Coefficient [µm²/N]
Despite growing dominance of the diamond wire process in 2017 and 2018, some PV wafer manufacturers still depend on slurry processes
Low Performance Process
Wire Diameter Class [µm]
Wire geometries change due to the wafering process Wire amplitudes (ai) decrease Wire period (Ti) increase Loss of wire tension Diameter decrease was determined Wire Period Elongation [%]
Wire Core Diameter Loss [%]
Wire Tension Force Loss [%]
Analysis of Wire Structure Measurement of wire structure for 100 mm of wire length
Identification of major wire parameters by unique Software
x-direction 0.2 mm increment Y-direction 1 µm increment
Diameter Class [µm]
Diameter Class [µm]
Diameter Class [µm]
CONCLUSION Performance ratio was established to figure out the best wafering process (in this study 105µm and 115µm wire at F800 slurry) z y x
Structured Wire Projection in xy-Plane Projection in xy-Plane
Spatial geometry of a structured wire (left) can be described by periods T1, T2 and amplitudes a1, a2 (right) resulting from the fabrication
Loss of wire tension force can be calculated by considering the change of wire parameters Clear correlation to wafering performance will be observed in additional investigations
LITERATURE [1] O. Anspach, B. Hurka, K. Sunder, “Structured wire: From single wire experiments to multi-crystalline silicon wafer mass production”, Solar Energy Materials and Solar Cells, 2014 [2] Koepge, R., Brinnig, S., Kaule, F., Schwabe, H., Schoenfelder, S., „Advanced Analysis of Multi Wire Wafering Processes“, 44th IEEE Photovoltaic Specialists Conference (PVSC-44), Washington D.C. (U.S.A.), 2017
This work was supported by the German Federal Ministry of Education and Research within the research project MechSi (contract no. 03IPT607X).
