VSCS

The VSCS is a valved Selenium cracker source, employed in high efficiency CIGS solar cell growth and other II-VI semiconductor material deposition processes.

Selenium beam pressure is generated in a heated large capacity crucible. The sulfur flow rate is controlled and switched on/off by a specially designed selenium-resistant valve whose outlet opens into an injection tube that includes an independently heated cracking zone. The temperature within the cracking zone can be adjusted to generate either uncracked or cracked selenium. The use of a beam shaping nozzle at the end of the injection tube provides excellent flux uniformity on the substrate.
The valve design features a large cross-section orifice which allows very good pumping properties of the reservoir. Its robust wide angle valve design effectively eliminates the risk of locking, which is a frequently observed problem with needle valves.

Technical details of the construction have been optimized to meet the specific requirements of research deposition applications and MBE systems. Simple system integration and excellent long-term run-to-run stability have been demonstrated. Different crucible sizes of 300 cm³ or 500 cm³ are offered on DN63CF (O.D. 4.5”).

For very large capacity industrial sources please see PVSS. The figure on the right-hand side shows an industrial version, applied in selenization processes that are part of solar cell manufacturing and other industrial thin film applications.