Let's dive somewhat deeper into the process with an example how to deposit a 'p-n junction' onto a flexible substrate, which is an essential part of the photovoltaic (PV) solar cell to convert sunlight into electrons. Two silicon layers with different dopants have to be applied on top of each other in separate process chambers. In this case, the process medium is silane (SiH4) and hydrogen (H2) with a trace gas, which is phosphine (PH3) for the n-doped layer and diborane (B2H6) for the p-doped layer. To clean the vacuum process chambers between the deposition steps using a plasma, gaseous NF3 is added.
Related application story
A feature of the EL-FLOW Select thermal mass flow devices is that they can be provided with several (~5) calibration curves for different gases, which has the advantage that a relative low number of these mass flow controllers can be used - each for gases that are somewhat comparable. This efficient use of devices leads to cost reduction.
These devices are also suitable to be applied in adjacent application areas that use vacuum technology, such as the semiconductor industry, and to manufacture light emitting diodes (LEDs) for displays and lighting.