COVERSTORY
Having experience with these processes in the semiconductor industry, abatement manufacturers had to scale up their tools to meet the requirements of the solar industry with the corresponding higher gas volumes
Having a closer look on the processes required for PV manufacturing it becomes obvious the need for public consultation to explain the industry need but more importantly, the ability of technology to deal with the potentially dangerous materials. The outcomes from such consultations has ensured that EHS (Environment, Health & Safety) standards are helping to protect employee’s health, improve production processes and contribute to protecting the environment.
Thin Film Technologies Thin Film Technologies such as amorphous silicon (a-si) and micromorph silicon (mc-si) create difficult waste gases in the following three areas:
Deposition: When a thin film of silicon is deposited on a substrate. Abatement tools need to treat the waste products from the process tool. These could include unreacted Silane (SiH4) and dopants such as Phosphine (PH3), Trimethylborane (TMB) and Diborane (B2H6) which are exhausted from the process tool.
In-situ Cleaning: The reaction chamber needs to be periodically cleaned to prevent build up the deposition materials within the
chamber.This is typically achieved using gases such as Sulpur hexafluoride (SF6) or Nitrogen trifluoride (NF3). This cleaning step prevents the build up of rest material on the inside wall of the process chamber which can result in defects caused by particles dropping on to the substrate.
Front/Back contacting: A transparent conductive layer is deposited on to the substrate. After this deposition step, gases such as Diethylzinc (DEZ) need to be treated.
Having experience with these processes in the semiconductor industry, abatement manufacturers
had to scale up their tools to meet the requirements of the solar industry with the corresponding higher gas volumes. One key development is that of a clogging resistant abatement tool due to the high volumes of silane (SiH4). This important process was key to master by abatement suppliers in order to protect the waste gas inlets, the burner and exhaust pipes from clogging. The change from SF6 to NF3 as chamber cleaning gases and the increased flow rates were also big challenges.
While all the three steps mentioned above can be abated with
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www.solar-pv-management.com Issue V 2011
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