Abstract:
Rorze shutter type N2 purge LP (Patent pending) offers a highly stable humidity control for wafers in FOUP at better than 2% RH with FOUP door open on the EFEM. Even during wafer load and unload the humidity does not fluctuate. This is accomplished while consuming 1/3 to ½ less in volume of Nitrogen. A typical LP in contrast can only manage humidity at no better than 30% RH and consumes higher volumes of N2. Increased N2 consumption will increase N2 exposure hazard and other issues.
With the advances in technology node, and the advent of 3D process, if wafer is exposed to even low levels of moisture/humidity while sitting in the FOUP during process step, it is a cause for concern now. To mitigate the negative impact of O2 and Humidity, N2 purge LP is adopted. However a typical N2 purge LP as noted above is unable to offer better than 30% RH average and fluctuates during wafer load and unload sequence, where the wafer acts as a guide to move FFU flow in to the open FOUP. So high flow of N2 is set to minimize the impact of FFU on the open FOUP.
In order to reduce the wait time on tool and to minimize wafer exposure to these levels of humidity, it has been known for wafer fabs to reduce the number of wafers in a FOUP. This would mean added wafer moves that stresses the already burdened OHT and can actually further delay wafer delivery. In addition increased wafer moves means added risk and cost involved in wafer handling.
However with Rorze patented shutter type N2 purge LP, one can accomplish very low (<2%) and highly stable humidity control with FOUP door open on the EFEM and even during load and unload. This is accomplished by Rorze’s design of shutter like mechanism that will be in front of the FOUP. Even with the FOUP door open, shutters will be blocking the FFU flow going in to the FOUP as the shutters will stay closed. At the instance of load or unload, only a single shutter 9mm tall will open at a specific slot near the FOUP that needs access for handling. This will allow a low N2 flow in the FOUP to combat the FFU impact on the FOUP. Hence we are able to provide a highly stable environment and much lower levels of moisture than a traditional N2 purge LP. Rorze shutter type N2 LP is BOLTS compatible and can be easily integrated to any process tool.
We believe this will likely be the only way for the 3D process and advanced nodes to reach the humidity levels during process to address defect and yield related to humidity in FOUP during process wait.