Process Development and Integration within the National Center for Photovoltaics (Text Version)
This is a text version of the video "Process Development and Integration within the National Center for Photovoltaics." You can also learn more about the Process Development and Integration Laboratory and its capabilities.
In this animation, we first explain the need for process development and integration within the National Center for Photovoltaics (NCPV). Then we illustrate its conceptual implementation.
The NCPV's existing equipment for deposition, processing, and characterization systems is limited due to a lack of two things: first, a standard way of loading samples, so that they can be moved easily between functions; and second, a standard sample size, thus requiring the manual handing of samples between capabilities.
Here is a substrate that conforms to our new standard sample size of 157 by 157 millimeters—or just over 6 by 6 inches. The sample is being loaded into a frame with a back plate, or platen. The platen is placed into a load lock, where it can then be introduced into a vacuum chamber.
Before the sample is loaded into a vacuum chamber, the air is pumped out of the load lock.
This keeps the chamber from being regularly cycled to air, thus maintaining a clean vacuum environment.
Then, after opening the valve, the sample is loaded into the chamber. Shown here, the sample is being loaded into a heating stage within the chamber.
This chamber could have processing, characterization, or deposition capabilities, as in this example.
The heater is turned on to heat the sample to a desired temperature. A film is deposited onto the sample and can then be characterized. It is advantageous to measure these properties in place (or in situ), and ideally, as the sample is grown.
So we are also designing these tools to incorporate as many in-situ and real-time characterization capabilities as possible.
After deposition, the sample would normally be returned to the load lock. However, the animation now demonstrates our newest capability. Here, we see the sample being loaded into a separate mobile transfer chamber, or pod. Once the sample is loaded, the valves are closed, and processing of other samples in the chamber is now possible.
The mobile pod has a cassette capable of holding up to six samples. This allows scientists great flexibility in their research.
For example, they can make a batch of the same films and change experimental parameters further down the process sequence. Or they can first make films with different properties and then go through a standard process sequence downstream.
The pod has a battery-powered ion pump, keeping the samples in high vacuum while other samples are processed—and even when being moved between equipment.
Note that there is a valve on both the tool and the pod. Once the pod is loaded, both valves are closed and the region of small volume between the valves can be vented to air. These valves allow both the chamber and the pod to remain under vacuum when disconnected, thus controlling the sample ambient exposure.
Once the region between the valves is vented, the pod can be disconnected from the tool and wheeled to the next step in the experimental sequence. In this example, we see it being moved to a cluster tool or platform.
Once the pod is connected to the new docking location, the air is evacuated from the region between the two valves. This enables a vacuum transfer to the new tool.
The pod is now docked to a chamber that contains a vacuum-compatible robotic arm. This robotic arm can take a sample out of the pod and deliver it to any of the chambers around the circumference of the transfer chamber. There is an advantage to having a collection of capabilities around a central robotic transfer chamber. Specifically, any combination of deposition, processing, or measurements can be done in any sequence. This is in contrast to an inline production environment, where the processing sequence is fixed due to the chamber configuration matching the device structure.
The strength of process integration is the ability to move a sample between any part of the compatible equipment. This greatly reduces the exposure of a sample's surface to particulates. And it reduces reactions with molecules in the air, such as oxygen or water vapor.
This transfer can occur within a platform. Or it can occur between unconnected equipment by using the transfer pod. This is essentially the vacuum equivalent to a standard mechanical interface used by the microelectronics industry to keep silicon wafers free of particulates. But, with the added advantage of limiting surface reactions due to the vacuum transfer.
Two significant cost advantages of these micro-clean environments are that we can integrate equipment without having to build expensive cleanrooms, and that we have controlled-ambient access to expensive capabilities without needing to replicate these capabilities on platforms.
This inter-platform sample transfer is a new capability for the NCPV. And being able to do so with samples up to 6 inches by 6 inches is a unique feature.
This integrated collection of equipment assembled in the process development and integration lab (or PDIL) allows us to more quickly close the gaps between laboratory and industrial processes.
Credits: Steve Robbins, for computer-aided design and modeling. Brent Nelson, for leading the Process Development and Integration project. Al Hicks, for three-dimensional layout and animation. James Rawesthorne, for captioning. Mo Nelson, for narration. And Don Gwinner, for project coordination.
Disclaimer: This animation of the photovoltaic process integration project is provided by the National Renewable Energy Laboratory (NREL), which is operated by the Alliance for Sustainable Energy for the Department of Energy (the Government).
Reference herein, directly or indirectly, to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the Government, the Alliance, or NREL.
This animation is provided "as is" and neither the government, the Alliance, NREL nor any of their employees makes any warranty, express or implied, including the warranties of merchantability and fitness for a particular purpose, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any such information disclosed in the animation or of any apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.