Minimizing Energy and Resource Usage in Semiconductor Manufacturing
By Dustin Ho and Andreas Neuber
The semiconductor industry’s use of energy and other resources is increasing as wafer-processing grows more complex and as the industry expands production worldwide. In the face of rising costs and stringent government regulations, it is imperative to operate more efficiently.
The subfab currently consumes more energy than any other part of a fab, but a significant portion of it is wasted. When a production tool is idle, the pumps and abatement connected to it continue to run, needlessly increasing costs, resource utilization, and greenhouse gas (GHG) and other emissions (see figure 1).
Figure 1. The traditional priority in semiconductor manufacturing has been effective implementation of manufacturing processes. Striving to increase energy- and resource conservation in the support equipment located in the subfab has been a lesser goal. However, the wide range of subfab equipment as illustrated in the chart offers many opportunities to save energy and other resources.
To reduce this waste, suppliers of subfab equipment have implemented a variety of energy- and resource-saving solutions. One of them incorporates a hot standby idle mode in subfab control systems. More than 3,000 pieces of subfab equipment in customer fabs are connected to Applied Materials iSystem™ and predecessor control systems where this energy-saving feature has been implemented.
These control systems communicate between a production tool and its support equipment in the subfab. They receive data about tool and chamber status and the chemistries being run, and send signals matched to those specific requirements to trigger energy- and resource savings in the support equipment. Data collected by the Applied Materials iSystem controller is also used to produce resource consumption and emissions reports as needed.
However, idle mode is reactive by nature. It is designed to return support equipment to standard operating mode in less than 10 seconds when prompted so as not to interfere with a tool’s production activities. But major support equipment like pumps can’t be recovered so quickly; nor can gas or pipe temperatures be changed so fast. Therefore, idle mode can’t always be put to use, limiting the energy- and resource savings that fabs can achieve.
To overcome this limitation and also to take advantage of new opportunities provided by the increasing amount of data in fabs, Applied Materials is developing a new predictive control technology based on the requirements of SEMI standard E175.[1,2]
One of its features, now available, is a sleep mode that reduces the resource consumption of support equipment to much lower levels than is possible during hot standby idle (see figure 2). For example, savings from the use of sleep mode with thermal/wet scrubbers (TW), process control water (PCW) and power for support equipment can amount to as much as $5,000 per tool per year.
Figure 2. A sleep mode for greater energy- and resource savings in subfab equipment becomes possible when that equipment is directly connected to a tool controller for better fab/subfab synchronization and is monitored by the Applied Materials iSystem controller. The red areas in the schematic indicate additional savings sleep mode brings vs. hot idle mode in thermal/wet scrubbers (TW), process control water (PCW) and power. These savings can amount to as much as $5,000 per tool per year.
Studies conducted by Applied Materials have shown that, in practice, sleep mode could double the energy and resource savings available with idle mode (see figure 3).
Figure 3. Using a sleep mode for subfab equipment can yield double the savings available from hot standby idle mode.
A key aspect of the technology is that, for the first time, support equipment in the subfab is connected directly to a tool’s controller as well as to a supervisory control system using standardized signaling. This allows the tool controller to trigger the operation of the support equipment itself, with no risk to wafer processing.
By having the tool controller sequence the operation of the pumps, abatement and other support systems serving the tool, longer periods of tool inactivity can be anticipated. Pumps and abatement can be put in sleep mode to maximize energy and resource savings to the fullest extent possible.
Sleep mode does require a longer wake-up time than idle mode, but because timing information resides in the tool controller/fab operation system, this requirement can be predicted and taken into account.
Applied Materials is also working to integrate production and subfab data through an Applied Materials iSystem central monitoring system for even greater fab/subfab operational synchronization (see figure 4). Leveraging this data to provide tighter control opens up potential benefits in areas beyond resource savings, such as improved fab safety, maintenance management, diagnostics and fault detection, among others.
Figure 4. Applied Materials is developing a new control scheme for greater fab/subfab operational synchronization. It relies on a direct connection between subfab equipment and tool controllers using standardized signaling, and on Applied’s iSystem controller for continuous monitoring. The schematic shows the architecture of such a system, which would overlay time-stamped process information with subfab component information and external sensors to provide tight synchronization between the two systems.
Sleep mode is the next evolution in subfab control, and will reduce energy and resource consumption to the absolute minimum.
Beyond sleep mode, Applied Materials is working on a new control paradigm in which subfab data is collected and harmonized with process information so that a better understanding of potential issues can be achieved to improve operational and maintenance processes. The ultimate goal is to leverage enough data so that deep-learning algorithms can be introduced to reduce operating costs and improve operations still further.