Wireless sensor netw ork impr o sev semiconductor wafer fab efficienc y

Right: Predicting toxic gas usage with software analytics – Real-time gas usage readings are wirelessly sent to plant software which predicts gas replenishment schedules and helps in capacity planning

wirelessly sent to plant software which predicts gas replenishment

schedules and helps in capacity planning

Left: Improving Left: Improving

manufacturing efficiency - Semiconductor

companies use real-time monitoring to squeeze

manufacturing efficiency - Semiconductor

more efficiency out of the manufacturing process

companies use real-time monitoring to squeeze more efficiency out of the manufacturing process

By Ross Yu, product marketing ger, D st N tworks prod

By Ross Yu, product et ts an

facilities manager, Linear Technology NETWORK SOLVLVES THE PROBLEM In order to solve the wiring problem

Enrique Aceves, rem te office facilities m

ritical to the manufacturing of semiconductor wafers is the

“Linear Technology’s Dust Networks products arre chips and pre-certified PCB modules complete with wireless mesh networkingetwtwo softwareware


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Linea Tec etwtwo

inear Te wi eleles

echchnololog oducts


modu es comp wirirerelessss mes soffttwtwar ”

ogy gy’s’s DusDustust

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e chip mpletete wi plelet witithth eshsh networkinrkingking ger, Linear Technol gy NETWORK SOLVES C

meticulous, precision deposition of many layers of chemical materials to formthe thousands, to millions, and in some cases, billions of transistors that make up a wide variety of complex integrated circuits (ICs). During the fabrication process of these ICs, different chemical gases are precisely metered at every step with usage varying widely as dictated by the different processes. For the most part, these steps are highly automated. What is not automated, interestingly, is the simple keeping of adequate supply of these gases.

At Linear Technology Corporation’s Silicon Valley fab near San Jose,

California, over 175 specialty gas cylinders are used in the wafer manufacturing process. These gas cylinders are closely monitored to ensure uninterrupted

supply. Any unplanned interruption of gas supply would result in hundreds of thousands of dollars of wafer scrappage, revenue loss and create unacceptable delay in product shipments to customers. To avoid downtime, technicians manually log the pressure of each gas cylinder in the fab three times a day. This manual process is prone to human error and is expensive tomaintain.


Below: Gas gloset in semiconductor

pervasive metal and heavy concrete construction

manufacturing facility – ng

perform reliably amo Wireless nodes must

Below: Gas gloset in semiconductor manufacturing facility – Wireless nodes must perform reliably among pervasive metal and heavy concrete construction

approximately eight-year runn g life on normal operation. So no additional wiring and no unnecessary downtime is required to install the network, and only infrequent periodicmaintenance is required to change out the batteries. Despite the concrete construction andme tal structures in the fab, the network has proven to be highly reliable. At time of writing, the network has been up continuously for over 83 days, and has transmitted over 26 million data packet readings with only one packet lost, which translates into

without disrupting the fabrication process, a 32 node SmartMesh IP wirelessmesh network is initially deployed tomonitor the pressure of each gas tank in the closet (below). Every node is powered by a pair of lithiumAA L91 batteries to provide for in

>99.99999 per cent reliability. This is 100 times better than the stringent ‘five nines’ reliability expected of high availability

systems. This level of network communication networks and

ensures the factory to sustain

maintenance free as well as to allow for adverse changes in the factory and RF environment.

In the gas closet, each cylinder is measured for both tank pressure and regulated pressure and these readings are communicated to a central

computer reliability

Previously, this manual datalogging was used because communications wiring is deemed expensive and impractical in the fab. Cylinders are located throughout the facility, and for most of the cylinders, there are no AC power outlets or Ethernet jacks nearby. The building is constructed of concrete walls for safety and seismic (earthquake) reasons, making it cost- prohibitive to install new wires.

manager, Dust Networks products and wires would disrupt themanufacturing Enrique Aceves, remote office

process, causing factory downtime.

Furthermore, a large construction projoject to install power and communications

Right: Predicting toxic gas usage with software analytics – Real-time gas usage readings are

monitoring systemvia the SmartMesh wireless network. Each SmartMesh node is connected to a pair of cylinders and sends readings through the wireless mesh network to a web server across the building. In the control room, the fab’s site management software tools display real-time readings and automatically calculate run rates and trend lines to predict regular schedules for cylinder replacement (left) needs. In addition, low-pressure thresholds are set to alert facility technicians should cylinders reach advanced warning levels prior to the scheduled replacement. Alerts are displayed on the control room monitor and via Internet messaging to both

facility technician and plant managemen t on a 24/7 basis .


By using real-time gas consumption rates, technicians can precisely predict when gas cylinders will need to be replaced, reducing waste from unused gas due to premature cylinder changes. The benefits extend beyond efficiencies in day-to-day operations. By centrally collecting gas usage data and making it readily available to plant management, this systemenables trend analysis which further identifies opportunities to streamline plant operations by correlating readings with specific semiconductor fab processes and geometries. This helps to optimise fab capacity growth as the need arises .


For semiconductor wafer processing facilities, optimising uptime and

increasing operational efficiency results in increased production output, improved yield and reduced down time. SmartMesh IP wireless mesh networks enable non- disruptive installation to retrofit a

running fab and monitor its gas cylinder usage. The wireless nodes fit within existing space confines and work reliably in the metal and concrete structure, while relaying real-time readings to plant management software. This data enables quick and a ccurate gas usag e estimation, ensuring timely

used to aid capacity wasted gas. Data po

www www.

Linear Technology


replenishment, reducing downtime and ints are logged and planning.

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