SC26 Magnetic Field Cancelling System
The SC26 is a wide bandwidth system that can cancel magnetic fields from DC to above 9 kHz. To achieve its wide bandwidth, the SC26 uses low inductance field cancelling cables, installed in the electron beam tool enclosure. Wafer transport robots in 300mm wafer fabs. make 9 kHz fields that limit the performance of electron beam tools and are a barrier to achieving the next semiconductor CD node.
Manufacturer
Spicer Consulting
Spicer Consulting has built a world-wide reputation in magnetic field cancelling for electron microscopes and similar instruments. Today, working with equipment manufacturers and users alike, the company is recognised as an industry expert in maximising the performance of electron microscopes, electron beam lithography systems, CD-SEM and focused ion beam tools. Spicer Consulting magnetic field cancelling systems protect sensitive equipment in the world's leading laboratories, universities and semiconductor manufacturing plants, as well as in the test facilities of electron and ion beam equipment manufacturers. Its magnetic field, vibration and acoustic analysis systems have been adopted as standard equipment for the conduct of site surveys by leading equipment manufacturers.
Key Features
- Makes the ambient magnetic field “OK” for electron beam tools in 300 mm wafer fabs
- Real time, wideband cancelling from DC to > 9 kHz fields
- Adapts to field amplitude and frequency changes within 10 μs
- Touch screen intelligent user interface with automatic setup and DC reset
- Simultaneous AC & DC field display with choice of Tesla or Gauss units
- Mixes dual sensors to create virtual sensor “inside” the EM column
- Built-in test field generator
- Ethernet and USB ports for remote operation and monitoring
Overview
The SC26 has inputs for two 200 kHz AC field sensors (blue) that it can mix to optimise the electron beam tool performance. These provide useful cancelling down to 10 Hz. Cancelling can be extended down to DC by adding a “Sensor SC24/DC+AC” and a sensor combiner for each input channel used.
The SC26 cannot be used with larger cables in a “room” installation like our SC24 system which operates at lower frequencies. system.
Touch Screen Display
The SC26 user interface is a touch screen LCD display panel. This is a typical display for an SC26 with one or two “Sensor SC26/AC” when the system is cancelling and the field is OK. The DC field values are not displayed because no DC sensors are installed.
The “Reset” button clears the “trip” indicators and resets the “zero field” operating point of the DC sensors. The “Cancel/Standby” button turns cancelling on and off. Magnetic field amplitudes are displayed with 100pT (1.0 μGauss) resolution. The DC field amplitudes are only displayed for DC sensors.
Adjustment Menu
The “adjust” button enables entry to the adjustment menu (for expert users), typical display in Fig. 2. It also gives the option to “lock” the touch screen and reset the Ethernet password. When the screen is “locked” the five buttons are replaced by a new button that allows unlocking if pressed for five seconds.
The “Mixer”, “Auto Reset”, “Field Generator” and “Trip Level” touch buttons control the adjustments.
Downloads
Brochure for the full SC26 system
Which Magnetic Field Cancelling System Is For You?
Options
Field cable installation
To specify the installation of the SC26 system we have chosen typical enclosure dimensions of 1.75x1.75x 2.0 metres. (For actual tool dimensions, we consult with the tool manufacturer.) The 1 metre spacing between the cable loops is optimum to generate the best uniform field inside the enclosure. The loops are centred on the electron beam column. The cables are deliberately not attached along the frame edges. Tool frames typically have welded or bolted construction which can create a closed conducting loop. Attaching the cables to this loop creates an air-cored transformer that can short out the cancelling field at frequencies above about 100Hz. See the SC26 user manual for details of this effect.
Minimal Installation
A simpler minimal installation with single loop cables that has been used with the previous SC20Fast system. The field uniformity is poor but useful improvement in the tool performance can often be obtained by careful choice of the sensor position. The cables are shielded and have 4 cores. They are 5.0mm diameter.
Sensor SC24/DC+AC
Contains small Helmholtz coils that surround its field sensing elements. They are used to offset the DC component of the ambient field including the earths field. At reset, the microcomputer in the sensor adjusts and remembers the currents in the coils to set the X, Y, Z sensor outputs to zero. The reset process takes 1 second. The sensor must be reset if it is moved. The electron beam tool may make large DC fields during its operation, for example when loading wafers. These fields may overload the field cancelling system. The SC26 can detect the overload and automatically reset the sensor outputs.
Sensor SC26/AC
With Sensor AC26/AC the SC26 provides useful cancelling from 2.5Hz to 5kHz. The ratio of the ambient field to the cancelled field is called the cancelling factor. It is a function of frequency and is greater than 50 at 60Hz. Adjusts to the new DC level automatically but the transient may overload it for several seconds. There may be image position drift until the sensor adjusts.
SC26 Sensor Combiner
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