FTA2000 Multi-Fluid Programmable Analyzer
The FTA2000 was completely re-designed in 2002. As its predecessor, it provides a high level of automation to characterizing surfaces of high value products such as silicon wafers, disk platters, and LCD panels. Contact angles, wetting tensions (cosine of contact angle times surface tension of fluid), and surface energy measurements can now be easily made over 2-D surfaces. The instrument makes point measurements on a grid covering the surface, then software computes a topographic map of the surface to assist in visualizing how the surface chemistry varies from one location to another.
Each individual point measurement is made by placing a drop of test fluid on the surface and capturing the drop profile image as a function of time. Image analysis automatically provides the contact angle. The wetting tension is then computed directly. One or more contact angle measurements (perhaps with different fluids) are combined to make a surface energy measurement.
A grid of typically 50 to 500 points is laid out on the surface and a measurement made at each point. While the data set can be simply treated statistically (by mean, variance, etc.), often patterns reveal systemic variations across the surface which are of interest to process engineers. Built-in 3-D graphing facilitates visualizing these.
Semiconductor and disk surfaces are non-absorbing, so one would expect their contact angles to be static. However, the drop will spread slowly on many surfaces as the test fluid interacts with surface to change it. When water is the test fluid, this is called hydration. The FTA2000 uniquely can carry carry out this time-domain analysis for each point on the grid.
While the instrument can be run manually in the normal fashion, it also has a Sequencer that can be programmed to carry out repetitive measurements. The Sequencer is a script interpreter, much like a simple Basic. A Sequencer script can be be saved as a file and loaded when desired. The script language includes all of the capabilities present under manual operation, plus subroutines and loops. It also has the capability of communicating with external robots to control loading of new samples.
An R-theta-Z stage moves the desired grid point under the dispense needle. Rather than a Cartesian X-Y-Z stage, the FTA2000 employs a rotating stage (through 360 degrees), which in turn is carried on a linear stage for R. There is a 25 millimeter Z stage. This combination enables the instrument to handle relatively large samples in a small footprint on the benchtop. Any point can be reached within a 12 inch or 300 millimeter diameter circle. This arrangement is particularly effective for round specimens. However, the stage can be programmed in Cartesian X-Y coordinates, which is more convenient for rectangular specimens.
The FTA2000 now incorporates a rotary autosampler with six independent arms and tips. The tray holds 17 standard vials. Any tip can reach any vial. The pump is connected to one of the six tips through a 6-way distribution valve. The way the system is organized, sample fluid never reaches further into the system than the disposable Luer hub needle. System fluid, DI water, is self-primed by the pump and is always separated from sample fluid in the tip by a small airgap. This provides the best of all possible worlds: no syringe to clean, no syringe to fill, sample fluid only touches disposable tips and the system is self-priming.
The robot picks up just enough test fluid from a reservoir in the tip, then carries it to the measurement location where it is dispensed. After the measurement is completed, as much fluid as possible is picked up from the surface and taken to a waste station. The pipette will handle drop volumes from 3 to 10 microliters with 0.1 microliter resolution.
Clean Room Compatibility
The FTA2000 is designed from the start to be compatible with clean rooms. Airflow may be directed through the enclosure to capture particles and prevent them from falling on the specimen.
The entire instrument is enclosed for protection against unwanted air currents and rapid variations in room temperature. As an option, the baseplate of the instrument may be temperature controlled up to 40C with built-in electrical heaters. Temperature and relative humidity are automatically measured and the data added to movies.
Doors are provided for convenient sample change or optics adjustment. The doors and sides are transparent so the activity of the machine may be observed at any time. The top is opaque to reduce interference from room lighting.
Cameras and Optics
The main microscope can operate either in a direct view (horizontal mode) or a 6 degree look-down mode. This allows the specimen to be larger than the working distance of the lens. The field of view is optimized for drops ranging in diameter from 1mm to 5mm. A 6:1 zoom enables the drop to always be the appropriate size for the automatic analysis algorithms.
Stepper-motor driven autofocus and autozoom are available as options. These mean the optics need not be focused manually and that magnification is always known for any zoom position.
An optional 90 degree turning mirror is available so the camera can look directly down on the top of the drop. A hole in the mirror allows the dispense needle to pass through and deposit drops. This allows direct and accurate measurements of contact angles that go as low as zero degrees and where the liquid actively spreads over the surface.
The system is capable of making single point measurements at a rate of 4 points per minute, including pickup and dispense of test drop, image capture, analysis, and clean up of drop. This presumes that only the initial contact angle need be measured. The time required by dynamic measurements is obviously set by the observation time, but 50-100 seconds is representative per point.
The uncertainty in the angle measurement will typically cause 1% uncertainty in wetting tension or surface energy calculations.
The software will run on Windows 98/ME/NT/2000/XP. On-line operator's manual and Help file are included. Software updates and upgrades are furnished without charge to users. Software licenses are sitewide, meaning the software may run on any number of the owner's computers.
Automatic Tip Changer
An optional tip changer will automatically discard the old tip and pickup a new tip from a tray of 96 tips, all under control of the Sequencer.