Model 290 Hot/Cold module leakage current

Posted on February 26, 2020 by Randy

The 10-325 specimen stage, which is commonly used on PHI Physical Electronics 5600 through 5800 XPS X-ray photo-electron spectrometer surface analysis systems, is often equipped with the model 290 Hot/Cold module.

The design of the Model 290 Hot/Cold module incorporates some zirconium oxide ceramics to electrically and thermally isolate the specimen holder from the specimen stage. Zirconium oxide has a very low thermal conductivity that is about 10% of the thermal conductivity of the more common alumina (aluminum oxide) ceramic material used on many UHV optics units. Zirconium oxide is a good choice for hot or cold specimen stages.

Over time, though, the evaporation of materials from specimens, as well as the evaporation of the filament on the Model 290, can coat the zirconium oxide ceramics. This coating can cause the specimen sample holder to become resistive to ground, which in turn affects the accuracy of target current measurements. The leakage current of a coated ceramic might be several hundred nano amps. This means that only target currents above that several hundred nano amps value would be measurable. ISS or static SIMS (both options on XPS systems) need the ion current to be set in the range of 1 to 2 nA. And aligning the monochromator requires measuring currents of 3 nA or less. If the specimen stage leakage current is high, then it would be impossible to accurately measure or set those currents.

To test your target leakage current, simply measure the target current using the +90V bias box and picoammeter without any electron, ion, or X-ray source turned on. Typically, the leakage current will be just a few 10s of picoamps. If the leakage current is much higher than low picoamps, the zirconium ceramics shown in the image below may be coated and should be replaced the next time the system is up to air for maintenance.

The replacement procedure is simple.

Vent the chamber and remove the specimen stage.
Place the specimen stage on a workbench with some aluminum foil (UHV foil preferred) so that you can catch parts that will come off the specimen stage while you are working on it.
Remove the end screw and washer and slide out the first long ceramic.
Install a new long ceramic and replace the washer and screw.
Repeat for the other long ceramic.
For the back short ceramic, first remove the bearing by removing the C clamp on the shaft and sliding the shaft out. Note that two thin washers that will come off the bearing shaft as you pull it out.
Next loosen the two pan head slotted screws and slide out the old ceramic and replace it with the new one. Tighten the 2 flat head slotted screws and then replace the bearing.
For the front short ceramic, just loosen the two pan head slotted screws and remove the old ceramic and replace it with the new ceramic. Then tighten the two pan head slotted screws.

After replacing all of the zirconium oxide ceramics, the leakage current should be minimal.

Reinstall the 10-325 specimen stage then pump down and bake out the chamber.

The RBD part number for the set of 4 ceramics is 290CK-4RE. Contact us for more information

9103 USB Picoammeter Winter 2020 News

Posted on February 12, 2020 by Joe Caterinicchio

Last year, RBD introduced an updated 9103 USB Picoammeter, with 3 new models:

High-speed: 500 reads / second compared to 40 for the Standard Model
High-voltage: an isolated signal input with the ability to float the 9103 Picoammeter to ±5000 VDC.
High-speed / High Voltage: One model combining both features.

This year we’ll be working on adding new features to our Actuel application software and providing more comprehensive support and programming documentation.

Actuel 1.6 is Released

The latest version of Actuel (1.6) is now available, as is an updated User Guide. The guide has new information on setting up and programming the 9103 for high-speed communications. Both can be found here.

This release replaces the Beta release and has full support for high-speed sampling and data recording and graphing.

9103 TechSpot Article Series

This year, we’ll be running a series of articles here on the TechSpot blog with more information on the new 9103 models and features, as well as detailed configuration, application, and programming advice.

Some of the topics we’ll be covering include:

Programming the 9103 for high-speed data collection
Using the high-voltage reference
Proper use of the input ground
Troubleshooting 9103 communications

Keep your eye on here on TechSpot for these and other articles covering all of RBD’s products, and please consider subscribing.

Troubleshooting electronics resources

Posted on January 30, 2020 by Randy

1-30-20 I updated this blog post to include a video on how to isolate a thermally unstable electronic component using a heat gun and cool spray.

When a problem develops with your XPS or AES spectrometer and you contact RBD Instruments for assistance, we frequently hear the same question – “What could be the source of the problem?”. The troubleshooting electronics tips below may help to find out.

Most problems on XPS and AES spectrometers can be broken into two broad categories – Optics problems and electronics problems. Optics (electron optics) are parts of the system that are installed on the vacuum chamber and include things like spherical capacitive analyzers, cylindrical mirror analyzers, sputter ion guns, x-ray sources, neutralizers and so on. Electronics include units such as power supplies and controllers.

Optics can generally (but not always) easily be tested by simply measuring the resistances on the electrical feedthroughs as specified in the optic’s manual. For example, a 04-303 ion gun should have contact between pins 1 and 2 (the filament) only. All other pins should be open to each other and to ground. By open, we mean that the electrical resistance is infinite. If pin 3 were shorted to ground, we would know that the objective lens inside the ion gun has a flake that is shorting it out, and the ion gun needs to be taken apart and rebuilt. But an optic component can have correct resistances and still have a problem (such as an open contact). Sometimes a short in an optic can also cause a failure in an electronic unit.

Electronic units are the source of problems with XPS and AES spectrometers more often than optics. Most of the students who use XPS and AES spectrometers in a university environment do not have enough training or experience with electronics to really dig into the electronic circuitry, but there are still a number of simple steps that can be taken that may result in a successful repair.

First of all, make sure that all power is off to any electronic unit that you work with. Measurements of voltages should always be performed by personal who have been training to work with electronic components and (often) high voltage. Potentially lethal voltages are present in these types of systems. If you are not properly trained, do not attempt to measure voltages in electronic units.

But, as long as the power is off and the unit is unplugged, you can safely visually inspect the unit and the boards inside of the unit for obvious signs of damage. For the most part, these are indicated by discoloration of the circuit boards, melted traces, melted transistors, dried up capacitors, and burnt resistors. If you find some components that are visibly damaged, then replacing them may solve the problem. Or, there may also be additional problems and the damaged components are just a symptom.

Some things to look for include:

Heat damage to a circuit board: Discoloration of the board which indicates that a component has been running very hot.

Melted components: Transistors (the plastic type) can actually melt when overheated. This is easy to spot.

Cracked capacitors: When capacitors dry out (after say 20 years or more) they can fail. See the links below for detailed instructions on how to test a capacitor. Be careful with larger value capacitors as they can hold a charge for a long time. Just to be safe, discharge capacitors before you measure them by clipping a resistor (a few hundred to a few thousand ohms is typical) across the contacts. This is not necessary for small value low voltage capacitors.

Burnt resistors: Resistors that burn up can turn to carbon and be difficult to identify without a schematic and board layout. Measure the resistance of suspect resistors with an ohmmeter. Sometimes you need to lift one end of the resistor (desolder one end of the resistor from the board) when measuring resistors in circuit as other components that may be in parallel with the resistor can affect the reading.

Shorted diodes and transistors: You can use a DVM in the diode check mode to test diodes and transistors for shorts. See the links below for detailed instructions on how to do that.

Dullness on transistor housing: If a metal housing (cover) transistor overheats often the finish on the transistor housing may be dull as a result of overheating. You can compare the finish to other similar transistors and then use a DVM in the diode check mode to test the suspected transistor. Plastic housing transistors that have melted are readily apparent.

Below I have listed some links to troubleshooting electronics resources. If you can’t fix the problem on your older Physical electronics (PHI) electronic unit yourself after following the steps in this post, we can provide you with technical support, repair services, loaners or exchange units. Contact us for more info.