A blog on the repair, operation and calibration of surface analysis systems and components including electron spectrometers, sputter ion guns and vacuum related hardware. Click on the Index tab below to see a list of all posts. Visit our website at http://www.rbdinstruments.com
This blog will describe the symptoms and solution for lens elements that charge up due to an oxidized graphite coating.
Overview – The Physical Electronics SCA (Spherical Capaitive Analyzer) has a series of 2 or 4 lenses that focus electrons into the energy analyzer section of the SCA. The first two lenses determine the analysis area and the second two lenses focus the electrons into the SCA for optimal counts and energy resolution. The voltages applied to the lenses change as a function of the kinetic energy of the electrons being detected. The sketch below shows the general concept on an SCA that uses a Position Sensitive Detector. Most SCAs today have a MCD multi-channel detector but the lenses work the same way.
SCA Lens Concept
The 5600 XPS system lenses are constructed out of stainless steel. In order to reduce the secondary electron yield (a lower secondary electron yeild improves energy resolution), Aquadag is sprayed on the inside of the lens surfaces. Aquadag is basically pure carbon, and carbon has a low secondary electron yield.
Problem – unstable data at higher pass energies, larger analysis areas, or higher x-ray source power.
Normally charging presents itself as unstable data with very high spikes in the counts followed by rapid discharges. In this case, the problem presented itself more like a digital step problem with very repeatable steps in the data at particular eVs. Another interesting effect was the ratio of peak heights would also change as a function of the pass energy, analysis area or x-ray source power.
Initially the symptoms pointed to the MCD multi channel detector or the chevron plates. The MCD was pulled and inspected an no problems were seen. The chevron (channel) plates were replaced and that did not change the symptoms.
Another clue was that if the lens cables were removed from the SCA and the lens elements shorted to ground, the data looked correct. In addition, one lens could be grounded and the other lens could have voltage applied to it and the data would also look correct. However, if the area of one of the the lenses were changed (by selecting large area mode) the problem would return, even with the other lens still grounded.
The conclusion was that the surfaces of the lenses must be charging, but only at large areas where more electrons would fill the lenses.
The SCA lens was removed and the resistivity of the lens elements were measured. The resistance of the lens coating would vary from tens of ohms to thousands of ohms depending on where the measurements were made. These resistance measurements matched the symptoms as a high resistance surface would not conduct the electrons that hit the inside of the lens cylinders.
Aquadag works well to reduce secondary electrons. But if exposed to air for extended periods of time it (evidently) can form an oxide layer which increases the resistance of the coating substantially.
A clean stainless steel scouring pad with a very light touch was used to break the oxide layer without removing too much of the Aquadag coating.
The technique used was to lightly rotate the scouring pad inside the lens elements and then check the resistance of the lens coating. The resistance would gradually drop with each rotation of the scouring pad. When the resistance dropped close to a few ohms, no further scouring was done.
Lens element
When this process was completed, the inside of the lens elements were conductive but still black, so most of the Aquadag coating was still intact.
After reinstalling the lens, pumping down and baking the vacuum chamber, the SCA performed correctly.
The first step is to remove the bolts on the flange that hold the lens to the chamber. Then, tilt the SCA back so that it rests on the arm stop. Remove the aperture size knob and the two lens feedthroughs. Next remove the nipple. Then, remove the magnetic shield (4 long screws) and finally the lens assembly (2 screws).Once the lens assembly is out you need to separate all of the sections in order to be able to use the scouring pad. The lens sections are held in place with screws and ceramics.Close up of lens electrical contacts. The top one has been removed by unscrewing the rod CCW.
If you are experiencing this problem please contact RBD Instruments for more details.
This blog post is a compilation of notes which are helpful when troubleshooting or calibrating the 80-365 (and 80-366) SCA analyzer control.
The 80-365 SCA analyzer control provides all of the voltages to the SCA (spherical capacitive analyzer) used on older PHI XPS (X-ray photoelectron spectroscopy) systems. Those include the retard voltage, the pass energy, the lens voltages and the electron multiplier voltage.
To troubleshoot or calibrate the 80-365, follow the calibration procedure in the 80-365 manual. Note that high voltages are present on the 80-365 boards, always refer these types of measurements to technicians who have been properly trained in working with high voltage!
If are unable to repair the 80-365 yourself, please contact RBD Instruments and we can repair the boards for you.
80-365/66 Lens Board DAC bit test
To test individual bits: Write out on DR11 A CSR 1
Note: Write the low order byte out first, then the high order byte. If you get out of sequence you need to turn off the card rack power to reset the board and start over.
Lens 2
Measure from the left side of R62 to the right side of R94/G4
Bit
Low byte
High byte
DAC voltage
0
1600
1600
0.0000
1
1602
1600
0.0012
2
1604
1600
0.0024
3
1606
1600
0.0049
4
1610
1600
0.0098
5
1620
1600
0.0195
6
1640
1600
0.0391
7
1680
1600
0.0781
8
1600
1601
0.1563
9
1600
1602
0.3125
10
1600
1604
0.6250
11
1600
1608
1.250
12
1600
1610
2.500
13
1600
1620
5.00
14
16FF
163F
10.00
Lens 3
Measure from the right side of R70 to the right side of R94/G4
Bit
Low byte
High byte
DAC voltage
0
1800
1800
0.0000
1
1802
1800
0.0012
2
1804
1800
0.0024
3
1806
1800
0.0049
4
1810
1800
0.0098
5
1820
1800
0.0195
6
1840
1800
0.0391
7
1880
1800
0.0781
8
1800
1801
0.1563
9
1800
1802
0.3125
10
1800
1804
0.6250
11
1800
1808
1.250
12
1800
1810
2.500
13
1800
1820
5.00
14
18FF
183F
10.00
80-365 Lens board calibration notes
For XPS and AES, the output voltages are positive, and the fine supplies are negative. Make sure that you set the polarity before programming on dual polarity boards.
1310 is + polarity for L3
1320 is + polarity for L2
Common data values
L2 Output
C53/G5 Fine Supply – lead ground side R143 + lead right side R142/G5
1801,1800 – Adjust R45/A3 for -20V on fine supply
1800, 1808 – Adjust R77/B4 for – 20V on fine supply Adjust R67/G3 for +409.6V on C53
18D4, 1830 – Adjust R67/G3 for +2500.0 V on C 53 output. Readjust R77/B4 for -20V on fine supply
1800, 1800 – zero
L3 Output
C41/E5 Fine supply – lead ground side R127/E5 + lead left side R120/E5
1601, 1600 – Adjust R52/C3 for -20V on fine supply
1600,1608 – Adjust R87/D4 for–20V on fine supply Adjust R59/E3 for +409.6V on C41
16D4, 1630 – Adjust R59/E3 for +2500.0V on C 41 output. Readjust R87/D4 for -20V on fine supply
1600,1600 – Zero
NOTE: If you have issues with the +5V supply dropping and voltages not loading properly, look at the local power supply board. You may need to replace the 3524 regulator on the local power supply board.
80-365/66 Pass Energy board DAC bit test
To test individual
bits:
Pass energy range = is 0 to 10V on the DAC = 1920 or 2145 depending on the model number of your analyzer control.
Write
out on DR11 A CSR 1
Note: Write the low order byte out first, then the high order byte. If you get out of sequence you need to turn off the card rack power to reset the board and start over.
To set the DAC back to zero between bits, write out 1a00 twice
The following table shows the voltage on the DAC measured from TP24 / C2 to TP24B /C2
0000
0000 0000 0001
bit
0
0.022
V
1a01, 1a00 = .0001525 V on the DAC
0000
00000000 0010
bit
1
.044
V
1a02, 1a00 = .0003052 V on DAC
00000
0000 000 0100
bit
2
.088
V
1a04, 1a00 = .000 6V on DAC
0000
0000 0000 1000
bit
3
.019
V
1a08, 1a00 = .00122 V on DAC
0000
0000 0001 0000
bit
4
0.35
V
1a10, 1a00 = .00244 V on DAC
0000
0000 0010 0000
bit
5
0.7
V
1a20, 1a00 =.00488 V on DAC
0000
0000 0100 0000
bit
6
1.4
V
1a40, 1a00 = .0097 V on DAC
0000
0000 1000 0000
bit
7
2.8
V
1a80, 1a00 =.019 V on DAC
0000
0001 0000 0000
bit
8
5.63
V
1a00, 1a01 =.039 V on DAC
0000
0010 0000 0000
bit
9
11.25
V
1a00 ,1a02 = .078 V on DAC
0000
0100 0000 0000
bit
10
22.5
V
1a00 ,1a04 = .156 V on DAC
0000
1000 0000 0000
bit
11
45
V
1a00 ,1a08 = .3125 V on DAC
0001
0000 0000 0000
bit
12
90.02
V
1a00 ,1a10 = .625 V on DAC
0010
0000 0000 0000
bit
13
180.03
V
1a00,1a20 =1.25 V on DAC
0100
0000 0000 0000
bit
14
360.06
V
1a00 ,1a40 = 2.5 V on DAC
1000
0000 0000 0000
bit
15
720.13
V
1a00 ,1a80 = 5.0 V on DAC
All
Bits:
1A00, ,1aFF = 10 V on DAC
1920 or 2145 VDC on the output across C56
80-365 / 366 Pass energy board range note
The 80-365 and 80-366 pass energies have different maximums.
The 80-365 is 1920V
The 80-366 is 2145V
Make sure that you have the correct procedure when you calibrate the board.
Measuring the Pass Energy output voltages
There are some scale factors involved when measuring the pass energy voltages.
If you are measuring the pass energy voltage across C56 on the pass energy board, the scale factor is approximately X 1.34. For example, if you set the pass energy to 187.85, the output voltage across C56 is 187.85 X 1.34 = 251.8 VDC. You can calculate any pass energy actual voltage value by multiplying the pass energy in the software (set up an alignment or survey) by 1.34.
If you are measuring the test points in the filter box, the scale factor is to divide by 1.7. For example, a pass energy of 187.5 divided by 1.7 = 110.3 VDC. If you set up the pass energy to 187.5 in the software, you will see approximately 110.3 VDC between the IC and OC test points in the filter box. The resistors in the filter box divide the voltages so that they are correct on the IC, OC and MR contacts in the analyzer.
To summarize –
C56 output on pass energy board = Pass Energy X 1.34
Test points in filter box = Pass Energy divided by 1.7
80-365 Local Power supply board notes
Capacitor
Voltage
Comments
C33
22V +/1 1.5V adjust R27
Transformer
output before regulator
C35
+15
Pass energy
board power
C36
-15
Pass energy
board power
C34
+5V
Pass energy
board power
C9
22V +/1 1.5V adjust R3
Transformer
output before regulator
C10
+15
Lens board
power
C7
-15V
Lens board
power
C12
+5V
Lens board
power
CR35 cathode
to CR36 anode
+225V
Pass energy
board power
CR 37 anode
to CR36 anode
-225V
Pass energy
board power
CR17 cathode
to CR17 anode
+150V
CR18 anode to
CR17 anode
-150
TIP: If the voltages are low when the pass energy or lens boards are installed, most likely the issue is a weak 3524 regulator. Replace it with a new SG3524N
80-365 Retard supply bytes
bit
low byte (hex)
hi
byte (hex)
DAC V
0
1100
1200
0
1
1101
1200
0.00015259
2
1102
1200
0.00030518
3
1104
1200
0.00061035
4
1108
1200
0.0012207
5
1110
1200
0.00244141
6
1120
1200
0.00488281
7
1140
1200
0.00976563
8
1180
1200
0.01953125
9
1100
1201
0.0390625
10
1100
1202
0.078125
11
1100
1204
0.15625
12
1100
1208
0.3125
13
1100
1210
0.625
14
1100
1220
1.25
15
1100
1240
2.5
16
1100
1280
5
All
11FF
12FF
10
80-365 Lens Board Single Polarity modification
The dual polarity lens board high voltage switching relays can breakdown at voltages above 1kV and cause a variety of intermittent problems. Since most systems do not use the negative polarity, removing the high voltage switching relays and converting the lens board to a the single (positive) polarity can solve the breakdown problem and make the board more reliable.
Modification Procedure:
Remove the red cover (3 screws) that shields the high voltage components.
Unsolder and remove the two Kilovac high voltage relays (K1, K2)
Jumper the relays as shown in the pictures below.
Solder a jumper on the back of the board on IC 22 between pins 2 and 3.
Solder a jumper on the back of the board on IC 21 pins 6 and 7.
Remove ICs U13, U21 and U22 (Note that some boards do not have sockets in which case you need to un-solder the ICs before putting the jumper in).
Cover the open sockets on U13, U21 and U22 with electrical tape. That will make it easier if the board ever needs to be repaired again as it will indicate that those IC sockets are not used.
Check the Single Polarity box on the upper left-hand side of the board.
You can also remove these components as they are no longer used –
For Part 3 of our series on programming the 9103 with Python, we’ve written an application that controls the 9103 in High-speed mode (which can sample as quickly as 500 samples/second) and parses the high-speed messages so they are output to a text file using the same format as standard speed. (All Python samples for the 9103 can be found here.)
(The High-speed option for the 9103 is available as an option when purchasing. The 9103 is also available with a High-voltage option and 90 V fixed or external bias)
Setup the 9103 for High-Speed Sampling
The 9103 has two different modes of operation – high-speed and standard-speed. These run the serial COM ports at different baud rates, so the port needs to be opened at the appropriate rate (the 9103 recalls the last baud rate used). This application does not detect / switch modes, but in our last post we programmed a utility to do just that – it’s part of the set of python scripts included in the download.
The only difference between the code to open the port in standard speed or high speed is the baud rate (57.6k for standard, 230.4k for high) . All oher parameters are the same.
High vs. Standard Speed Interval Sampling
When interval sampling in Standard-speed mode, only the ‘I’ command is available, which provides one sample per message. High-speed mode adds an additional command – ‘i’ – which passes 10 samples per message, thereby reducing the round-trip overhead per sample. You would typlically only use this command for speeds faster than 40 samples / sec., however if can be used at slower speeds. We run a slower speed in our sample application to make it easier to observe the sample messages in the terminal.
(You would probably not choose to use the ‘i’ command for slower sampling rates, because it can only provide one stability warning and range for every 10 samples
Parsing the High Speed Sample Messages
The format for a High-speed sample includes the range and units, along with 10 samples:
For this application, we write to a data-logging file just as we do in the Standard-speed Python application. However, we need to parse the 10 sample data to produce a similar, one-sample-per-line output if we want to be able to use the data interchangeably.
The only difference between the samples is that the High-speed samples are prefaced with a lower-case ‘s’ (which could be easily replaced if necessary):
s=,Range=002nA,+0.0013,nA
.
Here’s the code for parsing the high-speed sample message:
def parse_message_for_high_speed_sample( msg): if '&s' in msg: msg = msg.strip('\0') msg = msg.strip('&') list = msg.split(',') i = 0 stability = '' range = '' new_msg = '' units = list[-1] # gets last item list.pop() # remove last item which is units for value in list: if i==0: stability = value elif i==1: range = value else: new_msg = new_msg + stability + ',' + range + ',' + value + units + '\n' i=i+1 return new_msg else: return ''
That’s about all that’s necessary to create a compatible message, allowing you to mix High-speed and Standard-speed messaging in a compatible data-logging format
