Ion Gun tests and calibration

Check ion gun alignment, try to optimize focus etc.

Operating Conditions

Max current at condenser 66, Obj 61 for 2 kV.
Similar at 4 kV.

Recorded current, clean copper sample no bias:

66   3.5 uA

70   2.2

80   0.27

85   0.11

90  0.05

Not much beam shift with Cond, Obj

At 1 kV, center shifts to (-0.5,-0.5) from (-0.9, 0.2), FWHM increases to ~ 1.5

Cond 60 387 nA

62  692

64   950

66  1070

68  860

70  590

75  193

80  65

85  27

Update profile Obj 61 Cond 66

Sputter test

Change to oxide on Si sample, (old and dirty, lots of particles).

2 kV no raster, offset -.9, -.5, cond 66 obj 61, 25 mA emission, 20 mPa gas

After 60 sec carbon reduced, oxygen little change except peak shift.

150 s Si peak LVV starts to evolve, no SEM change yet. Ar peak starts to appear

Approx 300 um diameter spot, ~ 430 um below center. (Aligned by max count rate with apertures open) 

Clear contrast in auger image 93 pass 10, weak contrast SE2, more with inlens

Additional sputter, spot size does not change much. Now try line raster. Also record ion excited Auger. Clear Si, Ar, S

Move to lower end of test area. Center on sputter signal with 2 mm aperture. 

Record Ar excited Auger during sputter. SiO peak and O peaks clear.

So-called ion excited spectra may actually be ions+electrons...

Do not see expected sputter crater. May be shadowed at low angle or problems due to tip transfer lever.

Remove sample. Si sputtered clean except shadow area.

New Test

Second SiO piece same wafer. Put in round beveled 6 mm holder. This one with Faraday Cup, shows 17.8 nA for 3 kV max. 

Had to slightly pull out plate (away from back stop) to get current measurement.

30 deg tilt, 5 kV sputter no raster. Current exceeds 10 uA during sputter. 

Sputter 250 sec total, not thorough yet. Notice noise on AES. Look at beam current stability. Occasional glitches. Effect of sputter? SiO sputter test 3.aes spec 9, 10. 

After several spectra checking stability, spot mode, big C peak. 

Gets better. spec 11 same spot, spec 12 elsewhere, lots of C???? 

Sputter into contamination layer? Was gone before. Contaminated sputter gas?

EIS crashes, most data was saved.

Turn on mass spec, close gun valve, start turbo, close ion pump. 

Turbo only (was not run for a while, may not be that clean. 

Pressure to 3.6e-9, 

MS 28 - 20%,

2 17%

40  12.5

18 8.3

15 7.9

16 7.6

44 5.8

27 4.5

26 4.0

MS 200 uA emission, baseline 3.7 nA H peak 8.8, 28 peak 4.8

Open leak 2e-8, baseline 3.3, Ar+ 8.5, Ar 4.7, H 4.9, 28 3.6

Trend graph Ar+:++ is 70%, 14% or ~ 5:1

slight relative increase in 28.

Open leak 1/8 turn, pressure to 1.3e7

20 rises to 36%, 40 drops to 62%. H2 is 2%. 

Baseline 3.0 nA, 20 is 4.55, 40 is 5.0, H 3.2, 28 3.08

Strange, Ar pressure above ~ 1.5e-8, mass 40 drops wrt 20

Flash TSP close Ar pressure to 1.9e-9 dropping.

Open Ion Pump, 1.5e-9

Much later, +50 s sputter no C but still oxide.

Total 360 sec, now get spot, poor quality, 620 um shifted.

93 eV auger 10 eV pass

Fresh spot

2 kV ions offset -0.9, -0.5 (should have been, first shot -5.0)

First had no effect, sample current was 50 nA at -5, now 5 uA at -0.5.

Now 300 s sputter removes C, oxide still present, peak increased no contamination

1050 s burnthrough, ~ 250 um diameter, 460 um low

93 eV pass 10