1. Non-Contact Gap Measurement
Breakdown 17th August R. Santiago Kern

2. Non-Contact Gap Measurement
The eq. for the FE current is:
In order to predict the gap distance:
Set 1st gap going into contact: reference position. Record (I,V,Beta)
Increase/decrease the gap with micrometer wihout going into contact. Record sets of data (I,V,Incx).
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3. Non-Contact Gap Measurement
Overview of data sets:
Data Data 1 Data 2 Data 3 Data 4 Data 5 Data 6
Spot X Spot X Spot X Spot Y Spot X Spot X Spot Y
(Bad) (Good) (Bad) (Bad) (Good) (Bad) (Bad)
1 Beta meas.
FN Eq.
3 Beta meas.
Least-squares
System I System II
Method? Repeat.? Spot? Microm. Cal.? Repeat.? Contact?
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4. Non-Contact Gap Measurement
1st method:
All lines have approx. same slope, only intercept varies
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5. Non-Contact Gap Measurement
1st method
From reference line get the value of Ae:
Considering Ae to be constant, Beta can be calculated from the interception point of each line
And the gap d from each of the corresponding intercept
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6. Non-Contact Gap Measurement
Problem: Beta can’t be reproduced for the same gap, lines are displaced even for the same gap.
( )um
FE1-FE6: um
FE4-FE7: um
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7. Non-Contact Gap Measurement
2nd method
Measure FE several times (x3) for each gap.
Apply a non-linear fit to all the obtained lines, i.e. minimized the least-squares.
[X’s] = [1/V]
[Y’s] = [ln(I/V^2)]
[Y’s] = f (Ae, Beta, Inc x)
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8. Non-Contact Gap Measurement
Data series 1 (System I)
Spot X (contact)
Ref: FE1 line
FE1-FE9: 14.4um (ref)
FE2-FE8: 18.72um
FE3-FE7: 20.16um
FE4-FE6: 21.02um
FE5: um
Ae: [m^2]
Beta:
Gap: [um]
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9. Non-Contact Gap Measurement
Data series 2 (System I)
Spot X (contact)
Ref: FE1 line
FE1-FE9: 14.4um (ref)
FE2-FE8: 18.72um
FE3-FE7: 20.16um
FE4-FE6: 21.02um
FE5: um
Ae: [m^2]
Beta:
Gap: [um]
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10. Non-Contact Gap Measurement
Data series 3 (System I)
Spot Y (contact)
Ref: FE1 line
FE1-FE9: 14.4um (ref)
FE2-FE8: 18.72um
FE3-FE7: 20.16um
FE4-FE6: 21.02um
FE5: um
Ae: [m^2]
Beta:
Gap: [um]
Breakdown 17th August R. Santiago Kern

11. Non-Contact Gap Measurement
Data series 4 (System II)
Spot X (contact)
Ref: FE1 line
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Ae: [m^2]
Beta:
Gap: [um]
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12. Non-Contact Gap Measurement
Data series 4 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
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13. Non-Contact Gap Measurement
Data series 4 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Small decays in current
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14. Non-Contact Gap Measurement
Data series 5 (System II)
Spot X (contact)
Ref: FE1 line
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Ae: [m^2]
Beta:
Gap: [um]
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15. Non-Contact Gap Measurement
Data series 5 (System II)
Spot X (contact)
Ref: FE1 line
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Ae: [m^2]
Beta:
Gap: [um]
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16. Non-Contact Gap Measurement
Data series 5 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
FE1_1 Discontinuity
FE3_i have low values
FE3_2 has a jump in current
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17. Non-Contact Gap Measurement
Data series 6 (System II)
Spot Y
Ref: FE1 line
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Ae: [m^2]
Beta:
Gap: [um]
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18. Non-Contact Gap Measurement
Data series 6 (System II)
Spot Y
Ref: FE1 line
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Ae: [m^2]
Beta:
Gap: [um]
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19. Non-Contact Gap Measurement
Data series 6 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Breakdown 17th August R. Santiago Kern

20. Non-Contact Gap Measurement
Data series 6 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Breakdown 17th August R. Santiago Kern

21. Non-Contact Gap Measurement
Data series 6 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
Breakdown 17th August R. Santiago Kern

22. Non-Contact Gap Measurement
Data series 6 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
All FE lines have a discontinuity at 1.6E-9 A
Only in this spot Impurity?
1.6E-9 A
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23. Non-Contact Gap Measurement
Data series 6 (Cont’d)
FE1-FE6: 18.82um (ref)
FE2-FE5: 22.48um
FE3-FE4: 29.71um
FE7-FE9: 15.12um
FE8: um
FE8_1 no spread in original graph, but has discontinuities
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24. Non-Contact Gap Measurement
Conclusions:
FE characteristics does not yield a realistic gap measurement, with or without going into contact.
Parallel dispersion in the FN graph means discontinuities in the I-V characteristics (i.e. Data 6, FE1 and FE8)
Breakdown 17th August R. Santiago Kern