NINO RO chip qualification with the laser test system Sakari and Fadmar.

NINO RO chip qualification with the laser test system

Sakari and Fadmar

Fadmar Osmić – P326 GTK Meeting, December 11, 2007 -2-

Diode specifications - reminder

• Pixelized diode from the IRST wafer– 200 um thickness– 300 um x 300 um pixel dimension (nominal)– 3 x 20 pixel matrix– 1 pixel under study neighboring pixels grounded– An opening in the Al-layer covering the p+-pad etched to

allow laser illumination


Opening in the Al-layer

• From the previous measurements it was seen that there’s a big uncertainty on focusing the laser beam into the diode

A better mechanical stability was achieved An opening in the Al-layer of the diode to provide better

photon injection was etched• The opening was made by Serge Ferry (chemical lab)

– The hole was done with chemical etching. A photo-resist was placed to protect the rest of the Al-layer. The diameter of the opening is ~100 um

• With the opening the laser may be manually scanned to the center providing a maximum photon injection


Opening in the Al-layer


IRST diode pixelized and wire-bonded


Connection to the NINO chip


Laser position scan

The higher the pulse width, the more photons enter the diode, meaning thelaser is better focused to the hole

The dark red color shows the ‘hot spot’, meaning the center of the hole. The redcircle shows the assumed ~100um diameter hole.

To make sure all the photons are injected in to the diode, the laser beam is manually focused by measuring the output pulse width at different positions.


Height scan

Laser fibre heigt scan

7

7.5

8

8.5

9

9.5

18.4 18.6 18.8 19 19.2 19.4 19.6 19.8

height of the laser fibre [100 um]

pu

lse

wid

th [

ns

] SATURATION

Complete illumination with the laser light

calibration possible using an ALICE SPD assembly (same sensor specifications)

Measurements

Laser Calibration


Calibration of the laser light

• Reminder: W/O calibration between the laser and input charge the measurements with a calibration capacitance and the diode are incomparable

• BUT!!! Cross calibration possible with an Alice SPD assembly

• Assumptions: – The complete laser beam illuminates the detector demonstrated

(plateau reached in the fiber height scan)– Sensors of the ALICE SPD assemblies have the same specifications

as the detector under study they come from Si-wafers with same specifications

• Response of the ALICE SPD assembly to two different radioactive sources (109Cd and 55Fe) calibrates the laser beam at different settings


Pulse Area vs Laser Bias

Laser Calibration Optical head

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05

Laser Bias [V]

Pu

lse

area

[p

Vs]


Laser Calibration

Laser Calibration

0.00

10000.00

20000.00

30000.00

40000.00

50000.00

60000.00

70000.00

80000.00

1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05

Laser Bias [V]

ge

ne

rate

d e

-h-p

air

s [

mV

]

extrapolation 1.48 - 1.50 V

Scaling via pulse area to 1.48 V

Scaling via pulse area to 1.50 V

Measurements

Laser Bias Scan


Jitter

Jitter vs. input charge(w/ opened detector,no time-walk correction)

Jitter vs. laser bias(w/ detector,no time-walk correction)

Laser bias (V)

300ps300ps

Laser bias (V)

2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7

Generated charge (fC)

2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7



Jitter


Jitter vs. laser bias(w/ 100fF calibration capacitanceno time-walk correction)

Laser bias (V)

50ps300ps

2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7



Pulse Width

Pulse width vs. laser bias(w/ opened detector)

Pulse width vs. laser bias(w/ detector)

Laser bias (V) Laser bias (V)1.5 2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7


1.5 2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7



Pulse Width


Pulse width vs. laser bias(w/ 100fF calibration capacitance)

Laser bias (V)1.5 2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7



Time-walk vs. Pulse width

Time-walk vs. Pulse width(w/ opened detector)

Time-walk vs. Pulse width (w/ detector)


Time-walk vs. Pulse width


Time-walk vs. Pulse width (w/ 100fF calibration capacitance)

Measurements

Detector Bias Scan


Pulse width and Jitter

Pulse width vs. detector bias(w/ opened detector)

Jitter vs. detector bias(w/ opened detector)

=~3 MIPs =~3 MIPs

Measurements

NINO Threshold Scan


Jitter as function of the NINO threshold for 3 different laser bias settings

jitter

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

400.00

450.00

45 65 85 105 125 145 165 185 205 225

NINO threshold [mV]

jitte

r [p

s]

Laser Bias 1.8 V

Laser Bias 1.7 V

Laser Bias 2 V

1


Conclusions

• Mechanical stability achieved– New precision mechanics installed– NINO board fixed to a reference plane – repeatability tested and improved system mechanically stable

• Opening in the Al-layer allows the complete illumination with the laser light– Procedure established with TS/DEM group – Verified on 5 samples openings range from 100 um – 3 mm– laser calibration finally! possible

• Measurements on the NINO chip show improved results: jitter <200 ps for high det-bias and >1.8 V laser bias (~3 MIPs)– With the current RO-setup (detector wire-bonded to the NINO chip,

no pre-amp) NO further improvement possible!– Next step: demonstrator


SPARE SLIDES


Jitter Comparison 1pF


Jitter vs. laser bias(w/ 1pF calibration capacitanceno time-walk correction)

Laser bias (V)

300ps300ps

2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7



Pulse Width Comparison 1pF


Pulse width vs. laser bias(w/ 1pF calibration capacitance)

Laser bias (V)1.5 2.6 3.6 4.7 6.3 7.3 8.3 9.2 10 10.7



Time-walk vs. Pulse widthComparison 1pF


Time-walk vs. Pulse width (w/ 1pF calibration capacitance)

NINO RO chip qualification with the laser test system Sakari and Fadmar.

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