Irradiation at IUCF We irradiated 5 chips from Sintef wafer 9 (7,39,42,44,46) at Indiana University Cyclotron Facility on 30th November. Pixel 7,44 and 46 are baseline design. Pixel 42 spiral ring and pixel 39 single ring design. Pixel 7,39,42 and 46 were exposed to a fluence of 1x10 14 p/c.m. 2. Pixel 44 were exposed to 6x10 14 p/c.m. 2 We measured the properties of the chips at 21 0 C, -5 0 C & C

Pixel side up

Conducting rubber sheet Wire bond Wire bond (1st GR) Cu tape Cu tape Guard RingsDiodeN + ring Ammeter Hi Wire Bulk Material N+N+ P+P+ Pixels are bumped but not bonded with anything. The whole structure was kept inside the refrigerator and the wire came out of the refrigerator. Measurement Technique

What we expected Increase in current  I= .V.  eq (This equation gives the change of current in the plateau region of the IV curve. For these pixels the plateau region is between 50V to 250V)  = 4.0x A/cm 1, V = cm 3  eq = 1(6)x10 14 cm -2  I = 3.0x10 -5 (17.9x10 -5 ) A A single pixel x0.015 cm 2 Increase in current through a single pixel  I single pixel =  I x 0.015x0.015/(0.2493) A = 27.0 (162) nA 1 Value of  from Rose Collaboration -

What we got For Pixel 7 I 200V = 2.67x10 -5 A I 300V = 6.94x10 -5 A For Pixel 39 I 200V = 3.11x10 -5 A I 300V = 4.98x10 -5 A For Pixel 42 I 200V = 2.80x10 -5 A I 300V = 5.69x10 -5 A For Pixel 46 I 200V = 2.85x10 -5 A I 300V = 3.90x10 -5 A] For Pixel 44 I 200V = 1.16x10 -4 A I 300V = 2.77x10 -4 A Pixel 44 received 6 times higher fluence than the other pixels. Leakage current of pixel 44 is 4(5) times higher than the other pixels at 200(300)V.

Comparison

Pixel 46 Design A Fluence -1x10 14

This indicates that the current is coming from diode (pixels). Current compliance was 1mA Extra Current

Pixel 7 - Depletion Voltage Design A Fluence -1x10 14 Full Depletion at 33 V Leakage current at depletion voltage is 0.71  A (1.1nA/pixel)

Summary We have to understand the rise of current at the kink between 200 to 300V. We plan to do the measurement at -20 We plan to bump bond this pixel arrays to ROC and to measure them with source.

Is it possible to measure the potential of a central pixel when the guard region is biased ? Silver Epoxy Pixel First the measurement was done without grounding the epoxy. Next the measurement was done with the epoxy grounded. Measurement was done with one probe at the center pixel, one probe at the silver epoxy and a wire bond connection with the diode. This measurement was done on SINTEF wafer 24 Pixel 46 before irradiation. We haven’t done the measurement after irradiation.

Connection Setup for measuring the voltage at a center Pixel Wire bondGuard RingsDiode N + ring Hi Probe Bulk Material N+N+ P+P+ V Probe

Inter Pixel Capacitance before irradiation

Connection Setup for measuring the Interpixel Capacitance Wire bondGuard RingsDiode N + ring Hi Probe Bulk Material N+N+ P+P+ C Probe ~