Christina Hägemann,UNM Sensor Testing at University of New Mexico C. Hägemann, M. Hoeferkamp, D. Fields, A. Zimmerman, M. Malik VTX Meeting 03 June 2005

Christina Hägemann,UNM 2 Sensor QA Testing Sensor QA Testing – Visual Sensor QA Testing – Electrical Sensor QA Testing – Mechanical

Christina Hägemann,UNM 3 Sensor QA Testing Sensor QA Testing – Visual Sensor QA Testing – Electrical Sensor QA Testing – Mechanical

Christina Hägemann,UNM 4 Production Test Stand Semiautomatic probestation, 2 Keithley 706 scanners with 10 and 3 Keithley7058 low current scanner cards respectively

Christina Hägemann,UNM 5 Production Test Stand Cleanroom

Christina Hägemann,UNM 6 Production Test Stand

Christina Hägemann,UNM 7 Production Test Stand

Christina Hägemann,UNM 8 Visual Testing As seen before: Equipment is functional, Visual Testing can be easily performed Sintef Wafers: A1 and A3 are scratched; Not seen on the other wafers

Christina Hägemann,UNM 9 Sensor QA Testing-Electrical Test stand using scanner and probecard is fully operational Tests that will be performed on the wafer: Current Scan (Measure I Leak at each strip; V Bias = const) Capacitance Scan (Measure C at each strip; V Bias = const) IV Measurement (on 10% of the strips) CV Measurement (on 10% of the strips)

Christina Hägemann,UNM 10 Current Scan 6 measurements total, each with 64 needles (melted needles on probe card) Strip #3, 67, 131,…: either bad needle or bad cable V Bias = 100 V

Christina Hägemann,UNM 11 Current Scan What is the difference between the 3 rd measurement and the last three ?

Christina Hägemann,UNM 12 Current Scan Only 61 needles are actually touching pads Change of the magnitude of the current by 100 → indicates bad strip?

Christina Hägemann,UNM 13 IV Characteristic IV curve of a p-n-junction Def V Break : Point where IV curve starts rising exponentially

Christina Hägemann,UNM 14 IV Def V Break where I > 2.5*I nominal ~ 2.5nA V Break ~ 320 V

Christina Hägemann,UNM 15 Capacitance Scan OPEN correction accounts for test fixture on LCR meter Measure Capacitance of each channel when needles are above the wafer Plot C corr. = C uncorr. – C correction vs Channel Number No V Bias

Christina Hägemann,UNM 16 Capacitance Scan Same shape as data seen from BNL (~1pF; we don’t get any peaks in the middle) -> due to wafer / probecard? V Bias = 150V

Christina Hägemann,UNM 17 Capacitance Scan Same shape as data seen from BNL (~1pF; we don’t get any peaks in the middle) -> due to wafer / probecard?

Christina Hägemann,UNM 18 CV On each sensor, measure 10% of the strips Substract C correction for each particular strip measured Inquire about AC frequency dependence of measured C first (LCR meter)

Christina Hägemann,UNM 19 CV Other wafers/channels look about the same

Christina Hägemann,UNM 20 CV → Should use AC frequency of at least 10kHz Other wafers/channels look the same

Christina Hägemann,UNM 21 CV Plot 1/C 2 to find V Depletion This defines V Bias : 150 V or V Depletion + 50V V Depletion ~ 70 V

Christina Hägemann,UNM 22 Sensor QA Testing-Mechanical We have made wafer thickness and flatness measurements on the eight Pre Production wafers. Use our E+H MX203 Contactless Wafer Geometry Gauge Performs contactless measurements with capacitive sensors on both sides of wafer, there are no moving parts during measurement Resolution 0.1  m

Christina Hägemann,UNM 23 Summary / Next Steps Probestation is fully functional with all the VI’s working and tested Compare V Break and V Depletion for all the wafers Investigate further into the effect of the guard ring on current scan Once we get Hamamatsu wafers & new probe card - Compare measurements BNL – UNM - Remember: Need to normalize I to 20°C - Define what we mean with “bad sensor” - Start some thickness/flatness measurements