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RC chip

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  1. RC chip Junji Tojo RIKEN VTX Meeting February 9th, 2005

  2. Pad connected to GND Pad connected to sensor Pad connected to R/O chip Poly-silicon resistor Coupling capacitor RC Chip • “RC chip” is one of solutions to make AC coupling btw stripixel sensor (DC coupling) & SVX4 chip. • Technology • Usual p-on-n AC coupling silicon strip sensor fabrication technology. Hamamatsu (HPK) has experience. (See page 2) • Resistor w/ poly-silicon • Coupling capacitor w/ p+-SiO2-Al • Discussion items for RC chip • Required R&C values • HPK design rule • Design for stripixel detector • R&D w/ ROC + sensor + RC chip Schematic layout of RC chip

  3. An Example of RC Chip (HPK) N-sub pad (connected to n-bulk) DC pad (wire-bonded to sensor) AC pad (wire-bonded to R/O chip) GND pad Poly-silicon resistor Coupling capacitor

  4. Discussion Items • Required R&C values : Inputs from Zheng & Veljko • R~10 MOhm, generally • C~10×Cstrip for better charge collection • Cstrip will be measured by HPK, using pre-production sensors. • (Additionally, leakage current per strip will be also measured.) • HPK design rule • Wafer & thickness • p-on-n, 4” wafer process • t=275-650μm (standard), 200μm (possible), 150μm (limit) • Poly-silicon resistor • If we ask ~10 MOhm, length will be a few hundred μm or less than 1mm. • Coupling capacitor • 200 pF/mm2 (standard), 400 pF/mm2 by using thin SiO2 layer (R&D required)

  5. Discussion Items • Design for stripixel detector • Concern is available space for RC chip on ROC • ROC : 60×30 mm2 , RCC : 7×7 mm2 , SVX4 chip : 6.40×9.11 mm2 • RC chip : ~7×5 mm2 • Poly-silicon resistor : 10 MOhm, no problem. • Coupling capacitor • 48μm pitch, ~5mm : C~200×0.048×5=48 pF or 440×0.048×5=106 pF Probably too small. • 60μm pitch, ~5mm : C~200×0.048×5=60 pF or 440×0.048×5=132 pF Still too small. • Possible solution : SVX4 chip stacked on RC chip Chip stacking is an usual MCM technology.

  6. ROC (Al-Kapton flex) Sensor t~500(625) μm SVX4 chip area~6.40 x 9.11 mm2 t~300 μm RC chip area~8 x 15 mm2 t~200 μm Discussion Items • Design for stripixel detector • RC chip & SVX4 stacking • RC chip : ~15mm length (maximum), coupling capacitor : ~14 mm length • C~ 440×0.048×14 = 296 pF (maxium), probably OK. • See next page.

  7. RC Chip Design for Stripixel Detector Locate AC pads to the left side and modify the pad layout matched to SVX4 Modify the pad layout matched to the sensor Length ~ 8mm Length ~ 15mm Coupling capacitor : C~296pF Pitch=48μm Length ~ 14mm (440pF/mm2) Poly-silicon resistor : R=10 MΩ Length < 1mm

  8. Comments • Length of RC chip • ~15mm is too long for available space on ROC. • To be determined from measured strip capacitance. • Material budget of RC chips per ROC • 12 RC chips per 1 ROC (30×60 mm2) • 0.171 % for 200μm thick, 0.128 % for 150μm thick • Metal pad for SVX4 backplane • SVX4 backplane should be grounded. Thus, Al pad to stack SVX4 chip (& corresponding WB pad(s)) is required on RC chip. • HPK’s response • Under consideration : (1) Thickness, (2) 440 pF/mm2 and (3) metal pad on RC chip. • ~1.5 weeks are required. • Fabrication : 1 month for design & 2 months for processing