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

2 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 + -SiO 2 -Al Discussion items for RC chip –Required R&C values –HPK design rule –Design for stripixel detector –R&D w/ ROC + sensor + RC chip Poly-silicon resistor Coupling capacitor Pad connected to R/O chip Pad connected to sensor Pad connected to GND Schematic layout of RC chip

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

4 Discussion Items Required R&C values : Inputs from Zheng & Veljko –R~10 MOhm, generally –C~10×C strip for better charge collection –C strip 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= μm (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/mm 2 (standard), 400 pF/mm 2 by using thin SiO 2 layer (R&D required)

5 Discussion Items Design for stripixel detector –Concern is available space for RC chip on ROC ROC : 60×30 mm 2, RCC : 7×7 mm 2, SVX4 chip : 6.40×9.11 mm 2 RC chip : ~7×5 mm 2 –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 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. SVX4 chip area~6.40 x 9.11 mm 2 t~300 μm RC chip area~8 x 15 mm 2 t~200 μm ROC (Al-Kapton flex) Sensor t~500(625) μm

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 Poly-silicon resistor : R=10 MΩ Length < 1mm Coupling capacitor : C~296pF Pitch=48μm Length ~ 14mm (440pF/mm 2 ) Length ~ 15mm Length ~ 8mm

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 mm 2 ) –0.171 % for 200μm thick, % 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/mm 2 and (3) metal pad on RC chip. –~1.5 weeks are required. –Fabrication : 1 month for design & 2 months for processing