RC chip

Junji TojoRIKEN

VTX MeetingFebruary 9th, 2005

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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

Poly-silicon resistorCoupling capacitor

Pad connectedto R/O chip

Pad connectedto sensor

Pad connectedto GND

Schematic layout of RC chip

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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)

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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 1m

m.

– Coupling capacitor• 200 pF/mm2 (standard), 400 pF/mm2 by using thin SiO2 layer (R&D requ

ired)

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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.

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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 chiparea~6.40 x 9.11 mm2

t~300 μm

RC chiparea~8 x 15 mm2

t~200 μm

ROC (Al-Kapton flex)

Sensort~500(625) μm

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RC Chip Design for Stripixel DetectorLocate AC pads to the left sideand modify the pad layout matched to SVX4

Modify the pad layout matched to the sensor

Poly-silicon resistor : R=10 MΩLength < 1mm

Coupling capacitor : C~296pFPitch=48μm Length ~ 14mm(440pF/mm2)

Length ~ 15mm

Length ~ 8mm

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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 chi

p (& corresponding WB pad(s)) is required on RC chip.

• HPK’s response– Under consideration : (1) Thickness, (2) 440 pF/mm2 and (3) metal pa

d on RC chip.

– ~1.5 weeks are required.

– Fabrication : 1 month for design & 2 months for processing