# Presentation: 485464

## RC chip

- Junji Tojo
- RIKEN
- VTX Meeting
- February 9th, 2005

## “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

- “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

## 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)

## 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)

## 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.

## 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.

## 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/mm2)

- Length ~ 15mm

- Length ~ 8mm

## 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