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Jaap Velthuis, University of Bristol
SPiDeRFirst beam test results of the FORTIS sensor
• FORTIS• 4T MAPS• Deep PWell• Testbeam results• CHERWELL• Summary
J.J. Velthuisfor the
SPIDER collaboration
Jaap Velthuis, University of Bristol
SPiDeRFORTIS• FORTIS is the first 4T MAPS
aimed at Particle Physics• 0.18µm CMOS• 12µm epi layer• Uses INMAPS technology• 13 different type of pixels• Tested 3 types of sensors:
– Standard epi– Standard epi + deep Pwell
islands– High res epi + deep Pwell
islands
• Deep Pwell islands are first step towards in-pixel data processing
STFC IP STFC IP
STFC IP
STFC IPSTFC IP
STFC IP
Jaap Velthuis, University of Bristol
SPiDeRMAPS
• Charged particle generates free charge carriers in epitaxial layers.
• Due to doping profiles, electrons are confined to epitaxial layer.
• Electrons diffuse.• When close to diode
electrons collected
Jaap Velthuis, University of Bristol
SPiDeRFORTIS
• FORTIS is the first 4T MAPS for Particle Physics– 3T CMOS
• Simple architecture• Readout and charge collection node are the same
– 4T CMOS• Three additional elements• Readout and charge collection area are at different
points
Jaap Velthuis, University of Bristol
SPiDeR4T Pixel Advantages• Low Noise
– readout node separated from charge collection area
– The reset noise and pixel fixed pattern noise (FPN) can be removed by in-pixel correlated double sampling read out (CDS)
• High Conversion Gain– Charge is collected on large
diode then transferred to the floating diffusion
– Large C gives larger depleted area and complete charge collection
– Small C yields large gain
e-e-
V = q/C small
V = q/C large
5
Jaap Velthuis, University of Bristol
SPiDeRDeep Pwell• Problem in MAPS:
– PMOS electronics need Nwell
– Nwell acts as charge collection diode
– So can’t make PMOS without losing huge amount of Q
• New development: make deep pwell with Nwell inside can do CMOS– Road to data processing in
pixel
• Some FORTIS have empty deep pwell islands to test effect of Q collection
Jaap Velthuis, University of Bristol
SPiDeRSubstrate Resistivity
• High resistivity (intrinsic) silicon enlarges the depletion region to fully occupy the pixel– Majority of deposited
charge now falls in a depletion region and is collected by electric field
– Improved charge collection efficiency
– Faster charge collection (drift vs diffusion)
• Some FORTIS have high res
Jaap Velthuis, University of Bristol
SPiDeRSome test beam
pictures
Jaap Velthuis, University of Bristol
SPiDeRWe see hits…
• Beam at SPS
• 120 GeV pions
• Using EUDET telescope
C2
on F
1.1
hig
h r
es
Jaap Velthuis, University of Bristol
SPiDeREUDET telescope
• Telescope 6 planes, 18.4µm pitch, binary readout– single hit resolution: 18/√12=5.3µm
• FORTIS at 572 mm
• Simulated telescope error 3.2±0.2µm– Consistent EUDET values, only is different error in X and Y
(see talk Ingrid Gregor)
simulation
Jaap Velthuis, University of Bristol
SPiDeRC-structures• 4 test pixels:
– 128 × 128 pixels– 15µm pitch– C structures have different W and L for
source follower
• Three different wafers– standard epi – standard epi plus Deep PWell islands – high resistivity epi plus Deep PWell
islands plus implant to prevent FD and diode from merging
• Read out speed 15 frames per second
STFC IP
STFC IP
STFC IP
STFC IP
Jaap Velthuis, University of Bristol
SPiDeRC-structures: Noise• Noise is spread around pedestal after hit
removal• All 4 pixel types have same noise.• Difference in noise between various wafers
minimal– 21.9 ADC high resistivity plus Deep PWell
islands – 20.3 ADC Standard epi– 18.7 ADC Standard epi + deep PWell islands DPWHres Std
Jaap Velthuis, University of Bristol
SPiDeRC-structures: Signal• Cluster search: seed 5×noise, neighbours 2×noise,
max cluster size 5×5 pixels• Low signal peaks due to incomplete clusters.• Signals in standard epi + deep Pwell islands
highest• Signals in high res epi layer lowest.
– Naively expected to be higher: high res should increase depleted area and thus charge collection efficiency
DPWHres Std
Jaap Velthuis, University of Bristol
SPiDeRC-structures: Cluster
size
• Cluster size for high res much larger. – Charge travels much further– Charge per pixel much lower
• Deep PWell islands no effect cluster size
DPWHres Std
Jaap Velthuis, University of Bristol
SPiDeRC-structure: summary
table
• First time a 4T structure was successfully used for the detection of MIPs
• S/N ratios very high– S/N>100
Jaap Velthuis, University of Bristol
SPiDeRC-structures: position resolution
• Positions reconstructed using: – CoG, – 2 pixel clusters– eta
• Resolution worse for High res: due to large charge spread.
• Number still contains 3.2µm telescope uncertainty
DPWHres Std
Jaap Velthuis, University of Bristol
SPiDeRC-structure: summary
table (II)
• Resolutions corrected for telescope uncertainty. Large errors due to uncertainty in telescope error.
• Algorithms do not make much difference in resolution indicating that the charge division is reasonably linear.
Jaap Velthuis, University of Bristol
SPiDeRThe future: Cherwell
• Uses Deep Pwell and 4T to achieve 100% fill factor with integratedsensor and readout electronics
• Incorporation of complex logic within a pixel
• Investigation of data reduction/clustering
– CDS in-pixel and in-pixel amplification– Low power using rolling shutter readout
• First attempt housing ADC in the islands has been received.
4T
SELECT
COL
RESET
4T
COL
4T
COL
50 um pixel boundary
1xSRAM
4T
SELECT
COL
RESET
4T
COL
4T
COL
50 um pixel boundary
1xSRAM
Pixel
Bo
un
dary
Jaap Velthuis, University of Bristol
SPiDeRSummary• FORTIS is first 4T MAPS for Particle Physics• Using the Deep Pwell technology, we can incorporate full
CMOS circuits in pixel.• Tested three different wafers:
– Standard epi– Standard epi with Deep Pwell islands– High resistivity epi with Deep Pwell islands
• Deep Pwell islands have no detrimental effect on the signal.• FORTIS works really well:
– S/N>100 observed for 15µm pitch pixels– Position resolution <2µm
• Cherwell: first device with ADC in deep Pwell islands has been received.
• We thank the EUDET collaboration for the provided infrastructure and travel funds