Radiation-hard Active Pixel Sensors for HL-LHC Detector Upgrades based on HV-CMOS Technology

Luminosity upgrades are discussed for the LHC (HL-LHC) which would make updates to the detectors necessary, requiring in particular new, even more radiation-hard and granular, sensors for the inner detector region. A proposal for the next generation of inner detectors is based on HV-CMOS: a new family of silicon sensors based on commercial high-voltage CMOS technology, which enables the fabrication of part of the pixel electronics inside the silicon substrate itself. The main advantages of this technology with respect to the standard silicon sensor technology are: low material budget, fast charge collection time, high radiation tolerance, low cost and operation at room temperature. A traditional readout chip is still needed to receive and organize the data from the active sensor and to handle high-level functionality such as trigger management. HV-CMOS has been designed to be compatible with both pixel and strip readout. In this paper an overview of HV2FEI4, a HV-CMOS prototype in 180 nm AMS technology, will be given. Preliminary results after neutron and X-ray irradiation are shown.

Source Scan Occupancy waveform).The response of the HitOR signal to a charge injection issued in the sensor by the USBpix system (a) as well as by a particle originating from a radioactive source (b) is shown.especially with the small pixel size of the HV2FEI4 pixels and the connection scheme with neighboring HV2FEI4 pixels that are connected to neighbor pixels in the FE-I4 (figure 7.3).The cluster size de-  response of each individual FE-I4 pixel while injecting charges into the HV2FEI4 is necessary.This is    Rela,ve"Amplifier"Gain"(%)" Dose"(Mrad)" Pixel"One" Pixel"Two" Pixel"Three" Pixel"Four" 10 days @ 22 C annealing Adjustment of settings

Figure 7
Figure 7.5: Occupancy maps of the HV2FEI4 glued to an FE-I4 readout chip obtained with electrons from a 90 Sr source.The full FE-I4 map (a) with entries in the HV2FEI4 position and a zoom into the region of the HV2FEI4 (b).

FullFigure 7
Figure7.6:The TOT information recorded by the FE-I4 (a).The TOT is not correlated to the charge collected in the sensor.The color coded mean TOT per pixel in the area covered by the HV2FEI4 (b) and the mean TOT projection along the columns (c).
Figure 7.7: The hit timing information within a time window of 16 times 25 ns (a).The cluster size in FE-I4 pixels measured in the Sr 90 source scan (b).
Figure7.8:The TOT response of a single FE-I4 pixel as a function of the discriminator output amplitude of the HV2FEI4 and the three sub-pixels within the HV2FEI4 (a).The TOT spectrum measured by the FE-I4 with a dedicated output amplitude setting for each of the three sub-pixels.
Edges have a bit lower e ciency !might be so à Reduced efficiency at edges and around dead pixels to be investigated à Again column dependency à Powering of HVCMOS columns to be detected late due to the time-walk e↵ect.With the HV2FEI4 as sensor, the two time-walk sources introduced in chapter 3.3.2are present twice, in the preamplifier and the discriminator of the sensor, and of the readout chip.A dedicated time-walk scan algorithm, sub-FE-I4-pixel resolution, and a cluster algorithm considering the sub-pixel connection scheme are necessary to investigate the timewalk in this configuration.The present algorithm clusters the FE-I4 pixel information.A significant amount of multi-pixel clusters is expected to be generated by the traversing electrons from a beta source.Multi hit clusters are expected expected
for threshold scan of HVCMOS C09 increasing e ciency with increasing column number for all à Drop in efficiency for high threshold à Efficiency depends on column à Global threshold setting smaller than column threshold variation COLUMN EFFICIENCY Thr.[a.u.] Channel # Irradiation Studies -Bulk Damage Tento Workshop 2014 -28/02/2014 Malte Backhaus 16 à à Decrease of Preamplifier gain with irradiation à Annealing periods observable à Parameter tuning recovers to 90 % gain after ~ 900 Mrad