Radiation hardened double sided Low-Gain Avalanche Diode (LGAD) with small pixel readout for 5D tracking

The current generation of Low-Gain Avalanche Diodes (LGADs) utilize “reach-through” deep implants to provide high field gain layer. These are a recent class of silicon devices developed (mainly) to detect MIPS. They are built on thin silicon substrates, order of 50 microns, and they are engineered to have an amplification in the order of a few tens. They provide fast signals at the expense of a poor spatial resolution, being impossible to pattern them finely. New generation of LGADs are therefore needed and a few have arisen at the attention of the scientific community: Cactus Materials, Inc. is developing radiation hardened AC-LGADs and Deep-Junction LGADs, having a 100% fill factor (no dead areas) and arbitrarily fine-pitch electrodes. Phase I of the project completed preliminary studies of a new family of LGAD structures to provide 5D (X, Y, Z, T, theta) tracking information The concept consists of a double sided (inverted) LGADs (iLGADs) with small pixel readout. Results from Phase I TCAD simulation confirmed current pattern is used to measure angle and position. During Phase I of the project, mask design and a fabrication scheme established including a prototype fabrication. A testing will be performed in Q2 this year in remaining time of the Phase I. Phase II of the project will continue to estimate radiation hardness of the device using TCAD simulation. Ron Lipton of Fermi National Lab will be performed the simulation in collaboration with Cactus Materials, Inc. Two additional cycles of fabrications will be performed at Cactus Materials, Inc. in larger sizes of wafers to mimic scale up foundry process. The fabrication leverages from the capabilities of Cactus Materials of performing AC-LGADs and 3D integration technology previously developed or in progress through SBIR fundings. Radiation hardened testing will be performed at the test team of Fermilab, and Testing will be performed in collaboration of Brookhaven National Lab (BNL) and Cactus Materials. Dr. Islam, PI of this project, has extensive experience in semiconductor fabrication while worked at Intel Corporation, EVG, Inc and Cactus Materials, Inc. and Dr. Ron Lipton from Fermi Lab will conduct TCAD simulation and Gabriele Giacomini of BNL will be testing the final devices. Key application for these LGADs sensors ranges from high energy physics (HEP) to healthcare. 5D sensors for tracking particles in HEP, scintillator coupling for photon detection applicable in healthcare such as medical imaging in positron emission tomography (PET) scanner, soft x-ray cameras with higher frame rate and other applications are foreseen. Interest in angle information is motivated by the current CMS track trigger stub concept and possible future FCC-hh and muon collider background reduction applications