ALICE is planning to replace its three innermost tracking layers with a fully cylindrical, bent sili- con tracker during LHC Long Shutdown 3 (LS3, targeting 2024-25). The new detector will reach an unprecedented low material budget of below 0.05% X0 per layer, combined with an intrinsic spatial resolution below 5 μm in z- and rφ -directions. Its main building part is an ultra-thin (20 μm to 40 μm), wafer-scale (300 mm) CMOS Monolithic Active Pixel Sensor, that will be developed in 65 nm technology for this purpose. The sensor dimensions reach up to 280 by 94 mm, and, owing to the flexible nature of silicon at these thicknesses, is bent into half-cylinders of radii of 18, 24, and 30 mm, respectively, to form the new concentric layers.
This contribution addresses the detector R&D road map as well as projected improvements in per- formance and related physics yields. The combination of reduced material budget, closer proxim- ity to the interaction point, and high intrinsic resolution translate into a significant advancement in the measurement of short-lived particles and low-mass di-electrons, which are amongst the main physics goals of ALICE.