Abstract: The High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker (ITk). Radiation-hard n+-in-p micro-strip sensors were developed for use in the ITk. During quality control (QC) and quality assurance (QA) procedures performed on ATLAS18 production sensors and test chips, ATLAS ITk strip sensor institutes identified instances of low p-stop density in certain production batches. To investigate the origin of these issues and to try some technological improvements, two dedicated sample batches with four variations of the p-stop fabrication process were produced. These process types (1-4) were systematically evaluated to determine their effectiveness and uniformity. In total, 56 full-size sensors, along with numerous miniature sensors and test chips, were tested. A number of samples were used in the irradiation campaign reaching the maximum expected levels for the HL-LHC operation after 10 years – with neutrons up to 1.6 & times; 1015 neq/cm2, and with gamma rays from a 60Co source up to 66 Mrad. The goal of this evaluation program is to assess the impact of p-stop fabrication process variations on interstrip isolation performance and to provide feedback for future sensor development. This paper describes the applied test procedures and presents the corresponding results, which demonstrate good sensor performance for all investigated p-stop types. The findings confirm the reliability of the evaluated designs and identify specific advantages that can inform further optimization of strip sensor fabrication.