{'fraction_non_alphanumeric': 0.055327868852459015, 'fraction_numerical': 0.022540983606557378, 'mean_word_length': 4.548295454545454, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 2, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Critical Device Performance Issues in Ta-seed Based Perpendicular-STT MRAM

Perpendicular spin-transfer-torque magnetic-random-access-memory (p-STT MRAM) has been developed as a promising nonvolatile memory to replace current dynamic-random-access memory beyond 20-nm design rule. p-STT MRAM require four critical device performance parameters such as high TMR ratio of 150 %, a high anti-ferromagnetic-coupling-strength (Jex) for a synthetic anti-ferromagnetic layer (SyAF) of > 0.7 erg/cm 2 , a thermal stability (Δ) of > 74 and a low critical current density (JC) of 13.4 MA/cm 2 (1). In particular, four critical device performances should be achieved above 350 o C of back-end-of-line (BEOL). In this presentation, we will review four critical device performances for the Ta-seed based p-MTJ spin valves. It showed that the TMR ratio was obtained from interface-perpendicular magnetic anisotropy (i-PMA) at the interface between amorphous Co2Fe6B2 free layer or pinned layer and b.c.c. crystalline MgO tunneling barrier, as shown in in Figs. 1(a) and (b). However, the Ta-seed degraded gradually i-PMA characteristic of Co2Fe6B2 free layer because of the degradation of the MgO crystalline linearity induced by the Ta diffusion into the MgO tunneling barrier when ex-situ annealing temperature raised above 300 o C, resulting in the TMR ratio degradation, as shown in Figs. 1(c) and (d). In addition, the Ta-seed degraded rapidly i-PMA characteristic of the Co2Fe6B2 pinned layer when ex-situ annealing temperature raised above 300 o C, since the Co2Fe6B2 pinned layer was textured with f.c.c. crystalline structure induced by the Pd diffusion from the (Co/Pd)n-SyAF, resulting in the TMR ratio degradation, as shown in Fig. 2. Thus, we developed a p-MTJ spin-valve structure to solve these issue via introducing a sponge structure (MgO/CoFeB free layer/Ta/MgO/Ta seed) and (Co/Pt)n-SyAF, achieving 140 % of the TMR ratio for 12 inch based wafers.