PSTO MTJ Tunnel Barrier Oxidation for Low RA and Stable PMA

The oxidation process is divided into multiple sequential steps with different oxygen pressures and durations. The first step uses low oxygen pressure (1-10 mtorr) for a short duration (5-30 seconds) to form an initial oxide layer, followed by a second step with higher oxygen pressure (50-100 mtorr) for longer duration (60-300 seconds) to complete the oxidation. This segmented approach prevents overoxidation of magnetic layers while achieving the desired low RA product.

The oxidation process parameters (oxygen pressure, temperature, duration) are precisely controlled and changed between steps. The first oxidation step uses oxygen pressure of 1-10 mtorr at room temperature for 5-30 seconds, then the second step uses 50-100 mtorr at room temperature for 60-300 seconds. This parameter control ensures sufficient oxidation for low RA while preventing PMA loss.

The first oxidation step is performed as a preliminary action before the second oxidation step. This initial oxidation at low oxygen pressure (1-10 mtorr) for 5-30 seconds creates a controlled oxide layer that prevents excessive oxygen penetration into magnetic layers during the subsequent second oxidation step, thereby preventing PMA degradation while still achieving low RA.

The oxidation is performed in two stages where the first stage applies partial oxidation (low oxygen pressure for short time) and the second stage completes the oxidation (higher oxygen pressure for longer time). This partial then complete approach ensures sufficient oxidation for low RA without excessive oxidation that would degrade PMA in magnetic layers.