Control method for sidewall contamination of MRAM magnetic tunnel

A method for controlling contaminants on a sidewall of a magnetic tunnel junction (MTJ) of a magnetic random access memory (MRAM), comprising:

• providing a base structure, wherein the base structure comprises a substrate, a lower electrode, a MTJ layer, and an upper electrode, which are arranged in the above-listed sequence along a first direction, and the first direction is perpendicular to the substrate and points from the substrate to the lower electrode;
• performing first etching on a surface of the upper electrode away from the substrate, until the substrate is exposed, wherein after the first etching, a portion of the lower electrode adjacent to the substrate tapers along the first direction, and a size of another portion of the lower electrode is uniform along the first direction;
• performing second etching after the first etching, wherein:
• after the second etching, a size of the whole lower electrode is uniform along the first direction, and a funnel-shaped trench is formed in the substrate,
• the funnel-shaped trench comprises a first part away from a bottom surface of the substrate and a second part close to the bottom surface of the substrate, and
• the first part expands gradually along the first direction, and a size of the second part is uniform along the first direction;
• and
• removing metallic contaminants at a bottom of the funnel-shaped trench.