Spin-torque transfer memory cell structures with symmetric switching and single direction programming

A spin torque transfer magnetic random access memory (STT-MRAM) cell structure, comprising:

• a nonmagnetic region having at least a first side, a second side, and a third side;
• a first region with a fixed magnetization orientation disposed along the first side of the nonmagnetic region;
• a second region with a fixed magnetization orientation disposed along the second side of the nonmagnetic region;
• and
• a region with a free magnetization orientation disposed along the third side of the nonmagnetic region, wherein the first region with a fixed magnetization orientation is configured to be grounded such that a programming current through the region with a free magnetization orientation to the nonmagnetic region and to the first region with a fixed magnetization orientation results in electrons propagating from the first region with a fixed magnetization orientation, through the nonmagnetic region, and through the region with a free magnetization orientation to switch a magnetization of the region to be parallel with a magnetization of the first region with a fixed magnetization orientation.

A spin torque transfer magnetic random access memory (STT-MRAM) cell structure, comprising:

• a nonmagnetic region having at least a first side, a second side, and a third side;
• a first region with a fixed magnetization orientation disposed along the first side of the nonmagnetic region;
• a second region with a fixed magnetization orientation disposed along the second side of the nonmagnetic region;
• and
• a region with a free magnetization orientation disposed along the third side of the nonmagnetic region;
• a first interface where the first region with a fixed magnetization orientation contacts the nonmagnetic region, wherein electrons passing from the first region with a fixed magnetization orientation through the first interface accumulate in the nonmagnetic region, wherein the passing electrons are spin polarized to a magnetization of the first region with a fixed magnetization orientation;
• and
• a second interface where the second region with a fixed magnetization orientation contacts the nonmagnetic region, wherein electrons reflecting from the second region with a fixed magnetization orientation into the nonmagnetic region accumulate in the nonmagnetic region, wherein the reflecting electrons are spin polarized to a magnetization opposite of the second region with a fixed magnetization orientation, and wherein the passing electrons and the reflecting electrons are spin polarized to a substantially similar direction.

A spin torque transfer magnetic random access memory (STT-MRAM) cell configured to be programmed by a unidirectional programming current, wherein the STT-MRAM cell comprises:

• a first region with a fixed magnetization orientation having a magnetization in a first direction;
• a second region with a fixed magnetization orientation having a magnetization in a second direction;
• a nonmagnetic region between the first region with a fixed magnetization orientation and the second region with a fixed magnetization orientation;
• and
• a region with a free magnetization orientation disposed over the nonmagnetic region, wherein the region with a free magnetization orientation is configured to be switched in magnetization by a unidirectional programming current to have a magnetization that is either parallel with or antiparallel to the magnetization of the first region with a fixed magnetization orientation.

A spin torque transfer magnetic random access memory (STT-MRAM) cell configured for symmetrical programming, wherein the STT-MRAM cell comprises:

• a first region with a fixed magnetization orientation having a first magnetization;
• a second region with a fixed magnetization orientation having a second magnetization;
• a nonmagnetic region disposed between the first region with a fixed magnetization orientation and the second region with a fixed magnetization orientation;
• and
• a region with a free magnetization orientation disposed over the nonmagnetic region, wherein the region with a free magnetization orientation is configured to be switched by a first programming current to have the first magnetization or switched by a second programming current to have the second magnetization, wherein a magnitude of the first programming current is substantially similar to a magnitude of the second programming current.

A method for forming a cell structure, the method comprising:

• forming a recess in a substrate;
• forming a transistor in the recess;
• forming a region with a free magnetization orientation in the recess and over the transistor;
• forming a nonmagnetic region over the region with a free magnetization orientation, such that the region with a free magnetization orientation contacts a first side of the nonmagnetic region;
• and
• forming a first region with a fixed magnetization orientation and a second region with a fixed magnetization orientation, such that the first region with a fixed magnetization orientation directly contacts a second side of the nonmagnetic region and the second region with a fixed magnetization orientation directly contacts a third side of the nonmagnetic region, wherein none of the region with a free magnetization orientation, the first region with a fixed magnetization orientation, or the second region with a fixed magnetization orientation are touching.

A method for forming a cell structure, the method comprising:

• forming a recess in a substrate;
• forming a transistor in the recess;
• forming a region with a free magnetization orientation in the recess and over the transistor;
• forming a nonmagnetic region over the region with a free magnetization orientation, such that the region with a free magnetization orientation contacts a first side of the nonmagnetic region;
• forming a first region with a fixed magnetization orientation and a second region with a fixed magnetization orientation, such that the first region with a fixed magnetization orientation contacts a second side of the nonmagnetic region and the second region with a fixed magnetization orientation is adjacent to a third side of the nonmagnetic region, wherein none of the region with a free magnetization orientation, the first region with a fixed magnetization orientation, or the second region with a fixed magnetization orientation are touching;
• forming a top electrode over the transistor and forming the region with a free magnetization orientation over the top electrode;
• and
• forming a spacer region over the top electrode and depositing the region with a free magnetization orientation within an inner perimeter of the spacer region.

A method for forming a cell structure, the method comprising:

• forming a recess in a substrate;
• forming a transistor in the recess;
• forming a region with a free magnetization orientation in the recess and over the transistor;
• forming a nonmagnetic region over the region with a free magnetization orientation, such that the region with a free magnetization orientation contacts a first side of the nonmagnetic region;
• forming a first region with a fixed magnetization orientation and a second region with a fixed magnetization orientation, such that the first region with a fixed magnetization orientation contacts a second side of the nonmagnetic region and the second region with a fixed magnetization orientation is adjacent to a third side of the nonmagnetic region, wherein none of the region with a free magnetization orientation, the first region with a fixed magnetization orientation, or the second region with a fixed magnetization orientation are touching;
• and
• forming a switch to ground either the first region with a fixed magnetization orientation or the second region with a fixed magnetization orientation.