Abstract: Following CMP, a magnetic tunnel junction stack may protrude through the oxide that surrounds it, making it susceptible to possible shorting to its sidewalls. The present invention overcomes this problem by depositing silicon nitride spacers on these sidewalls prior to oxide deposition and CMP. So, even though the stack may protrude through the top surface of the oxide after CMP, the spacers serve to prevent possible later shorting to the stack.

Abstract: An MRAM reference cell sub-array provides a mid-point reference current to sense amplifiers. The MRAM reference cell sub-array has MRAM cells arranged in rows and columns. Bit lines are associated with each column of the sub-array. A coupling connects the bit lines of pairs of the columns together at a location proximally to the sense amplifiers. The MRAM cells of a first of the pair of columns are programmed to a first magneto-resistive state and the MRAM cells of a second of the pair of columns are programmed to a second magneto-resistive state. When one row of data MRAM cells is selected for reading, a row of paired MRAM reference cells are placed in parallel to generate the mid-point reference current for sensing. The MRAM reference sub-array may be programmed electrically or aided by a magnetic field. A method for verifying programming of the MRAM reference sub-array is discussed.

Abstract: An MRAM array has a plurality of MRAM devices that are arranged in rows and columns with segmented word lines. A magnetic biasing field is coupled to each of the MRAM devices. The MRAM devices are programmed by providing a bidirectional bit line current to a selected bit line of the plurality of bit lines and a word line current pulse to one word line segment of one row of word line segments by discharging coupled word line segments. The field biasing device may be permanent magnetic layers or write biasing lines in proximity to the fixed magnetic layer of each of the MRAM and has a magnetic orientation equivalent to the magnetic orientation of a word line segment magnetic field generated by the word line current pulse.

Abstract: An MRAM structure is disclosed where the distance from a bit line or word line to an underlying free layer in an MTJ is small and well controlled. As a result, the bit line or word line switching current is reduced and tightly distributed for better device performance. A key feature in the method of forming the MRAM cell structure is a two step planarization of an insulation layer deposited on the MTJ array. A CMP step flattens the insulation layer at a distance about 60 to 200 Angstroms above the cap layer in the MTJ. Then an etch back step thins the insulation layer to a level about 50 to 190 Angstroms below the top of the cap layer. Less than 5 Angstroms of the cap layer is removed. The distance variation from the free layer to an overlying bit line or word line is within +/?5 Angstroms.

Abstract: An MTJ in an MRAM array or in a TMR read head is comprised of a capping layer with a lower inter-diffusion barrier layer, an intermediate oxygen gettering layer, and an upper metal layer that contacts a top conductor. The composite capping layer is especially useful with a moderate spin polarization free layer such as a NiFe layer with a Fe content of about 17.5 to 20 atomic %. The capping layer preferably has a Ru/Ta/Ru configuration in which the lower Ru layer is about 10 to 30 Angstroms thick and the Ta layer is about 30 Angstroms thick. As a result, a high dR/R of about 40% is achieved with low magnetostriction less than about 1.0 E?6 in an MTJ in an MRAM array. Best results are obtained with an AlOx tunnel barrier layer formed by an in-situ ROX process on an 8 to 10 Angstrom thick Al layer.

Abstract: A method of using an MTJ MRAM cell element having two magnetization states of greater and lesser stability. During switching, the free layer is first placed in the less stable state by a word line current, so that a small bit line current can switch its magnetization direction. After switching, the state reverts to its more stable form as a result of magnetostatic interaction with a SAL (soft adjacent layer), which is a layer of soft magnetic material formed on an adjacent current carrying line, which prevents it from being accidentally rewritten when it is not actually selected and also provides stability against thermal agitation.

Abstract: An MTJ MRAM cell is formed between ultra-thin orthogonal word and bit lines of high conductivity material whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. Because the lines require thinner depositions, there is no necessity of removing material by CMP during patterning and polishing. Therefore, there is a uniform spacing between the lines and the cell free layer.

Abstract: An MTJ MRAM cell is formed between or below an intersection of ultra-thin orthogonal word and bit lines of high conductivity material whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. The fabrication of a cell with such thin lines is actually simplified as a result of the thinner depositions because the fabrication process eliminates the necessity of removing material by CMP during patterning and polishing, thereby producing uniform spacing between the lines and the cell free layer.

Abstract: An improved TMR device is disclosed. The ferromagnetic layers of the device, particularly those that contact the dielectric tunneling layer have an amorphous structure as well as a minimum thickness (of about 15 ?). A preferred material for contacting the dielectric layer is CoFeB. Ways of overcoming problems relating to magnetostriction are disclosed and a description of a process for manufacturing the device is included.

Abstract: Magnetic Random Access Memory (MRAM) can be programmed and read as fast as Static Random Access Memory (SRAM) and has the non-volatile characteristics of electrically eraseable programmable read only memory (EEPROM), FLASH EEPROM or one-time-programmable (OTP) EPROM. Due to the randomness of manufacturing process, the magnetic tunnel junctions (MTJ) in MRAM cells will require different row and column current combinations to program and not to disturb the other cells. Based on adaptive current sources for programming, this disclosure teaches methods, designs, test algorithms and manufacturing flows for generating EEPROM, FLASH EEPROM or OTP EPROM like memories from MRAM.

Abstract: A configurable MRAM device is achieved. The device comprises a memory array of magnetic memory cells. A first part of the array comprises the memory cells that can be accessed for reading and writing during normal operation. A second part of the array comprises the memory cells that can be read only during a power up initialization. The second part of the array is used to store configuration data for altering the physical operation of the memory array. Programmable current sources and timing delays use the stored configuration data to optimize device performance. A redundant section of memory cells is activated by the configuration data.

Abstract: An MTJ element is formed between orthogonal word and bit lines. The bit line is a composite line which includes a high conductivity layer and a soft magnetic layer under the high conductivity layer. During operation, the soft magnetic layer concentrates the magnetic field of the current and, due to its proximity to the free layer, it magnetically couples with the free layer in the MTJ. This coupling provides thermal stability to the free layer magnetization and ease of switching and the coupling may be further enhanced by inducing a shape or crystalline anisotropy into the free layer during formation.

Abstract: An MRAM reference cell sub-array provides a mid-point reference current to sense amplifiers. The MRAM reference cell sub-array has MRAM cells arranged in rows and columns. Bit lines are associated with each column of the sub-array. A coupling connects the bit lines of pairs of the columns together at a location proximally to the sense amplifiers. The MRAM cells of a first of the pair of columns are programmed to a first magneto-resistive state and the MRAM cells of a second of the pair of columns are programmed to a second magneto-resistive state. When one row of data MRAM cells is selected for reading, a row of paired MRAM reference cells are placed in parallel to generate the mid-point reference current for sensing. The MRAM reference sub-array may be programmed electrically or aided by a magnetic field. A method for verifying programming of the MRAM reference sub-array is discussed.

Abstract: Following CMP, a magnetic tunnel junction stack may protrude through the oxide that surrounds it, making it susceptible to possible shorting to its sidewalls. The present invention overcomes this problem by depositing silicon nitride spacers on these sidewalls prior to oxide deposition and CMP. So, even though the stack may protrude through the top surface of the oxide after CMP, the spacers serve to prevent possible later shorting to the stack.

Abstract: An MTJ (magnetic tunneling junction) device particularly suitable for use as an MRAM (magnetic random access memory) or a tunneling magnetoresistive (TMR) read sensor, is formed on a seed layer which allows the tunneling barrier layer to be ultra-thin, smooth, and to have a high breakdown voltage. The seed layer is a layer of NiCr which is formed on a sputter-etched layer of Ta. The tunneling barrier layer for the MRAM is formed from a thin layer of Al which is radically oxidized (ROX), in-situ, to form the layer with characteristics described above. The tunneling barrier layer for the read sensor formed from a thin layer of Al or a HfAl bilayer which is naturally oxidized (NOX), in-situ, to form the barrier layer. The resulting device has generally improved performance characteristics in terms of GMR ratio and junction resistance.

Abstract: Magnetic Random Access Memory (MRAM) can be programmed and read as fast as Static Random Access Memory (SRAM) and has the non-volatile characteristics of electrically eraseable programmable read only memory (EEPROM), FLASH EEPROM or one-time-programmable (OTP) EPROM. Due to the randomness of manufacturing process, the magnetic tunnel junctions (MTJ) in MRAM cells will require different row and column current combinations to program and not to disturb the other cells. Based on adaptive current sources for programming, this disclosure teaches methods, designs, test algorithms and manufacturing flows for generating EEPROM, FLASH EEPROM or OTP EPROM like memories from MRAM.

Abstract: An MTJ (magnetic tunneling junction) MRAM (magnetic random access memory) cell is formed on a conducting lead and magnetic keeper layer that is capped by a sputter-etched Ta layer. The Ta capping layer has a smooth surface as a result of the sputter-etching and that smooth surface promotes the subsequent formation of a lower electrode (pinning/pinned layer) with smooth, flat layers and a radical oxidized (ROX) Al tunneling barrier layer which is ultra-thin, smooth, and to has a high breakdown voltage. A seed layer of NiCr is formed on the sputter-etched capping layer of Ta. The resulting device has generally improved performance characteristics in terms of its switching characteristics, GMR ratio and junction resistance.

Abstract: A method of forming a high performance MTJ in an MRAM array is disclosed. A Ta/Ru capping layer in a bottom conductor is sputter etched to remove the Ru layer and form an amorphous Ta capping layer. A key feature is a subsequent surface treatment of the Ta capping layer in a transient vacuum chamber where a self-annealing occurs and a surfactant layer is formed on the Ta surface. The resulting smooth and flat Ta surface promotes a smooth and flat surface in the MTJ layers which are subsequently formed on the surfactant layer. For a 0.3×0.6 micron MTJ bit size, a 35 to 40 Angstrom thick NiFe(18%) free layer, an AlOx barrier layer generated from a ROX oxidation of an 9 to 10 Angstrom thick Al layer, and a Ru/Ta/Ru capping layer are employed to give a dR/R of >40% and an RA of about 4000 ohm-?m2.

Abstract: An MTJ MRAM cell element, whose free layer has a shape induced magnetic anisotropy, is formed between orthogonal word and bit lines. The bit line is a composite line which includes a high conductivity current carrying layer and a soft adjacent magnetic layer (SAL). During operation, the soft magnetic layer concentrates the magnetic field of the current and, due to its proximity to the free layer, it magnetically couples with the free layer to produce two magnetization states of greater and lesser stability. During switching, the layer is first placed in the less stable state by a word line current, so that a small bit line current can switch its magnetization direction. After switching, the state reverts to its more stable form as a result of magnetostatic interaction with the SAL, which prevents it from being accidentally rewritten when it is not actually selected and also provides stability against thermal agitation.

Abstract: A high performance MTJ in an MRAM array is disclosed in which the bottom conductor has an amorphous Ta capping layer. A key feature is a surfactant layer comprised of oxygen that is formed on the Ta surface. The resulting smooth and flat Ta capping layer promotes a smooth and flat surface in the MTJ layers which are subsequently formed on the surfactant layer. For a 0.3×0.6 micron MTJ bit size, a 35 to 40 Angstrom thick NiFe(18%) free layer, an AlOx barrier layer generated from a ROX oxidation of an 9 to 10 Angstrom thick Al layer, and a Ru/Ta/Ru capping layer are employed to give a dR/R of >40% and an RA of about 4000 ohm-?m2. The MTJ configuraton is extendable to a 0.2×0.4 micron MTJ bit size.