During the 1950s and 1960s, magnetic core memories were the predominant storage technology for the working memory of computing systems. The magnetic core memory technology was costly. In the 1970s, magnetic core memories were replaced with integrated circuits, including dynamic random access memory (DRAM) and including static random access memory (SRAM). Non-volatile memories, such as FLASH memory for example, have been developed to address the problem of data volatility. Because of the rapid advancement in semiconductor density coupled with the advent of the DRAM cell, magnetic storage technology was not used for high-speed on-line memory, but rather was left to be used for low-cost, high-density memory in the form of various disk drive technologies.
The semiconductor industry continuously strives to reduce the size and cost of memory, increase the speed for accessing memory, and improve the reliability of memory. One particular problem confronting the semiconductor industry is that of reducing the size of the memory cell in a Random Access Memory (RAM).
Magnetic storage such as Magnetic Random Access Memory (MRAM) technology has been proposed as a replacement or supplement to the DRAM. In the MRAM structures that are being proposed, the capacitor storage element of the DRAM cell is replaced by a magnetic element that has a magnetic moment and is characterized by a predominant or easy axis of magnetization. In the absence of an external magnetic field, the magnetic moment is oriented along the easy axis of magnetization in one of two stable states. In magnetoresistance technology, one of the stable states for the magnetic moment of the magnetic element is a high resistance state and the other of the stable states is a low resistance state.
Conventional etching processes for MRAM have been found to be too aggressive which results in etching layers that are not intended to be etched. Unintentional etching may create undesirable residues such as metals, metal alloys, etc., which in some applications include tantalum (Ta). The residues have been found to form footings adjacent the bases of bit masks. Aggressive etching techniques must be employed to remove the footings. However, aggressive etching causes further unwanted etching of MRAM layers. Etching of the MRAM layers may cause shorting of the MRAM bit or create a defective device.
Without the aggressive etching techniques mentioned above the footings remain adjacent the bit mask base. The presence of footings negatively affects critical dimensions (CD) of the MRAM bit etch mask, which are the desired shape and size of the mask layer. An unintentionally large MRAM bit created because of footing issues may exceed dimensioning tolerances and thus contact other MRAM bits, which degrades performance and may prevent MRAM function, or other integrated circuit structure function.
Therefore, there is a need in the art to overcome the problems attributable to defining an MRAM bit etch mask.
USPTO Backgrounds
USPTO Backgrounds