Fabrication Method for Hexagonal Boron Nitride Layers

Computer memory devices may employ any of various mechanisms for storing data, e.g., using memory cells each of which may be programmed to be in any of two or more states. Non-volatile memory includes memory cells each of which operates by changing the resistance across an active switching layer, e.g., an insulator, through the formation of conductive filaments. This type of technology may be referred to as resistive random-access memory (RRAM or ReRAM); each programmable-resistance memory element may be referred to as a memristor. Such memory cells may be combined, on a Si substrate, with computing elements (constructed, e.g., using CMOS circuits, such as CMOS flipflops, CMOS gates, and CMOS inverters), to form compute-in-memory hardware which may be employed for artificial intelligence/machine learning applications.

A memristor may include two electrodes and, between the electrodes, a suitable material capable of being in a plurality of different resistive states (e.g., based on the respective abundance and conductivity of conductive paths in each of the states). Suitable materials may include 2D layered materials, such as hexagonal boron-nitride (h-BN). Such a material may include one or more 2D atomically-thin nanosheets, each of which is a 2D crystal. The nanosheets may interact through relatively weak forces.

Various methods may be used to form h-BN for use in a memristor.  One is chemical-vapor deposition; however, high growth temperatures used in this method may damage CMOS circuitry on a wafer. Another method, transferring of h-BN films from the growth substrates onto the silicon wafer, could be used. Such a process may, however, not readily scale to larger wafer sizes and may damage or introduce contaminants to the transferred film, degrading device performance and reliability.

Researchers at Arizona State University have developed a deposition method of fabrication of hexagonal boron nitride (h-BN) thin films. This method results in vertically-aligned h-BN nanosheets that form polycrystalline films with controllable number of native defects that benefit the stable formation and rupture of conductive filaments.

Potential Applications:

• Microelectronic products related to non-volatile memory and compute-in-memory technologies

Benefits and Advantages:

• Low temperature deposition of the h-BN films ensures compatibility with Si-based CMOS microelectronics technology
• Deposition method is better suited for wafer-scale integration with improved uniformity, crystallinity, and functionality
• Structure of the resistive switching layer composed of vertically aligned h-BN nanosheets is associated with high stability and precision in the programming of multiple conductive states within the same device
• Easy incorporation of method into any existing Si-based microelectronic process and fabrication flow (e.g., for semiconductor manufacturers)