Resistive-switching memory elements having improved switching characteristics

#The present invention relates generally to semiconductor memories. More specifically, resistive-switching memory elements having improved switching characteristics are described.

#Non-volatile memories are semiconductor memories that retain their contents when unpowered. Non-volatile memories are used for storage in electronic devices such as digital cameras, cellular telephones, and music players, as well as in general computer systems, embedded systems and other electronic devices that require persistent storage. Non-volatile semiconductor memories can take the form of removable and portable memory cards or other memory modules, can be integrated into other types of circuits or devices, or can take any other desired form. Non-volatile semiconductor memories are becoming more prevalent because of their advantages of having small size and persistence, having no moving parts, and requiring little power to operate.

#Flash memory is a common type of non-volatile memory used in a variety of devices. Flash memory uses an architecture that can result in long access, erase, and write times. The operational speeds of electronic devices and storage demands of users are rapidly increasing. Flash memory is proving, in many instances, to be inadequate for non-volatile memory needs. Additionally, volatile memories (such as random access memory (RAM)) can potentially be replaced by non-volatile memories if the speeds of non-volatile memories are increased to meet the requirements for RAM and other applications currently using volatile memories.

#Various embodiments of the invention are disclosed in the following detailed description and the accompanying drawings:

#FIG. 1 illustrates a memory array of resistive switching memory elements;

#FIGS. 2A and 2B illustrate a memory element including a resistive-switching material and a select element;

#A detailed description of one or more embodiments is provided below along with accompanying figures. The detailed description is provided in connection with such embodiments, but is not limited to any particular example. The scope is limited only by the claims and numerous alternatives, modifications, and equivalents are encompassed. Numerous specific details are set forth in the following description in order to provide a thorough understanding. These details are provided for the purpose of example and the described techniques may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the embodiments has not been described in detail to avoid unnecessarily obscuring the description.

#According to various embodiments, resistive-switching memory elements are described herein. The memory elements generally have a metal-insulator-metal (MIM) structure in which resistive-switching insulating layers are surrounded by two conductive electrodes. Some embodiments described herein are memory elements that include electrodes of different materials (e.g. one electrode is doped silicon and one is titanium nitride) surrounding a resistive-switching layer of a metal oxide (e.g. hafnium oxide (HfO2), thickness ˜20-100 Å) and a coupling layer that is substantially thinner than the resistive-switching layer (e.g. less than 25% the thickness of the resistive-switching layer). In some embodiments, the coupling layer can be a metallic material such as titanium. Memory elements including the coupling layer have exhibited improved switching characteristics (e.g. lower set, reset, and forming voltages, and better retention). In some embodiments, the resistive-switching layer includes a higher bandgap material (i.e. a material having a bandgap greater than 4 eV such as HfOx, AlOx, TaOx, YOx, ZrOx, CeOx, etc.), however other resistive-switching layers may include materials having a bandgap less than 4 eV (e.g. TiOx).

#In other embodiments, a metal-rich metal oxide switching layer and techniques for forming the metal-rich switching layer are described. The metal-rich switching layer includes increased numbers of defects (e.g. oxygen vacancies), which can be manipulated to improve switching characteristics. The metal-rich switching layer can be deposited, for example, by reducing the degree of oxidation that is occurs in an atomic layer deposition (ALD) or plasma-enhanced ALD (PEALD) process. In another embodiment, the coupling layer is a metallic layer (e.g. metallic titanium) that, when the memory is annealed, attracts oxygen from the adjacent metal oxide switching layer. This results in an at least partially oxidized coupling layer (e.g. the coupling layer becomes at least partially titanium oxide) and a switching layer that is metal rich. In further embodiments, techniques for removing or controlling the size of an interface layer between an electrode and a switching layer deposited thereon are described.