1. Field of the Invention
The present invention relates to metal oxide based memory devices and methods for manufacturing such devices.
2. Description of Related Art
Resistive random access memory, RRAM, is a type of nonvolatile memory that provides the benefits of small cell size, scalability, ultrafast operation, low-power operation, high endurance, good retention, large On/Off ratio, and CMOS compatibility. One type of RRAM includes metal oxide layers than can be caused to change resistance between two or more stable resistance ranges by application of electrical pulses at levels suitable for implementation in integrated circuits.
In prior methods of forming a transition metal oxide (TMO) memory layer, photoresist is used as an etching mask to protect the portions of TMO in a designated region that will be the memory layer, while other portions of TMO that are not part of the memory layer are etched away. After etching, the photoresist is stripped and this stripping may cause damage to the TMO memory layer. Prior methods of avoiding this damage caused by stripping have included using a hard mask such as SiO2 or Si3N4 prior to oxidization to define surfaces to be oxidized to form the TMO memory layers. By defining which regions to oxidize, the step of etching away unwanted oxidized regions is eliminated. However, this process of using a hard mask adds two extra processes to the previously described method involving damage caused by the photoresist strip. These additional steps in the process add time and cost to production, which are undesirable.
It is therefore desirable to provide a memory cell and method of manufacture that eliminates the possibility of damage to the TMO memory layer caused by a photoresist strip while adding a minimal amount of manufacturing steps in order to provide a cost-effective method of manufacture.