The present disclosure is related to resistive switching device or an RRAM. More particularly, embodiments according to the present invention provide a circuitry and an associated method to program a resistive switching device. But it should be recognized that embodiments according to the present invention can have a much broader range of applicability.
The inventor of the present invention has recognized the success of semiconductor devices has been mainly driven by an intensive transistor down-scaling process. However, as field effect transistors (FETs) approach sizes less than 100 nm, physical problems such as short channel effect begin to hinder proper device operation. For transistor based memories, such as those commonly known as Flash memories, other performance degradations or problems may occur as device sizes shrink. With Flash memories, a high voltage is usually required for programming of such memories, however, as device sizes shrink, the high programming voltage can result in dielectric breakdown and other problems. Similar problems can occur with other types of non-volatile memory devices other than Flash memories.
The inventor of the present invention recognizes that many other types of non-volatile random access memory (RAM) devices have been explored as next generation memory devices, such as: ferroelectric RAM (Fe RAM); magneto-resistive RAM (MRAM); organic RAM (ORAM); phase change RAM (PCRAM); and others.
A common drawback with these memory devices include that they often require new materials that are incompatible with typical CMOS manufacturing. As an example of this, Organic RAM or ORAM requires organic chemicals that are currently incompatible with large volume silicon-based fabrication techniques and foundries. As another example of this, Fe-RAM and MRAM devices typically require materials using a high temperature anneal step, and thus such devices cannot be normally be incorporated with large volume silicon-based fabrication techniques.
Additional drawbacks with these devices include that such memory cells often lack one or more key attributes required of non-volatile memories. As an example of this, Fe-RAM and MRAM devices typically have fast switching (e.g. “0” to “1”) characteristics and good programming endurance. However, such memory cells are difficult to scale to small sizes. In another example of this, for ORAM devices reliability of such memories is often poor. As yet another example of this, switching of PCRAM devices typically includes Joules heating and undesirably requires high power consumption.
The inventors of the present invention have recognized that programming of RRAM devices should be performed under controlled conditions. If too much current is applied across the terminals of an RRAM device, the RRAM device may be irreversibly programmed, and the RRAM device may not be erasable.
From the above, an improved semiconductor device architecture is desirable. RRAM devices utilizes the programmability of electrical resistance of a non-conductive material configured in a cross point of a pair of electrodes. In a simplest way, an RRAM cell can be programmed to be in a high resistance state and a low resistance state though multilevel cells have been reported. In continuing pursuit of device shrink, RRAM provides a feature size that can be further scaled down by ways of vertical integration.