Charge storage structures can be used in a variety of semiconductor devices, including non-volatile memory devices. The charge storage structures in semiconductor devices can include nanodots to store charge in the structure. Nanodots may be used in a wide variety of optical devices including light emitting diodes (LEDs), laser diodes (LDs), and photodetectors. Nanodots may also be used in single electron transistors. Through the use of nanodots, it may be possible to improve the performance of a device by reducing the threshold current of the device, improving retention characteristics, and/or increasing the optical gain.
For example, when a plurality of nanodots are distributed throughout a charge storage structure (e.g., floating gate) of a flash memory device, the voltage required for storing information may be smaller than the current required for a conventional flash memory device having no nanodots, and thus, the amount of power consumed may be decreased by using the nanodot device. The improved characteristics exhibited by the nanodot device may be attributed to Coulomb blockage at room temperature when nanodots smaller than approximately ten (10) nanometers (nm) in diameter are used for a charge storage structure, with the result that a threshold voltage shift may be quantized and multi-bit information may be stored. Accordingly, nanodot technology is considered promising for next-generation technology.
The size of semiconductor memory devices, and the thin dielectric films that are used in these devices, has been scaled down in order to accommodate the diminishing feature size of elements on a chip. One problem with the continued scaling down in floating gate memory devices is that the charge retention characteristics of the devices are sensitive to the presence or absence of defects in the tunnel oxide. A reduction in the thickness of the tunnel oxide, to allow for further scaling down can have drawbacks such as increased risk of defects occurring in the tunnel oxide, among other drawbacks.