Physics of Semiconductor Devices

Physics of Semiconductor Devices
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Abstract
Currently, most memory devices increasingly play important role in microelectronics
technology and considered as the technology drivers, whereas electronic memories cover up
to 20% of semiconductors available in the market. Ideally, these memory devices are divided
into two types, for example, volatile memories and non-volatile memories. The speed of
write-erase operations in volatile memories such as SRAM and DRAM are very high, while
these memories will lose data when the supply voltage is removed. In contrast, nonvolatile
memories have a very low write-erase speed with the need for high voltage and longer
retention time, usually more than 10 years.
These different types of memories have different functions or in other words, fill a particular
function in a particular system. For example, SRAM memories are used by microprocessors
of computers as off-chip or on-chip cache to store copies of memory locations that are most
frequently used, to reduce the memory access time average. Compared to other types of
volatile memories SRAM memories are expensive and tend to have a high write-erase speed
than DRAMs. DRAM memories provide random access storage when used in main memory
computers that make them relatively large and cheap as compared to static RAMs and this
makes them faster as compared to non-volatile memories
Introduction.
The MIS fabrication process will be undertaken using various available equipment in the
EMTERC research group [1]. A p-type semiconductor made up of a silicon substrate,
containing a thin native oxide (1-2 nm) will be provided. A standard organic solvent cleaning
procedure is used to perform the cleaning of the silicon wafer.to establish ohmic contact,
Aluminium and annealing are evaporated in nitrogen at five hundred degrees Celsius by
performing the bottom contact. The Sn coating of the silicon wafer on the polished side, of

thickness 3 nm (approximately), by thermal evaporation. This is then followed by deposition
of Si nanostructures (a floating gate in the above schematic diagram). The Device is
completed by deposition of the silicon nitride layer and top aluminium contact. A reference
sample, without the deposition Sn and silicon nanostructures, will also be fabricated at the
same time [2].
Results and Discussions
Q1.
Metal-insulator-semiconductor has a thin insulating layer that allows a given amount of
current known as the tunnel current to flow between metal and semiconductor and causes the
semiconductor to depart from the thermal equilibrium. The diode has a negatively charged
source of electric charges and a positively charged control gate that helps in creating the
potential for the flow of electrons. For flash memory with a nanostructure as the floating gate,
the negative and the positive electric charges which exist at the source and the control gate
respectively helps to draw electrons into the Nanostructure floating gate. Semiconductor
fabricated Flash memories works by charging or discharging electrons to and from a floating
gate. A bit's zero or one state depends upon whether or not the Nanostructure floating gate is
charged or uncharged. Due to the presence of electrons on the floating gate, tunnel current
can't flow through the semiconductor transistor and the bit state is Zero. This defines the
normal state for a Nanostructure floating gate transistor when a bit is programmed. When
electrons are removed from the floating gate, current is allowed to flow and the bit state is
one. [3].