22-11-2012, 05:16 PM
LINEAR INTEGRATED CIRCUITS
LINEAR INTEGRATED CIRCUITS.pdf (Size: 143.27 KB / Downloads: 267)
Define an Integrated circuit.
An integrated circuit(IC) is a miniature ,low cost electronic circuit consisting of
active and passive components fabricated together on a single crystal of silicon.The
active components are transistors and diodes and passive components are resistors and
capacitors.
2.What are the basic processes involved in fabricating ICs using planar technology?
1.Silicon wafer (substrate) preparation
2.Epitaxial growth
3.Oxidation
4.Photolithography
5.Diffusion
6.Ion implantation
7.Isolation technique
8.Metallization
9.Assembly processing & packaging
Stacking faults:
Structural defects in the silicon lattice is called oxidation induced stacking
faults.The growth of stacking faults is a strong function of substrate orientation ,
conductivity type & defect nuclei present.The stacking faults formation can be
suppressed by the addition of HCl.
Oxide isolation defects :
The stress along the edges of an oxidised area produce severe damage in the
silicon. Such defects results in increased leakage in nearby devices.High temperatures
(around 950oC ) will prevent stress induced defect formation.
What is lithography?
Lithography is a process bywhich the pattern appearing on the mask is transfered
to the wafer.It involves two steps: the first step requires applying a few drops of
photoresist to the surface of the wafer & the second step is spinning the surface to get an
even coating of the photoresist across the surface of the wafer.
Define diffusion.
The process of introducing impurities into selected regions of a silicon wafer is
called diffusion. The rate atwhich various impurities diffuse into the silicon will be of the
order of 1μm/hr at the temperature range of 900oC to 1100oC .The impurity atoms have
the tendency to move from regions of higher concentrations to lower concentrations.
18.What is dielectric isolation?
In dielectric isolation, a layer of solid idelectric such as SiO2 or ruby completely
surrounds each components thereby producing isolation , both eletrical & physical.This
isolating dielectric layer is thick enough so that its associated capacitance is
negligible.Also, it is possible to fabricate both pnp & npn transistors within the same
silicon substrate.