IC Fabrication
IC Fabrication
IC Fabrication
INTEGRATED CIRCUITS
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.
1.Crystal growth &doping 2.Ingot trimming & grinding 3.Ingot slicing 4.Wafer policing & etching 5.Wafer cleaning
Typical wafer 5
Epitaxial growth
1. Epitaxy means growing a single crystal silicon structure upon a original silicon substrate, so that the resulting layer is an extension of the substrate crystal structure. The basic chemical reaction in the epitaxial growth process of pure silicon is the hydrogen reduction of silicon tetrachloride. 1200oC SiCl+ 2H <-----------> Si + 4 HCl
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Oxidation
1. SiO2 is an extremely hard protective coating & is unaffected by almost all reagents except by hydrochloric acid. Thus it stands against any contamination. 2. By selective etching of SiO2, diffusion of impurities through carefully defined through windows in the SiO2 can be accomplished to fabricate various components.
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Oxidation
The silicon wafers are stacked up in a quartz boat & then inserted into quartz furnace tube. The Si wafers are raised to a high temperature in the range of 950 to 1150 oC & at the same time, exposed to a gas containing O2 or H2O or both. The chemical action is Si + 2HO-----------> Si O2+ 2H2
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Photolithography
The process of photolithography makes it possible to produce microscopically small circuit and device pattern on si wafer
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Photographic mask
The development of photographic mask involves the preparation of initial artwork and its diffusion. reduction, decomposition of initial artwork or layout into several mask layers.
Photo etching
Photo etching is used for the removal of SiO2 from desired regions so that the desired impurities can be diffused
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Diffusion
The process of introducing impurities into selected regions of a silicon wafer is called diffusion. The rate at which various impurities diffuse into the silicon will be of the order of 1m/hr at the temperature range of 9000 C to 11000C .The impurity atoms have the tendency to move from regions of higher concentrations to lower concentrations
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2.
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Ion Implantation
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Dielectric isolation
In dielectric isolation, a layer of solid dielectric such as SiO2 or ruby completely surrounds each components thereby producing isolation, both electrical & 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.
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Metallization
The process of producing a thin metal film layer that will serve to make interconnection of the various components on the chip is called metallization.
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Aluminium Metallization
Aluminium Metallization
21/12/11
IC packages available
1. 2. 3. Metal can package. Dual-in-line package. Ceramic flat package.
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Dual-in-line package.
Dual in-line package (DIP ) is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins.
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