lecture33 - Lecture#33 OUTLINE IC Fabrication Technology...

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Lecture 33, Slide 1 EECS40, Fall 2003 Prof. King Lecture #33 OUTLINE IC Fabrication Technology –Dop ing – Oxidation – Thin-film deposition – Lithography –E tch Reading (Rabaey et al .) • Chapter 2.1-2.2 Lecture 33, Slide 2 EECS40, Fall 2003 Prof. King Integrated Circuit Fabrication Goal: Mass fabrication ( i.e. simultaneous fabrication) of many “chips”, each a circuit (e.g. a microprocessor or memory chip) containing millions or billions of transistors Method: Lay down thin films of semiconductors, metals and insulators and pattern each layer with a process much like printing (lithography). Materials used in a basic CMOS integrated circuit: Si substrate – selectively doped in various regions •S i O 2 insulator Polycrystalline silicon – used for the gate electrodes Metal contacts and wiring
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Lecture 33, Slide 3 EECS40, Fall 2003 Prof. King Si Substrates (Wafers) Crystals are grown from a melt in boules (cylinders) with specified dopant concentrations. They are ground perfectly round and oriented (a “flat” or “notch” is ground along the boule) and then sliced like baloney into wafers. The wafers are then polished. Typical wafer cost: $50 Sizes: 150 mm, 200 mm, 300 mm diameter 300 mm “notch” indicates crystal orientation Lecture 33, Slide 4 EECS40, Fall 2003 Prof. King Suppose we have a wafer of Si which is p-type and we want to change the surface to n-type. The way in which this is done is by ion implantation . Dopant ions are shot out of an “ion gun” called an ion implanter, into the surface of the wafer. Typical implant energies are in the range 1-200 keV. After the ion implantation, the wafers are heated to a high temperature (~1000 o C). This “annealing” step heals the damage and causes the implanted dopant atoms to move into substitutional lattice sites. Adding Dopants into Si Eaton HE3 High-Energy Implanter, showing the ion beam hitting the end-station x SiO 2 Si + + + + + + As + or P + or B + ions
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Lecture 33, Slide 5 EECS40, Fall 2003 Prof. King e.g. AsH 3 gaseous source As + , AsH + , H + , AsH 2 + Ion source translational motion As + accelerator Energy: 1 to 200 keV Dose: 10 11 to10 16 /cm 2 Inaccuracy of dose: <0.5% Nonuniformity: <1% Throughput: ~60 wafers/hr ion beam wafer spinning wafer holder Ion Implanter F = q( v × B ) analyzer magnet resolving aperture
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lecture33 - Lecture#33 OUTLINE IC Fabrication Technology...

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