John C. Bean WeCanFigureThisOut.org Podcasts

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Making an Integrated Circuit

John C. Bean - WeCanFigureThisOut.org

7y ago7y ago

Daily+

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How Van de Graaff Generators Work

John C. Bean - WeCanFigureThisOut.org

7y ago7y ago

Daily+

This podcast is drawn from the "Virtual Lab" of WeCanFigureThisOut.org. This Virtual Lab uses 3D virtual reality animations to explain electronics, microelectronics and nanotechnology. This podcast explains how Van de Graaff generators work by using a motor to separate charges.

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show series

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Let's go inside an Intel 4004 microprocessor to see an individual transistor 0:13

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Do you know how Van de Graaff generators work? Let's turn it on. 0:14

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Turn it off and the charge stays on the dome. 0:03

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To make this transistor, first oxide then nitride layers are grown 0:11

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To understand what is going on, let's look inside. 0:11

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A shadow mask then exposes a photographic emulsion 0:12

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There is only a motor, powering a pulley, connected to a belt, almost touched by a copper comb. 0:21

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Exposed nitride is then etched away 0:07

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Oxygen reacts with the Si to grow more oxide 0:12

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The pulley is made of a special plastic. Let's fade away all but a few (exaggerated) plastic atoms. 0:15

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The pulley's plastic atoms will transfer electrons to the inside of the belt (it's just "static electricity"). 0:16

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By heating in silane, polycrystal Si is then grown 0:04

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A stripe is exposed in a second photographic emulsion 0:10

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The inside of the belt becomes more and more negative. 0:16

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Exposed polycrystal Si is etched away leaving the transistor gate 0:09

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But now let's go back and figure out what the bottom copper comb does. 0:09

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Phosphorus ions then penetrate thin oxide to create the source and drain 0:12

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Electrons jump from the comb trying to reach the increasingly positive pulley. 0:14

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Heating in oxygen grows an insulating coat on the gate 0:06

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But these electrons cannot penetrate the belt and are carried away. 0:11

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This is an electron's worst nightmare as both sides of the belt are now negative! 0:19

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A third photographic emulsion defines windows above the source and drain 0:10

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But as they reach the top, the outer electrons can jump onto a second comb ... 0:18

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Openings are then etched in the exposed oxide 0:07

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and then spread out on the metal dome. 0:18

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Metal is sprayed on to the surface 0:03

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A fourth photographic emulsion is patterned 0:10

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So the Van de Graaff uses the motor's work pushing electrons upward to build up "electrostatic energy." 0:30

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Unwanted metal is etched away completing the transistor 0:09

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And finally, here is the circuit symbol for the transistor 0:08

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This podcast is drawn from the Virtual Lab presentations of WeCanFigureThisOut.org. The copyrighted material of this site was developed under funding from National Science Foundation CCLI, NIRT, MRSEC ... 0:33

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This podcast is drawn from the Virtual Lab presentations of WeCanFigureThisOut.org. The copyrighted material of this site was developed under funding from National Science Foundation CCLI, NIRT, MRSEC ... 0:33

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All of the scenes together 4:18

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All of the scenes together 3:09

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