01. Silicon and Aluminum

Silicon and Aluminum is the starting point for the design of the computer. The circuits of a computer are made of silicon and aluminum and maybe some copper. The name of this context comes from lectures I experienced, that were on software design, which emphasized that the bottom level of the computer was “silicon and aluminum”. But in that class we never got to the “silicon and aluminum” since we were involved in software not hardware. 

This Pictures the Processes that Define Transister Capability for Computer Processing

The Basic Basic Circuit of the Computer Using a Transistor

This video shows on example of the basic computer circuit. 

It also shows the Truth Table associated with this circuit and 

demonstrates how the Truth Table works in the circuit action.

Etching Circuits

The circuits of the computer are built on a chip of single crystal silicon, often called a wafer. The single crystal silicon wafer (using a single crystal is for special electrical properties) is crystalized in a crucible by allowing the silicon to slowly crystalize unto a seed crystal. Then this single crystal ingot is sliced into wafers to be used in further processing. The wafers are cut to a precise size. All this processing of wafers and circuits must be done using clean room techniques. A speck of dust would destroy a circuit and lots of dust would destroy all the circuits.

In some of the processes the electrical properties of the chip are changed locally (particular areas on the chip) by doping. This provides the various internal circuit properties a transistor needs. The type of doping done and the type of materials added show the versatility of the processing of integrated circuits. The doping process generally adds boron (or a material like boron) for p doping and phosphorous (or a material like phosphorus) for n doping. Boron has one less electron in the outer ring so as it fits into the crystal it has holes where there should be electrons, thus p doping. Phosphorous has one extra electron in its outer ring so as it fits into the crystal it has extra electrons where they are not needed in the crystal, thus n doping.

Doping Type by Valence

It is the valence of the atom that makes it p or n type with silicon.

Belows is a cross sectional view of the manufacture of integrated circuits.

We also begin doping areas of the chip surface.

The circuit design used here originated with Wikimedia Commons

(By Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=16935119).

This is how the circuits are made.

Of course the processes are on a very small scale to show process details.

Ending Processes