fog37 said:
Thanks everyone.
So, monocrystalline silicon is used because it is cheap, easier make and to control, etc.
Silicon is the most common semiconductor material used, but is not the only one. Gallium and germanium are also used in some specialized semiconductors, but neither is as plentiful as plain old silicon.
By doping (altering) different regions of the blank silicon wafer at different level and with different substances we can create different electronic components (like resistors, capacitors, transistors, diodes) that are embedded into the material itself, i.e. from the silicon itself. Are the connecting wires between those created components made the same way (by doping) or are metal traces added later?
Some components are connected by conducting channels created on the wafer itself; others are connected by special metal layers which are deposited on the surface of the chip. Some processor chips contain millions of transistors and other components, which would be too costly to wire up as if they were discrete components. ICs were invented to prevent making all these connections separately.
Most circuit boards have both IC and the standard lumped components (capacitors, resistors, etc.). Why? Why not make everything in the IC form?
Because it would be too expensive, and for some components, impractical or impossible. For example, inductors still have to be made by coiling a wire around something; no practical semiconductor analog exists. To an extent, the same is true for capacitors; if you want a certain size capacitor, a discrete component is used.
It takes roughly a billion dollars to set up a production line for a complex semiconductor, like a processor, exclusive of the cost of developing the design. There are some "computers on a chip" out there, but for maximum flexibility in configuring a computer system, it's still easier and cheaper to use ICs to make only a portion of the entire system.
Is the process of photomasking and photolithography used to first map where the various components are supposed to be on the silicon substrate, before the doping step and before the components are actually created?
thanks,
fog37
The various masks are created from the design of the chip. The circuit logic (i.e., the various components and pathways connecting them) is created and checked by a chip designer, and the mask to make that particular arrangement of circuitry is then produced from this design.
An un-doped wafer is coated with a light-sensitive material, and this coated wafer is exposed to light. The portions of the coating exposed to light change chemically, and are washed away by treating them with a special cleaner. The masked portions of the wafer are protected from absorbing the doping material during that part of the manufacturing process.
This article discusses some of the IC manufacturing aspects:
https://en.wikipedia.org/wiki/Semiconductor_device_fabrication
