INSIDE THE CPUJune 24, 2019
We all think of the CPU as the “brains” of a computer but unlike the human brain which does more of processing and storage, the CPU does more of the processing than the storage. Ever wondered what goes into the manufacturing of the CPU?
The CPU design and manufacturing depends primarily on its circuit diagram, experts from around the globe collaborate to design circuit diagrams of sophisticated integrated circuits like microprocessors, graphics processors (GPUs), and wireless communication ICs. Simply put the circuit diagram is the graphical representation of a circuit showing all electrical connections. Think of the circuit diagram as a plan for building the CPU, just like a building plan diagram which the design of the building is based on.
The disk substrate (base or underlying layer on which other components are mounted) of the microchip is made from quartz sand and is referred to as silicon wafer. The wafers are made from huge monocrystal from purified silicon melt which ends up as a perfect silicon lattice into which the transistors will latter be fitted, however there are impurities(dust) that pose a threat to the fabrication process.
The manufacturers make sure the wafer fabrication activities are done in extremely clean environment that are anticipated to be about 100 thousand times cleaner than an operating theater with extra precautions on the side of the workers themselves. They wear protective clothing to prevent any potential threat on their body, they cover their whole body in protective clothing before entering the site of fabrication.
The wafers are now moved to the clean room where 25 wafers are packed into it hermetically sealed container and sent of the next lines of manufacturing processes (some of these processes may not be mentioned).
The circuit structures are now transferred(printed) onto the wafers through processes called Photolithographic techniques ….think of it like a printing process that uses plates made from photographic images. The success of the whole circuit transfer depends on a solid mastery of light, the silicon disk is spin coated with a photosensitive resist.
UV light is used to transfer the circuit structures depicted on a mask to the wafer(silicon disk). The exposed parts or the resist is soluble and are removed by a developer (photographic equipment consisting of a chemical solution). The unprotected parts of the water surface are now etched away. The outcome of these processes is the transferred structure used as a template.The structures of billions of small current switches (tiny transistor) are generated on each wafer.
We will now discuss Ion Implantation the stage where the electrical properties of the transistors are specified. Engineers depend largely on one of silicon’s most important properties semi conductivity meaning it has no static conductivity level hence it conductivity can change via a high-precision emplacement of the so-called ‘dopant atoms’.
Dopant Atoms are injected into the silicon structures where they are randomly distributed in the silicon lattice, high temperature is then used to make the doping atom flexible so as to take a fixed position in the atomic structure.While the complex processes are being monitored, automated manufacturing goes on in sealed production lines.Copper dominates the next step where it is used to linkup separate transistors to produce an integrated circuit.
Cleaning is the next thing right before copper(interconnection lines) is used since impurities may be lurking at every stage in the manufacturing process. Before copper is poured into the structure trenches for the interconnects, a barrier layer is applied to avoid short circuit and guarantee reliability. The trenches are then filled with copper. Lastly the excess copper is ground down to the edges if the trenches to insulate each interconnect from the other.
Thin silver pallets are applied on the wafer to link the chip to the frame, with the finest saw blade, the chips are then cut of the wafer.The flip chip method is used to bond the chip to the frame then it is sealed with a cover.