How are integrated circuits made?

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Integrated circuit fabrication involves a process of creating very thin surface layers of semiconductor material on top of a substrate layer, usually made of silicon, which can be chemically altered at the atomic level to create the functionality of various types of circuit components, including transistors, capacitors, resistors and diodes. It’s an advance over previous circuit designs where individual components of resistors, transistors, and more were connected by hand to a connecting breadboard to form complex circuits. An integrated circuit manufacturing process works with components so small that billions of them can be created in an area of ​​just a few square centimeters as of 2011, through various photolithography and etching processes in a microchip manufacturing plant.

An integrated circuit, or IC, chip is literally a layer of semiconductor material in which all circuit components are interconnected in a series of manufacturing processes so that all components no longer have to be individually manufactured and assembled later. The first form of microchip integrated circuit was produced in 1959 and was a crude assembly of several dozen electronic components. The sophistication of integrated circuit manufacturing increased exponentially, however, with hundreds of components on IC chips in the 1960s and thousands of components by 1969, when the first true microprocessor was created. Electronic circuits as of 2011 have IC chips a few inches long or wide that can contain millions of transistors, capacitors, and other electronic components. Computer system microprocessors and memory modules that contain mostly transistors are the most sophisticated form of IC chip as of 2011 and can have billions of components per square centimeter.

Because the components in integrated circuit manufacturing are so small, the only effective way to create them is to use chemical etching processes that involve reactions on the wafer surface from exposure to light. A mask or some sort of pattern is created for the circuit and light is beamed through it onto the wafer surface which is coated with a thin layer of photoresist material. This mask allows patterns to be etched into wafer photoresist which is then fired at a high temperature to solidify the pattern. The photoresist material is then exposed to a dissolving solution which removes the irradiated region or the masked region of the surface depending on whether the photoresist material is a positive or negative chemical reagent. What is left is a thin layer of interconnected components a width of the wavelength of light used, which can be ultraviolet light or X-rays.

After masking, the fabrication of integrated circuits involves either doping the silicon or implanting individual atoms usually phosphorus or boron atoms into the surface of the material, which imparts a positive or negative electrical charge to local regions of the crystal. These charged regions are known as the P and N regions, and where they meet, they form a transmission junction to create a universal electrical component known as a PN junction. Such junctions are about 1,000 to 100 nanometers wide as of 2011 for most integrated circuits, making each PN junction the size of a human red blood cell, which is about 100 nanometers wide. The process of creating PN junctions is chemically customized to exhibit various types of electrical properties, allowing the junction to act like a transistor, resistor, capacitor, or diode.

Due to the very fine level of components and connections between components on integrated circuits, when the process stops and there are bad components, the entire wafer has to be thrown away as it cannot be repaired. This level of quality control is raised to an even higher level by the fact that most modern IC chips as of 2011 consist of many layers of ICs stacked on top of each other and connected together to create the chip final itself and give it more computing power. Insulating layers and metallic interconnection layers must also be interposed between each circuit layer, so as to make the circuit functional and reliable.

While many scrap chips are produced in the integrated circuit manufacturing process, those that function as end products that pass electrical tests and microscopic inspections are so valuable that they make the process highly profitable. Integrated circuits now control nearly every modern electronic device in use as of 2011, from computers and cell phones to consumer electronics like televisions, music players and gaming systems. They are also essential components of automobile and aircraft control systems and other digital devices that offer a level of programming capability to the user, ranging from digital alarm clocks to room thermostats.

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