How Many Process Steps Are There in Wafer Manufacturing?

A basic IC process involves forming transistors, resistors, inductors and capacitors along with metal wiring layers. This is done on silicon wafers.

Abrasive chemicals and machines polish the uneven surface of the wafer for a mirror-smooth finish. This allows circuit patterns to be printed more easily.

Dicing separates individual silicon chips — called die — from each other on the wafer. This is a complex, multi-step process that requires precise control to minimize back-side chipping.

Photolithography

Photolithography is the process of printing circuit patterns on a wafer coated with a light-sensitive material called photoresist. This step is key because finer printed patterns enable more components to fit into a chip, increasing device density and lowering production costs.

The photoresist is covered with a pattern on a glass or silicon-based mask, and the system’s optics (lenses in a UV or EUV system or mirrors in an EB) shrink and focus this image onto the wafer. Then the photoresist is sprayed with developer, which removes the resist where the pattern was not transferred. After that, a dry plasma etch is performed which etches the integrated circuit in the wafer. A low-defectivity anisotropic etch process is required to ensure that only the selected area is removed.

Deposition

The process of creating a semiconductor wafer begins with the creation of a single crystal of silicon, known as a boule. The crystal is produced using either the Czochralski or float-zone methods, and it contains impurities that determine whether the chip will be n-type or p-type.

The raw silicon is not a perfect insulator or conductor, so electrically charged ions are directed to the wafer to tune its electrical properties. The ions also form silicide on gates, sources, and drains of transistors to reduce contact resistance with metal wiring layers.

Dicing is a dangerous and challenging process that must be optimized to minimize damage to the delicate chips inside the wafer. This requires the use of advanced Wafer dicing systems that provide precision, reduced vibration and energy, and better contamination control.

Etching

Once the circuit diagram is printed on the wafer, etching processes remove any excess material. This process can be conducted by spraying developer on the wafer, exposing and developing it, removing the photoresist that covers the pattern, and then using liquid, gas, or plasma to remove the unselected parts of the wafer.

Once the wafers are separated into individual IC chips, they can be waxed or mounted on tape to improve their backside support. This allows them to be tested for mechanical and thermal performance, wire pull, die shear, and other critical attributes. It also allows the individual chips to be tested for defect-free, accurate dimensions and positioning. This testing enables manufacturers to optimize the dicing process and ensure high-quality, reliable products. The result is superior quality products that offer better electrical and thermal management, and lower overall production costs.

Grinding

The silicon used in most chips is created as a single, mono-crystalline crystal ingot using either the Czochralski or float-zone methods. It is then sliced into thin, circular discs known as wafers.

Photolithography processes create the pattern on the wafer that will eventually become a microchip. Once that is done, the semiconductor material must be etched to remove any excess oxide film and leave only the circuit diagram on the surface.

This step uses a plasma, or ionized gas mixture with an electric field applied to it, that selectively removes the wafer material along the predetermined cut lines. The process is often a cause of yield problems for fabs, mainly due to the inaccuracy in positioning the cutting blade and the large variation in kerf width.

Sorting

Wafer sort is one of the most important processes in a semiconductor facility. It is the first testing stop for completed wafers and provides valuable feedback to multiple departments. If yield results are low, changes need to be made. If yields are high or as expected, this indicates that the manufacturing process is running smoothly and without issues.

The next step is to cut the wafer into individual circuit chips. This is done using a precision diamond saw. The final steps include electrical die sorting (EDS), back-end processing, and packaging testing. This ensures that every chip is functional and undamaged.