Cleaning Process

The process of turning a wafer into semiconductor chips takes anywhere between one and two months, and involves hundreds of processes from diffusion and photolithography to etching, deposition, and ion implantation. But there is one crucial process carried out repetitively between the diffusion, etching, polishing and other steps. It’s the cleaning process. Humans have come to wash ourselves frequently to prevent infection from bad germs and bacteria. Likewise, nano-scale semiconductors need to be cleaned repetitively in order to produce flawless chips. We’ll find out more about the cleaning that is critical to improving semiconductor yield. Cleaning: An essential process to ensure semiconductor quality

Cleaning is a process by which impurities on a wafer surface are removed through chemical treatment, gas, or physical methods. For the semiconductor processes of microscopic scale, any particles, metal fragments, organic matter, naturally forming oxide layers and trace amounts of impurities on the surface of a wafer can result in pattern defects and deterioration of electrical properties. These issues can harm semiconductor yield and reliability. This is why cleaning is so important in the semiconductor process. Cleaning is usually carried out between processes, such as before the diffusion process in which a thin film is formed and after the etching process where unnecessary parts are cut away to form a circuit pattern. Cleaning is performed repetitively, making the number of times it's carried out approximately double the other processes, and serves as a bridge between processes. Different ways of cleaning

There are two major ways of cleaning: dipping and spraying. The dipping method used to be the most common way of cleaning, and involves dipping the wafer into a chemical or ultra-pure deionized water. Spraying involves spraying a chemical in liquid or gas form onto a spinning wafer to remove impurities.

In the past, batch type dipping was the most frequently used method for its ability to clean large numbers of wafers at the same time. Recently, however, semiconductor processes have scaled and the types of materials used have changed, resulting in a more widespread use of single wafer type spraying methods. And because a broad variety of impurities can be found on the surface of wafers, a range of different wafer cleaning methods are used. Cleaning determines semiconductor yield and the end product quality. As semiconductor processes scale, the importance of cleaning will only increase.