Introduction to semiconductor cleaning process
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Introduction to semiconductor cleaning process

Posted Date: 2024-01-14

According to the different cleaning media, current semiconductor cleaning technology is mainly divided into two process routes: wet cleaning and dry cleaning. Wet cleaning is based on different process requirements, using specific chemical solutions and deionized water to clean the wafer surface non-damagingly to remove particles, natural oxide layers, organic matter, metal pollution, and sacrifices during the wafer manufacturing process. layer, polishing residue and other substances, auxiliary technical means such as ultrasonic cleaning, heating, and vacuum can be used at the same time; dry cleaning refers to cleaning technology that does not use chemical solvents, mainly including plasma cleaning, supercritical gas phase cleaning, beam cleaning and other technologies . Dry cleaning mainly uses gaseous hydrofluoric acid to etch irregularly distributed structured wafer silicon dioxide layers. Although it has the advantage of high selectivity for different films, the cleanable pollutants are relatively single. Currently, at 28nm Logic products and storage products with technology nodes of and below have applications in wafer manufacturing production lines. Wet cleaning is usually the main method. A small number of specific steps use a combination of wet and dry cleaning to complement each other and build a cleaning solution. In the future, the wet process and dry process of cleaning equipment will continue to coexist and develop in the direction of more advanced technology nodes, diversified functions, small size, high efficiency, and low energy consumption in their respective fields. In the short term, wet process and dry process will continue to develop. There is no tendency for dry processes to replace each other. At present, wet cleaning is the mainstream cleaning technology route, accounting for more than 90% of the number of cleaning steps in chip manufacturing.

Mainly used in tank cleaning equipment, the wafer to be cleaned is soaked in the solution, and the pollutants are removed through the chemical reaction between the solution and the wafer surface and impurities. Widely used, low chemical consumption for different impurities; easy to use different chemical liquids; high production capacity, multiple wafer soaking processes can be performed at the same time: low cost, shared among each wafer cross-contamination.

Two-fluid cleaning method:

Deionized water SC-1 solution. Deionized water, etc., a refined water-gas two-fluid atomization nozzle. Liquid medium and high-purity nitrogen are introduced at both ends of the nozzle. High-purity nitrogen is used as power to assist the micro-atomization of the liquid into extremely fine liquid particles. It is sprayed onto the wafer surface to achieve the effect of particle removal. It has high cleaning efficiency and is widely used in cleaning steps to assist particle removal: there is a risk of damage to the fine wafer pattern structure, and the ability to remove small-sized particles is insufficient.

Ultrasonic cleaning method:

Chemical solvents and ultrasonic auxiliary cleaning are used to clean under 25-40KHz frequency ultrasonic waves. Cavity bubbles are generated inside, and surface impurities are desorbed when the bubbles disappear. It can remove large pieces of contamination and particles attached to the wafer surface, which can easily cause damage to the wafer pattern structure. The appropriate ultrasonic cleaning frequency needs to be selected according to the cleaning process requirements.

Megasonic cleaning method:

Chemical solvent plus megasonic wave assisted cleaning, and

Ultrasonic cleaning

Similar, but using a megasonic cleaning machine with a process frequency of 1-3MHZ. It has excellent removal effect on small particles and has obvious advantages in cleaning high aspect ratio structures. After precise control of cavitation bubbles,

Megasonic cleaning machine

It can also be used to clean fine wafer pattern structures; the cost is relatively high.

Rotary spray cleaning method:
High-pressure spray deionized water or cleaning fluid, the cleaning chamber is equipped with a turntable, which can load at least two wafer boxes at a time. During the rotation process, the liquid is continuously sprayed on the wafer surface through the liquid spray column to remove impurities on the wafer surface. Compared with traditional tank cleaning, the usage of chemical liquids is lower; the machine occupies a small area; there is a risk of cross-contamination between chemical liquids. If a single wafer generates fragments, all wafers in the entire cleaning chamber will be There is a risk of scrapping.


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