Wafer drying is a technique done in wet processing in order to heighten the wafer's performance. It is done at the end of almost every wet process technique. Now that wafers are ranging in sizes and increasing in number, drying has had to be adjusted in order to meet the demand of bigger wafers. The complexities of wafer geometries have created new techniques for drying wafers after wet processing.
With the drying of larger wafers of the 300 mm scale, a few different things have changed within the wafer drying process. First of all, smaller particle sizes now come into focus, being able to get to within 0.1 micrometers in diameter. What's more, the mechanical stress normally experienced by the wafer must be avoided as much as possible. There have also had to be adjustments in regards to the hydrophobic and hydrophilic surfaces of these larger wafers, so machines must be adjusted to fit the individual needs of each wafer being dried.
There are many wafer drying technologies, but not all of them will be around for much longer as the industry advances. Spin dryers are still a widely used method in chip production but because of the stress that it places on the wafers, it is not an adequate method. Some plants also use IPA-vapor dryers but these require isopropyl alcohol (as the name would suggest), and can be a huge risk to the safety of the plant. It also can be more expensive for plants to utilize. Despite the future problems that may be faced, these techniques can still be used for semiconductor manufacturing today.
With all of these techniques for wafer drying slowly becoming obsolete, it would seem that there is no where to go in the future. One technique, however, based on the Marangoni effect, shows some room for improvement. This would include finding a new way to place alcohol into the process chamber of the device. These devices use ultrasonic oscillation, which allows for the use of several other potentially advantageous features, like a low-velocity spray, micro-flow, and an extensive spray shape. With more development, the Marangoni effect could lead to a wafer drying device that produces low stress and has few problems with dangerous chemicals.
Wafer drying is perhaps the most important step of wet processing, as it enables the wafer for performance and removes the excess particles from it. Though methods for this are becoming out of date due to the high amount of stress and chemicals that are produced, they are still being utilized today. With techniques in development to meet the demands of the semiconductor industry, there will soon be instruments that can keep up with larger wafers and more numerous ones as well.