Silicon wafer manufacturers are aware of the different steps involved in producing a single wafer, from crystal growth to wafer testing and shipping. In this article, we will focus on etching and the different types of processes involved in this step.
Wafer etching is a process that involves removing unwanted materials from a wafer right after the photolithography step. Silicon wafer manufacturers use two main types of etching: wet etching and dry etching.
Wet etching involves the use of chemicals. The process begins with a batch of wafers carefully submerged into a highly concentrated pool of acid. The exposed parts of the wafers are etched away. What's great about using this method is that it can etch many wafers at a time, making it affordable and quicker options. Its only disadvantage is that wet etching isn't suitable for generating smaller critical geometries that are required for today’s chips.
Instead of using chemicals, dry etching utilizes gas to etch unwanted materials off a wafer’s surface. Dry etching is advantageous because it is capable of generating small detailed geometry patterns that are required for today’s chips.
Plasma etching uses gas that has been subjected to an extreme electric field to produce a plasma state of matter. The electric field is generated through coils that are wrapped around a chamber and exposed to a high-level RF source. Gases that are in plasma form are very reactive, which makes it very effective for etching the unwanted materials on a wafer's surface. The only drawback of using this method is that the wafers can be damaged from the RF exposure.
This method is carried out at a lower pressure and utilizes a combination of physical and chemical methods to etch the unwanted materials on a wafer’s surface.