Today’s semiconductor manufacturers produce more ultra flat wafers to meet the increasing consumer demand for slimmer electronic devices. For this reason, they've developed different wafer thinning techniques to achieve the desired flatness.
The etching process is widely used in microfabrication. It involves the elimination of unwanted substances from the surface of the wafer by removing one or more layers. Semiconductor manufacturers typically use wet etching and dry etching to get the job done.
Dry etching is a major type of etching process that uses plasmas or etchant gases to remove wafer layers. This process produces gaseous products that diffuse into bulk gas before a vacuum system is used to expel it. Moreover, dry wafer etching can be done through chemical reactions, physical removal, and a combination of both.
Manufacturers typically use dry etching because of its capability for automation and its ability to use various etch gases with different process settings. Additionally, the process reduces material consumption because it requires little to no hardware change. It also promotes excellent industrial hygiene because it is performed in a vacuum chamber away from the operator.
Although dry etching techniques require specialized equipment, its by-products are easier to dispose of than those of wet etching. What's more, the cost of chemical disposal is considerably lesser compared to wet etching.
Wet etching is another etching process that takes off layers of substrate material by using liquid chemicals or etchants. The partially protected wafer is immersed in a chemical solution that etches the unprotected wafer surface during the process. The most common etching agents include corrosive leeches, liquid solvents, and acids.
Besides having high etch rates, wet etching also achieves high selectivity due to the simplicity of its equipment. In most cases, it only requires a spray system or a chemistry-specific immersion tank.
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