Hobbies And Interests
Etching
Etching is the selective removal of material. There are two main ways to etch material. A chemical etch is often used to selectively remove a certain material while leaving other areas of the sample intact. An example is the use of hydrofluoric acid to selectively remove silicon dioxide. A second way to etch is to place the sample into a vacuum chamber then introduce a gas, such as argon. The argon is then ionized by a set of electrodes and accelerated against the sample. The ions bombard the sample and remove material. Since all parts of the sample are bombarded, it is not a selective etch, and all surfaces exposed will have material removed.
Reduction in Metal Thickness
Exposing any metallic sample to an etch will reduce the sample's thickness. This is often the desired outcome of the etch. In order to remove a certain amount of material, the metal needs to be exposed to the etch for a fixed amount of time, for example, one minute. The thickness then needs to be measured in order to get an etch rate, such as 10 nanometers per second.
Film Roughness
Although the aim with an etch is to reduce the metal thickness, this normally comes at a price. The metallic film roughness can be a very important quantity and is typically measured with a device called an atomic force microscope. Generally, the longer a material is etched, the greater the metallic film roughness becomes.
Grain Size
Metallic films consist of many millions of tiny grains that are typically in the size range of 5 to 100 nanometers. As metallic films are etched, the average size of the grain size can be reduced, but this is highly dependent upon the type of etch, the etch time and etch power if it is an ion etch.