Etching (electrochemical machining) is a process that uses electricity to remove material from substrate. Etching has become an integral part of semiconductor and microchip manufacturing, as well as the production of fine chemicals and metals.
1) REASONS FOR USING ETCHING:
For engineering precise and smooth 3D surfaces, removing materials from substrate is done by chemical etching which mainly includes acid etchants such as HF based on hydrofluoric acid or KOH based solution used in Deep Reactive Ion Etch (DRIE). There are also other alternatives such as plasma or wet chemical methods such as alkaline solutions including potassium hydroxide (KOH), ammonium hydroxide (NH4OH), tetramethylammonium hydroxide (TMAH), or sodium hydroxide (NaOH).
2) ETCHING CLASSIFICATION:
Etching can be divided into wet etching and dry etching. Wet etchants are generally alkaline in nature, i.e., based on ammonia, silane, potassium fluoride or hydrogen peroxide. Dry etchants are gaseous fluorine-based chemicals such as silicon tetrachloride SiCl4.
3) ADVANTAGES OF USING AN ETCHED SUBSTRATE:
The advantage of using substrates that have been etched is that they can achieve smooth finishes with high precision because the products manufactured using this technique are free residues. Since the process eliminates the need for manufacturing additional equipment to smooth the substrate, it is advantageous because it reduces costs.
4) USE IN ELECTRONICS:
Etching can be used to create substrates that are needed by the semiconductor industry. For example, etchable glass substrates are widely used as an insulator layer on wafers made of silicon or gallium arsenide. Etching is also useful in creating transistors, capacitors and diodes on a silicon wafer which includes electrical circuits etched into its surface. Another use of etching processing is to remove select materials from selective regions of different layers on top of one another.
5) THE FUTURE OF ETCHING:
As new technologies are being developed using sub-20 nanometer etching techniques, companies are coming up with new methods of creating smaller and more precise products. This will be useful for the development of smaller semiconductor components that can lead to faster computing speeds, more power efficient chips, better-performing screens and other electronic devices.
6) THE HISTORY OF ETCHING:
Etching was first used as an artistic technique in which images or designs were cut into a surface using sharp tools. It is widely used by sculptors, printmakers and painters alike.
7) ETCHING TYPES:
There are two major types of electrical machining processes namely wet chemical etchants (wet etches) and dry plasma etchers (dry etches). A third type of electrical machining process, electrochemical etching (ECM), is also used for these purposes.
Semiconductor devices such as transistors and capacitors are made using etching processes. Etching can also be used to create substrates that are needed by semiconductor industry. Wet chemical or alkaline etchants are mainly used in wet etches whereas dry plasma or fluorine-based chemicals are used in dry etchants. Wet chemical methods include ammonium hydroxide (NH4OH), tetramethylammonium hydroxide (TMAH) or sodium hydroxide (NaOH). Dry plasma consists of silicon tetrachloride SiCl4 which is mostly used in the dry plasma etching process. Electrochemical etching (ECM) is another type of electrical machining process used to create substrates that are needed by semiconductor industry.