Etching in chip manufacturing

2020-11-17

In chip manufacturing, there are three core processes: thin film deposition, lithography, and etching.

Among them, lithography is the most complex, critical, costly, and time-consuming process; etching is second only to lithography in cost, and its importance is constantly rising; thin film deposition is also an indispensable and important process. In manufacturing, in order to achieve the layered structure of large-scale integrated circuits, the deposition-etching-deposition process needs to be repeated.

The importance of etching in chip manufacturing can also be seen from the following figure.

Etching can be broadly divided into two technical solutions: wet etching and dry etching.

Wet etching, as the name suggests, uses liquid chemical reagents to corrode and dissolve the texture patterns on the wafer surface that need to be removed.

Dry etching, obviously, does not use liquid chemical reagents. It generally uses energy beams, such as ion beams, electron beams, and laser beams.

Currently, the most commonly used is the ion beam, or more accurately, plasma. The plasma is bombarded onto the wafer surface, reacting chemically or physically (or both chemically and physically) with the wafer to achieve etching.

Currently, the mainstream solution in the etching equipment field is dry etching, accounting for at least 90%.

This is mainly because wet etching has some drawbacks.

First, wet etching uses a large amount of corrosive chemicals that are harmful to human health and the environment, so it is gradually being phased out in the manufacturing of large-scale integrated circuits.

Second, wet etching has an isotropic problem, meaning that because wet etching uses chemical reagents, which are liquids, the directionality is not easy to control during the chemical reaction. During etching, it may also react with the surrounding parts at the bottom of the pattern, even hollowing it out, which is not what people want to see.

Because of this problem, wet etching is difficult to use in sub-micron (less than 1μm) semiconductors, and dry etching must be used.

Dry etching has high precision and leaves no pollutants; in short, it is more advanced.

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