Many people involved in atomic layer deposition (ALD) know that selective atomic layer deposition is a hot topic today. A variety of papers, seminars, and blog posts are emerging, explaining in detail the various new methods that can achieve selective growth. In a sense, selective ALD uses an effect that has long plagued ALD users, that is, due to the chemical reaction characteristics of ALD, the nucleation of film growth depends on the surface of the substrate. Generally speaking, people in the ALD field have been studying how to minimize this effect. For example, plasma ALD usually has a negligible delay, but for selective ALD, the nucleation delay is amplified.

So the question is, which ALD equipment will people choose to study selective ALD? I believe that some functions in our system are useful, such as:

◆A variety of chemical precursors can be used. The gas box can contain a variety of gases, and the flow is controlled by MFC

◆Inhibitor molecules (such as NH3 or CO during precursor injection) can be used

◆Use hydrogen groups as inhibitors: Use hydrogen plasma (or other plasma) to inhibit the growth of specific surfaces before injecting the precursor

◆Fluoride plasma: Use CFX or F as inhibitor, before precursor injection, or during selective ALD growth, that is, etching in the same cavity every few growth cycle steps (note that O2 plasma can Etching Ru, H2 plasma can etch ZnO).

◆Injection of self-assembled monolayer (SAMS) to inhibit growth

◆Multi-cavity integrated system, such as combined with inductively coupled plasma chemical vapor deposition (ICP-CVD) chamber (growing amorphous silicon), sputtering (sputtering) chamber or atomic layer etching (ALE) chamber

◆Substrate bias for original surface modification or etching

The equipment can achieve excellent control effects including:

◆Through MFC, fast ALD valve and fast automatic pressure control, precise and adjustable precursor/gas injection can be obtained to realize the phenomenon of nucleation on one side and no nucleation on the other side.

◆Using the pre-vacuum chamber and turbo-charged molecular pump to maintain the high vacuum of the system, so that the suppression phenomenon will not be affected for a long time.

◆Clean the cavity with plasma to restore the atmosphere of the cavity.

◆Growth monitoring equipment with real-time diagnostic function: ellipsometry, mass spectrometry and emission spectroscopy

Based on the combination of selective ALD method and etching, once again reminded me of the problem of atomic scale processing, which I discussed in a previous blog post. It is conceivable that by combining selective ALD and other processes, new metamaterials (special materials) and unique structures can be grown. For example, by growing graphene in selectively exposed copper, or by periodically etching the same deposition plane (eg, locally selective ALD), the material can only grow effectively on the sides of the structure. Therefore, whether it is an ordinary plasma etching machine or a FlexAL with substrate bias characteristics, the combination of guided ion exposure may be an advantage. In general, I look forward to surprising new discoveries, new structures and new materials being born in a controlled manner.