Metal thin film adhesion, Au-Si deposition

In summary, when using electron beam evaporation to achieve good stable 100nm Au adhesion onto a Si substrate, it is common to use a primer layer of either Cr or Ti at around 5nm thickness. Both materials are commonly discussed and have their own advantages and disadvantages. When using other metals such as Al on Si, a primer layer may not be necessary. However, when using Ge as the substrate, the native oxide is less stable and can be soluble, so Ge itself may be used as an adhesion layer. The same Cr or Ti protocol can be used for Ge as for Si, but some people also insert Pt to block diffusion. The choice between Cr or Ti is not a significant factor as long as the device is
  • #1
minerva
93
6
What protocol should I use to get a good stable 100nm Au adhesion onto a Si substrate using electron beam evaporation? I've heard talk of primer layers of either Cr or Ti at around 5nm thickness, as the typical way to do it.

Which material should I choose? What the advantages or disadvantages of both Cr and Ti (or some other material)? They're both commonly discussed and I don't know which one to pick. (I have both available for loading sources in the lab.) When other metals such as Al is used, onto Si, it will work well with no additional adhesion layer right?

What about if Ge is used as the substrate? I know the native oxide is significantly different on Ge, it's less stable and can be soluble, compared to native SiO2. I've heard that Ge itself adheres to things well and can be used as an adhesion layer. If Ge was used as the underlying substrate (same Au deposition) could the same Cr or Ti protocol still be used (same as Si), to have confidence in reliable adhesion of the metal?
 
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  • #2
I've used both Cr and Ti as an adhesion layer for Au to Si. The Ti was used in the context of an implantable medical device—Ti was perceived to be more biocompatible. One factor is that the adhesion layer inevitably diffuses somewhat into the Au, especially at higher temperatures, which can change the layer's resistivity, among other properties. However, I never did any rigorous tests to see whether Cr or Ti is worse in this respect. Some people insert Pt to block this diffusion. But really, the choice of Cr or Ti is a very small decision as long as your device is working correctly.

I haven't put Al on Si or worked with Ge, sorry.
 

What is metal thin film adhesion?

Metal thin film adhesion refers to the strength of the bond between a thin layer of metal and its underlying substrate material. It is an important factor in the manufacturing of electronic devices and other products that utilize metal thin films.

What is the significance of Au-Si deposition in metal thin film adhesion?

Au-Si deposition is a common method used to deposit thin films of gold (Au) onto silicon (Si) substrates. This process is important in metal thin film adhesion because it helps to improve the bond strength between the gold layer and the silicon substrate, resulting in better overall adhesion.

What factors affect the adhesion of metal thin films?

Several factors can influence the adhesion of metal thin films, including the surface roughness of the substrate, the cleanliness of the substrate surface, and the type and thickness of the metal being deposited. Other factors such as temperature, pressure, and the presence of impurities can also impact adhesion.

How can the adhesion of metal thin films be tested?

There are several methods used to test the adhesion of metal thin films, including the tape test, scratch test, and peel test. These tests involve applying force to the film in different ways and measuring the resulting adhesion strength. Other techniques such as microscopy and surface analysis can also be used to assess adhesion.

Why is good adhesion important in metal thin film applications?

Good adhesion is crucial in metal thin film applications because it ensures the stability and durability of the product. Poor adhesion can lead to delamination and failure of the metal thin film, resulting in malfunction or damage to the device or product. Therefore, understanding and optimizing adhesion is essential in the design and manufacturing of metal thin film-based products.

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