Magnesium vs. Magnesium Oxide Targets – Which One Gets Better Film on Silicon?
High-quality thin films play a big role in electronic and optical devices. Over the years, the choice of sputtering target has been shown to significantly influence film properties. When depositing magnesium oxide films on silicon, the selected target—either pure magnesium or magnesium oxide—affects the film’s crystal structure, appearance, and performance.
Target Types and Deposition Process
The deposition mechanisms for each target type are as follows. When a pure magnesium target is used, atoms are sputtered from the target surface as magnesium. Upon reaching the silicon substrate, these magnesium atoms react with oxygen in the chamber, either from residual gases or intentionally introduced, forming magnesium oxide during or after deposition.
When using a magnesium oxide target, the film forms directly as magnesium oxide from the beginning. Both methods employ radio frequency magnetron sputtering, but the differences in the starting material result in subtle yet significant differences in the final film.
Film Orientation and Structural Differences
Film orientation and structural properties differ notably between the two target types. In films deposited from a pure magnesium target, the crystalline orientation can shift with the temperature of the substrate. At lower temperatures, these films tend to favor the (200) plane. When the substrate temperature increases, the films show a tendency to shift toward the (111) plane. This change in orientation could affect the film’s strength and the way it interacts with light.
In contrast, films produced from a magnesium oxide target usually grow with a steady (200) orientation. This consistent growth reflects a stable crystalline structure, making these films easier to predict in their performance. A film with a known and stable structure allows for more predictable performance in devices such as sensors or semiconductor components.
Implications for Performance
The differences in film structure have clear practical consequences. For one, films deposited using the magnesium target can have varied grain sizes. This variation in grain size may lead to changes in electrical resistivity and also influence optical behavior. Structural variations can influence device performance, including waveguides and sensors, as even small changes in the film structure may affect functional behavior.
On the other hand, the consistent orientation of films from the magnesium oxide target has its benefits. For example, such films typically deliver predictable optical results. This uniformity is appreciated by engineers who are working on components where precise control over film properties is required. Consider tasks like manufacturing optical fibers or semiconductor switches; reliability and consistency often lead to better, more reproducible performance.
Slight adjustments in deposition temperature can lead to measurable changes in film behavior. This demonstrates that while magnesium targets allow some control over the film’s structure through temperature adjustments, they might also bring unpredictability. In contrast, magnesium oxide targets produce films that are largely unaffected by such variations. In practical applications, this makes magnesium oxide targets a good choice when consistency is needed.
Conclusion
As we look back, it is clear that choosing the right sputtering target depends on the needs of your project. If you wish to adjust and control the crystalline orientation by changing substrate conditions, using a pure magnesium target gives you that flexibility. However, if you prefer a more uniform and stable deposition, the magnesium oxide target is the better bet.
It is important to keep in mind that each method has its own advantages. Both outcomes have been observed and measured in research and practical applications. The key is to match the method with the desired outcomes in your device or experiment. For both approaches, a good quality target is essential, and the reliability of your deposition process will directly reflect your choice of materials.
For those working in the lab, it is reassuring to know that high-quality sputtering targets are available to support your experiments. At Stanford Advanced Materials (SAM), we provide reliable magnesium and magnesium oxide targets to support a wide range of electronic and optical applications.
