Chemical mechanical planarization (CMP), relies on several nanoscale surface interaction processes, and so does a successful CMP result. Irrespective of whether your ambition is to develop and customize high performing slurries, to improve contamination control, or to achieve reliable CMP protocols, it all starts with an understanding, and control of, the surface-molecule interactions involved.
QSense® QCM-D technology is used in molecule-surface interaction analysis and optimization of CMP-related processes. The method can, for example, be used to analyze
- additive - surface interaction
- residue removal
- surface etching
Characterize and optimize the chemical part of your CMP process
The chemical part of CMP represents a key aspect of the method. It is therefore important that this is optimized for the end use. Both in the development of new slurries and protocols, as well as in the improvement of existing ones, it is important to understand the chemistry and the surface interactions involved. With QSense technology you can study surface processes related to, for example, slurry additives and their interaction with the surface. Questions that could be answered are for example:
- How does this slurry additive interact with the target surface?
- How does the effect of the additive vary with concentration? Which concentration is optimal?
- What is the additive removal rate?
- How efficiently does this post CMP cleaner remove the residue?
- How does the slurry etch this surface material?
Analyze material uptake and removal to get the full picture of the surface interactions
QSense is a surface sensitive technology that gives you a new set of eyes in the study of surface interaction processes. It is based on the Quartz Crystal Microbalance with Dissipation monitoring technology (QCM-D) which allows you to study nanoscale mass, thickness and viscoelastic changes of your surface material or coating. The QCM-D method is time-resolved, which means that you can follow the interaction processes in real-time. Interactions and events that can be analyzed are for example adsorption, desorption, molecular binding, and structural changes such as swelling and crosslinking. For example, you can analyze and compare how additives, additive mixtures, and abrasives interact with the surface of interest, Fig. 1.
Figure 1. Schematic illustration (not to scale) of how the performance and behavior of different additives can be compared using QSense analysis. The example shows four different measurements where the parameter settings, in blue text, are varied relative to the measurement conditions in (A). In (B) the additive concentration is reduced, in (C) the surface material is changed, and in (D) a different additive is used. The time-resolved mass curves reveal the additive - surface interaction rate and the additive net mass uptake in the respective measurement.
Study real-life conditions
Surface interaction processes are highly dependent on the conditions where they take place. Therefore, when working with a real-life system, it is important to mimic these conditions in the experimental set up. As exemplified in Fig. 1, QSense allows you to vary all the key parameters in your process.
Vary for example:
- Surface material/chemistry
- Solution pH
- Temperature
- Chemical additive
- Additive concentration
Concluding remarks
QSense analysis can be used to understand the chemical part of the CMP process. For example, it can be used to
- measure selectivity by varying the surface material of the CMP process
- measure post CMP cleaning – determine if extra steps are needed to remove residue
- measure point of use additives and their effect on etching or passivation
- analyze slurry chemical removal or etch rates
Download the overview to learn more about how QSense analysis can be used in slurry development, customization and optimization
