Stability Tests for Electronics Applications

The stability of suspensions used in the electronic field is critical for guaranteeing the level of quality associated with high-technology end-products. For example, ultra-high-definition displays rely on unique optical coatings and surface engineering of thin film structures to generate images of high quality. A chemical-mechanical polishing (CMP) uses slurries to polish the surfaces of semiconducting materials. The functionalities of fuel cells and batteries are improved with solution-processed nanoparticle coatings. There are myriad examples of the use of suspensions in established and cutting-edge electronic applications. Stability tests of suspensions can ensure that electronic devices in commercial and industrial spaces are fit for requirements.

Stability Tests for CMP Solutions

CMP techniques use abrasive and corrosive chemical slurries to planarize the surfaces of substrate materials in preparation for lithographic electronic printing. Cerium (IV) oxide, or ceria, is routinely used as a chemical catalyst in the abrasive process. It accelerates the weakening of metallic surface particles on the semiconductor substrate and a mechanical polishing pad removes these particles from the surface. This process reduces topographic irregularities to provide a surface that is flat at the Angstrom level.

Ceria is a highly efficient polishing media for semiconductor surface engineering, but it displays significant colloidal instability with a tendency for dispersed particles to sediment and agglomerate. This behavior can damage the efficiency of CMP surface engineering and cause mechanical defects in the semiconducting wafer. Surface variations of microscale proportions can significantly reduce the efficiency and functionalities of thin-film structures. This highlights the importance of performing robust stability tests of ceria suspensions used for CMP processing.

Stability tests for CMP suspensions are used to determine the efficiency of polymeric dispersants within ceria slurries, which are designed to inhibit the migration of dispersant particles in the liquid phase media. The Turbiscan LAB particle stability and size analyzer have been used for stability tests of ceria slurries based on the molecular weight of dispersants. Tests conducted at ambient temperatures of 35°C showed that ceria suspensions commonly display increased backscattered light at the bottom of the sample and increased transmission at the top of the sample. This is due to particle sedimentation over time.

These stability tests have enabled analysts to determine the short-term stability of formulations of various molecular weights, with results indicating that dispersants of higher molecular weights (longer polymer chains) allow for longer colloidal stability.

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