Brush Deformation Effects on Poly Vinyl Acetal Brush Scrubbing

The use of polyvinyl acetal (PVA) brushes is one of the most effective and prominent techniques applied for the removal of chemical mechanical planarization (CMP) contaminants. However, the brush can be a source of defects by entrapping the abrasives inside its porous structure during brush scrubbing. In this study, the effect of brush top skin layer was extensively studied on contamination, cross-contamination, and cleaning performance by comparing brushes with and without skin layer. The presence of a dense top skin layer resulted in larger contact areas and high ceria particle adsorption on the skin layer. This leads to higher cross-contamination of the wafers during scrubbing along with high cleaning performances. Conversely, the brushes without skin layer showed lower contamination and negligible cross-contamination with a reduced cleaning performance (removal of ceria particles from oxide surface). Therefore, the role of the brush skin layer is significant and needs to be considered while designing a post-CMP cleaning process.

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Effect of Skin Layer on Brush Loading, Cross-Contamination, and Cleaning Performance during Post-CMP Cleaning

Sahir¹,

Cho²,

Jalalzai³

et al. 2022

“…Brush surface has skin layer which is generated during brush fabrication process. [17][18][19][20] The skin layer of brush has dense structure and hard surface. As brush life increases, the skin layer is worn out and inner porous structure of brush becomes open.…”

Section: Resultsmentioning

confidence: 99%

A New Approach to the Formation Mechanism of Tungsten Void Defect in Chemical Mechanical Polishing

Kim¹,

Egan²,

Shi³

et al. 2018

The advanced node semiconductor device fabrication needs tungsten chemical mechanical polishing as a critical process to enable transistor formation as well as metal interconnection. Accordingly, CMP induced defect concerns have drawn attention to the process integration. Tungsten voids by CMP are one of the major defects to detract device yield. Their formation mechanism has been known as electrochemical corrosion or an optical induced corrosion phenomenon associated with polishing slurry chemistry. However, this paper proposes a new mechanism of tungsten void formation. Different from known corrosion mechanisms, it is observed that tungsten void frequency has strong correlation with CMP in-situ cleaner brush lifetime. At early brush life, tungsten void forms more frequently. Moreover, this paper reveals that CMP brush cleaning play a critical role in the formation of tungsten voids. Tungsten etch rate dependence on brush condition, tungsten void defect density correlation to brush life, and surface chemical analysis of tungsten blanket wafers show that tungsten voids are induced by combined effect of friction force and oxidation in brush cleaner module, which is a new approach to the formation mechanism of tungsten void defect.

“…4,5 The contact conditions between the substrate and the PVA brush has also been investigated. 6 This technique is essential to understand interfacial phenomena such as polishing or cleaning of wafers. Second, the detached particles are removed by liquid flow from the wafer.…”

mentioning

confidence: 99%

Experimental and Modelling Investigation of Re-Adhesion Mechanism of Detached Nanoparticles to Wafer Surface in Spin Rinse Process

Handa

Hiyama

Amagai

et al. 2020

Self Cite

Adhesive particles on polished wafers are detached by e.g. scrubbing, and removed by liquid flow from the wafer. However, the relationship between the characteristic of liquid flow and the removal of detached particles has not yet been examined in detail. Therefore, the re-adhesion of detached particles to wafer surfaces in liquid flow on rotating wafers was experimentally investigated. The number of residue particles on a wafer was counted using a defect inspection tool after de-ionized water (DIW) rinse for particle removal. To discuss the mechanism of particle removal, a model was constructed and compared with experimental results. The model is based on boundary layer theory of fluid dynamics and advection diffusion theory of transport phenomena for particle removal in liquid flow near the wafer surface. The model results confirmed that detached particles in liquid flow moved into the sublayer and re-adhered to the wafer surface by diffusion. Moreover, particles in the sublayer, where the liquid velocity is several hundred um/s, could not be moved from the sublayer and removed from the wafer. It was also found that the number of particles re-adhering to the wafer surface depends on the Sherwood number.