The Effects of Friction and Temperature in the Chemical–Mechanical Planarization Process

Abstract

Chemical–mechanical planarization (CMP) represents the preferred technology in which both chemical and mechanical interactions are combined to achieve global planarization/polishing of wafer surfaces (wafer patterns from metal with a selective layer, in this paper). CMP is a complex process of material removal process by friction, which interferes with numerous mechanical and chemical parameters. Compared with chemical parameters, mechanical parameters have a greater influence on the material removal rate (MRR). The mechanical parameters manifest by friction force (Ff) and heat generated by friction in the CMP process. The Ff can be estimated by its monitoring in the CMP process, and process temperature is obtained with help of an infrared rays (IR) sensor. Both the Ff and the MRR increase by introducing colloidal silica (SiO2) as an abrasive into the selective layer CMP slurry. The calculated wafer non-uniformity (WNU) was correlated with the friction coefficient (COF). The control of Ff and of the slurry stability is important to maintain a good quality of planarization with optimal results, because Ff participates in mechanical abrasion, and large Ff may generate defects on the wafer surface. Additionally, the temperature generated by the Ff increases as the SiO2 concentration increases. The MRR of the selective layer into the CMP slurry showed a non-linear (Prestonian) behavior, useful not only to improve the planarization level but to improve its non-uniformity due to the various pressure distributions. The evaluation of the Ff allowed the calculation of the friction energy (Ef) to highlight the chemical contribution in selective-layer CMP, from which it derived an empirical model for the material removal amount (MRA) and validated by the CMP results. With the addition of abrasive nanoparticles into the CMP slurry, their concentration increased and the MRA of the selective layer improved; Ff and MRR can be increased due to the number of chemisorbed active abrasive nanoparticles by the selective layer. Therefore, a single abrasive was considered to better understand the effect of SiO2 concentration as an abrasive and of the MRR features depending on abrasive nanoparticle concentration. This paper highlights the correlation between friction and temperature of the SiO2 slurry with CMP results, useful to examine the temperature distribution. All the MRRs depending on Ef after planarization with various SiO2 concentrations had a non-linear characteristic. The obtained results can help in developing a CMP process more effectively.

Investigation of Polisher Head and Slurry Sweep Effect in Oxide Film Polishing

“…This phenomenon can be attributed to the contingency of the removal amount on the frictional energy during polishing, with friction serving as the primary heat source for the process. 33 Elevated temperatures correspond to increased friction forces between the pad and wafer surface. Notably, ceria polishing generates more frictional heat than silica polishing, even when utilizing the same polishing protocol.…”

Novel Process Modeling of Magnetic-Field Assisted Finishing (MAF) with Rheological Properties

“…With the development of metal additive manufacturing (AM) [5][6][7][8][9], which is capable of producing various complex designs and shapes that are not feasible with any conventional subtractive manufacturing, there has been an increasing demand for viable finishing technologies for complex AM-fabricated geometries. Although there are other advanced finishing processes that can improve the surface quality of the parts to a fine scale such as elastic emission machining (EEM) [10] and chemical-mechanical polishing (CMP) [11], thanks to the shape-adaptive flexible polishing brush, MAF has garnered much interest regarding the post processing of additively manufactured components [12][13][14]. The MAF process was implemented to polish various kinds of materials, such as mold steels [15], glass [16], ceramics [17], sheet metals [18], and titanium alloys [19].…”

“…Lubricants 2023, 11, x FOR PEER REVIEW 2 of 23 surface quality of the parts to a fine scale such as elastic emission machining (EEM) [10] and chemical-mechanical polishing (CMP) [11], thanks to the shape-adaptive flexible polishing brush, MAF has garnered much interest regarding the post processing of additively manufactured components [12][13][14]. The MAF process was implemented to polish various kinds of materials, such as mold steels [15], glass [16], ceramics [17], sheet metals [18], and titanium alloys [19].…”