Effect of Various CVD-Coated Conditioning Disc Designs and Polisher Kinematics on Fluid Flow Characteristics during CMP

Abstract

A novel experimental technique utilizing UV-enhanced fluorescence was developed and used to measure fluid film thicknesses and general flow patterns during conditioning on a polishing pad. The method was successfully applied to several case studies for analyses of how conditioners with different working face designs (i.e. complex vane, full-face and partial-face), in conjunction with different platen angular velocities, affected fluid transport. In general, for all discs types, fluid across the pad followed similar trends where films were thickest near the wafer track center and thinnest near the pad edge (measurements showed a thickness range of appx. 0.5 to 1.1 mm). For all discs, the time for the film thicknesses to reach steady-state increased in proportion to the distance away from the pad center (times ranged between 12 and 62 s). The full-face conditioner consistently produced the thinnest films and reached steady-state the fastest. In contrast, the complex vane conditioner created the thickest films and took longest to reach steady-state. The work demonstrated the significance of understanding and visualizing the mechanisms that can contribute to fluid transport during CMP and how our novel technique could contribute, in the near future, to a greater understanding of fluid transport during in-situ conditioning.

Impact of Polisher Kinematics and Conditioner Disc Designs on Fluid Transport during Chemical Mechanical Planarization

“…The example in Figure 3a continues on in Figure 3b demonstrating how the fluid thickness data had been shifted by 5 secs and 0.17 mm. The resulting data in Figure 3b was then best described by fitting to a curve expressed in the following equation, (42) = − [ − ( ) ]…”

“…(45)(46)(47) The pad was broken-in using a 3M PB32A brush conditioner for 30 minutes with due to the fact that its protruding areas had the ability to effectively retain fluid. (42) In contrast, the 1.3K disc contained exactly 1,300 micro-replicated tips (with a 45 × 45 μm 2 square face and being 50 μm tall), which were uniformly micro-machined in a square grid pattern throughout, and then subjected to a blanket CVD diamond film deposition process. This disc was classified as a "fullface" conditioner, as defined by Mariscal et al (42) It should be noted that the entire face of this disc was not able to contact the pad surface during conditioning, however micro-machined raised areas made the disc behave as a full face disc from a fluid transport perspective.…”

“…(42) In contrast, the 1.3K disc contained exactly 1,300 micro-replicated tips (with a 45 × 45 μm 2 square face and being 50 μm tall), which were uniformly micro-machined in a square grid pattern throughout, and then subjected to a blanket CVD diamond film deposition process. This disc was classified as a "fullface" conditioner, as defined by Mariscal et al (42) It should be noted that the entire face of this disc was not able to contact the pad surface during conditioning, however micro-machined raised areas made the disc behave as a full face disc from a fluid transport perspective. This was due to the fact that the raised features were only 50 microns tall, and since the pad likely deformed more than 50 microns at the given disc downforce, the disc was not able to retain fluid as effectively as the partial-face conditioner.…”

“…(26) Building on the work of previous researches and taking into consideration the above noted complications in analyzing fluid flow in CMP, especially when conditioning is involved, Mariscal et al recently introduced a comprehensive quantitative and qualitative method for analyzing fluid transport and fluid thicknesses globally on polishing pads suitable for processing 300 mm wafers. (42) The method of analysis was based on a UV-enhanced fluorescence technique. During the study, platen rotational speeds affected fluid flow, whereas this study will use both conventional and CVD-coated conditioner discs (both types are currently used in state-of-the-art HVM IC factories) with completely different designs.…”

Effective Particle Analysis on Wafer in the EKF-CMP System

“…13 Therefore, one of the most fundamental factors in the CMP process is considered as the slurry flow velocity. 14,15 The slurry flow has many properties including slurry flow rate, fluid pressure, the viscosity and density of the slurry, abrasive particle concentration (wt%), abrasive particle size, particle deformation, chemical additives, pH value, and temperature. 16 Almost all these parameters have influence on wafer surface quality.…”