Experimental and Numerical Analysis of A Novel Ceria Based Abrasive Slurry for Interlayer Dielectric Chemical Mechanical Planarization

Bahr

et al. 2017

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In this work, the position of the novel slurry injection system (SIS) was optimized to achieve a more cost-effective and environmentally benign chemical mechanical planarization process using a widely-adopted ceria-based “reverse slurry”. SIS was configured with different angles in order to investigate slurry dilution characteristics caused by residual pad rinsing with ultrapure water (UPW) that affected silicon dioxide removal rates. UPW dilution effect on removal rate, coefficient of friction and pad surface temperature was explained by maintaining a constant dilution ratio for each of the SIS configuration tests. Results indicated that the negative rotation angle of the SIS increased the actual slurry dilution ratio on top of the polishing pad. This generated more Ce3+ which boosted the removal rate. Application of negatively rotated SIS allowed significantly lower slurry flow rate and/or shorter polishing time leading to achieve a more environmental friendly semiconductor manufacturing process. Finally, it was confirmed that variations in SIS configuration had no impact on silicon dioxide to silicon nitride removal rate selectivity.

Section: Resultsmentioning

confidence: 85%

Effect of Various Slurry Injection System Configurations on Removal Rates of Silicon Dioxide Using a Ceria-Based Chemical Mechanical Planarization Slurry

Bahr

et al. 2017

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“…via the Arrhenius relationship) and has been shown by our research team to have an appreciable apparent activation energy of about 0.43 eV. 32 Fig. 4 shows the trends in coefficient of friction (COF) and pad surface temperature for most slurry dilution conditions reported in Fig.…”

Section: Resultsmentioning

confidence: 90%

Effect of Slurry Injection System Position on Removal Rate for Shallow Trench Isolation Chemical Mechanical Planarization Using a Cerium Dioxide Slurry

Bahr

et al. 2017

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In this study, the effects of ultrapure (UPW) water dilution of a ceria-based slurry on silicon dioxide removal rates were investigated. Results indicated that removal rates increased with dilution up to a slurry to UPW ratio of 1:7.5 before reaching a plateau in the pre-mix dilution case. The concentration of Ce3+ was thought to increase with dilution up to a ratio of 1:7.5. Further dilution resulted in reduced friction and temperature which halted any further increases in removal rate. Mixing the slurry and UPW at point-of-use resulted in a similar removal rate trend to pre-mixing, but with higher removal rates at each dilution ratio due to reduced particle agglomeration. A novel slurry injection system (SIS) was employed at various rotation angles. Each SIS angle produced a different retaining ring bow wave thickness, which led to different extents of dilution and therefore different removal rates. The SIS at −8° produced the highest removal rates of all angles at an average value of 2,595 Å/min. A third dilution ratio test was performed using point-of-use mixing through the SIS at −8°, which resulted in a similar removal rate trend as the previous tests but with dramatically higher removal rates at each dilution ratio.

“…Simulation results.-To understand the non-Prestonian behavior observed in Figure 3 and to more fully characterize the polishing process, a two-step modified Langmuir-Hinshelwood model is used to simulate the silicon dioxide removal rate as well as the chemical and mechanical rate constants. 17,18 While this model has been successfully used in the past by our research team for copper, tungsten, titanium, ILD and STI applications using a variety of application-specific silicabased and ceria-based slurries and polyurethane pads, 6,12,[17][18][19][20][21][22][23] no previous work has been published on the possible utility of this model for cobalt "buff step" using a Fujibo H800-CZM pad and a slurry intended for this application. As such, we believe that our contribution to the field of polishing the dielectric surrounding cobalt plugs and local interconnects in MOL metallization is original.…”

Section: Resultsmentioning

confidence: 99%

Cobalt “Buff Step” Chemical Mechanical Planarization

Stuffle

et al. 2018

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In this study, silicon dioxide wafers were polished as part of a cobalt "buff step" CMP using a novel and state-of-the-art applicationspecific slurry and pad combination to study the thermal, tribological, and kinetic attributes of the process. Removal rate and mean pad temperature showed increases with higher polishing pressures and sliding velocities, while coefficient of friction stayed relatively constant across all investigated conditions. Under all conditions, the process was tribologically robust as it remained in "boundary lubrication". As the removal rate exhibited a non-Prestonian behavior, a well-established Langmuir-Hinshelwood model was used to simulate, for the first time for this process and this set of consumables, removal rate data such that chemical and mechanical rate constants could be extracted and understood in light of the process parameters chosen. Results indicated that the process was mechanically limited at nearly all combinations of pressure and velocity except at the highest values investigated, indicating that small deviations from set polishing power can greatly affect material removal rate.