Defect reduction of replacement metal gate aluminum chemical mechanical planarization at 28nm technology node

In this work, a new aluminum gate chemical mechanical planarization (CMP) model is proposed in high-k metal gate (HKMG) process for controlling and simulating the metal gate height variation. It systematically captures the effects of mechanical abrasion and concentrations of different types of chemical reagents on material removal rate and surface height evolution. Based on the fundamentals of steady-state oxidation reaction and etched removal in addition to mechanical abrasion, the combinational synergistic interaction is described by separate kinetic parameters such as process parameters, pad properties and slurry chemistry. It can be seen that the removal rate and the coupled effects of the chemical additives are determined from a closed-form equation, making use of the concepts of chemical mechanical equilibrium, chemical kinetics and contact mechanics. The model prediction results show good agreement with the collected experimental data. The metal gate dishing post-Al-CMP is found to increase with increasing the pattern density when the line space is fixed. The dishing value increases with increasing the pattern density up to a certain maximum and then it decreases for a fixed pitch. The present model can be adopted to analyze the influence of the design pattern structures, slurry properties, pad characteristics and polishing conditions on removal rate and wafer surface evolution. The governing equation of aluminum removal and dishing effect reveal some insights into the polishing process and can be used for assisting in HKMG test pattern design and performing the sensitivity analyzes of operating parameters on surface topography during Al-CMP.With the steady shrinkage of the feature size and device geometry of modern integrated circuits (ICs), chemical mechanical planarization (CMP) has emerged as one of the most important solution for surface local and global planarization. Aluminum metal CMP (Al-CMP) process was once a key solution to form the Al damascene interconnects in back-end-of-line (BEOL) application. 1,2 However, due to the low resistivity and better reliability performance of copper, the Cu damascene approach has eventually taken up the mainstream in BEOL interconnect structures.In recent years, the introduction of high-k metal gate (HKMG) structure has enabled the resumption of Moore's Law at the 45/32 nm nodes, when conventional Poly/SiON gate stacks run out of steam. HKMG technology which adopts a replacement metal gate (RMG) approach promises to enable conventional scaling of the transistor as well as reduced stand-by power. Intel had the first 45 nm HKMG processor in volume production in 2007 and most of the foundries introduce HKMG to fabricate their 32/22 nm devices and products. 3 Correspondingly, poly opening polish (POP) processing before dummy poly removed and Al-CMP implementation after work function metal deposited, have been developed to fabricate the HKMG products. 4,5 During the Al metal gate CMP process, the combinational effect of the polishing pad, abrasive particles and chemi...

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confidence: 99%

An Aluminum Gate Chemical Mechanical Planarization Model for HKMG Process Incorporating Chemical and Mechanical Effects

Chen

2014

“…1,2 The new application of "high-k metal gate" structure (HKMG) is an alternative to SiON/polysilicon gate structure, the former of which can reduce the problem of RC delay and decrease leakage quantity as much as ten times. [3][4][5][6][7] However, the HKMG structure contains porous and fragile materials, and the thickness of the Al layer becomes thinner as well, thus the device can withstand relatively smaller manufacturing pressure due to low mechanical strength of the new HKMG structure. 4,[7][8][9][10] As a consequence, the CMP process must be carried out under low down pressure to ensure its integrity, that is, the CMP pressure is required to reduce to less than 6.895kPa (1psi).…”

mentioning

confidence: 99%

“…[3][4][5][6][7] However, the HKMG structure contains porous and fragile materials, and the thickness of the Al layer becomes thinner as well, thus the device can withstand relatively smaller manufacturing pressure due to low mechanical strength of the new HKMG structure. 4,[7][8][9][10] As a consequence, the CMP process must be carried out under low down pressure to ensure its integrity, that is, the CMP pressure is required to reduce to less than 6.895kPa (1psi). At present, the application of CMP technology requires to be carried out under high pressure (greater than 13.78kPa) to achieve high material removal rate.…”

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confidence: 99%

“…At present, the application of CMP technology requires to be carried out under high pressure (greater than 13.78kPa) to achieve high material removal rate. But these porous and fragile materials are difficult to withstand the high pressure in CMP process owing to its relatively lower mechanical strength, [7][8][9][10][11][12][13] which is easy to produce cracks, delamination and material deformation. 14,15 Therefore, it is the future development tendency to achieve the Al CMP at low down pressure.…”

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confidence: 99%

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In Situ Electrochemical Behavior of Aluminum Chemical Mechanical Polishing at Low Down Pressure in Environmentally Friendly and Weakly Alkaline Slurry

Liu

Wang

Zhao

et al. 2018

The lower pressure tendency in chemical mechanical polishing (CMP) process requires a lower adhesive inhibitor with environmentally friendly corrosion properties to replace the conventional benzotriazole (BTA) inhibitor for aluminum (Al) CMP. Open circuit potential test, potentiodynamic polarization curve test, linear sweep voltammetry and potential drop investigated by in-situ electrochemical mechanical polishing (ECMP) platform were used to reveal the controlled evolution process of corrosion inhibitor films at low pressure during Al CMP. The comparison between BTA and 1,2,4-triazole (TAZ) shows that TAZ has lower current density, wider potential inhibition interval, and high planarization efficiency, although TAZ has lower adhesion on Al surface. Finally, the surface roughness of Al after CMP with TAZ in weakly alkaline slurry at pressure of 1 psi was observed by atomic force microscopy (AFM) with a value of 0.19 nm. This studies demonstrated that the conventional BTA can be replaced by environmentally friendly corrosion inhibitor TAZ, which is a promising alternative candidate to the Al CMP at low down pressure.

“…However, scratch would be the most detrimental defect during CMP. [5][6][7][8][9] Because the other types of defects produced could be removed by other means during post CMP cleaning process, but the removal of scratches is not an easy task. [10][11][12][13] Scratches, such as micro-scratches on the wafer surface may lead to device failure and yield reduction as well as potential reliability issues.…”

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confidence: 99%

Role of Dispersant Agent on Scratch Reduction during Copper Barrier Chemical Mechanical Planarization

Liu

Wang

et al. 2018

The chemical mechanical planarization (CMP) has been one of the major manufacturing process to provide global and local surface planarizations in integrated circuits (IC) fabrications. Defects such as micro-scratches generated during CMP can lead to severe circuit failure, which affects yield. In the present work, ethoxylated decylalchohol (EDA) was used as dispersant agent to prevent the particles agglomeration to reduce scratches. Firstly, the effect of EDA on particle size distribution (PSD) of the slurry was investigated by dynamic light scattering (DLS) method. Then the effect of EDA on large particle counts (LPC) was studied through a dual sensor single particle optical sensing (SPOS) analysis method. The wetting ability of slurries as a function of EDA concentration was also studied. Finally, the defect scan tool and scanning electron microscope (SEM) reviewer were used to identify the scratch defects. The results show that the addition of EDA into the slurry can enhance the dispersity of colloidal silica abrasives and significantly reduce the number of large particles in the slurry, the SEM review results show that the scratch counts remarkably decreases with EDA concentration increasing. It can be demonstrated that the EDA can effectively reduce the scratch counts.