Role of Penetrating Agent on Colloidal Silica Particle Removal during Post Cu CMP Cleaning

Abstract

The cleaning of copper surface after chemical mechanical planarization (CMP) is a critical step in integrated circuits (ICs) fabrication. Because the copper surface would be contaminated by particles, such as silica abrasives, which may cause device failure. The purpose of this work is to propose a kind of penetrating agent for particle removal. The cleaning solution consisted of FA/O II as a chelating agent and primary alcobol ethoxylate (PAE) as a penetrating agent. The removal of particles was characterized using scanning electron microscope (SEM). The wettability of the cleaning solutions as a function of PAE concentration was quantified using contact angle measurements. The effect of PAE on surface tension was also studied. The surface quality of copper after cleaning was monitored using atomic force microscope (AFM) measurements. The test results showed that PAE can reduce the surface tension of cleaning solutions and contact angle on surface. SEM results showed that PAE could effectively remove the silica particles and a lower surface roughness was obtained after cleaning. The cleaning performance on copper patterned wafers also showed that PAE could reduce defect count effectively.

Review—Post-Chemical Mechanical Planarization Cleaning Technology

“…The presence of surfactants in the cleaning solution enhances particle removal efficiency by reducing the interfacial shear force. 88 The various surfactants used for post-CMP cleaning as reported in the literature are ammonium dodecyl sulfate (ADS) 83 -anionic surfactant, dodecyl benzenesulfonic acid (LABSA) 91 -anionic surfactant; hexadecyltrimethylammonium bromide (CTAB) -cationic surfactant; polyethylene glycol octyl phenyl ether (Triton X-100) 92 nonionic surfactant, fatty alcohol polyethylene ether (JFCE) 91 nonionic surfactant.…”

“…The chelating agents prevent the formation of complicated metal complexes, whereas inhibitors, especially hydrophilic ones, are used to eradicate surface problems (such as corrosion) that arise due to hydrophobicity. Some of the commonly used chelating agents are arginine, 79 1.2-bis-(3-aminopropylamino) ethane (TAD) (comprises of both carboxylic and amine groups), 94 ethylenediamine, 95 novel chelating agent containing multi-amine and multi-hydroxyl organic group-FA/O 96 and FA/O II, 92 etc. Inhibitors used in post-CMP cleaning solution are ethylene glycol, 97 sarcosine, and its salts, 98 cysteine, 95 uric acid 95 etc.…”

“…Other Chemicals.-The addition of primary alcohol ethoxylate (PAE) as a penetrating agent increases the hydrophilicity of the surface and thereby reduces the surface roughness and defect counts of wafers. 92 Penetrating agents are mainly used to remove abrasives (silica) used in the CMP process.…”

“…176 Minimum defects and contaminants in Cu wafer were observed using 75 ppm FA/O as a chelating agent. 96 However, Wang et al 92 reported that an alkaline cleaning solution comprising of 200 ppm Arginine and 200 ppm FA/ O II as main chelating agents and 1800 ppm Triton X-100 as an auxiliary wetting agent could effectively remove the Cu-BTA residues along with other micro defects. This combination gave an increased surface wettability (contact angle reduces by 42.5˚) and a roughness value of 2.03 nm.…”

“…PAE reduces the surface tension of the cleaning solution to yield better cleaning performance along with reduced roughness. 92 The tabulation of various post-CMP chemistries for Cu is given in Table VI. Apart from the various causes of contamination after Cu CMP, fine impurities of particulate residue from the PVA brush also contaminate the Cu surface.…”