Conditioning is the process of removing the glazing area from a polishing pad surface and restoring the quality of the surface to maintain a stable polishing performance. However, the conditioning process can induce a non-uniform profile variation of the pad, which can result in nonuniform material removal rates across the wafer. In this paper, a kinematical model based on Preston's equation is proposed to examine the pad profile variation (PPV) induced by swing arm conditioning with a diamond disk. The proposed model was simulated with various swing arm velocity profiles (SAVPs), and the results were compared with experimental results. The results showed the relationship between kinematical parameters and the PPV. The PPV was proportional to sliding distance based on the kinematical model, and then the sliding distance distribution across the pad was dependent on the SAVP. This study has proven the effectiveness of the kinematical model on the PPV during conditioning in chemical mechanical polishing (CMP).
The amount of OH radicals generated varied according to the complexing agent or Cu ion, and the accelerating effect of OH radicals on the rate of Cu oxide formation was found in acidic pH. When Cu͑I͒ ions and oxalic acid were added to H 2 O 2 -based slurry, the decreases in etch and removal rates of Cu were observed because more generation of OH radicals resulted in the formation of thicker Cu oxide compared to additive-free slurry. Therefore, proper control of the formation and dissolution of Cu oxide led to an increase in etch and removal rates.Cu has been introduced as an interconnection material due to its low electrical resistance and high resistance to electromigration compared to W or Al. 1-3 The damascene process based on chemical mechanical polishing ͑CMP͒, which is used to remove the protruding part and planarize the whole wafer surface, makes it possible to use Cu as an interconnection material.During Cu CMP, the Cu surface is oxidized by an oxidizing agent through the oxidation of Cu to cuprous or cupric ions ͑Eq. 1͒. Among such oxidizing agents, hydrogen peroxide ͑H 2 O 2 ͒ is widely used for Cu CMP and its properties have been widely investigated. 4-8 Also, various organic additives were added into the slurry to maximize specific characteristics during the Cu CMP. To inhibit Cu corrosion, benzotriazole ͑BTA͒ or 5-aminotetrazole ͑ATRA͒ is commonly used. 9-11 An organic additive of the carboxylic group was added as a complexing agent to improve the removal rate of Cu. At present, citric acid, 12-14 oxalic acid, 15 and glycine 16-18 were introduced as the complexing agent and their properties and performance investigated. The complexing agents react with oxidized Cu and form complexes on the Cu surface. In an acidic pH, Cu cations, especially Cu͑I͒ ions, react with H 2 O 2 and then H 2 O 2 is converted into OH radicals and hydroxyl ions through the so-called Fenton reaction ͑Eq. 2͒. 19 The oxidation potential of the OH radical is higher than that of H 2 O 2 , which is well known to be one of the most powerful oxidizing agents Cu → Cu + + e or Cu 2+ + 2e ͓1͔It has been reported that OH radicals enhanced the removal rates of Cu in an H 2 O 2 -based slurry, including an amino acid at alkaline solution, 16 and that citric acid and oxalic acid improved the removal rate of Cu in the acidic solution. When using citric acid and oxalic acid as the complexing agent in weak acidic pH, the effect of OH radicals in the slurry on Cu CMP performance has not been reported. Therefore, the objective of this study is to understand the effect of OH radicals on Cu CMP. ExperimentalElectrochemical measurements.-For the electrochemical experiments, a 99.9% Cu rod with a surface area of 0.5 cm 2 was used. A Pt electrode and a saturated calomel electrode ͑SCE͒ were used as a counter and a reference electrode, respectively. Potentiodynamic studies were performed with an EG&G model 263 potentiostat/ galvanostat corrosion measurement system. The potentiodynamic polarization measurements were obtained with a scan rate of 10 mV/s a...
The material removal characteristics of a silicon wafer were experimentally investigated with respect to the chemical dissolution and mechanical abrasion of the wafer during silicon chemical mechanical polishing (CMP) using an alkali-based slurry. The silicon surface without native oxide is rapidly dissolved by the slurry containing an amine agent, which effectively leads to the reduced hardness of the loaded silicon wafer due to Si-Si bond breaking during polishing. The abrasive particles in the slurry easily remove the reacted silicon surface, and the removal rate and wafer non-uniformity for abrasive concentrations of 1.5 -3 wt % are better than those for other concentrations because of the low and steady coefficient of friction (COF) owing to the evenness of abrasive particles between the wafer and pad. Also, it was found that a high slurry flow rate of 700 -1000 cm 3 /min improves wafer non-uniformity owing to the reduced temporal variation of temperature, because the slurry acts as a good cooling source during polishing. However, the removal rate remains almost constant upon varying the slurry flow rate because of the effective dissolution characteristic of the slurry with abundant amine as an accelerator, regardless of the reduction of average temperature with increasing slurry flow rate. In the break-in process used to stabilize the material removal, the viscoelastic behaviors of the pad and the ground wafer surface with native oxide and wheel marks cause a temporal change of the friction force during polishing, which is related to the removal rate and wafer non-uniformity. As a result, the stabilization of removal rate and wafer non-uniformity is achieved through a steady-state process with elevated temperature and reduced COF after a total polishing time of 60 min, based on the removal process of the wafer surface and the permanent deformation in the viscoelastic behavior of the pad. #
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