Papers by Keyword: Chemical Mechanical Planarization

Abstract: Accurate determination of a chemical mechanical planarization (CMP) process reaching the end point is an important problem in the CMP process. In present work, the variation of the motor power signal of the polishing platen in the CMP process has been investigated, and the moving average method with 121-points moving window was used to smooth the original signal curve. Experiment results showed that the processed signal could facilitate the extraction of end-point feature for the in-situ end-point detection (EPD) system and it was relatively steady before and after the layer transition stage, which made it more reliable to detect the end point in situ. Comparing with other EPD methods, the system was less complicated, and it was easier to code for algorithm development. Finally, further analysis was performed and series of experiments provided a planarized via-revealed surface with low via dishing.

Abstract: The polishing process was optimized according to the polishing rate and its consistency of HE slurry with different dilution multiple on the copper wafers, it can be confirmed that: the best pressure value of HE1, HE10, HE20, HE50 type slurries was 6890Pa, the best flow rate value of the preceding three slurries was 300ml/min, the best value of the HE50 slurry was 400ml/min. Through the planarization effects of the slurries with different dilution multiple, it can be obtained that: the initial dishing and erosion heights of the samples were both 1270nm and -500nm, and the two values respectively changed to 539.3nm, -75.7nm and 796.3nm, -191.3nm after being treated by HE1 and HE10 slurries, the step height of the wafer changed from 117nm to 72nm after being treated by HE20 slurry, the step height of the wafer changed from 88nm to 71nm after being treated by HE50 slurry. It was concluded that: the HE slurry shows strong ability for step removal when the slurry is diluted by 1 times and 10 times, the HE slurry also owns high planarization ability when the slurry is diluted by 20 times and 50 times.

Abstract: According to the Bernoulli equation and Darcy formula, the flow model of slurry in micro-channels was established, it indicated that slurry viscosity is the main factor affecting the slurry mean velocity. According to the characteristics that liquid viscosity is mainly determined by the liquid temperature and the property that mechanical friction can improve the liquid temperature, the effects of slurry temperature, working pressure and polishing speed on the heterogeneity of polishing rate were investigated. The results showed that the effect of removal rate of each parameter on the central part of the copper film can be described as: slurry temperature > working pressure > polishing speed. In order to obtain the best planarization process, through the central composite experimental method, the technological parameters were optimized regarding the heterogeneity of polishing rate as response value. It was finally concluded that: when the slurry temperature was 21.60°C, the working pressure was 8.83kpa, the system speed was 43.92rpm, the predicted minimum value of the heterogeneity of polishing rate (HOPR) was 0.0574.

Abstract: Silica abrasive plays an important role in chemical mechanical planarization (CMP) of copper. In this paper, effect of different silica abrasive concentrations on copper removal rate and planarization performance of copper was investigated. The results show that the copper removal rate was increased as the concentration of silica abrasive increase. However, excessive abrasive will lead to a decreased copper removal rate. The initial step height values of the multilayer copper wafers were all about 2500Å, and after being polished for 30s, the remaining values of step height of slurry A, B, C and D were 717 Å, 906 Å, 1222 Å and 1493 Å. It indicates that alkaline copper slurries with different abrasive concentrations all had a good planarization performance on copper patterned wafer CMP. As the abrasive concentration increased, the planarization capability was enhanced.

Abstract: The Chemical mechanical planarization (CMP) process has become a primary planarization technique required for the manufacture of advanced integrated circuit (IC) devices. As the feature size of IC chips shrinks down to 65 nm and below, the role of CMP as a robust planarization process becomes increasingly important. In this work, we evaluated surface roughness of CMP pad to correlate the roughness with CMP performance such as material removal rate (MRR) and pad lifetime. Pad surface was analyzed by 3-dimensional profiler and scanning electron microscope (SEM). We found that MRR could be varied with the pad life time and roughness. We also found that suitable roughness range is exist to get stable CMP performance. Finally, we introduced ‘pre-conditioning’ method to manage the roughness of CMP pad to get stable CMP performance at the initial pad life time.

Abstract: With low-k dielectric materials taking the place of oxide dielectrics as the primary dielectric materials, the low-k dielectric materials and interconnection Cu metals during Chemical Mechanical Planarization (CMP) is becoming a critical surface quality issue as well. In this study, experiments are carefully designed and conducted to investigate the effects of colloidal silica under compared acidic slurry and self-prepared alkaline slurry on k value of low-k dielectric materials, and in both of the slurry, colloidal silica (20~30nm) was used as polishing abrasive. The results showed that k value of low-k dielectric materials both increased within a similar range (self-prepared alkaline slurry, 3.27~3.33; commercial acidic slurry, 3.26~3.32), however, the results showed a obviously different result from reference’s report.

Abstract: With the microelectronic technology node moves down to 45 nm and beyond, and to reduce the RC delay time, low-k dielectric materials have been used to replace regular dielectric materials. Therefore, the down force of chemical mechanical planarization (CMP) needs to decrease based on the characteristics of low-k materials: low mechanical strength. In this study, the effect of new complex agent on copper dissolution in alkaline slurry for CMP was investigated. Based on the reaction mechanism analysis of Cu in alkaline slurry in CMP, the performance of Cu removal rate and surface roughness condition were discussed. It has been confirmed that Cu1 slurry demonstrates a relatively high removal rate with low down force. And also, by utilizing the Cu1 slurry, good result of Cu surface roughness were obtained.

Abstract: Chemical mechanical polishing (CMP) of Cu pattern wafer based alkaline slurry in GLSI with R(NH₂)_n as complexing agent was investigated. In Cu CMP procedure, it is necessary to minimize the surface dishing and erosion while maintaining good planarity. This requirements are met through the complexing agents. Based on the reaction mechanism analysis of Cu in alkaline slurry with R(NH₂)_n as complexing agent in CMP, the performance of Cu dishing and erosion were discussed. The results showed that the slurry stability can be improved obviously by the addition of R(NH₂)_n as complexing agent, both Cu1 and Cu2 have good dishing and erosion performance. Furthermore, the dishing condition of Cu2 (180-230nm) is better than that of Cu1 (280-370nm), and the erosion condition of Cu2 (230-260nm) is also better than that of Cu1 (450-500nm).

Abstract: Chemical mechanical planarization (CMP) of Cu pattern wafer based alkaline Cu slurry in GLSI was investigated. The performance of Cu removal rate and dishing condition were discussed in this paper. Different formation of alkali CMP slurry (Cu1 and Cu2 slurry) were observed by removal rate experiments and showed that alkaline slurry provided a robust polishing performance on initial removal rate, which Cu1 and Cu2 slurry were higher than that of commercial acidity slurry, and in addition, alkaline slurry also have good ending removal rate both in Cu1 and Cu2 slurry and favorable dishing in Cu2 slurry. Furthermore, the result indicated that Cu alkaline slurry with a complexing agent of R(NH2)n, compared with commercial acidity slurry with a inhibitor of Benzotriazol (BTA), have better application foreground for 45nm nod and more advanced nodes.