Evaluation Of Planarization Performance For Alkaline Copper Slurry Under A Reduced Down Pressure And Low Abrasive Concentration

With the integrated circuit developed into GLSI, the layer of multilayer metal interconnection is up to more than 10 layers, in order to achieve the required precision of nanometer lithography, each layer must be approved by three-step planarization,which are the copper chemical mechanical planarization(CMP) and barrier layer CMP. Chemical mechanical planarization(CMP) is a critical process in deep sub-micron integrated circuit manufacturing, while the development of CMP technology and key polishing material slurry has become one of the bottlenecks restricting the development of microelectronic technology.Owing to the introduction of fragile low-k dielectrics, Cu CMP is necessary to be carried out at a reduced down pressure. Colloidal silica is a material that is used as an abrasive of slurry to improve the polishing rate. It will cause depression, microscopic scratches and damage, and it bring great difficulties to the cleaning steps. So the CMP ought to be performed under the condition of low pressure and low abrasive concentration. As the key of Cu CMP, it is very important to enhance the chemical reaction of the slurry with the development of the copper slurry and polishing technology.This paper studied the influences of ingresients of slurry and CMP process on the key parameters of multi-layer copper wiring CMP. The slurry which can meet the need of development for microelectronics was developed and optimized. This study aims to improve the planarization capability of slurry, while minimizing the mechanical action of pressure and silica abrasive. However, the reduced mechanical action may bring about the decline of polishing rate, and further resulting in the decrease of throughput. Therefore, we take an approach to compensating for the loss of mechanical action by optimizing the composition of slurry to enhance the chemical action of chelating agents FA/O and HⅤ 2O2 in CMP process. So 3wt% abrasive concentration of alkaline slurry for copper polishing was developed, it can achieve planarization efficiently at a reduced pressure of 1.5psi. The settling time of the slurry is up to 12 hours, and the result can satisfy the requirements of industrial applications basically.Based on a new chelating agents FA/O Ⅵ, it developed a 3wt% abrasive concentration of alkaline copper slurry, the feasibility of the slurry used in copper bulk eliminate process and residual copper eliminate process with different process parameters, was analyzed. The planarization experimental results show that an excellent planarization performance is obtained with a relatively high copper removal rate in bulk eliminate process. Meanwhile, after residual copper eliminate process, the dishing value increased inconspicuously, in a controllable range, and the wafer surface roughness is small after polishing. By comparison, the planarization performance and surface quality of alkaline slurry are almost no large differences with the commercial acid slurries after polishing. Compared to the acidic slurry, The compositions of the alkaline slurry are simple, and it did’t have conventional inhibitor BTA. It also had a high polishing rate and planarizaton efficiency, which obtained a good planarization performance in bulk eliminate process. Dishing can be effectively controlled in residual copper eliminate process. All the results above show that the slurry can be applied in multi-layers copper CMP.