Development Of A Testing Platform For Confined Etchant Fabrication

In the manufacturing process of integrated circuit (IC), the copper interconnect layer need to be planarized. Chemical mechanical polishing (CMP) is the only technique that provides global planarization in IC industry. With the continuing shrinking of IC feature size, the contact pressure in CMP process, which will induce surface damage, must be constantly reduced to satisfy the demands of planarization of Cu/low-k interconnects with low mechanical strength. But, with the further development of IC, the CMP which relies on the mechanical force to achieve the material removal has been unable to meet the equirement of the planarization of the extremely low strength structural of Ultralow-k/Cu. Confined etchant layer technique (CELT), as a stress free chemical processing method, has many advantages such as high accuracy and no damage, etc. It has shown great potential in the fabrication of three-dimensional micro/nano structure, and it is principally feasible to planarize the surface of copper interconnect layer by CELT. In the machining based on CELT, the material removal rate is very sensitive to the spacing of the electrode and the workpiece, thus, the control of electrode-workpiece gap is one of the key technologies for the planarization process by CELT.In this paper, for the need of confined etchant processing, a test bench is designed and developed. This test bench has X, Y, Z and C-axis independent motion control functions, the Z-axis has macro-micro composite feed mechanism. The electrolytic cell is mounted on the C-axis rotary table, and it has an inclination adjustable function. The micro force sensor is mounted on the Z-axis, it is used to analyze the contact of the electrode and the workpiece. In this paper, a dedicated control software is designed and development, it has high precision motion control and real-time data acquisition and processing functions.In this paper, the macro-micro composite feed mechanism is designed and analyzed, the theoretical analysis and finite element simulation about the stiffness, maximum stress and natural frequency of the flexible hinge mechanism are done. While the piezoelectric ceramic preload on the micro-feed institutional performance is analyzed, it is obtained that, increase the reload within a certain range can enhance the performance of the micro-feed mechanism. Based on the calculation analysis and experiment, the micro-feed mechanism has20nm feed resolution and100nm positioning accuracy.Finally, the control method of electrode workpiece gap in confined etchant processing is researched, the control methods based on micro-feed mechanism, squeeze film theory and the theory of hydrostatic are proposed, the control method based on micro-feed mechanism has the highest accuracy, the method based on hydrostatic technology makes the inter-electrode gap consistency. At last, the confined etchant system used in the processing of copper is preferred, the machining experiment is researched using the line-shaped platinum electrodes and the test bench developed in this paper, the confined etchant test bench has reliability and stability.