Investigation On Chemical Mechanical Polishing Of Copper Wire Under Low Pressure

After entering 65 nm technology nodes,the layer of integrated circuit copper wiring is up to more than ten layers,and the copper film is becoming more and more thin.It is easy to cause the copper film falling off and the low-k dielectric material collapsing if the work pressure of chemical mechanical polishing is too high,but if the pressure is too small that will reduce the polishing rate,which can not satisfy the industrial requirement.So the pressure is often chosen as 2 psi in industrial production.With the declining of line width after entering 20¹4 nm technology nodes,the polishing pressure must be declined sustainable.Therefore it is necessary to study the copper chemical mechanical polishing under the condition of low pressure.This paper was made a prospective study of Cu CMP under low pressure.Enhancing the chemical action to increase the polishing rate can compensate the loss of rate caused by the low work pressure.Using the FA/O chelating agent which was independent researched by our research group,a kind of slurry was prepared and the polishing rate can reach 700nm per minute at the pressure of 1.5 psi which can satisfy the requirement of industrial application.Next the influence of abrasive on Cu CMP and the change of particle size after polishing under the condition of low pressure were discussed.Results showed that a better polishing performance was gotten and the particle size change was small under the pressure of 1.5 psi using 100 nm size of SiO₂ abrasive which mass fraction was 1wt%⁴wt%.It had a certain guiding significance for the selection of abrasive and the recycling use in the future.The existence of Cu₂O under the condition of low pressure has not been verified in our research before.By the method of static corrosion?dynamic polishing and electrochemical experiment,the complexing mechanism of four complexing agents was researched and glycine was selected as complexing agent.XPS was used to analysis the surface chemical composition of copper after corroded.The experiments showed that there were only Cu₂O and Cu on copper surface which improved and validated the complexing and amination technical route under the condition of low pressure developed by our before research.At last,the influence of technological parameter,such as rotate speed and polishing pressure on the open circuit voltage was studied by the rotating disk electrode connecting with electrochemical workstation to simulate the process of CMP under the condition of low pressure.Moreover,the concentration of H₂O₂ and FA/O?also influence the open circuit voltage.The results indicated the rotate speed,the polishing pressure,the different proportion of H2O2 and FA/O?can affect the open circuit voltage.This method can be used to guide the selection of process parameters in industrial production and optimize distribution of each component in polishing slurry which is good for saving the cost of industrial development.