Study On The Control Of Dishing And Erosion In GLSI Multilayer Copper Interconnect

In the CMP process of multilayer copper interconnects,barrier polishing is an important and complex step,which mainly involves the simultaneous removal of Cu,Ta,TEOS and other materials,and also needs to correct the dishing and erosion generated in residual copper elimination process.The existence of dishing and erosion will cause wafer become short circuit or circuit break,and seriously affect the product yield.At present,international slurry for Ta-based barrier is dominant by acidity,but the acidic slurry is highly corrosive,easy to cause corrosion to the equipment,shorten the service life,and toxic and in order to inhibit the extension of dishing and erosion,toxic and difficult to clean BTA is added in the slurry.Therefore,It is an urgent problem to study the mechanism and process of controlling dishing and erosion without BTA.In this paper,alkaline slurry without BTA is mainly studied.The theoretical and technical research that is removal rate of Cu,Ta and TEOS in CMP and the control of dishing and erosion,is researched in-depth.The main contents are as follows:1.Firstly,according to the experience of industrial production,the polishing process parameters(such as rotation speed,flow rate and pressure)were adjusted to obtain the profile of Cu/TEOS material removal rate.Polishing process was identified as rotation speed of 80/78 rpm,flow rate of 300 ml/L,pressure RR/Z1/Z2/Z3/Z4/Z5 of4.4/4.2/1.8/1.75/1.65/1.55 psi,the depth of dishing and erosion was controlled to±10(?)across the surface of the wafer.2.The removal mechanism of barrier materials Cu,Ta and TEOS was explained by theoretical and experimental model,for the removal mechanism of Cu,the consistency between the removal mechanism and the theory was verified by the dissolution method,and the state of each element on the surface of Cu coated film was analyzed by X-ray photoelectron spectroscopy to further verify the consistency between the removal mechanism and the theoretical analysis.The influence of each component in the slurry on the removal rate of Cu,Ta and TEOS was studied by single factor experimental method.It was found that FA/O II chelating agents could effectively improve the removal rate of copper,and potassium citrate(CAK)could effectively improve the removal rate of Ta and TEOS.Therefore,the two complexing agents were used in combination to improve the removal rate of Cu,Ta and TEOS,and a better selection ratio could be obtained.3.The removal rate selection ratio of Cu,Ta and TEOS was controlled by the method of complex complexing agent,so as to control the dishing and erosion,and realized the adjustable and controllable dishing and erosion.The results showed that when the slurry composition was 18 wt%Si O₂,2 wt%FA/O II chelating agent,1 wt%CAK,0.05 vol.%H₂O₂,5 vol.%FA/O Z surfactant,the dishing and erosion were 573(?)and 445(?)after polishing,which met the needs of industrial production and could replace the existing imported slurry.At the same time,when the slurry composition was 20 wt%Si O₂,0.5 wt%FA/O II chelating agent,3 wt%CAK,0.025 vol.%H₂O₂,5 vol.%FA/O Z surfactant,the dishing and erosion were 5(?)and 3(?)after polishing.