Slurry Selectivity

Similar to copper and STI CMP, tungsten CMP constructs vias and sometimes lines as a part of the interconnect in IC fabrication. The ability to form these microstructures enables the multilevel interconnect network that shortens the 

The current slurry formulation used for W CMP consists of fumed silica abrasive particles, ferric nitrate, and hydrogen peroxide as the key components. Can you think of other key components that could be used to develop additional W CMP slurries  

The post-W CMP cleaning with ammonia in the past has caused wafer surface defect issues. Is it possible for you to determine alternative cleaning chemistries for the post-W CMP process Explain why you think they will provide a more efficient process. 

The tungsten oxide selectivity is vital to achieve a longer overpolishing window. Do you think it is possible to add an additive to the W slurry to protect the oxide surface to enhance the overpolishing window If so, what type of additive would you recommend Keep in mind that this additive should not hinder the W material removal rate. 

What is the best regulation point for W CMP platen temperature Explain why. 

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Slurry selectivity a is commonly defined as the ratio of the polishing rate of blanket wafers at a given polishing pressure and speed, a = Large cr... 

With these expressions for the various pressures, it is possible to predict the maximum steady-state dishing depth /zqo at which the removal rate effects of higher pressure on the ILD balance with those of higher slurry selectivity for the metal. The result is shown in Equation 5.9. 

Fig.7 shows the effect of slurry selectivity between oxide and nitride on the erosion at various densities. Slurry plays an important role in STI CMP. As can be seen in the diagram slimy selectivity has a big effect on the amount of erosion. At high slurry selectivities, erosion can be kept at a minimal level for high aetive densities. But as can be seen in Figure 6, erosion increases rapidly at low active densities. Therefore to minimize erosion, a slurry with optimum selectivity for a given active density and density distribution needs to be used. Inchip planarity after STI CMP can be simply expressed by the following equation ... 

A quantified model that explains planarity characteristics is established and this in turn make it possible to identify and quantify various planarity factors. The proposed model allows one to represent erosion as functions of initial step height, slurry selectivity, over-CMP... 

Figure 7. The effect of slurry selectivity between oxide and silicon nitride on the erosion at various aetive pattern densities. (H = 6000A, 5 = 200A, pE=p)...

Factors evaluated in this program include slurry selectivity, polish time, trench etch, film deposition, and dummy structure. Finally, plysical and electrical data are correlated to determine if the process window is robust enough for volume production. 

Pattern density dependency, arising for system-on-a-chip design, is characterized with CMP process optimization, slurry selectivity, over-polish extent and dummy pattern structure. For low density devices, dummy structure is desirable under conditions that the supportive dense structure could exceed a threshold value for reduction of CMP erosioa Physical and electrical evaluations help to identify the process window for different density structure. The characterized SIT process feature will allow designers to print circuit patterns more efficiently and cram more fiinctions onto the silicon. 

RDX plus 0.03 percent desensitizer from composition A-3 RDX from composition B RDX from composition C-3 The wax is removed (leaving the RDX) by selective solution using a batch process in which a benzene-water azeotrope is continuously circulated through an agitated composition A-3/benzene slurry. Selective solution of TNT and desensitizer with benzene in a closed system. Selective solution of all but the RDX content of the composition is accomplished by agitation of a slurry of composition C-3 and methanol (or acetone) in a kettle. 

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