Dielectric erosion

With the growing level of control of copper CMP process comes the requirement for temperature control. Copper CMP is highly temperature sensitive, so hot slurry will enhance the removal of bulk copper. However, barrier metals are significantly less reactive (with the slurries currently available), so there is a significantly greater mechanical contribution to the removal of the barrier layer(s). Consequently, hot slurry is of little benefit for barrier layer removal and may soften the pad and aggravate metal dishing and dielectric erosion. 

Erosion Dielectric erosion depends on pattern density and has to be kept below 50nm in microelectronic array structures [14]. Erosion can also occur in microfabrication when pattern arrays have to be planarized. Due to larger vertical and lateral dimensions, the requirements are relaxed compared to microelectronics. 

Electro discharge (spark erosion) techniques rely heavily on the ability of EDM oil to act as an electrical insu-lant, to dissipate heat from the electrode, and to flush away erosion debris from the workpiece. EDM oils also are suitable for all die-sinking spark erosion operations. They should have low aromatic levels, good filterability, low fuming, high dielectric strength, excellent oxidation resistance and low color level. 

As the abrasive particles are specifically designed to interact with copper surface, the removal rate on the barrier and dielectric materials are very low (Table 7.3). This will allow longer overpolishing without incurring significant erosion. 

Figure 2 Comparison of array metal thickness for an initially recessed array at M2 due to Ml induced topography versus the same array at M2 over Ml field. Field dielectric shielding at M2 reduces M2 array erosion for the initially recessed structures.

In the final analysis, it is the pad-slurry system s performance (under the application and tool conditions) that determines the optimum processing condition. For interlayer dielectric (ILD) oxides, this will often be measured by the removal rate value and uniformity. For other processes, additional metrics, such as dishing and erosion, must be examined for optimization. The evaluation of these additional qualifiers is more complex, because circuit pattern density plays a major role. Often the judgment will include an examination of dishing across a spread of line widths, and an examination of erosion across a spread... 

The generator core damage by electro-erosion, produce by arc flash, is shown in Fig. 3.5.I.2. The arc flash must begin by a magnitude voltage that broke the dielectric distance. For that distance, it is estimated an overvoltage that exceeding 100 kV. 

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