Tribological, Thermal and Kinetic Attributes of 300 vs. 450 mm Chemical Mechanical Planarization Processes

Abstract

An existing 300 mm CMP tool has been modified to polish 450 mm wafers in order to demonstrate experimentally whether any differences exist in the tribological and thermal characteristics of the two processes, and from that, to infer whether one can expect any removal rate differences between the two systems. Results suggest that, within the ranges of parameter investigated, the two systems behave similarly in terms of their coefficients of friction and lubrication regimes. Additionally, it is shown that the 450 mm process, once adjusted for its platen velocity, runs only slightly warmer (by 1-3 • C) than its 300 mm counterpart. Experimental data, coupled with copper removal rate simulations show that the wafer surface reaction temperature of the 450 mm process is slightly higher (by 1-2 • C) than the 300 mm process. Consequently, simulated copper removal rates for the 450 mm process are slightly higher (2-13%) than those of the 300 mm process at most polishing conditions. The above results indicate that when the current 300 mm CMP process is scaled up to 450 mm, the tribological, thermal, and kinetic attributes of the process remain similar and do not undergo significant changes.Several integrated circuit (IC) makers have announced plans for adopting 450 mm wafers which would involve a significant investment in tools and fabrication facilities. 1-3 M. Watanabe and J. S. Pettinato have discussed certain scaling issues associated with adopting 450 mm silicon wafers, and technology decisions to minimize the transition risks associated with 450 mm wafers, respectively. 4, 5 Our research team has previously investigated several key questions resulting from such a possible scale-up by simulating hypothetical 300 and 450 mm processes on rotary polishers. 6 Using our proprietary 3D thermal model, we have been able to simulate frictional heat generation by the wafer and retaining ring and the transport and transfer of heat throughout the tool by the slurry and by the rotation of the polishing head and the platen. The simulation results 6 have shown that wafer temperature distribution for 450 mm is a smooth extension of the distribution for 300 mm wafers. That is, wafer body temperature does not change appreciably with scale-up. On the other hand, temperature rise in contacting pad summits, or the surface reaction temperature increment, 7 has been shown to be different between the two systems. Most of the heat in CMP is generated at the contact points between pad summits and the wafer or the retaining ring. Mechanically mediated material removal of chemical reaction products formed on the wafer also occurs at the contacts. Since the real contact area is often less than 0.1% of the wafer area, 8 contacting pad summits are probably hotter than the wafer and their temperature may therefore dominate the chemistry. Since summits spend more time in contact with the ring and wafer on a 450 mm tool due to the lower platen rotation rate (lowering the rotation rate is necessary since the 450 mm process has a larger platen diameter, ...

Method for Ultra Rapid Determination of the Lubrication Mechanism in Chemical Mechanical Planarization

“…As such, our Stribeck curve can be simplified by replacing the Sommerfeld number with the ratio of the sliding velocity to the polishing pressure. 19 Now, if we plot the log of instantaneous COF vs. the log of v/P in the previously mentioned example, a Stribeck+ curve can be generated (Figure 3).…”

Effect of Pad Surface Micro-Texture on Tribological, Thermal and Kinetic Characterizations during Copper Chemical Mechanical Planarization

“…It must be noted that the P × V value is equivalent to the mechanical power exerted by the polishing system, therefore, increasing values of P × V, coupled with the fact that COF values remain somewhat constant, indicate an increasing frictional force between the wafer and the pad thus leading to higher frictional heat generated between pad and wafer. 15 We will analyze this further and resolve the effect of temperature in our simulation work later on in this paper. 4 and 5 show examples of reflected images collected at the pad-wafer contact region using the laser confocal microscope for the Disc A and Disc B, respectively.…”

Lubrication in Chemical and Mechanical Planarization

“…Finally, the effective slurry film thickness δ eff can be assumed as the arithmetic average roughness of the pad based on slurry film thickness measurement results by dual emission laser induced fluorescence (DELIF) [20][21][22]. In some cases, the pseudo Sommerfeld number (V/p) is used to replace Sommerfeld number for simplicity [23].…”

“…On the other hand, if we just simply connect data points to obtain the Stribeck curve, it could be not accurate if the data points are not enough. Zhuang and Jiao et al proposed an alternative method to construct the Stribeck curve by only performing one wafer polishing experiment [23,24]. Pressure and sliding velocity are varied separately or together for a desired length of time, so that multiple measurements (COF, V, p) can be taken within one run.…”