Slurry Testing

FIGURE 4.24 AE values (marked) and COF during polishing using slurry 1 and slurry 2 (from Ref. 27). 

FIGURE 4.25 Complete Cu removal process monitoring with change in COF and AE values (a) Cu polishing with slurry 3, where Cu is removed after 439 s of polishing, and (b) Cu polishing with slurry 4, where Cu polishing takes only 200 s [27]. 

The coefficient of friction and acoustic emission signal can be effectively utilized for functional testing of consumables. An example of such a utility is illustrated in Fig. 4.26. For a quantitative, fast, and inexpensive estimate of the functional properties of two different products from a manufacturer, the slurry samples were tested on a CMP tester equipped with capability for continuous acquisition of the frictional and acoustic signals. The collected signals allow the determination of three important functional parameters, namely, time of complete tungsten removal, time of complete underlayer removal, and intensity of polishing (characterized by the level of acoustic signal). 

It was found that six of the seven batches removed both the tungsten and the underlayer before the maximum amount of time allocated to it, whereas one batch (batch 1) took much longer time to remove the tungsten layer (the underlayer did not get fully removed during the test duration). This is consistent with the fact that the slurry gives a low acoustic emission signal, that is, not an aggressive interaction of surface asperities of pad and wafer or wafer 

FIGURE 4.26 Quality control testing of tungsten slurry (from Ref. 31). 

---

Further work is needed to build a physical model that allows prediction of the concentration effect from the primary properties of the slurry or from a limited amount of slurry testing. 

A preliminary test for the biodegradability of the 3-phenyl- and 3-carbamoyl-2(lH)pyridones was conducted in a barnyard humus suspension. The analysis by HPLC showed some loss, and the fluorescent compounds seemed to be adsorbed onto the solid. The 3-carbamoyl-2(lH)pyridone (II) also hydrolyzed to 3-carboxylic acid-2(lH)pyridone both in the slurry test and in water solutions that had been left standing 1-2 weeks. In preliminary tests both the 3-phenyl- and the 3-carbamoyl-2(lH)pyridones apparently adsorbed to some extent on silica sand columns. In addition, the solubility of both 1-H compounds was somewhat low, 1.3 x 10 M for II, and 1.0 x 10 M for IV. 

To quantify the effects of handling on slurries, a series of experiments were performed. Tests 16 included handling and filtration experiments performed using silica-M slurry, whereas Tests 7-13 included experiments with silica-H slurry. Tests 14-15 and 16-17 involved handling and filtration tests conducted using low wt% abrasive alumina and ceria slurries, respectively. LPC and PSD from Tests 1-11 will be presented and discussed, and key findings of Tests 12-17 will be summarized as follows. 

Test 8 Silica-H was recirculated in an AOD pump at 28 psi back pressure, 63.4turnovers/h, 81pm, for 6h (380 turnovers). Figure 18.28a shows the LPC distribution, which is significantly different than that of MLC pump Test 7. These LPC results are very similar to those results seen for AOD pump silica-M slurry test earlier (Test 4). There is a larger increase in LPC throughout from 0.56 to 10 pm, but a smaller increase in LPC between 0.56 and 0.60 pm as... 

Coal/Oil Slurry Tests. Coal/oil flow tests were conducted at ANL s SLTF in 1982. The cross-correlation flow instrument that was used contains Teflon windows and broad-band transducers (0.5-2 MHz). The transducer separation was 12.7 cm, i.e., 2.42 times the pipe diameter (2-in. Schedule 40 pipe). Amplitude demodulation was used to analyze the correlation signals. Ohio 9... 

If the change was solely because of the water present during the CMP process, then most slurries would show similar behaviors however, that was not observed to be the case. In Figure 4.20, the refractive index change caused on ULK films polished on the same pad (Pad X) with two different slurries are compared, showing that the decrease in refractive index with the second slurry tested is far more muted. This was confirmed by k-value tests showing that the decrease in k-value over pad life was also not as... 

Figure 9.16 Rotary abrasive slurry test setup [86].

After reading this chapter, some readers may get the feeling that designing a slurry flow is a combination of science and art. Slurry dynamics may appear to be an exercise of examining each mixture for its properties, much as the physician must examine each patient before administering the cure. The flow of coarse particles in water or mixtures of coarse and fine solids in a liquid is complex. When data is not well accumulated, it is recommended to conduct slurry tests in a pump test loop. 

---