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Slurry Injection Systems

Figure 1: Araca SIS-100M for the AMAT Mirra® polisher.

Figure 1: Araca SIS-100M for the AMAT Mirra® polisher.

The slurry injection system (SIS) is our flagship product. Easily installed on most mainstream rotary polishers used in IC manufacturing and silicon polishing, SIS has proven to successfully reduce polishing defects (by up to 4X less) and slurry consumption (by up to 67 percent less) for myriad of CMP and polishing processes. We currently have 46 units is use in high volume manufacturing on AMAT and Ebara polishers, and are engaged in various stages of a dozen or so beta tests worldwide.

In most commercial CMP polishers, slurry is applied onto the center of the pad as shown in Figure 4(a). As the pad rotates during polishing, centrifugal forces cause large amounts of fresh slurry to flow directly off the pad surface without entering the pad-wafer interface. This results in low slurry utilization.

Figure 2:  Araca SIS-100E222 for the Ebara EPO-222® polisher.

Figure 2: Araca SIS-100E222 for the Ebara EPO-222® polisher.

Moreover, as the spent slurry containing polishing by-products and pad debris mixes with the fresh slurry and reenters pad-wafer interface during polishing, it affects removal rate and causes wafer-level defects.

Furthermore, as large amounts of ultra-pure water (UPW) are used to rinse the pad surface between polishing wafers to remove slurry residue and pad debris off the pad surface, there is an appreciable amount of UPW residing on the pad surface and inside the grooves after rinsing. This creates a dilution effect during the next wafer polishing that contributes to lower material removal rates.

Figure 3: Araca SIS-100RLK for the AMAT Reflexion® polisher.

Figure 3: Araca SIS-100RLK for the AMAT Reflexion® polisher.

 

Different from the above standard pad center area slurry application, SIS is designed to efficiently introduce fresh slurry inside the pad-wafer interface. As shown in Figure 4(b), SIS is placed on top of the pad during polishing and fresh slurry is applied through the SIS and over the wafer track in a uniformly thin film.

 

 

 

 

Figure 4: Top view schematic comparison of (a) standard pad center area slurry applicationmethod, and (b) SIS. Note: the pad and wafer are rotating counter-clockwise.

Figure 4: Top view schematic comparison of (a) standard pad center area slurry application method, and (b) SIS. Both pad and wafer are rotating counter-clockwise.

Compared with the standard pad center area slurry application (POR), due to its intrinsic design, SIS has the following major advantages:

  • Improved slurry utilization by efficient delivery of fresh slurry to the pad-wafer interface (up to 2X reduction in slurry mean residence time).
  • Reduced mixing of spent slurry (and residual water) with fresh slurry supplied during polishing. This causes higher material removal rate at the same slurry flow rate (by up to 30 percent), or an equivalent material removal rate at lower slurry flow rates (by up to 67 percent).
  • Effective capture of foam (due to hydrogen peroxide and surfactants) and pad fragments (due to conditioning). This results in lower wafer-level defects (by up to 4X) at POR or lower flow rates.

Table 1 summarizes the performance of the SIS as compared to the standard pad center area slurry application (POR) for different CMP processes based on data collected thus far at various HVM fabs worldwide.

Table 1: SIS Result Summary

Table 1: SIS result summary.

A video showing the SIS operating on an AMAT Mirra® polisher can be seen here. SIS is very stable during operation. A bow wave is formed in front of the injector’s leading edge, which contains used slurry and pad conditioning debris that can cause polishing defects. By blocking the used slurry and the pad conditioning debris from mixing with the fresh slurry and re-entering the pad-wafer interface, SIS has been able to achieve lower polishing defects than the standard pad center area slurry application (POR).

This video shows the slurry flow comparison between the standard pad center area slurry application (POR) and the SIS. To generate these videos, a fluorescent dye (4-methyl-umbelliferone) was added to the slurry which fluoresced UV light. The fluorescent light was then captured by a high resolution charged coupled device camera.

The above videos show that SIS quickly spreads the slurry across the pad surface and provides a much more uniform slurry distribution to the pad-wafer interface than POR. In addition, a thick bow wave is formed in front of the injector leading edge as SIS blocks the used slurry from mixing with the fresh slurry and re-entering the pad-wafer interface. Because of the injector’s barrier effect, pad conditioner oscillation has minimum impact on the slurry distribution in the pad-wafer interface during wafer polishing.

SIS is totally passive and does not require power or specialized software to be integrated with commercial polishers. Simple retrofit kits are available for all AMAT and Ebara polishers as well as most other rotary polishers such as SpeedFam-IPEC, Lapmaster and KCTech.

Our intellectual property re: the SIS is protected by multiple patents worldwide (see Figure 5 below). More patent filings are in the works.

Figure 5: SIS patent family tree as of July 1, 2015.

Figure 5: SIS patent family tree as of July 1, 2015.

Please contact us for more information on how to schedule a beta test at your facility to determine how SIS may be able to reduce your overall COO by saving you slurry and rinse water as well as increasing the overall yield of your CMP or polishing module.