Pad conditioning

Pad conditioning is the process of revitalizing a polish pad to produce reproducible, consistent results [44,45]. During CMP, several processes take place that generate material that can be deposited on the pad and in 

Inorganic material is removed from the topmost film on the wafer via chemical and/or mechanical processes. 

Slurry particle agglomeration can take place in the slurry in which abrasive particles and colloids coalesce to form extended particles. 

Any and all of these particles can become attached to the pad. As the surface of the pad accumulates more and more particles, the surface glazes and becomes smoother and less abrasive. Consequently, the removal rate declines. Also, as the pad becomes glazed it becomes smoother, which causes a decline in the ability of the polish pad to distribute slurry under the wafer. At present there is considerable debate as to whether CMP takes place in a contact regime or in a lubrication regime. It is likely that resolution of this issue will be necessary to establish what fundamental limits there are on slurry flow, as well as how these limits affect pad conditioning. 

Some work has been done to correlate oxide CMP performance with pad properties [46]. This work indicated that the specific gravity of the pads and the cross-linking densities affect polish performance. Other work has been done to correlate CMP performance with slurry composition [47]. This work suggests that the friction during polish is proportional to the removal rate when the abrasive content is greater than 10%, and inversely proportional to the removal rate when it is less than 10%. 

From the discussions in the previous sections, it is clear that surface roughness and surface porosity play an important role in 

In addition to between wafer conditioning, pad break-in techniques are often performed before the pad is first used. Pad break-in often involves the same techniques employed for conditioning, along with running dummy wafers to stabilize the pad performance before running product wafers. In addition to setting the surface roughness, pad break-in is also likely to stabilize other pad properties such as water absorption. 

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Pad conditioning serves to reverse the pore-clogging process, and there are two general approaches that seek to apply any of several pad-conditioning methods. One approach consists of concurrent pad conditioning. In this... 

Fig. 11. Plot of instantaneous removal rate without pad conditioning vs polish time using Klebosol 1501 slurry and a Freudenberg FX9 polish pad.

Fig. 12. Plot of removal rate as a function of wafer number showing the effect of pad conditioning. (Data c. 1993.)...

A. Inamdar, M. A. Fury, D. Towery, A. B. Stubbman, J. W. Zimmer, Cost of Ownership Implications of a Novel CMP Pad Conditioning Device, Third International Chemical-Mechanical Polish (CMP) for VLSI Multilevel Interconnection Conference, pp. 169-171, Feb. 19-20, 1998. 

B. Mullany, G. Byrne, and M. Power, The Effect of Polishing Pad Conditioning on the Planarisation Capability of the Chemical-Mechanical Polishing Process, Proc. of CMP-MIC, pp. 147-150, Feb. 1999. 

If the step height of a certain pattern feature can not be planarized, the nonplanarity problem may cause more serious outcomes, such as the metal stringers, which lead to short circuits [6]. Sometimes, poor planarity is not caused by the smaller delta thickness polished. If the end effector for the pad conditioning does not function normally and/or the pad austerity cannot be restored effectively after conditioning, deposit more-polish more may not truly resolve the poor planarity problems. 

FIGURE 2.9 TMA scan for the pad conditioned at RT and tested using a penetration microprobe. Temperature dependence of CTE shows three different ranges ... 

PadProbe allows either continuous or periodic in situ, in-process control of two crucial CMP parameters pad life (dynamics of pad wear) and pad condition (dynamics and level of pad friction). Data obtained from such a... 

FIGURE 4.12 Pad condition during polishing with (right) and without (left) conditioning (from Ref 22). 

Pad condition during polishing with periodic conditioner sweeps (from... 

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