Polishing performance

However, compared with a large amount of CMP studies for IC manufacturing, very few researches on CMP of hard disk substrate have been reported to date except some patents on slurries [101-107]. In these patents, the influences of slurry parameters, such as abrasive size, abrasive content, oxidizer content, and pH value on the polishing performances, and the CMP mechanism of disk substrate have seldom been involved. 

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%. 

K. Achuthan, D. Hetherington, M. Oliver, Pad Characteristics and Polish Performance, presented at the 3rd Annual Workshop on Chemical Mechanical Polishing, Lake Placid, NY, Aug. 16-19, 1998. 

A related issue has to do with the initial wafer-level uniformity (wafer thickness, wafer warp and bow, thicknesses of thin films across the wafer surface, uniformity of stress in such thin films across the wafer) and the subsequent impact on wafer-level polish performance. Some examination has been made of the impact of wafer warp and bow on the polish performance [68], where it was found that the initial warpage can have significant impact (with the implication that reclaimed wafers may not be appropriate monitors of wafer-level polish performance). Other work has considered inherent variation due to Von Mises stress concentrations at the edge of the wafer (conceptually, a downward pressure on the wafer causes lateral stress buildup near the edge of the wafer) [64]. 

The composite microstructure (and, therefore, its composite properties and polishing performance) is largely determined by the mode of manufacture. A summary of the major process variables associated with pad manufacturing and the anticipated effects on physical properties is given in Table II. 

Fury, M., James, D. (1996). Relationships between physical properties and polishing performance of planarization pads. SPIE Microelectronic Manufacturing Symposium. Austin Oct. 16, 1996. (unpublished). 

Initially do as told and stick to the rules, but as a wider range of competences is acquired start to manipulate situations. Practical skill coupled with an ability to tune into situations leads to efficiency, effectiveness, virtuosity - a polished performance but sticking basically to established or approved scripts. This is the manager developing from apprentice to craftsperson. 

PHYSICAL PROPERTIES OF CMP PADS AND THEIR EFFECTS ON POLISHING PERFORMANCE... 

Multilayer or stacked pads are commonly used in the CMP processes for better polishing performance such as uniform material removal and good planarization across the wafer surface. A multilayer or stacked pad usually consists of a stiff, hard top layer and a soft, flexible subpad, and possibly some medium layer(s), as shown in Fig. 5.3. 

TABLE 5.3 Relationships between Pad Properties and Polishing Performance [1]. 

S.2.4.3 Pad Hardness, Young s Modulus, Stiffness, and Thickness Effects Pad hardness has an influence on many aspects of polishing performance. A harder... 

CMP is a wet process with DI water and/or polishing slurry present. During polishing, pad is under the attack of water, slurry chemicals, and abrasive particles at elevated temperature due to the friction force among wafer-particle-pad contact. This leads to changes in pad s physical and mechanical properties that influence polishing performance. 

Readers are urged to read the above-mentioned publications for model details. The following subsection will give some modeling details of pad effects on polishing performance. 

What is the purpose of grooves on a pad surface and how could they influence polishing performance Suggest some additional designs. 

List and explain the advantages and disadvantages of nonporous pad versus porous pad in terms of polishing performance. 

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