Polishing

Polishing
	Schematic representation of the CMP process
Technology Details
Other Names	CMP,
Technology	Mechanical finishing
Equipment	CMP Strasbaugh 6ec
Materials	semiconductors

Polishing is the process that modifies the surface of a material from rough to optically smooth mechanical action between abrasive particles and the surface. Lapping refers to thinning an specimen, polishing is to make the surface shiny, Chemical Mechanical Polishing (CMP) combines both the abrasive action and the chemical action on a surface to either reduce the surface roughness or planarize the surface.

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Equipment

Logitech Lapper

The PM5 Lapping and Polishing system from Logitech is a bench-top, R&D-scale machine. This lapper/polisher can be used with many different materials, including compound semiconductors, silicon, glass, quartz, metals and geological samples. The PM5 has an integral abrasive auto feed system. Available platens allow for polishing/lapping of both soft and hard materials, as well as 4" wafers, 3" wafers and odd shaped samples as large as 4", as long as they can be mounted on the carrier disc.

Strasbaugh CMP

The Polishing is a single-wafer planarizer designed for the research and development environment. This CMP has both 4" and 6" capabilities, VIPRR wafer carrier, in-situ pad conditioner, and interchangeable platten to accommodate different processes.

Method of operation

Polishing is to reduce the surface roughness by the action of the abrasive and the pad on the sample surface. Abrasive can be impregnated in the pad or added as a slurry. Polishing and lapping only differ in the amount of material removed, hence polishing requires finer size abrasive. The platen used can be circular (rotating) or an infinite belt. Factors to consider are pressure, speed of the platen and size of the slurry particles. All these factors affect the polishing rate, but rate is not the only important factor, planarity is also important, especially in the case of flat samples. Polishing basic theory is described by the Preston model

MRR=k_pP v

Where MRR is the material removal rate, k_p is the Preston coefficient, P is the applied Pressure and vis the relative velocity between the pad and the surface.

Applications

How is this technology used in nanofabrication and what types of devices/research areas is it useful in?

Parameters

Pressure

Pressure (P=F/A) will be proportional to the removal rate (Preston's equation above). The equation tell us that the pressure, and the removal rate will inversely depend on the sample size.

Platen speed

Increasing the rotational speed of the platen will increase the removal rate. When increasing the platen speed the hydrodynamic regime will change, this can result in equipment and sample damage.

Pad Material

There are many polishing pads available, both types, for slurry polishing as well as abrasive impregnated. The choice of pad is crucial. Many factors will decide the type of pad used, for example the slurry type, the sample characteristics, the finish desired, sample material, etc.

Sample composition

The dependence of the removal rate with sample composition is given by Preston's equation through the Preston coefficient, though the Preston coefficient also considers the abrassive used, slurry, etc. Sample hardness and integrity must be considered when deciding the process parameters.

Chemical Mechanical Polishing (CMP)

CMP is to modify a surface from rough to optically smooth by the mechanical and chemical action between abrasive particles or chemical and the surface. There are different types depending on the type of abrasive used. Lapping refers to thinning an specimen, polishing is to make the surface shiny, Chemical Mechanical Polishing (CMP) combines both the abrasive action and the chemical action on a surface to either reduce the surface roughness or planarize the surface.

Describe any sub-technologies of this technology.

Materials

Optional description of materials that can be processed by technology. I think the best example of where this comes in handy would be with LPCVD describing the difference between HTO and LTO.

References

↑ http://what-when-how.com/nanoscience-and-nanotechnology/atomic-force-microscopy-simulation-of-interaction-forces-in-cmp-applications-part-1-nanotechnology/