Plasma etching selectivity

The raw plasma etch rate in dif t plasmas is a useful number to conq>are, but even more useful is die plasma etch selectivity toward the substrate of interest Both of these criteria are inqxntant, however there may even be more value in determining the time to strip the resist in a given plasma as a n asure of plaana etch resistance for die t resists that are required for 157-nm lithognqihy. The allowable resist thickness is dependent on the absorbance of the resist defined as some value of optical density per unit thickness. The time to strip the resist is therefore a function of bodi the resist thickness allowed at a defined optical density and the resist etch rate. 

We have found that hydrophilic oiganic polymers treated with TiCLi have much higher etching selectivities than organosilicon polymers in an O2 plasma. This paper examines some of the parameters that influence the reaction of TiCLi with a variety of polymers. We find that TiCLi, readily functionalizes hydrophilic as well as moderately hydrophobic polymers, but fails to functionalize very hydrophobic films. Rutherford backscattering analysis reveals that TiCl4 is hydrolyzed at hydrophilic polymer surfaces that have sorbed water. Lack of surface water on hydrophobic polymers explains the absence of a TiC>2 layer on these polymer surfaces. 

Plasma etching. (PE) Physical-chemical etching with free radicals, supported by ions. Etching profile anisotropic-isotropic, good selectivity. 

In the development of plasma etching processes, it is important to adjust the process parameters to meet requirements such as high etch rates for silicon, good selectivity over both mask and underlying layer, precise control of the line width, good uniformity, underetching as small as possible, and good control of the wall profiles. 

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