A new adsorption model in surface reaction of dry-etching process is proposed. The model allows the simulation of micro-loading phenomena in the etching rate, profile and selectivity of Si02 hole etching with hydrofluorocarbon gases. A new 2D-string model with Boolean operation is further developed to simulate the precise profile.
1 IntroductionIn dry etching processes, the etching rate, profile and selectivity in a hole geometry strongly depend on the aspect ratio of the geometry.This undesirable phenomenon for VLSl fabrication is called micro-loading. Hence, reliable simulational tool in dry-etching has been required to understand and predict this phenomenon. The usefulness of surface reaction model[l], [2], which considers the radical adsorption layer on the substrate, was recently demonstrated for solving these problems. However, the previous model was insufficient for the modeling of radical adsorptions on the radical layers, and was restricted to the application of profile prediction and cont ro I.In this paper, two different types of radical adsorption models are newly introduced for solving micro-loading phenomena in etching rate, selectivity as well as profiles. A 2D-string model based on Boolean operation is also developed. Figure 1 shows a schematic explanation for the adsorption model of radicals. Two types of radical adsorptions are considered.
2 Simulation ModelOne is a non-depositive type adsorption shown in Fig.1 (a). CFx radicals are adsorbed on Si02 surface with a finite sticking probability. However, few CFx radicals are adsorbed on the surface covered with CFx(f1uorocarbon) radicals. This adsorptive radical that does not cause a polymer deposition is thus introduced into the surface reaction model as the non-depositive type radical. Most of reactive radicals which contribute to ion-assisted etching with high etching rate are non-depositive type.The other is a depositive type adsorption shown in Fig. 1 (b) . CmHnFx( h yd rof luo rocarbon) radicals are adsorbed not only on Si02 surface but also on the surface covered with CmHnFx radicals. These radicals cause apolymer deposition. Effective sticking probability &(r) of radical adsorption is modeled by the following linear combination: J Here, ,$kj is an elemental sticking probability of radical k o n the adsorption layer of radical j, 6 ke is that of radical k on the clean substrate surface e. The values of elemental sticking probabilities for CFx and CmHnFx radicals are shown in Tabel 1. ASj(r) is the covered ratio of the area occupied by adsorbed radical j to the small area defined at each point r, and ES(r) is the covered ratio of the area occupied by clean substrate[l]. These values have the following relation: c ASj(r)+ES(r)=l . j The method of radical flux calculation inside the hole geometry is explained in Fig.2[3]. Total radical flux Frdk(r) at the position r is thus calculated by the following equation:Frd (r)=p(r)t (l&(r'))K(r,r')P"(r')dr' I (l&(r"))K(r',r">P'(r")dr"dr'+ .....Here, K(r,r') is a probability that a radical emitted from t...
We propose a new resolution enhancement technology (RET) for enhancing the resolution of contact hole patterns. The technology uses an attenuated mask with phase shifting aperture. The phase shifter is laid out based on the OL-PSM and CL-PSM algorithm. These RETs are called "Mask Enhancer". Aerial images of random hole patterns are strongly enhanced by using the Mask Enhancer. We used the Mask Enhancer in 100-nm hole pattern fabrication in ArF lithography. The process window is strongly improved and the MEEF is drastically reduced compared to att-PSM.
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