Optimization of Submicron Polysilicon Etching and the Effect of Organic and Inorganic Masks, and Their Aspect Ratios

Abstract

The change in resistivity and composition of WSi~ films is studied. The following facts are observed. The resistivity of CVD WSix films which are more than 1000]~ thick reaches a maximum at an annealing temperature ranging from 500 ~ to 600~ Logarithmical resistivities before and after 1000~ annealing have a linear relation to the film composition. The ratio of change in resistivity between the as-deposited state and after 1000~ annealing becomes larger as the composition changes, i.e., the Si/W ratio becomes smaller and reaches the stoichiometric value. CHANGES IN RESISTIVITY 1479The change in composition between the as-deposited state and after 1000~ annealing becomes larger as the film become richer in Si. Excess Si, which is generated by annealing, segregates into the boundary between WSi~. and poly-Si. A decrease in film thickness of about 15% after 1000~ annealing is observed for WSi~.4 on SIO2. This value is smaller than the calculated value.Fluorine and hydrogen are contained in the films on the order of 10~-102~ cm -3 and 102~ cm -3, respectively. Fluorine diffuses into the gate SiO2 by annealing. From this fact, it is assumed that degradation of gate SiO2 in terms of dielectric breakdown strength can occur. ABSTRACTFactors that influence the etching properties of LPCVD deposited polysilicon were investigated. These included pressure, power, CCI4 concentration, surface preparation, polysilicon doping, mask angle, mask material, and mask aspect ratio. Organic mask etch rate was found to depend on the type of resist (PMMA, PCMS, AZ1470), while resist preparation and mask aspect ratio were seen to influence the etch profiles. We were able to obtain vertical etch profiles using inorganic masking (Si3N4). A new phenomenon of transition from anisotropic to nonanisotropiC etching was observed when the height-to-gap-width aspect ratio of the organic masks became greater than 6: i. The degree of negative undercut became more severe with increasing aspect ratio. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.211.208.19 Downloaded on 2015-03-15 to IP

Anisotropic Reactive Ion Etching of MoSi2 and In Situ Doped n+ and p+ Polysilicon Using Cl2 and BCl3

“…The reactive ion etching of polysilicon films has been studied for chlorinated plasma such as BC1JC12 (7), CC]4 (8,9), CC14/O2 (10), CF2C1JO2 (11), SIC14/C12 (12), C2Fs/C12 (13), and CFC13 (13,14). The polysilicon films used in these studies were typically doped by ion implantation or POC13 diffusion and subsequently annealed prior to etching.…”

“…The deposition on a cooled substrate results in amorphous silicon films sufficient hydrogen incorporation to neutralize the dangling bonds in the film network, such that a good quality a-Si:H film can be obtained. The results on our HOMOCVD experiments will be published separately (9). The HOMOCVD study shows that in order to obtain a reasonable growth rate, we need a rather high pressure of silane.…”