Field-oxide-ungrowth (FOU) phenomenon in recessed local oxidation of silicon (R-LOCOS) isolation process has been studied. Field oxidation temperature has been revealed to play a decisive role in the occurrence of FOU and nitrogen-containing polymers originated from the etching process are believed to be converted into oxidation barrier materials at a certain temperature and above. This transition temperature lies between 1000 and 1050°C, independent of the ambient in the furnace. Although field oxidation below the transition temperature can eliminate the FOU, it causes severe thinning of the field oxide at a small isolation spacing. In order to remove the FOU and at the same time to minimize the field oxide thinning, we propose a new field oxidation method which is a combination of a breakthrough field oxidation at below the transition temperature and a high temperature field oxidation.

An anomalous field-oxide-growth phenomenon in a recessed local oxidation of silicon (LOCOS) structure with a nitride spacer (R-LOCOS), in which the field oxide growth at the center of the opening area is suppressed when isolation spacing is small, is reported. The field-oxide-ungrowth (FOU) phenomenon was found to have strong structural dependence, on the aspect ratio of the opening area, active pattern density, and silicon recess depth. By changing process conditions, such as dry etching and wet cleaning conditions, however the FOU was not affected. Since the tendency of the FOU occurrence was coincident with that of the microloading effect in reactive ion etching, the FOU was believed to originate from a residue on the exposed silicon surface after the etching process. When silicon was not recessed, the FOU was not observed at any of the structural variations. From a two-dimensional simulation of field oxidation, it has been found that in a nonrecessed LOCOS structure, a residue on the silicon surface does not significantly affect field oxide growth, but in the recessed LOCOS structure, field oxide growth is very sensitive to the existence of a residue on the recessed surface. Thus, to successfully use the recessed LOCOS structure with a subquarter micron design rule avoiding the occurrence of the FOU, structural factors that include an active pattern layout should be carefully chosen.

No abstract

the dishing profille, a model which represents the pad by a network of springs, was introduced. We demonstrated that with this approach the experimental data are well fitted. With the equations presented and these models, erosion and dishing for metal CMP can be predicted. These calculations can be performed for different oxide and metal combinations with the knowledge of only a few parameters. This will help to reduce the time required to develop new technologies. AcknowledgmentsWe like to thank Ewald Giinther for valuable discussions. Technical assistance from Peter Schon is also grate-0,2 0,4 0,6 0,8 1,0 fully acknowledged. Cross section [pm]Fig. 11. Simulated dishing profiles (dashed lines) and AFM dishing data (solid line) for a 1 pm metal line. For the calculations, the downforce has been varied as indicated. ConclusionsWe discussed two major effects correlated with metal CMP: erosion and dishing. The presented experimental data revealed that the erosion increases linearly with polishing time and nonlinearly with pattern factor. The dishing within tungsten lines and contacts was found to depend on the type of oxide, on the pattern factor, and on the groove width, but not on the overpolish time. Deduced from Preston's law a set of equations was presented to fit the experimental data for erosion and dishing. To simulate ABSTRACT The field oxide thinning behavior in a modified local oxidation of silicon isolation process has been studied. The oxidation rates of silicon were deliberately modified by implantation or by high pressure oxidation (HiPOX). Although oxidation of heavily doped silicon with arsenic (As) or germanium (Ge) greatly enhanced the oxidation rate on the wide-field region, severe field oxide thinning was observed at the small isolation spacings. The dry HiPOX process also showed aggravated thinning compared to the atmospheric dry oxidation process. These results can be attributed to the increased oxide stresses during field oxidation due to low temperature and to fast oxidation rate, respectively. These results suggest that, in order to mitigate the thinning, the stress should be relieved by the slower oxide growth at the higher oxidation temperatures. Much reduced thinning was observed, as was expected, when the stress was relieved by introducing an interanneal during field oxidation.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.174.255.116 Downloaded on 2015-03-09 to IP

No abstract