Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Recessed oxide by localized oxidation
Patent
1997-03-31
2000-08-29
Bowers, Charles
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Recessed oxide by localized oxidation
438370, 438373, H01L 2176
Patent
active
061108022
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing a structure having a low dislocation density comprising an oxide layer buried in a semiconductor substrate. It more specifically relates to the production of silicon on insulator or SOI structures using an oxygen implantation process known as Separation by IMplantation of OXygen or SIMOX. The invention has numerous applications in microelectronics and in particular in the production of integrated circuits of the Complementary Metal-Oxide Semiconductor or CMOS type.
PRIOR ART
For the development of technologies relating to SOI structures with the SIMOX process, one of the main aims is the reduction of the density of crystal defects.
Crystal defects and in particular dislocations of SOI structures of the SIMOX type constitute certain of the main disadvantages thereof. SOI structures have a silicon film, whose crystal imperfections constitute an obstacle or at least a limitation with respect to the production of certain components or circuits.
This is in particular true for components of the bipolar type, junction field effect transistors (JFET) and for applications of advanced technologies of the CMOS ULSI (Ultra Large Scale Integration) type, where integration densities are very important.
Documents (1), (2) and (3), described at the end of the description, give examples of the behaviour of defects of structures of the SOI type following the epitaxy of a semiconductor material layer.
Liaw et al (document (1)) concludes that silicon epitaxy makes it possible to moderately reduce the defect density in the silicon film by trapping dislocations between them (from 2.5.10 cm.sup.-2 to 4.10.sup.6 cm.sup.-2 for an epitaxy of 18.2 .mu.m). This mechanism is only effective in the case of high defect densities. A simple calculation, considering an inclination of dislocations of 35.degree. relative to the perpendicular, shows that for an epitaxy of 1 .mu.m, the defect density must exceed 2.10.sup.7 cm.sup.-2 so that there is a non-zero probability of interaction between two dislocations. Liaw et al conclude that the quality of the layer formed is not dependent on the pre-epitaxy heat treatments.
Document (2) arrives at an identical conclusion showing that on a sample having a high dislocation density (10.sup.9 cm.sup.-2) an epitaxy of a layer 5 .mu.m thick makes it possible to obtain a slightly lower dislocation density (10.sup.8 cm.sup.-2).
These different studies indicate that for high dislocation densities (>10.sup.7 cm.sup.-2), the epitaxy of a significant silicon thickness (>4 .mu.m) makes it possible to slightly reduce the dislocation density, whereas for low epitaxied silicon thicknesses no defect density modification occurs (document (3)).
Thus, in all cases, the only mechanism used is the trapping of the dislocations between them.
It would appear that the dislocations in the structures obtained by the SIMOX process essentially have two origins, which are on the one hand the surface state of the substrate and on the other the state of the disturbed area at the interface between the buried layer and the semiconductor material.
An object of the invention is to propose a process making it possible to obtain a structure with a dislocation density very significantly below those of the known structures.
DESCRIPTION OF THE INVENTION
To this end, the invention more particularly relates to a process for producing an epitaxied structure with a low dislocation density, said structure comprising an oxide layer in a semiconductor material substrate, the process successively involving: of the latter in order to form a buried oxide layer, temperature below the melting point of the semiconductor material, the semiconductor material of the substrate and that of the material of the epitaxied layer in order to eliminate most of the dislocations of the structure in an unstable energy configuration, temperature making it possible to substantially dissolve all the oxide precipitates formed during the implantation, in order to free the dislocations w
REFERENCES:
Stanley Wolf Silicon Processing for the VSLI Era vol. 1 Lattice Press p. 157, 1986.
Stanley Wolf Silicon Processing for the VSLI Era vol. 1 Lattice Press p. 305, 1986.
Buczkowski et al Conductivity-Type Conversion in Multiple-Implant/Multiple-Anneal SOI IEEE Transactions vol. 38, Jan. 1991.
Aspar Bernard
Margail Jacques
Pudda Catherine
Blum David S
Bowers Charles
Commissariat a l''Energie Atomique
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