Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Patent
1999-07-20
2000-12-26
Chaudhari, Chandra
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
438246, 438960, H01L 218242
Patent
active
061658359
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to methods for manufacturing silicon capacitors. More specifically, the present invention relates to a method for manufacturing silicon capacitors whereby an auxiliary layer is formed on top of the lower layers and under a compressive mechanical stress to offset the bending or warping caused by the formation of the underlying conductive zone.
BACKGROUND OF THE INVENTION
European Patent Application No. 05 028 281 A2 teaches a silicon capacitor which comprises an n-doped silicon substrate whose surface is structured in a characteristic fashion by an electrochemical etching in an acidic electrolyte containing fluoride in which the substrate is connected as an anode. In the electrochemical etching, more or less regularly arranged hole structures form at the surface of the substrate. The hole structures have an aspect ratio of up to around 1:1000. The surface of the hole structures is provided with a dielectric layer and a conductive layer. The conductive layer, dielectric layer and silicon substrate form a capacitor in which specific capacities of up to 100 .mu.V/mm.sup.3 are achieved due to the surface expansion that is effected by the hole structures. To increase the conductivity of the substrate, it is suggested to provide an n.sup.+ -doped region at the surface of the hole structures.
Silicon capacitors are typically produced in silicon disks. A bending of the silicon disk is established, which is brought into connection with mechanical strains by the n.sup.+ -doped zone at the surface of the hole structures, which are up to 300 .mu.m thick. This bending of the silicon disk leads to problems in further procedural steps such as lithography, disk thinning and isolation which are necessary for the installation of the silicon capacitor in a housing.
German Patent No. 44 28 195 C1 teaches a method for producing a silicon capacitor of this type. In order to compensate mechanical strains on the silicon substrate which are effected by the doping of the doped zone, the doped region is additionally doped with geranium. The additional doping with geranium leads to an increase in the complexity of processing
Therefore, there is need for a method for the production of a silicon capacitor which is simpler than the known method.
The above need is met by the inventive method wherein a plurality of hole structures are generated in a main surface of a silicon substrate. The hole structures comprise a round or polygonal cross-section and sidewalls that are essentially perpendicular to the main surface.
Along the surface of the hole structures, a conductive region is created which is provided with electrically active dopant. The conductive region forms a capacitor electrode in the finished silicon capacitor. It is preferably doped with phosphorous or boron.
A dielectric layer and a conductive layer are deposited on the surface of the conductive zone so as not to fill the hole structures. On the surface of the conductive layer, an auxiliary layer with essentially conformal edge coverage is formed, which layer is subjected to a compressive mechanical stress. Lastly, the hole structures are filled.
Due to the conductive zone which is provided with dopant and which extends along the surface of the hole structures, there results a concave bending of the silicon substrate if the dopant has a smaller covalent bond radius than silicon. This is true of phosphorous and boron. The use of the auxiliary layer, which is under a compressive mechanical stress and which is inserted in the hole structures with conformal edge coverage, effects a bending of the silicon substrate in the direction of a convex shape. This compensates the concave bending of the substrate that is effected by the conductive zone. Problems in the production of the silicon capacitor are thereby avoided. The concave bending of the silicon substrate has the disadvantage that, in conventional production devices, the substrates are held on carriers by low air pressure (what is known as vacuum chucks). A conc
REFERENCES:
patent: 5378907 (1995-01-01), Melzner
patent: 5431766 (1995-07-01), Propst et al.
patent: 5753526 (1998-05-01), Ozaki
Article entitled "A novel capacitor technology based on porous silicon", Lehmann et al., Thin Solid Films, 276 (1996) 138-142.
Gruning Ulrike
Honlein Wolfgang
Lehmann Volker
Reisinger Hans
Spitzer Andreas
Chaudhari Chandra
Siemens Aktiengesellschaft
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