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EP1889296A1 - Channel transistor based on germanium encased by a gate electrode and method for producing this transistor - Google Patents

Channel transistor based on germanium encased by a gate electrode and method for producing this transistor

Info

Publication number
EP1889296A1
EP1889296A1 EP06764670A EP06764670A EP1889296A1 EP 1889296 A1 EP1889296 A1 EP 1889296A1 EP 06764670 A EP06764670 A EP 06764670A EP 06764670 A EP06764670 A EP 06764670A EP 1889296 A1 EP1889296 A1 EP 1889296A1
Authority
EP
European Patent Office
Prior art keywords
layers
germanium
silicon
source
drain
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06764670A
Other languages
German (de)
French (fr)
Inventor
Yves Morand
Thierry Poiroux
Maud Vinet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STMicroelectronics SA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
STMicroelectronics SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commissariat a lEnergie Atomique CEA, STMicroelectronics SA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP1889296A1 publication Critical patent/EP1889296A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/78—Field effect transistors with field effect produced by an insulated gate
    • H01L29/785—Field effect transistors with field effect produced by an insulated gate having a channel with a horizontal current flow in a vertical sidewall of a semiconductor body, e.g. FinFET, MuGFET
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
    • H01L29/423—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions not carrying the current to be rectified, amplified or switched
    • H01L29/42312—Gate electrodes for field effect devices
    • H01L29/42316—Gate electrodes for field effect devices for field-effect transistors
    • H01L29/4232—Gate electrodes for field effect devices for field-effect transistors with insulated gate
    • H01L29/42384—Gate electrodes for field effect devices for field-effect transistors with insulated gate for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
    • H01L29/42392—Gate electrodes for field effect devices for field-effect transistors with insulated gate for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor fully surrounding the channel, e.g. gate-all-around

Definitions

  • the invention relates to a transistor comprising at least one channel embedded by a gate electrode, and source and drain electrodes each consisting of alternating first layers based on silicon and second layers made of germanium and silicon compound.
  • DG double gate
  • GAA gate-all-around
  • the "5nm-Gate Nanowire FinFET” article by F. L. Yang and Al. (2004 Symposium on VLSI Technology) describes a transistor having a cylindrical channel completely surrounded by the gate. This transistor has a very good electrostatic control of the channel by the gate, which makes it possible to produce a transistor having a gate length as small as 5 nm.
  • germanium transistors As for the materials used, pure germanium has a mobility twice as high for electrons and four times higher for holes than silicon.
  • the disadvantage of germanium transistors is the cost of the substrate which is about 10 times higher than that of a solid silicon substrate.
  • it is very difficult to stack several germanium channels by epitaxial germanium of good quality on a silicon substrate.
  • the manufacture of these transistors requires many developments due to the instability of the germanium oxide.
  • US2003 / 0215989 discloses a transistor having a channel embedded by a gate electrode.
  • the channel is constituted by the central part of a silicon layer.
  • An SiGe layer is removed in the area below the channel to free the space for the gate electrode.
  • the source and drain electrodes correspond to the zones disposed on either side of the channel.
  • the source and the drain are formed by ion implantation in active layers.
  • the source and drain electrodes each consist of alternating first and second layers.
  • the first layers are silicon.
  • the second layers have a germanium concentration of between 20% and 30%.
  • the channel connects two first silicon layers of the stack constituting the source and drain electrodes.
  • the object of the invention is to propose a transistor that makes it possible to obtain a very high integration density and a large amount of current, while using standard methods, in particular methods for integrating transistors onto silicon.
  • the channel is based on germanium, the first layers being composed of germanium and silicon with a germanium concentration of between 0% and 10% and second layers having a germanium concentration between 10% and 50%, the channel connecting two second layers respectively source and drain electrodes.
  • the invention also aims at a method of manufacturing a transistor, comprising successively: the production, on a substrate, of an alternation of first and second layers of germanium and silicon compound, the first layers having a concentration of germanium between 0% and 10% and the second layers having a germanium concentration of between 10% and 50%, the etching, in said stack, of source and drain zones intended to constitute the source and drain electrodes and a narrow zone connecting the source and drain zones, the surface thermal oxidation of said stack, so as to oxidize, in the narrow zone, the silicon of the germanium and silicon compound having a germanium concentration of between 10% and
  • Figures 1 to 3 show, respectively in top view, in section along the axis B-B, and in section along the axis AA, a particular embodiment of a transistor according to the invention.
  • FIGS. 4 to 6, 7 to 9, 10 to 12 and 13 to 15 respectively represent four steps of a particular embodiment of a method of manufacturing a transistor according to the invention, respectively in plan view, in section along the BB axis and in section along the axis AA.
  • a transistor comprises two channels 1 coated with a gate electrode 2.
  • the channels 1 are based on germanium.
  • the transistor has electrodes source 3 and drain 4 which are each constituted by an alternation of first (5) and second (6) layers composed of germanium and silicon.
  • the first layers 5 have a germanium concentration of between 0% and 10% and the second layers 6 have a germanium concentration between 10% and 50%.
  • the first layers 5 are, for example, silicon. All second layers 6 may have the same concentration of germanium.
  • the first layers 5 are in Si and the second layers 6 in SiGe x , so as to obtain a SiGe type stack x / Si / SiGe x / Si.
  • Second layers 6 may also have different germanium concentrations.
  • the second layers 6 are respectively SiGe x , SiGe y and SiGe 2 and the first layers 5 are Si, so as to obtain a SiGe type stack x / Si / SiGe y / Si / SiGe z / Si.
  • the first layers 5 are not necessarily silicon.
  • the first layers 5 also comprise germanium, so as to obtain a stack of type
  • the first layers having a germanium concentration of less than 10% and the second layers having a germanium concentration between 10% and 50%.
  • the upper layer of the stack of layers 5 and 6 is preferably a first silicon layer.
  • the first and / or second layers (5, 6) can be doped during their growth by injection of precursors such as diborane, phosphine, arsine.
  • Each channel connects two second layers 6 of SiGe respectively source 3 and drain 4 electrodes.
  • the channels 1 are separated from the gate electrode 2 by a dielectric 7 of wire rack.
  • the sources 3 and drain 4 are preferably separated from the gate electrode 2 by spacers 15 and by the gate dielectric.
  • a portion of the first layers 5 disposed opposite the channel 1 is oxidized, before deposition of the gate dielectric 7, so as to make the spacers 15 between the first layers 5 of the source 3 and drain 4 and the gate electrode 2.
  • the upper channel 1 connects the second upper layer 6a of the source electrode 3 to the second upper layer 6b of the drain electrode 4.
  • the layers 5 and 6 are formed in parallel on a substrate 8.
  • second upper layer 6a is disposed at a predetermined level of alternating layers of the source electrode 3 and also at a predetermined level with respect to the substrate 8.
  • the corresponding second upper layer 6b of the drain 4 is disposed at a predetermined level of the alternating layers of the drain electrode 4 and also at a predetermined level with respect to the substrate 8.
  • the second upper layers 6a and 6b corresponding to the same channel 1 are thus at the same level.
  • the two second layers 6 connected by a channel 1 and the channel 1 are arranged in the same plane parallel to the substrate 8, as represented by the axis C-C.
  • the gate electrode 2 completely surrounds the channel 1.
  • a method of manufacturing a transistor according to the invention comprises producing, on the substrate 8, a stack of alternating layers 5 and 6 respectively in Si and SiGe 1 as shown in FIGS. 4 to 6.
  • the stack is carried out, for example, by SiGe / Si heteroepitaxy on a silicon-on-insulator ("SOI: silicon on insulator") substrate.
  • SOI silicon on insulator
  • the thickness of the second SiGe layers 6 is preferably between 5 nanometers and 30 nanometers.
  • the thicknesses of the first and second layers 5 and 6 are, for example, each of the order of ten nanometers.
  • the germanium concentration of the second layers is preferably 30%.
  • the number of second SiGe layers 6 determines the number of germanium-based channels 1 formed by the method.
  • the stack of alternate layers 5 and 6 may be protected by a protective layer (not shown), for example a silicon nitride layer, to protect the outer faces of the stack against subsequent oxidation.
  • a protective layer for example a silicon nitride layer, to protect the outer faces of the stack against subsequent oxidation.
  • etching in said stack, a source zone 9 and a drain zone 10, designed respectively to constitute the source 3 and drain 4 electrodes, and a narrow zone 11 connecting the zone from source 9 to the drain zone 10.
  • Said zones (9, 10 and 11) are delimited, for example, by deposition of a resin, lithography (for example photo-lithography or electronic lithography) of the resin, anisotropic plasma etching stacking layers 5 and 6 and removing the resin.
  • the alternations of layers 5 and 6 constituting the source 3 and drain 4 electrodes are formed in the same stack of layers 5 and 6.
  • the narrow zone 11 corresponds to the location of the channels 1 which are formed later.
  • the narrow zone 11 has lateral dimensions of between 3 and 50 nanometers and longitudinal dimensions greater than 5 nanometers and can reach micrometric dimensions.
  • FIGS. 10 to 12 a superficial thermal oxidation of said stack, shown in FIGS. 10 to 12, is carried out.
  • the oxygen enters the stack of layers to a predetermined depth represented by a dotted line 12 in FIG. 10.
  • the interior of the electrodes source 3 and drain 4 is not oxidized during thermal oxidation.
  • the silicon of the narrow zone 11 is completely oxidized during thermal oxidation.
  • all of the silicon of the part of the layers 5 and 6 corresponding to the narrow zone 11, that is to say the silicon of the Si layers 5 and the silicon of the SiGe layers 6, are oxidized.
  • the germanium of the SiGe is thus condensed inside the portions of the layers 6 corresponding to the narrow zone 11 and concentrated, on a central axis of the layers 6 connecting the source 3 and the drain 4, so as to forming the channels 1 based on germanium, while the silicon forms an oxide 13 on the surface of the channel 1 based on germanium.
  • the dimensions of the germanium-based channels are determined by the lateral and longitudinal dimensions of the narrow zone 11 and by the thicknesses of the second SiGe layers 6 as well as by the initial germanium concentration of the SiGe.
  • the portions of the first silicon layers 5 corresponding to the narrow zone 11 are completely converted to silicon oxide 13.
  • a surface oxide layer 14 is disposed on the walls of the source 3 and drain 4 electrodes.
  • germanium condensation that is to say the increase in germanium concentration of a SiGe silicon and germanium compound when it is subjected to an oxidizing treatment, is usually used for the production of substrates of the type germanium on insulator.
  • the narrow zone 11 is oxidized laterally, by its two sides, the condensation of the germanium automatically results in substantially cylindrical channels, as shown in FIGS. 12, 15 and 3.
  • the cylindrical shape of the channels makes it possible in particular to later obtain a very good electrostatic control of the channel through the grid.
  • the silicon oxide 13 of the narrow zone 11 is eliminated, so as to release the channels 1.
  • the elimination of the silicon oxide 13 may be accompanied by a selective etching of residual silicon of the narrow zone 11 arranged between the channels 1, when the previous thermal oxidation is carried out so as to only partially oxidize the silicon of the first layers 5 of the narrow zone 11.
  • the silicon of the first layers 5 may oxidize less rapidly than SiGe.
  • the channels 1 are thus released completely via the selective etching of the residual silicon (not shown).
  • a layer of doped silicon is deposited during epitaxial steps.
  • additional thermal oxidation is performed to reduce the parasitic capacitances of the transistor.
  • all the materials discovered undergo oxidation, in particular silicon and germanium-based channels.
  • a step of producing the spacers 15 is carried out by oxidation (for example thermal or plasma) followed by a selective dissolution of the oxide of germanium in the water.
  • the gate dielectric 7 (for example a material based on Hf 1 Si, O or N, for example HfO 2, HfSiON or a material such as LaAlO 3) is deposited on the condensed germanium constituting the channels 1, in order to coat the channels 1.
  • the gate dielectric 7 is also deposited on the source 3 and the drain 4, as represented in FIG. 2.
  • a gate material for example a metal (for example TiN, WSi, TaN) or a semiconductor (for example polycrystalline silicon, polycrystalline germanium, SiGe), is deposited on the gate dielectric 7, so as to coat the together the channels 1 and the dielectric 7 and, thus, form a coating grid 2, as shown in Figures 2 and 3.
  • the grid 2 is made, for example, by depositing a metal layer on the entire stack of layers 5 and 6 and channels 1, followed by a resin deposit, the photolithography of the resin, the anisotropic etching of the metal layer and the removal of the resin.
  • the grid 2 is delimited so as to fill the space between the channels 1 and so as to completely cover the narrow zone 11 as well as the adjacent part of the source 3 and drain 4 electrodes, as represented in FIG. 2.
  • the dimensions of the grid 2 correspond in particular to the lateral and longitudinal dimensions of the channels 1, to which is added the alignment tolerance of the lithography tool used, typically 20nm for the electron jet apparatus and 60nm for the apparatus of the type photolithography, for example UV, deep UV or extreme UV.
  • the gate dielectric 7 on the germanium constituting the channels 1 Before the deposition of the gate dielectric 7 on the germanium constituting the channels 1, it is possible, in known manner, to selectively doping the two zones 9 and 10 intended to constitute the source 3 and drain 4 electrodes.
  • the selective doping can for example, be performed via ion implantation.
  • the energies of the ions can be chosen so as to dope the source 3 and the drain 4 whereas the channels 1 are simply crossed by the ions without being doped.
  • the number of channels may be greater than or less than two.
  • Several channels arranged one above the other in particular allow to obtain a better integration density.
  • Various standard steps can be added to the production methods, for example the production of spacers, doping steps of the source and drain zones or siliciding of the source and drain zones.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Thin Film Transistor (AREA)
  • Insulated Gate Type Field-Effect Transistor (AREA)

Abstract

Source electrodes (3) and drain electrodes (4) are each constituted of an alternation of first layers (5) and second layers (6) made of a germanium and silicon composite. The first layers (5) have a concentration of germanium ranging from 0 % to 10 %, and the second layers (6) have a concentration of germanium ranging from 10 % to 50 %. At least one channel (1) connects two second layers (6a, 6b), respectively, of the source electrodes (3) and drain electrodes (4). The invention involves the etching of source and drain regions connected by a narrow area, in a stack of layers (5, 6). Next, a superficial thermal oxidation of said stack is effected whereby oxidizing the silicon of the germanium and silicon composite having a concentration of germanium ranging from 10 % to 50 % and condensing the germanium Ge. The silicon oxide of the narrow area is eliminated and a gate dielectric (7) and a gate (2) are deposited on the condensed germanium of the narrow area.

Description

Transistor à canal à base de germanium enrobé par une électrode de grille et procédé de fabrication d'un tel transistorGermanium channel transistor coated by a gate electrode and method of manufacturing such a transistor
Domaine technique de l'inventionTechnical field of the invention
L'invention concerne un transistor comportant au moins un canal enrobé par une électrode de grille, et des électrodes de source et de drain constituées chacune par une alternance de premières couches à base de silicium et de secondes couches en composé de germanium et silicium.The invention relates to a transistor comprising at least one channel embedded by a gate electrode, and source and drain electrodes each consisting of alternating first layers based on silicon and second layers made of germanium and silicon compound.
État de la techniqueState of the art
Pour la réalisation de circuits intégrés en microélectronique, on cherche à concilier une très grande densité d'intégration avec une grande quantité de courant. Dans la littérature, afin_d'améliorer les performances de transistors de type CMOS sur silicium, sont proposées des modifications au niveau de l'architecture des transistors et au niveau des matériaux utilisés.For the realization of integrated circuits in microelectronics, one seeks to reconcile a very high density of integration with a large amount of current. In the literature, in order to improve the performance of CMOS transistors on silicon, changes are proposed in the architecture of the transistors and in the materials used.
Des architectures de type double-grille (« DG : double gâte ») et de type grille enrobante (« GAA : gate-all-around »), par exemple, présentent des courants de fuite plus faibles et des courants de saturation plus importants que des transistors de type simple grille (« SG : single gâte »), pour une longueur de grille donnée.For example, dual-gate ("DG: double gate") and gate-all-around (GAA) architectures have lower leakage currents and higher saturation currents than simple gate type transistors ("SG: single gate"), for a given gate length.
L'article « A Novel Sub-50 nm Multi-Bridge-Channel MOSFET (MBCFET) with Extremely High Performance » de S. -Y. Lee et. Al. (2004 Symposium on VLSI Technology) décrit des transistors multi-canaux ayant des grilles enrobantes. Ces transistors présentent d'excellentes performances statiques et offrent une très grande densité d'intégration par rapport au niveau de courant débité. En revanche, leur principe de fabrication repose sur l'empilement par épitaxie de couches en silicium-germanium (SiGe) et en silicium (Si) et sur la gravure sélective du SiGe par rapport au Si pour réaliser des canaux suspendus, ce qui impose que le matériau du canal soit en silicium ou bien en silicium-germanium. Par ailleurs, cette architecture présente intrinsèquement de fortes capacités parasites dues au fait qu'il est difficile de réaliser des espaceurs entre les canaux.The article "A Novel Sub-50nm Multi-Bridge-Channel MOSFET (MBCFET) with Extremely High Performance" from S. -Y. Lee and. Al. (2004 Symposium on VLSI Technology) describes multi-channel transistors with embedding grids. These transistors exhibit excellent static performance and offer a very high density of integration with respect to the level of current flow. On the other hand, their manufacturing principle is based on the epitaxial stacking of silicon-germanium (SiGe) and silicon (Si) layers and on the selective etching of SiGe with respect to Si to produce suspended channels, which imposes that the channel material is silicon or silicon-germanium. Moreover, this architecture inherently has high parasitic capacitances due to the fact that it is difficult to make spacers between the channels.
L'article « 5nm-Gate Nanowire FinFET » de F. L. Yang et Al. (2004 Symposium on VLSI Technology) décrit un transistor ayant un canal cylindrique complètement entouré par la grille. Ce transistor présente un très bon contrôle électrostatique du canal par la grille, ce qui permet de réaliser un transistor ayant une longueur de grille aussi faible que 5nm.The "5nm-Gate Nanowire FinFET" article by F. L. Yang and Al. (2004 Symposium on VLSI Technology) describes a transistor having a cylindrical channel completely surrounded by the gate. This transistor has a very good electrostatic control of the channel by the gate, which makes it possible to produce a transistor having a gate length as small as 5 nm.
Concernant les matériaux utilisés, le germanium pur présente une mobilité deux fois plus importante pour les électrons et quatre fois plus importante pour les trous que le silicium. L'inconvénient des transistors en germanium est Ie coût du substrat qui est environ 10 fois plus élevé que celui d'un substrat de silicium massif. De plus, il est très difficile d'empiler plusieurs canaux en germanium par épitaxie de germanium de bonne qualité sur un substrat de silicium. Par ailleurs, la fabrication de ces transistors requiert de nombreux développements du fait de l'instabilité de l'oxyde de germanium.As for the materials used, pure germanium has a mobility twice as high for electrons and four times higher for holes than silicon. The disadvantage of germanium transistors is the cost of the substrate which is about 10 times higher than that of a solid silicon substrate. In addition, it is very difficult to stack several germanium channels by epitaxial germanium of good quality on a silicon substrate. Moreover, the manufacture of these transistors requires many developments due to the instability of the germanium oxide.
Le document US2003/0215989 décrit un transistor comportant un canal enrobé par une électrode de grille. Le canal est constitué par la partie centrale d'une couche en silicium. Une couche en SiGe est enlevée dans la zone disposée sous le canal, de manière à libérer l'espace pour l'électrode de grille. Les électrodes de source et de drain correspondent aux zones disposées de part et d'autre du canal. La source et le drain sont formés par implantation d'ions dans des couches actives. Les électrodes de source et de drain sont chacune constituées par une alternance de premières et secondes couches. Les premières couches sont en silicium. Les secondes couches ont une concentration de germanium comprise entre 20% et 30%. Ainsi, le canal relie deux premières couches en silicium de l'empilement constituant les électrodes de source et de drain.US2003 / 0215989 discloses a transistor having a channel embedded by a gate electrode. The channel is constituted by the central part of a silicon layer. An SiGe layer is removed in the area below the channel to free the space for the gate electrode. The source and drain electrodes correspond to the zones disposed on either side of the channel. The source and the drain are formed by ion implantation in active layers. The source and drain electrodes each consist of alternating first and second layers. The first layers are silicon. The second layers have a germanium concentration of between 20% and 30%. Thus, the channel connects two first silicon layers of the stack constituting the source and drain electrodes.
Objet de l'inventionObject of the invention
L'invention a pour but de proposer un transistor permettant d'obtenir une très grande densité d'intégration et une grande quantité de courant, tout en utilisant des procédés standard, notamment les procédés d'intégration de transistors sur silicium.The object of the invention is to propose a transistor that makes it possible to obtain a very high integration density and a large amount of current, while using standard methods, in particular methods for integrating transistors onto silicon.
Selon l'invention, ce but est atteint par les revendications annexées et, plus particulièrement, par le fait que Ie canal est à base de germanium, les premières couches étant en composé de germanium et silicium avec une concentration de germanium comprise entre 0% et 10% et les secondes couches ayant une concentration de germanium comprise entre 10% et 50%, le canal reliant deux secondes couches respectivement des électrodes de source et de drain.According to the invention, this object is achieved by the appended claims and, more particularly, by the fact that the channel is based on germanium, the first layers being composed of germanium and silicon with a germanium concentration of between 0% and 10% and second layers having a germanium concentration between 10% and 50%, the channel connecting two second layers respectively source and drain electrodes.
L'invention a également pour but un procédé de fabrication d'un transistor, comportant successivement : la réalisation, sur un substrat, d'une alternance de premières et secondes couches en composé de germanium et silicium, les premières couches ayant une concentration de germanium comprise entre 0% et 10% et les secondes couches ayant une concentration de germanium comprise entre 10% et 50%, la gravure, dans ledit empilement, de zones de source et de drain destinées à constituer les électrodes de source et de drain et d'une zone étroite reliant les zones de source et de drain, l'oxydation thermique superficielle dudit empilement, de manière à oxyder, dans la zone étroite, le silicium du composé de germanium et silicium ayant une concentration de germanium comprise entre 10% etThe invention also aims at a method of manufacturing a transistor, comprising successively: the production, on a substrate, of an alternation of first and second layers of germanium and silicon compound, the first layers having a concentration of germanium between 0% and 10% and the second layers having a germanium concentration of between 10% and 50%, the etching, in said stack, of source and drain zones intended to constitute the source and drain electrodes and a narrow zone connecting the source and drain zones, the surface thermal oxidation of said stack, so as to oxidize, in the narrow zone, the silicon of the germanium and silicon compound having a germanium concentration of between 10% and
50% et de manière à condenser le germanium, l'élimination du silicium oxydé de la zone étroite, le dépôt d'un diélectrique de grille sur le germanium condensé de la zone étroite, le dépôt d'un métal de grille sur ledit diélectrique de grille.50% and so as to condense the germanium, the removal of the oxidized silicon from the narrow zone, the deposition of a gate dielectric on the condensed germanium of the narrow zone, the deposition of a gate metal on said dielectric of wire rack.
Description sommaire des dessinsBrief description of the drawings
D'autres avantages et caractéristiques ressortiront plus clairement de la description qui va suivre de modes particuliers de réalisation de l'invention donnés à titre d'exemples non limitatifs et représentés aux dessins annexés, dans lesquels :Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given by way of non-limiting example and represented in the accompanying drawings, in which:
Les figures 1 à 3 représentent, respectivement en vue de dessus, en coupe selon l'axe B-B, et en coupe selon l'axe AA, un mode de réalisation particulier d'un transistor selon l'invention.Figures 1 to 3 show, respectively in top view, in section along the axis B-B, and in section along the axis AA, a particular embodiment of a transistor according to the invention.
Les figures 4 à 6, 7 à 9, 10 à 12 et 13 à 15 représentent respectivement quatre étapes d'un mode de réalisation particulier d'un procédé de fabrication d'un transistor selon l'invention, respectivement en vue de dessus, en coupe selon l'axe B-B et en coupe selon l'axe AA.FIGS. 4 to 6, 7 to 9, 10 to 12 and 13 to 15 respectively represent four steps of a particular embodiment of a method of manufacturing a transistor according to the invention, respectively in plan view, in section along the BB axis and in section along the axis AA.
Description de modes particuliers de réalisationDescription of particular embodiments
Dans le mode de réalisation particulier représenté aux figures 1 à 3, un transistor comporte deux canaux 1 enrobés par une électrode de grille 2. Les canaux 1 sont à base de germanium. Le transistor comporte des électrodes de source 3 et de drain 4 qui sont chacune constituées par une alternance de premières (5) et secondes (6) couches en composé de germanium et silicium. Les premières couches 5 ont une concentration de germanium comprise entre 0% et 10% et les secondes couches 6 ont une concentration de germanium comprise entre 10% et 50%.In the particular embodiment shown in FIGS. 1 to 3, a transistor comprises two channels 1 coated with a gate electrode 2. The channels 1 are based on germanium. The transistor has electrodes source 3 and drain 4 which are each constituted by an alternation of first (5) and second (6) layers composed of germanium and silicon. The first layers 5 have a germanium concentration of between 0% and 10% and the second layers 6 have a germanium concentration between 10% and 50%.
Les premières couches 5 sont, par exemple, en silicium. Toutes les secondes couches 6 peuvent avoir la même concentration de germanium. Par exemple, les premières couches 5 sont en Si et les secondes couches 6 en SiGex, de manière à obtenir un empilement de type SiGex/Si/SiGex/Si.The first layers 5 are, for example, silicon. All second layers 6 may have the same concentration of germanium. For example, the first layers 5 are in Si and the second layers 6 in SiGe x , so as to obtain a SiGe type stack x / Si / SiGe x / Si.
Les secondes couches 6 peuvent aussi avoir des concentrations de germanium différentes. Par exemple, les secondes couches 6 sont respectivement en SiGex, SiGey et SiGe2 et les premières couches 5 sont en Si, de manière à obtenir un empilement de type SiGex/Si/SiGey/Si/SiGez/Si.Second layers 6 may also have different germanium concentrations. For example, the second layers 6 are respectively SiGe x , SiGe y and SiGe 2 and the first layers 5 are Si, so as to obtain a SiGe type stack x / Si / SiGe y / Si / SiGe z / Si.
Les premières couches 5 ne sont pas nécessairement en silicium. Par exemple les premières couches 5 comportent également du germanium, de manière à obtenir un empilement de typeThe first layers 5 are not necessarily silicon. For example the first layers 5 also comprise germanium, so as to obtain a stack of type
SiGeu/SiGev/SiGew/SiGex/SiGe/SiGez, les premières couches ayant une concentration de germanium inférieure à 10% et les secondes couches ayant une concentration de germanium comprise entre 10% et 50%.SiGe u / SiGe v / SiGe w / SiGe x / SiGe / SiGe z , the first layers having a germanium concentration of less than 10% and the second layers having a germanium concentration between 10% and 50%.
La couche supérieure de l'empilement de couches 5 et 6 est, de préférence, une première couche en silicium.The upper layer of the stack of layers 5 and 6 is preferably a first silicon layer.
Avantageusement, les premières et/ou secondes couches (5, 6) peuvent être dopées pendant leur croissance par injection de précurseurs tels que le diborane, la phosphine, l'arsine. Chaque canal relie deux secondes couches 6 en SiGe respectivement des électrodes de source 3 et de drain 4. Les canaux 1 sont séparés de l'électrode de grille 2 par un diélectrique 7 de grille. Comme représenté à la figure 2, les source 3 et drain 4 sont, de préférence, séparés de l'électrode de grille 2 par des espaceurs 15 et par le diélectrique de grille. Par exemple, une partie des premières couches 5 disposée en regard du canal 1 est oxydée, avant dépôt du diélectrique 7 de grille, de manière à réaliser les espaceurs 15 entre les premières couches 5 des source 3 et drain 4 et l'électrode de grille 2.Advantageously, the first and / or second layers (5, 6) can be doped during their growth by injection of precursors such as diborane, phosphine, arsine. Each channel connects two second layers 6 of SiGe respectively source 3 and drain 4 electrodes. The channels 1 are separated from the gate electrode 2 by a dielectric 7 of wire rack. As shown in FIG. 2, the sources 3 and drain 4 are preferably separated from the gate electrode 2 by spacers 15 and by the gate dielectric. For example, a portion of the first layers 5 disposed opposite the channel 1 is oxidized, before deposition of the gate dielectric 7, so as to make the spacers 15 between the first layers 5 of the source 3 and drain 4 and the gate electrode 2.
Sur la figure 2, le canal 1 supérieur relie la seconde couche supérieure 6a de l'électrode de source 3 à la seconde couche supérieure 6b de l'électrode de drain 4. Les couches 5 et 6 sont formées parallèlement sur un substrat 8. La seconde couche supérieure 6a est disposée à un niveau prédéterminé de l'alternance de couches de l'électrode de source 3 et également à un niveau prédéterminé par rapport au substrat 8. De la même façon, la seconde couche supérieure 6b correspondante du drain 4 est disposée à un niveau prédéterminé de l'alternance de couches de l'électrode de drain 4 et également à un niveau prédéterminé par rapport au substrat 8. Les secondes couches supérieures 6a et 6b correspondant à un même canal 1 sont ainsi au même niveau.In FIG. 2, the upper channel 1 connects the second upper layer 6a of the source electrode 3 to the second upper layer 6b of the drain electrode 4. The layers 5 and 6 are formed in parallel on a substrate 8. second upper layer 6a is disposed at a predetermined level of alternating layers of the source electrode 3 and also at a predetermined level with respect to the substrate 8. In the same way, the corresponding second upper layer 6b of the drain 4 is disposed at a predetermined level of the alternating layers of the drain electrode 4 and also at a predetermined level with respect to the substrate 8. The second upper layers 6a and 6b corresponding to the same channel 1 are thus at the same level.
Sur la figure 2, les deux secondes couches 6 reliées par un canal 1 et le canal 1 sont disposés dans un même plan parallèle au substrat 8, comme représenté par l'axe C-C. Comme représenté à la figure 3, l'électrode de grille 2 entoure complètement le canal 1.In FIG. 2, the two second layers 6 connected by a channel 1 and the channel 1 are arranged in the same plane parallel to the substrate 8, as represented by the axis C-C. As shown in FIG. 3, the gate electrode 2 completely surrounds the channel 1.
Un procédé de fabrication d'un transistor selon l'invention comporte la réalisation, sur le substrat 8, d'un empilement des couches alternantes 5 et 6 respectivement en Si et en SiGe1 comme représenté aux figures 4 à 6. L'empilement est réalisé, par exemple, par hétéro-épitaxie de SiGe/Si sur un substrat de type silicium sur isolant (« SOI : silicon on insulator »). L'épaisseur des secondes couches 6 en SiGe est, de préférence, comprise entre 5 nanomètres et 30 nanomètres. Les épaisseurs des premières et secondes couches 5 et 6 sont, par exemple, chacune de l'ordre de la dizaine de nanomètres. La concentration de germanium des secondes couches est, de préférence, de 30%. Le nombre de secondes couches 6 en SiGe détermine le nombre de canaux 1 à base de germanium formés par le procédé.A method of manufacturing a transistor according to the invention comprises producing, on the substrate 8, a stack of alternating layers 5 and 6 respectively in Si and SiGe 1 as shown in FIGS. 4 to 6. The stack is carried out, for example, by SiGe / Si heteroepitaxy on a silicon-on-insulator ("SOI: silicon on insulator") substrate. The thickness of the second SiGe layers 6 is preferably between 5 nanometers and 30 nanometers. The thicknesses of the first and second layers 5 and 6 are, for example, each of the order of ten nanometers. The germanium concentration of the second layers is preferably 30%. The number of second SiGe layers 6 determines the number of germanium-based channels 1 formed by the method.
L'empilement des couches alternantes 5 et 6 peut être protégé par une couche de protection (non-représentée), par exemple une couche en nitrure de silicium, permettant de protéger les faces externes de l'empilement contre l'oxydation ultérieure.The stack of alternate layers 5 and 6 may be protected by a protective layer (not shown), for example a silicon nitride layer, to protect the outer faces of the stack against subsequent oxidation.
Ensuite sont délimitées par gravure (figures 7 à 9), dans ledit empilement, une zone de source 9 et une zone de drain 10, destinées à constituer respectivement les électrodes de source 3 et de drain 4, et une zone étroite 11 reliant la zone de source 9 à la zone de drain 10. Lesdites zones (9, 10 et 11 ) sont délimitées, par exemple, par dépôt d'une résine, lithographie (par exemple photo-lithographie ou lithographie électronique) de Ia résine, gravure plasma anisotrope de l'empilement de couches 5 et 6 et retrait de la résine. Ainsi, les alternances de couches 5 et 6 constituant les électrodes de source 3 et de drain 4 sont formées dans un même empilement de couches 5 et 6. La zone étroite 11 correspond à l'emplacement des canaux 1 qui sont formés ultérieurement. La zone étroite 11 a des dimensions latérales comprises entre 3 et 50 nanomètres et des dimensions longitudinales supérieures à 5 nanomètres et pouvant atteindre des dimensions micrométriques.Then, etching (FIGS. 7 to 9), in said stack, a source zone 9 and a drain zone 10, designed respectively to constitute the source 3 and drain 4 electrodes, and a narrow zone 11 connecting the zone from source 9 to the drain zone 10. Said zones (9, 10 and 11) are delimited, for example, by deposition of a resin, lithography (for example photo-lithography or electronic lithography) of the resin, anisotropic plasma etching stacking layers 5 and 6 and removing the resin. Thus, the alternations of layers 5 and 6 constituting the source 3 and drain 4 electrodes are formed in the same stack of layers 5 and 6. The narrow zone 11 corresponds to the location of the channels 1 which are formed later. The narrow zone 11 has lateral dimensions of between 3 and 50 nanometers and longitudinal dimensions greater than 5 nanometers and can reach micrometric dimensions.
Puis, on effectue une oxydation thermique superficielle dudit empilement, représenté aux figures 10 à 12. L'oxygène pénètre dans l'empilement de couches jusqu'à une profondeur prédéterminée représentée par une ligne pointillée 12 à la figure 10. L'intérieur des électrodes de source 3 et de drain 4 n'est donc pas oxydé lors de l'oxydation thermique. Dans le mode de réalisation particulier représenté aux figures 10 à 12, le silicium de la zone étroite 11 est complètement oxydée lors de l'oxydation thermique. Ainsi est oxydée la totalité du silicium de la partie des couches 5 et 6 correspondant à la zone étroite 11 , c'est-à-dire le silicium des couches 5 en Si et le silicium des couches 6 en SiGe. Dans la zone étroite 11 , le germanium du SiGe est ainsi condensé à l'intérieur des parties des couches 6 correspondant à la zone étroite 11 et concentré, sur un axe central des couches 6 reliant la source 3 et le drain 4, de manière à former les canaux 1 à base de germanium, tandis que le silicium forme un oxyde 13 à la surface du canal 1 à base de germanium. Les dimensions des canaux à base de germanium sont déterminées par les dimensions latérales et longitudinales de la zone étroite 11 et par les épaisseurs des secondes couches 6 en SiGe ainsi que par la concentration initiale en germanium du SiGe. Sur les figures 11 et 12, les parties des premières couches 5 en silicium correspondant à la zone étroite 11 sont transformées complètement en oxyde 13 de silicium. Sur la figure 11 , une couche superficielle d'oxyde 14 est disposée sur les parois des électrodes de source 3 et de drain 4.Then, a superficial thermal oxidation of said stack, shown in FIGS. 10 to 12, is carried out. The oxygen enters the stack of layers to a predetermined depth represented by a dotted line 12 in FIG. 10. The interior of the electrodes source 3 and drain 4 is not oxidized during thermal oxidation. In the mode of Specific embodiment shown in Figures 10 to 12, the silicon of the narrow zone 11 is completely oxidized during thermal oxidation. Thus, all of the silicon of the part of the layers 5 and 6 corresponding to the narrow zone 11, that is to say the silicon of the Si layers 5 and the silicon of the SiGe layers 6, are oxidized. In the narrow zone 11, the germanium of the SiGe is thus condensed inside the portions of the layers 6 corresponding to the narrow zone 11 and concentrated, on a central axis of the layers 6 connecting the source 3 and the drain 4, so as to forming the channels 1 based on germanium, while the silicon forms an oxide 13 on the surface of the channel 1 based on germanium. The dimensions of the germanium-based channels are determined by the lateral and longitudinal dimensions of the narrow zone 11 and by the thicknesses of the second SiGe layers 6 as well as by the initial germanium concentration of the SiGe. In FIGS. 11 and 12, the portions of the first silicon layers 5 corresponding to the narrow zone 11 are completely converted to silicon oxide 13. In FIG. 11, a surface oxide layer 14 is disposed on the walls of the source 3 and drain 4 electrodes.
Le phénomène de condensation de germanium, c'est-à-dire l'augmentation en concentration de germanium d'un composé de silicium et germanium SiGe lorsqu'il est soumis à un traitement oxydant, est habituellement utilisé pour la fabrication de substrats de type germanium sur isolant. Dans le présent cas, où la zone étroite 11 est oxydée latéralement, par ses deux côtés, la condensation du germanium résulte automatiquement dans des canaux sensiblement cylindriques, comme représenté aux figures 12, 15 et 3. La forme cylindrique des canaux permet notamment d'obtenir ultérieurement un très bon contrôle électrostatique du canal par la grille.The phenomenon of germanium condensation, that is to say the increase in germanium concentration of a SiGe silicon and germanium compound when it is subjected to an oxidizing treatment, is usually used for the production of substrates of the type germanium on insulator. In this case, where the narrow zone 11 is oxidized laterally, by its two sides, the condensation of the germanium automatically results in substantially cylindrical channels, as shown in FIGS. 12, 15 and 3. The cylindrical shape of the channels makes it possible in particular to later obtain a very good electrostatic control of the channel through the grid.
Ensuite, comme représenté aux figures 13 à 15, l'oxyde 13 de silicium de la zone étroite 11 est éliminé, de manière à libérer les canaux 1. L'élimination de l'oxyde 13 de silicium peut être accompagnée d'une gravure sélective du silicium résiduel de la zone étroite 11 disposé entre les canaux 1 , lorsque l'oxydation thermique antérieure est effectuée de manière à n'oxyder que partiellement le silicium des premières couches 5 de la zone étroite 11. En effet, le silicium des premières couches 5 peut s'oxyder moins rapidement que le SiGe. Les canaux 1 sont ainsi libérés complètement par l'intermédiaire de la gravure sélective du silicium résiduel (non-représentée). Avantageusement, afin d'augmenter la vitesse d'oxydation, on dépose une couche de silicium dopé pendant des étapes d'épitaxie.Then, as shown in FIGS. 13 to 15, the silicon oxide 13 of the narrow zone 11 is eliminated, so as to release the channels 1. The elimination of the silicon oxide 13 may be accompanied by a selective etching of residual silicon of the narrow zone 11 arranged between the channels 1, when the previous thermal oxidation is carried out so as to only partially oxidize the silicon of the first layers 5 of the narrow zone 11. In fact, the silicon of the first layers 5 may oxidize less rapidly than SiGe. The channels 1 are thus released completely via the selective etching of the residual silicon (not shown). Advantageously, in order to increase the oxidation rate, a layer of doped silicon is deposited during epitaxial steps.
Avantageusement, une oxydation thermique supplémentaire est effectuée pour diminuer les capacités parasites du transistor. Ainsi, tous les matériaux découverts subissent l'oxydation, notamment le silicium et les canaux à base de germanium. Un nettoyage présentant une sélectivité de gravure de l'oxyde de germanium par rapport à l'oxyde de silicium, par exemple un rinçage à l'eau, permet ensuite d'éliminer sélectivement l'oxyde de germanium et laisse intact l'oxyde de silicium. Il s'ensuit une épaisseur d'oxyde de silicium (non-représentée) sur les flancs de silicium permettant de réduire fortement les capacités parasites du transistor.Advantageously, additional thermal oxidation is performed to reduce the parasitic capacitances of the transistor. Thus, all the materials discovered undergo oxidation, in particular silicon and germanium-based channels. A cleaning having a selectivity of etching of the germanium oxide with respect to the silicon oxide, for example a rinsing with water, then makes it possible to selectively remove the germanium oxide and leave the silicon oxide intact. . It follows a thickness of silicon oxide (not shown) on the silicon flanks to greatly reduce the parasitic capacitance of the transistor.
Avantageusement, après l'étape d'élimination du silicium oxydé de la zone étroite, on effectue une étape de réalisation des espaceurs 15 (figure 2) par oxydation (par exemple thermique ou plasma) suivie d'une dissolution sélective de l'oxyde de germanium dans l'eau.Advantageously, after the step of removing the oxidized silicon from the narrow zone, a step of producing the spacers 15 (FIG. 2) is carried out by oxidation (for example thermal or plasma) followed by a selective dissolution of the oxide of germanium in the water.
Après libération des canaux 1 , le diélectrique 7 de grille (par exemple un matériau à base de Hf1 Si, O ou N; par exemple HfO2, HfSiON ou un matériau tel que LaAIO3) est déposé sur le germanium condensé constituant les canaux 1 , de manière à enrober les canaux 1. Le diélectrique 7 de grille se dépose également sur la source 3 et le drain 4, comme représenté à la figure 2. Puis, un matériau de grille, par exemple un métal (par exemple TiN, WSi, TaN) ou un semiconducteur (par exemple silicium polycristallin, germanium polycristallin, SiGe), est déposé sur le diélectrique 7 de grille, de manière à enrober l'ensemble des canaux 1 et du diélectrique 7 et, ainsi, former une grille 2 enrobante, comme représenté aux figures 2 et 3. Le fait que la grille 2 enrobe le canal 1 , donne un excellent contrôle des effets de canal court. La grille 2 est réalisée, par exemple, par dépôt d'une couche métallique sur l'ensemble de l'empilement de couches 5 et 6 et des canaux 1 , suivi par un dépôt de résine, la photo-lithographie de la résine, la gravure anisotrope de Ia couche métallique et le retrait de la résine. Ainsi, la grille 2 est délimitée de manière à remplir l'espace entre les canaux 1 et de manière à recouvrir complètement la zone étroite 11 ainsi que la partie adjacente des électrodes de source 3 et de drain 4, comme représenté à la figure 2. Les dimensions de la grille 2 correspondent notamment aux dimensions latérales et longitudinales des canaux 1 , auxquelles on ajoute la tolérance d'alignement de l'outil de lithographie utilisé, typiquement 20nm pour les appareils à jet d'électrons et 60nm pour les appareils de type photolithographie, par exemple UV, UV profond ou UV extrême.After the channels 1 have been released, the gate dielectric 7 (for example a material based on Hf 1 Si, O or N, for example HfO 2, HfSiON or a material such as LaAlO 3) is deposited on the condensed germanium constituting the channels 1, in order to coat the channels 1. The gate dielectric 7 is also deposited on the source 3 and the drain 4, as represented in FIG. 2. Then, a gate material, for example a metal (for example TiN, WSi, TaN) or a semiconductor (for example polycrystalline silicon, polycrystalline germanium, SiGe), is deposited on the gate dielectric 7, so as to coat the together the channels 1 and the dielectric 7 and, thus, form a coating grid 2, as shown in Figures 2 and 3. The fact that the gate 2 surrounds the channel 1, gives excellent control of short channel effects. The grid 2 is made, for example, by depositing a metal layer on the entire stack of layers 5 and 6 and channels 1, followed by a resin deposit, the photolithography of the resin, the anisotropic etching of the metal layer and the removal of the resin. Thus, the grid 2 is delimited so as to fill the space between the channels 1 and so as to completely cover the narrow zone 11 as well as the adjacent part of the source 3 and drain 4 electrodes, as represented in FIG. 2. The dimensions of the grid 2 correspond in particular to the lateral and longitudinal dimensions of the channels 1, to which is added the alignment tolerance of the lithography tool used, typically 20nm for the electron jet apparatus and 60nm for the apparatus of the type photolithography, for example UV, deep UV or extreme UV.
Avant le dépôt du diélectrique 7 de grille sur le germanium constituant les canaux 1 , on peut effectuer, de manière connue, un dopage sélectif des deux zones 9 et 10 destinées à constituer les électrodes de source 3 et de drain 4. Le dopage sélectif peut, par exemple, être effectué par l'intermédiaire d'une implantation ionique. Les énergies des ions peuvent être choisies de manière à doper la source 3 et le drain 4 alors que les canaux 1 sont simplement traversés par les ions sans être dopés.Before the deposition of the gate dielectric 7 on the germanium constituting the channels 1, it is possible, in known manner, to selectively doping the two zones 9 and 10 intended to constitute the source 3 and drain 4 electrodes. The selective doping can for example, be performed via ion implantation. The energies of the ions can be chosen so as to dope the source 3 and the drain 4 whereas the channels 1 are simply crossed by the ions without being doped.
L'invention n'est pas limitée aux modes de réalisation particuliers représentés. En particulier, le nombre de canaux peut être supérieur ou inférieur à deux. Plusieurs canaux disposés les uns au-dessus des autres permettent notamment d'obtenir une meilleure densité d'intégration. Différentes étapes standard peuvent être ajoutées aux procédé de réalisation, par exemple la réalisation d'espaceurs, des étapes de dopage des zones de source et de drain ou une siliciuration des zones de source et de drain. The invention is not limited to the particular embodiments shown. In particular, the number of channels may be greater than or less than two. Several channels arranged one above the other in particular allow to obtain a better integration density. Various standard steps can be added to the production methods, for example the production of spacers, doping steps of the source and drain zones or siliciding of the source and drain zones.

Claims

Revendications claims
1. Transistor comportant au moins un canal (1 ) enrobé par une électrode de grille (2), et des électrodes de source (3) et de drain (4) constituées chacune par une alternance de premières couches (5) à base de silicium et de secondes (6) couches en composé de germanium et silicium, transistor caractérisé en ce que Ie canal (1) est à base de germanium, les premières couches (5) étant en composé de germanium et silicium avec une concentration de germanium comprise entre 0% et 10% et les secondes couches (6) ayant une concentration de germanium comprise entre 10% et 50%, le canal (1) reliant deux secondes couches (6a, 6b) respectivement des électrodes de source (3) et de drain (4).A transistor comprising at least one channel (1) encased by a gate electrode (2), and source (3) and drain (4) electrodes each consisting of alternating first silicon-based layers (5). and second (6) layers composed of germanium and silicon, characterized in that the channel (1) is based on germanium, the first layers (5) being composed of germanium and silicon with a germanium concentration between 0% and 10% and the second layers (6) having a germanium concentration between 10% and 50%, the channel (1) connecting two second layers (6a, 6b) respectively source (3) and drain electrodes (4).
2. Transistor selon la revendication 1 , caractérisé en ce que les premières couches (5) sont en silicium.2. Transistor according to claim 1, characterized in that the first layers (5) are silicon.
3. Transistor selon l'une des revendications 1 et 2, caractérisé en ce que les secondes couches (6) ont des concentrations de germanium différentes.3. Transistor according to one of claims 1 and 2, characterized in that the second layers (6) have different germanium concentrations.
4. Transistor selon l'une des revendications 1 et 2, caractérisé en ce que les secondes couches (6) ont la même concentration de germanium.4. Transistor according to one of claims 1 and 2, characterized in that the second layers (6) have the same concentration of germanium.
5. Transistor selon l'une quelconque des revendications 1 à 4, caractérisé en ce que la seconde couche (6a) reliée par le canal (1) et appartenant à l'électrode de source (3) est disposée au même niveau de l'alternance de couches de l'électrode de source (3) que la seconde couche (6b) correspondante de l'électrode de drain (4).5. Transistor according to any one of claims 1 to 4, characterized in that the second layer (6a) connected by the channel (1) and belonging to the source electrode (3) is arranged at the same level of the alternating layers of the source electrode (3) than the corresponding second layer (6b) of the drain electrode (4).
6. Transistor selon l'une quelconque des revendications 1 à 5, caractérisé en ce que les alternances de couches (5, 6) constituant les électrodes de source (3) et de drain (4) sont formées dans un même empilement de couches (5, 6).6. Transistor according to any one of claims 1 to 5, characterized in that the alternations of layers (5, 6) constituting the electrodes of source (3) and drain (4) are formed in the same stack of layers (5, 6).
7. Transistor selon l'une quelconque des revendications 1 à 6, caractérisé en ce que le canal (1 ) est sensiblement cylindrique.7. Transistor according to any one of claims 1 to 6, characterized in that the channel (1) is substantially cylindrical.
8. Transistor selon l'une quelconque des revendications 1 à 7, caractérisé en ce que l'électrode de grille (2) entoure complètement le canal (1).8. Transistor according to any one of claims 1 to 7, characterized in that the gate electrode (2) completely surrounds the channel (1).
9. Transistor selon l'une quelconque des revendications 1 à 8, caractérisé en ce qu'il comporte plusieurs canaux (1 ).9. Transistor according to any one of claims 1 to 8, characterized in that it comprises a plurality of channels (1).
10. Procédé de fabrication d'un transistor selon l'une quelconque des revendications 1 à 9, caractérisé en ce qu'il comporte successivement : la réalisation, sur un substrat (8), d'une alternance de premières (5) et secondes (6) couches en composé de germanium et silicium, les premières couches (5) ayant une concentration de germanium comprise entre 0% et 10% et les secondes couches (6) ayant une concentration de germanium comprise entre 10% et 50%, la gravure, dans ledit empilement, de zones de source et de drain destinées à constituer les électrodes de source (3) et de drain (4) et d'une zone étroite (11 ) reliant les zones de source et de drain, l'oxydation thermique superficielle dudit empilement, de manière à oxyder, dans la zone étroite (11), le silicium du composé de germanium et silicium ayant une concentration de germanium comprise entre 10% et10. A method of manufacturing a transistor according to any one of claims 1 to 9, characterized in that it comprises successively: the realization, on a substrate (8), an alternation of first (5) and second (6) layers of germanium and silicon compound, the first layers (5) having a germanium concentration of between 0% and 10% and the second layers (6) having a germanium concentration of between 10% and 50%, the etching, in said stack, source and drain zones for constituting the source (3) and drain (4) electrodes and a narrow zone (11) connecting the source and drain zones, the oxidation thermal superficial of said stack, so as to oxidize, in the narrow zone (11), the silicon of the germanium and silicon compound having a germanium concentration of between 10% and
50% et de manière à condenser le germanium, l'élimination du silicium oxydé (13) de la zone étroite (11), le dépôt d'un diélectrique (7) de grille sur le germanium condensé de la zone étroite (11), le dépôt d'un métal de grille sur ledit diélectrique (7) de grille. 50% and so as to condense the germanium, the removal of the oxidized silicon (13) from the narrow zone (11), the deposition of a gate dielectric (7) on the condensed germanium of the narrow zone (11), depositing a gate metal on said gate dielectric (7).
11. Procédé selon la revendication 10, caractérisé en ce que l'épaisseur des secondes couches (6) est comprise entre 5 et 30 nanomètres.11. The method of claim 10, characterized in that the thickness of the second layers (6) is between 5 and 30 nanometers.
12. Procédé selon l'une des revendications 10 et 11 , caractérisé en ce que la zone étroite (11 ) a des dimensions latérales comprises entre 3 et 50 nanomètres et des dimensions longitudinales comprises entre 5 nanomètres et 1 micromètre.12. Method according to one of claims 10 and 11, characterized in that the narrow zone (11) has lateral dimensions of between 3 and 50 nanometers and longitudinal dimensions of between 5 nanometers and 1 micrometer.
13. Procédé selon l'une quelconque des revendications 10 à 12, caractérisé en ce que l'élimination du silicium oxydé (13) de la zone étroite (11) est accompagnée d'une étape de gravure sélective du silicium résiduel de la zone étroite (11).13. Method according to any one of claims 10 to 12, characterized in that the removal of the oxidized silicon (13) from the narrow zone (11) is accompanied by a step of selective etching of the residual silicon of the narrow zone. (11).
14. Procédé selon l'une quelconque des revendications 10 à 13, caractérisé en ce que les premières et/ou secondes couches (5, 6) sont dopées.14. Method according to any one of claims 10 to 13, characterized in that the first and / or second layers (5, 6) are doped.
15. Procédé selon la revendication 14, caractérisé en ce qu'il comporte, avant le dépôt du diélectrique (7) de grille sur le germanium, un dopage sélectif des deux zones destinées à constituer les électrodes de source (3) et de drain (4).15. Method according to claim 14, characterized in that it comprises, before the deposition of the gate dielectric (7) on the germanium, a selective doping of the two zones intended to constitute the source (3) and drain electrodes ( 4).
16. Procédé selon l'une quelconque des revendications 10 à 15, caractérisé en ce que, avant dépôt du diélectrique (7) de grille, une partie des premières couches (5) disposée en regard du canal (1) est oxydée de manière à réaliser des espaceurs (15) entre les premières couches (5) des source (3) et drain (4) et l'électrode de grille (2). 16. Method according to any one of claims 10 to 15, characterized in that, prior to deposition of the dielectric (7) gate, a portion of the first layers (5) disposed opposite the channel (1) is oxidized so as to making spacers (15) between the first layers (5) of the source (3) and drain (4) and the gate electrode (2).
EP06764670A 2005-06-06 2006-05-23 Channel transistor based on germanium encased by a gate electrode and method for producing this transistor Withdrawn EP1889296A1 (en)

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FR0505700A FR2886761B1 (en) 2005-06-06 2005-06-06 A CHANNEL ELECTRODE-CONTINUOUS CHANNEL-BASED CHANNEL TRANSISTOR AND METHOD FOR MANUFACTURING SUCH TRANSISTOR
PCT/FR2006/001177 WO2006131615A1 (en) 2005-06-06 2006-05-23 Channel transistor based on germanium encased by a gate electrode and method for producing this transistor

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