Classifications

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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02107—Forming insulating materials on a substrate
  • H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
  • H01L21/0226—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process
  • H01L21/02263—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase
  • H01L21/02266—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process deposition from the gas or vapour phase deposition by physical ablation of a target, e.g. sputtering, reactive sputtering, physical vapour deposition or pulsed laser deposition
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02107—Forming insulating materials on a substrate
  • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
  • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
  • H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
  • H01L21/02126—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
  • H01L21/0214—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC the material being a silicon oxynitride, e.g. SiON or SiON:H
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  • H01L21/02107—Forming insulating materials on a substrate
  • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
  • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
  • H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
  • H01L21/02164—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material being a silicon oxide, e.g. SiO2
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02107—Forming insulating materials on a substrate
  • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
  • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
  • H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
  • H01L21/0217—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material being a silicon nitride not containing oxygen, e.g. SixNy or SixByNz
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02107—Forming insulating materials on a substrate
  • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
  • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
  • H01L21/02172—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides
  • H01L21/02175—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal
  • H01L21/02181—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal the material containing hafnium, e.g. HfO2
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  • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
  • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
  • H01L21/02172—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides
  • H01L21/02175—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal
  • H01L21/02183—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal the material containing tantalum, e.g. Ta2O5
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02104—Forming layers
  • H01L21/02107—Forming insulating materials on a substrate
  • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
  • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
  • H01L21/02172—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides
  • H01L21/02175—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal
  • H01L21/02186—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing at least one metal element, e.g. metal oxides, metal nitrides, metal oxynitrides or metal carbides characterised by the metal the material containing titanium, e.g. TiO2
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
  • H01L21/2003—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy characterised by the substrate
  • H01L21/2007—Bonding of semiconductor wafers to insulating substrates or to semiconducting substrates using an intermediate insulating layer
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  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/76—Making of isolation regions between components
  • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
  • H01L21/7624—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology
  • H01L21/76251—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques
  • H01L21/76254—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond
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  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/314—Inorganic layers
  • H01L21/316—Inorganic layers composed of oxides or glassy oxides or oxide based glass
  • H01L21/31604—Deposition from a gas or vapour
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  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
  • H01L21/314—Inorganic layers
  • H01L21/318—Inorganic layers composed of nitrides

Definitions

• the invention relates to a method for manufacturing a microelectronic structure involving a molecular bonding. It aims in particular, but not exclusively, a manufacturing process involving the formation, along the bonding interface, of a thin layer.
• a "microelectronic structure” is an element, or a set, made from means or techniques of microelectronics and can be used in particular in the manufacturing processes of microelectronic and / or optical components and / or micro-mechanics; such a structure may comprise a substrate, for example a semiconductor material, optionally combined with one or more other layers or substrates, so as to allow the formation of these components. These processes often involve substrates formed themselves of several layers, which explains this denomination of structure, even in the case of a single substrate.
• Smart Cut allows the detachment of a thin film vis-à-vis a donor substrate (or substrate or starting structure) and its transfer to another substrate (or layer) called receptor (there may be the intervention of an intermediate receptor substrate between the starting substrate and the final receiving substrate).
• This drug is particularly covered by US Pat. No. 5,374,564 (Bruel) and / or its improvements (one can refer in particular to the document US Pat. No. 6,020,252 (Aspar et al.)).
• the thin layer thus separated from the donor substrate has been transferred to an intermediate receptor substrate, there may be subsequent steps involving the intimate contact of the thin-film face released by the separation from the donor substrate, with a final receiving substrate.
• the substrate can be (on the surface or in its mass) of very varied natures; it is often silicon, but it can also be, in particular, other semiconductor materials, for example those of Group IV of the Mendeleev Table, such as germanium, silicon carbide or alloys silicon-germanium, or materials of the group IM-V or the group M-Vl (GaN, GaAs, InP, etc.).
• molecular bonding also called “direct bonding” since there is no addition of material and therefore no interposition of any adhesive
• direct bonding is a particularly interesting method of connection, insofar as it is capable in principle of ensuring very good mechanical strength, good thermal conductivity, good uniformity of thickness of the bonding interface, etc.
• the donor substrate is a base substrate surmounted by a layer or a stack of layers.
• a silicon donor substrate is typically covered with a layer of thermal silica obtained by simple heat treatment of this donor substrate.
• thermal oxide layer which is easily formed on silicon, is that it makes it possible to obtain a molecular bond of very good quality. It is therefore normal that one sought to form, for other materials, such oxide layers suitable for leading to an effective molecular bonding.
• the material of the donor substrate considered, at least in its portion intended to give the thin layer may not itself be compatible with good molecular bonding with the receiving substrate to which it is to be brought into intimate contact. It may then be necessary to provide for the interposition of at least one so-called bonding layer (with reference to the particular type of connection envisaged). Since such bonding layers can not then be obtained simply by heat treatment of the surface of the donor substrate, a specific deposition treatment is required.
• the substrates to be bonded depositing, on at least one of the substrates to be bonded, one or more thin layers (typically of thicknesses between a few tenths and a few hundred microns); these thin layers are chosen so, not only to allow a good molecular bonding with a substrate, but also to have good adhesion to the substrate on which they are deposited.
• some materials may not withstand a temperature above a critical threshold, typically between 200 ° C. and 700 ° C. depending on the materials.
• a critical threshold typically between 200 ° C. and 700 ° C. depending on the materials.
• the germanium should not be brought to a temperature higher than 600 0 C because it is then formed an oxide GeO x which is unstable temperature; it is understood that the formation of such an oxide must be avoided. It follows that during a possible deposition of a bonding layer, care must be taken not to reach or exceed the critical threshold of any of the constituent materials of the donor substrate.
• some materials can not be worn beyond a boundary temperature between the implantation step and the bonding step, as this could cause a phenomenon of blistering or exfoliation resulting from local untimely separations. level of the implanted layer.
• level of the implanted layer Such a risk appears, for example, from 350 0 C with a GaN donor substrate and from 15O 0 C with a LiTaO 3 donor substrate.
• the desired roughness is less than or equal to 0.6 nm RMS in atomic force microscopy AFM, on 1x1 ⁇ m 2 zones on silicon (the expression AFM here refers to "Atomic Force Microscope").
• AFM atomic force microscopy
• this operation involves increasing the deposited thickness by a value equal to that which will then be removed by polishing to achieve the desired roughness. But there are cases where the increase in the thickness of the deposit is not possible, or is not desirable for economic reasons for example.
• oxides thus deposited for molecular bonding applications often have a number of disadvantages.
• the first frequent drawback is related to the significant roughness observed on the surface after such a PECVD or PVD deposit.
• the value of this roughness increases in general with the thickness of the deposited layer, at least for the very thin layers (that is to say, in the present context, layers whose thicknesses are of the order of a few tens of nanometers).
• mechano-chemical polishing means or so-called “smoothing" etching it is therefore necessary to resort to mechano-chemical polishing means or so-called “smoothing" etching; but, as indicated above, such polishing consumes a portion of the thickness of the deposited layer.
• a second frequent disadvantage is related to the low relative density of CVD type oxide deposits, especially in comparison with the thermal oxide of silicon.
• the density of the deposit often guarantees a good bondability due to a high rate of bonds that can be activated on the surface just before bonding, and especially good thermal stability during subsequent annealing, especially for high temperature applications ( greater than 600 ° C., or even greater than 1000 ° C., for the epitaxial deposition of a layer of GaN, for example).
• the solution adopted is to anneal the bonding layers after the deposit.
• a third frequent disadvantage is related to the high level of hydrogen incorporated in the CVD oxide layers, which is inherent in this deposition process.
• the hydrogen content is higher as the oxide is deposited at low temperature.
• these types of layers generally transform (densification) by releasing a portion of the hydrogen which can then accumulate at the bonding interface with the underlying substrate and cause significant defectivity.
• the increase of the pressure of the gases, accumulated around the defects of the interface opposes the adhesion forces and can generate catastrophic detachment forces which cause the separation of the previously glued plates at ambient temperature.
• the invention proposes taking advantage of a particular type of deposition, in particular of oxide, namely an ion beam sputtering deposit ("Ion Beam Sputtering" in English, or IBS for short), which can be generated at very low temperature (typically less than 100 ° C., or even less than 50 ° C.).
• ion Beam Sputtering in English, or IBS for short
• such a layer of deposited oxide spray IBS has particularly advantageous properties for subsequent molecular bonding with a substrate; indeed, such a layer has a very low roughness after deposition, even in the case where the deposited layer has a thickness equal to or even greater than 400 nm, and a good density which gives it good thermal stability (without the need to apply subsequent densification annealing treatment); in addition, such a layer deposition can be preceded, in the same vacuum cycle as that of this deposition, by a step of attacking the receiving face, promoting adhesion, or by the deposition of other layers, by example one or more metal layers (Cr, Pt, Al, Ru, Ir, in particular).
• IBS ion beam sputtering
• This particular technique differs from known PVD techniques for making layers (see above) in that it is carried out at low temperature (for example at room temperature) while ensuring good adhesion of the deposited layer.
• evaporation techniques can also be performed cold, but do not allow to obtain such adhesion.
• the oxides thus deposited without ion beam heating have, at the deposition stage, morphological and thermochemical characteristics which are closer to those of a thermal silicon oxide than those of a conventional CVD deposit:
• IBS-type deposits a high ability to molecularly bond substrates or microelectronic structures.
• oxides of the IBS type are deposited at very low speed (typically of the order of one angstrom per second), close to that of the thermal oxidation of silicon, which allows a good control of the deposited thickness (within one nanometer).
• the respective roughness values of a deposit of 400 nm of silicon oxide produced on silicon by IBS and in the form of a thermal oxide are, respectively, of:
• SiS 2 , TiO 2 , Ta 2 Os, etc. by IBS, in the field of optics or optronics, because of their optical characteristics ( thickness, refractive index, in particular), related to the fact that this technology allows both a good control of the stoichiometry and thickness of deposited layers (thanks to the moderate rate of deposition).
• SiO2 one can notably refer to the article "Effect of the working gas of the ion-assisted source on the optical and mechanical properties of SiO2 films deposited by dual ion beam sputtering with Si and SiO2 as the starting materials by Jean-Yee Wu and Cheng-Chung Lee, in Applied Optics, Vol 45n No. 15, May 20, 2006, pp. 35103515.
• these layers have both a low surface roughness even for high thicknesses (a few hundred nanometers, or a few tenths of a micron), a high density (or compactness) and a large thermal stability (a low level of hydrogen bonds incorporated in the layers compared with conventional bonding layers, for example of the CVD type, which makes it possible to reduce hydrogen degassing during annealing, which results in good stability).
• the IBS deposits have, for an identical or even lower deposition temperature, fewer silanol (Si-OH) type bonds than the CVD type oxides conventionally used as a molecular bonding layer.
• the IBS layers can be deposited at a low temperature (close to ambient temperature), their use makes it possible to produce molecular bonding layers on structures that prevent significant heating (for example in the case of a structure having an interface previously implanted and can induce a separation (case of the "Smart Cut ®" process).
• the IBS technology makes it possible to deposit not only oxides, but also nitrides, metallic species, oxynitrides (in particular SiO x Ny), etc.
• the invention thus proposes a method of manufacturing a microelectronic structure, comprising:
• IBS ion beam sputtering
• the above definition includes the case where, as will be indicated below, at least one underlying layer is interposed between the first structure and the coating layer: the coating layer is not formed directly on the surface of the first structure (formed of the first material); however, since it is formed in close proximity to it, it is well located on the surface of this structure, albeit indirectly through one or more underlying layer (s).
• the implementation of the ion beam spraying is done at low temperature and leads to the formation of a bonding layer whose properties allow the subsequent realization of a molecular bonding very good quality.
• the implementation of the method of the invention leads to the formation of a structure comprising, on a starting substrate, at least one thin layer of IBS type allowing a molecular bonding of the donor substrate (or structure) with a substrate (or structure) receiver.
• the formation of the coating layer is carried out after pickling of the surface of the first structure inside the chamber where the spray deposition is carried out.
• another coating layer is formed on the second structure before molecular bonding.
• This other coating layer is preferably also carried out by ion beam sputtering.
• This other layer of coating can be made in the same second material as the first coating layer, which guarantees a good molecular bonding.
• the implementation of the invention is advantageously combined with the formation of a thin layer, that is to say that ions are implanted in at least one of the first and second structures in order to form a buried layer of micro-cavities and, after molecular bonding, the fracture of this structure is caused at this buried layer of micro-cavities.
• the implantation step can be performed, either before the formation of the IBS layer, or after this formation, without risk of causing bubbling and separation of the implanted film during the deposition step.
• This second material is preferably an oxide, preferably a silicon oxide. More generally, the bonding layer is advantageously composed of an oxide layer selected from SiO 2 , TiO 2 , Ta 2 O 5 , HfO 2 , etc.
• this second material is a nitride, for example selected from the group consisting of Si 3 N 4 , TiN, WN, CrN.
• the second material is an oxynitride, for example silicon.
• the relative proportions of oxygen and nitrogen of the oxynitride can be fixed, or on the contrary vary in the thickness of the layer (to do this, it is sufficient to vary the parameters of the ion beam sputtering) .
• the second material is a metal element or a metal alloy, for example selected from the group consisting of Cr, Pr, Al, Ru, Ir.
• more than one layer is deposited on the donor substrate, ie there is, under the coating layer, at least one underlying layer, advantageously deposited by sputtering. ion beam.
• the underlying layer is made of a metallic material or a metal alloy and where the coating layer is oxide, which amounts to forming a buried electrode.
• the bonding layer is advantageously amorphous.
• the material on which the IBS layer is formed is preferably a group IV material of the periodic table of the elements, for example a semiconductor material such as silicon. It can also be a material included among the following materials: germanium, gallium nitride, gallium arsenide, lithium tantalate and lithium niobate.
• the thickness of the IBS oxide bonding layer is preferably between a few nanometers and a few hundred nanometers; the thickness of the layer is in fact advantageously less than 1 micron, preferably at most equal to 600 nanometers.
• the structure thus obtained has in practice a roughness of less than about 0.25 nm RMS.
• the surface of the IBS layer for example, in a conventional manner, by means of a chemical mechanical polishing or a UV-ozone treatment, or via a reactive plasma.
• the invention thus proposes a method of manufacturing a microelectronic structure (the term "micro-technological” is sometimes also used) by molecular bonding of a first structure and a second structure, in which at least one of the two structures is formed with a bonding layer having a thickness of less than one micron, preferably less than 600 nm, by sputtering. ion.
• this bonding layer is an oxide, a nitride or an oxynitride of a different element from that of which the underlying structure is constituted; this underlying structure is advantageously constituted by a material different from silicon, having no stable thermal oxide, such as, in particular, germanium, gallium nitride, gallium arsenide, lithium tantalate and lithium niobate, while the bonding layer preferably comprises silicon oxide.
• This bonding layer may be separated from this underlying structure by a metal layer, advantageously deposited, also, by ion beam sputtering.
• This bonding layer is advantageously an electrical insulator and the molecular bonding is advantageously followed by a fracture step, at a temperature at most equal to 400 ° C., preferably at most equal to 200 ° C., at a layer micro-cavities resulting from a previous step ion implantation in the other structures so as to form a semiconductor-on-insulator structure.
• ion beam sputtering is mentioned, fortuitously, in document US 2007/0017438, for the formation of a tangential stressing layer of underlying islands, about a Si-W alloy, but that, to ensure such stressing, this layer is very thick (between several microns and several millimeters), so as to avoid any phenomenon of waviness; this is fundamentally different from the formation of a thin coating (less than one micron) intended to serve as a bonding or bonding layer to allow good molecular bonding between two structures which otherwise could not be effectively bonded molecular way.
• the IBS layer is a bonding layer which, as a result, is normally intended to be buried
• the bonding layer proposed by the aforementioned document is only intended to be released as a surface layer, then etched and heated to alter the stress level of the underlying islands.
• FIG. 1 is a sectional view of a donor substrate being implanted to form a weakened layer
• FIG. 2 is a sectional view of this substrate after deposition of a layer by ion beam sputtering
• FIG. 3 is a view after molecular bonding
• FIG. 4 is a view after separation at the level of the weakened layer
• FIG. 5 is a view of the rest of the donor substrate, ready for a new cycle
• FIG. 6 is a block diagram of an ion beam spray deposition installation.
• Figures 1 to 5 show an example of a method embodying the invention.
• This process comprises the following steps:
• a substrate 1 constituting a first structure having, at least on the surface (or in the immediate vicinity thereof if a thin layer is deposited therein), a first material
• This method thus comprises, in a case of layer transfer (reference 2) from a donor substrate (or first structure) 1 to a receiving substrate (or second structure) 4, a step consisting of an oxide deposition 3, controlled thickness from a few nanometers to a few tenths of a micron, by IBS.
• This deposit is made “cold”, that is to say at a temperature below 100 0 C, typically to 40 0 C (this temperature corresponds to the surface temperature of the substrate due to the deposit), or even at the temperature room.
• This deposit can therefore be made on any substrate, processed or not, without risk of degradation of the result of the previous steps or properties of the surface of the donor substrate.
• This layer 3 sprayed IBS has, in the example of Figures 1 to 5, the main function of being a bonding layer. However, it may have, in addition, other functions such as, in particular:
• Sacrificial layer for example for producing microsystems such as acceleration or pressure sensors, etc.
• Mirror layer or optical filter possibility of introducing an optical function by a stack of layers of different types and / or thicknesses
• Buried electrode for example a metal layer between a substrate and an oxide layer
• Barrier layer for example nitride such as TiN, WN, etc.
• the constituent material of the layer deposited by IBS sputtering is thus an oxide (during the production of a bonding layer), but may therefore alternatively be a nitride, an oxynitride, a metal element or alloy, etc. It should be noted that it is not necessary to carry out densification treatment of IBS oxides since they are already very dense, from the time of deposition, with a density compatible with a very good quality bonding.
• the deposition of the IBS layer takes place before implantation.
• a cleaning is performed in the deposition chamber IBS, before deposition, so as to prepare the surface of the donor substrate, and thus improve the adhesion of the deposited layer on the surface of this substrate.
• Such cleaning may indeed consist of a bombardment of the surface with neutral ions, such as argon or xenon (this preparation can be described as pickling).
• RIBS technology or “Reactive IBS”
• Reactive IBS Reactive IBS
• DIBS Direct IBS
• assistance beam which makes it possible to increase the compactness of the layers but also to control the stoichiometry of the layer during the deposition. possibly playing on an additional gas supply (for example oxygen, in the case of an oxide deposit).
• FIG. 6 is a block diagram of an installation adapted to the implementation of this DIBS technology, in the case, for example, of the formation of a silicon oxide coating on a set of substrates.
• an ion source (sputtering source) 11 which generates a beam 12 of mono-energetic ions (typically between 500 and 1500 eV) positive, defined spatially.
• the beam here formed of argon ions, bombards a target 13 made of the material to be deposited (in this case, SiO2). Sprayed species are emitted in the half-space facing the target and come to condense on the substrates 14 (here carried by a planetary support 14A) to form the coating layer 3 of FIG. 2 (not shown in this FIG. 6),
• an assistance source 15 emitting ions of lower energy (typically from 50 to 100 eV), according to a beam 16 which aims to increase the compactness of the layers deposited on the substrates, but also to control the stoichiometry of these thin layers being deposited (in this case, it is possible to substitute all or part of the ionized neutral gas stream of the source 15 with oxygen or another gas reactive with the layer being formed); this source of assistance can also be used as a source of stripping flux of the substrates before starting the actual deposit.
• this source of assistance can also be used as a source of stripping flux of the substrates before starting the actual deposit.
• the pumping of the deposition chamber is advantageously of "dry" type, to avoid any particulate and organic contamination: the limit vacuum is typically 2.10 8 Torr.
• Layers of typical thickness of 0.1 to 1 micron can be made with or without a source of assistance.
• this assistance source is advantageously used only for stripping the surface of the substrates, for 5 minutes, for example.
• the neutral gas may be argon or xenon.
• deposition gun xenon: voltage of 1000V, intensity of 100mA, and flow rate of 2.1 sccm (that is to say 2.1 cm 3 standard per minute ("standard cubic centimeters per minute"),
• the IBS technology corresponds to very low deposition rates (typically of the order of one angstrom per second, compared with deposition rates of the order of 100 to 1000 angstroms per second in the case of PECVD or LPCVD technologies), which contributes to their high density.
• One way to evaluate the density of a thin coating is to measure the rate of chemical etching (the density of a coating is inversely proportional to this speed).
• PECVD LF deposit around 300 ° C.: speed of 1600 angstroms / min
• HTO DCS HTO DCS
• deposit around 900 ° C. speed of 1550 angstroms / min.
• HTO DCS means "High Temperature Oxide DiChloroSiloxane”
• the etching rate of the coating obtained by sputtering IBS is only slightly greater than that of the thermal oxide, so that its density is only slightly less than that of this thermal oxide. It is observed, on the other hand, that the etching rate of this IBS coating is substantially lower than that of coatings obtained by CVD type techniques, and that its density is therefore substantially higher.
• the oxides deposited by IBS thus allow a quality of bonding comparable to that of a thermal oxide, even when it is not a question of the oxide of the material constituting the carrier substrate, with the advantage of being realized at very high temperatures. low temperature, so to be compatible with any type of substrate, especially processed.
• the implantation takes place in the first structure; alternatively, this implantation takes place in the second structure (there may even be an implantation in the two structures).
• the coating layer is formed on the surface of this first structure, and in a direct manner (therefore directly on the part of this substrate having the first material on the surface); alternatively, this coating layer is made on the second structure; this coating layer may also be deposited indirectly on the surface of this first or second structure, on an underlayer (or underlying layer), formed on the surface of this structure (possibly also by sputtering). ion). There may also be a coating layer on each of the two structures.
• a crystalline GaN substrate ( 70 Ga 14 N) is implanted with H ions under the following conditions:
• a SiO 2 layer with a thickness of between 500 nm and 1 micron is then deposited by IBS sputtering onto the implanted substrate.
• the GaN substrate Prior to the actual deposition step, the GaN substrate is cleaned, in situ (in the IBS deposition chamber), by a stripping step for 5 minutes.
• the GaN substrate carrying the oxide layer is then adhesively bonded to a sapphire substrate.
• a plasma treatment is carried out on the surface of the oxide layer, for example an O 2 plasma.
• the fracture at the level of the implanted layer is then caused by a heat treatment in the range from 200 ° C. to 400 ° C.
• the oxide layer obtained by IBS is, by its density, quite suitable for a subsequent step of epitaxy at high temperature (typically between 1000 0 C and 1100 0 C) to form the active layers of the diodes LED.
• LiTaO 3 substrate is implanted, through the oxide layer, with H ions under the following conditions:
• the LiTaO 3 substrate, with the oxide layer, is then adhesively bonded to a LiTaO 3 substrate, covered with a chromium bonding layer.
• the bonding is for example carried out by a chemical cleaning, by a bath called "Caro" (H2SO4 / H2O2).
• a LiTa ⁇ 3 / SiO 2 / Cr / LiTaO 3 structure is thus obtained which can, for example, be used for the production of ferroelectric memories.
• the substrate is then implanted, through the oxide layer, with H ions under the following conditions:
• the substrate, with the oxide layer is then adhesively bonded to a silicon substrate coated with a thermal oxide layer.
• a chemical-mechanical polishing of the oxide layer followed by brushing and rinsing the plates.
• the fracture is then caused at the level of the implanted layer, by a heat treatment of 330 0 C - 1 h.
• GeOI Germanium on insulator or "Ge On Insulator”
• This substrate is bonded, by molecular adhesion, to another LiTaO 3 substrate, on which IBS sputtering has previously been deposited. 400 nm Si ⁇ 2 layer, using chemical mechanical polishing and brushing.
• the fracture is provoked at a temperature below 200 ° C., for example by application of mechanical stresses.
• a LiTa ⁇ 3 / electrode / insulator / LiTaO 3 structure is thus obtained.
• He-ions are implanted in this substrate under the following conditions:
• SiO 2 layer 600 nm thick is then deposited by IBS sputtering.
• This substrate coated with SiO 2 is adhesively bonded to a second silicon substrate, covered with a 600 nm layer of SiO 2 also by IBS sputtering.
• the fracture is caused at the level of the implanted layer and obtains a Si / Si ⁇ 2 / LiNb ⁇ 3 structure , which therefore comprises a buried insulating layer.

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