Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
  • B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
  • B81B3/0002—Arrangements for avoiding sticking of the flexible or moving parts
  • B81B3/001—Structures having a reduced contact area, e.g. with bumps or with a textured surface
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • 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
  • H01L21/76256—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 using silicon etch back techniques, e.g. BESOI, ELTRAN
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B81—MICROSTRUCTURAL TECHNOLOGY
  • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
  • B81C2201/00—Manufacture or treatment of microstructural devices or systems
  • B81C2201/11—Treatments for avoiding stiction of elastic or moving parts of MEMS
  • B81C2201/112—Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts

Definitions

• the general field of the invention is that of the manufacture of microstructures from substrates ("wafer level" in English), for example by means of micromachining or chemical treatment techniques used in microelectronics (deposition and etching of layers, photolithography , And so on).
• the invention relates more particularly to certain MEMS type microstructures (initials of the English words “Micro-Electro-Mechanical Systems”, ie “Microscopic Electro-Mechanical Systems”), such as various detectors and actuators, which are obtained by release of moving parts (for example membranes or earthquakes).
• a first technique is thinning (mechanical by rectification and / or smoothing, and / or chemical, and / or mechanical-chemical).
• a second technique is the fracture at the level of a fragile zone, this fragile zone having been created, before lad ite ad molecular hesitation, at a certain depth in one of the two plates, for example by implantation of one or more gaseous species:
• patent application FR-2681472 discloses such a process, which is now known as the "Smart-Cut ®” (see for example the article of B. Aspar et al. entitled “the Nature of Generic the Smart-Cuf Process for Thin- Film Transfer ”, in Journal of Electronic Materials, vol. 30, n ° 7, 2001).
• the material constituting a sacrificial layer is therefore different, from the chemical or crystallographic point of view, from the material constituting the “non-sacrificial” layers, ie intended to be kept after elimination of the sacrificial layer.
• the layer of silicon oxide plays the role of “sacrificial layer”, and the layers of silicon that of “non-sacrificial layers”.
• This embodiment is relatively simple to implement, and it makes it possible to obtain a variety of microstructures. For example, good quality pressure sensors can thus be produced.
• This accelerometer comprises, within a thin layer, a first part cut from this thin layer and a second part constituted by the rest of the thin layer, the first part being connected to the second by means of flexible beams allowing this first part, or "sensitive" part, to move with a certain amplitude in the plane of the thin layer.
• This device is used to measure the accelerations of any system of which it is integral, by means of a variation in electrical capacity caused by said displacement.
• Other detailed examples of such microstructures can be found in the article by B. Diem et al., Entitled “SOI 'SIMOX'; from bulk to surface micromachining, a new age for silicon sensors and actuators ”, in Sensors and Actuators, vol. A 46 - 47, pages 8 to 16 (1995).
• a first known means for preventing this sticking consists in reducing the sticking energy of the released layer and the substrate.
• these techniques use methods of chemical preparation of surfaces which are incompatible with the high temperatures usually required for the subsequent stages of manufacturing MEMS.
• a second known means for preventing this sticking consists in arranging so that, when these two surfaces are brought together, the effective contact area is small. Such a method has been disclosed in patent FR 9 508 882.
• This method consists in keeping the released layer and the substrate at a distance by etching the intermediate sacrificial layer so as to create stops on each of the faces facing the released layer and of the substrate.
• Another such method has been described in the article by RL Alley et al. «Surface Roughness Modification of Interfacial Contact Polysilicon in Microstructures” (Proceedings of the 7th International Conference on Sensors and Actuators Semiconductors).
• This article proposes a process for developing components with movable parts including steps to lead to a component whose free facing faces have a "roughness” capable of avoiding undesirable sticking between said faces (for a statistical definition of "roughness , "We will refer to this article; we can for example make roughness measurements with an atomic force microscope exploring areas, for example, of 1 ⁇ m x 1 ⁇ m).
• This process consists, during the chemical release stage of the structure, of roughening the surfaces concerned so that the effective contact area is limited to the tops of the roughness of these surfaces.
• the article by RL Alley et al. Its main purpose is to study how the bonding strength decreases when the roughness increases.
• this method provides for the deposition of a surface film on the substrate of the stacked structure;
• this deposition is not always possible.
• this method does not make it possible to obtain a surface film to be released which is monocrystalline if the material of the sacrificial layer is amorphous; it also does not make it possible to obtain a monocrystalline film, of silicon for example, on a sacrificial layer of polymer material due to the incompatibility between the deposition temperature of this silicon film and the temperatures that a polymer can usually withstand .
• the present invention therefore relates to a method of manufacturing a stacked structure, if necessary of large dimensions, if necessary over the entire surface of a wafer having for example a diameter of 200 mm, and subsequently allowing the production of any which MEMS type component without bonding mobile or deformable mechanical structures.
• This manufacturing process must be able to be applicable whatever the characteristics of said components, in particular their size or the materials used, in particular when the surface layer to be (at least partially) released is monocrystalline, or cannot be deposited simply on the structure. stacked required.
• the invention therefore proposes, according to a first aspect, a method of manufacturing a stacked structure, said method being remarkable in that it comprises the following steps: a) a first plate and a second plate are taken, such that at least one of said first and second plates has a structured surface, at least in part, b) a sacrificial layer is produced on at least part of the surface of the first plate and / or the surface of the second plate, and c) the two plates are glued together.
• the implementation of the method according to the invention provides a stacked structure comprising a sacrificial layer located between two substrates, and in which at least one of the two substrates is such that at least part of its surface in contact with said sacrificial layer is "structured".
• a surface is "structured" when it is found to be essentially incapable of sticking to another predetermined substrate.
• a surface can for example be structured due to the physicochemical nature of this surface, or of a coating applied to this surface; a surface can also be structured due to a roughness greater than a predetermined threshold, for example equal to approximately 0.2 nm RMS.
• the production of structured surface (s) takes place before or during the manufacture of the stacked structure, and therefore independently of the manufacture of a MEMS type component. Thanks to the invention, it is advantageously possible to choose, to constitute the stacked structure, any set of materials which may subsequently be useful for the production of a MEMS component. For example, it is possible to obtain a stack comprising a thin layer of silicon on a sacrificial layer of polymer, or a thin layer of monocrystalline silicon on a sacrificial layer of silicon oxide. It will also be noted that the method according to the invention does not impose any limitation on the lateral dimensions of the stacked structure obtained.
• the free surface of a sacrificial layer or, where appropriate, of the two sacrificial layers, and / or, where appropriate, is smoothed. of the free surface of one of said plates.
• This bonding may for example be a molecular bonding, or else a bonding using a sacrificial glue, that is to say an adhesive capable of being subsequently removed, for example when using said stacked structure to manufacture a component comprising a part mobile or deformable.
• step c) can be "assisted" for example by mechanical means and / or by plasma and / or heat treatment, these operations being carried out during or after this bonding, under a specific atmosphere or at 'outdoors. Thanks to these provisions, it is possible, in particular, to consolidate the various interfaces and / or make them compatible with the future stages of production of the MEMS components. It is also thus possible to make adherent two rough surfaces which would not stick to each other spontaneously. According to yet other particular characteristics of the invention, following step c), at least one of the two plates is thinned.
• the parts of a MEMS type component which will become mobile after elimination of the sacrificial layer situated in contact with these parts.
• the two plates as well as the sacrificial layer can, of course, be either simple or composite, that is to say formed themselves from a stack of layers of various materials.
• the stacked structure thus obtained can advantageously be of the SOI type.
• the first plate, as well as the second plate can be made of silicon, or of a semiconductor other than silicon, for example SiC, GaN, or InP, or else a non-semiconductor material, such as LiNbO 3 , LiTaO 3 , a glass, fused silica, or a superconductive material.
• the first plate, as well as the second plate can also be any combination of these materials, in particular a stack of monocrystalline / Si polycrystalline, or SiC / Si, or InP / Si, or SiC monocrystalline / SiC polycrystalline, or else Polycrystalline SiC / SiO 2 / SiC.
• the material constituting the sacrificial layer produced on the first plate and / or the material constituting the sacrificial layer produced on the second plate can be, for example, silicon oxide or a polymeric material.
• at least one of said plates initially has a surface layer.
• this surface layer can have the effect of structuring the surface of the plate on which it rests, due to the physicochemical nature of this surface layer.
• the invention also relates to various stacked structures. It thus relates, firstly, to a stacked structure which has been manufactured by any of the methods succinctly described above.
• the invention relates to a stacked structure, said structure being remarkable in that it comprises a sacrificial layer situated between a first substrate and a second substrate, and in that at least one of said first and second substrate has a structured surface , at least in part.
• the two substrates as well as the sacrificial layer can, of course, be either simple or composite, that is to say formed themselves by a stack of layers of various materials.
• the stacked structure thus obtained can in particular be of the SOI type.
• the first substrate, as well as the second substrate can be made of silicon, or of a semiconductor other than silicon, for example SiC, GaN, or InP, or of a non-semi-material conductor, such as LiNbO 3 , LiTaO 3 , a glass, fused silica, or a superconductive material.
• the first substrate, as well as the second substrate can also be any combination of these materials, in particular a stack of monocrystalline / Si polycrystalline, or SiC / Si, or InP / Si, or SiC monocrystalline / Si polycrystalline, or else Polycrystalline SiC / SiO 2 / SiC.
• the material constituting the sacrificial layer can be, for example, silicon oxide or a polymeric material.
• At least one of the two substrates is a thin layer.
• the advantages offered by these materials are essentially the same as those offered by the corresponding manufacturing processes. Other aspects and advantages of the invention will appear on reading the detailed description, which will be found below, of particular embodiments given by way of nonlimiting examples.
• This description refers to the accompanying drawings, in which: - Figure 1 shows a silicon wafer before the implementation of the invention, - Figure 2 shows the same silicon wafer after application of a first step of a manufacturing method according to an embodiment of the invention, - Figure 3 represents a second step of this method, - Figure 4 represents a third step of this method, - Figure 5 represents a fourth step of this method, and - Figure 6 shows a fifth step in this process.
• a standard silicon wafer 1 whose surface 2 has a roughness r 2 which is usually of the order of 0.1 nm (FIG. 1).
• This surface 2 is then "structured" (FIG. 2), for example by creating a roughness f 2 on the surface 2 of the plate 1.
• a roughness r " 2 will be created in the range from 0.2 nm to a few
• the roughness to choose depends in particular, for example, on the thickness of the sacrificial intermediate layer, on the geometric parameters of the future component with moving parts targeted, and stresses in the surface film. Those skilled in the art will be able to determine the roughness to be used to avoid any undesirable sticking within this component.
• a sacrificial layer 3 is produced (FIG. 3), on the surface of this plate 1.
• the layer 3 can for example be made of silicon oxide.
• this layer 3 can be obtained by thermal oxidation in a dry or humid atmosphere, or by deposition (LPCVD, PECVD, or any other method adapted).
• the roughness r at the surface 4 of this layer 3 can be of the same order of magnitude as the initial roughness of the plate 1, or higher (it is known to increase the roughness by depositing successive films, the roughness increasing with the number of films deposited and their thickness), or reduced by means, for example, of the deposition of a smoothing oxide (not shown) produced at low temperature and whose creep on the surface can be caused, for example, by a heat treatment adapted.
• a smoothing oxide not shown
• a roughness r, ⁇ somewhat less by performing, in a third step (figure 4), a surface smoothing, such as by a slight chemical mechanical polishing and / or by a heat treatment under a specific atmosphere and / or by depositing a smoothing layer (not shown).
• a second plate 5 is taken, for example made of polycrystalline silicon (which may moreover possibly have on the surface a layer 9 of another material, for example monocrystalline silicon or SiC ), which is bonded to layer 3, preferably by molecular adhesion. Bonding can also be carried out using a type of sacrificial glue, that is to say which can be selectively removed, for example a photosensitive polymer.
• a “bonding aid” firstly by bringing the surfaces into contact, where appropriate after application of a plasma treatment of these surfaces, then by applying mechanical stress and / or heat treatment to the stacked structure, under a specific atmosphere or in the open air.
• a heat treatment, applied during or after bonding also makes it possible to consolidate the various interfaces and / or make it compatible with the future stages of production of MEMS components.
• at least one of the two plates 1 and / or 5 can be thinned (plate 5 in FIG. 6), so as to obtain a stacked structure 100, for example of the type
• Thinning can be carried out according to any of the known methods, such as those described in the introduction. It will be noted that it is perfectly possible, according to a variant of the invention, to place steps of the process for producing the microstructure, for example etching in the sacrificial layer of the areas in contact with the moving parts, in the middle of the steps. that we have just described, for example before the bonding step.
• the movable parts may possibly also be defined before the bonding step in the subsequently thinned plate; after bonding and thinning of the plate comprising the movable parts, it is possible to apply a heat treatment to reinforce the bonding interface of the stacked structure without pressure constraint (said zones underlying the movable parts emerging at the surface) .
• the method can relate to all or only part of the surface of at least one of the plates or of one of the treated films.
• one can obtain a predetermined structure on a localized area using a lithography process.
• the "structuring" of a given surface can be obtained without necessarily making this surface rough.
• the surface to be structured can be treated by nitriding.
• a layer of an “anti-sticking” material that is to say whose physicochemical nature is such that it opposes any undesirable subsequent sticking (naturally , we can optionally combine the roughness creation techniques and surface treatment or making an "anti-sticking” layer). It is thus possible, initially, to deposit a surface layer 6 (not shown), for example made of Si 3 N, on a first plate 1 of any roughness. We can then create on the surface 2 of this surface layer 6, as explained above, a roughness, for example due to the conformation by deposition on a rough surface.
• the surface of this surface layer 6 so as to make it incompatible with an undesirable bonding with the substrate intended to be located opposite the surface layer 6; it is possible, for example, according to known methods, to make the surface of a surface layer 6 of Si 3 N hydrophobic; other materials than silicon nitride Si 3 N can be used here, such as diamond, or AI 2 O 3 or even ZrO 2 .
• the sacrificial layer 3 is then deposited on the surface layer 6 which is, as explained above, suitable for bonding, for example molecular bonding, with the plate 5 (which is made of silicon in this embodiment), possibly after a step of planarization by means of chemical mechanical polishing or heat treatment.
• the collage can be "assisted” as explained above.
• the selective attack of the layer 3 will make it possible to free the structured surface of the surface layer 6: during this selective attack, for example using hydrofluoric acid, the material used for the sacrificial layer 3, for example silicon oxide SiO 2 , will be attacked, while that used for the surface layer 6, for example silicon nitride Si 3 N 4 , will not be.
• the material used for the sacrificial layer 3 for example silicon oxide SiO 2
• that used for the surface layer 6, for example silicon nitride Si 3 N 4 will not be.
• Embodiments have been described above in which only the surface 2 of the first plate 1 has been structured; but it is clear that, in the context of the invention, it is equally possible, in addition or instead, to structure the surface 7 (not shown) of the second plate 5 (the latter optionally comprising a surface layer 9, as described above).
• a sacrificial layer 3 was produced only on the first plate 1; but it is clear that, in the context of the invention, it is equally possible, in addition or instead, to produce a sacrificial layer 8 (not shown) on the second plate 5. Then the two plates are bonded as described above, after, optionally, smoothing the surface 10 (not shown) of this sacrificial layer 8. It is clear that it is possible, for example by localized deposition or by etching, to produce a sacrificial layer which n 'is not continuous; this makes it possible to define already stacked areas in the stacked structure.
• any structure comprising a thin layer adhering to a buried layer to be sacrificed locally, for example of silicon oxide, the latter resting on a support which may be other than silicon.
• a person skilled in the art can combine several of the methods described here for the production of specific stacked structures according to the invention.
• the surface structure required by the invention is not necessarily homogeneous over the whole extent of the surfaces concerned: for certain applications, it may for example be advantageous to produce a surface whose structure is distributed randomly, or else respects a certain distribution on the surface of one of the plates.

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• 2003
  • 2003-07-21 FR FR0308865A patent/FR2857953B1/fr not_active Expired - Fee Related
• 2004
  • 2004-07-15 AT AT04767683T patent/ATE414673T1/de not_active IP Right Cessation
  • 2004-07-15 JP JP2006520855A patent/JP2006528422A/ja active Pending
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