WO2005018090A1 - Microsystem incorporating at least one resonant structure in a cavity under a controlled atmosphere, and method for producing the same - Google Patents

Microsystem incorporating at least one resonant structure in a cavity under a controlled atmosphere, and method for producing the same Download PDF

Info

Publication number
WO2005018090A1
WO2005018090A1 PCT/CH2004/000491 CH2004000491W WO2005018090A1 WO 2005018090 A1 WO2005018090 A1 WO 2005018090A1 CH 2004000491 W CH2004000491 W CH 2004000491W WO 2005018090 A1 WO2005018090 A1 WO 2005018090A1
Authority
WO
WIPO (PCT)
Prior art keywords
cavity
silicon
resonant structure
microsystem
substrate
Prior art date
Application number
PCT/CH2004/000491
Other languages
French (fr)
Inventor
David Ruffieux
Original Assignee
Csem-Centre Suisse D'electronique Et De Microtechnique
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 Csem-Centre Suisse D'electronique Et De Microtechnique filed Critical Csem-Centre Suisse D'electronique Et De Microtechnique
Publication of WO2005018090A1 publication Critical patent/WO2005018090A1/en

Links

Classifications

    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02Details
    • H03H9/05Holders; Supports
    • H03H9/10Mounting in enclosures
    • H03H9/1007Mounting in enclosures for bulk acoustic wave [BAW] devices
    • H03H9/105Mounting in enclosures for bulk acoustic wave [BAW] devices the enclosure being defined by a cover cap mounted on an element forming part of the BAW device
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H03H2003/027Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the microelectro-mechanical [MEMS] type
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/24Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
    • H03H9/2405Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive of microelectro-mechanical resonators
    • H03H2009/241Bulk-mode MEMS resonators

Definitions

  • the present invention relates to a microsystem and, more particularly, a microsystem incorporating at least one resonant silicon structure in a cavity under controlled atmosphere as well as its manufacturing process.
  • the precise time bases that can be found today, for example in electronic watches, are all based on a quartz resonator which is encapsulated, under vacuum, in a metal case so as to offer a high quality factor.
  • Such a resonator must be associated with an integrated circuit to constitute an oscillator having a stable frequency reference.
  • These two elements generally have separate substrates and encapsulation methods which require the use of different manufacturing techniques. After their manufacture, the resonator and the integrated circuit are assembled during the assembly process.
  • the most common resonator for watchmaking applications, is a 32 kHz tuning fork type quartz resonator which oscillates in a bending mode. Once encapsulated, it has a diameter of approximately 1 mm and is commercially available at a price not exceeding 0.1 to 0.2 Swiss francs.
  • the integrated circuit is most often produced in CMOS technology and is mounted on a printed circuit to which the resonator is also fixed and electrically connected. The need to use different basic materials and manufacturing techniques for these two elements increases their manufacturing cost and prevents compact production of the assembly.
  • an object of the present invention is a microsystem incorporating at least one resonant silicon structure, in a cavity under controlled atmosphere, and the manufacture of which is compatible with that of integrated circuits.
  • Another object of the invention is a method for producing and assembling resonant structures, produced in a silicon substrate on insulator and associated with an integrated circuit produced in a silicon substrate.
  • Yet another object of the invention is a method of assembling resonant structures associated with an integrated circuit making it possible to obtain an assembly of relatively thin thickness.
  • Another object of the invention is an assembly bringing together at least one resonant structure in a vacuum cavity and an integrated circuit to which said structure is electrically connected.
  • the microsystem of the invention incorporating at least one resonant silicon structure in a cavity under controlled atmosphere is characterized by the fact that said at least one resonant structure is produced in a silicon base, itself fixed on a silicon substrate by through an insulating layer and so as to form, at least partially, said cavity and in that it comprises a cover, on the one hand, fixed to said base by closing means ensuring the closing and the sealing of said cavity and, on the other hand, connected to said at least one resonant structure by connection means for electrically connect the latter to the outside of said cavity.
  • the microsystem of the invention also has all or some of the characteristics set out below: - the cover is made of silicon and comprises one or more layers of conductive lines; - The cover further includes an integrated circuit; - the resonant structure is a resonator; - the resonant structure is a set of two resonators; - The closure means are made of a polymer material; - The connection means are made of an alloy of tin and lead.
  • the microsystem of the invention can be manufactured with manufacturing techniques compatible with those of the integrated circuit with which it is associated.
  • the method of manufacturing a microsystem according to the present invention is characterized in that it comprises the steps of: - oxidizing one face of a silicon base so as to form a layer of silicon oxide; - make at least one cavity; assembling said silicon base and said substrate so as to constitute an SOI type substrate; producing, in said silicon base, at least one resonant structure disposed, at least partially, above said cavity; attaching to said SOI type substrate a cover by closing means ensuring the tightness of said cavity and connection means ensuring the connection of said resonant structure to the outside of said cavity.
  • FIG. 1 shows, seen from above, a set of two resonators made in a silicon substrate;
  • Figures 2.a and 2.b show, in section, the wafers intended to produce the resonators of Figure 1;
  • Figure 3 shows, in section, the resonators of Figure 1;
  • FIGS. 4.a to 4.e show steps for producing electrodes on either side of a piezoelectric activation layer;
  • Figure 5 shows a microsystem according to the invention.
  • the resonators 2 and 3 of FIG. 1 have been described in the aforementioned French patent application. They are made in a silicon on insulator substrate called, thereafter, SOI substrate.
  • This SOI substrate comprises a silicon base 10, one face of which has been oxidized to give a layer 11 of silicon oxide (Si0 2 ), and a silicon substrate 20, to which said base 10 is welded (FIG. 2). This welding is done by pressing the base 10 and the substrate 20 one against the other under controlled atmosphere and temperature. This technique is called "Silicon Fusion Bonding". As shown in the figure, cavities were made in the silicon substrate before the two substrates were welded. After welding, the SOI substrate is thinned, for example by grinding its upper part, to a thickness of approximately 50 ⁇ m, and then polished, the resonant structures are produced in the manner described in the aforementioned patent application.
  • Figure 3 is a sectional view, along the axis AA of Figure 1, of the resonators 2 and 3 after manufacture.
  • the resonators 2 and 3 are cut from the silicon base 10 on which were deposited, by "sputtering", metal electrodes 32 and 33. Simultaneously with the deposition of the electrodes 32 and 33, contacts 31 are made on the base 10.
  • a layer of aluminum nitride (42, 43) is deposited which constitutes the piezoelectric actuation layer of said resonators.
  • This AIN layer receives a new metallic layer which will serve as a second electrode (52, 53) for said resonators.
  • the cavities, above which the resonators 2 and 3 are arranged are produced, not by attacking the substrate 20 but, by attacking the oxide layer 11 after the cutting of said resonators .
  • This attack on the oxide layer can be done wet using a hydrofluoric acid (HF) solution.
  • FIG. 4 shows in detail the steps for producing the electrodes and the AIN layer of the resonators.
  • the base 10 is assumed to have been welded on a substrate 20, provided with cavities as shown in FIG. 2, via the layer of oxide 11.
  • This base 10 was thinned prior to its assembly with the substrate to a thickness of approximately 50 ⁇ m and then polished. It is then covered on its external face with a metallic layer 30, for example of platinum, by "sputtering”.
  • This layer is then structured using a plasma etching process, for example "Inductively-Coupled Plasma", to give a first electrode 32.
  • a layer of AIN 40 is then deposited by "Sputtering” then a second metallic layer 50, for example of aluminum, is deposited, also by “Sputtering".
  • the metal layers 30 and 50 have a thickness of a hundred nanometers while the AIN layer has a thickness of the order of a micrometer.
  • the metal layer is etched to give a second electrode 52 and then the AIN layer is also etched to give the piezoelectric activation layer of the corresponding resonator.
  • the aluminum layer intended to constitute said second electrodes is doped with silicon to prevent electro-diffusion of the electrode material.
  • FIG. 5 shows the assembly constituted by the resonators of FIG. 3 and a wafer 60.
  • the wafer 60 can be an integrated circuit incorporating various functionalities, such as oscillator, division chain, etc., or comprise one or more levels of conductive layers for making electrical connections.
  • the wafer 60 also has a mechanical function by serving as a hermetic cover for the cavities produced in the substrate 20, thus allowing said resonators to be placed under a controlled atmosphere.
  • the substrate 20 is thinned, for example chemically, then solder pads, for example made of tin and lead alloy, are produced on the electrodes 31, 52, 32, 33, 53. These studs can be obtained by screen printing or by electroplating.
  • the wafer 60 is fixed, according to the so-called "Flip-Chip" technique to all of the resonators (2, 3) and their substrate 20 under controlled temperature and atmosphere.
  • the temperature must be sufficient to perform the welding between the wafers and the pressure must be such that it ensures a relative vacuum allowing the resonators to reach a high quality factor.
  • the weld 81 must follow a closed curve, preferably circular.
  • the seal of the closure can be produced, not by means of a tin-lead solder, but by means of a circular joint 81 made of a polymer material as described in patent application EP 0 803 729.

Abstract

The invention relates to a microsystem incorporating at least one resonant structure, produced in a silicon base that is fixed to a silicon substrate (20) with which it forms a cavity, said silicon base also being fixed to a cover (60) by fixing means (81) which ensure that the cavity is sealed, and connection means (82 to 85) which ensure that the resonant structure is connected to the cover, and thus, to the outside of the cavity.

Description

Microsystème incorporant au moins une structure résonante dans une cavité sous atmosphère contrôlée et procédé pour sa fabrication La présente invention se rapporte à un microsystème et, plus particulièrement, un microsystème incorporant au moins une structure résonante en silicium dans une cavité sous atmosphère contrôlée ainsi que son procédé de fabrication. Les bases de temps précises que l'on peut trouver aujourd'hui, par exemple dans les montres électroniques, reposent toutes sur un résonateur à quartz qui est encapsulé, sous vide, dans un boîtier métallique de manière à offrir un facteur de qualité élevé. Un tel résonateur doit être associé à un circuit intégré pour constituer un oscillateur présentant une référence de fréquence stable. Ces deux éléments ont généralement des substrats et des procédés d'encapsulation distincts qui nécessitent l'utilisation de techniques de fabrication différentes. Après leur fabrication, le résonateur et le circuit intégré sont assemblés lors du processus de montage. Le résonateur le plus courant, pour les applications horlogères, est un résonateur à quartz de type diapason à 32 kHz qui oscille selon un mode de flexion. Une fois encapsulé, il présente un diamètre d'environ 1 mm et il est commercialement disponible à un prix n'excédant pas 0.1 à 0.2 francs suisses. Le circuit intégré est, quant à lui, le plus souvent réalisé en technologie CMOS et il est monté sur un circuit imprimé auquel est également fixé et électriquement connecté le résonateur. La nécessité de recourir à des matériaux de base et à des techniques de fabrication différentes pour ces deux éléments augmente leur coût de fabrication et empêche une réalisation compacte de l'ensemble.The present invention relates to a microsystem and, more particularly, a microsystem incorporating at least one resonant silicon structure in a cavity under controlled atmosphere as well as its manufacturing process. The precise time bases that can be found today, for example in electronic watches, are all based on a quartz resonator which is encapsulated, under vacuum, in a metal case so as to offer a high quality factor. Such a resonator must be associated with an integrated circuit to constitute an oscillator having a stable frequency reference. These two elements generally have separate substrates and encapsulation methods which require the use of different manufacturing techniques. After their manufacture, the resonator and the integrated circuit are assembled during the assembly process. The most common resonator, for watchmaking applications, is a 32 kHz tuning fork type quartz resonator which oscillates in a bending mode. Once encapsulated, it has a diameter of approximately 1 mm and is commercially available at a price not exceeding 0.1 to 0.2 Swiss francs. The integrated circuit is most often produced in CMOS technology and is mounted on a printed circuit to which the resonator is also fixed and electrically connected. The need to use different basic materials and manufacturing techniques for these two elements increases their manufacturing cost and prevents compact production of the assembly.
On a présenté dans le passé, voir notamment le brevet européen No. 079 5953, des résonateurs réalisés dans un substrat de silicium mais ces derniers présentaient une dérive thermique telle, qu'on ne pouvait envisager de les utiliser dans des applications de garde-temps sans un thermomètre intégré servant à compenser ladite dérive thermique. Cependant, la stabilité dans le temps des thermomètres intégrés reste très insuffisante pour garantir celle des bases de temps qui en font usage. Dans la demande de brevet français No. 030 5833 de la demanderesse, est décrit, toutefois, un ensemble de deux résonateurs réalisés dans un même substrat de silicium et dont les propriétés dimensionnelles et les modes d'oscillation sont tels qu'ils peuvent être utilisés pour constituer une référence de fréquence extrêmement stable en température et au cours du temps. De plus, leur technologie de fabrication est tout à fait compatible avec celle des circuits intégrés de sorte qu'ils peuvent être fabriqués après et par-dessus les circuits intégrés auxquels ils sont associés. En terminologie anglo-saxonne, une telle technique est appelée: "Above-IC Post-Processing". Toutefois, l'obligation d'une encapsulation sous vide conduit, selon les méthodes de fabrication conventionnelles, à l'utilisation d'au moins trois niveaux de substrat pour permettre la réalisation de cavités à l'échelon du wafer; ce qui, compte tenu de l'épaisseur de chacun des substrats, produit un assemblage bien trop épais pour beaucoup d'applications. Aussi un objet de la présente invention est un microsystème incorporant au moins une structure résonante en silicium, dans une cavité sous atmosphère contrôlée, et dont la fabrication est compatible avec celle des circuits intégrés.Resonators produced in a silicon substrate have been presented in the past, see in particular European patent No. 079 5953, but these exhibited such thermal drift that they could not be considered for use in timepiece applications without an integrated thermometer to compensate for said thermal drift. However, the stability over time of the integrated thermometers remains very insufficient to guarantee that of the time bases which make use of it. In the French patent application No. 030 5833 of the applicant, there is described, however, a set of two resonators produced in the same silicon substrate and whose dimensional properties and the oscillation modes are such that they can be used. to constitute a frequency reference extremely stable in temperature and over time. In addition, their manufacturing technology is fully compatible with that of integrated circuits so that they can be manufactured after and over the integrated circuits with which they are associated. In Anglo-Saxon terminology, such a technique is called: "Above-IC Post-Processing". However, the obligation of vacuum encapsulation leads, according to conventional manufacturing methods, to the use of at least three levels of substrate to allow the production of cavities at the wafer level; which, given the thickness of each of the substrates, produces an assembly that is far too thick for many applications. Also an object of the present invention is a microsystem incorporating at least one resonant silicon structure, in a cavity under controlled atmosphere, and the manufacture of which is compatible with that of integrated circuits.
Un autre objet de l'invention est un procédé de réalisation et d'assemblage de structures résonantes, réalisées dans un substrat de silicium sur isolant et associées à un circuit intégré réalisé dans un substrat de silicium.Another object of the invention is a method for producing and assembling resonant structures, produced in a silicon substrate on insulator and associated with an integrated circuit produced in a silicon substrate.
Encore un autre objet de l'invention est un procédé d'assemblage de structures résonantes associées à un circuit intégré permettant d'obtenir un ensemble d'épaisseur relativement mince.Yet another object of the invention is a method of assembling resonant structures associated with an integrated circuit making it possible to obtain an assembly of relatively thin thickness.
Un autre objet de l'invention est un ensemble réunissant au moins une structure résonante dans une cavité sous vide et un circuit intégré auquel ladite structure est électriquement connectée. Le microsytème de l'invention incorporant au moins une structure résonante en silicium dans une cavité sous atmosphère contrôlée se caractérise par le fait que ladite au moins une structure résonante est réalisée dans une base en silicium, elle- même fixée sur un substrat de silicium par l'intermédiaire d'une couche isolante et de manière à former, au moins partiellement, ladite cavité et en ce qu'il comprend un couvercle, d'une part, fixé à ladite base par des moyens de fermeture assurant la fermeture et l'étanchéité de ladite cavité et, d'autre part, connecté à ladite au moins une structure résonante par des moyens de connexion pour connecter électriquement cette dernière à l'extérieur de ladite cavité.Another object of the invention is an assembly bringing together at least one resonant structure in a vacuum cavity and an integrated circuit to which said structure is electrically connected. The microsystem of the invention incorporating at least one resonant silicon structure in a cavity under controlled atmosphere is characterized by the fact that said at least one resonant structure is produced in a silicon base, itself fixed on a silicon substrate by through an insulating layer and so as to form, at least partially, said cavity and in that it comprises a cover, on the one hand, fixed to said base by closing means ensuring the closing and the sealing of said cavity and, on the other hand, connected to said at least one resonant structure by connection means for electrically connect the latter to the outside of said cavity.
Le microsystème de l'invention possède encore toutes ou certaines des caractéristiques énoncées ci-après: - le couvercle est en silicium et comporte une ou plusieurs couches de lignes conductrices; - le couvercle comporte en outre un circuit intégré; - la structure résonante est un résonateur; - la structure résonante est un ensemble de deux résonateurs; - les moyens de fermeture sont en un matériau polymère; - les moyens de connexion sont en un alliage d'étain et de plomb.The microsystem of the invention also has all or some of the characteristics set out below: - the cover is made of silicon and comprises one or more layers of conductive lines; - The cover further includes an integrated circuit; - the resonant structure is a resonator; - the resonant structure is a set of two resonators; - The closure means are made of a polymer material; - The connection means are made of an alloy of tin and lead.
Grâce à ces caractéristiques, le microsystème de l'invention peut être fabriqué avec des techniques de fabrication compatibles avec celles du circuit intégré auquel il est associé. Le procédé de fabrication d'un microsystème selon la présente invention, est caractérisé en ce qu'il comporte les étapes de: - oxyder une face d'une base en silicium de manière à former une couche d'oxyde de silicium; - réaliser au moins une cavité; assembler ladite base en silicium et ledit substrat de manière à constituer un substrat de type SOI; réaliser, dans ladite base en silicium, au moins une structure résonante disposée, au moins partiellement, au- dessus de ladite cavité; fixer audit substrat de type SOI un couvercle par des moyens de fermeture assurant l'étanchéité de ladite cavité et des moyens de connexion assurant la connexion de ladite structure résonante à l'extérieur de ladite cavité.Thanks to these characteristics, the microsystem of the invention can be manufactured with manufacturing techniques compatible with those of the integrated circuit with which it is associated. The method of manufacturing a microsystem according to the present invention is characterized in that it comprises the steps of: - oxidizing one face of a silicon base so as to form a layer of silicon oxide; - make at least one cavity; assembling said silicon base and said substrate so as to constitute an SOI type substrate; producing, in said silicon base, at least one resonant structure disposed, at least partially, above said cavity; attaching to said SOI type substrate a cover by closing means ensuring the tightness of said cavity and connection means ensuring the connection of said resonant structure to the outside of said cavity.
D'autres objets, caractéristiques et avantages de la présente invention apparaîtront à la lecture de la description suivante d'un exemple de réalisation, ladite description étant faite à titre d'exemple non limitatif et en relation avec les dessins joints dans lesquels:Other objects, characteristics and advantages of the present invention will appear on reading the following description of an exemplary embodiment, said description being given by way of nonlimiting example and in relation to the accompanying drawings in which:
- la figure 1 montre, vu de dessus, un ensemble de deux résonateurs réalisés dans un substrat de silicium; les figures 2.a et 2.b montrent, en coupe, les wafers destinés à réaliser les résonateurs de la figure 1 ; la figure 3 montre, en coupe, les résonateurs de la figure 1 ; les figures 4.a à 4.e représentent des étapes de réalisation d'électrodes de part et d'autre d'une couche d'activation piézoélectrique; et la figure 5 montre un microsystème selon l'invention. Les résonateurs 2 et 3 de la figure 1 ont été décrits dans la demande de brevet français précitée. Ils sont réalisés dans un substrat de silicium sur isolant appelé, par la suite, substrat SOI. Ce substrat SOI comporte une base en silicium 10, dont une face a été oxydée pour donner une couche 11 d'oxyde de silicium (Si02), et un substrat de silicium 20, auquel ladite base 10 est soudée (figure 2). Cette soudure est faite en pressant la base 10 et le substrat 20 l'une contre l'autre sous atmosphère et température contrôlées. Cette technique porte le nom de "Silicon Fusion Bonding". Comme indiqué sur la figure, des cavités ont été réalisées dans le substrat de silicium avant la soudure des deux substrats. Après soudure, le substrat SOI est aminci, par exemple par meulage de sa partie supérieure, jusqu'à une épaisseur d'environ 50 μm, et poli puis les structures résonantes sont réalisées de la manière décrite dans la demande de brevet précitée. La figure 3 est une vue en coupe, selon l'axe A-A de la figure 1 , des résonateurs 2 et 3 après fabrication. Les résonateurs 2 et 3 sont découpés dans la base en silicium 10 sur laquelle ont été déposées, par "Sputtering", des électrodes métalliques 32 et 33. Simultanément au dépôt des électrodes 32 et 33, des contacts 31 sont réalisés sur la base 10. Sur les bras des résonateurs 2 et 3 et dans leur partie médiane, est déposée une couche de nitrure d'aluminium (42, 43) qui constitue la couche d'actuation piézoélectrique desdits résonateurs. Cette couche d'AIN reçoit une nouvelle couche métallique qui servira de deuxième électrode (52, 53) pour lesdits résonateurs. Selon une variante de réalisation de l'invention, les cavités, au-dessus desquelles sont disposés les résonateurs 2 et 3, sont réalisées, non par attaque du substrat 20 mais, par attaque de la couche d'oxyde 11 après la découpe desdits résonateurs. Cette attaque de la couche d'oxyde peut être faite par voie humide à l'aide d'une solution d'acide fluorhydrique (HF).- Figure 1 shows, seen from above, a set of two resonators made in a silicon substrate; Figures 2.a and 2.b show, in section, the wafers intended to produce the resonators of Figure 1; Figure 3 shows, in section, the resonators of Figure 1; FIGS. 4.a to 4.e show steps for producing electrodes on either side of a piezoelectric activation layer; and Figure 5 shows a microsystem according to the invention. The resonators 2 and 3 of FIG. 1 have been described in the aforementioned French patent application. They are made in a silicon on insulator substrate called, thereafter, SOI substrate. This SOI substrate comprises a silicon base 10, one face of which has been oxidized to give a layer 11 of silicon oxide (Si0 2 ), and a silicon substrate 20, to which said base 10 is welded (FIG. 2). This welding is done by pressing the base 10 and the substrate 20 one against the other under controlled atmosphere and temperature. This technique is called "Silicon Fusion Bonding". As shown in the figure, cavities were made in the silicon substrate before the two substrates were welded. After welding, the SOI substrate is thinned, for example by grinding its upper part, to a thickness of approximately 50 μm, and then polished, the resonant structures are produced in the manner described in the aforementioned patent application. Figure 3 is a sectional view, along the axis AA of Figure 1, of the resonators 2 and 3 after manufacture. The resonators 2 and 3 are cut from the silicon base 10 on which were deposited, by "sputtering", metal electrodes 32 and 33. Simultaneously with the deposition of the electrodes 32 and 33, contacts 31 are made on the base 10. On the arms of the resonators 2 and 3 and in their middle part, a layer of aluminum nitride (42, 43) is deposited which constitutes the piezoelectric actuation layer of said resonators. This AIN layer receives a new metallic layer which will serve as a second electrode (52, 53) for said resonators. According to an alternative embodiment of the invention, the cavities, above which the resonators 2 and 3 are arranged, are produced, not by attacking the substrate 20 but, by attacking the oxide layer 11 after the cutting of said resonators . This attack on the oxide layer can be done wet using a hydrofluoric acid (HF) solution.
La figure 4 montre en détail les étapes de réalisation des électrodes et de la couche d'AIN des résonateurs. Bien que, par souci de simplification, cela n'apparaisse pas sur la figure 4, la base 10 est supposée avoir été soudée sur un substrat 20, pourvu de cavités comme représenté à la figure 2, par l'intermédiaire de la couche d'oxyde 11. Cette base 10 a été amincie préalablement à son assemblage avec le substrat jusqu'à une épaisseur d'environ 50 μm puis polie. Elle est ensuite recouverte sur sa face externe d'une couche métallique 30, par exemple de platine, par "Sputtering". Cette couche est ensuite structurée à l'aide d'un procédé de gravure par plasma, par exemple "Inductively-Coupled Plasma", pour donner une première électrode 32. Une couche d'AIN 40 est alors déposée par "Sputtering" puis une deuxième couche métallique 50, par exemple en aluminium, est déposée, également par "Sputtering". Les couches métalliques 30 et 50 ont une épaisseur d'une centaine de nanomètres alors que la couche d'AIN a une épaisseur de l'ordre du micromètre. Après dépôt, la couche métallique est gravée pour donner une deuxième électrode 52 et ensuite la couche d'AIN est également gravée pour donner la couche d'activation piézoélectrique du résonateur correspondant. Préférablement, la couche d'aluminium destinée à constituer lesdites deuxièmes électrodes est dopée au silicium pour empêcher l'électro-diffusion du matériau des électrodes.FIG. 4 shows in detail the steps for producing the electrodes and the AIN layer of the resonators. Although, for the sake of simplicity, this does not appear in FIG. 4, the base 10 is assumed to have been welded on a substrate 20, provided with cavities as shown in FIG. 2, via the layer of oxide 11. This base 10 was thinned prior to its assembly with the substrate to a thickness of approximately 50 μm and then polished. It is then covered on its external face with a metallic layer 30, for example of platinum, by "sputtering". This layer is then structured using a plasma etching process, for example "Inductively-Coupled Plasma", to give a first electrode 32. A layer of AIN 40 is then deposited by "Sputtering" then a second metallic layer 50, for example of aluminum, is deposited, also by "Sputtering". The metal layers 30 and 50 have a thickness of a hundred nanometers while the AIN layer has a thickness of the order of a micrometer. After deposition, the metal layer is etched to give a second electrode 52 and then the AIN layer is also etched to give the piezoelectric activation layer of the corresponding resonator. Preferably, the aluminum layer intended to constitute said second electrodes is doped with silicon to prevent electro-diffusion of the electrode material.
La figure 5 montre l'assemblage constitué par les résonateurs de la figure 3 et un wafer 60. Le wafer 60 peut être un circuit intégré incorporant des fonctionnalités diverses, telles qu'oscillateur, chaîne de division, etc., ou comporter un ou plusieurs niveaux de couches conductrices pour la réalisation de connexions électriques. Le wafer 60 a également une fonction mécanique en servant de couvercle hermétique aux cavités réalisées dans le substrat 20, permettant ainsi la mise sous atmosphère contrôlée desdits résonateurs. Après la fabrication des résonateurs (figure 3), le substrat 20 est aminci, par exemple par voie chimique, puis des plots de soudure, par exemple en alliage d'étain et de plomb, sont réalisés sur les électrodes 31 , 52, 32, 33, 53. Ces plots peuvent être obtenus par sérigraphie ou par galvanoplastie. Ensuite, le wafer 60 est fixé, selon la technique dite "Flip-Chip" à l'ensemble des résonateurs (2, 3) et de leur substrat 20 sous température et atmosphère contrôlées. La température doit être suffisante pour opérer la soudure entre les wafers et la pression doit être telle qu'elle assure un vide relatif permettant aux résonateurs d'atteindre un facteur de qualité élevé. Pour assurer l'étanchéité des cavités abritant les résonateurs, la soudure 81 doit suivre une courbe fermée, de préférence circulaire. Selon une variante, l'étanchéité de la fermeture peut être réalisée, non pas au moyen d'une soudure étain-plomb, mais grâce à un joint circulaire 81 en un matériau polymère comme décrit dans la demande de brevet EP 0 803 729. Bien qu'on ait présenté, dans la description précédente, la structure et la réalisation d'un seul microsystème, on comprendra aisément, qu'à l'instar des circuits intégrés, en fait une pluralité de ces mêmes microsystèmes est simultanément réalisée, ce qui en réduit considérablement le coût de fabrication. FIG. 5 shows the assembly constituted by the resonators of FIG. 3 and a wafer 60. The wafer 60 can be an integrated circuit incorporating various functionalities, such as oscillator, division chain, etc., or comprise one or more levels of conductive layers for making electrical connections. The wafer 60 also has a mechanical function by serving as a hermetic cover for the cavities produced in the substrate 20, thus allowing said resonators to be placed under a controlled atmosphere. After the manufacture of the resonators (FIG. 3), the substrate 20 is thinned, for example chemically, then solder pads, for example made of tin and lead alloy, are produced on the electrodes 31, 52, 32, 33, 53. These studs can be obtained by screen printing or by electroplating. Then, the wafer 60 is fixed, according to the so-called "Flip-Chip" technique to all of the resonators (2, 3) and their substrate 20 under controlled temperature and atmosphere. The temperature must be sufficient to perform the welding between the wafers and the pressure must be such that it ensures a relative vacuum allowing the resonators to reach a high quality factor. To seal the cavities housing the resonators, the weld 81 must follow a closed curve, preferably circular. According to a variant, the seal of the closure can be produced, not by means of a tin-lead solder, but by means of a circular joint 81 made of a polymer material as described in patent application EP 0 803 729. Although we have presented, in the previous description, the structure and construction of a single microsystem, it will be readily understood that, like integrated circuits, in fact a plurality of these same microsystems is simultaneously produced, this which considerably reduces the manufacturing cost.

Claims

Revendications claims
1. Microsystème incorporant au moins une structure résonante (2, 3) dans une cavité (100) sous atmosphère contrôlée, caractérisé en ce que ladite au moins une structure résonante est réalisée dans une base en silicium ,(10), elle-même fixée sur un substrat de silicium (20) par l'intermédiaire d'une couche isolante (11 ) et de manière à former, au moins partiellement, ladite cavité et en ce qu'il comprend un couvercle (60), d'une part, fixé à ladite base par des moyens de fermeture (81) assurant la fermeture et l'étanchéité de ladite cavité et, d'autre part, connecté à ladite au moins une structure résonante par des moyens de connexion (82 à 85) pour connecter électriquement cette dernière à l'extérieur de ladite cavité.1. Microsystem incorporating at least one resonant structure (2, 3) in a cavity (100) under a controlled atmosphere, characterized in that said at least one resonant structure is produced in a silicon base (10), itself fixed on a silicon substrate (20) by means of an insulating layer (11) and so as to form, at least partially, said cavity and in that it comprises a cover (60), on the one hand, fixed to said base by closing means (81) ensuring the closing and sealing of said cavity and, on the other hand, connected to said at least one resonant structure by connection means (82 to 85) for electrically connecting the latter outside said cavity.
2. Microsystème selon la revendication 1, caractérisé en ce que ledit couvercle est en silicium et comporte une ou plusieurs couches de lignes conductrices.2. Microsystem according to claim 1, characterized in that said cover is made of silicon and comprises one or more layers of conductive lines.
3. Microsystème selon la revendication 2, caractérisé en ce que ledit couvercle comporte en outre un circuit intégré.3. Microsystem according to claim 2, characterized in that said cover further comprises an integrated circuit.
4. Microsystème selon l'une des revendications 1 à 3, caractérisé en ce que ladite au moins une structure résonante est un résonateur.4. Microsystem according to one of claims 1 to 3, characterized in that said at least one resonant structure is a resonator.
5. Microsystème selon l'une des revendications 1 à 3, caractérisé en ce que ladite au moins une structure résonante est un ensemble de deux résonateurs.5. Microsystem according to one of claims 1 to 3, characterized in that said at least one resonant structure is a set of two resonators.
6. Microsystème selon l'une des revendications 1 à 5, caractérisée en ce que lesdits moyens de connexion sont en alliage d'étain et de plomb. 6. Microsystem according to one of claims 1 to 5, characterized in that said connection means are made of tin and lead alloy.
7. Microsystème selon l'une des revendications 1 à 6, caractérisée en ce que lesdits moyens de fermeture sont en un matériau polymère.7. Microsystem according to one of claims 1 to 6, characterized in that said closure means are made of a polymer material.
8. Procédé de fabrication d'un microsystème selon l'une des revendications précédentes, caractérisé en ce qu'il comporte les étapes de: - oxyder une face d'une base en silicium (10) de manière à forme une couche d'oxyde de silicium (11); - réaliser au moins une cavité (100); - assembler ladite base en silicium et ledit substrat de manière à constituer un substrat de type SOI; - réaliser, dans ladite base en silicium, au moins une structure résonante (2,3) disposée, au moins partiellement, au-dessus de ladite cavité; - fixer audit substrat de type SOI un couvercle (60) par des moyens de fermeture (81) assurant l'étanchéité de ladite cavité et des moyens de connexion (82 à 85) assurant la connexion de ladite structure résonante à l'extérieur de ladite cavité. Procédé selon la revendication 8, caractérisé en ce que ladite cavité (100) est réalisée dans ledit substrat de silicium (20) et ce, préalablement à son assemblage avec ladite base en silicium (10).8. Method of manufacturing a microsystem according to one of the preceding claims, characterized in that it comprises the steps of: - oxidizing one face of a silicon base (10) so as to form an oxide layer silicon (11); - make at least one cavity (100); - Assemble said silicon base and said substrate so as to constitute a SOI type substrate; - Realize, in said silicon base, at least one resonant structure (2,3) arranged, at least partially, above said cavity; - Attaching to said SOI type substrate a cover (60) by closing means (81) ensuring the tightness of said cavity and connection means (82 to 85) ensuring the connection of said resonant structure to the outside of said cavity. Method according to claim 8, characterized in that said cavity (100) is produced in said silicon substrate (20) and this, prior to its assembly with said silicon base (10).
10 Procédé selon la revendication 8, caractérisé en ce que ladite cavité (100) est réalisée, après la fabrication de ladite structure résonante, par attaque de ladite couche d'oxyde de silicium (11 ).10 Method according to claim 8, characterized in that said cavity (100) is produced, after the manufacture of said resonant structure, by etching of said layer of silicon oxide (11).
11 Procédé selon l'une des revendications 8 à 10, caractérisé en ce que ladite base en silicium est amincie préalablement à son assemblage avec ledit substrat de silicium. Procédé selon l'une des revendications 8 à 11 , caractérisé en ce que lesdits moyens de fermeture sont en un matériau polymère. Procédé selon l'une des revendications 8 à 12, caractérisé en ce que lesdits moyens de connexion sont en un alliage d'étain et de plomb. 11 Method according to one of claims 8 to 10, characterized in that said silicon base is thinned prior to its assembly with said silicon substrate. Method according to one of claims 8 to 11, characterized in that said closure means are made of a polymer material. Method according to one of claims 8 to 12, characterized in that said connection means are made of an alloy of tin and lead.
PCT/CH2004/000491 2003-08-14 2004-08-05 Microsystem incorporating at least one resonant structure in a cavity under a controlled atmosphere, and method for producing the same WO2005018090A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0309956A FR2858890B1 (en) 2003-08-14 2003-08-14 MICROSYSTEM INCORPORATING AT LEAST ONE RESONANT STRUCTURE IN A CAVITY UNDER CONTROLLED ATMOSPHERE AND METHOD FOR MANUFACTURING THE SAME
FR03/09956 2003-08-14

Publications (1)

Publication Number Publication Date
WO2005018090A1 true WO2005018090A1 (en) 2005-02-24

Family

ID=34112783

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CH2004/000491 WO2005018090A1 (en) 2003-08-14 2004-08-05 Microsystem incorporating at least one resonant structure in a cavity under a controlled atmosphere, and method for producing the same

Country Status (2)

Country Link
FR (1) FR2858890B1 (en)
WO (1) WO2005018090A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6275122B1 (en) * 1999-08-17 2001-08-14 International Business Machines Corporation Encapsulated MEMS band-pass filter for integrated circuits
US20030042567A1 (en) * 2001-04-19 2003-03-06 Hendrikus Tilmans Method and system for fabrication of integrated tunable/switchable passive microwave and millimeter wave modules
US20030048520A1 (en) * 2001-09-07 2003-03-13 Intel Corporation Vacuum-cavity MEMS resonator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6275122B1 (en) * 1999-08-17 2001-08-14 International Business Machines Corporation Encapsulated MEMS band-pass filter for integrated circuits
US20030042567A1 (en) * 2001-04-19 2003-03-06 Hendrikus Tilmans Method and system for fabrication of integrated tunable/switchable passive microwave and millimeter wave modules
US20030048520A1 (en) * 2001-09-07 2003-03-13 Intel Corporation Vacuum-cavity MEMS resonator

Also Published As

Publication number Publication date
FR2858890A1 (en) 2005-02-18
FR2858890B1 (en) 2006-02-03

Similar Documents

Publication Publication Date Title
EP1568129B1 (en) Acoustic resonator support, acoustic resonator and corresponding integrated circuit
CA2321360C (en) Process for encapsulating electronic components
EP1060562B1 (en) Device with acoustic waves guided in a fine piezoelectric material film bonded with a molecular bonding on a bearing substrate and method for making same
FR2943175A1 (en) METHOD FOR MANUFACTURING AN ELECTRONIC UNIT AND THE ELECTRONIC UNIT OBTAINED
EP0156146B1 (en) Piezoelectric oscillator
CH625372A5 (en)
US6606772B1 (en) Method for manufacturing piezoelectric oscillator
FR2616995A1 (en) METHOD FOR MANUFACTURING ELECTRONIC MODULES
EP1863174A1 (en) Component containing a BAW filter
WO2019243744A1 (en) Method for transferring at least one layer of material from a first substrate to a second substrate
WO1999022212A1 (en) Structure equipped with electric contacts formed through said structure substrate and method for obtaining said structure
EP1760880A1 (en) Acoustic resonator support and corresponding integrated circuit
EP1458095B1 (en) Method of manufacturing a piezoelectric tunable microresonator
EP0336859A1 (en) Piezo-electric unit with lateral electrical connector pincers
EP0086739A1 (en) Piezoelectric resonator with mounting possibilities
FR2987169A1 (en) METHOD FOR BONDING A FIRST ELECTRONIC COMPONENT TO A SECOND COMPONENT
WO2005018090A1 (en) Microsystem incorporating at least one resonant structure in a cavity under a controlled atmosphere, and method for producing the same
EP1431243B1 (en) Device for the encapsulation of integrated microelectromechanical systems and method for its manufacture
FR2743225A1 (en) PIEZOELECTRIC RESONATOR
EP2782868B1 (en) Method for manufacturing an encapsulation device
EP2730025B1 (en) Volume wave resonator using excitation/detection of vibrations
FR2520931A1 (en) COLLECTIVE METHOD OF MANUFACTURING MICROFREQUENCY DIODES WITH INCORPORATED ENCAPSULATION AND DIODES OBTAINED THEREBY
EP1536439B1 (en) Component comprising a variable capacitor
WO2002061181A2 (en) Large-dimension electrode
EP0793269A1 (en) Semiconductor device having a chip with via hole soldered on a support, and its method of fabrication

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BW BY BZ CA CH CN CO CR CU CZ DE DK DM DZ EC EE EG ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NA NI NO NZ OM PG PH PL PT RO RU SC SD SE SG SK SL SY TJ TM TN TR TT TZ UA UG US UZ VC VN YU ZA ZM ZW

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): BW GH GM KE LS MW MZ NA SD SL SZ TZ UG ZM ZW AM AZ BY KG KZ MD RU TJ TM AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LU MC NL PL PT RO SE SI SK TR BF BJ CF CG CI CM GA GN GQ GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase