WO2003064316A1

WO2003064316A1 - Integrated structure on a mobile piece, in particular an integrated optical structure

Info

Publication number: WO2003064316A1
Application number: PCT/FR2003/000263
Authority: WO
Inventors: Michel Bruel
Original assignee: Opsitech-Optical System On A Chip
Priority date: 2002-02-01
Filing date: 2003-01-28
Publication date: 2003-08-07
Also published as: FR2835516B1; FR2835516A1

Abstract

The invention relates to an integrated structure comprising a base layer (2) made from an electrically-conducting material, an intermediate layer made from an electrically-insulating material and an upper layer (4) made from an electrically-conducting material. The upper layer (4) is perforated and the intermediate layer and possibly the base layer (2) are excavated in such a manner as to produce a cavity (5) in which at least one region of the upper layer comprises a suspended piece (6) connected to the rest of the upper layer. The suspended piece can thus be displaced, from a stable position against the elastic force of the connection (10, 11) thereof with the rest of the upper layer, in a direction towards or away from the base layer when the suspended piece and the base layer are subjected to an electrical energy supply. The structure can furthermore comprise an optical guide means (22) in two pieces between which a part (7) of the suspended piece (6) may be placed.

Description

Integrated structure with moving part, in particular integrated optical structure.

The present invention relates to the field of integrated structures and more particularly integrated optical structures, with a movable part.

Integrated optical structures are already known which include beams or platforms, provided with electrodes located at a distance from fixed electrodes, so that when these electrodes are subjected to a source of electrical energy, the beams deform or the platforms move parallel to the plane of the layers of the structures, the displacements of the beams or the platforms making it possible in particular to perform optical switching. Such arrangements are described in particular in patents FR-A-90 03 902 and FR-A-95 00 201.

In the prior art, mention may also be made of documents US-A-5,907,425 and EP-A-417,523, which each describe a structure which comprises a platform symmetrical with respect to a pivot axis constituted by opposite arms as well as electrodes carried by the platform and the rest of the structure, the rest of the structure carrying independent electrodes placed on either side of the pivot axis so as to selectively pivot the platform form on one side or the other, as well as document US-A-4,956,619 which describes a structure having a platform connected by an arm with the rest of this structure so as to constitute a platform in overhang, this platform and a lower layer of the structure constituting electrodes able to move the platform perpendicular to the lower layer. The object of the present invention is to propose an improved integrated structure capable of being advantageously applied in the field of the transmission of optical waves, of very different construction and operation from those currently known. The present invention relates firstly to an integrated structure which comprises a base layer of an electrically conductive material, an intermediate layer of an electrically insulating material, and an upper layer of an electrically conductive material.

According to an object of the invention, said upper layer is perforated and said intermediate layer and possibly said base layer are released so as to form a cavity in which at least one region of said upper layer constitutes a suspended part which is connected to the rest of this upper layer by two opposite connecting arms defining a pivot axis and which comprises at least two opposite branches or beams extending in the extension of one another, on either side of said pivot axis, and facing said base layer. According to the invention, said opposite branches or beams are dimensioned so that, when said base layer and said suspended part of said upper layer are subjected to a difference in electrical potential, this suspended part is subjected to a resulting torque causing its tilting along said pivot axis, from a stable position and against the elasticity of its connection by said opposite arms with the rest of this upper layer.

According to the invention, said structure comprises or is preferably provided with at least one optical guide means having two parts which extend in the extension of one another and whose adjacent ends are separated by a space, said suspended part comprising a portion capable of moving in this space in order to act on the optical coupling between said parts of said optical guide means through said space.

According to an object of the invention, said upper layer is perforated and said intermediate layer and possibly said base layer are released so as to form a cavity in which at least one region of said upper layer constitutes a suspended part connected to the rest of this top layer, so that when said base layer and said suspended portion of said layer upper are subjected to a difference in electric potential, this suspended part is subjected to a resulting torque causing its tilting along said pivot axis, from a stable position and against the elasticity of its connection by said arms opposite with the rest of this top layer.

According to the invention, the above structure comprises or is provided with at least one optical guide means having two parts which extend in extension of one another and whose adj acent ends are separated by a space, and said suspended part comprises a portion moving in said space in order to act on the optical coupling between said parts of said optical guide means through this space when this suspended part rocks.

According to the invention, said suspended part preferably comprises at least one cantilever beam. According to the invention, said suspended part is preferably connected to the rest of said upper layer by two opposite connecting arms determining an axis of pivoting.

According to the invention, said optical guide means can comprise at least one integrated optical micro-guide. According to the invention, said optical guide means can comprise at least one optical fiber.

According to the invention, said optical guide means can comprise at least four parts forming a cross, two of which are located on one side of said space and the other two on the other side. According to the invention, said optical guide means can extend above said upper layer and said portion of said suspended part is preferably capable of penetrating into said space when this suspended part and said base layer are subjected to a difference in electrical potential. According to the invention, the sides or faces of said suspended part, corresponding to said space, can be optically absorbent.

According to the invention, the sides or faces of said suspended part, corresponding to said space, can be optically reflective. According to the invention, said upper layer preferably has at least one trench of electrical insulation, distant from its connection with its suspended part and the ends of which open into said cavity. According to the invention, said suspended part may have a reduced width on the side of its connection to the rest of said upper layer. The present invention will be better understood from the study of integrated optical structures described by way of nonlimiting examples and illustrated by the drawing in which: - Figure 1 shows a top view of a first integrated optical structure according to the present invention ;

- Figure 2 shows a cross section along II-II of the structure of Figure 1;

- Figure 3 shows a section along 111-111 of the structure of Figure 1;

- Figure 4 shows a longitudinal section along IV-IV of the structure of Figure 1, in a stable position;

- Figure 5 shows a longitudinal section corresponding to Figure 4 of the structure of Figure 1, in the deformed position; - Figure 6 shows a top view of an alternative embodiment of the structure of Figures 1 to 5;

- Figure 7 shows another alternative embodiment of the above optical structure;

- Figure 8 shows a partial section along VIII-VIII of the structure of Figure 7;

- And Figure 9 shows a top view of a group of integrated optical structures.

Referring to FIGS. 1 to 5, it can be seen that an integrated optical structure 1 has been shown which comprises, on top of each other, a base layer 2, an intermediate layer 3 and an upper layer 4.

The base layer 2 is made of an electrically conductive material, for example silicon, the intermediate layer 3 is made of an electrically non-conductive material, for example silica, and the upper layer 4 is made of an electrically conductive material, for example monocrystalline silicon.

In an exemplary embodiment, the intermediate layer 3 can have a thickness between 10 and 15 microns, the upper layer 4 can have a thickness between 60 and 80 microns, while the base layer is relatively thicker.

The upper layer 4 is perforated or cut and the intermediate layer 3 and the base layer 2 are released, so as to produce a cavity 5 in which there remains a region of the upper layer 4 making it possible to constitute a suspended part 6 connected to the rest of this top layer 4.

More specifically, this suspended part 6 comprises two opposite longitudinal branches or beams 7 and 8, which overhang, extending in the extension of one another and on either side of an axis pivot 9 determined by two opposite transverse link arms 10 and 11 joining two opposite longitudinal sides 12 and 13 of the cavity 4.

In the example shown, the beams 7 and 8 of the suspended part 6 are, in top view, rectangular and substantially the same lengths, the width of the beam 7 being very much smaller than the width of the beam 8. The beam 8 has, on the side of the pivot axis 9, lateral recesses 14 and 15 making it possible to lengthen the link arms 10 and 11.

In an exemplary embodiment, the length of the beams 7 and 8 can be between 50 and 100 microns, the width of the beam 7 can be between 5 and 10 microns and the width of the beam 8 can be between 50 and 200 microns.

The cavity 5 is formed so as to present two other longitudinal sides 16 and 17 which extend a short distance from the end parts of the longitudinal sides 18 and 19 of the beam 7 of the suspended part 6.

By way of example, the distance separating respectively the sides 16 and 17 of the cavity 5 and the sides 18 and 19 of the beam 7 can be between 3 and 5 microns. The base layer 2 and the upper layer 4 are electrically connected to an electrical control device 20 including a source of electrical energy 21.

As shown in particular in FIGS. 2 to 4, when the base layer 2 and the upper layer 4 are not connected to the source of electrical energy, the suspended part 6 extends substantially in the plane of the upper layer 4 .

When the base layer 2 and the upper layer 4 are connected to the source of electrical energy, there is in the cavity 5 an electrostatic effect between the base layer 2 and the suspended part 6 of the upper layer 4 tending to bring together and generating in fact, along the transverse axis 9 determined by the connecting arms 10 and 11, a couple on the beam 7 and a couple on the beam 8 which oppose.

The beam 7 and the beam 8 of the suspended part 6 are dimensioned on the surface with respect to each other so that these couples are of different values. There therefore occurs a tilting of the suspended part 6 along the transverse axis 9 such that, due to the resulting torque, the beam 7 pivots and moves away from the base layer 2 while rising and the beam 8 pivots and approaches the bottom 5a of the cavity 5, the beam 7 leaving the cavity 5 and the beam 8 by sinking into the latter. Figure 5 shows the hanging part 6 in a tilted position.

The above tilting of the hanging part 10 occurs by causing a twist of the link arms 10 and 11 of the hanging part 6 against their elasticity.

When the electric power source 21 is electrically disconnected from the base layer 2 and the upper layer 4, the suspended part 6 returns to its initial stable position substantially in the plane of the upper layer 4, under the effect of the elasticity of its link arms 10 and 11.

The angular amplitude of the tilting movement of the suspended part 6 along the pivot axis 9 is a function of the potential difference applied between the base layer 2 and the upper layer 4, so that it is possible to cause angular tilting determined by operating the control device 20 in all or nothing, and / or that it is possible to modulate the amplitude of the tilting of the suspended part 6 by modulating the electric energy delivered by the electric control device 20 and determining said potential difference.

The structure 1 further comprises an integrated optical micro-guide 22 produced transversely on the surface 4a of the upper layer 4 and having in its central part an optical guide core 22a.

The integrated optical guide 22 comprises two parts 23 and 24 whose adjacent ends 25 and 26, transverse to their transmission cores 23a and 24a, extend in the plane of the sides 16 and 17 of the cavity 5 so that the space 27 separating these end surfaces 25 and 26 corresponds substantially to the distance separating these sides 16 and 17. When the suspended part 6 is in its stable position described above, its beam 7 extends in the plane of the upper layer 4 and consequently below the space 27 of the optical micro-guide 22. The optical wave transported by this optical micro-guide 22 passes from one of its parts 23 and 24 to the other through the space 27. When the suspended part 6 and the base layer 2 are subjected to the electrical control device 20, the end part of its beam 7 engages and moves while rising in space 27 separating the faces d end 25 and 26 of parts 23 and 24 of the microguide optical 22. The beam 7 then constitutes an obstacle to the transmission or propagation of the optical wave from one of the parts 23 and 24 of the optical micro-guide 22 to the other.

The beam 7 of the suspended part 6 can either constitute a total obstacle to this transmission so as to produce an optical switch or constitute a partial obstacle so as to produce an optical attenuator, this depending on the amplitude of the tilting movement of the suspended part 6 as described above. To manufacture the integrated optical structure 1, it is possible to proceed in the following manner. Having stacked layers 2, 3 and 4 and the integrated optical microguide 22, we proceed in particular by successive etchings to produce the space 27 separating the parts 23 and 24 of the optical micro-guide 22 and the cavity 5 by perforating or digging the upper layer 4 and making a clearance in the intermediate layer 3 and the base layer 2 so as to obtain the suspended part 6.

The electrical connection is made between the control device 20 and on the one hand the base layer 2 and on the other hand the upper layer 4, for example by providing an electrical connection pad on the layer 4 and an electrical connection pad on the base layer 2 at the bottom of a well 20a produced in the upper layer 4 and the intermediate layer 3.

In order to avoid any risk of short circuit between the suspended part 6 and the base layer 2, a thin insulator could also be deposited in the bottom of the cavity 5, for example parylene or Teflon. In this case, the bottom of the cavity 5 can serve as an end-of-travel stop for the beam 8 and therefore as an end-of-tilting stop for the suspended part 6 and for limiting the travel of the beam 7.

One could also perform a treatment of the faces 18 and 19 of the beam 7 so as to improve their light reflection capacity, either by depositing a reflective metal or by performing a heat treatment at high temperature so as to obtain a state surface area desired by displacement of atoms.

In the example above, the parts 23 and 24 of the micro-guide 22 could be replaced by portions of optical fibers fixed for example in grooves made on the front face of the upper layer 4 as described below with reference to Figure 8.

Referring to FIG. 6, it can be seen that an alternative embodiment of the integrated optical structure 1 has been shown, in which the upper layer 4 has two trenches 28 and 29 made in its thickness, at a distance from the arms 10 and 11 and opening into the cavity 5 on either side of these arms. Alternatively, these trenches 28 and 29 could be filled with an electrically insulating material. Thus, the suspended part 6 is connected to two regions 30 and 31 lateral to the cavity 5 and anchored on the intermediate layer 3, so that the suspended part 6 and the regions 30 and 31 are electrically isolated from the rest of the upper layer 4. In this variant, the electrical control device 20 will then have to be connected for example to a pad 32 of the region 30.

Referring to Figures 7 and 8, it can be seen that there is shown an integrated optical structure 33 which differs from the integrated optical structure 1 described above only by the following points. The integrated optical micro-guide 22 previously produced on the upper layer 4 is eliminated.

This upper layer 4 has in its upper face 4a grooves 34 in which are partially engaged and fixed, for example by gluing, the end portions of optical fibers 35 whose end faces 36 are placed in the plane of the sides 16 and 17 from cavity 5.

In the example shown, the integrated optical structure 33 has four optical fibers 35 extending in a cross and inclined substantially at 45 degrees relative to the beam 7 of the suspended part 6, the end faces 36 of the fibers 35 being substantially in the plane of the sides 16 and 17. The optical fibers 35 could have thinned diameters.

When the beam 7 is in its aforementioned stable position, an optical wave arriving by one and / or the other of the optical fibers located on one side of the beam 7 is transferred to the optical fiber located opposite or in its extension , through the space between their ends.

In a variant, the sides 18 and 19 of the beam 7 can be optically absorbent thanks in particular to the materials chosen or to their roughness or thanks to a deposit of an absorbent material on these sides such as amorphous silicon. In this case, when the beam 7 is in the raised position described above, it can then constitute an optical switch or an optical attenuator of the optical waves flowing in the optical fibers 35 located in the extension of one another. In another variant, the sides 18 and 19 of the beam 7 can be optically reflective, in particular by polishing these sides or by depositing on these sides a reflective material such as aluminum and the axes of the two fibers. optics located on one side of the beam 7 may intersect on the corresponding side of this beam or in a neighboring location. In this case, when the beam 7 is in its raised position described above, an optical wave arriving by one of the optical fibers 35 is reflected on the corresponding face of the beam 7 and directed towards the other optical fiber located on the same side. of this beam.

The arrangement of this other variant therefore constitutes a two-way to two-way optical switch.

Of course, the optical fibers 35 could be replaced by integrated optical micro-guides. Referring now to FIG. 9, it can be seen that a bar 37 has been shown, constructed in a basic structure identical to that of FIGS. 1 to 5 and comprising, respectively in several zones 38i, several suspended parts 6 produced in several corresponding cavities 5 and associated with several optical micro-guides 22, the upper layer 4 having trenches 39 for electrical insulation of the different zones 38i.

The zones 38i can then be connected in parallel or independently to one or different electrical control devices 20 to operate and be used as described above with regard to the integrated optical structure 1.

The present invention is not limited to the examples described above. Many alternative embodiments are possible without departing from the scope defined by the appended claims.

Claims

1. Integrated structure, characterized in that it comprises a base layer (2) of an electrically conductive material, an intermediate layer (3) of an electrically insulating material, and an upper layer (4) of a conductive material electricity ; and in that said upper layer (4) is perforated and said intermediate layer (3) and possibly said base layer (2) are released so as to form a cavity (5) in which at least one region of said upper layer (4) constitutes a suspended part (6) which is connected to the rest of this upper layer by two opposite connecting arms (10, 1 1) defining a pivot axis (9) and which comprises at least two opposite branches or beams ( 1, 8) extending in the extension of one another, on either side of said pivot axis (9), and facing said base layer (2); said opposite branches or beams (1, 8) being dimensioned such that, when said base layer (2) and said suspended part (6) of said upper layer (4) are subjected to a difference in electrical potential, this part suspended (6) is subjected to a resulting torque causing it to tilt along said pivot axis (9), from a stable position and against the elasticity of its connection by said opposite arms (10, 1 1) with the rest of this top layer.

2. Structure according to claim 1, characterized in that it comprises or is provided with at least one optical guide means (22, 35) having two parts (23, 24) which extend in line with the one from the other and whose adjacent ends are separated by a space (27), said suspended part comprising a portion (7) capable of moving in this space in order to act on the optical coupling between said parts of said means of optical guidance through said space.

3. Integrated structure, characterized in that it comprises a base layer (2) of an electrically conductive material, an intermediate layer (3) of an electrically insulating material, and an upper layer (4) in one electrically conductive material, and said upper layer (4) is perforated and said intermediate layer (3) and optionally said base layer (2) are released so as to produce a cavity (5) in which at least one region of said upper layer (4) constitutes a suspended part (6) connected to the rest of this upper layer , so that when said base layer (2) and said suspended part (6) of said upper layer (4) are subjected to an electrical potential difference, this suspended part (6) is subjected to a resulting torque causing its tilting along said pivot axis (9), from a stable position and against the elasticity of its connection by said opposite arms (10, 1 1) with the rest of this upper layer; and by the fact that it comprises or is provided with at least one optical guide means (22, 35) having two parts (23, 24) which extend in extension of one another and whose adjacent ends are separated by a space (27), and that said suspended part (6) comprises a portion (7) moving in said space (27) in order to act on the optical coupling between said parts of said optical guide means through this space (27) when this suspended part (6) rocks.

4. Structure according to claim 3, characterized in that said suspended part (6) comprises at least one cantilever beam (7, 8).

5. Structure according to one of claims 3 and 4, characterized in that said suspended part (6) is connected to the rest of said upper layer by two opposite arms (10, 1 1) defining a pivot axis (9) .

6. Structure according to any one of claims 2 to 5, characterized in that said optical guide means (22) comprises at least one integrated optical micro-guide (22).

7. Structure according to any one of claims 2 to 5, characterized in that said optical guide means comprises at least one optical fiber (35).

8. Structure according to any one of claims 2 to 7, characterized in that said optical guide means comprises at least four parts (35) forming a cross, two of which are located on one side of said space (27) and the other two on the other side.

9. Structure according to any one of claims 2 to 8, characterized in that said optical guide means (22, 35) extends above said upper layer (4) and that said portion (7) of said suspended part (6) is capable of entering said space (27) when this suspended part and said base layer are subjected to a difference in electrical potential.

10. Structure according to any one of claims 2 to 9, characterized in that the sides or faces (1 8, 19) of said suspended part, corresponding to said space, are optically absorbent.

1 1. Structure according to any one of claims 2 to 9, characterized in that the sides or faces (1 8, 19) of said suspended part, corresponding to said space, are optically reflective.

12. Structure according to any one of the preceding claims, characterized in that said upper layer (4) has at least one trench of electrical insulation (28, 29; 39), distant from its connection (10, 1 1) with its suspended part (6) and the ends of which open into said cavity.

13. Structure according to one of the preceding claims, characterized in that said suspended part (6) has a reduced width (14, 15) on the side of its connection to the rest of said upper layer.