FR2839712A1 - Micromechanical device for use in liquid input control and liquid pressure detection elements and medical micro-pumps has mobile element formed in an insulating layer and prevented from adhering to a stopping surface formed on support - Google Patents

Abstract

Micromechanical, especially fluidic, device (100) comprises a support (36), insulating layer (34) covering at least part of the support, and mono- or poly-crystalline silicon layer (32) on the insulating layer. Recess (35) formed in insulating layer defines a residual mobile element (40) connected to the silicon layer. Adhesion of a stopping surface (42) to the mobile element is prevented. A micromechanical device (100), especially a fluidic device, comprises a stack (30) consisting of a support (36), an insulating layer (34) covering at least part of the support, and a mono- or poly-crystalline silicon layer (32) on the insulating layer. A recess (35) is formed in the insulating layer, in order to define a residual mobile element (40) connected to the silicon layer (32). A stopping surface (42) is formed on the surface of the support (36), facing the mobile element (40) and in at least part of the recess (35). The stopping surface (42) possesses physico-chemical properties that prevent adhesion of the mobile element (40) to the stopping surface (42). Independent claims are given for the following: (1) a process for fabricating the micromechanical device; (2) a liquid input control element; (3) a liquid pressure detection element; (4) a micro-pump comprising at least one fluidic device according to the invention; and (5) utilization of the micro-pump as an implantable medical pump and as an external medical pump, for the regular and controlled supply of liquid medicinal compositions.

Description

(12) when the lifting means (26) is inactive.

  The invention relates to a micromechanical device and its

manufacturing process.

  In particular, but in a nonlimiting manner, the invention relates to a fluidic device and in particular particular forms of fluidic devices constituting a liquid input control member which is for example a form of a non-return valve, or a organ of

  pressure detection, in particular liquid pressure.

  The present invention also relates to a micropump constituting a fl uidic device and q u i n particular, ma is no n exclusively, forms a micropump for medical use that delivers

  regularly a controlled amount of a liquid drug.

  The manufacture of these micromechanical devices, and in particular of these fluidic devices and in particular of these micropumps, is based on micro-machining technologies of silicon or of any other micro-machinable material, in particular by means of lithographic photo techniques and chemical etching, laser ablation, micro

replication or others.

  For the particular application mentioned above, and in still other cases, it is necessary to provide an input control member for self-priming the cage of the micropump. The control of the micropump is effected by varying the volume of the pumping chamber (alternation of decreases and increases), for example at

  means of a command realized by a piezoelectric actuator.

  The European patent application published under No. 453,532 and the international application published under No. WO 99/09321 present such a micropump. However, such a micropump is sometimes not able to function, because the liquid input control member has a membrane that fails to separate, in its area intended to be mobile, the substrate, which This leads to an absence of deflection of the membrane which remains stuck to the substrate thus preventing any pumping phenomenon. This problem is in particular present and particularly sensitive between a silicon substrate and a silicon membrane which have every reason to bond together in an integral manner during the anode welding step between this silicon substrate and the plate.

outside glass.

  As regards other types of micromechanical devices having a structure with a movable member that must be "free" from the rest of the structure, there may be mentioned, for example, capacitive structures, such as those used in accelerometers or gyroscopes, or still structures with a membrane operating in flexion, as

in some pressure sensors.

  In particular, this type of micromechanical structure, fluidic or not, is made with a stack comprising a support plate, in particular made of silicon, covered with a layer of silicon oxide (or more generally with a layer of insulating material), itself covered with a layer of silicon. This stack is available in

  trade and is usually referred to as SOI ("SILICON-ON-

INSULATOR ").

  The use of this type of stack makes it possible to obtain a micromechanical device, in particular a fluidic device, having constant and strictly controlled thicknesses while at the same time implementing

a simple manufacturing process.

  In all cases, it is sought to obtain a movable member, formed in particular in the silicon layer of the stack, capable of reversibly passing from a position spaced to a close position or contact with respect to a surface this surface is, for example, the face of the support plate rotated in the direction of the silicon layer (surface parallel to the stack) or a "transverse" surface of the silicon layer (non-parallel surface, in

  particular perpendicular to the stack) ..

  This surface, from which the movable member moves towards and away forms either a surface on which the movable member comes into abutment in normal operation, or a surface whose movable member approaches without coming into contact eVou support in operation normal, support being able in this second case to intervene in case of a problem like

  safety limiting the movement of the movable member.

  This round-trip movement thus occurs in a given direction, which varies according to the micromechanical devices considered: for example, in a direction perpendicular to the plane of different layers of the element ("perpendicular" motion). > of the mobile organ) or in a direction parallel to the plane of the different layers of the stack ("parallel" movement of the organ

  mobile), or in another direction.

  This m obil ite of the body mobi is not a systematically obtained test, an inadvertent and irreversible bonding may occur during the manufacture of the micromechanical device, so that this bondage damages the functionality of the device and in particular the organ which is supposed to be free for movement in a given direction ("perpendicular", "parallel" or other motion), but which is locked in a fixed position against the surface facing another layer of stacking, in particular against the support plate, after a "perpendicular" movement and a connection that

  inopportune and which we seek to prevent.

  In the following, the term "stop surface" is used to denominate the facing surface against which the movable member tends to get closer and to stick, or even to fix, during a "perpendicular" movement >>, this phenomenon being avoided thanks to the

present invention.

  Depending on the type of movement ("perpendicular", "parallel" or other) of the movable member in its normal operation, this stop surface actually corresponds to the surface of which the movable member approaches and distance ("perpendicular" movement), this stop surface does not correspond to the surface of which the body

  mobile is moving closer and further away ("parallel" movement).

  In particular, in the case of fluidic devices and in particular micropumps with liquid pumping, during manufacturing steps to obtain mobile parts (valves, pumping membranes, etc.), this bonding may in particular occur during a drying step, occurring after the chemical attack which releases the movable member from the rest of the structure: during this drying step, the capillarity forces resulting from the surface tensions of the residual water tend to cause the mobile member to bend ("perpendicular" motion) so as to connect it almost definitively to

a surface opposite.

  In this situation, or in other cases, there is in fact an unexpected adhesion between the movable member and the facing surface, by simple contact, tail regardless of the temperature, and even at room temperature. This bonding can also intervene, possibly in addition to the precise phenomenon, during the fixing between the SOI stack and a closure plate by the plate welding technique, and in particular anodic welding in the case of a closure plate. In the course of this welding, the entire assembly is heated to a temperature of more than 300 ° C. (generally 400 ° C.) while a negative potential of several hundred volts is applied to the closure plate. In the latter case, electrostatic forces tend to bend the movable member towards a facing surface (perpendicular movement K>), the temperature then achieving a definitive fixation.

in the form of a weld.

  In addition to the situation of a plate welding, more generally the simple fact of carrying more than 250 C, and a fortiori more than 300 C, the structure causes a worsening of unexpected adhesion

  aforementioned which is transformed into irreversible solidarity.

  In order to improve this aspect, some techniques have been proposed among which various methods of liberation avoiding the capillary forces or, incidentally, certain techniques of deposit

  a layer of an anti-adhesion material on the surfaces concerned.

  However, the techniques proposed until now have not

  responded satisfactorily to this problem.

  The present invention aims to provide a micromechanical device, and in particular a fluidic device, which can be manufactured in a simplified manner and constitute a micromechanical device gable in its function of round-trip of the movable member avoiding any

  adhesion eVou fixation (such as gluing, welding ...).

  In the particular case of the fluidic device and quite specifically in the case of a liquid inlet control member or a liquid outlet control member or a micropump, it is sought to obtain a fluidic device gable in its pumping function. For this purpose, according to the invention, there is provided a micromechanical device comprising a stack comprising a support plate (or wafer), a layer of insulating material partially covering said support plate, and a layer of monocrystalline silicon or polycrystalline silicon covering said layer of insulating material, said layer of insulating material eVou the silicon layer being machined to form, in said layer of insulating material, at least one recess completely free of said insulating material, so defining in said silicon layer a movable restart member relic to said silicon layer, a stop surface being formed on the face of said support plate rotated towards said movable member, at least opposite a said recess portion, said butee surface presenting physicochemical properties preventing a solidarization between

  the movable member and said abutment surface.

  In certain types of micromechanical devices, the latter further comprises a closure plate covering said silicon layer of the stack, said support plate comprises at least one conduit passing right through it and orienting in the extension to said recess, said closure plate eVou said silicon layer being machined (s) to define, between said closure plate and said silicon layer, a cavity, said movable member being defined in said layer

  silicon, between said cavity and said recess.

  In this case, if a "perpendicular" movement is necessary for the operation of the device, said movable member is

  then able to approach, in a reversible manner, said

  support, the face of said support plate rotated towards said layer of insulating material forming, at least around the opening to said conduit,

said abutment surface.

  Advantageously, said abutment surface extends substantially opposite at least the periphery of the opening of the conduit

  turn to said insulating material.

  In the case of the type of micromechanical devices mentioned above, it happens, particularly but not only for fluidic devices, that said silicon layer presents a clearance completely.

  free of material relic audit said recess and said cavity.

  In this case, this clearance allows a localized separation of the movable member from the rest of the silicon layer, which facilitates increases the possibilities of movement of the movable member: if a "perpendicular" movement is required for operation of the device, said movable member can more easily come into contact with

said abutment surface.

  In particular, said physicochemical properties of said abutment surface preferably prevent a securing between the mobile organ and said abutment surface during a treatment.

  thermal having a temperature of more than 250 C.

  Preferably, said physicochemical properties of said abutment surface prevent bonding between the movable member and said abutment surface at a temperature of more than 300 ° C., when a negative potential of at least several hundred volts is applied to

  said closure plate (case of anodic welding).

  According to a first preferential embodiment, said physico-chemical properties of said abutment surface comprise the fact that the surface state is such that the roughness is greater than 0.5 nm rms

  ("root mean square"), preferably between 2 and 100 nm rms.

  Indeed, it has been found that such roughness forms a surface state of the abutment surface which prevents fixation, by adhesion or

  bonding, or by welding, the adjacent movable member.

  According to a second embodiment, said abutment surface is made of a refractory material or of polycrystalline silicon (pSi), and it is preferably a refractory material which preferably comprises silicon nitride, nitride titanium, aluminum nitride, silicon carbide, titanium oxide, carbide

  titanium, amorphous diamond (DLC), and polycrystalline diamond.

  In this case, the chemical stiffness of the refractory material or the roughness of the polycrystalline silicon (p-Si) prevents the attachment, by adhesion or bonding, or by welding, of the adjacent mobile member on the surface.

butee surface.

  These two embodiments may be formed when said abutment surface is made of a refractory material or polycrystalline silicon (p-Si) and has a roughness greater than

0.5 nm rms.

  In particular, some wind deposition techniques are more favorable for obtaining a rough layer (for example the PECVD or "Plasma Enhanced Chemical Vapor Deposition" deposit, in particular silicon nitride), in particular it is known to to increase the roughness of the surface by techniques such as chemical attack, attack

plasma or ion bombardment.

  It is understood that the invention is based on the fact that the abutment surface has specific physicochemical properties with a surface state (in particular roughness) and / or chemical reactivity, or rather a chemical inertia, preventing adhesion. of the mobile organ

on this butee surface.

  In particular, but in a limiting manner, the present invention relates in particular to a fluidic-type micromechanical device: in this case, said cavity is intended to be filled with fluid, and said movable member is adapted to approach in a reversible manner from said

  support plate under fluid pressure in said cavity.

  More particularly, the present invention relates to a

  fluidic device or the fluid is a liquid.

  By way of non-limiting example, the present invention relates to a liquid input control member forming a valve

  non-return device comprising such a fluidic device.

  As will become apparent below, according to another feature of the present invention, the method of manufacturing the micromechanical device realizes the specific physico-chemical properties of the surface of the

  butee before the training audit mobile organ.

  According to another object of the present invention, there is provided a method for manufacturing the micromechanical device of the precise type, this manufacturing method being characterized in that it comprises the following steps: a) a support plate is provided having a free face, b ) at least one layer of insulating material at least partially covering said free face of the support plate is deposited; and c) a physico-chemical treatment of at least said layer of insulating material is performed so as to create at least a portion of the free face of the support plate, a stop surface having physicochemical properties preventing a bond with silicon, d) providing a monocrystalline or polycrystalline silicon layer having a free face,

  e) said silicon layer is disposed on said layer of

  an insulating material on the side of the face of said silicon layer opposite said free face, f) confined by a physicochemical operation the surfaces opposite said silicon layer and said layer of insulating material, g) thinning said free face of said silicon layer to give said silicon layer a predefined thickness, and h) polishing said free face of said layer of silicon.

Silicon.

  Among the various manufacturing steps, there is the term "machining", reserved for machining, intended to vary the thickness of a plate or certain areas of a plate, the term "structure", reserved for machining which favors the conservation of the material of a layer in certain zones and the removal of all the thickness of the

  material of this layer in other areas.

  According to a first embodiment of the manufacturing method, steps b) and c) are formed as follows: b) the deposition of an underlayer of insulating material is carried out on said support plate and then the deposit of a layer of refractory material on said underlayer of insulating material, and c) is machined by structuring ['together constitutes said sub-layer of insulating material and said layer of refractory material, in order to keep the insulation and insulation material only in the zones forming the abutment surface which is

  thus constituted to said refractory material.

  According to a second and a third embodiment of the

  method of manufacture, step c) comprises performing a chemical etching structure of said layer of insulating material to form said recess by completely removing the material from said layer.

of insulating material.

  In addition, in the case of the second embodiment of the manufacturing method, the following steps are carried out between steps c) and d): c1) the deposition of a layer of polycrystalline material (in particular polycrystalline silicon p-Si) on the free face of said insulating material layer and at said location on said free face of the support plate c2 planarization is performed on said layer of polycrystalline material and said insulating material layer for removing all said layer of polycrystalline material in areas covering said layer

of insulating material.

  In the case of the third embodiment of the manufacturing method, said chemical etching of said layer of insulating material is carried out so that the free surface of said support plate has a surface state such as roughness is greater than

  0.5 nm rms, preferably between 2 and 100 nm rms.

  According to a fourth embodiment of the manufacturing method, the following step is furthermore carried out between steps a) and b): a1) a physicochemical treatment, for example a chemical etching, of said support so that the free surface of said support plate has a surface state such that the roughness is greater than 0.5 nm rms, preferably between 2 and 100 nm rms before the deposition of said layer of insulating material made a step b). In particular, in the case of the fourth embodiment of the manufacturing method step c) is to polish the free face of said layer of insulating material to facilitate the step f) fixing. Whatever the manufacturing process among the first

  the fourth embodiments presented above, it includes in

  in addition to the following steps mentioned below: i) said cavity is machined from said closure plate eVou of the free face of said silicon layer by photolithography et etching, j) at least one said at least one duct is machined through on the basis of said support plate by photolithography and chemical etching, k) a chemical etching of said layer of insulating material at least by said conduit is carried out so as to remove the insulating material in the zones forming said recess so that a zone said silicon layer is released from said layer of insulating material by forming said movable member, I) at least said closure plate is provided, m) releasably sealed by a physico-chemical method, preferably by welding. plate, said closure plate has said

  surface of the silicon layer that has not been milled.

  The invention will be better understood, and features secon

  and their advantages will appear during the description of the

  various embodiments of the invention given by way of examples.

  It is understood that the description and the drawings are not

  quta indicative and non-limiting.

  Reference will be made to the accompanying drawings, in which: FIG. 1 shows a longitudinal sectional view of a fluid inlet control member forming a fluidic device constituting an aspect of the micromechanical device according to the present invention, FIG. represents a stack, for example of the SOI type, from which the fluidic device of FIG. 1 is manufactured; FIGS. 3A to 3F represent the different manufacturing steps of the stack of FIG. 2 according to a first embodiment of FIG. manufacturing method according to the invention, FIGS. 4A to 4F show the different manufacturing steps of the stack of FIG. 2 according to a second embodiment of the manufacturing method according to the invention, FIGS. 5A to 5E represent the different manufacturing steps of the stack of FIG. 2 according to a third embodiment of the manufacturing method according to the invention, FIGS. 6A to 6F represent the different manufacturing steps of the stack of FIG. 2 according to a fourth embodiment of the manufacturing method according to the invention, and FIG. 7 represents a longitudinal sectional view in partial perspective of a micropump forming another aspect of the invention.

  micromechanical device according to the present invention.

  In these figures, an identical element represents on several

  figures always carry the same numerical reference.

  In addition, for reasons of clarity, it should be noted that the thicknesses of the various elements represented have been greatly exaggerated in the drawings so that they are not strictly scaled. According to a first aspect of the micromechanical device according to the present invention, there is considered a fluidic device forming a liquid input control member, one embodiment of which is illustrated in FIG.

Figure 1.

  This liquid inlet control member 100, intended to form a one-way valve or non-return valve, comprises a glass closure plate 20 disposed above a stack 30 which has been previously manufactured for the formation of the different parts

  functionalities of this control organ 100.

  This stack 30 consists of a silicon layer 32 surmounting a layer of silicon oxide 34, or more generally a layer of insulating material, itself arranged above a plate

silicon support 36.

  It should be noted that other materials than silicon can be used to form the support plate 36, in particular quartz

or sapphire.

  This type of stack commonly known as SOI (KSILICON-ON-INSULATOR,) is commercially available in the form of wafers or "wafers" especially used in the semiconductor electronics industry. The role of these three elements of the stack 30 determines substantially different thicknesses: the silicon support plate 36 serving as a rigid base, the latter preferably has a thickness of between 50 and 1000 μm, advantageously between 300 and 600 μm, the silicon oxide layer 34 is intended to connect the silicon support plate 36 and the silicon layer 32 while maintaining a constant gap between them, while being easily removable in certain zones so that its thickness must remain very small, preferably between 100 nm and 2 μm, and advantageously between 0.2 and 1 μm, and the silicon layer 32 is intended to be machined in all its thickness to form liquid passages or else in only a portion of its thickness (about half) to delimit, with the glass closure plate 20, a cavity 38, and in some cases a movable member; this silicon layer 32, which may be produced in monocrystalline or polycrystalline silicon, has an initial thickness preferably of between 1 and 100 μm, and advantageously

between 10 and 50, um.

  The stack 30 is machined by conventional photolithography and etching techniques in order to obtain the various functional elements of the input control member 100, in particular a cavity 38 and a movable member 40, before carrying out the link between the

  glass closure plates 20, 20 'and this stack 30.

  This connection between the closure plate 20 and the free face of the silicon layer 32 is. in a known manner, carried out by plate welding (anodic welding when the closure plate is made of glass), after which a fixing in the form of a tight connection is obtained. Instead of using glass closure plates 20, 20 ', it is also possible to use indifferently, for one or the other, or for

  the two glass closure plates 20, 20 ', a silicon plate.

  A liquid inlet conduit 102 passes through the lower glass closure plate 20 'and the silicon support plate 36 throughout their thickness, from a first end 102a to a second end 102b. This second end 102b is adjacent to a circular zone 35 of the silicon oxide layer 34 completely free of silicon oxide which extends well beyond the

  liquid inlet duct 102 and forming a recess 35.

  The silicon layer 32 has been machined in part of its thickness on the opposite side to the silicon support plate 36, in order to

form the cavite 38.

  In addition, a clearance 104, corresponding to a material shrinkage in the entire thickness of silicon dioxide 32, is located in the extension of the cavity 38 and the oxide-free zone 35. of silicon, close to, but not directly opposite, the second end 102b of the liquid inlet conduit 102 which is rotated towards the

silicon oxide layer 34.

  The cavity 38 extends at least opposite this zone 35 and the

liquid inlet duct 102.

  In this way, a member 40 is formed in the silicon layer 32, this member 40 not being connected to the glass closure plate 20 (cavity 38) or to the silicon oxide layer 34 (recess 35) and this member 40 being separated from the remainder of the silicon layer 32 by the clearance 104. This member 40 may have different shapes in the orthogonal plane in FIG. 1: some possible forms are represented in FIGS. 1A and 1B of the application published under the

WO 01/90577.

  The very thin thickness of this member 40 (less than 50 μm and preferably of the order of 10 m) makes it elastically mobile in a direction perpendicular to the main plane of the stack 30 or the glass closure plate 20, to know from top to bottom as indicated

  the double-headed arrow in Figure 1.

  In this figure 1,1 'organ 100 forming an inlet valve is shown in the rest position, that is to say partially open. When the liquidearrive through the entry conduit 102''emobile member 40 is raised under the pressure of liquid which is then higher in the inlet conduit 102 to that in the cavity 38, so that the valve is placed in its seat. open position and allows the liquid to enter the zone or recess 35, to go into the clearance 104, in order to reach

the cavite 38.

  This member 100 is capable of being inserted into a more complex fluidic assembly in which the member 100 constitutes an element

upstream of the liquid inlet.

  Thus, it is understood that the liquid present in the cavity 38 is likely to have a higher pressure than the liquid pressure in the inlet duct 102, which then allows the closure of the organ by the lowering of the movable member 40 which comes into sealed contact against the face of the silicon support plate 36 rotated towards the silicon layer all around the second end 102b of the

leads 102.

  The relative elasticity of the thinned silicon layer 32 at the location of the cavity 38 allows the flexion, in particular at the level of a connecting arm 41 connecting the movable member 40 to the remainder of the

silicon 32.

  Thus, when the liquid pressure in the cavity 38 is no longer greater than the liquid pressure in the conduit 102, a return of the member 40 to its initial position as shown in FIG.

  that is to say, a partial closure of organ 100, is realized.

  When the liquid pressure in the conduit 102 becomes less than the liquid pressure in the cavity 38, the movable member 40 is fully lowered until it comes into sealing contact against the support plate 36, the input control member liquid 100 is then closed. It is understood that this member 100 forms an inlet valve in which the body of the valve is constituted by the face of the movable member 40 rotated towards the silicon support plate 36 and in which the seat of the valve is formed by the region of the face of the silicon support plate 36 rotated towards the

  silicon 32 which surrounds the second end 102b of the conduit 102.

  In the following, this region of the face of the silicon support plate 36 turned towards the silicon layer 32 which surrounds the second end 102b of the conduit 102 and which forms the seat of the valve will be referred to as a stop surface and door. 42. In FIG. 1, this abutment surface is represented by a layer of material 42. In fact, as will be explained in detail in FIG.

  following the description, especially in relation to the different modes

  proposed embodiment of the manufacturing process of the stack 30 in the situation of FIG. 2, either this stop surface 42 is directly integral with the free face of the silicon support plate 36, or this stop surface 42 is formed of the free face of a layer of additional material 44 deposited on the free face of the

support plate 36.

  In a preferential but nonlimiting manner, when this abutment surface 42 is formed of the free face of an additional layer 44, a layer 44 made of a refractory material and having a thickness of between 0.1 and 5 μm, is used.

preferably between 0.1 and 0.3 m.

  In particular, said additional layer 44 having the abutment surface 42 is. preferably, made of a material

- -15

  Part of the group consists of silicon nitride, titanium nitride, aluminum nitride, silicon carbide, titanium oxide, titanium carbide, amorphous diamond (DLC) and polycrystalline diamond. Also, said additional layer 48 comprising said

  stop surface 42 may be made of polycrystalline silicon (p-Si).

  Indeed, with an additional layer 44 or 48 made in one of the aforementioned materials, a stop surface 42 is created which has physicochemical properties, and in particular a chemical inertness and / or a sufficient roughness with respect to the silicon constitute the support plate 36, which prevents any adhesion, fixation and welding

  between the movable member 40 and the support plate 36.

  In the case where this abutment surface 42 is directly integral with the free face of the silicon support plate 36, so as to form an anti-adhesion surface, the surface state of this surface is modified. surface of stop 42 in silicon, creating a sufficient roughness to overcome the gluing problems mentioned in the introduction. In the specific case, it is ensured that said abutment surface has a surface state which is such that the roughness is greater than 0.5 nm rms, preferably between 2 and 100 nm rms. This roughness is measured in the form a statistical value of the height differences from a perfect plane, considering the square root of the average of the deviations to the edge, rms

meaning "root mean square".

  Thus, it is understood that the stop surface 42 is "treated" either by an adaptation of its roughness when it is part of the silicon support plate 36, or by depositing an additional layer 44 or 48, to form a surface intended to come into contact with the movable member 40 around the second end 102b of the duct 102 while avoiding the problems of eVou bonding possible welding of

the former art.

  It should be noted that these two solutions are cumulative since it is possible to "treat" the stop surface with the use of an additional layer 44 or 48 deposited on the free face of the plate.

  support 36, whose free face has the aforementioned roughness properties.

  These properties of roughness (roughness greater than 0.5 nm rms, and preferably between 2 and 100 nm rms) appear in fact as those to privilege among the different possibilities of properties.

  physicochemicals preventing adhesion and welding.

  In particular, it should be noted that this "treatment" is carried out at the time of manufacture of the SOI stack 30 and that it is therefore possible to limit it to the area forming the stop surface 42 or to apply it to

the entire surface of the stack.

  Also shown in FIG. 1 are stop elements 46 disposed on the face of the glass closure plate 20 facing towards stack 30. These optional stop elements 46 are preferably made of titanium in order to prevent too much noise. large deflection of the movable member 40 in its open position correspond to a deflection upwards from the position of the

figure 1.

  The inlet valve 100 shown in FIG. 1 is a result of an emulsion 30 which shines on FIG. 2 in an intermediate stage of manufacture, in which the stack 30 itself is entirely made, but prior to the formation of the cavity 38 in the silicon layer 32 and the closure of the structure by the glass closure plates 20 and 20 '.

  Several embodiments of the manufacturing method of

  Stack 30 of Figure 2 will now be described.

  A first embodiment of this manufacturing method is described with reference to FIGS. 3A to 3F successively showing the following steps: a) a support plate 36, preferably made of silicon, having a free face (FIG. 3A) is provided; b) depositing an undercoat of insulating material 34 on the free side of the support plate (in particular a layer of silicon oxide with a thickness of about 0.2 μm made by oxidation thermal), then the deposition of a layer of refractory material 44 on said insulating material sub-layer 34 (Figure 3B), the refractory material belonging preferably to the group is silicon nitride, titanium nitride, aluminum nitride, silicon carbide, titanium oxide, titanium carbide, amorphous diamond (DLC) and polycrystalline diamond; c) the structure formed by the underlayer of insulating material 34 and the layer of refractory material 44 is formed in order to preserve this assembly only in the areas intended to form the abutment surface 42 (FIG. 3C) which is made of refractory material 44; c1) the deposition of a layer of insulating material 46, preferably of silicon dioxide and obtained by LOCOS oxidation of a thickness of about 1 m, on the face of the support plate 36 carry the layers 34 and 44, in the areas of this face that do not wind covered by this set 34 and 44 (Figure 3D); d) providing a monocrystalline or polycrystalline silicon layer 32 having a free face ("wafer"); e) the silicon layer 32 is disposed on the layer of insulating material 46 and on the whole forms layers 34 and 44 on the side of the face of said silicon layer 32 opposite said free face; f) sealingly affixed by the physico-chemical operation (plate welding and in particular direct plate welding) the facing surfaces of the silicon layer 32 and the layer of insulating material 46 (Figure 3E); g) thinning the free face of the silicon layer 32 to give this silicon layer 32 a predetermined thickness (Figure 3F); and

  h) the polishing of the free face of the silicon layer 32 is carried out.

  In the context of this first embodiment, the layer of refractory material 44 is preferably made of silicon nitride, which forms the anti-adhesion and anti-welding layer at the surface of the surface.

stop 42.

  In particular, the deposition of the silicon nitride layer 44 may be carried out by techniques such as the Low Pressure Chemical Vapor Deposition (LPCVD) method or by the PECVD method.

  ("Plasma Enhanced Chemical Vapor Deposition").

  We can privilege the second precise process that gives

  a greater surface roughness.

  According to this first embodiment of the manufacturing method, the use of a layer of refractory material 44, in particular of silicon nitride, provides the necessary chemical inertia for

  prevent any connection between the movable member 40 and the support plate 36.

  However, it can also be decided to increase the roughness of the abutment surface 42, that is to say of the free face of the layer of refractory material 44: such an increase in roughness can be obtained for example by the fact that after the deposition step of the refractory material layer 44, a treatment is made of the free face of the layer of refractory material, in order to increase the roughness thereof until having a surface such that the roughness is greater than 0 , 5 nm rms,

  preferably between 2 and 100 nm rms.

  Such treatment may include, for example, an attack

plasma or ion bombardment.

  The refractory material layer has a thickness of between 100 and 1000 nm. The structuring indicated in step c) is carried out, like all the structures mentioned, by conventional photolithography techniques, that is to say by the use of

  masks and chemical etching, including RIE ("Reactive lon Etching").

  Referring now to Figures 4A to 4F showing the different steps of the manufacture of a stack according to Figure 2, according to a second embodiment of this manufacturing method. According to this second embodiment, the following steps are successively carried out: a) a support plate 36 having a free face is provided; b) depositing a layer of insulating material 34 (thermal oxidation is performed to form a silicon oxide layer having a thickness of about 0.2 m) covering the entire free face of the support plate 36 (FIG. 4A ); c) etching (e.g., RIE) of the insulating material layer 34 is performed to form the recess 35 by completely removing the material from the layer of insulating material 34 in at least one circular zone which will be located in the extension of the entry duct of the liquid 102 and facing the periphery of the second end 1 02b of this duct 102 (Figures 1 and 4B); c1) depositing a layer of polycrystalline material 48 on the free face of the layer of insulating material 34 and the location of the recess 35 on the free face of the support plate 36 (FIG. 4C ); c2) a planarization is carried out (such as a lapping or polishing, in particular a CMP chemical mechanical polishing or

  "Chemical Mechanical Polishing") on the layer of poly-

  crystalline material 48 and the insulating material layer 34, in order to flatten the rotated face in the direction opposite to said support plate 36 of all the layers 34, 48 by removing all said layer of polycrystalline material 48 in the zones covering said layer of insulating material 34 (FIG. 4D): this planarization step is performed to a sufficient thickness so that, at the locations where the layer of insulating material 34 is located, this backside is no longer superimposed by a polycrystalline material thickness 48 ; d) providing a layer 32 of monocrystalline silicon or polycrystalline having a free face; e) the silicon layer 32 is placed on the layer of insulating material 34 and on the polycrystalline material layer 48 (or more exactly on the flat free face resulting from the preceding planarization step) on the side of the layer face. silicon 32 opposed to said free face; f) the surfaces opposite the silicon layer 32 and the insulating material layer 34 (or, more exactly, the overall shape of the insulating material layer 34) are fixed by means of a physico-chemical operation; of the polycrystalline material layer 48) (FIG. 4E produced for example by plate welding and in particular by direct welding); g) the free face of the silicon layer 32 is thinned to give it a predetermined thickness (thinner step at which it leads to the situation illustrated in FIG. 4F); and

  h) the polishing of the free face of the silicon layer 32 is carried out.

  The layer 48 of polycrystalline material is preferably composed of polycrystalline silicon (p-Si) deposited in particular by a low pressure chemical vapor deposition (LPCVD) process, which results in a surface state of this layer of

  polysilicon having satisfactory roughness.

  Other polycrystalline materials may constitute layer 48 of polycrystalline material provided that they exhibit surface properties with sufficient roughness (roughness superior to

  0.5 nm rms, and preferably between 2 and 100 nm rms).

  In particular, it can be predicted that layers 34 and 48

  each have a thickness of about 0.2 μm.

  If it is desired to increase the roughness of the surface of the layer of polycrystalline material 48, it is possible to add, between steps c1) and c2), a treatment of the free face of this layer of polycrystalline material,

  in particular plasma attack or ion bombardment.

  We recall that the roughness searched is greater than

  0.5 nm rms, and preferably between 2 and 100 nm rms.

  In the case of this second embodiment, it is understood that the physico-chemical properties of the abutment surface 42 will be constituted by the intrinsic roughness of the layer of polycrystalline material 48 which has thus been realized localized integration a

  Location of this abutment surface 42.

  A third embodiment of the method for manufacturing stack 30 of FIG. 2 will now be described in relation with FIGS. 5A to 5E which successively illustrate the following steps: a) a support plate 36 having a free face (FIG. 5A); and b) depositing a layer of insulating material 34 covering the entire free face of said support plate 36 (in particular, a thermal oxidation step is carried out for the formation of a silicon oxide layer having a thickness of about 0.2 m to 1 μm) (Fig. A); c) a physicochemical treatment of the insulating material layer 34 is carried out so as to create a stop surface 42 having physicochemical properties preventing solidarization with silicon: in particular, as it appears on FIG. 5C shows a chemical etching pattern (RIE or "reactive lon etching") of the insulating material layer 34 to form the recess 35 by total removal of the material from the layer of insulating material 34 at least in the zone which will correspond to the second end 102b of the conduit 102 of FIG. 1; it is understood that this step results in the formation of the abutment surface 42 at which the support plate 36 has a high roughness (indeed, the chemical etching of the insulating material layer 34 is carried out so that the surface free of the support plate 36 has a surface state such that the roughness is greater than 0.5 nm rms, and preferably between 2 and 100 nm rms); d) providing a layer 32 of monocrystalline silicon or polycrystalline having a free face; e) the silicon layer 32 is placed on the layer of insulating material 34 on the side of the face of the silicon layer 32 opposite the free face; f) the surfaces facing the silicon layer 32 and the insulating material layer 34 (by plate welding, in particular by anodic welding) are fixed in a sealed manner by a physico-chemical operation (FIG. 5D); g) thinning the free face of the silicon layer 32, to give this back a predetermined thickness (slimming step); and h) polishing the free face of the silicon layer 32

(Figure 5E).

  It will be understood that this third embodiment realizes the local roughening of the silicon wafer surface constituted by the support plate 36 in the zone which will form the recess 35 and the

stop surface 42.

  The step of roughening the surface of the polysilicon can be carried out by techniques other than the RIE attack: by etching, especially wet (KOH, TMAH, NaOH ...), by plasma etching or by ion bombardment, etc. . Other techniques, possibly comprising multiple steps, can also be implemented to obtain roughness

  satisfactory surface of the support plate 36 of silicon.

  A fourth embodiment of the manufacturing method of the stack 30 is now described in relation with FIGS. 6A to 6F which successively illustrate the following steps: a) a support plate 36 is provided; and a1) a physico-chemical treatment is carried out (for example by etching, especially RIE) of the entire free face of the support plate 36, so that the free face of this support plate 36 (which will form the surface of Butee 42 in Figure 1) has a surface condition such that the roughness is greater than 0.5 nm rms, preferably between 2 and 100 nm rms (Figure 6B); b) then depositing a layer of insulating material 34 (silicon oxide preferably obtained by thermal oxidation to a thickness of about 1 μm or more) on the free and rough face of the support plate 36 (Figure 6C); c) a physicochemical treatment of the free surface of the layer of insulating material 34 is carried out in order to create a stop surface 42 having physicochemical properties preventing a bond with silicon: in particular, a step of polishing the free face of the layer of insulating material 34: in fact, it is the step of roughening the entire surface of the silicon "wafer" (support plate 36) which will in itself later prevent further gluing and welding of the movable member 40, which will be formed in the silicon layer 32, with the free face of the support plate 36 (abutment surface 42), the polishing step serving in fact to facilitate the subsequent fixing when step f); d) providing a layer 32 of monocrystalline silicon or polycrystalline having a free face; e) the silicon layer 32 is placed on the layer of insulating material 34 which has been poked, on the side of the face of the silicon layer 32 opposite the free face; f) the surfaces opposite the silicon layer 32 (free face) and the layer of insulating material 34 (poke face) are fixed in a sealed manner by a physico-chemical operation (FIG. 6E); g) thinning the free face of the silicon layer 32 to give the silicon layer 32 a predetermined thickness; and h) polishing the free face of the silicon layer 32

(Figure 6F).

  Step a1) chemical etching for the attention of the rugged looking rugosity of the entire surface of the silicon support plate 36 can be replaced by multiple variants: wet etching silicon (KOH, TMAH, NaOH), plasma attack In particular, it has been found that this fourth embodiment of the method of manufacturing the stack 30 gives very good results for a process which is relatively simple to implement. Another advantage of the fourth method of manufacturing the element 30 described in relation to FIGS 6A to 6 F, co nsiste da ns the fact that the entire surface of the silicon support plate 36 has the desired roughness , so that the location of the cavity 35 and, in particular, of the abutment surface 42, is not already imposed in contrast to the first to third embodiment of the manufacturing process of FIG.

the stack 30.

  It is understood that the four embodiments that come

  1 to be described with reference to the method of manufacturing a stack 30 according to FIG. 1, may be applied in addition to a liquid inlet member as illustrated in FIG. 1, to other micromechanical components. ,

fluidic or not.

  In particular, these methods can be applied to the realization of another form of inlet valve as illustrated in FIG. 2 of the international application published under WO 01/90577, to the pressure sensor illustrated in FIG. Figure 3 of the same international application or

  still as control member of liquid outlet.

  The present invention also relates to a micropump comprising at least one fluidic device such as those just mentioned, in particular a device for controlling the entry of liquid as illustrated in FIG. an example of such a micropump 500 is shown in FIG. 7 where the inlet valve 100 of FIG.

  in the left part of Figure 7.

  In this case, the cavity 38, intended to be filled with liquid, comprises a pumping chamber 504 at a pumping part 502, this pumping part 502 comprising control means (of the actuator type, in particular for the operation of piezoelectric type, magnetostrictive, electrostatic, electromagnetic, pneumatic or memory shape, which can be integrated directly to the micropump, by fixing on the face of the glass plate 20 'rotated in the opposite direction to the stack 30 and by fixing on a mobile part 514, or be external to the micropump 500 being connected indirectly to the pumping membrane 506, these means of

  com m and e are not represe nt).

  These wind control means provided with a pumping membrane 506 integrated with the micropump 500, to cause a periodic change in the volume of the pumping chamber 504, the micropump 500 further comprising output control means

  liquid in the form of an outlet valve 200.

  In this case, the mobile member 40 constitutes the valve of the organ

  liquid entry control 100.

Furthermore, as shown in FIG. 7, the closure plate 20 is a first glass closure plate and the micropump further comprises a second glass closure plate 20 'attached to the face of the glass plate. support 36 opposed to the

  first glass closure plate 20.

  This micropump 500 also comprises a liquid pressure detector 400 located downstream of the control order of the input of

  liquid 100 and upstream of the liquid outlet control member 200.

  Other types of micropumps falling within the scope of the present invention and which may include a stack 30 such as that of FIG. 2 are particularly described in patent applications.

  WO 98/29661 or WO 99/09321.

  These micropumps can be used in many applications, such as pumps for medical use for the continuous delivery of a liquid medicament. In particular, such a micropump can be regulated thanks to its very small dimensions, of the "implantable" type, that is to say that can be placed under the skin of the patient, or "external" type and connected, by its 100 liquid entry control organ, to the blood circulatory system of the patient by a

port of entry at the level of the skin.

Claims (42)

- Claims   A micromechanical device (100) comprising a stack (30) having a support plate (36), a layer of insulating material (34) at least partially covering said support plate, and a monocrystalline or polycrystalline silicon layer (32). covering said layer of insulating material (34), said layer of insulating material (34) and / or silicon layer (32) being machined to form, in said layer of insulating material (34), at least a recess (35) completely free of said insulating material (34), in order to define, in said silicon layer (32), a movable member (40) restart connected to said silicon layer (32), a stop surface (42); ) being formed on the face of said support plate (36) rotated towards said movable member (40), at least opposite a portion to said recess (35), said abutment surface (42) having physicochemical properties preventing a solidarity between the organ   mobile (40) and said stop surface (42).   2. Device according to claim 1, characterized in that it further comprises a closure plate (20) covering said silicon layer (32) of the stack (30), in that said support plate (36) comprises at least one duct (102) passing right through it and oriented in the extension to said recess (35), in that said closing plate (20) and / or said silicon layer (32) is machined (s) to define, between said closure plate (20) and said silicon layer (32), a cavity (38), said movable member (40) being defined in said silicon layer (32), between said cavity (38) and said recess (35). 3. Device according to claim 2, characterized in that said silicon layer (32) has a clearance (104) fully   material free from said recess (35) and said recess (38).   4. Device according to claim 2 or 3, characterized in that said closure plate (20) is made of glass and in that said physicochemical properties of said abutment surface (42) em puncture a bond between movable member (40) and said abutment surface (42) at a temperature of more than 300 C, when a negative potential of several hundred volts at least is applied to said closure (20).   5. Device according to any one of the claims   preceding, characterized in that said physico-chemical properties of said abutment surface (42) comprise the fact that the surface state is such that the roughness is greater than 0.5 nm rms, preferably included between 2 and 100 nm rms.   6. Apparatus according to claim 3, characterized in that said micromechanical device (100) is of fluidic type, in that said cavity (38) is intended to be filled with fluid, and in that said movable member (40) is adapted to move reversibly toward said support plate (36) under fluid pressure in said cavity (38) 7. Device according to claim 6, characterized in that said fluid is a liquid.   8. Device according to any one of the claims   preceded, characterized in that said support plate (36) is in silicon, quartz or sapphire.   9. Device according to any one of the claims   precedents, characterized in that said support plate (36) presents   a thickness between 50 m and 1mm.   10. Device according to claim 9, characterized in that said support plate (36) has a thickness of between 300 m and 600 .mu.m.   11. Device according to any one of the claims   precedents, characterized in that said layer of insulating material (34) is in silicon oxide.   12. Device according to any one of the claims   precedents, characterized in that said layer of insulating material (34)   has a thickness between 100 nm and 2 m.   13. Device according to claim 12, characterized in that said layer of insulating material (34) has a thickness included between 0.2 μm and 1 μm.   14. Device according to any one of the claims   precedents, characterized in that said silicon layer (32)   has a thickness of between 1 m and 100 μm.   15. Device according to claim 14, characterized in that said silicon layer (32) has a thickness of between 10 m and 50 m.   16. Device according to any one of claims 2 to 15,   characterized in that said abutment surface (42) extends nsily over at least the periphery of the conduit opening (102b).   turns to said insulating material (34).   17. Device according to any one of the claims   preceding, characterized in that said abutment surface (42) is made of a material (44; 48) having a thickness between   0.1 and 5 m, preferably between 0.1 and 0.3 m.   18. Device according to any one of the claims   precedents, characterized in that said abutment surface (42) is   made of a refractory material.   19. Device according to claim 18, characterized in that said abutment surface (42) is made of a material belonging to the group is silicon nitride, titanium nitride, aluminum nitride, silicon carbide, Titanium dioxide, carbide   titanium, amorphous diamond (DLC) and polycrystalline diamond.   20. Device according to claim 17, characterized in that said abutment surface (42, 48) is made of polycrystalline silicon. (P-Si).   21. Device according to claim 17, characterized in that said abutment surface (42) is made of silicon and has a surface state which is such that the roughness is greater than 0.5 nm rms, preferably between 2 and 100 nm rms 22. Method of manufacturing a micromechanical device according to   any of the preceding claims, characterized in that   comprises the following steps: a) providing a support plate (36) having a free face, b) depositing at least one layer of insulating material (34, 46) at least partially covering said free face of the support plate, c) a physico-chemical treatment is carried out at least of said layer of insulating material (34, 46) so as to create, on at least a portion of the free face of the support plate (36), a stop surface ( 42) having physicochemical properties preventing a bonding with silicon, d) providing a layer (32) of monocrystalline silicon or polycrystalline having a free face, e) is disposed said silicon layer (32) on said layer of material insulating (34, 46) on the side of the face of said silicon layer (32) opposite said free face, f) sealingly affixed by a physico-chemical operation the facing surfaces of said silicon layer (32) and said layer of insulating material (34,46), g) amin cit said said free face of said silicon layer (32) to give said silicon layer (32) a predefined thickness, and h) polishing said free face of said silicon (32).   23. Process for manufacturing a micromechanical device according to claim 22, characterized in that steps b) and c) are formed as follows: b) the deposition of an underlayer of insulating material is carried out (34) on said free face of the support plate (36) then the deposition of a layer of refractory material (44) on said underlayer of insulating material (34), and c) is machined by structuring ['together by said underlayer of iso-material (34) and said scale of refractory material (44) so as to retain said underlayer of insulating material (34) and said refractory material (44) only in the areas forming said surface of   butee (42) which is therefore constituted to said refractory material (44).   24. A method of manufacturing a micromechanical device according to claim 23, characterized in that said refractory material (44) belongs to the group consisting of silicon nitride, titanium nitride, aluminum nitride, silicon carbide. , titanium oxide,   titanium carbide, amorphous diamond (DLC) and polycrystalline diamond.   25. Process for manufacturing a micromechanical device according to claim 22, characterized in that step c) comprises performing etching by etching said insulating material layer (34) to form said recess (35). by total withdrawal of the material   of said layer of insulating material.   26. A method of manufacturing a micromechanical device according to claim 22 or 25, characterized in that between steps c) and d), the following steps are further performed: c1) the deposition of a layer of polycrystalline material (48) on the free side of said layer of insulating material (34) and, at the location evident to said (35), on said free face of the support plate (36), c2) is carried out planarizing on said layer of polycrystalline material (48) and said layer of insulating material (34) to remove all said layer of polycrystalline material (48) in the areas   covering said layer of insulating material (32).   27. A method of manufacturing a micromechanical device according to claim 24 or 26, characterized in that, after the step of depositing said layer of refractory material (44) or polycrystalline material (48), a treating the free face of said layer of refractory material (44) or polycrystalline material (48) to increase its roughness until having a surface condition such that the roughness is   greater than 0.5 nm rms, preferably between 2 and 100 nm rms.   28. Process for manufacturing a micromechanical device according to claim 27, characterized in that said treatment comprises a   chemical attack, plasma attack or ion bombardment.   29. The method of manufacturing a micromechanical device according to claim 25, characterized in that said chemical etching of said layer of insulating material (34) is carried out so that the free surface of said support plate (36) presents a state. surface area such that the roughness is greater than 0.5 nm rms, preferably between 2 and nm rms.   30. The method of manufacturing a micromechanical device according to claim 22, characterized in that between steps a) and b), the following step is further performed: a1) a physicochemical treatment of said support plate (36) is carried out; ) so that the free face of said support plate (36) has a surface state such that the roughness is greater than 0.5 nm rms, preferably between 2 and 100 nm rms before the deposit of said   layer of insulating material (34) made in step b).   31. A method of manufacturing a micromechanical device according to claim 30, characterized in that said physicochemical treatment of step a1) consists in performing a chemical etching, a plasma etching or an ion bombardment of said support plate ( 36) 32. Process for manufacturing a micromechanical device according to claim 30 or 31, characterized in that step c) consists of polishing the free face of said layer of insulating material (34).   to facilitate step f) fixing.   33. Process for manufacturing a micromechanical device according to   any of claims 21 to 32, characterized in that   further comprises the following steps: i) said cavity is machined from said closure plate (20) eVou of the free face of said silicon layer (32) by photolithography and etching, j) at least said conduit is machined (102) passing right through said support plate (36) by photolithography and etching, k) chemically etching said insulating material layer (34) at least through said conduit to remove the material insulation (34) in the regions forming said recess so that an area of said silicon layer (32) is released from said insulating material layer (34) by forming said movable member (40); said closure plate (20), m) is sealed by a physicochemical process, preferably by plate welding, said closure plate (20) has   said surface of the silicon layer (32) which has not been machined.   34. Liquid inlet control member forming an anti-stick valve   return, comprising a fluidic device (100) according to claim 7.   35. Pressure sensing device, comprising a device   Micromechanical device (100) according to one of Claims 1 to 21.   36. Micropump (500) comprising at least one fluidic device (100) according to claim 7, characterized in that said cavity (38) intended to be filled with liquid comprises a pumping chamber (504), in that said movable member (40) constitutes the valve of a liquid inlet control member (100), said micropump (500) further comprising a pumping section (502) comprising control means provided with a pumping membrane (506). ), to cause a periodic change in the volume of the pumping chamber (504), and control means of liquid outlet.   37. Micropump (500) according to claim 36, characterized in that said closure plate (20) is a first glass closure plate and in that it further comprises a second glass closure plate (20 '). fixed on the face of the plate   support (36) opposing said first glass closure plate (20).   38. Micropump (500) according to claim 37, characterized in that said control means of the micropump are located opposite the pumping chamber (504) and integrated directly into the micropump, by fixing on the face of the second plate closing   turn in the opposite direction to the stack.   39. Micropump (500) according to any one of the claims   36 to 38, characterized in that said means for controlling the micropump wind external to the micropump and connected indirectly to said pumping membrane (506).   40. Micropump (500) according to any one of the claims   36 to 39, characterized in that said control means operate in a piezo-electric, magnetostrictive, electrostatic manner,   electromagnetic, pneumatic or memory form.   41. Use of a micropump (500) according to any one of   claims 36 to 40, as a pump for medical use << implantable >>.   42. Using a micropump (500) Solon rune any of   claims 36 to 40, as a pump for medical use of