WO2012072917A1 - Microsystem having a microelectrical and microfluidic function, and method for manufacturing same - Google Patents

Abstract

The present invention relates to a microsystem including both a microelectronic and microfluidic function, as well as to a method for manufacturing such a system, which can be used, in particular, with microsystems dedicated to bioanalysis, such as a lab-on-a-chip, a cell-based array, or a DNA or protein chip array (microarray). The method includes a step of creating a microelectronic chip on a first substrate, said chip being capable of implementing the microelectronic function, and a step of creating a microfluidic structure on a second substrate, said structure being capable of implementing the microfluidic function. In addition, the method includes a step of transferring the second substrate onto the electronic circuit and the first substrate, and the step of creating the microfluidic structure is implemented after said step of transferring the second substrate onto the electronic circuit and the first substrate. The method of the invention thus enables the problems associated with assembling a previously produced microfluidic structure with a previously produced microelectronic structure in terms of manufacturing costs, as well as in terms of spatial resolution, to be overcome. Indeed, the assembly is carried out prior to producing the mircofluidic structure by transferring the second substrate, which serves as a base for the microfluidic structure, onto the microelectronic structure. The method of the invention thus makes it possible to create complex microfluidic structures which are assembled with complex microelectronic structures.

Description

 MICRO-ELECTRONIC AND MICROFLUIDIC FUNCTION MICROSYSTEM AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a microsystem comprising both a microelectronic function and a microfluidic function, as well as a method of manufacturing such a system. It is particularly applicable to microsystems dedicated to biological analysis, such as lab on chip, cell-based array or microarray chips. ).

 In such microsystems, it is often necessary to combine a structure implementing an electronic function, generally of electronic circuit type, with a structure implementing a microfluidic function, generally consisting of several patterns on a substrate, such as microchannels, microreservoirs, micromixers or microreactors for manipulating a liquid or gaseous product to be analyzed or synthesized.

 In particular, terahertz type spectroscopic analysis is used for the characterization of materials in the liquid phase.

 Such an analysis is difficult to implement with the current known means, insofar as these are based on free-space propagation. Consequently, polar liquids, and more particularly liquids with a high water content, are practically impossible to analyze or require an extremely complex analysis procedure.

 In addition, with these means, it may be difficult to obtain measurements on which such an analysis is based, reliable and reproducible.

In addition, microscopic or nanoscopic dimensions of microfluidic structures are encountered for the analysis of objects of microscopic or nanoscopic size, which are not always compatible with the constraints of realization of the electronic circuits intended to implement the electronic function or functions required for the analysis.

 We are particularly interested in the analysis of biological entities without fluorescent labels ("label free"), non-invasively, in real time and in the natural environment. Such a procedure can be obtained thanks to the specificity of terahertz type spectroscopy.

 In fact, terahertz spectroscopy makes it possible to directly probe low-intensity atomic bond energies. Such connections form the foundation of the structuring of living matter.

 Spectroscopic analysis of terahertz type can therefore give useful information, particularly in the field of proteomics. In this field, the information analyzed is sensitive, for example, to the hydration rate of a protein or its conformation. With terahertz spectroscopic analysis, the information and these data can be obtained without special treatment of the biological solution.

 Also, this type of analysis can be usefully applied for the aracterization of liquid or gaseous fluids or microscopic objects in these fluids, in the environmental, food, energy industry (gas, oil) .

 More generally, today, in the field of analysis in the life sciences, we are no longer limited to the functions of detection and recognition of entities, but we are also interested in interaction phenomena. Real-time monitoring of these interactions requires fluid movement and rapid measurement.

 Microfluidic microsystems try to meet these needs. In particular, optical methods developed on the basis of resonant surface plasmons are one example.

These methods have limitations in terms of spatial resolution, since the measurement is global over a sufficiently large area to have a measurable sensitivity.

The interest of terahertz spectroscopy has already been demonstrated. But most of the time, it requires a great deal of work in preparing the sample to be analyzed, for example by desiccating it. Indeed, the terahertz-type rays are extremely sensitive to all media with a high water content, because their power absorption coefficient, of the order of 10 ¹⁸ to 1 THz for 1 mm of pure water, is considerable. . It follows that direct measurement by spectr type spectroscopy on aqueous solutions is difficult and highly subject to external measurement conditions (temperature, sample thickness).

 Solutions have already been proposed, but which remain very complex, for example by using inverse micelles as nano reservoir of biological solutions, all immersed in an apolar solution.

Other solutions consist in using microsystems whose main advantage is to offer excellent reproducibility of the measurements, but which are based on the focusing of the THz-type beam with spatial resolutions that can not fall below the mm ² .

 For the realization of such microsystems combining a microfluidic function and a microelectronic function, it is necessary on the one hand to produce a microfluidic structure comprising patterns such as channels, and secondly to produce a microelectronic structure, generally of circuit type. microelectronics, including the necessary microelectronic components, and to assemble the two structures.

The manufacturing process of such microsystems is therefore complex and costly, since it corresponds to the implementation of a method of manufacturing a microfluidic system, the implementation of a method of manufacturing a microelectronic circuit, and the implementation of an assembly method, of bonding type of a structure to another. The more the microelectronic circuit and / or the microfluidic structure is complex, the more difficult the assembly is and in particular prevents reaching high spatial resolutions.

 In particular, if it is desired to have a microfluidic structure comprising numerous patterns, such as channels, of very small size, it will be necessary to "stick" a microfluidic structure from which a lot of material has been removed, corresponding to the different patterns. microfluidics, on the microelectronic structure.

 The assembly may not hold, or one may damage the microfluidic structure during assembly, or even damage the electronic circuit.

 The invention therefore aims to solve the aforementioned problems among other problems, related on the one hand to the importance of having microsystems combining both microelectronic functions and microfluidic functions, and on the other hand the difficulties of realization of such microsystems.

 The invention thus relates, according to a first aspect, to a method of manufacturing a microsystem comprising at least one microelectronic function and at least one microfluidic function.

 The method comprises a step of creating, on a first substrate of electrically insulating or semiconductor material, a microelectronic circuit capable of implementing the microelectronic function, and a step of creating, in a second substrate, a structure microfluidic capable of implementing the microfluidic function.

In addition, the method comprises a step of transferring the second substrate of electrically insulating or semiconductor material to the electronic circuit and the first substrate, and the step of creating the microfluidic structure is implemented after this step of transfer of the second substrate on the electronic circuit and the first substrate. Thus, the method of the invention makes it possible to overcome the problems associated with the assembly of a microfluidic structure previously produced, with a microelectronic structure previously produced, in terms of manufacturing cost, but also spatial resolution.

 Indeed, with the method of the invention, the assembly is implemented before the microfluidic structure is produced, by transfer of the second substrate which serves as a base for the microfluidic structure, on the microelectronic structure.

 The method of the invention thus makes it possible to create complex microfluidic structures, assembled with complex microelectronic structures.

 In a first implementation variant, the step of transferring the second substrate comprises a step of bonding, preferably by thermocompression, of the second substrate on the first substrate.

 This step of bonding the second substrate to the first substrate is preferably followed by a step of thinning, for example by etching, of the second substrate.

 Moreover, this step of bonding the second substrate to the first substrate is preferably preceded by a step of depositing a polymer layer on the first substrate and the microelectronic circuit.

 This step of depositing the polymer layer may comprise a step of centrifuging the polymer on the first substrate and the microelectronic circuit.

 This centrifugation step of the polymer is preferably preceded by a deposition step, for example by centrifugation, of a layer of a material promoting adhesion of the polymer to the first substrate.

Furthermore, this centrifugation step of the polymer is preferably followed by a step of annealing the polymer layer. In a second implementation variant, possibly in combination with the previous one, the step of creating the microfluidic structure in the second substrate comprises a step of etching, preferably of deep etching type, of the second substrate.

 This step of etching the second substrate is preferably preceded by a step of depositing an etching mask on the second substrate.

 This step of depositing an etching mask on the second substrate may comprise a step of depositing a layer of photoresist, preferably by centrifugation.

 This step of depositing the photosensitive resin layer is preferably preceded by a step of depositing a metal layer, for example aluminum, preferably by spraying.

 Furthermore, this deposition step of the photoresist layer is preferably followed by an ultraviolet irradiation step, optionally after a step of annealing the photoresist layer.

 This ultraviolet irradiation step is itself preferably followed by a step of developing the photosensitive resin and optionally etching the metal layer.

 In addition, the etching step of the second substrate is preferably followed by an etching step, for example of plasma etching type, of the polymer layer deposited on the first substrate and the microelectronic circuit.

This step of etching the second substrate, and optionally the step of etching the polymer layer deposited on the first substrate and the microelectronic circuit, are preferably followed by a step of removing the etching mask, and possibly the layer. metal, for example by dilution in an acetone solution which may be followed by wet etching using for example a solution basic chemical.

 In yet another alternative embodiment, possibly sn combination with one or more of the previous, the step of creating the microfluidic structure is followed by a step of creating a cover of the microfluidic structure cover.

 This step of creating a cover for covering the microfluidic structure preferably comprises a step of depositing a polymer layer on a third substrate of electrically insulating material of the semiconductor.

 This step of depositing the polymer layer on the third substrate preferably comprises a step of centrifuging the polymer on the third substrate, optionally preceded by a deposition step, for example by centrifugation, of a layer of a promoter material. adhesion of the polymer to the third substrate, and optionally followed by a step of annealing this polymer layer.

 The step of depositing the polymer layer on the third substrate is preferably followed by a step of bonding, for example by thermocompression, of the third substrate on the second substrate.

 Furthermore, the step of creating the cover of the microfluidic structure can be followed by a step of cutting the cover so that it covers the microfluidic structure without covering the entire first substrate.

 In yet another implementation variant, possibly sn combination with one or more of the preceding, the step of creating on the first substrate of the microelectronic circuit, comprises a step of depositing a mask on the first substrate.

 This step of depositing the mask on the first substrate preferably comprises a step of deposition, for example by centrifugation, of a layer of photoresist on the first substrate.

This step of depositing the photoresist layer on the first substrate is preferably followed by a step of insulating the photoresist layer with ultraviolet rays, and a step of developing this photosensitive resin.

 This step of insulating the photoresist layer with ultraviolet rays is preferably preceded by an annealing step, and optionally followed by another annealing step.

 The step of depositing the photosensitive resin layer on the first substrate is preferably preceded by a step of deposition, for example by centrifugation, of a layer of a material promoting adhesion of the photosensitive resin on the first substrate. first substrate.

 Furthermore, the step of depositing the photosensitive resin layer on the first substrate, and optionally the step of depositing the layer of adhesion promoter material of the photosensitive resin on the first substrate, are preferably preceded by a dehydration annealing step of the first substrate, this dehydration annealing step possibly being preceded by a cleaning step of the first substrate, for example in a solution comprising acetone and / or ethanol.

 The step of depositing the mask on the first substrate is preferably followed by a step of depositing, for example by evaporation, a metal layer on the mask and the first substrate.

 The step of depositing the metal layer on the mask and the first substrate is preferably followed by a step of withdrawal, for example by a "lift off" type shrinkage, of the mask.

 The invention also relates, according to a second aspect, to a method of manufacturing at least a first and a second microsystem each comprising at least one microelectronic function and at least one microfluidic function, each microsystem being manufactured by the method such as presented above.

The first substrate used for the manufacture of the first microsystem is the same as the first substrate used for Manufacturing the second microsystem.

 Preferably, in the variant in which a covering cap is created from the deposition of a polymer layer on a third substrate, this third substrate used for the manufacture of the first microsystem is the same as the third substrate used for manufacturing of the second microsystem.

 In addition, the method may comprise a step of cutting the first substrate, and possibly the third substrate, so as to separate the first and second microsystems.

 In an alternative embodiment of the methods for manufacturing a multiple microsystem DU presented above, the microfluidic structure comprises at least one microchannel and / or at least one microreservoir.

 Moreover, the electronic circuit comprises at least one waveguide.

 The first substrate may be a glass or quartz substrate.

The invention also relates, according to a third aspect, to a microsystem comprising at least one microelectronic function and at least one microfluidic function obtained by one of the processes presented above.

 The microfluidic structure of the microsystem may comprise at least one microchannel or recess of width less than or equal to 5 μm, preferably less than or equal to 2 μm.

 The microfluidic structure may also comprise at least two microchannels or recesses of width greater than or equal to 2 μm, preferably greater than or equal to 5 μm, spaced from each other by a distance of less than or equal to 5 μm, of preferably less than or equal to 2 μηι.

Other features and advantages of the invention will become apparent more clearly and completely in reading the following description of the preferred embodiments of implementation and embodiment, which are given by way of non-limiting examples and with reference to the accompanying drawings:

 FIG. 1 schematically represents the stages of creation of a microelectronic structure,

 FIG. 2 schematically represents the step of transferring a second substrate to the microelectronic structure represented in FIG. 1;

 FIG. 3 schematically represents the step of creating the microfluidic structure on the structure formed at the end of the step of transferring the second substrate to the microelectronic structure,

 FIG. 4 schematically represents the step of creating a hood, as well as the fabrication of several microsystems on the basis of the same substrate.

 FIG. 1 diagrammatically represents, in one implementation example, three sub-steps (A1), (A2) and (A3) of the creation step (A) of an electronic circuit 2 which preferably comprises at least a waveguide 2, for example of the Goubau line type, on a glass substrate 1.

 For the realization of this electronic circuit 2, a mask 8 is deposited on a substrate 1 of electrically insulating material or semiconductor, such as a glass substrate 1, during step (Al).

 The deposition of this mask 8 on the glass substrate 1 can be obtained by a deposition step (A14) of a photoresist layer 8, for example by centrifugation.

By way of example, it is possible to use a resin of the AZn Lof 2020 type, that is to say a negative photosensitive resin intended for implementing the "Lift Off" process. The parameters for implementing such a deposition by centrifugation are, by way of example:

 - speed = 2500 rpm,

 - acceleration = 1000 rpm,

 - duration = 20 s,

 - thickness = 1.5 Mm.

 The layer 8 of photosensitive resin is then irradiated with ultraviolet rays during an insolation step (A16), the implementation parameters of which may be:

 wavelength = 325 nm,

 - duration = 4.8 s,

- surface density of power = 11 mW / cm ² .

 The photoresist layer, after insolation, then undergoes a development step (A18), using for example an AZ326MIF type developer for 55 seconds.

 Prior to the insolation step (A16), an annealing step (A15) can be carried out for 1 minute at a temperature of 100 ° C.

 It is also possible to implement another annealing step (A17), after the insolation step (A16), also for 1 minute and at a temperature of 100 ° C.

 Prior to the deposition of the photoresist layer 8 during the deposition step (A14), it is preferable to implement a deposition step (A13) of a layer of a resin adhesion promoter material photosensitive 8 on the first substrate 1.

 In the case where the light-sensitive resin used is of the AZn Lof 2020 type, as presented above, it is possible to use HexaMethylDiSilazane (HMDS) as an adhesion-promoting material for the resin 8 on the glass substrate 1.

Preferably also, prior to the deposition of the material adhesion promoter of the photosensitive resin 8 on the substrate 1 *, it is possible to implement a dehydration annealing step (A12) of the glass substrate 1, for example at a temperature of 200 ° C. for a period of 5 minutes.

 Care will also be taken, preferably, to clean the glass substrate 1 before dehydration annealing, in a cleaning step [AlI], for example using acetone and / or ethanol.

 The succession of sub-steps (A 1) to (A 18) described above, therefore, corresponds to the deposition step (Al) of the mask 8 on the substrate 1, and thus leads to the structure represented in FIG. 1.

 Then, a deposition step (A2) of a metal layer 2 is carried out, for example by evaporation, on the mask 8. By way of example, it is possible to use Ti (thickness 500 Å) - Au ( thickness 4000) - Al (thickness 500 Å) for this step of deposition of the metal layer 2 by evaporation.

 The mask 8 comprising an opening in the layer of photoresist 8 insolated and developed as explained above, the metal layer 2 is deposited on the surface of the mask 8 but also sn surface of the glass substrate 1 at the opening in the mask 8.

 Finally, a removal step (A3) of the mask 8, for example by a "lift off" type technique, is implemented, for example using a "remover 1165" type product, at a temperature of 70 ° C. .

 At the end of this removal step (A3), the resin mask 8 is removed with the metal layer deposited on its surface. All that remains is the metal layer 2 deposited on the surface of the glass substrate 1, at the location of the opening previously formed in the mask 8.

FIG. 2 diagrammatically represents the transfer step (B) of a second substrate 4 made of electrically or semiconducting insulating material, such as a silicon substrate 4, on the circuit microelectronics 2, forming the microelectronic structure of the microsystem according to the invention, produced on the surface of the glass substrate 1 as previously explained with reference to FIG.

 For depositing this silicon substrate 4 on the electronic circuit 2 and on the glass substrate 1, it is possible to implement a bonding step (B2), for example by thermocompression for 1 hour, at a temperature of 250 ° C. and at a pressure of 2 bar.

 Prior to this bonding step (B2) of the silicon substrate 4, in order to stick, and more marginally to protect the microelectronic circuit 2, during the subsequent production of the microfluidic structure 4 in the silicon substrate 4, it is necessary to a step of depositing (B1) a polymer layer 3 on the microelectronic circuit 2 and on the glass substrate 1.

 The deposition of the polymer layer 3 can be obtained by a centrifugation step (B12) of a polymer such as BCB3022-46 (BenzoCycloButene), whose parameters can be, by way of example:

 - speed = 2500 rpm,

 - acceleration = 1500 rpm,

 - duration = 40 s,

 - thickness = 2 μηι.

 Optionally, prior to the deposition of the polymer layer 3, a deposition step (B11) of a layer of material promoting adhesion of the polymer to the glass substrate 1 is carried out. This step may also be obtained by centrifugation.

 For example, an AP3000 type material (Adhesion Promoter3000) may be used to promote the adhesion of BCB to the glass substrate 1.

The parameters for implementing such a deposition of the adhesion promoter material by centrifugation are, by way of example: - speed = 2500 rpm,

 - acceleration = 1000 rpm,

 - duration = 20 s,

Optionally, the microsystem is subjected to an annealing step (B13), after the deposition step (B12) of the polymer layer 3, for example at a temperature of 110 ° C, for 15 minutes, under N ₂ .

 Finally, it is preferable to thin the silicon substrate 4 after the gluing step (B2), during a thinning step (B3).

 This thinning step may, for example, consist of an SF6 etching, for example making it possible to pass from a silicon substrate 4 with a thickness of 250 μm to a silicon substrate with a thickness of 180 μηι.

 At the end of the deposition step (B) of the silicon substrate 4 on the microelectronic circuit 2 and the glass substrate 1, represented in FIG. 2, the micro system represented more specifically with reference to the step is obtained. (B3).

 At this stage, the base of the microfluidic structure 4, consisting of the silicon substrate 4, has been assembled by gluing on the microelectronic structure 2, without it being necessary to worry about the presence of the fluidic microstructures which could interfere with the assembly, since the microstructures have not yet been created.

 FIG. 3 schematically represents the main step of creating (C) the microfluidic structure 4 in the silicon substrate 4, once the latter has been put in place on the microelectronic structure 2.

 The microfluidic structure, which will be represented in this example by a simple microchannel, is carried out during an etching step (C2), for example of deep etching type, in the silicon substrate 4.

For this etching, it is possible, for example, to implement a Bosch type plasma etching process SF ₆ -C ₄ F ₈ for 45 minutes. Prior to the etching step (C2), a deposition step (C1) of an etching mask 6 is used to enable the silicon substrate 4 to be etched only at the location provided for the microchannel. .

 This deposition of the etching mask 6 can be obtained by a deposition step (C12), preferably by centrifugation, of a photoresist layer 6.

 For this deposition step (C12) by centrifugation, it is possible to use a positive photosensitive resin of the AZ9260 type, with parameters that can be, by way of example:

 - speed = 1500 rpm,

 - acceleration = 3000 rpm,

 - duration = 40 s,

 - thickness = 10 Mm.

 Optionally, prior to the deposition of the etching mask 6, Dn implements a deposition step (Cil) of a thin layer of a metal 5 such as aluminum, in order to maintain the good dimensional characteristics of the structure microfluidic 4.

 This deposition of the metal layer 5 can be obtained by plasma spraying Ar, to a thickness of the order of 100 nm.

 After depositing the mask of the photoresist layer 6, it undergoes a step of insolation (C14) to ultraviolet rays, after a possible annealing step (C13) for example for 3 minutes at a temperature of 110 ° C.

 The implementation parameters of this insolation step (C14) can be:

 wavelength = 325 nm,

 - duration = 20 s,

- surface density of power = 11 mW / cm ² .

The photoresist layer 6, after exposure, then undergoes a development step (C15), for example using a developer type AZ351B for 4 minutes.

 Furthermore, the metal layer 5 is removed by etching at the opening formed in the etching mask 6 during development.

 The succession of steps (Cil) to (C15) therefore constitutes the deposition step (Cl) of the etching mask 6 as represented in FIG. 3, which precedes the etching step (C2) presented above and also represented in Figure 3.

Then, an etching step (C3) of the polymer layer 3 is implemented. This etching step (C3), shown in FIG. 3, can for example be of the CF ₄ / O ₂ plasma etching type, for a duration of 7 minutes.

 Then, a step of removal (C4) of the etching mask 6 and the metal layer 5, is implemented, as shown in Figure 3.

 This removal can for example be obtained by dilution in an acetone solution, then using an AZ351B type developer.

 At the end of the creation step (C) of the microfluidic structure 4, a microfluidic pattern, in the present example a microchannel, is created in the silicon substrate 4, opposite the microelectronic circuit 2, and Dn obtains effectively the microsystem shown more specifically sn reference to step (C4) of Figure 3.

 FIG. 4 schematically represents subsequent steps of creating (D) a covering cap 7, cutting (E) of this covering cap 7, and cutting (F) of the glass substrate 1, or first substrate 1, in the context of the manufacture of several microsystems 9, 10 on the same glass substrate 1.

The step of creating (D) a covering cover 7 comprises a step of depositing (D1) a polymer layer on a third substrate 7 made of electrically insulating or semi-conductive material, such as a glass substrate 7 . The deposition of the polymer layer on this third substrate 7 can be obtained by a centrifugation step (D12) of a polymer such as BCB3022-46 already presented above, with the following parameters, by way of example:

 - speed = 2500 rpm,

 - acceleration = 1250 rpm,

 - duration = 40 s,

 - thickness = 2 μηι.

 This centrifugation step (D12) of the polymer is preferably preceded by a deposition step (DU), for example also by centrifugation, of a material promoting adhesion of said polymer to the glass substrate 7.

 This adhesion promoter material may be of AP3000 type, as already described above. The parameters of this deposition by centrifugation are, for example:

 - speed = 2500 rpm,

 - acceleration = 1250 rpm,

 - duration = 20 s.

 The centrifugation deposition step (D12) of the polymer layer on the third substrate 7 can optionally be followed by a step of annealing this polymer layer.

 Then, a bonding step (D2) of the third substrate 7 on the silicon substrate 4 is carried out, for example by thermocompression for 1 hour, at 250 ° C. and under 2 bars.

 Optionally, a cutting step (E) of the cover 7 thus formed is implemented, to ensure that the cover 7 covers the microfluidic structure 4 and / or the microelectronic structure 2, without covering the entire first substrate 1 .

As illustrated in FIG. 4, the method of the invention advantageously makes it possible to produce several microsystems 9, 10 combining a microelectronic function and a microfluidic function, on the same glass substrate 1.

 Once the plurality of microsystems 9, 10 have been made, it is necessary to implement a cutting step (F) of the first substrate 1 to separate the microsystems 9, 10.

 If a cover 7 has been previously installed, as explained above sn reference to step (D), and if the cutting step (E) of the covers 7, described above, is not implemented. Of course, it is of course also necessary to cut the third substrate 7 or cover 7 to obtain the separation of the microsystems 9 and 10.

 Thus, with the method according to the invention, it has been possible to produce microsystems combining a microelectronic circuit such as a waveguide and a microfluidic structure having one or more microchannels of width less than or equal to 3 μm, and even, in some cases, at 2 μηι, without encountering the problem of plugging these microchannels with a bonding material as is the case in the state of the art.

Moreover, with the method according to the invention, it has been possible to produce microsystems combining a microelectronic circuit such as a waveguide and a microfluidic structure comprising a plurality of large microchannels, in particular with a width greater than or equal to 2 μηι, or even greater than or equal to 5 mm, for example of the order of 50 mm, very slightly spaced from each other, for example spaced only 5 mm,

 Such an embodiment poses problems with the solutions of the state of the art insofar as, in such a configuration, there is not much material left on the substrate, which weakens it enormously. Bonding becomes impossible without damaging the substrate.

On the contrary, with the process of the invention, it is therefore possible to greatly increase the density of microfluidic units relative to to the solutions of the state of the art of carrying one structure over the other.

 With the method of the invention, deep etchings are attained until the substrate is pierced, while maintaining a high level of density of microfluidic units, whereas the methods of the state of the art require that the choice be one or the other: large depth of gravure or high density of microfluidic patterns. Also, these methods of the state of the art pose a problem that is not encountered with the method of the invention: that of clogging the small channels with the glue if the depth is not sufficient. In the state of the art, Dn can solve this problem by using the technique of "anoding-bonding". But this technique requires a high temperature (450 to 800 ° C) which makes it not applicable in the presence of a microelectronic circuit.

 In addition, the method of the invention makes it possible to implement a single industrial process for producing in parallel several microsystems on the same substrate or "wafer", for example up to 24 microsystems, with several cutouts, instead of an implementation of several times, up to 24 times, the industrial process for producing a microsystem after cutting.

 Also, the method of the invention makes it possible to complicate the etching of the microfluidic structure, without risk of damaging the glass substrate.

 The present description is given by way of illustration, the examples presented above not being limiting of the invention.

 In particular, to illustrate the invention, the microfluidic structure has been represented by a simple microchannel or recess. It could equally well be a microreservoir, or a combination of several microfluidic patterns.

Furthermore, the description illustrates the invention on the basis of a example in which the first substrate 1 is glass, but more generally extends to devices and methods in which the first substrate 1 is of electrically insulating material or semiconductor.

 Glass or quartz are particularly suitable materials in the example presented above, in which the microelectronic circuit created on the first substrate comprises a very high propagation line. Indeed, the use of glass or quartz allows in this case to limit losses and thus to obtain excellent propagation characteristics.

 Likewise, the invention has been illustrated with an example of a microelectronic structure or microelectronic circuit comprising a Goubau type line for forming a waveguide intended for analysis by terahertz type spectroscopy. Other microelectronic circuits can of course be envisaged, such as active microelectronic circuits, particularly if a substrate of semiconductor material such as silicon is used rather than a substrate of glass or quartz.

 It will be preferred to use glass, in certain applications in which transparency is important, for both the first substrate 1 and the third substrate or cover 7.

 More generally, these remarks on the choice of an electrically or semiconducting insulating material, therefore apply both for the first substrate 1, for the second substrate 4 and the third substrate 7.

 It will be added that the use of transparent materials is made possible by the method of the invention, so that the transparency necessary for visible microscopy analyzes can be obtained, while having a microsystem enabling analyzes to be carried out. microfluidics and microelectronics. This is of great interest in biology, also admitted, more generally for the observation of chemical phenomena.

Claims

A method for manufacturing a microsystem comprising at least one microelectronic function and at least one microfluidic function, comprising a creation step (A), on a first substrate (1) made of electrically insulating or semiconductor material, of a microelectronic circuit (2) capable of implementing said microelectronic function, and a creation step (C), in a second substrate (4) of electrically insulating or semiconductor material, of a microfluidic structure capable of implementing said function microfluidics, characterized in that it further comprises a transfer step (B) of the second substrate (4) on the electronic circuit and the first substrate (1), and in that the creation step (C) of the microfluidic structure is implemented after the transfer step (B) of the second substrate (4) on the electronic circuit and the first substrate (1).  2. Method according to claim 1, characterized in that the transfer step (B) of the second substrate (4) comprises a bonding step (B2), preferably by thermocompression, of the second substrate (4) on the first substrate. (1).  3. Method according to claim 2, characterized in that the bonding step (B2) of the second substrate (4) on the first substrate (1) is followed by a step (B3) of thinning, for example by etching of the second substrate (4). 4. Method according to any one of claims 2 and 3, characterized in that the bonding step (B2) of the second substrate (4) on the first substrate (1) is preceded by a deposition step (Bl) a polymer layer (3) on the first substrate (1) and the microelectronic circuit (2). 5. Method according to claim 4, characterized in that the deposition step (B1) of the polymer layer (3) comprises a centrifugation step (B12) of the polymer on the first substrate (1) and the microelectronic circuit ( 2).  6. Method according to claim 5, characterized in that the centrifugation step (B12) of the polymer is preceded by a deposition step (Bll), for example by centrifugation, of a layer of a promoter material. adhesion of the polymer to the first substrate (1).  7. Method according to any one of claims 5 and 6, characterized in that the centrifugation step (B12) of the polymer is followed by a step (B13) of annealing the polymer layer (3).  8. Method according to any one of claims 1 to 7, characterized in that the step of creating (C) the microfluidic structure in the second substrate (4) comprises a step (C2) of etching, preferably of type deep engraving, of the second substrate (4).  9. Method according to claim 8, characterized in that the step (C2) of etching of the second substrate (4) is preceded by a deposition step (Cl) of an etching mask (6) on the second substrate (4).  10. The method of claim 9, characterized in that the step of depositing (C1) an etching mask (6) on the second substrate (4) comprises a step of depositing (C12) a layer of resin photosensitive, preferably by centrifugation. 11. The method of claim 10, characterized in that the step of depositing (C1 2) of the photosensitive resin layer is preceded by a deposit step (Cil) of a metal layer (5), for example in aluminum, preferably by spraying. 12. Method according to any one of claims 10 and 11, characterized in that the deposition step (C12) of the photoresist layer is followed by a step of insolation (C14) ultraviolet rays, optionally after an annealing step (C13) of the photoresist layer.  13. The method of claim 12, characterized in that the ultraviolet irradiation step (C14) is followed by a development step (C15) of the photoresist and optionally etching of the metal layer ( 5).  14. The method of claim 4 and any one of claims 8 to 13, characterized in that the step (C2) of etching the second substrate (4) is followed by an etching step (C3), for example plasma etching type, the polymer layer (3) deposited on the first substrate (1) and the microelectronic circuit (2).  15. Method according to any one of claims 8 to 14, characterized in that the step (C2) of etching the second substrate (4), and optionally the step of etching (C3) of the polymer layer (3). ) deposited on the first substrate (1) and the microelectronic circuit (2), are followed by a step of removal (C4) of the etching mask, and optionally of the metal layer (5), for example by dilution in a solution acetone followed by wet etching using, for example, a basic solution.  16. A method according to any one of claims 1 to 15, characterized in that the creation step (C) of the microfluidic structure is followed by a step of creating (D) a covering cover of the structure microfluidics. 17. The method of claim 16, characterized in that the step of creating (D) a cover of the microfluidic structure comprises a step of deposition (Dl) of a layer of polymer on a third substrate (7).  18. The method of claim 17, characterized in that the step of deposition (Dl) of the polymer layer on the third substrate (7) comprises a centrifugation step (D12) of the polymer on the third substrate (7), optionally preceded by a deposition step (DU), for example by centrifugation, of a layer of a material promoting adhesion of the polymer to the third substrate (7), and possibly followed by a step of annealing this polymer layer.  19. Method according to any one of claims 17 to 18, characterized in that the deposition step (D1) of the polymer layer on the third substrate (7) is followed by a bonding step (D2), preferably by thermocompression, of the third substrate (7) on the second substrate (4).  20. Method according to any one of claims 16 to 19, characterized in that the step of creating (D) the cover of the microfluidic structure is followed by a cutting step (E) of said cover so that it covers the microfluidic structure and / or the microelectronic structure without covering the entire first substrate (1).  21. Method according to any one of claims 1 to 20, characterized in that the creation step (A) on the first substrate (1) of the microelectronic circuit (2) comprises a deposition step (Al) of a mask (8) on the first substrate (1).  22. Method according to claim 21, characterized in that the deposition step (Al) of the mask (8) on the first substrate (1) comprises a deposition step (A14), for example by centrifugation, of a layer of photosensitive resin (8) on the first substrate (1). 23. The method according to claim 22, characterized in that the step of depositing (A14) the photoresist layer (8) on the first substrate (1) is followed by a step of insolation (A16) of the photoresist layer (8) with ultraviolet rays, and a development step (A18) of this photoresist. 24. A method according to claim 23, characterized in that the step of insolation (A16) of the photoresist layer (8) with ultraviolet rays is preceded by an annealing step (Al 5), and optionally followed by another annealing step (A17).  25. Method according to any one of claims 21 to 24, characterized in that the deposition step (A14) of the photoresist layer (8) on the first substrate (1) is preceded by a deposition step (A13), for example by centrifugation, a layer of a material promoting adherence of the photoresist (8) on the first substrate (1).  26. Process according to any one of claims 21 to 25, characterized in that the deposition step (A14) of the photoresist layer (8) on the first substrate (1), and optionally the deposition step (A13) of the layer of adhesion promoter material of the photosensitive resin (8) on the first substrate (1), are preceded by a dehydration annealing step (Al 2) of the first substrate (1), this said dehydration annealing step (A12) possibly being preceded by a cleaning step (Ail) of the first substrate (1), for example in a solution comprising acetone and / or ethanol.  27. Method according to any one of claims 21 to 26, characterized in that the deposition step (Al) of the mask (8) on the first substrate (1) is followed by a deposition step (A2), for example by evaporation, a metal layer on the mask (8) and the first substrate (1). 28. The method of claim 27, characterized in that the step of depositing (A2) the metal layer on the mask (8) and the first substrate (1) is followed by a removal step (A3), for example by a "lift off" type shrinkage, of the mask (8).  29. A method of manufacturing at least one first and second microsystems (9, 10) each comprising at least one microelectronic function and at least one microfluidic function, each microsystem (9, 10) being manufactured by the method according to one of the following: any of claims 1 to 28, characterized in that the first substrate (1) used for the manufacture of the first microsystem (9) is the same as the first substrate (1) used for the manufacture of the second microsystem (10).  30. The method of claim 29, each microsystem (9, 10) being manufactured by the method according to any one of claims 16 to 20 and optionally according to any one of claims 21 to 28, characterized in that the third substrate (7) used for the manufacture of the first microsystem (9) is the same as the third substrate (7) used for the manufacture of the second microsystem (10).  31. Method according to any one of claims 29 and 30, characterized in that it comprises a cutting step (F) of the first substrate (1), and optionally the third substrate (7), so as to separate the first and second microsystems (9, 10). 32. Method according to any one of claims 1 to 31, characterized in that the microfluidic structure comprises at least one microchannel and / or at least one microreservoir.  33. Method according to any one of claims 1 to 32, characterized in that the electronic circuit comprises at least one waveguide.  34. Process according to any one of claims 1 to 33, characterized in that the first substrate (1) is a glass or quartz substrate.