EP2232070B1 - Micropump - Google Patents

Description

State of the art

The invention relates to a micropump according to the preamble of claim 1H.

Micropumps for controlled and highly accurate delivery of insulin are known in principle. However, previous micropumps suffer from complex manufacturing processes with many non-standard process steps. The many special process steps of the prior art make such micropumps expensive and lower the manufacturing yields.

In addition, known micropumps are not accurate enough in terms of delivered drug levels. However, micropumps for insulin delivery must work very precisely with high dosing accuracy, without the need for elaborate sensors to detect delivered insulin volumes. An active flow measurement is very problematic in connection with insulin, because the substance reacts to elevated temperatures, such as in connection with so-called hot-film sensors for flow measurement, harmful.

A serious disadvantage of previous micropumps is also the lack of security: for example, in micropumps according to the prior art, the emitted Amount of insulin depends on the pre-pressure in the insulin reservoir, which, when designed as a flexible bag, can be mechanically pressurized. For example, setting, or lying the pump wearer on the insulin micropump the reservoir to an unwanted insulin delivery, or lead to an unwanted increase in the dose just delivered. In view of the dangers of insulin overdose, this should be avoided at all costs.

In the EP 1 651 867 B1 a method for manufacturing a micropump is described. The production of the known micropump is extremely complicated, since during the manufacturing process, in which different silicon layers are structured from two opposite sides, again and again, for example in FIGS. 3b and 3c of the document, fragile intermediate states arise, which must be laboriously supported to avoid destruction of the micropump already during their production. From the DE 10 2005 032452 A1 For example, a method for producing communicating cavities is known, wherein all process steps are applied essentially from one side to the silicon substrate. From the DE 10 2005042648 A1 Such a method is also known.

The EP 1393469 A2 shows a semiconductor device with regions of different pore structure and a corresponding manufacturing method. The semiconductor substrate has two partial regions which differ in their pore structure.

The DE 10 2005 052 039 A1 shows a method for manufacturing a micropump and a micropump made by this method, in which the micropump is made of a composite substrate and of a semiconductor material and an anodically bondable glass. In this case, internal structures are first defined in the Andean bondable glass and at the same time further internal structures are defined in a second planar substrate to be applied.

The EP 0424087 A1 describes a micropump having piezoelectric means which form part of a wall of a reservoir to thereby convey liquid into and out of the reservoir. In this case, a valve flap can be held by a spring.

The US 5520522 describes a micropump which works by means of magnetstrictive or electrostrictive elements in order to dispense with faulty elements.

Revelation of Enfinung

The invention leads to a micropump, in particular for the highly precise delivery of insulin, the micropump having a plurality of functional elements, such as at least one inlet valve and at least one outlet valve and at least one pumping chamber. A micropump designed according to the concept of the invention is characterized in that all such functional elements of the micropump are produced exclusively by structuring layers from one direction. In other words, the functional elements are not generated by two-sided structuring processes, but merely by structuring processes that take place from one direction and one side. As a result, fragile production conditions can be avoided and the micropump thus be produced on a large scale with high yield.

Of particular advantage in the invention, in which the at least one, preferably exclusively an inlet valve, comprises at least one coil spring, which is arranged such that it has a in Z direction ensures soft suspension of the valve stem of the intake valve. Particularly preferred is an embodiment with several nested spiral springs in order to reduce unwanted material stress can.

In a development of the invention, the micropump has a carrier layer, in particular of borosilicate glass, in which at least one fluid channel, in particular an inlet channel and / or an outlet channel, is / are introduced. Preferably, the carrier layer additionally limits the pumping chamber directly.

With regard to use of the micropump as an insulin delivery pump for high-precision insulin dosing an embodiment is particularly preferred in which the inlet valve of the micropump by means of at least one actuator, preferably a piezoactuator, is actively sealable, so an embodiment in which the inlet valve of the micropump by a corresponding activation of at least one actuator can be kept closed so as to prevent insulin entry into the micropump even in the event that the insulin reservoir itself has been pressurized. In other words, the delivery volume of the micropump is thereby independent of the admission pressure in the insulin storage container. As a result, a high dosing accuracy can be achieved. The described embodiment suppresses undesired active agent flows or refluxes of a required metered quantity and strictly limits the metering output to a so-called "stroke volume", which is the quantity corresponding to a pump stroke or "stroke".

An embodiment is preferred in which a valve sealing surface of the inlet valve, in particular arranged on a valve stem, can be pressed against the carrier layer by means of at least one actuator so as to avoid undesired inflow of fluid, in particular insulin, into the micropump. Also preferred is a valve sealing surface an exhaust valve by means of at least one actuator actively pressed against the carrier layer.

To produce a micropump according to the invention, a method is suitable in which the generated inlet valve structure and / or the outlet valve structure comprise at least one spiral spring section. The at least one coil spring preferably carries the valve stem of the respective valve. It can also several, for example, two to five, such coil springs, preferably three coil springs, are nested in one another, that the central valve stem is held completely symmetrical of these and can completely degrade any residual stress in the springs by a minimal rotation of the valve stem. Due to the relatively large spring lengths while a soft suspension of the central valve stem in the Z direction (ie perpendicular to the surface extension of the first and second carrier layer) realized, the spring height corresponds to almost the entire functional layer height. In this state, the at least one inlet valve punch and / or the at least one outlet valve punch still sits firmly on the stop or sacrificial layer arranged below the functional layer.

In particular, in order to make the inlet valve plunger adjustable in the Z direction and / or to enlarge the pumping chamber and / or the outlet valve chamber, in a further development of the invention, the stop layer adjacent to the functional layer (upper) serves as the sacrificial layer, for example with the aid of liquid or vapor Hydrofluoric acid removed in a conventional manner. After this etching process, the functional unit "inlet valve" is freely movable and can thus be deflected in the Z direction. The spacing of the at least one spiral spring from the base layer now preferably corresponds to the thickness of the previously removed_stop layer (sacrificial layer) of preferably approximately 4 up to 5 μm. It is advantageous that in the described etching process as many areas of the mentioned stop layer are removed as they would later enter undesired compressive stresses into the mechanical structure of the micropump.

The method of operation of a preferred embodiment of a micropump is described below. Preferably, the micropump, including an active ingredient supply (preferably an insulin supply) and possibly also connected injection needle or microneedle array, is preferably mounted as a so-called "disposable" - a disposable item - in a device, in particular clipped, which represents the so-called "pump" for the end user. The "pump" preferably contains the control electronics, the energy supply eg by batteries or accumulators, a user interface and / or a wireless interface to a user interface or to a telemedical device, or possibly also a wireless interface to a blood sugar value determination device, the measured Blood glucose data sent to the "pump" for further processing. The "pump" preferably also contains the actuators of the micropump. These are up to three actuators, preferably three actuators, which act on the micropump at locations provided for this purpose, preferably on the inlet valve, on the pump membrane (ie on the pumping chamber) and on the outlet valve. The up to three actuators can preferably be embodied in the form of so-called piezo-stacks, ie arrangements of cascade-like piezoelectrical disks or individual elements connected to a piezoactuator which shortens or extends in length by an applied electrical voltage, depending on the polarity of the electrical voltage relative to the polarization of the piezo elements.

First, the pumping function will be described with an arrangement of three actuators, although it is also possible to dispense with individual actuators and give up the corresponding associated subfunction or additional safety.

• ● Sodass ein erster Aktuator auf eine Membran (vorzugsweise Basisschicht) unter dem Einlassventilstempel drückt und über diese Membran das Einlassventil gegen die zweite Trägerschicht geschlossen und blockiert wird,
• ● sodass ein zweiter Aktuator auf der Membran (vorzugsweise Basisschicht) der Mikropumpe gerade eben aufliegt und so deren "Ausgangslage" definiert, oder alternativ einfach die Membran bis zum von der zweiten Trägerschicht gebildeten Anschlag durchdrückt;
• ● sodass ein dritter Aktuator auf den Bereich des Auslassventilstempels (insbesondere auf die Basisschicht) drückt und diesen gegen die zweite Trägerschicht schließt und blockiert.

After installation of the micropump in the receptacle provided for this purpose ("pump"), the actuators are conditioned, ie once brought into a defined position and fixed there:

• ● So that a first actuator presses on a membrane (preferably base layer) under the inlet valve plunger and the inlet valve is closed and blocked against the second carrier layer via this membrane,
• ● so that a second actuator on the membrane (preferably base layer) of the micropump just rests and so defines their "starting position", or alternatively simply pushes the membrane to the stop formed by the second carrier layer;
• ● so that a third actuator presses on the area of the outlet valve punch (in particular on the base layer) and closes and blocks it against the second carrier layer.

The conditioning can be done manually or preferably automatically (for example motor-driven), for example by an actuator block comprising the three relatively positioned actuators being moved forward as a unit, until such as a resonance sequence change of one of the actuators (Preferably the piezo stack) indicates that a contact with the micropump, in particular the base layer or a force on the actuators takes place. Advantageously, as the actuator block is moved forward as a unit and the individual actuators from the block have been properly positioned relative to one another by the manufacturer, the measurement on a single actuator, in particular on a single piezo element, is sufficient to detect that the entire assembly is the correct one Location has reached. For example, the contact of the actual pump membrane (preferably base layer) by the second actuator via its vibration behavior in electrical resonance excitation is very easy to detect. The core idea of this conditioning method is that when only one actuator is advanced in its nominal position, the nominal positions of the other actuators automatically also vote automatically because they have been adjusted relative to one another on the actuator block. Particularly simple, because feasible without measurement, the method is simply to bring an actuator to a hard stop, so for example, to block the inlet valve and / or the outlet valve or push through the pump diaphragm to the stop. For this purpose, the actuator block is advanced with a defined force until, due to the hard stop, no further movement is possible. In this case, an active measurement of the actuator position is unnecessary (for example due to resonance frequency change).

In a particularly preferred embodiment of the conditioning process, the conditioning is carried out with the aid of at least one simple spring or spring arrangement, which simply presses the actuator block forward against the micropump without further motor action. If at least one the valves, either the inlet valve or the exhaust valve, to be blocked mechanically, so at least one of the two actuators unabated acts on the micropump or its valve seats, the desired position of the actuator is always defined relative to the micropump. It is never provided during operation of the pump that both the inlet valve and the outlet valve would both be released simultaneously, so both associated actuators would be shortened. This feature allows a particularly simple positioning of the actuator block by means of a spring, which only has to be strong enough to securely lock the two valves and to press against their stops - their valve seats. This also defines the position of the entire actuator block. The micropump is then inserted or clipped into the "pump" only in the position provided for this purpose, for example within a guide or in a side frame, wherein the actuator block, for example manually, has to be pushed back slightly, for example, in order to be able to receive the micropump. Once the micropump is in position, the spring of the actuator block simply pushes the latter against the micropump, thereby blocking both the inlet valve and the outlet valve and at the same time exactly defining the actuator associated with the pump diaphragm in its position relative to the pump diaphragm.

In particular, when it is desired to dispense with high dynamics of the pumping process, it is possible, for example, to save the pump membrane actuator (second actuator) and to replace it, for example, by a rigid spacer element which presses on the pump membrane (preferably base layer). In this case, the two valve actuators sufficient to apply over the actuator block and the spacer and the pumping action itself. If, for example, the outlet valve is to be released and then the pump membrane is brought into abutment by "stroke", the outlet valve actuator can be withdrawn by the thickness of the base layer of, for example, about 20 μm plus an additional offset of about 5 μm, preferably taking advantage of the piezoelectric effect. Subsequently, the intake valve actuator, for example, by slightly less than the base layer thickness, so for example 19.5μm withdrawn, whereby the, in particular middle, spacer along with the Aktuatorblock advances by just this distance and the pump diaphragm (preferably base layer) against its stop (preferably second carrier layer) or almost against their attack auslängt. In all the cases described, it is very easy to bring the actuator block automatically, only by at least one simple spring or spring assembly in the desired position relative to the micropump, which means a comfortable handling when inserting the micropump and also intrinsic safety brings with it: passive spring action ensures that all valves are blocked in an electrically de-energized state, ie a "normally closed behavior" is present. In this constellation, insulin can not pass through the micropump even if the reservoir is pressurized because both the inlet and outlet valves are depressed by one actuator at a time.

The micropump operates in the case of providing three actuators as follows:

Before a surge, the actuator directly associated with the exhaust valve is retracted, for example by applying an electrical voltage to the piezo stack, whereby the exhaust valve is released. This does not mean that the exhaust valve is opened, but rather remains closed until it is opened by an overpressure inside the micropump. Only then can insulin leave the micropump. Since the inlet valve is still preferably blocked, insulin can not enter the micropump from the insulin supply.

Now, the actuator directly associated with the diaphragm of the micropump is extended, preferably by applying an electrical voltage, and pushes the pump diaphragm (preferably the base layer) to the top stop, i. preferably through to the second carrier layer. The so-called "stroke volume" is discharged through the outlet valve.

As a next step, the exhaust valve is blocked by extending the associated actuator (for example, by removing the electrical voltage that had shortened the actuator or briefly reverse the voltage and then set to zero) and then the intake valve associated with the first actuator, for example by applying shortened electrical voltage, whereby the inlet valve is released, but not yet opened. The inlet valve remains rather closed, even against an overpressure from the outside in the insulin reservoir, because nothing can flow out of the micropump due to the blocked outlet valve. Only when the second, the pumping chamber associated actuator is shortened, for example by removing the electrical voltage on Piezo stack and the pump diaphragm (preferably the base layer) moves back to its original position, the inlet valve is opened and a "stroke-volume" insulin enters the micropump. Thereafter, the first, the inlet valve associated actuator is again electrically de-energized, whereby it expands to its original length and blocks the inlet valve again. Then the pumping process can be repeated. The third actuator (exhaust valve actuator) releases the exhaust valve, the second actuator (pump actuator) performs a "Stroke", and the "Stroke Volume" is delivered through the exhaust valve from the micropump. The third actuator then blocks the outlet valve and the first actuator releases the inlet valve, whereupon the second actuator returns the pump membrane to its original position, via the inlet valve the previously discharged "stroke volume" from the insulin reservoir is replaced again and enters the micropump , whereupon the inlet valve is blocked again by means of the first actuator, etc.

It is essential that always only the "stroke volume" enters the micropump, regardless of any form in the storage container, and always exactly this "stroke volume" is conveyed from the micropump, without a harmful reflux into the micropump back. As a result, the dosage is very accurate and the micropump intrinsically safe, even with overpressure in the storage container. Because of their high longitudinal stiffness, actuators are piezoactuators, by means of which the function of the micropump has been described by way of example. However, it is also possible other actuators, such as thermal or electrical actuators, in particular with appropriate Use spring mechanisms as actuators in addition to or as an alternative to piezo actuators.

Brief description of the drawings

Fig. 1 - 2:

zwei anfängliche Verfahrensschritte zur Herstellung einer Mikropumpe ausgehend von einem Siliziumwafer als erster Trägerschicht,

Fig. 3

einen alternativen Startpunkt für ein Herstellungsverfahren zur Herstellung einer Mikropumpe, ausgehend von einem SOI-Wafer,

Fig. 4 - 12

wichtige Herstellungsschritte zur Herstellung einer Mikropumpe, wobei bei den gezeigten Verfahrenschritten die erste Trägerschicht als Siliziumwafer ausgebildet ist,

Fig. 13 - 15

wesentliche Verfahrensschritte bei der Herstellung einer Mikropumpe, wobei hier die erste Trägerschicht Teil des SOI-Wafers ist, wobei der Verfahrensschritt gemäß Fig. 13 dem Verfahrensschritt gemäß Fig. 9, der Verfahrenschritt gemäß Fig. 14 dem Verfahrensschritt gemäß Fig. 11 und der Verfahrensschritt gemäß Fig. 15 dem Verfahrensschritt gemäß Fig. 12 entspricht, und

Fig. 16

eine perspektivische Darstellung einer noch nicht fertigen erfindungsgemäßen Mikropumpe bei deren Herstellung.

Show in:

Fig. 1 - 2:

two initial process steps for producing a micropump starting from a silicon wafer as the first carrier layer,

Fig. 3

an alternative starting point for a manufacturing method for producing a micropump, starting from an SOI wafer,

Fig. 4 - 12

important production steps for producing a micropump, wherein in the method steps shown, the first carrier layer is formed as a silicon wafer,

Fig. 13 - 15

essential process steps in the production of a micropump, in which case the first carrier layer is part of the SOI wafer, wherein the method step according to Fig. 13 the method step according to Fig. 9 , the process step according to Fig. 14 the method step according to Fig. 11 and the method step according to Fig. 15 the method step according to Fig. 12 corresponds, and

Fig. 16

a perspective view of a not yet finished micropump according to the invention in their preparation.

Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1 starts the production of a micropump starting from a silicon wafer as a first carrier layer 1, which is provided on its front side V with a (thermal) oxide as the lower stop layer 2, in which at suitable location contact holes 3 for electrical contacting of the base support layer material silicon to subsequently applied silicon layers be created. The electrical contacts are advantageous for a later, so-called anodic bonding process, in which a current flow for entering a high-strength connection to a, for example in Fig. 10 shown, second carrier layer 4 (here: glass substrate) is required.

Fig. 2 shows another intermediate stage of the micropump, in their manufacture, wherein on the front side of the lower stop layer 2, a base layer 5 formed as EpiPoly silicon layer was applied. In this embodiment, the thickness of the base layer 5 is 11 μm. The base layer 5 can optionally be planarized, for example by a CMP step.

Fig. 3 shows an alternative starting point for the manufacturing process, wherein of a so-called SOI wafer 6 as Starting material is started. The steps of the films 1 and 2 can then be omitted, since a higher-quality semifinished product is already used as the starting material. However, a disadvantage in this case is that no electrically conductive connection from the lower, first carrier layer 1 to the upper, arranged on the front side V of the first carrier layer 1, base layer 5 of the SOI wafer 6 via contact holes is available. For later anodic bonding, suitable contact means must be provided over the wafer edge, eg, clamps or spring contacts, which electrically contact, for example, the upper base layer 5 of the SOI wafer 6 from the edge.

Fig. 4 shows the continuation of the manufacturing process, regardless of whether the variant according to the Fig. 1 and 2 or the variant according to Fig. 3 is pursued. Illustrated below is based on the 4 to 12 the variant according to Fig. 1 and 2 in which a silicon wafer is assumed as the starting point (first carrier layer 1) - the "SOI wafer" variant can be easily derived therefrom.

On the front side of the base layer 5, a thick oxide is deposited as an upper stop layer 7 and structured such that the stop layer 7 serving as the sacrificial layer remains on selected surfaces. These selected areas are all areas in later manufacturing steps, in which a silicon plasma etching process must be stopped and / or a cantilevered movable structure is to arise. It is essential that immediately above the contact holes 3, a stop layer 7 is provided.

The thickness of the upper stop layer 7 is in the embodiment shown about 4 to 5 microns. In the variant "SOI wafer", for example, a thermal oxide grown to a thickness of 2.5 .mu.m and above a still 1.8 .mu.m thick oxide are deposited, such as in the form of TEOS or plasma oxide, which in total a stop layer thickness of about 4 , 3μm yields. In the variant in which starting from a silicon wafer as the first carrier layer, a thermal oxidation is not recommended, as this unacceptable stress gradients would be registered in the base layer material (epipoly-silicon), which would make further use as a mechanical layer material impossible. For the latter case, the deposition of the full stop layer thickness (oxide thickness) is preferably carried out as TEOS or plasma oxide at relatively low temperatures of, for example, 300 ° C. to 450 ° C.

In Fig. 5 a manufacturing step is shown, in which on the front side of the base layer 5 and on the front side of the stop layer 7, a functional layer 8 having a thickness of about 15 to 24 microns was deposited. The functional layer 8 consists in the embodiment shown of an EpiPoly silicon layer. Since on the front side (layer surface) of the functional layer 8 must be later anodically bonded, a planarization of the surface, for example by a CMP process at this point is highly recommended, regardless of whether previously the base layer 5 planarized or for the Base layer, an SOI wafer layer was used. The planarization step must level the topography of the surface and "smoothen" the surfaces microscopically for bonding.

In Fig. 6 is the wafer stack after applying and structuring an Antibond layer 9, which on the later Valve sealing surfaces must remain, shown. The Antibond layer 9 may for example consist of silicon nitride, silicon carbide or graphite. In addition, recesses 10, 11 have been etched around the anti-bonding layer surface areas 9 to a depth of about 2 to 5 microns. These recesses 10, 11 are later not to come into contact with the second carrier layer 4 to be bonded in order to guarantee a mobility of microfluidic functional elements to be produced, here an inlet valve punch 14 and an outlet valve punch 17.

In Fig. 7 the functional layer 8 has been structured inter alia in the region below the recesses 10, 11. In other words, provided by the microfluidic functional elements 12, namely an inlet valve 13 with an inlet valve punch 14, on the front side of which the antibond layer 9 is located as a valve sealing surface. Furthermore, a pumping chamber 15 and an outlet valve 16 having an outlet valve punch 17 has been created, wherein on the front side of the outlet valve punch 16 there is likewise an anti-bonding layer 9 as a sealing surface. The functional elements 12 are in accordance with the method step Fig. 7 not finished yet. For this it is still necessary, as is apparent Fig. 8 results in selectively removing the upper stop layer 7 (sacrificial layer). This can be carried out by liquid or vapor hydrofluoric acid in a conventional manner. After this etching, the inlet valve 13 or the inlet valve punch 14 is freely movable and can be deflected in particular in the Z direction. The distance of the inlet valve punch 14 to the base layer 5 corresponds to the thickness of the previously removed oxide (upper stop layer 7 (sacrificial layer)) of 4 to 5 μm. It is worth mentioning at this point the formation of the inlet valve 13. This includes in the embodiment according to Fig. 7 a spiral spring 18, which in a plan view below the wafer stack in Fig. 7 is shown. The coil spring 18 carries the end of the inlet valve stem 14, whereby a soft storage of the inlet valve stem 14 is given in the Z direction and material stress can relax.

An enfindungsgemäße embodiment of the inlet valve 14 results from the perspective view according to Fig. 16 , Evident are three nested coil springs 18, all of which are connected at one end to the inlet valve stem 14 and although at evenly distributed circumferentially arranged locations. The central inlet valve punch 14 is held completely symmetrical by the coil springs 18 and any residual stress of the coil springs is completely degraded by a minimum rotation of the inlet valve punch 14. Due to the relatively large spring lengths, a soft suspension of the central intake valve plunger in the Z direction is realized, with the spring height corresponding to almost the entire sacrificial layer height. Furthermore, it follows Fig. 16 the structure and the arrangement of the exhaust valve 16 with its central valve stem 17th Off Fig. 16 It can be seen that both an inlet valve chamber and an outlet valve chamber and the pumping chamber 15 are contoured circular and are interconnected via large opening cross-sections.

As mentioned before, is in Fig. 8 an intermediate step of manufacturing the micropump, in which the (top) stop layer 7 (sacrificial layer) was selectively removed. First As a result, the inlet valve 13 is released. Previously, the inlet valve punch 14 was still firmly on the thick, the stop layer 7 (sacrificial layer) forming oxide, which has also formed the etch stop for the plasma etching process for structuring the functional layer 8.

In particular from the Fig. 6 to 8 It is clear that the production of the functional elements 12 is carried out exclusively by Vorderseitenstrukturierung, ie by structuring in one direction to the front side V of the first carrier layer. The carrier layer 1 was not affected thereby, for example because it would have been structured through it.

Fig. 9 illustrates an anodic bonding process: The pre-structured second carrier layer 4, here a borosilicate glass wafer (for example a Pyrexglaswafer) has holes at corresponding points as fluid channels 19, 20. In this case, the left in the drawing fluid channel 19 forms an inlet channel for supplying active ingredient (insulin) and the fluid channel 20, which is located in the plane of the right, an outlet channel for discharging a "stroke" volume. The fluid channel 19 is preferably connected to a storage tank or storage bag with insulin, and the fluid channel 20 is connected to an injection needle or particularly preferably a microneedle array, for example of porous silicon, etc. The peripheral edges of the lower ends of the fluid channels 19, 20 form the valve seats for the inlet valve plunger 14 and the outlet valve plunger 17, respectively. The anti-Bonn layer surface portions form the sealing surfaces of the inlet valve 13 of the outlet valve 16. In addition or as an alternative to the anti-adhesive layer 9, it is not possible Anti-bonding surfaces shown are provided as seats on the back of the second carrier layer 4.

For the anodic bonding process, the functional layer 8 has to be contacted with an electrical voltage source and poled positively with respect to the second carrier layer 4, which has been set up in an adjusted manner. In the variant shown, starting from a silicon wafer as the first carrier layer 1, this contacting is possible without problems via the first carrier layer 1 due to the contact holes 3 in the lower stop layer 2. In this case, voltages of a few 100 V to a few 1000 V are used in a manner known per se, depending on the thickness of the second carrier layer 4. The anodic polarity of the front side or the silicon surface of the sacrificial layer 8 against the second carrier layer 4 results in a high-strength, high-precision and achieved irreversible connection of the contact surfaces to each other, without the need for an adhesive. The latter is crucial in the context of the limited stability and bioactivity of insulin, which would be compromised by many materials, such as many plastics or adhesives in its effectiveness. In the micropump shown, the insulin within the micropump comes into contact only with silicon, borosilicate glass and the antibond layer - all these substances are well insulin-compatible.

Fig. 10 shows the bonded wafer assembly after performing the anodic bonding process.

In Fig. 11 the first carrier layer 1 has been removed. The back-thinning of the first carrier layer 1 can be done by back grinding, plasma etching or by a combination of back grinding and plasma etching. Alternatively, you can
also be etched wet, such as in hot caustic potash using an etching mask as anterior protection. The removal of the complete first carrier layer 1 by plasma etching is particularly gentle, since no mechanical action takes place here. Since it is not necessary per se to etch anisotropically, it is possible, for example, to etch with an isotropic SF ₆ process with advantageously higher removal rates of 50 to 100 pm / min or more, so that the removal of the first carrier layer 1 takes only a few minutes. Since an etching attack on the overlying base layer (in this case silicon) up to the (second) stop layer 7 takes place via the contact holes 3, it is advantageous to switch from pure isotropic plasma etching to an at least partially anisotropic plasma etching in the final phase of the process. The advantage of anisotropy is in the case that the contact holes 3 may be over-etched, for example to compensate for Ätzenhomogenitäten or wafer thickness variations over the wafer surface, without the etchings in the base layer laterally in the contact hole areas are getting larger. The disadvantage is the lower etching rate for anisotropic etching. Switching from a purely isotropic etching process to an at least partially anisotropic plasma etching process can be realized by correspondingly teaching DE 42 410 45 A1 the isotropic SF ₆ etching step is carried out alternately with so-called passivation steps with, for example, C ₄ F ₈ or C ₃ F ₆ as the passivation gas toward the end of the etching back. The recognition of this transition can, for example, by means of an optical end point detection via "Optical Emissions Spectroscopy" - so-called OES - done in which the achievement of the lower (first) stop layer 2 detected at any point and then the Passivierschritte be inserted for Weiterätzen or further over-etching to be already in etching not laterally extended contact holes 3 during overetching. In the vertical direction, the thick oxide region, which is opposite to the contact hole 3, is etch-limiting. With this procedure, inhomogeneities of the etching process itself or wafer thickness fluctuations can be compensated by overetching with impunity. The OES endpoint recognition system also indicates when the first carrier layer, ie all silicon, has been removed from the lower stop layer 2 and the process has reached its end.

Fig. 12 shows the removal of the remaining stop layers 2, 7: on the one hand, the planar lower stop layer 2, on the other hand, the upper stop layer 7 (sacrificial layer) (Ätzstoppbereich over the open contact holes 3). The removal can in turn be carried out by liquid or vaporous hydrofluoric acid. Since, in particular, oxide layers introduce strong compressive stresses into the mechanical structure, it is advantageous to remove all oxide layers at the end of the process.

Further, on Fig. 12 a possible arrangement of a first actuator A1, a second actuator A2 and a third actuator A3 shown. In this case, the first actuator A1 is directly associated with the inlet valve 13, the second actuator A2 directly with the pumping chamber 15 and the third actuator A3 directly with the outlet valve 16. It can be seen that all the actuators A1 to A3 act directly on the base layer 5, which limits the micropump on the side remote from the second carrier layer 4. With regard to the mode of operation and a possible activation of the actuators A1 to A3, reference is made to the general description part. In particular, it is pointed out if necessary, for example, the second actuator A2 can be dispensed with (compare general description part).

Fig. 13 illustrates the bonding process in the case of the "SOI wafer variant." Except for the difficulty of electrically contacting the top SOI layer (base layer 5) via contact springs, etc. from the side or over the wafer edge, because there are no vias to the bottom , First carrier layer 1 are present, the structure and the procedure corresponds exactly to the counterpart of Fig. 9 ,

Fig. 14 shows the bonded wafer stack after removing the first carrier layer 1. Since there are no contact holes in the lower stop layer 2 in the SOI structure, the removal of the first carrier layer 1 by etching back in plasma is particularly easy and simple. It is advantageous to control the isotropic silicon etching with SF ₆ plasma with an end point recognition system (OES). This indicates when no more silicon is etched and when all has arrived on the lower stop layer 2, the lower stop layer 2 represents the etch stop for this etching process. In this case, an overetching can also be provided for safety in order to actually remove all silicon completely from the lower stop layer 2 and to compensate for prone inhomogeneities. Since the complete process can be carried out isotropically, removal rates are extremely high (typically 100 μm / min or more) and the process time is very short (only a few minutes). Alternatively, it is also possible to wet etch, for example in hot potassium hydroxide solution using an etching mask as front side protection.

Fig. 15 shows the state of the wafer day after removal of the lower stop layer 2 by liquid or vapor HF. Also in this case, it is advisable to remove all the oxide to remove unwanted compressive stresses from the mechanical structure. The function of the shown actuators A1 to A3 will be explained in the general part of the description.

In summary, a manufacturing process is proposed in the figures, which in both variants shown (silicon wafer / SOI wafer) is based exclusively on standard process steps of microsystem technology or semiconductor technology. At no point in the process do fragile wafer states or intermediate wafer states occur, in which the wafer or the wafer structure would have to be stabilized by films or similar costly special measures. Rather, in all stages of the process, it has to do with robust structures that can be handled and processed without special features. All channels through which liquids are to flow during operation of the micropump have comparatively large channel heights of, for example, 15 to 24 .mu.m and consequently low flow resistance and low "dead volumes". All this is realized with a comparatively simple and particularly cost-effective process.

Claims (6)

1. Micropump having a plurality of functional elements (12), the functional elements (12) being produced solely as a result of structuring from one direction, characterized in that the inlet valve (13) of the micropump has a plurality of coil springs (18) symmetrically holding an inlet valve plunger (14) and nested one in the other, and in that the coil springs (18) are all connected at one end to the inlet valve plunger (14) at locations arranged so as to be distributed uniformly in the circumferential direction.
2. Micropump according to Claim 1, characterized in that the micropump has a carrier layer (1, 4) in which at least one fluid duct (19, 20) is introduced and which directly delimits the pumping chamber (15).
3. Micropump according to one of the preceding claims, characterized in that the inlet valve (13) and/or the outlet valve (16) of the micropump can be actively sealed off by means of at least one actuator (A1-A3).
4. Micropump according to Claim 3, characterized in that a valve sealing surface of the inlet valve (13) and/or a valve sealing surface of the outlet valve (16) can be pressed against the carrier layer (1, 4) by means of an actuator (A1-A3).
5. Micropump according to one of the preceding claims, characterized in that the inlet valve (13), the outlet valve (16) and the pumping chamber (15) are in each case directly assigned at least one actuator (A1-A3).
6. Micropump according to one of Claims 1 to 4, characterized in that only the inlet valve (13) and the outlet valve (16) are in each case directly assigned at least one actuator (A1, A3), and in that the pumping action can be controlled by the activation of at least one of these actuators (A1, A3).

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