Integrated microvalve and method for manufacturing a microvalve

An integrated microvalve has a substrate, a first function layer applied to the substrate, and a second function layer applied to the first function layer, the first function layer being designed as a diaphragm in at least one valve area, the second function layer being removed in the valve area and in a fluid discharge area, and an anvil connected essentially only to the diaphragm being exposed from the substrate in the valve area, a plate being applied to the second function area to form a valve space.

FIELD OF THE INVENTION

The present invention relates to an integrated microvalve for controlling the flow of a fluid. The present invention furthermore relates to a method for manufacturing such a microvalve.

BACKGROUND INFORMATION

Microfluidics is concerned with the transport and processing of small amounts of gaseous or liquid substances, known as fluids. Microvalves are provided for controlling the amount of transported substance. Such microvalves are used as flow limiters for liquids transported in microfluidic components.

In miniaturized fluid valves the reduced sealing surface areas quickly result in leakages in the event of particle contamination. Sealing may be achieved, for example, by a sufficiently high actuating force or a sufficiently large sealing surface area, which is difficult to achieve in an integrated form.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to provide a microvalve which has a simple construction and is suitable for reliably controlling the fluid flow.

According to a first aspect of the present invention, an integrated microvalve is provided with a substrate having a first function layer applied to the substrate and a second function layer applied to the first function layer. The first function layer is designed as a diaphragm in one valve area. The second function layer is removed in the valve area and/or in a channel area. An anvil is exposed from the substrate in the valve area; this anvil is connected essentially only to the diaphragm. A plate is applied to the second function area to form a valve space. The diaphragm is pressed against a surface of the plate to seal the microvalve.

The microvalve according to the present invention has the advantage that it may be constructed in a simple manner just by applying two function layers onto a substrate and by structuring these layers in a suitable manner. The microvalve according to the present invention furthermore offers the advantage that the anvil formed by the first function layer in the valve area and from the substrate is movable from the outside using an actuator, so that the actuating force may be adjusted in a simple manner to the closed state of the valve, to its sealing state in particular.

The plate preferably has an orifice in the valve area for conducting a fluid, through which the fluid may be transported to and from the valve area.

As an alternative, the anvil may have a supply channel in the valve area for conducting the fluid. The fluid may be supplied and discharged through the substrate via this channel, so that the plate may be essentially unstructured when constructing the microvalve. This considerably facilitates the manufacture of the microvalve according to the present invention, because it is not necessary for two structured components to be connected in a certain precisely adjusted manner.

In particular, the second function area may have a fluid channel connected to the valve space formed in the valve area. In this way, the flow of the fluid to and from the microvalve may be formed by an integrated fluid channel. The manufacture of the fluid channel may be connected in a simple manner with the manufacture of the valve area, in particular by etching the second function layer. The microvalve is preferably connected to a flow sensor via a fluid channel for measuring the fluid flow. In particular, the microvalve may be controlled as a function of the measured fluid flow.

The first and/or second function area is preferably applied as an epitaxial layer, in particular as a silicon epitaxial layer, onto the substrate.

According to a further aspect of the present invention, a method is provided for manufacturing a microvalve. For this purpose, a first function layer is applied to a substrate and subsequently an etch stop layer, at which a subsequent deep etching step stops, is applied to the first function layer in a valve area. A second function layer is then applied to the first function layer and to the etch stop layer. The second function layer is subsequently masked in such a way that the second function layer is removed in the valve area in a deep etching step. The second function layer in the valve area is deep etched according to the mask in a subsequent deep etching step. The substrate is structured in such a way, in particular using a trench etching process, that an anvil is formed, which is connected only to the first function layer. To finish the microvalve, a plate is applied to the second function layer to form the valve space.

This manufacturing method for a microvalve has the advantage that it is easy to implement and the essential structures may be implemented in a substrate having functional layers applied. The microvalve is formed by applying an essentially unstructured plate to the second function layer. It is furthermore possible to actuate the valve via an unintegrated actuator, which makes it possible to adjust the actuating forces to the requirements.

The first and/or second function layer is/are preferably applied by depositing polycrystalline silicon as an epitaxial layer.

The sealing plate is preferably applied to the second function layer by anodic bonding. This represents a relatively simple method for permanently bonding a plate, in particular a plate made of suitable glass such as borosilicate glass, to the second function layer made of a silicon material.

DETAILED DESCRIPTION

FIGS. 1athrough1fshow a method for manufacturing a microvalve according to a first embodiment of the present invention. InFIG. 1a, a first function layer2is deposited onto a substrate1, preferably a silicon substrate1. The first function layer is preferably made of polysilicon, which is preferably manufactured using an epitaxial deposition method as an epitaxial polysilicon layer having an epitaxial starting layer and an epitaxial polysilicon layer.

The thickness of first function layer2and thus the thickness of the diaphragm of the microvalve is accurately determined by the thickness of the deposited first function layer2and/or by a possible finishing surface treatment procedure (polishing).

An etch stop layer3is deposited on first function layer2and structured, thus defining a valve area. After being structured, etch stop layer3thus exists only at locations on the surface of first function layer2at which a subsequent deep etching process is to be stopped in order to form a diaphragm. A second function layer4is applied to first function layer2and etch stop layer3, essentially in the same way as first function layer2, preferably as an epitaxial polysilicon layer. In particular, the second function layer is made up of a second epitaxial start layer and a second epitaxial polysilicon layer. A planarization step may then follow to facilitate sealing of the channels after completion of the processing, using anodic bonding, for example.

FIG. 1bshows that an anvil is exposed from the substrate by trench etching and is essentially connected only to first function layer2. Anvil14is exposed by masking the surface of substrate1opposite the surface which has function layers2,4applied and by subsequent trench etching. The depth of the trench etching process may be controlled via the etching time or by providing an etch stop layer (not shown) between the substrate and the first function layer where etching stops. The etch stop layer is provided either as a flat layer between the substrate and the first function layer or only at the locations of the trenches for anvil14, depending on which other structures are integrated into the substrate. Anvil14is preferably provided with a circular cross section, so that the trenches shown form a circle around anvil14.

As shown inFIG. 1c, after structuring the substrate, the surface of second function layer4is masked using a masking layer6in such a way that the valve area and a channel area are excluded from a subsequent deep etching process. Masking layer6on second function layer4is formed for forming the microvalve essentially as a complement to the structuring of etch stop layer3. The deep etching process etches second function layer4in the areas not covered by masking layer6as far as etch stop layer3, thus exposing diaphragm7in the valve area.

Subsequently a plate8having an orifice9in valve area7is applied to the remaining second function layer4. The plate is preferably formed from a suitable glass and is preferably applied by anodic bonding to second function layer4made of silicon. A planarization process, for example, in the form of a polishing step, may be carried out before structuring function layers2,4, which also removes masking layer6, to ensure that plate8essentially rests on all areas of second function layer4and is tightly bonded thereto.FIG. 1dshows the microvalve according to the first embodiment of the present invention in an open state, a fluid flowing through plate8via orifice9.

Simultaneously with the structuring of the valve area of the microvalve, a fluid channel10may be formed by also removing at least second function layer4at the locations of fluid channel10. Depending on whether fluid channel10is to have a larger cross section, the etch stop layer may be omitted in forming the fluid channel, so that, in addition to second function layer4, parts of first function layer2or the entire function layer2may also be removed by controlling the intensity or the duration of the deep etching step.

FIG. 1eshows the microvalve according to the present invention in a closed state. The diaphragm, together with the anvil, is pressed to bottom of plate8by an external actuator (not shown), so that the diaphragm is deformed in the area of the deep etchings in substrate1and seals orifice9.

FIG. 1fshows a top view onto the microvalve according to the present invention. In this case, it has a round cross section, the diaphragm, i.e., the valve area formed by the anvil, being concentric to the orifice in plate8.

FIGS. 2athrough2fshow the method for manufacturing a microvalve according to a second embodiment of the present invention. InFIG. 2a, essentially the same layer arrangement used for manufacturing the microvalve of the first embodiment is assumed. The anvil is etched into the substrate in the same way by a trench etching process, a fluid supply channel being etched through substrate1concentrically to the shape of the anvil, for example. The fluid supply channel passes through substrate1and first function layer2. To end the trench etching process for exposing the anvil at the first function layer, the fluid supply channel, however, is etched as far as the second function layer, a further etch stop layer13, which does not exist in the area of the fluid supply channel, may be formed in the area of trenches12between the substrate and first function layer2. Etching the fluid supply channel is then only stopped at etch stop layer3between first function layer2and second function layer4.

AsFIG. 2cshows, after forming the anvil, second function layer4is etched as in the previously described process for the first embodiment. The valve area and fluid channel10are masked by masking layer6in such a way that these are accessible to a subsequent deep etching process. The deep etching process ends at etch stop layer3, which is located in the valve area between first function layer2and second function layer4.

The microvalve is finished by applying an unstructured plate, in particular a plate12made of a suitable glass, to second function layer4. For example, plate12may be bonded to second function layer4using anodic bonding. For this purpose, second function layer4must be planarized in such a way that plate12rests essentially evenly on the entire surface of second function layer4. This may be accomplished, for example, by a planarizing process such as polishing, which also removes masking layer6.

By actuating anvil14, for example using an external actuator, diaphragm7is pressed to the surface of plate12associated with the substrate, and thus fluid supply channel11is closed.FIG. 2dshows the valve in a closed state, andFIG. 2eshows the valve in an open state. The fluid channel is manufactured as the microvalve of the first embodiment.FIG. 2fshows a top view onto the microvalve according to the present invention. It is apparent that plate12is essentially unstructured, so that no adjustment between the microvalve structure and sealing plate12is needed when manufacturing the microvalve.

FIG. 3shows an exemplary integrated fluidic component, in which a microvalve20according to the present invention is provided. Microvalve20is connected via a fluid channel21to a flow sensor22for measuring the fluid flow using the heating point method, for example. Piezoelectrically driven atomizing nozzles23, which may be manufactured in the same way in the predefined layer structure, are located downstream from flow sensor22. A piezoelectric actuator25for driving the atomizing nozzles is provided in or on plate24provided for sealing the microfluidic structures.