US20090307906A1

US20090307906A1 - Method of producing components for controlling a fluid flow and components produced by this method

Info

Publication number: US20090307906A1
Application number: US12/305,286
Authority: US
Inventors: Tjalf Pirk; Stefan Pinter
Original assignee: Nissan Motor Co Ltd
Current assignee: Robert Bosch GmbH; Nissan Motor Co Ltd
Priority date: 2006-08-29
Filing date: 2007-07-10
Publication date: 2009-12-17
Also published as: EP2059698B1; DE102006040343A1; JP2010501810A; CN101512200A; CN101512200B; EP2059698A1; WO2008025601A1

Abstract

A method for producing a micromechanical component for controlling a fluid flow and a component produced according to this method are described. The method for producing a micromechanical component for controlling a fluid flow includes: producing an oscillatory diaphragm on a surface of a substrate by forming an underlying cavity from the same side of the surface, covering the substrate with an intermediate layer, patterning the intermediate layer, and covering the intermediate layer with a covering layer sealing the micromechanical component. It is characterized by the fact that the intermediate layer is patterned in such a way that a sealing element of a fluid valve forms on the diaphragm, which element seals and/or surrounds a valve opening formed in the covering layer.

Description

FIELD OF INVENTION

The present invention relates to a micromechanical component for controlling a fluid flow, and a method for producing the micromechanical component.

BACKGROUND INFORMATION

A method for producing communicating hollow spaces is described in German Patent Application No. DE 10 2005 042 648.4. For this purpose, the patterning of a silicon substrate from only one side of the wafer is provided, which entails clear time, and thus cost, advantages relative to production methods in which the wafer is processed from both sides. To form the communicating hollow spaces, this printed publication teaches the depositing and patterning of additional so-called functional layers in the form of epitaxially grown silicon supplementary layers, which are produced using epitaxy oxide layers, resist masks, and corresponding etching methods. A covering glass layer having access openings formed in it for the so-called “fluidic structures” forms the seal of this multilayer structure.
An electrochemically produced cavity, which is covered by a diaphragm in the form of a silicon layer on the surface of the silicon substrate, forms the basis of these communicating hollow spaces. The form and position of the diaphragm is shaped by rearranging the porous silicon, and as a moving element, it forms a sealing element for controlling a microfluid together with elements of the other functional layers.
In this context, the large number of method steps required for producing these communicating hollow spaces having valve and pump functions for microfluidic applications is considered disadvantageous.

SUMMARY OF THE INVENTION

Therefore, the present invention is based on an objective of improving the related art described at the outset.
Accordingly, the present invention relates to a method for producing a micromechanical component for controlling a fluid flow and includes the following steps:

producing an oscillatory diaphragm on a surface of a substrate by forming an underlying cavity from the same side of the surface,
covering the substrate with an intermediate layer,
patterning the intermediate layer, and
covering the intermediate layer with a covering layer sealing the micromechanical component.

It is characterized by the fact that the intermediate layer is patterned in such a way that a sealing element of a fluid valve forms on the diaphragm, which sealing element seals and/or surrounds a valve opening formed in the covering layer.
This procedure has the advantage that to produce a micromechanical valve only two layers have to be processed using a surface-micromechanical processing method without requiring special process steps. The third layer, the so-called covering layer, may be prepared in a separate processing process and, to complete the valve, deposited onto the base and intermediate layer prepared in this manner, and may be connected in a fixed manner to them when adjusted accordingly.
Relative to the previously known related art, it is thus possible to dispense with a plurality of process steps, in particular non-standard process steps, which are necessary for forming additional intermediate layers that were previously required due to the standards of semiconductor technology.
In this context, the intermediate layer may be patterned in such a manner that a hollow space forms around the sealing element. This makes it possible to create an interior chamber for the valve on the one hand, and, on the other hand, to functionally pattern or contour the sealing element itself.
Also advantageously, it is provided that a fluid-conducting through opening through the diaphragm to the underlying cavity be produced when patterning the intermediate layer. For example, this allows for a pressure equalization between the cavity, which is preferably produced by rearranging porous silicon under the diaphragm, and the hollow space above it in the intermediate layer. In this manner, the diaphragm may on the one hand oscillate freely, and on the other hand this connection expands the total existing interior volume of the valve, which may be advantageous when producing an intake valve, for example.
In contrast, when producing a discharge valve, it may be advantageous that the through opening in the diaphragm is patterned such that it connects the cavity lying under the diaphragm to the valve opening.
Thus, a pressure equalization between the external pressure surrounding the micromechanical component in the valve opening region and the internal pressure prevailing in the cavity is possible.
In this context, it is to be noted that this cavity is also formed in the interior of the micromechanical component, and the position of the above-lying diaphragm is able to be influenced by changing the external pressure and the accompanying force effect on its underside.
A further option for modifying the position of the diaphragm is to correspondingly modify the pressure on the opposite diaphragm side, that is, the side facing the intermediate layer and the covering layer. To this end, it is necessary to modify the internal pressure in the hollow space around the sealing element in question, which hollow space is separated from the underlying cavity in a fluid-tight manner. Such a pressure modification may be brought about by a pressure increase in the hollow space surrounding the sealing element, for example. When the pressure difference between the pressure in the hollow space around the sealing element and the external pressure, which also prevails in the interior of the cavity formed under the diaphragm, is sufficiently high, the diaphragm may be pushed so far into the interior space of the cavity that the sealing seat between the sealing element and a valve output opening may be opened in a fluid-conducting manner. In this manner, the fluid under excessive pressure in the hollow space around the sealing element is able to flow out.
To prevent a sealing element of a valve patterned in this manner from adhering to the underside of the covering layer, which may be a pre-drilled glass plate, for example, an anti-stick layer may be deposited between the sealing element and the covering layer. The anti-stick layer may be deposited and patterned on the silicon or on the glass plate, or on both. Instead of and/or in addition to an anti-stick layer, it is also possible to implement an anti-stick function by correspondingly modifying the surface of one or also both contact regions, glass and/or silicon. SiC, Si-nitride, or the like is particularly advantageously suitable for this purpose. This may be provided both in an intake valve and in a discharge valve, preferably in both. Anodic bonding bonds silicon and glass very firmly. If the covering layer (glass) is deposited by anodic bonding, an electric layer, such as nitride or SiC (silicon carbide), may be applied and patterned beforehand, for example.
To achieve a higher production level when producing such a micromechanical component, it may additionally be advantageous when producing the first oscillatory diaphragm to produce at least one additional oscillatory diaphragm on the surface of the substrate by forming a cavity below it.
For example, two different valves may be produced next to each other on a wafer segment in this manner. These may be either two different intake or two different discharge valves; however, in a particularly preferred specific embodiment, it may also be an intake valve and a discharge valve.
For example, the combination of an intake and a discharge valve provides the option of producing a micromechanical pump using a surface-micromechanical (SMM) process of this type for processing a substrate, in the form of a silicon wafer, for example. To this end, it is seen as particularly advantageous that during the patterning of the intermediate layer and/or the substrate, a fluid-conducting connection is produced between the first hollow space formed around the first sealing element and an additional hollow space formed around an additional sealing element.
This fluid-conducting connection may, for example, be a pump chamber of a correspondingly designed micromechanical pump that connects the above-described hollow spaces around the respective sealing elements in a fluid-conducting manner.
The internal pressure of this fluid-conducting connection, for example, in the form of a pump chamber, may be influenced in that a third oscillatory diaphragm is formed adjacent to the fluid-conducting connection and/or adjacent to one of the two hollow spaces, for example. The position of this diaphragm may then be influenced by a suitable means in a manner that modifies the volume of the pump chamber.
In a first embodiment, such a means modifying the position of the diaphragm could be a pneumatic actuator. For example, it could be characterized by the fact that a separate fluid connection is formed for a cavity sealed by the third oscillatory diaphragm.
Using this separate fluid connection, overpressure or underpressure may be applied to the diaphragm such that the volume of the pump chamber is reduced or increased. When volume increases, an underpressure results in the pump chamber, so that the intake valve connected to it opens and fluid is able to flow into the pump chamber. When the pump volume is reduced, an overpressure arises, so that starting at a specific differential pressure between this overpressure and the external pressure prevailing in the discharge region of the discharge valve, this discharge valve opens to let out the fluid located in the pump.
In a further embodiment, it may be provided that the micromechanical pump is not activated by a fluid actuator, but rather by another means. For example, to this end, it may be provided that an element is positioned on or affects the third oscillatory diaphragm, which element exercises a push and/or a pull effect on the diaphragm when activated. For example, this could be a piezoelectric oscillator, a plunger, or an electromagnet, or the like.
Furthermore, it is seen as advantageous if the elements that jointly form a valve, diaphragm, sealing element, antistick layer, and covering layer, are patterned such that when the micromechanical component, in particular, a micromechanical pump, is in the assembled state, the sealing element seals the valve opening under prestressing. In this manner, by prestressing the respective valve, it is possible to directly influence the pressure differential on both sides of the valve sealing seat or the valve flap, which pressure differential is required to open the respective valve. Thus, it is possible to produce pumps having pump parameters that are respectively adapted to different application cases.
In addition to the production method, the present invention also relates to a corresponding micromechanical component for controlling a fluid flow having a substrate, a patterned intermediate layer, and a covering layer sealing the micromechanical component, an oscillatory diaphragm and a cavity below it being formed on the surface of the substrate facing the intermediate layer by processing from the same side, and forming a valve together with a sealing element and a valve opening. This component is characterized by the fact that, viewed from outside, valve tensioning means for an intake valve and/or for a discharge valve are arranged behind the valve sealing seat in the interior of the micromechanical component. This structure has the advantage, which was already explained above with regard to the method, that in addition to the substrate, only one single intermediate layer is required for production.
In this context, it may be particularly advantageous that the valve tensioning means for the intake valve, and/or the valve tensioning means for the discharge valve, include at least parts of its diaphragm. Such a part of the diaphragm may be a diaphragm arm, for example, and/or a diaphragm anvil that connects this diaphragm arm with another diaphragm arm. Oscillating because of being fastened to the diaphragm and thus actuating the valve in its function, the above-described sealing element, for example, may be set upon such a diaphragm anvil.
Furthermore, it may be advantageous if the valve tensioning means for the intake valve and/or the valve tensioning means for the discharge valve include a sealing element and/or an anti-stick layer and/or a fluid-conducting connection between the cavity of the discharge valve and the exterior of the micromechanical component. Furthermore, it may be advantageous that the valve opening of the intake valve and/or the valve opening of the discharge valve is/are formed in the covering layer. The advantages of such specific embodiments were already explained above in the description of the corresponding method steps.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 show one cross-section, respectively, through a substrate of a micromechanical component for controlling a fluid flow, in different processing steps, for a first exemplary embodiment.

FIGS. 3 a and 4 a show, respectively, the top view of FIGS. 3 and 4.

FIGS. 5 through 6 a show the sectional view and the top view of another exemplary embodiment that is modified relative to the first exemplary embodiment in FIGS. 3 through 4 a, again in two different process steps.

FIGS. 7 through 8 a show two additional structural elements of a micromechanical component, in sectional view and top view, respectively.

FIGS. 9 and 10 show two further exemplary embodiments of micromechanical components in the form of micromechanical pumps.

DETAILED DESCRIPTION

In detail, FIG. 1 shows a section through a substrate 2, in particular in the form of a silicon wafer, in which a cavity 3 and above it a diaphragm 4 were produced by rearranging porous silicon.
FIG. 2, on the other hand, shows substrate 2 in accordance with FIG. 1 having a patterned intermediate oxide layer 5 deposited on it, an intermediate layer 6 on top of patterned intermediate oxide layer 5, and again a resist layer 7 deposited in a patterned manner on intermediate layer 6.
The patterning of intermediate oxide layer 5 acts as a foundation for the reproducible patterning of underlying substrate 2 in a subsequent etching process, as may be seen from FIGS. 3 through 6, for example.
The patterning of the resist layer corresponds to the usual masking in a silicon processing using a subsequent etching process. The layer regions covered by the resist layer remain standing, while the remaining layer regions are removed by the etching process. However, despite its continuance over time, the effect of the etching process may be restricted locally in its effect, for example, through the etch-resistant intermediate oxide layer 5, as may be seen from the illustrations of the additional process steps in FIGS. 3, 3 a, 5 and 5 a, for example.
Micromechanical component 1 for controlling a fluid flow thus develops stepwise through the processing of the silicon wafer using surface-micromechanical technology (SMM technology). In this context, the illustrations in FIGS. 3 through 4 a show two process steps in sectional view and top view for producing an intake valve, and FIGS. 5 through 6 a show the corresponding illustrations for producing a discharge valve.
After the production process is concluded, together with an additional element, such as shown in FIGS. 7, 7 a or 8, 8 a, for example, they form a micromechanical pump that has, for example, a pneumatic diaphragm actuator according to the illustration of FIG. 9, and in the illustration according to FIG. 10, an additional actuator, for example, in the form of a piezoelement.
FIG. 3 shows micromechanical component 1 in a process step that follows the illustration in FIG. 2, after both epitaxy layer 6 and diaphragm 4 have been etched in a trenching step. Intermediate oxide layer 5 served as a selective etch stop. The underlying silicon layer, which forms the diaphragm, was etched only where this intermediate oxide layer 5 was removed.
Three wedge-shaped through openings 9 may be seen in the top view in FIG. 3 a, between which one diaphragm arm 10 respectively is visible as a diaphragm part that was not etched away. Cylinder-shaped sealing element 8 is shown in the middle, which seals valve opening 12 in covering layer 11, which is subsequently still to be deposited (FIG. 4).
This etching process formed a hollow space 15 around sealing element 8, which hollow space 15 may communicate via through opening 9 in diaphragm 4 with cavity 3 arranged under diaphragm 4. The functioning method of this intake valve shown in FIG. 4 is comparable to that of passive, hydrostatic valves. As soon as the pressure is higher on the outside than it is on the inside, the valve flap in the form of sealing element 8 lying on oscillatory diaphragm 4 is pressed down and the liquid or gaseous medium may flow into inner space 15 of the valve. When the pressure outside is less than or equal to the pressure inside, the valve flap is again pressed against covering layer 11, which may be a glass plate, for example.
To prevent valve flap 8 from adhering in sealing region 16 between sealing element 8 and covering layer 11, an anti-stick layer 13 may be deposited additionally in this region. The anti-stick layer may be deposited both on the glass and also alternatively on the Si surface, or on both, and may be patterned accordingly.
Through the layer elevation that results from depositing the anti-stick layer, the valve flap is lightly prestressed, as shown in FIG. 4. By varying the parameters responsible for the prestressing, such as geometry or elasticity of the diaphragm, for example, the operating range of the intake valve is able to be influenced with regard to the differential pressure required for releasing the valve. Thus, it is possible to implement intake valves that remain closed even in the event of a slightly higher external pressure.
Using the production method provided here, a micromechanical component for controlling a fluid flow, such as the above-described intake valve, may be implemented by merely depositing and patterning a single intermediate layer, along with the subsequent sealing through a cover plate. Relative to the known related art presented at the outset, this means a massive reduction in the number of process steps required for production and a restriction to standard processes of microsystem technology, in particular the semiconductor process technology. In this way, the required expense, both in terms of time and money, for producing such an element is reduced significantly.
FIGS. 5 and 6, and 5 a and 6 a show, analogously to the illustrations in FIGS. 3 through 4 a, two process steps for producing a micromechanical discharge valve 17.
To create the structure of this discharge valve, the resist mask for preparing the etching process was shaped, in a manner that deviates from the illustration of FIG. 2, such that a passage 19 is formed centrally in sealing element 18. The formation of a hollow space 21 around sealing element 18 is the same. On the other hand, the patterning of intermediate oxide layer 5 deposited on the surface of the substrate is different again. As may be seen in FIG. 5 a, this intermediate oxide layer 5 is omitted only centrally in the middle, beneath passage 19, above diaphragm 4 a. During the etching process, this creates a through opening 20 to underlying cavity 3 a.
The finished micromechanical discharge valve is shown in cross-section in FIG. 6, and in top view in FIG. 6 a. The lines of intersection in the different top view illustrations III/III through VIII/VIII respectively show the position of the associated sectional view in the relevant figures.
Cavity 3 a of discharge valve 17 from FIG. 6 thus communicates in a fluid-conducting manner with the external environment of micromechanical component 1 via the connection through opening 20, passage 19, and valve opening 22. In this instance, valve opening 22 is disposed in sealing covering layer 11, in accordance with the specific embodiment of intake valve 14 from FIGS. 3 through 4 a. These valve openings 12 and 22 are formed in a prepared work step, in the glass plate acting as covering layer 11. A fundamental advantage of valves 14, 17 patterned in this way lies in the arrangement of valve prestressing means 34, 35 in the interior of the micromechanical component, behind valve sealing seat 16 or 16 a.
Additionally, to prevent adhesion between sealing element 18 and glass plate 11, an anti-stick layer 23 is deposited in sealing region 16 a. Like anti-stick layer 13 in sealing region 16, this anti-stick layer 23 is deposited either on the appropriate Si surfaces, or the glass surface, or on both the Si and the glass, and is patterned accordingly. Through the geometric expansion of this anti-stick layer 23, the valve flap of this discharge valve 17 may be prestressed in accordance with intake valve 14.
To activate intake valve 14 or discharge valve 17, in accordance with the micromechanical pumps shown in FIGS. 9 and 10, another pump chamber 24 whose pressure may be influenced by an appropriate means is required in micromechanical component 1. To this end, FIGS. 7 and 8 show two different exemplary embodiments.
FIG. 7 shows a pneumatic pump actuator, in which a cavity 25 is formed, in accordance with cavities 3 of intake valve 14 and of discharge valve 17, in substrate 2 when the micromechanical component is produced. This cavity 25 is separated from pump chamber 24 in a fluid-conducting manner and has a separate fluid connection 26, as shown in FIG. 7 a. This connection 26 is used to pressurize cavity 25, to press above-lying diaphragm 27 upward in accordance with the illustration in FIG. 7, and thus to reduce the volume of pump chamber 24. This volume reduction causes the pressure inside pump chamber 24 to rise, so that the discharge valve may open. Anti-stick layer 28 in turn prevents diaphragm 27 from adhering to covering layer 11, in accordance with the explanations regarding the intake and discharge valve.
After discharging the overpressure in cavity 25, diaphragm 27 sinks down, so that a differential pressure may form between pump chamber 24 and valve opening 12 of the intake valve, which differential pressure opens the intake valve. This intake process of the micromechanical pump may further be supported by applying an underpressure in cavity 25. In this case, diaphragm 27 would bend toward the floor of cavity 25, and thus increase the volume of pump chamber 24. Pump part 29 is thus the third element of micromechanical component 1, which may be produced together using the above described production processes, based on substrate 2.
FIG. 8 illustrates a specific embodiment of a pump part 30, which is modified relative to FIG. 7, in which a diaphragm 31 is fastened on covering layer 11 by a supporting and sealing element 32. In this instance, pump chamber 24 is likewise sealed toward the outside, so that lowering diaphragm 31 again results in a reduction of the volume in pump chamber 24.
Diaphragm 31 is lowered by activating actuator 33, for example, in the form of a piezoelement or piezo-plunger, or a magnetic armature, which acts on the diaphragm from the outside. Depending on the specific embodiment, in this instance too it is possible to raise diaphragm 31 above a preferably horizontal normal position by applying a pull effect to diaphragm 31. In accordance with the pneumatic or possibly hydraulic valve actuator, this produces the support for generating an underpressure relative to the intake valve. However, diaphragm 31 and also diaphragm 27 are preferably restored to their rest positions by their inherent restoring forces.
FIGS. 9 and 10 show both exemplary embodiments of a micromechanical component 1 in the form of a micromechanical pump having the individual elements intake valve 14, discharge valve 17, and pump part 29 and 30, respectively, in the activated state when pump chamber volume 24 is reduced.

Claims

1-25. (canceled)

26. A method for producing a micromechanical component for controlling a fluid flow, the method comprising:

producing an oscillatory diaphragm on a surface of a substrate by forming an underlying cavity from a same side of the surface;

covering the substrate with an intermediate layer;

patterning the intermediate layer; and

covering the intermediate layer with a covering layer sealing the micromechanical component;

wherein the intermediate layer is patterned in such a way that a sealing element of a fluid valve is formed on the diaphragm, thereby at least one of sealing and surrounding a valve opening formed in the covering layer.

27. The method according to claim 26, wherein the intermediate layer is patterned such that a hollow space develops around the sealing element.

28. The method according to claim 26, wherein when the intermediate layer is patterned, a fluid-conducting through-hole through the diaphragm to the underlying cavity is produced.

29. The method according to claim 28, wherein a first through-hole in a first diaphragm is patterned such that it connects a first cavity lying under the first diaphragm to a first hollow space surrounding a first sealing element.

30. The method according to claim 28, wherein a second through-hole in a second diaphragm is patterned such that it connects a second cavity lying under the second diaphragm to a second valve opening.

31. The method according to claim 26, further comprising:

one of depositing an anti-stick layer and implementing an anti-stick functionality in a sealing region between the covering layer and the sealing element of the fluid valve.

32. The method according to claim 31, wherein the anti-stick layer is deposited on at least one of glass and silicon.

33. The method according to claim 31, wherein the anti-stick functionality is implemented on at least one of glass and silicon.

34. The method according to claim 31, wherein the anti-stick layer is made up of silicon.

35. The method according to claim 31, wherein the anti-stick layer is a silicon nitride.

36. The method according to claim 26, further comprising:

during the production of a first oscillatory diaphragm, producing at least one additional oscillatory diaphragm on the surface of the substrate by forming a second underlying cavity.

37. The method according to claim 36, wherein when at least one of the intermediate layer and the substrate is patterned, a fluid-conducting connection is produced between a first hollow space formed around a first sealing element and an additional hollow space formed around an additional sealing element.

38. The method according to claim 37, further comprising:

forming a third oscillatory diaphragm adjacent to at least one of the fluid-conducting connection and one of the two hollow spaces.

39. The method according to claim 38, wherein a separate fluid connection is formed for a cavity sealed by the third oscillatory diaphragm.

40. The method according to claim 38, further comprising:

positioning an element on the third oscillatory diaphragm, which element exercises at least one of a push and a pull effect on the diaphragm when activated.

41. The method according to claim 31, wherein the valve, the diaphragm, the sealing element, the anti-stick layer, and the covering layer are patterned such that in an assembled state of the micromechanical component, the sealing element seals the valve opening under prestressing.

42. A micromechanical component for controlling a fluid flow, comprising:

a substrate;

a patterned intermediate layer;

a covering layer sealing the micromechanical component;

an oscillatory diaphragm and an underlying cavity formed on a surface of the substrate facing the intermediate layer through processing from a same side, and forming a valve together with a sealing element and a valve opening; and

means for valve tensioning for at least one of an intake valve and a discharge valve disposed behind, viewed from outside, a valve sealing seat in an interior of the micromechanical component.

43. The micromechanical component according to claim 42, wherein the means for valve tensioning for at least one of the intake valve and the discharge valve includes at least parts of the diaphragm.

44. The micromechanical component according to claim 42, wherein the means for valve tensioning for at least one of the intake valve and the discharge valve includes at least one of the sealing element and one of an anti-stick layer and anti-stick functionality.

45. The micromechanical component according to claim 44, wherein the anti-stick layer is deposited on at least one of glass and silicon.

46. The micromechanical component according to claim 44, wherein the anti-stick functionality is deposited on at least one of glass and silicon.

47. The micromechanical component according to claim 44, wherein the anti-stick layer is made up of silicon.

48. The micromechanical component according to claim 44, wherein the anti-stick layer is a silicon nitride.

49. The micromechanical component according to claim 42, wherein a fluid-conducting connection is provided between the cavity of the discharge valve and the outside of the micromechanical component.

50. The micromechanical component according to claim 42, wherein the valve opening of at least one of the intake valve and the discharge valve is formed in the covering layer.