HERMETIC SEAL FOR USE IN AN IMPLANTABLE METRONOMIC DRUG PUMP AND A MEHTOD OF MANUFACTURING THE SAME

Abstract

A method of hermetically bonding components of an implantable pump made of biocompatible materials comprises the steps of providing a first SiO.sub.2 layer of predetermined first thickness onto a selected bonding surface of a first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below a first predetermined magnitude; providing a second SiO.sub.2 layer of predetermined second thickness onto a selected bonding surface of a second biocompatible component of the implantable pump to reduce the surface roughness of the selected bonding surface; and bringing the first and second SiO.sub.2 layers into contact with each other at a low temperature with a low pressure to form a high quality hermetic bond and seal between first and second SiO.sub.2 layers. The invention includes an implantable pump having a hermetic seal manufactured by the method.

Claims

1. A method of hermetically bonding components of an implantable pump made of biocompatible materials comprising: providing a first SiO.sub.2 layer of predetermined first thickness onto a selected bonding surface of a first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below a first predetermined magnitude; providing a second SiO.sub.2 layer of predetermined second thickness onto a selected bonding surface of a second biocompatible component of the implantable pump to reduce the surface roughness of the selected bonding surface; and bringing the first and second SiO.sub.2 layers into contact with each other at a low temperature with a low pressure to form a high quality hermetic bond between first and second SiO.sub.2 layers.

2. The method of claim 1 where the first biocompatible component is composed of silicon, where the second biocompatible component is composed of titanium, and where providing a first SiO.sub.2 layer of predetermined first thickness onto a selected bonding surface of a first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below a first predetermined magnitude comprises providing the first SiO.sub.2 layer as a native SiO.sub.2 layer of the order of 2 nm thickness onto silicon bonding surface of the first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below approximately 0.5 nm or less.

3. The method of claim 1 where the first biocompatible component is composed of silicon, where the second biocompatible component is composed of titanium, and where providing a second SiO.sub.2 layer of predetermined second thickness onto a selected bonding surface of a second biocompatible component of the implantable pump to reduce the surface roughness of the selected bonding surface comprises providing the second SiO.sub.2 layer of the order of 1.5 m thickness onto a selected bonding surface of the second biocompatible titanium component of the implantable pump to reduce the surface roughness.

4. The method of claim 3 further comprising chemical mechanical polishing the selected bonding surface of the second SiO.sub.2 layer of the second biocompatible titanium component of the implantable pump before bringing the first and second SiO.sub.2 layers into contact with each other.

5. The method of claim 3 further comprising providing the second biocompatible titanium component of the implantable pump with a native titanium oxide layer of the order of 50 nm thickness before providing the second SiO.sub.2 layer of predetermined second thickness.

6. The method of claim 2 where providing a second SiO.sub.2 layer of predetermined second thickness onto a selected bonding surface of a second biocompatible component of the implantable pump to reduce the surface roughness of the selected bonding surface comprises providing the second SiO.sub.2 layer of the order of 1.5 m thickness onto a selected bonding surface of the second biocompatible titanium component of the implantable pump to reduce the surface roughness.

7. The method of claim 6 further comprising chemical mechanical polishing the selected bonding surface of the second SiO.sub.2 layer of the second biocompatible titanium component of the implantable pump before bringing the first and second SiO.sub.2 layers into contact with each other.

8. The method of claim 6 further comprising providing the second biocompatible titanium component of the implantable pump with a native titanium oxide layer of the order of 50 nm thickness before providing the second SiO.sub.2 layer of predetermined second thickness.

9. The method of claim 8 further comprising chemical mechanical polishing the selected bonding surface of the second SiO.sub.2 layer of the second biocompatible titanium component of the implantable pump before bringing the first and second SiO.sub.2 layers into contact with each other.

10. The method of claim 1 where bringing the first and second SiO.sub.2 layers into contact with each other at a low temperature comprises bringing the first and second SiO.sub.2 layers into contact with each other at approximately 100 C. or less.

11. The method of claim 1 bringing the first and second SiO.sub.2 layers into contact with each other with a low pressure comprises bringing the first and second SiO.sub.2 layers into contact with each other with a few grams pressure or the weight of the first or second biocompatible component.

12. A method where an implantable pump is a piezoelectric pump with a piezoelectric membrane included in a first biocompatible component and a titanium mount plate included in a second biocompatible component comprising: providing a first SiO.sub.2 layer of the order of 2 nm thickness onto a bottom bonding surface of the first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below approximately 0.5 nm or less; providing a titanium oxide layer of the order of 50 nm thickness on the titanium mount plate; providing a second SiO.sub.2 layer of the order of 1.5 m thickness onto the titanium oxide layer of the second biocompatible component of the implantable pump; chemical mechanical polishing the second SiO.sub.2 layer; and bringing the first and second SiO.sub.2 layers into contact with each other at approximately 100 C. or less with a pressure of a few grams or the weight of the first or second biocompatible components to form a high quality hermetic bond between first and second SiO.sub.2 layers.

13. A hermetic bond of a biocompatible implantable pump between a first and second biocompatible component comprising: a first SiO.sub.2 layer of a predetermined first thickness disposed onto a selected bonding surface of the first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below a first predetermined magnitude; a second SiO.sub.2 layer of predetermined second thickness disposed onto a selected bonding surface of the second biocompatible component of the implantable pump to reduce the surface roughness; and where the first and second SiO.sub.2 layers are brought into contact with each other at a low temperature with a low pressure to form a high quality hermetic bond between first and second SiO.sub.2 layers.

14. The hermetic bond of the biocompatible implantable pump of claim 13 where the implantable pump is a piezoelectric pump with a piezoelectric membrane included in the first biocompatible component and a titanium mount plate included in the second biocompatible component, where the first SiO.sub.2 layer is of the order of 2 nm thickness and is disposed onto a bottom bonding surface of the first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below approximately 0.5 nm or less; where a titanium oxide layer of the order of 50 nm thickness is disposed on the titanium mount plate; where the second SiO.sub.2 layer is of the order of 1.5 m thickness and is disposed onto the titanium oxide layer of the second biocompatible component of the implantable pump; where the second SiO.sub.2 layer is chemical mechanical polished; and where the first and second SiO.sub.2 layers are brought into contact with each other at approximately 100 C. or less with a pressure of a few grams or the weight of the first or second biocompatible components to form a high quality hermetic bond between first and second SiO.sub.2 layers.

15. The hermetic bond of the biocompatible implantable pump of claim 13 where the first biocompatible component is composed of silicon, where the second biocompatible component is composed of titanium, and where the first SiO.sub.2 layer has a predetermined first thickness and is disposed onto a selected bonding surface of a first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below a first predetermined magnitude, and where the first SiO.sub.2 layer is a native SiO.sub.2 layer of the order of 2 nm thickness and is disposed onto silicon bonding surface of the first biocompatible component of the implantable pump to reduce the surface roughness, Ra, available for bonding below approximately 0.5 nm or less.

16. The hermetic bond of the biocompatible implantable pump of claim 13 where the first biocompatible component is composed of silicon, where the second biocompatible component is composed of titanium, and the second SiO.sub.2 layer has a predetermined second thickness and is disposed onto a selected bonding surface of a second biocompatible component of the implantable pump to reduce the surface roughness of the selected bonding surface, where the second SiO.sub.2 layer is of the order of 1.5 m thickness and is disposed onto a selected bonding surface of the second biocompatible titanium component of the implantable pump to reduce the surface roughness.

17. The hermetic bond of the biocompatible implantable pump of claim 16 where the selected bonding surface of the second SiO.sub.2 layer of the second biocompatible titanium component of the implantable pump is chemical mechanical polished before the bringing the first and second SiO.sub.2 layers into contact with each other.

18. The hermetic bond of the biocompatible implantable pump of claim 16 where the second biocompatible titanium component of the implantable pump includes a native titanium oxide layer of the order of 50 nm thickness for disposition with the second SiO.sub.2 layer of predetermined second thickness.

19. The hermetic bond of the biocompatible implantable pump of claim 15 where the second SiO.sub.2 layer of predetermined second thickness is disposed onto a selected bonding surface of a second biocompatible component of the implantable pump, and is of the order of 1.5 m thickness and is disposed onto a selected bonding surface of the second biocompatible titanium component of the implantable pump to reduce the surface roughness.

20. The biocompatible implantable pump of claim 13 where the first and second SiO.sub.2 layers are brought into contact with each other at a low temperature with a low pressure with a few grams pressure or the weight of the first or second biocompatible component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a top perspective view of the piezoelectric pump 10 of the illustrated embodiment of the invention.

[0028] FIG. 2 is an exploded perspective view of pump of FIG. 1.

[0029] FIG. 3 is a cross-sectional perspective view of the assembled pump of FIGS. 1 and 2,

[0030] FIG. 4 is a cross-sectional perspective view of the assembled similar to FIG. 3 except that the piezoelectric chip, piezoelectric membrane, and hermetic mount plate are shown as combined into a subassembly apart from fluid plate.

[0031] FIG. 5 is a top perspective view of the chip, piezoelectric membrane, and hermetic mount plate combined.

[0032] FIG. 6 is a bottom perspective view of hermetic mount plate and illustrates a defined outlet cavity in the plate and a defined inlet cavity in the plate.

[0033] FIG. 7 is a diagrammatic illustration of the method by which the chip is hermetically sealed or bonded to hermetic mount plate.

[0034] The disclosure and its various embodiments can now be better understood by turning to the following detailed description of the preferred embodiments which are presented as illustrated examples of the embodiments defined in the claims. It is expressly understood that the embodiments as defined by the claims may be broader than the illustrated embodiments described below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] FIG. 1 is a top perspective view of the piezoelectric pump 10 of the illustrated embodiment of the invention. Pump 10 is mounted on an 8 mm8 mm Si chip 12 on which a circular piezoelectric membrane 14 is mounted. Chip 12 is hermetically sealed and bonded to a titanium hermetic mount plate 16 as described in greater detail below. Pump 10 is disposed on a metal fluid plate 18 of a middle layer of the implanted pump system as shown and described in FIG. 2 of the incorporated specifications. A 10 mm10 mm0.64 mm titanium hermetic mount plate 16 is, when assembled, laser welded to metal fluid plate 18 along its entire joint periphery 20. The system circuitry is included in an upper layer of the implanted pump system and the entire system is contained within a sealed flat cylindrical stainless steel case.

[0036] FIG. 2 is an exploded perspective view of pump 10 as seen in FIG. 1. Hermetic mount plate 16 is disposed into a mating cavity 22 defined in fluid plate 18 on top of a polymeric or rubber double ring pump seal 24 that provides for a leak tight seal between the bottom of plate 16 and floor 26 of cavity 22. An outlet orifice 28 is defined in one side of floor 26 encircled by one half of double ring pump seal 24 and an inlet orifice 30 is defined in the other side of floor 26 encircled by the other half of double ring pump seal 24.

[0037] FIG. 3 is a cross-sectional perspective view of the assembled pump 10 of FIGS. 1 and 2, which illustrates how the various features of chip 12, piezoelectric membrane 14, hermetic mount plate 16, fluid plate 18, cavity 22, pump seal 24, outlet 28 and inlet 30 align and combine to form the completed pump 10. FIG. 4 is a cross-sectional perspective view of the assembled pump 10 similar to FIG. 3 except that chip 12, piezoelectric membrane 14, and hermetic mount plate 16 are shown as combined into a subassembly apart from fluid plate 18. The perspective view of FIG. 5 illustrates a top perspective view of chip 12, piezoelectric membrane 14, and hermetic mount plate 16 combined. FIG. 6 is a bottom perspective view of hermetic mount plate 16 and illustrates a defined outlet cavity 32 in plate 16 and a defined inlet cavity 34 in plate 16. Also shown in FIG. 6 is a pump outlet chamber 36 defined into overlying layer 12 aligned with outlet cavity 32 and a pump inlet chamber 38 defined into overlying layer 12 aligned with outlet cavity 34. Outlet cavity 32 and inlet cavity 34 are defined in plate 16 and separated from each other by an inlet/outlet separation distance 40. The alignment and structural relationship of pump outlet chamber 36 defined into overlying layer 12, outlet cavity 32, pump inlet chamber 38 defined into overlying layer 12 and outlet cavity 34 can be better seen in the cross-sectional views of FIGS. 3 and 4.

[0038] The pump structure now having been generally described, turn and consider the hermetic bonding of Ti hermetic plate 16 to the underside of chip 12. The Ti surface of plate 16 is too rough for a direct bond to Si and SiO.sub.2. Instead we added 1.5 um of silicon dioxide layer 46 onto the Ti of plate 16 to reduce the surface roughness below 1 nm to achieve a low temperature hermetic bond as shown in FIG. 7. To develop a biocompatible hermetic bond at low temperature, we relied on titanium, a common biomedical material used in implants and silicon dioxide for the bonding process. The drug reservoir was created from titanium to hold the drug methotrexate (i.e. commonly used to treat cancer of the breast, skin, head and neck, or lung). A hermetic bond will easily form when both mating surfaces have a surface roughness less than 1 nm. Attempts to use chemical mechanical polishing (CMP) of titanium produced a surface roughness 10-20 nm, which was too rough for a hermetic bond to form. This problem was overcome by depositing a thin layer 46 of silicon dioxide on to the titanium reservoirs mating surface of plate 16 then use CMP to form a new low roughness surface for hermetic bonding to the silicon dioxide micropump surface 44.

[0039] The conventional CMP process uses an abrasive and corrosive chemical slurry (commonly a colloid) in conjunction with a polishing pad and retaining ring, typically of a greater diameter than the wafer or substrate. The pad and wafer are pressed together by a dynamic polishing head and held in place by a plastic retaining ring. The dynamic polishing head is rotated with different axes of rotation (i.e., not concentric). This removes material and tends to even out any irregular topography, making the wafer flat or planar. This may be necessary to set up the wafer for the formation of additional circuit elements. For example, CMP can bring the entire surface within the depth of field of a photolithography system, or selectively remove material based on its position. Typical depth-of-field requirements are down to angstrom levels for the latest 22 nm technology.

[0040] The method of forming the hermetic sealing between chip 12 carrying the piezoelectric membrane 14 and hermetic mount plate 16 is unconventional in order to achieve long term sealing and operability of the pump 10. FIG. 7 is a diagrammatic illustration of the method by which chip 12 is hermetically sealed or bonded to hermetic mount plate 16. FIG. 7 shows only the portion of underlying Si pump layer 42 of chip 12 into which pump outlet chamber 36 and pump inlet chamber 38 are defined (not shown in FIG. 7). It is to be understood that the remaining layers and structures of chip 12, including piezoelectric membrane 14, are carried above layer 42 shown in FIG. 7. The bottom surface of layer 42 is provided with a 2 nm thick native silicon oxide layer 44 with a prepared roughness average (Ra), defined in this specification as an average distance or height of the peaks and valleys from a mean line, of less than 0.5 nm. Similarly, the opposing upper surface of hermetic mount plate 16 is a prepared 1.5 m thick silicon oxide layer 46 that is chemical mechanical polished. Below layer 46 is a 50 nm thick native titanium oxide layer 48 on the top surface of titanium hermetic mount plate 16. The means of disposing the titanium oxide layer 48 onto layer 64 for planarization may be accomplished a conventional spin-on-glass technique (See Interconnect. Dielectrics, Application Note No. 1, Honeywell) as well as chemical vapor deposition. When the surfaces of SiO.sub.2 layers 44 and 46 are brought into contact at approximately 100 C. with a low pressure, e.g. a few grams or just the weight of the components themselves, a high quality hermetic bond and seal is formed between layers 44 and 46.

[0041] Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the embodiments. Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the embodiments as defined by the following embodiments and its various embodiments.

[0042] Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the embodiments as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the embodiments includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations. A teaching that two elements are combined in a claimed combination is further to be understood as also allowing for a claimed combination in which the two elements are not combined with each other, but may be used alone or combined in other combinations. The excision of any disclosed element of the embodiments is explicitly contemplated as within the scope of the embodiments.

[0043] The words used in this specification to describe the various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself.

[0044] The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim, Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of subcombination.

[0045] Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.

[0046] The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the embodiments.