EP2652831A1

EP2652831A1 - Housing, in particular for a biofuel cell

Info

Publication number: EP2652831A1
Application number: EP11797307.3A
Authority: EP
Inventors: Pascale Mazoyer; Aomar Halimaoui
Original assignee: STMicroelectronics SA; STMicroelectronics Crolles 2 SAS
Current assignee: STMicroelectronics SA; STMicroelectronics Crolles 2 SAS
Priority date: 2010-12-16
Filing date: 2011-12-12
Publication date: 2013-10-23
Also published as: US20130273440A1; FR2969392A1; WO2012080162A1; FR2969392B1; US9219286B2; JP2014505966A

Abstract

The invention relates to a housing, including a body (1) comprising a first silicon element (10) and a second porous silicon element (20), at least one first cavity (31) provided in the porous silicon, a first electrically conductive contact area (41), which is electrically coupled to at least a portion (310) of at least one inner wall of said at least one cavity (31), a second electrically conductive contact area (42), which is electrically coupled to a different portion (320) of said second element (20) of the inner walls of said at least one first cavity (31), the two contact areas (41, 42) being electrically insulated from each other.

Description

Housing, especially for biopile

The invention relates to microelectronics, and more particularly to boxes capable, for example, but not exclusively, of being used for producing biopiles.

A biopile, also known as the Anglo-Saxon BioFuel Cell, is a fuel cell that uses enzymes or microorganisms such as bacteria to convert some of the available energy into a biodegradable substrate.

In general, a biopile comprises an electrode, forming anode, placed in contact with enzymes ensuring the transformation of the biodegradable substrate, for example glucose, especially electrons captured by the anode. The biopile also comprises a cathode at which an electron acceptor, for example air, is reduced, for example in water.

A potential difference therefore appears between the anode and the cathode when they are connected to a load.

There are many publications in the field of biopiles.

The article by Philippe Cinquin and others, entitled "A Glucose BioFuel Cell Implanted in Rats", PLoS ONE / www. plosone.org, May 2010 / volume 5 / Issue 5 / el0476, which describes the realization of an experimental biopile implanted in a rat. This biopile is capable of producing in vivo electricity through the oxidation-reduction phenomenon mentioned above, from the oxygen and glucose present in the physiological fluids of the rat. Two different powders are used respectively at the anode and the cathode.

The article by Lewis Dartnell entitled "Sparks of Life" is also available at http://www.ucl.ac.uk/~ucbplrd/sparks_page.htm. This article describes a biopile using at the level of the anode bacteria named Rhodoferax ferrireducens.

It is now advisable to propose industrially acceptable solutions which make it possible in particular to reduce the size of the implants and to increase the power generated by these biopiles.

According to one embodiment, there is provided a housing capable of being used in particular but not exclusively as part of a biopile, which is industrially feasible, and compatible with implantation in the human body.

According to one aspect, there is provided a housing comprising a body comprising a first silicon element and a second porous silicon element, at least a first cavity formed at least in the porous silicon, a first electrically conductive contact zone and electrically coupled to at least a portion of at least one inner wall of said at least one first cavity, a second electrically conductive contact zone and electrically coupled to a portion of the housing extending at least in the second element, different from the inner walls of said at least a first cavity, the two contact zones being mutually electrically isolated.

According to a variant, the body furthermore comprises at least a second cavity formed at least in the porous silicon, and said portion of the housing different from the internal walls of said at least one first cavity comprises at least a portion of at least one inner wall of said at least one second cavity.

According to another variant, said portion of the housing comprises pores of porous silicon.

In other words, according to this other variant, unlike the previous variant, there is not provided a second cavity in the porous silicon.

Whatever the variant, according to one embodiment, the first contact zone is situated above a first face of the first element of the body, and the body comprises first means. electrically conductive bonding means extending through the first member from said first contact zone to said at least a portion of said at least one inner wall of said at least one first cavity.

Although the electrically conductive means may be formed of silicon, it is preferred that the first bonding means comprise a first region formed of a metal silicide, surrounded by an insulating region. This makes it possible to avoid oxidation, in particular when the electrically conductive connection means are in contact with a liquid active product.

According to one embodiment, said at least one first cavity opens on the free face of the second element, opposite said first face of the first element.

According to one embodiment, the second contact zone is located above said first face of the first body element, and the body comprises second electrically conductive connecting means extending through said first element from said second contact zone. up to said portion of the housing.

Again, it is preferable that these second connecting means comprise a second region formed of a metal silicide.

This second region is also preferably surrounded by an insulating region.

In the variant according to which there is at least one second cavity provided at least in the porous silicon, this second cavity can lead to the free face of the second element opposite to said first face of the first element. In other words, according to this embodiment, said at least one first cavity and said at least one second cavity open on the same free face of the body.

It is also possible for said at least one second cavity to open on said first face of said first element. In other words, according to this embodiment, said at least one first cavity and said at least one second cavity open on two opposite sides of the body.

The pore size of the porous silicon is advantageously of the order of a few nanometers and the housing has, according to one embodiment, a size compatible with implantation in the human body.

According to another aspect, there is provided a device, comprising a housing as defined above, a first active product, for example a compacted enzyme powder, contained in said at least one first cavity, a second active product, for example another compacted enzymatic powder, contained in said at least one second cavity, first means for sealing said at least one first cavity and second means for closing said at least one second cavity.

When the housing does not comprise a second cavity, there is provided a device comprising a housing as defined above, a first active product contained in said at least one first cavity, and first closure means of said at least one first cavity.

At least one of the first and second active products comprises, for example, a powder whose grain size is greater than the pore size of the porous silicon.

The porous silicon therefore acts advantageously as a membrane.

According to another aspect, it is proposed to use the device as defined above, as a biopile, when an active fluid, for example a biological fluid, circulates through the porous silicon to interact with the active product (s) contained in said cavity or cavities, a potential difference being generated between the two electrically conductive contact zones.

Other advantages and characteristics of the invention will appear on examining the detailed description of embodiments, which are in no way limiting, and the appended drawings in which: 1 schematically illustrates a first embodiment of a housing according to the invention, Figure 2 schematically illustrates a first embodiment of a device according to the invention, Figures 3 to 7 schematically illustrate an example of the manufacture of a housing according to the invention, FIGS. 8 to 9 schematically illustrate a second embodiment of a housing according to the invention,

FIG. 10 schematically illustrates a second embodiment of a device according to the invention, FIG. 11 schematically illustrates a third embodiment of a box according to the invention, and FIG. 12 schematically illustrates a third embodiment of FIG. a device according to the invention. In FIG. 1, the reference BT denotes a housing comprising a body 1. This body 1 comprises a first silicon element 10 and a second porous silicon element 20. The two elements 10 and 20 are contiguous to each other. A first cavity 31 is formed in the second porous silicon element 20 and opens on the free face F2 of the second element.

A second cavity 32 is formed in the second porous silicon element 20 and also opens on the free face F2 of the second element.

Above the first face F1 of the first element 10, face F1 which is opposite the free face F2 of the second element, there are provided a first electrically conductive contact zone 41 and a second electrically conductive contact zone 42.

The first electrically conductive contact zone 41 is electrically coupled to a portion 310 of the bottom internal wall of the first cavity 31.

Similarly, the second electrically conductive contact zone 42 is electrically coupled here to a portion 320 of the bottom internal wall of the second cavity 32. However, it is possible alternatively that the electrically conductive contact zone or zones are electrically coupled to several internal walls of the corresponding cavities.

The first electrically conductive contact zone 41 here comprises a first metal contact pad 412 while the second electrically conductive contact zone 42 comprises a second metal contact pad 422.

The body 1 also comprises first electrically conductive connection means 410 extending through the first element 10 from the first contact zone 412 to the portion 310 of the bottom internal wall of the first cavity 31.

These first connecting means here comprise a first region 410 formed of a metal silicide, for example titanium silicide, surrounded by an insulating region 411.

Similarly, the second electrically conductive connection means here comprise a second region 420 also formed of a metal silicide, for example also titanium silicide, surrounded by an insulating region 421.

The first contact pad 412 comes into contact with the first silicide region 410 through an opening formed in an insulating layer 45, for example a silicon nitride layer.

Similarly, the second contact pad 422 comes into contact with the second silicide region 420 through another opening of this layer 45.

Finally, the upper parts of the two contact pads 412 and

422 are mutually isolated by an insulating layer 43, for example silicon dioxide.

The two contact zones 41 and 42 are therefore mutually electrically isolated.

The dimensions of the housing BT are, in this embodiment, advantageously chosen so that the housing BT can be easily implanted in the human body. By way of non-limiting example, the length L of the LV housing is of the order of a few millimeters, for example between 1 and 20 mm while the height H of housing is of the order of a few micrometers, for example between 100 and 750 micrometers and that the depth P (width) of the housing BT is of the order of a few millimeters, for example between 1 and 20 mm.

Moreover, the pore size of the porous silicon is, in this embodiment, of the order of a few nanometers, typically from 2 to 3 nanometers.

Of course, although the housing has been shown here in parallelepiped shape, its shape could be any, for example cylindrical.

In FIG. 2, the reference DIS designates a device that can be used as a battery. More specifically, in the example described here, the first cavity 31 is filled with a first active product PA1, for example a product in the form of compacted powder, while the second cavity is filled with a second active product PA2, for example example also a compacted powder.

A sealing means 5, such as for example a silicon wafer or a glass plate, is bonded to the face F2 of the housing by any known means.

An active fluid LQA, or electrolyte, can then flow through the porous silicon by penetrating into the device by all the free faces of the second porous silicon element 20, to react with the active products PA1 and PA2. The active fluid LQA can also escape through other free faces of the porous silicon.

Of course, the grain size of the powders PA1 and PA2 as well as the pore size of the porous silicon, are adjusted so that the active products PA1 and PA2 do not escape cavities 31 and 32, while being able to react with the active fluid LQA.

In other words, the pore size of the porous silicon may be larger than 2 or 3 nanometers if the size of the powder grains allows it.

Furthermore, the first silicide region 410 is in contact with the active product PA1 while the second silicide region 420 is in contact with the active product PA2. The first contact zone electrically conductive 41 then forms, for example, the anode AN of the cell, while the second contact zone 42 forms, for example, the cathode CT of the cell. By the interaction between the active products PA1, PA2, in contact with the silicided regions 410 and 420, with the active liquid LQA, a current can flow between the anode and the cathode and consequently a voltage difference V is available at terminals 41 and 42 of the device.

When the housing is of such size that it can be implanted in the human body, the DIS device can then be used as a biopile. It is then possible, by way of example, to use as active products PA1 and PA2 and as liquid LQA, those described in the article by Philippe Cinquin mentioned above.

In general, a BT housing can be easily made using conventional techniques known per se, used in microelectronics for the manufacture of integrated circuits.

Generally, several LV boxes are made simultaneously from the same silicon wafer. Then, after completion of the constituents of the housing, the plate is cut so as to individualize the housings obtained.

The housings can for example be made with a 0.35 micron technology, on semiconductor wafers or "wafers" of 200 mm diameter, or in plates of 300 mm diameter with advanced CMOS technology.

Reference will now be made more particularly to FIGS. 3 to 7 to illustrate an exemplary embodiment of a housing such as that illustrated in FIG. 1. For the sake of simplification, only the embodiment of a single housing will be described here.

In a first step, illustrated in FIG. 3, porous silicon is formed in the silicon substrate. As is well known to those skilled in the art, porous silicon is obtained by electrochemical anodization of solid silicon in a solution of hydrofluoric acid (HF).

Those skilled in the art will be able to adjust the parameters of electrochemistry so as to obtain the desired height for silicon porous and the desired size for the pores. By way of example, porous silicon having a pore size of the order of a few nanometers, for example from 1 to 3 nanometers, can be obtained by using anodized P-type doped silicon at a current density of 20 mA / cm ² in a 35% solution of hydrofluoric acid.

After this electrochemical anodization, the structure illustrated in FIG. 3, comprising the first silicon element 10 having, for example, a height less than 10 microns, and the second porous silicon element 20 having a thickness of about 740, are obtained. microns for a total height of the two elements of the order of 750 micrometers.

The doping of intrinsic silicon is for example 10 ¹⁵ atoms / cm \ Higher doping values (greater than 10 ¹⁷ atoms / cm ³⁾ may also be used. Then, as illustrated in FIGS. 4 and 5, the insulating trenches 411 and 421 are formed using a conventional etching mask, not shown here. For the realization of these trenches, it is possible to use a technique identical to that used in microelectronics for the formation of vias traversing a substrate, commonly designated by those skilled in the art by the acronym "TSV" (Through-Silicon Vias). "). For example, trenches having a depth of the order of 3 to 10 microns were formed and filled with an insulating material, for example silicon dioxide.

Then, as illustrated in FIG. 6, a mask is defined for the formation of the silicide zones 410 and 420. This mask may be formed of an insulating layer, for example silicon nitride, the openings of which correspond to the bounded internal space. by insulating trenches 411 and 421.

Silicon and porous silicon are then conventionally silicided through the mask 45 so as to obtain the silicide regions 410 and 420.

Then, as illustrated in FIG. 7, the cavities 31 and 32 are produced using, for example, plasma chemical etching using a fluorocarbon compound (for example SF6 CF4) of to obtain cavities of desired depth and width. For example, the depth of the cavities may be of the order of 740 microns or more, while the width may be of the order of 80 microns.

The bottom walls of the two cavities 31 and 32 formed here in the porous silicon, therefore come into contact with the silicided zones at the portions 310 and 320 of these bottom walls.

It should be noted here that the etching operation can etch part of the insulating regions 411 and the silicide region 410.

It would also be possible by the etching operation that at least one of the cavities extends into the silicon.

The contact pads 412 and 422 are then conventionally made by depositing metal in the orifices of the insulating layer 43 (FIG. 1).

FIG. 8 illustrates another embodiment of the LV housing in which the two cavities 31 and 32 open on the two opposite faces F1 and F2 of the body.

More specifically, the first cavity 31 opens on the rear face F2 while the second cavity 32 opens on the front face Fl.

Furthermore, the second silicide region 420 extends laterally to the cavity 32 (FIG. 8 and FIG. 9) so as to come into contact with a part of the lateral internal wall of this cavity 32.

Furthermore, as illustrated in FIG. 9, the silicide region 420 projects beyond the cavity 32 so that the contact pad 422 can come into contact with this silicide region 420 while allowing, as illustrated in FIG. 10, the application a cover 52, so as to close the cavity 32 after filling thereof by the second active product PA2.

The device DIS of FIG. 10 also comprises, on the rear face, a cover 51 which closes off the first cavity 31 after it has been filled with the first active product PA1.

Again, the covers 51 and 52 may for example be silicon or glass covers. The device DIS can also be used as a battery or as a biopile, again using the first contact 412 as the anode AN and the second contact 422 as the CT cathode.

Of course, whether in the embodiment of Figure 1 or the embodiment of Figure 9, the size of the cavities may be different. Thus, it is possible to provide a larger cavity on the anode side than on the cathode side, or even several first cavities electrically connected together on the anode side.

Figure 11 illustrates another embodiment of the LV housing having a single cavity 31, or at most a set of several cavities 31 connected together.

In the example illustrated in Figure 11, a single cavity 31 is illustrated.

For this part of the LV housing, there is a structure similar to that described with reference to the preceding figures.

On the other hand, there is no provision for a second cavity in contact with the second silicide region 420. In this embodiment, the second silicide region 420 opens directly into pores 322 of the porous silicon.

The LV box of FIG. 11 can also be used as a component of a DIS device that can form a battery or a biopile.

More precisely, as illustrated in FIG. 12, this time only an active product PA1, for example in powder form, is housed in the cavity 31. Then, in a manner analogous to that described above. , a cover 5 is glued on the rear face so as to close the cavity.

The active fluid LQA comes on the one hand, to interact with the silicide region 420 and on the other hand, with the active product PA1 itself in contact with the silicide region 410. The first electrical contact electrically coupled to the active product PA1 forms by For example, the anode AN while the second contact electrically coupled to the active fluid circulating in the porous silicon forms the cathode CT of the cell. The device can also be used as a biopile using an active product PA1 and an active fluid LQA suitable, for example those described in the article entitled "Sparks of Life" above.

When the devices which have just been described are intended to be used as biopiles, they may for example be housed in a pocket or an appropriate envelope itself implanted in the human body, in a manner similar to that described. in the article by P. Cinquin mentioned above.

Claims

Housing, comprising a body (1) comprising a first element (10) of silicon and a second element (20) made of porous silicon, at least a first cavity (31) formed at least in the porous silicon, a first zone of electrically conductive contact (41) and electrically coupled to at least a portion (310) of at least one inner wall of said at least one first cavity (31), a second electrically conductive contact area (42) and electrically coupled to a portion (320) of the housing extending at least in said second member (20) and different from the inner walls of said at least one first cavity (31), the two contact areas (41, 42) being mutually electrically isolated.

2. Housing according to claim 1, wherein the first contact zone (41) is located above a first face (F1) of the first element (10) of the body, and the body comprises first electrically conductive connecting means. (410) extending through the first member (10) from said first contact zone (41) to said at least one portion (310) of said at least one inner wall of said at least one first cavity.

The housing of claim 2, wherein the first connecting means comprises a first region (410) formed of a metal silicide surrounded by an insulating region (411).

4. Housing according to claim 2 or 3, wherein said at least one first cavity (31) opens on the free face (F2) of the second element (20), opposite to said first face (F1) of the first element (10). .

5. Housing according to one of claims 2 to 4, wherein the second contact zone (42) is located above said first face (F1) of the first body member, and the body comprises second electrically connecting means conductors (420) extending through said first member (10) from said second contact area (42) to said housing portion (320).

The housing of claim 5, wherein the second connecting means comprises a second region (420) formed of a metal silicide.

The housing of claim 6, wherein said second region (420) is surrounded by an insulating region (421).

8. Housing according to one of the preceding claims, wherein the pore size of the porous silicon is of the order of a few nanometers.

9. Housing according to one of the preceding claims, having a size compatible with implantation of the housing in the human body.

10. Housing according to one of the preceding claims, wherein the body further comprises at least a second cavity (32) formed at least in the porous silicon and said portion (320) of the housing comprises at least a portion of at least an inner wall of said at least one second cavity (32).

11. Housing according to claims 2 and 10, wherein said at least one second cavity (32) opens on the free face (F2) of the second element opposite to said first face of said first element.

12. Housing according to claims 2 and 10, wherein said at least a second cavity (32) opens on said first face (Fl) of said first element.

Housing according to one of claims 1 to 9, wherein said portion (320) of the housing comprises pores of porous silicon.

14. Device comprising a housing according to one of claims 10 to 12, a first active product (PA1) contained in said at least a first cavity (31), a second active product (PA2) contained in said at least a second cavity (32), first closure means (5) of said at least one first cavity, and second closure means of said at least one second cavity.

Device, comprising a housing according to claim 13, a first active product (PA1) contained in said at least one first cavity, and first closure means (5) of said at least one first cavity.

16. Device according to claim 14 or 15, wherein at least one of the first and second active products (PA1, PA2) comprises a powder whose grain size is greater than the pore size of the porous silicon.

17. Use of the device according to one of claims 14 to 16, as a biopile when an active fluid (LQA) circulates through the porous silicon to interact with the active product or products contained in said cavity or cavities, a difference potential (V) being generated between the two electrically conductive contact zones.