Method of forming hydrophobic areas on a substrate

Abstract

Method for forming hydrophobic areas on a substrate The present description relates to a method for forming hydrophobic areas comprising the following steps: - providing a structure comprising a substrate of interest (200) bonded to a temporary substrate (100), the temporary substrate (100) comprising a base substrate (110) locally covered with pads (120) and raised elements (130, 140) having a height less than the height of the pads (120), the raised elements (130, 140) surrounding the pads (120) and extending to the edge of the temporary substrate (200), interstices separating the substrate of interest (200) from the raised elements (130, 140), - contacting the structure with a solution (300) comprising a hydrophobic compound or an etching agent, whereby the solution (300) infiltrates into the interstices and hydrophobic areas are formed on the substrate of interest (200) with respect to the relief elements (130, 140). Figure for the abstract: Fig. 1A.

Description

Title of the invention: Method for forming hydrophobic zones on a substrate Technical field

[0001] The present description relates generally to the field of microelectronics, and more particularly, to substrates for chip-to-plate type bonding. Prior art

[0002] In chip-to-plate bonding, the chips must be positioned on a plate in predefined areas. To facilitate the positioning of the chips, it is possible to create, on the plates, hydrophilic areas surrounded by hydrophobic areas. The chips, brought with a liquid (typically water), will then spontaneously place themselves on the hydrophilic areas.

[0003] To form hydrophobic areas around hydrophilic areas on a wafer, it is common to bond a wafer having a hydrophilic surface with a temporary wafer covered with pads. The pads protect the areas on which the chips will later be positioned. The structure thus obtained is then brought into contact, by immersion for example, with a liquid capable of making the surface of the wafer hydrophobic. The objective is to spread the liquid around the pads to make the surface around the pads hydrophobic. The part positioned under the pads is not in contact with the liquid and remains hydrophilic.

[0004] However, in some cases, this penetration is quite slow and air bubbles can become trapped between the two plates, which prevents the liquid from spreading and leads to areas that remain hydrophilic instead of becoming hydrophobic, which is particularly inconvenient for the positioning of the chips. Summary of the invention

[0005] There is a need for a method for reliably creating hydrophobic areas around hydrophilic areas.

[0006] This aim is achieved by a method of forming hydrophobic zones on a substrate of interest, the method comprising the following steps: - providing the substrate of interest comprising a first hydrophilic surface and a temporary substrate comprising a base substrate locally covered with pads and raised elements having a height less than the height of the pads, a first part of the raised elements being peripheral elements surrounding the pads and a second part of the raised elements being fluidic connection elements (140) from the peripheral elements to the edge of the temporary substrate, - gluing the pads of the temporary substrate onto the first hydrophilic surface of the substrate of interest, whereby the substrate of interest is separated from the relief elements by gaps, - contacting the substrate of interest with a solution comprising a hydrophobic compound or an etching agent, whereby the solution infiltrates into the interstices and hydrophobic areas are formed on the substrate of interest opposite the relief elements.

[0007] Advantageously, the raised elements have a height representing less than 50% and, preferably, less than 10% of the height of the studs.

[0008] Advantageously, the interstices have a height of between 0.1 and 10 μm, preferably between 1 and 5 μm.

[0009] Advantageously, the pads have a height of between 10 and 100 μm.

[0010] Advantageously, the fluidic connection elements form a perimeter on the base substrate.

[0011] Advantageously, the fluidic connection elements are positioned discontinuously around the periphery of the base substrate, so as to form vents between the fluidic connection elements.

[0012] Advantageously, the raised elements have a width of between 10 μm and 2.5 mm.

[0013] Advantageously, the pads have a surface area of ​​between 0.25 and 400 mm2.

[0014] Advantageously, the substrate comprises areas of stronger topographies and / or metallic interconnections, on which the pads are bonded.

[0015] Advantageously, only one edge of the substrate of interest is brought into contact with the solution, at the level of a fluidic connection element.

[0016] This object is also achieved by a substrate having a first surface comprising hydrophilic zones surrounded by hydrophobic zones, preferably having a width of between 10 μm and 2.5 mm, hydrophobic lines connecting the hydrophobic zones to the edge of the substrate. Brief description of the drawings

[0017] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0018] [Fig.lA], [Fig.lB], [Fig.lC], [Fig.lD] and [Fig.lE] schematically represent different steps of a method for manufacturing a substrate of interest covered by hydrophobic zones;

[0019] [Fig.2] and [Fig.3] represent, schematically and in top view, a substrate of interest according to different particular embodiments of the invention;

[0020] [Fig.4A], [Fig.4B], [Fig.4C], [Fig.4D], [Fig.4E], [Fig.4F] and [Fig.4G] schematically represent different stages of a method of manufacturing a temporary substrate according to a particular embodiment of the invention. Description of the embodiments

[0021] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0022] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed.

[0023] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0024] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0025] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0026] Even if the description refers particularly to substrates for chip-to-plate type bonding, the method is particularly interesting for all applications requiring the propagation of a liquid around pads over a certain width or at specific locations without necessarily wetting the entire free space between the plates.

[0027] We will now describe in more detail the method of forming hydrophilic zones ZI surrounded by hydrophobic zones Z2 on a substrate of interest 200 with reference to FIGS. 1A, 1B, 1C, 1D and 1E.

[0028] The method comprises the following steps: a) providing the substrate of interest 200 and a temporary substrate 100, the substrate of interest 200 having a first hydrophilic surface 201 and a second surface 202, the temporary substrate 100 comprising a base substrate 110 having locally on the surface pads 120 and raised elements 130, 140 having a height less than the height of the pads 120, a first part of the raised elements corresponding to so-called peripheral elements 130 surrounding the pads 120, a second part of the raised elements corresponding to so-called fluid connection elements 140 going from the peripheral elements 130 to the edge of the temporary substrate 200, ([Fig.lA]), b) gluing the temporary substrate 100 onto the first surface 201 of the substrate of interest 200, and more particularly gluing the pads 120 of the temporary substrate 100 onto the first surface 201 of the substrate of interest 200, the substrate of interest 200 being separated from the raised elements 130, 140 by interstices ([Fig. IB]), c) placing the structure, obtained in step b), in contact with a solution 300 comprising a compound making it possible to make the surface 201 of the substrate of interest 200 hydrophobic, whereby the solution 300 infiltrates into the interstices and hydrophobic zones Z2, Z3 are formed on the first surface 201 of the substrate of interest 200 opposite the raised elements 130, 140 (figures IC, 2 and 3), d) preferably, clean the substrate ([Fig.lD]), e) separating the temporary substrate 100 and the substrate of interest 200 ([Fig. 1E]).

[0029] Between the two substrates 100, 200, there are several different types of spacing (or gap): - interstices (areas of small gaps) between the substrate of interest 200 and the relief elements 130, 140, - spaces (large gap areas) between the substrate of interest 200 and the base substrate 110 of the temporary substrate 100.

[0030] The gaps have a height representing less than 50% and, preferably, less than 10% of the height of the large gap zones.

[0031] The interstices having a very low height compared to the height of the spaces between the substrate of interest 200 and the base substrate 110 of the temporary substrate 100, the wetting will take place preferentially at the level of the interstices (i.e. between the two surfaces separated by the smallest spacing) because the capillary forces will be the strongest at this level.

[0032] Such a method makes it possible to efficiently propagate the liquid between the pads 120 of two plates glued to each other.

[0033] With such a method, it is possible to obtain partial wetting and to increase the wetting kinetics by varying the height of the interstices.

[0034] The substrate of interest 200 is preferably a plate.

[0035] The substrate of interest 200 is, for example, a substrate made of semiconductor material (preferably Si, Ge, SiC, AsGa), sapphire or silica.

[0036] The substrate of interest 200 provided in step a) may be an SOI ('Silicon on Insulator') substrate, i.e. comprising a support substrate successively covered by a thin layer of buried oxide and a layer of silicon.

[0037] Alternatively, it may be a solid substrate made of semiconductor material (silicon for example) covered with a dielectric layer, in particular an oxide layer (silicon oxide in particular).

[0038] The substrate of interest 200 has a first surface 201 and a second surface 202. The first surface 201 is a hydrophilic surface.

[0039] The first surface 201 comprises first zones ZI that it is desired to keep hydrophilic and second zones Z2 surrounding the first zones that it is desired to make hydrophobic (figures 2 and 3). The first zones ZI will be protected by the pads 120 of the temporary substrate 100 after the bonding of step b).

[0040] The first ZI zones may be zones of higher topography and / or metal interconnection zones intended to be connected to chips. By high topography, it is meant that the first ZI zones protrude by at least 100 nm and more particularly by 500 nm or even by 1 pm from the surface of the substrate.

[0041] The first zones ZI may be arranged regularly or irregularly. They may be of the same size or of different sizes.

[0042] The temporary substrate 100 comprises the base substrate 110, the pads 120 (pillars or columns) and the relief elements 130, 140.

[0043] The base of the pads 120 can be of different shapes. It can be square, rectangular or even circular.

[0044] The solution 300 being brought to the areas to be made hydrophobic thanks to the interstices, the pads 120 can be spaced by short distances or by longer distances. The spacing of the pads 120 will be chosen according to the desired application. The pads 120 are, for example, spaced by more than 10 pm or even more than 50 pm or less. They can also be spaced by a few millimeters.

[0045] The raised elements 130, 140 have a height less than the height of the studs 120. The different raised elements 130, 140 may have identical or different heights. Preferably, the heights are identical or substantially identical.

[0046] The relief elements 130, 140 preferably have a width of between 10 μm and 2.5 mm.

[0047] A first part of the raised elements corresponds to so-called peripheral elements 130 positioned around the pads 120. They form the peripheral part of the pads 120. During bonding, the part of the substrate of interest 200 arranged opposite the peripheral elements 130 corresponds to the zones Z2 which it is desired to make hydrophobic.

[0048] A second part of the raised elements corresponds to so-called fluid connection elements 140 making it possible to connect the peripheral elements 130 positioned around the pads 120 to the edge of the substrate. During bonding, the interstices formed opposite these elements form flow paths or channels of the solution which opens at the edge of the substrate of interest 200.

[0049] Each peripheral element 130 is connected to the edge of the substrate by means of a fluidic connection element 140. A fluidic connection element 140 can make it possible to connect several peripheral elements 130 to the edge of the substrate.

[0050] The fluidic connection elements 140 are, for example, arranged in line in the center of the base substrate 110.

[0051] The relief elements may further cover part or all of the perimeter of the base substrate 110.

[0052] According to a first variant, the raised elements cover the entire perimeter of the base substrate 110.

[0053] According to another variant, the raised elements cover only a part of the perimeter of the base substrate 110. This makes it possible to create one or more vents to allow, if necessary, the air expelled by the inlet of the solution 300 to escape.

[0054] The base 110, the pads 120 and the raised elements 130 may be made of different materials. Preferably, they are made of the same material. It may be a metal or a semiconductor material for example. Preferably, it is made of silicon.

[0055] The temporary substrate 100 is preferably obtained from a solid substrate.

[0056] In particular, the temporary substrate 100 may be manufactured with photolithography steps. For illustration purposes, as shown in FIGS. 4A to 4H, the substrate may be manufactured according to the following steps: - provide a substrate 110 ([Fig.4A]), - locally deposit a resin 150 on the substrate 110 ([Fig.4B]), - etch the parts of the substrate not covered by the resin 150 to delimit the upper part of the pads 120 ([Fig.4C]), - remove the resin 150 ([Fig.4D]), - deposit an additional resin 160, on the one hand, on the top and on the sides of the upper part of the pads 120, to be able to finalize the formation of the pads 120 and to be able to form the peripheral elements 130 surrounding the pads, and on the other hand, locally on the substrate 110 at the level of the future zones of the fluidic connection elements 140 ([Fig.4E]), - etch the substrate 110 to form the pads 120 and the relief elements 130, 140 ([Fig.4F]), - remove the additional resin 160 ([Fig.4G]), - possibly, cut out the substrate 110 ([Fig.4H]).

[0057] The trimming of the plate edge 110 makes it possible to avoid possible edge contact between the temporary substrate 100 and the substrate of interest 200, in particular if the pad 120 is not very thick.

[0058] The clipping can be carried out, for example, by photolithography / engraving or even by mechanical trimming using a diamond saw. The width of the trimming, in the plane of the substrate, is, for example, between 1 and 5 mm and / or its depth, in a plane perpendicular to that of the substrate, is, for example, between 100 and 250 pm.

[0059] Prior to step b), it is possible to carry out one or more pre-treatments on the surface of the temporary substrate 100 and / or on the surface of the substrate of interest 200 so as to make them compatible with direct bonding.

[0060] The pre-treatment can be chosen from the following pre-treatments: thermal annealing, plasma, polishing and wet cleaning.

[0061] By way of example, it is possible to form an oxide layer on the surface of the temporary substrate 100 and / or to carry out a polishing step on the temporary substrate 100 and / or on the substrate of interest 200 to obtain a roughness compatible with direct bonding (typically a roughness less than 0.5 nm RMS). It is possible to implement methods which combine, for example, a plasma and an aqueous solution, in particular an oxygen plasma followed by CARO wet cleaning (H2SO4, H2O2 in a proportion of 5:1) associated with SCI (H2O, NH3, H2O2 in a proportion of 5:1:1).

[0062] During step b), the temporary substrate 100 and the substrate of interest 200 are bonded.

[0063] The two substrates 100, 200 can be assembled by direct bonding. The use of marks on the substrates 100, 200 can facilitate their alignment. An accuracy of about 100 nm can be achieved. It is also possible to align them, without using marks, by using the edges of the substrates as well as their notch (or 'notch'). The accuracy is lower (+ / - 50 pm) but sufficient for certain applications.

[0064] Direct bonding can be carried out at atmospheric pressure (i.e. 1013.25 hPa) or under vacuum. The assembly does not necessarily need to be consolidated by heat treatment. Nevertheless, annealing, at a temperature preferably lower than 200°C, can advantageously be carried out. It is possible to anneal at a higher temperature but there is a risk of damaging the surfaces during the final detachment between the two substrates 100 and 200.

[0065] During bonding, the pads 120 of the temporary substrate 100 are bonded to the first surface 201 of the substrate of interest 200, and more particularly to the first hydrophilic zones Z1 of the substrate 200 that it is desired to protect during step c). The peripheral relief elements 130 around the pads 120 are positioned opposite the second zones Z2 of the substrate 100 that it is desired to make hydrophobic (Figures 2 and 3).

[0066] During bonding, the height of the spaces between the substrates 110, 200 (large gap areas) varies, for example, between 10 μm and 100 μm. The height of the large gap areas may be constant within the same assembly, but it may also vary slightly (typically less than 10%).

[0067] The bonding leads to the formation of interstices between the first surface 201 of the substrate of interest 200 and the relief elements 130, 140 of the temporary substrate 100. The thickness (or height) of the interstices varies, for example, between 0.1 pm and 10 pm, preferably between 1 pm and 5 pm.

[0068] The height of the small gap zones is generally constant on the plate to within 10% but it can also intentionally vary. This can be interesting to have different wetting kinetics depending on the location on the plate.

[0069] A first group of interstices is formed between the peripheral relief elements 130 and the substrate of interest 200. The thickness (or height) of the interstices corresponds to the difference in height between the pads 120 and the peripheral relief elements 130.

[0070] A second group of interstices is formed between the first surface 210 of the substrate 200 and the raised fluid connection elements 140. These interstices thus form privileged paths for the liquid (step c)). The thickness of these interstices depends on the difference in height between the pads 120 and the raised fluid connection elements 140.

[0071] The structure comprises one or more paths for guiding the solution 300 from outside the substrates to the zones Z2 to be made hydrophobic. The zones Z3 of the substrate of interest 200 positioned under these circulation paths of the solution 300 will also be hydrophobic at the end of the process (Figures 2 and 3).

[0072] During step c), the substrate of interest 200 is brought into contact with a solution 300. The solution 300 is a solution for making the surface hydrophobic. It is generally a solution comprising hydrophobic compounds which locally attach to the surface of the substrate of interest 200 to make it locally hydrophobic. It is also possible to make the surface hydrophobic by carrying out an etching, in particular of a surface layer to expose an underlying hydrophobic material.

[0073] The substrate of interest 200 may be brought into contact with the solution 300 by total or partial immersion or by insertion or injection of the solution 300 into the interstices formed during bonding. Preferably, only one edge of the substrate of interest is brought into contact with the solution 300.

[0074] The solution 300 infiltrates into the interstices positioned under the raised fluid connection elements 140 up to the zones Z2 positioned under the peripheral raised elements 130.

[0075] The penetration of the solution through the narrow paths is made possible by capillary forces. As shown in Figures 2 and 3, when the arrival of the solution is located at the edge of a path termination, the capillary forces will spontaneously allow the solution to fill all the paths without it being necessary to completely immerse the assembly. This avoids contamination of the two external faces of the assembly by the solution.

[0076] Trimming facilitates the entry of liquid at the edge of the bonded structures.

[0077] In a first variant, the surface of the substrate 200 in contact with the solution becomes hydrophobic following the formation of a hydrophobic layer 250 at the interstices ([Fig. 1E]).

[0078] The choice of the hydrophobic layer 250 will depend, in particular, on the substrate of interest 200.

[0079] The obtained hydrophobic layer 250 has, for example, a thickness of between 2 nm and 100 nm.

[0080] The hydrophobic layer 250 can be obtained from a polymer, a silyl (also called organosilyl) or a silane.

[0081] The chosen hydrophobic compound preferably comprises one or more halogen groups, in particular fluorine or chlorine groups. Preferably, the hydrophobic compound comprises a carbon chain of at least 5 carbon atoms.

[0082] The silane can be a chlorosilane such as octadecyltrichlorosilane (OTS = CH3 (-CH2)i7-SiCl3) marketed by the company Sigma Aldrich.

[0083] The polymers may be fluorinated polymers such as, for example, the Novec™ 1720 EGC polymer marketed by the company 3M™, Optool marketed by the company DAIKIN and the Novec™ 2202 EGC polymer marketed by the company 3M™. The hydrophobic compound may be chosen from chlorosilanes such as per-fluorodecyltrichlorosilane (FDTS = Cl3Si(CH2)2(CF2)7CF3) marketed by the company Sigma-Aldrich, perfluorodecyldimethylchlorosilane (FDDMCS = CF3(CF2)7 (CH2)2(CH3)2SiCl) marketed by the company Sigma-Aldrich.

[0084] Alternatively, the surface of the substrate 200 in contact with the solution may become hydrophobic by selective local etching of the surface layer of the substrate 200 locally exposing a hydrophobic material of the substrate 200.

[0085] For example, if the surface of the substrate 200 is made of silicon, it is possible to make it hydrophobic by etching the native oxide layer present on the surface of the silicon with hydrofluoric acid (HF), for example with a solution containing 1% HF.

[0086] After step c), a cleaning step d) by means of rinsing and, optionally, a drying step can be carried out. Drying can be carried out by centrifugation.

[0087] Annealing may allow the hydrophobic layer 250 to be dried and / or stabilized.

[0088] During step e), the temporary substrate 100 is separated from the substrate of interest 200. The assembly can be disassembled by inserting, for example, a wedge between the two substrates 100, 200.

[0089] The temporary substrate 100 can be used in a new bonding / etching cycle. Cleaning is advantageously carried out between each use.

[0090] For example, it is possible to recycle it by implementing an oxygen plasma treatment followed by wet cleaning.

[0091] Alternatively, since the bases of the pads 120 of the temporary substrate 100 have not been exposed to the hydrophobic compound, they are still compatible with direct bonding. The temporary substrate 100 can therefore be directly reused.

[0092] At the end of the process, a substrate 200 is obtained having a first surface 201 comprising hydrophilic zones ZI surrounded by hydrophobic zones Z2 (FIGS. 2 and 3). Each hydrophilic zone ZI is surrounded by a hydrophobic zone Z2.

[0093] The hydrophilic zones ZI have, for example, a surface area of ​​between 0.25 and 400 mm2.

[0094] The hydrophobic zones Z2 are zones covered by a hydrophobic layer or zones of a hydrophobic material exposed by chemical etching.

[0095] The hydrophobic zones Z2 preferably have a width of between 10 μm and 2.5 mm. For a substrate on which the chips will be bonded collectively, the width of the hydrophobic zones is, for example, between 400 μm and 2.5 mm. For a substrate on which the chips will be bonded individually, the width of the hydrophobic zones is, for example, between 10 μm and 2.5 mm, or even between 40 μm and 2.5 mm. Indeed, the individual placement of chips is generally much more precise than the collective placement.

[0096] Hydrophobic lines Z3 connect the hydrophobic zones Z2 to the edge of the substrate 200.

[0097] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0098] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

[0099] Illustrative and non-limiting examples of different embodiments

[0100] Example 1:

[0101] On a silicon wafer with a diameter of 200 mm, a photolithography / etching process makes it possible to form 10 x 10 mm2 pads having a thickness of 1 μm as well as linear raised elements, intended to form the interstices after bonding making it possible to bring / distribute the liquid towards the areas to be made hydrophobic, and an annular raised element around the plate.

[0102] A second photolithography / etching process makes it possible to etch the entire the surface and form the large gap areas by etching, for example, 100 pm of silicon while protecting the small gap areas as well as the pads of interest. The small gap areas have a width of 2.5 mm. The edge of the wafer is trimmed with a diamond saw with a width of 3 mm and a depth of 200 pm. This trimming is less wide than the raised annular element which therefore remains after this step.

[0103] The surface of the temporary plate is cleaned by an O2 plasma followed by cleaning which promotes the wetting of the surface of the pads by the solution. The surface is thus also compatible with a direct bonding process. Cleaning can be carried out, for example, by wet CARO, SCI.

[0104] An SOI wafer of interest has a 205 nm silicon film and a 400 nm buried oxide layer. It undergoes CARO / SC1 wet cleaning to make it compatible with a direct bonding process.

[0105] The substrate of interest and the temporary substrate are directly bonded.

[0106] Then, the assembly is immersed in a solution comprising the fluorinated compound Novec™ 1720 EGC marketed by the company 3M™. During this immersion, the solution will preferentially penetrate through and along the low gap areas. Ultrasonic activation can be carried out. The assembly is then dried by centrifugation.

[0107] The temporary substrate is dismantled by inserting a wedge into the structure. A silicon plate of interest is obtained which has hydrophilic zones of 10*10mm2 surrounded by hydrophobic zones of a width corresponding to the width of the zones of the small gaps (2.5mm).

[0108] Example 2:

[0109] On a temporary silicon wafer with a diameter of 200 mm, a photolithography / etching process makes it possible to form 11 x 11 mm2 pads with a thickness of 1 pm as well as raised elements (lines) making it possible to bring the liquid from the edge of the plate and distribute it towards the pads and an annular raised element (ring) around the plate.

[0110] A second photolithography / etching process makes it possible to etch the entire surface and to form the large gap areas by etching, for example, 100 pm of silicon while protecting the small gap areas as well as the pads of interest. The width of the small gap areas is 2.5 mm. The edge of the temporary plate is trimmed with a diamond saw with a width of 3 mm and a depth of 200 pm.

[0111] The surface of the wafer is cleaned by an O2 plasma followed by CARO, SCI wet cleaning so as to make it hydrophilic and thus facilitate its wetting by the solution of interest. The temporary substrate is thus compatible with a direct bonding process.

[0112] An SOI wafer of interest has a 205 nm silicon film and a 400 nm buried oxide layer. This wafer undergoes a photolithography / etching process to form 10 x 10 mm2 and 1 pm thick pads. Then, CARO / SC1 wet cleaning makes it possible to make the surface of these pads compatible with a direct bonding process.

[0113] The two substrates are bonded directly by aligning the pads of the substrate of interest and the temporary substrate. A solution comprising the fluorinated compound Optool marketed by the company DAIKIN is then brought locally by a pipe to the mouth of a low gap zone. During this contact, the liquid will penetrate preferentially through and along the low gap zones. Then the assembly is dried by centrifugation. Advantageously, here the rear faces of the two substrates are not at all contaminated by the Optool liquid.

[0114] The temporary plate is dismantled by inserting a wedge into the structure. A silicon plate of interest is obtained which has 10*10mm2 hydrophilic pads surrounded by hydrophobic zones of a width corresponding to the width of the small gap zones.

[0115] Example 3:

[0116] On a temporary silicon wafer with a diameter of 200 mm, a photolithography / etching process is used to form, initially, the distribution lines and not the pads. The lines are used to bring the liquid from the edge of the wafer and distribute it to the pads with a 1 pm etching. A distribution ring around the wafer is also created.

[0117] A second photolithography / etching process makes it possible to form pads of 11 x 11 mm2 and a thickness of 5 pm.

[0118] A third photolithography / etching process makes it possible to etch the entire surface and to form the large gap areas by etching, for example, 100 pm of silicon while protecting the small gap areas as well as the pads of interest. The edge of the temporary substrate is trimmed using a diamond saw with a width of 3 mm and a depth of 200 pm.

[0119] The surface of the temporary wafer is cleaned by an O2 plasma followed by CARO, SCI wet cleaning in order to make it hydrophilic and thus facilitate the wetting of the substrate with the solution of interest. The substrate is thus compatible with a direct bonding process. The different etching heights allow for different penetration speeds.

[0120] An SOI wafer of interest has a 205 nm silicon film and a 400 nm buried oxide layer. It undergoes a photolithography / etching process to form 10 x 10 mm2 and 1 pm thick pads. Then a CARO / SC1 wet cleaning makes it possible to make the wafer compatible with a direct bonding process. surface of these plots.

[0121] The temporary substrate and the substrate of interest are directly bonded by aligning the pads of the two substrates. The assembly is only on a small portion of the assembly, taking care that at least one area with a small gap touches and often penetrates the liquid. The liquid is a solution comprising the fluorinated compound Optool marketed by the company DAIKIN. Then, the assembly is dried by centrifugation. During this soaking, the liquid will preferentially penetrate through and along the areas with a small gap. The liquid will go faster along the areas of small gaps which surround the pads of interest, which makes it possible to quickly distribute the liquid around the pads which then surround each other more slowly. In this example, the majority of the surface of the rear faces of the two substrates has not seen the liquid and will therefore not need to be cleaned.

[0122] The temporary plate is dismantled by inserting a wedge into the structure. A silicon plate of interest is obtained which has 10*10mm2 hydrophilic pads surrounded by hydrophobic zones of a width corresponding to the width of the small gap zones.

Claims

Claims

1. A method of forming hydrophobic zones (Z2, Z3) on a substrate of interest (200), the method comprising the following steps: - providing the substrate of interest (200) comprising a first hydrophilic surface (201) and a temporary substrate (100) comprising a base substrate (110) locally covered with pads (120) and raised elements (130, 140) having a height less than the height of the pads (120), a first part of the raised elements being peripheral elements (130) surrounding the pads (120) and a second part of the raised elements being fluidic connection elements (140) extending from the peripheral elements (130) to the edge of the temporary substrate (200), - bonding the pads (120) of the temporary substrate (100) to the first hydrophilic surface (201) of the substrate of interest (200), whereby the substrate of interest (200) is separated from the relief elements (130, 140) by gaps,- contacting the substrate of interest (200) with a solution (300) comprising a hydrophobic compound or an etching agent, whereby the solution (300) infiltrates into the interstices and hydrophobic zones (Z2, Z3) are formed on the substrate of interest (200) opposite the relief elements (130, 140).,

2. Method according to claim 1, characterized in that the relief elements (130, 140) have a height representing less than 50% and, preferably, less than 10% of the height of the pads (120).

3. Method according to one of the preceding claims, characterized in that the interstices have a height of between 0.1 and 10 pm, preferably between 1 and 5 pm.

4. Method according to any one of the preceding claims, characterized in that the pads (120) have a height of between 10 and 100 pm.

5. Method according to any one of claims 1 to 4, characterized in that the fluidic connection elements (140) form a perimeter on the base substrate (110).

6. A method according to any one of claims 1 to 4, characterized in that the fluidic connection elements (140) are positioned discontinuously around the periphery of the base substrate (110), so as to form vents between the fluidic connection elements. (140).

7. Method according to any one of the preceding claims, characterized in that the relief elements (130, 140) have a width of between 10 μm and 2.5 mm.

8. Method according to any one of the preceding claims, characterized in that the pads (120) have a surface area of ​​between 0.25 and 400 mm2.

9. Method according to any one of the preceding claims, characterized in that the substrate (200) comprises zones (Zl) of stronger topographies and / or metallic interconnections, on which the pads (120) are bonded.

10. Method according to any one of the preceding claims, characterized in that only one edge of the substrate of interest (200) is brought into contact with the solution (300), at the level of a fluidic connection element (140).

11. Substrate (200) having a first surface (201) comprising hydrophilic zones (Z1) surrounded by hydrophobic zones (Z2), preferably having a width between 10 pm and 2.5 mm, hydrophobic lines (Z3) connecting the hydrophobic zones (Z2) to the edge of the substrate (200).

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