Method for forming hydrophobic zones on substrate

Abstract

To provide a substrate and a method for reliably forming a hydrophobic zone around a hydrophilic zone.SOLUTION: A method of forming hydrophobic zones includes the following steps: providing a structure comprising a substrate of interest (200) bonded to a temporary substrate (100), the temporary substrate including a base substrate (110) locally covered with pads (120) and with raised elements (130, 140) having a height lower 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 (100), where interstices separate the substrate of interest (200) from the raised elements (130, 140); bringing the structure into contact with a solution comprising a hydrophobic compound or an etchant, so that the solution seeps into the interstices and hydrophobic zones are formed on the substrate of interest (200) opposite the raised elements (130, 140).SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present disclosure generally relates to the field of microelectronics, and more specifically to substrates for chip-wafer bonding.

Background Art

[0002] In chip-wafer bonding, it is necessary to place the chip within a predetermined zone on the wafer. To facilitate the placement of the chip, it is possible to form a hydrophilic zone surrounded by hydrophobic zones on the wafer. Thus, the chip carried by a liquid (usually water) will spontaneously position itself on the hydrophilic zone.

[0003] To form hydrophobic zones around the hydrophilic zones on the wafer, it is common to bond a wafer having a hydrophilic surface to a temporary wafer covered with pads. The pads protect the zones where the chips will be subsequently placed. Then, the structure thus obtained is brought into contact with a liquid capable of making the surface of the wafer hydrophobic, for example by immersion. The purpose is to propagate the liquid around the pads and make the surface around the pads hydrophobic. The portion located under the pads does not come into contact with the liquid and remains hydrophilic.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in some cases, this penetration is relatively slow and air bubbles may be trapped between the two wafers, preventing the propagation of the liquid. As a result, the zones remain hydrophilic instead of becoming hydrophobic, which is particularly inconvenient for chip placement.

[0005] There is a need for a method that can reliably form hydrophobic zones around hydrophilic zones.

Means for Solving the Problems

[0006] This object is a method for forming hydrophobic zones on a target substrate, - Providing a temporary substrate having a target substrate with a first hydrophilic surface and a base substrate locally covered with pads and raised elements having a height lower than that of the pads, wherein a first portion of the raised elements is a peripheral element surrounding the pads, and a second portion of the raised elements is a fluid connection element extending from the peripheral element to an edge of the temporary substrate; - Separating the target substrate from the raised elements by a gap by bonding the pads of the temporary substrate to the first hydrophilic surface of the target substrate; and - Contacting the target substrate with a solution containing a hydrophobic compound or an etching solution, so that the solution penetrates into the gap and forms a hydrophobic zone on the target substrate facing the raised elements is achieved by a method.

[0007] It is advantageous that the height of the raised element is less than 50% of the height of the pad, preferably less than 10%.

[0008] It is advantageous that the height of the gap is in the range of 0.1 to 10 μm, preferably in the range of 1 to 5 μm.

[0009] It is advantageous that the height of the pad is in the range of 10 to 100 μm.

[0010] It is advantageous that the fluid connection element forms a peripheral portion on the base substrate.

[0011] It is advantageous that the fluid connection elements are intermittently arranged along the peripheral portion of the base substrate so as to form air holes between the fluid connection elements.

[0012] It is advantageous that the width of the raised element is in the range of 10 μm to 2.5 mm.

[0013] It is advantageous that the surface area of the pad is in the range of 0.25 to 400 mm 2 ².

[0014] It is advantageous for the target substrate to have a topography and / or a zone of metal interconnections that is higher than where the pads are coupled.

[0015] It is advantageous to bring only one edge of the target substrate into contact with the solution at the location of the fluid connection element.

[0016] This object is further achieved by a substrate having a first surface, which is surrounded by a hydrophobic zone and has a hydrophilic zone, preferably having a width in the range of 10 μm to 2.5 mm, and a hydrophobic line connecting the hydrophobic zone to an edge of the substrate.

Brief Description of the Drawings

[0017] The foregoing and other features and advantages are described in detail in the remainder of the present disclosure of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings.

[0018]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 1E

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 4E

Figure 4F

Figure 4G

Figure 4H

DETAILED DESCRIPTION OF THE INVENTION

[0019] In various drawings, similar features are denoted by similar reference numerals. In particular, structural and / or functional features common to various embodiments may have the same reference numerals and may have the same structural characteristics, dimensional characteristics, and material characteristics.

[0020] For clarity, only the steps and elements useful for understanding the described embodiments are shown and detailed.

[0021] Unless otherwise indicated, when referring to two elements connected together, this represents a direct connection without any intermediate element other than a conductor, and when referring to two elements coupled together, this represents that these two elements can be connected or can be coupled through one or more other elements.

[0022] In the following description, when referring to absolute positions such as "front", "rear", "top", "bottom", "left", "right", etc., or words limiting relative positions such as "top", "bottom", "upper side", "lower side", etc., or words limiting directions such as "horizontal", "vertical", etc., unless otherwise specified, this language refers to the orientation of the drawing.

[0023] Unless otherwise specified, the expressions "about", "substantially", "essentially" and "degree" represent plus or minus 10% of the corresponding value, preferably plus or minus 5%.

[0024] This specification specifically refers to a substrate for chip - wafer bonding, but this method is particularly advantageous for all applications that require the propagation of a liquid around a pad over a given width or to a specific location without necessarily wetting the entire free space between the wafers.

[0025] With reference to FIGS. 1A, 1B, 1C, 1D and 1E, a method for forming a hydrophilic zone Z1 surrounded by a hydrophobic zone Z2 on a target substrate 200 will be described in more detail.

[0026] This method comprises a) providing a target substrate 200 having a first hydrophilic surface 201 and a second surface 202, and a temporary substrate 100 having a base substrate 110, the base substrate locally having pads 120 and raised elements 130, 140 of a height lower than that of the pads 120 on its surface, a first portion of the raised elements corresponding to so - called peripheral elements 130 surrounding the pads 120, and a second portion of the raised elements corresponding to so - called fluid connection elements 140 extending from the peripheral elements 130 to the edge of the temporary substrate 100 (FIG. 1A); b) bonding the temporary substrate 100 to the first surface 201 of the target substrate 200, more specifically, bonding the pads 120 of the temporary substrate 100 to the first surface 201 of the target substrate 200, and separating the target substrate 200 from the raised elements 130, 140 by a gap (FIG. 1B); c) contacting the structure obtained in step b) with a solution 300 containing a compound capable of making the first surface 201 of the target substrate 200 hydrophobic, so that the solution 300 penetrates into the gap and hydrophobic zones Z2, Z3 are formed on the first surface 201 of the target substrate 200 facing the raised elements 130, 140 (FIGS. 1C, 2, and 3); d) preferably, a step of cleaning the substrate (FIG. 1D); and e) a step of separating the temporary substrate 100 from the target substrate 200 (FIG. 1E). It has.

[0027] Between the two substrates 100 and the substrate 200, - The gap between the target substrate 200 and the raised elements 130, 140 (narrow gap zone) - The space between the target substrate 200 and the base substrate 110 of the temporary substrate 100 (wide gap zone) There are a plurality of different types of intervals (or gaps).

[0028] The height of the gap is less than 50% of the height of the wide gap zone, preferably less than 10%.

[0029] Compared with the height of the space between the target substrate 200 and the base substrate 110 of the temporary substrate 100, the height of the gap is very small, so the capillary force is strongest at this level. Therefore, it is preferable that wetting occurs in the gap (i.e., between two surfaces separated by the smallest interval).

[0030] By such a method, it is possible to efficiently propagate a liquid between the pads 120 of two wafers bonded to each other.

[0031] In such a method, it is possible to cause partial wetting, and by adjusting the height of the gap, it is possible to increase the wetting rate.

[0032] The target substrate 200 is preferably a wafer.

[0033] The target substrate 200 is a substrate formed of, for example, a semiconductor material (preferably Si, Ge, SiC, AsGa), sapphire, or silica.

[0034] The target substrate 200 prepared in step a) may be a SOI ("Silicon-On-Insulator") substrate, i.e., a substrate including a support substrate continuously covered with a thin film of buried oxide and a silicon layer.

[0035] Alternatively, the substrate may be a solid substrate formed of a semiconductor material (e.g., silicon) covered with a dielectric layer, particularly an oxide layer (particularly silicon oxide).

[0036] The target substrate 200 has a first surface 201 and a second surface 202. The first surface 201 is a hydrophilic surface.

[0037] The first surface 201 has a first zone Z1 where it is desired to maintain hydrophilicity and a second zone Z2 surrounding the first zone where it is desired to make it hydrophobic (Figs. 2 and 3). The first zone Z1 is protected by the pad 120 of the temporary substrate 100 after the bonding in step b).

[0038] The first zone Z1 may be a zone of higher topography and / or a metal interconnect zone configured to be connected to a chip. Higher topography means that the first zone Z1 protrudes at least 100 nm, particularly 500 nm, and further 1 μm from the surface of the substrate.

[0039] The first zone Z1 may be arranged regularly or irregularly. The first zones may be of the same size or of different sizes.

[0040] The temporary substrate 100 has a base substrate 110, pads 120 (columns or pillars), and raised elements 130, 140.

[0041] The base of the pad 120 may have different shapes. The pad may be square, rectangular, or circular.

[0042] The solution 300 is conveyed to a zone that makes it hydrophobic through a gap, and the pads 120 may be arranged at a small distance or a larger distance apart. The spacing of the pads 120 is selected according to the desired application. The pads 120 may be arranged at intervals greater than, for example, 10 μm, or greater than 50 μm, or less than that. The pads may further be arranged at intervals of several millimeters.

[0043] The height of the raised elements 130, 140 is lower than the height of the pad 120. The various raised elements 130, 140 may have the same height or different heights. It is preferable that the heights are the same or substantially the same.

[0044] The width of the raised elements 130, 140 is preferably in the range of 10 μm to 2.5 mm.

[0045] The first part of the raised element corresponds to a so-called peripheral element 130 arranged around the pad 120 and forms the peripheral part of the pad 120. During bonding, the part of the target substrate 200 facing the peripheral element 130 corresponds to a zone Z2 that desirably becomes hydrophobic.

[0046] The second part of the raised element corresponds to a so-called fluid connection element 140 and enables the peripheral element 130 arranged around the pad 120 to be connected to the edge of the substrate. During bonding, the gap formed opposite these elements forms a flow path or channel for the solution, and the flow path or channel opens to the edge of the target substrate 200.

[0047] Each peripheral element 130 is connected to the edge of the substrate by a fluid connection element 140. The fluid connection element 140 may enable a plurality of peripheral elements 130 to be connected to the edge of the substrate.

[0048] The fluid connection element 140 is arranged, for example, in a row at the center of the base substrate 110.

[0049] The raised element may further cover part or all of the peripheral edge of the base substrate 110.

[0050] According to the first modification, the raised element covers the entire peripheral edge of the base substrate 110.

[0051] According to another modification, the raised element covers only a part of the peripheral edge of the base substrate 110. For this reason, one or more ventilation holes can be formed, and when the ventilation holes are provided, the air released by the inflow of the solution 300 can escape.

[0052] The base substrate 110, the pad 120, and the raised element 130 may be formed of different materials. It is desirable that the base substrate 110, the pad 120, and the raised element 130 are formed of the same material. The material may be, for example, a metal or a semiconductor material. The semiconductor material is preferably formed of silicon.

[0053] The temporary substrate 100 is preferably obtained from a solid substrate.

[0054] In particular, the temporary substrate 100 may be manufactured by a photolithography process. By way of example, as shown in FIGS. 4A to 4H, the substrate is - a step of preparing the substrate 110 (FIG. 4A), - a step of locally depositing the resin 150 on the substrate 110 (FIG. 4B), - a step of etching the portion of the substrate not covered with the resin 150 to define the upper part of the pad 120 (FIG. 4C), - a step of removing the resin 150 (FIG. 4D), - On the one hand, additional resin 160 can be deposited on the uppermost part and the upper side surface of the pad 120 to complete the formation of the pad 120 and form a peripheral element 130 surrounding the pad. On the other hand, a step of locally depositing additional resin 160 on the substrate 110 according to a future zone of the fluid connection element 140 (FIG. 4E), - A step of etching the substrate 110 to form the pad 120 and the raised elements 130, 140 (FIG. 4F), - A step of removing the additional resin 160 (FIG. 4G), and - Optionally, a step of trimming the substrate 110 (FIG. 4H) It may be manufactured according to.

[0055] By trimming the edge of the wafer 110, any edge contact between the temporary substrate 100 and the target substrate 200 can be avoided, especially when the pad 120 is not too thick.

[0056] Trimming may be performed, for example, by photolithography / etching or by mechanical trimming using a diamond saw. The width of trimming on the substrate surface is, for example, in the range of 1 to 5 mm, and / or the depth of trimming in a plane perpendicular to the substrate surface is, for example, in the range of 100 to 250 μm.

[0057] Before step b), it is possible to perform one or more pre-treatments on the surface of the temporary substrate 100 and / or the surface of the target substrate 200 to make them compatible with direct bonding.

[0058] The pre-treatment may be selected from pre-treatments of thermal annealing, plasma, polishing, and wet cleaning.

[0059] As an example, it is possible to form an oxide layer on the surface of the temporary substrate 100, and / or perform a polishing process on the temporary substrate 100 and / or the target substrate 200 to obtain a roughness compatible with direct bonding (usually a roughness of less than 0.5 nm RMS). For example, it is possible to perform a treatment combining plasma and an aqueous solution, particularly wet CARO cleaning (H2SO4:H2O2 at a ratio of 5:1) involving oxygen plasma and subsequent SC1 (H2O:NH3:H2O2 at a ratio of 5:1:1).

[0060] In step b), the temporary substrate 100 and the target substrate 200 are bonded together.

[0061] The two substrates 100, 200 may be assembled by direct bonding. The alignment of the substrates may be facilitated by using marks on the substrates 100, 200. An accuracy of about 100 nm can be achieved. It is further possible to align the substrates by using the edges and notches of the substrates without using marks. The accuracy is lower (+ / -50 μm), but it is sufficient for certain applications.

[0062] The direct bonding may be performed at atmospheric pressure (i.e., 1,013.25 hPa) or in a vacuum. The assembly does not necessarily have to be strengthened by heat treatment. However, it may be advantageous to perform annealing preferably at a temperature of less than 200 °C. Annealing can be performed at higher temperatures, but there is a risk of damaging the surface during the final separation of the two substrates 100 and substrate 200.

[0063] During bonding, the pad 120 of the temporary substrate 100 is bonded to the first surface 201 of the target substrate 200, more specifically to the first hydrophilic zone Z1 of the target substrate 200 that should be protected during step c). The peripheral raised element 130 around the pad 120 is arranged to face the second zone Z2 of the substrate 100 that is desirably made hydrophobic (FIGS. 2 and 3).

[0064] During bonding, the height of the space (large-gap zone) between the substrate 110 and the substrate 200 varies, for example, within the range of 10 μm to 100 μm. The height of the large-gap zone may be constant within the same assembly, but may also vary slightly (usually less than 10%).

[0065] Due to the bonding, a gap is formed between the first surface 201 of the target substrate 200 and the raised elements 130, 140 of the temporary substrate 100. The thickness (or height) of the gap varies, for example, within the range of 0.1 μm to 10 μm, and preferably within the range of 1 μm to 5 μm.

[0066] The height of the small-gap zone is generally constant within a range of 10% on the wafer, but may also be intentionally different. This can be advantageous in that the wetting rate varies depending on the position on the wafer.

[0067] The first group of gaps is formed between the peripheral raised element 130 and the target substrate 200. The thickness (i.e., height) of the gap corresponds to the height difference between the pad 120 and the peripheral raised element 130.

[0068] The second group of gaps is formed between the first surface 201 of the substrate 200 and the raised fluid connection element 140. Therefore, these gaps form a preferential path for the liquid (step c)). The thickness of these gaps is determined according to the height difference between the pad 120 and the raised fluid connection element 140.

[0069] The structure has one or more paths for guiding the solution 300 from the outside of the substrate to the zone Z2 that should be made hydrophobic. The zone Z3 of the target substrate 200 under these flow paths of the solution 300 also becomes hydrophobic at the end of the treatment (FIG. 2 and FIG. 3).

[0070] In step c), the target substrate 200 is brought into contact with the solution 300. The solution 300 is a solution capable of making the surface hydrophobic. The solution is generally a solution containing a hydrophobic compound that locally binds to the surface of the target substrate 200 to locally make the surface of the target substrate 200 hydrophobic. In particular, by etching the surface layer to expose the underlying hydrophobic material, it is further possible to make the surface hydrophobic.

[0071] The target substrate 200 may be brought into contact with the solution 300 by overall or partial immersion, or by inserting or injecting the solution 300 into the gap formed during bonding. It is preferable to bring only one edge of the target substrate into contact with the solution 300.

[0072] The solution 300 penetrates from the gap under the raised fluid connection element 140 to the zone Z2 under the peripheral raised element 130.

[0073] The penetration of the solution through the narrow path is enabled by capillary force. As shown in FIGS. 2 and 3, when the solution is at the edge of the end of the path, capillary force enables the solution to spontaneously fill all the paths without the need to fully immerse the assembly. Accordingly, contamination of the two outer surfaces of the assembly by the solution is avoided.

[0074] Trimming makes it easier for liquid to enter the edge of the bonded structure.

[0075] In the first modification, the surface of the substrate 200 in contact with the solution becomes hydrophobic by forming a hydrophobic layer 250 at the position of the gap (FIG. 1E).

[0076] The selection of the hydrophobic layer 250 is determined particularly according to the target substrate 200.

[0077] The formed hydrophobic layer 250 has a thickness in the range of, for example, 2 nm to 100 nm.

[0078] The hydrophobic layer 250 may be obtained from a polymer, silyl (also referred to as organosilyl), or silane.

[0079] The selected hydrophobic compound preferably contains one or more halogen groups, particularly fluorine or chlorine groups. The hydrophobic compound preferably contains a carbon chain of at least 5 carbon atoms.

[0080] The silane may be a chlorosilane such as octadecyltrichlorosilane (OTS = CH3(-CH2) 17 -SiCl3) sold by Sigma Aldrich.

[0081] The polymer may be, for example, a fluoropolymer such as Novec (trademark) 1720 EGC polymer sold by 3M (trademark), Optool sold by Daikin Industries, Ltd., and Novec (trademark) 2202 EGC polymer sold by 3M (trademark). The hydrophobic compound may be selected from chlorosilanes such as perfluorodecyltrichlorosilane (FDTS = Cl3Si(CH2)2(CF2)7CF3) sold by Sigma Aldrich and perfluorodecyldimethylchlorosilane (FDDMCS = CF3(CF2)7(CH2)2(CH3)2SiCl) sold by Sigma Aldrich.

[0082] As a modification, the surface of the substrate 200 in contact with the solution may be made hydrophobic by selectively and locally etching the surface layer of the substrate 200 to locally expose the hydrophobic material of the substrate 200.

[0083] For example, when the surface of the substrate 200 is formed of silicon, the surface can be made hydrophobic by etching the original oxide layer present on the surface of the silicon with a hydrofluoric acid (HF) solution, for example, a solution containing 1% HF.

[0084] After step c), a cleaning step d) by rinsing and optionally a drying step may be performed. Drying may be carried out by centrifugation.

[0085] Annealing may also be possible to dry and / or stabilize the hydrophobic layer 250.

[0086] During step e), the temporary substrate 100 is separated from the target substrate 200. The assembly may be disassembled, for example, by inserting a wedge between the two substrates 100, 200.

[0087] The temporary substrate 100 may be used in a new bonding / etching cycle. It is advantageous to perform cleaning between each use.

[0088] For example, it is possible to recycle the temporary substrate by performing oxygen plasma treatment and subsequent wet cleaning.

[0089] Alternatively, since the base of the pad 120 of the temporary substrate 100 was not exposed to the hydrophobic compound, the base of the pad is still compatible with direct bonding. Thus, the temporary substrate 100 may be reused directly.

[0090] At the end of the process, a substrate 200 (Figs. 2 and 3) is obtained having a first surface 201 that includes a hydrophilic zone Z1 surrounded by a hydrophobic zone Z2. Each hydrophilic zone Z1 is surrounded by a hydrophobic zone Z2.

[0091] The hydrophilic zone Z1 has a surface area, for example, in the range of 0.25 to 400 mm 2 within the range.

[0092] The hydrophobic zone Z2 is a zone covered with a hydrophobic layer or a zone of hydrophobic material exposed by chemical etching.

[0093] The width of the hydrophobic zone Z2 is preferably in the range of 10 μm to 2.5 mm. In the substrate to which the chips are collectively bonded, the width of the hydrophobic zone is, for example, in the range of 400 μm to 2.5 mm. In the substrate to which the chips are individually bonded, the width of the hydrophobic zone is, for example, in the range of 10 μm to 2.5 mm, or in the range of 40 μm to 2.5 mm. In fact, the individual placement of the chips is generally much more accurate than the collective placement.

[0094] The hydrophobic line Z3 connects the hydrophobic zone Z2 to the edge of the substrate 200.

[0095] Various embodiments and variations are described. Those skilled in the art will understand that they can combine certain features of these various embodiments and variations, and other variations will be obvious to those skilled in the art.

[0096] Finally, the actual implementation of the described embodiments and variations is within the scope of the skills of those skilled in the art based on the functional representations described above.

[0097] Exemplary and non-limiting examples of various embodiments

[0098] Example 1 On a silicon wafer with a diameter of 200 mm, by photolithography / etching method, a 10×10 mm pad with a thickness of 1 μm, and after bonding, a linear raised element and an annular raised element around the wafer that are configured to form a gap capable of transporting / distributing liquid to the zone to be made hydrophobic can be formed. 2 The second photolithography / etching process can form a large gap zone by etching the entire surface while protecting the small gap zone and the pads of interest, for example, by etching 100 μm of silicon. The width of the small gap region is 2.5 mm. Trimming of the edge of the wafer with a width of 3 mm and a depth of 200 μm is performed using a diamond saw. This trimmed portion is narrower than the annular raised element and thus remains after this step.

[0099] ​

[0100] The surface of the temporary wafer is cleaned by a cleaning that favors wetting of the pad surface by O2 plasma and subsequent solution. Thus, the surface is more compatible with the direct bonding process. The cleaning may be performed, for example, by wet CARO, SC1 treatment.

[0101] The SOI wafer of interest has a 205 nm silicon film and a 400 nm buried oxide layer. The SOI wafer is subjected to wet CARO / SC1 cleaning to make it compatible with the direct bonding process.

[0102] Bond the target substrate and the temporary substrate directly.

[0103] Next, immerse the assembly in a solution containing Novec (trademark) 1720 EGC fluorinated compound sold by 3M (trademark). During this immersion, the solution preferably penetrates through and along the small gap zone. Ultrasonic activation may be performed. Thereafter, dry the assembly by centrifugation.

[0104] Remove the temporary substrate by inserting a wedge into the structure. A silicon wafer of interest having a hydrophilic zone of 10×10 mm surrounded by a hydrophobic zone having a width corresponding to the width of the small gap zone (2.5 mm) is obtained. 2 is obtained.

[0105] Example 2 On a temporary silicon wafer with a diameter of 200 mm, by photolithography / etching treatment, a pad with a thickness of 1 μm and a size of 11×11 mm 2 and raised elements (lines) capable of transporting liquid from the edge of the wafer and distributing the liquid to the pad and an annular raised element (ring) around the wafer can be formed.

[0106] By the second photolithography / etching method, it is possible to form a large-gap zone by etching the entire surface while protecting the small-gap zone and the pads of interest, for example, by etching 100 μm of silicon. The width of the small-gap zone is 2.5 mm. Trimming of the edge of the temporary wafer with a width of 3 mm and a depth of 200 μm is performed using a diamond saw.

[0107] The surface of the wafer is made hydrophilic, and thus the surface of the wafer is cleaned by O2 plasma and subsequent wet CARO and SC1 cleaning to facilitate wetting by the solution of interest. Therefore, the temporary substrate is compatible with the direct bonding process.

[0108] The SOI wafer of interest has a 205 nm silicon film and a 400 nm buried oxide layer. Photolithography / etching treatment is performed on this wafer to form pads of 10×10 mm with a thickness of 1 μm. 2 Therefore, by wet CARO / SC1 cleaning, the surfaces of these pads can be made compatible with the direct bonding process.

[0109] The two substrates are directly bonded by aligning the pads of the target substrate and the pads of the temporary substrate. Then, a solution containing an Optool fluorinated compound sold by Daikin Industries, Ltd. is locally supplied to the opening of the small-gap zone through a tube. During this contact, the liquid preferably penetrates through and along the small-gap zone. Then, the assembly is dried by centrifugation. Here, it is advantageous that the back sides of the two substrates are not contaminated at all by the Optool solution.

[0110] The temporary wafer is removed by inserting a wedge into the structure. A silicon wafer of interest with 10×10 mm hydrophilic pads surrounded by a hydrophobic zone with a width corresponding to the width of the small-gap zone is obtained. 2

[0111] Example 3 On a temporary silicon wafer with a diameter of 200 mm, it is possible to form distribution lines rather than pads in the first step by photolithography / etching processes. The distribution lines can carry liquid from the edge of the wafer and distribute the liquid to the pads using a 1-μm etched portion. A distribution ring is further formed around the wafer.

[0112] By the second photolithography / etching process, it is possible to form pads that are 11×11 mm with a thickness of 5 μm. 2

[0113] By the third photolithography / etching process, while protecting the small-gap zone and the pads of interest, it is possible to etch the entire surface and form a large-gap zone, for example, by etching 100 μm of silicon. The edge of the temporary substrate with a width of 3 mm and a depth of 200 μm is trimmed using a diamond saw.

[0114] The surface of the temporary wafer is made hydrophilic, and thus the surface of the temporary wafer is cleaned by O2 plasma and subsequent wet CARO and SC1 cleaning to facilitate wetting of the substrate by the solution of interest. Therefore, the substrate is compatible with the direct bonding process. With various etching heights, it is possible to obtain various penetration rates.

[0115] The SOI wafer of interest has a 205-nm silicon film and a 400-nm buried oxide layer. A photolithography / etching method is performed on this wafer to form pads that are 10×10 mm with a thickness of 1 μm. Next, the surface of these pads can be made compatible with the direct bonding process by wet CARO / SC1 cleaning. 2

[0116] ​​The temporary substrate and the target substrate are directly bonded by aligning the pads of the two substrates. Assembly is performed only on a very small part of the assembly while ensuring that the small gap zone is in contact with and in many cases penetrates the liquid. The liquid is a solution containing an Optool fluorinated compound sold by Daikin Industries, Ltd. The assembly is then dried by centrifugation. During this immersion, the liquid preferably penetrates through and along the small gap zone. Since the liquid moves faster along the small gap zone surrounding the pad of interest, the liquid can be rapidly redistributed around the pad, and the pad is then surrounded more slowly. In this example, since most of the back surface of the two substrates is not in contact with the liquid, it does not need to be cleaned.

[0117] The temporary wafer is removed by inserting a wedge into the structure. A silicon wafer of interest having hydrophilic pads of 10×10 mm surrounded by a hydrophobic zone having a width corresponding to the width of the small gap zone 2 is obtained.

Claims

1. A method for forming hydrophobic zones (Z2, Z3) on a target substrate (200), comprising: - providing a target substrate (200) having a first hydrophilic surface (201) and a temporary substrate (100) having a base substrate (110) locally covered by pads (120) and raised elements (130, 140) having a height lower than that of the pads (120), wherein a first portion of the raised elements is a peripheral element (130) surrounding the pads (120), and a second portion of the raised elements is a fluid connection element (140) extending from the peripheral element (130) to an edge of the temporary substrate (100); - bonding the pads (120) of the temporary substrate (100) to the first hydrophilic surface (201) of the target substrate (200), thereby separating the target substrate (200) from the raised elements (130, 140) by a gap on one hand and from the base substrate (110) of the temporary substrate (100) by a large-gap zone on the other hand; - contacting the target substrate (200) with a solution (300) containing a hydrophobic compound or an etching solution, such that the solution (300) penetrates into the gap by capillary action to form hydrophobic zones (Z2, Z3) on the target substrate (200) opposite to the raised elements (130, 140); and - separating the target substrate (200) from the temporary substrate (100). A method comprising the above steps.

2. The method according to claim 1, wherein the height of the gap is less than 50% of the height of the large-gap zone, preferably less than 10%.

3. The method according to claim 1 or 2, wherein the height of the gap is in the range of 0.1 to 10 μm, preferably in the range of 1 to 5 μm.

4. The method according to any one of claims 1 to 3, wherein the height of the pads (120) is in the range of 10 to 100 μm.

5. The method according to any one of claims 1 to 4, wherein the fluid connection element (140) forms a peripheral portion on the base substrate (110).

6. The method according to any one of claims 1 to 4, wherein the fluid connection elements (140) are intermittently arranged at the peripheral portion of the base substrate (110) so as to form air holes between the fluid connection elements (140).

7. The method according to any one of claims 1 to 6, wherein the width of the raised element (130, 140) is in the range of 10 μm to 2.5 mm.

8. The surface area of the pad (120) is within the range of 0.25 to 400 mm 2 The method according to any one of claims 1 to 7

9. The method according to any one of claims 1 to 8, wherein the target substrate (200) has a topography and / or a zone (Z1) of metal interconnection that is higher than where the pad (120) is coupled.

10. The method according to any one of claims 1 to 9, wherein only one edge of the target substrate (200) is brought into contact with the solution (300) at the position of the fluid connection element (140).

11. A substrate (200) having a first surface (201), comprising a hydrophilic zone (Z1) surrounded by a hydrophobic zone (Z2) and preferably having a width in the range of 10 μm to 2.5 mm, and a hydrophobic line (Z3) connecting the hydrophobic zone (Z2) to an edge of the substrate (200).

Images