Process for transforming a support

Abstract

Title: Method for transforming a support The invention relates to a method for transforming a support comprising the following steps: providing a support (10) having an upper face (11), producing a protective coating (100) at least partially covering a peripheral zone (14) of the upper face forming a closed contour around a central zone (15) of the upper face. The method is characterized in that the production of the protective coating comprises the following steps: forming a first layer (20) of a reversible photosensitive resin covering the upper face of the support, exposing a first portion (24) of the first layer of photosensitive resin with a first exposure dose greater than the inversion dose of the resin, the first portion covering strictly the same surface of the upper face as the protective coating, so as to form the protective coating. Figure for abstract: Fig. 2C

Description

Title of the invention: Method for transforming a support Technical field

[0001] The present invention relates to the field of microelectronics. It finds particularly advantageous application in all manufacturing processes in which the periphery of the wafer must be protected. Such wafers correspond to the supports or substrates, generally based on semiconductor materials such as silicon, on which microelectronic components, such as chips, are manufactured; the components are singularized by cutting the wafer. STATE OF THE ART

[0002] When manufacturing microelectronic devices on a wafer - more commonly referred to by the English term "wafer" - it is important to protect the periphery of the latter, that is to say the area located at the edge of the wafer. This edge area, commonly referred to as "bevel", is in fact exposed to a large number of manufacturing steps that can damage its surface condition or contaminate it. Protection of the wafer extending beyond its periphery may also be sought. This is particularly the case for applications where small substrates are arranged on a large substrate so that they can be handled and transformed with conventional machines and processes. In such a situation, it may be desired to protect the entire area located outside the small substrates to prevent it from having an impact during the processes.

[0003] Today, an existing technique for protecting the bevel is a technique of depositing material, most often an oxide (e.g.: SiO2) or a nitride (e.g.: SiN), on the periphery of the wafer and encapsulating the bevel. This technique is developed on certain plasma phase deposition equipment.

[0004] However, this solution has many disadvantages. First of all, depositing material (SiO2 or SiN) on the bevel involves a significant transfer of material and therefore a possible degradation of the surface state of the bevel, which is in the opposite direction to the desired effect. Reactions at the interface between the substrate and the deposited layer can also occur, which has the consequence of further degrading the surface state of the bevel.

[0005] Another drawback of this solution is that it must be implemented in a step that is completely independent of the rest of the process and cannot be carried out online.

[0006] Furthermore, the deposited oxide or nitride layer must be removed in order to allow the subsequent implementation of certain processes, for example of the gluing type.

[0007] Finally, due to technical limitations, a dielectric deposit is only carried out correctly over 1 to 4 mm, or sometimes even only 3 mm, which limits the extent of the bevel protection.

[0008] Another way to protect the bevel is the use of a ring (or annulus) which, by being brought close to or even in contact with the wafer, allows an exclusion zone to be created on the edge of the plate. The use of such a ring requires the use of machines specifically designed for this.

[0009] There is therefore a need to provide a solution for satisfactorily protecting the bevel of a wafer during different stages of transformation of this same wafer and this in standard equipment. SUMMARY

[0010] To achieve this objective, according to one embodiment, a method of transforming a support is provided comprising the following steps: • Provide a support having an upper face extending mainly along a plane formed by a first direction and a second direction, called the transverse plane, • Create a protective coating at least partially covering a peripheral zone of the upper face forming a closed contour around a central zone of the upper face, the peripheral zone and the central zone together forming the entirety of the upper face.

[0011] The method is characterized in that the production of the protective coating comprises the following steps: • Form a first layer of a photosensitive resin covering the upper face of the support, the photosensitive resin being such that: i. when the resin is exposed to a dose of insolation D <Dinversion, elle présente un comportement de résine positive et se dissout lorsqu’elle est mise en contact avec un développeur, et ii. when the resin is exposed to an insolation dose D>Dinversion, it exhibits negative resin behavior and does not dissolve when brought into contact with the developer, • Expose a first portion of the first layer of photosensitive resin with a first dose of exposure Dl> Dinversion, the first portion covering strictly the same surface of the upper face as the protective coating, so as to form the protective coating, • Expose a second portion of the first layer with a second dose of D2 exposure <Dinversion ou ne pas insoler la deuxième portion, la second portion overlying at least part of the central zone.

[0012] The protective coating constitutes a protective layer for the underlying parts of the support. The remainder of the support, located under the second portion of the resin layer, can be treated without altering the bevel, covered by the coating. This prevents any metallic or particulate contamination which may occur in particular during etching steps of the central area of ​​the support.

[0013] The protective coating is formed during a photolithography step that can be very easily integrated into the overall support treatment process. The formation of the protective coating can thus take place in-line and does not present any technological constraints. The invention therefore allows a reduction in the number of manufacturing steps and therefore a significant time saving during the production of microelectronic devices.

[0014] Furthermore, the photosensitive resin layer can be deposited on the support in a conformal manner. The step of exposing the first portion of the resin does not in any way alter the conformity of the deposit. The dimensions of the first portion can thus be chosen without prejudice to the conformity of the protective coating.

[0015] Another advantage of the protective coating formed by the method according to the invention is that it can provide good mechanical strength to the wafer during a subsequent step of cutting and individualizing chips made on its surface.

[0016] The method according to the invention also makes it possible to produce a wafer holder (commonly referred to by the English term "holder") more simply than by current methods. The formation of a holder according to the method described in the present application is also advantageous compared to current methods (e.g.: grinding) in that it brings much less mechanical stress to the system.

[0017] A second aspect of the invention relates to a microelectronic device comprising: • a support having an upper face extending mainly along a plane formed by a first direction and a second direction, called the transverse plane, • a protective coating, at least partially covering a peripheral zone of the upper face forming a closed contour around a central zone of the upper face, the peripheral zone and the central zone together forming the entirety of the upper face.

[0018] The device is characterized in that the protective coating is based on a negative photosensitive resin. BRIEF DESCRIPTION OF THE FIGURES

[0019] The aims, objects, as well as the characteristics and advantages of the invention will emerge better than the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0020] [Fig. 1A] Figures 1A and 1B represent the formation of a protective coating on the periphery of a wafer according to the prior art.

[0021] [Fig.lB]

[0022] [Fig.2A] Figures 2A to 21 show a method of transforming a support according to one of the embodiments of the present invention. These figures are all side views of the support and the layers overlying it. [Fig.2A] shows the provision of the support.

[0023] [Fig.2B] [Fig.2B] illustrates the formation of a first layer of photosensitive resin on the support.

[0024] [Fig.2C] [Fig.2C] illustrates the exposure of a first portion of the first resin layer adjacent to a second portion of the first resin layer, which is not exposed.

[0025] [Fig.2D] [Fig.2D] represents the obtaining of a protective coating on the periphery of the wafer following the exposure of the first portion of the first layer of resin.

[0026] [Fig.2E] [Fig.2E] represents the exposure of the first layer of resin through a photolithography mask.

[0027] [Fig.2F] [Fig.2F] represents the formation of photolithography patterns in the second portion of the first layer of resin.

[0028] [Fig.2G] [Fig.2G] represents the development of the patterns, making it possible to reveal areas to be treated on the upper face of the support.

[0029] [Fig.2H] [Fig.2H] illustrates a step of etching the support from the areas to be treated.

[0030] [Fig.21] [Fig.2I] shows the removal of the protective coating and the parts remaining from the second portion of the first layer of resin.

[0031] [Fig.2J] [Fig.2J] represents the obtaining of a protective coating on the periphery of the wafer following the exposure of the first portion of the first layer of resin, in the case where the protective coating does not extend to the edge of the wafer.

[0032] [Fig.3A] Figures 3A to 3M show a method of transforming a support according to another of the embodiments of the present invention. These figures are all side views of the support and the layers overlying it. [Fig.3A] shows the provision of the support.

[0033] [Fig.3B] [Fig.3B] illustrates the formation of a first layer of photosensitive resin on the support.

[0034] [Fig.3C] [Fig.3C] illustrates the insolation of a first portion of the first resin layer adjacent to a second portion of the first resin layer, which is not exposed.

[0035] [Fig.3D] [Fig.3D] represents the obtaining of a protective coating on the periphery of the wafer following the exposure of the first portion of the first layer of resin. The coating can however be obtained only at the step represented by [Fig.3F],

[0036] [Fig.3E] [Fig.3E] illustrates the exposure of the first portion and the second portion of the first resin layer.

[0037] [Fig.3F] Figures 3F and 3G illustrate the development of the second portion of the first resin layer.

[0038] [Fig.3G]

[0039] [Fig.3H] [Fig.3H] illustrates the formation of a second layer of resin on the support.

[0040] [Fig.31] [Fig.31] represents the exposure of the second layer of resin through a photolithography mask.

[0041] [Fig.3J] [Fig.3J] shows the formation of photolithography patterns in the second resin layer.

[0042] [Fig.3K] [Fig.3K] represents the development of the patterns in the second layer of resin, making it possible to reveal areas to be treated on the upper face of the support.

[0043] [Fig.3L] [Fig.3L] illustrates a step of etching the support from the areas to be treated.

[0044] [Fig.3M] [Fig.3M] shows the removal of the protective coating and the remaining parts of the second portion of the second resin layer.

[0045] [Fig.3N] [Fig.3N] represents the protective coating when it does not extend to the edge of the wafer.

[0046] [Fig.4A] Figures 4A and 4B represent a top view of the steps illustrated by Figures 2D and 3D on the one hand and 3G on the other hand.

[0047] [Fig.4B]

[0048] [Fig.4C] [Fig.4C] is a variation of [Fig.4A] in which the protective coating does not extend to the edge of the support.

[0049] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, the dimensions are not representative of reality. DETAILED DESCRIPTION

[0050] Before commencing a detailed review of embodiments of the invention, are set out below are optional features that may be used in combination or alternatively:

[0051] According to an advantageous embodiment, the support has a first lateral flank and the protective coating has a second lateral flank, the first lateral flank and the second lateral flank being separated, in the transverse plane, by a radial distance dl03 of less than 0.5 cm, preferably less than 0.2 cm. This makes it possible to ensure good protection of the edge of the support. According to an advantageous example, dl03 is substantially equal to 0 cm.

[0052] According to one embodiment, the method further comprises the following steps: Expose a plurality of areas of the central area of ​​the support, called areas to be treated, Treat the support starting from the areas to be treated.

[0053] According to one example, the areas to be treated comprise areas to be etched and the treatment step comprises a step of etching the support from the areas to be etched.

[0054] According to one example, the areas to be treated comprise areas to be implanted and the treatment step comprises a step of implanting the support from the areas to be implanted.

[0055] According to an advantageous embodiment, the step of exposing the areas to be treated comprises the following steps: Expose the first layer with a third dose D3 such as 12 mJ / cm2 <D3<Dinversion au travers d’un masque de photolithographie, Effectuer une étape de développement en mettant en contact la résine photosensible avec le développeur de sorte à faire se dissoudre les parties exposées avec D3.

[0056] According to an advantageous embodiment, the method further comprises, after the step of exposing the first portion, the following steps: Remove the second portion, Form a second layer of photosensitive resin over the support,

[0057] and the step of exposing the areas to be treated includes the following steps: Expose the second layer with a third dose D3 such as 12 mJ / cm2 <D3<Dinversion au travers d’un masque de photolithographie, Effectuer une étape de développement en mettant en contact la résine photosensible avec le développeur de sorte à faire se dissoudre les parties exposées avec D3.

[0058] According to an advantageous example, the first portion extends in the transverse plane over a radial dimension 124, with 3mm < 124, preferably 5mm < 124. According to one example, 124 < 3 cm. According to another example, 124 < 2 cm.

[0059] According to an advantageous example, the photosensitive resin is composed of at least 5% of a polyhydroxystyrene derivative, at least 55% ethyl lactate and at least 20% propylene glycol methyl ether acetate (PGMEA).

[0060] According to an advantageous example, the support is based on at least one material from among the following materials: Si, SiC, GaN, SiGe, Ge, sapphire, glass, InP, AsGa. The support is advantageously based on a III-V material, for example a III-N material. The support may also be a substrate of the silicon-on-insulator type (commonly referred to as SOI, from the English Silicon-On-Insulator), of the silicon-on-silicide-on-insulator type (commonly referred to as SSOI, from the English Silicon-On-Silicide-On-Insulator), or of the germanium-on-insulator type (commonly referred to as GeOI, from the English Germanium-On-Insulator).

[0061] According to an advantageous example, the protective coating has in a third direction perpendicular to the transverse plane a thickness elOO greater than 250 nm, preferably greater than 500 nm. Typically, elOO < 1 pm.

[0062] According to an advantageous example, Dl>90mJ / cm2.

[0063] According to an advantageous example, in the transverse plane, the central zone has the shape of a disc and the peripheral zone has the shape of a circular crown.

[0064] It is specified that, in the context of the present invention, the terms "on", "overcomes", "covers", "underlying", "facing" and their equivalents do not necessarily mean "in contact with". Thus, for example, the deposition, transfer, bonding, assembly or application of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it or by being separated from it by at least one other layer or at least one other element.

[0065] A layer may also be composed of several sub-layers of the same material or of different materials.

[0066] A substrate, a layer, a device, “based” on a material M, is understood to mean a substrate, a layer, a device comprising this material M only or this material M and possibly other materials, for example alloying elements, impurities or doping elements. Thus a material based on an IILN material may comprise an IILN material with added dopants. Similarly, a GaN-based layer typically comprises GaN and AlGaN or InGaN alloys.

[0067] The term "III-V material" refers to a semiconductor composed of one or more elements from column III and column V of Mendeleev's periodic table. Elements in column III include boron, gallium, aluminum, and indium. Column V contains, for example, nitrogen, arsenic, antimony, and phosphorus.

[0068] The term “selective etching with respect to” or “etching having a se selectivity with respect to » an etching configured to remove a material A or a layer A with respect to a material B or a layer B, and having an etching rate of the material A greater than the etching rate of the material B. The selectivity is the ratio between the etching rate of the material A and the etching rate of the material B. The selectivity between A and B is noted SA:B.

[0069] In the present patent application, we will preferentially speak of thickness for a layer and of height for a structure or a device. The thickness is taken along a direction normal to the main extension plane of the layer, and the height is taken perpendicular to the base plane XY. Thus, a layer typically has a thickness along z, when it extends mainly along an XY plane, and a projecting element, for example an isolation trench, has a height along z. The relative terms “on”, “under”, “underlying” preferentially refer to positions taken along the z direction.

[0070] A parameter “substantially equal / greater / less than” a given value means that this parameter is equal / greater / less than the given value, plus or minus 20%, or even 10%, close to this value. A parameter “substantially between” two given values ​​means that this parameter is at least equal to the smallest given value, plus or minus 20%, or even 10%, close to this value, and at most equal to the largest given value, plus or minus 20%, or even 10%, close to this value.

[0071] In the context of the present invention, a resin is defined as an organic or organo-mineral material that can be shaped by exposure to a beam of electrons, photons, X-rays, a beam of light in the ultraviolet, extreme ultraviolet (UEV) or deep ultraviolet (Deep UV) range, typically in the wavelength range from 193 nm to 248 nm, the emission lines of a mercury lamp, i.e.: 365 nm for the I line, 435 nm for the G line and 404 nm for the H line. The invention also applies to resins that can be shaped mechanically, in particular by thermally assisted printing or by ultraviolet rays.

[0072] In the context of the present invention, the resins used are positive tone resins usually used in lithography. These positive tone resins can have their tone inverted, to exhibit negative tone resin behavior when they receive a dose greater than an inversion dose.

[0073] A positive resin is said to have its tone reversed to become a negative resin if, after exposing an area of ​​the positive resin by applying a dose D>Dinversion, the pattern defined by the exposed area does not dissolve when it is brought into contact with a developer that dissolves the same resin when it exhibits its initial behavior as a positive resin. This exposed area therefore remains in place at the end of a classic development step, a development step which would make it possible to remove the areas of this resin exposed to a dose lower than an activation dose Dactivation. Furthermore, as long as it is not exposed to a dose higher than Dactivation, the resin is also sensitive to a new coating of resin, and more particularly to the solvent of this resin.

[0074] It is understood that a development step may comprise one or more contactings of the resin with a developer, called development sub-steps. The different development sub-steps may be implemented using the same developing solution or several developing solutions. It is also possible to follow the development step with a cleaning step to remove resin residues. To determine whether a resin has this ability to have its tone reversed, several methods exist. For example, a contrast curve (usually referred to as a "contrast curve"), well known to those skilled in the art, may be produced for this resin.To produce this curve, the thickness of the resin remaining after development can be measured as a function of the exposure dose applied to the resin, this exposure dose being chosen in a range well above the range usually used for this resin.

[0075] The contrast curve then shows on the abscissa axis the applied doses and on the ordinate axis the measured thicknesses of resin after each exposure and development cycle. Typically, for an abscissa value between zero and Dactivation, the curve corresponds to a thickness of the resin which remains constant and which is substantially equal to the initial thickness of the resin. For a dose D greater than or equal to Dactivation, the thickness becomes zero because the resin is developed. Then, if an increase in the abscissa of the exposure dose causes an increase in the thickness of the resin, this means that this resin exhibits this inversion behavior. This increase in thickness also makes it possible to identify the exposure threshold Dinversion beyond which this inversion takes place. Preferably, beyond this threshold Dinversion the thickness of the resin remains constant and is close to its initial thickness.

[0076] Examples of resins conventionally used in microelectronics include resins based on methacrylate (for example Polymethyl methacrylate PMMA), polyhydroxystyrene (PHS) and resins based on photodecomposition principles such as azide quinone resins, ie, diazonaphthaquinone (DQ). For example, it is possible to use a resin belonging to the M series marketed by JSR Life Sciences, for example the M78Y and M79Y resins.

[0077] In the present description, a dose is defined as a quantity of energy received by a resin per unit area. This energy may be in the form of photons (photolithography) for a photosensitive resin. The dose is then usually expressed in Joules per m2, or more often in milli Joules (mJ) per cm2 (102 m2) or in mJ / m2.

[0078] This energy can also be in the form of electrons (electron lithography) for an electrosensitive resin. The dose is then usually expressed in Coulombs per m2, or more often in micro Coulombs (pC) per cm 2 (10 2 m2) or in pC / m2.

[0079] The term "nature" of a material such as a resin means its chemical composition, that is to say the nature and proportion of the species constituting the material. Two layers are considered to be made of the same resin if they have the same chemical composition.

[0080] The same resin may have areas whose behaviors differ with respect to the development solutions. The differentiation of these areas is obtained by the energy dose applied during an exposure to each of these areas. Thus, these areas differ by their molar mass. For example, these molar masses can be measured by chromatography or by mass spectrometry.

[0081] Thus two portions or zones of the same resin can be of the same chemical composition but have different tones.

[0082] The steps of the method as claimed are understood in the broad sense and may optionally be carried out in several sub-steps.

[0083] A reference frame, preferably orthonormal, comprising the axes x, y, z is represented in figures 1A, 2A, 3A and 4A. This reference frame is applicable by extension to the other figures.

[0084] Several examples of embodiments of the method for transforming a support 10 will now be described with reference to FIGS. 2A to 3M.

[0085] [Fig.2A] illustrates the provision of the support 10. This support is typically a wafer, commonly referred to by the English term “wafer”. It is conventionally a silicon wafer. It can also be a SiC or GaN substrate or even an SOI (“Silicon-On Insulator”) or GeOI (“Germanium-On-Insulator”) stack.

[0086] The support 10 has an upper face 11 and a lower face 12 both extending mainly in the XY plane of the orthogonal reference frame XYZ. It also has a lateral flank 103, called the first lateral flank 103, joining the upper face 11 and the upper face 12.

[0087] In a completely conventional manner, the support 10 and therefore its upper face 11 have the shape of a disc in the XY plane. The upper face 11 of the support 10 is made up of two zones: • a central zone 15 preferably also having the shape of a disc in the XY plane, • a peripheral zone 14 advantageously having the shape of a crown circular in the XY plane.

[0088] The peripheral zone 14 forms a closed contour around the central zone 15. The central zone 15, the peripheral zone 14 and the upper face 11 are preferably concentric in the XY plane.

[0089] As illustrated in [Fig.2B], a first layer 20 of a photosensitive resin is then formed on the upper face 11 of the support 10. It also has an upper face 21 and a lower face 22 both extending mainly in the XY plane.

[0090] The photosensitive resin has the characteristic, as described extensively above, of having: • Positive resin behavior as long as it has not been exposed to a dose higher than the Dinversion dose. The resin then dissolves when brought into contact with a developer. • Negative resin behavior when exposed to a dose greater than the Dinversion dose.

[0091] A first portion 24 of the first layer 20 is exposed to an insolation dose DI greater than or equal to Dinversion. The first portion 24 is located directly above at least part of the peripheral zone 14. A second portion 25 of the first layer 20 is exposed to an insolation dose strictly less than Dinversion, or is not insolated at all. The second portion 25 covers at least part of the central zone 15 of the upper face 11 of the substrate 10.

[0092] Once exposed to a dose greater than Dinversion, the first portion 24 is therefore resistant to contact with a developer. A protective coating 100 is thus obtained consisting of the negative-toned resin, which corresponds to the first portion 24. This is illustrated by FIGS. 2D and 4A, constituting respectively a profile view and a top view of the stack.

[0093] Another embodiment of the protective coating 100 will now be described with reference to FIGS. 3A to 3G.

[0094] Figures 3A and 3B illustrate steps similar to those illustrated by Figures 2A and 2B, respectively.

[0095] In this embodiment, the protective coating 100 is obtained, in a similar manner to the previous embodiment, by exposing the first portion 24 to an insolation dose greater than the inversion dose Dinversion. However, this time it is provided that the first portion 24 undergoes two insolation steps, illustrated in FIGS. 3C to 3F: • A first exposure to a dose Dl' of the first portion 24 only, • A second exposure to a dose Dl” of the first portion 24 and the second portion 25.

[0096] The total dose received by the first portion 24 makes it possible to make it negative: Dl'+Dl” > Dinversion. It is conceivable that the first exposure is sufficient to reverse the behavior of the resin constituting the first portion 24, i.e. that Dl' > Dinversion. It is also entirely possible to provide that the inversion of behavior takes place during the second exposure, i.e. that Dl' < Dinversion but Dl'+Dl” > Dinversion. In all cases, we have Dl” < Dinversion: the second portion retains a positive resin behavior following the second exposure.

[0097] The second exposure can also simultaneously constitute a conventional photolithography step: the dose D1” can be calibrated so as to allow development of the second portion 25. The latter can in fact, following its exposure to the dose D1”, be developed using a developer and thus be removed by dissolution, as illustrated by the transition from [Fig.3F] to [Fig.3G]. This step is also illustrated by the transition from [Fig.4A] to [Fig.4B], pendants in top view of figures 3F and 3G.

[0098] The protective coating 100 is obtained either during the first exposure (transition from [Fig.3C] to [Fig.3D]), or during the second exposure. It does not undergo any damage during the development of the second portion 25.

[0099] Following the obtaining of the protective coating 100 by one of the embodiments described above, the method can continue with steps of treatment of the central zone 15. More particularly, it may be sought to treat only certain parts of the central zone 15, called zones to be treated 13. Depending on the framework in which the method according to the invention is implemented, the treatment in question can be an etching - wet or dry -, an implantation, a cutting or singulation step, etc.

[0100] It is thus possible, following the first embodiment of the protective coating 100 described above, to expose the first layer 20 to a dose of insolation through a photolithography mask 1000 ([Fig.2E]). The behavior of the protective coating 100 will remain unchanged after this insolation, while the exposed patterns 26 of the second portion 25 can be developed by bringing them into contact with a developer (Figures 2F and 2G).

[0101] The parts of the upper face 11 of the support 10 updated during the removal of the patterns 26 correspond to the areas to be treated 13.

[0102] The areas to be treated 13 can then be treated without altering the bevel, protected by the protective coating 100. This treatment can comprise one or more steps. Among the possible treatment steps, we can cite for example an etching - wet or dry -, an implantation, a cutting step or singula- rization... [Fig.2H] illustrates for example a step of etching the support 10 from the areas to be treated 13. As illustrated, thanks to the presence of the protective coating 100, the peripheral area 14, or at least the part of the peripheral area 14 underlying the first portion 24, comprising the bevel, does not suffer any damage due to the etching (or any other treatment step).

[0103] As illustrated in [Fig.2I], the remaining parts of the first layer 20 as well as the protective coating 100 can be removed during a step subsequent to the support treatment steps. A support is then obtained having an intact, uncontaminated bevel and with an excellent surface condition. This removal can for example be carried out by stripping, for example plasma (in English “plasma stripping”), and wet etching.

[0104] After this removal, it is possible, for example, to proceed with bonding the support with another element. The quality of this bonding is improved compared to the prior art due to the good state of cleanliness and the excellent integrity of the bevel.

[0105] In this first embodiment, the first layer 20 therefore has a dual role: it allows both, at its first portion 24 which is transformed into a protective coating 100, to protect the bevel, and to carry out a conventional photolithography step at its second portion 25. The protection of the bevel and the treatment of the central zone 15 of the support are therefore both enabled by a single resin deposit. The method according to this embodiment is therefore particularly simple and allows a reduction in the number of process steps - and therefore a significant saving in time.

[0106] Another embodiment of the continuation of the method for treating the support 10 after obtaining the protective coating 100 according to the steps illustrated by FIGS. 3A to 3G will now be described with reference to FIGS. 3H to 3M.

[0107] As shown in [Fig.3H], a second layer 30 of photosensitive resin is deposited on the support 10. More precisely, the second layer 30 directly covers the central zone 15 of the upper face 11 of the support and the upper face 101 of the protective coating 100. The latter corresponds to the part of the upper face 21 of the first layer 20 extending above the first portion 24. Such a full-plate deposition has the advantage of being very easy to carry out technically. The fact that the second layer 30 extends over the protective coating has no impact on the rest of the process.

[0108] The photosensitive resin of the second layer 30 may be the same as that used for the first layer 20. This has an advantage in terms of the behavior at the interface between the first layer 20 and the second layer 30. However, it may also be another photosensitive resin. In particular, it is not necessary for the resin of the second layer 30 to be invertible.

[0109] The second layer 20 can then be exposed to an insolation dose through a photolithography mask 1000 ([Fig.31]). The exposed patterns 36 of the second layer 30 can be developed using a developer.

[0110] As in the embodiment described previously, this removal makes it possible to update certain parts of the upper face 11 of the support 10 corresponding to the areas to be treated 13.

[0111] As previously, the areas to be treated 13 can then be treated (etching, implantation, etc.) without this altering the bevel, protected by the protective coating 100. [Fig. 3L] illustrates, for example, a step of etching the support 10 from the areas to be treated 13. The bevel, being under the protective coating 100, does not suffer any damage due to the etching (or any other treatment step).

[0112] [Fig.3M] illustrates an optional step of removing the remaining parts of the second layer 30 as well as the protective coating 100. A support is then obtained having an intact, uncontaminated bevel and with an excellent surface condition.

[0113] Whatever the method of carrying out the process, the dimensions of the protective coating are chosen so as to protect the bevel.

[0114] The protective coating 100 has in the transverse plane XY a radial dimension 1100 measured from the center O of the wafer. In the same way, a radial dimension 114 of the peripheral zone 14, a radial dimension 124 of the first portion 24, a radius RI5 of the central zone and a radius R25 of the second portion are defined. By construction, the protective coating being formed by insolation of the first portion 24, we have 1100=124.

[0115] The distance from the protective coating 100 to the extreme periphery of the support 10 is characterized by the radial distance dl03 in the XY plane between the flank 13 of the support, called the first lateral flank 13, and the flank 103 of the coating 100 (see [Fig.4C]). As shown in the figures, the flank 13 of the support may be curved. The position in the XY plane of this first lateral flank 13 is then assimilated to the position of the joint between the flank 13 and the upper face 11 of the support.

[0116] Advantageously, the distance dl03 is less than or equal to 0.5 cm, preferably less than or equal to 0.2 cm. Preferably, the lower face 102 of the protective coating 100 extends from the periphery of the support 10 in order to obtain the best protection for the bevel: the distance dl03 is then substantially zero, as illustrated in FIGS. 2D, 3G and 4A.

[0117] Advantageously, the protective coating 100 covers the entire peripheral zone 14 and we thus have 1100=124=114.

[0118] For a wafer of radius R, 1100 is advantageously between 1% and 20% of R, preferably between 5% and 15%, preferably between 5% and 10%. For a wafer of 300 millimeters in diameter, 1100 is preferably between 0.5 and 3 cm.

[0119] During its formation, the protective coating 100 also has a thickness el00 along the direction. This thickness is chosen according to the level of degradation that the coating 100 will undergo during the subsequent steps of treatment of the central zone 15. The coating 100 must in fact be sufficiently thick to protect the bevel until the end of these steps. For example, if these steps include one or more steps of etching the support, the choice of the thickness el00 is made, among other things, according to the selectivity of the etching between the material of the support and the photosensitive resin. Typically, el00 is greater than or equal to 250 nm, preferably greater than or equal to 500 nm.

[0120] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

Claims

1. Method for transforming a support comprising the following steps: • Provide a support (10) having an upper face (11) extending mainly along a plane formed by a first direction (X) and a second direction (Y), called the transverse plane (XY), • Producing a protective coating (100) at least partially covering a peripheral zone (14) of the upper face (11) forming a closed contour around a central zone (15) of the upper face (11), the peripheral zone (14) and the central zone (15) together forming the entirety of the upper face (11), the production of the protective coating (100) comprising the following steps: • Form a first layer (20) of a photosensitive resin covering the upper face (11) of the support (10), the photosensitive resin being such that: i. when the resin is exposed to a dose of insolation D <Dinversion, elle présente un comportement de résine positive et se dissout lorsqu’elle est mise en contact avec un développeur, et ii. when the resin is exposed to an insolation dose D>Dinversion, it exhibits negative resin behavior and does not dissolve when brought into contact with the developer, • Exposing a first portion (24) of the first layer (20) of photosensitive resin with a first dose of exposure Dl> Dinversion, the first portion (24) covering strictly the same surface of the upper face (11) as the protective coating (100), so as to form the protective coating (100), • Expose a second portion (25) of the first layer (20) with a second dose of D2 exposure <Dinversion ou ne pas insoler la deuxième portion (25), la deuxième portion (25) overcoming at least a part of the central zone (15), the method being characterized in that it further comprises the following steps: • Exposing a plurality of zones of the central zone (15) of the support (10), called zones to be treated (13), • Treating the support (10) from the zones to be treated (13), the step of exposing the zones to be treated (13) comprising the following steps: • Exposing the first layer (20) with a third dose D3 such as 12 mJ / cm2 <D3<Dinversion au travers d’un masque de photolithographie (1000), • Effectuer une étape de développement en mettant en contact la résine photosensible avec le développeur de sorte à faire se dissoudre les parties exposées avec D3.

2. Method according to the preceding claim, in which the support (10) has a first lateral flank (13) and the protective coating (100) has a second lateral flank (103), the first lateral flank (13) and the second lateral flank (103) being separated, in the transverse plane (XY), by a radial distance dl03 less than or equal to 0.5 cm, preferably less than or equal to 0.2 cm.

3. Method according to the preceding claim, in which dl03 is substantially equal to 0 cm.

4. A method according to any preceding claim, wherein the areas to be treated (13) comprise areas to be etched (13) and wherein the treatment step comprises a step of etching the support (10) from the areas to be etched (13).

5. A method according to any preceding claim, wherein the areas to be treated (13) comprise areas to be implanted (13) and wherein the treatment step comprises a step of implanting the support (10) from the areas to be implanted (13).

6. Method according to any one of the preceding claims in which the first portion (24) extends in the transverse plane (XY) over a radial dimension 124, with 3mm < 124, preferably 5mm < 124.

7. A method according to any one of the preceding claims wherein the photosensitive resin is composed of at least 5% of a polyhydroxystyrene derivative, at least 55% of ethyl lactate and at least 20% of propylene glycol methyl ether acetate (PGMEA).

8. Method according to any one of the preceding claims in which the support (10) is based on at least one material among the following materials: Si, SiC, GaN, SiGe, Ge, sapphire, glass, InP and AsGa.

9. Method according to any one of the preceding claims in which the protective coating (100) has in a third direction (Z) perpendicular to the transverse plane (XY) a thickness elOO greater than 250 nm, preferably greater than 500 nm.

10. A method according to any preceding claim wherein Dl>90mJ / cm2.

11. A method according to any preceding claim wherein, in the transverse plane (XY), the central area has the shape of a disc and the peripheral area has the shape of a circular crown.

Images