METHOD FOR MANUFACTURING A HANDLE SUBSTRATE INTENDED FOR TEMPORARY BONDING OF A SUBSTRATE

Abstract

A method for manufacturing a handle substrate, the method including the steps of: a) providing a support substrate comprising a receiving face, b) forming a film by depositing an anti-adherent formulation including a first solvent over the receiving face of the support substrate, c) depositing a liquid formulation over a face of the film, before the complete evaporation of the first solvent, the liquid formulation being intended to form an adhesive layer, and has a γ.sub.l(liquid) surface energy, and d) evaporating the first solvent so as to obtain anti-adherent film from the film in order to obtain the handle substrate, the anti-adherent film allowing obtaining a bonding energy with the adhesive layer that is low enough: <1.2 J/m.sup.2 or advantageously <0.4 J/m.sup.2.

Claims

1. A method for manufacturing a handle substrate, the method comprising the steps of: a) providing a support substrate comprising a receiving face, b) depositing an anti-adherent formulation comprising a first solvent over the receiving face of the support substrate so as to form a film, c) depositing a liquid formulation over a face of the film, before the complete evaporation of the first solvent, the liquid formulation being intended to form an adhesive layer, and d) evaporating the first solvent so as to obtain anti-adherent film from the film in order to obtain the handle substrate and to obtain a bonding energy between the anti-adherent film and the adhesive layer lower than about 1.2 J/m.sup.2.

2. The method for manufacturing a handle substrate according to claim 1, wherein step c) is carried out when said face of the film has a water drop angle smaller than 65 degrees during the deposition of the liquid formulation at step c), so as to avoid any risk of dewetting of the liquid formulation.

3. The method for manufacturing a handle substrate according to claim 1, comprising, between step b) of forming the film and step c) of depositing the liquid formulation, the completion of a step i) of storing the structure comprising the film deposited over a receiving face of a support substrate in an enclosure saturated with the first solvent so as to keep the first solvent within the film.

4. The method for manufacturing a handle substrate according to claim 1, wherein steps a) and/or b) are carried out in an enclosure saturated with the first solvent.

5. The method for manufacturing a handle substrate according to claim 1, wherein step d) is carried out by application of a heat treatment.

6. The method for manufacturing a handle substrate according to claim 1, wherein the support substrate is selected from silicon, silica, glass, sapphire, SiC, germanium, a III-V material, a piezoelectric material or a metal, the anti-adherent film comprises an anti-adherent material and the adhesive layer comprises an organophilic material.

7. A method for manufacturing a detachable substrate, the method comprising the steps of: k) providing the handle substrate obtained according to claim 1, l) providing a substrate comprising a front face and a rear face, the rear face being intended to receive electronic components, m) setting the front face of the substrate and an exposed face of the adhesive layer of the handle substrate in contact, so as to obtain a detachable by temporary bonding of the substrate to the handle substrate.

8. The method for manufacturing a detachable substrate according to claim 7, wherein the method comprises, after step m), a step n) of heat treatment for reinforcing the bonding between the substrate and the handle substrate.

9. The method for manufacturing a detachable substrate according to claim 7, wherein the method comprises, after step m), a step o) of applying to the rear face of the substrate at least one treatment step intended for the manufacture of electronic components, such as a rectification, a thinning, a chemical-mechanical polishing, an etching, a dielectric or metal deposition, a patterning, a passivation, a heat treatment, or a combination of at least one of these treatments.

10. The method for manufacturing a detachable substrate according to claim 8, comprising a step p) of detachment at the interface between the anti-adherent film and the adhesive layer so as to detach the substrate.

Description

[0084] Other aspects, objects and advantages of the present invention will appear better upon reading the following description of an embodiment thereof, provided as non-limiting examples and made with reference to the appended drawings. In the following description, for simplicity, identical, similar or equivalent elements of the different embodiments bear the same reference numerals. To improve readability, the figures are not necessarily to the scale of all of the represented elements, wherein:

[0085] FIG. 1 illustrates steps a) to d) of a method for manufacturing a handle substrate according to an embodiment of the invention, and

[0086] FIG. 2 illustrates the step i) of storing a structure obtained at step b) of the method for manufacturing a handle substrate, and

[0087] FIG. 3 illustrates steps k) to p) of a method for manufacturing a detachable substrate according to an embodiment of the invention.

[0088] FIG. 1 represents a method for manufacturing a handle substrate 100 according to an embodiment of the present invention. As illustrated, a support substrate 1 is provided according to step a) of the method. The deposition of an anti-adherent formulation over a receiving face of the support substrate 1 is carried out according to step b) of the method. This deposition leads to the formation of a film 2 composed by an anti-adherent material and by a first solvent. According to a possibility that is not shown in FIG. 1, the deposition is carried out by spreading the anti-adherent formulation by spin coating. According to a non-illustrated variant, the deposition is carried out by spreading by immersion or by spraying.

[0089] According to step c) of the method, a liquid formulation intended to form an adhesive layer 3 is deposited over an exposed face of the film 2 so as to form a layer 5. This step c) is performed before the elapse of a predetermined duration Δt to be counted as of the exposure of said film 2 to ambient air to avoid the complete evaporation of the first solvent. Indeed, the formation of this layer 5 without unwetting is made possible by the fact that the film 2 contains enough first solvent for its drop angle to remain smaller than 65 degrees and preferably smaller than 60 degrees at the time of deposition of the liquid formulation according to step c). The liquid formulation comprises an organic material and a second solvent. It has a surface energy γ.sub.l (liquid).

[0090] According to a possibility that is not shown in FIG. 1, the deposition of the layer 5 is carried out by spreading the liquid formulation by spin coating.

[0091] Afterwards, a step d) of evaporating the first solvent is performed to lead to the formation of the anti-adherent film 4 from the film 2 obtained at step b). If it is structured alone (without the deposition of the adhesive layer before the end of the evaporation of the solvent), the anti-adherent film 4 would have a (‘natural’) surface energy γ.sub.s(substrate) that is lower than the surface energy of the liquid adhesive formulation γ.sub.l(liquid), and preferably γ.sub.l(liquid)−γ.sub.s(substrate)>5 J/m.sup.2 and still preferably γ.sub.l(liquid)−γ.sub.s(substrate)≥10 J/m.sup.2.

[0092] The second solvent is evaporated concomitantly and an adhesive layer 3 is obtained from the liquid formulation deposited at step c).

[0093] According to one possibility, step d) is carried out by application of a heat treatment on the structure obtained at step c). The heat treatment accelerates the kinetics of evaporation of the first solvent and of the second solvent, where appropriate.

[0094] According to other variants, step d) is carried out by leaving the structure obtained at step c) at ambient temperature under an ambient atmosphere or by placing the structure obtained at step c) in vacuum.

[0095] The handle substrate 100 obtained in this manner includes a support substrate 1, an anti-adherent film 4 formed over the receiving face of the support substrate 1, an adhesive layer 3 deposited over the anti-adherent film 4. Should it be structured alone, the anti-adherent film would have a lower surface energy γ.sub.s(substrate) than the surface energy of the liquid adhesive formulation γ.sub.l(liquid), preferably γ.sub.l(liquid)−γ.sub.s(substrate)>5 J/m.sup.2 and still preferably γ.sub.l(liquid)−γ.sub.s(substrate)≥10 J/m.sup.2.

[0096] It should be noted that the surface energy γ.sub.finitial(initial film) of the film 2 at step c) is higher than the surface energy γ.sub.l(liquid) enabling the deposition without unwetting.

[0097] The support substrate 1 is selected from silicon, silica, glass, sapphire, SiC, germanium, a III-V material such as AsGa, GaN or InP, a piezoelectric material such as LNO/LTO or a metal (for example molybdenum, tungsten, titanium, platinum and copper). The anti-adherent film 4 comprises an anti-adherent material such as a hydrophobic polymer, for example a fluorinated polymer such as EGC 2702, EGC 1700, a FDTS or an organosilane polymer such as OTS. It has a thickness smaller than 50 nm and preferably comprised between 1 and 15 nm. A thicker anti-adherent film 4 considerably reduces the evaporation capacity of the first solvent and thus the anti-adherent nature of the film 4 obtained at step d). The drop angle measurements of such anti-adherent films 4 obtained on completion of a complete drying are larger than 80 degrees and preferably larger than 100 degrees.

[0098] The adhesive layer 3 of the handle substrate 100 comprises an organic material, such as an organic polymer, preferably BrewerBOND®305, BsiT09001A supplied by Brewer Science. Its thickness is comprised between 20 and 50 micrometers. The drop angles of such an adhesive layer 3 are comprised between 50 and 60 degrees.

[0099] These pairs of anti-adherent films 4 and adhesive layers 3 allow limiting the adherence energy of the detachable substrate 400 targeted by the present invention as it will be shown hereinafter.

[0100] According to a variant of the method for manufacturing the handle substrate 100, illustrated in FIG. 2, step c) is preceded by a step i) of storing the structure 200 obtained at step b) comprising the film 2 formed over a receiving face of the support substrate 1, in an enclosure 300 saturated with the first solvent so as to limit the evaporation of the first solvent contained in the film 2. Thus, the drop angle of the film barely varies during the storage and the structure 200 could be used to perform step c) even after several hours and even 24 hours or more.

[0101] For this purpose, the inventors have considered an enclosure 300 comprising a reactor provided with two sealed compartments, contiguous to one another and configured so as to enable a fluidic communication therebetween, as illustrated in FIG. 2. A first compartment 6 is configured to receive a source 7 of a first solvent intended to generate an atmosphere saturated with the first solvent. The second compartment 8 is configured to receive said structure 200. The sequence of steps of handling the enclosure 300 for storage is illustrated by the contiguous diagrams of FIG. 2, according to a chronological order. The second compartment 8 comprises an outer wall throughout which a sealed door 9 is formed and configured for the introduction of said newly spread structure (and for removal thereof). A sealed open-close device 11 disposed between the two compartments is open to enable the circulation of the solvent in both compartment. Configured this way, the sealed reactor has an optimum effectiveness to avoid the evaporation of the first solvent contained in the film 2 before carrying step c).

[0102] These precautions taken in the storage in an enclosure 300 saturated with the first solvent and the fact that step c) is carried out before the elapse of a predetermined duration Δt to be counted as of the exposure of the film 2 to ambient air, outside the enclosure 300, (or under a N2, He atmosphere), allow keeping the surface energy γ.sub.finitiai(initial film) higher than that of the liquid formulation γ.sub.l(liquid) and thus depositing the liquid formulation of an organophilic material to form the layer 5 over an anti-adherent film.

[0103] Indeed, depending on the kinetics of the evolution of the drop angle of the film 2 after step b), the drop angle increases with the duration of contact with air (or N2, He) and the evaporation of the first solvent present in the film 2. Thus, the predetermined duration Δt is determined according to the value of the drop angle which directly depends on the surface energy of the film. Also, the predetermined duration Δt is shorter than or equal to 30 min for an example of a material consisting of EGC 2702 diluted in a first solvent EGC 2700 so as to maintain a drop angle smaller than 65° during the completion of step c).

[0104] According to a variant that is not shown in FIG. 2, the support 1 is directly provided in the enclosure 300 saturated with the first solvent (step a), and then step b) of depositing the anti-adherent formulation for the formation of the film 2 is also carried out in the enclosure 300 saturated with the first solvent. A storage step i) may prolong the stay of the structure 200 in the enclosure 300 before carrying step c).

[0105] According to another aspect illustrated in FIG. 3, the invention provides the manufacture of a detachable substrate 400. For this purpose, a substrate 12 having a front face 13 and a rear face 14 and a handle substrate 100 as previously described are provided according to steps k) and l) of the method. An exposed face of the adhesive layer 3 of the handle substrate 100 is set in contact with the front face 13 of the substrate 12 for a temporary bonding according to step m) of the method enabling the obtainment of the detachable substrate 400. Then, a heat treatment for reinforcing the bonding is applied according to a step n) (not shown in the figures). Typically, the adherence energy of the detachable substrate 400 obtained in this manner is comprised between 150 and 1200 mJ/m.sup.2.

[0106] The material of the substrate 12 is selected from silicon, glass, sapphire, germanium, SiC, a III-V material such as AsGa, GaN, InP, a piezoelectric material such as LNO/LTO or a metal such as molybdenum, tungsten, titanium, platinum and copper, depending on the nature of the desired subsequent operations.

[0107] According to an arrangement that is not shown in the figures, when the liquid formulation is LC 5200 supplied by 3M®, the substrate 12 is advantageously made of glass to enable the insulation of the compound LC5200 throughout the glass and complete the temporary bonding with the substrate 12.

[0108] The obtained detachable substrate 400 is then subjected to the application of a treatment step o) intended for the manufacture of electronic components and applied on the exposed rear face 14 of the substrate 12 (that is to say the surface devoid of any bonding or complementary layer as the front face 13 is bonded to the handle substrate 100). For example, this treatment step comprises a rectification, a thinning, a chemical-mechanical polishing, an etching, a dielectric or metal deposition, a patterning, a passivation, a heat treatment, or a combination of at least one of these treatments.

[0109] Afterwards, a detachment step p) is carried out on the detachable substrate 400 prepared in this manner so as to detach the substrate 12 at least partially treated or functionalized. This detachment step p) is conventionally done through a series of chemical and/or mechanical actions.

[0110] Some control examples and examples of carrying out the method for manufacturing a handle substrate 100 and a detachable substrate 400 according to the present invention are given hereinbelow.

[0111] The following examples have been performed by means of 200 mm diameter silicon wafers.

EXAMPLE 1

Anti-Adherent Film 4 Comprising the Fluorinated Polymer EGC 2702

[0112] The fluorinated polymer EGC 2702 is commercialized as a solution in the solvent EGC 7200.

[0113] Controls: Over a silicon wafer, 40 μm of BrewerBOND®305, available from the company Brewer Science, are spread by spin coating. Afterwards, the substrate is annealed at 200° C. and then bonded at 200° C. to a second silicon wafer. The adherence of this structure is estimated to 2000 mJ/m.sup.2.

[0114] Over a silicon wafer, a film of EGC 2702 is spread and then annealed at 150° C. The surface features a water drop angle of 105°. Spreading by spin coating of 40 μm of the adhesive BrewerBOND®305 at the surface of this treated substrate leads to an unwetting of the adhesive.

[0115] Example of implementation of the invention: Over a support substrate 1 made of silicon, a film of EGC 2702 in the first solvent 7200 is spread according to step b) of the method. After the elapse of a predetermined duration Δt of 20 min after spreading, this structure 200 is stored according to step i) in an enclosure 300 saturated with EGC 7200. After one day, the structure 200 is extracted from the enclosure 300 and a liquid formulation of BrewerBOND®305 is immediately spread by spin coating according to step c) in order to form an adhesive layer 3 of 40 μm over the surface of the film 2. The adhesive layer 3 is homogeneous and no unwetting is observed. The set is annealed by a heat treatment at 200° C. for 5 minutes according to step d) of the method so as to obtain the handle substrate 100.

[0116] Setting this handle substrate 100 in contact at 200° C. with a rear face 14 of a silicon substrate according to step m) leads to the obtainment of a detachable substrate 400 having a low adherence energy of 400 mJ/m.sup.2 which confirms the organophobic and anti-adherent nature of the fluorinated film 4 structured this way.

EXAMPLE 2

Anti-Adherent Film 4 Comprising Perfluorodecyltrichlorosilane (FDTS)

[0117] The fluorinated polymer FDTS is solubilized in isooctane.

[0118] Control: Over a silicon wafer, a liquid formulation of the adhesive BsiT09001A is spread by spin coating over a 50 μm thickness. Afterwards, this substrate is annealed at 200° C. for 5 minutes and then bonded at 200° C. to a second silicon wafer. The adherence energy of this structure is estimated to 2000 mJ/m.sup.2.

[0119] Example of implementation of the invention: Over a support substrate 1 made of silicon, a formulation comprising FDTS dissolved in isooctane at 5.Math.10.sup.−3 mol/L is spread according to step b) of the method. Spreading by immersion consists in soaking the support substrate 1 in a solution of FDTS in isooctane for 5 minutes. The formed film has a thickness of 10 nm and the water drop angle is 40°. After the elapse of a predetermined duration Δt of 20 min after spreading, this wafer is placed in an enclosure 300 saturated with isooctane according to step i). After 24 h, the wafer is extracted from the enclosure 300, the water drop angle is 50 degrees (versus 120 degrees for the anti-adherent film 4 whose first solvent has totally evaporated). A liquid formulation of the adhesive BsiT09001A is spread by spin coating to form an adhesive layer 3 of 50 μm over the face of the film according to step c). The layer of the adhesive is homogeneous and no unwetting is observed. A heat treatment is performed at 200° C. for 5 minutes according to step d) of the method in order to obtain the handle substrate 100. Setting this handle substrate 100 in contact with a face of a silicon substrate according to step m) followed by a heat treatment applied at 200° C. according to step n) lead to the obtainment of a detachable substrate 400 having a low adherence energy of 900 mJ/m.sup.2 which confirms the anti-adherent nature of the fluorinated film structured this way.

EXAMPLE 3

Anti-Adherent Film 4 Comprising EGC 1700

[0120] The fluorinated polymer EGC 1700 is commercialized as a solution in the first solvent EGC 7100.

[0121] Control: Over a silicon wafer, 40 μm of the liquid formulation BrewerBOND®305 are spread by spin coating. Afterwards, the substrate is annealed at 200° C. and then bonded at 200° C. to a second silicon wafer. The adherence energy of this structure is estimated to 2000 mJ/m.sup.2.

[0122] Over a silicon wafer, a film of EGC 1700 is spread and then annealed at 120° C. The surface features a water drop angle of 105°. Spreading by spin coating of 40 μm of the adhesive BrewerBOND®305 at the surface of this treated substrate leads to an unwetting of the adhesive.

[0123] Example of implementation of the invention: Over a substrate made of silicon, a formulation of EGC 1700 in the first solvent 7100 is spread according to step b). After the elapse of a duration of 10 min, 40 μm of a liquid formulation of the adhesive BrewerBOND®305 is spread by spin coating over the face of the film according to step c). The adhesive layer 3 is homogeneous and no unwetting is observed. The set is annealed at 200° C. for 5 minutes according to step d). The hot bonding (200° C.) of this handle substrate 100 to a silicon substrate leads to the obtainment of a detachable substrate 400 having a low adherence energy of 200 mJ/m.sup.2 which confirms the organophobic and anti-adherent nature of the fluorinated film structured this way.

EXAMPLE 4

Anti-Adherent Film 4 Comprising the Compound OTS: CH.SUB.3.(CH.SUB.2.).SUB.17.SiCl.SUB.3

[0124] The compound OTS (CH.sub.3(CH.sub.2).sub.17SiCl.sub.3) is solubilized in isooctane at a concentration of 5.Math.10.sup.−3 mol/L.

[0125] Controls: Over a silicon wafer, 20 μm of the liquid formulation BrewerBOND®305 are spread by spin coating. Afterwards, the substrate is annealed at 200° C. and then bonded at 200° C. to a second silicon wafer. The adherence energy of this structure is estimated to 2000 mJ/m.sup.2.

[0126] Over a silicon wafer, a film of OTS is spread. Thus, a few mono-layers of OTS are grafted onto the silicon surface. The surface of the film features a water drop angle of 110°. Spreading by spin coating of 20 μm of the adhesive BrewerBOND®305 at the surface of this treated substrate leads to an unwetting of the adhesive.

[0127] Example of implementation of the invention: Over a support substrate 1 made of silicon, a film of OTS is spread according to step b). After the elapse of a predetermined duration of 20 min after spreading, this wafer is stored according to step i) in an enclosure 300 saturated with isooctane. After one day, the wafer is extracted from the enclosure 300 and a liquid formulation of the adhesive BrewerBOND®305 is spread by spin coating over its face so as to form an adhesive layer 3 having a thickness of 20 μm. The adhesive layer 3 is homogeneous and no unwetting is observed. The set is annealed at 200° C. according to step d). The hot bonding (200° C.) of this handle substrate 100 to a silicon substrate leads to the obtainment of a detachable substrate 400 having a low adherence energy of 80 mJ/m.sup.2 which confirms the anti-adherent nature of the film structured this way.

[0128] Thus, the present invention provides a method that is ingenious, easy to implement and inexpensive for the manufacture of a handle substrate 100 intended for temporary bonding of a substrate 12 to be treated.

[0129] It goes without saying that the invention is not limited to the embodiments described hereinabove as examples but it encompasses all technical equivalents and variants of the described means as well as combinations thereof.