Method for transferring a sealing layer

Abstract

The invention relates to a method for transferring a layer onto a carrier substrate, comprising: a) a step of forming cavities in the carrier substrate, said cavities being open via a main face, b) a step of transferring a sealing layer intended to seal all of said cavities formed during step a); a step a) is performed such that all the cavities are regularly distributed over a main region of the main face and such that the main face comprises a peripheral ring without cavities and within which the main region is circumscribed, the peripheral ring extending from an edge of the carrier substrate a length L shorter than a predetermined length Lp, lower than the length Lp, the sealing layer is free of non-transfer regions in the peripheral ring.

Description

Technical Field

[0001] This invention relates to the field of electromechanical microsystems and / or substrates, and particularly to the field of film-based devices.

[0002] Specifically, the present invention relates to a method for transferring layers intended to co-seal multiple cavities formed on a carrier substrate.

[0003] More specifically, the transfer method according to the invention aims to limit the occurrence of regions (referred to as non-transfer regions) that are prone to appear in the contour of the carrier substrate. Background Technology

[0004] Layer transfer methods are now widely used when forming suspended membranes and / or sealed cavities.

[0005] In this regard, such methods may include performing the following steps:

[0006] Ai) provides donor substrate 1 ( Figure 1 ) and carrier substrate 2 ( Figure 2 In the step of ), the carrier substrate is provided with a plurality of cavities 3, and the plurality of cavities open in the main surface 4 of the carrier substrate 2.

[0007] The step of assembling donor substrate 1 and acceptor substrate 2 to seal cavity 3 (Bi) Figure 3 ),

[0008] Ci) The step of thinning the donor substrate 1 so as to retain only a portion of the substrate 1 known as the sealing layer 5.

[0009] According to the first aspect, mechanical polishing and / or chemical etching can be used to perform the thinning step Ci), thereby permanently thinning the donor substrate. Figure 4 ).

[0010] Furthermore, the uniformity of the sealing layer at the completion of step Ci) is highly dependent on the technique used during step Ci) and is difficult to control.

[0011] To overcome problems related to uniformity and thin film acquisition, the "Smart-Cut" method described in document EP533551 can be used. ™ The method enables the transfer of the sealing layer by separating it from the donor substrate along a fracture region. The fracture region, formed by implantation and / or amorphization, allows for the definition of a relatively thin sealing layer.

[0012] However, implementing this method without other considerations leads to the formation of defects, and more specifically, to the appearance of non-transfer zones or voids through the sealing layer. Figure 5 An example of this situation is shown. Specifically, Figure 5These are photographs of voids that appear near the edge of the sealing layer and in a region radially opposite to the notches in the carrier substrate. These voids adversely affect the overall performance of the method under discussion and are also sources of contamination.

[0013] One object of the present invention is to provide a method for sealing multiple cavities using a sealing layer, which limits the occurrence of defects in the sealing layer. Summary of the Invention

[0014] The object of the present invention is achieved by a method for transferring a layer onto the main surface of a carrier substrate, the method comprising:

[0015] a) The step of forming a cavity in a carrier substrate, the cavity opening in a major surface of the carrier substrate.

[0016] b) The step of transferring a layer, referred to as the sealing layer, from the donor substrate to cover the main surface and seal all cavities in the cavity formed during step a).

[0017] Step a) is performed such that all cavities in the cavity are regularly distributed on a region called the main region of the main surface, and such that the main surface includes a peripheral ring without cavities, and the main region is circumscribed within the peripheral ring, the peripheral ring extending a length L from the edge of the carrier substrate, the length L being less than a predetermined length Lp, the predetermined length Lp being such that below this length, the sealing layer has no non-transfer region in the peripheral ring.

[0018] According to one embodiment, step a) of forming the cavity includes the following sub-steps:

[0019] a1) A sub-step of forming a peripheral mask to cover the peripheral ring and protect the peripheral ring from physical grinding or chemical etching.

[0020] a2) The sub-step of forming a master mask to cover the master region and at least partially cover the peripheral mask, the master mask including an opening defining the location and size of the cavity to be formed.

[0021] a3) An etching sub-step that results in the formation of a cavity in the main region.

[0022] a4) A sub-step to remove the main mask and the outer mask to expose the entire main face to the external environment.

[0023] According to one embodiment, the peripheral mask is made using a negative photosensitive resin via a photolithography process.

[0024] According to one embodiment, the master mask is made using a photosensitive resin and another photolithography process.

[0025] According to one embodiment, the layer transfer step results in the formation of an edge ring on the main surface, the edge ring extending a distance D from the edge of the carrier substrate, the edge ring being the region where the sealing layer is not present, the length L being greater than the distance D and less than the sum of the distance D and the distance H, H being less than 500 μm, advantageously less than 200 μm, and even more advantageously less than 100 μm.

[0026] According to one embodiment, the length L is between 500 μm and 2500 μm, advantageously between 500 μm and 1500 μm, even more advantageously between 500 μm and 1000 μm, even more advantageously between 500 μm and 800 μm, and even more advantageously between 500 μm and 700 μm.

[0027] According to one embodiment, the cavity is rectangular, and each side of the cavity has a length between 2 μm and 500 μm, advantageously between 2 μm and 500 μm, and even more advantageously between 2 μm and 40 μm.

[0028] According to one embodiment, step b) is performed such that the sealing layer has a thickness between 100 nm and 2000 nm.

[0029] According to one implementation, step b) includes the following sequence of sub-steps:

[0030] b1) The step of forming an embrittlement plane in the volume of the donor substrate, the embrittlement plane defining the sealing layer together with a surface of the donor substrate referred to as the assembly surface.

[0031] b2) The step of assembling the donor substrate and the carrier substrate by bringing the assembly surface into contact with the main surface.

[0032] b3) A fracture step designed to induce a fracture wave along the embrittlement plane so that the sealing layer can be separated from the donor substrate.

[0033] According to one embodiment, the sub-step b1) of forming the embrittled plane includes the injection of a substance.

[0034] According to one embodiment, sub-step b2) includes the molecular bonding of the assembly surface to the main surface.

[0035] According to one implementation, sub-step b3) includes a heat treatment designed to induce the propagation of the fracture wave. Attached Figure Description

[0036] Other features and advantages of the invention will become apparent from the following detailed description with reference to the accompanying drawings, in which:

[0037] [ Figure 1 ] Figure 1This is a schematic diagram of one facet of a donor substrate that can be used when performing a layer transfer method known in the prior art, specifically implemented to seal onto a acceptor substrate. Figure 2 The cavity formed on (as shown in the figure)

[0038] [ Figure 2 ] Figure 2 This is a schematic diagram of a acceptor substrate that can be used when performing layer transfer methods known in the prior art, specifically represented by a surface in which a cavity opens.

[0039] [ Figure 3 ] Figure 3 This is a schematic diagram of assembly step Bi) of a layer transfer method known in the prior art. The schematic diagram shows the donor substrate and the carrier substrate in cross-section in a plane perpendicular to the main surfaces of the two substrates.

[0040] [ Figure 4 ] Figure 4 This is a schematic diagram of the thinning step Ci) in a known layer transfer method in the prior art. The schematic diagram shows the sealing layer and the acceptor substrate in cross-section in a plane perpendicular to the main surface of the acceptor substrate.

[0041] [ Figure 5 ] Figure 5 The photograph shows voids observed in a sealing layer transferred according to a transfer method known in the prior art.

[0042] [ Figure 6 ] Figure 6 This is a schematic diagram of a sequence of steps performed during the implementation of a method according to an advantageous embodiment of the present invention.

[0043] [ Figure 7 ] Figure 7 This is a schematic diagram of a sequence of steps performed during the implementation of an advantageous embodiment of the method according to the present invention.

[0044] [ Figure 8 ] Figure 8 This is a schematic diagram of a carrier substrate on which a photosensitive negative resin layer is formed, specifically shown in cross-section in a plane perpendicular to its main surface.

[0045] [ Figure 9 ] Figure 9 This is a schematic diagram of the irradiation of a resin layer formed on the main surface of a carrier substrate, which is specifically shown in cross-section in a plane perpendicular to its main surface.

[0046] [ Figure 10 ] Figure 10This is a schematic diagram of developing a negative resin layer after irradiation to crosslink the negative resin on a peripheral region, which extends along length L from the edge of a carrier substrate, which is shown in cross-section in a plane perpendicular to its main surface.

[0047] [ Figure 11 ] Figure 11 This is a schematic diagram of a carrier substrate. A photosensitive resin layer covering the main region and the peripheral region is formed on the main surface of the carrier substrate. The carrier substrate is shown in cross-section in a plane perpendicular to its main surface.

[0048] [ Figure 12 ] Figure 12 This is a schematic diagram of a master mask formed on the main surface of a carrier substrate. The master mask is formed to apply a pattern to a cavity to be formed by etching. The carrier substrate is shown in cross-section in a plane perpendicular to its main surface.

[0049] [ Figure 13 ] Figure 13 This is a schematic diagram of a carrier substrate having a cavity formed on its surface after the steps of etching through the master mask and removing the master mask and the peripheral region. The carrier substrate is shown in cross-section in a plane perpendicular to its master surface.

[0050] [ Figure 14 ] Figure 14 This is a schematic diagram of a carrier substrate to which a sealing layer is transferred, specifically to cover the main surface and seal the cavity. The carrier substrate is shown in cross-section in a plane perpendicular to its main surface.

[0051] [ Figure 15 ] Figure 15 This is a schematic diagram of step b1) of the method according to the invention, where arrows indicate material injection via the free surface of a donor substrate, which is shown in cross-section in a plane perpendicular to its free surface.

[0052] [ Figure 16 ] Figure 16 This is a schematic diagram of step b2) of the method according to the invention, which specifically shows the assembly of the donor substrate and the carrier substrate, both of which are shown in cross-section in a plane perpendicular to the main surface.

[0053] [ Figure 17 ] Figure 17 This is a schematic diagram of step b3) of the method according to the invention, which in particular shows the fracture sub-step that causes the sealing layer to transfer to the main surface of the carrier substrate, which is shown in cross-section in a plane perpendicular to the main surface. Detailed Implementation

[0054] The present invention relates to a method for transferring a sealing layer to the main surface of a carrier substrate. In particular, the sealing layer is transferred to cover (and seal) cavities formed in the carrier substrate that open in the main surface of the carrier substrate.

[0055] Therefore, the present invention relates to a method for transferring a layer onto the main surface of a carrier substrate, the method comprising:

[0056] a) The step of forming a cavity in a carrier substrate, the cavity opening in a major surface of the carrier substrate.

[0057] b) The step of transferring a layer, referred to as the sealing layer, from the donor substrate to cover the main surface and seal all cavities formed during step a).

[0058] Step a) is performed such that all cavities are regularly distributed on a region called the main region of the main surface, and such that the main surface includes a peripheral ring without cavities, and the main region is circumscribed within the peripheral ring, the peripheral ring extending a length L from the edge of the carrier substrate, the length L being less than a predetermined length Lp, the predetermined length Lp being such that below this length, the sealing layer has no non-transfer region in the peripheral ring.

[0059] "No non-transfer areas" means that the sealing layer has no voids and, in particular, no through-holes.

[0060] Figure 6 The steps performed during the implementation of the method are illustrated schematically. In particular, the method according to the invention includes step a) of forming a cavity in a carrier substrate, the cavity opening in the main surface of the carrier substrate.

[0061] Advantageous and as Figure 7 As illustrated, step A) may include performing a set of sub-steps. In particular, step a) may include the following sub-steps:

[0062] a1) A sub-step of forming a peripheral mask to cover the peripheral ring and protect the peripheral ring from physical grinding or chemical etching.

[0063] a2) The sub-step of forming a master mask to cover the master region and at least partially cover the peripheral mask, the master mask including an opening defining the location and size of the cavity to be formed.

[0064] a3) An etching sub-step that results in the formation of a cavity in the main region.

[0065] a4) A sub-step to remove the main mask and the outer mask to expose the entire main face to the external environment.

[0066] Still advantageous and as Figure 7As shown, step b) may include performing a set of sub-steps. In particular, step b) may include the following sub-steps:

[0067] b1) The step of forming an embrittlement plane in the volume of the donor substrate, the embrittlement plane defining the sealing layer together with a surface of the donor substrate referred to as the assembly surface.

[0068] b2) The step of assembling the donor substrate and the carrier substrate by bringing the assembly surface into contact with the main surface.

[0069] b3) A fracture step designed to induce a fracture wave along the embrittlement plane so that the sealing layer can be separated from the donor substrate.

[0070] This invention relates to donor substrates and carrier substrates. It should be understood that, according to the principles set forth in this disclosure, the substrate comprises two surfaces that are substantially parallel to each other and connected by a contour or edge. Furthermore, the contour or edge delineates a circle.

[0071] In addition, the substrate may include a notch, which in particular enables the determination and / or definition of its crystal orientation.

[0072] The remainder of the disclosure of this invention is dedicated to description. Figure 7 The illustrated implementation method.

[0073] Sub-step a1) in Figure 8 , Figure 9 and Figure 10 Example in.

[0074] therefore, Figure 8 The carrier substrate 10 is shown on one side, referred to as the main surface 11, on which a resin layer 12 is formed. It should be understood that the resin layer completely covers the main surface 11. Furthermore, the resin used is advantageously M78Y negative resin (sold by JSR Corporation).

[0075] After the resin layer 12 is formed, an irradiation step is performed, such as... Figure 9 As illustrated. Specifically, this irradiation step defines a peripheral region 13 and a central region 14 bounded by the peripheral region 13 in the resin layer 12. Specifically, the peripheral region 13 extends a length L from the edge of the carrier substrate 10. In other words, the peripheral region 13 forms a ring defined externally by an outer edge and internally by an inner edge, the inner edge being a distance L from the edge of the carrier substrate 10.

[0076] Specifically, an irradiation step is performed such that only the peripheral region 13 is exposed to light radiation, thereby crosslinking the peripheral region. In this regard, a mask (not shown) may be used to mask the central region 14 of the resin layer 12.

[0077] After irradiation, the resin layer undergoes a development step, in which the central region 14 of the resin layer 12 is removed to expose the main region 15 of the main surface 11 to the external environment. Figure 10 It should be understood that the development step allows the peripheral region 13 to be retained, which covers the outer ring 16 of the main surface 11 and is externally connected to the main region 15 within the peripheral region. Furthermore, the resin forming the resin layer 12 is designed to protect the peripheral region 16 from physical abrasion and / or chemical etching.

[0078] Sub-step a2) in Figure 11 and Figure 12 Example in.

[0079] Therefore, sub-step a2) first includes forming a resin layer 17 covering the main region 15 and the peripheral region 13. Figure 11 ).

[0080] like Figure 12 As illustrated, resin layer 17 is exposed (or irradiated) to light radiation, particularly ultraviolet light radiation, and subsequently developed to form master mask 17a. The exposure (or irradiation) of the resin layer is achieved using photolithography equipment (e.g., a photographic copier) that irradiates resin layer 17 through a photolithographic mask designed to print a predefined pattern. Therefore, after development, master mask 17a includes an opening 18 that defines the printing of cavities to be formed by an etching step.

[0081] Sub-steps a3) and a4) in Figure 13 Example in.

[0082] in this regard, Figure 13 This refers to the carrier substrate 10 after the etching step performed by the main mask 17a is completed and after the main mask and peripheral region 13 are removed following etching. Specifically, the carrier substrate 10 includes a cavity 19 opening in the main surface 11 of the carrier substrate 10. It should be understood that with the peripheral region 13 masking the peripheral ring 16, the cavity is formed only in the main region. This is because the peripheral region 13 protects the peripheral ring 16 from etching, thus providing an area without the cavity 19.

[0083] By way of example, the cavity 19 may be rectangular, and each side of the cavity may have a length between 2 μm and 500 μm, advantageously between 2 μm and 500 μm, and even more advantageously between 2 μm and 40 μm.

[0084] According to the invention, the outer ring 16 extends from the edge of the carrier substrate by a length L.

[0085] The method according to the invention also includes step b), which involves transferring a layer referred to as sealing layer 21 from donor substrate 20 to cover main surface 11 and seal all cavities in cavity 19 formed during step a).

[0086] Figure 14 An example of this step is shown.

[0087] Furthermore, step b) can be performed to give the sealing layer a thickness between 100 nm and 2000 nm.

[0088] According to an advantageous implementation, the transfer step b) can be based on Figure 7 It is implemented based on the principles described in the text.

[0089] In particular, Figure 15 The illustrated step b1) includes the step of forming an embrittlement plane 23 in the volume of the donor substrate 20. The embrittlement plane 23 specifically defines the sealing layer 21 together with a surface of the donor substrate 20 referred to as the assembly surface 24.

[0090] Sub-step b1) of forming the embrittled plane may include the injection of a substance. The substance may include at least one of the following elements: hydrogen and helium.

[0091] Step b) also includes assembling sub-step b2). Specifically, and as follows: Figure 16 As illustrated, sub-step b2) includes bringing the assembly surface 24 and the main surface 11 into contact. Sub-step b2) may also include initiating a bonding wave. In particular, this initiation of the bonding wave can be achieved by applying pressure that tends to bring the assembly surface and the main surface closer together. This pressure is typically applied using a pin or finger on the side of the donor substrate opposite to the assembly surface and near a notch in the substrate.

[0092] "Close to the notch" means a distance of less than 1 cm from the notch.

[0093] This pressure creates localized contact between the assembly surface and the main surface, close enough to create a weak localized connection (e.g., a hydrogen bond) between the two surfaces in question. This tight contact gradually extends across the entire interface in the form of a bonding wave.

[0094] Therefore, advantageously, sub-step b2) includes the molecular bonding of the assembly facet and the main facet.

[0095] Step b) further includes a fracture sub-step b3) designed to induce a fracture wave along the embrittlement plane so that the sealing layer can be separated from the donor substrate. Figure 17 Advantageously, sub-step b3) may include heat treatment designed to induce the propagation of the fracture wave.

[0096] The specific implementation of the invention, and in particular, provides a cavity-free outer ring 16 that limits or eliminates voids in the sealing layer after the sealing layer is transferred to the main surface.

[0097] Specifically, the inventors have observed that excluding the outer ring according to the terminology of the invention inevitably leads to voids in the sealing layer. In particular, the inventors have also observed that these voids are substantially located in regions radially opposite to the region initiating the bonding wave.

[0098] Therefore, according to the present invention, the length L is less than a predetermined length Lp, which is a length below which the sealing layer has no non-transfer area in the outer ring.

[0099] Furthermore, it is known that the layer transfer step results in the formation of an edge ring on the main surface, which extends a distance D from the edge of the carrier substrate, and this edge ring is the region where no sealing layer exists. This distance D can be determined experimentally.

[0100] Therefore, according to the invention, the length L is advantageously greater than the distance D and less than the sum of the distances D and H, where H is less than 500 μm, advantageously less than 200 μm, and even more advantageously less than 100 μm.

[0101] Alternatively, the length L is between 500 μm and 2500 μm, preferably between 500 μm and 1500 μm, even more preferably between 500 μm and 1000 μm, even more preferably between 500 μm and 800 μm, and even more preferably between 500 μm and 700 μm.

[0102] The length L described above slows down the binding wave in the outer ring during the execution of sub-step b2), thereby limiting bubble capture when the binding wave reaches and closes the region radially opposite to the initiation point.

[0103] Naturally, the present invention is not limited to the described embodiments, and variations may be made thereto without departing from the scope of the invention as defined in the claims.

Claims

1. A method for transferring a layer onto the main surface of a carrier substrate, the method comprising: a) The step of forming a cavity in a carrier substrate, the cavity opening in a major surface of the carrier substrate. b) The step of transferring a layer, referred to as a sealing layer, from the donor substrate to cover the main surface and seal all cavities in the cavity formed during step a). Step a) is performed such that all cavities in the cavity are regularly distributed on a region called the main region on the main surface, and such that the main surface includes a peripheral ring without cavities, and the main region is externally connected within the peripheral ring, the peripheral ring extending from the edge of the carrier substrate by a length L, the length L being less than a predetermined length Lp, the predetermined length Lp being a length below which the sealing layer has no non-transfer region in the peripheral ring.

2. The transfer method according to claim 1, wherein, Step a) to form the cavity includes the following sequence of sub-steps: a1) A sub-step of forming a peripheral mask to cover the peripheral ring and protect the peripheral ring from physical grinding or chemical etching. a2) A sub-step of forming a master mask to cover the master region and at least partially cover the peripheral mask, the master mask including an opening defining the location and size of the cavity to be formed. a3) An etching sub-step that results in the formation of the cavity in the main region. a4) A sub-step to remove the main mask and the peripheral mask to expose the entire main surface to the external environment.

3. The transfer method according to claim 2, wherein, The peripheral mask is made using a negative photosensitive resin and a photolithography process.

4. The transfer method according to claim 2 or 3, wherein, The master mask is made using a photosensitive resin and another photolithography process.

5. The transfer method according to any one of claims 1 to 4, wherein, The layer transfer step results in the formation of an edge ring on the main surface, the edge ring extending a distance D from the edge of the carrier substrate, the edge ring being the region where the sealing layer is absent, the length L being greater than the distance D and less than the sum of the distance D and the distance H, H being less than 500 µm, advantageously less than 200 µm, and even more advantageously less than 100 µm.

6. The transfer method according to any one of claims 1 to 4, wherein, The length L is between 500 µm and 2500 µm, advantageously between 500 µm and 1500 µm, even more advantageously between 500 µm and 1000 µm, even more advantageously between 500 µm and 800 µm, and even more advantageously between 500 µm and 700 µm.

7. The transfer method according to any one of claims 1 to 6, wherein, The cavity is rectangular, and each side of the cavity has a length between 2 µm and 500 µm, advantageously between 2 µm and 500 µm, and even more advantageously between 2 µm and 40 µm.

8. The transfer method according to any one of claims 1 to 7, wherein, Perform step b) to give the sealing layer a thickness between 100 nm and 2000 nm.

9. The transfer method according to claim 1, wherein, Step b) includes the following sequence of sub-steps: b1) The step of forming an embrittlement plane in the volume of the donor substrate, wherein the embrittlement plane, together with a surface of the donor substrate referred to as the assembly surface, defines the sealing layer. b2) The step of assembling the donor substrate and the carrier substrate by bringing the assembly surface and the main surface into contact. b3) A fracture step designed to induce a fracture wave along the embrittlement plane so that the sealing layer can be separated from the donor substrate.

10. The transfer method according to claim 9, wherein, The sub-step b1) that forms the embrittled plane includes the injection of material.

11. The transfer method according to claim 9 or 10, wherein, Sub-step b2) includes the molecular bonding of the assembly surface to the main surface.

12. The transfer method according to any one of claims 9 to 11, wherein, Sub-step b3) includes a heat treatment designed to induce the propagation of the fracture wave.

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