Method for manufacturing a substrate, and substrate

Abstract

The invention relates to a method for manufacturing a substrate, wherein an adhesive layer 115 arranged sandwiched between a handling substrate 100 and a piezoelectric substrate 101 is polymerized in a polymerization site, and, following the polymerization step, the heterostructure 107 is displaced to another site. The method is characterized in that, during the polymerization step, the heterostructure 107 is cooler than the ambient temperature of the other site. The invention also relates to a substrate 119 comprising an adhesive layer 115 arranged sandwiched between a manipulation substrate 100 and a piezoelectric substrate 101, characterized in that when the substrate 119 has a temperature between 20°C and 25°C, in particular between 20°C and 22°C, the adhesive layer 115 is under compression, particularly with respect to the manipulation substrate 100, in such a way as to induce a bend (BOW) of the substrate. Figure 1

Description

Title of the invention: Method for manufacturing a substrate, and substrate

[0001] The present invention relates to a method for manufacturing a substrate comprising a handling substrate and a piezoelectric substrate. The invention also relates to such a substrate.

[0002] It is known in the art of manufacturing piezoelectric-on-insulator (POI) wafers, also called wafers, by means of a single-layer transfer manufacturing process, also known as "Smart Cut". The Smart Cut process involves the use of an intermediate manufacturing substrate, called a donor substrate, which is a composite substrate comprising a piezoelectric substrate. The Smart Cut process includes the implantation of ions, for example hydrogen, into the piezoelectric substrate of the donor substrate in order to generate a weakening zone along which a thin layer of piezoelectric material can be detached from the piezoelectric substrate of the donor substrate.

[0003] A donor substrate is manufactured by means of an adhesive layer sandwiched between a handling substrate and the piezoelectric substrate. The appearance of defects such as cracks in the adhesive layer, or delamination zones at the adhesion interface, reduces the process yield. In particular, cracks in the adhesive layer can propagate into the piezoelectric substrate and be transferred to the final POI following detachment of the thin layer.

[0004] In view of the foregoing, the present invention aims to increase the yield of a known substrate manufacturing process, and in particular to reduce the occurrence of cracks during substrate manufacturing.

[0005] The object of the invention is achieved by means of a method for manufacturing a substrate, comprising the steps of: - provide a manipulation substrate and a piezoelectric substrate; - apply an adhesive layer of a material, in particular liquid, photo-polymerizable on a surface of the handling substrate and / or on a surface of the piezoelectric substrate; - form a heterostructure comprising the manipulation substrate, the piezoelectric substrate and the adhesive layer, the adhesive layer being arranged in a sandwich between the manipulation substrate and the piezoelectric substrate; - polymerize the adhesive layer of the heterostructure in a polymerization site; And, - move the heterostructure to another location following the polymerization step characterized in that during the polymerization step, the heterostructure is colder than the ambient temperature of the other location.

[0006] The adhesive layer is thus polymerized and mechanically fixed at a first temperature. When the heterostructure is moved to another location with an ambient temperature higher than the first, the handling substrate and the piezoelectric substrate undergo thermal expansion. This thermal expansion induces mechanical stress, in particular compression, in the adhesive layer. Surprisingly, substrates manufactured using this process are less susceptible to being compromised by the appearance of cracks in the adhesive layer.

[0007] According to one aspect of the process of the invention, the process may include a step of cooling the heterostructure before and / or during the polymerization step to obtain the heterostructure cooler than the ambient temperature of the other location. The cooling step makes it possible to obtain the heterostructure cooler than the ambient temperature of the other location. This cooling step may take place during and concurrently with the polymerization step. The cooling step may also take place, for example, immediately upstream of the polymerization step. The cooling step may also be initiated upstream of the polymerization step and continued throughout the polymerization process.

[0008] According to one aspect of the process of the invention, the cooling step may include a step of placing the manipulation substrate on a wafer support configured for cooling. Placing the manipulation substrate on the wafer support allows the manipulation substrate to be cooled first, and then, by thermal conduction, the adhesive layer and the piezoelectric substrate. Thus, the volume to be cooled remains essentially limited to the substrate itself.

[0009] According to one aspect of the method of the invention, the wafer support may include an integrated cooling means. This further reduces the volume to be cooled and reduces heat loss.

[0010] According to one aspect of the process of the invention, during the polymerization step, the heterostructure may be cooler than the ambient temperature of the polymerization site. In this configuration of the process, the fabricated substrate may already undergo an additional thermal expansion, known as preliminary thermal expansion, prior to its movement to the other location. In particular, in this configuration of the process, the fabricated substrate undergoes preliminary thermal expansion as soon as the cooling step is completed and the substrate heats up to the ambient temperature of the location. polymerization, before being moved.

[0011] According to one aspect of the process of the invention, the ambient temperature of the polymerization area can be between 20°C and 25°C, in particular between 20°C and 22°C. Thus, a standard cleanroom temperature can be used.

[0012] According to one aspect of the process of the invention, the cooling step may include a step of reducing the ambient temperature of the polymerization site relative to the ambient temperature of the other site. By reducing the ambient temperature of the polymerization site, for example by controlling the temperature of a cleanroom in which the polymerization takes place, the cooling of the heterostructure can be faster and more uniform than, for example, by cooling only the wafer support.

[0013] According to one aspect of the method of the invention, the ambient temperature of the other location can be between 20°C and 25°C, in particular between 20°C and 22°C. Thus, a standard cleanroom temperature can be used for the other location.

[0014] According to one aspect of the process of the invention, the process may include, after the polymerization step, a thinning step of the heterostructure, in particular at the other location. A thinning step makes it possible to prepare the fabricated substrate for subsequent use, for example for application in a thin-film transfer process, for example of the Smart Cut type, onto a support substrate having a coefficient of thermal expansion comparable to or equal to the handling substrate.

[0015] According to one aspect of the process of the invention, the thinning step may include a grinding, or sanding, step of the piezoelectric substrate. In particular, the thinning step may include a plurality of successive grinding steps, for example, a first coarse grinding step and a second fine grinding step. Such a thinning step can facilitate adapting the raw piezoelectric substrate to a thickness suitable for further processing.

[0016] According to one aspect of the process of the invention, the thinning step may include a chemical-mechanical planarization (CMP) step. In particular, the CMP step may be performed between a first grinding step and a second grinding step. Such a CMP step can facilitate the application of the substrate in a subsequent Smart Cut process.

[0017] According to one aspect of the process of the invention, during the polymerization step, the heterostructure may have a temperature at least 1°C lower than the ambient temperature of the other location. In particular, during the polymerization step, the heterostructure may have a temperature 2°C to 15°C lower, preferably 4°C to 8°C lower, than the ambient temperature of the other place. With a temperature at least 1°C colder, sufficient mechanical stress, particularly compression, can be observed in the adhesive layer, and / or the rate of cracking in the manufactured substrate is reduced.

[0018] According to one aspect of the process of the invention, during the polymerization step, the heterostructure may have a temperature between 11°C and 21°C. In particular, during the polymerization step, the heterostructure may have a temperature between 15°C and 18°C. In this configuration, the process may be operated in such a way as to achieve cooling relative to the ambient temperature of the other location and / or the ambient temperature of the polymerization location, which may be maintained at a standard cleanroom temperature and thus reduce the occurrence of cracking.

[0019] According to one aspect of the process of the invention, the polymerization step is carried out in such a way and the substrate is maintained in environmental conditions such that the polymerized adhesive layer is maintained in the compression state until a layer of the piezoelectric substrate is transferred onto a support substrate.

[0020] According to one embodiment, after the polymerization step, an annealing step of the heterostructure can be carried out, in particular at a temperature above 90°C, specifically between 190°C and 210°C, and preferably for a duration of 30 minutes to 20 hours. This annealing consolidates the heterostructure by limiting delamination.

[0021] The invention also relates to a substrate comprising a handling substrate, a piezoelectric substrate, and a polymerized adhesive layer, the polymerized adhesive layer being arranged in a sandwich between the handling substrate and the piezoelectric substrate. The inventive substrate is characterized in that when the substrate is at a temperature between 20°C and 25°C, particularly between 20°C and 22°C, the adhesive layer is under compression. Such an arrangement of the adhesive layer ensures a substrate having a heterostructure that does not exhibit cracks in the adhesive layer, or at least exhibits fewer cracks in the adhesive layer.

[0022] According to one aspect of the inventive substrate, when the substrate is at said temperature, the adhesive layer may be under compression relative to the handling substrate. According to one aspect of the inventive substrate, when the substrate is at said temperature, the adhesive layer may be under compression in such a way as to induce a curvature, or a BOW (Bow-Out) according to the Anglo-Saxon term, of the substrate.

[0023] According to one aspect of the inventive substrate, the induced curvature can be a positive curvature of at least 30 pm, when the piezoelectric substrate is positioned over the manipulation substrate, in particular when the manipulation substrate is positioned on a measurement reference plane.

[0024] According to one aspect of the inventive substrate, the induced curvature may be a curvature positive between 50pm inclusive and 150pm inclusive, preferably between 55pm inclusive and 65pm inclusive.

[0025] According to aspects of the process and substrate of the invention, the coefficient of thermal expansion of the handling substrate may be different from, in particular lower than, the coefficient of thermal expansion of the piezoelectric substrate.

[0026] According to aspects of the process and substrate of the invention, the manipulation substrate may be a substrate comprising, in particular based on, a material selected from silicon, sapphire, aluminum nitride, silicon carbide, and gallium arsenide. These substrates are particularly suitable for manipulation within the framework of a layer transfer process onto a support substrate such as a Smart Cut process, since the same type of support substrate can be used, thus reducing the problem related to the difference in coefficient of thermal expansion between the piezoelectric material and the support substrate material.

[0027] According to aspects of the process and substrate of the invention, the piezoelectric substrate is a substrate comprising, in particular based on, a material selected from quartz, lithium tantalate, lithium niobate, aluminum nitride, gallium nitride, gallium orthophosphate, zinc oxide, lead zirconate titanate, barium titanate, langasite, langanite, and langatate. These piezoelectric substrates are desirable for manufacturing a POI by a layer transfer process, for example by a Smart Cut process.

[0028] The objects, features and advantages of the invention as set forth above will be more fully understood and appreciated by studying the following more detailed description of embodiments of the invention, with the aid of the accompanying drawings.

[0029] Fig. 1 illustrates a method for manufacturing a substrate according to a first embodiment of the invention.

[0030] Figure [Fig.2] illustrates a method for manufacturing a substrate according to a third embodiment of the invention.

[0031] The technical features and associated advantages of the embodiments described below can be freely combined one by one or adapted to particular embodiments, provided that the spirit of the invention as described above is respected.

[0032] In the following, identical reference numerals in the figures and the description are used to designate elements of the same nature. Unless explicitly stated otherwise in the text, the objects illustrated in the figures are not to scale relative to each other, nor to scale in their Cartesian dimensions relative to each other.

[0033] A method for manufacturing a substrate according to a first embodiment of the invention is described with reference to [Fig.1].

[0034] The process begins with a first step A of supplying a substrate of A manipulation substrate 100 and a piezoelectric substrate 101 are used. In this case, the manipulation substrate 100 is a bulk silicon substrate, and the piezoelectric substrate 101 is a lithium tantalate (LTO) substrate. This piezoelectric substrate 101 has a coefficient of thermal expansion between 9 × 10⁶ K⁻¹ and 16 × 10⁶ K⁻¹, depending on the crystal direction. Thus, the piezoelectric substrate 101 has a coefficient of thermal expansion higher than that of the manipulation substrate 100, which is on the order of 2.5 × 10⁶ K⁻¹. The piezoelectric substrate 101 can have a thickness between 300 µm and 500 µm, preferably 350 µm, and the manipulation substrate can have a greater thickness, preferably at least 500 µm.

[0035] Alternatively, a manipulation substrate 100 based on sapphire, aluminum nitride, silicon carbide, or gallium arsenide may be chosen. In addition, alternatively, a piezoelectric substrate 101 based on lithium niobate (LNO), aluminum nitride, gallium nitride, gallium orthophosphate, zinc oxide, lead zirconate titanate, barium titanate, langasite, langanite, or langatate may be chosen.

[0036] In a second step B, a liquid adhesive layer 103 of a photopolymerizable material is applied to a first exposed surface 105 of the silicon handling substrate 100. By way of non-limiting example, the adhesive layer 103 may be a layer of a material marketed under the reference "NOA 61" by NORLAND PRODUCTS. Other examples of "photo-resist" type materials, in particular hydrocarbon polymer materials composed of non-volatile compounds, are equally conceivable. Preferably, the adhesive layer 103 is applied to a thickness of between 0.1 µm and 25 µm, preferably between 2 µm and 8 µm, by spin coating.

[0037] Next, in a third step C, the piezoelectric substrate 101 is positioned on the manipulation substrate 100, which is equipped with the liquid adhesive layer 103, so that the adhesive layer 103 is sandwiched between the manipulation substrate 100 and the piezoelectric substrate 101. This forms a heterostructure 107 composed of the manipulation substrate 100, the piezoelectric substrate 101, and the adhesive layer 103 sandwiched between the manipulation substrate 100 and the piezoelectric substrate 101. The heterostructure 107 has a temperature Tl corresponding to the ambient temperature of the formation site of the heterostructure 107, for example, a controlled ambient temperature between 20°C and 25°C. Preferably, the temperature Tl is between 20°C and 22°C, for example, 21°C.

[0038] The heterostructure 107 is, according to a fourth step D, brought into a poly locus The polymerization layer is placed on a wafer support 109 in the polymerization zone. Temperature T2 corresponds to the ambient temperature of the (subsequent) polymerization zone of the liquid adhesive layer 103. Preferably, the temperature T2 is the same as Tl or within the range [Tl -1°C; Tl + 1°C]. For example, T2 can be controlled between 20° and 25°, preferably between 20°C and 22°C, for example at 21°C.

[0039] The insert holder 109, referred to as a "chuck" in Anglo-Saxon terminology, according to the present first embodiment of the invention, is a insert holder 109 that can be cooled. Thus, the insert holder 109 includes a cooling means 111, for example a system for circulating a coolant, for example water, allowing the temperature of the insert holder 109 to be reduced relative to the ambient temperature of the environment surrounding the insert holder 109. Preferably, the coolant has a temperature between 10°C and 17°C.

[0040] The wafer support 109 is then at a temperature T3 lower than the temperature T2, which is the ambient temperature of the location where the wafer support 109 is situated. The heterostructure 107 is placed on the wafer support 109 such that a second surface 113, opposite the first surface 105, of the manipulation substrate 100 enters into mechanical and thermal contact with the wafer support 109. Preferably, the heterostructure 107 is placed on the wafer support 109 such that the entire second surface 113, or at least most of it, is in mechanical and thermal contact with the wafer support 109.

[0041] Thus, the manipulation substrate 100, and by thermal conduction the entire heterostructure 107, have a temperature T4 lower than the temperature of the polymerization site T2. For example, the heterostructure 107 can be cooled to a temperature T4 that is at least 1°C below the ambient temperature T2. Alternatively, the heterostructure 107 can be cooled to the temperature T3 of the wafer support 109.

[0042] In the next step E, the liquid adhesive layer 103 is polymerized in the same location to become, after polymerization, a polymerized adhesive layer 115. In this embodiment, the liquid adhesive layer 103 is polymerized by irradiating it with ultraviolet (UV) light. According to a non-limiting example, the adhesive layer 103 is irradiated with UV radiation 20 times for five seconds each, for a total of 100 seconds. Preferably, the adhesive layer 103 can be irradiated with a power of 100 mW / cm² and / or with an irradiation wavelength of 365 nm. After step E, the adhesive layer 115 is polymerized. In general, the wavelength is chosen according to the material of the adhesive layer 103 to be polymerized and the material that the light must pass through, here the LTO of the piezoelectric substrate 101.

[0043] In this embodiment, the wafer support 109 is kept cooled at the same temperature until the end of the fifth step E. Thus, the cooling step of the heterostructure 107 coincides with the fourth and fifth steps D and E. In alternative embodiments, the wafer support 109 is cooled only during polymerization step E, or only during step D upstream of polymerization step E.

[0044] Next, in a sixth step F, the heterostructure 107 is moved to another location, for example, to perform another treatment of the heterostructure or to store it pending further treatment. The other location has an ambient temperature T5 that is higher than T4. Here, the temperature T5 may be the same as the temperature T1 and / or the temperature T2. Thus, the temperature T5 is controlled between 20°C and 25°C, preferably between 20°C and 22°C, for example at 21°C. Thus, the piezoelectric substrate 101, previously cooled to temperature T3, ceases to be cooled by the wafer support 109, and reaches the ambient temperature T5 at the latest upon arrival at the other location. The piezoelectric substrate 101 may also reach the ambient temperature T5 before arriving at the other location, for example, if the temperature T5 is equivalent to the temperature T2.

[0045] Since the piezoelectric substrate 101 has a coefficient of thermal expansion greater than that of the handling substrate 100, the piezoelectric substrate 101 expands more than the handling substrate 100. Thus, a mechanical stress is exerted on the adhesive layer 103 during the transition from T4 to T5. This mechanical stress can induce compression of the adhesive layer 103 relative to the handling substrate 100. The mechanical stress can also induce a positive curvature B, also known as BOW in the semiconductor wafer industry. Depending on the choice of the temperature T4 of the heterostructure 107 relative to the ambient temperature of the other location T5, BOW values ​​of at least 30 pm, particularly between 50 pm and 100 pm, are observed.

[0046] An example of further processing is illustrated in step G. The heterostructure 107 is thinned to obtain a thinner piezoelectric substrate 103'. The thinning treatment is applied to the exposed surface 117 of the piezoelectric substrate 101 at temperature T5. In this particular case, the thinning step G may successively comprise a first coarse grinding, a chemical polishing, a second fine grinding, and contouring. Preferably, the thickness can be reduced to a value between 10 µm and 50 µm, or even more advantageously to a value between 20 µm and 30 µm.

[0047] The substrate 119 obtained at the end of step G comprises the handling substrate 100, the thinned piezoelectric substrate 101', and the polymerized adhesive layer 115, the adhesive layer 115 being arranged in a sandwich between the handling substrate 100 and the piezoelectric substrate 101'. When the substrate 119 is at temperature T5, therefore typically between 20°C and 25°C, in particular between 20°C and 22°C, the adhesive layer 115 is in compression relative to the handling substrate 100, in particular in such a way as to induce a curvature (BOW) B of the substrate 119.

[0048] The substrate 119 corresponds to a second embodiment of the invention. The substrate 119 can, in particular, serve as a donor substrate, also called a pseudo-donor substrate (PSD), in the context of implementing a process for transferring a piezoelectric layer onto a support substrate, particularly one made of silicon. Such a process is known as Smart Cut. During this type of process, a weakened zone is formed in the piezoelectric substrate 101' of the substrate 119, for example, by implanting atomic species, such as hydrogen or helium ions. Then, the free surface 117 of the piezoelectric substrate 101' is bonded to the surface of a support substrate by atomic force, also called molecular bonding. After an application of energy, thermal and / or mechanical, the piezoelectric layer detaches from the rest of the substrate 119 to be transferred onto the support substrate.According to alternative methods, a dielectric layer, such as silicon oxide and / or silicon nitride, can be formed on the surface of the support substrate and / or the surface of the piezoelectric substrate prior to bonding to facilitate atomic force bonding.

[0049] A method for manufacturing a substrate according to a third embodiment of the invention is now described with reference to [Fig. 2]. The method of the third embodiment differs from the method of the first embodiment with respect to the method of cooling the heterostructure. That is, it differs with respect to the means of obtaining the heterostructure at a temperature lower than the ambient temperature of the other location to which the heterostructure is transferred after polymerization. The method of the third embodiment begins with a first step A' of supplying a handling substrate 200 and a piezoelectric substrate 201. Here, step A' is identical to step A of the first embodiment, and the substrates 200 and 201 are respectively identical to the substrates 100 and 101.

[0050] Then, in a second step B', an adhesive layer 203 of a photo-polymerizable material is applied to a first surface 205 of the piezoelectric substrate 201. Here, the adhesive layer 203 is applied to the surface 205 in the same way as the application of the adhesive layer 103 to the surface 105. According to an alternative, the adhesive layer 203 can also be applied to the surface of the manipulation substrate 200 as in the first embodiment.

[0051] A heterostructure 207 is formed in a third step C by positioning the piezoelectric substrate 201 equipped with the adhesive layer 203 on the manipulation substrate 200. Thus, the heterostructure 207 comprises the piezoelectric substrate 201, the manipulation substrate 200, and the adhesive layer 203 arranged in a sandwich between the manipulation substrate 200 and the piezoelectric substrate 201.

[0052] In a fourth step D', the heterostructure 207 is brought into a poly locus The polymerization site 209 has a controlled ambient temperature Tl'. The temperature Tl' is maintained below the ambient temperature of another location, to which the heterostructure 207 will be subsequently moved following the polymerization step. Thus, here, the temperature Tl' is controlled to a temperature between 11°C and 21°C, specifically between 15°C and 18°C. The heterostructure 207, brought to the polymerization site with a controlled temperature Tl', then also reaches the temperature Tl'. Here, the polymerization site 209 can be the interior of the device in which the polymerization will take place in the next step.

[0053] The heterostructure 207 is then polymerized in a fifth step E', carried out here in the same or corresponding manner as the polymerization in step E of the first embodiment, in particular by using ultraviolet (UV) radiation. Thus, in the polymerization step E', the adhesive layer 203 is polymerized to become a polymerized adhesive layer 211. During the polymerization step E', the polymerization site 209 is maintained at ambient temperature T1'. Thus, a cooling step coincides with steps D' and E' to obtain the heterostructure 207.

[0054] In a sixth step F', the heterostructure 207 is moved to another location 213 having an ambient temperature T2' at the same ambient temperature T2' as the polymerization location 209. Here, the ambient temperature T2' is between 20°C and 25°C, in particular between 20°C and 22°C. Moreover, the ambient temperature T2' is at least 1°C higher than the cooled temperature Tl'. Specifically, the ambient temperature Tl' is reduced, i.e., lower, by 2°C to 15°C, preferably by 4°C to 8°C, compared to the temperature T2'. According to one embodiment, it is also possible to keep the polymerization location 209 at the standard cleanroom temperature, and raise the temperature of the other location 213, for example by means of a heating device.

[0055] Similar to the process in the first embodiment, during the sixth step F', the heterostructure 207 is no longer cooled and reaches ambient temperature T2'. The divergence in thermal expansion between the manipulation substrate 200 and the piezoelectric substrate 201 generates the same mechanical stress, in particular compression, in the polymerized adhesive layer 211 as in the first embodiment. This compression strengthens the fabricated substrate so as to reduce its susceptibility to cracking.

[0056] According to an optional seventh step G', the heterostructure 207 is subjected to a consolidation anneal to obtain the final substrate 215 manufactured by the process of the third embodiment. For this purpose, the heterostructure 207 is placed in a furnace 217 and heated to a temperature above 100°C, preferably to a temperature between 190°C and 210°C for a predetermined time, typically between 30 minutes and 8 hours. A consolidation anneal can also be carried out using the method of the first embodiment.

[0057] After the annealing step, a thinning step such as step G of the first embodiment can also be carried out.

[0058] The final substrate 215 obtained at the end of step G', or where applicable after thinning, comprises the handling substrate 200, the piezoelectric substrate 201, and the polymerized adhesive layer 211, the adhesive layer 211 being arranged in a sandwich between the handling substrate 200 and the piezoelectric substrate 201, whether thinned or not. When the final substrate 215 has a temperature between 20°C and 25°C, in particular between 20°C and 22°C, the adhesive layer 211 is under compression relative to the handling substrate 200, in particular in such a way as to induce a bend (BOW) of the final substrate 215 produced. Thus, a final substrate 215 is obtained as in the second embodiment of the invention. The final substrate 215 can then also serve as a donor substrate in a transfer process as described above.

[0059] A statistical study carried out on the manufacturing process according to the first embodiment of the invention revealed a significant reduction in the rate of cracking in the manufactured PSDs. Thus, for a temperature T4 of 19°C without an annealing step and a temperature T5 of 21°C, a near absence of cracking was observed, and for a process with an annealing step of 5 hours at 100°C, a near absence of cracking was observed for a temperature T4 between 15°C and 17°C.

[0060] Reference signs 100 manipulation substrate 101 piezoelectric substrate 103 adhesive layer 105 first surface of the manipulation substrate 107 heterostructure 109 plate support 111 means of cooling 113 second surface of the manipulation substrate 115 polymerized adhesive layer 117 exposed surface of the piezoelectric substrate 119 PSD T1 ambient temperature of a heterostructure formation site T2 ambient temperature of a polymerization site T3 temperature of the cooled wafer support, T4 temperature of the cooled heterostructure, T5 temperature of the other location, 200 manipulation substrate 201 piezoelectric substrate 203 liquid adhesive layer 205 first surface of the manipulation substrate 207 heterostructure 209 polymerization site 211 polymerized adhesive layer 215 final substrate 217 oven The ambient temperature of the site of heterostructure formation and polymerization T2' ambient temperature of the other location

Claims

Demands

1. Method of manufacturing a substrate, comprising the steps of: - providing a handling substrate (100, 200) and a piezoelectric substrate (101, 201); - applying an adhesive layer (103, 203) of a material, in particular liquid, photo-polymerizable on a surface (105) of the handling substrate (100, 200) and / or on a surface (205) of the piezoelectric substrate (101, 201); - to form a heterostructure (107, 207) comprising the manipulation substrate (100, 200), the piezoelectric substrate (101, 201) and the adhesive layer (103, 203), the adhesive layer (103, 203) being arranged in a sandwich between the manipulation substrate (100, 200) and the piezoelectric substrate (101, 201); - to polymerize the adhesive layer (115, 211) of the heterostructure (107, 207) in a polymerization site (209); and, - to move the heterostructure (107, 207) to another site following the polymerization step;characterized in that during the polymerization step, the heterostructure (107, 207) is colder than an ambient temperature of the other location (T5, T2').;

2. A method according to claim 1, comprising a step of cooling the heterostructure (107, 207) before and / or during the polymerization step to obtain the heterostructure (107, 207) cooler than the ambient temperature of the other location (T5, T2').

3. Method according to claim 2, the cooling step comprising a step of placing the handling substrate (100, 200) on a wafer holder (109) configured to be cooled, in particular a wafer holder (109) comprising an integrated cooling means (111).

4. A process according to claim 3, wherein during the polymerization step, the heterostructure(107, 207) is colder than an ambient temperature of the polymerization site (T2, Tl'), in particular the ambient temperature of the polymerization site (T2, Tl') being between 20°C and 25°C, in particular between 20°C and 22°C.

5. A process according to claim 2 or 3, the cooling step comprising a step of reducing the ambient temperature of the polymerization site (TT) relative to the ambient temperature of the other location (T2').

6. A method according to any one of claims 1 to 5, wherein the ambient temperature of the other location (T5, T2') is between 20°C and 25°C, in particular between 20°C and 22°C.

7. A method according to claim 1 to 6, comprising, after the polymerization step, a thinning step of the heterostructure (107, 207), in particular a grinding step of the piezoelectric substrate (101, 201) and / or a chemical mechano-polishing (CMP) step of the piezoelectric substrate (107, 207) at the other location (209).

8. A process according to any one of claims 1 to 7, wherein during the polymerization step, the heterostructure (107, 207) has a temperature that is at least 1°C cooler, in particular 2°C to 15°C cooler, preferably 4°C to 8°C cooler, relative to the ambient temperature of the other location (T5, T2').

9. A process according to any one of claims 1 to 8, wherein during the polymerization step, the heterostructure (107, 207) has a temperature (T4) between 11°C and 21°C, in particular between 15°C and 18°C.

10. A process according to any one of claims 1 to 9, comprising, after the polymerization step, an annealing step of the heterostructure (107, 207), in particular at a temperature above 90°C, in particular between 190°C and 210°C.

11. A method according to any one of claims 1 to 10, wherein the coefficient of thermal expansion of the handling substrate (100, 200) is different from, in particular lower than, the coefficient of thermal expansion of the piezoelectric substrate (101, 201).

12. A method according to any one of claims 1 to 11, wherein the manipulation substrate (100, 200) is a substrate comprising, in particular based on, a material selected from silicon, sapphire, aluminum nitride, silicon carbide, and gallium arsenide.

13. A method according to any one of claims 1 to 12, wherein the piezoelectric substrate (101, 201) is a substrate comprising, in particular based on, a material selected from quartz, lithium tantalate, lithium niobate, aluminium nitride, gallium nitride, gallium orthophosphate, zinc oxide, lead zirconate titanate, barium titanate, langasite, langanite, and langatate.

14. Substrate comprising a handling substrate (100, 200), a piezoelectric substrate (101, 201) and a polymerized adhesive layer (115), the polymerized adhesive layer (115) being arranged in a sandwich between the manipulation substrate (100, 200) and the piezoelectric substrate (101, 201), characterized in that when the substrate has a temperature between 20°C and 25°C, in particular between 20°C and 22°C, the polymerized adhesive layer (115) is in compression, in particular with respect to the manipulation substrate (100, 200) in such a way as to induce a curvature (BOW) of the substrate.

15. Substrate according to claim 14 having, when the piezoelectric substrate is positioned over the handling substrate (100, 200), a positive curvature of at least 30pm, preferably between 50pm and 100pm.

16. Substrate according to claim 14 or 15, wherein the coefficient of thermal expansion of the handling substrate (100, 200) is different from, in particular lower than, the coefficient of thermal expansion of the piezoelectric substrate (101, 201).

17. Substrate according to any one of claims 14 to 16, wherein the manipulation substrate (100, 200) is a substrate comprising, in particular based on, a material selected from silicon, sapphire, aluminum nitride, silicon carbide, and gallium arsenide.

18. Substrate according to any one of claims 14 to 17, wherein the piezoelectric substrate (101, 201) is a substrate comprising, in particular based on, a material selected from quartz, lithium tantalate, lithium niobate, aluminium nitride, gallium nitride, gallium orthophosphate, zinc oxide, lead zirconate titanate, barium titanate, langasite, langanite, and langatate.

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