Methods and structures for transferring semiconductor devices

Abstract

An object of the invention is a method of transferring a semiconductor device (100) by infrared laser ablation. An active layer is transferred from a donor substrate to a transfer substrate (3) made of silicon by performing bonding with a separation layer (20) between the active layer and the transfer substrate (3). Thereafter, the semiconductor device (100) is formed starting from the active layer over the transfer substrate (3). Thereafter, the semiconductor device (100) is assembled to the acceptor substrate (2) and then released under infrared radiation passing through the transfer substrate (3). Advantageously, the separation layer (20) comprises a metal release layer (21) and a mineral absorption layer (22). Another object of the invention is to provide a transfer structure that enables the implementation of the transfer method.

Description

Technical Field

[0001] The present invention relates to the fields of microelectronics and optoelectronics. It has particularly advantageous applications in the batch transfer of semiconductor devices (such as silicon-based GaN light-emitting diodes). Background Art

[0002] Semiconductor devices generally include at least one so-called "active" semiconductor layer involved in the operation of the device. For example, without limitation, semiconductor devices refer to CMOS circuits, i.e., based on complementary metal oxide semiconductor transistors (CMOS is the acronym for "complementary metal oxide semiconductor"), or refer to microelectromechanical systems MEMS (the acronym for "microelectromechanical systems"), or refer to LED type (the acronym for "light-emitting diode"). Next, one or more LEDs or micro-LEDs are selected as non-limiting examples to illustrate the transfer methods and structures.

[0003] Generally, in order to form a self-emitting display screen including a plurality of RGB pixels (the acronym for "red, green, blue") that emit their own light, different LEDs are assembled on a screen support, which includes, for example, control electronics.

[0004] LEDs are generally formed on a donor substrate or a growth substrate and then individualized - i.e., separated from each other - and then transferred to a screen support or a receptor substrate. Not all of the LEDs on the donor substrate have to be transferred to the receptor substrate.

[0005] Preferably, the growth substrate of the LEDs is silicon-based to benefit from the production capabilities of the equipment in the microelectronics industry. To transfer a large number of LEDs integrally from a silicon-based growth substrate, one solution includes using a transfer substrate made of glass, on which the LEDs are bonded with an organic glue. The growth substrate is removed and then the LEDs are individualized and brought into contact with the receptor substrate. Then, UV laser radiation passes through the transfer substrate made of glass to degrade the organic glue, so as to release the LEDs and assemble them with the receptor substrate. This UV laser ablation method requires a transfer substrate made of glass, which is hardly compatible with the production equipment in the microelectronics industry (substrate inspection, mechanical deformation). In addition, the organic glue is temperature-sensitive. They can cause considerable deformation of the plates. They also degrade under the action of temperature. Therefore, it becomes more complicated to perform intermediate technical steps on the LEDs after removing the growth substrate.

[0006] To overcome these drawbacks, document WO2022111141A1 discloses a solution that includes using a mineral bond, such as an "oxide-oxide" bond between the devices of the transfer substrate and the donor substrate. In this solution, a transfer substrate made of silicon is used, which is compatible with an inorganic separation layer (usually aluminum-based). Subsequently, infrared laser radiation is allowed to pass through the transfer substrate made of silicon to degrade the separation layer so as to release the device assembled with the receptor substrate. In practice, this solution requires a very energy-intensive infrared laser and can partially degrade the device to be transferred.

[0007] Document US2022406621A1 describes another laser ablation process using an inorganic separation layer. This solution also requires a high-energy infrared laser.

[0008] The present invention aims to at least partially overcome the drawbacks of the above solutions.

[0009] In particular, one object of the present invention is to provide an optimized method for transferring semiconductor devices. Another object of the present invention is to provide a transfer structure for semiconductor devices that allows the implementation of the transfer method.

[0010] Other objects, features, and advantages of the present invention will become apparent from a review of the following description and the drawings. It should be understood that other advantages can be incorporated therein. In particular, some features and some advantages of the transfer method can be applied to the transfer structure with necessary modifications, and vice versa. Summary of the Invention

[0011] To achieve the above object, on the one hand, it relates to a method for transferring at least one semiconductor device from a so-called first donor substrate to a so-called second receptor substrate using a silicon-based transfer substrate.

[0012] The method at least includes the following steps: - Providing the donor substrate, which includes at least one active layer intended to be integrated into the semiconductor device at a first face, - Providing the silicon-based transfer substrate, which has a second face, - Forming a separation layer on at least one of the first face and the second face, the separation layer being inorganic, - Assembling the donor substrate with the transfer substrate via the separation layer, - Removing the donor substrate while holding the at least one active layer above the transfer substrate and forming at least one semiconductor device starting from the at least one active layer, - Providing the receptor substrate, - Assembling the at least one semiconductor device with the receptor substrate, - Irradiating the separation layer through the transfer substrate with infrared radiation to at least partially eliminate the separation layer so as to detach only the at least one semiconductor device from the transfer substrate, Advantageously, forming the separation layer includes forming a metal release layer on one side of the active layer and forming a mineral absorption layer on one side of the transfer substrate such that the separation layer includes the metal release layer and the mineral absorption layer, and the mineral absorption layer is configured to absorb at least 20% of the infrared radiation when irradiated.

[0013] Thus, the separation layer is in the form of a bilayer which advantageously allows the separation of the functions of each of the metal release layer and the mineral absorption layer.

[0014] The metal release layer is intended to be melted or evaporated by the action of the heat transferred by the absorption layer that absorbs infrared radiation. The metal release layer also protects the at least one semiconductor device from infrared radiation by reflecting the infrared radiation towards the absorption layer.

[0015] The mineral absorption layer allows efficient absorption of infrared radiation to generate sufficient heat to partially or completely melt or evaporate the metal release layer. Thus, the energy of the infrared radiation can be reduced.

[0016] In the context of the development of the present invention, it has been observed that although this can be considered theoretically, due to the reflectivity of aluminum, using a simple aluminum layer as the separation layer requires very high laser power in practice. In practice, a pulsed infrared laser "picosecond" (ps) cannot be used.

[0017] For example, the addition of a mineral absorption layer based on transition refractory nitrides allows a sufficient reduction in the energy required to melt / evaporate the metal release layer such that a pulsed infrared laser delivering an energy of less than or equal to 10 microjoules (µJ) can be used.

[0018] As an alternative to the separation layer, document WO2022111141A1 provides an aluminum layer or a light / heat conversion layer. In the first case, as indicated, due to the reflectivity of aluminum, the required energy is very high. In the second case, the reflectivity of the layer is reduced and the device is no longer protected from infrared radiation.

[0019] The practical development carried out in the context of the development of the present invention has led to the consideration of a combination of an absorption layer and a release / reflective layer, which is not considered in the alternatives suggested by document WO2022111141A1.

[0020] This combination advantageously allows reducing the required energy delivered by the pulsed infrared laser while protecting the device to be transferred.

[0021] Preferably, the metal release layer is in direct contact with the mineral absorption layer. There is no intermediate layer between the metal release layer and the mineral absorption layer. This allows the metal release layer to be melted / vaporized with locally reduced energy because all the energy absorbed by the mineral absorption layer is directly transferred to the metal release layer. This makes it possible to use a reduced energy density to release the semiconductor device from the transfer substrate via fusion / vaporization of this metal release layer. Different from the laser ablation process disclosed in the US2022406621A1 document which requires inserting a silicon-based layer between the metal release layer and the mineral absorption layer, a power density of less than or equal to 10E11 watts / cm 2 is generally sufficient.

[0022] On the other hand, there is provided a transfer structure including, one stacked on top of the other in the following order: - A so-called first receptor substrate, - At least one active layer intended to be integrated into at least one semiconductor device, - A separation layer, - A silicon-based transfer substrate, The stack is configured such that when irradiated with infrared (IR) radiation through the transfer substrate, the separation layer is at least partially eliminated to detach the transfer substrate (3) from the stack.

[0023] Advantageously, the separation layer includes: - A metal release layer located on one side of the active layer, - A mineral absorption layer located on one side of the transfer substrate, the mineral absorption layer being configured to absorb at least 20% of the infrared radiation when irradiated.

[0024] Such a transfer structure advantageously allows implementing the transfer method described above.

[0025] The stack of layers does not include any organic layer. Thus, this stack can advantageously be processed by conventional process steps of the microelectronics industry, for example to form semiconductor devices starting from the active layer after removing the donor substrate and before detaching the transfer substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The objects, aims, features and advantages of the present invention will become better apparent from the following detailed description of embodiments illustrated by the following drawings, in which: Figures 1A to 6 The steps of a transfer method according to an embodiment of the present invention are schematically illustrated.

[0027] Figures 7 to 14 Schematically illustrates the steps of a transfer method according to another embodiment of the present invention.

[0028] The accompanying drawings are given by way of example and do not limit the present invention. They constitute a schematic overview representation intended to facilitate understanding of the present invention and are not necessarily drawn to scale of actual application. In particular, the dimensions of the different layers and parts of the transfer structure and the LED do not necessarily represent the actual situation. Detailed Description

[0029] Before beginning a detailed review of the embodiments of the present invention, it should be recalled that, according to a first aspect of the present invention, the present invention particularly includes alternative features that may be used combinatorially or alternatively hereinafter.

[0030] According to one example, the at least one semiconductor device includes a plurality of semiconductor devices, each semiconductor device having a feature size less than or equal to 100 µm, preferably less than or equal to 10 µm, and preferably less than or equal to 5 µm.

[0031] According to one example, the irradiation is configured to detach only some of the plurality of semiconductor devices. Thus, the method enables local transfer of micro-components.

[0032] According to one example, the semiconductor devices among the plurality of semiconductor devices are separated from each other before irradiation, and the semiconductor devices remain supported by the separation layer above the transfer substrate. The semiconductor devices are typically individualized before detachment by laser irradiation.

[0033] According to one example, the irradiation is performed by a pulsed infrared laser that produces infrared radiation having an energy included between 0.1 µJ and 10 µJ, preferably between 1 µJ and 10 µJ, within a duration included between 100 femtoseconds (fs) and 10 picoseconds (ps). Advantageously, such a laser emits "low" energy radiation that can be shaped to be directed at the individualized semiconductor devices.

[0034] According to one example, the infrared radiation has a wavelength shorter than or equal to 2.5 µm.

[0035] According to one example, the irradiation is performed with a pulsed infrared laser that produces pulsed infrared radiation, and the energy of one pulse is included between 0.1 µJ and 10 µJ. According to one example, the duration of one pulse is included between 100 femtoseconds (fs) and 10 picoseconds (ps).

[0036] For example, the mutual separation of semiconductor devices is performed by anisotropic etching in a direction normal to the second face. According to one example, the anisotropic etching extends to the metal release layer, preferably to the mineral absorption layer, preferably to the second face. Removing the separation layer can advantageously make the decoupling clearer or more precise. The semiconductor devices are locally detached from the transfer substrate. The semiconductor devices can be removed individually or in small groups. The transfer of the semiconductor devices is not total. The plurality of semiconductor devices are not transferred to the receptor substrate. According to one example, the mineral absorption layer has a resistivity included between 50 µ.ohm.cm (micro-ohm-centimeter) and 1 m.ohm.cm (milli-ohm-centimeter). Such an absorption layer allows the conduction of charge carriers generated when absorbing infrared radiation. Advantageously, these charge carriers are conducted towards the metal release layer to increase the heat transferred to the metal release layer.

[0037] According to one example, the mineral absorption layer is selected to be made of a refractory material having a melting point higher than or equal to 1500 °C. This enables the implementation of most and possibly all heat treatments in the microelectronics industry without degrading the mineral absorption layer. Thus, the thermal degradation under infrared irradiation is limited to the metal release layer.

[0038] According to one example, the mineral absorption layer is selected to be made of a refractory material based on transition materials, preferably a refractory material based on Ti, V, Zr, Ta, Hf, Nb, W.

[0039] According to one example, the mineral absorption layer is selected from transition metals such as Ti, V, Zr, Ta, Hf, Nb, W.

[0040] According to one example, the mineral absorption layer is selected from transition refractory nitrides based on transition metals such as TiN, VN, ZrN, TaN, HfN, NbN or their alloys. According to another example, the mineral absorption layer is selected from transition refractory carbides based on transition metals. According to another example, the mineral absorption layer is selected from transition refractory borides based on transition metals.

[0041] According to one example, the mineral absorption layer has a thickness included between 10 nm and 100 nm.

[0042] According to one example, for irradiation wavelengths shorter than or equal to 2.5 µm, the mineral absorption layer has an extinction coefficient greater than 1.

[0043] According to one example, the metal release layer has a reflectivity higher than or equal to 97% in the infrared region. This allows protecting the semiconductor devices from the infrared radiation when irradiated.

[0044] According to one example, the metal release layer has a resistivity included between 2.5 µ.ohm.cm (micro - ohm - centimeter) and 50 µ.ohm.cm (micro - ohm - centimeter).

[0045] According to one example, the metal release layer has a thickness included between 30 nm and 200 nm.

[0046] According to one example, the metal release layer is based on simple metals such as aluminum, tin, zinc or on metal alloys having a melting point lower than or equal to 700 °C.

[0047] According to one example, the metal release layer has a melting point lower than or equal to 700 °C.

[0048] According to one example, the mineral absorption layer is made of a refractory material having a melting point higher than or equal to 2500 °C.

[0049] According to one example, the mineral absorption layer is based on transition refractory nitrides selected from TiN, VN, ZrN, TaN, HfN, NbN or alloys of said transition refractory nitrides.

[0050] Except in incompatible cases, the technical features described in detail for a given embodiment can be combined with the technical features described in the context of other embodiments described as non - limiting examples to form another embodiment that is not necessarily illustrated or described. Of course, the present invention does not exclude such an embodiment.

[0051] In the present invention, the method is particularly dedicated to transferring semiconductor devices, particularly devices having micron dimensions such as light - emitting diodes (LEDs). An LED or an individualized semiconductor device generally has dimensions included between 2.5 µm X 2.5 µm and 100 µm X 100 µm in the projection on the base plane xy.

[0052] The present invention can be implemented for different microelectronic or optoelectronic devices and possibly more broadly for electromechanical devices or micro - systems MEMS. For example, the present invention can be implemented in the context of lasers or photovoltaic devices.

[0053] Unless explicitly stated, it is stipulated that in the context of the present invention, the relative arrangement of a third layer interposed between a first layer and a second layer does not necessarily mean that the layers are in direct contact with each other, but means that the third layer is in direct contact with the first layer and the second layer, or is separated from these layers by at least one other layer or at least one other element.

[0054] Thus, the terms and idioms "carry" and "cover" or "lie on top of" do not necessarily mean "contact".

[0055] The steps of the claimed method should be understood in a broad sense and may be implemented as several sub-steps.

[0056] In this patent application, the terms "light-emitting diode", "LED", or simply "diode" are used as synonyms. Where appropriate, "LED" may also be understood as "micro-LED" or smart LED.

[0057] A part or element described as "sacrificial" means that this element is intended to be "sacrificed", i.e., removed during subsequent steps of the method.

[0058] By a substrate, layer, device "based on" material M, it should be understood to include only this material M or a substrate, layer, device that includes this material M and possibly includes other materials (e.g., alloying elements, impurities, or doping elements). Thus, a GaN-based diode typically includes GaN and an AlGaN or InGaN alloy.

[0059] In some figures, a reference system including axes x, y, z is represented, preferably an orthogonal reference system. This reference system can be extended to apply to other figures on the same page.

[0060] In this patent application, the thickness of a layer and the height of a structure or device will preferably be discussed. The thickness is considered in the direction normal to the main plane of extension of the layer, and the height is considered perpendicular to the base plane xy. Thus, when a layer extends mainly along the plane xy, the layer typically has a thickness according to z, and a protruding element (e.g., a device) has a height according to z. The related terms "above", "below", "beneath" preferably refer to positions considered in the direction z.

[0061] Dimension values should be understood within manufacturing tolerances and measurement tolerances.

[0062] The terms "substantially", "about", "within the range of" mean that when they relate to a value, within "10% of" this value, or when they relate to an angular orientation, within "10° of" this orientation. Thus, a direction substantially normal to a plane means a direction having an angle of 90 ± 10° with respect to this plane.

[0063] In this patent application, the optical absorption coefficient denoted as α or a is defined by the ratio of the absorbance to the length of the optical path followed by electromagnetic radiation in a given medium (in or expressions).

[0064] The extinction coefficient, denoted as k (also known as the attenuation coefficient) of the medium measures the energy loss of electromagnetic radiation passing through this medium. Similar to the absorption coefficient, in addition to absorbance, it also takes into account the effects due to diffusion and luminescence. It depends on the material and the wavelength. It is the imaginary part of the complex refractive index: n = n' + in'', where k = n''. Transparent materials have a low extinction coefficient, while opaque materials have a high extinction coefficient.

[0065] In the context of the present invention, for wavelengths included between 1 µm and 2.5 µm, irradiation is performed in the infrared wavelength domain, preferably in the near-infrared domain.

[0066] An object of the present invention is to transfer a semiconductor or optoelectronic device onto a receptor substrate (such as a screen support) via a transfer structure and an infrared laser ablation process. The principle of the present invention includes performing transfer and bonding via a separation layer (preferably in direct contact with each other) including a metal release layer and a mineral absorption layer. In the context of the said transfer method, the metal release layer is a sacrificial layer. In particular, the absorption layer absorbs infrared light and converts it into heat. In particular, this heat diffuses towards the metal release layer. This generally causes partial melting or partial evaporation of the metal release layer at the interface between the two layers. Then the interface between the two layers is degraded, and the two layers can be separated. An unmelted portion of the release layer can remain on one side of the transferred device.

[0067] Figure 1A and Figure 1B Illustrates two variants, where the separation layer 20 is directly formed on top of the transfer substrate 3 respectively ( Figure 1A ), or directly formed on top of the donor substrate 1 ( Figure 1B ).

[0068] According to Figure 1A the first example illustrated in, a donor substrate 1 is provided, which generally includes an active layer 10 covered by a mineral bonding layer 11. Preferably, the donor substrate 1 is silicon-based.

[0069] For example, the active layer 10 can be based on GaN (p-GaN and / or n-GaN) and / or AlGaN and / or InGaN epitaxially grown on the donor substrate 1. It generally includes an active layer, which includes, for example, a PN junction or a quantum well, configured to form a semiconductor device, such as one or more LEDs. The active layer 10 can also include three-dimensional structures arranged adjacent to each other, such as based on InGaN, such as nanowires or nanopillars. The active layer 10 can also include sub-layers, which can be structured and intended to form, for example, electrical contacts based on transparent conductive oxides (TCO) on p-GaN or on n-GaN, for example.

[0070] The mineral bonding layer 11 is typically silicon dioxide SiO2. In particular, it allows for the planarization of the active layer 10 to obtain a planar surface 201 suitable for mineral bonding and enables the direct bonding of SiO2 on SiO2.

[0071] The transfer substrate 3 is silicon-based. In this example, the separation layer 20 is formed on the surface 202 of the transfer substrate 3. The exposed surface 203 of the separation layer 20 is typically planar and suitable for mineral bonding. For example, mineral bonding can include molecular bonding. The mineral bonding between the transfer substrate 3 and the donor substrate 1 is performed herein between the surface 201 and the surface 203.

[0072] The separation layer 20 includes at least one mineral absorption layer 22 and at least one metal release layer 21. The mineral absorption layer 22 is formed on one side of the transfer substrate 3, for example, directly on the surface 202. The metal release layer 21 is formed on the mineral absorption layer 22 such that the mineral absorption layer 22 is interposed between the transfer substrate 3 and the metal release layer 21. In this case, the exposed surface 203 of the separation layer 20 corresponds to one surface of the metal release layer 21. According to a possibility not illustrated, a silicon dioxide layer is formed on the surface 203 of the separation layer 20. Then, bonding is performed by SiO2 - SiO2 type molecular bonding.

[0073] The mineral absorption layer 22 is typically at least partially conductive and preferably has a resistivity included between 50 µ.ohm.cm and 1 m.ohm.cm. This allows for optimizing the heat transfer and electron transfer between the mineral absorption layer 22 and the metal release layer 21. The mineral absorption layer 22 has a thickness according to z, which is preferably included between 10 nm and 100 nm. For wavelengths shorter than or equal to 2.5 µm, it typically has an optical extinction coefficient k greater than 1 in the near-infrared domain. This allows for absorbing at least 20%, and possibly at least 30% or at least 40% of the infrared radiation in this near-infrared domain. The mineral absorption layer 22 can be based on transition metals, such as Ti, Ta, W, Zr, Nb, Hf. Alternatively, it can be based on nitrides of these transition metals, called transition refractory nitrides, such as TiN, TaN, VN, ZrN, HfN, NbN. Alternatively, it can be based on carbides of these transition metals, called transition refractory carbides, such as TiC, TaC, VC. Alternatively, it can be based on borides of these transition metals, called transition refractory borides, such as TiB2, TaB, TaB2, VB2, HfB2. The mineral absorption layer 22 can be based on a combination or alloy of these materials, such as C5HfTa4. Preferably, the mineral absorption layer 22 has a melting point higher than or equal to 1500 °C. This avoids the thermal degradation of the mineral absorption layer 22 when irradiated. Thus, after irradiation, the integrity of the mineral absorption layer 22 is maintained.

[0074] The metal release layer 21 is generally conductive and preferably has a resistivity between 2.5 µ.ohm.cm and 50 µ.ohm.cm. Preferably, the metal release layer 21 has a thickness according to z, which thickness is included between 30 nm and 200 nm. For wavelengths shorter than or equal to 2.5 µm, it generally has an optical reflectivity higher than or equal to 97% in the near-infrared domain; when irradiating through the transfer substrate 3, the infrared radiation transmitted by the mineral absorption layer 22 is thus reflected by the metal release layer 21. This allows protecting the semiconductor layer 10 and / or the semiconductor device formed starting from the semiconductor layer 10 from infrared radiation. The metal release layer 21 can be based on a simple metal, such as Al, Sn, Zn. Preferably, the metal release layer 21 has a melting point lower than or equal to 700 °C. Thus, the melting point difference between the metal release layer 21 and the mineral absorption layer 22 is large enough to ensure the partial (not illustrated) or complete melting / vaporization of the metal release layer 21 while maintaining the integrity of the mineral absorption layer 22.

[0075] The characteristics of the different layers 10, 11, 21, 22, in particular the characteristics of the mineral absorption layer 22 and the metal release layer 21, are common to other embodiments described later.

[0076] According to Figure 1B In the second example illustrated in, the separation layer 20 is formed on the face 201 of the donor substrate 1. Here, the exposed face 204 of the separation layer 20 corresponds to one face of the mineral absorption layer 22. The mineral bonding between the transfer substrate 3 and the donor substrate 1 is performed here between the faces 202 and 204. According to a possibility not illustrated, one or more silicon oxide layers are formed on the face 204 of the separation layer 20 and on the face 202 of the transfer substrate 3. The bonding is then performed by SiO2-SiO2 type molecular bonding.

[0077] In this example, the metal release layer 21 is formed on one side of the donor substrate 1, for example directly on the face 201. The mineral absorption layer 22 is formed on the metal release layer 21 such that the metal release layer 21 is interposed between the donor substrate 1 and the mineral absorption layer 22.

[0078] As Figure 2 illustrated in, regardless of whether the separation layer 20 is formed on the face 201 or on the face 202, the donor substrate 1 and the transfer substrate 3 are generally assembled by molecular bonding via the separation layer 20.

[0079] As Figure 3 illustrated in, the donor substrate 1 is then removed, for example partially by trimming and partially by chemical mechanical polishing (CMP) or by selective chemical etching with respect to the active layer 10. The active layer 10 and the oxide layer 11 are retained on the transfer substrate 3.

[0080] AsFigure 4 As illustrated in, after that, the active layer 10 and the oxide layer 11 are structured to form individualized semiconductor devices 100, such as LEDs. This structuring can include a step of annealing at a temperature of several hundred degrees Celsius. Advantageously, the layers 21, 22 of the separation layer 20 withstand these temperatures. Thus, the structuring can be carried out after the initial layers 10, 11 are transferred onto the transfer substrate 3. Therefore, the transfer method has less constraint on the order of the steps for forming the device 100. In Figure 4 In the example illustrated in, the semiconductor device 100 includes an insulating and transparent part 111, an active part 110 that is generally configured to emit light, and contact pads 112. In particular, forming the individualized device 100 can include one or more anisotropic etchings according to z. Etching the oxide layer 11 is generally selective with respect to the metal release layer 21. According to a non-illustrated possibility, the anisotropic etching intended to separate the devices 100 from each other extends to the mineral absorption layer 22 or even to the transfer substrate 3. The separation layer 20 can thus be sculpted according to all or part of its thickness according to z. As Figure 5 As illustrated in, after forming the device 100, the transfer substrate 3 is opposed to a receptor substrate 2 (such as a screen support) intended to receive at least some of the devices 100. The face 205 of the receptor substrate 2 generally has contact pads 211 at the positions intended to receive the devices 100. After aligning the contact pads 112 and the contact pads 211, a bonding is performed, such as by thermocompression or by Cu-Cu bonding between the contact pads 112, 211. Then, the separation layer 20 is irradiated by infrared radiation passing through the transfer substrate 3. This infrared radiation is generally only localized above the devices 100 to be transferred. The layer 22 generally absorbs at least 20%, preferably at least 30% or at least 40% of this infrared radiation. The energy of the infrared radiation thus absorbed is transmitted to the metal release layer 21 in the form of heat.

[0081] As Figure 6 As illustrated in, the metal release layer 21 is locally melted or evaporated under the action of the heat caused by the infrared radiation, thereby releasing some of the devices 100a assembled on the receptor substrate 2. The infrared radiation is localized, and other devices 100b can be held on the transfer substrate 3 via the unmelted part 21p of the metal release layer 21. Then, the transfer substrate 3 can be taken to another position to perform another transfer, such as for the devices 100b.

[0082] Infrared radiation generally has a wavelength included between 1 µm and 2.5 µm, preferably included between 1.5 µm and 2 µm. Preferably, it is generated in the form of pulses by a pulsed laser. Preferably, the energy of the infrared radiation pulses is included between 0.1 µJ and 10 µJ, preferably included between 1 µJ and 10 µJ, for example in the range of 7 µJ or 8 µJ. Preferably, the duration of the infrared radiation pulses is included between 100 fs and 10 ps, preferably included between 1 ps and 10 ps. A single infrared radiation pulse may be sufficient to detach the device 100a from the transfer substrate 3. Irradiation can be carried out by a beam (usually a laser beam) having a power lower than or equal to 10 E 11 watts / cm².

[0083] Figures 7 to 14 Another embodiment of the transfer method is illustrated. In this embodiment, first the semiconductor layer 10 is transferred from the growth substrate 1a to an intermediate substrate 1b, for example silicon-based. After the active layer 10 is grown on the substrate 1a ( Figure 7 ), the intermediate substrate 1b is bonded to the active layer 10 via one or more oxide layers 11 (for example silicon oxide-based) ( Figure 8 ). Thereafter, the growth substrate 1a is removed, for example partly by trimming and partly by chemical mechanical polishing (CMP) or by selective chemical etching with respect to the active layer 10, to expose the face 200 of the active layer 10 ( Figure 9 ).

[0084] As Figure 10 illustrated, the intermediate substrate 1b carrying the active layer 10 is bonded to the transfer substrate 3 via a separation layer 20. The separation layer 20 may be pre-formed on the face 200 of the active layer 10 or on the face 202 of the transfer substrate 3. Here the intermediate substrate 1b corresponds to the donor substrate 1 of the previously described embodiment. A mineral absorption layer 22 is formed to be positioned on one side of the transfer substrate 3. A metal release layer 21 is formed to be positioned on one side of the active layer 10.

[0085] As Figure 11 illustrated, after bonding, the intermediate substrate 1b is removed, for example by trimming and / or polishing and / or chemical etching. Preferably, the oxide layer 11 is also removed to expose the active layer 10, for example by polishing and / or chemical etching.

[0086] As Figure 12As illustrated, the active layer 10 can then be structured to form individualized devices 100. In this example, the device 100 generally includes an active portion 110 configured to emit light, for example, and contact pads 112. As before, forming the individualized devices 100 can specifically include one or more anisotropic etches according to z. The active layer 10 is generally etched anisotropically with respect to the underlying metal release layer 21. As before, the anisotropic etches intended to separate the devices 100 from each other can extend to the mineral absorption layer 22 or even to the transfer substrate 3. The separation layer 20 can thus be sculpted according to all or part of its thickness according to z.

[0087] As before, after forming the device 100, the transfer substrate 3 is brought opposite the receptor substrate 2. The contact pads 112 and the contact pads 211 are aligned and bonded together. Then, local irradiation of the separation layer 20 is performed with infrared radiation passing through the transfer substrate 3 ( Figure 13 ). The metal release layer 21 is locally melted or evaporated under the action of the heat caused by the infrared radiation, thereby releasing the device 100a assembled on the receptor substrate 2 and holding the other devices 100b on the transfer substrate 3 ( Figure 14 ). The transfer substrate 3 can then be brought to another location to perform another transfer, for example, for the remaining devices 100b.

[0088] Thus, as illustrated in all the previous examples, the transfer structure and method according to the present invention advantageously allow a single semiconductor device to be formed at the time of transfer, after removal of the donor substrate, and to transfer them to the receptor substrate in a localized manner.

[0089] However, the present invention is not limited to the embodiments described previously.

[0090] Specifically, the number, shape, and arrangement of the semiconductor devices can be adjusted according to the target application.

Claims

1. A method for transferring at least one semiconductor device (100, 100a) from a so-called first donor substrate (1, 1b) to a so-called second acceptor substrate (2) using a silicon-based transfer substrate (3), the method comprising at least the following steps: • Providing the donor substrate (1, 1b), the donor substrate (1, 1b) including at least one active layer (10) intended to be integrated into the semiconductor device (100, 100a, 100b) at a first face (201, 200), • Providing the silicon-based transfer substrate (3), the silicon-based transfer substrate (3) having a second face (202), • Forming a separation layer (20) on at least one of the first face (201, 200) and the second face (202), the separation layer (20) being inorganic, • Assembling the donor substrate (1, 1b) with the transfer substrate (3) via the separation layer (20), • Removing the donor substrate (1, 1b) while maintaining the at least one active layer (10) above the transfer substrate (3) and forming a plurality of semiconductor devices (100, 100a, 100b) starting from the at least one active layer (10), • Separating the semiconductor devices among the plurality of semiconductor devices (100a, 100b), the semiconductor devices being held by the separation layer (20) above the transfer substrate (3), • Providing the acceptor substrate (2), • Assembling the semiconductor devices (100, 100a, 100b) with the acceptor substrate (2), • Irradiating the separation layer (20) with infrared radiation (IR) through the transfer substrate (3) to at least partially eliminate the separation layer (20) to detach only some of the plurality of semiconductor devices (100, 100a, 100b) from the transfer substrate (3), The method is characterized in that forming the separation layer (20) includes forming a metal release layer (21) on one side of the active layer (10) and forming a mineral absorption layer (22) on one side of the transfer substrate (3), such that the separation layer (20) includes the metal release layer (21) and the mineral absorption layer (22), the mineral absorption layer (22) being configured to absorb at least 20% of the infrared radiation when irradiated.

2. The method according to the previous claim, wherein the metal release layer (21) is in direct contact with the mineral absorption layer (22).

3. The method according to any one of the preceding claims, wherein each semiconductor device (100) among the plurality of semiconductor devices (100a, 100b) has a feature size less than or equal to 10 µm.

4. The method according to any one of the preceding claims, wherein the irradiation is performed by a pulsed infrared laser that generates infrared radiation having an energy included between 0.1 µJ and 10 µJ within a duration included between 100 femtoseconds (fs) and 10 picoseconds (ps).

5. The method according to any one of the preceding claims, wherein the irradiation is performed by a beam having a power of less than or equal to 10 E 11 watts / cm².

6. The method according to any one of the preceding claims, wherein the mutual separation of the semiconductor devices (100, 100a, 100b) is achieved by anisotropic etching in a direction normal to the second face (202), the anisotropic etching extending to the metal release layer (21), preferably extending to the mineral absorption layer (22), preferably extending to the second face (202).

7. The method according to any one of the preceding claims, wherein the mineral absorption layer (22) has a resistivity included between 50 µ.ohm.cm (micro - ohm - centimeter) and 1 m.ohm.cm (milli - ohm - centimeter).

8. The method according to any one of the preceding claims, wherein the mineral absorption layer (22) is selected to be made of a refractory material having a melting point higher than or equal to 1500 °C.

9. The method according to any one of the preceding claims, wherein the mineral absorption layer (22) is selected to be made of a refractory material based on transition metals, preferably made of a refractory material based on Ti, V, Zr, Ta, Hf, Nb, W.

10. The method according to any one of the preceding claims, wherein the mineral absorption layer (22) is selected from transition refractory nitrides based on transition metals, such as TiN, VN, ZrN, TaN, HfN, NbN or their alloys.

11. The method according to any one of the preceding claims, wherein the metal release layer (21) has a reflectivity higher than or equal to 97% in the infrared region.

12. The method according to any one of the preceding claims, wherein the metal release layer (21) has a resistivity included between 2.5 µ.ohm.cm (micro - ohm - centimeter) and 50 µ.ohm.cm (micro - ohm - centimeter).

13. The method according to any one of the preceding claims, wherein the metal release layer (21) has a melting point lower than or equal to 700 °C.

14. A transfer structure, the transfer structure comprising, stacked one on top of the other in the following order: • A silicon - based transfer substrate (3), • A separation layer (20), • A plurality of mutually separated semiconductor devices (100a, 100b), each semiconductor device comprising at least an active part (110) and a contact pad (112), the contact pad (112) being intended to be bonded to a contact pad (211) arranged on top of a receptor substrate (2), The transfer structure is configured such that, when irradiated with infrared (IR) radiation through the transfer substrate (3), the separation layer (20) is at least partially eliminated to detach some of the plurality of semiconductor devices (100, 100a, 100b) (100a) from the transfer substrate (3). The separation layer (20) comprises: - A metal release layer (21) located on one side of the plurality of semiconductor devices (100a, 100b), - A mineral absorption layer (22) located on one side of the transfer substrate (3), the mineral absorption layer (22) being configured to absorb at least 20% of the infrared radiation when irradiated.

15. The structure according to the preceding claim, wherein the metal release layer (21) is in direct contact with the mineral absorption layer (22).

16. The structure according to any one of claims 14 to 15, wherein the mineral absorption layer (22) has a resistivity included between 50 µ.ohm.cm (micro - ohm - centimeter) and 1 m.ohm.cm (milli - ohm - centimeter).

17. The structure according to any one of claims 14 to 16, wherein the mineral absorption layer (22) is made of a refractory material having a melting point higher than or equal to 1500 °C.

18. The structure according to any one of claims 14 to 17, wherein the mineral absorption layer (22) is selected to be made of a transition - metal - based refractory material, preferably made of a refractory material based on Ti, V, Zr, Ta, Hf, Nb, W.

19. The structure according to any one of claims 14 to 18, wherein the mineral absorption layer (22) is based on a transition refractory nitride among TiN, VN, ZrN, TaN, HfN, NbN or an alloy of the transition refractory nitrides.

20. The structure according to any one of claims 14 to 19, wherein the metal release layer (21) has a reflectivity higher than or equal to 97% in the infrared region.

21. The structure according to any one of claims 14 to 20, wherein the metal release layer (21) has a resistivity included between 2.5 µ.ohm.cm (micro - ohm - centimeter) and 50 µ.ohm.cm (micro - ohm - centimeter).

22. The structure according to any one of claims 14 to 21, wherein the metal release layer (21) has a melting point lower than or equal to 700 °C.

Images