Production of a thin substrate layer

Abstract

Method for producing a thin substrate layer (30) with a thickness of at most 100 µm, wherein - the substrate layer (30) is detached from the ingot (20) by generating a tensile stress input on the ingot (20), wherein the ingot (20) consists of germanium, - the tensile stress input is caused by means of a stressor layer structure (10) that is materially connected to a first surface (22) of the ingot (20), - the stressor layer structure (10) comprises a titanium-containing adhesive layer (12) and a nickel-containing layer (14), - the titanium-containing adhesive layer (12) adjoins the first surface (22) of the ingot (20) with an underside and the titanium-containing adhesive layer (12) comprises at least 30% titanium, - the nickel-containing layer (14) abuts a top side of the titanium-containing adhesive layer (12) and the nickel-containing layer (14) comprises at least 30% nickel, - the nickel-containing layer (14) and the ingot (20) have different coefficients of thermal expansion and - after the substrate layer (30) has been detached from the ingot (20), the stressor layer structure (10) is removed from the substrate layer (30), characterized in that - the stressor layer structure (10) comprises only the one nickel-containing layer (14) and the one titanium-containing adhesive layer (12), - the stressor layer structure (10) is applied to the ingot (20) at a first temperature (T1), - the substrate layer (30) together with the stressor layer structure (10) is heated to a second temperature (T2) and then cooled to a third temperature (T3), - the substrate layer (30) together with the stressor layer structure (10) is detached at the third temperature (T3), - the second temperature (T2) is higher than the first temperature (T1) by a temperature difference, - the third temperature (T3) is lower than the second temperature (T2), - the third temperature (T3) differs from the first temperature (T1) by no more than 50°C or no more than 30°C, - the second temperature (T2) is at most 240°C or at most 220°C or at most 200°C.

Description

[0001] The invention relates to a method for producing a thin substrate layer.

[0002] Thin layers of a substrate, e.g. a semiconductor material, are produced relatively inexpensively, among other methods, by peeling the substrate layer from an ingot.

[0003] As described in US 5,374,564 A and US 6,100,166 A, a predetermined breaking point can be created within the ingot by generating a porous layer at a distance from the ingot's surface. The thin layer of the ingot extending from the porous layer to the surface is then detached after the metallurgical application of a film to the ingot's surface, along with the film itself.

[0004] A method for producing a thin substrate layer is known from US Patent 2007 / 0249140A1, wherein the substrate layer is detached from the ingot by controlled stress input. The stress is applied by depositing another layer onto a surface of the ingot, whereby the coefficients of thermal expansion of the ingot and the additional layer differ, and the temperature of the ingot and the additional layer is altered. Further methods for producing a thin substrate layer are known from US Patent 2010 / 0310775A1, US Patent 2007 / 0249140A1, and US Patent 2009 / 0280635A1.

[0005] Against this background, the object of the invention is to provide a device that further develops the state of the art.

[0006] The problem is solved by a method for producing a thin substrate layer with the features of claim 1. Advantageous embodiments of the invention are the subject of dependent claims.

[0007] According to the subject matter of the invention, a method for producing a thin substrate layer with a thickness of at most 100 µm is provided, wherein the substrate layer is detached from the ingot by generating a tensile stress input onto an ingot and the tensile stress input is effected by means of a stressor layer structure that is materially bonded to a first surface of the ingot.

[0008] The stressor layer structure comprises a titanium-containing adhesive layer and a nickel-containing layer, wherein the titanium-containing adhesive layer adjoins the first surface of the ingot with an underside and comprises at least 30% titanium.

[0009] The nickel-containing layer borders the titanium-containing adhesive layer with an underside and comprises at least 30% nickel.

[0010] The nickel-containing layer and the ingot have different coefficients of thermal expansion.

[0011] After heating to the second temperature, the ingot with the stressor layer is cooled to a third temperature.

[0012] At the third temperature, the substrate layer and the stressor layer are separated from the ingot.

[0013] The third temperature differs from the first temperature by no more than 50°C or no more than 10°C. Preferably, the third temperature is higher than the first temperature.

[0014] The third temperature is lower than the second temperature.

[0015] The second temperature is at most 240°C or at most 220°C or at most 200°C.

[0016] In a further process step, not described in detail, after the substrate layer with the stressor layer structure has been detached, the substrate layer with the stressor layer structure is deposited onto a support, and then the stressor layer structure is removed from the thin substrate layer. Alternatively, after the substrate layer with the stressor layer structure has been detached, the detached layer structure is processed further without being deposited onto a support.

[0017] It should be noted that the ingot and, consequently, the thin substrate layer to be produced, typically consists of a single-crystal semiconductor material, e.g., GaN, Ge, or GaAs.

[0018] The detached thin layer is called a wafer and serves as a substrate for the production of electronic components. The components are formed within the wafer and / or on its surface using semiconductor processes.

[0019] It is understood that when the mass fraction is given as a percentage, the proportion of the respective element or compound to the total mass of the layer is always understood.

[0020] Heating increases the adhesion between the nickel-containing layer and the adhesive layer.

[0021] Limiting the second temperature ensures that no plastic deformation occurs within the nickel-containing layer, particularly after detachment at the third temperature.

[0022] Studies have shown that limiting the second temperature and slow cooling reduces or even completely avoids curvature and / or deformation of the detached substrate layer.

[0023] The present method allows for the reliable and reproducible production of particularly flat, thin substrate layers.

[0024] In one embodiment, the detached layer can be processed directly without being deposited onto a support substrate. Furthermore, additional process steps for smoothing the thin substrate layer are no longer necessary, thus reducing production costs.

[0025] Another advantage of reliable and simple production of thin substrate layers is that the use of problematic materials such as GaAs or Ge can be reduced, and production costs decrease.

[0026] In one embodiment, the temperature difference is at most 200°C, or at most 150°C, or at most 100°C.

[0027] In another embodiment, the nickel-containing adhesive layer has a thickness between 20 µm and 150 µm or a thickness between 30 µm and 70 µm.

[0028] According to another embodiment, the titanium-containing layer has a thickness of at most 1 µm or at most 50 nm.

[0029] In one further development, the detachment of the substrate layer is initiated by a mechanical impulse. In other words, a force is applied to the side surface of the ingot. In another further development, the detachment also occurs spontaneously, i.e., without the application of a force.

[0030] According to another method, the titanium-containing adhesive layer consists of titanium and the nickel-containing layer consists of nickel.

[0031] The stressor layer structure preferably comprises only one nickel-containing layer and one titanium-containing adhesive layer.

[0032] According to another embodiment, the first temperature is room temperature or lies in a range between 15°C and 25°C. The third temperature preferably corresponds to the first temperature.

[0033] In a further training process, the ingot with the stressor layer structure is heated to the second temperature at a heating rate of at most 10°C per minute, or at most 6°C per minute, or at most 4°C per minute, and then cooled to a third temperature at a cooling rate of at most 10°C per minute, or 5°C per minute, or 1°C per minute, or 0.1°C per minute.

[0034] The invention is explained in more detail below with reference to the drawings. Similar parts are labelled with identical designations. The illustrated embodiments are highly schematic; that is, the distances and the lateral and vertical extents are not to scale and, unless otherwise indicated, do not exhibit any derivable geometric relationships to one another. The drawings show: Fig. 1. A view of process steps for producing a thin substrate layer.

[0035] The illustration of Fig. Figure 1 outlines a method for producing a thin substrate layer 30 according to a first embodiment.

[0036] In a first process step, at a first temperature T1, e.g. room temperature, a stressor layer structure is applied to a surface 22 of an ingot 20, e.g. made of germanium, whereby a bottom side of the stressor layer structure 10 is bonded to the top side 22 of the ingot.

[0037] The stressor layer structure 10 comprises a titanium-containing adhesive layer 12, e.g., consisting entirely of titanium, and a nickel-containing layer 14, e.g., consisting entirely of nickel. The titanium-containing adhesive layer 12 forms the underside of the stressor layer structure 10 and borders the surface 22 of the ingot 20. The nickel-containing layer 14 follows the adhesive layer 12.

[0038] In a subsequent process step, the ingot 20 with the stressor layer structure 10 is heated by a first heating rate to a second temperature T2, e.g., 200°C, and then cooled to a third temperature T3. The third temperature T3 is therefore lower than the second temperature T2 and higher than or equal to the first temperature T1.

[0039] Preferably, the ingot (20) with the stressor layer structure (10) is heated to the second temperature (T2) at a heating rate of at most 10°C per minute or at most 6°C per minute or at most 4°C per minute and then cooled to a third temperature (T3) at a cooling rate of at most 10°C per minute or 5°C per minute or 1°C per minute or 0.1°C per minute.

[0040] Due to the tensile stress input on the ingot 20 caused by the different coefficients of thermal expansion of the ingot 20 and the stressor layer structure 10, in particular the nickel-containing layer 14, a thin substrate layer 30 with the stressor layer structure 10 detaches from the ingot 20 at the third temperature T3 either spontaneously or preferably by means of a mechanical impulse MP.

[0041] In a further process step, which is not shown in detail, the substrate layer 30 with the stressor layer structure 10 is placed on a support 40 and then the stressor layer structure 10 is removed from the thin substrate layer 30.

Claims

[1] Method for producing a thin substrate layer (30) with a thickness of at most 100 µm, wherein - the substrate layer (30) is detached from the ingot (20) by generating a tensile stress input on an ingot (20), wherein the ingot (20) consists of germanium, - the tensile stress input is effected by means of a stressor layer structure (10) which is materially bonded to a first surface (22) of the ingot (20), - the stressor layer structure (10) comprises a titanium-containing adhesive layer (12) and a nickel-containing layer (14), - the titanium-containing adhesive layer (12) is adjacent to the first surface (22) of the ingot (20) with a lower side and the titanium-containing adhesive layer (12) comprises at least 30% titanium, - the nickel-containing layer (14) has a bottom side adjacent to a top side of the titanium-containing adhesive layer (12) and the nickel-containing layer (14) comprises at least 30% nickel, - the nickel-containing layer (14) and the ingot (20) have different thermal expansion coefficients and - after detaching the substrate layer (30) from the ingot (20), the stressor layer structure (10) is removed from the substrate layer (30), characterized by , that - the stressor layer structure (10) comprises only the one nickel-containing layer (14) and the one titanium-containing adhesive layer (12), - the stressor layer structure (10) is applied to the ingot (20) at a first temperature (T1), - the substrate layer (30) together with the stressor layer structure (10) is heated to a second temperature (T2) and then cooled to a third temperature (T3), - the substrate layer (30) together with the stressor layer structure (10) is removed at the third temperature (T3), - the second temperature (T2) is higher than the first temperature (T1) by a temperature difference, - the third temperature (T3) is lower than the second temperature (T2), - the third temperature (T3) differs from the first temperature (T1) by no more than 50°C or 30°C, - the second temperature (T2) is not more than 240°C or not more than 220°C or not more than 200°C. [2] Method according to claim 1, characterized by that the temperature difference is not more than 200° C or not more than 150° C or not more than 100° C. [3] Method according to claim 1 or claim 2, characterized by that the nickel-containing layer (14) has a thickness between 20 µm and 150 µm or a thickness between 30 µm and 70 µm. [4] Method according to one of claims 1 to 3, characterized by that the titanium-containing adhesive layer (12) has a thickness of at most 1 µm or at most 50 nm. [5] Method according to one of claims 1 to 4, characterized bythat the detachment of the substrate layer (30) is initiated by a mechanical impulse (MP). [6] Method according to one of claims 1 to 5, characterized by that the titanium-containing adhesive layer (12) consists of titanium and the nickel-containing layer (14) consists of nickel. [7] Method according to one of claims 1 to 6, characterized by that the first temperature (T1) is between 15°C and 25°C. [8] Method according to one of claims 1 to 7, characterized by that the third temperature (T3) matches the first temperature (T1). [9] Method according to one of claims 1 to 8, characterized bythat the ingot (20) with the stressor layer structure (10) is heated to the second temperature (T2) at a heating rate of at most 10° C per minute or at most 6° C per minute or at most 4° C per minute and is then cooled to a third temperature (T3) at a cooling rate of at most 10° C per minute or 5° C per minute or 1° C per minute or 0.1° C per minute.

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