semiconductor component

Abstract

A semiconductor component (10) for emitting light, having a base body (14) and electrical contacts (20), the base body comprising a mesa (16) having an emission area (18) for light, the mesa being assigned a first mirror section, a second mirror section (14) and an active section, the active section being arranged between the two mirror sections and serving for generating light, the electrical contacts serving for feeding electrical energy to the active section, at least one stress element (20) being attached to a surface (22) of the base body (14) and generating a material stress (25) in the base body (14), which has an influence on properties of the emitted light, such as the polarization extinction ratio. A method for generating a material stress (25) in a semiconductor component.

Description

Technical Field

[0001] The present invention relates to a semiconductor component for emitting light and a method for generating material stress within the substrate of the semiconductor component. Background Technology

[0002] Due to their small size, strong electric fields are generated, and these fields affect the refractive index of the materials that form the basis of the semiconductor components. For example, this effect is problematic in the case of VCSELs (Vertical-Cavity Surface-Emitting Lasers), where the polarization direction of the emitted light is not permanent under all operating conditions.

[0003] However, light-emitting semiconductor components such as VCSELs (which may also be equipped with, for example, integrated photodiodes, especially for sensor applications) require that the polarization of the emitted light is stable in the polarization direction, preferably linear. Summary of the Invention

[0004] The present invention provides a semiconductor component for emitting light, the semiconductor component comprising a substrate including a mesa having a light-emitting region, the mesa being designated with a first mirror section, a second mirror section, and an active section disposed between the two mirror sections and for generating light, and the semiconductor component including electrical contacts for feeding electrical energy into the active section, and at least one preferably mechanical stress element attached to the surface of the substrate and generating additional material stress in the substrate in a preferred direction, the additional material stress affecting characteristics of the emitted light, such as polarization extinction ratio.

[0005] The substrate and mesa contain at least partially crystalline semiconductor material through which light can propagate so that it can exit from the emitting region to the outside. The crystalline semiconductor material exhibits birefringence. The emitted light is essentially polarized in two independent, preferably orthogonal, directions. The ratio of the intensities in the two polarization directions is called the polarization extinction ratio (PER).

[0006] The material stress additionally generated by the stress element can have a curve in terms of stress intensity that gradually decreases from the stress element in the direction inside the matrix. Furthermore, the stress element preferably generates material stress that acts primarily in one direction within the matrix material.

[0007] The characteristics of emitted light, particularly the polarization extinction ratio, can be altered by changing material stress. Specifically, the polarization extinction ratio can be changed by modifying the birefringence properties of the crystalline material forming the matrix. Depending on the alignment of the material stress relative to the crystal axis, for example, according to the Miller indices in the (110) or (1-10) direction, changes in intensity can occur in two polarization directions. In particular, the intensity of the first polarization direction increases, while the intensity of the second polarization direction decreases.

[0008] In particular, the semiconductor component can be a surface emitter (VCSEL; vertical-cavity surface-emitting laser). The light can be coherent laser light emitted divergently from the emission region. The light can be polarized, collimated, or focused by optical elements, which preferably include diffraction, refraction, and / or photonic metamaterials. In particular, the semiconductor component can be a combination of at least one VCSEL and at least one integrated photodiode.

[0009] Advantageous embodiments and extensions of the invention can be achieved through the measures given in the dependent claims.

[0010] Advantageously, at least one of the electrical contacts includes a stress element, which may in particular be a metal layer on the mesa. Here, the stress element may be conductive and have an electrical connection with the electrical contact. The stress element may be an integral part of the electrical contact. The functional connection between the stress element and the electrical contact ensures a compact structure for the semiconductor component.

[0011] A further advantage is that the stress element is designed in a strip shape, preferably extending between the emission region and the connection section of the electrical contact. With the strip-shaped stress element, a force acting primarily along the longitudinal extension of the stress element acts on the material volume, and this force manifests as additional material stress within the matrix material. Therefore, the material stress is distinguished by its magnitude, primarily oriented along the longitudinal extension of the stress element. Preferably, material stress extending transversely to the longitudinal direction of the stress element can be ignored.

[0012] In one extended embodiment, at least two independent stress elements can be disposed on the substrate, each stress element generating a principal material stress in a different direction, preferably at angles of 0°, 45°, and / or 90° relative to each other and / or relative to the crystal axis of the semiconductor device material. In particular, it is conceivable to arrange exactly two mutually perpendicular stress elements on the surface of the substrate, said stress elements generating two substantially mutually perpendicular material stresses. The semiconductor component may preferably comprise two mesa bodies, each mesa body being specifically assigned a stress element. Due to the numerous possibilities for arranging advantageous stress elements, material stress can be formed in the substrate in almost any desired manner.

[0013] Preferably, at least one, preferably two or three stress elements terminate in the emission region. Therefore, the force generated by the stress elements can induce material stress in the region of the emission region, preferably in the mesa. By inducing material stress in the mesa, the polarization direction of the emitted radiation can be influenced, and thus the polarization extinction ratio can be affected, in a particularly effective manner.

[0014] To obtain an alternative for altering the material stress within the mesa, at least one stress element can be directed across the emission region, extending beyond it. This allows for the generation of material stress that extends laterally relative to the emission region, forming along its entire extent. The material stress is substantially formed in the forming material of the mesa, which lies below the plane of the surface in which the emission region is arranged.

[0015] Specifically, the longitudinal extension of the stress element can be configured to form an angle of 0°, 45°, and / or 90° with the crystal axis of the substrate. The crystal axis is given by the crystal structure of the crystal beneath the material of the semiconductor component. For example, the crystal axis can be given by mutually independent spatial directions within the crystal. Preferably, the crystal axis is given by directions within the crystal in which the periodic repetition of the crystal structure has the shortest distance. These crystal directions are also referred to as the principal crystal directions. In the case of gallium arsenide, these directions may be in the (110) or (1-10) directions.

[0016] For example, applying an additional layer to the stress element via atomic layer deposition and / or plasma-enhanced chemical vapor deposition (PECVD) can advantageously influence the material stress generated by the stress element, said layer preferably also covering the remaining surface. Here, the material stress can be amplified in a simple manner through this optional layer without the need for an additional stress element.

[0017] Furthermore, the polarization grating can interact with the emission region and can preferably be arranged on the surface of the mesa. The grating arrangement of the polarization grating particularly includes angles of 0°, 45° and / or 90° with the crystal axis of the semiconductor device and / or with the direction of the primary material stress and / or the longitudinal extension of the stress element. The grating arrangement is determined by the longitudinal extension of the grating ribs.

[0018] The stress element is particularly preferably implemented having at least two layers, which in particular comprise titanium, nickel, platinum, and gold. For example, these layers can be produced by evaporation and / or electroplating deposition methods (e.g., for gold) and / or any other deposition method. By combining different metals, the effect of the stress element on the stress intensity of the material can be influenced.

[0019] In particular, the stress element can be at least >1 μm long, >0.1 μm wide, and >0.01 μm high.

[0020] Furthermore, the matrix may contain indium, gallium, arsenic and / or phosphorus.

[0021] Furthermore, the present invention proposes a method for generating material stress within a substrate of a semiconductor component, the method comprising applying, preferably metallic, and in particular strip-shaped, stress elements to the surface of the substrate during an annealing step. Here, the apparatus of the present invention can be a product of the method described above. Here, the stress elements can be applied during the annealing step by, for example, an evaporation method or any other deposition method.

[0022] Material stress arises, particularly from the cooling of the matrix with the applied stress element. In particular, material stress is caused by the different behaviors of the material during temperature changes.

[0023] According to this method, a layer (also known as an ALD layer) can be applied to a stress element and / or a substrate via atomic layer deposition. This layer can generate material stress and / or advantageously influence these material stresses.

[0024] It should be understood that the features given above and the features to be described below can be used not only in the separately given combinations, but also in other combinations.

[0025] The scope of this invention may be defined solely by the claims. Attached Figure Description

[0026] The present invention will now be described in more detail based on exemplary embodiments and with reference to the accompanying drawings.

[0027] In the attached diagram:

[0028] Figure 1 A semiconductor component for emitting light is shown, having a substrate and a mesa body.

[0029] Figure 2 The surface of a semiconductor component with multiple stress elements is shown.

[0030] Figure 3 Different embodiments of electrical contacts with stress elements are shown.

[0031] Figure 4 A cross-section of a semiconductor component with a stress element is shown.

[0032] Figure 5 Different embodiments of a mesa body having at least one stress element are shown, and

[0033] Figure 6 A flowchart illustrating a method for generating material stress is shown. Detailed Implementation

[0034] Figure 1 The diagram shows a semiconductor component 10 configured to emit light 12. Light 12 can be coherent light, such as laser light. Here, wavelengths in the range of 550 nm to 1500 nm are particularly possible, especially wavelengths between 700 nm and 1000 nm. Light 12 can, in particular, be coherent laser light emitted divergently from an emission region. Light 12 can be polarized, collimated, or focused by optical elements, which preferably include diffraction, refraction, and / or photonic metamaterials.

[0035] Semiconductor component 10 includes a substrate 14 having a mesa 16 with an emitting region 18 for light 12. Both the substrate 14 and the mesa 16 may at least partially comprise a crystalline semiconductor material containing indium, gallium, arsenic, and / or phosphorus. The emitting region 18 is the surface location from which light 12 exits the semiconductor component 10 into the surrounding environment. The surrounding environment may include optical devices for refraction and diffraction (in which light 12 enters), but may also simply be an inflated or evacuated space. The mesa 16 may be tower-shaped, particularly cylindrical, wherein the radius or diameter may be approximately ≤30 μm, and a diameter ≤20 μm is also possible. Alternatively, the diameter may be greater than 30 μm.

[0036] A first mirror section, a second mirror section, and an active section are assigned to a mesa 16. The active section is arranged between the two mirror sections and is used to generate light 12. Although material stress may also affect the mirror sections and the active section, they are not shown in the figures. They may be wholly or partially surrounded by the mesa 12. In particular, the mirror sections and the active section are arranged in a substrate 14.

[0037] The crystalline semiconductor material of the substrate 14 and / or mesa 16 exhibits birefringence, and therefore the light 12 propagating through the semiconductor material is polarized in two different directions. The emitted light 12 is substantially polarized in two preferably mutually orthogonal polarization directions 171, 172. The two polarization directions 171, 172 are elliptically polarized after emission due to the mixing of their intensities, with the longitudinal extension of the resulting ellipse pointing towards the polarization direction 171, 172 with greater intensity. However, it is ideal to seek linear polarization of the emitted light.

[0038] The ratio of the intensities of the two polarization directions 171 and 172 is called the polarization extinction ratio. Material stress in crystalline semiconductor materials can affect the polarization extinction ratio.

[0039] Especially in sensor applications, light-emitting semiconductor components 10, such as VCSELs, require a time-stable polarization extinction ratio for the emitted light 12. This can be achieved by keeping the intensity of polarization directions 171 and 172 stable over time. Here, it is preferable to have one polarization direction, especially the one with higher intensity.

[0040] Figure 2 A surface 22 of an exemplary semiconductor component 10 is depicted, the semiconductor component having a first mesa 161 and a second mesa 162 on a preferably shared substrate 14. Electrical contacts 201, 202, and 203 are applied to the surface 22 for feeding electrical energy into the active sections of the mesa 161 and 162.

[0041] Electrical contacts 20; 201, 202, and 203 are divided into two so-called p contacts and one n contact. P contacts 201 and 202 are directly guided to... Figure 2 The p-contacts 10 and 201 have a platform 16; 161, 162, and an n-contact is arranged between two p-contacts. This configuration is not mandatory. Each p-contact 20; 201, 202 has a stress element 24; 241, 242, and each p-contact 20; 201, 202, 203 has a connection section 26; 261, 262, 263, which are configured to electrically connect the semiconductor component 10 to a peripheral device not depicted herein. Only one p-contact 20; 201, 202 may be equipped with a stress element 24; 241, 242. Alternatively, all p-contacts 20; 201, 202 may be equipped with stress elements. In an embodiment not depicted herein, the n-contact 203 may also have a stress element 24.

[0042] The stress elements 24; 241, 242 are strip-shaped designs, and the stress elements 24; 241, 242 preferably extend between the corresponding emission regions 181, 182 and the respectively assigned connection sections 26; 261, 262.

[0043] exist Figure 2 In an exemplary embodiment, a first strip stress element 241 extends along a first crystal axis 271, and a second strip stress element 242 extends along a second crystal axis 272. For example, crystal axes 271 and 272 can be represented by Miller indices (011) and (01-1). Other Miller indices are also possible. The two stress elements 24; 241, 242 are arranged substantially perpendicular to each other in the plane of surface 22.

[0044] Forces, primarily along the longitudinal extension of the stress elements 24, 241, and 242, act on the material volume through the strip stress elements 24, 241, and 242. These forces manifest as material stress 25 within the substrate 14. When the stress elements 24, 241, and 242 are arranged on the mesa 16, these stress elements also generate material stress 25 within the mesa 16. The material stress 25 generated by the stress elements 24, 241, and 242 affects the birefringence properties of the crystalline semiconductor material, thus influencing the polarization extinction ratio. In particular, the intensity of the first polarization direction 171 increases, while the intensity of the second polarization direction 172 decreases, and vice versa.

[0045] In the case of strip stress elements 24; 241, 242, the material stress 25 is distinguished by its magnitude or intensity, primarily oriented along the longitudinal extension of the stress elements 24; 241, 242. Preferably, the material stress 25 extending transversely to the longitudinal extension of the stress elements 24; 241, 242 can be ignored. Here, the material stress 25 is strongest, particularly in the region of surface 22, and decreases with increasing depth perpendicular to surface 22.

[0046] In particular, the stress elements 24; 241, 242 can be at least >1 μm long, >0.1 μm wide, and >0.01 μm high. Preferably, the stress elements 24; 241, 242 extend from the mesa body 16 in a strip-like manner.

[0047] Preferably, the stress elements 24; 241, 242 may have at least two layers of different metals. In particular, these layers may comprise titanium, nickel, platinum, or gold. For example, these layers can be produced by evaporation or any other deposition method. By combining different metals, the stress elements 24; 241, 242 can increase the intensity of material stress without requiring a thicker stress element than one made of a single metal. In other words, a multilayered stress element preferably constructed of different metals can generate greater material stress at the same thickness. Further, the stress elements preferably generate material stress 25, which acts primarily in one direction within the material of the substrate 14 and / or the mesa 16.

[0048] Alternatively, polarization gratings 30; 301, 302 can be arranged on the corresponding emission regions 18; 181, 182. Polarization gratings 30; 301, 302 are preferably arranged on the surfaces 22 of the mesa bodies 16; 161, 162. Alternatively, polarization gratings 30; 301, 302 can also be arranged within the semiconductor component 10.

[0049] according to Figure 1The first polarizing grating 301 has a grating arrangement of 90°, and the second polarizing grating 302 has a grating arrangement of 0°, these directions being relative to the stress elements 241, 242 assigned to the respective mesa bodies 161, 162. The grating arrangement is determined by the angle between the longitudinal extensions of the grating ribs of the polarizing gratings 301, 302 and the longitudinal extensions 321, 322 of the respective assigned stress elements 241, 242, and thus has the direction of the primary material stress 25. A stress element 241, 242 extends from the respective mesa bodies 161, 162.

[0050] exist Figure 3 In the images A, B, C, and D, different arrangements of the stress elements 241 and 242 of the semiconductor component 10 with the substrate 14 and the two mesa bodies 16 are depicted. The arrangement in image A corresponds to... Figure 2 The arrangement of stress elements 241 and 242 is characterized by the fact that the polarization extinction ratio of the first mesa 161 is less than 15 dB, and the polarization extinction ratio of the second mesa 162 is greater than 15 dB, particularly greater than 20 dB.

[0051] In image B, the corresponding stress elements 241 and 242 have segments 19 extending from the corresponding mesa bodies 161 and 162, and forming 45° angles with the first crystal axis 271 and the second crystal axis 272, respectively. The two segments 19 of the stress elements 241 and 242 are flush with each other in the 45° direction relative to the crystal axes 271 and 272. This configuration of the stress elements 241 and 242 is characterized in that the polarization extinction ratio of the first mesa body 161 and the second mesa body 162 exceeds 15 dB, wherein the polarization extinction ratio of the second mesa body 162 is higher than that of the first mesa body 161.

[0052] Image C shows the configuration of stress elements 241, 242, which corresponds to the configuration in image A in terms of their arrangement in the longitudinal directions 321, 322. However, the width of stress elements 241, 242 in the plane of surface 22 is less than half of their width. This configuration of stress elements 241, 242 is characterized in that the polarization extinction ratio of the first mesa 161 and the second mesa 162 exceeds 15 dB, and the polarization extinction ratio of the second mesa 162 is higher than that of the first mesa 161, preferably exceeding 20 dB.

[0053] Image D shows the configuration of stress elements 241, 242, wherein the longitudinal extensions 321, 322 of stress elements 241, 242 are arranged at least partially parallel to the second crystal axis 272. In particular, compared to image A, segment 19 of the first stress element 241 is offset by 90° and is therefore parallel to the second crystal axis 272. The widths of stress elements 241, 242 are approximately the same as those in image C. This configuration of stress elements 241, 242 is characterized in that the polarization extinction ratio of the first mesa 161 and the second mesa 162 exceeds 15 dB, wherein the polarization extinction ratio of the first mesa 161 is higher than that of the second mesa 162, and the two polarization extinction ratios preferably exceed 20 dB.

[0054] Figure 4 The image shows a cross-section of the semiconductor component 10, which extends along a plane passing through the mesa body 16, the emission region 18 having the polarization grating 30, and the stress element 24.

[0055] The stress element 24 is electrically connected to the semiconductor component 10 via a power supply device 23. The power supply device 23 may be attached to the top side facing the surface 22, close to the emission region 18. The mesa body 16 is surrounded by a polymer or silicon nitride carrier layer 15, to which the stress element 24 has been at least partially applied. Material stress 25 is introduced into the mesa body 16 at least partially via the carrier layer 15.

[0056] Applying an additional layer 28 to the stress element 24 via atomic layer deposition 40 can advantageously influence the material stress 25 generated by the stress element 24. The layer 28 preferably also covers the remaining surface 22, wherein the layer 28 does not cover the emission region 18 and the connection section 26.

[0057] Figure 5 Different exemplary embodiments of the stress element 24 on the mesa body 16 are depicted in images A through F. Embodiments A through F can be combined with each other on the semiconductor component 10.

[0058] Image A depicts a single stress element 24, one end of which terminates in the emission region 18, wherein the stress element 24 forms a 0° grating arrangement with the polarization grating 30.

[0059] Two stress elements 24 are arranged in image B, positioned opposite each other on the emission region 18, with their ends facing each other. The stress elements 24 form a 0° grating arrangement with the polarization grating 30, and the stress elements 24 are preferably flush with each other.

[0060] In image C, two stress elements 24 are arranged and guided through the emission region 18, wherein these stress elements 24 extend beyond the emission region 18. The stress elements 24 are preferably longer than the emission region 18. The stress elements 24 form a 0° grating arrangement with the polarizing grating 30 and are parallel to each other and parallel to the grating ribs. The emission region 18 is arranged between the stress elements 24.

[0061] Image D shows an embodiment similar to that in Image C, except that the stress element 24 has the same length as the emission region 18, and the stress element 24 preferably has a smaller width than in the case of Image C.

[0062] In image E, three parallel stress elements 24 are arranged on one side of the emission region 18, preferably reaching approximately the polarization grating 30. The stress elements 24 and the polarization grating 30 form a 0° grating arrangement and are arranged adjacent to each other.

[0063] Image F depicts a forked stress element 24 with two forked segments, similar to the construction shown in image D regarding the emission region 18. These two forked segments are interconnected by an intermediate segment aligned at 90° relative to the polarization grating 30. Here, the intermediate segment connects the two ends of the forked segments arranged on the same side of the emission region 18. A connecting segment 26 extends away from the intermediate segment, with its direction away from the emission region 18.

[0064] Figure 6 This is a flowchart of a method for generating material stress 25 within a substrate 14 of a semiconductor component 10. The method includes a step 34 during an annealing step 36, during which a preferably metallic, particularly strip-shaped stress element 24 is applied to the surface 22 of the substrate 14. Here, the stress element 24 can be applied during the annealing step 36 by, for example, evaporation methods and / or plasma-enhanced chemical vapor deposition and / or any other deposition method.

[0065] Material stress 25 is generated, particularly due to the cooling of the substrate 14 with the applied stress element 24. In particular, material stress 25 is formed because the crystalline semiconductor material and the material of the stress element 24 exhibit different behavior during temperature changes. When the temperature of the semiconductor component 10 remains constant, material stress 25 remains constant, and thus the polarization of the emitted light 12 is stabilized.

[0066] According to this method, a layer 28 (also called an ALD layer) can be applied to the stress element 24 and / or the substrate 14 by atomic layer deposition 40. Layer 40 can generate material stress and / or amplify these stresses. In particular, layer 40 is applied after or during cooling 38.

[0067] A thin titanium layer can be applied between the ALD layer and the stress element 24.

[0068] Figure Labels

[0069] 10 Semiconductor Components 241 First Stress Element

[0070] 12 light 242 second stress element

[0071] 14 Matrix stress 25 Material stress

[0072] 15 Carrier layer 26 Connecting section

[0073] 16-faceted body 261 First connecting section

[0074] 161 First platform 262 Second connecting section

[0075] 162 Second platform 263 Third connecting section

[0076] 171 First polarization direction 271 First crystal axis

[0077] 172 Second polarization direction 272 Second crystal axis

[0078] 18 launch areas, 28 ALD layers

[0079] 181 First emission region 30 polarization grating

[0080] 182 Second emission region 301 First polarization grating

[0081] Section 19, 302, second polarization grating

[0082] 20 electrical contacts, 32 longitudinal extensions

[0083] 201 First contact point 321 First longitudinal extension

[0084] 202 Second contact point 322 Second longitudinal extension

[0085] 203 Third contact 34 applied

[0086] 22 Surface 36 Annealing Step

[0087] 23 Power supply equipment 38 Cooling

[0088] 24 stress elements, 40 atomic layer deposition

Claims

1. A semiconductor component (10) for emitting light (12), the semiconductor component having a base body (14) and electrical contacts (20), the base body comprising at least one mesa (16) having an emission area (18) for the light (12), the mesa being assigned a first mirror section, a second mirror section and an active section, the active section being arranged between the two mirror sections and for generating the light (12), the electrical contacts for feeding electrical energy into the active section, wherein, At least one stress element (24) is attached to the surface (22) of the base body (14), which stress element generates a material stress (25) in the base body (14), which has an influence on the polarization extinction ratio of the emitted light (12), wherein a polarization grating (30) interacts with the emission area (18) and is arranged on the surface (22) of the mesa body (16), wherein the grating arrangement of the polarization grating is at 0°, 45° or 90° to the direction of the longitudinal extension (32) of the stress element (24).

2. The semiconductor component (10) according to claim 1, characterized in that At least one electrical contact (20) has a stress element (24), wherein the stress element (24) is a metal layer on the mesa body (16).

3. The semiconductor component (10) according to claim 1 or 2, characterized in that The stress element (24) is designed in strip form and extends between the emission area (18) and a connection section (26) of the electrical contact (20).

4. The semiconductor component (10) according to one of the preceding claims, characterized in that At least two independent stress elements (24) are attached to the base body (14), which stress elements generate a predominant material stress (25) in different directions, respectively.

5. The semiconductor component (10) according to one of the preceding claims, characterized in that At least one stress element (24) ends in the emission area (18).

6. The semiconductor component (10) according to one of the preceding claims, characterized in that The at least one stress element (24) is guided through the emission area (18) and extends beyond the emission area (18).

7. The semiconductor component (10) according to one of the preceding claims, characterized in that The longitudinal extension (32) of the stress element (24) is at 0°, 45° or 90° to a crystal axis (27) of the base body (14).

8. The semiconductor component (10) according to one of the preceding claims, characterized in that A layer (28) is applied to the stress element (24) by atomic layer deposition and / or plasma-enhanced chemical vapor deposition.

9. The semiconductor component (10) according to one of the preceding claims, characterized in that The stress element (24) comprises at least two layers.

10. The semiconductor component (10) according to one of the preceding claims, characterized in that The stress element (24) is at least > 1 pm long, and > 0.1 pm wide, and > 0.01 pm high.

11. The semiconductor component (10) according to one of the preceding claims, characterized in that The base body (14) comprises indium, gallium, arsenic and / or phosphorus.

12. A method for generating material stress (25) within a base body (14) of a semiconductor component (10) as claimed in one of the preceding claims, characterized in that During an annealing step (36), a strip-shaped stress element (24) of a metal is applied (34) to a surface (24) of a base body (14), and a polarization grating (30) interacting with an emission area (18) is arranged on a surface (22) of a mesa body (16), wherein the grating arrangement of the polarization grating is at 0°, 45° or 90° to the direction of the longitudinal extension (32) of the stress element (24).

13. The method of claim 12, wherein, Cooling (38) the base body (14) with the stress element (24) so that a material stress (25) is formed.

14. The method of claim 12 or 13, wherein, Applying a layer (28) on the stress element (24) and / or the base body (14) by atomic layer deposition (40).

Images