Method for treating at least one layer or area of ​​a component

Description

Technical field

[0001] The invention relates to a method for treating at least one layer or area of ​​a component by means of a laser beam to produce an amorphous layer or area according to the preamble of claim 1 (see e.g. WO 2019 / 236616 A1). State of the art

[0002] A method for treating at least one layer of a component with the features of the preamble of claim 1 is known from DD 217 738 A1. In the known method, which serves to produce an amorphous layer on the surface of the metallic component, a laser beam is passed over the surface of the component and the material of the component is melted at the surface. To produce the amorphous layer, it is necessary that, when the molten layer solidifies, the atoms cannot arrange themselves in a regular crystal structure and only possess short-range order, but not long-range order. For this, a very high cooling rate of more than 10⁶ Kelvin per second is required.To this end, it proposes a method known from the aforementioned document, namely to cover the component, at least in the area of ​​the treated surface, with water as a cooling medium during its surface treatment in order to achieve the required high cooling rate or heat dissipation via the water. Due to the necessary cooling, the method known from the aforementioned document thus requires a relatively high level of equipment complexity.

[0003] WO 2019 / 236616 A1 discloses a laser processing device for machining a workpiece. US 2009 / 0280623 A1 discloses a method for manufacturing a semiconductor wafer. US 2017 / 0189999 A1 discloses a method and a device for interrupting the propagation of an incident crack through a transparent material. Disclosure of the invention

[0004] The inventive method for treating at least one layer or area of ​​a component to produce an amorphous layer or area in the component with the features of claim 1 has the advantage that it can be used to form almost any 3-dimensional structures or shapes of amorphously solidified material in a material of a component that is transparent to the wavelength of the laser beam, without requiring additional cooling measures to increase the cooling rate during the solidification of the material melted by the laser beam.

[0005] For this purpose, the inventive method according to the teaching of claim 1 proposes that the laser beam has laser pulses with a repetition rate in the megahertz or gigahertz range, that a material transparent to the wavelength of the laser beam is used as the material, and that the area of ​​influence of the laser beam in the component is achieved by a fixed positioning of the focus area of ​​the laser beam in relation to a direction running in the component in the direction of propagation of the laser beam.

[0006] The invention is based on the idea of ​​keeping the energy input into the component material during melting so low, or limiting it over time, that a sufficiently high cooling rate is achieved even without cooling measures, leading to amorphous solidification of the material. This is achieved because the low energy input also means that only a relatively small amount of heat energy needs to be dissipated. To produce amorphous solidification of the material, it is necessary that the atoms cannot arrange themselves in a regular crystal structure when the molten layer or area solidifies, so that only short-range order, but not long-range order, is present. This requires a very high cooling rate of more than 10⁶ K per second.This is made possible by the spatially highly localized absorption and heat input during the short-term application of a very high repetition rate of the laser pulses, which allows cooling rates of more than 10⁶ < K per second, preferably more than 10⁹ < K per second, to be achieved compared to the remaining, unheated material.

[0007] The volume melted by the laser beam is determined by the nonlinear focal volume, which is influenced by the spatial and temporal intensity distribution of the laser pulse. Thus, energy deposition and the creation of an amorphous volume are possible even below the Abbe limit. The aforementioned melted and subsequently solidified volumes have a diameter, depending on the wavelength of the laser beam, ranging from a few hundred nm to a few micrometers, typically between 500 nm and 5 µm. It is advantageous if the lateral deviation when moving the laser beam relative to the component is less than 10 µm. However, tracking the focal plane (in a direction parallel to the propagation direction of the laser beam) is only possible to a limited extent with transparent materials.not necessary, since in many transparent materials the absorbing volume becomes opaque or at least temporally opaque upon solidification, and the absorption of subsequent pulses already takes place at the boundaries of the processing volume, causing it to grow in the direction of the laser beam.

[0008] Advantageous further developments of the inventive method for treating at least one layer or area of ​​a component are listed in the dependent claims.

[0009] To create a three-dimensional amorphous structure within the component, the laser beam can be applied sequentially to different layers or areas within the component, aligned with the direction of laser beam propagation. This is particularly advantageous if the material does not become opaque during amorphous solidification. Furthermore, this method enables precise energy coupling into the area to be melted.

[0010] For this purpose, it is particularly preferred that the laser beam first acts on the layer or area furthest away from the component surface on the side of the laser beam, and that the subsequent layers or areas on which the laser beam acts successively have a smaller distance to the component surface.

[0011] Laser pulse repetition rates between 50 megahertz and 20 gigahertz, preferably 1.6 gigahertz, are particularly preferred.

[0012] Furthermore, pulse packets with 10 to 1000 laser pulses, preferably between 50 and 200 laser pulses, are preferably used.

[0013] The interval between two laser pulses is between 10 picoseconds and 100 nanoseconds, preferably about 500 picoseconds.

[0014] Furthermore, it is preferred that the thickness of a molten layer or molten area of ​​the component is less than 10 µm, preferably less than 2 µm. This allows homogeneous amorphous areas or layers to be achieved across the entire volume.

[0015] Furthermore, it is advantageous if the focus diameter of the laser beam is between 1 µm and 1000 µm, preferably between 100 µm and 1000 µm. Short description of the drawing

[0016] The single figure shows, in a schematic representation, a device for generating amorphous volumes on a component. embodiment of the invention

[0017] The single figure shows a device 100 for generating at least one amorphous volume 1 in the region of a component BT. The component BT is shown purely by way of example as a plate-shaped or planar component BT, which lies or is positioned on a work surface 5.

[0018] To generate the amorphous volume 1 within component BT, the device 100 comprises a laser beam unit 10, which is designed in the form of an ultrashort pulse laser. The laser beam unit 10 generates a laser beam LS with pulse packets at a repetition rate of approximately 1.6 gigahertz. The pulse packets each comprise approximately between 20 and 1000 laser pulses, preferably between approximately 50 and 250 laser pulses. The pulse duration of the laser pulses is between 100 femtoseconds and 50 picoseconds.

[0019] The component BT consists of a material that is transparent to the wavelength of the laser beam LS. This is particularly relevant for glasses or monocrystalline insulators and / or semiconductors such as crystalline silicon dioxide, which is used to manufacture quartz wafers. Applications with alkali metals, some of which are transparent to UV light, are also conceivable.

[0020] The energy input, which is on the order of one nanojoule to a few microjoules per laser pulse, creates an amorphous volume with a diameter of less than 10 µm.

[0021] The device 10 further comprises an adjustment device 20 for relative movement between the laser beam LS and the surface O of component BT, which is designed as a 5-axis adjustment device 20. During the application of the laser beam LS, component BT, or rather its surface O, is in contact with the surrounding air or, if applicable, with a protective gas atmosphere. The device 100 also includes an optical device 30 for influencing or guiding the laser beam LS, typically in the form of a scanner.

[0022] To generate volume 1, energy input by the laser beam LS begins in the region of the layer S of the component BT material that is furthest from the surface O of component BT on the side facing the laser beam LS, i.e., in the region of the deepest layer S. In this region, depending on the lateral extent of the amorphous layer S to be generated, a corresponding lateral movement of the laser beam LS relative to component BT then takes place. If the material of component BT becomes opaque during amorphous solidification, the three-dimensional structure of volume 1 builds up on the previously solidified layer S in the direction of surface O after solidification and subsequent repeated energy input. Alternatively, the focus can also be set to the region of the layer S closest to surface O.

Claims

1. Method for treating at least one layer (S) or a region of a component (BT), in the course of which a laser beam (LS) acts on the at least one layer (S) or the region and melts the material of the component (BT) in the region of action of the laser beam (LS) in such a way that the melted material amorphously solidifies as it cools down or as a result of cooling down, characterized in that the laser beam (LS) comprises laser pulses with a repetition rate in the megahertz or gigahertz range, in that the material used for the component (BT) is a material which is transparent to the wavelength of the laser beam (LS), and in that the region of action of the laser beam (LS) is effected by establishing the focus region of the laser beam (LS) in the direction of a direction running in the propagation direction of the laser beam (LS) in the component (BT).

2. Method according to Claim 1, characterized in that, to create a 3-dimensional amorphous structure or volume (1) in the component (BT), the laser beam (LS) acts on various layers (S) or regions in the component (BT) in succession that run in the propagation direction of the laser beam (LS).

3. Method according to Claim 2, characterized in that the laser beam (LS) firstly acts on the layer (S) or region furthest away from the surface (O) of the component (BT) on the laser beam (LS) side, and the subsequent layers (S) or regions on which the laser beam (LS) acts are at successively smaller spacings from the surface (O) of the component (BT).

4. Method according to one of Claims 1 to 3, characterized in that the repetition rate is between 50 megahertz and 20 gigahertz, preferably 1.6 gigahertz.

5. Method according to one of Claims 1 to 4, characterized in that pulse packets of 10 to 1000 laser pulses are generated, preferably pulse packets of 50 to 250 laser pulses.

6. Method according to one of Claims 1 to 5, characterized in that the interval between two laser pulses is between 10 picoseconds and 100 nanoseconds, preferably about 500 picoseconds.

7. Method according to one of Claims 1 to 6, characterized in that the thickness of a melted layer (S) or a melted region of the component (BT) is less than 10 micrometres, preferably less than 2 micrometres.

8. Method according to one of Claims 1 to 7, characterized in that the focus diameter of the laser beam (LS) is between 1 µm and 1000 µm, preferably between 100 µm and 1000 µm.