DE102013201298A1 - Manufacturing a gallium nitride-based LED, comprises depositing a semiconductor layer structure comprising a gallium nitride-based semiconductor layer on a substrate, and partially removing the layer in local areas by laser machining - Google Patents

Abstract

The method comprises depositing a semiconductor layer structure on a substrate, where the structure comprises a gallium nitride (GaN)-based semiconductor layer, and partially removing the semiconductor layer in local areas by laser machining. The laser treatment is carried out by: exposing the semiconductor layer to a projection mask (4), which is illuminated with laser radiation of an ablation laser (1) such that exposure areas of the semiconductor layer is exposed through recesses in the projection mask; and occulting the GaN-based semiconductor layer shaded by the projection mask. The method comprises depositing a semiconductor layer structure on a substrate, where the semiconductor layer structure comprises a gallium nitride (GaN)-based semiconductor layer, and partially removing the GaN-based semiconductor layer in local areas by laser machining. The laser treatment is carried out by: exposing the GaN-based semiconductor layer to a projection mask (4), which is illuminated with laser radiation of an ablation laser (1) such that exposure areas of the GaN-based semiconductor layer is exposed through recesses in the projection mask; and occulting the GaN-based semiconductor layer shaded by the projection mask. A laser fluence of the ablation laser is above an ablation threshold of the GaN-based semiconductor layer. An excimer laser is used as the ablation laser, and has a wavelength of = 351 nm and a pulse length of = 40 nanoseconds. The semiconductor layer structure comprises an active region in the exposure areas. A luminous area of a semiconductor device is effected by removing the active region in the exposure areas by mechanical separation and electrical isolation. The exposure areas of the semiconductor layer structure are completely removed. A set of semiconductor devices is formed on a wafer that is perpendicular to the laser radiation. The removing step is repeated for five times. The method further comprises displacing the wafer such that the displacement of the wafer is perpendicular to the laser radiation, and etching step. The displacing step is carried out simultaneously with the removing step. An independent claim is included for an apparatus for processing a semiconductor device.

Description

The invention relates to a method for producing a semiconductor component according to the preamble of claim 1 and to an apparatus for processing a semiconductor component according to the preamble of claim 12.

For the production of semiconductor devices, it is known to produce these by means of photolithographic processes. In these photolithographic processes, semiconductor layers of the semiconductor components are structured by means of special lithography masks, the production of which is time-consuming and expensive.

Alternatively, it is known to structure the semiconductor layers of the semiconductor components by means of laser processing: For example, in US Pat R. Maser et al., "Laser Processing of GaN based LEDs with Ultradiode Picosecond Laser Pulses", Proc. Of SPIE, Vol. 8433, 2012 , a method in which a plurality of semiconductor layers are patterned in the manufacturing process of a light-emitting diode by means of direct laser processing.

A disadvantage of this method according to the prior art is that at high laser intensities due to the direct laser processing fractures in the semiconductor material arise. Another disadvantage is that a control of the removal depth can not be achieved by the laser processing in the desired accuracy.

The present invention is therefore based on the object to provide a method for the production of semiconductor devices, which makes it possible to structure the semiconductor layers of the semiconductor device in an inexpensive and time-saving process and thereby to guarantee a constant quality compared to the previously known methods. Furthermore, the invention is intended to provide a corresponding apparatus for processing such a semiconductor device.

This object is achieved by a method according to claim 1 and by a device according to claim 12. Advantageous embodiments of the method can be found in claims 2 to 11. Advantageous embodiments of the device can be found in the claims 13 to 15. Herewith, the wording of the claims included in the description by express reference.

The inventive method is preferably designed for implementation by means of the device according to the invention and / or a preferred embodiment thereof. The device according to the invention is preferably designed for carrying out the method according to the invention and / or a preferred embodiment thereof.

The invention is based on the applicant's finding that the structuring of the semiconductor layers of the semiconductor component by exposure to laser radiation through a projection mask enables the simultaneous structuring of the entire surface of a semiconductor component or of a plurality of semiconductor components by means of direct laser processing and thus leads to a fast and cost-effective production process.

• A Abscheiden einer Halbleiterschichtstruktur auf einem Substrat, welche Halbleitersichtstruktur zumindest eine GaN-basierte Halbleiterschicht umfasst,
• B Zumindest teilweises Entfernen zumindest der GaN-basierten Halbleiterschicht in lokalen Bereichen mittels Laserbearbeitung.

The method according to the invention for producing a semiconductor component comprises the following method steps:

• A depositing a semiconductor layer structure on a substrate, which semiconductor sight structure comprises at least one GaN-based semiconductor layer,
• B At least partial removal of at least the GaN-based semiconductor layer in local areas by means of laser processing.

It is essential that the laser processing in method step B takes place by means of exposure of the GaN-based semiconductor layer through at least one projection mask, which projection mask is illuminated with laser radiation of an ablation laser, such that exposure areas of the GaN-based semiconductor layer are exposed through recesses in the projection mask and shading areas of the GaN-based semiconductor layer can be shadowed by the projection mask. In this case, the laser fluence of the ablation laser lies in the exposure regions above the ablation threshold of the GaN-based semiconductor layer.

The method according to the invention thus differs in essential aspects from previously known methods: The laser processing of the GaN-based semiconductor layer is effected by means of exposure through a projection mask. This results in particular in the advantage that the entire surface of the semiconductor component can be simultaneously, ie simultaneously structured, by the projection mask imaging the desired structure on the surface of the semiconductor component. In this case, the exposure areas are exposed through recesses in the projection mask, so that ablation of the GaN-based semiconductor layer is effected by ablation, since the laser fluence of the ablation laser lies above the ablation threshold of the GaN-based semiconductor layer in the exposure areas.

For the purposes of this description, "laser processing" includes ablation of the material. The shading areas are determined by the Shadow projection screen. There is thus no material removal on the surface of the semiconductor component. Exposure areas and shading areas are substantially complementary on the surface of the semiconductor device. It is likewise possible to structure a plurality of semiconductor components simultaneously. In this case, the exposure takes place simultaneously through the projection mask in the case of the majority of the semiconductor components. This enables a fast and cost-effective production of structured semiconductor components.

It is within the scope of the invention that the semiconductor component is formed as a light-emitting diode and / or a precursor of a light-emitting diode during the manufacturing process. It is also within the scope of the invention that the semiconductor device is formed with a different function.

In the context of this description, the semiconductor layer structure can be formed as a single layer or as a multilayer. In this case, the semiconductor layer structure comprises at least one GaN-based semiconductor layer. However, it is also within the scope of this invention that the semiconductor layer structure additionally comprises layers of other materials.

In the context of this description, "GaN-based" means that a semiconductor layer is formed, which is formed of a material from the nitridic material system, in particular GaN, GaInN, AlGaInN and / or AlGaN.

In a preferred embodiment, an excimer laser is used as the ablation laser, which excimer laser has a wavelength less than or equal to 351 nm and a pulse length in the range of 40 nanoseconds or less. Excimer lasers have high pulse energies and thus allow the illumination of a large area with sufficiently high power densities. This results in the advantage that not only the entire surface of a semiconductor device can be exposed simultaneously and thus structured, but also a plurality of semiconductor devices can be simultaneously patterned in an exposure step.

In addition, at wavelengths less than the band gap (about 365 nm at room temperature) GaN has an increased absorption coefficient compared to wavelengths greater than the band gap. The use of laser radiation having a wavelength smaller than the bandgap results in a reduced penetration of the laser radiation into the semiconductor material. This has the advantage that a defined depth of abrasion is possible. In addition, there is no damage, in particular no fading of the semiconductor material (Dynamic Burnstein-Moss Shift). Therefore, the use of an excimer laser having a wavelength of 351 nm or shorter is advantageous. Most preferably, an excimer laser having a wavelength of 248 nm is used. This has the advantage that due to the further reduced penetration depth into the GaN-based semiconductor material, said semiconductor material can be selectively removed superficially. This allows an efficient, fast and cost-effective production of a large number of semiconductor devices with constant quality compared to previously known methods.

In a further preferred embodiment, the projection mask on the GaN-based semiconductor layer is reduced in size upon exposure, preferably in the range of 2 to 20 times reduced, particularly preferably 10 times smaller shown. There is thus a scaling of the predetermined by the projection mask structure, that is, a reduction of the recesses in the projection mask on the desired scale on the surface of the semiconductor device. The dimension of the recesses is preferably scaled larger by a factor of 10 than the desired structure, since a preferably 10-fold reduction is achieved by means of the focusing optics when imaging the projection mask on the surface of the semiconductor component. The exposure area on the surface of the semiconductor device thus corresponds to one tenth of the dimension of the recesses in the projection mask. This has the advantage that the production of the projection mask is simplified by the larger dimensions of the structures, that is to say the recesses in the projection mask, in comparison to the desired structures on the semiconductor surface. Likewise, the imaging scale can be adjusted flexibly via the focus optics (for example, by exchanging the objective for focusing) so that the structure with different magnitudes can be imaged onto the surface of the semiconductor component, that is to say on the surface of the semiconductor component, starting from the same projection mask can be removed.

In another preferred embodiment, the semiconductor device is formed as a GaN-based light emitting diode. The production of the GaN-based light-emitting diode can thus be carried out only by means of direct laser processing, ie without the use of photolithographic methods:
A GaN-based light emitting diode typically includes a lower doped GaN-based semiconductor layer and an upper doped GaN-based semiconductor layer and an active region therebetween. The formation of an LED layer structure is, for example, in Nakamura et al. "High Brightness InGaN Blue, Green and Yellow Light-Emitting Diades with Quantum Well Structures", Jpn. J. of Appl. Phys., Vol. 34, 1995 , described. The production preferably takes place on the basis of a wafer on which a plurality of light-emitting diodes or precursors are arranged in the production process of the light-emitting diode.

For contacting the lower doped semiconductor layer contacting trenches are formed in the GaN-based semiconductor layers. In this case, the upper doped semiconductor layer and the active region are preferably removed by means of an embodiment of the method according to the invention in the regions for the contacting trenches. Preferably, the removal depth is controlled by means of the pulse energy of the ablation laser and / or the number of laser pulses. As a result, the lower doped semiconductor layer is exposed, so that a contacting structure can be applied.

In order to form mesa structures, for example for defining a luminous active surface of the light-emitting diode, preferably at least the upper doped semiconductor layer is removed by means of an embodiment of the method according to the invention in local regions. Preferably, the removal depth is controlled by means of the pulse energy of the ablation laser and / or the number of laser pulses.

To form mechanical insulations of the individual light-emitting diodes of a wafer for later separation of the individual light-emitting diodes, separation trenches, so-called sawing streets, can be formed. Here, preferably, the upper doped semiconductor layer, the active region and the lower semiconductor layer are removed to the substrate by means of an embodiment of the method according to the invention in the areas for the separation trenches.

This results in the advantage that by means of an embodiment of the method according to the invention, the structuring steps mentioned above can be carried out simultaneously by means of direct laser processing, preferably with only one exposure for the entire surface of the semiconductor component. Likewise, a plurality of light-emitting diodes can be structured in a similar manner, preferably with only one exposure, and thus produced.

In the context of this description, the lower semiconductor layer means the semiconductor layer which faces the substrate. Upper semiconductor layer means the semiconductor layer which faces away from the substrate. This is for convenience of reference only, and is particularly independent of the actual physical location of the entire structure during manufacture and / or during use.

The doping types for the upper and the lower semiconductor layer are the p-type doping and the opposite n-type doping. It is within the scope of the invention that the lower semiconductor layer is formed as an n-doped semiconductor and the upper semiconductor layer is formed as a p-doped semiconductor or vice versa. Preferably, the upper semiconductor layer is formed as a p-doped semiconductor layer and the lower semiconductor layer is formed as an n-doped semiconductor layer.

In a further preferred embodiment, the semiconductor layer structure comprises an active region, which active region in method step B is at least partially, preferably completely removed, in the exposure regions. As a result, an electrical isolation between different areas of the semiconductor device is provided. For example, in the manufacture of a light-emitting diode, it is thus possible to define a luminous surface. The active region can consist of a plurality of semiconductor layers and is preferably designed as a layer system comprising a plurality of undoped semiconductor layers in a manner known per se. In particular, the active region can have one or preferably a plurality of quantum wells.

In a further preferred embodiment, in method step B, the semiconductor layer structure is completely removed in the exposure areas. In this way, in addition to an electrical insulation simultaneously creates a mechanical isolation and there is the advantage that so the separation of the semiconductor devices is simplified without their damage.

In a further preferred embodiment, in method step B, at least one luminous region of the light-emitting diode is defined by mechanically separating and electrically insulating the luminous region by removing at least the active region in the exposure regions. A mechanical separation and electrical insulation of the luminous region of the light-emitting diode from a non-luminous surrounding region of the light-emitting diode takes place. This results in the advantage that mechanical separation and electrical isolation of the illuminated area takes place without the formation of shunts.

In a further preferred embodiment, a plurality of semiconductor components is produced on a wafer. This results in the advantage that by means of the exposure of the wafer by a correspondingly structured projection mask a plurality of semiconductor devices simultaneously exposed, that is, can be structured.

In a further preferred embodiment, which wafer is arranged displaceably. This results in the advantage that the wafer, and thus preferably the semiconductor component to be processed, can be positioned precisely. Particularly preferably, the wafer is arranged displaceably perpendicular to the laser radiation of the ablation laser. For positioning the wafer, that is to say for moving the wafer, a per se known X-Y displacement unit is used.

In a further preferred embodiment, the method step B is repeated. Preferably, process step B is repeated between once and twenty times, particularly preferably five times. This results in the advantage that a multiple exposure can take place at the same position on the semiconductor component and / or the wafer. Thus, a defined depth of abrasion can be achieved in a controlled manner.

In a further preferred embodiment, in a method step C1, after the method step B, the wafer is displaced. As a result, different desired positions can be approached on the wafer. This has the advantage that the entire wafer surface can be patterned by scanning with the same projection mask. A preferred shift strategy is the "step and repeat" method:
In a method step C0, the first desired position is approached. The structuring is then carried out by exposure to laser light in method step B. The method step B can be repeated several times in order to achieve a desired removal depth. After the desired number of repetitions of method step B, the next desired position is approached in method step C1. Here, the structuring then takes place by means of exposure to laser light in method step B. The method step B can be repeated several times in order to achieve the desired removal depth. This sequence can be repeated several times in total to rasterize the entire surface of the wafer.

In an alternative preferred embodiment, the wafer is displaced in a method step C2, the method step C2 being performed simultaneously with method step B. A preferred shift strategy is the "fire on the fly" method:
In a method step C0, the first desired position is approached. The structuring then takes place by means of exposure to laser light in method step B. In method step C2, the wafer is displaced. In this case, the method step C2 takes place simultaneously with the method step B. This means that the wafer is moved virtually continuously, while the method step B is repeated several times, each time at a new position on the wafer surface. This simultaneous sequence can be repeated several times to process the entire surface of the wafer. In order to achieve the desired removal depth, the wafer can be processed several times, so that at each desired position a multiple exposure takes place up to the desired depth removal.

In a further preferred embodiment, an etching step is carried out in an additional method step D after the method step B. Advantageously, the etching step takes place by means of immersion in an ammonia bath, this is called "etch dip". In an etch dip, the surface of the light emitting diode is completely wetted with an etching solution for a short period of time. The etching step avoids that a shunt is formed between the conductive layers, in particular between the p-doped and the n-doped semiconductor layer, and thus a short circuit occurs. Preferably, the surface of the light-emitting diode is completely wetted with an etching solution, preferably an aqueous ammonia solution with 3% ammonia, for at least a period of 10 minutes.

In an alternative preferred embodiment, the etching step in method step D after method step B is carried out by means of immersion in a KOH solution and / or wetting of the surface of the semiconductor component with a KOH solution. This has the advantage that any shunts that may have arisen due to the laser ablation of the semiconductor material are removed.

In an alternative preferred embodiment, the etching step in method step D after method step B is carried out by means of immersion in an HCl solution and / or wetting of the surface of the semiconductor component with an HCl solution. This has the advantage that any shunts that may have arisen due to the laser ablation of the semiconductor material are removed.

The object described above is furthermore achieved by a device for processing a semiconductor component according to claim 12. The device according to the invention is preferably designed for carrying out the above-described method according to the invention or preferably a preferred embodiment of the method according to the invention.

The device for processing a semiconductor device, which semiconductor device comprises at least one GaN-based semiconductor layer, comprises a laser, means for beam expansion and means for focusing, wherein a laser beam path from the laser through the means for beam expansion extends to the means for focusing.

It is essential that the laser is designed as an excimer laser and that in the beam path of the excimer laser at least one projection mask between the means for beam expansion and the means for focusing and is arranged such that laser radiation strikes the projection mask and this at least in Radiated sections. In this case, exposure regions of the semiconductor component can be acted on by means of the irradiating laser radiation, and shading regions of the semiconductor component are shaded by the projection mask.

Thus, in one process step, the entire surface of a semiconductor device can be structured simultaneously. It is likewise possible for a plurality of semiconductor components to be structured simultaneously, that is to say in an exposure step.

This results in particular the advantage that a large number of semiconductor devices can be produced inexpensively and time-saving means of the device according to the invention.

In a preferred embodiment, a beam homogenizer is arranged and configured between the means for beam expansion and the projection mask such that laser radiation strikes the projection mask with a substantially homogeneous intensity profile. The laser radiation preferably impinges on the projection mask with a square top hat beam profile. The laser radiation with the homogeneous intensity profile impinges on the projection mask and radiates through it in the areas of the recess of the projection mask, that is, any shape of the laser beam can be "cut out" here. This has the advantage that the laser intensity is essentially the same in all points of a beam cross section. Thus, a constant material removal over the entire exposed semiconductor surface is guaranteed.

In a further preferred embodiment, the projection mask is structured by means of optical or electron beam lithography and / or by means of direct laser ablation. As the projection mask, for example, a 4 "Cr / quartz lithographic mask prepared by known methods can be used, which is commercially available. Advantageously, the projection mask is formed such that it has recesses which correspond in terms of the shape of the recesses of the structure to be removed on the surface of the semiconductor device. The laser radiation radiates through the projection mask in said recesses and thus impinges on the surface of the semiconductor layer structure.

Advantageously, the dimensions of the recesses of the projection mask are increased compared to the desired structures on the semiconductor surface. Due to the focusing optics, the recesses are scaled to the desired size during the imaging of the projection mask onto the surface of the semiconductor component. This has the advantage that it is possible to fall back on known methods for structuring the projection mask. It is equally advantageous that the recesses of the projection mask can be formed in a larger and thus easier to handle order of several millimeters.

In a further preferred embodiment, the projection mask is arranged and designed in such a way that a plurality of semiconductor components can be acted on simultaneously by means of the irradiating laser radiation.

The projection mask is advantageously designed such that a plurality of structuring templates for the desired structure of the surface of a semiconductor component, that is to say a plurality of recesses which correspond to a template for the desired structuring, are arranged on the projection mask. For example, 3 × 3 recesses or templates may be arranged on the projection screen. This results in the advantage that a plurality of semiconductor components can be structured simultaneously in an exposure process.

The device according to the invention and the method according to the invention are fundamentally suitable for applications in which GaN-based semiconductor layers are to be structured.

The device according to the invention and / or the method according to the invention are preferably designed for the production of light-emitting diodes in large numbers:
Starting from the implementation of the method according to the invention or a preferred embodiment for producing light-emitting diodes using an excimer laser with a pulse energy of up to 2 joules, an area of 1 cm ² can be illuminated with the necessary power density. Modern light-emitting diodes have a chip area of 1 × 1 mm ² . Considering the distance between the individual chips, so over 60 light-emitting diodes can be processed simultaneously. Typically, in the manufacture of light emitting diodes, round wafers with a diameter of 150 mm are used. Using the above-described "Fire on the Fly" strategy with a wafer displacement speed of 100 mm / s, five processing passes for a preferably desired depth of cut will take about two minutes. Taking into account a short period of time under one minute for the adjustment, more than 10,000 light-emitting diodes can thus be processed in less than three minutes of machining time.

Further preferred features and embodiments of the method according to the invention and of the device according to the invention are explained below on the basis of exemplary embodiments and the figures. Showing:

1 schematic representation of an embodiment of the device according to the invention for processing a semiconductor device,

2 schematic cross-sectional representation of a light-emitting diode, which was produced by carrying out an embodiment of the method according to the invention,

3 schematic representation of an embodiment of a projection mask for the simultaneous definition of the luminous surface of a plurality of light-emitting diodes.

In the figures, like reference numerals designate like or equivalent elements.

1 shows a schematic representation of an apparatus for processing a semiconductor device. The device comprises a laser 1 , a collimator 2a . 2 B , a jet homogenizer 3 , a projection mask 4 , a focusing optics 5 as well as a holder 7 for a semiconductor wafer 6 ,

The laser 1 is designed as an excimer laser and has emission wavelengths of 351 nm, 308 nm, 248 nm, 193 nm or 157 nm, in this case 248 nm. The excimer laser is a pulsed laser with a pulse length less than 40 nanoseconds, in the present case 20 ns and with a pulse repetition rate of up to 600 Hz, in this case 20 Hz. The excimer laser has a very high pulse energy of up to 2 joules. The beam path of the laser radiation 8.1 proceeds from the excimer laser 1 to the collimator 2 ,

The collimator 2 serves to widen the laser radiation 8.1 to a beam cross section of present 2 × 2 cm ² . The collimator typically includes a diffuser lens 2a and a condenser lens 2 B , Following the collimator the beam path runs 8.2 essentially as a parallel beam to the Strahlhomogenisierer 3 ,

The jet homogenizer 3 generated from the Gaussian intensity profile of the original laser radiation 8.2 laser radiation 8.3 with a homogeneous intensity profile, in the present case a square top hat beam profile, in this case by using crossed microlens arrays. Starting from the jet homogenizer 3 runs the beam path of the expanded, collimated and homogenized laser beam 8.3 to the projection mask 4 , The projection mask 4 in the present case has a size of 10 × 10 cm ² and is with a square beam 8.3 the size 2 × 2 cm ² lit. As a result, a plurality of different structure templates (for example different exposure steps) can be arranged on the mask and during the processing of a semiconductor wafer 6 by moving the projection mask 4 be exposed.

The projection mask 4 includes a metallization, which metallization partially recesses (structural templates). Through the recesses, the laser radiation 8.3 the projection mask 4 by radiation. As a result, exposure areas on the surface of the semiconductor device 6 subjected to laser radiation. In the other areas, the laser light passes through the metallization of the projection mask 4 blocked. As a result, the shading regions which are complementary to the exposure regions become on the surface of the semiconductor component 6 shadowed. The recesses of the metallization of the projection mask 4 (Structural templates) are designed such that they correspond in shape to the desired structure, which is to be removed on the surface of the semiconductor device by means of the laser radiation. The dimensions of the recesses of the projection mask 4 are designed by a factor of 10 larger than the desired structure, which on the surface of the semiconductor device 6 to be removed by means of laser radiation. By lateral, that is perpendicular to the beam path of the laser radiation 8th , Moving the projection screen 4 Different forms can be irradiated. Thus, it is possible different embodiments of semiconductor devices with a projection mask 4 on the same wafer 6 without making major modifications to the manufacturing apparatus.

The laser radiation 8.4 which the projection mask 4 radiates through, meets the focusing optics 5 , The focusing optics 5 is designed as a multi-lens lens and forms the laser radiation 8.4 on the surface of the semiconductor device 6 from. Here is the focusing optics 5 designed such that the projection screen 4 penetrating laser radiation 8.4 greatly reduced, in the present case reduced to 10% on the surface. The structure of the projection mask 4 ie, the recesses in the metallization of the projection mask can thus be 10 times larger than the desired structure to be removed on the surface of the semiconductor device. This results in the advantage that the projection mask is easier to manufacture compared to a mask or stencil, which must have dimensions in the order of the desired structure, which is to be removed on the surface of the semiconductor device.

The semiconductor device 6 is on a bracket 7 appropriate. The holder 7 is movable in X, Y and Z directions. In addition, the bracket 7 rotated by an angle Θ about an axis parallel to the beam path of the laser radiation, in the present case up to about 360 °.

2 shows a schematic cross-sectional view of a light-emitting diode, which was prepared by carrying out an embodiment of the method according to the invention. The light-emitting diode 9 includes a substrate 11 , an n-type GaN semiconductor layer 12 , an active area 13 , a p-type GaN semiconductor layer 14 , a p-contact 15 and a n-contact 16 ,

Typically, the light emitting diode is on a sapphire substrate 11 educated.

By the method according to the invention was in the field 16a a region of the p-type GaN semiconductor layer 14 to the n-doped semiconductor layer 12 removed to the n-type semiconductor layer 12 expose. On the thus exposed n-doped semiconductor layer 12 then could the n-contacting structure 16 be applied. In this case, the depth of the removal of the p-doped semiconductor layer 14 in the present case 230 nm. This depth removal was achieved by means of an excimer laser with a power density of 1.69 J / cm ² and a 5-times exposure.

The dimensions of the n-contacting structure 16 are so on the ditch 16a adapted that between the p-doped semiconductor layer 14 and the n-contacting structure 16 neither a mechanical nor an electrically conductive contact exists. The ditch 16a for the n-contacting structure 16 typically has a width of about 50 microns. The n-contacting structure 16 is at a distance to the walls of the trench 16a formed from about 5-10 microns on both sides.

In the ditch 16a becomes the n-type contacting structure 16 applied by means of a shadow mask in a Elektronenstrahlverdampfungs-, or sputtering process as a structured metallic contacting structure. Likewise, on the p-doped semiconductor layer 14 by means of a shadow mask in a Elektronenstrahlverdampfungs- or sputtering process, the metallic p-contacting structure 15 applied as a structured metallic contacting structure. The application of the p-contacting structure 15 and the n-contacting structure 16 by electron beam evaporation or sputtering process can be done in one process step. Likewise, the application of the p-contacting structure 15 and the n-contacting structure 16 also be done by known lithographic techniques.

Likewise was in the range 17 by means of the method according to the invention, the p-doped semiconductor layer 14 away. As a result, electrical insulation of the various regions of the light-emitting diode has been achieved. By electrically insulating various regions of the light-emitting diode, for example, a luminous surface of the surface of the light-emitting diode can be defined. Likewise, a defined area of an energization can be essentially excluded and thus a dark area can be defined. In this case, the depth of the removal of the p-doped semiconductor layer 14 in the present case 230 nm. This depth removal was achieved by means of an excimer laser with a power density of 1.69 J / cm ² and a 5-times exposure.

In the area 18 By carrying out the method according to the invention, both the p-doped semiconductor layer was obtained 14 as well as the active area 13 and the n-type semiconductor layer up to the substrate 11 away. This results in a mechanical separation of the individual semiconductor components on the wafer, that is, it is a separation trench 18 formed, which serves as Sägestraße for separating the plurality of light-emitting diodes of a wafer. The depth of the dividing trench 18 is 2-10 microns, preferably 6 microns. For this depth removal, the exposure repetition rate in the present case is 150 pulses.

3 shows a schematic representation of an embodiment of a projection mask 4 , As a projection mask 4 For example, a standard square lithography mask, 10 × 10 cm ² in size, is used. The projection mask 4 consists of a UV-transparent substrate, preferably quartz, in this case with a thickness of 2 mm, are applied to the structured reflective, non-UV-transparent regions of metal, in this case chromium having a thickness of 100 nm. In the reflective area no laser transmission and therefore no semiconductor processing takes place. The mask is produced by means of Electron beam or photo lithography and wet chemical etching of Cr metal. As an alternative, an absorbing coating can also be applied to the metal in order to suppress reflections.

The recesses 19 . 21 in the metallization of the projection mask 4 as structural templates correspond to the desired structure that is to be removed on the surface of the semiconductor device. On the projection screen 4 is a non-transparent metallization 20 applied. in this area is the projection screen 4 not irradiated. On the surface of the semiconductor device, the corresponding areas are shaded and thus not processed. The semiconductor layer is thus not removed and thus defines the luminous surface of an LED (corresponding to FIG 2 . 14 ). In the recesses 21 the projection mask 4 becomes the projection mask 4 from the laser radiation 8.3 irradiated. The semiconductor surface is thus exposed to laser radiation in the corresponding areas and removed. In the presently resulting trenches then the n-contact can be applied (corresponding to 2 . 16a ). The projection mask 4 has a plurality of structural templates 22 in the present case four, so that four semiconductor devices can be exposed simultaneously. It is also possible that adjacent to the present four identical structural templates 22 a number, for example, four equal to each other, to the illustrated four structural templates 22 different structure templates on the projection screen 4 are arranged. This makes it possible on the one hand, the wafer 6 in different areas to work with different structures, for example, to produce small series of different semiconductor devices on a wafer. Likewise it is possible to use the same area on the surface of the wafer 6 in several exposure steps with different structure templates to structure.

In the present case, the dimension of the recesses is scaled up by a factor of 10, since a reduction to the present 10% is achieved by means of the focusing optics when imaging the projection mask on the surface of the semiconductor component. The exposure area on the surface of the semiconductor device thus corresponds to one tenth of the dimension of the recesses in the projection mask.

Based on the use of an excimer laser with a pulse energy of up to 2 joules, an area of 1 cm ² can be illuminated with the necessary power density. Modern light-emitting diodes have a chip area of 1 × 1 mm ² . Taking into account the distance between the individual chips, so can by means of the implementation of the method and the projection mask 4 at the same time over 60 light-emitting diodes are processed.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• R. Maser et al., "Laser Processing of GaN based LEDs with Ultradiode Picosecond Laser Pulses", Proc. Of SPIE, Vol. 8433, 2012 [0003]
• Nakamura et al., "High Brightness InGaN Blue, Green and Yellow Light-Emitting Diades with Quantum Well Structures", Jpn. J. of Appl. Phys., Vol. 34, 1995 [0019]

Claims (15)

A method for producing a semiconductor component, comprising the following method steps: A depositing a semiconductor layer structure on a substrate, which semiconductor layer structure comprises at least one GaN-based semiconductor layer, B at least partially removing at least the GaN-based semiconductor layer in local areas by means of laser processing, characterized in that the laser processing in method step B by means of exposure of the GaN-based semiconductor layer by at least one projection mask, which projection mask is illuminated with laser radiation of an ablation laser, such that exposure areas of the GaN-based semiconductor layer are exposed through recesses in the projection mask and shading areas of the GaN-based semiconductor layer Shadowed projection mask, wherein the laser fluence of the ablation laser in the exposure areas above the ablation threshold of the GaN-based Halbleitichich t lies. A method according to claim 1, characterized in that an excimer laser is used as Ablationslaser, which excimer laser has a wavelength less than or equal to 351 nm and a pulse length in the range 40 nanoseconds or less. Method according to one of the preceding claims, characterized in that reduced on exposure to the projection mask on the GaN-based semiconductor layer, preferably in the range 2 to 20-fold reduced, particularly preferably 10-fold reduced illustrated. Method according to one of the preceding claims, characterized in that the semiconductor component is formed as a GaN-based light-emitting diode. Method according to claim 4, characterized in that the semiconductor layer structure comprises an active region, which active region in method step B is at least partially, preferably completely removed in the exposure regions, in particular that in method step B at least one luminous region of the light-emitting diode is defined by By removing at least the active area in the exposure areas, a mechanical separation and electrical isolation of the illuminated area takes place. Method according to one of the preceding claims, characterized in that in method step B, the semiconductor layer structure in the exposure areas is substantially completely removed. Method according to one of the preceding claims, characterized in that a plurality of semiconductor components is produced on a wafer, in particular that the wafer is arranged perpendicular to the laser radiation of the ablation laser displaceable. Method according to one of the preceding claims, characterized in that the method step B is repeated, preferably between once and twenty times, particularly preferably repeated five times. Method according to one of the preceding claims, characterized in that in a method step C1 after the method step B, a displacement of the wafer takes place, such that the displacement of the wafer is perpendicular to the laser radiation of the ablation laser. Method according to one of claims 1 to 8, characterized in that in a method step C2, a displacement of the wafer, wherein the method step C2 takes place simultaneously with the method step B. Method according to one of the preceding claims, characterized in that in an additional process step D after step B, an etching step, preferably an etch-dip step is performed. Device for processing a semiconductor component, which semiconductor component comprises at least one GaN-based semiconductor layer, comprising a laser, means for beam expansion and means for focusing, wherein a laser beam path from the laser through the means for beam expansion to the means for focusing, characterized the laser is embodied as an excimer laser and in that at least one projection mask is arranged and configured in the laser beam path of the excimer laser between the means for beam expansion and the means for focusing such that laser radiation impinges on the projection mask and transmits it at least in subregions, wherein exposure areas of the semiconductor component can be acted upon by means of the irradiating laser radiation and shading areas of the semiconductor component are shadowed by the projection mask. Apparatus according to claim 12, characterized in that a jet homogenizer between the means for beam expansion and the Projection mask is arranged and designed so that laser radiation with a substantially homogeneous intensity profile, preferably laser radiation with a top hat beam profile, in particular square top hat beam profile, meets the projection screen. Apparatus according to claim 12 or 13, characterized in that the projection mask is structured by means of optical or electron beam lithography and / or by means of direct laser ablation. Device according to one of claims 12 to 14, characterized in that the projection mask is arranged and designed such that by means of the irradiating laser radiation, a plurality of semiconductor devices can be acted upon simultaneously.

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