TW200419667A - Method to roughen a surface of a body and optoelectronic component - Google Patents

Abstract

This invention relates to a method to roughen a surface of a body (1), with the following steps: coating the surface with a mask-layer (2), applying preformed mask-bodies (3) on the mask-layer (2), etching-through the mask-layer on the positions uncovered by the mask-bodies (3), etching the body (1) on the positions, which are free from the mask-layer (2), of its surface. In addition, this invention relates to an optoelectronic component. By using the mask-layer (2) as additional auxiliary masks, the methods with lower selectivity against the polystyrole-balls can be used to etching.

Description

200419667 (1) Description of the invention: [Technical field to which the invention belongs] The present invention relates to a method for roughening the surface of a semiconductor body, wherein the roughening is achieved by etching. The roughened surface can be used in particular in connection with a light emitting diode (LED) advantageously because of the pre-emission property of the semiconductor body used to form the substrate for the LED. There are usually ^ larger refractive index jumps, where the refractive index of the semiconductor material is usually n = 3.5. The refractive index of the resin surrounding the semiconductor body is usually η = 1.5. This causes a large refractive index jump for the radiation emitted by the semiconductor body. Therefore, a small total reflection angle is formed on the surrounding resin, which is about 26G. This total reflection angle allows only a small portion of the light generated in the semiconductor body to be emitted. Typically, in the cube-shaped LED used in the process, the radiation that is not emitted from the emission cone in the range of about 26 ° will still fall in the semiconductor crystal, because its angle with respect to the surface normal will not Changes due to multiple reflections. Sooner or later, the light beam will disappear mainly in these areas such as the contact area, the active area, or the substrate due to absorption. The roughening of the surface of the semiconductor body can now advantageously be used to radiate radiation transmitted outside the exit cone into such cones. This is mainly of interest in LED-wafers (especially thin-film-LEDs) with transparent substrates or effective reflective surfaces under the active area. This advantage also applies to organic LEDs. [Prior Art] It is known from the document US 3 7 3 92 17 that the light emitted when gallium-phosphorus crystal is emitted. 200419667 The property can be improved by roughening the surface. By R. Windisch et al. "40% Efficient Thin-Film Surface-

Textured Light-Emitting Diodes by Optimization of Natural

Lithography55, IEEE Transactions on Electron Device, Vol. 47, No. 7, 2000, p 1492-1498, is known to roughen a semiconductor body mainly composed of aluminum-gallium-arsenic so that light can be emitted from the semiconductor body. The injection properties can be improved. Therefore, the method for roughening described below is used. A ball made of polystyrene is applied on the surface of the semiconductor body, which can be prepared, for example, in a single layer on a water surface and then transferred to the surface of the semiconductor body by immersion. After the water is dried, the beads adhere to the surface of the semiconductor body. The surface is then dry-etched, so that pillars remain at the positions of the small balls and the space between the pillars is removed by dry etching in order to be etched from the semiconductor body. A disadvantage of the conventional method for roughening the surface of the semiconductor body described above is that it is not suitable for use in a semiconductor body composed of materials such as aluminum-gallium-in-phosphide or aluminum-gallium-in-nitride. The reason is that the dry etching method used has too little selectivity for the polystyrene-beads. This means that the semiconductor body can only be etched at a much slower rate than the beads. This is why the spheres used as etching masks have been wasted at an early point in the etching process (at this time only a small structural depth is etched into the surface of the semiconductor body). As a result, the ratio of the required etching depth to the structure width (rati0) cannot reach 0.25 to 5. This ratio is needed so that the 200419667 light can be effectively improved when emitted from the semiconductor body. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for roughening the surface of a semiconductor body, which is suitable for use in many different materials. This objective is achieved by the method of the first patent application scope. Other advantageous forms of this method are described in the appended items of the scope of patent application. The basic idea of the present invention is to reduce the selectivity problem of the etching method used. In this case, in addition to the masking effect achieved by the polystyrene beads, another auxiliary mask is used. The material used to form the auxiliary mask is not only different from the material of the semiconductor body to be etched, but also different from the materials of the beads. With the help of the other mask, the etching process can be divided into two steps, in which the structures of the balls arranged on the surface in the first step are transferred to the auxiliary mask. In a second step, the structure of the auxiliary mask is transferred into the surface of the semiconductor body to be etched. Since in addition to each ball another material is also added as a mask, the material combination can be very selective, wherein each process can be targeted at the increased selectivity between the mask material and the material to be etched Be optimized. For example, an etching method may be formed, which is not suitable for a specific material combination formed by a small ball and a semiconductor body to be etched, but this method can be used for the first etching step according to the current two-step etching method. In addition, it is now also possible to etch the body to be roughened by a method which is not necessarily performed selectively on the small balls on the surface. Conversely, it is sufficient when the second etching step has high selectivity for the material of the auxiliary mask on the one hand and high selectivity for the body to be etched on the other hand. 200419667 Provides a method for roughening the surface of a body, which includes a step of T: In a first step, a surface of the body is coated with a masking layer. In the next step, a pre-formed mask body is applied on the mask layer. In the next step, the mask layer is etched and is performed at a position not covered by each mask body. In the next step, the body is etched on its surface at a location exposed by the mask layer. The advantage of this method is that by adding another etching mask, the etching process can be divided into two steps, one of which is an etching process (which is very selectively performed on the body relative to the pre-formed mask body). Etching) is no longer needed. Conversely, by changing the material of the mask body and the masking layer, a broad spectrum can be used in the possible etching methods, that is, a wider spectrum can be used in the etching method in the etching process. In one embodiment of the method, the body contains aluminum-gallium-in-phosphide (A1 G a I η P). Such semiconductor materials can be advantageously used in light emitting diodes emitting in the red spectral region or the blue spectral region. Such a semiconductor material is optionally deposited on silicon carbide or a gallium-arsenic-substrate. In another advantageous embodiment of the method, the body contains aluminum-gallium-in-nitride (A1 GainN). This material is also particularly suitable for use in luminescent diodes in the red spectral region or the blue spectral region. In one embodiment of the method, a masking layer is applied, which consists of a dielectric. Consider SlxNY (for example, Sl3N4, Slon, Sl02, Ai203) and similar materials as the dielectric. But other materials can also be used to cover the 200419667 overlay. What is important is that the material of the masking layer allows an etch process to selectively etch the mask body and the body allows a different etching process to selectively etch the mask layer. In one embodiment of the method, pellets made of polystyrene can be used in a shaped mask body. Due to their good chemical stability and the fact that the polystyrene-beads can be made in large pieces in a simple-and inexpensive device, these polystyrene-beads are particularly suitable for use in the above method as Mask body. Each masking body can be applied to the surface of the masking layer in a random configuration to be a single layer or a regular configuration. In an advantageous embodiment of the method, the etching step is performed by a dry etching method. For example, consider using reactive ion etching (RIE = Reactive Ion Etching), ion beam etching (IBE = Ion Beam Etching), and chemically-assisted ion beam etching (CAIBE ^ Chemical Assisted Ion Beam Etching) 0 For example, Consider using an inductively coupled plasma etching method (ICP = Inductive Coupled Plasma) as the dry uranium etching method. The advantage of the dry etching method in this method is that no fluid is required, which can improve the local stability of the mask body, because the flow phenomenon in the fluid will no longer occur. In an advantageous implementation form of the method, it is carried out in such a manner that the structures are maintained on the surface of the body, and the ratio of the width b of each structure to the etching depth t is: 0.1 < t / b < 10. 200419667 This method is preferably performed under the following conditions: 0.25 < t / b < 5. This ratio of depth to width is particularly advantageous in order to improve the scattering properties on the surface of the optical semiconductor crystal, and It also improves the emission of light from the crystal. The above-mentioned ratio of etching depth to width can be achieved by appropriately selecting the etching process and the size and material of the mask body.

In another form of the method, the mask body is removed directly after the mask layer is etched. In another different form, the mask body remains on the surface of the mask so that it can be used there as another etching mask during the second etching process. The mask layer is removed after the uranium engraving process is completed, but the mask layer may remain on the surface of the body.

This method advantageously enables the etch depth in the body to be between 50 and 100 nir. This etch depth can be achieved by using an etching process that has a suitable selectivity between the mask layer and the body to be etched. In addition, the etching period must be appropriately selected to achieve the desired depth. In the above method, it is preferable to apply a masking layer having a thickness between 10 and 100 nm. Here, a minimum thickness is required for the mask layer, otherwise the mask layer cannot be used reliably as a mask for the body. However, a specified maximum thickness cannot be exceeded in order to keep the time required for the masking layer during etching to a limit. In order to achieve the above-mentioned ratio of the uranium depth to the structure width, it is advantageous to use a mask body whose lateral dimension on the mask layer is between 150-10-200419667 and 300 nm. The method described here can advantageously use a process' in the first etching step, which has a poor selectivity for the mask body and the body to be roughened. Therefore, it is necessary to consider the use of a process whose uranium engraving strength to the mask body is greater than that to the roughened body, but this is limited to the following cases: the etching process has a suitable Of selectivity. For example, the masking layer can be etched by a device used for reactive ion etching. A fluorination process can advantageously be used here, in which a gas mixture of CHF3 and argon is used. A standard RIE device with a parallel plate reactor is usually used here. The second etching step can be performed by, for example, an ICP-equipment in which a mixture of CH4 and H2 is used as an etching gas. In addition, the present invention also provides a photovoltaic module having a semiconductor body. The semiconductor body contains aluminum-gallium-in-phosphide or aluminum-gallium-in-nitride. In addition, the surface of the body is structured, wherein the width of the structure relative to the respective depth of the structure during etching must conform to: 0.25 < t / b < 5. In addition, the same component is provided, but the semiconductor body contains aluminum-gallium-in-nitride instead of aluminum-gallium-in-phosphide. Such a photovoltaic module (e.g., an LED) can be manufactured in the first time by the method described above. Methods known in the prior art are not suitable for achieving the ratio of t to b described herein. The so-called "structure" refers to what protrudes from the surface of a semiconductor body after etching. The width of each structure can be, for example, the 200419667 file "40% Efficient Thin-Film Surface-Textured Light-Emitting Diodes by Optimization of Natural Lithography5, IEEE, on Electron Devices, Vol. 47, No, written by R. Windisch et al. 7, 2000, pi 492-1 1 498 The width of a cylinder or a bell tower. [Embodiment] The present invention will be described below based on the implementation in the drawings.

It must be pointed out here: Figures 1 to 4 do not represent a cross section. In addition, the same reference symbols indicate the same elements or at least elements having the same-or similar functions. FIG. 1 shows a body 1, which can be, for example, a semiconductor body. A masking layer 2 is applied on the surface of the body 1. The masking layer 2 can advantageously have a thickness d between 10 and 100 nm. A masking body 3 is applied to the masking layer 2, which in the special case considered here forms on the one hand a single layer and on the other hand has the form of small balls. The lateral dimension A of each sphere is therefore between 150 and 300 nm. However, other forms of mask bodies with other suitable materials may be used.

Fig. 2 shows the arrangement state of Fig. 1 after the first etching step. The mask layer 2 is etched when it is in a state covered by the mask body 3. Therefore, a perforated masking layer 2 can be formed, wherein the masking body 3 is usually still disposed on the surface of the masking layer 2. However, the volume of the mask body 3 is smaller than that of the first figure by the unavoidable etching. This is caused by the fact that almost all of the etching methods used when the mask layer 2 is etched will usually etch the mask body 3 even if it is only in a small range. -12- 200419667 Then the mask body 3 on the surface of the mask layer 2 is removed. However, this step does not necessarily require 'conversely', so that the mask body 3 remains on the surface of the mask layer 2. Figure 3 shows the configuration of Figure 1, but a second uranium engraving step has been performed. The following indicates that the surface of the body 1 has a structure 4 already. The remainder of the masking layer 2 remains on the surface of the structure 4.

FIG. 4 shows the arrangement state after removing the mask layer 2 in FIG. 3. The ratio of the width b of the structure 4 to the etching depth t must meet the following conditions = 0.25 < t / b < 5. Each structure 4 may have the form of a cylindrical bell tower, for example. Each structure 4 can be positioned regularly, for example, along a mesh defined by the configuration of the mask body 3 in the leading edge array. However, the structures 4 can also be randomly distributed on the surface of the body 1. [Schematic description] Figure 1 A body to be etched, with a masking layer and mask applied to it

mm body. Figure 2 is the body of Figure 1 after the first etching step. Figure 3 is the body of Figure 2 after the second etching step. Fig. 4 The body of Fig. 3 after the mask layer is removed. Symbol table of main components: 1 body 2 mask layer 3 mask body -13- 200419667 4 structure A horizontal dimension b width d thickness t depth

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Claims (1)

200419667 Patent application scope: 1. A method for roughening the surface of the semiconductor body (1), which is characterized by the following steps: a) coating the surface with a masking layer (2), b) applying a The pre-formed mask body (3) is on the mask layer (2), c) the mask layer (2) is engraved with uranium at a position not covered by the mask body (3), d) Etching the body (1) on the surface of the body without the mask layer (2)! J. 2. The method according to item 1 of the patent application scope, wherein the body (1) contains aluminum-gallium-in-phosphide. 3. The method of claim 1, wherein the body (1) contains aluminum_gallium_in-helium. 4. The method according to any one of items 1 to 3 of the patent application, wherein the mask layer (2) is formed of a dielectric. 5 · Method for applying any one of patents 1 to 4 in which A small ball made of polystyrene is used as a pre-formed mask body (3). 6. The method according to any one of claims 1 to 5, wherein the etching step is performed by a dry etching method. 7 · The method of any one of items 1 to 6 of the patent application, such as applying the method so that each structure (4) remains in the surface of the body (1), and the width (b) of each structure The ratio of the etching depth ⑴ must conform to: 0.1 < t / b < 10. 8 · If the method of any one of claims 1 to 7 is applied, the method of this -15-200419667 is performed to make each structure (4) Remaining on the surface of the body (1), the ratio of the width of each structure (b) to the depth of etching (t) must conform to: 0.25 < t / b < 5. 9 The method of any one of items 1 to 8, wherein the remaining portion of the mask body (3) is removed from the mask layer (2) directly after step c). 1 0. The method according to any one of claims 1 to 9, wherein the etching depth ⑴ in the body (1) is between 50 and 100 nm. 1 1. The method according to any one of claims 1 to 10 of the scope of patent application, wherein a masking layer (2) is applied, and a thickness (d) thereof is between 10 and 100 nm. 12. The method according to any one of claims 1 to 11, wherein the mask body (3) on the mask layer (2) has a lateral dimension (A) between 150 and 3 0 0 nm. 1 3. The method according to any one of claims 1 to 12 in the scope of patent application, wherein the first etching step uses a uranium engraving strength of the mask body (3) to be greater than that of the body (1). Process. 14. The method according to any one of claims 1 to 13 of the scope of patent application, wherein the etching of the masking layer (2) is performed by a reactive ion engraving equipment. 15. The method according to item 14 of the scope of patent application, wherein a mixture of CHF3 and Ar is used as an etching gas. 16. The method according to any one of claims 1 to 15 of the scope of patent application, wherein the etching of the body (1) is performed by a device suitable for inductively coupled plasma. -16-200419667 17. The method according to item 16 of the patent application, wherein a mixture of CH4 and thorium is used as an etching gas. 18 · —A photovoltaic module comprising a semiconductor body containing a semiconductor-aluminum-gallium-caustic-phosphide and a structured surface, characterized in that the width (b) of each structure (4) and each structure (4) The ratio of the uranium engraved depth (t) must meet: 0.25 < t / b < 5. 19. A photovoltaic module comprising a semiconductor body containing an indium-gallium-in-nitride and Its surface is structured and is characterized by: The ratio of the width (b) of the structures (4) to the etching depth ⑴ of each structure (4) must meet: 0.25 < t / b < 5. -17-