Method for fixing a matrix-free electrophoretically deposited layer on a semiconductor chip for the production of a radiation-emitting semiconductor component, and radiation-emitting semiconductor component

Abstract

A method can be used for fixing a matrix-free electrophoretically deposited layer on a semiconductor chip. A semiconductor wafer has a carrier substrate and at least one semiconductor chip. The at least one semiconductor chip has an active zone for generating electromagnetic radiation. At least one contact area is formed on a surface of the at least one semiconductor chip facing away from the carrier substrate. A material is electrophoretically deposited on the surface of the at least one semiconductor chip facing away from the carrier substrate in order to form the electrophoretically deposited layer. Deposition of the material on the at least one contact area is prevented. An inorganic matrix material is applied to at least one section of a surface of the semiconductor wafer facing away from the carrier substrate in order to fix the material on the at least one semiconductor chip.

Claims

1. A method for making a semiconductor chip, the method comprising: providing a semiconductor wafer, wherein the semiconductor wafer has a carrier substrate and a semiconductor chip, wherein the semiconductor chip has an active zone for generating electromagnetic radiation, and wherein a contact region is disposed at a surface of the semiconductor chip facing away from the carrier substrate; electrophoretically depositing a material on a surface of the semiconductor chip facing away from the carrier substrate in order to form an electrophoretically deposited layer, wherein none of the material is deposited on the contact region; and applying an inorganic matrix material to a region of a surface of the semiconductor wafer facing away from the carrier substrate in order to fix the material on the semiconductor chip, wherein the matrix material is removed on a surface of the electrophoretically deposited material facing away from the semiconductor chip such that the surface is free of the matrix material.

2. The method according to claim 1, wherein applying the matrix material comprises initiating a chemical reaction in at least the region of the surface of the semiconductor wafer facing away from the carrier substrate.

3. The method according to claim 2, wherein, during the chemical reaction, a metal oxide layer is formed as matrix material at least on the region of the surface of the semiconductor wafer facing away from the carrier substrate.

4. The method according to claim 3, wherein the metal oxide layer is applied in a plasma-enhanced vapor deposition process, and wherein a tetraethyl orthosilicate is made available as starting material in order to deposit the metal oxide layer on at least the region of the surface of the semiconductor wafer facing away from the carrier substrate.

5. The method according to claim 3, further comprising: bonding the semiconductor chip through the metal oxide layer onto the contact region; and singulating the semiconductor wafer.

6. The method according to claim 3, further comprising: removing the matrix material at least in a region of the contact region; bonding the semiconductor chip; and singulating the semiconductor wafer.

7. The method according to claim 6, wherein removing the matrix material in the region of the contact region is effected by reactive sputtering, by a plasma process, or by an anisotropic structuring method.

8. The method according to claim 1, wherein the matrix material is deposited in an atomic layer deposition process on at least the region of the surface of the semiconductor wafer facing away from the carrier substrate.

9. The method according to claim 1, wherein the matrix material is applied by spin casting or spin coating on at least the region of the surface of the semiconductor wafer facing away from the carrier substrate.

10. The method according to claim 9, further comprising: removing the matrix material at least in the region of the contact region; curing the matrix material that remains on the surface of the semiconductor wafer facing away from the carrier substrate; and singulating the semiconductor wafer.

11. The method according to claim 10, wherein removing the matrix material in the region of the contact region is effected by wet-chemical etching.

12. The method according to claim 9, wherein the matrix material comprises a spin-on glass or a spin-on silicone.

13. The method according to claim 1, wherein the electrophoretic layer comprises particles of a luminophore or particles of a reflective material.

14. The method according to claim 1, wherein the contact region is kept potential-free during the electrophoretic deposition.

15. A radiation-emitting semiconductor component, comprising: a carrier substrate, a semiconductor chip, wherein the semiconductor chip has an active zone for generating electromagnetic radiation, wherein the semiconductor chip is arranged on the carrier substrate, and wherein a contact region is disposed at a surface of the semiconductor chip facing away from the carrier substrate; an electrophoretically deposited material arranged on the surface of the semiconductor chip facing away from the carrier substrate, the contact region being free of the electrophoretically deposited material; and a matrix material adjoining the electrophoretically deposited material in places, wherein a surface of the electrophoretically deposited material facing away from the semiconductor chip is free of matrix material, and wherein the surface of the electrophoretically deposited material facing away from the semiconductor chip has traces of a removal process for removing the matrix material.

16. A method for making a semiconductor chip, the method comprising: providing a semiconductor wafer, wherein the semiconductor wafer has a carrier substrate and a semiconductor chip, wherein the semiconductor chip has an active zone for generating electromagnetic radiation, and wherein a contact region is disposed at a surface of the semiconductor chip facing away from the carrier substrate; electrophoretically depositing a material on the surface of the semiconductor chip facing away from the carrier substrate in order to form an electrophoretically deposited layer, wherein none of the material is deposited on the contact region; and applying an inorganic matrix material to a region of a surface of the semiconductor wafer facing away from the carrier substrate in order to fix the material on the semiconductor chip, wherein the matrix material comprises a metal oxide layer, wherein the metal oxide layer is applied in a plasma-enhanced vapor deposition process, wherein a tetraethyl orthosilicate is made available as a starting material in order to deposit the metal oxide layer on at least the region of the surface of the semiconductor wafer facing away from the carrier substrate, and wherein the matrix material completely surrounds the material of the electrophoretic layer.

17. The method according to claim 16, wherein applying the matrix material is effected by initiating a chemical reaction in at least the region of the surface of the semiconductor wafer facing away from the carrier substrate.

18. The method according to claim 17, wherein the metal oxide layer is applied during the chemical reaction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The method and the component are explained in greater detail below on the basis of exemplary embodiments and the associated figures.

(2) FIG. 1 shows a plan view of a semiconductor wafer before the process of applying the electrophoretic layer;

(3) FIG. 2 shows an excerpt from the semiconductor wafer from FIG. 1 after the process of applying the electrophoretic layer;

(4) FIG. 3 shows a cross section of the semiconductor wafer from FIG. 2 after the process of applying the matrix material;

(5) FIG. 4 shows a cross section of a radiation-emitting component;

(6) FIG. 5A shows a cross section of a part of the semiconductor wafer from FIG. 2 in accordance with a further exemplary embodiment;

(7) FIG. 5B shows the cross section from FIG. 5A after a further process step;

(8) FIG. 6 shows a cross section of the semiconductor wafer from FIG. 2 after the process of applying the matrix material in accordance with a further exemplary embodiment; and

(9) FIGS. 7A and 7B show one exemplary embodiment of a radiation-emitting component.

(10) Elements that are identical, of identical type or act identically are provided with the same reference signs in the figures. The figures and the size relationships of the elements illustrated in the figures among one another should not be regarded as to scale. Rather, individual elements may be illustrated with an exaggerated size in order to enable better illustration and/or in order to afford a better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(11) FIG. 1 shows a semiconductor wafer 1. The semiconductor wafer 1 has a carrier substrate 5 and nine semiconductor chips 2. The semiconductor wafer 1, wafer 1 for short, can also have more than nine semiconductor chips 2, however. In one alternative exemplary embodiment, the wafer 1 can also have fewer than nine semiconductor chips 2, for example, six semiconductor chips or one semiconductor chip 2.

(12) The semiconductor chips 2 are suitable for emitting electromagnetic radiation, preferably light. The semiconductor chips 2 are arranged and fixed, e.g., soldered, on the carrier substrate 5. The carrier substrate 5 serves for mechanically stabilizing the semiconductor chips 2.

(13) The carrier substrate 5 has separating trenches 6. The separating trenches constitute depressions or furrows of the surface of the carrier substrate 5 which faces the semiconductor chips 2. The semiconductor chips 2 are separated from one another by the separating trenches 6. The separating trenches 6 serve for facilitating the singulation of the wafer 1 into individual radiation-emitting components (see FIG. 4, for example).

(14) The semiconductor chips 2 have a surface 4 facing away from the carrier substrate 5. On the surface 4, the respective semiconductor chip 2 has a contact location 3 or bonding pad for electrically contacting the semiconductor chip 2.

(15) In order to produce individual radiation-emitting components, after the process of fixing the semiconductor chips 2 on the carrier substrate 5, firstly a material 7 in the form of an electrophoretic layer is deposited on the surface 4 of the respective semiconductor chip 2 facing away from the carrier substrate 5 (see FIG. 2).

(16) The material 7 can comprise particles of a luminophore, e.g., phosphor particles, or particles of a reflective material. In the present case, the material 7 serves to at least partly convert the primary radiation emitted by the respective semiconductor chip 2 into an electromagnetic secondary radiation. The material 7 is a wavelength conversion material in the present exemplary embodiment.

(17) The wavelength conversion material is applied by electrophoresis. By means of the electrophoresis, a layer composed of the wavelength conversion material, that is to say a wavelength conversion layer, is applied or electrophoretically deposited on a part of the surface 4 of the semiconductor chip 2 facing away from the carrier substrate 5. The respective contact location 3 of the semiconductor chip 2 remains in particular free of wavelength conversion material. This procedure is described thoroughly in the German patent application having the file reference 10 2012 105 691.9 already cited previously.

(18) During the electrophoretic deposition of the wavelength conversion material, the region of the separating trenches 6 can also be at least partly omitted, for example, by means of a mask, such that only a thin or no wavelength conversion layer or electrophoretically deposited layer at all is applied in the region of the separating trenches 6 (see FIGS. 2 and 3, for example).

(19) The wavelength conversion layer is free of a matrix material, e.g., glass or ceramic. In particular, in this exemplary embodiment, the wavelength conversion layer consists exclusively of the particles of the luminophore.

(20) In a next step, a matrix material 8 is applied at least on a part of the surface of the wafer 1 which faces away from the carrier substrate 5 (see FIG. 3, for example), in order to fix or mechanically stabilize the wavelength conversion layer.

(21) The matrix material 8 can be applied in various ways, which are explained in greater detail below:

(22) In a first exemplary embodiment (see FIGS. 3 and 4), the matrix material 8 is applied by a PECVD method. With the aid of TEOS as starting material, in this method a metal oxide layer (e.g., SiO.sub.2) is deposited on the surface of the wafer 1 facing away from the carrier substrate 5. In this method, the SiO.sub.2 grows reactively at the surface of the wafer 1 and encapsulates the wavelength conversion layer, such that the latter is protected and fixed by the matrix material 8.

(23) In accordance with the exemplary embodiment shown here, the layer composed of matrix material 8 covers the entire surface of the wafer 1 (see FIG. 3, for example). As an alternative thereto (not explicitly illustrated), however, the matrix material 8 can also be deposited only on the wavelength conversion layer, such that the wavelength conversion layer is completely enveloped by the matrix material. This can be achieved with the aid of a shadow mask which leaves free only the region of the wavelength conversion layer for the deposition.

(24) The layer composed of matrix material 8 deposited by the PECVD method has a thickness of 50 nm to 500 nm, for example, 200 nm. Depending on the thickness of the layer, for example, for a thickness of more than 200 nm, in a further step the matrix material 8 is removed in the contact region 3 (not explicitly illustrated), in order to ensure later bonding of the respective semiconductor chip 2. The removal of the matrix material 8 can be carried out before or after the singulation of the semiconductor wafer 1, which is described in detail later.

(25) The removal process is carried out, for example, by means of reactive sputtering or by means of a plasma process. In this case, it is also possible to remove the matrix material 8 in the region of the separating trenches 6, if the wafer 1 is singulated at a later point in time (not explicitly illustrated). After the removal process, the wavelength conversion layer is still completely enveloped by the matrix material 8.

(26) By contrast, if the layer composed of matrix material 8 is very thin, if the thickness is 200 nm or less, for example, then it is possible to carry out the bonding of the semiconductor chip 2 through the layer composed of matrix material 8 onto the contact region 3, as will be described later (see FIG. 7B). In this case, it is not necessary for matrix material 8 to be removed.

(27) In a second exemplary embodiment (see FIGS. 5A and 5B), the matrix material 8 is applied by means of an ALD method. With the aid of a gaseous starting material, in this method a thin metal oxide layer (e.g., SiO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, HfO.sub.2) is deposited on the surface of the wafer 1 facing away from the carrier substrate 5.

(28) The metal oxide completely envelops the wavelength conversion material and in particular the individual particles of the wavelength conversion layer. In this method, accordingly, the matrix material 8 is also introduced between and below the individual particles of the wavelength conversion layer. Furthermore, the surface of the wavelength conversion layer is encapsulated with the metal oxide layer (see FIG. 5A, for example).

(29) The layer composed of matrix material 8 deposited by the ALD method has a thickness of 50 nm to 200 nm, for example, 150 nm. In particular, the layer composed of matrix material 8 deposited by the ALD method is substantially thinner than the layer composed of matrix material 8 deposited by the PECVD method. The layer composed of matrix material 8 is not planar on account of its only small thickness, but rather assumes the contours of the particles of the wavelength conversion layer arranged underneath (see FIG. 5A).

(30) In order to enable later bonding of the respective semiconductor chip 2, in a further step it is necessary to remove the matrix material 8 in the contact region 3 (see FIG. 5B). The removal process can be carried out before or after the singulation of the wafer 1. In this case, the removal process is carried out, for example, in an anisotropic structuring method, for example, in a dry etching method. In this case, it is also possible to remove the matrix material 8 in the region of the separating trenches 6 (not explicitly illustrated).

(31) Furthermore, the matrix material 8 which was deposited by the ALD method on the surface of the wavelength conversion layer facing away from the semiconductor chip 2 is also removed in this step. Therefore, matrix material 8 remains only between and below the particles of the wavelength conversion layer, i.e., within the wavelength conversion material, as is illustrated in FIG. 5B. Furthermore, matrix material 8 remains at the side surfaces of the wavelength conversion layer. In other words, the component available at the end of the process comprises a wavelength conversion layer whose surface facing away from the semiconductor chip 2 is free of matrix material 8.

(32) The surface of the wavelength conversion layer facing away from the semiconductor chip has traces of the anisotropic structuring method, for example, the dry etching method. By way of example, the surface is roughened or furrowed (not explicitly illustrated).

(33) In a third exemplary embodiment (see FIG. 6), the matrix material 8 can also be applied by spin casting or spin coating. The matrix material used in this case can comprise a spin-on glass or a spin-on silicone.

(34) It is once again possible for the entire surface facing away from the carrier substrate 5 to be covered by the matrix material 8 in this case (not explicitly illustrated). As an alternative thereto, for example, through the use of a mask, it is also possible for only the semiconductor chip 2 to be covered by the matrix material 8, as is indicated in FIG. 6. In particular, through the use of a mask, the region of the separating trenches 6 can be kept free of matrix material 8.

(35) The matrix material 8 comprising spin-on glass or spin-on silicone is then removed again in the contact region 3 of the semiconductor chip 2 (not explicitly illustrated). The removal can be carried out by means of wet-chemical etching, for example. In this case, it is also possible to remove the matrix material 8 in the region of the separating trenches 6 of the carrier substrate 5, if no mask was used (not explicitly illustrated). After this step, the matrix material 8 preferably remained only on the surface 4 of the semiconductor chip 2 applied the carrier substrate 5 with the exception of the contact location 3. After the removal process, the wavelength conversion layer is still completely enveloped by the matrix material 8.

(36) The matrix material 8 that remained on the surface 4 of the semiconductor chip 2 is then cured, for example, by exposure of the matrix material 8.

(37) After the process of applying the matrix material 8 in accordance with one of the three exemplary embodiments, the wafer 1 is singulated in this exemplary embodiment (see FIG. 4, for example). In particular, the carrier substrate 5, for example, with the aid of a laser, is separated at the location of the separating trenches 6. As a result, a multiplicity of components are obtained, wherein each component has a piece of the carrier substrate 5 and a semiconductor chip 2 with the above-described wavelength conversion layer and the matrix material 8.

(38) A further step involves electrically contacting the component and in particular the respective semiconductor chip 2. In this case, a bonding wire 10 (see FIG. 7B) is connected to the contact location 3 of the semiconductor chip 2. The bonding wire 10 is soldered, for example, onto the contact location 3. In the case of a very thin layer composed of matrix material 8, for example, 200 nm or less, the contacting can be effected in this case through the matrix material 8, as is illustrated in FIG. 7B.

(39) In a further step, the respective component is introduced into a housing 9 (see FIG. 7A) and in particular fixed, for example, soldered, on a bottom of the housing 9.

(40) The housing 9 can furthermore be filled with a potting material 11, for example, silicone (see FIG. 7B). The potting material 11 serves for protecting the component.

(41) By virtue of the covalent linkage of the particles of the wavelength conversion layer to the matrix material 8 deposited thereon, it is possible, particularly in the case of the first exemplary embodiment (PECVD method) and the third exemplary embodiment (spin casting or spin coating), to prevent wetting of the individual particles of the wavelength conversion layer with the potting material 11. An optimum heat exchange between the particles of the wavelength conversion layer thus remains ensured.

(42) Alternatively or additionally, in a further step (not explicitly illustrated), a beam shaping element, e.g., a lens, can be disposed downstream of the component.

(43) The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. However, the invention encompasses any novel feature and also any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.