Conversion medium body, optoelectronic semiconductor chip and method of producing an optoelectronic semiconductor chip

A method of producing an optoelectronic semiconductor chip includes providing a semiconductor layer sequence with at least one active layer, providing a one-piece conversion medium body, wherein a matrix material is incompletely crosslinked and/or cured, and wherein the conversion medium body exhibits at room temperature a hardness of Shore A 0 to Shore A 35 and/or a viscosity of 10 Pa·s to 150 Pa·s, placing the conversion medium body onto the semiconductor layer sequence such that they are in direct contact with one another, and curing the conversion medium body wherein after curing the hardness of the conversion medium body is Shore A 30 to Shore D 80.

RELATED APPLICATIONS

This is a §371 of International Application No. PCT/EP2010/061648, with an international filing date of Aug. 10, 2010 (WO 2011/026716, published Mar. 10, 2011), which is based on German Patent Application No. 10 2009 040 148.2, filed Sep. 4, 2009, the subject matter of which is incorporated by reference.

TECHNICAL FIELD

This disclosure relates to a conversion medium body and an optoelectronic semiconductor chip with a conversion medium body, as well as a method of producing an optoelectronic semiconductor chip.

BACKGROUND

It could be helpful to provide a conversion medium body which exhibits elevated adhesion to a semiconductor layer sequence. It could also be helpful to provide an optoelectronic semiconductor chip with such a conversion medium body and a method of producing such an optoelectronic semiconductor chip.

SUMMARY

I provide a conversion medium body for an optoelectronic semiconductor chip; including a matrix material, and conversion medium particles, which are embedded in the matrix material, wherein the matrix material is incompletely cured and/or crosslinked, and at room temperature the conversion medium body exhibits a hardness of between Shore A 0 and Shore A 35 inclusive and/or a viscosity of between 10 Pa·s and 150 Pa·s inclusive.

I also provide an optoelectronic semiconductor chip, including a semiconductor layer sequence including at least one active layer, and a one-piece conversion medium body with a matrix material, in which conversion medium particles are embedded, wherein the conversion medium body is in direct contact with the semiconductor layer sequence and is mounted on the semiconductor layer sequence without any bonding agent, and the hardness of the conversion medium body amounts to at least Shore A 30 and at most Shore D 80.

I further provide a method of producing an optoelectronic semiconductor chip including the steps providing a semiconductor layer sequence with at least one active layer, providing a one-piece conversion medium body with a matrix material, in which are embedded conversion medium particles, wherein the matrix material is incompletely crosslinked and/or cured, and wherein the conversion medium body exhibits at room temperature a hardness of between Shore A 0 and Shore A 35 inclusive and/or a viscosity of between 10 Pa·s and 150 Pa·s inclusive, placing the conversion medium body onto the semiconductor layer sequence, such that they are in direct contact with one another, and curing the conversion medium body, wherein after curing the hardness of the conversion medium body amounts to at least Shore A 30 and at most Shore D 80.

DETAILED DESCRIPTION

A conversion medium body may be mounted on an optoelectronic semiconductor chip. The semiconductor chip may comprise a photodiode, a laser diode or, preferably, a light-emitting diode. In particular, the conversion medium body has geometric dimensions comparable to those of the semiconductor chip. For example, an average lateral dimension of the semiconductor chip and/or of the conversion medium body is 0.3 mm to 10.0 mm, in particular 0.5 mm to 3.0 mm.

The conversion medium body may comprise a matrix material and conversion medium particles embedded in the matrix material. One kind or a plurality of different kinds of conversion medium particles may be used.

The matrix material may be incompletely cured and/or incompletely crosslinked. In other words, it is possible to increase the hardness and/or modulus of elasticity of the matrix material by a further curing process or crosslinking process.

The conversion medium may exhibit at room temperature a hardness of Shore A 0 to Shore A 35 or Shore A 2 to Shore A 15 and/or a viscosity of 10.0 Pa·s to 150 Pa·s or 15.0 Pa·s to 70 Pa·s. Room temperature is in particular intended to mean a temperature of approx. 293 K. The conversion medium body with the incompletely cured and/or crosslinked matrix material is thus comparatively soft.

In the conversion medium body which is intended for an optoelectronic semiconductor chip, the body may comprise a matrix material and conversion medium particles embedded in the matrix material. The matrix material is incompletely cured and/or incompletely crosslinked and the conversion medium body exhibits at room temperature a hardness of Shore A 10 to Shore A 35 and/or a viscosity of 10 Pa·s to 70 Pa·s.

The conversion medium body may be mounted interlockingly on a semiconductor layer sequence in the incompletely cured and/or crosslinked state. A particularly strong mechanical bond between the conversion medium body and the semiconductor layer sequence can be achieved by subsequent curing of the conversion medium body. The service life of the semiconductor chip may be extended in this manner.

The matrix material may comprise or consist of a silicone. It is likewise possible for the matrix material to comprise or consist of an epoxy or a silicone-epoxy hybrid material.

The conversion medium heed not contain a thixotroping agent. It has been found that, in particular by using long-chain primary materials for a silicone and/or a high viscosity starting material for the matrix material, it is possible to prevent segregation and/or settling of the conversion medium particles in the uncured matrix material. In this way, it is possible to dispense with a thixotroping agent assuming in particular particulate, especially nanoparticulate, form.

The proportion by weight of the conversion, medium particles is 20% to 75%, preferably 55% to 70%. In other words, the conversion medium particles account for a considerable proportion by weight of the conversion medium body.

The conversion medium body may be shaped in one piece. In other words, the matrix material forms a cohesive, uninterrupted unit in which are embedded the conversion medium particles. In particular, the conversion medium body then does not comprise any sub-zones with a plurality of conversion medium particles which are delimited from one another for instance by phase boundaries and/or which differ from one another with regard to average material composition and/or a physical property.

An optoelectronic semiconductor chip is furthermore provided which comprises, for example, a conversion medium body according to one or more of the above-stated examples. Features of the conversion medium body are therefore also disclosed for the optoelectronic semiconductor chip described herein and vice versa.

The optoelectronic semiconductor chip may comprise a semiconductor layer sequence with at least one active layer. The semiconductor chip furthermore contains a one-piece conversion medium body with a matrix material, in which are embedded the conversion medium particles. The conversion medium body is in direct contact with the semiconductor layer sequence and furthermore placed on the semiconductor layer sequence without any bonding agent. A hardness of the conversion medium body is at least Shore A 30 to Shore D 80, preferably at least Shore A 60 to Shore D 80, in particular at least Shore D 30 to Shore D 75.

“Without any bonding agent” may mean that no bonding agent such as an adhesive, adhesive film or solder is located between the semiconductor layer sequence and the conversion medium body. Stating that the semiconductor layer sequence and the conversion medium body are in direct contact with one another at least in places may mean that the matrix material is, at least in places, in physical contact with a semiconductor material of the semiconductor layer sequence.

Electrical contact structures which are, for example, placed directly on a semiconductor material of the semiconductor layer sequence, may be deemed to belong to the semiconductor layer sequence if the contact structures are directly, strongly, durably and/or integrally connected with the semiconductor material. In other words, “in direct contact with the semiconductor layer sequence” may also mean that the conversion medium body is placed directly on such electrical contact structures which are, for example, formed of a metal or a transparent conductive oxide.

A radiation passage area and flanks of the semiconductor layer sequence may be each at least 90% covered by the conversion medium body. The degree of coverage should in particular be determined in a direction perpendicular to the respective areas of the semiconductor layer sequence.

The conversion medium body may lie interlockingly on at least one boundary face of the semiconductor layer sequence. This means that, in particular on a microscopic scale, the conversion medium body and the boundary face cling to one another. Specifically, roughened portions of the semiconductor layer sequence may be reproduced at the boundary face by the conversion medium body. In this way, in particular on a microscopic scale, an interlocking connection may be obtained between the semiconductor layer sequence and the conversion medium body, whereby a particularly high level of adhesion may be achieved between the conversion medium body and semiconductor layer sequence. The contact surface between the semiconductor layer sequence and the conversion medium body is likewise enlarged such that bonding is also increased by adhesive forces. The side of the conversion medium body remote from the boundary face of the semiconductor body may be of smooth or planar construction such that, for example, roughening is not reproduced on this side.

Flanks of the semiconductor chip, namely lateral boundary faces in particular parallel to the growth direction of the semiconductor chip, may at most be 15% or at most 5% covered by the conversion medium body in a direction perpendicular to the flanks. In particular, the flanks are not covered by the conversion medium body.

A method of producing an optoelectronic semiconductor chip is furthermore provided. The semiconductor chip is for example configured according to one or more of the above-stated examples. Features of the conversion medium body and the optoelectronic semiconductor chip are therefore also disclosed for the method described herein and vice versa.

The method may comprise:providing a semiconductor layer sequence with at least one active layer,providing a one-piece conversion medium body with a matrix material in which are embedded conversion medium particles, wherein the matrix material is incompletely crosslinked and/or cured, and wherein the conversion medium body exhibits at room temperature a hardness of Shore A 0 to Shore A 35 and/or a viscosity of 10 Pa·s to 150 Pa·s,placing the conversion medium body on the semiconductor layer sequence such that they are in direct contact with one another,curing the conversion medium body, wherein after curing the hardness of the conversion medium body amounts to at least Shore A 30 to Shore D 80, and completing the optoelectronic semiconductor chip.

In the method, the conversion medium body may be placed on a backing film and covered with a covering film. In other words, the conversion medium body is located between the backing film and the covering film. At least the covering film may be removed non-destructively from the conversion medium body, in particular also as long as the matrix material of the conversion medium body is not yet completely cured.

Both the backing film and the covering film may be removed from the conversion medium body without damaging the latter, as long as the matrix material is not completely cured.

The backing film and/or the covering film may at least be partially radiation-transmissive in the ultraviolet and/or in the blue spectral range. In this way it is possible for the matrix material to be photochemically crosslinkable and/or curable for example through the backing film.

The conversion medium body may be provided such that the latter comprises lateral dimensions and/or shapes of the semiconductor chip, in particular with a tolerance of at most 25% or of at most 5%. The conversion medium body may thus, even before placing on the semiconductor chip, be shaped and/or cut to size in the manner of or approximately in the manner of a radiation passage area of the semiconductor chip. The conversion medium body is thus in particular shaped congruently with the radiation passage area, for example, on the backing film and placed on the semiconductor chip.

A component described herein and a method described herein will be explained in greater detail below with reference to the drawings and with the aid of examples. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, but rather individual elements may be shown exaggeratedly large to assist in understanding.

FIG. 1shows an example of an optoelectronic semiconductor chip1. The semiconductor chip1comprises a semiconductor layer sequence3which contains at least one active layer. The semiconductor layer sequence3is, for example, a light-emitting diode which, when in operation, in particular emits ultraviolet and/or blue radiation. Roughening is produced on a radiation passage area32of the semiconductor layer sequence3. The roughening increases the outcoupling of light from the semiconductor layer sequence3on the radiation passage area32. Flanks34are lateral boundary faces of the semiconductor layer sequence3.

The semiconductor chip1furthermore comprises a conversion medium body5. The conversion medium body5comprises conversion medium particles55embedded in a matrix material50. The conversion medium particles55are distributed randomly and/or homogeneously in the matrix material50. The conversion medium particles55convert radiation produced by the semiconductor layer sequence3when in operation partially or completely into radiation of another wavelength. The conversion medium body5is preferably photochemically resistant to the radiation emitted by the semiconductor layer sequence3and to the thermal stresses arising during operation.

An average diameter of the conversion medium particles55is, for example, 1 nm to 100 nm. It is likewise alternatively or additionally possible for the diameter of the conversion medium particles55or further conversion medium particles to be 1 μm to 20 μm. The matrix material50and conversion medium particles55are not shown in the remaining figures.

The one-piece conversion medium body5clings interlockingly to the roughening on the radiation passage area32of the semiconductor layer sequence3. This gives rise to interlocking on a microscopic scale between the roughening of the radiation passage area32and the matrix material50, whereby particularly stable adhesion can be achieved between the semiconductor layer sequence3and the conversion medium body5.

In the lateral direction, the conversion medium body5ends flush with the flanks34of the semiconductor layer sequence3. Lateral dimensions of the conversion medium body5and/or the semiconductor layer sequence3are preferably 300 μm to 3 mm, in particular 500 μm to 2 mm. The thickness of the conversion medium body preferably amounts to 20 μm to 125 μm, in particular between 30 μm to 70 μm. The thickness of the semiconductor layer sequence3preferably amounts to at most 200 μm, in particular at most 12 μm.

In the example according toFIG. 2, the conversion medium body5projects beyond the semiconductor layer sequence3in the lateral direction. The semiconductor layer sequence3is here placed on a carrier2. The semiconductor layer sequence3is here completely enclosed by the carrier2, the conversion medium body5and electrical contact structures (not shown inFIG. 2) for electrical contacting of the semiconductor layer sequence3. It is here possible for a cavity7to form at the flanks34of the semiconductor layer sequence3.

A boundary face of the conversion medium body5remote from the carrier2has a lenticular shape in a region over the radiation passage area32. In other words, the height of the conversion medium body5, relative to the carrier2, is not constant over the entire lateral extent.

Electrical contact structures6a-dare provided in the example according toFIG. 3. The contact structure6c, which takes the form of a bond wire, here completely penetrates the one-piece conversion medium body5in a direction perpendicular to the main direction of extension of the semiconductor layer sequence3.

The conversion medium body5here in each case covers at least 90% of the radiation passage area32and the flanks34. The electrical contact structure6bis for example vapor deposited onto a semiconductor material of the semiconductor layer sequence3.

In the example according toFIG. 4, the one-piece conversion medium body5placed directly on the semiconductor layer sequence3is completely penetrated by the contact structure6b, which is produced, for example, by vapor deposition and/or by a photolithographic process. Both the contact structure6band the conversion medium body5are completely covered by an electrical insulating layer11. The material of the insulating layer5preferably differs from the matrix material of the conversion medium body5.

The hardness of the conversion medium body5is Shore D 45 to Shore D 80. Thanks to this elevated hardness, the semiconductor layer sequence3may be mechanically protected by the conversion medium body5. In addition, the elevated hardness enables particularly effective interlocking and thus elevated adhesion between the structuring or roughening of the radiation passage area32and the matrix material50.

FIG. 5illustrates the shear force F as a function of time t of a conversion medium body, for example, according to one ofFIGS. 1 to 4, on a semiconductor layer sequence3. A temperature of 185° C. prevails over the entire period of time of 1000 h. The shear force at which the conversion medium body5is detached, for example, from a semiconductor layer sequence3according to one ofFIGS. 1 to 4, is at least 50 N.

FIG. 6illustrates a method of producing the semiconductor chip1. According toFIG. 6A, the conversion medium body5is placed on a backing film8which is, for example, an ethylene-tetrafluoroethylene film, in particular by means of a screen printing method. The conversion medium body5with the matrix material and the conversion medium particles is then partially cured by exposure to a temperature T of approx. 150° C. over a period of time of 4 min. The matrix material is, for example, LPS-AF500Y from the manufacturer Shin-Etsu. As a result of the partial curing, the conversion medium body has a hardness of Shore A 10 to Shore A 35 such that the conversion medium body may be placed on the semiconductor layer sequence by an automatic component insertion machine10(pick and place machine) as shown inFIG. 6B.

In an optional further method step not illustrated inFIG. 6, the conversion medium body5produced on the backing film8may be smoothed, so resulting in a particularly uniform thickness of the conversion medium body5, and/or be cut to size in lateral dimensions. It is also possible, unlike the representation inFIG. 6A, for the backing film8to end flush with the semiconductor body5in the lateral direction.

FIG. 6Cshows that the matrix material is then completely cured and/or crosslinked by exposure to a temperature T. The curing time preferably amounts to at least 10 min. Curing proceeds, for example, at a temperature of 150° C. over a period of time of 1 h. The conversion medium body5may optionally be pressed and/or held against the semiconductor layer sequence3by exposure to a pressure p over all or part of the thermal curing.

In the method according toFIG. 7, the conversion medium body5is located between the backing film8and a covering film9as shown inFIG. 7A. The conversion medium body5is partially cured through the backing film8, for example, by exposure to a temperature T and/or by ultraviolet or blue radiation. After partial curing, the conversion medium body5exhibits only a low level of hardness and/or only a comparatively low viscosity of 10 Pa·s to 70 Pa·s inclusive. The conversion medium body5is shaped, for example, by rolling arid optionally by subsequent singulation and/or cutting to size. Punching or compression molding is also possible, in particular if the conversion medium body5is shaped in lenticular manner.

According toFIG. 7B, after partial curing the covering film9is removed from the conversion medium body5. The conversion medium body5here remains on the backing film8.

FIG. 7Cshows that the conversion medium body5is mounted on the semiconductor layer sequence3by the backing film8. The one-piece conversion medium body5is cured by exposure to a temperature T or by photochemical curing, preferably with simultaneous exposure to pressure p. During curing, the backing film8may remain on the conversion medium body5or also, unlike the representation inFIG. 7C, already have been removed before complete curing and/or crosslinking of the conversion medium body5, for example before or immediately after the conversion medium body5is positioned on the semiconductor layer sequence3.

Unless the backing film8has already been removed before curing, it is taken off once the conversion medium body5is completely cured as shown inFIG. 7D.

FIG. 8shows conventional semiconductor components which likewise comprise a conversion medium body5. According toFIG. 8A, the conversion medium body5, which in particular comprises a silicone, is mounted on the semiconductor layer sequence3by way of a bonding agent4. The bonding agent4is, for example, a low viscosity silicone adhesive. Unlike the conversion medium body5, the bonding agent4is transparent or clear in a spectral range in which the semiconductor layer sequence3generates radiation when in operation.

Because the bonding agent4has only a low viscosity during placing, the bonding agent4may partially wet the flanks34of the semiconductor layer sequence3or indeed the carrier2in the lateral direction while the conversion medium body5is being placed. Such wetting is avoidable by a specific design of the carrier2or of the semiconductor layer sequence3and by particular cleaning steps of the carrier2. Such measures do, however, increase manufacturing costs. Because, for instance according toFIGS. 1 to 4, the conversion medium body5is placed without any bonding agent, there is no risk of the bonding agent4contaminating for example the carrier2and it is possible to dispense with a complex design of the carrier2and/or of the semiconductor layer sequence3.

According toFIG. 8B, the conversion medium body5is placed directly on the semiconductor layer sequence3by a screen printing method. Such a method entails elevated precision and is comparatively costly. To mount the conversion medium body5directly on the semiconductor chip3, the starting material and in particular also the finished conversion medium body5has only a comparatively low hardness, in particular, less than Shore A 80 or less than Shore A 60.

In addition to the material limitation with regard to hardness in the ease of a screen printing method directly onto the semiconductor layer sequence3, the thickness of the conversion medium body5is relatively uneven in comparison with a conversion medium body5according toFIGS. 1 to 4, whereby local variations in color location of wavelength-converted radiation may occur. Just as when a bonding agent4is used, direct printing of the conversion medium body5onto the semiconductor layer sequence3entails a risk of the material of the conversion medium body5contaminating the flanks34or the carrier2.

The bodies, chips arid methods described herein are not restricted by the description given with reference to the examples. Rather, the disclosure, encompasses any novel feature and any combination of features, including in particular any combination of features in the appended claims, even if the feature or combination is not itself explicitly indicated in the claims or examples.