The invention relates to a method for producing a plurality of semiconductor components comprising a semiconductor chip and a converter lamina.
In semiconductor components having a semiconductor chip and a converter lamina, the semiconductor chip emits a primary radiation during operation, wherein the converter lamina converts at least part of the primary radiation into a secondary radiation having a different wavelength. The resulting radiation arises from the superimposition of the primary radiation transmitted by the converter laminae and the secondary radiation generated. It is thus possible, for example, to produce semiconductor components which emit white light.
During the production of such components, the converter lamina is applied directly to the semiconductor chip usually by means of a screen printing method. However, a fluctuation of the color locus of the radiation (also referred to as chromaticity coordinate) emitted by the component can disadvantageously occur in this case. On account of the converter lamina being directly applied on the semiconductor chip, it is furthermore disadvantageous that defective converter laminae are applied to functioning semiconductor chips, and vice versa, and this can disadvantageously result in partly superfluous wear of the component parts of the components.
In the case where the converter lamina is directly applied on the semiconductor chip, it is disadvantageously not possible to assign a converter lamina to a semiconductor chip in a targeted manner depending on its converting property, in order thus to obtain a component having desired emission properties.
It is an object of the present application to specify a method wherein a converter lamina can be combined with a semiconductor chip in a targeted manner, wear of the component parts of the components simultaneously being reduced.
These objects are achieved, inter alia, by means of a production method comprising the features of claim 1. The dependent claims relate to advantageous developments of the production method.
In a development, the method for producing a plurality of radiation-emitting semiconductor components each having at least one semiconductor chip and a converter lamina comprises the following method steps:
a) providing a plurality of semiconductor chips in the wafer assembly, said semiconductor chips each being suitable for emitting a primary radiation,
b) providing a plurality of converter laminae on a common carrier, said converter laminae each being suitable for converting the primary radiation into a secondary radiation, and
c) mounting a converter lamina in each case on one semiconductor chip or onto a plurality of semiconductor chips by means of an automated method.
In this context, a converter lamina can in each case be mounted onto exactly one semiconductor chip. Alternatively, a common converter lamina can be disposed downstream of a plurality of semiconductor chips.
The converter laminae are thus separately produced laminae. A separately produced lamina should be understood to be, in particular, a lamina which is produced separately from the remaining constituent parts of the component. Accordingly, the lamina can be produced temporally before, in parallel with or after the production of the rest of the component. In the present case, the term “lamina” also encompasses layers which are flexible in a film-like manner and which can be produced separately and arranged onto the chip.
The conversion lamina is, in particular, a lamina in which part of the primary radiation emitted by the semiconductor chip is converted into a radiation having a different wavelength. The converter lamina can comprise a radiation-transmissive matrix material and a phosphor introduced in the matrix material. In this case, the matrix material determines the mechanical properties of the converter lamina. A radiation-stable and transparent material, in particular, is appropriate as matrix material. The matrix material is, for example, a thermoplastic or thermosetting plastic, for example silicone, or a ceramic. The refractive index of the matrix material is usually chosen in such a way that no undesirable scattering effects arise after the converter lamina has been applied on the semiconductor chip.
Phosphors introduced or embedded in the matrix material are described for example in the document WO 98/12757 A1, the disclosure content of which in this respect is incorporated by reference here.
The semiconductor chips each have an active layer, which preferably contains a pn junction, a double heterostructure, a single quantum well (SQW) structure or a multiquantum well (MQW) structure for generating radiation. In this case, the designation quantum well structure does not exhibit any significance with regard to the dimensionality of the quantization. It encompasses, inter alia, quantum wells, quantum wires and quantum dots and any combination of these structures.
The layers of the semiconductor chips each preferably comprise a III/V semiconductor. The semiconductor chips are in this case produced in the wafer assembly. A wafer assembly is, in particular, any arrangement which has a multiplicity of unpackaged semiconductor chips. This can be for example a semiconductor wafer, in particular a semiconductor wafer which has not been sawn, which has a multiplicity of individual semiconductor chips. The wafer assembly can likewise be a carrier on which a multiplicity of unpackaged, but already singulated semiconductor chips are applied, in order to enable further processing thereof.
The converter laminae can be applied to the wafer assembly individually or jointly in one piece, the wafer assembly subsequently being singulated. In this case, the semiconductor chips and possibly the converter laminae can be jointly singulated.
By means of the decoupling of the production of the converter laminae and of the semiconductor chips, it is possible to obtain, in particular, a production method wherein the color locus control of the radiation of the end product can be supervised better. Moreover, the wear of defective component parts is reduced, such as converter laminae or semiconductor chips, for example, since, prior to a combination of the converter laminae with the respective semiconductor chip, these can be tested and possibly removed by sorting.
A component produced in this way has the advantage, in particular, of near-chip conversion, wherein components which emit radiation in the white spectral range with narrow color locus distribution can be obtained. A maximum radiation efficiency of the component can be obtained on account of a targeted combination of the semiconductor chips with the converter laminae. Moreover, the production method is distinguished by low conversion costs and reduced problems in making contact with the semiconductor chip, for example making contact by means of a bonding wire. The decoupling of the methods for producing the converter laminae and the semiconductor chips furthermore has the advantage of an increased flexibility on account of the targeted combinations of converter lamina with respect to semiconductor chip.
The converter laminae can be embodied in a planar fashion or can have a three-dimensional structuring. The converter lamina can thus be configured as a flat lamina, wherein an exit surface of the lamina is fashioned as flat in this case. Alternatively, the exit surface of the lamina for desired coupling-out of light can have a three-dimensional structure, for example a lens-shaped structure, a curved structure or a roughened structure.
The converter laminae can contain ceramic or silicone, for example.
A plurality of converter laminae are produced simultaneously.
In a development, for mounting the converter laminae on the semiconductor chips, a conventional pick-and-place method is used, the principle of which is well known in semiconductor component mounting technology, in particular in chip mounting technology, and will therefore not be discussed in any greater detail at this juncture.
In a development, after method step b) and before method step c), the following method steps are carried out:
b1) measuring the degree of conversion of radiation of each converter lamina,
b2) sorting the converter laminae into a plurality of lamina groups depending on the degree of conversion of radiation,
b3) providing a plurality of semiconductor chip groups, wherein each group contains only semiconductor chips which emit a specific primary radiation,
b4) assigning a converter lamina group to a semiconductor chip group, such that each combination of converter lamina and semiconductor chip generates radiation that lies within a predetermined color locus range.
Such a method is distinguished, in particular, by the fact that the color control of the radiation of the end products can be supervised better. In particular, as a result of assigning a converter lamina group in which all laminae have the same degree of conversion or a degree of conversion within the same degree of conversion range to a semiconductor chip group in which all semiconductor chips have the same primary radiation or a primary radiation within the same emission range, groups of semiconductor components which have a very low color locus variation within the group can be produced in a comparatively simple manner.
In a development, the radiation of each combination of lamina group with semiconductor chip group lies within a common color locus range, in particular in the white color locus range.
In a development, the converter laminae are in each case fixed on the respective semiconductor chip by means of a clear silicone layer. The silicone layer is arranged on the semiconductor chips in particular by means of a jet process. In this case, the silicone layer is preferably applied prior to the mounting of the converter laminae on the semiconductor chips.
Alternatively, the converter laminae can in each case be applied by means of a layer composed of a material which has thermal, optical and adhesive properties that are the same as or similar to those of silicone.
In a development, the silicone layer is formed and applied as a drop on each semiconductor chip. In this case, each drop is preferably formed as a drop having a size of 5 nl to 20 nl inclusive. In this case, the size and extent of the drops are monitored in an automated manner, such that the sizes of the drops advantageously do not deviate, or do not deviate significantly, from the predetermined range. In this case, the silicone layer is applied to the semiconductor chips periodically. In particular, exactly one silicone drop is applied to each semiconductor chip.
Alternatively, the silicone layer or the layer composed of material having properties at least similar to those of silicone can be applied on each semiconductor chip by means of a jet process, a stamp process or a printing process. Moreover, there is the possibility, prior to the converter laminae being applied on the semiconductor chips, of arranging the silicone layer or the layer composed of material having properties at least similar to those of silicone on a side of the converter laminae, by which side the converter laminae are subsequently applied directly on the semiconductor chips.
In a development, prior to mounting the converter laminae on the semiconductor chips, the method involves determining whether the silicone layer is applied on each semiconductor chip. If it is ascertained in this case that no silicone layer is applied on a chip, no converter lamina is applied to said chip in the subsequent processing method. The determination of whether the silicone layer is applied on each semiconductor chip is made for example by means of a camera optical unit with polarization filters. What can thus be achieved is that no converter lamina is applied on a semiconductor chip which has no silicone.
In a development, the converter laminae are detached from the common carrier in each case by means of a vacuum process, in order subsequently to be able to be mounted on the semiconductor chips. It is thus possible to obtain a technique of picking up the converter laminae without needles, which is relevant in particular to converter laminae embodied as flexible silicone layers. Possible damage on account of the needles conventionally used can thus be avoided.
For the purpose of detaching the converter laminae from the common carrier, use is made of an adhesive layer arranged between the common carrier and the converter laminae, wherein, for the purpose of detaching the converter laminae, adhesive properties of the adhesive layer are reduced or eliminated by means of a heating process. For heating purposes, use is made of a so-called heating stamp. The latter is guided below the common carrier, such that the adhesive layer expands and loses its adhesive properties. The converter laminae can subsequently be detached from the common carrier without any problems by means of the vacuum process.
In a development, prior to mounting the converter laminae on the semiconductor chips, positions and orientations of the semiconductor chips in the wafer assembly are determined. The positions determined are registered in a so-called substrate map. The positions are determined for example on the basis of markings in the assembly, for example at the corner points of the assembly. With regard to the orientation of the semiconductor chips, what is of significance, in particular, is at what location in each semiconductor chip an upper contact area is formed. The contact areas are often arranged here in each case in a corner region of the semiconductor chips. These data, too, are determined and recorded.
If a position in the assembly has no semiconductor chip, this position is registered in the substrate map, such that no further processing takes place at this position.
In a development, prior to mounting the converter laminae on the semiconductor chips, positions and orientations of the converter laminae on the common carrier are determined. This determination is made for example by means of markings or on account of cutouts of the converter laminae in provided regions of the corner contact areas of the semiconductor chips.
In a development, in the course of mounting the converter laminae on the semiconductor chips, the orientation of the respective converter lamina is adapted to the respective orientation of the semiconductor chip. In particular, the converter laminae are in each case arranged on the semiconductor chips such that the cutout of the converter laminae is arranged above the corner contact of the semiconductor chip.
The orientation of the converter laminae is determined, for example, by means of a so-called uplooking camera (ULC), which is well known to the person skilled in the art and will therefore not be discussed in any greater detail at this juncture. In the course of mounting the converter laminae on the semiconductor chips, in particular a rotation of the converter laminae or semiconductor chips is taken into consideration, such that the converter laminae are applied with a similar form on the semiconductor chips.
After the individual components have been completed, the emission characteristics of said components can be checked by means of camera optical units. If the converter lamina is applied on the semiconductor chip in a rotated or displaced manner, then these components can be marked as “poor” in the substrate map, such that these components can subsequently be removed by sorting.
The wafer assembly with chips arranged thereon can subsequently be singulated into individual components, for example by means of sawing, wherein, after singulation, a respective component preferably comprises a semiconductor chip with converter laminae arranged thereon.
In a development, the preferably singulated semiconductor components are in each case arranged in a housing body in an additional method step d). Depending on the desired use, the desired type of housing body can be selected. The housing bodies can subsequently be potted after the mounting of the semiconductor components.
Further advantages and advantageous developments of the invention will become apparent from the exemplary embodiments described below in conjunction with
In the figures, identical or identically acting constituent parts may in each case be provided with the same reference signs. The illustrated constituent parts and their size relationships among one another should not be regarded as true to scale, in principle. Rather, individual constituent parts, such as, for example, layers, structures, component parts and regions, may be illustrated with exaggerated thickness or size dimensions in order to enable better illustration and/or in order to afford a better understanding.
In addition, a plurality of semiconductor chips in a wafer assembly are provided, as shown as an excerpt in the right-hand part of
The semiconductor chip is suitable for emitting a primary radiation. By way of example, the semiconductor chip 1 emits blue radiation. The converter laminae 2 are suitable for converting the primary radiation of the semiconductor chip/semiconductor chips 1 into a secondary radiation. By way of example, the converter laminae 2 are suitable for converting blue radiation into yellow radiation.
A converter lamina 2 is in each case detached from the common carrier 2a by means of an automated method 8, for example a pick-and-place method, and disposed downstream of the semiconductor chip 1 in the emission direction, as illustrated by the arrow in
The semiconductor chips can alternatively be embodied in a wafer assembly as a multiplicity of unpackaged, but already singulate semiconductor chips. In this case, the converter laminae are respectively disposed directly downstream of the semiconductor chips by the converter laminae being applied to a radiation exit side of the semiconductor chips.
The individual method steps are explained in greater detail in connection with
In this case, the common carrier 2a is embodied such that the converter lamina 2 is fixedly connected to the common carrier 2a, wherein this fixed connection can be reduced or eliminated by means of a heating process. A common carrier 2a embodied in this way is illustrated for example in
As illustrated in
For this purpose, a heating device 2c, for example a heating stamp, is arranged on that side of the common carrier 2a which faces away from the converter lamina 2, such that said heating device 2c heats the common carrier 2a and the adhesive layer 2b. On account of this heating process, the adhesive properties of the adhesive layer 2b are advantageously reduced as the adhesive layer 2b is foamed or expands due to the heating process. On account of this foaming that results in the adhesive properties of the adhesive layer 2b being reduced or eliminated, the converter lamina 2 can be lifted off from the common carrier 2a without any problems by means of a vacuum device, as illustrated in
The production method involves providing the components in the wafer assembly, as illustrated in
The checking of the semiconductor chips is illustrated in greater detail in
In order, as explained in conjunction with
In addition, the orientation of the semiconductor chips 1 in the wafer assembly is determined. This determination is illustrated in connection with
By means of such contact areas 1a and current distribution connections 1c on the surface of the semiconductor chips, electrical contact can be made with the semiconductor chips by means of a bonding wire, for example, after completion. Alternative contact-connections without the use of bonding wires, such as a planar contact-making technique, for example, can also be used. Such contact-making techniques are known to the person skilled in the art and will therefore not be discussed in any greater detail at this juncture.
Moreover, such a contact area 1a and current distribution connections 1c on the surface of the semiconductor chips are not absolutely necessary. The person skilled in the art knows, in particular, contact-making techniques in which a contact area on the top side is not necessary, such as, for example, a flip-chip contact-making technique, which will likewise not be explained in any greater detail at this juncture.
In addition to this, the position and the orientation of the converter laminae on the common carrier are determined. This determination takes place by means of a camera optical unit, wherein the orientation and positions of the converter laminae are likewise recorded in a so-called converter map. The converter laminae have a corner cutout, in which the contact area of the semiconductor chip is to be arranged. In this case, this cutout is to be arranged directly above the contact area of the semiconductor chip in a later method step.
The conductor lamina is arranged on that side of the semiconductor chip 1 which faces away from the carrier 9. In this case, the converter lamina is oriented in such a way that the cutout of the converter lamina 2 lies in the region of the contact area of the semiconductor chip 1. Moreover, the converter lamina 2 is oriented in such a way that no rotation with respect to the semiconductor chip 2 is present, the converter lamina 2 being arranged centrally on the semiconductor chip 1.
A component produced in this way can be checked by means of a camera optical unit after the production process. If, in this case, the orientation of the converter lamina 2 with respect to the semiconductor chip is not optimal, then these semiconductor chips are marked as poor in the substrate map.
The component 10 as illustrated in
In method step V1b, a plurality of separately produced converter laminae are made available. These laminae are arranged, in particular, on a common carrier.
In method step V2b, the degree of conversion of radiation of each lamina is measured. By way of example, the laminae can be measured individually by means of a measuring apparatus in which a semiconductor chip having a known wavelength distribution is arranged.
In method step V3b, all the converter laminae are sorted into lamina groups depending on the measured degree of conversion, such that all laminae in a lamina group have a specific common degree of conversion or lie within a specific common degree of conversion range.
If, in this case, a very precise color locus is desired in the finished semiconductor components, the laminae are preferably sorted into lamina groups which are in each case characterized by a very narrow degree of conversion range. If the permissible tolerance in the color locus control is higher in the finished semiconductor components, the degree of conversion range can be chosen to be wider.
In method steps V1a to V1a, the same analogously applies to sorting the semiconductor chips into semiconductor chip groups. Method step V1a involves providing a plurality of semiconductor chips in the wafer assembly, and their emission wavelength of the primary radiation is determined in method step V2a. Depending on the determined emission wavelength of the primary radiation, the semiconductor chips are classified in groups, the group classification being noted in the module map.
In the subsequent method step V4, the converter lamina groups are respectively assigned to a semiconductor chip group, such that each combination of converter laminae and semiconductor chips generates radiation which lies within a predetermined color locus range, preferably within a common color locus range, particularly preferably within a white color locus range. On account of this sorting, it is possible to obtain a method for producing components wherein the color locus variation of the radiation of the end product can be supervised better.
In method step V5, the converter laminae from the chosen lamina group are in each case mounted on the semiconductor chips from the chosen semiconductor chip group by means of an automated method, preferably a pick-and-place method. The mounting is effected, for example, by means of the silicone drop, as explained in
After the laminae of a lamina group have been mounted on the semiconductor chips of an assigned semiconductor chip group, a plurality of semiconductor components which all have radiation within a common color locus range have been produced. The semiconductor components of a lamina/semiconductor chip group in combination respectively belong to a semiconductor component group G1, G2 or G3.
If the permissible tolerance for color locus variation of the semiconductor components is high, the measurement of the degree of conversion of the laminae and/or of the primary radiation of the semiconductor chips and the assigning can be dispensed with. In this case, the laminae provided are mounted randomly onto semiconductor chips provided, by means of the automated method.
The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments, but rather 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.
This patent application claims the priorities of German patent applications 10 2010 056 571.7 and 10 2011 013 369.0, the disclosure content of which is hereby incorporated by reference.
Number | Date | Country | Kind |
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10 2010 056 571.7 | Dec 2010 | DE | national |
10 2011 013 369.0 | Mar 2011 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2011/072944 | 12/15/2011 | WO | 00 | 9/4/2013 |