Patent Application
20090104415
In modern microelectronics, electronic components are often labeled for their identification. However, some components present, as the external layer of the component casing, a low-contrast or transparent layer, for example, filled reaction resins (glob top), glass, quartz, etc. It is very difficult to apply a text by laser with such components because the surfaces of such components after laser irradiation do not present sufficient contrast to be recognized using common optical systems.
Moreover, conventional laser labeling on mold or glob top compositions have a penetration depth greater than 15 μm, up to approximately 70 μm. This means that more than 70 μm of ablatable or inscribable material thickness must be present to prevent damage caused by the laser to the chip to be labeled. Accordingly, the minimum required component height increases to greater than 70 μm.
To circumvent this problem, an additional labeling film is frequently applied by lamination to the component surface, which film presents a higher contrast value after laser labeling. Besides the contrast layer, such a film also usually presents an adhesive layer, resulting then in a total thickness greater than 20 μm, which amounts to a considerable contribution to the total thickness (height) of the component in miniaturized components.
In the case of components that have very stringent requirements for a (small) component height, this method is thus not the optimal solution. In addition, with some components, unavoidable difficulties arise to an extent due to the film lamination and the associated processes. Thus, for example, an adhesive film may become detached, particularly after sawing processes to separate the components that have been produced simultaneously and in parallel on a wafer. In the case of materials that present, between the film and the substrate of the component, a thermal expansion coefficient that is not adjusted, strong additional stresses can occur in the substrate and in the casing, which limit the lifespan of the component and can even lead to premature failure or malfunction.
Another possibility of laser labeling consists in applying one or more thin conducting metal layers to the surfaces of such components, which surfaces present contrast between each other and with respect to the substrate, and in labeling them with a laser by ablation. Such a labeled coating, however, cannot be used with electromagnetically sensitive components, such as SAW and FBAR components, because the metal layer used interferes considerably with the functioning of such components as a result of capacitive coupling with the active structures of the component.
In one aspect, the present invention provides a system for marking, such as labeling, which can produce sufficiently good optical contrast in a simple way and using a small height.
A first embodiment includes a component with a first layer or a body made of a first material and at least one release layer that is different from the former and applied on it. The release layer is released at least partially in a released area, where the released area forms a pattern. The release layer comprises an inorganic material, which is electrically nonconducting or semiconducting. The pattern that is formed in the unreleased, or at least partially released, release layer is machine-readable.
For example, a layer combination is proposed that includes a first layer or a first body and at least one release layer, which differs from the first layer and is applied over it. The release layer, in a release area, is partially released or ablated, resulting in a machine-readable pattern. For the release layer, an inorganic material that is electrically nonconducting or semiconducting is used.
The proposed layer combination has an advantage that the pattern can be produced in a simple way by laser labeling or by automatic acquisition with machines. The nonconducting or semiconducting materials used for the release layer make the latter suitable for combination with conventional electromagnetically sensitive components, so that the layer combination is suitable advantageously for labeling or marking miniaturized electrical and electronic components, in particular.
Suitable materials for the release layer are known from semiconductor technology, so that a simple manufacture of the release layer and high compatibility with the components are possible. These suitable materials, moreover, have the advantage that they can be produced in a thin layer thickness and that, by partial ablation, a machine-readable pattern that is optically easily detectable can be generated in it, already with a thin layer thickness. In the case of a minimum layer thickness of the layer combination, the total height of an electrical component provided with a pattern can be reduced to a minimum. The thickness of the release layer can be chosen to be less than 1 μm, and it is, for example, 0.005-0.50 μm, preferably 0.025-0.150 μm.
In comparison to a given release procedure, it is advantageous to produce the release layer with a material that can be released under milder conditions respectively more rapidly, or thus better, than the material of the first layer or of the first body. This can be achieved with a laser of appropriate wavelength, which can and is absorbed selectively in the release layer.
Because the release layer can be very thin, it is possible in components with this layer combination to prevent additional tensions generated by the latter.
In comparison to other labeling methods (methods for the manufacture of a pattern on a component) such as stamping, affixing an adhesive label, ink jet printing and other printing methods, laser labeling in the mentioned release layer presents the highest flexibility and efficiency, it uses the smallest component surface area for the labeling, and it requires the smallest additional layer thickness compared to an unlabeled one. However, other release methods can also be used. It is preferred to choose a release method in which the component chip or the component structures applied to them are not damaged. This applies particularly to the case where the release layer is applied directly to the component chip.
It is advantageous for the release layer to comprise silicon or germanium. These two materials can be applied in a simple way, by known methods, in thin and homogeneous layers and with good adhesion to a multitude of different surface materials. They can be applied with minimal electrical conductivity, and they present sufficient absorption in the visible spectrum. Therefore, a pattern produced in them can be read in the visible spectrum by means of appropriate pattern recognition with detectors. These release layers allow layer combinations with a number of first layers, which can definitely be transparent or low-contrast, without the machine readability of the produced pattern suffering as a result.
If the layer combination is used for marking an electrical component, then the first layer can be formed from the component itself, for example, from the component chip, its uppermost function layer, cover or casing. In a conventional unlabeled component, the release layer is then the only other applied layer, and the pattern is generated in it. Many components are encapsulated with a plastic, and they present a surface made of plastic, for example, a reaction resin molding material based on an epoxide. On such a surface, the mentioned dielectrical layers can be applied with good adhesion. Even in a very thin layer, they already present a good optical contrast with the plastic.
In the case of a component that should have a minimum component height, and where, for the first layer or the first body of the layer combination, a function layer is used, such as, for example, a cover or casing layer of the component, the thickness of the cover or casing layer can be minimized. Therefore, it is necessary, during the partial release of the release layer in the preparation of the pattern, to prevent entirely, or at least largely, any damage to the underlying uppermost component layer (first layer or first body). For this purpose, the release process is either not carried out entirely up to the surface of the first layer, or an appropriate material combination consisting of the first layer and a release layer is chosen that presents sufficiently different release properties in connection with a laser suitable for releasing the release layer. For example, for the release layer, a material is chosen that presents a high absorption coefficient compared to the laser. The latter absorbs the laser radiation well, so that the material is consequently heated rapidly, and a bursting off or vaporization of the release layer in the irradiated area is possible.
Besides using the appropriate material combination, it is also possible to design the surface of the first layer or of the first body, i.e., usually the surface of the component itself, in such a way that the laser beam is scattered or well reflected. One possibility to improve the scattering effect of the surface of the first layer would be to roughen it prior to the application of the release layer. This is particularly advantageous for those first layers that are transparent to the wavelength of the laser used, for example, glass, crystals, and similar materials. In this way, the laser beam is prevented from penetrating and advancing through the transparent first layer to the component structures, which could then be damaged by the laser.
For the release layer, silicon and germanium as well as their alloys in any ratio are particularly suitable. A release layer comprising silicon or germanium can also be doped with elements to facilitate the laser labeling by improving the optical properties of the layer. Such elements have been chosen in such a way that they do not lead to a higher or to a high conductivity of the release layer. Furthermore, for the release layer, compound semiconductors are suitable, such as, for example, gallium arsenide, silicon carbide, indium phosphide and others. Suitable deposition methods exist for these materials as well. The laser used for the release can be adapted in terms of its wavelength to the given release material.
Advantageously, the release layer is produced by CVD or PVD. These methods allow the manufacture of homogeneous layers. It is also possible to produce such layers from solution, or by means of a galvano-chemical method, on any first layers.
Besides the homogeneous layers, release layers are also suitable that comprise nanoparticles and comprise particularly of a conglomerate, i.e., of a densely packed layer of nanoparticles. Such a release layer can be obtained easily by spray application of a suspension containing the nanoparticles. The suspension can be carried out in a solvent and advantageously in water, and it can optionally also comprise a binder or a dispersant. By removing the solvent after the spray application of the layer, the latter can be converted into the desired firmly adhering state.
If a binder is used, then it can optionally also be burned out. However, it is also possible to use a thermally crosslinked binder which improves the stability and thus the resistance to abrasion of the nanoparticle layer.
The release layer can be structured from nanoparticles of at least two different materials. In this way, it is possible to set certain layer properties optimally, or to adapt them to the given material of a first layer. Here, it is possible to use a combination of electrically conducting and nonconducting particles, where the mixing ratio is adjusted in such a way that the release layer overall remains nonconducting. The nonconducting nanoparticles are preferably chosen in such a way that they present a high or imaginary refractive index for visible light or at least for a spectral range of visible light, so that, for the release layer, a high labeling contrast is already possible with thin layer thicknesses. A high contrast can already be achieved if, in the released area, the release layer is not yet removed completely, and respectively, the surface of the underlying first layer is not yet uncovered.
A nanoparticle release layer can be removed directly with a release procedure, for example, by laser ablation by direct laser writing. However, it is also possible to produce a machine-readable pattern indirectly, for example, by compacting or solidifying the release layer comprising nanoparticles with a laser in such a manner that it becomes resistant in comparison to the whole-surface dissolution method, so that only the compacted or fixed areas of the release layer remain and form the pattern.
Another possibility is to provide thermochromic or photochromic nanoparticles in the release layer, which present a color conversion after being irradiated with a laser of appropriate wavelength. In this way, layers that can be written on directly by laser radiation can be produced, which require no or only little release.
The release layer can also comprise fluorescent substances, in particular, nanoparticles that are sensitized with fluorescent substances. A pattern that has been produced by the release becomes apparent when the release layer is actively irradiated. The fluorescent substances can be chosen in such a way that a fluorescence in visible light is generated under irradiation with UV light, and thus the readability of the pattern is improved.
The release layer can present several layers, of which at least one must present the mentioned desired properties. For example, it is possible to use, for the release layer, a combination of a base layer and, on top of it, an additional laser absorbing layer. If the base layer presents a smaller absorption for laser radiation than the laser absorbing layer, then the depth of the generated pattern is successfully limited with this combined release layer. This is appropriate for first layers and, particularly, component surfaces that are sensitive to laser radiation and present a particularly high absorption and transparency. It is also possible to choose the partial layer of the release layer in such a way that, after the uppermost layer has been released and the base layer has been uncovered, a better contrast is produced than is the case, for example, for the combination with a first layer and a layer to be released.
A material for the base layer that presents a higher ablation threshold for the laser wavelength used can function as a stop layer for laser ablation, to protect the component from damage caused by the laser beam.
The base layer can also present a high scattering or a high reflection for the laser radiation, which also leads to a decreased ablation rate.
The proposed layer combination is suitable particularly for marking or labeling components that work with acoustic surface waves or with bulk waves, i.e., for example, for surface acoustic wave (SAW) components or film bulk acoustic resonator (FBAR) components.
Below, the invention is explained in further detail with reference to embodiment examples and the associated figures. The figures serve only to illustrate the invention, are executed only schematically, and are not true to scale.
a and 4b show methods for the manufacture of a layer combination; and
a and 5b show an alternative method for the manufacture of a component with a marking.
The following reference characters can be used in conjunction with the drawings:
The first layer FS can be any layer or any body, such as, for example, the component chip itself (for example, a piezoelectric material such as lithium tantalate (LT) or lithium niobate (LN)). Preferably it can be a function layer of a component, and consequently it can represent the uppermost layer of the component cover or the component casing. Accordingly, the first layer FS can be a crystalline, ceramic or semiconducting layer, as used for common chips or casings of miniaturized components.
The first layer FS can also be a polymer cover of an unencased component (e.g., a bare die), for example, a chip that is covered with a glob top. The first layer FS can also present several areas in which different materials form the surface of the first layer FS. The first layer FS can also be a component substrate, as used for electrical and electronic components, and, for example, for semiconductor components or components that work with acoustic waves. Accordingly, the first layer FS can be a substrate made of silicon, silicon germanium, gallium arsenide, indium phosphide or other semiconductors for a microelectronic component or a piezoelectronic substrate made of, for example, quartz, lithium tantalate, lithium niobate, aluminum nitride or zinc oxide, as used for components that work with acoustic waves. The surface of the first layer FS, however, can also present metal structures.
The cover layer AS can be a homogeneously structured layer made of an electrically insulating inorganic material, such as an insulation or semiconductor layer that can be produced in a layer deposition method of semiconductor technology such as CVD or PVD. The release layer can comprise a layer made of silicon oxide, silicon carbide or other insulating compounds, for example, metal oxides, a semiconductor, such as silicon, germanium or a compound semiconductor. The release layer can be doped, alloyed, or represent another homogeneous mixture of the mentioned materials.
However, it is also possible to produce the release layer from the mentioned nanoparticles in a sufficiently abrasion resistant layer. The nanoparticles can be made uniformly of a single material, which is chosen from the above-mentioned materials. However, it is also possible to use a composition of the release layer AS that includes a mixture of different nanoparticles, where it is also possible to embed conducting nanoparticles in a matrix made of nonconducting or electrically insulating nanoparticles.
For labeling, it is preferred to use direct laser labeling, where the selective parts of the release layer can be released. For a release layer made of Si or Ge, it is possible to use, for example, a green laser having, for example, a wavelength of 533 nm, for which a subjacent polymer layer (first layer FS) is transparent, so that it cannot be released, and is suitable as a bottom layer. However, for other materials and other combinations of release layers and a subjacent uppermost component layer, other selectively working wavelengths can also be used.
The release layer AS is absorbing particularly for visible light, and it presents, for example, at least one absorption band in the visible spectrum. Irrespective of this, the pattern MR that is detectable in the optical range can be formed from the surface of deeper layers, which has been uncovered therein, for example, of the base layer GS or of the first layer FS. This deeper layer, uncovered due to laser writing, forms an optical contrast with the intact release layer AS, which has not been released. Such a contrast can also form if the release layer AS is not removed completely and presents a narrowing layer thickness only in the area of the pattern, where the narrowing layer thickness leads to a change in the optical properties of the release layer AS.
However, it is also possible to produce the pattern MR produced in the release layer AS by phase conversion of the areas of the release layer AS, which have been inscribed with the laser. Such a phase conversion can be of a chemical or physical type, for example, a modified crystal structure. A chemical/physical conversion can also be achieved with a release layer that contains at least thermochromic or photochromic particles.
a and 4b, collectively
After the generation of the cover layer, the surface of the cover layer AS is brushed according to a predetermined pattern MR, with the help of a laser source LQ, which generates a laser beam LS. The laser beam LS is absorbed in the uppermost layer of the cover layer AS and, in the irradiated area, it leads to a vaporization or bursting off of a layer area, as represented in
The function layer FS is provided, for example, as a cover layer for a component that presents a component chip BC, usually a crystalline, for example, semiconducting or piezoelectric or simply only mechanically stable substrate, on which component structures BS can be arranged. These component structures BS that require a cover are now covered in a way which in itself is known with the function layer FS that is provided with a pattern MR. If the function layer FS is, for example, a plastic film, then the covering can be carried out in a simple way by lamination of the function layer, which, together with the release layer AS and the pattern MR in it, represents the layer combination.
This method can be carried out on the wafer plane, i.e., before the individualization of a plurality of components produced in parallel in a single wafer. Because the component chip BC with the component structures BS can be manufactured parallel to the layer combination provided with a pattern, which comprises the function layer FS, this type of production of a pattern can be carried out on the finished component BE in a particularly cost effective and time-saving way. Compared to the known component, which already presents the function FS, but no cover layer AS provided with a pattern, the total height of the component is increased only insubstantially. In such a combination, the release layer AS can present, for example, a thickness of 5-500 nm, where, for example, in the case of a release layer AS made of silicon, a 100 nm layer thickness is entirely sufficient for the release layer AS, for the purpose of achieving a good contrast with respect to a polymer film.
The release layer can be produced in a simple way by magnetron sputtering.
In such a release layer, the pattern MR can be produced, for example, a labeling that indicates the component type, with a green laser of 532 nm and an inscription height of, for example, 0.2 mm.
The embodiment examples according to
The invention is suitable, particularly for components with electromagnetically sensitive component structures, because the pattern, respectively, the release layer with the pattern is electromagnetically neutral. In addition, the invention is naturally also suitable for all components and, particularly, for miniaturized components, because it can be applied on practically all surfaces of components, component covers or component casings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 019 118.8 | Apr 2006 | DE | national |
This application is a continuation of co-pending International Application No. PCT/DE2007/000728, filed Apr. 24, 2007, which designated the United States and was not published in English, and which claims priority to German Application No. 10 2006 019 118.8 filed Apr. 25, 2006, both of which applications are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/DE2007/000728 | Apr 2007 | US |
| Child | 12258301 | US |
