2-in-1 process with mask-on-substrate unit for the production of a microelectronic ceramic circuit carrier with vertical and lateral fine structures

Abstract

The invention relates to a microelectronic ceramic circuit carrier with vertical and lateral fine structures with a structure width of < 20 µm, as well as a mask-on-substrate unit and a 2-in-1 process for producing such a circuit carrier. The 2-in-1 process allows offset-free contouring of the vertical and lateral fine structures in a single laser processing step. Contouring opens channel-like recesses for lateral conductor track fine structures and vertical vias (microvias). These recesses are then filled with conductive thick-film materials. The process saves material, time, and energy.

Description

Field of the invention

[0001] The invention relates to ceramic-based microelectronic circuit carriers for HDI structures for miniaturized circuits and a method for their production using thick-film technology. State of the art

[0002] Microelectronic circuit carriers based on ceramic substrates are widely used in microelectronic assembly and interconnect technology. LTCC substrates are used, on which lateral conductor structures with feature widths of 75 µm to 150 µm can be created using thick-film screen printing processes. However, this is not sufficient for flip-chip contacting of modern integrated semiconductor components with connection pitches of < 150 µm. (LTCC: Low-Temperature Co-fired Ceramics)

[0003] The transition to thin-film technology has made it possible to obtain conductor track structures with feature widths of 10 µm on LTCC substrates, although the surface roughness of the substrates (typical value: Ra > 0.3 µm) has a limiting effect, thus precluding even narrower feature widths [Reppe, G., Müller, J., Pohlner, J. et al.: Development and Evaluation of Fine Line Structuring Methods for Microwave Packages in Satellite Applications. 15th European Microelectronics and Packaging Conference & Exhibition, June 12-15, 2005, Oud Sint Jan, Brugge, Belgium].

[0004] By applying a thin glass layer with a typical thickness of 2 µm to an LTCC substrate using a sol-gel process, the surface roughness could be reduced to Ra = 45 nm, resulting in conductor track structures with feature widths of 2 µm on LTCC substrates [Bartsch, H., Brokmann, U., Goj, B., Weiss, R., Rädlein, E., Müller, J.: Sol gel thin films on LTCC ceramic multilayers enable their use as thin film substrates, In: Proceedings of 20th European Microelectronics and Packaging Conference (EMPC), September 14-16, 2015, Friedrichshafen, Germany]. A disadvantage of this process is that openings for vias must be subsequently introduced, which can lead to undesirable misalignment between the conductor track structures and the vias.

[0005] This results in a need for new thick-film processes in which conductor track structures with structure widths of 20 µm and less, comparable to thin-film processes, can be obtained.

[0006] When structuring ceramic substrates with thick-film processes, solid masks are used, which can be designed as mesh or stencil screens. Previous processes involve a multitude of standard manufacturing steps, beginning with punching or lasering microvias. Fill masks are also prepared by punching or lasering, and the vias are then filled with conductive materials. This is followed by fill printing of the lateral structures on the top and / or bottom of the substrate using a stencil or a stainless steel screen. Between the individual steps, the orientation of vias (microvias) relative to lateral structures can be disturbed, for example, by using different tools (screen printing tool, punching tool).This can lead to an incorrect arrangement, i.e. an undesirable misalignment of the lateral structures relative to the vias.

[0007] LTCC substrates are sintered at a temperature below 900°C. They are therefore suitable as circuit carriers for conductor track structures made of materials with high electrical conductivity but a comparatively low melting point T M in the range of 1000°C. Such materials are, for example, Au (T M = 1064°C), Ag (T M = 961°C), Cu (T M = 1085°C). Materials with a significantly higher melting point, e.g. Pt (T M = 1768°C) and alloys such as AgPd can also be used.

[0008] When processing LTCC substrates using thick-film technology, the track widths of conductor structures applied to the substrates are limited to > 80 µm. However, modern applications require track widths of < 20 µm. The production of fine structures using these processes is time-consuming and costly, as they require many process steps, which are described in the following references.

[0009] In [Schulz, A., Gutzeit, N., Stöpel, D., Welker, T., Hein, M., Müller, J.: High resolution patterning of LTCC-based microwave structures for Q / V-band satellite applications. In: German Microwave Conference (GeMiC), Bochum, Germany, 2016], several approaches for fabricating fine gold structures with a width of 50 µm and a pitch of 40 µm are compared: • Fine-line screen printing: A stainless steel mask with a mesh size of 37 µm (US: 400 mesh), a wire diameter of 18 µm, and a 15 µm particle size emulsion was used to print fine circuit patterns. Using an Au paste (DP 5740A from DuPont®), Au lines with a width of 50 µm and a pitch of 40 µm were obtained, which is insufficient. • Screen printing of a resin paste followed by electroplating: The low viscosity of the resin paste allows for the resolution typical for thin-film applications to be achieved in green and sintered LTCC substrates. A 150 nm thick Au resin paste (Heraeus RP 181208-15%) was screen-printed onto an LTCC substrate fired at a maximum temperature of 850°C. The resin paste served as an adhesion layer for the Au electroplating process. Using a negative photoresist mask with a resolution of 25 µm ± 2 µm, 5 µm thick Au conductor structures were electroplated.The disadvantage of this electroplating method is that a high number of work steps is required, that the limited resolution of the polymer mask used for the exposure of the photoresist does not allow for conductor track structures with widths < 25 µm, and that the electroplating process cannot be carried out on green, but only on sintered LTCC ceramic ribbons. • Laser ablation of sintered and unsintered (green) LTCC ceramic ribbons: A gold paste was screen-printed over the entire surface of the ceramic ribbon, which was then sintered. Lateral conductor track fine structures were carved out of the fully applied gold layer using a 3D picosecond UV laser system to remove all areas of the gold layer lying between the conductor track fine structures using laser ablation. Laser ablation does not require a physical mask; only a CAD mask (virtual mask) is loaded into the laser system and defines the areas to be ablated.Laser ablation was performed with a repetition frequency of 200 kHz, a laser power of 0.5 W for the sintered structures and 0.2 W for the unsintered structures, a cutting speed of 500 mm / s, and a contour spacing of the ablated lines on the surface of 3 µm for the sintered structures and 5 µm for the unsintered structures. Lateral structures with a width of 50 µm and a spacing of 40 µm were achieved. Although this process produces fine structures with the desired structural width, it has serious disadvantages: During laser ablation of the gold layer, the surface of the LTCC ribbon is also attacked due to the high laser power. The process is time-consuming and energy-intensive. Furthermore, it is associated with high material consumption, as the majority of the fully applied gold layer is removed during laser ablation. Recovery of the ablated material is not possible.

[0010] In addition, the previously described methods do not address the problem of misalignment between lateral conductor track fine structures and vertical microvias for through-contacts through the substrate that occurs in HDI structures (High Density Interconnect).

[0011] In the production of HDI structures, the lateral conductor fine structures are created using screen printing, for example, and the vias are created using punching. Production therefore takes place in separate process steps using different tools. The tools for screen printing and punching must be precisely aligned relative to each other. However, misalignment, which can amount to up to 30 µm, is unavoidable. Furthermore, the available punching technology only allows the production of microvias for vias with a minimum diameter of 75 µm. Smaller diameters are not achievable using punching. To achieve microvias with a smaller diameter, punching was switched to laser processing. The current state of the art enables the production of microvias with a diameter of 25 µm using a picosecond UV laser system [Gutzeit, N., Schulz, A., Fischer, M., Thelemann, T., Müller, J.: Picosecond Laser Structuring Technology for LTCC - the Improvement of Fine Line Structuring. In: 2. nd European Microelectronics and Packaging Conference & Exhibition (EMPC), Pisa, Italy, 2019]. However, the diameter of the microvias should correspond to the desired width of the conductor track fine structures (< 20 µm). This objective is not achieved in the state of the art, although several patents have been filed on the same topic.

[0012] For example, DE 10 2007 058 094 A1 describes the production of vias and trenches in ceramic substrates by laser processing. The invention uses a ceramic foil as a printing stencil to fill through-holes and perforated areas. An adhesive film is then used to remove the ceramic stencil, leaving the substrate with the conductive structures.

[0013] US 2004 / 0 056 345 A1 and DE 24 51 485 A1 describe two very similar processes for creating conductive connections using temporary masks on the top and bottom surfaces of a substrate. The masks can consist of a thin coating, a plastic film, or a dried liquid coating such as photoresist. The connections are created by laser or mechanical drilling or plasma etching. The conductive paths can be formed before or after the masks are produced. The connection areas are then filled using a screen printing process. Finally, the top and bottom masks are removed, leaving a substrate with filled conductive paths.

[0014] The focus of JP S54 79 473 A is the use of a Mylar carrier mask on an unsintered ceramic substrate. The mask is used to fill vertical and lateral structures in the substrate with conductive paste. A disadvantage is that the Mylar carrier mask can only be used for unsintered ceramic films and ceramic substrates (green films, green substrates).

[0015] DE 694 18 698 T2 describes a laser ablation process using an excimer laser to create patterns such as through holes and trenches, which are then filled in printed circuit boards using electroplating. Three approaches for applying the process are mentioned: (1) The first approach describes laser ablation of a dielectric substrate, first creating trenches and then holes. Then, a seed layer is deposited using a PVD process, followed by an electroplating process to fill the trenches and holes with conductive materials (Cu). The excess metallized area is then mechanically removed by grinding, polishing, or milling, followed by the lamination of two other dielectric substrates on either side of the substrate to create a multilayer printed circuit board (PCB). (2) The second approach describes the creation of trenches and holes using laser ablation through a stack of three laminated dielectric films, two of which (the upper and lower) are of the same type. The trenches are then created in the upper and lower dielectrics, while the holes are laser-cut through the middle dielectric film. A PVD process is used to create a seed layer for the electroplating to fill the trenches and holes with conductive material. (3) The third approach is similar to the second, except that the middle film is based on a photosensitive organic polymer that becomes electrically conductive when irradiated with laser light. Laser ablation then creates trenches in the top and bottom layers, as well as through-holes, making the middle film electrically conductive and facilitating the coating process. Object of the invention

[0016] The object of the invention is therefore to provide a method for structuring ceramic substrates that overcomes the aforementioned disadvantages of the prior art: The method should allow the production of lateral conductor track fine structures with a structure width of < 20 µm. Accordingly, it should allow the production of vias with a diameter of < 20 µm. The misalignment of the lateral conductor track fine structures relative to the vias should be reduced to zero. The method should be material-, time-, and energy-saving compared to the described prior art methods. In particular, the method should offer an alternative to laser ablation of fully applied metal layers. Solution to the task

[0017] The object of the invention is achieved by a 2-in-1 process according to claim 1. Advantageous embodiments of the 2-in-1 process are specified in claims 2 to 9. Furthermore, the object of the invention is achieved by a microelectronic circuit carrier according to claim 10.

[0018] The object of the invention is thus achieved by a ceramic-based microelectronic circuit carrier with vertical and lateral fine structures with a structure width of < 20 µm, as well as by a 2-in-1 process for producing such a circuit carrier. Starting from a mask-on-substrate unit, the 2-in-1 process allows offset-free contouring of the vertical and lateral fine structures in a single laser processing step (job). Contouring opens channel-like recesses for lateral conductor track fine structures and vertical vias (microvias). These recesses are then filled with conductive thick-film materials. The process saves material, time, and energy.

[0019] The 2-in-1 process thus allows the production of a microelectronic circuit carrier with HDI structures for miniaturized circuits, whereby two, vertical and lateral, structural elements, namely microvias and areas for lateral fine structures, are produced in a single job. Detailed description of the solution

[0020] The invention describes a novel 2-in-1 process for producing electrically conductive vias through a ceramic substrate suitable as a microelectronic circuit carrier and lateral conductor track fine structures on a surface of this ceramic substrate. The 2-in-1 process is suitable for both unsintered (so-called green) and sintered ceramic substrates. These can be either monolithic ceramic substrates or multilayer ceramic substrates. The ceramic substrates can comprise oxide, nitride, or oxynitride materials, e.g., unsintered (green) LTCC, sintered LTCC, Al2O3, AlN, AlN x O y . Other substrates, including non-ceramic ones, such as GaN, BeO, SiO2, Si coated with SiO2, SiC, and various glass substrates can also be used. This list is not exhaustive.

[0021] The invention enables the cost-effective and offset-free production of fine conductor track structures with minimum structure widths in the range of approximately 12 µm and vias whose minimum diameter is in the same range, i.e., approximately 12 µm. Therefore, in this application, microvias are always referred to. Larger dimensions are possible, but not advantageous for high-performance applications. Due to the thick-film processing, the surface roughness of the substrates is not critical. Vias with an aspect ratio AV in the range of 2.5 to 5 can be produced. The aspect ratio AV results from the length L of the via, here given by the substrate thickness, divided by the diameter d of the via: AV=L / d. The thickness of a commercially available unsintered LTCC substrate (DuPont Greentape 951) varies between 50.8 µm and 254 µm.Substrates with a thickness of 50.8 µm are preferred.

[0022] The inventive idea is to contour two structural elements in such substrates—namely, vertical microvias for vias and areas for lateral fine structures—in a single process. The process is therefore referred to as a 2-in-1 process. The 2-in-1 process comprises a single laser processing step. The vertical microvias also include angled microvias.

[0023] The 2-in-1 process begins with the application of a polymer layer to the ceramic substrate. A polymer film is manually applied to a surface of the ceramic substrate using a squeegee. The substrate is held in place on a vacuum table. This squeegeeing process is potentially automatable. Instead of a polymer film, a polymer layer in the form of a photoresist can also be applied to the surface of the ceramic substrate, provided it is a sintered ceramic substrate. The polymer layer thus forms a mask on the substrate, which is still unstructured.

[0024] The applied polymer layer adheres to the surface of the ceramic substrate by adhesion, thus forming a mechanically detachable bond to the surface. If the substrate is sintered and covered with a polymer layer in the form of a photoresist, this photoresist can also be chemically dissolved. A transparent polymer is preferably selected. A transparent polymer layer allows new structures created during subsequent laser processing (fine conductor track structures, microvias) to be precisely aligned with prefabricated structures already present in the substrate, e.g., in an LTCC substrate. If such prefabricated structures are not present in the substrate or if alignment is not required, the polymer layer can also be opaque.

[0025] In principle, any polymer can be used to produce the polymer layer (polymer layer) to be applied to the ceramic substrate. However, the material combination must be selected so that the adhesion force exerted by the polymer layer on the substrate is adapted to the stability of the substrate. The polymer is preferably selected from PVC and the polyimide and polyester groups, as these exhibit high strength and an adhesion force that depends on the polymer type and can therefore be adjusted. The following combinations are particularly preferred: Unsintered (green) LTCC substrate - Mylar film (polyester) Unsintered (green) LTCC substrate - Ultron sawing foil 1008R (PVC) Sintered LTCC substrate - Kapton® film (polyimide) AlzO3 substrate - Kapton® film (polyimide)

[0026] A person skilled in the art can easily identify other suitable combinations based on the material data sheets of commercially available polymer films. Due to their low stability, unsintered (green) substrates generally require a polymer film with low adhesion (adhesive strength) to prevent any substrate components from being torn off during subsequent removal of the polymer film, which occurs by peeling it off the surface. For sintered and solid substrates, which exhibit greater stability, a polymer film with high adhesion is permissible.

[0027] The polymer films used as the polymer layer can have a thickness between 20 µm and 100 µm, which gives them sufficient flexibility for application to the substrate surface by doctor blade at the beginning of processing and for subsequent removal by peeling off the substrate surface at the end of processing.

[0028] The structuring of the ceramic substrate with the applied polymer layer is performed by laser processing, which creates a structured mask on the substrate. Therefore, the assembly consisting of the ceramic substrate with the applied polymer layer is hereinafter referred to as a mask-on-substrate unit.

[0029] The mask-on-substrate unit is structured in a single laser processing step, also known as a job. The laser processing step (job) comprises two sub-steps (subjobs): a first sub-job for the formation of microvias and a second sub-job for the ablation of areas for lateral structures. No laser realignment occurs between sub-jobs. This eliminates any unwanted misalignment of the areas for lateral structures relative to the microvias.

[0030] The laser is preferably located in a high-quality filter chamber to eliminate particles released during laser processing. A pulsed laser is used as the laser, i.e. a picosecond or femtosecond laser (ps laser, fs laser), with the fs laser being preferred. The laser is located on an automatic xy translation platform or on an xyz translation platform, which allows the laser to be moved within a predetermined working area in a plane (x, y) or in space (x, y, z) with a resolution in the nm range. The pulsed laser is preferably a UV laser, e.g. an Nd:YAG laser with a wavelength of 355 nm. Since the structures to be produced have minimal dimensions on the order of 10 µm, this wavelength is sufficiently small. Lasers for the visible or IR range, e.g. B. with wavelengths of 532 nm or 1064 nm, can in principle also be used, preferably for structures with larger dimensions.

[0031] According to the invention, the laser is set up only once, before processing begins. This setup includes alignment with the mask-on-substrate unit to be processed and entering a work program into the laser's memory. The work program defines a job with two subjobs: The work program for the first subjob contains the laser specifications for producing the openings for the vias (microvias) of the mask-on-substrate assembly using laser drilling. The positions of the vias and the process parameters required for producing a microvia are entered: the laser power and the pulse processing duration for producing a via. Typically, the laser power in this subjob is 3 W to 5 W, depending on the substrate material.

[0032] The work program for the second subjob contains the laser specifications for producing the lateral conductor fine structures. The position and dimensions of the areas for the lateral conductor fine structures on the surface of the mask-on-substrate unit are entered, as well as the laser parameters for laser ablation of the areas for the lateral conductor fine structures defined by their position and dimensions. Furthermore, the laser parameters required to remove (ablate) the mask, i.e., the polymer layer, in these areas are specified, thus exposing the substrate surface in these areas. The laser power and the pulse processing duration per unit area required for ablation are specified. The laser power in this job is typically 0.5 W.

[0033] Once the laser is set up, laser processing is started and the two subjobs are executed. It is also possible to swap the order of the subjobs. It is also possible to switch between the two subjobs. This allows the microvias and the areas for the connected conductor structures to be processed without interruption.

[0034] The first subjob involves laser drilling microvias that taper across the thickness of the mask-on-substrate assembly. Typically, the diameter of the microvias on the processed surface is 12 µm and tapers to approximately 6 µm on the opposite (back) surface for a substrate approximately 50 µm thick. The microvias extend through the polymer layer, i.e., the mask, and through the substrate.

[0035] In the second subjob, the areas of the mask where fine conductor track structures are to be created on the substrate are removed by laser ablation, exposing the substrate surface in these areas. This creates recesses in the mask, which are then filled with a conductive paste in a subsequent step. The mask thus receives a negative image of the fine conductor track structures to be formed. It thus functions as a sacrificial mask.

[0036] As a result of the laser-performed job, channel-like recesses are opened for lateral conductor fine structures and vertical vias (microvias). Since the laser does not reposition between the two subjobs of the job, unwanted misalignment of the microvias relative to the areas for the lateral conductor fine structures is eliminated.

[0037] The 2-in-1 process according to the invention thus ensures offset-free contouring of the vertical and lateral fine structures in a single laser processing step.

[0038] After laser processing is complete, the microvias for the through-hole vias and the exposed areas for the lateral trace structures are filled with a conductive paste. This filling is done using a machine printing process (without a stencil or screen) or a manual printing process.

[0039] Conductive paste is a paste used to create electrically conductive connections. Thick-film conductive pastes containing conductive components such as Au, Pt, Ag, AgPd, Cu, and Ni can be used, although this list is not exhaustive. The microvias can also be filled with thermal paste to ensure thermal management of the ceramic circuit board.

[0040] The mask-on-substrate assembly is then subjected to an annealing process, during which the conductive paste is dried and cured. This annealing process typically takes place in a temperature range of 70°C to 90°C and lasts between 6 and 15 minutes. The lower the temperature, the longer the annealing process. A temperature of 80°C combined with a duration of 10 minutes is preferred. A person skilled in the art can easily determine suitable combinations of temperature and duration of the annealing process for different substrate materials using the material data sheets.

[0041] Finally, the mask, i.e., the polymer layer, is removed from the substrate. Removal can be performed manually by peeling the polymer layer, usually in the form of a polymer film, from (sintered or unsintered) substrates. However, the polymer layer can also be a photoresist, which is chemically removed from sintered substrates.

[0042] This completes the microelectronic circuit carrier. It comprises the substrate with conductive vias and standalone structures on one surface of the substrate. Advantages of the invention

[0043] Compared to the various processes known from the prior art, the 2-in-1 process according to the invention has the following advantages: • The vertical microvias for the vias and the areas for the lateral conductor track fine structures are manufactured in a single laser processing process (job), comprising two subjobs, using the same laser. The laser is set up before the laser processing process. The laser is not set up again during the laser processing process. This eliminates any unwanted misalignment of the microvias relative to the areas for the lateral conductor track fine structures. An offset of zero is achieved. In contrast, in state-of-the-art processes, the combination of different processing processes (screen printing, punching) and the associated use of different tools results in an offset of typically up to 30 µm, which can render the circuit carriers produced in this way unusable. • The number of production steps is reduced. • The use of rigid masks (mesh and stencil screens) is avoided. This eliminates the high time and cost involved in producing these masks. • Laser ablation of the mask (polymer layer) occurs at low laser power. Only small areas (the areas for the lateral conductor track fine structures) are ablated. This process is therefore fast and cost-effective. In contrast, state-of-the-art methods apply a metal layer over the entire surface of the substrate and then ablate it over a large area in a subtractive process until only the desired conductor track fine structures remain. This process occurs at high laser power. It is energy-intensive, time-consuming, and associated with high material consumption (metal), making it expensive. • The 2-in-1 process saves material because the conductive paste is applied in an additive process only in the areas of the substrate exposed by laser ablation and introduced into the microvias. • Using a transparent mask allows for precise optical alignment of the new structures to other prefabricated structures already present in the substrate. Optical alignment is performed at the beginning of laser processing. Short description of the drawings Fig. 1 shows a cross-sectional view of a ceramic substrate. Fig. 2 shows the application of a polymer film to the ceramic substrate. Fig. 3 shows a sectional view of a mask-on-substrate unit consisting of a ceramic substrate and an applied polymer layer forming a still unstructured mask. Fig. Figure 4 shows a cross-sectional view of the mask-on-substrate unit of the Fig. 3, comprising through-contacts (microvias) produced by laser processing. Fig. Figure 5 shows a cross-sectional view of the mask-on-substrate unit of the Fig. 4, additionally comprising regions for lateral conductor track fine structures in which the mask was removed by laser ablation. The regions for conductor track fine structures extend perpendicular to the plane of the drawing. Fig. Figure 6 shows a cross-sectional view of the mask-on-substrate unit of the Fig. 5, in which the microvias and the areas for the lateral conductor track fine structures are filled with a conductive paste. Fig. Figure 7 shows a cross-sectional view of the finished microelectronic circuit carrier after the mask has been removed. Fig. Figure 8 shows a photographic representation of a circuit carrier produced according to the invention with conductor track fine structures on its surface, corresponding to a plan view of the sectional representation in Fig. 7.

[0044] In Fig. 5, the areas for lateral conductor track fine structures 16 are shown in a broader manner for technical reasons in order to distinguish them from the microvias 14. The same applies to the filled structures (lateral conductor track fine structures 26 and vias 24) in Fig. 6 and Fig. 7. In practical applications, the diameter of the microvias 14 and the width of the lateral conductor track fine structures 26 can be the same or different.

[0045] The invention is explained below using the drawings in an embodiment. Example

[0046] An unsintered LTCC substrate 10 (DuPont Greentape 951) with a thickness of 50.8 µm is provided ( Fig. 1).

[0047] A polymer film 11 (Ultron saw film 1008R) is applied to the substrate surface by doctor blade ( Fig. 2).

[0048] As a result of adhesion forces, the polymer film 11 bonds reversibly with the substrate surface and forms a still unstructured mask on the substrate 10. This creates a mask-on-substrate unit ( Fig. 3).

[0049] The mask-on-substrate assembly is then structured in a single laser processing step (job) using an Nd:YAG laser from 3D Micromac, Chemnitz, Germany (picosecond laser, wavelength 355 nm), forming a now structured mask 12. Laser source: Lumentum PicoBlade, parameters: Maximum UV laser power: 14 W, cutting speed (mark speed): 500 mm / s, pulse duration < 10 ps, ​​pulse repetition rate: 200 kHz at 355 nm laser wavelength, laser focus diameter: 7 µm at 355 nm laser wavelength.

[0050] The job is loaded into the laser's memory. It includes two subjobs, a first subjob for the formation of microvias 14 ( Fig. 4) and a second subjob for the ablation of mask areas for lateral structures 16 ( Fig. 5). The subjobs are run with different laser powers, but no laser realignment is performed between the subjobs. The first subjob (drilling microvias 14 through the mask 12 and the substrate 10) is performed with an average laser power of 3 W, while the second subjob (ablation of mask areas for lateral structures 16) is performed with an average laser power of 0.5 W. The resulting microvias 14 have a diameter of 12.5 µm at the processed surface and taper, as shown in Fig. 4 and Fig. 5, toward the opposite surface. The resulting areas for lateral structures 16, which form recesses in the mask 12, have a width of 12.5 µm.

[0051] In the following process step, the microvias 14 for the through-hole platings and the exposed areas for the lateral conductor track fine structures 16 are filled with a Pt thick-film conductive paste (10001 / 145B H from Heraeus) by a machine printing process (without stencil or screen) or a manual printing process.

[0052] In the subsequent process step, the mask-on-substrate unit undergoes an annealing process, during which the Pt conductive paste is dried and cured. This annealing process takes place at a temperature of 80°C and lasts for 10 minutes. As a result of this annealing process, the desired electrically conductive vias 24 through the substrate 10 and the fine conductor track structures 26 made of platinum (Pt) are formed on the substrate surface ( Fig. 6).

[0053] In a final process step, the mask 12 is then manually removed from the mask-on-substrate assembly. Since the fine conductor track structures 26 have also been mechanically stabilized by the annealing process, they are not damaged when the mask 12 is removed, i.e., they are not torn from the substrate surface. After the mask is removed, the finished ceramic circuit carrier remains with the now exposed substrate surface 18, the vias 24, and the fine conductor track structures 26 (standalone structures) positioned without offset relative to the substrate surface. Fig. 7 shows a schematic sectional view of the finished ceramic circuit carrier. Fig. Figure 8 shows a concrete experimental result, namely a photographic representation of the processed substrate surface 18 of a circuit carrier produced according to this embodiment. Standalone conductor track fine structures 14 made of platinum with a width of 12.6 µm ± 0.2 µm are located on the surface 18. Fig. The single measured value reported in Figure 8 was 12.59 µm. Compared to the state of the art, the feature width is thus almost halved from 25 µm to 12.6 µm, opening up new high-performance microelectronic applications for ceramic substrates. A minimum spacing of approximately 90 µm between adjacent conductor structures was chosen, which can be further reduced. List of reference symbols 10 Substrate, ceramic substrate 11 Polymer film 12 Mask 14 microvias 16 ablated mask areas in the form of recesses for lateral conductor track fine structures 18 processed substrate surface 24 vias 26 lateral conductor track fine structures

Claims

[1] 2-in-1 process for producing a microelectronic circuit carrier with HDI structures for miniaturized circuits, wherein two, vertical and lateral, structural elements, namely microvias and areas for lateral conductor track fine structures, are produced in a single job, comprising the following steps: a) providing a substrate (10) and a polymer film (11), b) applying the polymer film (11) to a surface of the substrate (10) so that a mask-on-substrate unit consisting of the substrate (10) and the polymer film (11) is formed, wherein the polymer film (11) forms a detachable connection with the substrate (10) and forms a still unstructured mask on the substrate (10), c) Setting up a laser that can be moved on a moving platform for laser processing of the mask-on-substrate unit, whereby a job comprising two subjobs is programmed: c1) Input for subjob 1: Parameters for laser drilling of microvias (14) for vias through the mask-on-substrate unit, c2) Input for subjob 2: Parameters for laser ablation of defined areas (16) of the mask (12) for the subsequent application of lateral conductor fine structures, d) Execution of the job by the laser, whereby the microvias (14) are drilled through the mask (12) and the substrate (10) and the areas (16) of the mask (12) are removed, so that the substrate surface in these areas (16) is exposed for the subsequent application of lateral conductor fine structures, e) filling the exposed areas (16) and the microvias (14) with a conductive paste so that fine conductor track structures (26) and vias (24) are formed through the substrate (10), f) drying and curing the conductive paste by subjecting the mask-on-substrate unit to an annealing process, g) mechanically or chemically removing the mask (12) so that the surface (18) of the substrate (10) and the applied lateral conductor track fine structures (26) are exposed, whereby the microelectronic circuit carrier is completed. [2] 2-in-1 process according to claim 1, characterized by that the substrate (10) is a ceramic substrate selected from a list comprising unsintered LTCC, sintered LTCC, Al2O3, AlN, AlN x O y and GaN substrates, a glass substrate, a SiO2 substrate or a Si substrate coated with SiO2. [3] 2-in-1 process according to claim 1, characterized by that the polymer of the polymer film (11) is selected from a list comprising PVC, polyimides, polyesters, photoresists. [4] 2-in-1 process according to claim 1, characterized by that the polymer film (11) is transparent or opaque. [5] 2-in-1 process according to claim 1, characterized bythat the width of the conductor track fine structures (26) and the diameter of the vias (24) are less than 20 µm. [6] 2-in-1 process according to claim 1, characterized by that the filling of the microvias (14) and the exposed areas (16) with the conductive paste in step e) is carried out by means of a mechanical or a manual thick-film printing process. [7] 2-in-1 process according to claim 1, characterized by that the removal of the mask (12) in step g) is carried out manually or chemically. [8] 2-in-1 process according to claim 1, characterized by that the laser is a ps or fs laser. [9] 2-in-1 process according to claim 1, characterized by that the laser is a UV laser. [10] Microelectronic circuit carrier based on a substrate (10) with vias (24) and lateral conductor track fine structures (26) on a surface (18), produced using a 2-in-1 process according to one of claims 1 to 9 and with dimensions of the conductor track fine structures and the vias according to claim 5.

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