Substrate and method for producing substrate

Abstract

To provide a method for producing a substrate that forms a green sheet stack having smaller sintering shrinkage while ensuring reliable operation of components, and to provide a substrate produced by the method.SOLUTION: A substrate (20) includes a sintered ceramic base body (21) having a first volume region (4) and a second volume region (5), each containing a ceramic material, wherein: the first volume region (4) contains fewer secondary phases than the second volume region (5); the first volume region (4) and the second volume region (5) of the ceramic base body (21) form a layered structure, and a layer at an end of the layered structure is formed of the first volume region (4). The main components of the ceramic materials for the first and second volume regions are selected from the group consisting of AlN, Al2O3, Si3 N4, BN, SiC, BeO, and zirconia-toughened alumina (ZTA).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a substrate including a ceramic substrate, and to a substrate manufactured by the method. [Background technology]

[0002] Substrates are widely used components in industrial manufacturing for placing and contacting microelectronic components such as integrated circuits and power semiconductors such as LEDs, which are then easily integrated into other electronic components or circuits.

[0003] Due to the ever-increasing demand for miniaturization and performance of electronic components, it is necessary to increase the number of microelectronic components and power semiconductors that can be mounted on a given area of ​​a substrate. This results in increasing demands on the substrate. To meet these demands, multilayer substrates, including ceramic substrates with a multilayer structure, have traditionally been used. These multilayer substrates allow, for example, the integration of rewiring within the ceramic substrate.

[0004] Due to the ever-increasing demand for multilayer substrates, there is a corresponding increase in the demands on the methods for manufacturing such multilayer substrates.

[0005] The manufacturing method of a ceramic multilayer substrate typically involves laminating multiple green sheets to form a green sheet stack, which is then pressed and decarburized. Subsequent sintering of the pressed and decarburized green sheet stack produces the ceramic substrate of the multilayer substrate.

[0006] To meet the ever-increasing demands on these processes, it is particularly important to consider the sintering shrinkage that occurs during sintering of the green sheet stack. For example, large sintering shrinkage can generate stresses within the ceramic substrate that can lead to crack formation within the ceramic substrate. Furthermore, sintering shrinkage must also be considered when designing integrated redistribution, because failure to consider sintering shrinkage can result in partially unusable integrated redistribution within the ceramic substrate. Sintering shrinkage can occur in all three spatial directions for ceramic substrates.

[0007] A spatial direction is understood here and below to be a direction defined by the three axes of a Cartesian coordinate system, which, according to common convention, includes an x-axis, a y-axis and a z-axis, each of which defines a spatial direction.

[0008] Furthermore, sintering shrinkage is understood here and below to be the difference in edge length of one or more edges of a green sheet or pressed green sheet stack, respectively, before and after sintering, in other words, at least one edge of the green sheet or green sheet stack is longer before sintering than after sintering.

[0009] To determine sintering shrinkage, the edge length is measured before and after sintering, and the percentage deviation is calculated relative to the edge length before sintering. For example, the edge length may be 20 mm before sintering and 18 mm after sintering. A difference of 2 mm results in a sintering shrinkage of 10%. A large sintering shrinkage is considered here and hereinafter to be a value greater than 17%. In other words, a sintering shrinkage of 17% or less is considered here and hereinafter to be a small sintering shrinkage.

[0010] It should be noted that sintering shrinkage does not necessarily occur equally in all three spatial directions, so for example the sintering shrinkage of an edge extending in one spatial direction may be different from the sintering shrinkage of another edge extending in one of the other two spatial directions.

[0011] The greater the sintering shrinkage, the greater the risk of stresses occurring in the sintered greensheet stack that can lead to crack formation in the ceramic substrate. Furthermore, the integrated rewiring may become at least partially unusable after sintering because it is deformed or completely torn apart by the shrinkage of the greensheet stack that causes sintering shrinkage.

[0012] To reduce the number of unusable integrated rewirings, green sheets containing a ceramic material as a main component and additionally containing a sintering aid have been conventionally used to form ceramic substrates with integrated rewirings. Furthermore, a metal paste containing a predetermined proportion of ceramic material and sintering aid is used to apply the integrated rewirings. This allows the integrated rewirings to exhibit thermal length change behavior that is at least approximately the same as that of a green sheet stack. This reduces the percentage of unusable integrated rewirings in the ceramic substrate.

[0013] Nevertheless, large sintering shrinkage occurs in the green sheet stacks so produced, which in turn presents a significant risk for unusable integrated rewiring and crack development within the ceramic substrate.

[0014] In addition to sintering shrinkage, the composition of the ceramic substrate must also be considered. For example, sintering aids that accumulate on the surface of the ceramic substrate upon sintering can result in components containing such ceramic substrates no longer functioning reliably.

[0015] Thus, from Patent Document 1, a method is known in which sintering aids accumulated on the surface of a ceramic substrate by sintering are completely or partially removed by machining or etching, thereby enabling components including a ceramic substrate produced by the above-mentioned method to function reliably.

[0016] However, the method described in Patent Document 1 requires additional processing steps after sintering, making the production of the ceramic substrate more laborious and cost-intensive. Furthermore, subsequent processing of the ceramic substrate always carries the risk that the ceramic substrate will be damaged by the subsequent processing and therefore become unusable. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] European Patent Application Publication No. 3375767 Summary of the Invention [Problem to be solved by the invention]

[0018] It is therefore an object of the present invention to provide a method for manufacturing a substrate that ensures reliable operation of a component that includes the substrate, the method including the formation of a green sheet stack that generates less sintering shrinkage, and a substrate manufactured by the method. [Means for solving the problem]

[0019] This problem is solved by a method according to claim 1. Further embodiments of the method and substrates produced by the method can be seen from the further claims.

[0020] A method for manufacturing a substrate is provided in which a green sheet stack is formed including a first green sheet and a second green sheet, each containing a ceramic material as a main component, the second green sheet additionally containing a sintering aid, where the second green sheet experiences a larger sintering shrinkage than the first green sheet.

[0021] A further object of the present invention is to provide a substrate produced by the method, the substrate comprising a ceramic body having a first volumetric region and a second volumetric region each containing a ceramic material, the first volumetric region containing a sintering aid at a lower concentration than the second volumetric region.

[0022] The ceramic substrate is manufactured by sintering a stack of green sheets formed by the method described above.

[0023] The volumetric regions having different concentrations of sintering aid are created by laminating a second green sheet containing the sintering aid and a first green sheet without the sintering aid in a substrate manufacturing method. During sintering, the sintering aid partially diffuses from the second green sheet to the first green sheet. As a result, the volumetric region of the ceramic substrate originally formed by the first green sheet also contains a certain amount of sintering aid, although at a lower concentration than the volumetric region originally formed by the second green sheet.

[0024] The method can include forming a greensheet stack such that end layers of the greensheet stack each comprise at least one first greensheet.

[0025] Here and hereafter, the green sheets in a green sheet stack that are farthest away from an imaginary midplane are referred to as end layers. The imaginary midplane extends parallel to the green sheets and through the center of the green sheet stack. Typically, a green sheet stack has two end layers, with the imaginary midplane dividing the green sheet stack into two imaginary halves, and each end layer is located in one of the two imaginary halves. Each end layer can contain one or more green sheets.

[0026] The method can further include forming a greensheet stack having one or more greensheets formed between two second greensheets, and in particular, the first and second greensheets of the greensheet stack can have an alternating stacking order.

[0027] By forming a green sheet stack using first and second green sheets, sintering shrinkage can be significantly reduced. The inventors hypothesize that this effect is due to the fact that the first green sheet, which experiences smaller sintering shrinkage than the second green sheet, exerts a counterforce on the second green sheet. This counterforce counteracts the force that causes the second green sheet to experience larger sintering shrinkage. As a result, the sintering shrinkage of the entire green sheet stack does not occur to the extent that it would if the first green sheet were not present. By changing the stacking order of the first and second green sheets, the sintering shrinkage can be adjusted arbitrarily within a certain range.

[0028] Furthermore, the method can be carried out so that the sintered green sheet stack has a sintering shrinkage of less than 16% in each spatial direction in at least two of three spatial directions. Advantageously, the method can be carried out so that the sintered green sheet stack has a sintering shrinkage of less than 14% in each spatial direction in at least two of three spatial directions. This sintering shrinkage is significantly less than that achieved by conventional methods. Such low sintering shrinkage is achieved by forming a green sheet stack having two end layers, each including at least one first green sheet. Advantageously, the green sheet stack has two end layers, each including at least two first green sheets.

[0029] Furthermore, in this method, the ceramic material for the main component of the first and second green sheets can be selected from the group including AlN, Al2O3, Si3N4, BN, SiC, BeO, and zirconia-toughened alumina (ZTA). Advantageously, AlN can be used as the main component because it has very good thermal conductivity. This allows for the integration of power lines, particularly to power semiconductors, into the substrate. This allows for a more compact design of the substrate, thereby meeting the demand for further miniaturization of such components.

[0030] Furthermore, in the method, the ratio a of the sintering aid contained in the second green sheet relative to 100 wt % of the ceramic material may be selected as follows: 2wt%≦a≦10wt%

[0031] Furthermore, for the method, a sintering aid can be selected from the group comprising metal oxides and metal halides, in particular, the sintering aid can be selected from the group comprising Y2O3, CaO, CaF2, YF3 and rare earth oxides.

[0032] Furthermore, in this method, sintering of the green sheet stack can be carried out at a temperature selected from the range of 1600°C to 2000°C. Preferably, sintering can be carried out at a temperature selected from the range of 1800°C to 1850°C. Particularly advantageously, sintering can be carried out at a temperature selected from the range of 1810°C to 1840°C.

[0033] Furthermore, in this method, the green sheet stack can be sintered for a holding time selected from the range of 2 hours to 10 hours, preferably from the range of 4 hours to 6 hours. Particularly advantageously, sintering can be carried out for a holding time of 4 hours.

[0034] When the green sheet stack is sintered at a temperature and hold time within a specific range, the green sheet stack can be sintered to a desired high density without significant sintering shrinkage.

[0035] Furthermore, sintering of the green sheet stack can be carried out in a reducing atmosphere, which has an oxygen concentration so low that oxidation of the substrate components, including any integrated rewiring, during sintering is not possible. For example, a reducing atmosphere may contain a mixture of primarily N2 / H2, where the mixing ratio of the two gases is not limited to a specific value.

[0036] Sintering can also be carried out under atmospheric pressure or reduced pressure. Reduced pressure is understood to be a pressure lower than atmospheric pressure. Furthermore, sintering can also be carried out in vacuum or high vacuum. High vacuum is defined as 10 -3 ~10 -7 It should be understood that the vacuum has a residual pressure of 1000 psi.

[0037] Referring to the above-mentioned embodiment, the method may include the following steps: - providing a ceramic material; - providing a sintering aid; - producing a first green sheet containing said ceramic material; - preparing a second green sheet containing the ceramic material and the sintering aid; - applying a redistribution layer on the first green sheet and the second green sheet; - stacking the first and second green sheets to form a green sheet stack; - pressing said green sheet stack to obtain a pressed green sheet stack; - decarburizing the pressed green sheet stack to obtain a pressed decarburized green sheet stack; - sintering the pressed and decarburized green sheet stack to obtain a ceramic substrate for a substrate.

[0038] The first and second volume regions of the ceramic substrate can form a layered structure resulting from the stacking sequence of the original first and second green sheets.

[0039] Furthermore, the ceramic substrate may have a thickness ranging from 300 μm to 400 μm. Advantageously, the ceramic substrate has a thickness of 360 μm.

[0040] When the ceramic substrate has a thickness within the aforementioned range, the ceramic substrate has a flexural strength of at least 450 MPa. Advantageously, the ceramic substrate can have a flexural strength of at least 500 MPa. The flexural strength can be determined using a conventional three-point method. A flexural strength of at least 450 MPa is within the range of flexural strengths of typical high-strength substrates manufactured by conventional methods. This allows the substrate to have high robustness in addition to low sintering shrinkage.

[0041] Additionally, the ceramic substrate may have integrated rewiring and / or vias. The vias allow components to be mounted on both sides of the substrate. Furthermore, the integrated rewiring allows the substrate to mount a larger number of components on a given area of ​​the substrate, thereby allowing components, including the substrate with the components, to be more compact and / or have higher performance. Contact surfaces are disposed on the outer surface of the ceramic substrate for assembling components. The contact surfaces are conductively connected to the integrated rewiring and / or vias.

[0042] Furthermore, the redistribution lines can be formed from a material containing tungsten. The use of tungsten as a component for the integrated redistribution lines is advantageous because it does not become liquid and / or evaporate at the sintering temperatures mentioned above. Therefore, sintering does not significantly alter the integrated redistribution lines, thereby reducing the risk of unusable integrated redistribution lines.

[0043] In the following, the manufacturing method of the substrate is explained in detail based on a pressed green sheet stack, possible stacking sequences of the first and second green sheets in the green sheet stack, and a schematic diagram of the substrate. Furthermore, a scanning electron micrograph (SEM) of the cross section of the ceramic substrate is shown. [Brief explanation of the drawings]

[0044] [Figure 1] Shows the pressed green sheet stack. [Figure 2] The first stacking sequence of the greensheet stack is shown in cross section. [Figure 3] The second stacking sequence of the greensheet stack is shown in cross section. [Figure 4] The third stacking sequence of the greensheet stack is shown in cross section. [Figure 5] The substrate is shown in cross section. [Figure 6] 1 shows an SEM photograph of a portion of a cross section of a ceramic substrate. DETAILED DESCRIPTION OF THE INVENTION

[0045] Identical, similar or obviously identical elements are provided with the same reference numerals in the figures.The figures and the size ratios therein are not to scale.

[0046] FIG. 1 illustrates a pressed green sheet stack 10. The pressed green sheet stack 10 includes first and second green sheets (not shown). The spatial extent of the pressed green sheet stack 10 is indicated by the dimension arrows x, y, and z. Because the dimension arrows x, y, and z each extend parallel to the axes of the same name in a Cartesian coordinate system, the dimension arrows are also referred to herein and hereinafter as the corresponding axes of the coordinate system. In other words, the dimension arrows x, y, and z correspond to the x-axis, y-axis, and z-axis, respectively, in the Cartesian coordinate system. Because the following figures illustrate possible stacking sequences of the first and second green sheets (not shown) of the pressed green sheet stack 10, the axis names are used in the following figures in the same manner for all stacking sequences.

[0047] 2 shows, in cross section, a first stacking sequence of first green sheets 1 and second green sheets 2 to form a pressed green sheet stack 10 having a total of 14 green sheets. The pressed green sheet stack 10 has two end layers 3, each containing one first green sheet 1. All other layers of the pressed green sheet stack 10 consist of second green sheets 2. The cross section extends in a plane through the pressed green sheet stack 10, which plane extends parallel to the plane spanned by the x-axis and z-axis.

[0048] The first green sheet 1 includes a ceramic material containing AlN as a primary component. The second green sheet 2 includes a ceramic material containing AlN as a primary component and, relative to 100 wt% AlN, additionally containing 3.4 wt% Y2O3 as a sintering aid. The first green sheet 1 and the second green sheet 2 are laminated to form a green sheet stack (not shown). This is pressed to obtain a pressed green sheet stack 10. Subsequently, to obtain a first ceramic substrate (not shown) based on the pressed green sheet stack 10 having a first stacking sequence, the pressed green sheet stack 10 is first decarburized in air at 600°C and then sintered at 1810°C for 4 hours in an atmosphere containing mainly N2 / H2 at atmospheric pressure.

[0049] The first ceramic substrate (not shown) has a thickness of approximately 360 μm. Additionally, the first ceramic substrate exhibits a shrinkage of 15.9% along its x-axis and 15.8% along its y-axis relative to the pressed green sheet stack 10. This sintering shrinkage is significantly less than that experienced by conventional methods for producing comparable ceramic substrates.

[0050] Furthermore, the first ceramic substrate (not shown) has a flexural strength of 495 MPa, which is significantly higher than that achieved for ceramic substrates of similar thickness produced by conventional methods.

[0051] 3 illustrates, in cross section, a second stacking sequence of first green sheets 1 and second green sheets 2 to form a pressed green sheet stack 10 having a total of 14 green sheets. The cross section extends in a plane through the pressed green sheet stack 10, which plane extends parallel to the plane spanned by the x-axis and z-axis. According to the second stacking sequence, the pressed green sheet stack 10 includes end layers 3 each consisting of two first green sheets 1. Furthermore, all other layers of the pressed green sheet stack 10 are composed of second green sheets 2.

[0052] The compositions of the first green sheet 1 and the second green sheet 2 are the same as those of the first green sheet 1 and the second green sheet 2 described in the description of Figure 2. A method for manufacturing a second ceramic substrate (not shown) based on the green sheet stack 10 having the second stacking sequence is similar to the method described in the description of Figure 2.

[0053] The second ceramic substrate (not shown) has a thickness of about 360 μm. The second ceramic substrate (not shown) exhibits a sintering shrinkage of 13.7% along its x-axis and 13.8% along its y-axis for the pressed green sheet stack 10 having the second stacking sequence. This indicates that the construction of the end layer 3 using two first green sheets 1 results in a further reduction in sintering shrinkage.

[0054] Furthermore, the second ceramic substrate (not shown) has a flexural fracture strength of 516 MPa, which is also higher than the value obtained for the first ceramic substrate (not shown), as can be seen from the description of Figure 2. This high value of flexural fracture stress allows the highest demands on the robustness of the ceramic substrate to be met.

[0055] FIG. 4 shows, in cross section, a third stacking sequence of first green sheets 1 and second green sheets 2 to form a pressed green sheet stack 10 having a total of 14 green sheets. The cross section extends in a plane passing through the green sheet stack 10, which plane extends parallel to the plane subtended by the x-axis and z-axis. According to the third stacking sequence, the pressed green sheet stack 10 includes two end layers 3, each consisting of one first green sheet 1. Furthermore, the green sheet stack 10 having the third stacking sequence includes a first green sheet 1 formed between two second green sheets 2. Three second green sheets 2 are stacked one above the other between the first green sheet 1 forming the end layer 3 and the first green sheet 1 formed between the two second green sheets 2. Furthermore, the first green sheets 1 formed between the two second green sheets 2 are separated from each other by four second green sheets 2 stacked one above the other. Such a stacking sequence makes it possible to precisely influence the sintering shrinkage.

[0056] The compositions of the first green sheet 1 and the second green sheet 2 are the same as those of the first green sheet 1 and the second green sheet 2 described in the description of Figure 2. A method for manufacturing a third ceramic substrate (not shown) based on the green sheet stack 10 having the third stacking sequence is similar to the method described in the description of Figure 2.

[0057] FIG. 5 shows a cross-section of a substrate 20 including a ceramic substrate 21. The ceramic substrate 21 is based on a green sheet stack having a second stacking sequence. The compositions of the first and second green sheets are the same as those described in the description of FIG. 2. The sintering temperature and holding time are also the same as those described in the description of FIG. 2.

[0058] The ceramic substrate 21 has a first volume region 4 and a second volume region 5. The first volume region 4 has a lower sintering aid concentration than the second volume region 5. The substrate further includes integrated rewiring 6 and vias 7. The vias 7 allow the substrate to mount components on both sides via contact surfaces 8. Furthermore, the integrated rewiring 6 allows more components to be mounted on a given area of ​​the substrate 20 via contact surfaces 8 than would be possible without the integrated rewiring 6, thereby enabling further miniaturization.

[0059] FIG. 6 shows an SEM image of a portion of a cross section of a ceramic substrate 21 based on a green sheet stack having a second stacking sequence. Bright spots in the SEM image indicate secondary phases produced by sintering aids. It can be clearly seen that the second volume region 5, originally formed by the second green sheets, contains more secondary phases than the first volume region 4, originally formed by the first green sheets. The fact that the first volume region 4 is not completely free of secondary phases is due to the diffusion of sintering aids from the second green sheets to the first green sheets caused by sintering.

[0060] Nevertheless, the first volume region 4 has significantly less secondary phases. These secondary phases preferentially crystallize on the surfaces, significantly increasing the roughness of these surfaces. By using edge layers made from the first green sheet, the surface roughness can be significantly reduced.

[0061] The present invention is not limited to the illustrated embodiment, in particular the total number of green sheets in the green sheet stack and the stacking order of the first and second green sheets may be different. [Explanation of symbols]

[0062] 1. First Green Sheet 2. Second Green Sheet 3 Edge layer 4 First volume region 5 Second volume region 6 Integrated Rewiring 7 Via 8 Contact surface 10 Green Sheet Stacks 20 Substrate 21 Ceramic substrate

Claims

1. A substrate (20) comprising a sintered ceramic body (21) having a first volume region (4) and a second volume region (5), each containing a ceramic material, the first volume region (4) contains less secondary phase than the second volume region (5); The first volume region (4) and the second volume region (5) of the ceramic substrate (21) form a layer structure, and an end layer of the layer structure is formed from the first volume region (4); The main components of the ceramic material for the first and second volume regions are AlN, Al ２ O ３ , Si ３ N ４ , BN, SiC, BeO, Zirconia Toughened Alumina (ZTA).

2. The secondary phase is Y ２ O ３ , CaO, CaF ２ , Y.F. ３ and rare earth oxides.

3. A substrate (20) comprising a sintered ceramic body (21) having a first volume region (4) and a second volume region (5), each containing a ceramic material, the first volume region (4) contains less secondary phase than the second volume region (5); The first volume region (4) and the second volume region (5) of the ceramic substrate (21) form a layer structure, and an end layer of the layer structure is formed from the first volume region (4); The secondary phase is Y ２ O ３ , CaO, CaF ２ , Y.F. ３ and a sintering aid selected from the group including rare earth oxides.

4. The main components of the ceramic material for the first and second volume regions are AlN, Al ２ O ３ , Si ３ N ４ 4. The substrate of claim 3, wherein the substrate is selected from the group consisting of: BN, SiC, BeO, zirconia toughened alumina (ZTA).

5. The main component of the ceramic material for the first and second volume regions is Al ２ O ３ , BeO or zirconia toughened alumina (ZTA).

6. A substrate (20) comprising a sintered ceramic body (21) having a first volume region (4) and a second volume region (5), each containing a ceramic material, the first volume region (4) contains less secondary phase than the second volume region (5); The first volume region (4) and the second volume region (5) of the ceramic substrate (21) form a layer structure, and an end layer of the layer structure is formed from the first volume region (4); The ceramic substrate (21) is a substrate with integrated rewiring (6).

7. A substrate as described in claim 1, 3 or 6, wherein the secondary phase originates from a sintering aid contained in the second green sheet, the second volume region is formed from the second green sheet after a sintering step, and the ratio of the sintering aid in the second green sheet is 2 wt% to 10 wt%.

8. The substrate according to claim 7, wherein the proportion of the sintering aid is 2 wt% to 3.4 wt%.

9. The sintering aid is CaO, CaF ２ , Y.F. ３ 8. The substrate of claim 7, wherein the metal is selected from the group consisting of rare earth oxides and rare earth oxides.

10. A substrate (20) comprising a sintered ceramic body (21) having a first volume region (4) and a second volume region (5), each containing a ceramic material, the first volume region (4) contains less secondary phase than the second volume region (5); The first volume region (4) and the second volume region (5) of the ceramic substrate (21) form a layer structure, and an end layer of the layer structure is formed from the first volume region (4); The ceramic material is mainly composed of AlN, The secondary phase is composed of Y as a sintering aid. ２ O ３ and the ratio of the sintering aid to 100 wt % of the main component is 3.4 wt %.

11. The substrate of claim 1, 3, 6 or 10, wherein the ceramic substrate (21) has a thickness in the range of 300 μm to 400 μm and a flexural strength at break of at least 450 MPa.

12. 11. The substrate according to claim 1, 3, 6 or 10, wherein the ceramic substrate (21) comprises contact surfaces (8) for mounting components on the substrate, and / or integrated rewirings (6) and / or vias (7).

13. 13. The substrate according to claim 6 or 12, wherein the integrated redistribution line (6) is made from a material containing tungsten.

14. A method for manufacturing a substrate in which a green sheet stack (10) is formed, the green sheet stack (10) including a first green sheet (1) and a second green sheet (2), each containing a ceramic material as a main component, the method comprising: The method wherein the second green sheet (2) further comprises a sintering aid in addition to the ceramic material, and the green sheet stack (10) is sintered in a reducing atmosphere.

15. The reducing atmosphere is N ２ / H ２ 15. The method of claim 14, comprising a mixture consisting of:

16. A method for manufacturing a substrate in which a green sheet stack (10) is formed, the green sheet stack (10) including a first green sheet (1) and a second green sheet (2), each containing a ceramic material as a main component, the method comprising: The method wherein the second green sheet (2) further comprises a sintering aid in addition to the ceramic material, and the green sheet stack (10) is sintered under reduced pressure.

17. 17. The method of claim 16, wherein sintering is performed in a high vacuum.

18. 17. The method according to claim 14 or 16, wherein the first green sheet (1) does not contain sintering aids.

19. 17. The method according to claim 14 or 16, wherein the greensheet stack (10) is formed such that end layers (3) of the greensheet stack (10) each consist of at least one first greensheet (1).

20. 20. The method of claim 19, wherein the greensheet stack (10) comprises integrated rewiring (6).

21. 17. The method of claim 14 or 16, wherein the greensheet stack (10) is formed to have one or more first greensheets (1) disposed between two second greensheets (2).

22. 22. The method of claim 21, wherein the greensheet stack (10) is formed having an alternating stacking sequence of first and second greensheets (1, 2).

23. 17. The method according to claim 14 or 16, wherein two end layers (3) are formed in the greensheet stack (10), each including at least one first greensheet (1), and the greensheet stack (10) exhibits, after sintering, a sintering shrinkage per spatial direction of less than 16% in at least two of three spatial directions.

24. The main components of the ceramic material for the first and second green sheets are AlN, Al ２ O ３ , Si ３ N ４ 17. The method according to claim 14 or 16, wherein the material is selected from the group comprising: BN, SiC, BeO, ZTA.

25. 17. The method according to claim 14 or 16, wherein the proportion a of the sintering aid contained in the second green sheet (2) is selected relative to 100 wt % of the ceramic material as follows: 2wt%≦a≦10wt%

26. 17. The method of claim 14 or 16, wherein the sintering aid is selected from the group comprising metal oxides and metal halides.

27. The sintering aid is Y ２ O ３ , CaO, CaF ２ , Y.F. ３ and rare earth oxides.

28. The method according to claim 14 or 16, wherein the greensheet stack (10) is sintered at a temperature selected from the range of 1600°C to 2000°C.

29. The method according to claim 14 or 16, wherein the greensheet stack (10) is sintered for a holding time selected from the range of 2 hours to 10 hours.

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