Ceramic for the manufacture of ceramic plates for probe cards

Abstract

A ceramic, comprising 25,0 to 65,0 % by mass of Si3N4 as the first major component and 45,0 to 85,0 % by mass of ZrO2 as the second major component, characterized by 0,01 to 4,9 % by mass of one oxide or more further oxides solves the object of the invention to indicate a ceramic with a thermal coefficient of expansion that is as close as possible to that of a silicon wafer and has the highest mechanical strength possible.

Description

[0001] Ceramic for the manufacture of ceramic plates for probe cards

[0002] The invention concerns a ceramic according to the preamble of claim 1 .

[0003] From EP 3689 838 A1 , a ceramic used to produce a guiding plate, to build a probe card, is known. The probe card is used to test computer chips or electronic circuits. The computer chips are placed side by side on a silicon wafer. The computer chips can be electrically connected by contact needles on a surface opposite the silicon wafer. The contact needles penetrate or protrude a plate and are separated and electrically insulated by bridges.

[0004] The contact needles are arranged on the plate in such a way that they can securely contact each computer chip. To ensure the functionality, the chips are tested at several temperatures. If the silicon wafers and the ceramic plates are heated, they expand at different levels, so the contact needles change their position relative to the computer chips and do not contact them at the desired location of their surface. The production of chips starts with the drawing of a silicon ingot or monocrystal, followed by the sawing of thin wafers and the grinding and lapping of these wafers to obtain a mirror-smooth surface. After several lithography, implantation, etching and sputter steps a variety of chips can be produced from a single silicon wafer. A wafer typically contains hundreds of chips that need to be subjected to a test procedure to ensure their functionality, before they are separated.

[0005] Probe cards are used to test this functionality of electronic chips, such as memory chips or IC chips. A test set consists of a main plate with contact needles precisely placed on it, one or more thin ceramic plates to keep the contact needles in position, and a printed circuit board (PCB) to make connections to an electrical test device. The chips are examined by electrically connecting the contact needles with the chips.

[0006] To keep the contact needles in an exact position, thin ceramic plates are used. Up to several thousand or ten thousand contact needles are guided through guiding holes in a ceramic plate. The guiding holes are laser drilled and have a diameter in the micron range (e. g. 25 - 75 pm) and a distance of e. g. 10 - 50 pm relative to each other. Such a ceramic plate is used for several hundred thousand of test cycles.

[0007] This requires a material for the plate that can be machined very easily and precisely, with a high resistance to bending in order to be mechanically stable even at low thicknesses (e. g. 100 pm - 1000 pm). Furthermore, a high specific electrical resistance of the material is required to keep the contact needles electrically insulated from each other. In order to have optimal results when applying a laser, a dark grey or black color is preferred.

[0008] Silicon nitride is used in the production of such plates, because it shows the above properties in combination best. However, the design of the plates used for the examination has recently moved towards larger and thinner plates and towards lower distances between the contact needles to test downsized chips with increased power density. At the same time the size of silicon nitride plates in probe cards is continuously increased to test more chips simultaneously. The demand for larger plates requires a material with a high mechanical strength, in particular a high bending strength, and a thermal coefficient of expansion similar to silicon. The chips placed on a silicon wafer are tested at different temperatures, ranging from temperatures below zero degrees Celsius to several hundred degrees Celsius.

[0009] Due to the different thermal coefficient of expansion of the silicon wafer with the chips and the ceramic plate, in particular a silicon nitride plate with the contact needles, the exact positioning of the contact needles at various temperatures becomes increasingly difficult, especially with increasing plate size. It is therefore important to specify a ceramic plate material with a thermal coefficient of expansion close to that of silicon.

[0010] Against this background, the precision of laser drilling, with which guiding holes for the contact needles can be inserted into the ceramic, has continuously improved in recent years. However, the mechanical stability of a thin ceramic plate is very important in order to maintain lower distances between the contact needles.

[0011] The ceramics, which are revealed in EP 3 689 838 A1 and WO 2017 / 203 738 A1 , have thermal coefficients of expansion in the range of silicon and as well have a certain degree of mechanical strength. However, there is a need for more stable and thinner plates less than 500 pm, preferably less than 400 pm, more preferably less than 300 pm, most preferably less than 200 pm.

[0012] The object of the invention is therefore to indicate a ceramic with a thermal coefficient of expansion that is as close as possible to that of a silicon wafer and has the highest mechanical strength possible.

[0013] The object of the invention is achieved by means of the features of claim 1 . It was first recognized that EP 3 689 838 A1 and WO 2017 / 203 738 A1 do not focus on the microstructure, the electrical resistance and influence of various additives on mechanical stability. Furthermore, these documents do not indicate that very thin plates are machine processed. According to the invention, it was then recognized to produce a suitable ceramic for the production of a thin plate. Silicon nitride, zirconium oxide and oxides, preferably magnesium oxide or calcium oxide, are combined to give the ceramic a thermal coefficient of expansion close to that of silicon.

[0014] At the same time, the ceramic has an awarded bending strength that is very close to that of pure SisN4. Finally, it has also been recognized that the used materials may contain impurities, like HfO2, TiO2, SiC>2, AI2O3 and Y2O3 or other oxides without reducing the ability to produce a thin ceramic plate. This invention provides a ceramic that has a thermal coefficient of expansion very close to that of silicon. In addition, the ceramic has an excellent mechanical strength and a high electrical resistance. In addition, machine processing of the ceramic by grinding or lapping may be done very well, so that the ceramic can be made 120 pm - 1000 pm thin. The thickness of the ceramic may be in the range bigger than 0,1 pm and less than 600 pm, preferably less than 500 pm, more preferably less than 400 pm, most preferably less than 350 pm.

[0015] The ceramic according to the invention combines the high bending strength and the high electrical resistance of silicon nitride with the high thermal coefficient of expansion of zirconium oxide. The ceramic unites the advantages of both materials. According to the invention, the properties of the ceramic are improved by adding one or more oxides. Preferred are added MgO and / or CaO. Also, SC2O3 can be added. Instead of MgO, the Mg-content can also be achieved by adding MgZrOs in equal mol %.

[0016] In addition, there may be some impurities due to other oxides, which belong to the HfO2, TiO2, AI2O3, SiO2, and Y2O3 groups. However, the total percentage by mass of all oxides is less than 5 %. It has been recognized that some oxides, especially MgO and / or CaO increase the bending strength of the material. Impurities do not have an effect on the performance of the ceramic. The maximum bending strength of the ceramic can be achieved if the total mass of oxides is less than 5 %.

[0017] The percentage by weight of the further oxide or oxides may be determined by the molar fraction of the oxygen-related element of the respective oxide, taking into account only the molar fraction of that element that is not bound in other compounds or molecules of the ceramic. An example of this could have been obtained by a method of measuring (ICP) that in a ceramic, there are 24,3 g Mg, which corresponds to one mol Mg. Then one mol MgO would be supposed by calculation in the ceramic, provided that no Mg is bound in other compounds or molecules of the ceramic except in MgO. One mole of MgO weighs 40,3 g. If the ceramic weighed 1000 g, the proportion of mass of MgO would be 4,03 % by calculation. This method of measurement allows to precisely measure the mass fraction of all oxides present in the finished ceramic.

[0018] When the plane peak intensity of a-SisN4 by XRD is la and the plane peak intensity of p-SisN4 is l|3, the peak intensity ratio is l|3 1 (la + l|3). A silicon nitride composite material having a value of 0.80 or more, preferably > 0.85, more preferably > 0.9, most preferably > 0.95.

[0019] The further oxide or other oxides could be selected from MgO, CaO, SC2O3, and impurities selected from AI2O3, TiO2, HfO2, SiO2 and / or Y2O3. Preferred MgO and / or CaO are used because these oxides give the ceramic particularly good properties. Additional oxides may be present as impurities, additives or alternatives for MgO or CaO.

[0020] The mass of the further oxide or oxides could be in the range of 0,1 to < 5 %, preferably in the range of 0,5 to 4,8 % preferably in the range of 2 to 4,6 %. The total percentage by mass of oxides is less than 5 %, the oxides being preferably selected from MgO, CaO and SC2O3 with some impurities out of AI2O3, TiO2, HfO2, Y2O3, and / or SiO2. The percentage by mass of Y2O3 is less than 1 %, preferentially less than 0,5 %, especially less than 0,1 %.

[0021] ZrO2 occurs in three structural modifications. Pure ZrO2 is at room temperature monoclinic and transforms into the tetragonal at temperatures above 1170 °C. At temperatures above 2370 °C it transforms in the cubic modification. The conversion from tetragonal to monoclinic is of great importance for the mechanical properties. It is associated with a volume change of 5 - 8 %.

[0022] At increasing temperatures above 1170 °C, the transition from the monoclinic phase to the tetragonal phase occurs, which is related to a volume contraction. Accordingly, the conversion of the tetragonal phase into the monoclinic phase during cooling is related to a volume expansion. The conversion from tetragonal to monoclinic phase can also be released by stresses in the ceramic, for example during cracking. At the crack tip, the stresses are highest. The high stresses at the crack tip induce the tetragonal to monoclinic phase transition. The resulting increase in volume closes the crack. This is a very important mechanism to increase the bending strength of ZrO2 ceramics.

[0023] A disadvantage of the tetragonal to monoclinic transition during cooling is, that pure ZrO2 ceramics are destroyed during cooling due to the volume expansion. In order to make zirconium oxide sinterable, the tetragonal to monoclinic phase transition must be contained by doping.

[0024] Zirconia ceramics that contain transformable phases can be basically divided into two classes, the PSZ (Partially Stabilized Zirconia) and the TZP (Tetragonal Zirconia Polycrystals) type. Compared to TZP ceramics, PSZ ceramics often have a higher molar content of stabilizing elements. To produce a PSZ ceramic, pure zirconium oxides and the oxides of the stabilizing element in a powder mixture are used as raw materials so that the stabilizing element is incorporated into the zirconium oxide grid during the sintering (“in situ”). Therefore, typically higher sintering temperatures are needed.

[0025] TZP ceramics, are usually manufactured with raw materials into which the stabilizing element has already been introduced in a generally chemical process and this coprecipitate has then been calcined. The starting powders for TZP ceramics are also usually very fine, which enables comparatively low sintering temperatures.

[0026] Preferably, a Mg-PSZ (Magnesia Partially Stabilizes Zirconia) ceramic is used. MgO is preferably added to stabilize the cubic and tetragonal phase, which leads to a defined amount of tetragonal phase, which can transform to the monoclinic phase. For the Mg-PSZ ceramic, the Mg2+ions build into the Zr4+space in the grid and produce oxygen vacancies due to the lower charge. This partially stabilizes the cubic and tetragonal phase of ZrC at room temperature. During the cooling, a certain amount of tetragonal phase is stabilized and cannot be transformed to monoclinic phase. This leads to an optimal amount of tetragonal phase at room temperature and maximizes bending strength. All available Mg2+ions are integrated into the ZrO2 grid so that no free MgO is present in sintered material.

[0027] Further materials to stabilize the cubic and tetragonal phase are for example CaO and / or Sc2Os.The proportion of mass of CaO could be in the range of 1 to < 4 %, preferably in the range of 1 ,5 to 3,75 % preferably in the range of 1 ,75 to 3,5 %. The proportion of mass of MgO could be in the range of 1 to < 4 %, preferably in the range of 1 ,25 to 3,5 % preferably in the range of 1 ,5 to 3 %. The proportion of mass of Cao and MgO could be in the range of 1 to < 4 %, preferably in the range of 1 ,25 to 3,75 % preferably in the range of 1 ,5 to 3,5 %. Further materials to stabilize the cubic and tetragonal phase are for example CaO and / or Sc2Os.The total amount of MgO and / or CaO and / or SC2O3 mass could be 1 - 4 %, preferably 1 ,5 - 3,5 %, especially 1 ,8 - 3,2 %, with regard to the total mass. With higher > 5 % oxides, the amount of stabilized cubic and tetragonal phase is higher and therefore the bending strength decreases.

[0028] Due to the formation of Si2N2O, nitrogen is released out of SisN4 and some oxygen out of ZrO2. The released nitrogen is supposed to partially substitute the oxygen in the ZrO2 lattice, which leads to a stabilization of the cubic and tetragonal phase. For this reason, larger amounts than 5 % of mass of stabilization oxides are disadvantageous. In sintered ceramics, the proportion of oxides in mass is lower than in the powder raw mixture from which the ceramics are sintered.

[0029] A small amount of the added TiO2 can react with SisN4 to TiN, or titanium oxynitride eliminating some of the free TiO2 in the sintered ceramics. The percentage of mass of TiO2 could be 0,05 - 2 %, preferably 0,3 - 1 ,5 %, especially 0,4 - 1 %.

[0030] The free oxygen in the SisN4 raw powder reacts to SiO2 during the production of the raw powder. In the sintering process, the SiO2 reacts with SisN4 to Si2N2O. The mass fraction of SiO2 could be 0.05 - 2 %, preferably 0.3 - 1 .5 %, especially 0.4 - 1 %.

[0031] The mass fraction of SiO2 in the sintered ceramic body according to the invention is less than 0,6 %, preferably less than 0,4 %, preferably less than 0,2 %.

[0032] The mass fraction of SisN4 could be in the range of 20 to 60 %, preferably in the range of 28 to 45 %. Silicon nitride promotes the mechanical strength and electrical resistance of ceramics. At least 20 - 60 % SisN4 is required to achieve a thermal coefficient of expansion, which should be in the range 3.0 - 6.0 *10’6 / K at -50 to 400 °C. Due to the high sintering temperatures, the alpha - beta transition of silicon nitrides is completed by more than 80 %, preferably by more than 90 %, especially preferably by more than 95 %. In order to achieve the highest bending strength and keep the thermal coefficient of expansion in the target range, the |3 / (|3 + a) ratio should be > 0.8, preferably > 0.85, more preferably > 0.9, most preferably > 0.95. The beta-SisN4 occurs as small needles in the microstructure.

[0033] The proportion of mass of ZrO2 could be in the range of 50 to 75 %, preferably in the range of 55 to 70 %. ZrO2 increases the thermal coefficient of expansion of ceramics to achieve a value of 3,0 - 6,0 *10’6 / K in the temperature range -50 to 400 °C or more, at least 45 % zirconium oxide is required. More than 85 % lead to an thermal coefficient of expansion higher than 6,0 *10’6 / K.

[0034] The ceramic could comprise cubic, tetragonal and monocline crystal phases of ZrO2. Zirconium oxide has various crystal structures such as monoclinic, cubic and tetragonal. The tetragonal crystal structure shows the highest bending strength and is therefore preferred. In order to obtain zirconium oxide with a high proportion of tetragonal crystal structure, some percent of oxides, such as MgO, CaO, or SC2O3 or Y2O3, must be dissolved in it to stabilize the tetragonal phase. Without stabilization, the tetragonal phase is subjected to a phase transition, which occurs during cooling into a monocline phase. This results in an increase in volume. The percentage by mass of the monoclinal phase is preferably less than 50 %, more peferably less than 45 % and most preferably less than 40 %.

[0035] The percentage by mass of the monoclinic phase is 5 - 50 %, preferably 8 - 40 %, more preferably 10 - 35 %. The percentage by mass of the cubic phase is 2 - 35 %, preferably 7 - 32 %, more preferably 10 - 30 %. The percentage by mass of the tetragonal phase is 2 - 40 %, preferably 5 - 35 %, more preferably 8 - 30 %. In order to minimize the monoclinic phase and to achieve a high bending strength, 0,5 - 4 % mass of MgO and / or CaO and / or SC2O3, preferably 1 - 3,5 % of MgO and / or CaO and / or Sc2O3, and most preferably 1 ,2 - 3 % of MgO and / or CaO and / or Sc2O3 are added.

[0036] The percentage by mass of all oxides could therefore be in the range of 0, 1 % to < 5 %, preferably in the range of 0,5 to 4,8 %, preferably in the range of 1 to 4,6 %.

[0037] The ceramic could comprise a proportion of mass of Si2N2O as the third or other main component of 2 to 30 %, preferably 5 to 25 %, especially preferably 7 to 18 %. The ceramic could have 0 to 30 % by mass, preferably 2,5 to 25 %, preferably 5 to 18 %, of Si2N2O as the third or other major component. During the sintering of the ceramic, the material contains the release of Si2N2O. The present SiO2 in the silicon nitride reacts with this to Si2N2O. The precipitation has a length of less than 70 pm, preferably less than 50 pm, especially less than 30 pm. Small Si2N2O precipitations are advantageous because they result in higher bending resistance and a more consistent microstructure. The size of the Si2N2O precipitations depends on the sintering temperature.

[0038] The ceramic thus has a fine grain structure with beta-SisN4 and Si2N2O needles embedded in a zirconium matrix. The crystals of Si2N2O present in the ceramic could have an average grain size in the range of 2 pm up to 15 pm.

[0039] The ceramic could have a thermal coefficient of expansion, which is in a temperature range of -50 to 500 °C in a range of 2 to 7*10’6 / K, preferably in a range of 2.5 to 6.5 *10’6 / K, especially in a range of 3 to 6 *10’6 / K. This allows the ceramic to follow the thermal expansion behaviour of a silicon wafer with chips. The ceramic could have a bending strength in the range 600 MPa to 5000 MPa, preferably in the range 700 MPa to 5000 MPa, especially in the range 800 MPa to 5000 MPa. The ceramic could show a bending strength larger than 600 MPa, preferably larger than 700 MPa, especially preferably larger than 800 MPa. The highest bending strength can be achieved if the total oxide mass in the range 1 to less than 5 %. With amounts of oxides > 5 % the bending strength decreases. The preferred range for oxides is 1 - 5 %, preferably 1 ,5 - 4,8 %, more preferably 2 - 4,6 %. Due to an increasing porosity with < 1 ,5 % oxides, the bending strength also decreases. The bending strength allows the ceramic to be grinded to a very thin plate.

[0040] The ceramic could have a thickness in the range of 30 pm to 2000 pm, preferably in the range of 100 pm to 800 pm, especially in the range of 120 pm to 500 or 800 pm. Very thin sheets can be combined into a composite plate. Very thin plates allow the arrangement of shorter contact needles.

[0041] Two different surfaces can be achieved through the hard processing steps. The grinded version, which has a different reflection factor depending on the reflection angle, has a roughness less than 0,6 pm, preferably less than 0,5 pm. The lapped variant is independent of the reflection angle and has a roughness of less than 0,5 pm, preferably less than 0,4 pm, most preferably less than 0,3 pm.

[0042] The ceramic may have a pore size in the range 0.1 pm to 12 pm, preferably in the range 0.1 pm to 10 pm. By post-hipping the pore size can be reduced to less than 5 pm. This gives the ceramic a homogeneous structure and the high bending strength.

[0043] The ceramic could have inclusions or spaces with a diameter ranging from 0,1 pm to 30 pm. This makes the ceramic particularly fragile. The ceramic could have an electrical resistance in the range 1*10’9Q*cm to 1*10’11Q*cm. This electrical resistance is preferred at a temperature of 25°C. Such resistance allows the contact needles of a plate made of ceramic to be electrically insulated from each other particularly well.

[0044] A plate could comprise or been made of a ceramic of the kind described here. Such a plate can be used in a test set for chips, in particular for chips placed on a silicon wafer.

[0045] In the plate guiding holes could be arranged, in which contact needles for electrical contact are located. The contact needles can be used to contact the chips electrically.

[0046] Contact needles may also be located on such a plate. The plate can be used in the test set-up described above. The plate could be characterized by the abrasion behaviour of these contact needles.

[0047] In the drawings:

[0048] Fig. 1 is a diagram showing the thermal coefficient of expansion of materials of different compositions depending on temperature,

[0049] Fig. 2 is a diagram showing the thermal coefficient of expansion depending on the ratio of zirconium oxide and silicon nitride, wherein rules of mixture are compared with experimental values,

[0050] Fig. 3 shows in the upper view a photograph using a scanning electron microscope and in the lower view an XRD diagram quantifying the proportions of different molecules and structures, Fig. 4 is a diagram showing the bending strength of the ceramic in relation of mass % MgO

[0051] Fig. 5 is a diagram showing bending strength of a ceramic depending on sintering temperature,

[0052] Fig. 6 shows a schematic view of a test set-up which contains at least one plate of a ceramic of the type described here, which is penetrated by contact needles, and

[0053] Fig. 7a, b shows a table in which different ceramics are compared.

[0054] Fig. 1 shows a diagram showing the thermal coefficient of expansion of pure ZrO2, of pure SisN4, of pure silicon and of a ceramic according to the invention depending on temperature.

[0055] Fig. 2 shows a diagram showing the thermal coefficient of expansion depending on the ratio of zirconium oxide and silicon nitride. Fig. 2 shows two curves generated by mixing rules, a linear mixing rule and an excess mixing rule. It is recognized that the measured thermal coefficients of expansion are approximately between the calculated values according to these mixing rules.

[0056] Fig. 3 shows a photograph in the upper view using a scanning electron microscope and in the lower view an XRD diagram which quantifies the proportions of different molecules and structures. You can see that the Si2N2O precipitations are relatively small and very evenly distributed. This may surprisingly result in high strength. It is assumed that the total SiO2 content is converted to Si2N2O.

[0057] Fig. 4 shows a graph showing the bending strength of ceramics depending of their proportion of mass of MgO. The bending strength was measured at 5 mm x 20 mm x 0.18 mm bending bars. You can see that there's obviously a maximum of bending strength around 2,3 % of mass of MgO.

[0058] Fig. 5 shows a graph showing the bending strength of a ceramic depending on sintering temperature. It can be seen that the bending strength remains almost constant from 1700 °C. At 1650 °C, the a / |3 conversion of the SisN4 is not yet complete at 100% and the bending strength is therefore lower.

[0059] An example of the production of ceramic of the type described here is described below:

[0060] ZrO2 powder, SisN4 submicron powder and one or more oxides selected from the MgO, CaO, HfO2, TiO2, SC2O3, and SiO2 group are mixed and ground with water using a stirrer and bead mill with SisN4 balls. In addition, an additive can be used like a dispersant and a binder. The obtained slurry is spray-dried or freeze dried and formed in granules.

[0061] The resulting powder is sintered under high pressure and high temperature in a hot-pressing process or in a gas pressure sintering furnace. For the hot pressing process, the force can be in the range from 10 to 50 MPa in an argon atmosphere. The temperature is in the range between 1600 °C and 1850 °C. The temperature and pressure are maintained for 1 to 5 hours, depending on the dimensions. For the gas pressure sintering cycle, the temperature is in the range between 1600 °C and 1850 °C. The gas pressure (argon atmosphere) can be in the range of 3 to 20 MPa.

[0062] In order to describe the benefits of a ceramic according to the invention, SisN4 powder, ZrO2 powder and one or more of the oxides selected from the MgO, CaO, HfO2, TiO2, SC2O3, and SiO2 group were mixed, dispersed and bound in different mass conditions with water. The obtained slurries were ground with SisN4 grinding balls in a stirrer and bead mill and dried by a spray dryer. The granules obtained were loaded into a graphite form coated with boron nitride (BN) as a release agent.

[0063] A powder was compressed in an argon atmosphere at 1700 °C for three hours with 25 MPa. The sample obtained had a diameter of about 80 mm and a height of about 10 mm. Test samples for various measurements were taken from the sample obtained.

[0064] Example 1 :

[0065] 64 % ZrO2(CZP-5, ZirPro), 33,1 % Si3N4(UBE E10), 2,3 % MgO (Dr. Paul Lohmann GmbH & Co. KGaA) and 0,6 % TiO2(Kronos 1002) were mixed and milled as described above. After spray drying and hot pressing (1750°C, for 3h), the sample had a thermal coefficient of expansion of 4,4 *10’6 / K at 100 °C, a bending strength of more than 800 MPa and a density of 4,34 g / cm3

[0066] Example 2:

[0067] 64 % ZrO2(CZP-5, ZirPro), 33,1 % Si3N4(UBE E10), 2,8 % CaO (Carl Roth) and 0,6 % TiO2(Kronos 1002) were mixed and milled as described above.

[0068] Example 3:

[0069] 64 % ZrO2(CZP-5, ZirPro), 33,1 % Si3N4(UBE E10), 2,3 % MgO (Dr. Paul Lohmann GmbH & Co. KGaA) and 0,6 % TiO2(Kronos 1002) were mixed and milled as described above. After spray drying, shaping and gas pressure sintering (1740°C, for 3h at 9,5 bar), the sample had a thermal coefficient of expansion of 4,4 *10’6 / K at 100 °C and a density of 4,40 g / cm3.

[0070] The thermal coefficient of expansion was determined with a sample of 5 mm x 5 mm x 20 mm in accordance with DIN EN 1159-1 in the range -50 to 500 °C. The bending strength was determined with bending bars with dimensions of 5 mm x 25 mm x 0,18 mm. For this purpose, a plate was grinded to 0.18 mm and the bending bars were cut with a laser. The bending bars were then examined with a three-point bending test and a distance of 20 mm between the bearing rollers.

[0071] The density of the samples was measured according to DIN EN 623-2, the density measurement using the Archimedes method.

[0072] The crystallographic structure was performed by an XRD analysis according to DIN 13925 2003-07.

[0073] The grain size was determined by determining the largest diameter of grains with scanning electron microscope (SEM) images.

[0074] The machinability was determined on the basis of samples 50 mm x 50 mm (130 mm x 130 mm). These samples were ground or ground into thin sheets with thicknesses ranging from 0,1 - 1 mm, preferably 0,12 - 0,8 mm, with a special preference of 0,15 - 0,5 mm. After that, some of these samples were lapped to obtain a matt surface.

[0075] The outer dimensions of plates were cut with a laser. The outer dimensions of the plates can be up to 210 mm, round or square. All smaller dimensions can be realized and can be achieved by laser cutting.

[0076] The thickness and roughness of the ground or lapped plates was measured using Sentronics SemDex M1 , an optical measuring device. The principle of this device is based on a laser interferometer. A laser above the plate and a laser below the plate measure distances to the plate and calculate the thickness of the plate. The measuring device has an accuracy of + / - 1 pm. In addition, the flatness and thickness distribution can be calculated.

[0077] The roughness is determined using an additional roughness sensor. The roughness of the plates is less than 0.6 pm, preferable less than 0.5 pm, especially less than 0.4 pm by

[0078] 1. the choice of grinding wheel with diamond grains smaller than 100 pm during grinding or

[0079] 2. by using abrasive slurry with a grain size of 50 pm or less.

[0080] Fig. 6 shows a schematic view of a test set-up, which has a plate 1 made of a ceramic of the type described here, which is penetrated by contact needles 2.

[0081] The contact needles 2 are located on a main plate 3, which can also be made from the ceramic described here, and are separated to each other to be able to contact chips 4 on a silicon wafer 5 electrically.

[0082] Contact needles 2 are separated by walls 6 in the plate 1 , which have a very low thickness. The contact needles 2 stick out through laser-drilled guiding holes 7 with a diameter of 10 - 150 pm.

[0083] The contact needles 2 are separated from each other between 10 - 150 pm.

[0084] Such a ceramic plate 1 is used for a large number of test cycles. Reference numbers

[0085] 1 plate

[0086] 2 contact needle

[0087] 3 main plate

[0088] 4 chip

[0089] 5 silicon wafer

[0090] 6 wall

[0091] 7 guiding hole

Claims

Claims1 . Ceramic, comprising 25,0 to 65,0 % by mass of SisN4 as the first major component and 45,0 to 85,0 % by mass of ZrO2 as the second major component, characterized by 0,01 to 4,9 % by mass of one oxide or more further oxides.

2. Ceramic according to claim 1 , characterized in that the mass of the further oxide or oxides is determined by the molar fraction of the oxygen- related element of the respective oxide, taking into account only the molar fraction of this element that is not bound in other compounds or molecules of the ceramic.

3. Ceramic according to claim 1 or 2, characterized in that the further oxide or oxides is one or more from the group MgO, CaO, AI2O3, TiO2, MgZrOs, HfO2, SC2O3, and / or SiO2.

4. Ceramic according to one of the previous claims, characterized in that the mass of the further oxide or oxides is in the range of 0,1 to < 5 %, preferably in the range of 0,5 to 4,8 % preferably in the range of 2 to 4,6 %.

5. Ceramic according to one of the previous claims, characterized in that, when the plane peak intensity of a-SisN4 by XRD is la and the plane peak intensity of |3-Si3N4 is l|3, the peak intensity ratio is l|3 1 (la + l|3), the ceramic and / or a silicon nitride composite material has a value of 0.80 or more, preferably > 0.85, more preferably > 0.9, most preferably > 0.95.

6. Ceramic according to one of the previous claims, characterized in that the proportion of mass of MgO is in the range of 1 to < 4 %, preferably in the range of 1 ,25 to 3,5 % preferably in the range of 1 ,5 to 3 %.

7. Ceramic according to one of the previous claims, characterized in that the proportion of mass of CaO is in the range of 1 to < 4 %, preferably in the range of 1 ,5 to 3,75 % preferably in the range of 1 ,75 to 3,5 %.

8. Ceramic according to one of the previous claims, characterized in that the proportion of mass of Cao and MgO is in the range of 1 to < 4 %, preferably in the range of 1 ,25 to 3,75 % preferably in the range of 1 ,5 to 3,5 %.

9. Ceramic according to one of the previous claims, characterized in that the proportion of mass of SisN4 is in the range of 25 to 50 %, preferably in the range of 28 to 45 %.

10. Ceramic according to one of the previous claims, characterized in that the proportion of mass of ZrO2 is in the range of 50 to 75 %, preferably in the range of 55 to 70 %.11 . Ceramic according to one of the previous claims, characterized by cubic, tetragonal and monocline crystal phases of ZrO2.

12. Ceramic according to one of the previous claims, characterized by a proportion of mass of Si2N2O as the third or other main component of 2 to 30 %, preferably 5 to 25 %, especially preferably 7 to 18 %.

13. Ceramic according to one of the previous claims, characterized in that the crystals of Si2N2O present in the ceramic have an average grain size in the range of 2 pm up to 10 pm.

14. Ceramic according to one of the previous claims, characterized by a thermal coefficient of expansion, within a temperature range of -50 to 500, in a range of 2 to 7*10’6 / K, preferably in a range of 2.5 to 6.5 *10’ 6 / K, especially in a range of 3 to 6 *10’6 / K.

15. Ceramic according to one of the previous claims, characterized by a bending strength in the range 600 MPa to 5000 MPa, preferably in the range 700 MPa to 5000 MPa, especially in the range 800 MPa to 5000 MPa.

16. Ceramic according to one of the previous claims, characterized by a thickness in the range 30 pm to 2000 pm, preferably in the range 100 pm to 800 pm, especially in the range 120 pm to 800 pm.

17. Ceramic according to one of the previous claims, characterized by a pore size in the range 0.1 pm to 12 pm, preferably in the range 0.1 pm to 10 pm.

18. Ceramic according to one of the previous claims, characterized by inclusions or spaces with a diameter ranging from 0.1 pm to 30 pm.

19. Ceramic according to one of the previous claims, characterized by an electrical resistance in the range of 1*1 O’9Q*cm to 1 *10’11Q*cm20. Plate (1 ), comprising a ceramic according to one of the previous claims.21 . Plate according to claim 20, characterized in that the plate (1 ) has guiding holes (7) in which contact needles (2) for electrical contact are located.

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