Use of glass for passivation of an electronic component and passivated electronic component

Abstract

The invention relates to the use of a glass for passivating an electronic component, in particular a semiconductor component, a method for producing a glass-passivated electronic component and a passivated electronic component, wherein the glass is free of lead except for impurities and comprises the following oxide-based components in wt.%: where RO is the sum of BaO+MgO+CaO+SrO and the ratio (RO+B2O3) / (SiO2+Al2O3) is at least 0.39.

Description

[0001] The invention relates to the use of a glass for passivating an electronic component, in particular a semiconductor component, a method for producing an electronic component passivated with glass and a passivated electronic component.

[0002] Passivation of electronic components means, among other things, the creation or presence of a stable layer (so-called “passivation layer”) on electronic components.

[0003] The passivation or passivation layer protects the component against mechanical damage and other harmful influences, such as chemical effects, during production and / or during use of the component. Applications at high voltages (e.g. diodes with blocking voltages above 1 kV) are only possible through passivation with a highly dielectric strength material. The dielectric strength of air, at 1 kV / mm, is far too low to enable compact high-voltage electronics without passivation. The passivation of electronic components is usually achieved by applying a passivation agent that consists of glass or contains glass, whereby a thin passivation layer is usually created on the component. The passivation thus provides mechanical protection for electronic components, such as diodes, varistors, thyristors, transistors, power transistors, etc.Insulating gate bipolar transistors (IGBTs) represent the primary barrier between the semiconductor and the semiconductor device and also stabilize their electrical properties. The term "electronic components" is to be understood broadly within the meaning of the disclosure and also includes underlying intermediate products made of semiconductor materials, such as wafers or other substrates. The passivation layer is generally applied directly to the pn junction on the semiconductor. At the pn junction, the entire voltage (e.g., the reverse voltage of a diode) is distributed over a length of a few µm in the space charge region, thus generating very high field strengths on the order of 20 kV / mm and more.

[0004] Passivation is essential wherever such a zone with high electric field strength occurs at the edge of the component.

[0005] Passivation agents, particularly glasses and solders for semiconductor passivation, e.g., for the backend passivation of silicon wafers or the frontend passivation of diodes, are known in the art. The purpose of these glasses is to passivate the pn junctions. Good passivation is characterized by a high breakdown voltage and low leakage current.

[0006] In a method for producing a glass-coated electronic component, in particular a semiconductor component, a layer comprising a suitable glass is applied to the electronic component. A liquid coating method is frequently used for this purpose, in which a liquid or pasty preparation comprising the glass in powder form (i.e. a glass powder), i.e. a solid-liquid mixture, is applied in the form of a layer by means of a suitable coating method. Suitable methods can be, for example, spin coating, spraying, dipping, pouring, spreading, screen printing, pad printing, inkjet printing, offset printing, roll coating, doctor blade coating or other methods known to the person skilled in the art. The preparation can be, for example, a suspension, a paste or the like. The production of the layer can also include electrophoresis.By subsequently heating the electronic component, the applied glass layer is fired, forming a hermetically sealed glass body on the component. To reduce the risk of component damage due to high temperatures and to keep process costs low, firing should be carried out at the lowest possible temperatures. Therefore, glasses used for passivating electronic components should have a low melting point, i.e., a softening temperature as low as possible.

[0007] Today, many low-melting passivation glasses used in practice contain lead. Lead-containing glasses have very good resistance to acids, especially HF and HNO3, and exhibit low softening temperatures. However, lead is being replaced for environmental reasons.

[0008] Lead-free passivation glasses are described in the literature, for example those in the Zn-B-Si glass system (JP S61-242928 A, JP 2016-222498 A2, DE 10 2006 062428 A1).

[0009] Zinc borate glasses are, in principle, well-suited for passivation. However, their chemical resistance is insufficient. Good chemical resistance to acids is important for a passivation glass, since after a passivation layer has been applied to a component, such as a silicon wafer, the components must be cleaned with acids or otherwise treated. HNO3 or HF are typically used for this purpose in the semiconductor industry. Depending on the concentration and processing time, the passivation layer can be significantly damaged by acids. Furthermore, ZnO-rich glasses can form undesirable crystalline phases such as zinc borates under the influence of heat.

[0010] Furthermore, lead-free passivation glasses belonging to the Bi-B glass system (WO 2018 / 026402 A1) are described in the literature. Bismuth-containing glasses are chemically much more resistant than the zinc borate glasses described above. However, in addition to the high raw material costs, they have the significant disadvantage that bismuth can be reduced to metallic bismuth during semiconductor passivation due to the low-oxygen atmosphere used. This creates bubbles that lead to a non-passivated component at the pn junction.

[0011] US 20170323791 A1 describes a method for producing a semiconductor device with a glass layer comprising a lead- and alkali-free aluminoborosilicate glass with alkaline earth metal oxides and ZnO. The glass layer exhibits high resistance to a hydrofluoric acid-containing etchant (6%). The glass layer can be produced by an electrophoresis process or a screen printing process without an exposure step. Due to the higher ZnO content, the glass layers may exhibit lower resistance to the acid etchants used for cleaning. Furthermore, the glass compositions of US 20170323791 A1 exhibit high softening temperatures, i.e., high required firing temperatures, due to their high Al2O3 and / or SiO2 content and a low BaO content.

[0012] The RoHS regulations (Restriction of Hazardous Substances; EU Directive 2011 / 65 / EU) stipulate a ban on lead-containing glass, which is not yet in force in all areas due to exemptions. The ban requires the replacement of lead-containing glass with lead-free alternatives. It would be desirable to adapt established passivation processes to the new passivation agent only minimally or not at all. For example, a new passivation agent should have the lowest possible melting or softening temperature, particularly no more than 950°C, in order to enable the most economical passivation process and not jeopardize the stability of an electronic component, such as a silicon wafer.In addition, the passivating agent should also show a high resistance to acids and have a linear thermal expansion coefficient CTE (20-300°C) that is suitable for the materials used in the electronic components for the substrates or leads and electrodes, such as silicon, SiC, SiN, GaAs, GaN, AIN and / or mixtures thereof, ie in particular semiconductors with a large band gap.

[0013] Consequently, only special glasses with special properties can be used for passivation.

[0014] It is an object of the invention to meet the described need and to avoid the mentioned disadvantages.

[0015] The object is achieved by the use of selected glasses for passivating an electronic component according to claim 1, a method for producing a glass-passivated electronic component according to claim 8, and a passivated electronic component according to claim 10. Advantageous further developments are specified in the dependent claims and the description. use

[0016] In one aspect, the invention relates to the use of a glass for passivating an electronic component, in particular a semiconductor element, wherein the glass is free of Pb except for impurities and has the following components in % by weight on an oxide basis: SiO2 45.0 to 58.0 Al2O3 5.0 to 15.0 B2O3 4.5 to 16.0 BaO 8.0 to 27.0 RO 15.0 to 32.0 where RO is the sum of BaO+MgO+CaO+SrO and the ratio (RO+B2O3) / (SiO2+Al2O3) is at least 0.39.

[0017] The inventors recognized that, in order to meet the requirements placed on passivation glasses, it is important to select the components mentioned within the specified ranges, ensuring that a sufficient minimum BaO content is present, since BaO lowers the softening temperature more than the other alkaline earth metal oxides, i.e., MgO, CaO, SrO. Furthermore, the glass contains a special ratio of the softening temperature-lowering components RO and B2O3, i.e., (RO+B2O3), to the acid-resistant components SiO2 and Al2O3, i.e., (SiO2+Al2O3).

[0018] Such lead-free, i.e., Pb-free, glass can be used effectively for the passivation of an electronic component, in particular a semiconductor component – ​​such as a diode, thyristor, varistor, transistor, power transistor (e.g., IGBT), and similar electronic components – as well as an intermediate product – such as a substrate, wafer, etc. The materials for electronic components or substrates can include, for example, silicon, SiC, SiN, GaAs, GaN, AlN, and / or mixtures thereof, i.e., in particular, semiconductors with a wide band gap. Advantageously, the glasses exhibit good acid resistance comparable to lead-containing passivation glasses and a sufficiently low softening temperature for a passivation process.

[0019] In an advantageous embodiment, the glass has a softening point (Ew) of at most 930°C, preferably at most 900°C, preferably at most 880°C, in order to keep the firing temperature for producing a passivation layer low. The softening point is the temperature at which a melt of the glass has a viscosity of 10 7.6 dPas. An advantageous lower limit for the softening temperature can be at least 600°C, preferably at least 650°C, more preferably at least 700°C or at least 750°C. The softening temperature can be in the range from 600°C to 930°C, in particular in the range from 650°C to 900°C or in the range from 700°C to 880°C.

[0020] To enable economical production of the glass, the glass, in an advantageous embodiment, has a processing temperature (Va; English "working point") of at most 1200°C, preferably at most 1180°C, in some advantageous variants at most 1150°C. The processing temperature is the temperature at which the melt has a viscosity of 10 4 dPas has.

[0021] The transformation temperature T g of the glass can be at least 500°C or at least 550°C. In an advantageous embodiment, T g not exceeding 800°C, preferably not exceeding 780°C or in some variants not exceeding 750°C. If T g the glass cannot be used in the conventional passivation process. "T g “ is the transformation temperature according to ISO 7884-8:1987.

[0022] The softening temperature and / or the processing temperature can be determined using methods known to those skilled in the art for determining the viscosity of glass, e.g., according to ISO 7884-2:1987-12.

[0023] The glass preferably has an etch rate of at most 1.0 µm / min in 5% HF at room temperature (RT), i.e., approximately 20°C. Alternatively or additionally, the glass may have a weight loss of less than 3% in 65% HNO3 at 85°C and 10 minutes. Excessively high etch rates or weight losses may have a negative effect on the passivation layers, since the passivated components may be exposed to HNO3 and / or HF for cleaning purposes, e.g., during manufacture of the semiconductor component. An advantageous glass exhibits an etch rate in 5% HF at room temperature of at most or less than 0.9 µm / min or at most or less than 0.8 µm / min. The etch rate in 5% HF at room temperature may be at least 0.1 µm / min or at least 0.2 µm / min. In an advantageous embodiment, the weight loss in 65% HNO3 at 85°C and 10 minutes is less than 2%. The glass may exhibit a weight loss in 65% HNO3 at 85°C and 10 minutes of more than 0.5%.It has been found that the glasses used according to the invention can exhibit an etching rate or weight loss comparable to the chemical resistance of lead-containing glasses or sealing solders. Therefore, the glasses described in the invention can replace lead-containing passivation glasses or sealing solders.

[0024] The etching rate in 5% HF at room temperature was determined on solid glass. If a sample is to be tested in powder form, the powder is first melted (e.g. at temperatures in the range between the softening temperature and processing temperature of the glass) and fused into a mold to produce a solid sample. Sample preparation (cutting, grinding, polishing, cleaning, etc.) was carried out according to DIN 12116. The samples were then exposed to aqueous acid (5% HF) for 10 minutes at room temperature. After cleaning the samples and drying them in an oven according to the specifications of DIN 12116, the etching removal was determined. The etching removal was determined based on the loss in weight of the samples - the difference between the weight before and after the acid treatment - and converted to the sample surface in a known manner. For each glass, the etching rate was determined on three samples, and an average value was calculated from this.

[0025] The weight loss in 65% HNO3 at 85°C was also determined on solid glass. If a sample is to be tested in powder form, the powder is first melted (e.g., at temperatures between the softening temperature and processing temperature of the glass) and fused into a mold to create a solid sample. Sample preparation (cutting, grinding, polishing, cleaning, etc.) was carried out according to DIN 12116. The samples were then exposed to 65% HNO3 at a temperature of 85°C for 10 minutes. After cleaning the samples and drying them in an oven according to the specifications of DIN 12116, the weight loss of the samples - the difference between the sample weights before and after acid treatment - was determined. For each glass, the weight loss was determined on three samples, and an average value was calculated.

[0026] The compositional features discussed herein contribute to the advantageous properties of the glass. It has been found that particularly advantageous properties can be achieved by optimizing the contents of SiO2, Al2O3, B2O3, BaO, and RO. It has been found that one or more of the following measures—e.g., fine-tuning the amount of certain components relative to one another, maintaining certain sums and / or differences—contribute to promoting the desired, advantageous properties with regard to softening temperature and chemical resistance.

[0027] The glass used in the inventive application contains SiO2 in a content of 45.0 to 58.0 wt.%. A minimum content of 45.0 wt.% should not be undercut, as otherwise the resistance to acids, in particular HF and HNO3, is impaired. An upper limit of 58.0 wt.% should not be exceeded, as the softening temperature rises with increasing SiO2 content, which also increases the firing temperatures required to produce the passivation layer. In an advantageous embodiment, the glass has an SiO2 content of at least 45.5 wt.% or at least 46.0 wt.%. In an advantageous embodiment, the content can optionally be at most 57.5 wt.%, in particular at most 57.0 wt.% or at most 56.5 wt.% or at most 56.0 wt.% or at most 55.5 wt.%.

[0028] The glass used in the invention contains Al2O3 in a content of 5.0 to 15.0 wt.%. A minimum content of 5.0 wt.% should not be undercut, as otherwise the resistance to acids, in particular HF and HNO3, is impaired. An upper limit of 15.0 wt.% should not be exceeded, as otherwise the softening temperature of the glass and thus the temperature required to fire a passivation layer are increased. In addition, if the Al2O3 content is too high, i.e. > 15.0 wt.%, it has a negative effect on the acid resistance. In an advantageous embodiment, the glass contains at least 6.0 wt.%, at least 7.0 wt.%, at least 8.0 wt.% or at least 9.0 wt.% Al2O3. Advantageously, the content can be limited to a maximum of 14.5 wt.%, for some advantageous variants to a maximum of 14.0 wt.%, a maximum of 13.0 wt.% or a maximum of 12.0 wt.%.

[0029] In an advantageous embodiment, the sum of the contents of SiO2 and Al2O3 (SiO2+Al2O3) can be 50.0 to 72.0 wt.%. SiO2 and Al2O3 are both components that improve the chemical resistance of the glass, although the influence of SiO2 is more pronounced. If the total Al2O3 content is too high, the acid resistance decreases, which is why the Al2O3 content is limited, as described above. The upper limit of 72.0 wt.% should not be exceeded in order to obtain a glass with an advantageously low softening temperature. An advantageous upper limit for the sum can also be a maximum of 71.0 wt.% or a maximum of 70.0 wt.%. The sum of SiO2+Al2O3 is at least 50.0 wt.% for improved acid resistance in the glass. Advantageously, it can be at least 52.0 wt.% or at least 54.0 wt.%.

[0030] The glass used in the inventive application contains B2O3 in a concentration of 4.5 to 16.0 wt.%. B2O3 is a glass component that lowers the softening temperature and processing temperature of the glass and thus the firing temperatures required in the passivation process, which is why this component is present in the glass at a concentration of at least 4.5 wt.%. An upper limit of 16.0 wt.% should not be exceeded, as high levels have a negative impact on the chemical resistance of the glass. Since higher concentrations of boron or boron compounds are considered problematic for the environment, the release of B2O3 from the glass should be as low as possible. In an advantageous embodiment, the glass has a B2O3 content of at least 5.0 wt.%, at least 7.0 wt.%, at least 8.0 wt.%, at least 9.0 wt.%, or at least 10.0 wt.%. In an advantageous embodiment, the content can optionally be at most 15.5 wt.% or at most 15.0 wt.%.

[0031] The glass used in the inventive application contains RO in a content of 15.0 to 32.0 wt.%, where RO stands for the total sum of the alkaline earth metal oxides MgO+CaO+BaO+SrO. Alkaline earth metal oxides can be used to lower the softening temperature of the glass, which is why at least 15.0 wt.% RO is contained. An upper limit of 32.0 wt.% should not be exceeded, since otherwise the chemical resistance of the glass deteriorates and there is a risk of crystal formation in the glass (devitrification). In an advantageous embodiment, the glass contains at least 16.0 wt.%, at least 17.0 wt.%, at least 18.0 wt.%, at least 19.0 wt.% or at least 20.0 wt.% of RO. Advantageously, the content can be limited to a maximum of 30.0 wt.%, a maximum of 28.0 wt.% or a maximum of 27.0 wt.%. An advantageous RO range can also be 20.0 to 32.0 wt.%.

[0032] In an advantageous embodiment, the sum of the contents of B2O3 and RO (B2O3+RO) can be 26.0 to 48.0 wt.%. B2O3 and RO are components that contribute to lowering the softening temperature in the glass, which is why the sum should be at least 26.0 wt.%. An advantageous lower limit for the sum can also be at least 27.0 wt.%, at least 28.0 wt.%, at least 29.0 wt.%, or for some variants, at least 30.0 wt.%. The sum of B2O3+RO is at most 48.0 wt.%. Advantageously, it can be at most 46.0 wt.% or at most 44.0 wt.%.

[0033] The glass used in the inventive use has BaO in a content of 8.0 to 27.0 wt.%, i.e. the glass necessarily contains BaO as an alkaline earth metal oxide. BaO is present in the glass in a content of at least 8.0 wt.% because it is better suited than the other alkaline earth metal oxides, i.e. CaO and / or MgO and / or SrO, to achieving the desired low softening temperature in a passivation glass. If the BaO content is too high, the thermal expansion of the glass increases excessively, which is why an upper limit of 27.0 wt.% should not be exceeded. In an advantageous embodiment, the glass contains at least 9.0 wt.%, at least 10.0 wt.%, at least 11.0 wt.%, or at least 12.0 wt.% of BaO. Advantageously, the content can be limited to a maximum of 26.5 wt.%, a maximum of 26.0 wt.%, or a maximum of 25.5 wt.%.

[0034] In an advantageous embodiment, the glass can contain MgO in a content of 0.0 to 12.0 wt.%. If the glass is to contain MgO, it can advantageously contain at least 0.1 wt.% or at least 0.2 wt.% MgO. In an advantageous embodiment, the MgO content is limited to a maximum of 12.0 wt.%, a maximum of 11.0 wt.%, a maximum of 10.0 wt.%, a maximum of 8.0 wt.%, a maximum of 6.0 wt.%, a maximum of 4.0 wt.% or a maximum of 2.0 wt.% In an advantageous embodiment, the glass is free of MgO. It can be advantageous to reduce the MgO content or to dispense with MgO altogether in order to prevent crystal formation in the glass.

[0035] In an advantageous embodiment, the glass can contain CaO in a content of 0.0 to 12.0 wt.%. If the glass is to contain CaO, it can advantageously contain at least 0.1 wt.% or at least 0.2 wt.% CaO. In an advantageous embodiment, the CaO content is limited to a maximum of 12.0 wt.%, a maximum of 11.0 wt.%, a maximum of 10.0 wt.%, a maximum of 8.0 wt.%, a maximum of 6.0 wt.%, a maximum of 4.0 wt.% or a maximum of 2.0 wt.% In an advantageous embodiment, the glass is free of CaO. It can be advantageous to reduce the CaO content or to dispense with CaO altogether in order to prevent crystal formation in the glass.

[0036] In an advantageous embodiment, the glass can contain SrO in a content of 0.0 to 8.0 wt.%. If the glass is to contain SrO, it can advantageously contain at least 0.1 wt.% or at least 0.2 wt.% SrO. In an advantageous embodiment, the SrO content is limited to a maximum of 8.0 wt.%, a maximum of 6.0 wt.%, a maximum of 4.0 wt.% or a maximum of 2.0 wt.%. In an advantageous embodiment, the glass is free of SrO. It can be advantageous to reduce the SrO content or to dispense with SrO altogether in order to prevent crystal formation in the glass.

[0037] In an advantageous embodiment, the glass contains only a single alkaline earth metal oxide, i.e., only BaO. In this variant, the total RO content is formed solely by BaO. In this case, the total RO content is limited to 27.0 wt.%. In such a variant, the BaO content is 15.0 to 27.0 wt.%.

[0038] In other advantageous embodiments, the glass may contain one or more alkaline earth metal oxides in addition to BaO. These other alkaline earth metal oxides are collectively referred to as R'O. R'O is thus the sum of MgO+CaO+SrO. If the glass contains at least one other alkaline earth metal oxide in addition to BaO, R'O should be selected such that the total sum of R'O of all alkaline earth metal oxides (i.e., BaO+MgO+CaO+SrO) is within the range according to the invention.

[0039] The inventors have recognized that the softening temperature of the glass can advantageously be set specifically and lower when BaO has the highest proportion in the total RO, i.e. when more BaO than R'O (i.e., MgO+CaO+SrO) is contained in the glass. In an advantageous embodiment, the difference between the weight percentages of BaO and the sum of other alkaline earth metal oxides MgO, CaO, SrO, i.e. the difference BaO-(MgO+CaO+SrO) (also referred to as BaO-R'O), can be 1.0 to 27.0 wt.%. An advantageous lower limit for the difference BaO-R'O can also be at least 2.0 wt.%, at least 3.0 wt.%, at least 5.0 wt.%. As described above, it can be preferred if the glass contains significantly more BaO than R'O, preferably even contains only BaO and no R'O.

[0040] In an advantageous variant, the glass contains at least two alkaline earth metal oxides, ie necessarily BaO and at least one further alkaline earth metal oxide (R'O) selected from the group consisting of MgO, CaO and SrO.

[0041] In another advantageous variant, the glass contains at least three alkaline earth metal oxides, ie necessarily BaO and at least two further alkaline earth metal oxides (R'O) selected from the group consisting of MgO, CaO and SrO.

[0042] If, in an advantageous variant, the glass contains exactly two alkaline earth metal oxides, i.e. BaO and a single further alkaline earth metal oxide (MgO or CaO or SrO), the content of the further alkaline earth metal oxide is to be selected depending on the BaO content such that the total RO is maintained, i.e. in the range 15.0 to 32.0 wt.%. With regard to the softening temperature, it is also advantageous if the difference BaO-R'O is in the range 1.0 to 27.0 wt.%. To illustrate this, the glass can contain, for example, 25.0 wt.% BaO and 7.0 wt.% R'O, so that the difference BaO-R'O here is 18.0 wt.%.

[0043] If, in an advantageous variant, the glass contains exactly three alkaline earth metal oxides, i.e. BaO and two further alkaline earth metal oxides (MgO+CaO or MgO+SrO or CaO+SrO), the sum of the further alkaline earth metal oxides R'O is to be selected depending on the BaO content such that the total sum RO is maintained, i.e. in the range 15.0 to 32.0 wt.%. With regard to the softening temperature, it is also advantageous if the difference BaO-R'O is in the range 1.0 to 27.0 wt.%. To illustrate this, the glass can contain, for example, 20.0 wt.% BaO and 12.0 wt.% R'O, so that the difference BaO-R'O here is 8.0 wt.%.

[0044] If, in an advantageous variant, the glass contains all four alkaline earth metal oxides, i.e. BaO and three further alkaline earth metal oxides (MgO+CaO+SrO), the sum of the further alkaline earth metal oxides R'O is to be selected depending on the BaO content such that the total sum RO is maintained, i.e. in the range 15.0 to 32.0 wt.%. With regard to the softening temperature, it is also advantageous if the difference BaO-R'O is in the range 1.0 to 27.0 wt.%. To illustrate this, the glass can contain, for example, 17.0 wt.% BaO and 15.0 wt.% R'O, so that the difference BaO-R'O here is 2.0 wt.%.

[0045] The inventors have recognized that glasses within the composition ranges described above can advantageously be used as passivation glasses if the following condition is met: (RO+B2O3) / (SiO2+Al2O3) is at least 0.39. This means that the sums B2O3+RO and SiO2+Al2O3 are calculated from the weight percentages of the components mentioned, and these are then related to one another. Glasses that meet this ratio demonstrate a balance between good acid resistance and a low melting temperature. In an advantageous embodiment, the ratio (RO+B2O3) / (SiO2+Al2O3) is at least 0.40, advantageously at least 0.45, advantageously at least 0.50, for particularly advantageous variants at least 0.55, preferably at least 0.60 or at least 0.65.An advantageous upper limit for the ratio (RO+B2O3) / (SiO2+Al2O3) can be less than 1.00, in particular at most 0.96, in order to obtain a glass with good acid resistance and a low melting temperature, i.e., to achieve the desired balance between the two properties in the glass. In an advantageous embodiment, the upper limit can be at most 0.95, preferably at most 0.90. In some advantageous variants, the upper limit can be at most 0.85 or at most 0.80.

[0046] In an advantageous embodiment, the difference between the weight percentages of BaO and B2O3 (BaO-B2O3) can be 2.0 to 12.0 wt.%. This means that, with respect to these components, which both have a positive effect on lowering the softening temperature, more BaO than B2O3 is used in the glass, thereby improving chemical resistance. Therefore, the difference should be at least 2.0 wt.%. For some advantageous variants, a favorable lower limit for the difference can also be at least 4.0 wt.%, advantageously at least 6.0 wt.%, or at least 8.0 wt.%.

[0047] In one embodiment, the glass may contain proportions of ZnO, in particular 0.0 wt.% up to a maximum of or less than 5.0 wt.%. The content must be limited to a maximum of 5.0 wt.%, as the component has a negative effect on the acid resistance of the glass. A beneficial upper limit may also be a maximum of 3.0 wt.% or a maximum of 2.0 wt.%. If ZnO is to be contained in the glass, for example to specifically lower the softening temperature, at least 0.1 wt.% or at least 0.2 wt.% or at least 0.5 wt.% may be an advantageous lower limit. Preferred variants of the glass may be free of ZnO.

[0048] In an advantageous embodiment, the glass can comprise at least one of the following components: 0.0 to 4.0 wt.% ZrO2 and / or 0.0 to 6.0 wt.% TiO2 and / or 0.0 to 2.0 wt.% Ta2O5 and / or 0.0 to 2.0 wt.% Nb2O5. If one or more of these components is to be contained in the glass, 0.1 wt.% or 0.2 wt.% can be a suitable lower limit. The components ZrO2 and / or TiO2 can improve the chemical resistance, but they can also have a negative effect on the softening temperature of the glass and the risk of undesirable crystallization. An advantageous upper limit for ZrO2 can be a maximum of 3.0 wt.%, a maximum of 2.0 wt.% or a maximum of 1.0 wt.%. An advantageous upper limit for TiO2 can be at most 5.0 wt%, for some variants at most 4.0 wt%, at most 3.0 wt%, at most 2.0 wt% or at most 1.0 wt%.The components Ta2O5 and Nb2O5 can also improve the chemical resistance of the glass, although 1.0 wt.% for each component may be a favorable upper limit. Advantageous variants of the glass can be free of ZrO2 and / or TiO2 and / or Ta2O5 and / or Nb2O5.

[0049] To reduce costs and avoid defects in the resulting passivation layer, the glass, in an advantageous embodiment, contains a maximum of 2.0 wt.% or a maximum of 1.0 wt.% of Bi2O3. Particularly preferably, the glass is free of Bi2O3.

[0050] According to preferred embodiments, the glasses used according to the invention are low in alkali, and more preferably alkali-free, since alkali metal ions, particularly at elevated temperatures, diffuse from the glass, for example into a semiconductor component, e.g., a chip, and can thus impair the functionality of a semiconductor component, e.g., a diode. For the purposes of the present invention, low alkali is to be understood as meaning that the sum of the alkali metal oxides (Li2O+Na2O+K2O+Cs2O+Rb2O) in the glass is a maximum of 3 wt. %, advantageously a maximum of 2 wt. %, advantageously a maximum of 1 wt. %, advantageously a maximum of or less than 0.5 wt. %, preferably a maximum of or less than 0.1 wt. If only a single alkali metal oxide is present in the glass, the stated upper limits can apply to each alkali metal oxide individually. If two or more alkali metal oxides are present, the stated upper limits apply accordingly to any combinations.The alkali metal oxide content must be limited to achieve the desired high dielectric strength. Particularly preferred glass variants are alkali-free except for common impurities, i.e., free from the alkali metal oxides Li2O and / or Na2O and / or K2O, in particular free from Li2O, Na2O, K2O, Cs2O, and / or Rb2O.

[0051] According to preferred embodiments, the glasses used according to the invention are free of Cu and / or Fe and / or Cd and / or other coloring transition metals.

[0052] According to one embodiment, the glass consists of at least 94.0 wt.%, preferably at least 95 wt.%, in some advantageous variants at least 97 wt.% of the components SiO2, Al2O3, B2O3 and RO.

[0053] According to an advantageous variant, the glass is free of components not mentioned in the disclosure.

[0054] The terms "Pb-free or lead-free", "alkali-free" or more generally "free of a component x" are to be understood in the context of the present invention to mean that these substances or their oxides are not intentionally added as components to the passivation glass and are present at most in traces or as small residual amounts, i.e. at most as impurities in the glass. For lead, this means that the Pb content is less than 1000 ppm in order to comply with the current RoHS specifications. Advantageously, the Pb content can be less than 500 ppm, preferably less than 100 ppm. For example, for Li2O, Na2O, K2O, Cs2O, Rb2O, Cu, Fe, Cd and / or other components advantageously described above as "free of", the content per component can be less than 100 ppm, preferably less than 50 ppm.

[0055] In an advantageous further development, the glass can have the following components in wt.% on an oxide basis: SiO2 46.0 to 57.0 Al2O3 6.0 to 14.0 B2O3 8.0 to 15.5 BaO 10.0 to 27.0 RO 20.0 to 32.0

[0056] In an advantageous further development, the glass may comprise the following components in wt.% on an oxide basis, individually or in any combination: SiO2 46.0 to 56.0 Al2O3 7.0 to 13.0 B2O3 8.0 to 15.0 BaO 11.0 to 27.0 MgO 0.0 to 12.0 CaO 0.0 to 12.0 SrO 0.0 to 8.0 ZrO2 0.0 to 4.0 TiO2 0.0 to 6.0 RO 20.0 to 32.0

[0057] In one embodiment, the average thermal expansion of the glass used in the temperature range from 20°C to 300°C is less than 5.5*10 -6 K -1, i.e. a maximum of 5.5 ppm / K, or a maximum of 5.0 ppm / K or in some variants a maximum of 4.8 ppm / K. In particular, the thermal expansion can be in the range 3.5 to 5.5 ppm / K. The values ​​specified are the mean linear thermal expansion coefficient, also known as “CTE”, in a temperature range from 20 °C to 300 °C. It is determined in accordance with DIN ISO 7991:1987. In other words, in an advantageous embodiment the glass has a mean linear thermal expansion coefficient of 3.5 to 5.5 ppm / K in a temperature range from 20 °C to 300 °C. It has been shown that glasses with this thermal expansion are sufficiently adapted to the expansion of semiconductor materials, e.g. silicon, for example to avoid cracks in the passivation layer.

[0058] The glass used to passivate an electronic component can be used in the passivation process in powder form. For this purpose, a glass produced by melting technology with the desired composition is crushed and ground using a known milling process. The glass is thus in the form of glass powder. It has been found that the choice of particle size and particle size distribution influence the quality of a passivation layer on an electronic component. Furthermore, the choice of particle size and its distribution can influence acid resistance and the formation of gaps.

[0059] In an advantageous embodiment, the average particle size d50 of the glass powder is from 1.0 µm to 12.0 µm, in particular from 1.5 µm to 5.0 µm or from 2.0 µm to 3.0 µm. It has been shown that this particle size, preferably in combination with the range described below, combines advantageous results with regard to acid resistance during passivation.

[0060] In an advantageous embodiment, the glass powder can comprise a particle size distribution having a range (d90-d10) / d50 of at least 1.00, in particular at least 1.80. A larger range shows better packing density and thus a lower tendency of the glass or passivation glass to form gaps between the layer and the semiconductor component during heat treatment during the formation of a passivation layer. However, the range should not be too large, as this can reduce acid resistance. The range can be limited to a maximum of 6.00, a maximum of 4.50, or a maximum of 3.50, in particular a maximum of 3.00.

[0061] The particle sizes and particle size distributions specified in this description can be measured using dynamic light scattering, e.g., the method in ISO 13320:2009 can be used. The Fraunhofer method can be used for evaluation, and the measured values ​​can be represented as a volume distribution.

[0062] In the inventive use, the glass can be used alone or with an inorganic additive (also called "filler"), preferably a crystalline additive, in powder form. In one embodiment, the information on the particle size and / or particle size distribution applies equally to the glass content and the filler content. The filler can, for example, be selected from the group comprising: ZrO2, willemite, cordierite, fused silica, high-quartz solid solution, ß-eucryptite (Li2Al2Si2O8), aluminum titanate (Al2TiO5), and ZrW2O8. The use of a filler can be advantageous for adapting the expansion of the passivation layer to the components of the electronic component. Therefore, fillers with negative thermal expansion can be advantageous.

[0063] If glass, i.e. a passivation glass, is used with a filler in a passivation process, the combination of glass and filler can also be called a “melting solder”.

[0064] The proportion of filler in the solder can be at least 1.0 vol%, at least 2.0 vol%, at least 3.0 vol%, at least 4.0 vol%, or at least 5.0 vol%. In one embodiment, the proportion of filler can be up to 25.0 vol%, up to 20.0 vol%, up to 17.5 vol%, or up to 15.0 vol%.

[0065] In particular, the proportion of further components besides the glass portion and the crystalline additive can be limited to a maximum of 10.0 vol%, a maximum of 5.0 vol%, a maximum of 2.5 vol%, a maximum of 1.0 vol%, or a maximum of 0.5 vol%. In one embodiment, the solder comprises a proportion of glass relative to the solder of at least 80.0 vol%. In one embodiment, the proportion of glass in the solder is at least 85.0 vol% or at least 87.5 vol%. The proportion can optionally be up to 90 vol%. The solder can consist of the glass and the crystalline additive.

[0066] The solder can be in powder form. The particle sizes and size distributions described above for the glass powder can also be advantageously used for the solder. To avoid repetition, reference is made to the above explanations.

[0067] In an advantageous embodiment, the filler content can be 1.0 to 25.0 vol% and the proportion of glass in the solder can be 99.0 vol% to 75 vol%.

[0068] In a further aspect, the invention relates to the use of a glass for passivating an electronic component, in particular a semiconductor element, wherein the glass contains SiO2, Al2O3, B2O3 and BaO, is free of Pb except for impurities, and a ratio (RO+B2O3) / (SiO2+Al2O3) is at least 0.39, wherein the sums and the ratio are formed from the contents of the components in wt.% on an oxide basis and RO is the sum of BaO+MgO+CaO+SrO, wherein the glass preferably has a softening temperature of at most 930°C and / or an etching rate of at most 1.0 µm / min in 5% HF at room temperature.

[0069] Advantageously, the glass may contain the following components in % by weight on an oxide basis: SiO2 45.0 to 58.0 Al2O3 5.0 to 15.0 B2O3 4.5 to 16.0 BaO 8.0 to 27.0 RO 15.0 to 32.0

[0070] Details regarding the advantageous composition of the glass used, advantageous chemical and physical properties, and possible particle sizes and particle size distributions of a glass powder or a powder of a soldering compound made of glass and filler(s) have already been described above in connection with the description of the first aspect of the invention. This disclosure is incorporated in its entirety into the description of the further aspect of the invention. To avoid repetition, reference is made to it. Proceedings

[0071] In another aspect, the invention relates to a method for producing a glass passivated electronic component, comprising the following steps: - Providing an electronic component or a substrate, - processing a powder comprising or consisting of glass into a preparation, in particular a paste or suspension, - applying the preparation to the electronic component or substrate in the form of a layer, - heat-treating the electronic component or substrate with the applied preparation for melting the glass to produce a passivation layer, characterized in that a glass according to the inventive use described above is used for the process.

[0072] Details regarding the advantageous composition of the glass used, advantageous chemical and physical properties, and possible particle sizes and particle size distributions of a glass powder or a powder of a soldering compound made of glass and filler(s) have already been described above in connection with the use according to the invention. This disclosure is incorporated in its entirety into the description of the method according to the invention. To avoid repetition, reference is made to it.

[0073] An electronic component or a substrate to be passivated is provided. The electronic component can advantageously be selected from a diode, varistor, thyristor, transistor, or power transistor (e.g., IGBT). However, the term "electronic components" is to be understood broadly and also includes underlying intermediate products made of semiconductor materials, in particular substrates, for example wafers (e.g., silicon wafers) or other substrates. The electronic components can comprise materials such as silicon, SiC, SiN, GaAs, GaN, AlN, and / or mixtures thereof, i.e., in particular, semiconductors with a wide band gap.

[0074] The glass with the desired composition is ground to a fine powder, whereby the average particle size d50 of the glass can advantageously be from 1.0 µm to 12.0 µm, in particular from 1.5 µm to 5.0 µm or from 2.0 to 3.0 µm.

[0075] A preparation, in particular a solid-liquid mixture, in particular a paste or suspension, is produced from powder comprising or consisting of glass and other additives, wherein the preparation may contain further additives, for example dispersants, organic binders, solvents, etc. Depending on the specific requirements of the passivation layer, the powder used may consist solely of glass or - as described in connection with the first aspect of the invention - be a mixture comprising glass and filler.

[0076] The preparation is applied to the provided electronic component, preferably in the form of a layer, using known coating methods, in particular liquid coating methods. For example, the preparation can be applied by spin coating, spraying, dipping, pouring, brushing, screen printing, pad printing, inkjet printing, offset printing, roll coating, doctor blade coating, or other methods known to those skilled in the art. Doctor blade or screen printing methods can be used particularly advantageously. The application can be carried out on the electronic components or on a provided substrate in the case of substrate passivation (i.e., glass deposition on a substrate (in particular, wafers) before singulating the electronic components). The production of the layer can also include electrophoresis. The preparation should preferably not contain the fusion partners, for example, the substrate, metallic leads, and electrodes, etc.Wet well so that no cavities are created during firing and no chipping can occur.

[0077] This is followed by heat treatment (also called "firing") of the electronic component or substrate with the applied preparation for melting the glass to create a passivation layer. In an advantageous embodiment, the heat treatment takes place in a temperature range of 600°C to 930°C, preferably 640°C to 930°C. In an advantageous variant, the firing can be carried out at 700°C to 900°C or 700°C to 880°C. These temperatures can have a positive influence on chemical resistance, as the higher temperatures result in a more homogeneous melt and the destruction of grain boundaries in the powder, thereby reducing the surface area exposed to acids. Passivated electronic component

[0078] According to a further aspect, the invention also comprises an electronic component, in particular a semiconductor component, comprising at least one passivation layer comprising or consisting of glass according to the use according to the invention described above.

[0079] Details regarding the advantageous composition of the glass used, advantageous chemical and physical properties, and possible particle sizes and particle size distributions of a glass powder or a powder of a sealing solder made of glass and filler(s) have already been described above in connection with the inventive use. A method for production has also been described above. These disclosures are incorporated in their entirety into the description of the passivated electronic component according to the invention. To avoid repetition, reference is made to them.

[0080] The electronic component, in particular a semiconductor component, can advantageously be selected from the group consisting of diodes, varistors, thyristors, transistors, and power transistors, e.g., insulated-gate bipolar transistors (IGBTs). The term "electronic component" also encompasses an underlying intermediate product made of semiconductor material, for example, a substrate or a wafer. The materials for electronic components or substrates can include, for example, silicon, SiC, SiN, GaAs, GaN, AlN, and / or mixtures thereof, ie, in particular, wide-bandgap semiconductors.

[0081] The thickness of the passivation layer can advantageously be between 3 µm and 100 µm. In some advantageous variants, the thickness can be between 10 µm and 100 µm, in particular between 20 µm and 80 µm or between 20 and 50 mm.

[0082] It is understood that the features of the invention mentioned above and those to be explained below, which comprises several aspects, can be used not only in the combination specified in each case, but also in other combinations without departing from the scope of the invention. Examples

[0083] Glasses were melted from conventional raw materials, which, apart from unavoidable impurities, were essentially free of lead and alkali, at temperatures up to 1650°C in heated Pt crucibles. The melt was refined at this temperature for one hour, stirred for homogenization, and cast into ingots.

[0084] To produce glass powder, the melt can be passed through water-cooled metal rollers and the glass ribbon can then be ground.

[0085] In addition to the composition, the physical and chemical parameters and properties of the examples and comparative examples were determined.

[0086] The etching rate in 5% HF for 10 minutes at room temperature and the weight loss in 65% HNO3 for 10 minutes at 85°C were determined as stated above: Resistance to a 5% HF concentration was rated "good" if the etch rate, the measured values ​​of which are given in parentheses, was 1.0 µm / min or less. If the etch rate was higher, i.e., > 1.0 µm / min, the etch rate was rated "bad."

[0087] Resistance to HNO3 was rated "good" if the weight loss, based on the weight before and after acid treatment, was less than 3% and no deposit was visible on the sample surface. In contrast, HNO3 resistance was rated "bad" if the weight loss was at least 3%, regardless of whether a deposit was formed or not. Even with a weight loss of less than 3%, HNO3 resistance was classified as "bad" if a deposit was visible on the sample surface. A deposit is said to be present when the sample surface is visibly cloudy. This cloudiness is due to a chemical reaction between the acid and the glass and is undesirable.

[0088] Table 1 shows seven exemplary embodiments (Ex.) of the invention, while Table 2 lists comparative examples (Cf. Ex.). The exemplary embodiments, all of which have a ratio (RO+B2O3) / (SiO2+Al2O3) of at least 0.39, demonstrate good resistance to the tested acids comparable to that of a lead-containing passivation glass (see Cf. Ex. C1 in Table 2). In contrast, a passivation glass made of the Zn-B-Si glass system, which can currently be used as a passivation glass replacement for lead-containing glasses, exhibits significantly poorer acid resistance (see Cf. Ex. C3).

[0089] Although the softening temperatures of the glasses according to the invention (Examples 1 to 7) are higher than the softening temperature of the lead-containing glass (cf. Example C1), the softening temperatures are significantly below 930°C, and in Examples 1 to 6 even below 880°C, and can therefore be used in passivation processes below the firing temperatures possible there.

[0090] Comparative examples C2, C4 to C7 also show that glasses outside the claimed composition ranges are significantly inferior in terms of acid resistance and / or softening temperature to a lead-containing passivation glass, which can serve as a benchmark. In fact, no glass could be melted from the composition according to C5, i.e., the example was not meltable (ns). Table 1: Examples of implementation in wt.% Example No. . 1 2 3 4 5 6 7 SiO2 46,9 49,5 48,5 47,9 49,0 53,0 57,1 B2O3 14,4 15,2 14,8 14,7 15,0 11,6 4,7 Al2O3 9,6 10,1 9,9 9,8 10,0 11,1 14,5 BaO 23,9 25,2 24,7 24,5 25,0 13,8 12,5 MgO 1,8 11,2 CaO 2,9 SrO 5,8 ZrO2 3,1 TiO2 5,2 2,1 1,0 ZnO PbO sum 100,0 100,0 100,0 100,0 100,0 100,0 100,0 RO 23,9 25,2 24,7 24,5 25,0 24,3 23,7 SiO2+Al2O3 56,5 59,6 58,4 57,7 59,0 64,1 71,6 RO+B2O3 38,3 40,4 39,5 39,2 40,0 35,9 28,4 (RO+B2O3) / (SiO2+Al2O3) 0,68 0,68 0,68 0,68 0,68 0,56 0,40 BaO-B2O3 9,5 10,0 9,9 9,8 10,0 2,2 7,8 Characteristics Density [g / cm 3 ] 2,75 2,76 2,73 2,72 2,67 Tg [°C] 642 647 742 761 649 724 CTE 20-300°C [ppm / K] 5,0 4,5 4,5 4,4 4,6 5,0 4,0 Ew [°C] 819 844 833 850 831 869 909 Va [°C] 1114 1160 1174 1166 1204 5% HF, 10 min at RT, µm / min good (≤ 0.8) good (0.8) good (0.8) good (0.8) good (≤ 0.8) good (≤ 0.8) good (≤ 0.8) 65% HNO3, 10 min at 85°C good good good good good good good Table 2: Comparative examples in wt.% See example no. . C1 C2 C3 C4 C5 C6 C7 SiO2 38,0 14,9 70,0 71,8 59,2 48,4 B2O3 13,0 44,3 19,1 5,0 1,8 4,7 11,2 Al2O3 2,5 27,0 0,6 5,0 1,2 14,5 16,9 BaO 20,0 6,3 8,8 10,6 MgO 11,8 2,5 2,5 0,7 CaO 16,9 12,6 10,1 2,1 SrO 3,8 ZrO2 0,2 TiO2 ZnO 65,4 10,1 PbO 46,5 sum 100,0 100,0 100,0 100,0 100,0 100,0 100,0 RO 28,7 20,0 25,2 21,4 13,4 SiO2+Al2O3 27,0 15,5 75,0 73,0 73,7 65,3 RO+B2O3 73,0 19,1 25,0 27,0 26,1 24,6 (RO+B2O3) / (SiO2+Al2O3) 2,70 1,23 0,33 0,37 0,35 0,38 BaO-B2O3 -44,3 -19,1 15,0 4,5 4,1 -0,6 Characteristics Density [g / cm 3 ] 3,54 3,77 2,66 Tg [°C| 456 631 565 677 720 647 CTE 20-300°C [ppm / K] 4,8 6,5 4,1 3,9 4,6 3,8 Ew [°C] 651 668 653 936 935 885 Va [°C] 1344 1240 1147 ns 5% HF, 10 min at RT, µm / min good (0.8) bad (>1.0) bath (10) good (≤0.8) 65% HNO3, 10 min at 85°C good bathroom bathroom good QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2016-222498 A2

[0008] DE 10 2006 062428 A1

[0008] WO 2018 / 026402 A1

[0010] US 20170323791 A1

[0011]

Claims

[1] Use of a glass for passivating an electronic component, in particular a semiconductor element, wherein the glass is free of Pb except for impurities and has the following components in % by weight on an oxide basis: SiO2 45.0 to 58.0 Al2O3 5.0 to 15.0 B2O3 4.5 to 16.0 BaO 8.0 to 27.0 RO 15.0 to 32.0 where RO is the sum of BaO+MgO+CaO+SrO and the ratio (RO+B2O3) / (SiO2+Al2O3) is at least 0.

39. [2] Use according to claim 1, wherein a sum of RO+B2O3 is 26.0 to 48.0 wt% and / or a sum of SiO2+Al2O3 is 50.0 to 72.0 wt%. [3] Use according to claim 1 or 2, wherein a difference BaO-B2O3 is 2.0 to 12.0 wt% and / or wherein a difference BaO-(MgO+CaO+SrO) is 1.0 to 27.0 wt%. [4] Use according to any one of the preceding claims, wherein the BaO content is at least 11.0 wt% and / or the ZnO content is at most or less than 5.0 wt%. [5] Use according to any one of the preceding claims, wherein the glass comprises, individually or in any combination, the following components in % by weight on an oxide basis: MgO 0.0 to 12.0 CaO 0.0 to 12.0 SrO 0.0 to 8.0 ZrO2 0.0 to 4.0 TiO2 0.0 to 6.0 Ta2O5 0.0 to 2.0 Nb2O5 0.0 to 2.0 RO 20.0 to 32.0 [6] Use according to any one of the preceding claims, wherein the glass has at least one of the following features: - an etching rate of not more than 1.0 µm / min in 5% HF at room temperature, - a softening temperature (Ew) of not more than 930°C, - an average linear thermal expansion coefficient of 3.5 to 5.5 ppm / K in a temperature range of 20 °C to 300 °C. [7] Use according to any one of the preceding claims, wherein the glass is used in powder form, wherein the powder may advantageously have at least one of the following features: - an average particle size d50 of 1.0 µm to 12.0 µm, in particular of 1.5 µm to 5.0 µm, - a particle size distribution having a range (d90-d10) / d50 of at least 1.00, in particular at least 1.80 and / or at most 6.00, in particular at most 4.

50. [8] A method for producing a glass passivated electronic component, comprising the following steps: - Providing an electronic component, - processing a powder comprising or consisting of glass into a preparation, in particular a paste or suspension, - applying the preparation to the electronic component in the form of a layer, - heat-treating the electronic component with the applied preparation for melting the glass to produce a passivation layer, wherein a glass according to one of claims 1 to 7 is used for the process. [9] The method according to claim 8, wherein the heat treatment is carried out in a temperature range of 600°C to 930°C. [10] Electronic component, in particular semiconductor component, preferably wafer, diode, thyristor, varistor, transistor, IGBT comprising at least one passivation layer comprising or consisting of glass according to one of claims 1 to 7.