Glass for passivation of semiconductor components

Abstract

To provide a glass and a melt solder material for passivation of semiconductor components, the use of the glass or melt solder material for passivation treatment of semiconductor components, a passivated semiconductor component, and a method for passivating semiconductor components, which avoid drawbacks of the prior art.SOLUTION: A melt solder material has the following constituents in mol%: SiO2 of 15.0 to 30.0, Al2O3 of 0.5 to 8.0, B2O3 of 14.0 to 25.0, ZnO of 40.0 to 65.0, and MgO of 0.1 to 8.0. The solder material contains a crystalline additive, which contains magnesium and aluminum, in an amount of at least 1.0 vol.%.SELECTED DRAWING: Figure 5A

Description

Technical Field

[0001] The present invention relates to glass and a fusion solder for passivation of semiconductor components, use of the glass or the fusion solder for passivating semiconductor components, passivated semiconductor components, and a method for passivating semiconductor components.

Background Art

[0002] Passivation agents, in particular glass and fusion solders, for passivation of semiconductors, for example for back-end passivation of silicon wafers or for front-end passivation of diodes, are known in the prior art. The purpose of these glasses is to passivate pn junctions. Good passivation is characterized by a high breakdown voltage and a low leakage voltage. Currently, all of the passivation glasses actually used contain lead. Lead should be replaced from the perspective of environmental protection. Lead-free passivation glasses are described in the literature, for example, in the literature of Zn-B-Si glass systems (Japanese Patent Application Laid-Open No. 61-242928 (JPS61-242928A), Japanese Patent Application Laid-Open No. 2016-222498 (JP2016-222498A2), German Patent Application Publication No. 10 2006 062428 (DE10 2006 062428A1)), and in the literature of Bi-B glass systems (International Publication No. 2018 / 026402 (WO2018 / 026402A1)). In principle, zinc borate glass is suitable for passivation. However, the chemical resistance of this glass is not sufficient. After the glass formation on the silicon wafer, it has to be acid-etched for cleaning. For this purpose, HNO3 or HF is usually used in the semiconductor industry. Depending on the concentration and the process time, the passivation layer may be significantly damaged. In contrast, lead-containing glass has very good resistance to acids.

[0003] Glasses from the Zn-B-Si system have a relatively high elastic modulus. For example, the elastic modulus of Zn-B-Si glass is typically about 7 GPa higher than that of typical lead-containing passivation glass. This can lead to cracks during cooling. These cracks are caused by the stress in the passivation layer based on the difference in the coefficient of thermal expansion. The average coefficient of thermal expansion in the temperature range of 20 °C to 300 °C is about 3 ppm / K for polycrystalline silicon. In the case of lead-containing glass, since the elastic modulus is small, the mismatch in the coefficient of thermal expansion is not very important. Furthermore, in the case of zinc borate glass, gaps may be formed. These gaps are regions where the semiconductor and the passivation agent are disengaged at the contact surface. Such gaps are disadvantageous because their occurrence is not controllable, and there is a risk that the pn junction will be exposed. Such unpassivated elements are rejected as defective products in production.

[0004] The high elastic modulus of zinc borate glass results in a greater stress on the passivation agent with the same mechanical displacement (for example, when cooling the glass and silicon together) compared to lead-containing glass. The passivation layer may crack based on the volume shrinkage and the difference in the coefficient of thermal expansion during cooling. It has been shown that a mismatch in the coefficient of thermal expansion of 1.1 ppm / K is already sufficient to cause cracks in the passivation layer from zinc borate.

[0005] Bismuth-containing glass has a major drawback that, in addition to the high raw material cost, bismuth can be reduced based on the oxygen-deficient atmosphere in which it is used during semiconductor passivation. This results in the generation of bubbles, which leads to elements that are not passivated at the pn junction.

[0006] RoHS regulations (Restrictions on Hazardous R estriction o f H azardous SSubstances); EU Directive 2011 / 65 / EU) intends to prohibit lead-containing glass, but is not effective in all ranges based on exceptional authorization. The said prohibition requires replacing lead-containing glass with lead-free alternatives. It is desirable that the established passivation method does not conform to the new passivation agent at all or only minimally. For example, the new passivation agent should have a melting temperature as low as possible, especially less than 800 °C, enable a passivation process that is as economical as possible, and not threaten the stability of the silicon wafer. Furthermore, the passivation agent should not crack and should avoid the formation of gaps between the element to be passivated and the passivation layer. In the best case, the passivation agent also has high resistance to acids.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem of the present invention is to satisfy the above-mentioned needs and avoid the above-mentioned drawbacks.

Means for Solving the Problems

[0009] The above problems are solved by the glass, molten solder, semiconductor component, method and use described in the present application.

[0010] Fused solder material In one aspect, the present invention relates to the following components: [Table 1] A fused solder material having the following in mol%, and having a crystalline additive containing magnesium and aluminum at a ratio of at least 1.0% by volume. The above solder material has been found to have a low crack formation tendency during the passivation of semiconductor components. The inventors of the present invention believe that the addition of a crystalline additive during passivation forms a crystalline portion having a crystal phase, which is the cause of the low crack formation tendency. At this time, it is considered that a relatively large amorphous ratio and / or a small ratio of wollastonite in the passivation layer play a role. The crystalline additive should be distinguished from the crystalline portion formed in the passivation layer produced from the fused solder material. The crystalline additive does not necessarily exist in the crystalline portion of the passivation layer after the use of the fused solder material. Rather, the crystalline additive may dissolve during the heat treatment of the solder material and no longer exist as a crystal phase in the passivation layer. The above components of the fused solder material described in mol% include a crystalline additive. The ratio of the crystalline additive in the fused solder material may be at least 2.0% by volume, at least 3.0% by volume, at least 4.0% by volume, or at least 5.0% by volume. In one embodiment, the ratio of the crystalline additive is up to 25.0% by volume, up to 20.0% by volume, up to 17.5% by volume, or up to 15.0% by volume. The crystalline additive itself does not necessarily exist or no longer completely exists in the passivation layer formed from the fused solder material by melting. Instead, it has been found that a completely different crystal phase is formed by XRD inspection. It is even more surprising that the crystalline additive used in the present application has such an effect on the formation of the crystal phase during passivation. It is particularly surprising that the use of the crystalline additive leaves a relatively high amorphous ratio in the passivation layer, which avoids crack formation by reducing volume shrinkage.

[0011] The crystalline additive contains magnesium and aluminum. In one embodiment, it contains the following components by mass%:

Table 2

[0012] In particular, the crystalline additive may be magnesium aluminum silicate, and preferably the additive is Mg2Al4Si5O 18 and is.

[0013] In one embodiment, the molten solder has a proportion of glass of at least 75.0% by volume and / or at most 99.0% by volume. This means the proportion of glass before the molten solder is used for passivation. The molten solder is in particular in powder form. It can be obtained, for example, by mixing glass powder with a crystalline additive. The molten solder can consist essentially of a glass part and a crystalline additive. In particular, the proportion of further components other than the glass part and the crystalline additive can be limited to a maximum of 10.0% by volume, a maximum of 5.0% by volume, a maximum of 2.5% by volume, a maximum of 1.0% by volume, or a maximum of 0.5% by volume. In one embodiment, the molten solder has a proportion of glass of at least 80.0% by volume relative to the molten solder. In one embodiment, the proportion of glass in the molten solder is at least 85.0% by volume, or at least 87.5% by volume. The proportion can optionally be up to 90% by volume. The molten solder can consist of glass and a crystalline additive.

[0014] The molten solder material can exist in powder form. It has been found that the choice of particle size and particle size distribution affects the formation of the crystal phase when producing a passivation layer on a semiconductor component. Furthermore, the choice of particle size and its distribution can affect acid resistance and the formation of gaps. In one embodiment, the present invention relates to a molten solder material having a particle size distribution characterized in that the span (d90 - d10) / d50 is at least 1.00, in particular at least 1.80. The larger the span, the better the packing density, and thereby the tendency of the molten solder material to form gaps between the layer and the semiconductor component during heat treatment during the formation of the passivation layer is reduced. However, the span should not be too large, because it can reduce acid resistance. The span 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.

[0015] In one embodiment, the average particle size d50 of the molten solder material is from 1.0 μm to 10.0 μm, in particular from 1.5 μm to 5.0 μm or from 2.0 μm to 3.0 μm. This particle size has been shown to advantageously combine with the above-mentioned span to provide optimal results with respect to acid resistance, crystal formation and shrinkage during passivation.

[0016] In one embodiment, the volume fraction of particles having a size less than 1.0 μm is limited to a maximum of 30% by volume of the molten solder material, in particular a maximum of 27.0% by volume or a maximum of 20.0% by volume of the molten solder material. This achieves better acid resistance and fewer gaps in the passivation layer.

[0017] In one embodiment, the description of the particle size and / or particle size distribution applies equally to the glass part and the crystalline additive.

[0018] The particle size and particle size distribution described herein are measured using dynamic light scattering, and for example, the method in ISO13320:2009 can be used. The Fraunhofer method can be utilized for evaluation, and the measured values can be expressed as a volume distribution.

[0019] In one embodiment, the average coefficient of thermal expansion of the molten solder is 4.5×10 -6 K -1 or less, or 4.10×10 -6 K -1 or less, particularly 3.50 to 4.10 ppm / K, preferably 3.5×10 -6 K -1 exceeding. The coefficient of thermal expansion is measured in particular on a 5×5×50 mm sample by melting the solder at a temperature of 700 to 750°C. It has been shown that this coefficient of thermal expansion is well adapted to the expansion coefficient of silicon in order to avoid cracks in the passivation layer.

[0020] In one embodiment, the molten solder exhibits an average coefficient of thermal expansion that differs from the average coefficient of thermal expansion of polycrystalline silicon by 0.65 ppm / K or less over the temperature range of 300°C to Tg - 20°C, where Tg is the transition temperature of the glass portion contained in the solder, and the coefficient of thermal expansion is measured by melting the solder at a temperature of 700 to 750°C on a 5×5×50 mm sample.

[0021] The temperature range of 300°C to the Tg of the glass is particularly important with respect to the average coefficient of thermal expansion of the molten solder. Here, the upper limit of Tg - 20°C is selected because an accurate measurement at exactly Tg would only give inaccurate results. As is apparent from FIG. 1, in the temperature range up to 300°C, the expansion coefficients of the various glasses or molten solders and semiconductor materials are still generally the same. From 300°C onwards, it becomes more difficult to limit the deviation in the expansion coefficient. For the present invention, in particular in the range around Tg which is at least 550°C, the expansion coefficients completely deviate. Above Tg, the difference in the coefficient of thermal expansion is irrelevant because beyond Tg the glass or molten solder is ductile. Preferably, the molten solder has 0.50×10 -6 K -1The following may have an average coefficient of thermal expansion different from that of polycrystalline silicon. A certain difference in the average coefficient of thermal expansion of the glass compared to polycrystalline silicon is inevitable. The difference in the average coefficient of thermal expansion may be at least 0.05×10 -6 / K or at least 0.09×10 -6 / K. Such a difference in the expansion behavior is still acceptable based on the adjusted modulus of elasticity. The thermal expansion behavior of polycrystalline silicon is known to those skilled in the art. This can also be seen in Figure 1.

[0022] In a preferred embodiment, the molten solder has an average coefficient of thermal expansion of 0.2×10 -6 K -1 ~1.0×10 -6 K -1 in the temperature range of 300°C to Tg - 20°C.

[0023] In one embodiment, the molten solder shows a crystal formation of at most 40.0% by mass, i.e., a crystal ratio measured using X-ray diffraction and Rietveld simulation, by heat treatment of the solder at a temperature of 700 to 750°C. The crystal ratio described here relates to the crystal phase formed by heat treatment of the solder at a typical temperature for manufacturing the passivation layer. During the heat treatment, the molten solder may partially or completely melt. In one embodiment, the molten solder completely melts during the heat treatment. The crystal ratio should not be confused with the crystalline additive which is a component of the molten solder. The crystalline additive may form part of the crystalline portion, but this is not always the case. In particular, in the passivation layer, there may be a crystal phase other than the crystal phase of the crystalline additive. In one embodiment, the crystal ratio is less than 35.0% by mass, or less than 20.0% by mass. By having a low crystal ratio, crack formation in the passivation layer can be reduced. Surprisingly, by adding the aforementioned crystalline additive to the molten solder, the crystal ratio can be adjusted. In this case, as the ratio of the crystalline additive in the molten solder increases, the crystal ratio decreases.

[0024] In one embodiment, the molten solder has a low tendency to form willemite by melting the solder at a temperature of 700 to 750 °C, that is, it exhibits a ratio of up to 20% by mass of willemite measured using X-ray diffraction and Rietveld simulation. The low tendency to form willemite is advantageous for avoiding crack formation during passivation. By using the crystalline additives described in the present application in the molten solder, the above tendency is reduced.

[0025] The characteristics of the compositions discussed in the present application contribute to the advantageous properties of the molten solder. In particular, it has been found that the optimization of the contents of SiO2, ZnO and B2O3 can achieve particularly advantageous properties with respect to both the elastic modulus and the average coefficient of thermal expansion compared to polycrystalline silicon. It has been found that one or more of the following measures, or the fine-tuning of the amounts of specific components relative to each other, contribute to promoting the desirable properties according to the present invention with respect to elastic modulus, coefficient of thermal expansion, crystallization, and chemical resistance.

[0026] In one embodiment, the ratio of the total content of B2O3 and ZnO in the molten solder in mol% to the content of SiO2 is less than 7.0, or less than 5.5, in particular less than 4.0. In one embodiment, the above ratio is at least 2.0, at least 2.5, or at least 3.0.

[0027] The total content of SiO2 and ZnO in the molten solder may be at least 73.0 mol%, in particular at least 74.0 mol%. In one embodiment, the contents of these components are limited to a maximum of 85.0 mol%, a maximum of 80.0 mol%, or up to 79.0 mol% in total.

[0028] In one embodiment, the ratio of the total content of ZnO and SiO2 in the molten solder in mol% to the content of B2O3 is less than 8.0, less than 6.0, in particular less than 5.0. In one embodiment, the above ratio is at least 3.0, at least 3.5, or at least 4.0.

[0029] The molten solder material may have a ZnO content of up to 65.0 mol%, up to 63.0 mol%, or up to 61.0 mol%. In one embodiment, the content is at least 40.0 mol%, at least 42.0 mol%, or at least 45.0 mol%. This component contributes to the advantageous expansion behavior. When the ZnO content increases, the thermal expansion coefficient and elastic modulus decrease. When the content decreases, both the thermal expansion coefficient and the transition temperature Tg increase sharply.

[0030] The molten solder material may have a B2O3 content of up to 25.0 mol%, up to 23.0 mol%, or up to 22.0 mol%. In one embodiment, the content is at least 14.0 mol%, at least 15.0 mol%, or at least 16.0 mol%. This component contributes to the chemical resistance of the molten solder material. When the B2O3 content increases, the elastic modulus decreases, and the thermal expansion coefficient and transition temperature increase. When the content decreases, both the thermal expansion coefficient and the transition temperature Tg decrease sharply, and the elastic modulus increases.

[0031] In one embodiment, the molten solder material has a SiO2 content of at least 15.0 mol%, at least 16.0 mol%, or at least 16.5 mol%. The content may optionally be up to 30.0 mol%, in particular up to 28.0 mol%, or up to 27.0 mol%. If the SiO2 content is too high, it has an adverse effect on the elastic modulus and results in a high melting temperature, in particular a high Tg. When the SiO2 content increases, the elastic modulus decreases slightly, and the thermal expansion coefficient and transition temperature increase slightly. When the content decreases, the transition temperature Tg decreases slightly, and the elastic modulus increases slightly. Optionally, the ratio of the proportion of SiO2 in mole percent to the proportion of B2O3 is at least 0.75, at least 0.85, or at least 0.875. In one embodiment, the above ratio is 0.75 to 1.40, 0.80 to 1.30, or 0.85 to 1.25. In one embodiment, the above ratio is greater than 1.0, and in other embodiments, it is less than 1.0.

[0032] In one embodiment, the molten solder contains Al2O3. The content rate may be at least 0.5 mol%, at least 0.6 mol%, or at least 0.7 mol%. Optionally, the content rate is limited to a maximum of 8.0 mol%, a maximum of 7.5 mol%, or 6.0 mol%. If too much Al2O3 is used, the elastic modulus will increase. Al2O3 can be introduced via a crystalline additive, and in that case, it has the effects described for the crystalline additive in the present application.

[0033] The molten solder may contain MgO, in particular, at least 0.1 mol%, at least 0.15 mol%, or at least 0.2 mol% by proportion. In one embodiment, the content rate of MgO is limited to a maximum of 8.0 mol%, a maximum of 7.0 mol%, or a maximum of 6.0 mol%. MgO can be introduced via a crystalline additive, and in that case, it has the effects described for the crystalline additive in the present application.

[0034] In one embodiment, the molten solder and / or the glass contain at most a very small amount, in particular no amount, of specific components. For example, the content rate of Na, K, Li, Cs, Rb, Cu, Ag, Hg, Cd, Ce, Ti, Mo, Bi, V, Mn, Co, Ni, Cr and / or Fe is limited to a maximum of 100 ppm, or the molten solder may be free of these components. In one embodiment, the molten solder contains less than 1.0 mol% of Bi2O3, less than 100 ppm of PbO, less than 50 ppm of As2O3, and / or less than 50 ppm of Sb2O3.

[0035] As used herein, when it is stated that the glass or the molten solder is free of a certain component or does not contain a specific component, this means that these components can be present at most as impurities. This means that they are not added in substantial amounts and are not intentionally added. A non-essential amount is an amount less than 100 ppm, preferably less than 50 ppm, and most preferably less than 10 ppm. In one embodiment, the glass and / or the molten solder described in the present application are free of components not listed in the present application. In particular, the glass and / or the molten solder may consist of at least 90 mol%, at least 95 mol%, at least 97.5 mol%, or at least 99 mol% of SiO2, Al2O3, B2O3, ZnO, and MgO. In one embodiment, the molten solder and / or the glass are free of Bi and / or free of Cu. Optionally or additionally, the molten solder and / or the glass are free of Mo, free of Ti, and / or free of Ce.

[0036] In one embodiment, the molten solder has the following components in mol%: [Table 3]

[0037] In one embodiment, the molten solder has the following components in mol%: [Table 4]

[0038] Advantageously, the molten solder has an etching rate of less than 10.0 μm / min in 20% HNO3 at 20 °C and / or less than 15.0 μm / min in 5% HF. An etching rate that is too high may have an adverse effect on the passivation layer, because the parts to be passivated may be exposed to the action of HNO3 and / or HF for cleaning during the manufacture of semiconductor parts. In an advantageous embodiment, the etching rate in 20% HNO3 at room temperature is less than 8.5 μm / min, less than 7.5 μm / min, or less than 7.0 μm / min. The molten solder may have an etching rate of at least 2.0 μm / min or at least 3.0 μm / min in 20% HNO3 at room temperature. An advantageous molten solder exhibits an etching rate of less than 14.0 μm / min or less than 12.5 μm / min in 5% HF at room temperature. The etching rate in 5% HF at room temperature may be at least 5.0 μm / min or at least 8.0 μm / min. These etching rates have been found to be sufficient even if they do not fully reach the chemical resistance of lead-containing molten solders.

[0039] The etching rate can be measured as follows. To examine the etching rate, a sample was melted (e.g., at 650 - 750 °C), poured into a mold, cut into plates, and polished to a thickness of 3 mm. Subsequently, the sample was exposed to the above acid aqueous solution at room temperature, and the removal by etching was measured after 10 minutes. The removal by etching was determined using the mass loss and converted to the surface of the sample.

[0040] The glass transition temperature Tg of the molten solder may be at least 500 °C, at least 550 °C, at least 560 °C, or at least 570 °C. In one embodiment, Tg is 750 °C or less, less than 700 °C, less than 650 °C, or up to 600 °C. If Tg is too high, the molten solder cannot be used in a normal passivation process. The softening temperature, i.e., the temperature at which the solder has a viscosity of 10 7.6 dPas, may be in the range of 600 °C to 800 °C, particularly in the range of 700 °C to 800 °C, and advantageously above 750 °C.

[0041] To minimize jumps and discontinuities in the evolution of the electric field, it is better to keep the difference in relative permittivity (ε r ) between the semiconductor material and the molten solder as small as possible. The relative permittivity (ε Si ) of crystalline silicon is 11.68. Preferably, the absolute value of the difference in relative permittivity between silicon and the molten solder, |ε r - ε Si | is less than 6.0, less than 5.0, or less than 4.0.

[0042] · Glass In a further aspect, the invention relates to a glass in the form of glass powder comprising the following components:

Table 5

[0043] The glass may be the glass that forms the glass portion in the molten solder described above. In one embodiment, the glass has no crystalline additives.

[0044] The glass exists in powder form. It has been found that the choice of particle size and particle size distribution affects the formation of the crystal phase when producing a passivation layer on a semiconductor component. Furthermore, the choice of particle size and its distribution can affect acid resistance and the formation of gaps. In one embodiment, the invention relates to a glass having a particle size distribution characterized in that the span (d90 - d10) / d50 is at least 1.00, in particular at least 1.80. The larger the span, the better the packing density, and thereby the tendency of the glass to form gaps between the layer and the semiconductor component during melting during the formation of the passivation layer is reduced. However, the span should not be too large, because it can reduce acid resistance. The span 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.

[0045] In one embodiment, the average particle size d50 of the glass is from 1.0 μm to 10.0 μm, in particular from 1.5 μm to 5.0 μm or from 2.0 μm to 3.0 μm. This particle size has been shown to advantageously combine with the above-mentioned span to provide optimal results with respect to acid resistance, crystal formation and shrinkage during passivation.

[0046] In one embodiment, the volume fraction of particles having a size of less than 1.0 mm is limited to a maximum of 30% by volume of the glass, in particular a maximum of 27.0% by volume of the glass, or a maximum of 20.0% by volume. This results in better acid resistance and fewer gaps in the passivation layer.

[0047] In one embodiment, the average thermal expansion coefficient of the glass is less than 4.5×10 -6 K -1 in the temperature range from 20 °C to 300 °C, or less than 4.10×10 -6 K -1 in particular from 3.50 to 4.10 ppm / K, preferably less than 3.5×10 -6 K -1exceeds. The coefficient of thermal expansion is measured, in particular for a 5×5×50 mm sample, by melting the glass at a temperature of 700 to 750 °C. This coefficient of thermal expansion has been shown to be well adapted to the expansion coefficient of silicon in order to avoid cracks in the passivation layer.

[0048] In one embodiment, the glass exhibits an average coefficient of thermal expansion that differs by no more than 0.90 ppm / K from the average coefficient of thermal expansion of polycrystalline silicon over a temperature range of 300 °C to Tg - 20 °C, where Tg is the glass transition temperature of the glass, and the coefficient of thermal expansion can be measured by melting the glass at a temperature of 700 to 750 °C for a 5×5×50 mm sample.

[0049] Regarding the average coefficient of thermal expansion of the glass, the temperature range of 300 °C to Tg is particularly important. Here, the upper limit of Tg - 20 °C is selected because accurate measurement at exactly Tg only gives inaccurate results. As is clear from FIG. 1, in the temperature range up to 300 °C, the expansion coefficients of various glasses or solder glasses and semiconductor materials are still generally the same. From 300 °C onwards, it becomes more difficult to limit the deviation in the expansion coefficient. For the glass of the present invention, in particular in the range near Tg which is at least 550 °C, the expansion coefficients completely deviate. Above Tg, the difference in the coefficient of thermal expansion is irrelevant because above Tg the glass is ductile. Advantageously, the glass can have an average coefficient of thermal expansion that differs from the average coefficient of thermal expansion of polycrystalline silicon by only 0.75×10 -6 K -1 or less. A certain difference compared to polycrystalline silicon in the average coefficient of thermal expansion of the glass is unavoidable. The difference in the average coefficient of thermal expansion can be at least 0.10×10 -6 / K or at least 0.30×10 -6 / K. Such differences in the expansion behavior are still acceptable based on the adjusted modulus of elasticity. The thermal expansion behavior of polycrystalline silicon is known to those skilled in the art. This can also be seen in FIG. 1.

[0050] In a preferred embodiment, the molten solder material has an average coefficient of thermal expansion of 0.2×10 -6 K -1 ~1.0×10 -6 K -1 in the temperature range of 300 °C to Tg - 20 °C.

[0051] The glass can have a transition temperature Tg of at least 550 °C, at least 560 °C, or at least 570 °C.

[0052] Advantageously, the glass has an etching rate of less than 10.0 μm / min in 20% HNO3 at 20 °C and / or less than 15.0 μm / min in 5% HF. An etching rate that is too high can have an adverse effect on the passivation layer, because the parts to be passivated may be exposed to the action of HNO3 and / or HF for cleaning during the manufacture of semiconductor parts. In a preferred embodiment, the etching rate in 20% HNO3 at room temperature is less than 8.5 μm / min, less than 7.5 μm / min, or less than 7.0 μm / min. The glass can have an etching rate of at least 2.0 μm / min or at least 3.0 μm / min in 20% HNO3 at room temperature. A preferred glass exhibits an etching rate of less than 14.0 μm / min or less than 12.5 μm / min in 5% HF at room temperature. The etching rate in 5% HF at room temperature can be at least 5.0 μm / min or at least 8.0 μm / min. These etching rates have been found to be sufficient even if they do not fully achieve the chemical resistance of lead-containing molten solder materials.

[0053] The etching rate can be measured as follows. To examine the etching rate, the sample was melted (e.g., at 650 - 750 °C), poured into a mold, cut into plates, and polished to a thickness of 3 mm. Subsequently, the sample was exposed to the above acid aqueous solution at room temperature, and the removal by etching was measured after 10 minutes. The removal by etching was determined using the mass loss and converted to the surface of the sample.

[0054] The features of the composition discussed in the present application contribute to the advantageous properties of the glass. In particular, it has been found that optimizing the contents of SiO2, ZnO, and B2O3 can achieve particularly advantageous properties with respect to both the modulus of elasticity and the average coefficient of thermal expansion compared to polycrystalline silicon. It has been found that one or more of the following measures, or fine-tuning the amounts of specific components relative to each other, contribute to promoting the desired properties according to the present invention with respect to the modulus of elasticity, the coefficient of thermal expansion, crystallization, and chemical resistance.

[0055] In one embodiment, the glass the ratio of the total content of B2O3 and ZnO in mol% to the content of SiO2 is less than 7.0, or less than 5.5, in particular less than 4.0. In one embodiment, the above ratio is at least 2.0, at least 2.5, or at least 3.0.

[0056] The total content of SiO2 and ZnO in the glass may be at least 73.0 mol%, in particular at least 74.0 mol%. In one embodiment, the contents of these components are limited to a maximum of 85.0 mol%, a maximum of 80.0 mol%, or up to 79.0 mol% in total.

[0057] In one embodiment, the ratio of the total content of ZnO and SiO2 in mol% to the content of B2O3 in the glass is less than 8.0, or less than 6.0, in particular less than 5.0. In one embodiment, the above ratio is at least 3.0, at least 3.5, or at least 4.0.

[0058] The glass may have a ZnO content of up to 65.0 mol%, up to 63.0 mol%, or up to 61.0 mol%. In one embodiment, the content is at least 40.0 mol%, at least 42.0 mol%, or at least 45.0 mol%. This component contributes to an advantageous expansion behavior. As the ZnO content increases, the coefficient of thermal expansion and the modulus of elasticity decrease. As the content decreases, the coefficient of thermal expansion and the transition temperature Tg increase sharply.

[0059] The glass may have a B2O3 content of up to 25.0 mol%, up to 23.0 mol%, or up to 22.0 mol%. In one embodiment, the content is at least 14.0 mol%, at least 15.0 mol%, or at least 16.0 mol%. This component contributes to the chemical resistance of the glass. As the B2O3 content increases, the elastic modulus decreases, and the coefficient of thermal expansion and transition temperature increase. As the content decreases, both the coefficient of thermal expansion and the transition temperature Tg decrease sharply, and the elastic modulus increases.

[0060] In one embodiment, the glass has a SiO2 content of at least 15.0 mol%, at least 16.0 mol%, or at least 16.5 mol%. The content may optionally be up to 30.0 mol%, particularly up to 28.0 mol%, or up to 27.0 mol%. If the SiO2 content is too high, it will have an adverse effect on the elastic modulus and result in a high melting temperature, particularly a high Tg. As the SiO2 content increases, the elastic modulus decreases slightly, and the coefficient of thermal expansion and transition temperature increase slightly. As the content decreases, the transition temperature Tg decreases slightly, and the elastic modulus increases slightly. Optionally, the ratio of the percentage of SiO2 to the percentage of B2O3 in mole percent is at least 0.75, at least 0.85, or at least 0.875. In one embodiment, the above ratio is 0.75 - 1.40, 0.80 - 1.30, or 0.85 - 1.25. In one embodiment, the above ratio is greater than 1.0, and in other embodiments, it is less than 1.0.

[0061] In one embodiment, the glass contains Al2O3. The content may be at least 0.0 mol%, at least 0.5 mol%, at least 0.6 mol%, or at least 0.7 mol%. Optionally, the content is limited to a maximum of 8.0 mol%, a maximum of 7.5 mol%, or up to 6.0 mol%. If too much Al2O3 is used, the elastic modulus will increase.

[0062] The glass may contain MgO in a proportion of at least 0.0 mol%, at least 0.1 mol%, or at least 0.2 mol% in particular. In one embodiment, the content rate of MgO is limited to a maximum of 8.0 mol%, a maximum of 7.0 mol%, or a maximum of 6.0 mol%. In one embodiment, the glass is free of MgO.

[0063] In one embodiment, the glass contains a particular component at most in a very small amount, or in particular does not contain it at all. For example, the content rate of Na, K, Li, Cs, Rb, Cu, Ag, Hg, Cd, Cr and / or Fe is limited to a maximum of 100 ppm, or the glass may be free of these components. In one embodiment, the glass contains less than 1.0 mol% of Bi2O3, less than 100 ppm of PbO, less than 50 ppm of As2O3, and / or less than 50 ppm of Sb2O3.

[0064] The glass transition temperature Tg of the glass may be at least 500 °C, or at least 550 °C. In one embodiment, Tg is 750 °C or less, less than 700 °C, less than 650 °C, or up to 600 °C. If Tg is too high, the glass cannot be used in a normal passivation process. The softening temperature, that is, the temperature at which the glass has a viscosity of 10 7.6 dPas may be in the range of 600 °C to 800 °C, in particular in the range of 700 °C to 800 °C, and preferably above 750 °C.

[0065] Furthermore, when using the glass and / or the molten solder of the present invention, it has been found that a positive leakage current occurs through the volume of the passivation layer. This current is suitable for avoiding the electric field peak. Therefore, unlike the leakage current at the interface between the passivation layer and the semiconductor, this leakage current is advantageous. Since it drops to 1.6 kV at the pn junction, a high electric field strength occurs in a very small region. The glass and the molten solder of the present invention meet this requirement.

[0066] In order to minimize jumps and discontinuities in the transition of the electric field, the relative permittivity (ε between the semiconductor material and the glassr ) The difference in Si is preferably kept as small as possible. The relative dielectric constant (ε r ) of crystalline silicon is 11.68. Preferably, the absolute value of the difference in relative dielectric constant between silicon and the molten brazing material, |ε Si - ε

[0067] · Use, method and semiconductor component The use of the glass described in the present application or the molten brazing material described in the present application for the passivation treatment of semiconductor components, in particular silicon wafers, thyristors, varistors or diodes, is also according to the present invention.

[0068] The present invention also includes semiconductor components, in particular wafers or diodes, comprising at least one passivation layer made of the glass described in the present application or the molten brazing material described in the present application. The passivation layer can in particular be applied with a thickness of 10 - 100 μm, in particular 20 μm - 80 μm, or 20 - 50 mm.

[0069] In one embodiment, the present invention is a method for manufacturing a passivated semiconductor component, comprising the following steps: · Preparing a semiconductor component, in particular a wafer, thyristor, varistor or diode; · Heat-treating, in particular melting, the glass or molten brazing material described in the present application to provide at least one passivation layer including the above method.

[0070] In one embodiment, the temperature during the heat treatment is in the range of 600 °C to <800 °C, in particular 625 °C to 750 °C. These high temperatures have a beneficial effect on chemical resistance because they result in a homogeneous melt and the breakdown of grain boundaries, thereby reducing the attack surface for acids.

[0071] The glass and / or fusible filler may be mixed with highly dispersed silicon dioxide as a stabilizer before manufacturing the passivation layer in order to avoid precipitation of the passivation agent in a mixture with water. Optionally or additionally, nitrates can be added to promote burnout of the binder.

Brief Description of the Drawings

[0072]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

Examples

[0073] The above particle size and particle size distribution were measured by dynamic light scattering.

[0074] · Glass The following table shows Glass A and B according to the present invention, and various comparative glasses from the prior art in mol%. The glasses do not have a crystalline part.

[0075]

Table 6

[0076] The measurement of the coefficient of thermal expansion CTE was carried out with the remelted powder. At that time, the sample was melted as a slightly compressed bar material at 650 - 750 °C. The sample obtained therefrom was cut into a bar shape and polished. The final size was 5 × 5 × 50 mm. The measurement was carried out in air at a heating rate of 5 K / min.

[0077] · Brazing filler metal The following table shows the melting brazing filler metals A - C according to the present invention and the melting brazing filler metals of the prior art in mol%.

[0078]

Table 7

[0079] The measurement of the coefficient of thermal expansion CTE was carried out with the remelted powder. At that time, the sample was melted as a slightly compressed bar material at 650 - 750 °C. The sample obtained therefrom was cut into a bar shape and polished. The final size was 5 × 5 × 50 mm. The measurement was carried out in air at a heating rate of 5 K / min.

[0080] · Coefficient of thermal expansion The following table shows the coefficients of thermal expansion of the glasses and melting brazing filler metals of the present invention compared to silicon.

[0081]

Table 8

[0082] Figure 1 specifically shows the coefficients of thermal expansion of the glass and solder according to the present invention, compared to silicon and to conventional bismuth-containing glasses. The glass according to the present invention has a significantly smaller deviation in the coefficient of thermal expansion compared to silicon, especially in the vicinity of Tg (about 571 °C), and this is without the risk of bismuth elements during passivation.

[0083] · Etching rate The following table shows the calculated etching rates of the glass according to the present invention and the glass of the prior art. To calculate the etching rate, the samples were melted at the above melting temperature, poured into a mold, cut into plates, and polished to a thickness of 3 mm. Subsequently, the samples were exposed to the above acid aqueous solution at room temperature, and after 10 minutes, the removal by etching was measured. The removal by etching was determined using the mass loss and converted to the surface of the sample.

[0084]

Table 9

[0085] From the comparison between Glass A and Glass B, it can be seen that the smaller the particle size, the lower the etching rate, especially in HNO3. Furthermore, it is shown that the crystalline additive improves the acid resistance.

[0086] · Crystalline phase The addition of a crystalline additive to the solder (here in the form of magnesium aluminum silicate Mg2Al4Si5O 18 was investigated as to how it affected the composition of the passivation layer produced from the molten solder. The crystalline phase in the passivation layer was measured by XRD analysis (XRD diffraction) on the melted samples. The melting temperature was 700 - 750 °C. The quantitative measurement of each crystalline phase was carried out via Rietveld simulation. The proportion of amorphous was calculated by comparison with an internal standard CaF2 having a known crystalline phase (spiking method). The results are shown in the following table.

[0087]

Table 10

[0088] It was found that the proportion of amorphous in the sample increased due to the addition of magnesium and aluminum. A strong correlation between the proportion of the filler containing magnesium and aluminum and the proportion of amorphous is shown in Fig. 5A. Fig. 5B shows the influence of the amount of crystalline additive on the proportion of willemite. Glass C was not remelted. In the case of glass C, crystallization did not occur.

[0089] When the proportion of the amorphous phase in the crystal phase is high and especially the proportion of willemite is low, it is considered to affect the formation of cracks during the passivation of the semiconductor. For example, when the proportion of the amorphous phase is low, the formation of cracks was observed. When the proportion of amorphous is higher, for example, 66% or more, cracks were not observed. The inventors believe that the formation of different crystal phases impairs the homogeneity of the solder. Furthermore, since the crystal phase has a higher density than glass, holes are formed during cooling, which may impair the mechanical stability. Therefore, a higher proportion of amorphous is preferred.

[0090] · Dynamic differential scanning calorimetry (DSC) An investigation was made on how much the particle size of the glass or solder affects its crystallization behavior. The investigation was carried out using dynamic differential scanning calorimetry (DSC). The following table lists the temperatures at which peaks or shoulders were formed in the DSC curve based on exothermic crystallization. Fig. 6 shows the graph. As the temperature profile, 500 °C at 10 K / min and then 770 °C at 5 K / min were selected to be as close as possible to the process steps in the semiconductor industry.

[0091]

Table 11

[0092] The data indicate that the particle size has an impact on the formation of the crystal phase. In the case of a sample having a particle size of 1.5 μm, strong shrinkage occurred during the passivation of the semiconductor. There is a possibility that a crystal phase with a very high density is formed. The strong shrinkage results in voids between the passivation layer and the semiconductor. The use of larger particles, the limitation of particles less than <1.0 μm, and / or the use of glass or solder having a larger span can probably avoid or reduce this effect.

[0093] · Packing density A high packing density is advantageous because, in the case of a high packing density, there is less shrinkage during melting. Greater shrinkage results in more voids between the passivation layer and the semiconductor. Figure 4 shows the packing densities of various glasses and solders according to Andreasen, A.H.M.: On the stepwise change of particles and the relationship to the voids in the product from loose particles (along with some experiments), Kolloid-Zeitschrift, 1930. 50: pages 217 - 228. It can be seen that the larger the powder, the better the achievable packing density.

Claims

1. The following components: 【Table 1】 A glass powder having the following in mol%, wherein the total content of SiO₂ and ZnO in the glass is at least 73.0 mol%, and the ratio of (B₂O₃ + ZnO) / SiO₂ is at least 3.0, said glass powder, Magnesium aluminum silicate which is a crystalline additive In a fusion solder material having, said solder material, The following components: 【Table 2】 Having in mol% and said solder material having said crystalline additive in a proportion of at least 1.0% by volume, said solder material.

2. The fusion solder material according to claim 1, wherein the proportion of said crystalline additive is at least 3.0% by volume and / or up to 25.0% by volume.

3. The fusion solder material according to claim 1 or 2, wherein said crystalline additive has the following components: 【Table 3】 Having in mass%.

4. wherein the crystalline additive is Mg 2 Al 4 Si 5 O 18 The fusion brazing filler metal according to any one of claims 1 to 3, which is as described above.

5. The fusion solder material according to any one of claims 1 to 4, which is in the form of a powder.

6. Having a particle size distribution characterized in that the span (d90 - d10) / d50 is at least 1.00, especially at least 1.80, the fusion solder material according to claim 5.

7. The fusion solder material according to claim 6, wherein said span is at most 6.00, especially at most 3.

00.

8. Having an average particle size d50 of 1.0 μm to 10.0 μm, especially 2.0 to 3.0 μm, the fusion solder material according to any one of claims 5 to 7.

9. Measured by melting the solder material at a temperature of 700 to 750 °C with a 5 × 5 × 50 mm sample, having an average coefficient of thermal expansion in the temperature range of 20 °C to 300 °C in the range of 3.50 ppm / K or more and less than 4.50 ppm / K, the fusion solder material according to any one of claims 1 to 8.

10. Having an average coefficient of thermal expansion that differs from the average coefficient of thermal expansion of polycrystalline silicon by 0.50 ppm / K or less over the temperature range of 300 °C to Tg - 20 °C, where Tg is the transition temperature of the glass portion contained in the solder material, and said coefficient of thermal expansion is measured by melting the solder material at a temperature of 700 to 750 °C with a 5 × 5 × 50 mm sample, the fusion solder material according to any one of claims 1 to 9.

11. Having a proportion of crystals of at most 40% by mass measured by melting the solder material at a temperature of 700 to 750 °C with little crystal formation, that is, using X-ray diffraction and Rietveld simulation, the fusion solder material according to any one of claims 1 to 10.

12. A fusion brazing filler metal according to any one of claims 1 to 11, which has a low tendency to form willemite by melting the brazing filler metal at a temperature of 700 to 750 °C, that is, has a ratio of willemite of at most 20% by mass as measured using X-ray diffraction and Rietveld simulation.

13. A fusion brazing filler metal according to any one of claims 1 to 12, which has a ratio of glass of at least 75.0% by volume and / or at most 99.0% by volume.

14. The brazing filler metal having the following components: 【Table 4】 A fusion brazing filler metal according to any one of claims 1 to 13, which has [the components] in mol%.

15. At 20 °C, less than 10.0 µm / min in 20% HNO 3 The brazing filler metal according to any one of claims 1 to 14, having an etching rate of less than 15.0 µm / min in 5% HF and / or less than 10.0 µm / min in 20% HNO

16. The following components: 【Table 5】 A glass powder having a particle size distribution characterized in that the span (d90 - d10) / d50 is at least 1.00, in particular at least 1.80, and has [the components] in mol%, wherein the total content rate of SiO 2 and ZnO is at least 73.0 mol%, and the ratio of (B 2 O 3 + ZnO) / SiO 2 is at least 3.

0.

17. The glass powder according to claim 16, wherein the span is at most 6.00, in particular at most 3.

00.

18. The glass powder according to claim 16 or 17, which has an average particle size d50 of 1.0 μm to 10.0 μm, in particular 2.0 to 3.0 μm.

19. Having an average thermal expansion coefficient that differs from the average thermal expansion coefficient of polycrystalline silicon by 0.90 ppm / K or less, in particular 0.75 ppm / K or less, over a temperature range of 300 °C to Tg - 20 °C, where Tg is the glass transition temperature, and the thermal expansion coefficient is measured by melting the glass at a temperature of 700 to 750 °C in a 5 × 5 × 50 mm sample. The glass powder according to any one of claims 16 to 18.

20. The glass powder according to any one of claims 16 to 19, which has a transition temperature Tg of at least 550 °C.

21. At 20 °C, less than 20.0 µm / min in 20% HNO 3 The glass powder according to any one of claims 16 to 20, having an etching rate of less than 15.0 µm / min in 5% HF and / or less than 20.0 µm / min in 20% HNO.

22. The glass powder or fusion brazing filler metal according to any one of claims 1 to 21, which has Na, K, Li, Cs, Rb, Cu, Hg, Cd, Cr and / or Fe in a ratio of at most 100 ppm.

23. Less than 1.0 mol% of Bi 2 O 3 , less than 100 ppm of PbO, less than 50 ppm of As 2 O 3 , and / or less than 50 ppm of Sb 2 O 3 The glass powder or fusion solder according to any one of claims 1 to 22, having the above composition.

24. Use of the glass powder or fusion brazing filler metal according to any one of claims 1 to 23 for passivation treatment of semiconductor components, in particular silicon wafers, thyristors, varistors or diodes.

25. A semiconductor component, in particular a wafer, thyristor, varistor or diode, comprising a passivation layer made of glass powder or a fused solder according to any one of claims 1 to 23.

26. A method for manufacturing a passivated semiconductor component, comprising the following steps: - preparing a semiconductor component, in particular a wafer, thyristor, varistor or diode; - heat-treating the glass powder or the fused solder according to any one of claims 1 to 23 to provide a passivation layer. The method as described above.

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