JP2000086346A - Ceramic substrate - Google Patents

Abstract

(57) [Problem] To reduce the amount of deformation generated during heat treatment of a ceramic substrate at a high temperature. SOLUTION: The detection strength of a sintering aid component element with respect to the detection strength of a main component element on one main surface side and the other main surface side of the ceramic base material containing a sintering aid by fluorescent X-rays Are provided as a and b, respectively, and when a> b, a / b ≦ 1.3 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic base material containing a sintering aid as a subsidiary component, and more particularly to a ceramic base material having the same component uniformly distributed and having a small thermal deformation.

[0002]

2. Description of the Related Art Conventionally, sintering aids have been added to sintering ceramics in order to facilitate the sintering. In particular, when the main component is a non-oxide such as a nitride or carbide, a sintering aid is indispensable for obtaining a dense material due to its difficulty in sintering. In particular, ceramics containing nitride as a main component, such as aluminum nitride and silicon nitride, cannot be densified by themselves without sintering under high temperature and high pressure. Therefore, in this type of ceramics, the sintering aid plays a large role. For example, in the case of aluminum nitride ceramics whose main component is aluminum nitride, JP-A-63-190761,
JP-A-61-10071, JP-A-60-7157
No. 5, JP-A-2666942 and the like, it has been conventionally known to use an alkaline earth (IIa) element compound or a rare earth element.
(Group IIIa) elemental compounds have been commonly used. The same applies to silicon nitride ceramics. These components react with impurities in the main component during sintering to melt and promote densification, and finally form a grain boundary phase of the main component crystal grains.

In order to obtain a homogeneous ceramic sintered body, it is necessary to uniformly distribute the grain boundary phase containing a sintering aid component throughout the sintered body. For this reason, various measures such as reducing the amount of the auxiliary component and uniformly mixing the raw material powder have been considered. For example, (1) Tokuho 7
According to JP-A-121829, a molded body containing a sintering aid is buried in carbon and fired for a long time of 4 hours or more to reduce the amount of residual sintering aid to a minimum and achieve high heat conduction. We are trying to obtain a rate and homogenize the whole. According to (2) JP-A-1-203270,
A small amount of fine organic metal salt is added to the sintering aid to make the mixing of the raw material components uniform.

However, in the method (1), the sintering aid is largely evaporated from the surface of the sintered body by firing for a long time, and the distribution in the sintered body after burning becomes uneven. In addition, the energy cost becomes large. In the method (2), firing at a high temperature is necessary because the amount of the sintering aid is small from the beginning. As a result, similar problems are likely to occur. For ceramics, such as aluminum nitride ceramics and silicon nitride ceramics, for which the use of sintering aids is essential for their densification, their practical characteristics have been improved.
Research has been focused on sintering aids for improving the thermal conductivity of aluminum nitride ceramics and increasing the strength of silicon nitride ceramics, for example. Therefore, a great deal of research has been done on various sintering aids and the control of their amounts. However, there are few studies for distributing the sintering aid components uniformly, and no satisfactory results have yet been obtained.

[0005]

As a result of repeated studies focusing on this point, the present inventors have found that if the distribution of the sintering aid component in the sintered body is not sufficiently uniform, It was confirmed that the deformation promoted the deformation of the sintered body. In particular, in the case of ceramics containing nitride as a main component, it was confirmed that deformation was easily caused by heat treatment in an oxidizing atmosphere.
If the ceramic substrate is a thin plate as sintered,
The amount of warpage at the time of sintering increases. Further, in the case of a plate-shaped base material, even if both main surfaces are ground in parallel, warpage recurs due to the subsequent heat treatment. For example, when manufacturing a substrate for a hybrid IC using a thin plate of aluminum nitride ceramics, Ag, Ag-Pd, Cu
When a thick film circuit pattern containing such components was formed and then an oxide glass insulating layer was printed by paste and baked in the air, an increase in the amount of warpage of the ceramic substrate was confirmed. The present invention has been made based on such findings, and an object of the present invention is to homogenize the distribution of the sintering aid in the ceramic substrate after sintering, and thereby to achieve the above-described post-sintering. The purpose is to reduce the amount of deformation increased by the heat treatment.

[0006]

In order to solve the above problems, the ceramic substrate provided by the present invention has a small difference between the amount of the sintering aid on one main surface and that on the other main surface. Things. That is, the ceramic base material of the present invention contains a sintering aid, and the detection intensity of the sintering aid component element relative to the detection intensity of the main component element on one main surface side and the other main surface side by fluorescent X-rays. The ratios are a and b, respectively,
When a> b, the ceramic base material satisfies a / b ≦ 1.3. Therefore, the difference in the amount of the sintering aid component between the two main surfaces of the ceramic substrate of the present invention is within 30%.

[0007] Among them, the above-mentioned base material in which the main component of ceramics is nitride, and the same base material in which the ceramics are aluminum nitride ceramics.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the ceramic substrate provided by the present invention contains a sintering aid, and the difference between the amount of the sintering aid on one main surface side and that on the other main surface side. Is within 30%. The sintering aid amount in the present invention is indicated by a ratio of the combined intensity of the fluorescent X-ray peaks of the component elements constituting the sintering aid to the same intensity of the main component element. Although this original data is not a chemical analysis value, within the range confirmed by us, if the intensity ratio (that is, equivalent to the amount ratio) is taken between individuals within the same individual and between individuals within the same production lot, the fluorescent X-ray peak There is almost no difference between the strength and the chemical analysis value, and it is considered that there is not much problem.

The procedure for confirming the peak intensity ratio of fluorescent X-rays will be described below with reference to examples. For example, in the case of an aluminum nitride ceramics sintered body to which yttrium oxide (Y ₂ O ₃ ) is added as a sintering aid, the peak intensity (count number or Assuming that Y is the area of the recording peak) and X is the same strength of the Al element of aluminum nitride as the main component, the amount of the sintering aid (that is, the amount corresponding to the concentration of the sintering aid at the measurement point)
Is represented by Y / (X + Y). When calcium oxide (CaO) and yttrium oxide (Y ₂ O ₃ ) are combined as sintering aids with aluminum nitride ceramics, for example, the fluorescent X-ray peak intensities of the Ca element are Y ₁ , Y 2
Assuming that the same strength of the element is Y ₂ and the same strength of the main element Al is X, the amount of the sintering aid is represented by (Y ₁ + Y ₂ ) / (X + Y ₁ + Y ₂ ). Hereinafter, even if there are many sintering aid components, assuming that the sum of the peak intensities of all the component elements is ΔY, ΔY
/ (X + ΣY).

In the sintered body, a reaction compound is usually formed between a part of the main component or an impurity element contained in the main component and the sintering aid component (for example, the main component is aluminum nitride, If the sintering aid is yttrium oxide, yttrium aluminate, if calcium oxide and yttrium oxide are sintering aids, yttrium aluminate, calcium aluminate, yttrium calcium aluminate, etc. are produced as compounds) In the calculation of the amount of the sintering aid of the present invention, the amount of the sintering aid is expressed as the abundance of the same component element regardless of the formation of the compound. The peak of the fluorescent X-ray used should be the one having the maximum intensity. When a large number of auxiliaries are contained and their peak positions overlap each other, the peak intensity value of the overlapping sintering aid component element is set to the above Y value. Will be substituted for the value of If the peak position of the main component element and the peak position of the auxiliary sintering agent component overlap, for convenience, the overlapping peak intensity values are distributed by the weight ratio of the main component and the sintering auxiliary at the time of blending, The strength distribution value of the main component element and that of the sintering aid component element are used as respective strength data numerical values.

As described above, in the case of a ceramic base material containing a sintering aid, the difference between the amount of the sintering aid on one main surface side and that on the other main surface side becomes large, so that after heat treatment, The phenomenon of increase in the amount of deformation occurs in the sintered body. For example, in the case of a plate-shaped substrate having two main surfaces as described above, the warpage at the time of sintering is further increased by the subsequent heat treatment due to the difference in the amount of the sintering aid component between the two main surfaces. The degree of deformation is affected by the size of the main surface of the base material and the shape of the base material, but also increases with the number of firings. According to our confirmation, when the difference in amount exceeds 30%, the degree of deformation (for example, warpage in a plate-like base material) increases remarkably,
If the difference is within 30%, the increase in deformation is generally small. If the difference is within 15%, the amount of deformation increase is particularly small, which is more preferable. In other words, the ceramic base material of the present invention contains a sintering aid, and the detection intensity of the sintering aid component element relative to the detection intensity of the main component element on one main surface side and the other main surface side by X-ray fluorescence. Are a and b, respectively, and when a> b, a / b ≦
By using the ceramic base material of 1.3, an increase in the amount of deformation due to heat treatment after sintering can be reduced. In particular, by using a ceramic base material that satisfies a / b ≦ 1.15, the increase in the amount of deformation can be further reduced.

Although the mechanism is not clear, it appears particularly when the non-oxide ceramics sintered body is heat-treated in an oxidizing atmosphere. It is thought to promote deformation of the substrate. For example, it is supposed that a difference occurs in the oxidation rate of the substrate. Moreover, it has been confirmed by us that it appears remarkably in the case of non-oxide ceramics, especially in the case of ceramics mainly containing nitride. This is because, in the case of ceramics containing nitride as a main component, the sintering atmosphere is a non-oxidizing atmosphere, so that the added oxide-based sintering aid is easily volatilized. Therefore, it is presumed that a difference in the concentration of the sintering aid easily occurs in the sintering base material. Incidentally, when silicon carbide ceramics and silicon nitride ceramics are compared, the latter phenomenon appears more remarkably. Among the nitrides, it is particularly remarkable in aluminum nitride ceramics.

[0013] Such a phenomenon depends on the sintering method of the sintered body. Hereinafter, the method for producing a ceramic substrate of the present invention will be described. First, a first method for reducing the bias in the distribution of the amount of the sintering aid is to insert a setter between individual compacts when the compacts are charged for sintering. As the setter, a gas-permeable high-melting-point metal or high-melting-point ceramic, which does not react with the sintered component under the sintering conditions and does not soften and deform, is used. This reduces the difference in the rate of volatilization of the sintering aid between the overlapped surface and the surface directly exposed to the atmosphere, compared to the case of sintering a large number of compacts in direct contact with each other. The difference in the amount of the sintering aid after sintering can be reduced. In this case, the compacts and the setters are alternately overlapped, and the setter is also placed on the uppermost portion, so that both surfaces of all the compacts are brought into contact with the setters. As a result, the sintering aid that seeps on both surfaces of the molded article can be absorbed to the same extent.

In order to suppress the deformation of the compact during sintering, it is desirable that the surface of the setter is smooth and the whole surface has little undulation or unevenness. The surface roughness of the actual portion may be set to a level comparable to the surface roughness to be obtained by the sintered body. Although it depends on the use of the substrate, when the substrate is used as a substrate for mounting a semiconductor device, it is usually desirable that the surface roughness be 5 μm or less in Rmax. As such a setter material, for example, a high melting point metal such as tungsten or molybdenum or a carbonaceous material is used. As the form of the setter, it is most desirable to use a short-fiber-shaped one which is bundled, or a wool or cloth which contains a ceramic component which does not react with the molded body at high temperature and which is stable, and is press-molded. Depending on the size and shape of the molded body, a molded sheet made of nitride ceramics such as porous boron nitride (BN) that is stable at high temperatures, It is also possible to interpose a gas-permeable plate material that has been opened.

A second method for reducing the bias in the distribution of the amount of the sintering aid is that, when individual compacts are over-fired, they do not react with the compact under sintering conditions between their overlapping surfaces. This is a method of sintering by embedding in a powder material (for example, a material containing the above-described components) or a pure main component powder of a molded body. In this case, it is desirable to dispose a setter of the same material or a sheet of the same material, which has a low bulk density and can maintain its shape during firing, for the purpose of holding the load of the set of molded bodies. In this case, a thin layer of a setter material that does not react with the molded bodies may be formed in advance between the individual molded bodies. By doing so, the contact state of the atmosphere gas between the surface of the molded body exposed to the atmosphere and the surface of the molded body opposed to each other is leveled, and both surfaces are substantially uniform in atmosphere and heated. Condition.

According to the first and second sintering methods, the value of a / b of the sintered body is set to 1.30 or less regardless of the size.
Further, in the case of a molded article having a relatively small size, the value of a / b can be reduced to 1.15 or less. Further, it is also effective to almost stop the flow of the atmosphere gas at a temperature equal to or higher than the melting point of the sintering aid or to reduce the supply rate of the gas from the outside to reduce the influence of the flow of the atmosphere gas. For example, the molded body is charged in the above-described manner, and when the temperature reaches a temperature equal to or higher than the melting point of the compound containing the sintering aid, the flow rate of the atmospheric gas is reduced. For example, in the continuous feed type nitrogen gas normal pressure sintering, in the case of aluminum nitride ceramics, the gas flow rate at the time of temperature rise is about 20 to 50 liters / minute, but the flow rate is higher than the melting point of the sintering aid. Is desirably reduced to about 5 to 30% of that (ratio of the gas flow rate above the melting point of the sintering aid to the gas flow rate when the temperature is raised). In this case, the gas pressure in the furnace is kept substantially at atmospheric pressure. It is desirable that r be the same for other ceramics. By using the first and second charging methods and the atmosphere conditions together, the deviation can be reduced to 20% or less irrespective of the size of the compact and to 10% or less for small sizes. The setter used in the sintering of the present invention has a long life and can withstand repeated use.

Various means for obtaining the substrate of the present invention can be considered in addition to the above. For example, it is possible to devise the charging method and firing conditions according to the shape and processing amount of the molded body.
In short, in addition to controlling the atmosphere and temperature conditions that affect the balance of the movement of the sintering aid component after melting into and out of the compact, the uniformity of the material on each surface of the compact and the surrounding material Any appropriate means of realizing the interaction should be struck. The method for producing a ceramic substrate provided by the present invention may be any means that satisfies this basic principle,
The present invention is not limited to the above-described manufacturing method and the embodiments described below.

The procedure for confirming the amount of warpage of the ceramic substrate according to the present invention is as follows. Specifically, the ceramic substrate 1 is placed on a surface plate 2 as shown in FIG. The transmission is performed, and this is scanned from the end of the base material 1 in the diagonal direction (or in the case of a circular or elliptical main surface in the diametrical direction or the major diameter direction) to continuously check the distance d. The maximum difference dmax of the distance d is weighed to the order of μm (for example, in FIG.
a, and if d is the minimum at the position of b, when the value is db, dmax becomes da-db). The value obtained by dividing the dmax value by the entire scanning distance (in mm, for example, if L is a diagonal direction in the drawing, its length) was defined as the amount of warpage (unit: μm / mm).

In the present invention, when measuring the warpage immediately after sintering, it is intended that the warp be measured as it is in principle. However, when the surface roughness of the same sintered surface is large, both surfaces are easily polished and the surface roughness is 0.3 μm in Ra.
The following are targets. The simple polishing was
This is because if the degree of finish in polishing is increased, the state of warpage in sintering may change.

[0020]

EXAMPLES (Example 1) Aluminum nitride (AlN) powder, silicon nitride (Si ₃ N ₄ ) powder and aluminum oxide (Al
₂ O ₃ ) powder as a sintering aid component having an average particle size of 0.6 μm
Y ₂ O ₃ powder of m, CaO powder having an average particle diameter of 0.3 [mu] m, average particle size 0.5μm of Nd ₂ O _3, having an average particle size of 0.6 .mu.m Y
A b ₂ O ₃ powder, a SiO ₂ powder having an average particle diameter of 0.8 μm, and a MgO powder having an average particle diameter of 0.7 μm were prepared.
Combination of these powders in each row of the left column of Table 1
The components were weighed in a weight ratio composition and mixed in an ethanol solvent by a ball mill for 24 hours. In the case of Sample Nos. 26 to 29 containing aluminum oxide as a main component, the components and weight ratios are individually specified in the same column of Table 1. The numerical value after the chemical formula is the blending weight%. Total weight of powder weighed 10 for mixed powder
PVB (PolyVi) as an organic binder
Nyl Butyl) was added at 10% by weight to obtain a mixed slurry. This slurry was formed into a sheet by the doctor blade method. The thickness of this sheet was adjusted so that the thickness after sintering was 0.5 mm. Further, a compact having a size such that the size after sintering became 100 mm square was cut out from the completed sheet, and then the binder in the compact sample was removed.

Separately, various materials for setter and embedding described in the column of "Sintering charging method, setter" in Table 1 were prepared. Using these materials, various charging methods and sintering atmospheres shown in Table 1 were respectively held for 4 hours and fired. However, the atmosphere gas was all nitrogen (N ₂ ) as shown in the table, and the supply flow rate was 30 ° C. during the temperature rising process below the melting point of the sintering aid and during the cooling process below the melting point at the time of cooling. In the process above the melting point of the sintering aid, the supply flow rate was determined by multiplying r in the table by the same flow rate. For example, sample 1
The flow rate of nitrogen gas was reduced to 4.5 liters / minute in the case of (1) and to 15 liters / minute in the case of sample 16 in the course of the melting point or higher of the sintering aid. In the case of sample 17, r is 1
00% and the flow rate was 30 liter /
Minute constant. However, the temperature shown in the table indicates the maximum holding temperature, and the temperature was held at the same temperature for 4 hours.

In samples 1 to 17, 21, 26, and 27, five compacts were stacked on a BN sintered compact bottom plate having a surface roughness of Rmax of 5 μm, and between the compacts and on the uppermost compact,
A setter mainly composed of the materials described in the table was arranged. The thickness of all the setters is 0.5 mm. Among the setters, samples 1 to 8, 21, 26, and 27 were all press-formed from the materials listed in the table, impregnated with a paste containing pure BN powder as the main component, and heated and pressed again to form a sheet. The sample 9 is a sintered body having a solid portion with a relative density of 70% in which a hole penetrating in the thickness direction has been drilled in advance. The setters of Samples 10 to 17 were obtained by firing molded bodies of the described material powder at 1800 ° C. in nitrogen. In addition, the charging method of the samples 18 to 20 was to stack five molded bodies, but they were arranged on a BN sintered body similar to the above. However, a molded body was embedded in the material described in the column for sintering charging. In this case, a powder layer made of these materials was also arranged between the compacts. Samples 22, 23 and 28 had a surface roughness of Rmax
Is a charging method in which five compacts are directly stacked on a 5 μm BN sintered compact sheet, and samples 24, 25, and 29 are setters in the same BN sintered compact sealed case as the above-mentioned laminated board. This is a charging method in which only one molded body is disposed without using the method. In the table, Rm
ax indicates the surface roughness of the setter surface.

[0023]

[Table 1]

For each sample prepared as described above,
The values of the amounts a and b of the sintering aid elements near the front and back surfaces and the amount of warpage in the thickness direction were confirmed by the above-described method. For confirmation, both sides are easily polished with a brush and the surface roughness Ra is 0.3 μm.
Finished. In addition, the warpage amount before and after polishing was confirmed for some samples, but there was almost no difference. Thereafter, this sample was heat-treated at 850 ° C. for 1 hour in the atmosphere. In Table 2, the measured value of a / b is shown in the column of the sintering aid amount ratio, and the amount of warpage after sintering and the amount of increase in warpage after heat treatment are shown in the respective columns.

[0025]

[Table 2]

From the above data, it can be seen that the presence of the setter is effective in reducing the deformation (warpage) of the sintered body. In the case of aluminum oxide ceramics, the amount of warpage after sintering is remarkably reduced by interposing a setter, and the increase due to heat treatment after sintering is also small. Therefore, it can be seen that the method of the present invention is quite effective. Looking at the rate of increase in warpage due to heat treatment in an oxidizing atmosphere after sintering, it can be seen that aluminum oxide ceramics are much smaller than ceramics whose main component is nitride (conversely, those that slightly decrease is there). This is probably because ceramics containing an oxide as a main component are less affected by oxygen in the atmosphere because the heat treatment is performed in an oxidizing atmosphere. However, in the case of ceramics containing nitride as a main component, it can be seen that the effect of the setter insertion on the amount of deformation and the effect of the heat treatment on the reduction of the amount of increase are great. When this is compared with aluminum nitride ceramics and silicon nitride ceramics, it can be seen that the former is more effective. Based on the above results, the amount of deformation after sintering can be reduced by setting the difference a / b between the both sides of the sintering aid component to 1.3 or less, and particularly for ceramics mainly containing nitride, It can be seen that the increase in the amount of deformation due to the heat treatment in an oxidizing atmosphere after sintering can be kept small. Sample numbers 24, 25,
It can also be seen that even if every other sheet is loaded as in 29, the distribution of the sintering aid component after sintering cannot be made uniform and the level of deformation does not become small.

(Example 2) An Ag paste was printed and applied in a 90 mm square pattern on the main surface on the concave side with respect to the warping direction of each base material sample of Example 1, dried, and dried in air.
This was baked by heating at 0 ° C. for 30 minutes. As a result, the increase in the amount of warpage after firing was at the level shown in Table 2 for all samples. Thereafter, a SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ system glass paste was applied by printing on the substrate with the Ag layer, dried, heated and baked at 800 ° C. for 30 minutes in the air, and baked. As a result, the rate of increase in the amount of warpage after firing was 1/100 in Table 2 for all samples.
It was about 2 levels.

[0028]

As described above, according to the present invention, the distribution of the sintering aid in the ceramic substrate can be controlled uniformly, and as a result, the amount of deformation at the time of sintering becomes a practical obstacle. It can be suppressed to no extent. In addition, the increase in the amount of deformation of the base material when heat treatment is performed in the atmosphere during mounting of the base material can be suppressed to be lower than before. Therefore, it is possible to provide a highly reliable ceramic base material having excellent dimensional accuracy and capable of stably maintaining the same at the time of mounting and practical use.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a procedure for confirming the amount of warpage of a plate-shaped substrate according to the present invention.

[Explanation of symbols] 1, ceramic base material 2, surface plate 3, laser source 4, laser light

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Motoyuki Tanaka 1-1-1, Koyo Kita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Yasuhiro Murase 1-chome, Koyo-Kita, Itami-shi, Hyogo No. 1 in Sumitomo Electric Industries, Ltd. Itami Works

Claims (3)

[Claims] 1. A ceramic base material containing a sintering aid, wherein a sintering aid component element is detected with respect to the intensity of detection of the main component element on one main surface side and the other main surface side by fluorescent X-rays. A ceramic base material, wherein a / b ≦ 1.3 when the strength ratio is a and b, and a> b. 2. The ceramic substrate according to claim 1, wherein a main component of the ceramic is a nitride. 3. The ceramic substrate according to claim 2, wherein the ceramic is an aluminum nitride ceramic.