JP2002173361A - Ceramic substrate, thin film circuit substrate and method of manufacturing ceramic substrate - Google Patents

Abstract

(57) Abstract: A ceramic substrate having excellent heat dissipation and capable of reliably forming a thin film circuit layer with high film properties. In addition, a thin film circuit board on which a thin film circuit layer having a high coating property is formed is obtained. Further, a method for manufacturing a ceramic substrate in which warpage after polishing is prevented is obtained. The ceramic sintered body is characterized by having a warpage of 5 μm / inch or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate having excellent heat radiation and capable of forming a thin film circuit layer, a thin film circuit substrate, and a method of manufacturing a ceramic substrate.

[0002]

2. Description of the Related Art A circuit board on which a semiconductor element is mounted comprises a board and a circuit layer made of a conductor such as copper on at least one side of the board. Various materials such as resins, metals, and ceramics are known as substrate materials for circuit boards. Conventionally, a suitable material has been selected as a substrate material according to the use of the circuit board.

In recent years, a large-scale integrated circuit (LSI: Large S) in which a semiconductor element is highly integrated, operated at a high speed, and made into a large chip
call integration) has been put to practical use. With the increase in the degree of integration of semiconductor elements, the material characteristics required for the substrate have shifted from protection of mechanically stressed surfaces of semiconductor chips to electrical and thermal protection. Among resins, metals, and ceramics, ceramics have comprehensively excellent characteristics including heat dissipation, electrical characteristics, and reliability. For this reason, ceramic substrates are often used.

In recent years, since semiconductor elements have been further integrated, operated at higher speeds, and as chips have become larger, heat generation from the semiconductor elements during use has been increasing, and the temperature tends to further increase. Therefore, as a characteristic of the substrate material, a high heat radiation property capable of efficiently radiating heat generated from the semiconductor element to the outside is required. Therefore, ceramic substrates such as AlN sintered bodies, SiC sintered bodies, and Si ₃ N ₄ sintered bodies having high thermal conductivity are used.

In order to further improve the heat dissipation of the ceramic substrate, it is necessary not only to apply a material having a high thermal conductivity to the ceramic substrate but also to reduce the thermal resistance value by reducing the thickness of the ceramic substrate itself. Indispensable for ceramic substrates.

[0006]

However, when the thickness of the ceramic substrate is reduced by polishing, there is a problem that the ceramic substrate is warped and the coverage of a circuit layer formed on the ceramic substrate is reduced. . on the other hand,
In order to prevent polishing, there is a method of forming a thin ceramic molded body in advance and sintering it.However, since the ceramic molded body shrinks during sintering, even such a method completely warps. It was difficult to get rid of it. Also, even if the warpage can be reduced, only a baked surface of the ceramic sintered body can obtain only a rough surface roughness, and polishing is indispensable to increase the surface flatness. The above-described warping problem has occurred.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a ceramic substrate having excellent heat dissipation and capable of reliably forming a thin film circuit layer having a high coating property. Aim.

It is another object of the present invention to provide a thin-film circuit board in which a thin film circuit layer having high coatability is formed using the above-mentioned ceramic substrate.

Another object of the present invention is to provide a method of manufacturing a ceramic substrate which can prevent warpage after polishing even if the ceramic substrate is thin.

[0010]

Generally, a circuit layer made of a conductor such as copper is formed on the surface of a ceramic substrate in order to electrically connect electric and electronic components on the ceramic substrate.
When a circuit layer is formed as a thin film, a physical vapor deposition method such as a sputtering method or a vacuum vapor deposition method is used on a ceramic substrate. The physical vapor deposition method has an excellent property that it is easy to secure adhesion without being influenced by the material of the ceramic substrate, but when unevenness exists in the surface shape of the ceramic substrate, the thin film coverage at the step portion is poor. . For this reason, high flatness is required for the ceramic substrate surface. Actually, in order to form a thin film circuit layer by a vapor deposition film, it is necessary that the surface roughness Ra of the ceramic substrate surface is 0.5 μm or less. Therefore, it is necessary to perform a polishing process for flattening the surface of the ceramic substrate.

On the other hand, when a thin ceramic substrate is manufactured, a method of sintering by applying a uniform load using a straightening jig such as a setter is used to prevent deformation during sintering. However, the surface of the ceramic substrate after sintering depends on the surface condition of the straightening jig, and irregularities are inevitably generated on the surface of the ceramic substrate. For this reason, it is essential to polish the surface of the ceramic substrate after sintering.

Usually, when polishing a ceramic substrate, the lower surface of a horizontally disposed ceramic substrate is fixed, the upper end plate containing abrasive grains such as diamond is disposed on the upper surface, and the upper end plate is rotated or moved right and left. Single-side polishing for polishing a substrate surface is performed.

When single-side polishing is performed, a force is applied from one side of the ceramic substrate during polishing. This force generates stress inside the material of the ceramic substrate. When the ceramic substrate is thick, the stress generated inside the material is absorbed inside the ceramic substrate, and the ceramic substrate itself is not deformed. However, when a single-sided polishing is performed on a thin ceramic substrate, the stress generated inside the material of the ceramic substrate is not absorbed, and the stress inside the material directly deforms the ceramic substrate itself. As a result, warpage occurs after polishing. For example, in the case of a thin ceramic substrate having a substrate thickness of 0.5 mm or less, 50 μm /
Warpage of inches (about 50 μm per inch) occurs.

Further, during polishing, frictional heat is generated due to friction between the ceramic substrate and the upper end plate. This frictional heat easily deforms the ceramic substrate, which is one of the causes of warpage after polishing.

The present inventor, when polishing a thin ceramic substrate, simultaneously performs double-side polishing from both surfaces of the ceramic substrate to prevent deformation of the ceramic substrate due to stress generated inside the material of the ceramic substrate. It has been found that the occurrence of warpage of the ceramic substrate after polishing can be reduced. Then, as a result of reducing the occurrence of warpage of the ceramic substrate, the coatability by vapor deposition on the ceramic substrate can be greatly improved, and a thin circuit layer can be formed.

That is, the ceramic substrate of the present invention is formed of a plate-shaped ceramic sintered body, and is characterized in that the warpage is 5 μm / inch or less.

[0017] In the ceramic substrate of the above aspect, the plate thickness is desirably 0.2 to 0.5 mm, and the ceramic sintered body mainly contains one of aluminum nitride and silicon nitride. Is preferred.

Further, in the ceramic substrate of the above aspect, the surface roughness Ra of both surfaces of the ceramic substrate is 0.5
It is desirable that it is not more than μm.

The ceramic substrate has a substantially rectangular shape, and the length of the short side is 120 mm or less.

In the ceramic substrate according to the above aspect, at least one surface of the ceramic substrate has a thickness of 0.5 to 0.5 mm.
It is a thin film circuit board on which a 5.0 μm circuit layer is formed. Although the circuit layer of the present invention is preferably a thin film formed by the physical vapor deposition method as described above, a circuit layer using a metal paste is also applicable.

Further, in the method of manufacturing a ceramic substrate according to the above aspect, the ceramic powder is sintered into a plate-shaped ceramic sintered body, and both surfaces of the ceramic sintered body are simultaneously polished to obtain the ceramic sintered body. It is characterized in that a ceramic substrate having a surface roughness Ra of 0.5 μm or less on both surfaces of the body is obtained.

In the method of manufacturing a ceramic substrate according to the above aspect, it is preferable to use a ceramic sintered body having a plate thickness of 0.2 to 0.5 mm. Further, it is desirable to use a ceramic sintered body containing any one of aluminum nitride and silicon nitride as a main component.

In the case of an aluminum nitride substrate, Al
It is desirable to use a ceramic sintered body in which the average particle size of the N crystal particles is 3.0 μm or less. In particular, a particle size of 1.0
It is preferable to have a small diameter in the range of μm to 3.0 μm and a uniform average particle diameter, whereby the polishing property of the ceramic substrate can be improved. In the case of a silicon nitride substrate, the major axis diameter of the Si ₃ N ₄ crystal particles is 2.0 to 7.0 μm.
Within the range, the same effect can be obtained. Conventionally, single-side polishing in which the ceramic substrate is polished one by one has been performed. However, by improving the polishing property, double-side polishing can be performed simultaneously.

By using such a method for manufacturing a ceramic substrate according to the present invention, a ceramic substrate with a small warpage can be obtained despite its thinness of 0.2 to 0.5 mm.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below using Examples 1 to 14 and Comparative Examples 1 to 10.

Embodiment 1 In this embodiment, a ceramic substrate made of an aluminum nitride (AlN) sintered body was manufactured by the following method.

AlN raw material powder (average particle size 1.8 μm)
A sintering aid, for example, Y ₂ O ₃ is added in an amount of 5% by mass (similar to the amount by weight), an organic solvent and a binder are further added, and the mixture is mixed by a ball mill to produce a uniformly mixed slurry. did. The obtained slurry was formed into a sheet having a thickness of 0.8 mm by a doctor blade method. Then, after sintering, the sheet was cut in a state of being divided into 3 inch squares, and then degreased at 500 ° C. Thereafter, sintering was performed at 1750 ° C. for 4 hours in a non-oxidizing atmosphere to obtain an AlN sintered body. Here, the warpage of the AlN sintered body was measured once.

FIG. 1 is a view in which an AlN sintered body 2 is arranged on a flat plate 1 and viewed from the thickness direction of the AlN sintered body 2. First, the length A of the AlN sintered body 2 shown in FIG. 1 was measured, and then the maximum value B of the vertical distance from the flat plate 1 to the concave surface of the AlN sintered body 2 was measured. And the length A of the AlN sintered body 2
The vertical distance B per inch was calculated as the warpage. As a result, the warpage was 100 μm / inch.

From the fractured surface of this AlN sintered body, three arbitrary samples (unit area 50 μm × 50 μm) were selected. Each sample is enlarged 2000 times by the enlarged photograph,
The maximum diameter of each AlN crystal particle contained in the unit area was measured, and the average particle diameter was calculated. As a result, the average particle size of the particles was 2.5 μm.

As described above, both surfaces of the AlN sintered body 2 having a warpage of 100 μm / inch and an average particle diameter of 2.5 μm are simultaneously polished by the following method to obtain a sheet thickness of 0.1 μm.
A ceramic substrate having a thickness of 5 mm and a surface roughness Ra of 0.5 μm or less was obtained.

That is, as shown in FIG.
An upper end plate 3a and a lower end plate 4a that cover the entire surface of the AlN sintered body 2 were arranged on both side surfaces of the N sintered body 2, and the ends of the AlN sintered body 2 were fixed. Then, the upper end plate 3a and the lower end plate 4a were simultaneously moved to polish both side surfaces of the AlN sintered body 2.
The setting of the whetstone at this time was performed in the range of $ 200 to 1,000. When the size of the AlN sintered body 2 is large, as shown in FIG. 2B, an upper end plate 3b and a lower end plate 4b are arranged on a part of both side surfaces of the AlN sintered body 2, and Board 3
The AlN sintered body 2 may be polished by simultaneously moving the lower end plate 4b and the lower end plate 4b.

The warpage of the AlN substrate obtained by polishing both surfaces simultaneously was measured. As a result, as shown in Table 1 below, the warpage of the polished AlN substrate was 5%.
In μm / inch, the warpage was significantly reduced as compared with that before polishing.

Example 2 In this example, the sintering conditions and additives were changed as follows.

That is, the raw material powder of AlN (average particle diameter)
0.8 μm), a sintering aid such as Y ₂O₃In mass%
3%, and an organic solvent and a binder
Mixing with a mill to produce a uniformly mixed slurry.
Was. Thick the obtained slurry by the doctor blade method.
It was formed into a 0.8 mm sheet. And after sintering 3
The sheet was cut in a state where it was divided so that it became
Thereafter, degreasing was performed at 520 ° C. Then a non-oxidizing atmosphere
And sintered at 1800 ° C for 3 hours to obtain an average particle size of 2.0μ.
Thus, a plate-like AlN sintered body having a thickness of m was obtained.

Both sides of the AlN sintered body were simultaneously polished to obtain a ceramic substrate having a thickness of 0.5 mm, and the warpage was measured. As a result, as shown in Table 1, the warpage of the ceramic substrate was 3 μm / inch.

Example 3 In this example, the sintering conditions and additives were changed as follows.

That is, the raw material powder of AlN (average particle diameter)
1.5 μm) to a sintering aid such as Y ₂O₃In mass%
4%, and an organic solvent and a binder
Mixing with a mill to produce a uniformly mixed slurry.
Was. Thick the obtained slurry by the doctor blade method.
It was formed into a 0.7 mm sheet. And after sintering 3
The sheet was cut in a state where it was divided so that it became
Thereafter, degreasing was performed at 550 ° C. Then a non-oxidizing atmosphere
And sintered at 1820 ° C for 2 hours to obtain an average particle diameter of 2.3μ.
Thus, a plate-like AlN sintered body having a thickness of m was obtained.

The both sides of this AlN sintered body were simultaneously polished to a thickness of 0.4 mm and a surface roughness Ra of 0.05 μm.
The following ceramic substrate was obtained, and the warpage was measured. As a result, as shown in Table 1, the warpage of the ceramic substrate was 5
μm / inch.

Example 4 In this example, the sintering conditions and additives were changed as follows.

That is, a sintering aid such as Y ₂ O ₃ was added to the raw material powder (average particle size 1.8 μm) of Si ₃ N ₄ by mass%.
Then, 6% and TiO ₂ were added by 1%, and further, an organic solvent and a binder were added and mixed by a ball mill to prepare a uniformly mixed slurry. The obtained slurry was formed into a sheet having a thickness of 0.7 mm by a doctor blade method.
Then, after sintering, the sheet was cut in a state of being divided into three inch squares, and then degreased at 550 ° C. Then, it is sintered at 1800 ° C. for 3 hours in a non-oxidizing atmosphere,
Plate-like silicon nitride (Si) having an average particle diameter of 4.2 μm
₃ N ₄₎ to obtain a sintered body. The average particle size the _Si 3 _{N 4,} in fracture surface of the AlN sintered body likewise _Si 3 _{N 4} sintered body, the unit area 50 [mu] m × 50 [mu] m to select any three points, 2000 times the unit area In the enlarged photo of
It is obtained from the average value of the major axis diameters of the individual Si ₃ N ₄ crystal grains reflected there.

The both sides of the Si ₃ N ₄ sintered body were simultaneously polished to a thickness of 0.5 mm and a surface roughness Ra of 0.3 μm.
m and a warp was measured.
As a result, as shown in Table 1, the warpage of the ceramic substrate was 2 μm / inch.

Example 5 In this example, the sintering conditions and additives were changed as follows.

That is, Si₃N₄Raw material powder (average grain
Sintering aid such as Y₂O₃The mass%
At 5%, Yb₂O₃3%, TiO₂0.5% added
And further add an organic solvent and a binder to the ball mill.
To obtain a uniformly mixed slurry. Get
0.6m thick slurry obtained by doctor blade method
m. And, after sintering,
After cutting the sheet in a state where it is
Degreasing was performed at 0 ° C. Then, in a non-oxidizing atmosphere, 18
Sintering at 20 ° C for 3 hours to make the average particle size 5.1 μm
Plated Si₃N ₄A sintered body was obtained.

Both sides of the Si ₃ N ₄ sintered body were simultaneously polished to a thickness of 0.3 mm and a surface roughness Ra of 0.1 μm.
m and a warp was measured.
As a result, as shown in Table 1, the warpage of the ceramic substrate was 5 μm / inch.

Comparative Example 1 In this comparative example, the sintering conditions and additives were changed as follows.

That is, the raw material powder of AlN (average particle diameter)
2.8 μm), a sintering aid such as Y ₂O₃In mass%
4%, and an organic solvent and a binder
Mixing with a mill to produce a uniformly mixed slurry.
Was. Thick the obtained slurry by the doctor blade method.
It was formed into a 0.8 mm sheet. And after sintering 3
The sheet was cut in a state where it was divided so that it became
Thereafter, degreasing was performed at 550 ° C. Then a non-oxidizing atmosphere
Medium, and sintered at 1820 ° C. for 3 hours to obtain an average particle diameter of 4.5.
A plate-shaped AlN sintered body having a thickness of μm was obtained.

Both sides of the AlN sintered body were simultaneously polished to obtain a ceramic substrate having a thickness of 0.5 mm and a surface roughness Ra of 0.5 μm, and the warpage was measured. As a result, as shown in Table 1, the warpage of the ceramic substrate was 22 μm.
m / inch.

Comparative Example 2 In this comparative example, the sintering conditions and additives were changed as follows.

That is, the raw material powder of AlN (average particle diameter)
1.3 μm), a sintering aid such as Y ₂O₃In mass%
5%, and further, an organic solvent and a binder.
Mixing with a mill to produce a uniformly mixed slurry.
Was. Thick the obtained slurry by the doctor blade method.
It was formed into a 0.8 mm sheet. And after sintering 3
The sheet was cut in a state where it was divided so that it became
Thereafter, degreasing was performed at 500 ° C. Then a non-oxidizing atmosphere
Sintering at 1800 ° C. for 2 hours to reduce the average particle size to 2.0
A plate-shaped AlN sintered body having a thickness of μm was obtained.

One surface of the AlN sintered body was polished to obtain a ceramic substrate having a thickness of 0.5 mm and a surface roughness Ra of 0.5 μm, and the warpage was measured. As a result, as shown in Table 1, the warpage of the ceramic substrate was 50 μm.
m / inch.

Comparative Example 3 In this comparative example, the sintering conditions and additives were changed as follows.

That is, a sintering aid, for example, Y ₂ O ₃ was added to the raw material powder (average particle size: 3.0 μm) of Si ₃ N ₄ by mass%.
, And further, an organic solvent and a binder were added and mixed by a ball mill to prepare a uniformly mixed slurry. The obtained slurry was formed into a sheet having a thickness of 0.8 mm by a doctor blade method. And after sintering 3
After the sheet was cut in a state where the sheet was cut into an inch square, degreasing was performed at 500 ° C. Thereafter, in a non-oxidizing atmosphere, and 8 hours sintered at 1820 ° C., to obtain an average particle diameter (major axis diameter) and 8.7μm were plate-shaped _Si 3 _{N 4} sintered body.

Both surfaces of the Si ₃ N ₄ sintered body were simultaneously polished to a thickness of 0.5 mm and a surface roughness Ra of 0.5 μm.
Was obtained, and the warpage was measured. As a result, as shown in Table 1, the warpage of the ceramic substrate was 20 μm.
m / inch.

Comparative Example 4 In this comparative example, the sintering conditions and additives were changed as follows.

That is, a sintering aid such as Y ₂ O ₃ was added to the raw material powder (average particle size 1.8 μm) of Si ₃ N ₄ by mass%.
, And further, an organic solvent and a binder were added and mixed by a ball mill to prepare a uniformly mixed slurry. The obtained slurry was formed into a sheet having a thickness of 0.8 mm by a doctor blade method. And after sintering 3
After the sheet was cut in a state where the sheet was cut into an inch square, degreasing was performed at 500 ° C. Thereafter, sintering was performed at 1800 ° C. for 3 hours in a non-oxidizing atmosphere to obtain a plate-shaped Si ₃ N ₄ sintered body having an average particle diameter (major axis diameter) of 5.5 μm.

[0056] by polishing the one surface of the _Si 3 _{N 4} sintered body, a 0.5mm and a surface roughness Ra of the sheet thickness 0.5μm
Was obtained, and the warpage was measured. As a result, as shown in Table 1, the warpage of the ceramic substrate was 55 μm.
m / inch.

[0057]

[Table 1]

The above Examples 1 to 5 and Comparative Examples 1 to
As a result of manufacturing the ceramic substrate shown in Comparative Example 4 and measuring the warp, as shown in Table 1, in Comparative Examples 2 and 4 in which one side was fixed and polished, the warp was 50 μm / inch, 55
μm / inch. On the other hand, in Examples 1 to 5 in which both surfaces of the ceramic substrate were simultaneously polished, the warpage was 5 μm / inch or less, and it was found that the warpage could be greatly reduced.

Therefore, according to the present embodiment, even when the ceramic substrate is made thin, the ceramic substrate is polished on both sides and a force is applied from both sides of the ceramic substrate, so that the inside of the material of the ceramic substrate is formed. By canceling the generated stresses, warpage of the ceramic substrate after polishing can be prevented.

In Comparative Examples 1 and 3, the average particle diameter of the particles of the ceramic sintered body exceeded the preferred range of the present invention, and even when both surfaces of the ceramic substrate were simultaneously polished, the warpage was small. 22 μm / inch and 55 μm / inch occurred. On the other hand, in Examples 1 to 5 in which the average particle diameter of the ceramic sintered body was in a preferable range,
In each case, the warpage was 5 μm / inch, and the occurrence of warpage could be reduced.

Therefore, according to the present embodiment, by reducing the diameter of the particles of the ceramic sintered body to improve the polishing property,
It has been confirmed that the generation of frictional heat during polishing can be suppressed, and the occurrence of warpage can be further prevented.

Examples 6 to 10, Comparative Examples 5 to Comparative Examples
8 The circuit layers shown in Table 2 were provided on the ceramic substrates of Examples 1 to 5 and Comparative Examples 1 to 4 by a sputtering method. At that time, the rate of occurrence of defective sputtering was determined. Here, the term “sputter failure” indicates the percentage (%) of the cases in which a predetermined wiring shape was not obtained in spite of performing sputtering to obtain a predetermined wiring shape. Table 2 shows the results.

[0063]

[Table 2]

As can be seen from Table 2, since the ceramic substrate according to the example of the present invention has a small warpage, it was found that the rate of occurrence of spatter defects can be reduced. Also, since the ceramic substrate of the present invention is polished on both sides,
A circuit layer can be provided on both the front and back surfaces. Therefore, since there is no difference between the front surface and the back surface, it is not necessary to worry about the directionality when mounting the device on the sputtering apparatus, so that the workability is good.

On the other hand, it was found that the ceramic substrate of the comparative example had a large occurrence of defects due to large warpage, and was not suitable for providing a circuit layer by physical vapor deposition such as sputtering.

Examples 11 to 14, Comparative Example 9, Comparative
Example 10 Except that the substrate size was changed as shown in Table 3, the same ceramic substrates as in Example 1 were used as Example 11, Example 12, and Comparative Example 9. The same ceramic substrates as in Example 4 except that the substrate size was changed as shown in Table 3 were used as Example 13, Example 14, and Comparative Example 10. In addition,
Comparative Examples 9 and 10 have substrate sizes outside the scope of the present invention.

The above Examples 11 to 14 and Comparative Examples 9 to
The amount of warpage of Comparative Example 10 was measured. Table 3 shows the results.

[0068]

[Table 3]

As can be seen from Table 3, if the short side of the ceramic substrate is 120 mm or less, the warpage can be reduced to 5 μ / inch or less.

On the other hand, it has been found that the effects of the present invention cannot be sufficiently obtained when the substrate size is increased beyond the range of the present invention as in Comparative Examples 9 and 10. This is considered to be because if the substrate size is too large, it is difficult to reduce the stress during polishing.

[0071]

As described above, according to the method for manufacturing a ceramic substrate of the present invention, it is possible to obtain a ceramic substrate having excellent heat dissipation and reduced warpage after polishing. In addition, a circuit board in which a thin film circuit layer having a high coating property is formed on a ceramic substrate can be obtained, and a high-performance circuit component in which a semiconductor element is highly integrated, operated at high speed, and a large chip can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a warpage measuring method in an embodiment of the present invention.

FIGS. 2A and 2B are cross-sectional views illustrating polishing processing according to an embodiment of the present invention. FIG. 2A is a cross-sectional view illustrating polishing when the size of the ceramic substrate is small, and FIG. FIG.

[Explanation of symbols]

1 Flat plate 2 AlN sintered body 3a, 3b Upper plate 4a, 4b Lower plate A Length of AlN sintered body B Maximum value of vertical distance from flat plate to concave surface of AlN sintered body

Claims (11)

[Claims] 1. A ceramic substrate comprising a plate-shaped ceramic sintered body and having a warpage of 5 μm / inch or less. 2. The ceramic substrate according to claim 1, wherein the thickness of the ceramic substrate is 0.2 to 0.5 mm. 3. The ceramic substrate according to claim 1, wherein the ceramic sintered body mainly comprises one of aluminum nitride and silicon nitride. 4. The ceramic substrate according to claim 1, wherein both surfaces of the ceramic substrate have a surface roughness Ra of 0.5 μm or less. 5. The ceramic substrate according to claim 1, wherein the ceramic substrate has a substantially rectangular shape and a short side length is 120 mm or less. 6. The ceramic substrate according to claim 3, wherein the ceramic substrate contains aluminum nitride as a main component, and the average particle diameter of major axes of aluminum nitride crystal grains is 3.0 μm or less. Ceramic substrate. 7. The ceramic substrate according to claim 3, wherein the ceramic substrate contains silicon nitride as a main component, and the silicon nitride crystal particles have an average major axis diameter of 2.0 to 2.0.
A ceramic substrate having a thickness of 7.0 μm. 8. A ceramic substrate according to claim 1, wherein at least one surface has a thickness of 0.5.
A thin-film circuit board, wherein a circuit layer of up to 5.0 μm is formed. 9. Sintering a ceramic powder to form a plate-shaped ceramic sintered body, and polishing both surfaces of the ceramic sintered body at the same time to reduce the surface roughness Ra on both side surfaces of the ceramic sintered body. A method for manufacturing a ceramic substrate, comprising obtaining a ceramic substrate having a thickness of 0.5 μm or less. 10. The method of manufacturing a ceramic substrate according to claim 9, wherein a ceramic sintered body having a thickness of 0.2 to 0.5 mm is used. 11. The method for manufacturing a ceramic substrate according to claim 9, wherein a ceramic sintered body containing at least one of aluminum nitride and silicon nitride as a main component is used. .