JPH11189458A - Semiconductive ceramic and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a semiconductive ceramic capable of being inexpensively produced in a large amount by simplifying a production process by including alumina crystal grains and one ore more kinds of crystal grins of MnNb2 O6 , MnAlO4 and MnFe2 O4 and regulating a volume specific resistance to be at a specific value. SOLUTION: This semiconductive ceramic comprises 40-85 vol.% alumina crystal grains, and one or more kinds of crystal grains of MnNb2 O6 , MnAlO4 and MnFe2 O4 , and has 10<4> -10<12> Ω.cm volume specific resistance and >=10 kV/mm absolute breakdown voltage. The ceramic is obtained by mixing an alumina powder with one or more kinds of powders of manganese oxide, niobium oxide and iron oxide in prescribed proportions, compacting the obtained raw material by a press molding or the like to form a prescribed shape, and firing the obtained compact in atmospheric surrounding at 1,200-1,350 deg.C. In the production process, components such as SiO2 , MgO, CaO, Na2 O, ArO2 and Ta2 O5 which do not take part in the crystal phase are contaminated as impurities, but the total of the contaminated amounts is required so as to be regulated to be <=0.1 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antistatic member or a resistive substrate for use in parts (e.g., a transfer arm, a handling jig, a wafer transfer tweezer, etc.) that need to be protected from static electricity in a semiconductor manufacturing apparatus or the like. The present invention relates to semiconductive ceramics used for conductive materials, contacts, heaters, vacuum tube parts, spacers for magnetic disks, and the like.

[0002]

2. Description of the Related Art Conventionally, for example, parts (e.g., a transfer arm, a handling jig,
Antistatic member used for wafer transfer tweezers, etc.), resistor base, conductive material, contact, heater,
For vacuum tube parts and magnetic disk spacers, 10 ⁴ ~
Ceramics having a volume resistivity of about 10 ⁸ Ωcm are used.

[0003] As such a semiconductive ceramic, for example, a powder of an alkali metal, a compound containing a transition metal element, titanium, an oxide thereof, or the like is added to alumina powder and mixed in a dry or wet method. To obtain a desired resistance value by sintering in a reducing atmosphere (Japanese Patent Laid-Open No. 61-3616).
No. 4 gazette).

Alternatively, semiconductive ceramics obtained by adding a semiconductive metal oxide, metal nitride, metal carbide, or the like to other ceramics, or silicon carbide ceramics which itself has an appropriate semiconductive property. Has been used.

[0005]

However, these semiconductive ceramics need to be manufactured by a hot press, an isostatic press or the like in order to obtain a dense sintered body. Since the control of the atmosphere is required, there is a problem that the manufacturing process is complicated, the productivity is low, and the manufacturing cost is high.

[0006] Moreover, the expensive primary materials used for these semiconductive ceramics have also been a factor in increasing the cost.

[0007]

Accordingly, the present invention provides a method for manufacturing a semiconductor device comprising:
85% by volume of alumina crystal grains, MnNb ₂ O ₆ , Mn
It is characterized by a semiconductive ceramic containing one or more crystal grains of ₂ AlO ₄ and MnFe ₂ O ₄ , having a volume resistivity of 10 ⁴ to 10 ¹² Ω · cm and a withstand voltage of 10 kV / mm or more.

[0008] In the semiconductive ceramic of the present invention,
The reason why the alumina crystal grains are set to 40 to 85% by volume is that if the alumina crystal grains are more than 85% by volume, the volume resistivity becomes 10%.
^This is because it becomes larger than ¹² Ω · cm and approaches the insulator. On the other hand, if the content is less than 45% by volume, the strength of the sintered body is lowered, which is not preferable when used as a structural material. In addition, the withstand voltage becomes low, so that the sintered body cannot be used in a high voltage environment. This is because it becomes difficult to obtain a unity.

Also, MnNb ₂ O ₆ , Mn ₂ AlO ₄ ,
The reason for containing one or more crystal grains of MnFe ₂ O ₄ is that
This is because these crystal grains have semiconductivity and form a three-dimensional network in the sintered body, so that it is presumed that a conductive path is secured. This is presumed from the fact that when the ratio of alumina crystal grains in the semiconductive ceramic of the present invention is increased, the volume resistivity increases, and when the ratio is decreased, the volume resistivity decreases. Therefore, to obtain the desired volume resistivity,
One or more crystal grains of MnNb ₂ O ₆ , Mn ₂ AlO ₄ , and MnFe ₂ O ₄ are required.

In particular, MnNb ₂ O ₆ , Mn ₂ AlO ₄ ,
It is preferable to include all the crystal grains of MnFe ₂ O ₄ .

Moreover, these MnNb ₂ O ₆ , Mn ₂
The semiconductive ceramics of the present invention containing the crystal grains of AlO ₄ and MnFe ₂ O ₄ can be obtained by using only inexpensive raw materials and sintering only in a general atmosphere, thereby simplifying the manufacturing process. At the same time, mass production becomes possible at low cost.

That is, when producing the semiconductive ceramic of the present invention, one or more powders of manganese dioxide, niobium oxide and iron oxide are mixed with alumina powder, and the obtained raw material is formed into a predetermined shape by press molding or the like. And then firing at 1200 to 1350 ° C. in an air atmosphere.

In the above-mentioned primary raw material or manufacturing process, SiO ₂ , MgO, Ca which does not participate in the above-mentioned crystal phase is used.
Components such as O, Na ₂ O, ZrO ₂ and Ta ₂ O ₅ are mixed as impurities.
If it is 1% by weight or less, there is no effect on the characteristics.

[0014]

Embodiments of the present invention will be described below.

First, alumina powder, manganese dioxide powder, niobium oxide powder, and iron oxide powder were prepared, weighed, and wet-mixed in a rotary mill. The mixed slurry was dried by spray drying to obtain a raw material for a sintered body. This was press-formed and fired in the air at a temperature of 1200 to 1350 ° C. for 2 to 3 hours to obtain a disc-shaped sintered body having a diameter of 60 mm and a thickness of 3 mm.

Each sample was cut, the cross section was mirror-finished, the structure was observed with a scanning electron microscope, and the qualitative analysis of the elements of each crystal phase was performed with an X-ray diffractometer.

FIGS. 1, 2 and 3 show X when the ratio of alumina crystal grains is 85% by volume, 60% by volume and 40% by volume, respectively.
The figure shows a line diffraction chart. Thus, the semiconductive ceramics of the present invention has an alumina crystal, MnNb ₂ O ₆ , M
It can be seen that it is composed of n ₂ AlO ₄ and MnFe ₂ O ₄ crystals. Further, since the peak of the alumina crystal decreases, MnNb ₂ O ₆ , Mn ₂ AlO ₄ , Mn
It can be seen that the peak of each crystal of Fe ₂ O ₄ has increased.

Further, FIGS. 4, 5 and 6 are schematic views of photographs of each sample enlarged 3000 times by a scanning electron microscope.
When this sample was qualitatively analyzed using an X-ray microanalyzer, the elements shown in Table 1 below were detected.

From the results shown in Table 1, the light gray portions in the schematic diagrams of the photographs of FIGS. 4 to 6 indicate alumina crystals,
The white portion indicates the MnNb ₂ O ₆ crystal, and the dark gray (shaded) portion indicates that the Mn ₂ AlO ₄ crystal and the MnFe ₂ O ₄ crystal coexist.

[0020]

[Table 1]

Next, both ends of the sample of the disc-shaped sintered body were polished to a thickness of 2 mm. Electrodes were applied to both ends of the obtained sample, and the resistance value of this sample was measured based on the insulation resistance measurement method defined in JIS C2141. As defined in JIS C 2141, the volume resistivity is R = r × S / t (R: volume resistivity, r:
Resistance value, S: electrode area, t: sample thickness).

With respect to the obtained sample, the voltage (breakdown voltage) until dielectric breakdown was measured by the method specified in JOSC 2141, and the water absorption was measured by the Archimedes method.

The crystal phase of the obtained sintered body is obtained by crushing the sintered body, identifying the crystal phase in the sintered body by X-ray diffraction by a powder method, and determining the volume ratio from the weight ratio and specific gravity. Calculated.

The results are shown in Table 2. Table 2 shows that the volume resistivity increases as the ratio of alumina crystal grains increases. This is because when the alumina crystal grains increase, MnNb ₂ O ₆ and Mn ₂ Al having semiconductivity are obtained.
O _4, MnFe ratio in the sintered body of the ₂ O ₄ these grains inevitably small, hardly 3 dimensional network of these crystal grains is formed, because the volume resistivity of the sintered body becomes high is there. In addition, No. When the alumina crystal is more than 85% by volume as in 1, no network is formed even if a semiconductive crystal is present, and the volume specific resistance exceeds 10 ¹² Ω · cm and the area of the insulator is increased. Become.

Conversely, when the ratio of the alumina crystal grains decreases, the ratio of the semiconductive crystals increases, and the volume resistivity decreases. However, no. As shown in FIGS. 8 and 9, when the ratio of the alumina crystal grains is less than 40% by volume, the ratio of these crystals becomes too large and the withstand voltage becomes 10 kV /.
mm, the grain size of each crystal grain increases, and the strength of the sintered body decreases.

Therefore, the ratio of the alumina crystal grains is 40 to 85% by volume in view of the volume resistivity, the dielectric strength and the strength.
Is desirable.

[0027]

[Table 2]

[0028]

As described above, the semiconductive ceramic sintered body of the present invention has a structure in which alumina crystal grains and MnNb
_It contains at least one of ₂ O ₆ , Mn ₂ AlO ₄ and MnFe ₂ O ₄ , has a volume resistivity of 10 ⁴ to 10 ¹² Ωcm, and has a withstand voltage of 10 kV / mm or more.
For example, an antistatic member used for a part (such as a transfer arm, a handling jig, a wafer transfer tweezer, or the like) required to prevent static electricity in a semiconductor manufacturing apparatus or the like, or a resistor base, a conductive material, a contact, a heater, a vacuum tube part, It is possible to obtain a semiconductive ceramic which is most suitable for a magnetic disk spacer or the like.

Moreover, since the semiconductive ceramic of the present invention can be obtained only by firing in a general air atmosphere using an inexpensive material, the manufacturing process can be simplified and mass production can be performed at low cost.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction chart of a semiconductive ceramic of the present invention.

FIG. 2 is an X-ray diffraction chart of the semiconductive ceramic of the present invention.

FIG. 3 is an X-ray diffraction chart of the semiconductive ceramic of the present invention.

FIG. 4 is a schematic view of an electron micrograph showing a crystal structure of a semiconductive ceramic of the present invention.

FIG. 5 is a schematic view of an electron micrograph showing a crystal structure of a semiconductive ceramic of the present invention.

FIG. 6 is a schematic view of an electron micrograph showing a crystal structure of a semiconductive ceramic of the present invention.

Claims (2)

[Claims] 1. An alumina crystal grain comprising 40 to 85% by volume of M
It contains one or more crystal grains of nNb ₂ O ₆ , Mn ₂ AlO ₄ and MnFe ₂ O ₄ , and has a volume resistivity of 10 ⁴ to 10 ¹² Ω.
-Semi-conductive ceramics in cm. 2. A mixture of alumina powder finally having a volume of 40 to 85% by volume and at least one of manganese dioxide, niobium oxide, and iron oxide, and molding the obtained raw material. Baking at 1350 ° C., MnNb
_A method for producing a semiconductive ceramic, comprising a step of generating one or more crystal grains of ₂ O ₆ , Mn ₂ AlO ₄ , and MnFe ₂ O ₄ .