Ceramic resistor

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a ceramic resistor mainly made of aluminum nitride, which is suitable for a heater material, a vacuum tube outer tube, a charge removing material in a semiconductor manufacturing apparatus, a wafer transfer arm, a wafer handling jig, and the like.

【0002】

[Previous technology]

Conventionally, as a method for adjusting the electric resistance of insulating ceramics, it is generally practiced to add a conductive material to the insulating ceramics to control the resistance value. For example, titanium nitride is added to alumina to reduce the electrical resistance.

【0003】

On the other hand, aluminum nitride is a kind of non-oxidizing ceramics, and is expected to be applied as a structural material or a high-temperature material. Recently, it has been reported that it has excellent durability against plasma. Therefore, application of this aluminum nitride as a component in a semiconductor manufacturing apparatus such as an electrostatic chuck is considered. However, this aluminum nitride itself is a highly insulating material, and even at room temperature, it is 10¹⁶At present, it has not been put into practical use because it has a resistance value of Ω-cm or more.

【0004】

Attempts have been made to reduce the electrical resistance of such aluminum nitride. For example, it is proposed in Japanese Patent Application Laid-Open No. 56-4509 to adjust the specific resistance by adding a conductive material such as Al to the insulating ceramics of aluminum nitride or boron nitride. Further, in thin film ceramics, for example, it is proposed in Tokusho 55-50364 to obtain a thin film resistor having a small temperature coefficient of resistance by dispersing metallic aluminum in aluminum nitride.

【0005】

[Problems to be Solved by the Invention]

In general, the volume specific resistance value of an insulator tends to decrease with temperature, but in the case of aluminum nitride, for example, it is 10 at room temperature.¹⁶10 at 600 ° C from Ω-cm⁷It tends to decrease sharply to Ω-cm or less. Therefore, when it is used from room temperature to high temperature, it cannot be used stably because it cannot operate stably, or there is a problem that the operating temperature condition is limited.

【0006】

Further, in the method of controlling the electric resistance by adding a conductive material, there is a problem that the characteristics inherent in the insulating ceramics are impaired due to the characteristics of the conductive material itself. For example, it lacked corrosion resistance and durability, and the characteristics of aluminum nitride deteriorated.

【0007】

[Means to solve problems]

The present inventors have a particular electrical resistance of 10 for the above problems.¹⁴As a result of repeated studies from the viewpoint of its composition and structure as a ceramic resistor of Ω-cm or less, for example, 0.005 to 20 atomic% of oxygen is contained in an insulator mainly composed of aluminum nitride formed by a chemical vapor phase synthesis method. By containing and dissolving the oxygen in the aluminum nitride crystal to control the lattice constant of the aluminum nitride within a specific range, the volume specific resistance of the insulating layer is 10¹⁴We have found that the material properties can be adjusted in the range of Ω-cm or less, the temperature change is small, and stable material properties can be obtained in a wide temperature range, and the present invention has been made.

【0008】

That is, the ceramic resistor of the present invention is a ceramic resistor mainly composed of an aluminum nitride crystal phase, and oxygen is present in the resistor in an amount of 0.005 to 20 atomic%, and the lattice constant in the crystal phase is on the a-axis. It is 3.105 to 3.117 Å, 4.973 to 4.990 Å on the c-axis, and has a volume specific resistance of 10 at 25 ° C.¹⁴It is characterized by being Ω-cm or less.

【0009】

Hereinafter, the present invention will be described in detail. The ceramic resistor in the present invention is mainly composed of aluminum nitride, but contains 0.005 to 20 atomic% of oxygen atoms in terms of composition. This amount of oxygen is an important element for imparting conductivity to aluminum nitride. If the amount of oxygen is less than 0.005 atomic%, the desired resistance cannot be obtained, and if it exceeds 20 atomic%, the insulator AlON is likely to be generated, resistance control becomes difficult, and peeling and cracking are likely to occur in the thin film.

【0010】

In addition, this ceramic resistor is mainly composed of aluminum nitride crystals in terms of structure, and a part of oxygen in this resistor dissolves in the aluminum nitride crystal, but it dissolves in the crystal. A phase composed of aluminum oxide or aluminum nitride may be present in a proportion of 12% by weight or less due to unexhausted oxygen. In addition, aluminum nitride crystals have a lattice constant in the range of 3.105 to 3.117 Å on the a-axis and 4.973 to 4.990 Å on the c-axis due to the solid dissolution of oxygen. It has a lattice constant that is clearly different from Å and c-axis 4.994 Å), in other words, it is 0.003 to 0.015 Å smaller on the a-axis and 0.004 to 0.021 Å smaller on the c-axis than the lattice constant of aluminum nitride alone. ..

【0011】

The ceramic resistor of the present invention has 10 at 25 ° C due to the above configuration.¹⁴It has a volume specific resistance of Ω-cm or less, and its lower limit is about 10 Ω-cm. Moreover, as is clear from the examples described later, this resistor also has excellent resistance stability in which the change with respect to the resistance value of 25 ° C is 3 orders of magnitude or less in the temperature range from room temperature to 400 ° C. It is a feature.

【0012】

The method for producing the ceramic resistor of the present invention does not particularly limit the production method as long as the above configuration is satisfied, but the vapor phase growth method is particularly preferable in terms of ease of production. Specifically, it is formed by a physical vapor deposition method (PVD method) such as sputtering and ion plating, and a chemical vapor deposition method (CVD method) such as plasma CVD, optical CVD, and MO (Metal-organic) CVD. However, among these, the CVD method is preferable. According to these film forming methods, aluminum nitride in which oxygen is excessively dissolved can be synthesized, and a ceramic resistor containing 0.01 to 20 atomic% of oxygen used in the present invention and having a small lattice constant of an aluminum nitride crystal. Can be obtained. As a specific manufacturing method using the CVD method, N is used as the raw material gas.₂Gas, NH₃Gas, NO₂And AlCl₃Using gas, set the flow rate ratio of these gases to N₂/ AlCl₃= 5 ~ 70, NO₂/ NH₃= 0.001 ~ 1, NH₃/ AlCl₃It can be produced by setting = 0.1 to 10 and setting the film formation temperature to a relatively high temperature of 850 ° C or higher.

【0013】

On the other hand, any substrate that forms a film can be used, but specifically, Al.₂O₃, AlON, Si₃N₄, Diamond, mullite, ZrO₂, W, Mo, Mo-Mn, TiN, SiC, WC, carbon and Si semiconductor materials (n-type or p-type) are also mentioned, but among these, a sintered body mainly composed of aluminum nitride is most desirable.

【0014】

[Action]

Normally, aluminum nitride has a volume specific resistance of 10.¹⁴It is a high insulator exceeding Ω-cm, but when oxygen is dissolved in the aluminum nitride crystal and nitrogen is replaced with oxygen, one electron becomes excessive, which contributes to conductivity and increases the conductivity of the crystal. It is considered to be an action. Further, the solid solution of oxygen in the aluminum nitride crystal can be determined by the change in the lattice constant. For example, the lattice constant of aluminum nitride that does not contain oxygen is 3.120 Å on the a-axis and 4.994 Å on the c-axis, but it becomes smaller on both the a-axis and c-axis as the oxygen atom dissolves. And if the lattice constant is 3.105 to 3.117 Å on the a-axis and 4.973 to 4.990 Å on the c-axis, the volume angstrom is 10¹⁴It can be controlled to Ω-cm or less.

【0015】

Moreover, the ceramic resistor of the present invention has a small change in resistance with respect to temperature. For example, in the case of general aluminum nitride, it is 10 in the temperature range from room temperature (25 ° C) to 400 ° C.¹⁶Ω-cm to 10¹⁰While it varies up to Ω-cm, the ceramic resistor of the present invention has about 10¹³Ω-cm to 10¹¹It has the characteristic that it changes only 3 orders of magnitude or less from Ω-cm, and has stable resistance characteristics from at least room temperature to 400 ° C.

【0016】

Therefore, it is particularly useful for applications such as electrostatic chucks in semiconductor manufacturing equipment that require stable resistance from room temperature to high temperature.

【0017】

[Example]

Example 1 An AlN film was formed on the surface of a substrate made of an aluminum nitride sintered body by a chemical vapor deposition method. To form an AlN film, the substrate is placed in a furnace heated to 900 ° C by an external heating method, nitrogen is 8 SLM, ammonia is 1 SLM, and N of 0 to 0.5 SLM.₂The pressure was set to 50 torr by flowing O gas. In addition, aluminum chloride (AlCl₃) Was introduced at a flow rate of 0.3 SLM to initiate the reaction, and a film having a film thickness of 450 μm was formed. The obtained film was angle-corrected by the X-ray diffraction method using Si (SRM640b) as a standard sample, and calculated by the peak top method. The measurement surface indices were (100), (002), (101), (102), (110), (103), (112), and (004).

【0018】

[table 1]

【0019】

As is clear from the results in Table 1, the oxygen atomic weight and lattice constant in aluminum nitride are N.₂O Varies with flow rate, N₂When O is not introduced at all and the oxygen atomic weight is 0.0001 atomic% of the impurity level, the volume specific resistance is also 9 × 10.¹⁵It had high insulation of Ω-cm, but N₂As the flow rate of O was gradually increased, the amount of oxygen atoms in the membrane increased, the lattice constant gradually decreased, and the volume intrinsic resistance decreased to 30Ω-cm.

【0020】

The obtained aluminum nitride film was an AlN film oriented in (002) from the X-ray diffraction measurement. However, in the observation with a transmission electron microscope, an alumina crystal phase is present, and the amount is N.₂Correlation with O flow rate was observed. Also, a few crystalline phases were found in which aluminum, oxygen and nitrogen were detected.

【0021】

[Effect of the invention]

As described in detail above, according to the present invention, by controlling the amount of oxygen and the lattice constant in aluminum nitride, the volume specific resistance at room temperature is 10.¹⁴It is possible to obtain a resistor with a temperature change of Ω-cm or less and a small temperature change. Therefore, the resistance value can be changed without losing the characteristics of aluminum nitride, for example, corrosion resistance.