JPH08199349A - Production of chromium based sputtering target - Google Patents

Abstract

PURPOSE: To produce a chromium based sputtering target capable of obtaining stable discharge voltage by molding and vacuum firing a mixture of powder of an oxide and carbide of chromium, and then pulverizing the fired body, molding and vacuum firing the result. CONSTITUTION: The oxide and carbide of chromium are mixed. It is preferable as the starting raw material to mix Cr2 O3 powder and Cr3 C2 powder in the molar ratio of Cr2 O3 /Cr3 C2 =1.0-4.2 and to have <=100μm particle diameter. A ball mill can be used for mixing. The powder mixture is compacted by metallic die molding method or the like and the compact is vacuum fired at <=100Pa and at >=1200 deg.C. Cr2 O3 is reduced by Cr3 C2 by this method. The resultant fired mixture of metal Cr and Cr2 O3 is pulverized into <=150μm particle diameter by a jaw crusher or the like, pressed by a cold hydrostatic press method or the like and vacuum fired. As a result, meal chromium and chromium oxide are densely and uniformly dispersed and the target having no spot in the structure and capable of excellently a forming film with stable discharge voltage is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sputtering target used for forming a chromium oxide thin film in manufacturing a liquid crystal display panel or the like.

[0002]

2. Description of the Related Art Conventionally, reactive sputtering using a metallic chromium target has been employed for forming a chromium oxide thin film used for a black matrix of a liquid crystal display (LCD) panel. However, in the reactive sputtering using this metallic chromium target, the margin in the film forming conditions for forming the chromium oxide thin film is narrow, and the film forming rate is slower than other film forming processes such as DC sputtering, and the throughput is low. There was a problem such as being small.

Therefore, a Cr—Cr ₂ O ₃ sputtering target capable of forming a chromium oxide thin film by DC sputtering has been developed. This is a sputtering target composed of a sintered body containing metallic chromium and chromium oxide as main components, which is obtained by mixing metallic chromium powder and chromium oxide powder and sintering them in a non-oxidizing atmosphere. However, in the Cr-Cr ₂ O ₃ sputtering target produced by the method of easily become dispersed state nonuniform metallic chromium and chromium oxide in the target, as a result, particle size in black in the target tissue Many spots of chromium oxide of about several hundred μm were sometimes generated. If the dispersion of metallic chromium and chromium oxide is non-uniform and many spots as described above are present in the target structure, the discharge voltage will not be stable due to local concentration of discharge during sputtering, and as a result, it will be stable. There was a problem that the film could not be formed.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for producing a chromium-based sputtering target mainly composed of metallic chromium and chromium oxide, which solves the above-mentioned problems. That is, the dispersed state of metallic chromium and chromium oxide in the target is dense and uniform, there are no spots in the target structure, and as a result, the discharge voltage during sputtering is stable and film formation is performed well. An object of the present invention is to provide a method for producing a chromium-based sputtering target that can be used.

[0005]

In order to achieve the above object, in the method for producing a chromium-based sputtering target of the present invention, a fired product obtained by vacuum firing a molded body of a mixed powder of chromium oxide and carbide is used. It is crushed, and the crushed powder compact is fired in a vacuum. In the present invention, the vacuum firing means firing in a state where the pressure inside the firing furnace is kept at 100 Pa or less.

The method for producing the chromium-based sputtering target of the present invention will be described in more detail below.
In the present invention, chromium oxide powder and chromium carbide powder are used as raw material powders, and a series of processes of mixing-molding-first firing (reduction reaction) -milling-molding-second firing (sintering) -grinding process is performed. A chrome-based sputtering target is manufactured. FIG. 1 is a flowchart of an example of the manufacturing method of the present invention.
Shown in

The composition of chromium oxide used as a raw material is not particularly limited, and any oxide of chromium may be used, and Cr ₂ O ₃ which is easily available as a commercial product can be used. , Cr ₅ O ₁₂ , Cr ₃ O ₄ , CrO ₂ , C
rO, may be used Cr ₃ O ₂ and the like. The composition of chromium carbide used as a raw material is not particularly limited, and any chromium carbide may be used, and Cr ₃ C ₂ which is easily available as a commercial product can be used. In addition to this, for example, Cr ₇ C ₃ , C
r ₂₃ C _6, Cr ₂ C or the like may be used. Both raw material powders may be used alone or in combination of two or more. The particle size of the raw material powder is preferably 100 μm or less, more preferably 10 μm or less.

The mixing ratio of the above-mentioned chromium oxide powder as the raw material powder and the chromium carbide powder may be such that at least the carbon in the chromium carbide is consumed by the reduction reaction of chromium oxide. When Cr ₂ O ₃ powder and Cr ₃ C ₂ powder are used as raw material powders, the mixing ratio of both is Cr ₂ O ₃ in terms of molar ratio.
/ Cr ₃ C ₂ = 2/3 or more, but in order to obtain a chromium-based sputtering target exhibiting good characteristics, the mixing ratio of both is Cr ₂ O ₃ / Cr ₃ C ₂ = 1. ．
It is desirable that it is 0 to 4.2. This is because it is desirable that the obtained sputtering target has a sufficiently large conductivity and contains sufficient oxygen.
The method of mixing the above chromium oxide powder and the chromium carbide powder is not particularly limited, and ordinary ball mill mixing using balls made of zirconia, nylon, or the like may be performed. The molding of this mixed powder is carried out for the purpose of increasing the contact area between the two powders in order to effectively proceed the reduction reaction of chromium oxide by the subsequent vacuum firing. Just do it. Further, if necessary, it is desirable to perform pressure treatment by a cold isostatic pressing method.

The molded body obtained as described above is
By performing vacuum firing at a predetermined temperature as the firing, the chromium oxide in the molded body is reduced by the chromium carbide, and a fired product mainly composed of metallic chromium and chromium oxide is obtained. When Cr ₂ O ₃ powder and Cr ₃ C ₂ powder are used as the raw material powder, the firing temperature of this first firing is 1200.
It may be at least ℃, and the firing time is preferably 1 to 20 hours. In the first firing, CO gas is generated by the reduction reaction of chromium oxide with chromium carbide.
In order to make this reduction reaction proceed rapidly, it is necessary to reduce the pressure inside the firing furnace to 100 Pa or less, but in order to improve the dispersion state of metallic chromium and chromium oxide in the fired product. Further, it is more desirable to reduce the pressure in the furnace to 5 Pa or less.

Next, the above fired product is pulverized. The crushing method is not particularly limited, and a particle size, for example, a particle size of 150 μm, in which the crushed powder can be easily molded in the next step using a jaw crusher, a brown crusher, or the like
The crushing may be performed so as to be m or less. As a method for molding the pulverized powder, a molding method suitable for the target shape of the sputtering target may be selected, and examples thereof include a die molding method and a casting molding method. Further, if necessary, it is desirable to perform pressure treatment by a cold isostatic pressing method.

The molded body obtained as described above is used as a second
As firing, vacuum firing is performed at a predetermined temperature to sinter the molded body to obtain a sintered body mainly composed of metallic chromium and chromium oxide. The firing temperature of the second firing may be 1200 ° C. or higher, and the firing time is not particularly limited, but is preferably 1 hour to 20 hours.
Further, in order to prevent the metallic chromium in the produced sintered body from being oxidized more than necessary, the furnace pressure in the firing furnace is 100
Although it is necessary to reduce the pressure to Pa or less, it is more desirable to reduce the pressure in the furnace to 5 Pa or less in order to improve the uniformity of the dispersed state of metallic chromium and chromium oxide in the sintered body.

By grinding the sintered body mainly composed of metallic chromium and chromium oxide produced as described above and shaping it into a predetermined size, the discharge voltage and discharge current during sputtering are stable and stable. It is possible to manufacture a chromium-based sputtering target capable of forming various films.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples.

Example 1 196.7 g of commercially available chromium oxide (Cr ₂ O ₃ ) powder and 179.0 g of commercially available chromium carbide (Cr ₃ C ₂ ) powder (mixing ratio (molar ratio) of both: Cr ₂ O ₃ / Cr ₃ C ₂ = 1.30) was placed in a 5 liter polyethylene pot together with an iron core-containing nylon ball having a diameter of 15 mmφ and ethanol as a mixed medium, and ball mill mixing was carried out for 24 hours. After mixing, the slurry and balls were separated. The obtained slurry was put in an eggplant-shaped flask and dried by an evaporator. After granulating the dry powder, it was molded at a pressure of 0.2 ton / cm ² using a 150 mmφ mold, and further treated at a pressure of 3 ton / cm ² by a cold isostatic pressing method, and then in a furnace of a firing furnace. Firing was performed at 1400 ° C. for 15 hours with the internal pressure reduced to 5 Pa or less. The obtained calcined product was pulverized and granulated, then molded at a pressure of 0.2 ton / cm ² using a mold of 150 mmφ, and further processed at a pressure of 3 ton / cm ^{2 by} the cold isostatic pressing method. rear,
With the pressure inside the firing furnace reduced to 5 Pa or less, 14
Sintering was performed by firing at 00 ° C. for 5 hours. The surface of the obtained sintered body was ground by a surface grinder, and the side surface was ground by a cylindrical grinder to shape it, thereby preparing a chromium-based sputtering target. When the number of spots on the surface of the target to be sputtered (hereinafter referred to as the sputter surface) was examined by visual inspection, no spots were found. Further, this target was bonded to a backing plate and attached to a sputtering apparatus, and the discharge voltage and discharge current were observed for one hour while the discharge power was kept constant, and both showed constant values during the measurement. Moreover, when the composition of this target was analyzed, Cr: Cr ₂
The composition ratio (wt%) of O ₃ was 70:30.

[0015] Example 2 Cr ₂ O ₃ powder 231.9g, Cr ₃ C ₂ powder 127.
8 g (mixing ratio (molar ratio) of both: Cr ₂ O ₃ / Cr ₃ C ₂ =
A chromium-based sputtering target was produced in the same manner as in Example 1 except that the above procedure was changed to 2.15), and the same test as in Example 1 was performed. No spots were observed by visual inspection of the sputter surface of this target, and the discharge voltage and discharge current when the discharge power was constant showed constant values during the measurement for 1 hour. Moreover, when the composition analysis of the target was performed,
The composition ratio (wt%) of Cr: Cr ₂ O ₃ was 50:50.

Example 3 267.1 g of Cr ₂ O ₃ powder and 76.7 of Cr ₃ C ₂ powder
g (mixing ratio (molar ratio) of both: Cr ₂ O ₃ / Cr ₃ C ₂ =
A chromium-based sputtering target was produced in the same manner as in Example 1 except that the above was set to 4.13), and the same test as in Example 1 was performed. In the visual inspection of the sputter surface of this target, one spot was observed, but the discharge voltage and discharge current when the discharge power was constant showed constant values during the measurement for 1 hour. Further, when the composition of the target was analyzed, the composition ratio (wt%) of Cr: Cr ₂ O ₃ was 30:
It was 70.

Comparative Example 1 224 g of commercially available metallic chromium powder and C used in Example 1
With 96 g of r ₂ O ₃ powder, a diameter of 15 m was obtained in the same manner as in Example 1.
A nylon ball containing mφ iron core and ethanol as a mixed medium were placed in a polyethylene pot of 5 liters, and ball mill mixing was performed for 24 hours. After mixing
In exactly the same manner as in Example 1, the slurry and the balls were separated, the slurry was placed in an eggplant-shaped flask, dried by an evaporator, and granulated.
Molded at a pressure of 2 ton / cm ^2, further after treatment with a pressure of 3 ton / cm ² by cold isostatic pressing method, a furnace pressure sintering furnace in a state of reduced pressure below 5 Pa, 1400 ° C.
Sintering is carried out by firing for 5 hours, the surface of the obtained sintered body is ground by a surface grinder, and the side surface is ground by a cylindrical grinder to shape the Cr-Cr ₂ O ₃ sputtering target. did. When the number of spots on the sputter surface of this target was examined by visual inspection, 10 spots were recognized. Further, this was bonded to a backing plate and attached to a sputtering device in exactly the same manner as in Example 1, and the temporal changes in discharge voltage and discharge current were observed for 1 hour with the discharge power kept constant. Both were unstable during measurement. Met. Moreover, when the composition of the target was analyzed, the composition ratio (wt%) of Cr: Cr ₂ O ₃ was 70: 3.
It was 0.

Comparative Example 2 A Cr-Cr ₂ O ₃ sputtering target was prepared in exactly the same manner as in Comparative Example 1 except that the amount of metallic chromium powder was 160 g and the amount of Cr ₂ O ₃ powder was 160 g. The test was conducted. In the visual inspection of the sputter surface of this target, 22 spots were observed, and further, the discharge voltage and the discharge current when the discharge power was constant were unstable during the measurement for 1 hour. Further, when the composition of the target was analyzed, the composition ratio (wt%) of Cr: Cr ₂ O ₃ was 5
It was 0:50.

Comparative Example 3 A Cr-Cr ₂ O ₃ sputtering target was prepared in the same manner as in Comparative Example 1 except that 96 g of metal chromium powder and 224 g of Cr ₂ O ₃ powder were used, and the same as in Example 1. The test was conducted. Visual inspection of the sputtered surface of this target revealed 32 spots, and the discharge voltage and discharge current were unstable during a 1-hour measurement when the discharge power was constant. Further, when the composition of the target was analyzed, the composition ratio (wt%) of Cr: Cr ₂ O ₃ was 3
It was 0:70.

Table 1 collectively shows the results of the bulk characteristics and the discharge characteristics during sputtering of the targets obtained in the above-mentioned Examples and Comparative Examples. As is clear from this result, it was shown that the chromium-based sputtering target obtained by the present invention has excellent characteristics.

[0021]

[Table 1]

[0022]

According to the method for producing a chromium-based sputtering target of the present invention, the Cr-C conventionally used has been used.
Compared with the r ₂ O ₃ sputtering target, the dispersed state of metallic chromium and chromium oxide in the target can be made dense and uniform, and the generation of spots in the target structure can be prevented. As a result, the local concentration of the discharge is eliminated during the sputtering, and the discharge characteristics are stabilized, so that the film formation can be performed very stably.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of a manufacturing method of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G02F 1/1335 500 H01B 13/00 503 Z H01L 21/203 S

Claims (2)

[Claims] 1. A chromium-based sputtering machine characterized by crushing a fired product obtained by vacuum firing a shaped body of a mixed powder of chromium oxide and carbide, and firing the shaped body of the crushed powder in vacuum. Get manufacturing method. 2. The method for producing a sputtering target according to claim 1, wherein the starting material chromium oxide powder and chromium carbide powder are Cr ₂ O ₃ powder and Cr ₃ C ₂ powder, respectively, and the mixing ratio of the two is molar. The ratio is Cr ₂ O ₃ / Cr ₃ C ₂
= 1.0 to 4.2. A method for producing a chromium-based sputtering target, wherein: