JP3127824B2 - Sputtering target for forming ferroelectric film and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputtering target for forming a ferroelectric film such as a thin film for a capacitor such as a semiconductor memory.

[0002]

2. Description of the Related Art Generally, a composite oxide of Ba and Ti such as BaTiO ₃ (hereinafter referred to as BaTi composite oxide), a composite oxide of Sr and Ti such as SrTiO ₃ (hereinafter referred to as SrTi composite oxide) and ( Ba, S
r) forming a ferroelectric film having a perovskite structure using a sputtering target made of a sintered body such as a composite oxide of Ba, Sr and Ti such as TiO ₃ (hereinafter referred to as a BaSrTi composite oxide); It is known to be used as a thin film for a capacitor in a semiconductor memory or the like.

[0003] The sputtering target for forming a ferroelectric film formed of a sintered body of BaTi composite oxide, SrTi composite oxide or BaSrTi composite oxide is a commercially available Ba target.
Ti composite oxide powder, SrTi composite oxide powder or B
aSrTi composite oxide powder is purchased and this BaTi composite oxide powder, SrTi composite oxide powder or BaSrT
Pressure of i composite oxide powder: 150 kg / c
It is manufactured by hot pressing under the conditions of m ² , temperature: 1200 to 1350 ° C., and holding for 0.5 to 3 hours. The sintered body made of the hot-pressed BaTi composite oxide, SrTi composite oxide or BaSrTi composite oxide is machined and finished to a predetermined target shape.

[0004]

In recent years, for mass production and cost reduction of semiconductor memories, it has been attempted to form a ferroelectric film in a short time by sputtering at a high output and forming a film at a high speed. However, using a conventional sputtering target for forming a ferroelectric film, a film forming rate of 10
0 angstroms / min. When the high-speed sputtering film formation is performed, the target surface may peel off in a scale-like manner, or the entire target may be broken.
00 angstroms / min. In order to perform the above high-speed sputtering film formation, it is necessary to increase the density of the target and increase the strength and thermal conductivity of the target,
When a target is manufactured by hot pressing using conventional raw materials, cracks tend to occur due to hot press up,
Product yield was low.

[0005]

Means for Solving the Problems Accordingly, the present inventors have:
Conducted research to develop a sputtering target for ferroelectric film formation that does not cause cracking and peeling even when high-speed sputtering film formation is applied with high power, and that does not cause cracking during manufacturing of the sputtering target. As a result, (a) The conventional sputtering target for forming a ferroelectric film contains carbon in an amount of about 500 to 1000 ppm, and the cracks and peeling during the high-speed sputtering film formation are largely affected by carbon. ,
The carbon contained in the sputtering target for forming a ferroelectric film is preferably as small as possible, and it is necessary to suppress C: 300 ppm or less. (B) Used as a raw material powder of a conventional sputtering target for forming a ferroelectric film. Each of commercially available BaTi composite oxide powder, SrTi composite oxide powder and BaSrTi composite oxide powder contains 5 carbon atoms.
About 1000-1000 ppm, and this carbon
BaTi composite oxide powder, SrTi composite oxide powder or BaSrTi
When a sputtering target for forming a ferroelectric film is manufactured using a composite oxide powder, cracks occur due to hot pressing at the time of manufacturing the sputtering target. Well, it was found that it was necessary to suppress C: to 300 ppm or less.

The present invention has been made based on such findings, and (1) a sputtering target for forming a ferroelectric film, comprising a BaTi composite oxide sintered body having a C content of 300 ppm or less. (2) C content is 300pp
m, a sputtering target for forming a ferroelectric film comprising a SrTi composite oxide sintered body having a C content of 3 m or less.
(4) a sputtering target for forming a ferroelectric film, comprising a BaSrTi composite oxide sintered body of not more than 00 ppm;
Ba and Ti composite oxide powder having a C content of 300 ppm or less, Sr and T having a C content of 300 ppm or less
The present invention is characterized by a method for producing a ferroelectric film-forming sputtering target for sintering a composite oxide powder of i or a composite oxide powder of Ba, Sr and Ti having a C content of 300 ppm or less.

[0007] The C content contained in the target is preferably as small as possible because it greatly affects the cracking and peeling of the target during high-power sputtering. Undesirably, cracks and peeling occur in all the targets inside. Therefore, if the content of C is 30
It was determined to be 0 ppm or less. A more preferred range of the C content is 100 ppm or less.

A commercially available BaTi composite oxide powder containing about 500 to 1000 ppm of carbon, SrTi
When the composite oxide powder or the BaSrTi composite oxide powder is used as a raw material powder, cracks are generated by hot pressing because the sintering proceeds from the periphery toward the center and occurs at the center of the sintered body. It is considered that the released CO gas loses an escape place and destroys the sintered body.

A raw material powder used in the present invention, a BaTi composite oxide powder having a C content of 300 ppm or less, Sr
Ti composite oxide powder or BaSrTi composite oxide powder, commercially available BaTi composite oxide powder, SrTi composite oxide powder or BaSrTi composite oxide powder, in the air,
It can be manufactured by heating at a temperature of 1100 ° C. for 6 hours. These BaTi composite oxide powder, SrTi composite oxide powder or BaSrTi composite oxide powder do not sinter even when heated to 1100 ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

 Commercial purity: 99.9% BaTiO_ThreePowder, SrTi
O_ThreePowder, (Ba_0.75, Sr_0.25) TiO_ThreePowder, (B
a_0.5, Sr_0.5) TiO_ThreePowder and (Ba _0.25, S
r_0.75) TiO_ThreeAfter purchasing the powder and measuring the C content
At this time, C shown in Table 1 was included.

This commercially available BaTiO ₃ powder, SrTiO
₃ powder, (Ba _0.75 , Sr _0.25 ) TiO ₃ powder, (Ba
_0.5 , Sr _0.5 ) TiO ₃ powder and (Ba _0.25 , Sr
_0.75 ) The TiO ₃ powder was decarburized by heat treatment at 1100 ° C. for 1 hour in the air to produce an ultra-low carbon composite oxide powder having the component composition shown in Table 1.

[0012]

[Table 1]

EXAMPLE An ultra-low carbon composite oxide powder obtained by heat treatment and having a carbon concentration shown in Table 1 was put into a ball mill and pulverized to obtain an ultra-low carbon composite oxide having an average particle size of 1 to 5 μm. A powder is produced, and the obtained ultra-low carbon composite oxide powder is filled in a graphite mold. The temperature rising rate is 5 ° C./min, the heating temperature is 1300 ° C., the pressure is 150 ton / cm ² , and the holding time is 1 hour. After hot pressing under the conditions of: cooling: furnace cooling, the surface is ground to produce sputtering targets of the present invention (hereinafter, referred to as target of the present invention) 1 to 5 having dimensions of 350 mm in diameter and 6 mm in thickness. did. Table 2 shows the obtained C contents of the present targets 1 to 5.

Further, with respect to the targets 1 to 5 of the present invention, hot pressing was performed 10 times with the same raw material, and the number of successful hot pressing without cracks was measured. The results are shown in Table 2. . Next, the target that could be hot pressed without cracking was bonded to a water-cooled copper plate with In-Sn solder, set in a high-frequency magnetron sputtering apparatus, and an atmosphere gas: a mixed gas of Ar and oxygen (Ar: O = 1) :
1) Atmospheric pressure: 1 pa, frequency: 13.56 Mhz, output: 6000 W, time: 50 hours, sputtered, and observed whether or not a flake-like crack was generated on the target by silent observation. The results are also shown in Table 2.

Conventional Example A commercially available BaTiO ₃ powder having a carbon concentration shown in Table 1
rTiO ₃ powder, (Ba _0.75 , Sr _0.25 ) TiO ₃ powder, (Ba _0.5 , Sr _0.5 ) TiO ₃ powder and (Ba
_0.25 , Sr _0.75 ) TiO ₃ powder was hot-pressed under the same conditions as in the examples to produce conventional sputtering targets (hereinafter referred to as conventional targets) 1 to 5.
The C content contained in the obtained conventional targets 1 to 5 was measured, and the number of successful targets that could be hot-pressed without cracking by performing the same raw material 10 times was measured. Sputtering under the same conditions as in the example using the target that could be hot pressed without, observing with naked eye whether scaly cracks occurred in the target at that time,
The results are shown in Table 2.

[0016]

[Table 2]

[0017]

From the results shown in Tables 1 and 2, the C content obtained by using the ultra-low carbon composite oxide powder: 300
Each of the targets 1 to 5 of the present invention having a C content of not more than 1 ppm is obtained by using a commercially available composite oxide powder containing a C content of 500 to 1000 ppm. Cracks do not occur during production by hot pressing, and high-power and high-speed film formation can be performed without peeling or cracking during sputtering, and an industrially superior effect is achieved.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁷ identification code FI H01L 21/8242 H01L 27/10 651 27/108 (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 14/00 -14/58 C01G 23/00 C01G 25/00-57/00 C04B 35/42 C01F 11/16 C01B 13/16 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A sputtering target for forming a ferroelectric film, comprising a sintered oxide of Ba and Ti having a C content of 300 ppm or less. 2. A sputtering target for forming a ferroelectric film, comprising a sintered composite oxide of Sr and Ti having a C content of 300 ppm or less. 3. Ba and S having a C content of 300 ppm or less.
A sputtering target for forming a ferroelectric film, comprising a composite oxide sintered body of r and Ti. 4. A composite oxide powder of Ba and Ti having a C content of 300 ppm or less, a composite oxide powder of Sr and Ti having a C content of 300 ppm or less, or Ba, Sr and Ti having a C content of 300 ppm or less. A method for producing a sputtering target for forming a ferroelectric film, characterized by sintering a composite oxide powder of (1).