JPH06272033A - Production of abox high dielectric target for sputtering - Google Patents

Abstract

PURPOSE:To obtain a PZT based or PLZT based high dielectric target capable of unnecessitating wet treating process, improving the micronization of target structure and reducing ununiformity, and facilitating the control of the oxygen content of film. CONSTITUTION:In the producing method of the PZT based or PLZT based high dielectric target expressed by the general formula, ABOX (A=Pbm or Pbm-aLaa, B=Zrn-bTib and (x)=0-3.0, where 0.9<=(m)<=1.2, 0.9<=(n)<=1.2, 0.001<(a)<0.2, (b)<0.7), a raw material powder composed of the pure metal and/or oxide of Pb, Zr, Ti, La as the constituting elements of the target is mechanically alloyed to make the PZT based or PLZT based powder, which is formed into the target. The (x) is controlled by selecting whether the pure metal is used or the oxide is used as the raw material powder for the constituting elements. The low cost target small in the generating number of the particle and excellent in sputtering property is produced.

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 high dielectric constant target for sputtering for forming a capacitor material of a semiconductor device, and more particularly to a general formula A
The present invention relates to a method for manufacturing a PZT-based or PLZT-based high dielectric constant target for sputtering represented by BO _X (A = Pb or Pb + La, B = Zr + Ti and X = 0 to 3.0).

[0002]

2. Description of the Related Art A sputtering target is usually a disk-shaped plate which serves as a sputtering source for forming electrodes, gates, wirings, elements, protective films, etc. of various semiconductor devices on a substrate by sputtering. When the accelerated particles collide with the target surface, the atoms constituting the target are released into space by the exchange of momentum and are deposited on the facing substrate. As the sputtering target, Al alloy target, refractory metal and alloy (W, M
o, Ti, Ta, Zr, Nb etc. and its alloys like W-Ti) targets, suicides (MoSi _x , WSi)
_x , NiSi _x, etc.) targets, dielectric targets, etc. are typically used.

A SiO ₂ film is currently used as a capacitor material in DRAM semiconductor devices. Since the SiO ₂ film has good compatibility with the Si semiconductor process, at present (256 kb, 1 Mb, 4 M
b, up to around 16Mb), but VLS
As the degree of integration of I increases, it is almost the limit. This is because the permittivity of SiO ₂ is small, and when the device is scaled down and becomes thinner, the amount of accumulated charge is limited.

As a countermeasure, it is considered to cover the defect of SiO ₂ by enlarging the area, and to use SiO ₂ as a capacitor material and to consider the use of a high dielectric material having a larger dielectric constant. However, the measures described above lead to layering and three-dimensionalization, resulting in cost increase. As a high dielectric material, PZT-based, PLZT-based, BaSrTiO ₃ , BaT
Candidates such as iO ₃ are considered, but the utilization of these materials as a sputtering target is a subject for further study, and the current state of the high dielectric target has not been established yet.

After all, as a fundamental measure for the future, the use of SiO ₂ is a favorite because the dielectric constant is basically small and the amount of accumulated charge is limited. It seems to be. For several reasons
Among the high dielectric materials, it is expected that the PZT system and the PLZT system will be particularly important. Here, the PZT system and the PLZT system are basically the general formula ABO _x (A = P
b or Pb + La, B = Zr + Ti and X = 0-3.
0), which are Pb-Zr-Ti-O-based and Pb-La-Zr-Ti-O-based high dielectric materials, respectively. More specifically, the general formula ABO _x (A = Pb _m or Pb _ma La _a , B = Zr _nb Ti _b and X = 0 to
3.0, where 0.9 ≦ m ≦ 1.2, 0.9 ≦ n ≦ 1.
2, 0.001 ≦ a ≦ 0.2, b ≦ 0.7).

Although some attempts have been started for the production of such PZT-based and PLZT-based targets, in general, PZT-based powders (powder having a composition of PbZrTiO ₃ ) or PLZT-based powders (PbLaZrTiO ₃ composition) are used. Powder) is prepared by a wet process or a dry synthesis process including a coprecipitation method, and then cold pressing and subsequent hot pressing in a sintering or oxidizing atmosphere are performed.

[0007]

The wet process has an advantage that a uniform and fine powder can be obtained, but on the other hand, the process is complicated, there are many factors to be controlled, and it is very expensive. Although the dry synthesis method is relatively simple, it is difficult to control the composition because Pb having a high vapor pressure becomes PbO and volatilizes preferentially, and it is often the case that the dispersion of the constituents is insufficient. Are non-uniform and it is difficult to obtain fine powder.

When the target structure becomes non-uniform, a problem of particle generation occurs. The "particles" are particles that fly in the device during the formation of a thin film and are deposited on the substrate in clusters. Since many of these clustered particles have a diameter of up to several μm, When this is deposited on the substrate, it can be used for LSI, VLS, etc.
In the case of I, problems such as short circuit of wiring or conversely disconnection occur, which causes an increase in defective rate. These particles have various factors such as those caused by the target itself and those caused by the thin film forming apparatus. In order to reduce the amount of particles generated, it is necessary to make the crystal structure of the target uniform and fine. When such a further refinement of the structure is required, the specific surface area increases geometrically as the raw material powder becomes finer, which complicates the process and contaminates impurities such as oxygen, and causes problems of controlling oxygen concentration. . The crushing and classifying processes are practically impossible with conventional ball mills and sieving machines.

Furthermore, these methods are mindful of forming oxides or ABO _x (X = 3) in the powder stage, not taking into account the formation of those with X <3. Eventually, the oxygen content of the film composition must be controlled, but by varying the target oxygen content (lower than the stoichiometric composition), it becomes easier to control the oxygen content of the film composition, and in addition, sputtering The speed should also be able to be improved significantly.

An object of the present invention is to eliminate the need for a wet treatment process which leads to an increase in cost when manufacturing a sputtering target for forming a PZT-based or PLZT-based high dielectric film as a highly integrated DRAM capacitor material, and to improve the target structure. Through the improvement of non-uniformity and dispersion of components, it is to develop a technology for manufacturing a uniform high-quality low-cost target with a small amount of particles generated.

Another object of the present invention is to establish a method for facilitating control of the oxygen content of the film composition by making the oxygen content of the target variable (lower than the stoichiometric composition). That is.

[0012]

The present inventor has conceived to adopt a mechanical alloying method as a powder manufacturing process for manufacturing a PZT-based or PLZT-based high dielectric sputtering target. As a result of trial, it was found that a target having a uniform and fine crystal structure can be manufactured by using a PZT-based or PLZT-based high-dielectric powder obtained by mechanical alloying and targeting it. It has been found that mechanical alloying allows the use of relatively large raw material powder particles, thus avoiding the problems of oxygen contamination and oxygen control associated with the use of finer starting raw material powders. In addition, when the powder obtained by mechanical alloying is used, hot pressing can be avoided or the temperature can be made lower than before, and the hot pressing time can be shortened, which leads to Pb evaporation problems, oxidation problems and coarse crystal grains. It turned out that it is possible to obtain an unexpected benefit that the problem of reduction can be reduced. Therefore, mechanical alloying is beneficial not only in powder preparation but also in terms of target formation.

[0013] There are no literatures which describe the application of mechanical alloying to the target material for sputtering and the target material for high dielectric materials. For example, the Japan Institute of Metals, Vol. 27, No. 10 (1
988), some research reports are summarized as "Small feature: Recent research trends in mechanical alloying".
There is nothing about the high-dielectric PZT system or PLZT system, and no mention is made of problems specific to the sputtering target.

Based on these findings, the present invention provides
(1) General formula ABO _x (A = Pb or Pb + La, B =
Zr + Ti, and X = 0 to 3.0), in the method of manufacturing a PZT-based or PLZT-based target, target constituent elements Pb, Zr and Ti or Pb, Zr, Ti
And PZT-based or PLZ-based raw powder mixture consisting of pure metal and / or oxide of La by mechanical alloying
A method for producing an ABO _x high-dielectric target for sputtering, characterized in that it is formed as a T-based powder and as a target, and (2) the oxygen content X of the ABO _x high-dielectric target is made of pure metal as a raw material powder of constituent elements. There is provided a method for producing an ABO _x high dielectric constant target for sputtering according to the above 1, which is controlled by selecting whether to use an oxide or an oxide.

"Mechanical alloying" occurs when a hard ball or rod as a grinding medium and generally a mixture of a plurality of raw material powders are filled in a closed container and milled by rolling or mechanical stirring. It means to bring the components into ultrafine mixing, solid solution, and the amorphous state as the limit.

[0016]

The PZT system is a solid solution ceramic of PbZrO ₃ which is an antiferroelectric substance and PbTiO ₃ which is a ferroelectric substance.
The PLZT system is a PZT system doped with La. These are represented by the general formula ABO _x (A = Pb _m or Pb
_ma La _a , B = Zr _{n- b} Ti _b and X = 0-3.
It is represented by 0). In general, m and n and a and b can take the following ranges. 0.9 ≦ m ≦ 1.2, 0.9 ≦ n ≦
1.2, 0.001 ≦ a ≦ 0.2, b ≦ 0.7. PZT
In addition to the pure (genuine) ceramics, the PLZT system and the metal PZT and PLZT and modified products obtained by substituting Pb ²⁺ with Ba ²⁺ , Sr ²⁺ and the like are also included. According to the present invention, due to mechanical alloying, PZT which can be realized only by a conventional wet method which is costly
A dry method is used to achieve finer structure of PLZT powder or PLZT powder and to uniformly disperse and solidify components.

In the process of the present invention, a high energy mill such as a ball mill, a rod mill, a rolling mill, an attritor, etc., which is provided with measures against contamination from the grinding medium and the container, preferably has a mean particle size of 1 to 100 μm as PZT system or PLZ as raw material powder.
A raw material powder for producing a T-based powder is added. In the case of PZT system, the raw material powder is Pb or PbO, Zr or Z.
rO ₂ and Ti or TiO ₂ , and in the case of the PLZT system, La or La ₂ O ₃ is further added. Depending on the X of the ABO _x to be produced, the pure metal form or the oxide form can be selected. If the raw material powder to be charged has an average particle size of 100 μm or more, it takes time to form a solid solution, while if it is less than 1 μm, the raw material powder is expensive and handling is difficult, which is not economical.

The ratio of the amount of raw material input to the amount of grinding medium is 1: 1.
It is preferably 0 to 1: 100. This 1: 100
If it is less than, the amount of processing per batch is small and mass productivity is poor,
This is because if it is 1:10 or more, the time required for solid solution becomes long. It should be noted that oxygen contamination during mechanical alloying can be prevented by creating an inert atmosphere in the container after charging the raw materials.

The mechanical alloying time strongly depends on the particle size of the above-mentioned raw material and the ratio of the raw material input amount to the grinding medium. Mechanical alloying proceeds in four stages. The first stage is a stage in which pulverization and mixing of the fed raw material mixed powder progresses, and the second stage is rapid miniaturization and agglomeration of the raw material mixed powder repeatedly, resulting in each raw material being submicron or finer. This is the stage where agglomerates of powder with a particle size of several tens of microns are formed. In the third stage, the agglomerated powder gradually becomes equiaxed, and the raw material mixed powder is further homogenized in the inside, resulting in atomic level mixing and solid solution. At the fourth stage, the crystal structure of the solid solution raw material mixed powder is finally broken and becomes amorphous.

In the present invention, the target properties of the mechanical alloying powder are mainly the state of secondary particle powder in which the secondary particles of 5 μm or less corresponding to the above-mentioned third stage are aggregated to a size of about 10 μm or more. However, it is also possible to use amorphized grains in the fourth stage. Secondary particles obtained by aggregating such primary particles have excellent antioxidant ability because they have a form in which the primary particles are wrapped inside, and because they agglomerate to an appropriate size, they are excellent in press formability, so a sputtering target should be used. Suitable as a raw material for molding by pressing.
It is preferable to obtain a secondary particle powder that is aggregated to 10 μm or more, because if it is less than 10 μm, it is strongly subjected to oxygen contamination when taken out from the container after mechanical alloying. In addition, in the aggregate of primary particles that have not yet been solidified in the second stage, the solid solution in the later stage is burdened with solution, while in the amorphous particles that appear in the fourth stage, the milling time is long, Not suitable for mass production, but can be used.

The mechanically alloyed PZT-based or PLZT-based powder thus obtained is molded into a target by cold pressing. Since the constituent atoms have achieved a sufficient solid solution state by mechanical alloying, it is possible to obtain a good P by forming a target only by cold pressing and heat-treating the film formed by sputtering the target.
A ZT-based or PLZT-based film can be obtained. But,
Cold pressing may be followed by sintering or hot pressing in an atmosphere capable of preventing Pb evaporation.

For example, PL of ABO _x (X = 0.61)
Taking the case of manufacturing a ZT-based target as an example, Pb: 51.0 at% and La ₂ O ₃ : 1.4 at% are used as raw materials.
(Metal content), ZrO ₂ : 14.3 at% (metal content)
And Ti: 33.3 at% are mechanically alloyed by means such as a ball mill and an attritor to obtain a PLZT-based powder having extremely good dispersibility, cold pressed, finished by machining, bonded to a backing plate, and bonded to ABO _0.61. PLZT system target. If one wants to increase X, this can be accommodated by using TiO ₂ instead of pure metal Ti and / or PbO instead of Pb. On the contrary, if it is desired to reduce X, pure Zr may be used as a raw material instead of ZrO ₂ . Taking the case of manufacturing a PZT-based target of ABO _x (X = 1.5) as an example, as a raw material, PbO: 50a
t%, ZrO ₂ : 25 at% and TiO ₂ : 25 at%
Is mechanically alloyed with a means such as a ball mill and an attritor to obtain a PZT-based powder having extremely good dispersibility, cold pressed and sintered, and similarly ABO _1.5 PZT
System target. It is also possible to manufacture a PZT or PLZT metal target and oxidize it by sputtering in an O ₂ atmosphere.

Eventually, the oxygen content of the film composition must be controlled, but by making the oxygen content of the target variable (lower than the stoichiometric composition), it becomes easy to control the oxygen content of the film composition, In addition, the sputter rate can be greatly improved. As compared with the case where the oxide target is sputtered, it is possible to have a wider range of sputtering conditions, and finally a film having excellent characteristics can be manufactured. Further, the toughness of the target itself can be improved by controlling the oxygen content, and problems such as cracking and chipping can be solved.

The refinement of the target structure stabilizes the spatter and brings out the advantage of low particles.

The thus-produced target is deposited by sputtering in an inert atmosphere or an oxygen atmosphere, and if necessary, heat-treated at a temperature of 400 to 700 ° C.

[0026]

EXAMPLES Examples of the present invention will be shown below.

(Example 1) Pb: 3540 g, ZrO
₂ : 1039 g and Ti: 406 g were mixed and mechanically alloyed by a ball mill. The obtained powder was filled in a mold having a diameter of 310 mm and cold pressed to obtain a molded product having a diameter of 310 mm and a thickness of 10 mm.
This is machine-finished as it is and bonded to P
It was a ZT-based target. ABO _1.0 PZ with X = 1.0
A T-based target was obtained. This target was sputtered in an O ₂ atmosphere and heat-treated at 600 ° C. to obtain a good PZT-based film. The number of particles generated was small.

(Example 2) Pb: 3976 g, Zr: 8
76 g and Ti: 456 g were mixed and mechanically alloyed by a ball mill in the same manner as in Example 1.
The obtained powder was filled in a mold having a diameter of 310 mm and cold pressed to obtain a molded product having a diameter of 310 mm and a thickness of 10 mm. This was machine-finished and bonded as it was to obtain a metal PZT-based target. P for X = 0
A ZT-based target was obtained. This target was sputtered in an O ₂ atmosphere and heat-treated at 600 ° C. to obtain a good PZT-based film. The number of particles generated was small.

(Example 3) Pb: 3692 g, ZrO
₂ : 616 g, La ₂ O ₃ : 82 g and Ti: 559 g
Were mixed and mechanically alloyed by a ball mill in the same manner as in Example 1. 310 mm of the obtained powder
It is filled in a metal mold of diameter and cold pressed, 310 m
A molded body of m diameter × 10 mm thickness was obtained. This was machine-finished and bonded as it was to obtain a metal PLZT-based target. X = 0.59 ABO _0.59 PLZT
The system target was obtained. This target was sputtered in an O ₂ atmosphere and heat-treated at 600 ° C. to obtain a good PZT-based film. The number of particles generated was small.

[0030]

EFFECTS OF THE INVENTION When manufacturing a sputtering target for forming a PZT-based or PLZT-based high-dielectric film as a highly integrated DRAM capacitor material, a wet process step leading to an increase in cost is unnecessary, and the target structure is not uniform. Further, it is possible to improve the dispersion of components and to manufacture a low-cost target with a small amount of particles generated. By making the oxygen amount of the target variable (lower than the stoichiometric composition), the oxygen amount of the film composition can be easily controlled, and the sputtering rate can be greatly improved. Sputtering conditions can have a wider range than when an oxide target is sputtered, and finally a film with excellent characteristics can be produced, and the toughness of the target itself also controls the oxygen content. Can be improved and cracked,
Problems such as chipping can be solved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Yasui Koichi Yasui 187 Usba, Hwagawa Town, Kitaibaraki City, Ibaraki Prefecture 4 Stocks at Nikko Kyoiso Isohara Factory

Claims (2)

[Claims] 1. The general formula ABO _x (A = Pb or Pb + L
a, B = Zr + Ti and X = 0 to 3.0), the target constituent elements Pb, Zr and Ti or Pb,
Manufacture of ABO _x high dielectric constant target for sputtering, characterized in that a raw material powder mixture consisting of pure metals and / or oxides of Zr, Ti and La is made into PZT type or PLZT type powder by mechanical alloying and formed as a target. Method. 2. The sputtering method according to claim 1, wherein the oxygen content X of the ABO _X high-dielectric-constant target is controlled by selecting whether the raw material powder of the constituent elements is a pure metal or an oxide. ABO _X High-dielectric Target Manufacturing Method.