JP2000273623A - Ti-Al alloy sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a useful Ti-Al alloy sputtering target which can be used for forming a barrier film for preventing contamination generated by mutual diffusion of substances constituting a laminated thin film. Kind Code: A1 Abstract: Ti-Al containing 5-65 wt% of Al
An alloy sputtering target in which the content of each radioactive element such as U and Th is 0.001 ppm or less, the content of each alkali metal such as Na and K is 0.1 ppm or less, and 10.0 ppm of Fe as a transition metal
Hereinafter, Ni 5.0 ppm or less, Co 2.0 ppm or less,
Ti-Al having a Cr content of 2.0 ppm or less and a purity of 99.995% or more including other impurities
Alloy sputtering target.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a useful Ti-Al alloy sputtering target which can be used for forming a barrier film for preventing contamination generated by interdiffusion of substances constituting a laminated thin film.

[0002]

2. Description of the Related Art In recent years, the manufacture of semiconductor devices has made remarkable progress, and recently, a G (giga) byte scale DRAM has been developed.
Has been designed. Many thin films are formed in the manufacturing process of these semiconductor devices and the like. However, since the distance between the thin films is extremely small and the integration density has been improved, the substances constituting the thin films or the impurities contained in the thin films have been removed. The problem of diffusion into adjacent thin films occurred. As a result, the balance between the constituent materials of the self-film and the adjacent film is lost, and a major problem occurs in that the function of the film that must be originally possessed is reduced. In the process of manufacturing such a thin film, the thin film may be heated to several hundred degrees, and the temperature rises even during use of an electronic device incorporating the semiconductor device. Such an increase in the temperature further increases the diffusion coefficient of the substance, and causes a serious problem in that the function of the electronic device is reduced due to the diffusion.

One example is a capacitor using barium-strontium-titanate (BST). Generally, in this structure, a barrier layer (film) of TiAlN is provided between a silicide (TiSi ₂ ) layer and a BST layer. It is formed. This is for preventing contamination by diffusion of oxygen from the BST layer of the silicide layer. This TiAlN barrier layer is a dense layer, and hardly reacts with other substances with a little heat.
The function as a barrier layer can be sufficiently achieved at about nm.

In general, the barrier layer of TiAlN is formed by sputtering. Sputtering is a technique in which positive ions such as Ar + are physically collided with a target placed on a cathode to release metal atoms constituting the target with the collision energy. It can be formed by using a TiAl alloy and performing sputtering in a mixed gas atmosphere of argon gas and nitrogen.

Conventionally, such an extremely thin barrier layer of TiAlN has been considered to have a sufficient function, and therefore, a TiAl alloy target has been used without any special consideration. However, the alkali metal easily moves in the gate insulating film and degrades the interface characteristics of, for example, VLSI, and the radioactive element has a fatal effect on the operation reliability of the MOS device due to radiation from the element. Further, transition metals such as iron, nickel and cobalt and heavy metals such as chromium generate interface states and cause junction leakage.

When such impurities are mixed into the above-mentioned silicide from the barrier layer, for example, there is a problem that the function of the VLSI is gradually reduced. In addition, oxygen mixed as a gas component has a strong bond with titanium and aluminum, and when mixed in a large amount, not only deteriorates the function as a barrier layer of TiAlN (nitride film), but also the formation of a sputtering film is not smooth. There's a problem. Further, if gas, carbon, hydrogen, or nitrogen is present, an abnormal discharge which is considered to be caused by the gas occurs during sputtering, and a problem that a uniform film is not formed occurs.

As described above, most of the barrier layers made of TiAlN form an extremely thin film so as not to affect other functional thin films, so that a uniform and good dense film cannot be formed. This means that the function as a barrier film is very likely to be impaired. Further, it is necessary to avoid any impurities originating from the barrier film and those affecting other functional elements. For this reason, it is necessary to more carefully and strictly control the function as a barrier film. Conventionally, there has been no idea of controlling the components of the barrier film, and at present the above problems have been neglected.

[0008]

SUMMARY OF THE INVENTION The present invention effectively solves the above-mentioned problems, and in particular, effectively functions as a barrier film for preventing contamination caused by mutual diffusion of materials constituting a laminated thin film. It is another object of the present invention to provide a Ti—Al alloy sputtering target capable of forming a dense film by minimizing contaminants or influence generated from the barrier film.

[0009]

The technical means for solving the above problem is that a stable barrier film can be formed by controlling the components and impurities strictly controlled in the target. Obtained knowledge. Based on this finding, the present invention is directed to a Ti-Al alloy sputtering target containing 1 Al to 65 wt%, wherein the content of each radioactive element such as U and Th is 0.001 ppm or less, Na,
The content of each alkali metal such as K is 0.1 ppm
Hereinafter, the transition metal Fe of 10.0 ppm or less, Ni
5.0 ppm or less, Co 2.0 ppm or less, Cr content is 2.0 ppm or less, and 9% including other impurities.
Ti having a purity of 9.995% or more
-Al alloy sputtering target 2 Gas component oxygen 500 ppm or less, carbon 30p
2. The Ti-Al alloy sputtering target according to claim 1, wherein the sputtering target is not more than pm, not more than 20 ppm of hydrogen, and not more than 80 ppm of nitrogen.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The sputtering target of the present invention has an Al content of 5 to 65 wt%, a content of each radioactive element such as U and Th of 0.001 ppm or less, and a content of each alkali metal such as Na and K of 0%. .1 ppm or less,
Transition metal Fe 10.0 ppm or less, Ni 5.0 p
pm or less, Co 2.0 ppm or less, and the content of Cr is 2.
0 ppm or less and 99.99% including other impurities.
Ti-Al adjusted to have a purity of 5% or more
The alloy is uniformly melted and cast by vacuum arc melting, plasma melting, electron beam melting, induction melting using a water-cooled copper crucible, or the like. As described above, oxygen as a gas component is 500 ppm or less, carbon is 30 ppm or less, hydrogen 2
Since it is 0 ppm or less and nitrogen is 80 ppm or less, in any case, it is necessary to dissolve in a vacuum or in an inert atmosphere in order to prevent mixing of oxygen.

Since both titanium and aluminum have a strong bond with oxygen, it is desirable to use a calcia crucible or to deoxidize with calcium. When an oxide-based refractory material is used, oxygen from the refractory material is strongly taken in. Therefore, it is necessary to avoid this use as much as possible. A preferred melting method is an induction melting method using a water-cooled copper crucible or an induction melting method using a calcia crucible.

In addition to the above-described melting method, it can also be manufactured by powder metallurgy. For example, after mixing aluminum powder of 250 mesh or less and titanium powder of 100 mesh or less prepared as described above, cold isostatic pressure treatment (CIP treatment), and then temperature 500 to 600
A method of hot pressing at 700 ° C. and a pressure of 700 kgf / cm ² , or a CIP process, followed by a hot isostatic pressure process (HIP process) at the same temperature and pressure to produce a Ti—Al alloy target. In any case,
Strict control is required so that gas components that are easily mixed do not enter in the manufacturing process.

The ingot thus manufactured is cut into a target shape, and the surface is polished to obtain a Ti-Al alloy sputtering target with a limited amount of impurities. When performing sputtering, the Ti-A
l Brazing the alloy target to a copper backing plate or solid-phase bonding with an aluminum alloy backing plate, inserting this into a sputtering chamber, filling with a dilute mixed gas of nitrogen gas and argon gas, and reacting Performs reactive sputtering to form a TiAlN barrier film.

As the TiAlN barrier film, Al5 to 65 is used.
wt% is required, and the content of each radioactive element such as U and Th is set to 0.001 ppm or less. 0.001
Exceeding ppm is not preferred because radioactive elements may affect the radiation of the MOS. The content of each alkali metal such as Na and K is set to 0.1 ppm or less. If this amount is exceeded, the influence of the alkali metal from the barrier film causes the deterioration of the MOS interface characteristics due to the alkali metal moving in the gate insulating film, for example, to be ignored. Further, Fe, which is a transition metal or a refractory metal, is 10.0 ppm or less, Ni is 5.0 ppm or less, Co is 2.0 ppm or less, and the content of Cr is 2.0 ppm or less. As a result, generation of interface states and junction leakage can be effectively suppressed. Then, a Ti—Al alloy target adjusted to have a purity of 99.995% or more including other impurities is obtained. As a result, contaminants or influence generated from the barrier film can be reduced as much as possible, and a dense film effectively functioning as a barrier film can be formed.

Next, the present invention will be described based on examples and comparative examples. (Example 1) A was prepared by an induction melting method using a water-cooled copper crucible.
A Ti—Al alloy ingot containing 15.8 wt% of 1 concentration was produced, and a target was manufactured from this ingot. After that, impurity analysis of this target was performed.
The results are as follows. O: 370 ppm, C: 30 ppm, H: 20 ppm,
N: 80 ppm, U: <0.001 ppm, Th: <0.
001 ppm, Na: <0.05 ppm, K: <0.01
ppm, Fe: 7.1 ppm, Ni: 4.9 ppm, C
o: 1.3 ppm, Cr: 1.8 ppm. Next, the Ti-Al alloy target was solid-phase bonded to an aluminum alloy backing plate, and inserted into a sputtering chamber. Then, a dilute mixed gas of nitrogen gas and argon gas was filled and reactive sputtering was performed. And Ti
An AlN film was formed on the substrate. Then, the obtained thin film was examined for damage to the MOS due to radioactive elements, deterioration of the MOS interface due to alkali metal, generation of a MOS interface level / junction leak, and generation of abnormal discharge during sputtering. As a result, in this example in which the content of the radioactive element was 0.001 ppm or less, no damage to the MOS due to radiation was observed. Further, in this embodiment in which the content of each alkali metal such as Na and K is 0.1 ppm or less, the transition metal or the high melting point metal is not affected by the alkali metal from the TiAlN film (barrier film). No generation of interface states and no junction leakage due to the inclusion of Fe, Ni, Co, and Cr. In addition, oxygen, carbon,
In Example 1, in which gas components such as hydrogen and nitrogen were small, generation of abnormal discharge during sputtering was hardly observed.

(Example 2) Ti-A containing 25.0 wt% Al concentration by an induction melting method using a water-cooled copper crucible.
An alloy ingot was manufactured, and a target was manufactured from the ingot. After that, impurity analysis of this target was performed. The results are as follows. O: 220 ppm, C: 10 ppm, H: 10 ppm,
N: <10 ppm, U: <0.001 ppm, Th: <
0.001 ppm, Na: <0.05 ppm, K: <0.
01 ppm, Fe: 8.3 ppm, Ni: 1.4 pp
m, Co: 1.7 ppm, Cr: 1.6 ppm. Sputtering was performed using this target under the same conditions as in Example 1, and damage to the MOS due to radioactive elements in the thin film, deterioration of the MOS interface due to alkali metal, generation of MOS interface level / junction leak, and abnormalities during sputtering The amount of discharge generated was examined. As a result, in Example 2 in which the content of the radioactive element was 0.001 ppm or less, no damage to the MOS due to radiation was observed at all, as in Example 1, and the effect of the alkali metal from the TiAlN film was not observed. No interface state and no junction leak due to the inclusion of Fe, Ni, Co, and Cr, which are transition metals or refractory metals, did not occur. Furthermore, in Example 2 in which gas components such as oxygen, carbon, hydrogen, and nitrogen were small, occurrence of abnormal discharge during sputtering was hardly observed.

Comparative Example 1 Al concentration 2 by powder metallurgy
A Ti—Al alloy ingot containing 7.3 wt% was produced, and a target was manufactured from the ingot. After that, impurity analysis of this target was performed. The results are as follows. O: 670 ppm, C: 30 ppm, H: 15 ppm,
N: 35 ppm, U: <0.001 ppm, Th: 0.
003 ppm, Na: 12 ppm, K: 23 ppm, F
e: 16 ppm, Ni: 20 ppm, Co: 4 ppm,
Cr: 8 ppm. Using this target, sputtering was performed under the same conditions as in Examples 1 and 2, and MO
Damage to S, deterioration of MOS interface due to alkali metal, M
The occurrence of an OS interface level / junction leak and the amount of abnormal discharge during sputtering were examined. As a result, in Comparative Example 1 in which the content of each radioactive element such as U and Th exceeded 0.001 ppm, damage to the MOS due to radiation of the radioactive element was observed. However, the effect on MOS was not so great because the amount of radioactive elements was small. However, since the content of each alkali metal such as Na and K exceeds 0.1 ppm, the MOS interface due to the alkali metal moving in the gate insulating film is affected by the alkali metal from the TiAlN film (barrier film). Deterioration of characteristics occurred. In addition, since the contents of Fe, Ni, Co, and Cr, which are transition metals or refractory metals, are large, interface levels were generated and junction leakage occurred. Furthermore, since there are many gas components such as oxygen, carbon, hydrogen, and nitrogen, abnormal discharge occurs during sputtering, and a uniform and stable thin film cannot be formed.

(Comparative Example 2) Al concentration 4 by powder metallurgy
A Ti-Al alloy ingot containing 5.8 wt% was produced, and a target was manufactured from this ingot. After that, impurity analysis of this target was performed. The results are as follows. O: 1050 ppm, C: 24 ppm, H: 25 pp
m, N: 114 ppm, U: 0.002 ppm, Th:
0.003 ppm, Na: 11 ppm, K: 21 pp
m, Fe: 12 ppm, Ni: 25 ppm, Co: 3.
4 ppm, Cr: 7 ppm. Using this target, sputtering was performed in the same manner as in Examples 1 and 2 and Comparative Example 1. Damage to the MOS due to radioactive elements in the thin film, deterioration of the MOS interface due to alkali metal, and generation of MOS interface state and junction leakage The amount of abnormal discharge generated during sputtering was also examined. As a result,
The content of each radioactive element such as U and Th is 0.00
In Comparative Example 2 exceeding 1 ppm, damage to the MOS due to radiation of radioactive elements was observed. Na,
Since the content of each alkali metal such as K exceeds 0.1 ppm, deterioration of the MOS interface characteristics due to the alkali metal moving in the gate insulating film is affected by the alkali metal from the TiAlN film (barrier film). The transition metal or the high-melting-point metal Fe, Ni, Co, or Cr contained a large amount of the metal, which caused the generation of interface states and the occurrence of junction leakage. Furthermore, since there are many gas components such as oxygen, carbon, hydrogen, and nitrogen, abnormal discharge occurred during sputtering, and a uniform and stable thin film was not formed as in Comparative Example 1.

[0019]

According to the present invention, in particular, the function of a barrier film for preventing contamination generated by interdiffusion of substances constituting a laminated thin film can be effectively exerted, and contaminants or influences generated from the barrier film can be effectively exhibited. And a Ti—Al alloy sputtering target capable of forming a dense film as much as possible. Providing a more suitable barrier film for electronic devices such as semiconductor devices with an extremely high integration density, the effect of radioactive elements on MOS radiation, and the deterioration of MOS interface characteristics due to alkali metal moving in the gate insulating film. And an excellent feature that can effectively suppress the generation of interface states and junction leakage due to the incorporation of transition metals or refractory metals.

Claims (2)

[Claims] 1. Ti-A containing 5-65 wt% of Al
1 alloy sputtering target, wherein the content of each radioactive element such as U and Th is 0.001 ppm or less, the content of each alkali metal such as Na and K is 0.1 ppm or less, and Fe10. 0 ppm
Hereinafter, Ni 5.0 ppm or less, Co 2.0 ppm or less,
A Ti-Al alloy sputtering target having a Cr content of 2.0 ppm or less and a purity of 99.995% or more including other impurities. 2. A gas component of oxygen of 500 ppm or less,
Carbon 30ppm or less, hydrogen 20ppm or less, nitrogen 80p
pm or less.
Al alloy sputtering target.