JPS6379960A - Metal silicide target having high melting point and its production - Google Patents

Abstract

PURPOSE:To produce a high purity metal silicide target having a high m.p. by mixing a metal having a high m.p. with Si in a specified ratio, alloying the mixture by melting, regulating the amount of Si in the resulting alloy and melting the alloy at a proper temp. in a bottomed vessel made of the metal. CONSTITUTION:A high purity metal M having a high m.p. such as Ti, Zr, Ta, Mo or W is mixed with high purity Si in 1:(2-3) molar ratio. The mixture is alloyed by melting at a temp. between a eutectic point Ts positioned on the Si side in a phase diagram of the metal M and Si and the m.p. T of an alloy MSi2 in vacuum of <=about 5X10<-5>Torr. The resulting alloy ingot is crushed and excess Si is chemically leached out so that the compsn. of the alloy is represented by MSi2. Si is then added to the alloy powder to regulate the molar ratio of M:Si to 1:(2-3) again and the powder is put in a bottomed vessel made of the metal M. It is melted at a temp. between the m.p. T and the m.p. of an alloy MSin (n<2) in the phase diagram in vacuum and the melt is cooled.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a sputter target made of a silicide alloy (MSi2) of a high melting point metal (M) and silicon (Si), and further relates to For details, please refer to the high purity and composition MSi2
The present invention relates to a method for manufacturing a target according to No. 3 to 3.

(Prior art) The surfaces of various semiconductor devices have various types of coatings depending on their purpose of use.
A wiring network with a complex pattern is formed using a conductive metal material. In order to form this wiring network, first, a-St.
, AJJ, or the like is formed, and then this thin film is subjected to a predetermined etching process to remove portions other than the desired wiring circuit, leaving the wiring network.

Incidentally, recently, there has been progress in making elements lighter, thinner, and shorter, and as a link to this, efforts are being made to form wiring networks that are more susceptible to damage, that is, to narrow the circuit width and reduce the thickness of the circuit. .

As the degree of integration in semiconductor devices increases in this way, problems with signal delay may occur due to the wiring resistance of the wiring materials used, or if the material is a low melting point material, problems may occur during device operation. A problem begins to arise in that the movement and diffusion of crystal defects due to resistance heat generation in the wiring network causes wiring breakage.

For this reason, as a wiring material, it has a high melting point and low resistance, and is suitable for LSI.

There is a strong demand for materials that do not require major changes in VLSI and ULSI processes, but such materials include high melting point metals (M
), these disilicides of M are attracting attention.

In particular, in the case of disilicide, it is known that when the molar ratio of M:Si is 1:2 to 3, the thin film on the surface of the semiconductor element exhibits excellent low resistance and process compatibility.

On the other hand, the sputtering method is mainly applied to the step of forming a conductive metal thin film, which is a step before forming a wiring network on the surface of a semiconductor element.

This method is a method in which a predetermined ion species is incident on a target made of a material forming a thin film to be formed on the surface of a semiconductor element, and the material forming the target is knocked out and deposited on the surface of the semiconductor element.

When applying this sputtering method, it is necessary to manufacture a sputtering target from the above-described metal material.

That is, for example, when forming the above-mentioned wiring network of MSi2-3, materials of MSi2-3 are used as targets.

In this case, it is necessary that the MSi2-3 materials have high purity.

For example, if the MSi2-3 material contains oxygen as an impurity, the electrical resistance of the formed thin film increases and its brittleness also increases, leading to frequent accidents such as breakage of wiring networks. Ni.

Heavy metals such as Cr constitute the cause of leakage phenomena at the interface junction between VLSI and the formed thin film, and N
This is because alkali metals such as a and 2 easily migrate in the insulating film on the VLSI etc. and deteriorate the device characteristics. Moreover, U and Th cause malfunction of the device due to the α rays emitted by them, and as a result, the operational reliability of the device is significantly reduced.

By the way, the targets of MSi2 and MSi3 currently have the following aspects. That is, the first is T i , T
High purity powder such as a, W, Mo and high purity Si
This is a case where the mixed powder is mixed in a predetermined ratio (molar ratio 1:2 to 3), the mixed powder is sintered by a conventional method, and the obtained sintered body is used. $2 is an embodiment in which each or each metal lump of high melting point metal (M) and high purity Si is arranged separately in a mosaic shape and used as a target.

(Problem to be Solved by the Invention) However, in the case of the former target, since it is manufactured by a so-called powder metallurgy method, the specific surface area of each powder increases, so that, for example, about 200 pp of oxygen is added during manufacturing.
If more than m is adsorbed, the purity will decrease. As a result, a thin film formed by sputtering on the surface of a semiconductor element has a high resistance value and becomes brittle.

Further, in the latter case, there is a problem that the overall cost increases because the mosaic pieces need to be processed, and the resistance value of the formed thin film is also slightly high.

For this reason, attempts have been made to alloy M and Si by a melting method, but MSi2-3 produced by this method reacts violently with the crucible, causes contamination, and is generally brittle. However, during the process of solidifying from a molten state, cracks occur at various places, making it virtually impossible to install it in a sputtering device.

[Structure of the invention] (Means and effects for solving the problem) The present inventors M
Although Si2-3 has excellent properties as a thin film material, it is difficult to put it into practical use due to the various drawbacks mentioned above.As a result of extensive research, we have found that Si2-3 is difficult to put into practical use by the melting method The method of the present invention was developed as a method for manufacturing MSi2-3 targets.

That is, the method for manufacturing a high-melting point metal silicide target of the present invention is a method for manufacturing a sputter target whose main component is an alloy (MSi2-3) of a high-melting point metal (M) and silicon (Si), which includes (A) A step of mixing high melting point metal (M) and silicon (Si) at a molar ratio of 1:2 to 3; (B) The obtained mixture is mixed under vacuum with high melting point metal (M) and silicon (Si). A process of melting and alloying in the temperature range from the eutectic point temperature (TS) located on the silicon side in the phase diagram to the melting point (T) of the alloy (MSi2); (C) Crushing the obtained alloy Afterwards, excess St was chemically eluted to reduce the alloy composition to only MSi2, and then excess silicon (S) was added to this.
i) Adding the high melting point metal (M) and adjusting the molar ratio of silicon (Si) to 1:2 to 3 again; CD) Adding the crushed alloy with the adjusted molar ratio to the high melting point metal (M)
) and placed in a bottomed container consisting of alloy ( ) under vacuum.
From the melting point (T) of MSi2) to the alloy (MSin = where n
A step of melting in a temperature range up to the melting point of 2) and then cooling it.

First, step A is a step in which M and Si are mixed at a mixing ratio such that an alloy with an excess of St, whose composition corresponds to approximately MSi2 to 3, is obtained in order to obtain disilicide from M and Si.

Here, M is any one of Ti, Ta, Mo, and Wc7).

Both M and St represent state diagrams as illustrated in the figure. That is, composition: 2 with MSi2 in between
There are two eutectic points. In the present invention, among these eutectic points, the St-side eutectic point is called TS, and the M-side eutectic point is called TM. In this phase diagram, MSi (n<2) represents M-rich composition silicide.

Incidentally, the melting point of each M and the eutectic point temperature of each silicide are shown in the table.

In this step A, high purity granular raw materials, for example, are used for both M and Si. For example, in the case of Ti among M, those purified by the commonly used molten salt electrolysis method or iodide method are used. In any case, M is an impurity as mentioned above, that is, an enzyme.

It is preferable that polymeric metals such as Fe, Ni, Crc7), alkali metals such as Na, Ni, U, Th, etc. be as small as possible.

M and Si may each be mixed in the form of granules,
It may be mixed in small chunks.

However, in any case, since the target product has a composition of MSi2, the mixing ratio of M and Si is set to a molar ratio of M:S i = 1:2 or more, with an excess of St, and an Si Chemically dissolves only the silicide and prepares it to form disilicide.

Step B is a step in which the mixture prepared in Step A is melted and alloyed at a temperature described below.

Melting is carried out in a vacuum, with a degree of vacuum of 5
It is preferable that the pressure is 10 −5 Torr or less. Further, it is desirable that the temperature during melting be within the temperature range from TS to T as indicated in the phase diagram or table. For example, when M is Ti, the applied temperature is within the range of 1330-1540°C. If this temperature does not have a TS groove, the composition cannot be made uniform by complete melting, and if it is higher than T, the evaporation of Si and the contamination of the bottom material will be severe.

This step B is usually preferably carried out using an electron beam (EB) melting furnace.

Step C is obtained in Step B and its composition is approximately MSi2-3.
An ingot of an alloy having the following properties is crushed to a predetermined size, and only the excess Sj is chemically eluted to form only disilicide of a predetermined composition.

For this purpose, treatment with HF-HNO3 is desirable. Since the obtained powder is a clear disilicide, the process is to add Si according to the shortage of St and readjust the overall molar ratio to the correct 1:2 to 3. During crushing, prevent contamination of the alloy. For example, use a tool made of the same material as the selected M, or grind it with a carbon steel tool to remove the Fe powder from the powder.
Contamination is removed with aqua regia.

In step D, the crushed alloy obtained in step C is stored and charged into a bottomed container made of M, and then this charged alloy is melted and solidified to form MSi2~ integrated with this container. 3
This is the process of targeting.

The material constituting the container needs to have a melting point higher than the aforementioned Tn. Specifically, it is composed of M having a melting point higher than or equal to M of the target MSi2. For example, if the charging alloy is T i S i 2-3
In this case, it is preferable that the container be made of W rather than Ti. Further, the dimensions and shape of the container may be determined as appropriate depending on the sputtering apparatus in which the target is installed.

Melting is carried out in a vacuum, with a degree of vacuum of 5
It is preferable that the pressure is 10 −5 Torr or less. Further, it is desirable that the temperature is between T and T4. If this temperature is less than T, MSi2 will not dissolve;
If it is higher than n, the reaction with the container will proceed significantly, which is disadvantageous.

In addition, in the second process, M! The inner wall of the M container that comes into contact with 3i2-3 is slightly converted into an alloy of MSi2-3, forming an alloy layer there, but this alloy layer does not grow any further in the above temperature range. A situation where the container as a whole is eroded does not occur. Further, especially in the case of W, since WSi2 itself has a low resistance, the deterioration of characteristics due to reaction is very small.

If the whole is cooled in this state, the molten silicide will solidify inside the container, and a target integrated with the container will be obtained.

(Example of the invention) Acicular high-purity Ti powder manufactured by molten salt electrolysis method (oxygen content 100 to 160 ppm, Fe 10 ppm or less, C
r 18ppm or less, Ni about 1ppm, Na about 325
Approximately 175 PPI in ppm! l or less) 1.64 kg,
The mixture was mixed with 2.36 kg of crushed granules of Si single crystal for semiconductors, charged into an EB melting furnace, and melted under a vacuum of 5 x 10-5 mbar. The obtained ingot was crushed with a Ti hammer to form approximately 100 meshes, and then HF-HNO
Excess Si was eluted in Step 3 to obtain a powder containing only TiSi2.

Next, we set a target for the alloy composition to be TiSi2.5, and added 2.73 kg of this TiSi2 and Si 0.7
7 kg were mixed. Next, a circular container with an outer diameter of 270 mm and a height of 30 mm made from a W plate with a thickness of 3 mm was placed on the outside thereof, and a water-cooled copper mold was placed therein, and 3.5 kg of the charged alloy was contained therein, and the container was placed in an EB melting furnace. Vacuum inside the furnace 5x
After heating at 10''5 Torr and melting the crushed alloy, the furnace was cooled to solidify the molten alloy, and the whole was machined to 250φ x 15t to obtain the intended target.

In this target, the TiSi2 portion and the W container were in close contact, and no cracks were observed in the TiSi2. Also, the oxygen content in Ti5iz is 7
It was 6 to 132 ppm or less, which was about half less than the conventional one.

This target was incorporated into an actual machine, and V was applied to the surface of the Si wafer.
When a thin film for SLI was formed and its resistance value was measured, the original low resistance value of 1Ω/mouth was actually measured.

E. Effects of the Invention] As is clear from the above explanation, the method of the present invention can easily target disilicide of high melting point metal and silicon, which was difficult to target into parts. , its industrial value is a dog.

[Brief explanation of the drawing]

The figure is a phase diagram of a high melting point metal (M) and silicon (Si).

Claims (5)

[Claims] (1) A high melting point container comprising a bottomed container made of a high melting point metal (M) and an alloy (MSi_2 to _3) of the high melting point metal (M) and silicon (Si) provided inside the container. Metal silicide target. (2) High melting point metal (M) is titanium (Ti), zirconium (Zr), tantalum (Ta), molybdenum (Mo),
The refractory metal silicide target according to claim 1, which is any one of tungsten (W). (3) Alloy of high melting point metal (M) and silicon (Si) (M
In a method for producing a sputtering target containing Si_2 to_3) as a main component, (A) a step of mixing a high melting point metal (M) and silicon (Si) in a molar ratio of 1:2 to 3; (B) the obtained The resulting mixture is heated under vacuum to the eutectic point temperature (T_S) located on the silicon side in the phase diagram of high melting point metal (M) and silicon (Si).
(C) After crushing the obtained alloy, excess Si is chemically eluted to change the alloy composition to MSi_2. After that, an excess of silicon (Si) is added to this, and the molar ratio of high melting point metal (M) and silicon (Si) is again 1:2 to 3.
(D) The crushed alloy whose molar ratio has been adjusted is mixed with a high melting point metal (M
), and under vacuum, the melting point (T) of the alloy (MSi_2) changes from the melting point (T) of the alloy (MSi_n: where n<2) in the phase diagram of the high melting point metal (M) and silicon (Si). A method for producing a high melting point metal silicide target, comprising: melting in a temperature range up to the melting point and then cooling; (4) The manufacturing method according to claim 3, wherein the high melting point metal (M) is any one of titanium (Ti), tantalum (Ta), molybdenum (Mo), and tungsten (W). (5) The manufacturing method according to claim 3, wherein the bottomed container is made of any one of the high melting point metals (M) having a melting point higher than the melting point of the alloy (MSi_n, where n<2).