JP2002363736A - Sputter target, barrier film and electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tantalum sputter target by which a tantalum nitride barrier film having uniform film thickness is formed, the barrier film and an electronic part. SOLUTION: In a Ta sputter target, the variation of the intensity ratio, (110)/((110)+(200)+(211)+(220)+(310)), of the crystal surface to be sputtered with a position of a sputter surface part measured by X-ray diffraction is <=20%. The barrier film is composed of a TaN film film-deposited using the Ta sputter target in a gaseous nitrogen atmosphere. The electronic part possesses the barrier film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a tantalum sputter target, a barrier film formed by the target, and an electronic component having the barrier film.

[0002]

2. Description of the Related Art In recent years, the semiconductor industry represented by LSI has been rapidly advancing. Among them, 256 Mbit DRA
In semiconductor devices such as M, logic, system LSI, and the like, or later, the precision required for microfabrication technology is increasing as integrated circuits become more highly integrated, highly reliable, and highly functional. With the increase in density and speed of such integrated circuits, the width of metal wiring formed mainly of aluminum or copper is becoming 0.13 μm or less.

On the other hand, to operate an integrated circuit at high speed,
It is essential to reduce the electrical resistance of the aluminum or copper wiring. In order to reduce the electric resistance of the wiring, the height of the wiring (that is, the thickness of the wiring layer) when the conventional structure is used.
There is a way to make it thicker. However, in devices that require higher integration and higher density, when such a laminated structure is used, the coverage of the insulating film formed on the wiring becomes poor, and the yield may decrease. Inevitable.

Therefore, a dual damascene (DD) wiring technique different from the conventional wiring technique has been proposed. Here, the DD technique means that a metal mainly composed of aluminum or copper as a wiring material is formed in a wiring groove formed in a base film in advance by a sputtering method, a CVD method, or the like, and heat treatment (reflow) is performed. Into the ditch by CMP (Chemic
al Machanical Polishing) technology to remove excess wiring metal.

[0005] As a wiring material used for the above-described semiconductor device, a copper wiring having a lower resistivity than aluminum is mainly used. The advantage of copper wiring is that it has better electromigration properties than aluminum wiring. In the future high-speed devices, copper wiring will be the mainstream.

When copper wiring is applied, since copper may diffuse into silicon used as a substrate and the life of minority carriers may be shortened, the diffusion of copper between the silicon substrate and the copper wiring layer may occur. A barrier film is provided for the purpose of prevention. For example, a barrier film is formed from a titanium nitride (TiN) film or a tantalum nitride (TaN) film (Japanese Patent Application Laid-Open No. H10-242279). In particular, a barrier film made of a tantalum nitride film has attracted attention recently because it is thermally stable and has excellent barrier properties. Such a tantalum nitride film can be formed by reactive sputtering using a tantalum target in a nitrogen gas-containing atmosphere.

[0007] In an LSI device in which the design rules are increasingly strict, products having an aspect ratio exceeding 4 become commonplace. In order to cope with such a device, evaluation is performed by incorporating a conventional sputtering technique, that is, a collimation sputtering method, a long-distance sputtering method, a low-pressure sputtering method, and recently a bias sputtering method.

[0008]

As described above, a barrier film made of tantalum nitride is preferable in terms of thermal stability and barrier properties. However, a tantalum nitride film produced by reactive sputtering using a conventional tantalum sputter target has a problem that the film thickness is not uniform. If the barrier film is non-uniform, it may be difficult to lower the barrier property or to provide wiring on the barrier film, and a reduction in yield is inevitable. Enhancing the uniformity of the barrier film is important for further increasing the density and speed of an integrated circuit and increasing the diameter of a wafer during manufacturing.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by specifying a predetermined crystal plane intensity ratio determined by X-ray diffraction of a sputtered surface of a tantalum sputter target. Things.

Therefore, the tantalum sputter target according to the first aspect of the present invention has a (110) / {(110) / (110)
+ (200) + (211) + (220) + (310)}
Is characterized by that the variation of the intensity ratio between the positions of the sputter surface portion is within 20%.

The tantalum sputtering target according to the second aspect of the present invention has the above (110) / {(110) + (2)
2. The tantalum sputtering target according to claim 1, wherein an intensity ratio of (00) + (211) + (220) + (310)} is 0.4 or more and 0.6 or less.

According to a third aspect of the present invention, there is provided a tantalum sputter target having an average crystal grain size of 30 on a surface to be sputtered.
The tantalum sputter target according to claim 1 or 2, wherein the average crystal grain size is 0 μm or less, and the variation of the average crystal grain size depending on the location of the sputter surface is within 20%.

According to a fourth aspect of the present invention, there is provided a tantalum sputter target according to the present invention, wherein the total content of iron, nickel, chromium, copper, aluminum, sodium, potassium, uranium and thorium is 0.01% by weight or less. The tantalum sputter target according to any one of claims 1 to 3, characterized in that:

A tantalum sputter target according to a fifth aspect of the present invention is joined to a backing plate of copper, aluminum, or an alloy thereof, and is integrally formed therewith. It is a tantalum sputter target.

The tantalum sputter target according to the present invention is used when forming a barrier film made of a tantalum nitride film. It is a sputter target.

According to a seventh aspect of the present invention, there is provided a barrier film comprising a tantalum nitride film formed in a nitrogen gas atmosphere using the tantalum sputtering target according to any one of the first to sixth aspects. A barrier film.

The barrier film according to the invention of claim 8 is the barrier film according to claim 7, wherein the variation of the barrier film thickness depending on the location is within 5%.

According to a ninth aspect of the present invention, there is provided an electronic component comprising the barrier film according to the seventh or eighth aspect.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Tantalum sputter target>
The tantalum sputter target according to the present invention has a (11) crystal face determined by X-ray diffraction of the sputtered face.
0) / {(110) + (200) + (211) + (22
0) + (310)} is characterized by that the variation of the intensity ratio depending on the location of the sputter surface portion is within 20%. The above intensity ratio is 15% or less, and 1
Those having 0% or less are particularly preferred. By using such a tantalum sputter target with little variation, a barrier film with higher uniformity can be easily obtained.

Among the tantalum sputter targets of the present invention, the above intensity ratio, ie, (110) / {(110) +
The intensity ratio of (200) + (211) + (220) + (310)} is preferably 0.4 or more and 0.6 or less.
If the above intensity ratio is out of the above range, it becomes difficult to obtain a film with high uniformity. In the present invention, the intensity ratio is 0.4
5 to 0.57, more preferably 0.47
~ 0.53 is preferred. Here, the reason for defining the intensity ratio between the intensity of the (110) plane and the sum of the above-mentioned crystal plane intensities is as follows.
The (110) plane is the densest surface of Ta (BCC structure),
This is because the surface is most easily sputtered.

In the present invention, the “variation of the intensity ratio depending on the location on the sputter surface” is determined as follows. That is, as shown in FIG.
For example, 90% (the center is 0%, the radius is 100%) from the center of the disk-shaped sputtering target (position 1) and the center of four straight lines passing through the center and equally dividing the circumference. ) And 50% from the center (similar to the above, the center is 0% and the radius is 100%) (positions 10 to 10). 1
From 17), a total of 17 test pieces each having a length of 15 mm and a width of 15 mm are collected. # 1000 collected specimens
Polished and further buffed to make the surface a mirror surface. (110), (20) of this mirror-polished test piece
The X-ray diffraction intensities of the crystal planes of (0), (211), (220), and (310) are measured. The measurement of the X-ray diffraction intensity was performed 10 times or more for each test piece, and the above (1) was determined based on the average value.
10) / {(110) + (200) + (211) + (2
20) + (310)} is calculated. The value of the above-mentioned strength ratio is determined for each of the 17 test specimens collected.

The “variation of the X-ray diffraction intensity ratio depending on the location on the sputter surface” in the present invention is based on the maximum and minimum values of the 17 X-ray diffraction intensity ratios obtained as described above. (Maximum value-minimum value) / (maximum value + minimum value)｝ × 1
The average value of the values obtained based on the equation (00) is expressed in units (%).

The X-ray diffractometer is an X-ray diffractometer (XRD) manufactured by Rigaku Corporation under the following conditions.

Measurement conditions X-ray: Cu, k-α1, 50 kV, 100 mA, vertical goniometer, divergence slit: 1 deg, scattering slit:
1 deg, light receiving slit: 0.15 mm, scanning mode:
Continuous, scan speed: 1 ° / min, scan step: 0.01 °, scan axis: 2θ / θ, measurement angle: 30
１００100 ° The tantalum sputter target according to the present invention is high-purity tantalum, particularly iron (Fe), nickel (Ni), chromium (Cr), copper (Cu), aluminum (Al), sodium (Na), potassium (K). , High-purity tantalum having a total content of uranium (U) and thorium (Th) of 0.01% by weight or less is preferable. When the amount of impurities is large, it is difficult to form a uniform barrier film, and characteristics of the barrier film, for example, heat resistance, insulation, corrosion resistance, and the like may be reduced.

Further, the tantalum sputter target according to the present invention has a sputtered surface having an average crystal grain size of 300.
It is preferable that the average crystal grain size is not more than 20 μm and the variation of the average crystal grain size depending on the location of the sputter surface is within 20%. If the average crystal grain size exceeds 300 μm, the uniformity of the film thickness decreases, and if the variation of the average grain size depending on the location of the sputtering surface is 20% or more, the uniformity of the film thickness also decreases. May occur.

Here, the "variation of the average crystal grain size depending on the location on the sputter surface" is obtained from 17 points of the sputter target shown in FIG. Is measured 10 times or more, and from the maximum value and the minimum value of these 17 average particle diameter values, ｛(maximum value−minimum value) / (maximum value + minimum value)｝ × 1
The average value of the values obtained based on the formula of 00 is expressed in units (%).

The method and conditions for measuring the average particle size are as follows. That is, the number of crystal grains in the visual field of the microscope is counted, the plane area of one crystal grain is calculated, and then the average diameter of one crystal grain is calculated. The number of crystal grains per unit area (N _A ) can be measured as follows. In the micrograph of the metal structure, the number of crystal grains (N _W ) included in the area A of a certain circle and the number of crystal grains (N
_i ). In this case, it is desirable that a sufficient number of crystal grains (30 or more) are included in the circle. In this case the crystal grains of the sum _{(N T)} is given by _{N T = N W + (1/2} ) N i. Next, the average area per grain is calculated by A / _NT . The diameter of this average area is the average diameter.

Such a tantalum sputter target can be joined and integrated with a backing plate. A conventionally used backing plate, preferably copper, aluminum or an alloy thereof, can be used in the present invention. The bonding between the tantalum sputter target and the backing plate can also be performed by a conventional method, preferably by solder bonding and diffusion bonding. Examples of the bonding agent for the solder bonding include an indium-based or tin-based bonding material.

One preferred embodiment of the tantalum sputter target according to the present invention is used for forming a barrier film made of a tantalum nitride film.

The tantalum sputtering target according to the present invention can produce a barrier film having a very small variation in film thickness depending on a place.

<Manufacture of Tantalum Sputter Target> The tantalum sputter target according to the present invention can be manufactured by any method as long as the above-mentioned requirements regarding the intensity ratio obtained by X-ray diffraction are satisfied. For example, a Ta ₂ O ₅ ore used in the production of a known high-purity tantalum sputter target is subjected to an alkali melting method, a fractional crystallization method, and an ingot obtained by an electron beam melting method. It can be manufactured by subjecting to a cooling treatment and a recrystallization treatment.

The tantalum sputtering target according to the present invention has a (110) / {(110) + (200) +
As described above, it is preferable that the strength ratio of (211) + (220) + (310)} satisfy predetermined requirements with respect to the variation on the sputtering surface, the average crystal grain size on the sputtering surface, the variation thereof, and the like. is there. Therefore, the manufacturing of the tantalum sputtering target is also performed such that plastic working, heating and cooling treatment,
It is preferable to select the production conditions such as the recrystallization treatment as appropriate.

For example, during the plastic working, at least one
It can be manufactured by performing vacuum heat treatment twice and then performing a cooling process. For the plastic working, forging and rolling can be employed. The plastic working rate is 1
0-98%, especially 30-98%, is suitable. In the above vacuum heat treatment, the heating rate is 10 ° C./min or more, particularly 15 ° C./min.
Minutes or more, 1000-1600 ° C., especially 11
At a temperature of 00 to 1400 ° C. for at least 1 hour, in particular 3 hours
Those consisting of holding for more than an hour are preferred. The cooling treatment is preferably performed at a cooling rate of 50 ° C./min or more, particularly 100 ° C./min or more. The recrystallization treatment is 800 to 1400
° C, especially at a temperature of 1000-1200 ° C for 1 hour or more,
In particular, it is preferably performed for 1 to 3 hours. By adopting the recrystallization conditions, it is possible to prevent crystal grains from becoming coarse.

<Barrier Film> The present invention further comprises a barrier film on which the above-described tantalum sputter target is formed, specifically, a tantalum nitride film formed using the above-mentioned tantalum sputter target in a nitrogen atmosphere. A barrier film.

Such a barrier film according to the present invention has extremely high uniformity, such as a variation in film thickness depending on the location being within 5%. Therefore, characteristics such as insulating properties, thermal stability, and strength of the barrier film are uniform over the entire surface of the film, and the occurrence of extremely reduced portions is suppressed.

Here, the “variation of the barrier film thickness depending on the location on the sputtered surface” means that the barrier film was formed on the surface by sputtering.
The barrier film thickness of a test piece taken from the 17 points shown in FIG. 1 of the i-wafer was measured by a contact-type profilometer, and 最大 (maximum) Value-minimum value / (maximum value + minimum value)｝ × 1
The value obtained based on the equation of 00 is expressed in units (%).

The above-mentioned nitrogen atmosphere is typically composed of substantially only nitrogen gas and one composed of an inert gas containing nitrogen gas. As the method of the sputtering treatment performed in such a nitrogen gas atmosphere and the specific conditions thereof, any suitable one can be adopted.

In the present invention, since a barrier film having extremely high uniformity can be easily obtained by using a predetermined tantalum sputter target, the yield is extremely good even when applied to a large substrate. Also, the necessity of strictly controlling the conditions of the sputtering process and the like has been reduced.

<Electronic Component> An electronic component according to the present invention comprises the above barrier film.
The characteristics of the barrier film according to the present invention are remarkably recognized as those having a structure in which the barrier film is formed on a Si wafer substrate and a copper wiring is formed on the barrier film, particularly when the barrier film is highly integrated. Electronic components. For example, a semiconductor device, a liquid crystal display device, a plasma display device,
It can be used for magnetic recording devices, magnetic storage devices, and various applications.

[0040]

Next, specific examples of the present invention will be described. <Example 1> EB ingot of tantalum (φ250 × 3
0 mm) was cold forged to φ115 × 140 mm. Thereafter, vacuum heat treatment (1300 ° C. × 2 hours,
After the temperature was raised at a rate of 15 ° C./min), the mixture was placed in water, and rapidly cooled at a rate of 100 ° C./min. After that, φ250 × 30
mm and cold forged. Here, the reason why plastic deformation was performed from two axes by combining forging and upsetting forging is that when cold forging and cold rolling were performed in the uniaxial direction, coarse grains that were in the raw material ingot remained even after heat treatment. This is because

After the above upsetting forging, vacuum heat treatment is performed again.
(1200 ° C. × 2 hours, heating rate 20 ° C./min). After the vacuum heat treatment, it is immersed in water and quenched as in the first vacuum heat treatment. After quenching, cold rolling was performed under the conditions shown in Table 1 and recrystallization heat treatment was performed to machine a target shape. An aluminum backing plate was joined by a diffusion joining method to produce a tantalum sputter target according to the present invention.

In the obtained sputter target, Fe,
As a result of measuring the content of each element of Ni, Cr, Cu, Al, Na, K, U, and Th, the total amount thereof was 0.01
% By weight or less. Using the tantalum sputter target manufactured in this manner, a sputtering method: substrate-target distance = 300 mm, back pressure: 1 × 10 ⁻⁵ Pa,
Output DC: 18 kW, Ar: 5 sccm, N: 20 scc
m, sputtering time: 5 min, substrate bias: -100
Film formation was performed on an 8-inch Si wafer under the condition of V.

The (110) / {(110) + (200) +
The intensity ratio of (211) + (220) + (310)}, the variation thereof, the average crystal grain size, and the thickness of the barrier film are shown in Table 1.
Was as shown in FIG.

<Comparative Example 1> Under the same conditions as in Example 1, tightening forging, swaging forging, and vacuum heat treatment were performed. After the vacuum heat treatment, instead of quenching, gradual cooling was performed in the furnace (temperature reduction rate: 10 ° C./min). Thereafter, under the conditions shown in Table 1, the product subjected to cold rolling and recrystallization heat treatment was machined into a target shape, and the backing plate was similarly joined.

A barrier film was formed in the same manner as in Example 1 except that this tantalum sputtering target was used. As in the first embodiment, the (110) / {(110) + (200) + (211)) of the crystal plane of the tantalum sputtering target is obtained.
+ (220) + (310)} intensity ratio, its variation,
The average crystal grain size and the thickness of the barrier film were measured. The results obtained are as shown in Table 1.

[0046]

[Table 1] As is clear from Table 1, when the tantalum sputtering target according to the present invention is used, the variation in the barrier film thickness is 5%.
A barrier film having high uniformity within the above range can be obtained.

[0047]

As is apparent from the above description, the tantalum sputter target of the present invention can provide a tantalum nitride barrier film having high film thickness uniformity, which could not be achieved conventionally. According to such a tantalum sputter target of the present invention, a barrier film and an electronic component formed using the same, it is possible to significantly improve the product yield.

[Brief description of the drawings]

FIG. 1 is a diagram showing locations where test pieces are sampled in which the intensity ratio variation and average particle size variation of a tantalum sputter target and the thickness variation of a barrier film are measured.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Takashi Watanabe, Inventor 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Works Co., Ltd. (72) Takashi Ishigami 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Address Toshiba Yokohama Works (72) Inventor Yasuo Takasaka 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture F-term (reference) 4K029 BA58 BD00 DC03 DC21 DC22 4M104 BB32 BB37 DD40 DD42

Claims (9)

[Claims] 1. A crystal plane (110) / {(110) + (200) +
A tantalum sputter target characterized in that the intensity ratio of (211) + (220) + (310)} varies within 20% depending on the location of the sputter surface portion. 2. The above (110) / {(110) + (20)
2. The tantalum sputter target according to claim 1, wherein an intensity ratio of (0) + (211) + (220) + (310)} is 0.4 or more and 0.6 or less. 3. The average crystal grain size of the surface to be sputtered is 300.
3. The tantalum sputter target according to claim 1, wherein the tantalum sputter target has a thickness of not more than .mu.m and a variation in average crystal grain size depending on a position on a sputter surface is within 20%. 4. A high-purity tantalum having a total content of iron, nickel, chromium, copper, aluminum, sodium, potassium, uranium and thorium of 0.01% by weight or less. 4. The tantalum sputter target according to claim 1. 5. The tantalum sputter target according to claim 1, wherein the tantalum sputter target is integrated with a backing plate made of copper, aluminum, or an alloy thereof. 6. The tantalum sputtering target according to claim 1, wherein the tantalum sputtering target is used when forming a barrier film made of a tantalum nitride film. 7. A barrier film comprising a tantalum nitride film formed by using the tantalum sputter target according to claim 1 in a nitrogen gas atmosphere. 8. The barrier film according to claim 7, wherein the variation of the barrier film thickness depending on the location is within 5%. 9. An electronic component comprising the barrier film according to claim 7 or 8.