JP2003017491A - Sputter target, gate insulating film and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputter target, by which a gate insulating film having high uniformity of a film thickness and consisting of hafnium oxide or zirconium oxide can be formed, and to provide an insulation film and an electronic component. SOLUTION: The sputter target is made of hafnium, zirconium or their alloy. The average crystal grain diameter of its surfaces to be sputtered is <=500 μm, and the variance of the average crystal grain diameter lies within 20%. The gate insulation film consists of a hafnium oxide or zirconium oxide film, formed by using the sputter target in the atmosphere of gaseous oxygen. The electronic component is provided with the gate insulating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputter target made of hafnium, zirconium or an alloy thereof, a gate insulating film formed by the sputter target, and an electronic component having the gate insulating film.

[0002]

2. Description of the Related Art In recent years, the semiconductor industry represented by LSI has been rapidly progressing. Above all, 256 Mbit DRA
In M, logic, system LSI, and the like, or semiconductor elements thereafter, the precision required for fine processing technology is increasing more and more as the integrated circuit becomes highly integrated, highly reliable, and highly functional. With the increase in density and speed of such integrated circuits, the width of the metal wiring formed mainly of aluminum or copper is becoming 0.13 μm or less. When the width of the metal wiring is 0.13 μm or less, the thickness of the gate insulating film needs to be reduced to _{2 to 3} nm in terms of SiO ₂ .

However, if the gate insulating film is thinned to this extent, leakage current may increase or boron added to the polycrystalline Si gate electrode may penetrate into the substrate, deteriorating the transistor characteristics and reducing reliability. There is a problem that it is not possible to secure sufficient sex.

In order to overcome the limitation of thinning the gate insulating film, development of high dielectric constant gate insulating films (HfO ₂ and ZrO ₂ ) is in progress. According to this method, by introducing HfO ₂ or ZrO ₂ into the gate insulating film, further thinning (thickness 1.13 nm in terms of SiO ₂ ) can be expected. Since the relative permittivity of HfO ₂ is 30 and the relative permittivity of ZrO ₂ is as high as 25, this method causes a problem that oxygen in the insulating film escapes and silicon is oxidized to thicken the gate insulating film. Is less likely to occur.

[0005]

An oxide film obtained by reactive sputtering using a conventional hafnium or zirconium sputter target, that is, a hafnium oxide (HfO ₂ ) or zirconium oxide (ZrO ₂ ) film has a film thickness of There is a problem that the uniformity is not good.
Even with a Si wafer having a diameter of 8 inches, it was difficult to control the film thickness uniformity to 5% or less. In the future, 12-inch size Si wafers will need to have better uniformity.

When the thickness of the insulating film is not uniform, deterioration of the insulating property is unavoidable. Therefore, increasing the uniformity of the insulating film is intended to further increase the density, speed and yield of the integrated circuit. In addition, it is important for increasing the diameter of the wafer during manufacturing.

[0007]

The present invention is intended to solve the above problems by specifying the average crystal grain size of the sputtered surface of the sputter target and its variation.

Therefore, the sputter target according to the present invention of claim 1 is a sputter target made of hafnium, zirconium or an alloy thereof.
The average crystal grain size of the surface to be sputtered is 500 μm or less, and the variation of the average crystal grain size is within 20%.

The sputter target according to the present invention of claim 2 is the sputter target according to claim 1, wherein the total content of oxygen, nitrogen, carbon, sulfur and hydrogen is 800 ppm or less.

The sputter target according to the present invention of claim 3 is a sputter target of claim 1 or 2, wherein the sputter target is compositely integrated with a backing plate of copper or aluminum or an alloy material thereof. .

A gate insulating film according to the present invention of claim 4 is
A hafnium oxide film or a zirconium oxide film formed by using the sputter target according to any one of claims 1 to 3 in an oxygen gas atmosphere.

The gate insulating film according to the present invention of claim 5 is
The gate insulating film according to claim 4, wherein the variation in thickness depending on the location of the gate insulating film is within 5%.

An electronic component according to a sixth aspect of the present invention is characterized by having a film formed by using the sputtering target according to any of the first to third aspects.

According to a seventh aspect of the present invention, there is provided an electronic component including the gate insulating film according to the fourth or fifth aspect.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION <Sputtering Target> The sputtering target according to the present invention is a sputtering target made of hafnium, zirconium or an alloy thereof, and the average crystal grain size of the surface to be sputtered is 500 μm.
It is characterized in that it is below and the variation of the average crystal grain size is within 20%.

If the average crystal grain size is more than 500 μm, the uniformity of the film thickness is deteriorated and it becomes difficult to achieve the object of the present invention. In the present invention, the average crystal grain size is preferably 300 μm or less, more preferably 100 μm or less.

The variation of the above average crystal grain size depending on the location of the sputtered surface is within 20%, preferably within 10%, and more preferably within 5%. By using such a sputter target with less variation, a gate insulating film with higher uniformity can be easily obtained.

In the present invention, the "average crystal grain size" and the "variation depending on the location on the surface to be sputtered" are obtained as follows. That is, as shown in FIG. 1, 90% (0% of the center is 0% from the center of the disk-shaped sputter target (position 1) and the center of four straight lines that equally divide the circumference through the center. , The radius is 100%), and the point (position 2)
9), and 50% from the center (as in the above, the center is 0
%, The length of the radius is 100%), from the point (positions 10 to 17) at a distance of 15 mm, the length is 15 mm and the width is 15 m.
A total of 17 test pieces of m are collected. The collected test piece is polished to # 1000 and further buffed to make the surface mirror-finished. The average grain size of the mirror-polished test piece is measured. The measurement is performed 10 times or more, and the average crystal grain size is calculated based on the average value. The value of the average crystal grain size is determined for each of the 17 collected test pieces.

For the average crystal grain size, the number of crystal grains in the microscope field of each sample is counted, the plane area of each crystal grain is calculated, and then the average diameter per grain is calculated. Number of grains per unit area (N _A) can be measured as follows.

In a micrograph of a metal structure, a circle
Crystal grains (N_W) And part
Crystal grains (N_i) And count. In this case, a sufficient number of
It is desirable that the crystal grains (30 or more) are included in the circle.
Yes. The sum of the crystal grains at this time (N _T) Is N_T  = N_W  + (1/2) N_i Given in. Then A / N_TAnd average surface per grain
The product is calculated. The diameter of this average area is the average grain size
Become.

The "variation due to the location on the surface to be sputtered" of the average crystal grain size in the present invention is calculated from the maximum and minimum values of the 17 test pieces obtained as described above. -Minimum value) / (maximum value + minimum value)} x 1
The value obtained based on the formula of 00 is represented by the unit (%).

The sputter target according to the invention comprises high-purity hafnium or zirconium, in particular oxygen, nitrogen,
It is preferable to use high-purity hafnium or zirconium having a total content of carbon, sulfur and hydrogen of 800 ppm or less.

As described above, when the total content of the impurities (that is, oxygen, nitrogen, carbon, sulfur and hydrogen) in the sputter target is reduced to 800 ppm or less, the film thickness of the formed gate insulating film is reduced. 4% variation (uniformity)
It turns out that it can be suppressed to the following. Then, it has been found that reducing the total amount of the impurities in the sputter target to 800 ppm or less is effective in further reducing the leak current of the gate insulating film and further improving the insulating property.

Here, the reason why the insulating property of the formed gate insulating film is improved when the total amount of impurities in the sputter target is set to 800 ppm or less is that impurities such as oxygen, nitrogen, sulfur or hydrogen atoms are hafnium or zirconium. It is considered that this is because a compound easily forms with the atom, and this compound precipitates at the grain boundary as an inclusion and weakens the grain boundary, increasing the leak current, that is, lowering the insulating property.

The sputter target of the present invention comprises iron (Fe), nickel (Ni), chromium (C) as impurity elements.
r), copper (Cu), aluminum (Al), sodium (Na), potassium (K), uranium (U), and thorium (Th) are contained in high purity hafnium or zirconium having a total content of 100 ppm or less. It is preferable. In other words, Fe, Ni, Cr, Cu, A
A value obtained by subtracting the total amount of each content (mass%) of 1, 1, Na, K, U, and Th from 100% [100- (Fe + Ni + Cr
+ Cu + Al + Na + K + U + Th)] is 99.99%
It is preferable to use the above high-purity zirconium or hafnium.

The sputter target according to the present invention can be integrally bonded with the backing plate. As the backing plate, a conventionally used backing plate, preferably copper, aluminum or an alloy material thereof can be used in the present invention. The method of joining the sputter target and the backing plate has also been conventionally performed, preferably solder bonding and diffusion bonding,
Can be done by Examples of the bonding agent for solder bonding include indium-based or tin-based bonding materials.

<Manufacture of Sputter Target> The sputter target according to the present invention can be manufactured by any method as long as the above-mentioned requirements regarding the average crystal grain size of the surface to be sputtered and its variation are satisfied. For example, it can be manufactured by subjecting an ingot used in manufacturing a known sputter target to appropriate plastic working, heating and cooling, and recrystallization.

For example, after manufacturing an ingot, plastic working is performed using liquid nitrogen or the like while being extremely cold (-50 ° C to -150 ° C). For the plastic working, forging and rolling can be adopted. Plastic working rate is 10-98%, especially 30-9
0% is suitable. After that, recrystallization treatment is performed. The recrystallization treatment is preferably carried out at a temperature of 300 to 800 ° C., particularly 400 to 600 ° C. for 1 hour or longer, particularly 3 hours or longer.

<Gate Insulating Film> The present invention further includes a gate insulating film formed by using the above sputter target, specifically, an oxide film formed by using the above sputter target in an oxygen atmosphere. Which is a gate insulating film.

The gate insulating film according to the present invention as described above is
The uniformity is extremely high such that the variation of the film thickness depending on the location is within 5%. Therefore, the insulating property, thermal stability, strength, and other characteristics of the gate insulating film are uniform over the entire surface of the film, and the occurrence of a portion where these are extremely lowered is suppressed.

Here, the "variation in thickness depending on the location" of the gate insulating film means "Si having a gate insulating film formed on the surface".
The insulation film thickness of the test piece of the wafer, which was taken from the 17 points shown in FIG. 1, was measured by a contact profilometer, and from the maximum and minimum values of these 17 measured values, {(maximum value- (Minimum value) / (maximum value + minimum value)} x 1
The value obtained based on the formula of 00 is represented by a unit (%).

The above-mentioned oxygen atmosphere is typically one consisting essentially of oxygen gas and one consisting of an inert gas containing oxygen gas. As a method and specific conditions of the sputtering treatment performed in such an oxygen gas atmosphere, any purposeful one can be adopted.

According to the present invention, since a gate insulating film having extremely high uniformity can be easily obtained by using a predetermined sputter target, even if it is applied to a large-sized substrate, the partial retention becomes extremely good. Further, it is less necessary to strictly control the conditions of the sputtering process and the like.

<Electronic Component> An electronic component according to the present invention comprises a film formed by using the sputter target of the present invention, and is particularly characterized by comprising the above-mentioned gate insulating film. . The characteristics of the gate insulating film according to the present invention that are remarkably recognized are those having a structure in which the gate insulating film is formed on a Si wafer substrate, particularly highly integrated electronic components. For example, it can be used for various applications such as semiconductor devices and liquid crystal display devices.

[0035]

EXAMPLES Next, specific examples of the present invention will be described. <Example 1> Using iodide hafnium as a raw material, an electron beam melting (hereinafter referred to as EB melting) ingot (φ250 x 30 mm) of hafnium was prepared. This EB melted ingot was cooled in liquid nitrogen, and at a processing rate (60%),
Extreme cold rolling was performed. Then, recrystallization heat treatment was performed at 500 ° C. for 2 hours to machine the target shape.

A backing plate made of Al was bonded by a diffusion bonding method to manufacture a sputter target of Example 1-1 according to the present invention.

Using the sputter target manufactured in this manner, the EB melting conditions, the cryogenic rolling conditions and the recrystallization treatment conditions were changed in the same manner as in Examples 1-2, 1-3, and 1. -4 sputter target was manufactured. A film was formed on an 8-inch Si wafer.

The average crystal grain size, grain size variation, impurity content, film thickness variation and leak current density of the sputter target obtained above are as shown in Table 1.
The content of each element was measured by ICP-MASS, and the leak current density was measured. The amount of impurities in each target (Fe, Ni, Cr, Cu, Al, Na, K, U, T
The total amount of h) was 10 ppm or less.

As is apparent from Table 1, the sputter target of high purity hafnium according to the present invention can form a film having a small variation in film thickness and good insulation.

Example 2 Using commercially available hafnium as a raw material, hafnium EB melted ingot (φ250
× 30 mm) was produced. Then, the sputter target of Example 2-1 was manufactured by the same method as that of the example.

Further, the sputter targets of Examples 2-2, 2-3, and 2-4 were manufactured by appropriately changing the EB melting conditions, the cryogenic rolling conditions, and the recrystallization treatment conditions in the same manner. Film formation was performed in the same manner as in Example 1 except that these sputter targets were used. In the same manner as in Example 1, the average crystal grain size of the sputtering target, its variation, the impurity content, the film thickness variation, and the leak current density were measured. The results are as shown in Table 1. In addition,
Impurity amount of each target (Fe, Ni, Cr, Cu, A
The total amount of 1, Na, K, U, and Th) was 10 ppm or less.

As is clear from Table 1, the film formed from the sputter target according to the present invention in Example 2 has a small variation in film thickness and a good insulating property. However, compared with Example 1 in which the impurity content is small, the variation in film thickness and the insulating property are slightly inferior.

<Comparative Example 1> Under the same conditions as in Example 1, after the ingot was manufactured, cold rolling (working rate: 60%) was performed instead of extremely cold rolling using liquid nitrogen. Then 500
A recrystallization heat treatment was carried out at a temperature of 2 ° C. for 2 hours, a target shape was machined, and a backing plate was bonded in the same manner to manufacture a sputter target of Comparative Example 1-1.

Further, the sputter targets of Comparative Examples 1-2, 1-3, 1-5 and 1-6 were manufactured by appropriately changing the EB melting conditions, the cold rolling conditions and the recrystallization treatment conditions by the same method. did. Film formation was performed in the same manner as in Example 1 except that these sputter targets were used. In the same manner as in Example 1, the average crystal grain size, grain size variation, impurity content, film thickness variation, and leak current density of the sputter target were measured. The results are as shown in Table 1.

As is clear from Table 1, when the sputter target does not have a predetermined average crystal grain size and variation in grain size, a film having a variation in film thickness of 5% or less could not be obtained. Also, the insulation was low.

<Comparative Example 2> Using commercially available hafnium as a raw material, hafnium EB melted ingot (φ250
× 30 mm) was produced. Then, in the same manner as in Comparative Example 1, a sputter target of Comparative Example 2-1 was manufactured.

Further, the sputter targets of Comparative Examples 2-2 and 2-3 were manufactured by appropriately changing the EB melting conditions, the cold rolling conditions and the recrystallization treatment conditions by the same method.

This target shape was machined and backing plates were similarly bonded. Film formation was performed in the same manner as in Example 1 except that this sputter target was used.
In the same manner as in Example 1, the average crystal grain size, grain size variation, impurity content, film thickness variation, and leak current density of the sputter target were measured. The results are as shown in Table 1.

As is clear from Table 1, when the sputter target does not have a predetermined average crystal grain size and variation in grain size, a film having a variation in film thickness of 5% or less could not be obtained. Also, the insulation was low.

[0050]

[Table 1]

[0051]

As is apparent from the above, the sputter target of the present invention can obtain a gate insulating film of hafnium oxide or zirconium oxide having high film thickness uniformity and insulating property which could not be achieved conventionally. .

According to the gate insulating film and the electronic component formed by using the sputter target according to the present invention as described above, the product yield can be significantly improved.

[Brief description of drawings]

FIG. 1 is a diagram showing sampling points for measuring an average crystal grain size of a sputtering target, a variation in grain size, and a variation in film thickness of a gate insulating film.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Watanabe             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Inventor Takashi Ishigami             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office (72) Inventor Yasuhiro Takasaka             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F-term (reference) 4K029 BA43 BC00 BD01 CA06 DC03                       DC04                 5F058 BC03 BF13 BJ04                 5F140 AA19 AA39 BA01 BD11 BE09

Claims (7)

[Claims] 1. A sputter target made of hafnium, zirconium or an alloy thereof, wherein the average crystal grain size of the surface to be sputtered is 500 μm or less and the variation of the average crystal grain size is within 20%. Characteristic, sputter target. 2. The total content of oxygen, nitrogen, carbon, sulfur and hydrogen is 800 ppm or less,
The sputter target according to claim 1. 3. The sputter target according to claim 1, wherein the sputter target is compositely integrated with a backing plate made of copper, aluminum or an alloy material thereof. 4. A hafnium oxide film or a zirconium oxide film formed by using the sputter target according to any one of claims 1 to 3 in an oxygen gas atmosphere. Gate insulating film. 5. The gate insulating film according to claim 4, wherein the variation in thickness depending on the location of the gate insulating film is within 5%. 6. An electronic component having a film formed by using the sputter target according to claim 1. Description: 7. An electronic component, comprising the gate insulating film according to claim 4 or 5.