JP2002299320A - Etching method - Google Patents

Abstract

[PROBLEMS] To improve the accuracy of a pattern shape after etching in dry etching of a metal containing tantalum as a main component. A metal containing tantalum as a main component is 0.2%.
An etching method characterized by exposing to a chlorine-based gas containing more than 4% of oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method for etching a metal containing tantalum as a main component with a chlorine-based gas.

[0002]

2. Description of the Related Art The pattern size of a semiconductor device is becoming finer year by year. With the miniaturization of the pattern size, it is expected that the etching technology for forming a semiconductor circuit pattern by etching a thin film formed on a semiconductor substrate will have higher precision.

As the pattern size becomes finer, the aspect ratio of the pattern cross section, that is, the aspect ratio increases. When the pattern size is 0.1 μm or less, the aspect ratio of the pattern may reach nearly 10. When the aspect ratio is increased, the etching gas is difficult to be conveyed to the bottom of the pattern, so that a problem of a microloading effect in which the etching rate sharply decreases occurs. In addition, when the aspect ratio is high, it is difficult to form a protective film existing on the pattern side wall, and isotropic etching occurs, so that a good pattern shape cannot be formed. In addition, these factors cause a problem that a wiring pattern cannot be formed uniformly on the surface of the semiconductor substrate.

In order to solve such a problem, in order to etch a pattern with a high aspect ratio, a magnetron RIE or an ICP (Inductively Coated) is used.
A method of increasing the straightness of etching ions at a low pressure of several Pa or less using a high-density plasma source such as a coupled plasma, or a highly adsorbing additive gas such as a fluorine-based gas is used. Or a method of positively forming a protective film on a pattern side wall by lowering the temperature of a semiconductor substrate.

On the other hand, tantalum is widely used as an electrode material of a semiconductor circuit or a shield of an exposure mask. Since tantalum has a high etching rate using a chlorine-based gas, it is mainly etched using a chlorine-based gas. In addition, when the pattern has a high aspect ratio and is etched with high precision, the above-described magnetron RIE,
A method using ICP, a fluorine-based gas, a method for lowering the substrate temperature, and the like are also used.

However, when a fine pattern of 0.1 μm or less is formed, even if such a method is used, the pattern shape after etching is not optimized, and the controllability of the pattern shape deteriorates, and the microloading effect occurs. In addition, various problems such as a decrease in the etching selectivity are serious obstacles in the manufacture of semiconductor circuits and transfer masks.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for etching a metal mainly containing tantalum with a high aspect ratio and high accuracy. Aim.

[0008]

In order to achieve the above-mentioned object, the present invention relates to a method for producing a metal containing tantalum as a main component by using 0.2% of tantalum.
The present invention provides an etching method characterized by performing etching by exposing to a chlorine-based gas containing more than 4% and not more than 4% of oxygen.

The present invention also provides a step of forming a mask on a metal containing tantalum as a main component, and the step of forming a surface of the metal which is not covered by the mask with an oxygen content of more than 0.2% and 4% or less. A selective etching of the metal by exposure to a chlorine-based gas containing

At this time, it is preferable to use a chlorine-based gas containing 0.4% or more and 4% or less of oxygen.

Further, the present invention provides an etching method characterized in that a tantalum-based metal containing more than 0.2% and not more than 5% of oxygen is etched by exposing it to a chlorine-based gas. .

Further, the present invention provides a method of forming a mask on a tantalum-based metal containing more than 0.2% and not more than 5% of oxygen, and a surface of the metal not covered by the mask. A selective etching of the metal by exposing the metal to a chlorine-based gas.

At this time, it is preferable to use a tantalum-based metal containing 0.4% or more and 5% or less of oxygen.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have conducted experiments on the assumption that there is some solution to the oxygen concentration in a chlorine-based gas as an etchant and the aspect ratio of a pattern when etching a metal mainly containing tantalum. went.

FIG. 1 is a graph showing the relationship when the oxygen concentration in chlorine is plotted on the horizontal axis and the etching rate of tantalum is plotted on the vertical axis.

FIG. 1 shows that the etching rate of tantalum decreases extremely when the oxygen concentration exceeds 3%, and the etching is almost stopped in the region of 5% or more. This is mainly because tantalum is oxidized during etching, and a difficult-to-etch layer is formed on the surface. At the pattern side wall, etching by neutral particles such as chlorine radicals is dominant, but at the bottom of the pattern, etching by ions is dominant, so that the energy threshold required for etching is different. Further, the formation probability of the carbon-based polymer film that controls the etching shape is sensitive to a change in the etching rate of the object to be etched. Therefore, it is conceivable that the pattern shape can be controlled by controlling the oxygen amount to an appropriate value of less than 5%.

From such considerations, the oxygen concentration in the chlorine gas and the shape of the formed pattern were compared as a line width shift rate.

FIG. 3 shows the result. Here, the line width shift rate α is α = (x0− | x0−x1 |) / x0 where x0 is the width of the mask pattern and x1 is the width of the portion where the thickness of the tantalum pattern is ２. The closer α is to 1, the better the pattern shape whose cross section is closer to a rectangle.

As shown in FIG. 3, when the oxygen concentration of chlorine gas is more than 0.2% and 4% or less, the cross section becomes almost rectangular. Further, when the oxygen concentration of the chlorine gas is 0.4% or more and 4% or less, the line width shift rate becomes 0.7 or more, which is preferable.

The present inventors have considered that there is some solution to the oxygen concentration and the pattern shape in the tantalum film.

FIG. 2 shows the pattern shape of tantalum when the oxygen concentration in the tantalum film is changed.

As shown in FIG.
In the case of 2%, the pattern shape is isotropic, which is not preferable. This is a result of an isotropic etching in which an etching protection film was not formed on the tantalum side wall because the oxygen concentration was too low.

Further, as shown in FIG. 2B, when the oxygen concentration was 0.4%, the pattern side walls approached vertically and were excellent. In addition, as shown in FIG. 2C, when the oxygen concentration was 0.5%, although the taper angle was formed in the forward direction, it was good. These results are considered to be the result of the improvement of the anisotropy of the etching, because the favorable etching prevention film was formed on the pattern side wall by a trace amount of oxygen.

By controlling the amount of oxygen contained in such a small amount, the pattern shape of tantalum changes greatly. When tantalum is oxidized, the energy threshold for etching and the formation probability of the carbon-based polymer film change as described above. Therefore, by setting the oxygen concentration in the film to an appropriate value, the etching rate does not decrease significantly at the bottom of the pattern where the amount of incident ions is large, but the carbon supplied from the resist or the inner wall of the chamber at the side wall of the pattern. As a result, a desired etching shape can be obtained.

FIG. 4 is a graph comparing the oxygen concentration in the tantalum film with the shape of the formed pattern as a line width shift rate.

As shown in FIG. 4, when the oxygen concentration in the tantalum film is more than 0.2% and 5% or less, the cross section becomes rectangular. Furthermore, the oxygen concentration in the tantalum film is 0.4
% Or more, the line width shift rate is 0.9 or more, which is preferable.

Hereinafter, the etching method of the present invention will be specifically described. First, tantalum is etched using a mixture of chlorine gas and oxygen as an etchant.

First, a tantalum film is formed on an 8-inch silicon substrate by a conventional method. Next, a chemically amplified resist was applied on the substrate, followed by pattern transfer by an electron beam lithography apparatus. After exposure, the resist was developed to form a desired pattern of 0.1 μm or less.

Next, using the resist pattern as a mask, etching was performed with a mixed gas comprising chlorine and oxygen. The etching apparatus uses an ICP plasma apparatus, the gas pressure is 0.5 Pa, the oxygen concentration is 0.75%,
The substrate temperature was 25 degrees, the substrate bias was 150 W, and the applied power was 500 W. As a result, 0.06μ of tantalum
An m-line and space pattern was successfully formed.

The present invention is not limited to the embodiment described above. The metal is not limited to tantalum, and a metal containing tantalum as a main component can be used. The etching gas is not limited to chlorine, and a chlorine-based gas such as boron trichloride, a mixed gas mainly containing a chlorine-based gas, or the like can be used. Various modifications can be made without departing from the spirit of the invention.

Next, a metal containing oxygen in tantalum is
A method for etching with a chlorine-based etchant will be described.

First, a tantalum film 2 having a thickness of 0.5 μm was formed on an 8-inch silicon substrate using a high-frequency magnetron sputtering apparatus. At this time, a 100% pure tantalum target was used as a sputtering target, and a gas in which oxygen was mixed with argon was used as a sputtering gas. The applied high-frequency power is 1500 W, the gas pressure is 5 Pa, the distance between target substrates is 8 cm, and the oxygen concentration in the gas is 1.5%. By this reactive sputtering method,
Tantalum containing about 0.5% oxygen could be formed.

Next, a chemically amplified resist is applied on the substrate, then the pattern is transferred by an electron beam drawing apparatus, and after exposure, the resist is developed.
A desired pattern of 1 μm or less was formed.

Next, etching with chlorine gas was performed using the resist pattern as a mask. The etching apparatus used was an ICP plasma etching apparatus, the pressure of chlorine gas was 0.5 Pa, the substrate temperature was 25 degrees, the power applied to the substrate bias was 100 W, and the power applied to the antenna was 500 W. As a result, a 0.06 μm line and space pattern of tantalum was successfully formed.

The present invention is not limited to the embodiment described above. The metal is not limited to tantalum, and a metal containing tantalum as a main component can be used. The etching gas is not limited to chlorine, and a chlorine-based gas such as boron trichloride, a mixed gas mainly containing a chlorine-based gas, or the like can be used. Various modifications can be made without departing from the spirit of the invention.

Next, the case where the oxygen concentration of the etchant is changed will be described.

First, tantalum was formed to a thickness of 0.5 μm on an 8-inch silicon substrate using a high-frequency magnetron sputtering apparatus. At this time, a tantalum target containing 1% of oxygen was used as a sputtering target, and argon was used as a sputtering gas.
The applied high-frequency power is 1500 W, the gas pressure is 5 Pa, and the distance between target substrates is 8 cm. As a result, tantalum containing about 0.5% of oxygen could be formed. Next, a chemically amplified resist was applied on the substrate, followed by pattern transfer using an electron beam lithography apparatus. After exposure, the resist was developed to form a desired pattern of 0.1 μm or less.

Next, etching with chlorine gas was performed using the resist pattern as a mask. The etching apparatus used was ICP, the pressure of chlorine gas was 0.5 Pa, the substrate temperature was 25 degrees, the power applied to the substrate was 100 W, and the power applied to the antenna was 500 W. As a result, 0.06 of tantalum
A μm line and space pattern was successfully formed.

The present invention is not limited to the embodiment described above. The metal is not limited to tantalum, and a metal containing tantalum as a main component can be used. The etching gas is not limited to chlorine, and a chlorine-based gas such as boron trichloride, a mixed gas mainly containing a chlorine-based gas, or the like can be used. Various modifications can be made without departing from the spirit of the invention.

Next, the manufacturing process of an X-ray exposure mask using a pattern made of tantalum will be described. First, a method for sequentially forming an X-ray transmission film 2, an X-ray absorber film 3, and an etching mask film 4 on an X-ray support 1 will be described.

As shown in FIG. 5, a 4-inch silicon substrate 1 having a thickness of 625 μm and a plane orientation of (100) polished on both sides was placed in an LPCVD apparatus as a mask support 1 and mixed with silane, acetylene, hydrochloric acid and hydrogen. Using a gas, at a substrate temperature of 1100 ° C., a silicon carbide film 2 as an X-ray transmission film
Was deposited at 1 μm. Next, a silicon carbide film having a thickness of 0.05 μm was formed as an etching stopper film 5 on the X-ray transmission film 2 using a magnetron sputtering apparatus. Next, a tantalum film 3 as an X-ray absorber film was deposited thereon to a thickness of 0.5 μm. The conditions for forming the X-ray absorber film 3 are as follows:
The applied high frequency power was 1 kW and the gas pressure was 2.5 Pa. At this time, the tantalum film 3 contains 0.5% oxygen. Next, a 0.05 μm silicon oxide film was deposited as an etching mask film 4 on the X-ray absorber film 3 by a magnetron sputtering apparatus.

Next, as shown in FIG.
With a thickness of 4 mm made of quartz glass and an outer diameter of 125 mm
It was joined to the mask frame 6 having an inner diameter of 50 mm square by a direct joining method.

Next, as shown in FIG. 7, the X-ray support 1 was wet-etched with potassium hydroxide at a temperature of 95 ° C. to form a 30 mm square opening in the X-ray support 1.

Next, as shown in FIG. 8, a resist pattern 7 is formed on the etching mask film 4. As a resist, ZEP-520 having a thickness of 0.3 μm was used. After spin coating, the solvent in the resist was volatilized by heating to 170 ° C. in a nitrogen atmosphere. Thereafter, an acceleration voltage of 50 kV and a dose of 9 are applied on the resist by an electron beam lithography apparatus.
A desired pattern was drawn at 0 μC / cm ² , and then developed with a special developer ZEP-RD to form a resist pattern.

Next, as shown in FIG.
Using an IE apparatus, the etching mask film 4 was etched with a mixed gas containing a fluorine-based gas as a main component, using the resist pattern 7 as a mask. Next, the resist pattern 7 was removed by oxygen ashing. Thus, the etching mask pattern 8 was formed.

Next, as shown in FIG. 10, the X-ray absorber film 3 was etched by dry etching with ICP plasma using chlorine gas using an etching mask 8. The etching conditions were a gas pressure of 0.5 Pa, an applied high-frequency power of 500 W, a mask substrate temperature of 25 ° C. during the process, and a bias power of 100 W for the mask substrate.

Using the X-ray mask manufactured by the above steps, exposure was performed by an X-ray exposure stepper. The distance between the X-ray transmitting film and the semiconductor substrate during exposure is set to 10 μm,
A chemically amplified resist SAL606 having a thickness of 0.25 μm was used as the resist. After resist application, pre-baking is performed at 130 degrees for 2 minutes, and an exposure amount of 2 is applied with an X-ray stepper.
Exposure was performed at 100 mAs, and post-baking was performed at 120 degrees for 1 minute. Thereafter, development was performed for 3 minutes, and the X-ray exposure step was completed. When observing this substrate with a dimension SEM,
It was confirmed that the 0.06 μm line and space pattern was well resolved. As described above, the semiconductor circuit pattern was successfully transferred.

The present invention is not limited to the embodiment described above. The X-ray transmission film is not limited to silicon carbide, and silicon nitride, diamond, or the like can be used. The X-ray absorber is not limited to tantalum, and a metal containing tantalum as a main component can be used. The etching mask and etching stopper are not limited to silicon oxide, but include chromium nitride, IT
O, chromium compounds, aluminum compounds and the like can be used. The etching gas is not limited to chlorine,
A chlorine-based gas such as boron trichloride, a mixed gas mainly containing a chlorine-based gas, or the like can be used. In addition, various modifications can be made without departing from the scope of the present invention.

[0049]

As described in detail above, according to the present invention, a fine pattern can be formed with high accuracy and good pattern in the step of etching a metal mainly composed of tantalum with a chlorine-based gas. .

[Brief description of the drawings]

FIG. 1 is a graph showing an etching rate of tantalum in a mixed gas of chlorine and oxygen.

FIGS. 2A and 2B are diagrams showing an etched shape of tantalum, wherein FIG. 2A shows an oxygen concentration of 0.2%, and FIG.
%, (C) is a chlorine-based etchant containing 0.5% oxygen concentration.

FIG. 3 is a graph showing a relationship between an oxygen concentration in a chlorine-based gas and a line width shift rate.

FIG. 4 is a graph showing the relationship between the concentration of oxygen contained in tantalum and the line width shift rate.

FIG. 5 is a cross-sectional view showing an X-ray exposure mask formed by using the tantalum film etching method according to the present invention.

FIG. 6 is a sectional view showing an X-ray exposure mask formed by using the tantalum film etching method according to the present invention.

FIG. 7 is a cross-sectional view showing an X-ray exposure mask formed by using the tantalum film etching method according to the present invention.

FIG. 8 is a sectional view showing an X-ray exposure mask formed by using the tantalum film etching method according to the present invention.

FIG. 9 is a cross-sectional view showing an X-ray exposure mask formed by using the tantalum film etching method according to the present invention.

FIG. 10 is a cross-sectional view showing an X-ray exposure mask formed by using the tantalum film etching method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray support 2 ... X-ray transmission film 3 ... X-ray absorber 4 ... Etching mask 5 ... Etching stopper film 6 ... Mask frame 7 ... Resist pattern 8 ... Etching mask patterns

Continued on the front page F term (reference) 2H095 BA01 BA10 BB01 BB16 BC05 4K057 DA11 DA12 DB08 DC10 DE01 DE04 DE20 DG12 DM29 DN01 5F004 AA05 BA04 BA20 DA04 DA26 DB08 EA06 EA13 EB07 5F046 GD01 GD03 GD04 GD15

Claims (4)

[Claims] 1. A metal containing tantalum as a main component in an amount of 0.2%
An etching method characterized by exposing to a chlorine-based gas containing more than 4% of oxygen. 2. A step of forming a mask on a metal containing tantalum as a main component;
An etching method, wherein the metal is selectively etched by exposing the metal to a chlorine-based gas containing more than 2% and not more than 4% of oxygen. 3. An etching method characterized by exposing a metal containing tantalum as a main component containing oxygen of more than 0.2% and not more than 5% to a chlorine-based gas for etching. 4. A step of forming a mask on a tantalum-based metal containing more than 0.2% and not more than 5% of oxygen, and removing a surface of the metal not covered by the mask from a chlorine-based material. An etching method comprising selectively etching the metal by exposing the metal to a gas.