JP2003158119A - Method for dry-etching transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a higher etching rate than a conventional parallel flat RIE using capacitive coupling plasma. SOLUTION: Etching gas is introduced into a reaction container where a transparent conductive thin film which is mainly constituted of indium oxide of a material to be etched is etched. High frequency power is applied to an antenna disposed outside the reaction container. Inductively coupled plasma is generated in the reaction container by electromagnetic induction through a dielectric window constituted of a dielectric plate disposed in the reaction container, low frequency power in a degree for generating bias potential is applied to the electrode on which the material to be etched is placed, and dry etching is performed. Etching gas includes 5 to 100 vol.% of hydrogen iodide gas and 0 to 95 vol.% of one type selected from the group of inert gas constituted of helium, neon, argon and krypton.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for a transparent conductive film in the production of fine electronic components such as semiconductor devices, dielectric devices, magnetic devices and integrated circuits.

[0002]

Conventionally, ITO (I ndium T in
Wet etching has been mainly adopted for the etching of the transparent conductive thin film mainly composed of indium oxide represented by O xide). However, since the wet etching is isotropic etching, there are various problems such as so-called undercut occurring in the patterned ITO film to be obtained and a large amount of used waste liquid. Was there. Therefore, dry etching is drawing attention as the pattern becomes finer.

In dry etching of a transparent conductive thin film containing indium oxide as a main component, the etching gas is represented by a mixed gas of methane gas (CH ₄ ) and hydrogen (H ₂ ) and hydrogen iodide (HI). Hydrogen halide gas has been proposed. For example, in Japanese Patent Laid-Open No. 6-77174, as a gas for etching, a hydrocarbon gas, a hydrogen gas, and a gas containing an oxygen compound are introduced into an etching chamber to turn the gas into a plasma, and the gas is generated under the plasma. There has been proposed a dry etching method characterized by etching ITO, which is an object to be etched, which is arranged in the chamber. In JP-A-5-343365, an object to be etched containing ITO is placed in a reaction chamber,
A dry etching method in which a hydrogen bromide gas is used as an etching gas in a dry etching method in which plasma is generated by introducing an etching gas into the reaction chamber and applying high-frequency power to etch ITO in the reaction chamber. A method has been proposed. Further, in JP-A-8-97190, high frequency plasma of an etching gas containing a halogen gas or a halide gas is used to make In ₂ O ₃ or Sn on the substrate.
In a method of etching a conductive thin film containing O ₂ or ZnO as a main component, at least one selected from the group consisting of inert gases such as argon gas and helium gas.
Seed from 0.5 vol.% To 50 vol. %, A dry etching method for a transparent conductive film has been proposed, which is characterized by using a gas containing the same. For performing these dry etching methods, parallel plate type RIE ( R
eactive I on E tching) apparatus is used.

On the other hand, inductively coupled plasma has attracted attention as a method of obtaining a high density plasma as compared with the conventional parallel plate type capacitively coupled plasma. Suzu
kiet al. : Plasma Sources
Sci. Technol. , Vol. 7 (199
8) 13-20. Have been introduced in. In order to obtain the inductively coupled plasma, for example, high frequency power is applied to an antenna provided outside the reaction container, and the high frequency power is propagated through a dielectric window made of a dielectric plate installed in the reaction container.
When the high-frequency power applied to the antenna is increased, a so-called mode jump phenomenon is observed in which the discharge plasma mainly composed of capacitive coupling shifts to the discharge plasma mainly composed of inductive coupling due to an electromagnetic induction phenomenon. By inductively coupled plasma,
It is known that plasma with high ion density and high electron density can be generated. However, little is known about etching of transparent conductive films using inductively coupled plasma of hydrogen halide gas.

[0005]

The improvement of the etching rate of the transparent conductive film is very important from the viewpoint of shortening the processing time and reducing the processing cost. The dry etching method for the film has a problem that the etching rate is not always sufficient. An object of the present invention is to provide a faster dry etching method for a transparent conductive thin film containing indium oxide as a main component.

[0006]

Means for Solving the Problems As a result of intensive studies by the present inventors, when a mixed gas of hydrogen iodide gas and an inert gas such as argon is used as an etching gas, it is applied to an antenna provided outside the reaction vessel. It was found that inductively coupled plasma can be obtained without increasing the high frequency power so much that the etching rate of the transparent conductive thin film containing indium oxide as a main component becomes very high. Even in a very large area, a large etching rate was obtained, and a phenomenon not found in a parallel plate type RIE device using a capacitively coupled plasma, which has been conventionally used, was discovered.
The present invention has been completed.

That is, the present invention provides (1) a reaction vessel having at least a dielectric window made of a dielectric plate on which an antenna is installed outside, an etching gas introducing mechanism, and an electrode on which an object to be etched is placed. Low-frequency power that is sufficient to apply high-frequency power to the antenna and generate inductively coupled plasma in the reaction vessel by electromagnetic induction through the dielectric window, and to generate a bias potential on the electrode on which the object to be etched is placed. Is applied to dry-etch the object to be etched, wherein the etching gas is hydrogen iodide gas at 5 vol.% To 100 v
ol. %, And at least one selected from the group of inert gases consisting of helium, neon, argon and krypton in an amount of 0 to 95 vol. % Of the etching gas is a dry etching method for a transparent conductive film containing indium oxide as a main component. (2) At least one selected from the group of inert gases
Seed 50 vol.%-95 vol. %, The dry etching method according to (1). (3) The dry etching method according to (1) or (2), wherein the plasma generated in the reaction vessel has an electron density of 1 × 10 ¹⁰ cm ⁻³ or more. (4) The pressure of the etching gas is 0.5 Pa to 5 P
a, the frequency of the high frequency power applied to the antenna provided outside the reaction vessel is 10 MHz to 100 MHz, and the frequency of the low frequency power applied to the electrode on which the object to be etched is placed is 0.1 MHz to 10 MHz. (3)
The dry etching method described in. Regarding

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As an etching gas, hydrogen iodide gas is added in an amount of 5 vol.% To 100 vol. %, Preferably 5 vo
l.% to 50 vol. %, More preferably 15 vol.% ~
50 vol. %, And at least one selected from the group of inert gases consisting of helium, neon, argon and krypton in an amount of 0 to 95 vol. %, Preferably 50 vol.%
~ 95 vol. %, More preferably 50 vol.% To 85 v
ol. It is preferable that the etching gas contains 100%.
50 vol. % Or more, an inductively coupled plasma having a high plasma density can be generated without increasing the high frequency power so much that a higher etching rate can be obtained as compared with the parallel plate type RIE using the conventional capacitively coupled plasma. preferable. Further, hydrogen iodide is a gas that is generally much more expensive than an inert gas, so that the cost of the etching gas can be greatly reduced. The proportion of inert gas is 95 vol. If it is higher than 0.1%, the amount of ions or radicals generated from hydrogen iodide is too small, so that the etching rate of the transparent conductive thin film which is the object to be etched may be reduced.

The electron density of the plasma generated in the reaction vessel is 1 × 10 ¹⁰ cm ^-3 or more, and further 2 × 10.
It is preferably ¹⁰ cm ⁻³ or more. The electron density is measured using a probe method such as a single probe method or a triple probe method. The measurement position is a position 5 cm to 10 cm apart from the dielectric plate on the line connecting the centers of the electrodes on which the dielectric plate and the object to be etched are placed. When the electron density of the plasma is less than 1 × 10 ¹⁰ cm ⁻³ , the mode jump may not occur in the inductively coupled plasma, that is, the plasma in which the inductively coupled is the main component. The condition for mode jumping to inductively coupled plasma, that is, plasma mainly composed of inductive coupling, is not only the ratio of the inert gas, but also the shape of the antenna provided outside the reaction vessel and the magnitude of the high frequency power applied to the antenna provided outside the reaction vessel. Therefore, the conditions for generating plasma are appropriately adjusted so that the electron density of plasma is 1 × 10 ¹⁰ cm ⁻³ or more.

The pressure of the etching gas is 0.
5 Pa to 5 Pa, more preferably 1 Pa to 3 Pa,
The frequency of the high frequency power applied to the antenna provided outside the reaction vessel is 10 MHz to 100 MHz, more preferably 13.5 MHz to 100 MHz, and the frequency of the low frequency power applied to the electrode on which the etching target is placed is 0. .1
MHz to 10 MHz, more preferably 1 MHz to 10 MH
Being z is a preferred embodiment of the present invention. When the pressure of the etching gas is 0.5 Pa or less, inductively coupled plasma is unlikely to occur, and when it is 5 Pa or more, which is too high, variations in etching characteristics tend to increase.

The frequency of the high frequency power applied to the antenna provided outside the reaction vessel is preferably 10 MHz or higher so that ions in the plasma cannot follow so much, but if the frequency is too high, 100 MHz or higher, the antenna will be efficiently used. In some cases, high-frequency power cannot be applied, which is not preferable. On the contrary, as the frequency of the low frequency power applied to the electrode on which the object to be etched is placed, a low frequency that ions in the plasma can follow is selected, and the frequency is 0.1 to 10 MH.
z, and more preferably from 1 MHz to 10 MHz.

[Operation] Indium oxide, which is the main component of the transparent conductive thin film
Thing (In₂O₃) The etching reaction with hydrogen iodide is
It progresses through the following process. Inductively coupled plasma
Hydrogen radicals or ions generated in₂O₃
Reacts with surface oxygen, H ₂By generating O
Reduce the system. The reduced indium is coupled to the inductive coupling
Reaction with iodine radicals or ions generated in plasma
In response, InI₃Is generated. H generated by the reaction₂O
And InI₃Has a high vapor pressure, and therefore evaporates quickly.

In the present invention, the gas containing at least one selected from the group consisting of inert gases such as argon in the hydrogen iodide gas is used as the etching gas, so that the inductive coupling is generated from the discharge which is mainly capacitive coupling. It is possible to cause a so-called mode jump phenomenon that shifts to the main discharge without increasing the high frequency power applied to the antenna provided outside the reaction vessel. Since the inductively coupled plasma has a higher density of active ions and radicals that react with the transparent conductive thin film than the parallel plate type capacitively coupled plasma, the above etching reaction can be performed at high speed. Since the low frequency power is applied to the electrode on which the object to be etched is placed and the electrode has a negative bias potential, the high density ions generated from the inductively coupled plasma are accelerated to obtain large energy, It collides with the transparent conductive thin film whose main component is indium oxide, which is the object to be etched, and greatly accelerates the reaction with the object to be etched. Ions generated from an inert gas such as argon are also accelerated by the negative bias potential, and promote the reaction between the radicals and ions generated from hydrogen iodide and the object to be etched. for that reason,
Even if the inert gas concentration in the etching gas is very high,
A high etching rate can be obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of an etching apparatus used for carrying out the dry etching method for a transparent conductive film according to the present invention. A sample electrode 16 on which a transparent conductive thin film, which is the object to be etched 10, is placed, is arranged in the reaction container 15. The sample electrode 16 is the reaction container 1
5 is electrically insulated from the low frequency power applying mechanism 1
7 is connected. Further, an etching gas introducing mechanism 13 is connected to the reaction vessel 15, and it is possible to introduce a mixed gas of hydrogen iodide gas and an inert gas into the reaction vessel 15 at an arbitrary ratio and flow rate. . Further, the reaction container 15 is connected to an exhaust device through a connection port 14 of the exhaust device. A dielectric plate 11 is attached to the reaction container 15, and the dielectric plate 11 constitutes a dielectric window of the reaction container 15. Further, an antenna 12 for applying high frequency power is installed outside the dielectric plate 11. The size and shape of the antenna 12 are appropriately adjusted depending on the size of the sample electrode 16. Sample electrode 16
Is relatively small and the influence of the density distribution of the generated plasma is negligible, a one-turn loop antenna is adopted, for example. The high frequency power applied to the antenna 12 propagates into the reaction vessel 15 through the dielectric window formed by the dielectric plate 11 by electromagnetic induction, and generates inductively coupled plasma.

Dry etching of the transparent conductive film of the present invention is carried out by the following procedure. After the object to be etched 10 is set on the sample electrode 16, the reaction container 15 is evacuated. When the predetermined vacuum degree is reached, a mixed gas of hydrogen iodide gas and an inert gas is introduced into the reaction vessel 15 at a predetermined ratio and flow rate by the etching gas introduction mechanism 13 so that a constant pressure is obtained. Exhaust control is performed by the exhaust device. Then, a predetermined electric power is applied to the antenna 12 and the sample electrode 16 to perform etching. After a predetermined time, the application of electric power is stopped, the residual gas in the reaction container 15 is removed by an exhaust device, the reaction container 15 is opened to the atmosphere, and the object 10 to be etched is taken out. Particularly, the composition of the hydrogen iodide gas and the inert gas and the high frequency power applied to the antenna 12 are set so that the plasma generated in the reaction vessel 15 causes a mode jump phenomenon and the inductive coupling is the main discharge plasma. It It is preferable to set the conditions that satisfy the following expression (1).

Next, the result of actual dry etching of the transparent conductive film in the present invention using the above-mentioned etching apparatus will be described in detail. Here, a 1-turn loop antenna with a diameter of 100 mm is used as the antenna 12 provided outside the reaction container, and the frequency of the high-frequency power applied to the antenna 12 is 13.6 MHz and is applied to the sample electrode 16 on which the object to be etched is placed. The frequency of the low-frequency power used was 6.0 MHz. As the dielectric plate 11, a quartz plate having a thickness of 15 mm was used. The area of the dielectric window provided in the reaction vessel is about 300 cm ² , and the area of the sample electrode 16 is 7 cm ² .
It is 8.5 cm ² .

In the etching apparatus under such conditions, the high frequency power applied to the antenna provided outside the reaction vessel for mode jumping to the plasma mainly composed of inductive coupling and the etching gas composed of hydrogen iodide gas and inert gas are used. The relationship with the composition ratio approximately satisfies the following expression (1). P _i ≧ 6.6 · x _HI · S _w (1) where P _i is the high frequency power applied to the antenna provided outside the reaction vessel (unit is W, and P _i > 0 is satisfied), and S _w is Area of dielectric window (unit is cm ² ), x _HI is concentration of hydrogen iodide gas (where concentration of inert gas is x, X _HI + X =
1.0, satisfying 0 ≦ X ≦ 0.95).

Example 1 As an etching gas,
Mixed gas of hydrogen halide (HI) gas and argon (Ar) gas
With a mixed gas flow rate of 100 sccm (standard c
c / min) and the etching gas pressure was 1.7 Pa.
In addition, the high frequency applied to the antenna provided outside the reaction vessel
The power of 1 kW was applied to the sample electrode on which the object to be etched was placed.
The low frequency power applied was 10W. Dielectric window and sample electrode
The pole distance was 20 cm. As the object to be etched
Is a photoresist after forming an ITO film on a quartz substrate.
What was patterned by. Flow of HI and Ar
The ITO thin film is etched by changing the amount ratio and etching for 1 minute.
The etching depth was measured to determine the etching rate.
The results are shown in Figure 2. Ar gas concentration is 60 to 90 vo
l. Even though the area is as high as%, it is a big etch
The depth of the etching speed is shown, and high-speed etching is possible.
I understand that. In this concentration region, the etching depth is
It is an almost constant value. Ar gas concentration is 60 vol. % Not yet
Full, the obtained etching rate depth is small, plasma
The discharge is based on the inductive coupling required for the etching method of the present invention.
Not transferred to plasma discharge. By the way, with the sample electrode
The distance from the dielectric plate is 7.5 cm from the dielectric plate.
Insert a probe at a remote place, and
The Ar gas concentration was 60 vol. % Or less
Above, 7 × 10^Ten~ 1 x 10¹²cm^-3And Ar Ar
Concentration of 60 vol. If less than%, 2 × 10⁹~ 5 x 1
0⁹cm^-3Met. Also, the Ar gas concentration is 60 vo
l. % Or more, plasma discharge mainly due to inductive coupling
And the above-mentioned formula (1) is satisfied. The above formula
In (1), S_W= 300 cm²Then, Ar gas
The concentration is 60 vol. %, X = 0.6, x_HI= 0.4
Therefore, Pi ≧ 792W. Example 1 is P _i= 1 kW
Since it is the result carried out in step 1,
Becomes

Comparative Example 1 Etching was performed in the same manner as in Example 1 except that a mixed gas of hydrogen bromide (HBr) gas and argon (Ar) gas was used as the etching gas, and the etching depth of the ITO thin film was measured. Was measured. The results are shown in Figure 2. Ar gas concentration is 90 vol. %, The etching rate was maximized, and the etching rate tended to decrease as the Ar gas concentration decreased. Ar gas concentration is
30 vol. % Or more 90 vol. The etching rate gradually increases to less than%. Ar gas concentration is 30v
ol. %, The obtained etching depth is small, and the plasma discharge is not transferred to the inductively coupled plasma discharge required for the etching method of the present invention. By the way, when the electron density was measured as in Example 1, the Ar gas concentration was 30 vol. % Or more, 8 × 10 ¹⁰ to 1 × 10 ¹²
cm ⁻³ , and the Ar gas concentration is 30 vol. If it is less than%, it is 1 × 10 ^{9 to} 5 × 10 ⁹ cm ⁻³ . Also, Ar
The gas concentration is 30 vol. If it is more than%, it can be seen that the plasma discharge is mainly inductively coupled. However, the etching rate was as high as that of hydrogen iodide (H
I) Small compared to the case of gas.

[0019] (Comparative Example 2) etching gas, except for using chlorine (Cl ₂₎ gas in place of hydriodic gas (HI) is etched in the same manner as in Example 1, I
The etching depth of the TO thin film was measured. The results are shown in Figure 2. In the case of the mixed gas of Cl ₂ and Ar, the etching rate monotonously decreases with the decrease of the Ar gas concentration, the change in the depth is small, and the etching rate depth itself has the same values as those in Examples 1 and 2. It is smaller than. by the way,
When the electron density was measured in the same manner as in Example 1, the Ar gas concentration was 0 to 100 vol. In the range of%, 7 × 10 ¹⁰ ~
It was 1 × 10 ¹² cm ⁻³ . The plasma discharge jumps to a plasma discharge mainly composed of inductive coupling at all Ar concentrations, but in the case of a mixed gas of Cl ₂ and Ar, a large etching depth value is not obtained.

(Comparative Example 3) A comparative example shows the result of etching by a parallel plate type RIE apparatus using a conventionally used capacitively coupled plasma. The configuration of the parallel plate type RIE device used is shown in FIG. The frequency of the high frequency power applied to the sample electrode 26 is 13.6 MHz, and the sample electrode area is 78.5 cm ² . The distance between the sample electrode 26 and the counter electrode was 8 cm. As etching gas,
A mixed gas of hydrogen iodide (HI) gas and argon (Ar) gas was used, the flow rate of the mixed gas was 50 sccm, and the pressure of the etching gas was 6.7 Pa. The high frequency power applied to the sample electrode on which the object to be etched was placed was 100W.
The same material as in Example 1 was used as the object to be etched. The etching depth of the ITO thin film was measured by performing etching for 1 minute while changing the flow rate ratio of HI and Ar.
The results are shown in Fig. 4. Unlike Example 1, the Ar gas concentration was 0 to 20 vol. A relatively large etching depth is shown in a low concentration region of about%. Also, the obtained etching depth value itself is small. The result of FIG. 4 is shown in JP-A-8-9719.
The result is almost in agreement with the result shown in Japanese Patent No. 0. Therefore, the results of FIG. 2 and FIG. 4 show that the etching method for the transparent conductive thin film of the present invention is different from the conventionally proposed etching method.

[0021]

According to the method of dry etching a transparent conductive film of the present invention, an inductively coupled plasma having a high plasma density can be generated without increasing the high frequency power applied to the antenna provided outside the reaction vessel. As a result, a higher etch rate can be obtained as compared with the conventional parallel plate type RIE using capacitively coupled plasma. Further, unlike the conventionally used parallel plate type RIE using capacitively coupled plasma, the dry etching method of the present invention has a feature that a high etching rate can be obtained even if the amount of hydrogen iodide is small. is doing. Since hydrogen iodide is a gas that is generally much more expensive than an inert gas, the cost of the etching gas can be reduced by the dry etching method of the present invention. That is, the dry etching method of the present invention can contribute to further speeding up of dry etching of the transparent conductive film and further cost reduction.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an etching apparatus used for carrying out a dry etching method for a transparent conductive film according to the present invention.

FIG. 2 shows the results of the etching test conducted in Example 1 of the present invention and Comparative Examples 1 and 2, and shows the etching rate and Ar obtained by measuring the etching depth of the ITO thin film etched for 1 minute. It is the figure which showed the relationship with gas concentration.

FIG. 3 is a schematic diagram showing the configuration of a parallel plate type RIE apparatus using the capacitively coupled plasma used in Comparative Example 3.

FIG. 4 is a graph showing the relationship between the etching depth of an ITO thin film etched for 1 minute and the Ar gas concentration, which is the result of the etching test performed in Comparative Example 3.

[Explanation of symbols]

10 Etching object 11 Dielectric plate 12 antennas 13 Etching gas introduction mechanism 14 Connection to exhaust system 15 reaction vessels 16 Sample electrode 17 Low frequency power application mechanism 20 Object to be etched 23 Etching gas introduction mechanism 24 Connection to exhaust system 25 reaction vessels 26 Sample electrode 27 High frequency power application mechanism 28 Counter electrode

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Claims (4)

[Claims] 1. A high frequency power is used for an antenna by using at least a dielectric window made of a dielectric plate having an antenna installed on the outside, a reaction vessel having an etching gas introducing mechanism and an electrode for mounting an object to be etched installed therein. Is applied to generate inductively coupled plasma in the reaction vessel by electromagnetic induction through the dielectric window, and low-frequency power is applied to the electrode on which the object to be etched is placed to generate a bias potential, which is then etched. A method of dry etching an object, wherein the etching gas is hydrogen iodide gas at 5 vo
l.% ~ 100vol. %, And at least one selected from the group of inert gases consisting of helium, neon, argon and krypton in an amount of 0 to 95 vol. % Of the etching gas is a dry etching method for a transparent conductive film containing indium oxide as a main component. 2. At least one selected from the group of the inert gas is 50 vol.% To 95 vol. %, The dry etching method according to claim 1. 3. The plasma generated in the reaction vessel
Electron density is 1 × 10 ^Tencm^-3It is characterized by the above
The dry etching method according to claim 1 or 2. 4. The pressure of the etching gas is 0.5 Pa.
˜5 Pa, the frequency of the high frequency power applied to the antenna provided outside the reaction vessel is 10 MHz to 100 MHz, and the frequency of the low frequency power applied to the electrode on which the object to be etched is placed is 0.1 MHz to 10 MHz. The dry etching method according to claim 3.