JPH0855836A - Reactive dry etching method - Google Patents

Abstract

PURPOSE:To obtain a reactive dry etching method in which the damage of a resist as a mask is reduced in the dry etching operation of an ITO and in which the resist can be removed by a method wherein helium gas is mixed with an etching gas such as a chlorine-based gas, a methane-based gas or the like. CONSTITUTION:An ITO film 10 is formed on a substrate 9, and a resist pattern 11 as a mask is formed on the ITO film 10. CH4, Cl2 and helium gas (He) as reactive gases are supplied to a chamber 1 from a gas introduction port 4 through a gas-flow-rate controller 4c. High-frequency electric power is applied to a lower-part electrode 3 from a high-frequency power supply 7, a plasma is generated between electrodes 2, 3, accelerated ions are made to collide with the face of the ITO film 10 in a part which is exposed from a resist pattern 11 on the substrate 9, and the ITO film is etched. Thereby, a reactive dry etching operation which reduces the damage of a resist, which can remove the resist easily and which is suitable for a minute working operation can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactive dry etching method, and more particularly to indium oxide formed on a substrate,
The present invention relates to a method of plasma etching a tin oxide or indium tin oxide film with a chlorine-based gas or a methane-based gas.

[0002]

2. Description of the Related Art As a miniaturized and thinned image display device, a flat panel type display device such as a liquid crystal display device, a plasma display and an electroluminescent panel has been attracting attention in place of a CRT. Among them, liquid crystal display devices are widely used as display devices for TVs and graphic displays by taking advantage of their features such as thinness and low power consumption. Among liquid crystal display devices, thin film transistors (T
An active matrix type liquid crystal display device using FT) as a switching element has excellent high-speed response, is suitable for high definition, and has been attracting attention as a display screen of high quality, large size and color display.

In this active matrix type or simple matrix type liquid crystal display device, electrodes, signal lines and scanning lines formed on a transparent substrate are formed by a transparent conductive film, and ITO (indium tin alloy) is oxidized on this conductive film. Stuff) is used.

ITO is formed by sputtering and patterned for each pixel so that a voltage can be applied.

For patterning ITO, a wet etching method using a hydrochloric acid type etching solution is generally used. The wet etching method has the advantage that the equipment is simple, but has the drawbacks that it is difficult to control the etching rate by using a liquid and that there is a theoretical limit to the precision of fine processing.

On the other hand, with the improvement of the quality of the screen of the image display device, there is an increasing demand for the processing precision of ITO to be fine and highly accurate. The reactive dry etching method is used in the manufacturing process of the semiconductor circuit using the Si substrate or the Si thin film, and it is effective for the fine processing. It is necessary to examine the applicability of this reactive dry etching method to ITO. , Some suggestions have been announced. That is, as a reactive dry etching method for ITO, a mixture of methane gas and hydrogen or chlorine gas is used as an etching gas (JJAP, Vol. 29, No. 1).
0, October, 1990, pp1932-1935, Mikio. H, Hiraoka.
K, et al and 1991, Dry Pross Symposium I-6, PP3
3, Hiroyuki. S, Makoto. K. et al.).

[0007]

However, when methane gas and hydrogen are mixed or reactive dry etching is performed with an etching gas composed of chlorine gas, it is difficult to obtain a high etching rate, and the selection ratio to the resist used as a mask is low. Was hard to get.

If the plasma power is increased in order to increase the etching rate, the selectivity with the resist cannot be obtained, the resist is remarkably deteriorated, and etching with a good shape cannot be realized.

Further, the damaged resist cannot be completely removed by being denatured, resulting in inconvenience that it cannot proceed to the next process, and it is difficult to introduce the reactive dry etching technique into the manufacturing process. .

The present invention solves such a problem by providing a reactive dry etching method which reduces damage of a resist as a mask during dry etching of ITO or the like, enables removal of the resist and is practically usable. I will get it.

[0011]

The present invention is a reactive dry etching for etching an indium oxide, tin oxide or indium-tin oxide film in a chamber by plasma using chlorine gas or methane gas as etching gas. In the method, there is provided a reactive dry etching method characterized by mixing helium gas with the etching gas.

Further, the present invention provides a reactive dry etching method in which the mixing ratio of helium gas is 10 times or more with respect to the total amount of etching gas.

[0013]

The present inventors have examined the cause of damage to the resist that occurs during etching, and as a result, have found that the resist is damaged due to the temperature rise of the etching member during etching. In general reactive dry etching, the temperature of the electrode that holds the etching support base material is controlled during etching to control the temperature of the base material and suppress the temperature rise of the resist to reduce damage. .

However, when forming a circuit on a silicon semiconductor substrate, it is effective to control the temperature of the electrode from the viewpoint of thermal conductivity. However, in the production of an image display device using a glass substrate as a supporting base material, the heat of glass is used. Since the conductivity is low, the temperature of the resist cannot be sufficiently lowered by temperature control, and the resist is damaged.

Therefore, the present inventors, based on the above results,
It has been found that by mixing a predetermined amount of helium gas into the etching gas supplied into the reaction chamber for generating plasma, etching can be performed without greatly reducing the etching rate of ITO. Also,
It was confirmed that by mixing helium gas, plasma can be stabilized and etching can be made uniform.

That is, according to the present invention, when a chlorine-based or methane-based etching gas is used in a chamber to etch a member to be etched of an ITO film formed on a surface of a glass substrate as a supporting base material, the inside of the chamber is etched. Helium gas is introduced into and mixed with the etching gas. In this case, it is desirable to supply the helium gas in an amount 10 times or more the etching gas.

By supplying the helium gas mixed with the etching gas, a cooling effect is obtained in which the heat on the substrate generated by the plasma generation is taken by the helium. Therefore, it is possible to prevent the temperature of the substrate, which is the etching member, from rising, and to prevent the resist from being damaged by heat. By reducing the damage to the resist, the resist is not baked and the resist can be easily removed.
It becomes possible to introduce reactive dry etching of O into the manufacturing process.

The film to be etched to which the present invention is applied is indium oxide (In ₂ O ₃ ) or tin oxide (SnO ₂ ).
Or indium / tin oxide film ITO (In / Sn)
It is O.

As a chlorine-based etching gas, chlorine (Cl
₂ ), boron trichloride (BCl ₃ ) and hydrogen chloride (HCl) are used. Further, as the methane-based etching gas, methane (CH ₄ ), methanol (CH ₃ OH), or a mixed gas of these and hydrogen (H ₂ ) is used. It is also possible to use a mixed gas of chlorine and methane, such as CH ₄ + HCl. The effect of mixing helium in the present invention is the same for each etching gas, and the same good effect is obtained in each case.

The amount of helium gas supplied into the chamber is preferably 10 times or more the volume ratio of the etching gas, but if the amount of helium gas is less than 10 times, the cooling effect of helium becomes insufficient. This is because it becomes difficult to effectively suppress the deterioration of the resist.
Depending on the plasma discharge conditions, up to about 20 times is practical.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a pair of electrodes 2 and 3 facing each other in parallel are arranged in a reaction chamber 1 which can be evacuated to a vacuum. The upper electrode 2 has a box shape, a gas outlet 2b is installed on a surface 2a facing the lower electrode 3, and a base is connected to a gas introduction pipe 4. The gas introduction pipe 4 is connected to the etching gas source 4a and the helium gas source 4b. The gas flow rate of the gas supplied from these can be freely set by the gas flow rate controller 4c. Further, the chamber 1, the upper electrode 2, and the gas introduction pipe 4 are of a cathode coupling type and are grounded to generate plasma.

The lower electrode 3 is grounded via a matching circuit 6 and a high frequency power supply 7. The lower electrode 3 is the electrode 3
A circulating water pipe 5 is installed to control the temperature of the circulating water, and by controlling the temperature of the circulating water, the temperature of the lower electrode 3 can be controlled.

When a high frequency is input from the high frequency power supply 7 between the lower electrode 3 and the upper electrode 2, plasma is generated between the both electrodes. When plasma is generated, a self-bias voltage (V
dc) is generated, and the accelerated ions collide with the substrate 9 on the lower electrode 3. An exhaust pipe 8 is connected to the lower portion of the chamber-1, and a vacuum pump 8a including a rotary pump and a mechanical booster pump is connected to the exhaust pipe 8.

Next, the etching method of the present invention will be described using the reactive dry etching apparatus described above. . First, as shown in FIG. 2, an ITO film having a thickness of about 140 nm is formed on a substrate 9 made of quartz glass having a diameter of 5 inches and serving as an etching support base material by the sputtering method.
After forming the film 10, a resist pattern 11 was formed on the ITO 10 by a photolithography method as a mask for forming a pixel pattern of a liquid crystal display device. Subsequently, the substrate 9 was placed on the lower electrode 3 in the chamber-1 shown in FIG. Then, using the vacuum pump 8a, the inside of the chamber-1 was 1 × 10 ^-2 P
Evacuate to a and exhaust the residual gas to the exhaust pipe 8
Exhaust from. Then, reactive gases CH ₄ and C ₁₂ and helium gas (hereinafter referred to as “He”) are supplied to the chamber-1 from the gas inlet 4 through the gas flow rate controller, and further between the chamber-1 and the mechanical booster pump. The pressure is controlled by a conduction valve (not shown) at the position to stabilize the high-frequency power supply (13.56MHz).
300 W of high-frequency power is applied to the lower electrode 3 to generate plasma between the electrodes 2 and 3, and the accelerated ions are exposed from the resist pattern 11 of the substrate 9 in the ITO.
The ITO is etched by colliding with the surface of the film 10.

At this time, in the above embodiment, CH ₄ and H
Both of C1 are supplied by 75 sccm, the total flow rate is 150 sccm, and the He flow rate is a parameter.
When the relationship between the TO and the etching rate was examined, the characteristic A as shown in FIG. 3 was obtained. It should be noted that the exhaust amount was kept constant and the pressure was increased with the increase of He.

For the etching rate of ITO, after the reactive etching, the parallel plate type ashing device was used to remove the resist pattern, and then the step difference measuring device by the stylus method was used to measure the step difference and the data was obtained. Obtained.

As is clear from FIG. 3, the etching rate slightly decreases with the addition amount of He. However, the rate of decrease in etching rate due to addition is
It is about 10% compared with the case where He gas is added 10 times the etching gas and the case where He gas is not added.

On the other hand, the hatched area B in the drawing shows the area where the resist can be removed. Since He is not added,
If the etching gas flow rate is 10 times or less, the resist cannot be completely removed. The etching rates shown were calculated using the part that could be partially removed.

The obtained substrate is an active matrix substrate on which a TFT switching element is formed, and a liquid crystal composition is sandwiched between the active substrate and an opposing substrate having an opposing electrode arranged opposite thereto to form a liquid crystal display device.

Although the cathode-coupling-type reactive dry etching apparatus has been described in the above embodiment, the effect of mixing He can be similarly applied to the anode-coupling-type apparatus.

Further, the present invention can be applied to not only a liquid crystal display device but also a flat panel type display device such as a plasma display or an electroluminescent panel which uses an ITO film.

[0033]

INDUSTRIAL APPLICABILITY According to the present invention, an oxide of at least one of indium such as ITO and tin is formed on a glass substrate or a thin film formed on the glass substrate and applied to a resist during a reaction when patterning. The damage can be reduced, the resist can be easily removed, and a reactive dry etching method suitable for fine processing can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a reactive dry etching apparatus for explaining an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the shapes of a substrate subjected to reactive dry etching and an ITO film.

FIG. 3 is a curve diagram showing the relationship between the mixing ratio of etching gas and He gas and the etching rate of ITO.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Chamber 2 ... Upper electrode 3 ... Lower electrode 4 ... Gas introduction port 4a ... Etching gas source 4b ... Helium gas source 5 ... Cooling water introduction port 7 ... High frequency power supply 8 ... Exhaust port 8a ... Vacuum pump 9 ... Glass substrate 10 ... ITO film 11 ... Resist

Claims (3)

[Claims] 1. A reactive dry etching method of etching an indium oxide, tin oxide, or indium tin oxide film with plasma using a chlorine-based gas or a methane-based gas as an etching gas in a chamber, wherein the etching gas is helium. A reactive dry etching method characterized by mixing gases. 2. The reactive dry etching method according to claim 1, wherein the mixing ratio of the helium gas is 10 times or more with respect to the total amount of the etching gas. 3. The reactive dry etching method according to claim 1, wherein an indium oxide, tin oxide or indium tin oxide film is formed on a glass substrate.