JPH01285A - Dry etching method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a dry etching method for semiconductor devices.

In particular, the present invention relates to a dry etching method for electrodes mainly made of indium oxide in semiconductor devices.

Conventional technology Conventionally, transparent conductive films mainly made of indium oxide, i.e., IT
The O film was etched by a wet etching method using a solution containing hydrogen iodide or ferric chloride as a main component. However, since this method uses isotropic etching or etching by a reduction reaction, it is difficult to etch fine patterns, that is, pattern dimensions of 5 μm or less. However, as the density of integrated circuits has increased, it has become necessary to perform the etching process with high precision.

A dry etching method was introduced to solve this problem. Various methods and devices for this dry etching have been developed, including barrel dry etching, which is mainly used for resist ashing, reactive ion etching, which is suitable for microfabrication, and CD etching, which is characterized by uniformity and low resist damage.
E (Chemical Dry Etching)
) etc. are used. Among them, reactive ion etching (Reactive Ion Etching)
A method called RIE (abbreviated as RIE) is the mainstream of dry etching. This RIE will be briefly explained in the second drawing.

An electrode 25 in which a substrate 24 to be selectively etched is disposed and a counter electrode 26 are provided in a vacuum container 23 having an air supply port 21 and an exhaust port 22. The electrode 25 is electrically insulated from the vacuum vessel 23 by an insulator 27, and the substrate 24 is electrically insulated from the electrode 25 by an insulator 27. A reaction gas is supplied from the air supply port 22, the pressure in the vacuum container 23 is set to about 1 to 10 Pa, and electric power is supplied between the electrode 25 and the counter electrode 26 to form low-temperature plasma by glow discharge.

The ions and radicals formed in this low-temperature plasma collide with the substrate to etch the substrate in a state where sputtering and chemical reactions coexist. The power used for RIE is usually high frequency power, and a cathode coupling method is used.

A chlorine compound such as CCl4 was used as the reaction gas. However, when using this type of reactive gas, I n
20a, transparent conductive films such as ITO, metal materials such as AI, Cr, and Mo used as wiring materials, and Si,
It is difficult to obtain a large etching selectivity with silicides such as Si3N4.5i02.゛As a method to solve this problem, a method has been proposed in which a gas containing alcohol or carboxylic acid is used as a reactive gas (Japanese Unexamined Patent Publication No. 52-1
No. 19246). For example, a barrel type dry etching apparatus shown in FIG. 3 is used as a dry etching apparatus, the substrate 32 is placed in a vacuum vessel 31, methyl alcohol is introduced as a reaction gas through an air supply port 33, and the pressure inside the vacuum vessel 31 is increased. be maintained at 40 Pa (exhaust from the exhaust port 34, apply 150 to 600 W to the RF main power electrode 35,
Etches an ITO film, etc. It is reported that under the above conditions, the ITO film is uniformly etched as a gaseous compound by the radicals generated by the plasma without leaving any etching residue, and that the selectivity to 5in2, SiN, and Si is sufficient. However, the barrel type dry etching apparatus has a problem in that it cannot achieve sufficient pattern accuracy.

As a method to solve this problem, a reactive dry etching device is used, and at least one of N2, Ar, and He gas is used as a carrier gas1, and a material containing up to 20% alcohol is used as a reactive dry etching device. A method of using it as a gas was proposed (Japanese Patent Laid-Open No. 60-234325). For example, methyl alcohol and Ar are mixed, the pressure inside the vacuum container is maintained at 5 Pa, and RF main power of 0.6 W/j is applied.
ITO! Etched IGI etc. Under the above conditions, the etching rate for the ITO film is approximately 30 nm.
On the other hand, the etching rates of the AI film and Mo film are so small that they can hardly be measured. Metals do not react with alcohol, whereas ITO films react with (CH) m I
It has been reported that organic indium is represented by a chemical formula such as nn.

Problems to be Solved by the Invention It has been found that this method of performing RIE by mixing alcohol as a reactive gas and gases such as Ar, N, and He as a carrier gas still has problems.

The case where the Ar flow rate>so% condition, which is an example of the above report, will be explained. If the carrier gas contains, for example, Ar at 80% or more of the total gas flow rate, the resist will be subjected to physical sputtering so much that the selectivity ratio between the ITO film and the resist will be small, making it impossible to obtain sufficient pattern accuracy. I have a problem. In other words, it is presumed that the resist pattern becomes thinner due to sputtering of the resist pattern due to a large amount of activated Ar, resulting in a decrease in pattern accuracy. In this case, perhaps <ITOI! Although resist re-deposition occurs on the surface, a new ITO surface is always formed on the surface due to the mechanism in which it is removed again by the activated Ar present in large quantities at the same time.
It is believed that the etching of the ITO film progresses.

Next, a case where the Ar flow rate is 80% will be explained. In this case, there is a problem that a resist re-deposition film and an organic polymer film are formed on the ITO film, and the ITO film is not etched sufficiently. That is, although the mechanism is not clear, unlike the conventional example described above, the amount of activated Ar decreases due to the decrease in Ar flow rate, and the redeposited film and organic polymer film cannot be removed sufficiently, so that the ITO film is not etched sufficiently. It is assumed that this will not be done.

Means for Solving the Problems The present invention has been made in view of the above-mentioned objectives. That is, in a method of etching a layer containing In 203 by reactive ion etching, the gas mainly used for etching is at least one of alcohol and carboxylic acids, and at least one of N2, Ar, and He gas is used. Dry etching is carried out by containing 0% to 20% of the total gas amount and by setting the gas pressure for reactive ion etching to less than 5 Pa during no discharge.

Effect The manufacturing method according to the present invention in which a layer containing at least In2O3 is dry-etched by reactive ion etching as described above uses alcohol as a reactive gas, so that the etching selectivity is lower than that of metal materials such as AI and Cr. Furthermore, since N2, Ar, and He are used as a carrier gas at a low flow rate of 0% to 20% of the total flow rate, damage to the resist can be reduced. Further, when the pressure is set to less than 5 Pa during non-discharge and discharge is performed, there is no resist redeposition and formation of an organic polymer film, and dry etching can be achieved without affecting the etching rate.

EXAMPLE Hereinafter, an example of the dry etching method according to the present invention will be described with reference to FIG.

Also in the present invention, RIE will be explained using the apparatus shown in FIG. That is, the transparent substrate 24 with the ITO film is placed in the vacuum container 2.
3 and methyl alcohol at 100 s c c
Air is supplied from the n+ air supply port 21 into the vacuum container 12, which has been previously brought to a vacuum level of 10-3 Pa or less, and set to IPa, and then RF power of 0.2 W/cd is supplied to discharge. After discharging for a required time, the RFt force is stopped, the vacuum container 23 is purged with dry air, and the substrate 24 is taken out. Under the above conditions, I.T.
The etching rate for the O film was about 20 nm/min.

On the other hand, the Cr and AI films were hardly etched. Further, an organic polymer film formed as a result of alcohol discharge was not formed. The reason for this is that since it does not contain a carrier gas, there is little redeposition on the ITo film due to resist sputtering caused by activated ions of the carrier gas (and because the gas pressure is low, an organic polymer film is not formed). Also, even if formed very thinly, activated CH2 and CH3
, CO1O, etc., and is removed physically by sputter etching or plasma chemically, so it is thought that the ITO film is etched without forming an organic polymer film.

As a result of further studies on the present invention, it was found that the etching rate was dependent on the gas pressure during non-discharge, and was particularly excellent when the etching rate was less than 5 Pa.

This will be explained according to FIG. In the same figure, the solid line indicates the etching rate with respect to the gas pressure during no discharge.
At a vacuum level of less than 5 Pa, the etching speed is fast (which is a suitable region for etching. On the other hand, at a vacuum level of 5 Pa or more, etching remains are generated, which poses a manufacturing problem. In this case, the flow rate of alcohol decreases, which reduces the formation of an organic polymer film, and it is thought that the volatile ITO compound is more likely to be etched when the vapor pressure is low and the gas pressure during non-discharge is low.

As a result of experiments, it has been found that the reactive acid gas is not limited to methyl alcohol, but any alcohol may be used, and ethyl alcohol, isopropyl alcohol, etc., or carboxylic acids such as acetic acid have been found to have similar effects and are included in the present invention.

Next, a second example will be shown. That is, the substrate with ITOllI is placed in a vacuum container, and methyl alcohol is added to 101
005e, Ar was mixed for 12 s e c + s, and air was supplied from the air supply port 21 into the vacuum container 23, which had been previously set to a vacuum level of 10-3 Pa or less, and set to IPa, and then the RF power was set to 0.2
Supply W/cj power and discharge. After discharging for the required time, R
Stop the F power, purge the vacuum container with dry air, and take out the substrate. Under the above conditions, the etching rate for the ITO film was approximately 2
It was 0 nm/min. On the other hand, Crtll was hardly etched. Furthermore, an organic polymer film formed as a result of alcohol discharge was also not formed.

As shown in the first and second embodiments above, even if a small amount of carrier gas is added, no organic polymer film is formed, and the amount of carrier gas added can range from 0 to 20% of the total gas flow rate ( ,
In particular, a gas flow rate of 5% from O is particularly good since it causes little damage to the resist.

Effects of the Invention As is clear from the above explanation, the dry etching method according to the present invention does not use harmful gases such as CCl4, CF4, etc., and is effective for etching metal materials such as AI and Cr using a simple material such as alcohol. Since In2O3 and ITO can be selectively etched with a relatively high ratio and with little damage to the resist, it is extremely useful for manufacturing semiconductor devices containing In203 and ITO, and has great effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between gas pressure during no discharge and etching rate according to the present invention, and FIG. 2 is a cross-sectional view of a main part showing an example of an apparatus used for reactive ion etching according to an embodiment of the present invention. 3 are views showing a cross-sectional structure of a main part of a barrel-type dry etching apparatus according to a conventional example. 21...Air supply port, 22...Exhaust port, 23...
・Vacuum container, 24...substrate, 25...electrode, 2
6...Counter electrode, 27...Insulator. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1

Claims (1)

[Claims] In a method of etching a layer containing In_2O_3 by reactive ion etching, the gas mainly used for etching is at least one of alcohol and carboxylic acids, and the entire gas is at least one of N_2, Ar, and He gas. A dry etching method, characterized in that the gas is contained in an amount of 0% to 20%, and the gas pressure used for reactive ion etching is less than 5 Pa during non-discharge.