JPH04147621A - Dry etching method - Google Patents

Abstract

PURPOSE:To form a more accurate wiring pattern by making an etching gas, a mixed gas of methanol and chlorine, into a plasma at a reduced pressure to etch an aluminum film or aluminum-alloy film. CONSTITUTION:When an aluminum film or aluminum-alloy film is dry-etched, a chlorine gas is usually used. For the resist which is the material of a mask for forming an interconnection film, the organic resist, chief of which are C, H and O, is commonly used. During dry etching, a physical sputtering or chemical reaction acts even upon a resist film due to an ion species or radical species which is one of the components of a dry-etching gas. Therefore, the thickness of the resist film becomes smaller. Since CH3OH is added to the etching gas, the molecular weight of the etching gas is small and so the physical sputtering has a small influence upon the resist. Furthermore, C, H and O, which are components of the resist, show a relatively small chemical reaction due to a chlorine component since CH3OH is made into a plasma and then is dissolved to be a supply source of C, H and O. Therefore, a reduction in the resist film thickness during dry etching is remarkably lowered compared with that in the past.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry etching method, and is particularly suitable for etching aluminum group and alloy N whose main component is aluminum (hereinafter abbreviated as aluminum alloy). This invention relates to a dry etching method.

[Conventional technology]

In the conventional method, for example, as described in Japanese Patent Publication No. 59-14111, BO/3 (boron trichloride) and 0
It has been shown that a mixed gas with 12 (chlorine) is used for etching aluminum group or aluminum alloy films.

Hereinafter, a case in which etching is performed by a conventional method using the etching apparatus shown in FIG. 1 will be explained.

In Figure 1, the vacuum exhaust @ @ 10 is connected, and the vacuum with the corpse discharger above! In this case, the discharge tube (branch) having an open end on one side is configured to be airtight in the vertical direction in the fourth vessel (9). A waveguide ψ is installed on the outside of the discharge tube.
At the first outer side of the waveguide, magnetic field generating means, for example, a group of ring-shaped coils, are installed in two stages in the vertical direction.

There is also a magnetic field shield plate on the outside of the ring-shaped coil.

A horse chestnut, 47, is installed.

The waveguide ψ is connected to the microwave generating means via the microwave waveguide ω.

The vacuum container 2D is provided with a nozzle 4 for introducing etching gas, and the nozzle 4 is connected to an etching gas supply device via a gas conduit. A substrate electrode 110 is placed in the space 100 formed by the vacuum vessel I and the discharge tube (9).
is provided. The substrate electrode 110 has a high frequency electric current j12.
0 is connected, and a ground electrode 13G is connected to the grounded vacuum device powder.A group H140 is held by a substrate holder 150 made of an insulating material by pressure to the substrate electrode 110, and the space 100 is in a vacuum state. The exhaust system f10 depressurizes and exhausts with a predetermined pressure lid. Thereafter, etching gas is introduced into the space 100 at a predetermined flow rate from the etching gas supply device through the gas pipe (supply) and the nozzle 4.
The pressure of 00 is appropriately adjusted to a predetermined processing pressure by a vacuum evacuation device 10.

On the other hand, in the space 10G, an electric field by the microwave generated by the microwave generator @70 and a magnetic field by the annular coil are applied, and the etching gas present in the discharge region in the discharge tube I is turned into plasma, and the substrate is etched. High-frequency power is applied to the electrode 110 from a high-frequency electric current tIA120, thereby generating a high-frequency bias.

The ion energy of the substrate 140 is controlled by extremely precise adjustment of the high frequency power, and the etching process is performed with high precision.

Etching above! II and etching gas.
BO/3: 60cClmin, 0/z: 9
Using a mixed gas of 0 cClrnin, the pressure was 15 Torr.
When etching a substrate of an aluminum alloy film of Al-1, 5i-Q, and 5$Ou under the conditions of r, microwave power IKW, and high-frequency power 90W, etching rate = 900 to 1000 am/min, resist ratio = 2 to 3, vs. BiO2 selection: O = 12 [Ni1 to be solved by the invention] In the conventional method, noz3 and 0 were used as etching gases.
When the etching process is performed using a gas mixed with 72, the etching rate ratio (hereinafter referred to as resist selectivity) between the resist, which is a mask material for forming a wiring pattern, and the aluminum film or aluminum alloy film, which is the material to be etched, is It was a rice cake with 2-3 servings.

In recent years, LSI devices have become increasingly dense and miniaturized.
In particular, when etching an aluminum group or aluminum alloy film that is a wiring material, it has become necessary to etch a step structure that is approximately two to three times the thickness of the etching.

In the conventional method, there is no margin in the selectivity to the resist, so in some cases the resist disappears during the etching process, and even the aluminum group or aluminum alloy film to be masked is etched.

For two reasons, there was a time when a wiring pattern faithful to the mask could not be formed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry etching method capable of forming a more accurate wiring pattern in etching an aluminum group or aluminum alloy film.

[Means to solve the problem]

In order to achieve the above object, an aluminum group or aluminum alloy film is dry etched using OH or a mixed gas of OH and Olz.

[For production]

Chlorine-based gas is generally used in dry etching treatment of aluminum group or aluminum alloy films, and it is thought that aluminum reacts with the chlorine component and is mainly volatilized and removed as aluminum chloride. On the other hand, the resist that is the mask material for the bottom of the wiring pattern is generally an organic resist, and is composed of O, H, and 0 as main components.

However, during the dry etching process using the conventional method described above, the resist film thickness is reduced due to physical spattering and chemical reactions caused by the ions and radical heat in the dry etching gas components.

In the present invention, the amount of decrease in resist film thickness in the etching process 3181 is significantly reduced compared to the conventional method. Although the exact effect is not clear, the following are thought to be the causes. In other words, since 0H30H was used as an additive gas in the etching gas, the molecular weight was smaller than that of conventional B Ojs (the effect of physical alteration on the resist was small, and the chlorine components of O, H, and O in the resist components The amount of chemical reaction is relatively small because the additive gas 0H30H decomposes due to blurring and becomes a source of 0, H, and O. Due to the above reasons, the resist film thickness decreases during the dry etching process. It is expected that the amount will be significantly lower than before.

〔Example〕

An embodiment of the present invention will be described below.

In the present invention, an etching apparatus shown in Fig. gJ1 was used, and a mixed gas of 0H30H and O/2 was used as the etching gas. M-1% is applied to the substrate which is the dripping material to be machined.
A substrate with an aluminum alloy film of 8i-0.5%Ou was used, and the etching gas was 0H30H: 20cc/
min, O7l:2: 90cCl mi
A mixed gas of n was used. Other processing conditions were the same as before: gas pressure 16 mTorr, microwave power IKW.

The high frequency power was 90W. Table 1 shows the etching characteristics in this case.

jI! 1 As can be seen from the results in Table 1, the selection ratio between M and photoresist is 3.5 to 1.7 times the conventional ratio.
It has significantly improved to 4.

According to this example, even in the etching process of a step structure portion having a thickness 2 to 3 times the etching film thickness, the resist did not disappear and accurate patterning was possible.

[X Ming effect]

According to the present invention, since the aluminum group or aluminum alloy film is dry etched using a mixed gas of 0H30H and Olz, the resist selectivity between the aluminum group or aluminum alloy film and the resist mask can be improved. This method has the effect that even in etching processing with a high step height difference of 2 to 3 times the etching gas, it is possible to selectively etch an aluminum group or aluminum alloy film on a resist pattern.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of an apparatus for carrying out the dry etching method of the present invention. etc... Vacuum vessel, (capital)... Discharge tube,
Hammer: Waveguide, Father: External magnetic field generating means, θ: Microwave waveguide, π:
Microwave generating means, 110...Substrate electrode, 1
20... High frequency power supply, 130... Ground electrode, 140... Substrate, Sword... Discharge gas supply device agent Patent attorney Katsuo Ogawa 1
C.X-1□, -I/O I Flash

Claims (1)

[Claims] 1. A gas mixture of CH_3OH (methanol) and Cl_2 (chlorine) is used as an etching gas, and the etching gas is turned into plasma under reduced pressure to etch an aluminum film or an alloy film mainly composed of aluminum. Dry etching method.