JPH0499289A - Etching method - Google Patents

Abstract

PURPOSE:To etch an aluminum thin film with high accuracy by specifying the sample temp. and the pressure of chlorine-base discharge gas in a vacuum chamber to specified ranges. CONSTITUTION:An aluminum thin film on the sample surface is etched by generating a plasma by electron cyclotron resonance excitation in a vacuum chamber into which a chlorine-base discharge gas is introduced and by using active particles in the plasma. Etching is performed under conditions of the sample temp. set at 20-60 deg.C and the pressure of the chlorine-base discharge gas in the vacuum chamber at 3-8mTorr. Thereby, the aluminum thin film on the sample surface can accurately be etched into a desired pattern.

Description

[Detailed Description of the Invention] Ryosaku Retired Emperor Ridanko 1 The present invention relates to an etching method, and more specifically, a plasma is generated by electron cyclotron resonance excitation in a vacuum container into which a chlorine-based discharge gas is introduced, and the activity in the plasma is The present invention relates to an etching method for etching an aluminum or aluminum alloy thin film using particles.

Conventional technology Generally, aluminum alloy thin films are often used as wiring materials for semiconductor devices, and wiring patterns using aluminum alloy thin films are formed using lithography technology after vacuum-depositing the aluminum alloy thin film on the surface of the sample. This is done by etching unnecessary aluminum alloy thin film parts, leaving only the wiring pattern parts.

Conventionally, the above-mentioned etching process has been carried out using RTE (
This is carried out using a reactive ion etching (reactive ion etching) device. That is, in the RIE apparatus, a sample S is placed on one side of parallel plate electrodes 12 and 13 arranged in a vacuum chamber 11, and a high frequency power source 14 is placed on the side of the parallel plate electrode 12 on which the sample S is placed. The structure is such that high frequency is applied. The ions in the plasma generated by the high-frequency discharge move to the sample 24 on the parallel plate electrode 12, which has a negative potential.
The aluminum alloy thin film on the sample S is etched by the incident light S.

Etching with this RIE device is usually 10-2 to 10
Since etching is carried out in a pressure range of -' Torr, the mean free path of ions in the plasma is short, and the ions wrap around the etching sidewalls to some extent, resulting in low anisotropy in etching. For this reason, in the past, in order to accurately transfer the resist pattern to an aluminum alloy, 5iCj4 (silicon tetrachloride), CCji (carbon tetrachloride), cHcp were used.
Conventionally, a gas that easily forms a polymer film, such as No. 3 (chloroform), is introduced into the vacuum chamber 11 together with an etching gas, and the polymer film is formed on the etching side wall to prevent etching on the side wall. For example, CCQ gas and He gas with a flow rate of 11005 CC are introduced into the vacuum chamber 11, and the inside of the vacuum chamber 11 is
Etching was performed by generating plasma at a pressure of -' Torr, and thereby the etching shape was controlled.

However, in conventional RIE, as mentioned above, since a gas that easily forms a polymer film is used to protect the etching sidewalls, a polymer film also accumulates inside the vacuum chamber 11.
Problems such as difficulty in etching sample S with good reproducibility under the same etching conditions have arisen.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an etching method that can control the etched shape with high precision and perform etching under the same conditions with high reproducibility.

In order to achieve the above-mentioned objects, the etching method according to the present invention generates plasma by electron cyclotron resonance excitation in a vacuum container into which a chlorine-based discharge gas is introduced, and activates the plasma in the plasma. In an etching method in which particles are used to etch an aluminum or aluminum alloy thin film on the surface of a sample, the temperature of the sample is set at 20 to 60°C.
The etching is performed by setting the pressure of the chlorine-based discharge gas in the vacuum container to a range of 3 to 8 mTorr.

Production ■ Plasma generated by electron cyclotron resonance (ECR) excitation using microwave-generated high-frequency electric and magnetic fields exists stably even in the low gas pressure range of 10-5 to 0-'' Torr.

Since the ions in this plasma exist at low pressure, they have a long mean free path and are highly anisotropic.

According to the above method, plasma is generated by electron cyclotron resonance excitation and the active particles in the plasma are used to etch the sample, so the etched sidewall can be protected without using a gas that tends to form a polymer film. Also, during etching, the temperature of the sample should be 20 to 60℃.
At the same time, the pressure of the chlorine-based discharge gas in the vacuum container is set in the range of 3 to 8 mTorr, so that the wiring material such as the aluminum alloy thin film on the sample surface can be precisely shaped into the desired vacuum shape. It will be well formed. That is, if the sample temperature is lower than the optimum temperature range of 20 to 60°C, or if the pressure of the chlorine-based discharge gas in the vacuum vessel is lower than the R suitable range of 3 to 8 mTorr, the ), the etching selectivity with the resist 19 deteriorates, leaving etching residues 16 and residues 17 on the surface of the sample S along the base step 15.
occurs, and the electrical characteristics of the sample S deteriorate. On the contrary, sample 8
If the temperature of the chlorine-based discharge gas is higher than the above-mentioned optimum temperature range, or if the pressure of the chlorine-based discharge gas is higher than the above-mentioned optimum range, the aluminum alloy 18 on the bottom surface of the resist 19 will deteriorate as shown in FIG. 2(C). The side walls are hollowed out and no longer smooth, making wire breakage more likely. On the other hand, when the temperature of the sample S is controlled within the optimum temperature range of 20 to 60°C and the pressure of the chlorine-based discharge gas is controlled within the range of 3 to 8 mTorr, the temperature as shown in Fig. 2 ( As shown in b), the aluminum alloy 18 is etched into the desired etched shape.

Further, by not using a gas that tends to form a polymer film, there is less deposition of a polymer film in the vacuum container, and the sample can be etched with good reproducibility under the same etching conditions.

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

FIG. 1 is a sectional view schematically showing an apparatus for carrying out the etching method according to the present invention, and in the figure, reference numeral 21 indicates a plasma generation chamber which is a vacuum vessel. A microwave waveguide 23 is connected to the upper wall of the plasma generation chamber 21 via a microwave introduction window 22, and around one end of the plasma generation chamber 11 and the microwave waveguide 23, a plasma generation An excitation coil 24 is arranged approximately concentrically with the chamber 21 .

On the other hand, a plasma extraction window 25 is formed in the lower wall of the plasma generation chamber 21, and below the plasma extraction window 25 there is a sample chamber, which is a vacuum container, which communicates with the plasma generation chamber 21 through the plasma extraction window 25. 26 are arranged. Inside this sample chamber 26 is a plasma extraction window 25.
A sample stand 27 for holding the sample S is disposed at a location facing the sample S, and an electrode 29 to which a high frequency power source 28 is connected is embedded in the sample stand 27. Furthermore, an exhaust port 3 connected to a vacuum pump (not shown) is provided on one side wall of the sample chamber 26.
0 is formed.

When etching a sample S having an aluminum alloy thin film deposited on its surface using the etching apparatus configured as described above, first the plasma generation chamber 21 and the sample chamber 26 are etched.
is evacuated to about 10-6 Torr using a vacuum pump. Next, a chlorine-based discharge gas is supplied from a gas supply port (not shown) of the plasma generation chamber 21 or the sample chamber 26, and the gas pressure in the plasma generation chamber 21 and the sample chamber 26 is increased to 3-3.
8 mTorr, and the temperature of the sample S placed on the sample stage 27 is set in the range of 20 to 60°C.

Next, a current is passed through the excitation coil 24 to open the plasma generation chamber 2.
A divergent magnetic field is formed in the plasma generation chamber 21, and microwaves are introduced into the plasma generation chamber 21 from the microwave waveguide 23 to apply a high frequency electric field. Then, plasma is generated in the plasma generation chamber 21, and the generated plasma is guided from the plasma generation chamber 21 to the vicinity of the sample S in the sample chamber 26 through the plasma extraction window 25 by the above-mentioned divergent magnetic field. and sample S
A surface reaction occurs on the surface due to ions and radical particles in the plasma flow, and as a result, the aluminum alloy thin film on the surface of the sample S is etched. At this time, try i4
Since S is etched by ions and radical particles in the plasma, the etching sidewalls are protected even without the use of gases that tend to form polymeric films, and the aluminum alloy thin film on the surface of sample S can be etched into the desired pattern shape with high precision. It will be done.

Furthermore, since a gas that tends to form a polymer film is not used, there is little polymer film deposition in the plasma generation chamber 21 and sample chamber 26, and etching can be performed with good reproducibility under the same etching conditions.

In addition, in the above method, when etching is performed using chlorine and boron trichloride as the chlorine-based discharge gas and with the volume ratio of boron trichloride to chlorine being 20 to 60%, the aluminum alloy thin film on the surface of sample S can be etched to the desired extent. Not only can the pattern shape be etched with high precision, but the selectivity with the resist and with silicon dioxide or phosphate glass, which is the underlying film of the aluminum alloy, can be increased. It is also possible to increase the speed.

Next, using the method described above, apply A to the surface under the conditions shown below.
I! The results of etching a 6-inch sample S on which a -1%31 alloy thin film was deposited will be described.

Microwave power 800W Gas pressure: 4 mTorr Chlorine, boron trichloride ・60%, 40% (volume ratio) Sample S temperature: 50°C High frequency PA'7 for sample S application (13,56MH2):
200W At this time, the self-bias voltage applied to sample S was -6
0~-i oov, etching speed is 7000 people/mi
n, the selectivity to the resist was 2.5, and the selectivity to the underlying silicon dioxide was 10. FIG. 5 shows a photograph of sample S etched under the above conditions. FIG. 6 shows the results of etching the Al-1% Si alloy on the surface of sample S by the conventional etching method using a gas that easily forms a polymer film.

As is clear from FIGS. 5 and 6, when the method according to this embodiment is used, the Aρ-1% 81 alloy on the surface of sample S is etched into the desired shape with high precision, whereas in the case of the method according to the present example, It can be seen that when this method is used, etching remains are left.

Next, FIG. 7 shows the results of examining the reproducibility of etching under the same conditions using the conventional method and the method according to this embodiment.

In FIG. 7, ◯ indicates the case where the method according to this embodiment is used, and △ indicates the case where the conventional method is used.

As is clear from FIG. 7, compared to the conventional etching method, in the etching method according to this embodiment, the etching speed hardly decreases even if a large number of sheets are etched, and the reproducibility is good.

From the above, in the etching method according to this example, the aluminum alloy thin film on the surface of the sample S can be etched into the desired pattern shape with high precision, and the sample S can be etched with good reproducibility under the same etching conditions. It is obvious that it can be done.

In addition, as the aluminum alloy, 1-3 mentioned in the example
In addition to i series, A9-Cu series, AN-3i-Ca series, Al-
3i-Ti type etc. can be used. Furthermore, the method according to the present invention is also applicable to pure Aj.

Further, in the above embodiment, a case was described in which an etching apparatus was used in which the plasma generation chamber 21 and the sample chamber 26 were formed in series and used as a vacuum container, but the invention is not limited to this. It is also possible to use an etching apparatus in which a plasma generation chamber and a sample chamber are integrated to form a vacuum container 31 as shown in FIG.

Effects of the Invention As is clear from the above explanation, in the etching method according to the present invention, the temperature of the sample is set in the range of 20 to 60'C, and the chlorine-based discharge gas in the vacuum container is Since etching is carried out with the pressure set in the range of 3 to 8 mTorr, the aluminum or aluminum alloy thin film on the test surface can be etched accurately into the desired pattern shape.

Furthermore, since a gas that tends to form a polymer film is not used, there is less polymer film deposition in the vacuum container, and the sample can be etched with good reproducibility under the same etching conditions.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing an example of an apparatus for carrying out the etching method according to the present invention, and FIG.
b) and (c) are perspective views of the sample showing the effects of sample temperature and pressure of chlorine-based discharge gas on etching;
The figure is a cross-sectional view schematically showing another example of an apparatus for carrying out the etching method according to the present invention, FIG. 4 is a graph showing the relationship between etching speed and gas pressure, and FIG. Figure 6 is a photograph of a sample etched by the conventional method, and Figure 7 is a photograph of the reproducibility of etching under the same conditions by the conventional method and the method according to this example. A graph showing the results of the investigation,
FIG. 8 is a sectional view schematically showing a conventional parallel plate type RIE apparatus. 1... Plasma generation chamber (vacuum container) 6... Sample chamber (vacuum container) 8... Aluminum alloy ■... Vacuum container S... S type material

Claims (1)

[Claims] (1) In an etching method in which a plasma is generated by electron cyclotron resonance excitation in a vacuum vessel into which a chlorine-based discharge gas is introduced, and active particles in the plasma are used to etch an aluminum or aluminum alloy thin film on the surface of a sample. An etching method characterized in that the temperature of the sample is set in the range of 20 to 60° C., and the pressure of the chlorine-based discharge gas in the vacuum container is set in the range of 3 to 8 mTorr.