JPH0643638B2 - Etching method for aluminum film - Google Patents

Description

The present invention relates to a novel method for etching an aluminum film.

BACKGROUND OF THE INVENTION With the recent development of electronics, integrated circuits having various functions have been developed, and various metals are used for wiring of these integrated circuits.

Among these, the aluminum vapor deposition film is widely used as a wiring material, and is etched and used in a desired wiring pattern.

There are a wet method and a dry method as an etching method for the aluminum film provided on the substrate as described above, but recently, a dry method capable of advantageously performing highly precise microfabrication has been used. Many.

As a dry method, an ion etching method and a plasma etching method are generally known.

For example, Japanese Patent Publication No. 55-6108 discloses a method of etching aluminum or an aluminum base alloy using boron trichloride as an etching gas. The invention disclosed in this publication is an improvement of the conventional aluminum etching method, but further improvement is required in order to cope with the recent high integration.

In addition to the inventions disclosed in the above publications, conventionally used aluminum film etching methods are required to be further improved for the same reason.

[Object of the Invention] An object of the present invention is to provide an aluminum film etching method based on a principle different from the conventional aluminum film etching method.

SUMMARY OF THE INVENTION According to the present invention, BCl ₃ is pulse-irradiated with ArF excimer laser light having an energy of 1 mJ / shot / cm ² or more to decompose at least a part thereof, and the photolysis product is an aluminum film. The method for etching an aluminum film is characterized in that it is brought into contact with a portion to be etched.

[Advantages of the Invention] The present invention is a novel etching method that replaces conventionally known ion etching methods and plasma etching methods for etching aluminum films.

Since the etching method of the present invention does not contain high-energy particles in the reaction system and the reaction conditions are mild, there is little irradiation damage to the lower layer element due to high-energy ions contained in the reaction system, which has been a problem in the past. Therefore, it is suitable as a method for etching an aluminum film of an integrated circuit which tends to be highly integrated.

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on BC, which is basically a photodegradable chlorine-containing substance.
This is a method for etching an aluminum film, which comprises irradiating l ₃ with a light beam having a specific wavelength to decompose at least a part of this BCl ₃ and bringing the photolysis product into contact with a portion to be etched of the aluminum film. .

The aluminum film to be etched is a film of aluminum or an alloy containing aluminum as its main component (the "aluminum film" is a general term for both unless otherwise specified in the present invention). Examples of such an aluminum film include a silicon nitride film and an aluminum vapor deposition film in which a silicon wiring is vapor-deposited on the film.

The thickness of the aluminum film which is the object of the etching method of the present invention is usually 10 μm or less.

Usually, an aluminum oxide film is formed on the surface of the aluminum film to protect the aluminum metal. Also during etching, the oxide film acts to prevent a desired reaction. However, according to the study of the present inventor, in the etching method of the present invention, when BCl ₃ is used as the photodecomposable chlorine-containing substance, the influence of the oxide film formed on the surface of the aluminum film is small, and the etching of aluminum is particularly effective. It turns out that can be done. Therefore, the photodegradable chlorine-containing substance used in the etching method of the present invention must be BCl ₃ .

BCl ₃ may be used alone or in combination with another photodegradable chlorine-containing substance. Further, it can be diluted with a gas having substantially no reactivity with aluminum before use.

BCl ₃ is introduced into the reactor in which the etching object having the aluminum film is arranged. BC at this time
The pressure of l ₃ can be appropriately set in consideration of the thickness of the aluminum film, the type of light beam to be irradiated, and the like. Usually 1
Pa (1/133 torr) to 2 × 10 ⁵ Pa ((2 × 1
Within the range of 0 ⁵ ) / 133 torr.

Such BCl ₃ is pulse-irradiated with ArF excimer laser as a light beam having a specific wavelength to decompose, and a product of this photolysis is brought into contact with an aluminum film to generate a chloride of aluminum. Remove.

In addition, by utilizing the fact that the temperature of the light-irradiated part of the aluminum film or the atoms of the light-irradiated part are chemically activated and the reaction speed of that part becomes higher than other parts, only the light-irradiated part is etched. You can also do it.

An ArF excimer laser light generator can be cited as an example of a light source.

The wavelength of the ArF excimer laser light is 193 nm.

The energy of ArF excimer laser light is 1 mJ / shot
/ Cm ² or more. When ArF excimer laser light with energy less than 1 mJ / shot / cm ² is used, the decomposition of BCl ₃ may not proceed effectively.
Since the amount of chlorine supplied is small, the etching rate may be significantly reduced.

The temperature of the aluminum film at the time of etching can be set as appropriate, but is usually set in the following temperature range from room temperature to 300 ° C.

The etching time can be appropriately set in consideration of the thickness of the aluminum film and the like.

The etching method of the present invention is achieved by photolyzing BCl ₃ and bringing the photolyzed product into contact with the aluminum film to cause reaction, so that there are no high-energy particles that collide with the surface of the aluminum film, so that the device in the lower layer is Less likely to be damaged. There is also little damage to the photoresist or the mask used instead.

Since the etching method of the present invention has such advantages, it can be advantageously used in the field of manufacturing integrated circuits that are highly integrated.

Next, examples of the present invention will be described.

[Example 1] Preparation of sample Al was vapor-deposited on a crystalline Si plate by a conventional method. The thickness of the Al vapor deposition film was 2000Å.

Description of Apparatus An apparatus in which an etching apparatus and an analyzing apparatus used in the embodiment of the present invention are integrated is shown in FIG.

This apparatus basically comprises a reaction section 1, a induction section 2 and an analysis section 3.

The reaction unit 1 is provided with a vertically movable Moubin rod 5 on which a sample 4 is placed.

A quartz glass window 6 is provided on a part of the wall surface of the reaction section 1, and laser light generated from an ArF excimer laser light generator 7 located outside the reaction section 1 is passed through the quartz glass window 6 to make a sample. 4 can be irradiated.

Further, the reaction section 1 is provided with a gas introduction pipe 8 and a gas discharge port 9, and the gas discharge port 9 is a vacuum pump (not shown).
Is connected with. Therefore, by introducing BCl ₃ from the gas introduction port 8 while discharging the gas inside the reaction section 1 with a vacuum pop, the type and pressure of the gas filled in the reaction section 1 can be adjusted.

The reaction unit 1 and the analysis unit 3 are connected by the induction unit 2. Then, the reaction unit 1 and the guiding unit 2, and the guiding unit 2 and the analyzing unit 3
Are partitioned by partition walls 10a and 10b, respectively.
Further, the guide section 2 is also provided with a gas outlet 11 connected to a vacuum pump (not shown).

The analysis unit 3 is specifically an X-ray photoelectron spectroscopy apparatus capable of analyzing the surface of the sample 4 by in-situ observation X-ray photoelectron spectroscopy (XPS).

That is, the X-ray source 12 that irradiates the surface of the sample at the position indicated by the broken line with X-rays, and the binding energy analysis means 13 that analyzes the binding energy state of the photoelectrons emitted from the surface of the sample irradiated with X-rays. Consists of.

The analysis unit 3 also has a gas outlet 14 connected to a vacuum pump (not shown).

By using this device, it is possible to analyze the state of the surface of the etched sample without being affected by the atmosphere or the like.

Etching Operation The sample 4 prepared by the above method was placed on the top of the moving rod 5 as shown in FIG. 1, and the moving rod 5 was operated to move the sample to the analysis unit 3 to allow X-ray irradiation on the sample surface. The sample surface was analyzed by irradiating it with X-rays from the source 12.

The XPS measurement chart at this time is shown in (1) of FIG.

In the chart (1), the peak of the binding energy of 121 eV is the Al peak of Al ₂ O ₃ and the peak of 118 eV is the Al peak of aluminum metal.

Since no Si peak appears between 105 and 110 eV, it can be seen that the entire sample surface is covered with the aluminum vapor deposition film.

Next, the sample 4 is returned to the reaction part 1, and while the gas inside the reaction part 1 is being discharged from the gas discharge port 9, BCl ₃ having a purity of 99.9999% is introduced from the gas introduction port 8 to remove the gas inside the reaction part 1. The gas was replaced with BCl ₃ and the internal pressure was adjusted to 60 Torr (60 × 133 Pa).

After leaving the sample 4 for 5 minutes in this state, the moving rod 5 is raised to move the sample 4 to the guiding portion 2, and the partition 10
The flow between the reaction part 1 and the analysis part 3 was blocked by a and 10b, and the gas (mainly BCl ₃ ) in the induction part 2 was discharged and removed from the gas discharge port 11.

Then, the partition 10b was opened, the sample 4 was moved to the analysis part 3, and the sample was analyzed in the same manner as described above.

The XPS measurement chart at this time is shown in (2) of FIG.

Looking at the obtained chart (2), the Al peak of Al ₂ O ₃ has a binding energy of 12 as in the chart of (1).
The peak of Al of aluminum metal is 1 at the position of 1 eV.
It was confirmed at the position of 18 eV. That is, it was confirmed that the aluminum vapor deposition film still existed. However, a slight peak of adsorbed chlorine is observed at the binding energy of 200 eV.

Again, the sample 4 is moved to the reaction part 1, and this time, ArF excimer laser light having a frequency of 10 Hz, an energy of 20 mJ / shot / cm ² , and a wavelength of 193 nm is introduced from the quartz glass window 6 into the reaction part 1 from the ArF excimer laser generator 7. Irradiated. The irradiation time is 30 minutes.

After 30 minutes, the sample 4 was moved to the analysis unit 3 in the same manner as above, and the surface of the sample was analyzed in the same manner as above.

The measurement chart of in-situ XPS at this time is shown in (3) of FIG.

When the obtained chart (3) is examined, 1 of Al of Al ₂ O ₃ existing in the charts of (1) and (2) is obtained.
Both the 21 eV position peak and the Al metal 118 eV position peak disappeared, and instead a Si peak appeared at the binding energy 104 eV position.

This chart shows that BCl ₃ is decomposed by the irradiation of ArF excimer laser light, and the thickness of 2000
This means that all the aluminum deposition film of Å has been removed.

The peak around the binding energy of 190 to 195 eV is the peak of boron of B ₂ O ₃ and BClSi ₂ .

In addition, for confirmation, the above-mentioned sample 4 was held for 10 seconds (chart (4)), 1 minute (chart (5)), 5 minutes (chart (6) by an argon ion gun (not shown) placed in the measurement chamber. ) Argon ion etching was performed,
No Al peak was observed. That is, the disappearance of the Al peak in the chart (3) is not the disappearance due to the deposition of silicon on the aluminum vapor deposition film,
It was confirmed that this was due to the aluminum vapor deposition film being removed by etching.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an apparatus in which an etching apparatus and an analyzing apparatus used in the embodiment of the present invention are integrated. FIG. 2 is an XPS measurement chart of the sample surface. 1: reaction part, 2: induction part, 3: analysis part, 4: sample, 5:
Moving rod, 6: Quartz glass window, 7: ArF excimer laser generator, 8: Gas introduction tube, 9, 11, 1.
4: gas outlet, 10a, 10b: partition wall, 12: X-ray source, 13: binding energy analysis means

Claims (3)

[Claims] 1. BCl ₃ is pulse-irradiated with ArF excimer laser light having an energy of 1 mJ / shot / cm ² or more to decompose at least a part thereof, and the photodecomposition product is a portion to be etched in an aluminum film. A method for etching an aluminum film, which comprises bringing the aluminum film into contact with the aluminum film. 2. Only the light-irradiated portion utilizing the fact that the temperature of the light-irradiated portion of the aluminum film or the atoms of the light-irradiated portion are chemically activated and the reaction rate of that portion becomes higher than that of other portions Claim 1 to be etched
The etching method according to the item. 3. The etching method according to claim 1, wherein the pressure of the reaction system is in the range of 1 Pa to 2 × 10 ⁵ Pa.