JPS63235489A - Aluminum film 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] [Field of Industrial Application] The present invention is a novel etching method that replaces conventionally known etching methods such as reactive ion etching and plasma etching for etching aluminum films. , a desired wiring pattern is transferred by resistless etching the aluminum film.

Further, such a pattern transfer method can be applied not only to the semiconductor industry but also to the printing industry for transferring type.

[Conventional technology and its problems]

With the recent development of the electronic industry, integrated circuits having various functions have been developed, and research and development of molecular elements and various sensor elements is also being conducted.

Various metals are used for the wiring of these integrated circuits, molecular elements, and sensor elements.

Among these, aluminum vapor-deposited films are widely used as wiring materials, and are used after being etched into a desired wiring pattern.

Currently, a lithography technique using a resist as a mask is used as a method for etching a desired wiring pattern. However, when a resist is used as a mask, complicated steps such as resist application, mask alignment, exposure, and development are required.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of intensive studies on a new method for etching an aluminum film.

The present invention provides a method for etching an aluminum film in which a photodegradable chlorine-containing substance is irradiated with light having a wavelength of 400 nm or less to decompose at least a portion of the material, and the photodecomposition product is brought into contact with a portion of the aluminum film to be etched. ,
The present invention relates to an aluminum film etching method characterized in that a desired pattern is transferred by resistless etching by placing a mask at an appropriate distance from the aluminum film surface.

The present invention basically involves irradiating a photodegradable chlorine-containing substance with a light beam of a specific wavelength through a mask having a desired wiring pattern, decomposing at least a portion of the photodegradable chlorine-containing substance, and producing the photodegradable chlorine-containing substance. Bring the object into contact with the aluminum film,
It is also a method of selectively resistless etching the light irradiated area by raising the temperature of the light irradiated area due to light irradiation and activating a surface reaction by chemically activating adsorbed atoms or molecules in the irradiated area. .

The aluminum film to be etched is a film of aluminum or an alloy containing aluminum as a main component (in the present invention, the term "aluminum film" refers to both collectively unless otherwise specified). Examples of such an aluminum film include an aluminum film deposited on a silicon nitride film or a silicon oxide film.

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

A photodegradable chlorine-containing substance is a substance that generates chlorine in an active state when irradiated with light of a specific wavelength.

Examples of such substances include HCl, (1° and BC
Inorganic chlorine compounds such as
fCjl, and 1 to 1 of the chlorine atoms in the carbon tetrachloride molecule
Compounds in which three fluorine atoms are substituted (e.g., CF Clx
, CF2Cit, CF'301).

Aluminum is reactive with both active chlorine and fluorine. However, the aluminum fluoride produced by the reaction has a high boiling point and is difficult to remove from the aluminum surface during etching. On the other hand, aluminum chloride has a low boiling point and is quickly removed from the surface, so it can be etched advantageously.

Therefore, it is desirable that the photodegradable chlorine-containing substance does not contain reactive fluorine atoms in its molecules. In this respect, it differs from the etching gas used when etching Si or 5in2.

Furthermore, photodegradable chlorine-containing substances containing carbon atoms may contaminate the etched surface with carbon components during etching.

From this point of view, HCj2. The use of inorganic chlorine compounds such as Cf□ and BCl is suitable.

Usually, an aluminum oxide film is formed on the surface of the aluminum film to protect the aluminum metal. Even during etching, this oxide film acts to prevent the desired reaction. However, according to studies conducted by the present inventors, in the etching method of the present invention, when BCl among inorganic chlorine compounds is used, the influence of the oxide film formed on the surface of the aluminum film is small, and the etching of aluminum is particularly effectively carried out. It turns out that it can be done. Furthermore, when BCl and C12 are selected as the photodegradable chlorine-containing substance used in the etching method of the present invention, it is preferable because the etching rate of aluminum is high.

Note that the photodegradable chlorine-containing substances can be used alone or in combination. Furthermore, it can also be used after being diluted with a gas such as He that has no substantial reactivity with aluminum.

The photodegradable chlorine-containing material is introduced into a reactor in which an object to be etched with an aluminum film is placed. The pressure of the photodegradable chlorine-containing substance at this time 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) ~
It is within the range of 2×105 Pa ((2×10′)/133 Torr).

A photodegradable chlorine-containing substance such as 2 is irradiated with light of a specific wavelength to decompose it, and this photodecomposition product is brought into contact with an aluminum film to generate aluminum chloride, which is then removed from the surface of the aluminum film. Remove.

Therefore, when a mask is placed at an appropriate distance from the aluminum film, resistless etching can be selectively performed only on the portions irradiated with light through the mask. Therefore, there is an advantage that the process of etching the aluminum film is greatly simplified without including a complicated process such as a lithography process, which is a conventional wiring pattern forming technique. The distance between the aluminum film and the mask is not particularly limited, and if a long distance is desired, a projection exposure method may be used.

The wavelength of the irradiated light beam is 400 nm or less.

When using the light source described later, the wavelength is 126n.
In order to generate a light beam without grooves, generally a light beam within the wavelength range of 126 to 4'OOnm is used.In particular, considering the decomposition efficiency of photodegradable chlorine-containing substances, the wavelength 1.
The use of light in the range 70-250 nm is preferred.

Examples of light beam sources include rare gas excimer laser light generators (e.g., ArF excimer laser light generators, K
rF excimer laser light generator) laser light generator (e.g. ArF excimer laser light generator, KrF excimer laser light generator), Xe-He lamp and low pressure Hg
Examples include lamps.

In particular, it is preferable to use laser light generated using an ArF excimer laser light generator. The wavelength of ArF excimer laser light is 1000 m.

When using ArF excimer laser light, the energy of the laser light is preferably 0.1 mJ/5hot/cf1 or more. 0.1 mJ/5hot/
If ArF excimer laser light with an energy less than cJ is used, the decomposition of photodegradable chlorine-containing substances may not proceed effectively, and the activation of surface chemical reactions may be insufficient. Since the amount of chlorine used is reduced, the etching rate may be significantly reduced.

Note that coherent light with a short wavelength such as synchrotron radiation light (wavelength: about 5 Q nm) can also be used for ArF excimer laser light extraction.

The temperature of the aluminum film during etching can be set as appropriate, but is usually set within a temperature range from room temperature to 300° C. or less.

The etching time can be appropriately set in consideration of various conditions such as the thickness of the aluminum film, the type of light beam used, and the type of photodegradable chlorine-containing substance.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

Al was deposited in a conventional manner on a crab crystal Si substrate and a Si substrate covered with a silicon oxide film. The thickness of the deposited Al film was 7,000.

FIG. 1 shows the etching apparatus used in the embodiment of the present invention.

The reaction chamber 1 is equipped with a sample holder 4 having a heater 3 therein, on which a sample 2 (a mask 6 is placed with a spacer 5 in between) is placed.

A quartz glass window 7 is provided on a part of the wall surface of the reaction chamber 1, and a laser beam generated from an ArF excimer laser light generator 8 located outside the reaction chamber 1 is passed through the quartz glass window 7. The sample 2 is irradiated with the light (the mask 6 does not necessarily need to be installed inside the reaction chamber, and can also be projected onto the substrate through a suitable optical system outside the reaction chamber).

Further, the reaction chamber 1 is equipped with a gas introduction pipe 9 and a gas outlet 10, and the gas outlet 10 is connected to a vacuum pump (not shown). Therefore, by introducing a desired gas from the gas introduction tube 9 while discharging the gas inside the reaction chamber 1 using a vacuum pump, the type and pressure of the gas filled inside the reaction chamber 1 can be adjusted.

Sample 2 prepared by the above method was placed on a sample holder 4 as shown in FIG. 1, and a mask 6 was placed on top of the sample 2 with a spacer sandwiched therebetween. BCJI from gas introduction pipe 9! , ,C
A mixed gas consisting of 12 and He (standard state conversion flow rate;
BCI, 30cc/min, C1z 11.25cc
/min, He 160cc/min) was introduced, and the internal pressure was adjusted to 60 Torr (60×133 Pa). In this state, the ArF excimer laser light generator 8
From frequency 80Hz, energy 30 IIJ/5ho
t/c4. ArF excimer laser light with a wavelength of 193 nm was irradiated into the reaction chamber 1 through the quartz glass window 7. The substrate temperature was 80°C, and the irradiation time was 3 minutes.

Fig. 2(a) shows a schematic diagram of etching, and Fig. 2(b) shows a schematic diagram of etching.
) shows the results of measuring the level difference when the aluminum surface etched by the above method was measured using a surface level difference meter. In addition, Figures 3(a) and (b) show the state of the sample surface observed using an optical microscope when etching was performed in the same manner as above, except that the etching time was 2 minutes 40 seconds and 2 minutes 30 seconds, respectively. The results are shown below. From the above, it has been confirmed that resistless etching is possible in which the portion of the aluminum film irradiated with light through a mask is selectively removed.

〔Effect of the invention〕

According to the etching method of the present invention, this is achieved by photodegrading a photodegradable chlorine-containing substance and bringing the photodecomposition product into contact with an aluminum film to cause a reaction. Since there are no energetic particles and the reaction conditions are mild, there is less damage to underlying devices caused by high-energy ions, which has been a problem in the past. Furthermore, since no photoresist is used, the etching process can be greatly simplified, and the resist does not remain on the aluminum or miniram surface to contaminate it.

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, as well as in the production of molecular devices and sensor devices.

[Brief explanation of the drawing]

FIG. 1 schematically shows an etching apparatus used in an example of the present invention. FIG. 2(a) is a schematic diagram of etching, and FIG. 2(b) is a diagram showing the results of measuring the step difference on the surface of the sample after etching using a surface step meter. Figure 3 (
Figures a) and (b) are diagrams showing the sample surface after etching. 1...Reaction chamber, 2...Sample, 3...
... Heater, 4 ... Sample holder, 5 ... Spacer, 6 ... Mask, 7
...... Quartz glass window, 8 ... Excimer laser light generator, 9 ... Gas introduction tube, 10.
...Gas outlet, 11...Copper mesh,
12... Quartz glass patent applicant Ube Industries, Ltd. Figure 2 (a) Shi-sa'°-light, (b) Heat gate 100μm (b-100), +rn Procedural amendment (method) Showa June 1q, 62

Claims (6)

[Claims] (1) An aluminum film etching method in which a photodegradable chlorine-containing substance is irradiated with a light beam with a wavelength of 400 nm or less to decompose at least a portion of it, and the photodecomposition product is brought into contact with a portion of the aluminum film to be etched, A method for etching an aluminum film, characterized in that a desired pattern is transferred by resistless etching by placing a mask at an appropriate distance from the surface of the aluminum film. (2) The photodegradable chlorine-containing substances are BCl_3 and Cl_
2. The etching method according to claim 1, wherein: (3) The etching method according to claim 1, wherein the wavelength of the irradiating light source is within the range of 126 to 400 nm. (4) The etching method according to claim 3, wherein the wavelength of the irradiated light is within the range of 170 to 250 nm. (5) The etching method according to claim 3 or 4, wherein the light beam is an ArF excimer laser beam having an energy of 0.1 mJ/shot/cm^2 or more. (6) The etching method according to claim 1, wherein the pressure of the reaction system is within the range of 1 Pa to 2×10^5 Pa.