JPS5812338B2 - Dry etching process - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves applying a thin film of iron oxide on the object to be etched as a mask material in order to obtain a predetermined etching shape when performing so-called dry etching such as sputter etching or gas plasma etching. The present invention relates to a characteristic dry etching method.

Conventionally, in order to precisely etch thin films, patterns have been obtained using a photo-application process.

However, because it is immersed in an etching solution, there is a gap between the photoresist and the thin film during etching, and etching progresses in the lateral direction as well as in the depth direction. Causes cutting.

This phenomenon becomes a serious problem when dimensional accuracy is required, especially when the drawing width is 5 μm or less.

Furthermore, as the etching progresses, the etching solution becomes exhausted, so the etching time changes, making it difficult to manage the etching solution.

Furthermore, the used etching agent must be treated as waste water.

On the other hand, the so-called dry etching method, in which a gas is discharged under low pressure and etches a thin film by physically colliding with the thin film or chemically reacting with it, can faithfully reproduce the image width of photoresist. It is very advantageous because there is no need to manage the liquid and there are no problems with waste liquid treatment.

However, since the photoresist is corroded along with the thin film to be etched that is not covered with the photoresist, it is necessary that the etching rate of the object to be etched be several steps faster than the etching rate of the photoresist.

Therefore, when a photoresist is used as a mask for dry etching, the objects to be etched are limited, and a gas must be selected whose etching rate is several orders of magnitude higher than that of the photoresist.

Furthermore, since the image line of the photoresist is maintained until the etching of the object to be etched is completed, the image accuracy deteriorates when the thickness of the photoresist is increased.

Further, as the dry etching progresses, the photoresist decomposes due to heat generation, and the batten formed with the photoresist collapses. Therefore, if the etching time is long, a predetermined etched shape cannot be obtained.

For example, when applying a thin chromium film on a glass substrate, forming a pattern with photoresist, and using it as a mask for dry etching, using argon, which is used in normal sputtering, as the gas for sputter etching, the chromium etching is completed. The photoresist is attacked before it can be removed, making it impossible to obtain a clear seal.

The present invention solves the above-mentioned drawbacks, and will be described in detail below.

In the dry etching process, as described above, an etching pattern is obtained by the difference in etching rate between the material such as photoresist used as a mask and the object to be etched.

Since this photoresist is relatively easily attacked by the gas used in dry etching, a thin film of iron oxide, which is less easily attacked than the photoresist, is formed on the object to be etched.

By patterning this iron oxide thin film into a pattern to be etched and then performing an etching process, it is possible to improve the reproducibility of dry etching and to ease the processing conditions.

The iron oxide thin film can be formed by vacuum evaporation, sputtering, chemical vapor deposition using iron carbonyl, or thermal decomposition of polyvinylferrocene.

By controlling the formation conditions, iron oxide thin films can be formed using hydrochloric acid,
It is advantageous for batanization because it forms a thin film of iron oxide that is easily dissolved in hydriodic acid and the like.

Because iron oxide is an inorganic oxide, its dry etching rate is much lower than that of photoresists and common metals such as chromium, tantalum, and tungsten.

Furthermore, when argon is selected as the gas used for dry etching, the etching rate is slower than that of chromium oxide.

Therefore, it is very effective to use an iron oxide thin film as a mask for dry etching.

Furthermore, when forming a different pattern on an etched pattern, alignment operations are facilitated by using an iron oxide thin film as a mask because iron oxide is transparent to visible light.

Furthermore, if the iron oxide thin film is formed into a tapered batten shape in an etching solution and this is used as a mask, the object to be etched can also be made into a tapered shape.

Iron oxide thin films that are soluble in acids such as hydrochloric acid become difficult to dissolve in acids when irradiated with laser beams or electron beams.
Furthermore, as the intensity of the beam is further increased, the iron oxide evaporates, making it possible to directly form a pattern of iron oxide thin film without using a photoresist. It can be used as a mask button for the object to be etched.

As described above, using iron oxide as a mask for dry etching is very advantageous because it allows the use of a gas such as argon, which cannot be used as a mask with ordinary photoresists, and enables multi-stage etching and taper etching.

Examples of the present invention will be described below.

Example 1 After evaporating 80 nm of chromium on soda lime glass, approximately 1
chemical vapor deposition of 250 nm of iron oxide on the chromium in an atmosphere of iron carbonyl, carbon dioxide, and oxygen gas at 10 °C;
A bilayer film of chromium and iron oxide was formed.

Furthermore, a photoresist pattern was formed on the iron oxide film using a conventional photofap application.

The exposed iron oxide film was etched by immersing it in a hydrochloric acid solution of a predetermined concentration for about 20 seconds.

At this time, since chromium is passivated, the chromium layer below the iron oxide film is not etched.

FIG. 1 shows the cross-sectional shape of the iron oxide film after etching.

In the figure, 1 is a glass plate, 2 is a chromium film, 3 is an iron oxide film, and 4 is a photoresist.

After removing the photoresist, a chrome blank with an iron oxide mask was placed on the target part of a two-pole high frequency sputtering device, the system was evacuated, and Ar gas was introduced.

13.56MHz, 300W at approximately 4X10-2torr
Spatter etching was performed for 4 minutes by applying high frequency power.

Although the iron oxide film was hardly etched, the exposed chromium was completely etched to form a pattern.

No undercutting was observed.

It was possible to faithfully reproduce the 1 μm image width of the iron oxide film.

Iron oxide could be easily removed by immersing it in a hydrochloric acid solution without dissolving the chromium.

The chrome photomask, excluding the iron oxide mask, had better line accuracy than the chrome photomask made with a normal photofap application.

Also, if iron oxide is not removed, the surface reflectance will be -
It was lower at 25% compared to 70%, and there was little variation in the line width due to halation, which is a problem when using a chrome mask in the photo application process.

Example 2 Chromium oxide was deposited to a thickness of 220 nm on soda lime glass.

In the same manner as in Example 1, a pattern of iron oxide was made on chromium oxide and used as a mask.

Approximately 4X10-2to in a two-pole high frequency sputtering equipment
13.56MHz, 300MHz in argon gas atmosphere of rr
High frequency power of W was applied and sputter etching was performed for 8 minutes.

The exposed chromium oxide was completely etched to form a pattern.

In this case, the iron oxide thin film was slightly etched, but the underlying chromium oxide was retained.

When the iron oxide film was removed with a hydrochloric acid solution, the image accuracy was superior to that of a chromium oxide photomask made using a normal photofap application.

Example 3 After evaporating chromium to a thickness of about 160 nm on soda lime glass,
In the same manner as in Examples 1 and 2, a pattern of iron oxide was made on chromium and used as a mask.

Sputter etching was performed at 13.56 MHz and 300 W for 4 minutes on the target part in a bipolar high-frequency sputtering device to etch chromium to a thickness of 80 nm.

After removing the iron oxide mask, iron oxide was newly deposited on the entire surface by chemical vapor deposition.

A photoresist was applied to this, and a pattern of iron oxide was created in a photo-application process to create a mask.

In this case, since iron oxide was transparent, mask alignment was easy.

This was sputter etched for 4 minutes under the same conditions as above to remove the iron oxide film and obtain a pattern with a cross-sectional shape as shown in FIG.

In the figure, 5 is a glass plate, and 6 is a chromium film etched in two stages.

Example 4 After 80 nm of chromium was deposited on soda lime glass, iron oxide was chemically vapor deposited on top of the chromium.

A photoresist pattern was formed on the iron oxide using a conventional photofap application.

At this time, the pre-baking time was shortened by about 30% and the post-baking was omitted.

When immersed in a predetermined hydrochloric acid solution for about 20 seconds, a tapered iron oxide slam as shown in Figure 3 was formed.

In the figure, 10 is a glass plate, 11 is a chromium film, and 12 is an iron oxide film etched into a tapered shape.

This blank was placed in a two-electrode high frequency sputtering device and sputter etched in an argon gas atmosphere.

In the tapered, thin part of the iron oxide film, the iron oxide was sputter-etched, and then the chromium was also etched, resulting in a tapered chrome strip.

Example 5 After chromium was deposited on soda lime glass, 250 nm of iron oxide was deposited on the chromium by chemical vapor deposition.

An argon ion laser was scanned across the iron oxide film with a power of 2.5W.

The obtained blank was immersed in a hydrochloric acid solution.

The irradiated portions of the iron oxide film did not dissolve in the specified hydrochloric acid solution, while the non-irradiated portions dissolved in 20 seconds, making it possible to create an iron oxide pattern on the chromium.

This was placed on the target part of a two-pole high-frequency sputtering device and sputter etched in an argon atmosphere, and the exposed chromium part was etched to form a pattern.

The iron oxide on the chromium could be easily removed by continued sputter etching or with a hot solution of hydrochloric acid and ferrous chloride.

[Brief explanation of drawings]

The drawings show the steps of the present invention; FIG. 1 is a sectional view of Example 1, FIG. 2 is a sectional view of Example 3, and FIG. 3 is a sectional view of Example 4. 1,5.10...Glass plate, 2,6,11...
...Chromium film, 3,12...Iron oxide film, 4
...Photoresist.

Claims (1)

[Claims] 1. In the process of performing dry etching such as sputter etching or gas plasma etching, a thin film of iron oxide is formed on the object to be etched, and the thin film of e-oxide is formed into a batten and used as a mask for post-processing V-etching. A dry etching method characterized by: