JPS5835364B2 - plasma etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma etching method for forming aluminum wiring patterns in the fabrication process of integrated circuits.

Conventionally, aluminum patterns have been formed by a wet method using a mixed acid of phosphoric acid and nitric acid.

The wet method has the drawbacks that it is not suitable for forming fine patterns because the aluminum is side-etched under the photoresist, and the etching solution enters the interface between the photoresist and aluminum in the casing, making the pattern jagged. be.

Plasma etching is known as a dry method.

Generally, aluminum has an oxide film on its surface in the air with a thickness of about 30 mm, and when chlorine is used as a plasma generating gas, chlorine radicals are difficult to react with it.

Therefore, there is a drawback that etching does not proceed smoothly.

Similarly, when hydrogen chloride is used, etching does not proceed smoothly.

When chlorine or hydrogen chloride is used, it also has the disadvantage that the gas itself is corrosive and toxic.

Plasma etching of carbon tetrachloride and boron trichloride has recently been proposed.

In this case, radicals such as chlorine radicals, carbon trichloride radicals, carbon dichloride radicals, and boron dichloride that dissociate in the plasma are thought to etch aluminum.

The radicals other than chlorine radicals react with aluminum oxide on the aluminum surface, remove it, and etch the aluminum itself.

However, since chlorine radicals are present and have a long life, side etching occurs as in the wet method, and the edges of the enclosed pattern are attacked.

For this reason, there is a drawback that it is not suitable for forming fine patterns.

Another disadvantage is that after aluminum etching, residues that appear to be aluminum oxide remain on the exposed surface of the silicon dioxide film.

The aim of the invention is to eliminate the above-mentioned drawbacks.

The above object of the present invention is to provide a chlorine-based gas containing at least one selected from carbon tetrachloride, boron trichloride, hydrogen chloride, and chlorine at a molar ratio of 0.3:1 to 3:1. This can be achieved by a plasma etching method characterized by forming an aluminum wiring pattern by irradiating gas plasma containing hydrogen.

In plasma etching, the plasma temperature can easily be lower than 250°C.

At this temperature, hydrogen radicals generated by hydrogen dissociation selectively react with chlorine radicals to form hydrogen chloride.
Reduces long-lived chlorine radicals.

As a result, the aluminum oxide on the aluminum surface is completely reduced, and no residue is observed on the aluminum surface after etching.

Although the etching speed decreases due to the decrease in the number of chlorine radicals encased, it is possible to avoid the occurrence of side etching and the deterioration of pattern formation accuracy at the pattern edges, making it possible to form fine patterns of aluminum wiring by plasma etching. It can be formed reliably.

In the present invention, the molar ratio of hydrogen to chlorine gas is 0.
．． When it is less than 3:1, the effect of hydrogen mixing cannot be obtained,
When the ratio is larger than 3:1, the extent of photoresist removal increases, making it unsuitable for forming fine patterns.

The degree of vacuum of the gas in which hydrogen is mixed with at least one chlorine gas selected from carbon tetrachloride, boron trichloride, hydrogen chloride, and chlorine is suitably in the range of about 0.01 to about 0.5 Torr. .

Although the etching rate using the hydrogen-containing gas plasma was reduced to about 1/3 compared to the etching rate using the gas plasma containing only the chlorine-based gas, there was no particular problem.

The plasma generating apparatus used in this embodiment uses a parallel plate electrode type plasma etching apparatus. Carbon tetrachloride at a vacuum level of 0.05 Torr is mixed with hydrogen at a pressure of <0.05 Torr and then put into a plasma chamber at a frequency of 13. .56 MHz, power 1
Excitation was performed at 00 W, and aluminum on silicon dioxide was etched using a negative resist OMR-83 (manufactured by Tokyo Ohka) as a mask.

At this time, the etching rate of aluminum was 800/mi.
n, no side etching was observed in the obtained aluminum wiring, and no residue was observed on the surface of the silicon dioxide film exposed after aluminum etching.

Comparative Example In the above example, the same procedure as in the example was carried out except that hydrogen was not mixed.

The etching speed of aluminum was 2,000/n, but the aluminum wiring was side etched,
Jagged edges were observed at the edges of the housing pattern.

Note that residue was observed on the exposed surface of the silicon dioxide film.

Claims (1)

[Claims] 1 In a parallel plate electrode type plasma etching apparatus, a chlorine-based gas containing at least one selected from carbon tetrachloride, boron trichloride, hydrogen chloride, and chlorine was added at a molar ratio of 0.3:
A plasma etching method characterized by forming an aluminum wiring pattern by irradiating gas plasma containing hydrogen in a ratio of 1 to 3:1.