JPH0546096B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of finally finely processing a film to be etched by forming a fine pattern using a resist.

[Conventional technology]

Generally, in the manufacture of semiconductor integrated circuit devices, a resist such as photoresist, EB resist, ion beam resist, or line resist is applied onto a substrate, and then exposed and developed to form a desired fine pattern. The pattern is used as an etching mask to finely process the film to be etched.

However, with conventional microfabrication methods, when there is a step on the underlying substrate, there is a difference in the resist film thickness above and below the step, making it difficult to process fine patterns with the same precision above and below the step. , a three-layer resist process as shown in FIGS. 2a-f has been proposed.

The conventional three-layer resist process will be explained below using figures.

As shown in FIG. 2a, first, a film to be etched 2 is formed on a substrate 1, an organic film 3 such as a photoresist is coated and baked, and an intermediate film 4 such as a silicon oxide film is formed. , and then apply a resist 5 such as a photoresist on top of it.
After baking, the resist 5 is exposed and developed as shown in FIG. 2b.
form a fine pattern. Then, as shown in Figure 2c, the resist pattern is etched.
After etching the intermediate film 4 as a mask, the second
As shown in FIG. d, the organic film 3 is anisotropically etched using oxygen (O ₂ ) plasma. Using the fine pattern formed above as an etching mask, the film to be etched 2 is etched as shown in FIG. 2e, and then the resist 5, intermediate film 4 and A conventionally proposed three-layer resist process involves removing the organic film 3 and obtaining a microfabricated film 2 to be etched.

[Problem that the invention seeks to solve]

However, this method has the disadvantage that it requires a large number of steps and also that it is very difficult to remove the intermediate film 4. That is, when removing a silicon oxide (SiO ₂ ) film or an aluminum (Al) film, which is often used as the intermediate film 4, there is a risk of damaging the underlying substrate 1 or deteriorating the pattern accuracy of the film to be etched 2. There are drawbacks.

This invention was made to solve these problems, and provides a microfabrication method that can form fine patterns with high precision without damaging the underlying substrate using a method with fewer steps. The purpose is to

[Means for solving problems]

The microfabrication method according to the present invention is a method in which a film to be etched formed on a substrate is microfabricated using a three-layer mask consisting of a lower organic film, an intermediate film, and an upper resist film. The intermediate film is removed by etching during patterning, and then the film to be etched is selectively etched using the patterned organic film as a mask.

[Effect]

In this invention, since the intermediate film is removed by etching when patterning the lower resist film of the three-layer mask, the intermediate film is removed when the substrate surface is covered with the film to be etched. This prevents the underlying substrate from being damaged during the removal of the intermediate film, and in this case, the only processing after patterning the film to be etched is the removal of the underlying resist film.
It is also possible to suppress deterioration in pattern accuracy of the film to be etched.

〔Example〕

FIGS. 1A to 1E are cross-sectional views showing each step of a microfabrication method according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 2 indicate the same or corresponding parts.

The three-layer resist process of this example will be explained below with reference to the drawings.

First, as shown in FIG. 1a, an organic film 3 such as photoresist or polyimide resin is coated on a film to be etched 2 on a substrate 1 using a spinner or the like.
It is applied to a thickness of about 3 μm, and an intermediate film 4 is formed thereon. Furthermore, photoresist or
Apply a resist such as EB resist to a thickness of about 0.2 to 0.4 μm.

Next, as shown in FIG. 1B, the resist 5 is exposed and developed using a normal pattern forming method to form a fine resist pattern.

Thereafter, as shown in FIG. 1c, the intermediate film 4 is dry-etched using the resist pattern 5 as an etching mask.

Next, when the organic film 3 is anisotropically etched, the resist 5 and the intermediate film 4 are etched away at the same time as shown in FIG. 1d under the following conditions.
The shape will be as shown in .

For example, when using silicon nitride (Si ₃ N ₄ ) or silicon oxide (SiO ₂ ) as the intermediate film 4, oxygen (O ₂ ) and a halogen compound (e.g.
RF power using a mixed gas plasma of _CF4 )
By anisotropically etching the organic film 3 under the conditions of 800 W and a gas pressure of 5 Pa, the resist 5 and intermediate film 4 are also etched away at the same time.

For this purpose, the thickness of the resist 5 needs to be thinner than the thickness of the organic film 3.

Further, the halogen compound can be selected so as not to damage the film to be etched 2 during etching of the organic film 3. That is, the film to be etched 2
However, in the case of an aluminum (Al) film, carbon tetrafluoride (CF ₄ ) is used as a halogen compound, and in the case of a silicon oxide (SiO ₂ ) film, carbon tetrachloride (CCl ₄ ) is used.
All you have to do is choose.

Thereafter, the film to be etched 2 is etched using the organic film 3 as an etching mask, and the organic film 3 is removed using oxygen plasma or the like, thereby obtaining the shape shown in FIG. 1e.

In the method of this embodiment, the intermediate film 4 of the three-layer mask is removed by etching when patterning the lower resist film 3 of the three-layer mask. Since the surface of the base substrate 1 is covered with the film to be etched 2, it is possible to prevent damage to the base substrate 1, especially the stepped portion, when removing the intermediate film 4. In this case, the treatment after patterning the film to be etched 2 is the lower resist film 3.
, and the deterioration in pattern accuracy of the film to be etched 2 can be suppressed to a small level. Also,
Since mixed gas plasma of oxygen and halogen is used, the effect of increasing the anisotropic etching rate of the organic film 3 can also be obtained. In addition, after etching more than half of the organic film with gas plasma mainly containing oxygen,
The object of the present invention can also be achieved by etching the remaining organic film using a mixed gas plasma of oxygen and a halogen compound.

In the above example, a mixed gas plasma of oxygen and a halogen compound was used for etching the organic film, but the same effect can be obtained by providing a substance that generates a halogen element or a halogen compound in the etching apparatus instead of the halogen compound. It becomes possible to obtain. For example, if a Teflon plate is used as the electrode material of the etching device and oxygen plasma is generated, fluorine radicals are generated and the above object can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, in a method for finely processing a film to be etched formed on a substrate using a three-layer mask consisting of a lower organic film, an intermediate film, and an upper resist film, the lower organic film The intermediate film is removed by etching when patterning, and then the film to be etched is selectively etched using the patterned organic film as a mask, so that the fine pattern of the film to be etched is transferred to the underlying substrate. without causing damage
It has the advantage that it can be formed with high precision and with a small number of steps.

[Brief explanation of the drawing]

1A to 1E are sectional views showing each step of a microfabrication method according to an embodiment of the present invention, and FIGS. 2A to 2F are sectional views showing each step of a conventional micromachining method. 1... Substrate, 2... Film to be etched, 3... Organic film, 4... Intermediate film, 5... Resist. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A microfabrication method in which a film to be etched formed on a substrate is microfabricated using a three-layer resist process, comprising sequentially forming an organic film, an intermediate film, and a resist film on the film to be etched on the substrate. a first step of laminating to form a three-layer film; a second step of patterning the resist film to form a fine pattern thereof; and selectively forming the intermediate film using the patterned resist film as a mask. a third step of etching; a fourth step of performing anisotropic etching on the entire surface to pattern the organic film and simultaneously removing the resist film and the intermediate film immediately below it; and the patterned organic film. A microfabrication method comprising: a fifth step of patterning the film to be etched by performing an etching process using the film as a mask; and a sixth step of removing the remaining organic film. 2. The microfabrication method according to claim 1, characterized in that silicon nitride or silicon oxide is used for the intermediate film, and a mixed gas plasma of oxygen and a halogen compound is used for etching the organic film. . 3. The microfabrication method according to claim 2, wherein the thickness of the resist film is thinner than the thickness of the organic film.