JPH0637061A - Etching method for organic film - Google Patents

Abstract

PURPOSE:To acquire an anisotropic etching shape of a multilayer resist regardless of density of patterns on a substrate. CONSTITUTION:A multilayer resist structure is formed on an oxide film 7 or a nitride film and an Si film 8 is formed in a lower layer of a lower organic film 9 in the multilayer resist. The lower organic film 9 is dry-etched using gas formed by mixing halogen gas to oxygen gas as etching gas and by using the Si film 8 as a foundation. Since Si is used for a foundation of an organic film, added halogen species is consumed as halogenide and irregularities are not generated in a sidewall during additional etching even if density of patterns is irregular inside a substrate surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for an organic film used in a manufacturing process of electronic devices and the like.

[0002]

2. Description of the Related Art Conventionally, oxygen gas is used as an etching gas for etching a resist which is an organic substance as a volatile product. However, as the pattern becomes finer, dimensional shift occurs, and for the purpose of suppressing this, it has been attempted to lower the substrate temperature during etching and add Cl ₂ gas or HBr gas as an additive gas.

The additive gas reacts with the etching products to form deposits on the sidewalls of the pattern, which reduces undercutting and results in anisotropic shapes with no dimensional shift.

[0004]

However, in the conventional dry etching of the organic film, there is a problem that the etching shape depends on the density of the patterns formed on the same substrate. That is, for a pattern arrangement such as a line-and-space pattern in which a pattern to be etched is dense, if a condition that an anisotropic shape without a dimension shift is obtained, an isolated pattern that is a sparse pattern has unevenness at the bottom of the pattern. Occurs, and the formed line width is not constant. On the contrary, if you choose the condition that can anisotropically etch without dimensional shift without generating this unevenness in a sparse pattern, undercut occurs in a pattern such as a dense pattern line and space, and the dimension is Get smaller. That is, there is a drawback that the line and space pattern becomes thin.

An object of the present invention is to provide an etching method for an organic film which gives an anisotropic etching shape regardless of the density of patterns on a substrate.

[0006]

In order to achieve the above object, in the method for etching an organic film according to the present invention,
A method for etching an organic film in a multilayer resist structure formed on an oxide film or a nitride film, wherein the oxide film or the nitride film is etched using a multilayer resist process. Is obtained by depositing a Si film on an oxide film or a nitride film, which is a material to be etched, and then sequentially stacking a lower organic film, an intermediate layer, and an upper resist, or forming a lower organic film and a two-layer resist process exposure resist. The etching of the organic film is a process of dry etching using an etching gas in which a Si film is used as a base and a halogen is mixed with oxygen gas.

[0007]

The function of the dry etching of the organic film is that oxygen gas is decomposed in plasma, oxygen ions and oxygen radicals are generated, and reacts with the organic film to form CO, CO ₂ , H ₂ O and the like. The etching reaction proceeds. At this time, Cl ₂ and HB
When halogen gas such as r is added, CO and CO ₂ become Cl
CBrx or CBrx, which reacts with Ar and Br and does not easily volatilize, is deposited on the pattern side wall when the temperature of the substrate being etched is lowered.

This deposit serves as a side wall protective material and suppresses side etching. However, when the pattern is dense and dense in the substrate surface, the area of the substrate etched is different, and unevenness occurs on the pattern sidewall in the isolated pattern. The reason for this is that the products to be etched react with the halogen species that are the added gas to form sidewall deposits.Therefore, when the stage of additional etching is entered after the end of etching, excess halogen species are present. Then, uneven deposition occurs on the side wall, which is considered to be the cause of the unevenness on the side wall of the pattern.

If the frequency of unevenness is compared as the halogen species of the added gas, unevenness on the side wall of the pattern is likely to occur in the order of fluorine, chlorine, and bromine. This means that the halogen species having a lower etching rate of the oxide film and the nitride film, which are the base material, have a higher frequency of unevenness.

In other words, if a halogen species that does not etch the underlying oxide film and the nitride film is used, the halogen species is not consumed in the additional etching, so that excessive halogen species exist and uneven sidewall deposition occurs, resulting in sidewall Unevenness occurs.

In the present invention, these problems are solved by using Si as a base material for the organic film. S as the base
When i is present, the added halogen species are consumed as a halide of silicon by this Si, and during the additional etching, the side wall unevenness does not occur even if the pattern is uneven in the substrate surface.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which a Si substrate 6
It is the figure which showed typically the cross section of the multilayer process at the time of processing the upper oxide film 7 using a multilayer resist process.
In the figure, after depositing a Si film 8 on an oxide film 7 which is a material to be etched, a lower organic film 9, an intermediate layer 10 and an upper resist 11 are formed.
Is formed, the gas containing halogen is mixed with oxygen gas, the upper resist 11 is patterned, and the intermediate layer 10 is etched.

For comparison, a schematic sectional view of a conventional three-layer resist process is shown in FIG. In the conventional example of FIG. 2, since the oxide film 2 on the Si substrate 1 is processed, the organic film 3, the intermediate layer 4, and the upper layer resist 5 are deposited on the oxide film 2, and after the upper layer resist 5 is patterned, Layer 5 is etched. The thickness of the organic film 3 is 1500 nm, the intermediate layer 4 is a coating type oxide film of 150 nm, and the upper resist 5 is 100 nm.
It is 0 nm.

In the present invention, the oxide film 7 on the Si substrate 6 is used.
Before processing the lower layer organic film in processing, the Si film 8 is sputter deposited with a thickness of 30 nm by a sputtering apparatus, and then the lower layer organic film 9 is applied with a thickness of 150 nm.

After patterning the upper layer resist 11 and etching the intermediate layer 10 by a dry etching apparatus,
The lower organic film 9 is etched, and the etching conditions are set as follows. The dry etching apparatus used a He back surface cooling method to lower the substrate temperature, and the coolant temperature was set to -50 ° C.

ECR discharge was used as the discharge method. Also,
In this embodiment, O ₂ 90SCCM is used as an etching gas.
A mixed gas of 10 SCCM of chlorine gas and chlorine gas was used. The additional etching time was 50% after the etching end point was detected. Etching pressure, microwave, substrate bias 1
3.5 mhz RF power, 10mTorr in sequence
It was set to r, 100 mA, 50 W.

When the same conditions were applied to the conventional structure shown in FIG. 2 and etching was performed, it was possible to anisotropically etch the 250 nm line and space pattern. However, for an isolated pattern that has no pattern around it,
Uneven irregularities were generated on the side wall of the pattern. This is considered to be because chlorine was excessive during the additional etching as described above, and a non-uniform deposition reaction occurred on the sidewall.

However, in the structure of FIG. 1 which is an embodiment of the present invention, the unevenness of the sidewall did not occur at all even in the isolated pattern. At this time, the Si film 8 was etched by about 15 nm by additional etching.

In the above examples, the sputtering method was used as the Si film deposition method for the underlayer of the organic film, but other methods will not cause any problems. Further, in this embodiment, the multi-layer resist structure has three layers, but it goes without saying that the effect does not change even with two layers.

Although the ECR discharge method is used as the etching apparatus, other dry etching methods have no effect on the effect of the present invention. Although chlorine gas was used as the additive gas in this example, addition of a bromine-based halogen gas such as HBr was also effective. When F ₂ gas was used, though not directly related to the effect of the present invention, when the etching rate of the intermediate layer was high and the additional etching time was long, the corner drop of the intermediate layer occurred. The same effect was obtained in the multi-layer resist processing when processing the nitride film.

[0021]

As described above, according to the present invention,
During additional etching, excess halogen species are consumed as silicon halides without causing uneven sidewall deposition, and anisotropic etching shapes can be obtained regardless of the density of the pattern on the substrate. .

[Brief description of drawings]

FIG. 1 is a structural diagram showing an embodiment of the present invention.

FIG. 2 is a structural diagram of a conventional example.

[Explanation of symbols]

 6 Si substrate 7 Oxide film 8 Si film 9 Lower organic film 10 Intermediate layer 11 Upper layer resist

Claims (1)

[Claims] 1. An organic film etching method for etching an organic film in a multilayer resist structure formed on an oxide film or a nitride film, wherein the oxide film or nitride film is etched using a multilayer resist process. There is a multi-layer resist structure in which a lower organic film, an intermediate layer, and an upper resist are laminated in this order after depositing a Si film on an oxide film or a nitride film as a material to be etched, or a lower organic film and a two-layer resist process exposure. A method of etching an organic film, wherein a resist is formed, and the etching of the organic film is a dry etching process using an etching gas in which a Si film is used as a base and a halogen is mixed with oxygen gas.