JPH0737865A - Etching of organic film - Google Patents

Abstract

PURPOSE:To obtain an anisotropic pattern shape irrespective of the density of patterns by treating a substrate by a rare hydrofluoric acid solution after etching an organic film formed on the substrate by means of a dry etching method using mixed gas in which halogen gas or gas containing halogen is added. CONSTITUTION:An SOG film 4 is patterned by plasma etching using CHF3 gas while having an upper layer resist film 5 as a mask after patterning the upper layer resist film 5. At this time, a film thickness of the upper resist film 5 is reduced. Next, a lower layer resist 3 is etched while having the upper layer resist film 5 and the SOG film 4 as masks. After finishing the etching of the lower layer resist film 3, a rare hydrofluoric solution treatment is performed.

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 mainly used as an etching gas in dry etching of a polyimide film which has been used as an organic resist or an interlayer film. However, dimensional shift called side etching or undercut occurs under the mask. this is,
This is because the oblique incidence of ions and neutral active particles that cannot be electrically controlled react on the side wall of the etching pattern. In order to prevent this size shift, a method of adding a halogen gas to the oxidizing gas is used. Typical halogens are Cl ₂ gas and HBr gas. Further, for example, when a polyimide film is etched using a resist as a mask, a gas containing halogen such as SF ₆ is added to obtain the selection ratio. By adding SF ₆ , side wall deposition occurs, oblique incidence of ions and lateral etching due to neutral active particles can be prevented, and selectivity with a mask can be obtained.

[0003]

In the above-mentioned conventional dry etching of an organic film, the shape of the pattern formed by the etching depends on the density of the patterns formed on the same substrate. That is, if a condition that an anisotropic shape with no dimensional shift is obtained in a pattern arrangement such as a line-and-space pattern in which a pattern to be etched is densely present is selected, in an isolated pattern that is a sparse pattern, Unevenness occurs in the lateral direction of the hem portion, and the line width of the formed pattern is not constant. On the contrary, if you select the condition that this unevenness does not occur in a sparse pattern and there is no dimension shift and anisotropic etching is possible, undercut occurs in a dense pattern such as line and space and the dimension is small. Become. In other words, the line and space pattern can be thin.

FIG. 2 shows the gas flow rate dependency of the dimensional shift amount after etching. The line-and-space pattern and the isolated pattern have the same tendency, but it is extremely difficult to obtain etching conditions satisfying the dimensional control. Although the flow rate dependency was shown in FIG. 2, similar tendencies were observed for other etching parameters. That ’s
The dimensional shift amount of the isolated pattern has a greater parameter dependency than that of the line and space pattern in which the patterns are densely present.

An object of the present invention is to provide an etching method for an organic film capable of obtaining an anisotropic pattern shape by etching regardless of the density of a pattern formed on a substrate.

[0006]

A method for etching an organic film according to the present invention is a method in which an organic film formed on a substrate is etched by a dry etching method using a mixed gas obtained by adding a halogen gas or a gas containing halogen to an oxidizing gas. After that,
The substrate is treated with a dilute hydrofluoric acid solution.

[0007]

In the etching process of the organic film, oxygen gas is decomposed in plasma to generate oxygen ions and oxygen radicals, which react with the organic film to produce CO, CO ₂ , H ₂ O.
Etching reaction proceeds due to the formation of the like. On this occasion,
When halogen gas such as Cl ₂ or HBr is added, CO or C
O ₂ reacts with Cl and Br and is hard to volatilize CCl _x and C
It is believed that compounds such as Br _x are formed. These compounds can be used when the substrate being etched is cold.
Deposit on the sidewalls of the pattern to be formed. This deposit is
It serves as a side wall protective material and controls side etching. However, when the pattern is uneven in the surface of the substrate, the etched area of the organic film is different in the surface of the substrate. Therefore, in an isolated pattern having no pattern around it, unevenness occurs on the sidewall of the pattern. The sidewall deposit is formed by the reaction between the product of the film to be etched and the halogen species as the additive gas. However, after the completion of etching, when the step of overetching occurs, excess halogen species are partially present. This results in uneven deposition on the sidewall. It is considered that these are the causes of the unevenness on the side wall of the pattern.

In the present invention, after etching the organic film, a treatment with a dilute hydrofluoric acid solution is performed to remove the deposit. The organic film is not etched with dilute hydrofluoric acid, and uneven deposits with uneven sidewalls are easily removed by etching. That is, if the organic film is etched under the etching conditions that give an anisotropic shape, an anisotropic pattern shape appears after the dilute hydrofluoric acid treatment. As a result, a pattern of the lower organic film having no unevenness on the side wall can be obtained even if the pattern of the substrate to be etched is uneven.

[0009]

The present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a sectional view of a semiconductor chip for explaining the first embodiment of the present invention. This embodiment is an example applied to dry etching of an organic film used as a lower layer film of a multilayer resist structure.

First, an Al film or SiO _{2 is formed} on the silicon substrate 1.
After forming the film to be etched 2 such as a film, the lower resist film 3 is 1500 nm, and the SOG of the coating type oxide film is used as the intermediate layer.
The film 4 is formed to a thickness of 150 nm and the upper resist film 5 is formed to a thickness of 150 nm. Next, after patterning the upper resist film 5, the SOG film 4 is patterned by plasma etching using CHF ₃ gas using the upper resist film 5 as a mask. The film thickness of the upper resist film 5 decreases at this time. Next, the lower resist film 3 is etched using the upper resist film 5 and the SOG film 4 as a mask.

A microwave-excited dry etching apparatus was used as the etching apparatus. The etching conditions are
Microwave input is 100W, substrate bias input is 50
W, etching gas pressure is 10 mTorr, and gas flow rate is 160 SCCM. As the etching gas, oxygen gas to which 10% of Cl ₂ gas was added was used. The etching temperature was set to -50 ° C. at the coolant temperature by using the He backside cooling method to lower the substrate temperature. The etching time was increased by 50% after the etching end point was detected.

Width 250 as the pattern to be etched
The line and space pattern of nm could be anisotropically etched. However, in the isolated pattern having no pattern in the periphery, as shown in FIG. 1, the deposit 6 was generated on the side wall of the lower resist film pattern, and unevenness was formed in the lateral direction. As described above, it is considered that chlorine was excessive during overetching, and a non-uniform deposition reaction occurred on the sidewall. In this state, when the film to be etched 2 is etched using the SOG film 4 and the lower resist film 3 as a mask, the sidewall deposit serves as a mask to cause a dimensional shift.
Therefore, after etching the lower resist film 3, a dilute hydrofluoric acid solution treatment is performed.

The dilute hydrofluoric acid used in this embodiment was 1%, and the substrate was soaked for 30 seconds and washed with water. A rinser dryer was used for drying. After drying, the entire 6-inch wafer surface was observed, but no pattern collapse or peeling was observed. After this treatment, observation with an electron microscope showed that there was no dimensional shift in both the dense line-and-space region of the pattern and the isolated pattern region of the pattern, and an anisotropic pattern shape was obtained.

In this embodiment, the multilayer resist structure has three layers, but it goes without saying that the effect of this embodiment is the same even with two layers. Although a microwave excitation type dry etching apparatus is used as an etching apparatus, other dry etching apparatuses have no effect on the effect of the present invention. In this embodiment, the added gas is Cl
_Two gases were used, but the addition of brominated halogen gas such as HBr was also effective. When F ₂ gas was used, although it was not directly related to the effect of the present invention, when the etching rate of the SOG film was high and the overetching time was long, the corner drop of the SOG film occurred. Further, the substrate temperature can be selected according to etching conditions such as gas flow rate and mixing ratio. Not only one condition, but also the substrate temperature can be selected by selecting various etching parameters. In this example, an anisotropic etching shape is obtained by changing the conditions even at 0 ° C. To lower the temperature means 0 ° C or lower,
An anisotropic etching shape is more likely to be obtained when the temperature is lowered.

Further, the treatment time of the dilute hydrofluoric acid solution was set to 30 seconds in this embodiment, and the sidewall deposit could be removed by this,
The temperature of hydrofluoric acid and the immersion time vary somewhat depending on the dry etching time of the organic film and the etching conditions.
That is, the thickness of the side wall deposits is different.

Next, a second embodiment will be described. In the second embodiment, a polyimide mask as an interlayer insulating film is etched using a resist mask. The resist mask has a thickness of 1.5 μm, and the polyimide film has a thickness of 0.8 μm. In this case, since the organic films are S,
F ₆ was added to oxygen gas at a flow rate ratio of 30%, and etching was performed using the dry etching apparatus described above. Etching pressure, total gas flow rate, microwave input and RF bias are
10mTorr, 100SCCM, 150W,
It is 50W. After etching, 2 with 1% dilute hydrofluoric acid solution
It was treated for 0 seconds and washed with water. As a result, the etching shape was anisotropic and the dimension shift amount could be suppressed to within 0.01 μm.

[0017]

As described above, according to the present invention, after etching an organic film by a dry etching method using a gas in which chlorine or hydrogen bromide is added to oxygen gas or a gas in which SF6 is added, By treating with a dilute hydrofluoric acid solution, an anisotropic pattern shape with less dimensional shift can be obtained even in a dense line-and-space region of a pattern, a sparse isolated pattern region of a pattern, or formation of a contact hole. Was given.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor chip for explaining a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a dimension shift amount after etching and a gas flow rate in a conventional example.

[Explanation of symbols]

 1 Silicon substrate 2 Etching film 3 Lower layer resist film 4 SOG film 5 Upper layer resist film 6 Deposit

Claims (1)

[Claims] 1. An organic film formed on a substrate is etched by a dry etching method using a mixed gas in which a halogen gas or a gas containing halogen is added to an oxidizing gas, and then the substrate is treated with a dilute hydrofluoric acid solution. A method for etching an organic film, comprising: