JPS61144026A - Dry etching method - Google Patents

Abstract

PURPOSE:To obtain an anisotropic etching configuration even with a mask pattern having an approximately vertical profile, by adding nitrogen gas or a compound gas containing nitrogen into chlorine gas or a compound gas containing chlorine used as etching gas. CONSTITUTION:A material is disposed on a lower electrode 13 within a container 11 and CCl4 gas and N2 gas are introduced into the container 11 so that electric discharge is caused between the electrodes 12 and 13 and an AlSi alloy film 27 is etched thereby. The flow rate of the CCl4 gas is 200CCM and the flow rate of the N2 gas is 40CCM. The etching is performed for 12min while a high-frequency power is applied to supply 2A current between the electrodes 12 and 13. In this manner, an anisotropic etching configuration can be obtained exactly according to the mask pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a dry etching method, and particularly to a dry etching method for performing anisotropic dry etching.

[Technical background of the invention and its problems]

In recent years, microfabrication techniques used in semiconductor integrated circuit manufacturing techniques are required to have increasingly higher precision, and their dimensions are reaching the submicron range. Therefore, as an etching method faithful to the mask pattern, an anisotropic dry etching method has been widely studied.

On the other hand, the resolution of resist patterns used in masks suffers from the unevenness of the surface of the underlying substrate, and the degree of this decrease is significant on highly reflective substrates such as AJ2 alloy, making it difficult to control line width and improve resolution. . A multilayer resist method has been proposed as a method to solve this problem. This method is
This technology improves the resolution of the pattern formed on the top layer by flattening the irregularities on the substrate surface with a film that is thick enough compared to the steps, and processes the flattened layer faithfully to the pattern formed on the top layer. The processed planarization layer usually has a vertical or nearly vertical shape.

Further, a gas containing 0° C. is generally used for anisotropic dry etching of electrode forming materials such as aluminum alloys. Therefore, the present inventors performed dry etching using a mask pattern having a vertical or nearly vertical cross-sectional shape formed by a multilayer resist method. That is, using a positive photoresist formed by a multilayer resist method as a mask, the β film was selectively etched using a gas containing C2, as typified by A2 dry etching. In some cases, even though the conditions are such that a vertical machined shape can be obtained,
An undercut or inverted taper shape was obtained.

This result was Aa.

This was also observed in the processing of AM-8i, AQ, -Cu-8i, polycrystalline silicon films to which impurities were added, and it was difficult to process them faithfully to the mask pattern.

[Purpose of the invention]

An object of the present invention is to achieve an anisotropic etched shape even when using a mask pattern having a vertical or nearly vertical cross-sectional shape formed by a multilayer resist method, and is suitable for microfabrication of semiconductor devices. An object of the present invention is to provide a dry etching method.

[Summary of the invention]

The gist of the present invention is to add nitrogen gas or a compound gas containing nitrogen to chlorine gas or a compound gas containing chlorine gas used as an etching gas.

That is, in the present invention, a sample having a predetermined mask pattern on the object to be etched is placed on one side of parallel plate electrodes arranged in an etching chamber, and a gas is introduced into the etching chamber and a discharge is caused at each electrode r1. In this dry etching method, at least chlorine gas or a chlorine-containing compound gas and nitrogen gas or a nitrogen-containing compound gas are used as gases introduced into the etching chamber.

〔Effect of the invention〕

According to the present invention, by adding nitrogen gas or a nitrogen-containing compound gas, patterns with steep profiles formed by multilayer resist methods, etc., in which it has been difficult to perform anisotropic etching faithful to the mask pattern, can be etched. Also as a mask, dry etching of A2 alloy or the like using Ca-based gas can be achieved with high precision. That is, an anisotropic etching shape can be achieved, and etching can be performed faithfully to a mask pattern having a vertical or nearly vertical cross-sectional shape. Therefore, it is extremely effective for microfabrication of semiconductor devices.

Here, the reason why the above-mentioned anisotropic etching is achieved is that the etching of the side wall under the mask pattern, which conventionally occurs due to excessive chlorine radicals, etc., is effectively prevented by the N2 gas. That is, by adding N2 gas, a thin sidewall protective film is formed on the sidewall under the mask pattern, and this film prevents side etching and the like. In addition, in a normal mask pattern (having a tapered part on the side wall), the tapered part was sputtered off and was attached as a protective film to the side wall of the underlying object to be etched.

On the other hand, with a mask pattern having a vertical or nearly vertical cross-sectional shape, the sputtering efficiency is low, so that a film made of the above-mentioned mask material is hardly formed.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic diagram showing a dry etching apparatus used in an embodiment of the present invention. In the figure, reference numeral 11 denotes a vacuum container forming an etching chamber, and parallel plate electrodes 12 and 13 are accommodated within this container 11. Upper electrode 12
is grounded, and the lower electrode 13 is connected to a high frequency power source 15 via a matching circuit 14. The sample to be etched 16 is placed on the lower electrode 13.

On the other hand, the container 11 is provided with a gas inlet 17 (17a, 17b) for introducing C22 gas or N2 gas and a gas exhaust port 18 for exhausting the gas.

Further, in the figure, 19 (19a, 19b) indicates a valve, and 20 indicates an insulator.

Next, a dry etching method for patterning a wiring film using the above-mentioned apparatus will be explained.

FIGS. 2(a) to 2(Q) are cross-sectional views showing the patterning process of the wiring film. First, as shown in FIG. 2(a), an element isolation insulating film 22 and an MOS transistor are formed on a St substrate 21, and an interlayer insulating film 26 and an An
s; alloy y<object to be etched) 27 is formed. Note that 23 is a gate oxide film, 24 is a gate electrode, and 25a.

25b indicates a source/drain region.

Next, as shown in FIG. 2(b), a flattening resist 31 and a spion glass film (S
An OG film 32 and an uppermost resist layer 33 were formed in sequence.

Subsequently, the uppermost layer resist 33 was patterned as shown in FIG. 2(C), and then selective etching of 5O (J132) was performed using the resist 33 as a mask as shown in FIG. 2(d).

The etching at this time was anisotropic dry etching, and a 1=1 mixed gas of CHF3 and 02 FB was used as the etching gas.

Next, the flattening resist 31 was etched by anisotropic dry etching using 02 gas to form a mask pattern as shown in FIG. 2(e). At this time, the mask pattern had a vertical cross-sectional shape. Subsequently, by chemical dry etching using a mixed gas of CF4 and 02, <5OGI was etched as shown in FIG. 2(f).
I32 was removed.

Next, the A281 alloy film 27 was dry etched using the apparatus shown in FIG. That is, FIG. 2(f)
A sample as shown in FIG. 1 is placed on the lower electrode 13 in the container 11, CCn+ gas and N2 gas are introduced into the container 11, and a discharge is generated between the electrodes 12 and 13 to form the A281 alloy film 2.
7 etching was performed. Here, the flow rate of CCβ4 gas was 2000 CM, and the flow rate of N2 was 40 CCM.

When high-frequency power was applied to cause a current of 2 A to flow between the electrodes 12 and 13, etching was performed for 12 minutes, as shown in Fig. 2 (g
), an anisotropic etched shape faithful to the mask pattern could be obtained.

Furthermore, according to experiments conducted by the present inventors, when etching was performed using only CCl2 without using N2 as in the conventional process, side etching occurred in the Al25.1 alloy film 27. Admitted.

Thus, according to the method of this embodiment, anisotropic etching can be achieved using a 0° C. gas even if a mask pattern with a vertical cross-sectional shape is used. Therefore, it is extremely effective for microfabrication of semiconductor devices.

Note that the present invention is not limited to the method of the embodiment described above. For example, the mask pattern is not necessarily one formed by a multilayer resist method, but sufficient effects can be obtained by applying the present invention as long as it has a vertical or nearly vertical cross-sectional shape. Furthermore, RD-2
It is also applicable to a resist that forms a reverse taper pattern, such as 00ON (manufactured by Hitachi Chemical) resist. Further, in the example, 20 [%] of N2 gas was added to the C2-based gas, but it worked most effectively within the range of 5 to 10 [%] of N2 gas. In addition, the etching gas is CC (14
The gas is not limited to , and may be any Cλ2 gas or a compound gas containing C2. In general, the additive gas is not limited to N2 (it may also be a compound gas containing N2.

Furthermore, the object to be etched is not limited to Aj2Si alloy, but also A (1, W, Mo, Ti, Ta, etc. melting point metals,
Alternatively, these silicides may be used. Furthermore, it is also applicable to polycrystalline silicon and doped polycrystalline silicon. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a dry etching apparatus used in an embodiment of the method of the present invention, and FIGS. 2(a) to (Q) are sectional views showing a wiring pattern forming process using the above-mentioned apparatus. 11...Vacuum container (etching 1.12.13...
Parallel plate electrode, 14... Matching circuit, 15...
High frequency power supply, 16... Sample to be etched, 17...
Gas inlet, 18... Gas exhaust port, 27... Ais
an alloy film (object to be etched), 31. ... Planarization resist, 32... SOG film (intermediate layer), 33...
Top layer resist. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Z+ffl Figure 2 3F

Claims (3)

[Claims] (1) A sample with a predetermined mask pattern on the object to be etched is placed on one side of the parallel plate electrodes placed in the etching chamber, and a gas is introduced into the etching chamber and a discharge is generated between each electrode. In the dry etching method for etching the sample, at least chlorine gas or a compound gas containing chlorine and nitrogen gas or a compound gas containing nitrogen are used as the gases introduced into the etching chamber. (2) The dry etching method according to claim 1, wherein the mask pattern has a vertical or nearly vertical cross-sectional shape formed by a multilayer resist method. (3) The object to be etched is polycrystalline silicon provided on the substrate, impurity-doped polycrystalline silicon, Al, W, M
2. The dry etching method according to claim 1, wherein the electrode forming material film is made of a high melting point metal such as O, Ti, or Ta, or a high melting point metal silicide.