JPH11111693A - Contact hole formation method - Google Patents

Abstract

(57) [Problem] To provide a contact hole forming method capable of easily removing an insulating film in a contact hole when the insulating film remains on the lower surface of the bottom of the contact hole due to insufficient etching and is detected after removal of the resist. I will provide a. SOLUTION: In a contact hole forming method in which openings 15 and 15 'are formed by etching using an organic resist material 13 as a mask in an insulating film 11 formed on a base 10, the insulating film 11 Etching is performed while another inorganic insulating film 12 having a predetermined etching selectivity is stacked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a contact hole in a semiconductor device manufacturing process. More specifically, the present invention relates to a contact hole forming method that can easily cope with a case where an opening failure occurs due to etching.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, with the recent increase in the density of wiring patterns, contact holes for connecting a base layer such as a substrate or a lower layer wiring to an upper layer wiring have been increasing in aspect ratio. I have. This contact hole is formed by etching the interlayer insulating film on the base using the resist pattern as a mask. Such a contact hole is formed by SEM after the end of etching.
Non-destructive inspection by electron beam irradiation of (Scanning Electron Microscopy).

In the nondestructive inspection using the SEM, as shown in FIG. 3, the surface of the insulating film 3 on the substrate 2 in which the contact hole 1 is formed is scanned with an electron beam to charge the electron beam. In the contact hole 1, as shown in FIG. 3A, the electric charge escapes to the underlying substrate 2 side, so that the potential difference between the contact hole 1 and the peripheral portion becomes large, and the difference in contrast in the SEM image becomes large. The contact hole portion appears as a black image with respect to the white image.

On the other hand, as shown in FIG. 3B, if there is a remaining film 4 of the interlayer insulating film which has not been etched at the bottom of the contact hole 1 ', charges are charged to the remaining film 4 portion. For this reason, the potential difference between the peripheral portion and the peripheral portion becomes smaller than in the case of (A), and is displayed in gray on the screen. Thereby, it is observed that the contact hole 1 'is not completely opened, and it is detected that the contact hole is defective due to insufficient etching.

When such an inspection using an electron beam is performed in a state where the resist is left on the insulating film after the completion of the etching process, a normal contact with the insulating film 3 on the substrate 2 is obtained as shown in FIG. In both the case where the hole 1 is formed and the case where the defective contact hole 1 ′ in which the residual film 4 remains as shown in FIG. Charged in large quantities. For this reason, the potential difference from the surrounding due to the charges charged in the residual film 4 of the defective contact hole 1 ′ is:
There is almost no difference between the normal case of (A) and the defect case of (B), and the presence or absence of the residual film 4 cannot be identified. Therefore, as shown in FIG.
Inspection of the contact hole by electron beam irradiation is performed in a state in which is removed.

[0006]

However, when the inspection is carried out with the resist removed as described above and a defective contact hole 1 'which is insufficiently etched is detected, an etching process is further performed to remove the residual film 4 at the bottom. Even if an attempt is made to remove it, the resist cannot be repaired because the resist has already been removed.

On the other hand, as a contact hole forming method,
A method is disclosed in which polysilicon, which is a conductor, is laminated on an insulating film, patterned, and the resist is removed. Thereafter, an opening is formed in the insulating film using the polysilicon as a mask (Japanese Patent Laid-Open No. 6-275574). No.). However, the method described in this publication is intended to prevent the crown of the base material from being over-etched by the conductor mask, and does not address the insufficient etching of the bottom of the contact hole as described above.

Further, in a conventional semiconductor device, an antireflection film such as SiON is provided on an electrode in order to prevent halation or the like (see the above publication).

The present invention has been made in consideration of these prior arts, and when an insulating film remains on the lower surface of the bottom of a contact hole due to insufficient etching and is detected after the resist is removed, the inside of the contact hole is removed. It is an object of the present invention to provide a contact hole forming method capable of easily removing the insulating film.

[0010]

According to the present invention, there is provided a contact hole forming method for forming an opening in an insulating film formed on a base by etching using an organic resist material as a mask. A method for forming a contact hole, characterized in that etching is performed while another inorganic insulating film having a predetermined etching selectivity is laminated on the insulating film.

According to this structure, an inorganic insulating film is further laminated on the insulating film to be opened, and etching is performed to open a contact hole, and the resist is removed while leaving the inorganic insulating film. The contact hole is inspected by electron beam irradiation with the resist removed, and if a residual film is detected at the bottom of the contact hole, the residual film may be removed by additional etching using the inorganic insulating film as a mask. it can. In this case, since the inorganic insulating film does not charge, the inspection by the electron beam irradiation does not interfere. In addition, as the inorganic insulating material, a material having a predetermined necessary selection ratio with respect to the remaining insulating film material is selected, so that the etching process for removing the remaining film is smoothly performed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A, 1B, and 1C are cross-sectional views sequentially showing each process of a contact hole forming method according to an embodiment of the present invention.

First, as shown in FIG. 1A, an interlayer insulating film 11 made of SiO ₂ is formed on a Si substrate 10, and an inorganic insulating film 12 made of SiON is laminated thereon. The pattern 1 corresponding to the contact hole is formed on the inorganic insulating film 12.
A resist 13 of an organic material having 4 is printed and applied.
The Si composition in the SiON constituting the inorganic insulating film 12 is set so that the selectivity of SiON to SiO ₂ becomes approximately 3 or more in order to enable additional etching for removing a residual film described later. deep.

Next, as shown in FIG. 2B, a contact hole 15 is formed by etching according to the pattern 14 using the resist 13 as a mask. In this case, using the same resist 13 as a mask, SiON and S
It the iO ₂ continuously at one time in the process may be an etching process, or SiON and SiO or in a separate process under different conditions such as etching gas separate device
₂ may be separately etched. Alternatively, after etching the SiON first, the resist is removed, a SiO ₂ may be etched the SiON only as a mask.

Next, as shown in FIG. 1C, the resist is removed by ashing, and an opening inspection is performed by SEM.
In this case, since the SiON inorganic insulating film 12 on the SiO ₂ interlayer insulating film 11 is not charged with a large amount of electric charges as in the case of the resist shown in FIG. 4, the opening of the contact hole 15 is confirmed by electron beam irradiation. Can be done without any problems.

FIGS. 2A to 2D are cross-sectional views sequentially showing each process of the method of the present invention when a defect occurs in a contact hole. First, like FIG. 1A, FIG.
As shown in FIG. 1A, an interlayer insulating film 11 made of SiO ₂ is formed on a Si substrate 10, and an inorganic insulating film 12 made of SiON is laminated thereon. An organic material resist 13 having a pattern 14 corresponding to a contact hole is printed and applied on the inorganic insulating film 12.

Next, as in FIG. 1B, FIG.
As shown in FIG. 7, a contact hole is opened by etching using the resist 13 as a mask in accordance with the pattern 14. In this case, a defective contact hole 15 'in which a residual film 16 of SiO ₂ is left at the bottom due to insufficient etching is formed. Have been. The residual film 16 in such a defective contact hole 15 'is detected by an opening inspection by electron beam irradiation after removing the resist 13 as shown in FIG.

Contact hole 1 having such an opening defect
When 5 ′ is detected, as shown in FIG.
The remaining film 16 of SiO ₂ is removed by additional etching using the inorganic insulating film 12 as a mask. At this time, the composition is adjusted in advance so that the etching selectivity between SiO ₂ and SiO ₂ is, for example, 3 or more.
iON functions as a mask without being etched, and S
The remaining film 16 can be removed by effectively etching only iO ₂ . As a result, a normally opened contact hole 17 is formed.

Such an SiON film not only functions as a mask for etching, but also can change the dielectric constant and the reflectivity by appropriately selecting the Si content thereof. When used, it is possible to form a SiON film having a dielectric constant that suppresses halation with respect to the underlying wiring and leaves no trouble in the device.

[0020]

EXAMPLE An example of forming the inorganic insulating film 12 made of SiON will be described below.

Film forming apparatus: Plasma CVD apparatus Forming conditions: Plasma gas: SiH 4 / N 2 O / He = 200/400/800 sccm Temperature: 400 ° C. Film forming pressure: 2.5 Torr RF Power: 200 W Deposition rate: 360 nm / min or more Under the conditions (1) and (2), a SiON film having a uniformity of about ± 5% or less and a refractive index of about 2.1 (wavelength of 633 nm) and a dielectric constant of about 3 could be formed.

An example of additional etching for removing the residual film 16 at the bottom of the contact hole will be described below.

Etching apparatus: high density plasma SiO ₂
Dry etching equipment Etching conditions: Etching gas: C4F8 / CO / Ar / CHF3 = 10/300/500/20 s
ccm Pressure: 5 Pa Power: 1500 W SiON etch rate: 200 nm / min SiO ₂ etching rate: 600 nm / min selection ratio: the residual film 16 of SiO ₂ could be reliably removed at 3 or more.

In the above embodiment, SiN can be used as the inorganic insulating film instead of SiON in the above embodiment, depending on the material of the interlayer insulating film and the substrate, etching conditions, and the like.

[0025]

As described above, according to the present invention, an inorganic insulating film is further laminated on an insulating film to be opened, and etching is performed to open a contact hole.
The contact hole is inspected by electron beam irradiation in a state where the resist is removed while leaving the inorganic insulating film. If a residual film is detected at the bottom of the contact hole, the residual film is formed by etching using the inorganic insulating film as a mask. Can be removed. In this case, since the inorganic insulating film does not charge, the inspection by the electron beam irradiation does not interfere. In addition, this makes it possible to monitor the contact opening at that position and repair it if there is a defect in the line of the semiconductor manufacturing process, so that a highly reliable and high aspect ratio contact hole can be efficiently formed. As a result, the yield can be improved and the productivity can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of a principal part of a substrate, showing in order the process of the method of the present invention when a contact hole is normally opened.

FIG. 2 is a sectional view of a principal part of a substrate, showing in order the process of the method of the present invention when a defective contact hole is detected.

FIG. 3 is an explanatory view of a conventional contact hole inspection method.

FIG. 4 is an explanatory view of a conventional contact hole inspection method in which a resist is left.

[Explanation of symbols]

10: Si substrate, 11: interlayer insulating film (SiO ₂ film), 1
2: inorganic insulating film (SiON film), 13: resist, 1
4: pattern, 15, 17: normal contact hole,
15 ': defective contact hole, 16: residual film.

Claims (2)

[Claims] 1. A contact hole forming method for forming an opening in an insulating film formed on a base by etching using an organic resist material as a mask, wherein the contact hole has a predetermined etching selectivity with respect to the insulating film on the insulating film. A contact hole forming method, wherein etching is performed in a state where the inorganic insulating films are laminated. 2. The method according to claim 1, wherein the insulating film formed on the base is made of SiO ₂ , and the another inorganic insulating film is made of SiON.