JP2770398B2 - Method of forming contact hole - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a contact hole, and more particularly, to a method for forming a contact hole in an insulating film in which SOG (Spin on Glass) is laminated. is there.

[Summary of the Invention] The present invention provides a method of forming a contact hole, comprising: forming an SOG film on an interlayer insulating film, forming an opening in the SOG film, forming a protective film on a side wall of the opening, By forming an opening in the insulating film, damage to the peripheral wall of the contact hole is prevented, and a highly reliable wiring layer can be formed.

[Prior Art] In recent years, as semiconductor devices become more highly integrated, a technique for flattening an interlayer insulating film is required. As one of the techniques, a planarization method using SOG is known. As a method for forming a contact hole in a semiconductor device using this SOG, for example, as shown in FIG. 2, first, an SiO ₂ film 2 as an interlayer insulating film is formed on a silicon substrate 1 by a CVD method. Next, an SOG film 3 is formed, and an insulating film 4 made of SiO ₂ is formed by a CVD method. Thereafter, a resist mask is formed on the insulating film 4, and anisotropic etching is performed using the resist mask as a mask. To form contact holes. Then, in order to remove the natural oxide film (SiO ₂ ) on the silicon substrate 1 exposed in this manner, light etching is performed using an etching solution (dilute hydrofluoric acid solution or the like), and then a wiring material such as aluminum is removed. The wiring 5 is formed by being buried in the contact hole.

The conventional example shown in FIG. 4 is devised so as to form a contact hole having a diameter smaller than the limit of the photolithography technology. A first mask layer 8 is formed on the etching body 7, a second mask layer 9 is formed on the inner peripheral wall of the opening of the first mask layer 8, and anisotropically using these mask layers 8, 9 as a mask. In this method, a contact hole is formed by performing reactive etching (see Japanese Patent Application Laid-Open No. 63-110728).

[Problems to be Solved by the Invention] However, the above two conventional examples have the following problems.

That is, in the former, when light etching is performed, as shown in FIG.
Since the G film 3 has a higher etch rate than SiO ₂ , it is eroded and receded to form voids 3 a, and as shown in FIG.
There is a problem that the reliability (removal) of the semiconductor device is remarkably impaired due to the occurrence of peeling 3b between the upper and lower layers of the G film 3 (the upper layer is shown in the figure).

Assuming that the substrate 6 is made of silicon and the object 7 to be etched is made of SOG in the latter case, the light etching as described above is performed after the anisotropic etching of the object 7 to be etched, as shown in FIG. As described above, there is still a problem that the void 7a is generated.

[Means for Solving the Problems] Accordingly, the present invention provides a method of forming an SOG film on an interlayer insulating film,
Forming an opening in the SOG film, forming a protective film on a side wall of the opening, and then forming an opening in the insulating film;
This is the solution.

[Operation] Since a protective film is formed on the side wall of the opening formed in the SOG film, for example, when light etching is performed, SO
Prevents the G film from being damaged. In the case where an opening is formed in the interlayer insulating film, the protective film contributes to the reduction of the diameter of the contact hole (opening), and enables the formation of a contact hole smaller than the resolution limit in lithography, for example.

EXAMPLES Hereinafter, details of a method for forming a contact hole according to the present invention will be described based on examples shown in the drawings. In the present embodiment, description of, for example, a diffusion layer in a semiconductor layer, source / drain electrodes, a LOCOS separation film, and the like will be omitted.

First, in this embodiment, on the silicon substrate 10,
An SiO ₂ insulating film 11 is formed by a CVD method, and a silicon nitride (SiN) film 12 having a selectivity with SOG at the time of reactive ion etching is deposited on the SiO ₂ insulating film 11. The above-mentioned SiO ₂ insulating film 11 and silicon nitride film 12 constitute an interlayer insulating film.

Next, SOG is applied on the silicon nitride film 12 to perform planarization to form an SOG film 13, and furthermore, PSG which is an interlayer film is formed.
(Phosphosilicate glass) film 14 is deposited.

Further, on the PSG film 14, SOG and silicon nitride (Si
N), a titanium nitride (TiN) film 15 having a selectivity at the time of reactive ion etching is deposited (FIG. 1A).

Next, a resist mask (not shown) slightly larger than the designed value is provided by using a photolithography method, and an opening is formed by performing reactive ion etching using this as a mask, as shown in FIG. 1B. The etching is stopped when the silicon nitride film 12 is exposed as described above.

Next, as shown by a broken line in FIG. 1C, after depositing silicon nitride on the entire surface by the CVD method, the silicon nitride is etched back to form the protective film 16 made of the silicon nitride on the side wall of the opening. (FIG. 1C).

Finally, reactive ion etching is performed using the protective film 16 as a mask, an opening is formed in the SiO ₂ insulating film 11, and a contact hole 17 is completed on the silicon substrate 10 (FIG. 1D).

The reason for forming the titanium nitride film 15 in the present embodiment is that, after forming the protective film 16 and performing reactive ion etching, if the PSG film 14 is exposed, this film 14 is also etched. This is to prevent this.

In addition, the titanium nitride film 15 after the contact opening can be etched with ammonia peroxide if necessary.

Thus, even if the light etching for removing the natural oxide film on the surface of the silicon substrate 10 is performed before embedding the wiring in the completed contact hole 17, the SOG film 13 is not exposed, There is no inconvenience that retreat and peeling occur due to.

Although the embodiments have been described above, the present invention is not limited to this, but can be applied to various semiconductor device manufacturing processes, and is not limited to the materials and structures as in the above embodiments. In short, before the planarization by the SOG film, a material film having a sufficient selectivity with SOG may be formed in advance, and a material having the same type as the material film or a selectivity with SiO ₂ may be used. A protective film is formed using
What is necessary is just to deposit a material having a selectivity with O ₂ and SiN.

[Effects of the Invention] As is clear from the above description, in the method for forming a contact hole according to the present invention, exposure of the SOG film is prevented, and damage to the SOG film due to anisotropic etching such as reactive ion etching is prevented. Needless to say, there is an effect that the SOG film can be prevented from being damaged (erosion, interface deterioration, etc.) by light etching, and a highly reliable contact portion can be formed.

Further, the present invention has an effect of forming a fine contact hole having a resolution equal to or less than the resolution limit in the photolithography technology by forming the protective film.

[Brief description of the drawings]

1A to 1D are process diagrams of an embodiment of a contact hole forming method according to the present invention, and FIGS. 2 to 5 are cross-sectional views showing a conventional example. 11 ... SiO ₂ insulating film, 12 ... Silicon nitride film, 13 ... SOG
Film, 14 PSG film, 15 Titanium nitride film, 16 Protective film.

Claims (1)

(57) [Claims] An SOG film is formed on an interlayer insulating film, an opening is formed in the SOG film, a protective film is formed on a side wall of the opening, and then an opening is formed in the insulating film. Characteristic method of forming contact holes.