JPS59184531A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form the contact holes having uniform opening areas without expansion by a method wherein after an Si nitride film is formed on the contact hole opening parts, an Si oxide film is formed on a surface of the substrate except said parts and the PSG film formed over the whole surface after removing the Si nitride film is etched by using a resist as a mask. CONSTITUTION:An Si nitride film 22 is formed on a surface of a substrate 21 and resist 23 is formed. Patterning of the Si nitride film 22 is done by using the resist 23 as a mask so that the Si nitride film 22 is left only in the contact hole opening part on the substrate 21. Nextly, the oxidation treatment is performed to form an Si oxide film 24. After that, the Si nitride film 22 is removed. Then a PSG film 25 is grown over the whole surface, which is coated with resist 26 and an opening 27 is formed on the part where the Si nitride film 22 was removed. After that, the PSG film 25 is etched by using the opening 27 so far as the surface of the substrate 21 is exposed to form a contact hole 28. Lastly the resist 26 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of forming a contact hole.

(Prior Art) A conventional method for forming contact holes in a semiconductor device will be described with reference to FIG. In FIG. 1(a), 1 is a silicon substrate, 2 is a PS formed on its surface.
When using the G film, first, a resist 3 is applied on the PSG film 2. Then, an opening 4 is formed in this resist 3 at a location where a contact hole is to be formed. After that,
Using the opening 4, perform PS etching using an HF-based etching solution.
The G film 2 is etched to form a contact hole 5 as shown in FIG. 1(b). Finally, as shown in FIG. 1(e), the resist 3 is removed.

However, in this method, the opening area of the contact hole 5 (
There is a drawback that the opening area on the surface of the substrate 1 is larger than the area of the opening 4 of the resist 3.

In order to prevent such contact hole expansion 9, it is common at present to use a contact hole opening method as shown in FIG.

To explain this method, in FIG. 2(a), 11 is a silicon substrate, 12 is a PSG film on the surface of the silicon substrate, and first, a resist 13 is applied on the PSG film 1 and 2. An opening 14 is formed in the area where the contact hole is to be formed.

Thereafter, the PSG film 12 is etched halfway through the opening 14 using an HF-based etching solution as shown in FIG. 2(b).
Perform etching.

Thereafter, the resist 13 is poured downward by baking to form the shape shown in FIG. 2(c), that is, the opening 1
4, the resist 13 having PS
It is in a state where it is extended to the bottom of the four parts created in the G conversion 12.

Thereafter, the resist 13 is slide-etched using 02 plasma, and then the PSG film 12 is etched halfway again as shown by the peaks in FIG.

After this etching, baking is performed again and the resist 13 is poured down to form the shape shown in FIG. 2(e). A resist 13 having an opening 14
is extended to the bottom of the recess in the PSG film 12 by the second etching.

After drying, slide etching of the resist 13 is performed again, and then the third etching of the PSG film 120 is performed.

By this third etching, the recessed portion of the PSG film 12 reaches the substrate 11 as shown in FIG. 2(f). Tsuma fi
, a contact hole 15 has been opened in the PSG film 12.

Finally, as shown in FIG. 2(g), the resist 13 is removed to complete the contact hole forming process.

According to such a method, it is possible to prevent the contact hole from expanding. However, this method has the following drawbacks.

(1) Baking, slide etching, and re-etching of the PSG film 12 take time;
Since the flow of the resist 13 due to baking is not uniform, the opening area of the contact hole 15 is not uniform, and the work requires skill.

(2) Since slide etching is performed several times, the resist 13 may disappear in areas where the resist 13 is thin, such as at stepped portions. Needless to say, this will result in the production of defective products.

(3) When attempting to form contact holes 15 on silicon single crystal and silicon polycrystal at the same time, the dimensions of opening 14 in resist 13 differ significantly between the silicon single crystal and silicon polycrystal. This is a phenomenon caused by the existence of a step on the wafer surface and the fact that the reflected light and diffusely reflected light during exposure are different depending on whether the contact hole 15 is formed on a silicon single crystal or on a silicon polycrystal. The dimensions of the openings 14 in the resist 13 cause differences in the opening surface area of the contact holes 15.

(Objective of the Invention) The present invention was made in view of the above points, and it is possible to easily form a contact hole with a uniform opening area without spreading in a short time, and moreover, it can be formed easily on silicon single crystal and silicon polycrystal. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can simultaneously form contact holes with the same opening area and also prevent the occurrence of defects caused by the resist.

(Example) Hereinafter, a third example of the method for manufacturing a semiconductor device of the present invention will be described.
This will be explained with reference to the figures.

In FIG. 3 (aJ, 21 is a silicon substrate. First, the surface of this substrate 21 is covered with a silicon nitride film (Si3N4
22 to a thickness of 500 people.

Next, the surface of the silicon nitride film 22 is selectively coated with a resist (for example, a bore resist) as shown in FIG. 3(b).
form 23.

Then, by patterning the silicon nitride film 22 using the anisotropic etching technique using the resist 23 as a mask, the silicon nitride film 22 is formed on the substrate 21 as shown in FIG. 3(c). Leave it only in the area where the contact hole is planned to be drilled.

Next, after removing the resist 23 used in the patterning, an oxidation treatment is performed so that the surface of the substrate 21 other than that covered with the remaining silicon nitride film 22 is removed (see FIG. 3).
As shown in d), a silicon oxide film 24 is formed to a thickness of about 700X.

After that, using a phosphoric acid-based etching solution, the etching process shown in Fig. 3 (e
), the silicon nitride film 22 is removed.

After that, as shown in FIG. 3(f), a PSG film 25 is formed on the entire surface.
is grown to a thickness of 3000X using CVD technology.

Furthermore, a resist 26 is applied on the PSG film 2 as shown in FIG. 3(g). The resist 26 has an opening 2 on the removed portion of the silicon nitride film 22.
form 7.

Thereafter, using the opening 27, the PSG film 25 is etched with a (3)-based etching solution until the surface of the substrate 21 is exposed, thereby forming a contact hole 28 as shown in FIG. 3(h). . At this time, compared to the PSG film 25, the etching rate of the PSG film 2 and lower 5 underside silicon oxide [24] is less than 1/4, so even if the PSG film 25 is slightly overetched, the silicon oxide film 24 will be Almost never etched.

Finally, the resist 26 is removed as shown in FIG. 3(i).

In such an embodiment, the opening area of the contact hole 28 (opening area on the surface of the substrate 21) depends on the shape of the silicon nitride film 22 grown on the substrate 21 after patterning. Therefore, according to this embodiment, the contact hole 28 having a uniform opening area without spreading can be easily formed in a short time, and the contact hole 28 can be formed simultaneously on the silicon single crystal and the silicon polycrystal. In this case, both contact holes 28 can be formed with the same opening area. Also, resist 26
By patterning the silicon nitride film 22 using a bore resist and making full use of anisotropic etching technology, it becomes possible to form a contact hole 28 with a diameter of about 1.5 μm. Furthermore, according to the -laugh example, P S
By etching G#25 using a wet etching solution, the shape of the insulating film layer (PSG film 25) around the contact hole 28 becomes smooth, resulting in a good contact without the risk of disconnection of the electrode wiring. A hole shape is obtained. Further, in one embodiment, since the resist does not run out at necessary locations, it is possible to prevent defects caused by resist.

(Effects of the Invention) As detailed above, in the method of manufacturing a semiconductor device of the present invention, a silicon nitride film is selectively formed in a contact hole opening on a silicon substrate surface, and then the silicon nitride film is used to produce a semiconductor device. A silicon oxide film is formed on the surface of the substrate, then the silicon nitride film is removed, a PSG film is formed on the entire surface, and the PSG film is etched using a resist as a mask. A contact hole having an opening area can be easily formed in a short time, and when contact holes are simultaneously opened on silicon single crystal and silicon polycrystal, both can be formed with the same opening area.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing a conventional contact hole forming method, and FIG. 3 is a cross-sectional view showing an embodiment of the semiconductor device manufacturing method of the present invention. 21... Silicon substrate, 22... Silicon nitride film,
24... Silicon oxide film, 25... PSG film, 26
...Resist, 27...Opening, 28 River contact hole. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] A step of selectively forming a silicon nitride film on the area where a contact hole is to be formed on the surface of the silicon substrate, a step of forming a silicon oxide film on the surface of the silicon substrate other than that supported by this silicon nitride film, and then a step of removing the nitride film, a step of forming a PSG film on the entire surface after that, a step of applying a resist on the PSG film, and a step of forming an opening in the resist over the removed portion of the silicon nitride film; and removing the PSG film until the substrate surface is exposed using the opening.