JPS59114840A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a high aperture rate by stably and securely removing a product even when the dimension of the aperture becomes fine by a method wherein the product formed on the surface of an aluminum wiring at the aperture at the time of removing a photo resist is removed by reactive ion etching after forming the aperture through an insulation film on the aluminum wiring with the photo resist as a mask. CONSTITUTION:After forming a through hole 28, the photo resist 26 having served as the mask is removed. Removal of this photo resist 26 is performed by O2 plasma or by dipping in nitric acid series solution. At the time of removing this photo resist 26, an oxide 29 is produced on the surface of the first layer aluminum wiring 24 at the through hole part. Next, this oxide 29 is removed. Removal of this oxide 29 is performed by the reactive ion etching using a parallel flat type dry etching device. After removing the oxide 29 on the surface of the first layer aluminum wiring 24 at the through hole part, the second layer aluminum wiring 30 is so formed as to be connected to the first layer aluminum wiring 24 via the through hole 28.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method of manufacturing a semiconductor device, and more specifically, after forming an opening in an insulating film on aluminum wiring using a photoresist as a mask, when the photoresist is completely removed, the opening is removed. This invention relates to a method for removing products formed on the surface of aluminum wiring.

(Prior Art) One of the openings formed in an insulating film on aluminum wiring is a through hole in A/multilayer wiring. A conventional method for forming this through hole will be explained with reference to FIG.

In FIG. 1(a), 1 is a silicon substrate, on the surface of which a field oxide film 2 is formed.

Further, a first insulating film 3 is formed on the surface of the silicon substrate 1 including the field oxide film 2, and a first layer aluminum wiring 4 is formed on this first insulating film 3. After forming this first layer aluminum wiring 4''ft, a second insulating film 5 is formed thereon and on the first insulating film 3 by CVD or the like.

Next, a photoresist 6 is applied on the second insulating film 5,
A window 7 is formed in this photoresist 6 in a region where a through hole is to be formed. (See FIG. 1 6L)) Next, using the photoresist 6 as a mask, the second insulating film 5 is
etching. As a result, through holes 8 are formed in the second insulating film 5 in correspondence with the windows 7 of the photoresist 6. Here, the etching is carried out by a wet etching method in which the film is immersed in a 2% buffered hydrofluoric acid solution, or by a dry etching method in which a Freon gas is introduced into a parallel plate type dry etching apparatus. (See FIG. 1(b)) Thereafter, the photoresist 6 serving as a mask is removed. The photoresist 6 is removed by introducing oxygen into a cylindrical plasma etching device and using 0□ plasma, or by immersion in a nitric acid solution. (See FIG. 1(C)) After removing this photoresist 6, a second layer aluminum wiring 9 is formed so as to be connected to the first layer aluminum wiring 4 via a through hole 8. (See FIG. 1(d)) In such a conventional through-hole forming method, when the photoresist 6t-02 plasma or nitric acid solution is used to remove the photoresist, the surface of the first layer aluminum wiring 4 in the through-hole portion is An aluminum oxide 10 is formed. This is because aluminum is oxidized by active oxygen when 02 plasma is applied, and because the aluminum surface becomes passivated by oxide when immersed in nitric acid solution. It is.

Therefore, if the second layer aluminum wiring 9'i is formed as is, ohmic contact failure will occur at the through-hole portion due to the aluminum oxide 1o.

Therefore, in order to remove this oxide 1o, after removing the photoresist 6, 5% dilute acid solution phosphoric acid (95%), decanitric acid (1%), decafluoric acid (1%), decaglaic acetic acid (3% ) A method of immersing it in a solution is used.

However, in these wet treatments, when the size of the null hole becomes fine, air bubbles adhere to the through-hole part, making it difficult for the processing solution to enter the through-hole part. could not be removed reliably. Therefore, there was a drawback that the through-hole drilling yield was poor.

(Object of the Invention) The present invention has been made in view of the above points. For example, the oxide (
It is an object of the present invention to provide a method for manufacturing a semiconductor device that can stably and reliably remove products (products).

(Example) An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2(a), 21 is a silicon substrate, on the surface of which a field oxide film 22 is formed.

Further, a first insulating film 23 is formed on the surface of the silicon substrate 21 including the top of the field oxide film 22.
A first layer aluminum wiring 24 is formed on the insulating film 23.

After forming the first layer aluminum wiring 24, a second insulating film 25 is formed thereon and on the first insulating film 23. next,
A photoresist is coated on the second insulating film 25, and the photoresist 26 has windows 2 in the through-hole forming area.
form 7. (See FIG. 2(a)) Next, the second insulating film 25 is etched using the photoresist 26 as a mask. As a result, through holes 2 are formed in the second insulating film 25 corresponding to the windows 27 of the ζ photoresist 26.
form 8. Here, the etching is performed by dry etching (reactive ion etching) by introducing Freon gas into a parallel plate dry etching apparatus. An example of etching conditions in that case is 13.5
The electrodes are configured in an anodic coupling manner to a 6MHz RF power source, and C
zFa + (0~30%) CHF, mixed gas 30~
Install 120ac and perform etching with RF power 2 times. The reason why dry etching is used for etching this through hole is to avoid a complicated process. That is, in the case of wet etching, a film is required to be applied to the back surface to prevent the battery effect, since the battery effect causes smudges in the etching. Dry etching can avoid such a complicated process.

(See FIG. 2(b)) After forming the through hole 28 in this manner, the photoresist 26 serving as a mask is removed. This photoresist 26 is removed by 02 plasma or by immersion in a nitric acid solution. When this photoresist 26 is removed, an oxide 29 is generated on the surface of the first layer aluminum wiring 24 in the through hole portion. The thickness of this oxide (product) 29 was determined by orthogonal analysis.
It was found that 50 to 75 people were exposed to 02 plasma, and 100 to 150 times when immersed in a nitric acid solution. (See FIG. 2(c)) Therefore, next, this oxide 29 is removed.

This oxide 29 is removed by reactive ion etching using a parallel plate dry etching device. An example of the conditions in that case is that the introduced gas is 0
2F6 gas 5-30cc, pressure 0.3 torr or less (
For example, the frequency of the high frequency power supply is 13.56 MHz, the high frequency power is 2F, and under these conditions, it takes about 1 to 2 minutes (for example, 1.5 minutes)
Perform etching. Note that other freon-based gases such as CF, C, and F8 can also be used. (See FIG. 2(d)) Then, after removing the oxide 29 on the surface of the first layer aluminum wiring 24 in the through hole portion by active ion etching, the first layer aluminum wiring 24 is etched through the through hole 28. lol 2 layer aluminum wiring 30 to be connected to
form. (See FIG. 2(e)) As described above, in one embodiment, the oxide 29 generated on the surface of the first layer aluminum wiring 24 in the through hole portion in the process of removing the photoresist 26 is removed by reactive ion etching. . Therefore, even if the through-hole size becomes finer, the oxide 29 can be removed stably and reliably, and the yield of through-holes is improved.

Figure 3 C. Through-hole size and through-hole aperture ratio (
The correlation between the conventional method and the above-mentioned yield of this invention
FIG. 1 is a 1° view showing both examples and FIG. As is clear from this figure, according to the conventional method (indicated by broken line A), when the through-hole size becomes 3μ, the through-hole area ratio becomes 1.
However, according to one embodiment of the present invention (indicated by the English letter B), an aperture ratio of 90% or more can be obtained. Therefore, according to one embodiment of the present invention, even if the dimensions of the through holes are reduced, ohmic contact failures in the through holes hardly occur.

Further, when the through hole 28 is formed by dry etching, the through hole is etched, but when the oxide removal step (reactive ion etching step) is performed, the acute corner of the through hole is slightly etched. Therefore, the next second layer aluminum wiring 30
It is also possible to prevent defects such as disconnection of the second layer aluminum wiring 30 at the through hole portion when forming the second layer aluminum wiring 30.

Although the above embodiment deals with the case where the opening formed in the insulating film on the aluminum wiring is a through hole, the present invention can also be applied to the case where an opening other than a through hole is formed.

(Effects of the Invention) As detailed above, in the method of the present invention, the opening 1 is formed as a full photoresist mask on the insulating film on the aluminum wiring.
After complete formation, when the photoresist is removed, the products formed on the surface of the aluminum wiring in the opening are removed by reactive ion etching, so even if the dimensions of the opening become finer, the products can be removed. It can be removed stably and reliably to obtain a high porosity.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining the entire conventional method for forming a through-hole, FIG. 2 is a cross-sectional view for explaining an embodiment of the method for manufacturing a semiconductor device of the present invention, and FIG. 3 is a cross-sectional view for explaining the through-hole size. FIG. 3 is a diagram showing the correlation between the through-hole area ratio and the conventional method and the above-mentioned embodiment of the present invention. 24...First layer aluminum wiring, 25...Second layer wiring. Membrane, 26... Photoresist, 27... Window, 28...
Through hole, 29... oxide. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] A step of forming an opening in an insulating film formed on the aluminum wiring using a photoresist as a mask, a step of removing the photoresist as the mask, and a step of removing the photoresist that is formed on the surface of the aluminum wiring in the opening when removing the photoresist. A method for manufacturing a semiconductor device, comprising a step of removing a product by reactive ion etching.