JPS6171646A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To contrive to block the growth of bird beaks to element regions under a patterned nitride film by a method wherein the end of a pad oxide film after patterning and an Si substrate thereunder are made resistant to oxidation by nitriding and then subjected to field oxidation. CONSTITUTION:When nitriding treatment is carried out after a pad oxide film 12, a nitride film 13, and an SiO2 film 14 are laminated on a P type Si substrate 11 and patterned by selective etching, the exposed surface of the substrate 11 and its periphery, the end of the pad oxide film 12, and the SiO2 film 14 change into nitride films 15, 16, and 17, respectively. Next, the nitride film on the exposed surface of the substrate 11 is removed by RIE, whereas the nitride film 16 at the end of the nitride film 12 is left, and an SiO2 film 18 is grown by high temperature oxidation; then, channel stop ions are implanted to the surface part of the substrate 11 thereunder. Thereafter, a field oxide film 19 is grown by high temperature oxidation, and the nitride films 17, 13, and 16 and the nitride film 12 are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming an isolation region of a semiconductor device.

(Promoted technology) Conventionally, when forming an integrated circuit by forming a large number of elements on a 10-density substrate, the culture selection method has been widely used as a means of insulating and separating the valley elements. .

FIGS. 2(a) and 2(b) are cross-sectional views showing the steps of the conventional selective oxidation method.

First, as shown in FIG. 2(a), a 5-ounce pad oxide film 2 and a 2,000-meter nitride film 3 are sequentially grown on a silicon substrate 1, and these are patterned using a conventional selective etching method.

Next, the silicon substrate 1 is oxidized in a high temperature oxidizing atmosphere using the patterned nitride film 3 as a mask.
As shown in FIG. 2(b), a field oxide film 4 is grown on the exposed surface portion to a thickness of 6,000 wafers.

(Problems to be Solved by the Invention) However, in this method, during field oxidation, the oxide film grows to the bottom of the nitride film 3, which becomes the element region, and a so-called bird's beak occurs. Since this bird's beak corresponds to a transition region between the element region and the field region (tone separation region), it hinders the increase in the density of integrated circuits.

In addition, in order to reduce this bird's beak, the pad oxide film 2 should be made thinner, while the nitride film 3 should be made thicker.
If this is done, the occurrence of crystal defects at the ends of the patterned films 3, 2 will increase, resulting in deterioration of device characteristics.

(Means for Solving the Problem) Therefore, in the present invention, the end portion of the pad oxide film after patterning is nitrided to make it resistant to oxidation, and then field oxidation is performed.

(Function) By doing this, due to the oxidation resistance of the edge of the pad oxide film, during field oxidation, the oxidizing agent diffuses through the pad oxide film to a greater extent than through the normal pad oxide film. This prevents the bird's beak from growing into the device region under the patterned nitride film.

(21st example) The implementation of this envy will be explained with reference to the first example (a) to e).

First, as shown in FIG. 1(a), a padded oxide film (5iO2) 12 of about 500λ is grown on a P-type silicon substrate 11 having a (100) plane by high-temperature oxidation in a 1000°C 02 atmosphere. let Next, the pad oxide film 12
A reed nitride film (5isN<) 13 to 1 is applied on top by CVD method.
Grow to about sooA. Thereafter, on the nitride film 13, a SiO2 film 14 having a thickness of about 40λ is grown to serve as a buffer during etching by the RIE method described later. After that, SiO2 film 14 film chamber 4 film 13 and pad oxide film 1
2 is patterned using the usual selective etching method. As a result, the 5I02 film 14, the nitride film 13, and the band oxide film 12 are left only on the element region and removed from the field region, as shown in FIG. The surface of the base 11 is exposed.

After that, 1000℃ in a normal pressure ammonia gas atmosphere.
．． Nitriding treatment is performed for 5 hours. Then, as shown in FIG. 1 (bJ), the exposed surface portion of the silicon substrate 11 exposed to the reaction gas, the end portion of the bad decomposition film 12, and the 5i02 film 14 become nitride films 15, 16, and 17, respectively. This nitriding treatment may be performed by a plasma nitriding method other than the heat chamber method described above.

Next, by performing etching of about 100λ using RIE method, the 60 nm formed on the surface of the silicon substrate 11 is etched.
While the fake nitride film 15 is removed, the nitride film 16 at the end of the pad oxide film 12 is left. At this time, the nitride film 17 is etched at the same time, and the film thickness is reduced or the underlying distilled film 13 is exposed. Here, it is assumed that the film thickness is reduced and the nitride film 17 still remains.

Next, by performing high-temperature oxidation in a 100°C 02 atmosphere, the silicon substrate 1 exposed by removing the nitride film 15 is
As shown in Figure (C), the 5i02 film 18
is grown by 500λ.

Next, as shown in FIG.
1013i0nS/, 1). This channel stop ion implantation may be performed after the patterning shown in FIG. 1(a), or after the nitriding process shown in FIG. 1(b). Alternatively, ion implantation may be performed without growing the 5iOz film 18, but considering the uniformity of impurity ions, it is best to perform the ion implantation after forming the 5iOz film 18 in the process shown in FIG. 1(C). Best.

Thereafter, by performing oxidation for 3 hours in a 1000°C H2,02 high temperature oxidizing atmosphere, as shown in Figure 1(d),
The field oxide film 19 is nitrided at about 6000X and 114
17 and 13 are used as masks to grow on the surface of the silicon substrate 11.

Next, a thin oxide film (not shown) formed on the nitride film 17, 13 during the high temperature oxidation is removed using a hydrofluoric acid etching solution. Subsequently, the nitride films 17 and 13 are coated in a hot phosphoric acid bath.
．． 16 was removed, and the Sibarad oxidized 1111112 was removed again using a 7-sulfuric acid-based etching solution.
Obtain the structure e).

Thereafter, traces of thermal nitridation remain at the boundary between the element region where the surface of the silicon substrate 11 is exposed and the field region (confectionery separation region) where the field oxide film 19 is formed, and at the element region. Sacrificial oxidation is performed because it may cause trouble in later steps. That is, the surface of the silicon substrate 11 is oxidized by about several hundred λ, and the formed oxide film is removed by etching.

In the above embodiment, 5iOzi 14 is formed on the nitride film 13 in the step shown in FIG. 1(a), but this film serves as a buffer during etching by the RIE method. , if the membrane is a buffer (”
For example, it may be a polysilicon film or a PSG film. Furthermore, if the nitride film 13 is grown thickly in consideration of the loss of thickness due to direct etching, this buffer film is not necessarily required. In short, the nitride film 13 serves as an oxidation-resistant mask during field oxidation.
For example, in this example, it may be about 1000λ or more.

Further, when buttering is performed in the step of FIG. 1(a), it is sufficient that at least the nitride film 13 is etched.
It does not matter whether the pad oxide film 12 is completely etched or some amount remains.

Even if the pad oxide film 12 remains, nitridation occurs laterally in the next nitriding reaction, so the pad oxide film 12 under the end of the nitride film 13 becomes the nitride film 16. In addition, pad oxide film 1
2 remains, this pad oxide film 12 will come into contact with the diffused gas and the surface of the silicon substrate 11 will become nitride film 1.
It becomes 5. This nitride film 15 and the nitride film formed by nitriding the remaining pad oxide film thereon are removed by the subsequent RIE etching.

In addition, when forming a buffer film on the nitride film 13 in the process shown in FIG. However, in the nitriding process shown in FIG. 1(b), there is no problem because the interface with the nitride film 13 is nitrided, but when polysilicon is used, it is not completely nitrided and a portion remains as polysilicon. Field oxidation reduces the thickness to 5 iOz, and since the field oxide film 19 is also reduced when this is removed, several hundred people are required to carry out thicker field oxidation in the process shown in FIG. 1-(d).

(Effects of the Invention) As detailed above in one embodiment, the method of the present invention has the following effects:
The edge S of the pad oxide film after patterning is nitrided to improve its oxidation resistance, and then field oxidation is performed. During field oxidation, the diffusion of the oxidant through the pad oxide film is greatly inhibited compared to the diffusion through the normal pad oxide film, causing Lucara and bird's beaks to grow in the device region under the buttered nitride film. It can hinder your progress. In other words, it is possible to reduce bird's beaks, thereby making it possible to form element isolation regions by reducing the difference in dimensions (conversion difference) between patterning and finishing, as well as expanding the element area, which allows for higher integration. There is an advantage. Furthermore, since the bird's beak can be reduced, the thickness of the nitride film of the anti-platelet mask can be reduced, and the occurrence of crystal defects can be reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining a practical example of the method for manufacturing a semiconductor device according to the present invention, and FIG. 2 is a cross-sectional view for explaining a conventional resealing method. 11 ・1. P stone silicon certain type 12... notes
13...Nitride film, 16...Nitride film, 19
...Field oxide film. Patent Applicant Oki Electric Industry Co., Ltd. Figure 2 Procedural Amendment

Claims (1)

[Claims] In a method of manufacturing a semiconductor device in which an element isolation region is formed by field oxidation using a nitride film formed on a silicon substrate with a pad oxide film in between as a mask, the edge of the pad oxide film under the nitride film is 1. A method for manufacturing a semiconductor device, characterized in that a semiconductor device is modified to have oxidation resistance, and then field oxidation is performed.