JPH0458532A - Manufacture 0f semiconductor device - Google Patents

Abstract

PURPOSE:To restrain the dug amount of an Si substrate and to relax a stress acting on an SiN film and a LOCOS film when the LOCOS film is formed by a method wherein an SiO2 film and the SiN film are formed on the Si substrate, a dry etching operation is executed and, after that, a wet etching operation is executed. CONSTITUTION:An SiO2 film 2 and an SiN film 3 are formed on an Si substrate 1; and after that, a pattern 5 is formed by an exposure operation and a developing operation. At this time, the SiO2 film 2 and the SiN film 3 are dry-etched continuously at the pattern 5; and an SiO2 film 2a only in a proper film thickness is left. In addition, the SiO2 film 2a is wet-etched; and an undercut part 14 is produced under a pattern 13 of the SiN film 3. An SiN film 6 and an SiO2 film 7 are developed; and a sidewall 7a is formed by an etching-back process. An impurity layer 8 is formed; the SiO2 films 7a, 4 are removed; and a LOCOS oxide part 19 is formed by executing a LOCOS oxidation operation. In addition, the SiO2 film on the surface and the whole SiN films 3, 6 are removed; and a LOCOS film 9 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a method for manufacturing a semiconductor device, and more specifically to a method for making it possible to miniaturize the element isolation process in the semiconductor manufacturing process. be.

(b) Conventional technology In the element isolation process of LSI, conventionally, the LSI is formed using the LOCO8 method and two local oxidation method. This is done by depositing a SiN film on the active region and oxidizing the other parts through ion implantation to obtain a film thickness of around 1 μm. ~1 μm).

That is, FIG. 4 shows a process flow regarding the normal LOCO9 method.

As shown in FIG. 4(a), for example, after forming an underlying S + 02 film 42 on a P-type S] substrate 4I, an S 13N + film 4 is formed.
Deposit 3. Next, after forming a pattern 44 with photorenost, B (boron) 45 is ion-implanted [Fig. 4(b)]
reference]. After that, the remaining 5 is N4 film 43 and S1
0. An oxidation process is performed based on the film 42 to form a field SiO
4(c) to form two films 46.

In this method of separating the active regions S using a thick oxide film, the SiN film 43 is formed during the formation of the field oxide film.
5iOz invades the edge of the so-called bird's beak 47
As a result, the channel width is effectively reduced (see FIG. 5(a)). FIG. 5(b) shows the change in bird's beak length Q depending on the thickness of the underlying SiO2 film. From FIG. 5(b), it can be seen that when the bird's beak length becomes 06 to 1.0 μm on one side, the knot from the mask size reaches 12 to 20 μm.

To this end, an offset LOCOS method (O5ELO method) has been proposed in which the end of S I N @ is extended to the inside of the field part to shorten the bird's beak length.

That is, as shown in FIG. 3(a), an underlying Si film 32, a SiN film 33, and an oxide film (
A HTO film) 34 is deposited. Next, a pattern 35 is formed using a resist mask (see FIG. 3(b)). Furthermore, a SiN film 36 and an HTo film (oxide film) 37 are deposited [see FIG. 3(c)]. Next, etching is performed using a dry etcher to open the window 35a, and ions are implanted into the window 35a (see FIG. 3(d)). At this time, for example, 1B° is injected. After forming the impurity layer 38 (see FIG. 3(e)), the oxide films 34 and 37 are removed by wet etching (see FIG. 3(e)).
f) Perform Lacos oxidation (1050°C) as shown in Reference 2 and Figure 3 (g). After forming the LOGOS film 39,
L to remove SiN films 33, 36 and 5LOZ film 32
See Figure 3(h)].

Although this method is advantageous in miniaturization because knots from the mask can be suppressed, it does have the following problems.

(c) Invention or problem to be solved] 1. SiN to suppress the bird's beak length during local oxidation
Is it necessary to increase the offset width of the membrane?

At this point, it is necessary to thicken the underlying 5JOz film and SiN film, and due to variations in the underlying Si○ and variations in etching uniformity during etching, the underlying Si is dug too much and becomes grooves, which can be removed in subsequent steps. This may lead to defects in the product.

2. Furthermore, when 5iOz (local oxidation) is grown under such a film thickness, strong stress may be applied, which may cause damage to the field oxidation portion.

Specifically, as shown in FIG. 2(a), the 5102 film 32/SiN film 3 deposited on the Si substrate 31
3/ When the SiO2 film 34 is etched using a predetermined resist pattern as a mask, some portions 31a are created where Si is dug too much due to variations in film thickness and variations in etching. Si substrate 3 having this excessively dug portion 31a
An oxide film 37 is deposited on the wafer (Fig. 2(b)), an etch-back process (Fig. 2(c)) is performed, and the oxide film 37 is oxidized as shown in Fig. 2(d). -40 is shown in Figure 2 (e
), stress damage and Si grooves may occur.

That is, there is a possibility that a groove 39b is formed due to excessive digging of the damaged portion 39a1Si due to stress, and residual resist etc. will occur in a later process.

The present invention aims to solve the above-mentioned problems during the LS If) manufacturing process, by reducing the amount of digging in the base layer S1,
It also provides an effective method for alleviating stress.

(d) Means and operation for solving the problem This invention includes:
When forming an element isolation part on the S1 substrate using the offset locos method, (i) an underlying 5iOy film, a first SiN film, and a first SiO2 film are sequentially laminated on the entire surface of the Si substrate; , (11) Remove the first 5i02 film and the first SiN film on the element isolation formation region using a photorenost pattern, and further remove part of the underlying SiO2 film to form the S1 substrate. A window is formed while leaving the underlying 5iOy on top, and (iii) the remaining underlying Si film is removed by wet etching to form an element isolation region forming area directly under the SiN film on the window side wall. (IV) After sequentially laminating a second SiN film and a second 5102 film for sidewall formation on the entire surface of the Si substrate including the window, etching back was performed to remove the window side. Form a side wall on the wall part, (■)
After performing ion implantation to form an impurity layer in the element isolation region on the Si substrate and removing the (Vl) sidewall and the remaining first SiOx film, thermal oxidation is applied to the entire surface of the Si substrate. A LOCOS oxide film of SiOt is formed, followed by a 5i02 film on the surface and a LOCOS oxide film of SiOt.
This method of manufacturing a semiconductor device is characterized in that an iN film is removed to form an element isolation section.

That is, in this invention, after forming the underlying SiO2 film and SiN film, etching is performed using a photoresist pattern.
Thereafter, by performing a wet treatment process to etch the SiO2 film with a thickness of at least 100A, the base layer S1
The present invention is constructed by providing a method capable of suppressing the trench full and alleviating the stress acting on SiN and the LOCOS oxide film during formation of the LOCOS oxide film.

(e) Examples The present invention will be described in detail below based on embodiments shown in the drawings.

Note that this invention is not limited by this.

FIG. 1 shows one embodiment of the element isolation forming process according to the present invention, and is a thorough example.

First, as shown in FIG. 1(a), after forming an underlying 5iO film 2 and a SiN film 3 on a Si substrate 1, a photorenost 4 is applied, and a desired pattern 5 is exposed using a mask 4. At this time, using a dry etching device, the pattern 5 is etched with the underlying SiO2 and SiN, leaving an appropriate thickness of the 5IO2 film 2a.

Furthermore, the remaining SiO2 film 2 is etched using wet etching.
At the same time, a 100A type undercut portion 14 is formed under the notch 13 of the SiN film 3 [see FIG. 1(c)].

After that, a SiN film 6 for forming offset SiN is deposited, and then SiO! A film (HTO film) 7 is deposited [Fig.
d)], the entire surface of the wafer is etched by an etch-back process to create a sidewall 7a [see Fig. 1 (
e) Reference.

At this time, the undercut portion 14 allows the SiN film 6 and 5i to
A void 15 is created between the Op films 2. Also, an ion implantation window 16 is formed.

Thereafter, "B" ions 45 are implanted into the window 16 to form an impurity layer 8 [see FIG. 1(f)], and the 5i0z film 7 is formed.
i, 4 [see Fig. 1(g)], LOCOS oxidation is performed at 1050°C to form 5iOy LOCOS oxidized part 19 [see Fig. 1(h)], and then the SiO2 film on the surface and all LOGO5 film 9 by removing the SiN film 3.6.
7 See Figure 1 (i) 2 In this method, the LOGO is formed with the undercap part provided.
Since the S film is formed, compared to the conventional offset LOCOS film and T double pattern, there is no shape defect due to excessive digging of 81, and the stress generated above and below the LOCOS oxide film can be reduced by using the offset SiN film. Because of the relaxation, a defective LOCOS oxide film is obtained.

(F) Effects of the Invention As described above, according to the present invention, when using the so-called offset LOCOS method in the LSI element isolation process, an SiO2 film is formed on a silicon substrate, and then a SiN film is formed. Then, after depositing a SiO2 film and etching it using a photorenost pattern, a film of at least 100%
By performing a wet processing process to etch the SiO2 film with a thickness of Å or more, it is possible to minimize the amount of partial excavation of the underlying Si in the wafer due to variations in etching and variations in the deposited film, improving process margins. It is possible to do so.

Further, when forming the LOCOS oxide film, crystal defects caused by stress acting on the SiN and the LOCOS oxide film can be alleviated, and electrical defects (leakage, etc.) caused by crystal defects can be prevented.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the manufacturing process of an offset locos process showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the first manufacturing process to explain defects that occur during the conventional offset locos process, and Fig. 3 is an explanatory diagram of the manufacturing process of the offset locos process. 4 is an explanatory diagram of the manufacturing process of the conventional offset LOCO process, FIG. 4 is an explanatory diagram of the manufacturing process for explaining the normal LOCO3 method, and FIGS. 5(a) and (b) are the usual LOGOS process of FIG. 4, respectively. FIG. 2 is an explanatory diagram of a main part configuration and a characteristic diagram of underlay Sin and film thickness versus bird's beak length for explaining the drawbacks in FIG. 4...First SiO2 film, 5...First pattern (window), 6...Second SiN film, 7...Second SiC film, 7a... Side wall, 8... Impurity diffusion layer, 9... LOCO5 oxide film (Sift film), 13...
...Second pattern, 14...Undercut part. l...51 substrate, 2...underlying 5iO = film, 3...first SiN film, Figure 2, Figure 13, Figure 4, Figure 5, Figure 1 right 5i02! gA7% (nm)

Claims (1)

[Claims] 1. When forming an element isolation part on a Si substrate using the offset Locos method, (i) the underlying SiO_2 film, the first SiN film, the first SiN film, and the 1 SiO_2 films are sequentially stacked, (i
i) Using a photoresist pattern, remove the first SiO_2 film and first SiN film on the element isolation formation region, and further remove part of the underlying SiO_2 film to form an underlying film on the Si substrate. A window is formed while leaving SiO_2, and (iii) the remaining underlying SiO_2 film is removed by wet etching to form an undercut in the element isolation region forming area directly under the SiN film on the window side wall. (iv) a second SiN layer is formed on the entire surface of the Si substrate including the window;
After sequentially stacking a second SiO_2 film for forming a sidewall and a second SiO_2 film for forming a sidewall, etchback is performed to form a sidewall on the window side wall surface, and (v) ion implantation is performed to form an element isolation region on the Si substrate. (vi) forming an impurity layer on the sidewall and remaining first SiO_
After removing the 2 films, thermal oxidation is performed on the entire surface of the Si substrate to form a LOCOS oxide film of SiO_2, and then the SiO_2 film on the surface and all SiN films are removed to form an element isolation part. A method for manufacturing a semiconductor device, characterized in that: