JPH065587A - Method for manufacturing semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to inhibit a bird's-beak penetration or a pattern shift by eliminating an SiN film and an oxide film, using a specifically shaped- mask on an Si substrate where the oxide film and the SiN film are laminated and forming a side wall comprising the oxide film and the SiN film in an element isolation region and thereby forming an element isolation film. CONSTITUTION:After having grown a thermal oxide film on an Si substrate 1, an SiN film is formed where an SiO2 film 2 and an SiO film are etched by using a photo mask 14 which comprises a main pattern mask 2 having a broader width W1 in a longitudinal direction and an auxiliary pattern mask 3 having a narrower width W2 than the width W1, thereby forming an element isolation region and an active area. Then, the element isolation region is thermally oxidized so that the thermal oxide film may be grown and then the SiN film is formed, thereby forming a side wall which comprises an SiO2 film 4a and an SiN film 5a by carrying out anisotropic etching. Then, the exposed surface of the Si substrate is thermally oxidized, thereby forming an element isolation film 7. This construction makes it possible to inhibit a bird's-beak penetration or a pattern shift.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique for isolating a MOS transistor or a bipolar transistor.

[0002]

2. Description of the Related Art In the conventional technique of this type, as shown in FIG. 11, a SiO ₂ thin film 22 is formed on a Si substrate 21 and then a SiN film 23 is formed by a CVD method. Photomask patterns 24a, 24b, 24 having the shape shown
c and the photolithography technique are used to form the active region K.
Then, the element isolation region L where the surface 21a of the Si substrate is exposed is determined (see FIG. 12), and selective oxidation is performed to form the element isolation film 24 of SiO ₂ two-dimensionally (FIG. 13).
reference).

[0003]

At this time, in FIG. 13, an element isolation film 24 called bird's beak 25 enters the active region K. In order to prevent this, a method of forming a sidewall of SiN is often used. However, with the reduction in size of the device, the three-dimensional effect of the device isolation film cannot be neglected due to the selective oxidation, and in the conventional method, particularly when a narrow photomask pattern is used due to the reduction in size, the three-dimensional effect is generated. The bird's beak spreads due to the effect, and a large pattern shift may occur even if a SiN sudwall is formed.

[0004]

Means and Actions for Solving the Problems
(A) An oxide film and a SiN film are sequentially laminated on a Si substrate,
(B) An element isolation film is to be formed using a photomask including an auxiliary pattern mask and a rectangular main pattern mask that is connected by the auxiliary pattern mask and has a width wider than that of the auxiliary pattern mask. The oxide film and the SiN film in the element isolation region are removed, and (c) a new oxide film and a SiN film are sequentially formed in the element isolation region, and then a sidewall of SiN is formed by anisotropic etching. ) Thereafter, the method for manufacturing a semiconductor device comprises forming an element isolation film by selective oxidation.

That is, according to the present invention, first, the SiN film and the oxide film are removed using a photomask having a specific plane shape on the Si substrate in which the oxide film and the SiN film are sequentially laminated. At this time, element isolation regions and active regions having a shape corresponding to the pattern shape of the photomask are formed. This photomask is composed of a main pattern mask made of rectangular Cr and an auxiliary pattern mask connecting these. The width W ₁ , W of each pattern mask
₂ is 0.3 to 0.6 μm and 0.1 to 0.2 μm, respectively
Is preferred.

Next, according to the present invention, a sidewall made of an oxide film and a SiN film is formed in the element isolation region before forming the element isolation film. At this time, since the photomask having the above-described shape is used, the sidewalls can be made to continuously exist in the bird's beak intrusion direction, whereby bird's beak and pattern shift can be suppressed when forming the element isolation film. Further, since the pattern width W ₂ of the auxiliary pattern mask is sufficiently narrow, the element isolation portion can be formed by laterally penetrating.

[0007]

Embodiments of the present invention will be described in detail below.
The present invention is not limited thereby. First, a thermal oxide film of SiO ₂ is grown on a Si substrate 1 and then a SiN film is formed, and subsequently, as shown in FIG.
Cr having a wide width W ₁ in the longitudinal direction (R direction)
A photomask 14 composed of a pattern mask (main pattern mask) 2 and an auxiliary pattern mask 3 having a width W ₂ narrower than W ₁ is used to etch the SiO ₂ film and the SiN film to form element isolation regions and active regions. To do.

At this time, the width W ₁ of the Cr pattern mask 2 of the photomask 14 used is 0.4 μm, and the width W ₂ of the auxiliary pattern mask 3 is 0.1 μm, which is smaller than the width W ₁ . 2 is a plan view of the element isolation pattern 15 formed by the photomask 14.

Next, the element isolation region is thermally oxidized to SiO ₂
After growing the thermal oxide film, a SiN film is formed, and then anisotropic etching is used to form sidewalls composed of the SiO ₂ film 4a and the SiN film 5a as shown in FIGS. 4, 5 and 6. To do. At this time, the element isolation pattern 1 of FIG.
5, AA ', BB', CC 'and DD'
The views seen from the arrow direction of are shown in FIGS. 3, 4, 5, and 6, respectively. Further, reference numeral 4 represents S remaining after etching.
Reference numeral 5 is an SiO ₂ film, and Si is left after etching.
It is an N film. The surface of the Si substrate 1 in the element isolation region is also exposed by the above etching.

Next, the exposed surface of the Si substrate 1 is oxidized to form an element isolation film 7 of SiO ₂ having a thickness of 300 to 500 nm.
To form. At this time, the oxidized views corresponding to FIGS. 3, 4, 5 and 6 are shown in FIGS. 7, 8, 9 and 10, respectively.
Indicate. 9 and 10, reference numeral 6 is SiO.
It is a sidewall composed of the _two films 4a and the SiN film 5a.

As described above, in the present embodiment, since the photomask having a specific shape is used when the side wall made of the SiO ₂ film and the SiN film is formed in the element isolation region before the element isolation film is formed, The wall can be continuously present in the direction of the bird's beak intrusion,
As a result, bird's beaks and pattern shifts can be suppressed when the element isolation film is formed.

[0012]

As described above, according to the present invention, the sidewall can be continuously present in the element isolation region in the bird's beak intrusion direction by using a specific photomask, and then the element isolation film is formed. Since it is formed, bird's beak invasion and pattern shift can be suppressed.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a photomask used in one step of a manufacturing method in an embodiment of the present invention.

FIG. 2 is a configuration explanatory view showing an element isolation pattern formed by the photomask used in the above-mentioned embodiment.

FIG. 3 is a configuration explanatory view as seen from the direction of arrow AA ′ in FIG.

FIG. 4 is an explanatory view of the configuration as seen from the direction of arrow BB ′ in FIG.

5 is a configuration explanatory view as seen from the direction of arrows CC 'in FIG.

FIG. 6 is a configuration explanatory view as seen from the direction of arrow DD ′ in FIG. 2;

FIG. 7 is a view corresponding to FIG. 3 after the element isolation film is formed in the above-described embodiment.

FIG. 8 is a view corresponding to FIG. 4 after the element isolation film is formed in the above-described embodiment.

FIG. 9 is a view corresponding to FIG. 5 after the formation of an element isolation film in the above-described embodiment.

FIG. 10 is a view corresponding to FIG. 6 after the element isolation film is formed in the above-described embodiment.

FIG. 11 is a structural explanatory view showing a first step of a manufacturing process in a conventional method.

FIG. 12 is a structural explanatory view showing a second step of the manufacturing process in the conventional method.

FIG. 13 is a structural explanatory view showing a third step of the manufacturing process in the conventional method.

FIG. 14 is a structural explanatory view showing the shape of a photomask pattern used in a conventional method.

[Explanation of symbols]

1 Si substrate 2 Cr pattern mask (main pattern mask) 3 Auxiliary pattern mask 4, 4a SiO ₂ film (oxide film) 5 SiN film 5a SiN film sidewall 14 Photomask 15 Element isolation pattern formed by photomask

Claims (1)

[Claims] 1. An oxide film and a SiN film are sequentially laminated on a Si substrate, and (b) an auxiliary pattern mask is connected by this auxiliary pattern mask and has a width wider than the width of the auxiliary pattern mask. Using a photomask composed of a rectangular main pattern mask, the oxide film and the SiN film in the element isolation region where the element isolation film is to be formed are removed, and (c) a new oxide film and SiN film are formed in the element isolation region. A method of manufacturing a semiconductor device, which comprises sequentially forming films, forming sidewalls of SiN by anisotropic etching, and then (d) forming an element isolation film by selective oxidation.