JPH05206263A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a semiconductor device in which an element isolation for causing no bird's beak can be formed without complicated steps even at a wide or narrow element isolation region selectively. CONSTITUTION:After a silicon nitride film 3 is deposited on a patterned semiconductor substrate 1, it is etched back to obtain a structure in which its silicon nitride film 5a remains as a sidewall on a wide element active region and its silicon nitride film 5 remains uniformly on a narrow element active region. Then, locos oxidation is executed to form a LOCOS oxide film only on the wide element active region. Then, the remaining silicon nitride film is removed, the exposed substrate is etched to selectively form a groove, and the groove is filled in with the oxide film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing method. More specifically, the present invention relates to a device isolation forming method.

[0002]

2. Description of the Related Art FIG. 2 is a diagram for explaining a conventional method over time. First, the thermal oxide film 20 is formed on the silicon substrate 10, and the silicon nitride film 30 is sequentially formed on the thermal oxide film 20 [FIG. 3 (a)].

Next, the element isolation region P ₁₀ is patterned [FIG. 3 (b)]. Then, the locos oxide film 40 is formed by oxidizing at a high temperature [FIG. 3 (c)].

[0004]

However, as described above, in the conventional method, since the so-called bird's beak occurs, which is the so-called bird's beak, which penetrates into the active region of the locos oxide film 40, the effective active region is reduced and miniaturization is hindered. There was a problem that became. Therefore, for example, even if an improved Locos method such as OSELD is used, bird's beak occurs as long as Locos oxidation is performed, and therefore the above-mentioned problem still remains.

On the other hand, as a structure without a bird's beak, a method of etching silicon to bury an oxide film, that is, a so-called trench method has been proposed, but burying a vast region causes a problem that the process becomes complicated. ing.

The present invention has been made to solve the above problems, and it does not require complicated steps even in a wide area of an element isolation region and does not cause bird's beaks in a narrow area. It is an object of the present invention to provide a method for manufacturing a semiconductor device which can be formed separately and which can be easily manufactured separately.

[0007]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention includes a method of forming a first oxide film on a semiconductor substrate and then forming the first oxide film on the first oxide film. After forming a first silicon nitride film and then forming a second oxide film on the first silicon nitride film, the first silicon nitride film and the second oxide film immediately above the substrate to be the element isolation regions. To expose the first oxide film, and then deposit a second silicon nitride film of a predetermined thickness on the exposed first oxide film and the remaining second oxide film. By etching back until the second oxide film is exposed, the second silicon nitride film remains as a sidewall in the wide element isolation region, and the second silicon nitride film in the narrow element isolation region. Remain, then , Locos oxidation, then the second
The semiconductor substrate exposed by removing the silicon nitride film is etched to a predetermined depth to form a groove, and then the third oxide film is embedded in the groove.

[0008]

After the second silicon nitride film is deposited and etched back, the second silicon nitride film is formed as a sidewall in the wide element isolation region and the second silicon nitride film is uniformly formed in the narrow element isolation region. To obtain a structure in which the silicon nitride film is left. Therefore, next, by performing locos oxidation, the locos oxide film is formed only in the wide element isolation region. After that, by etching the exposed substrate by removing the remaining second silicon nitride film, a groove is selectively formed, and by filling the groove with an oxide film, even in a wide element isolation region, Even in a narrow element isolation region, element isolation is performed at the same time.

[0009]

Embodiments FIGS. 1 and 2 are views for explaining an embodiment of the present invention with time. 1 below, it demonstrates based on drawing. First, the thermal oxide film 2 is formed on the silicon substrate 1 to a thickness of 100 to 300Å. After that, after forming the silicon nitride film 3 on the thermal oxide film 2 to a thickness of 1000 to 2000Å,
The CVD oxide film 4 is formed to a thickness of 2000 to 4000 Å [FIG. 1 (a)].

Next, the CVD oxide film 4 and the silicon nitride film 3 are formed by photolithography and etching.
Are removed and patterning is performed to form patterns P ₁ and P ₂ . Pattern P ₁ and pattern P
₂ has a wide element isolation region and a narrow one. In this embodiment, the width of the pattern P ₂ is 0.2 to 0.6.
μm. [FIG.1 (b)].

Next, a silicon nitride film 5 is formed by the CVD method on the substrate in which the element isolation region is formed, 2000 to 400.
Form to a thickness of 0Å. The film thickness at this time can be freely changed by changing the width of the pattern P ₂ [FIG. 1 (c)].

Next, the silicon nitride film 5 is formed by the RIE method.
To etch back. In this step, the sidewalls 5a having a width of 0.2 to 0.4 μm are formed in the wide element isolation region, while the sidewalls are not formed in the narrow element isolation region, and the silicon nitride film 5 remains buried. Maintain [Fig. 1 (d)].

Next, wet oxidation is carried out under the temperature condition of 950 to 1100 ° C., so that 30
The locos oxide film 2a having a thickness of 00 to 5000Å is formed, while the locos oxide film is not formed in the narrow element isolation region [FIG. 2 (a)].

Next, the sidewall 5 is formed by the RIE method.
The silicon substrate 1 is exposed by removing a and the embedded silicon nitride film 5 [FIG. 2 (b)].
Further, by the RIE method, the width of the narrow element isolation region is the width, and the width of the sidewall 5a is the wide element isolation region,
A trench type groove is formed by etching the exposed silicon substrate 1 by 0.3 to 0.5 μm [FIG.
(C)].

Next, the thermal oxide film 2 and the silicon nitride film 3 on the silicon substrate 1 are removed by hydrofluoric acid and hot phosphoric acid treatment. Then, a CVD oxide film 6 such as an NSG film or a BPSG film is formed on the exposed silicon substrate 1 and locos oxide film 2a to a thickness of 4000 to 6000Å [FIG. 2 (d)].

Finally, the silicon substrate 1 is formed by the RIE method.
The desired final shape is obtained by performing etch back until the film is exposed [FIG. 2 (e)].

[0017]

As described above, according to the present invention, a fine trench type groove is formed around the locos oxide film in the wide element isolation region, while a trench type groove is formed in the narrow element isolation region. With this configuration, bird's beaks do not occur in the periphery of the element isolation region and the fine element isolation region, and miniaturization can be promoted. Moreover, since the wide element isolation region and the narrow element isolation region are separately formed using the side wall,
It can be easily formed without going through complicated steps such as adding a mask.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention over time.

FIG. 2 is a diagram illustrating an embodiment of the present invention over time.

FIG. 3 is a diagram illustrating a conventional example.

[Explanation of symbols]

1 ... Silicon substrate 2 ... Thermal oxide film 3, 5 ... Silicon nitride film 4, 6 ... CVD oxide film 2a ... Locos oxide film 5a ... Sidewall P ₁ , P ₂ ... ・ Pattern

Claims (1)

[Claims] 1. A first oxide film is formed on a semiconductor substrate, a first silicon nitride film is formed on the first oxide film, and then a second silicon nitride film is formed on the first silicon nitride film. After the oxide film is formed, the first silicon nitride film and the second oxide film immediately above the substrate to be the element isolation region are removed to expose the first oxide film, and then the exposed first oxide film is removed. After depositing a second silicon nitride film having a predetermined thickness on the oxide film and the remaining second oxide film, etching back is performed until the second oxide film is exposed. The second silicon nitride film is left as a wall and the narrow element isolation region is
After leaving the second silicon nitride film, and then performing locos oxidation, the semiconductor substrate exposed by removing the second silicon nitride film is etched to a predetermined depth to form a groove, After that, a third oxide film is embedded in the groove, which is a method of manufacturing a semiconductor device.