KR100281036B1 - Field oxide film manufacturing method - Google Patents

Abstract

The present invention relates to a method of forming a field oxide film, wherein when forming a field oxide film pattern, the pattern film is formed into a three-layer film consisting of an oxide film, a nitride film, and an oxide film, and the nitride film is etched in two steps to form a stepped pattern, thereby forming Budvik. By forming a thin film of the insulating film at the portion to be formed, it is possible to suppress the formation of Budvik at this portion and to reduce the occurrence of dislocation defects.

Description

Field oxide film manufacturing method

1 (a) to (f) are cross-sectional views of a conventional field oxide film production process.

Figure 2 (a) to (h) is a cross-sectional view of the field oxide film production process of the present invention.

<Explanation of symbols for main parts of drawing>

1 semiconductor substrate 2 first insulating film

3: second insulating film 3a, 3b: primary and secondary third insulating film

4: third insulating film 4a: third insulating film pattern

6: photosensitive film pattern 7: field oxide film

8: Chat stop layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for isolating semiconductor cells, and more particularly, to a method of manufacturing a field oxide film suitable for reducing the length of Birds Beak.

1 is a cross-sectional view for explaining a conventional method for forming a field oxide film, which will be described below.

As shown in FIG. 1A, an N-type or P-type semiconductor layer (N-well or P-well) is formed in the tack region of the semiconductor substrate (P-type or N-type) 1, and the first insulating film ( After the oxide film 2 is formed, a second insulating film (nitride film) 3 is formed as shown in (b).

Next, as shown in (c), the photosensitive film 5 is coated on the second insulating film 3, and a predetermined width of the photosensitive film 6 on the upper side of the region where the device is isolated is removed to form a pattern, and then the exposed second second film is exposed. The insulating film 3 is dry-etched and the remaining photosensitive film 5 is removed using an O ₂ plasma.

Then, a second insulating film (3a) a high concentration of boron (B) ion implantation with P ⁺ region in the semiconductor substrate 1 at the bottom of the exposed areas in the pattern formation to isolate the base cell to the cell as shown in (d) Form.

Then, as shown in (e), the semiconductor substrate 1 at the bottom of the exposed region is thermally oxidized to form the field oxide film 7 in the region formed during the patterning of the second insulating film 3a, and the channel at the bottom of the field oxide film 7 is formed. The stop layer 8 is formed.

As shown in (f), after removing the oxide film formed on the upper surface of the second insulating film 3 pattern with hydrofluoric acid (HF), the remaining second insulating film 3a pattern is replaced with phosphoric acid (H ₃ PO ₄ ). To separate the cell from the cell area.

In the conventional cell isolation technology, the thickness of the stress relaxation oxide (buffer or pad oxide) is reduced to reduce the length of Birds Beak to sufficiently secure the active area, thereby thermally expanding the nitride and oxide films during field oxide growth. Dislocation defects are generated from the interface where the nitride film is etched to the semiconductor substrate, and a leakage current is generated, resulting in unstable cell and cell isolation, thereby degrading device characteristics.

The present invention has been proposed to solve the problems of the prior art, by forming a thin nitride film thickness of the site where the bird beak is formed when forming the field oxide film to reduce dislocation defects and to grow Budvik The purpose is to reduce.

DETAILED DESCRIPTION Embodiments of the present invention for achieving the above object will be described in detail with reference to the accompanying drawings.

2 is a cross sectional view of the present technology, in which an N-type or P-type semiconductor layer (N-well or P-well) is formed in a selected region of the semiconductor substrate (P-type or N-type) 1 as shown in (a). After forming the first insulating film (oxide film) 2 on the semiconductor substrate 1, the second insulating film (nitride film 1000-1500 kV) 3 and the third insulating film (CVD oxide film 500-1000 kPa) as shown in (b). (4) are formed in sequence.

Subsequently, as shown in (c), a photosensitive film is coated on the third insulating film 4, the selection area of the photoresist film is removed, and the photosensitive film pattern G is formed to expose the selection area of the third insulating film 4.

Next, the exposed third insulating film 4 and the lower second insulating film 3 are dry etched to form a first patterned second insulating film pattern 3a having a thickness of 500 to 750 되고 after etching. do.

Subsequently, the photoresist pattern 6 is removed, and the photoresist pattern is formed on the third insulating film 4 such that the photoresist pattern is exposed on both sides of the third insulating film from the etching portion of the third insulating film as shown in (d). The third insulating film 4 is removed to form the third insulating film pattern 4a.

Next, as shown in (e), the photoresist film remaining on the third insulation film pattern 4a is removed using oxygen (O ₂ ) plasma, and then the exposed portions of the second insulation film pattern 3a are dry etched to form a stepped film. 2 An insulating layer pattern 3b is formed and a high concentration of boron B is injected into the exposed portion to form the isolation region, thereby forming a P ⁺ region in the semiconductor substrate 1.

Subsequently, as shown in (g), the semiconductor substrate 1 at the lower portion of the exposed region is oxidized to form a field oxide film 7.

At this time, a channel stop layer 8 is formed at the bottom of the field oxide layer 7 to isolate the cell from the cell. Next, as shown in (h), the remaining third insulating film pattern 4b and the second insulating film pattern 3a are removed with hydrofluoric acid (HF) and heated phosphoric acid (H ₃ PO ₄ ).

The present invention prevents leakage due to dislocation defects by mitigating dislocation defects generated during field oxide film formation in a state where a thick nitride film exists at an interface where Budvik is to be formed in the prior art. Therefore, the device characteristics can be improved, and the thin nitride film suppresses the growth of bird beak, thereby forming a field oxide film in a small size.

Claims (4)

Forming a first oxide film, a nitride film, and a second oxide film sequentially on the semiconductor substrate; forming a primary nitride film pattern by etching a selected width only from a surface of the second oxide film to a predetermined depth of the nitride film; and 1 Etching the second oxide film remaining on the upper side of the first nitride film pattern by a predetermined width to form a second oxide film pattern, and an exposed region of the first nitride film pattern using the second oxide film pattern as a mask Forming a stepped secondary nitride film pattern so that the surface of the first oxide film is exposed by etching, implanting impurity ions for channel stop in the exposed oxide film surface, and performing a thermal oxidation process on the injected region A method for producing a field oxide film, comprising the step of forming a field oxide film and a channel stop layer in a surface thereof. The method of claim 1, wherein the remaining film thickness of the first nitride film pattern is 500 to 750 Pa. The method of claim 1, wherein the width of the second etched pattern is re-etched from both sides of the first etched portion at 1000 μs. The method of claim 1, wherein the second oxide film formed on the nitride film is formed to a thickness of 500 to 1000 GPa.