JP2003158194A - Method for manufacturing semiconductor device - Google Patents

Abstract

[PROBLEMS] To provide a method for manufacturing a semiconductor device capable of forming a dual oxide by a simplified process of forming and patterning a protective film such as a photosensitive organic film, and forming an oxide film once. provide. SOLUTION: A semiconductor substrate 1 on which an isolation oxide film 2 is formed.
The photosensitive resin film 3 which is decomposed by oxygen plasma processing is patterned and formed on the upper thin film portion A, and the photosensitive resin film 3 is decomposed and removed by oxygen plasma processing.
Forming an oxide film on the thick film portion B from which the photosensitive resin film has been removed,
After the photosensitive resin film 3 is removed, the oxygen plasma treatment is continued for a certain time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device such as an IC or LSI, and more particularly, to a surface of a semiconductor substrate, a surface of a film made of various materials formed on the semiconductor substrate, or an insulating substrate. In a semiconductor device in which the surface of the formed semiconductor film is oxidized and the oxide film is used as a part of a semiconductor element, the thickness of the oxide film is different.
The present invention relates to a method of manufacturing a semiconductor device having so-called dual oxide formation, which is formed to have various kinds of thickness.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices, the operating voltage of semiconductor devices must be lowered. On the other hand, in order to maintain the interface with the external peripheral device, the semiconductor element of the peripheral circuit section which takes charge of the interface with the external device must still be designed to have a high operating voltage. In many current semiconductor devices, a semiconductor element that operates at a low operating voltage and a semiconductor element that operates at a high voltage are formed on the same substrate to make two types of semiconductor elements compatible. In this case, for example, in a MOS transistor, the gate oxide film is formed to have a thick portion and a thin portion.

FIG. 2 is a sectional view showing a conventional oxide film forming step of forming oxide films of two different thicknesses (dual oxide formation) on a semiconductor substrate. In the figure, 1 is a silicon (Si) substrate, 2 is an isolation oxide film, 3 is a photosensitive organic film, 5 is a buffer oxide film, 6 is a nitride film, 7a and 7b are intermediate films of a thick oxide film, and 7c is a thin oxide film. A film, 7d is a thick oxide film, A is a thin film portion where a thin oxide film is formed, B is a thick film portion where a thick oxide film is formed, and an internal circuit is formed in the thin film portion A. An external circuit that serves as an interface with the outside is formed in the thick film portion B.

First, as shown in FIG. 2A, a buffer oxide film 5 having a predetermined thickness is formed on the Si substrate 1 having the isolation oxide film 2 formed thereon by a method such as a thermal oxidation method. The buffer oxide film 5 is prepared for the formation of the nitride film 6 in the next step.

Next, the nitride film 6 and the photosensitive organic film 3 are sequentially formed on the buffer oxide film 5, and the photosensitive organic film 3 in the thick film portion B is formed.
Is removed by a photolithography technique to pattern the photosensitive organic film 3, and the nitride film 6 is removed by a dry etching technique using the patterned photosensitive organic film 3 as an etching mask (FIG. 2B).

Next, the photosensitive organic film 3 is removed by oxygen (O ₂ ) plasma treatment, and the buffer oxide film 5 in the thick film portion B is removed by a chemical solution such as hydrofluoric acid (HF), and then heat is applied again. A first oxide film 7a is formed on the thick film portion B by an oxidation method or the like (FIG. 2C). At this time, the nitride film 6 functions as an oxidation mask, and the buffer oxide film 7a in the thin film portion A does not change.

Next, the nitride film 6 is formed by a chemical solution such as hot phosphoric acid.
And then the buffer oxide film 5 of the thin film portion A is removed by a chemical solution such as HF (FIG. 2D). At this time, the first oxide film 7a of the thick film portion B is also etched at the same time, but the second oxide film 7b is left without being completely removed. In order to leave the second oxide film 7b, the first thick film portion B
The oxide film 7a must be formed thicker than the buffer oxide film 5.

Finally, the entire surface of the Si substrate 1 is oxidized by the thermal oxidation method or the like to form a thin oxide film 7c and a thick oxide film 7d which is thicker than the second oxide film 7b.

[0009]

As described above, the conventional method for forming a dual oxide comprises forming a buffer oxide film, forming a nitride film, patterning a photosensitive organic film, and etching using the photosensitive organic film as a mask. Complex processes such as patterning of the nitride film, removal of the buffer oxide film, first oxide film formation, removal of the nitride film and the buffer oxide film below the nitride film, and second oxide film formation are required. There was a problem of becoming.

The present invention solves the above-mentioned problems, and a dual oxide is formed by a simplified process of forming and patterning a protective film such as a photosensitive organic film and forming an oxide film by a single treatment. The present invention provides a method for manufacturing a semiconductor device capable of forming a semiconductor.

[0011]

A method of manufacturing a semiconductor device according to the present invention comprises a surface of a semiconductor substrate, a surface of a film formed on the semiconductor substrate, or a surface of a semiconductor film formed on an insulating substrate. In a method of manufacturing a semiconductor device in which oxide films having different thicknesses are formed by oxidation treatment, a protective film decomposed by the oxidation treatment is formed on the surface of the semiconductor substrate, the surface of the film formed on the semiconductor substrate, or the insulating substrate. A step of forming a film on the surface of the semiconductor film formed on the substrate, a step of removing the protective film in a region where a thick oxide film is formed and leaving the protective film in a region where a thin oxide film is formed, An oxide film is formed in a region in which a thick oxide film is formed while decomposing the protective film in a region in which a thin oxide film is formed, and even after the protective film in the region in which the thin oxide film is formed is decomposed and removed. Those having a step of oxidizing the entire surface of a region to form regions and thin oxide film to form a thick oxide film continues the oxidation predetermined time.

Further, the protective film is a photosensitive organic film containing a photosensitive organic material.

Further, the oxidation treatment is an oxygen plasma treatment.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, an oxide film having a different thickness is formed on a surface of a semiconductor substrate, a surface of a film formed on a semiconductor substrate, or a surface of a semiconductor film formed on an insulating substrate by an oxidation treatment. A method of manufacturing a semiconductor device in which a so-called dual oxide is formed, in which the surface of a semiconductor substrate, the surface of a film formed on the semiconductor substrate, or the surface of a semiconductor film formed on an insulating substrate is decomposed by an oxidation treatment. A protective film is formed, the protective film in the region where a thick oxide film is formed is removed, leaving the protective film in the region where a thin oxide film is formed, and the protective film in the region where a thin oxide film is formed is decomposed by oxidation treatment. Then, the oxidation treatment is performed while removing the oxidation treatment, and the oxidation treatment is continued for a certain time even after the protective film is completely decomposed and removed.

An oxide film is formed at the same time as the oxidation process in the region where the protective film is removed to form a thick oxide film, and even after the protective film in the region where a thin oxide film is formed is completely decomposed and removed. An oxide film is continuously formed, and in a region where a thin oxide film is formed, where the protective film remains, the protective film is completely decomposed and removed and then starts to be oxidized. A film is formed, and a thin oxide film is formed in a region where the thin oxide film is formed.

FIG. 1 is a sectional view showing an embodiment in a manufacturing process of a semiconductor device according to the present invention. In the figure, 1 is a semiconductor substrate made of silicon or the like, 2 is an isolation oxide film for element isolation, 3 is a photosensitive organic film (protective film), 4a is a thick oxide intermediate film, 4b is a thin oxide film, and 4c is A thick oxide film, A is a thin film portion where a thin oxide film is formed, B is a thick film portion where a thick oxide film is formed, and a thin film portion A
An internal circuit is formed in the thick film portion B, and an external circuit serving as an interface with the outside is formed in the thick film portion B.

First, as shown in FIG. 1A, an isolation oxide film 2 is formed on a semiconductor substrate 1. Although not shown here, a predetermined impurity is implanted into the surface of the semiconductor substrate 1 for the purpose of forming a channel of a MOS transistor or forming a diffusion layer as a lower electrode of a MOS capacitor depending on the type of element to be formed.

Next, as shown in FIG. 1B, by a photolithography technique of forming a photosensitive resin film on the entire surface of the semiconductor substrate 1, exposing pattern transfer, and developing for removing unnecessary portions with a chemical solution. Then, the pattern of the photosensitive resin film 3 is left on the thin film portion A, and the photosensitive resin film on the thick film portion B is removed.
The above-described impurity implantation into the surface of the semiconductor substrate 1 may be performed at this stage.

Next, oxygen plasma treatment is carried out. The oxygen plasma processing apparatus is an apparatus that introduces oxygen gas under reduced pressure, applies microwaves, radio waves, etc. from the outside, converts the oxygen gas into plasma to generate oxygen radicals and ozone, and oxidizes the sample surface. In particular, the oxidation treatment can be performed at a low temperature, and the organic matter can be decomposed and effectively removed.

By performing the oxygen plasma treatment, the surface of the semiconductor substrate 1 in the region B where a thick oxide film is formed is oxidized, and the photosensitive resin film 3 in the thin film portion A is decomposed and removed. As shown in FIG. 1C, the oxide film 4a having a predetermined thickness is formed in the region B where the thick oxide film is formed.

The film thickness of the photosensitive resin film 3 decreases with the lapse of time in the oxygen plasma treatment, and is finally completely removed. During this time, the photosensitive resin film 3 functions as a protective film,
An oxide film is prevented from being formed on the thin film portion A, and accurate patterning can be performed by the photolithography technique.

Furthermore, by continuing the oxygen plasma treatment for a certain period of time even after the photosensitive resin film 3 is removed,
As shown in FIG. 1D, an oxide film 4b having a predetermined thickness is formed on the thin film portion A, and a thick oxide film 4c is formed on the thick film portion B.

As described above, the photosensitive resin film 3 is reduced in thickness by the oxygen plasma treatment and is prevented from being oxidized in the thin film portion A until it is removed. The thickness of the oxide film formed on the thin film portion A is reduced.

In order to adjust the thickness of the oxide film 4c of the thick film portion B and the oxide film 4b of the thin film portion A, the initial film thickness of the photosensitive resin film 3 is adjusted. Further, the ratio of the removal rate of the photosensitive resin film 3 by the oxygen plasma treatment and the oxidation rate of the semiconductor substrate 1 depends on the plasma generation method of the oxygen plasma treatment apparatus, the sample temperature, etc. In order to achieve a desired value, it is necessary to optimize the oxygen plasma treatment method as well as adjusting the initial film thickness of the photosensitive resin film 3.

According to the embodiment shown in FIG. 1, the dual oxide is formed by the simple steps of forming and patterning the photosensitive resin film 3 as a protective film and oxygen plasma treatment as oxidation treatment. Can be formed.

Further, although the case where the protective film is the photosensitive resin film 3 and the oxidation treatment is the oxygen plasma treatment is shown as one embodiment, the thickness of the protective film decreases with the lapse of the treatment time due to the oxidation treatment. However, if it is removed,
In addition to oxygen plasma treatment, various methods such as thermal oxidation and anodic oxidation can be used for the oxidation treatment.

Further, the case where dual oxide is formed on the surface of the semiconductor substrate 1 is shown as one embodiment.
The method of manufacturing a semiconductor device for forming a dual oxide according to the present invention is applicable to a case where a dual oxide is formed on a film surface of a semiconductor or the like formed on the semiconductor substrate 1 or a semiconductor film surface formed on an insulating substrate such as a glass substrate. The same method can be applied to.

[0028]

According to the method of manufacturing a semiconductor device of the present invention, the surface of a semiconductor substrate, the surface of a film formed on the semiconductor substrate, or the surface of a semiconductor film formed on an insulating substrate is oxidized. In the method of manufacturing a semiconductor device in which oxide films having different thicknesses are formed, a protective film that decomposes by the oxidation treatment is formed on the surface of the semiconductor substrate, the surface of the film formed on the semiconductor substrate, or the insulating substrate. A step of forming a film on the surface of the formed semiconductor film, a step of removing the protective film in a region where a thick oxide film is formed and leaving the protective film in a region where a thin oxide film is formed, An oxide film is formed in a region in which a thick oxide film is formed while decomposing the protective film in a region in which a film is formed, and the oxidation treatment is performed even after the protective film in a region in which the thin oxide film is formed is decomposed and removed. Since it is provided with a step of oxidizing the entire surface of a region where a thick oxide film is formed and a region where a thin oxide film is formed for a certain period of time, an oxide film having a different thickness is formed by a simplified process. can do.

Further, since the protective film is a photosensitive organic film made of a photosensitive organic material, the protective film can be accurately patterned.

Further, since the oxidation treatment is an oxygen plasma treatment, the oxidation treatment can be performed at a low temperature.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a process in a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a step in a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

1 semiconductor substrate, 2 isolation oxide film, 3 photosensitive organic film,
4a thick intermediate oxide film, 4b thin oxide film, 4c
Thick oxide film, A thin film part, B thick film part.

Claims (3)

[Claims] 1. A semiconductor device in which an oxide film having a different thickness is formed on a surface of a semiconductor substrate, a surface of a film formed on the semiconductor substrate, or a surface of a semiconductor film formed on an insulating substrate by an oxidation treatment. In the manufacturing method, a step of forming a protective film that decomposes by the oxidation treatment on the surface of the semiconductor substrate, the surface of the film formed on the semiconductor substrate, or the surface of the semiconductor film formed on an insulating substrate, thick oxidation A step of removing the protective film in the region where the thin film is to be formed and leaving the protective film in the region where the thin oxide film is to be formed; A region for forming a thick oxide film by forming an oxide film in a region for forming a film and continuing the oxidation treatment for a certain time even after the protective film in the region for forming the thin oxide film is decomposed and removed. And a step of oxidizing the entire surface of a region where a thin oxide film is formed, a method of manufacturing a semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the protective film is a photosensitive organic film containing a photosensitive organic material. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the oxidation treatment is oxygen plasma treatment.