JPH06291091A - Dry etching method - Google Patents

Abstract

PURPOSE:To prevent the generation of etching residue while protecting a base film, by etching a natural oxide film or deposit formed on the surface of a crystallized silicon or noncrystal silicon or metal film. CONSTITUTION:A natural oxide film 4 formed on the surface of polycrystalline silicon 3 deposited on a step-difference pattern 2 on a silicon substrate 1 is subjected to first anisotropic etching by using SF6, HCl and CF4. A natural oxide film 4a which can not be eliminated by the first etching is left on the side wall of the step-difference pattern. The polycrystalline silicon 3 is subjected to second etching by using gas system composed of HCl, HBr and O2, and then subjected to third etching under the same condition as the first etching. Since the natural oxide film 4a is exposed by etching the polycrystalline silicon 3, the natural oxide film 4a is easily eliminated by the same gas system. The second etching is finished before an etching base 5 is exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art With the progress of miniaturization of semiconductor devices in recent years, various techniques such as anisotropic etching and high selectivity etching are required in the dry etching process. In particular, when dry-etching polycrystalline silicon or aluminum on a high step, it is necessary to completely etch the natural oxide film formed on the surface or the deposit formed during dry etching. In the etching of polycrystalline silicon, high selectivity etching is performed for a long time by a gas system containing oxygen.

[0003]

However, it is difficult to completely remove a natural oxide film formed on the surface of polycrystalline silicon or aluminum deposited on a high step by anisotropic etching. As a result, problems such as etching residue eventually occurred. Specific examples will be described below with reference to the drawings. 2A to 2D are sectional views showing the order of steps of a conventional dry etching method. Figure 2
In (a) to (d), 1 is a silicon substrate, 2 is a step pattern, 3 is polycrystalline silicon, 4 is a natural oxide film on polycrystalline silicon, 4a is a natural oxide film formed on the silicon substrate side, 5 is a silicon oxide film as an etching base, 6
Indicates a photoresist for forming a pattern.

Conventionally, polycrystalline silicon 3 on a high step pattern 2 formed on a silicon substrate 1 shown in FIG.
As shown in FIG. 2B, after removing the natural oxide film 4 on the surface of the polycrystalline silicon with a gas system containing fluorine as the first step, the polycrystalline silicon 3 is used as a base in the second step. Due to the high selection ratio condition with the silicon oxide film 5,
It was dry-etched. However, as the step becomes larger, the natural oxide film 4 on the side wall of the step shown in FIG.
It became difficult to completely remove it in the step of No. 2 and in the second step, the remaining natural oxide film 4a became a mask of the polycrystalline silicon 3 and could not be etched and remained (FIG. 2C). . Therefore, as one of the solutions, by extending the time of the second step, etching without residue was achieved. However, as the miniaturization of the semiconductor device progresses, the etching base 5 becomes thinner, and the extension of the etching time results in the reduction of the film thickness of the etching base 5 (FIG. 2D). Therefore, excessively lengthening the etching time causes defects and low throughput which are caused by the thinning of the underlying layer by etching. Further, if isotropic etching is performed instead of anisotropic etching in the first step to remove the natural oxide film on the side wall of the step, the side wall direction is significantly etched, and a good shape cannot be obtained.

The present invention solves the above-mentioned conventional problems, and achieves high throughput and protection of a base film when etching a crystallized silicon or amorphous silicon on a high step or a metal film containing at least aluminum. An object of the present invention is to provide a dry etching method which can be performed and can prevent the generation of a residue.

[0006]

To achieve this object, a dry etching method of the present invention comprises a first etching step of dry etching a crystallized silicon or amorphous silicon or a metal film containing at least aluminum, and On the surface of the crystallized silicon or the amorphous silicon or the metal film, a gas containing at least fluorine in the case of the crystallized silicon or the amorphous silicon, and a gas containing at least chlorine in the case of the metal film. A second etching step of etching the formed natural oxide film or a deposit formed by the etching step, and a third etching step of dry etching the crystallized silicon, the amorphous silicon or the metal film again. And the etching step of It is characterized by an etching process before the remaining film of the crystalline silicon or the amorphous silicon or the metal film reaches a thickness that is etched in the second etching step.

[0007]

According to the present invention, according to the method described above, the first etching step of dry etching a crystallized silicon or amorphous silicon or a metal film containing at least aluminum, and then, in the case of the crystallized silicon or the amorphous silicon, Is a gas containing at least fluorine, in the case of the metal film, a gas containing at least chlorine, the crystallized silicon, the amorphous silicon or the natural oxide film formed on the surface of the metal film, or the etching process. A second etching step of etching the generated deposit and a third etching step of dry-etching the crystallized silicon, the amorphous silicon, or the metal film again are performed in the order described above, and the third etching step is performed. The second etching step is performed by using the crystallized silicon or the non-crystallized silicon. By performing the process before the residual film of the crystalline silicon or the metal film reaches the film thickness to be etched in the second etching step, the natural oxide film or the deposit can be removed, and the underlying film can be obtained without lowering the throughput. It is possible to prevent the generation of etching residue while protecting the.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dry etching method according to an embodiment of the present invention will be described below with reference to the drawings together with a conventional example. 1A to 1E are process cross-sectional views of a dry etching method according to an embodiment of the present invention.

1A to 1E, 1 is a silicon substrate,
2 is a step pattern, 3 is polycrystalline silicon, 4 is a natural oxide film on polycrystalline silicon, 4a is a natural oxide film formed on the silicon substrate side, 5 is a silicon oxide film as an etching base, and 6 is a pattern formation Shows a photoresist for. Note that FIG. 1 (a) and FIG. 2 (a), FIG. 1 (b) and FIG.
(B) shows the same state.

First, as shown in FIG. 1A, a natural oxide film 4 is formed on the surface of polycrystalline silicon 3 deposited on a 1 μm step pattern 2 formed on a silicon substrate 1. Next, as shown in FIG. 1B, the natural oxide film 4 is formed with SF6 (20 sccm) and HCl (20 sccc).
m), CF4 (20 sccm), pressure 100 mTorr
Anisotropic etching is performed under the conditions of r and RF power of 350 W. At this time, the natural oxide film 4 which could not be removed by anisotropic etching remains on the sidewall of the step pattern 2.

Next, as shown in FIG. 1 (c), HCl
(20 sccm), HBr (40 sccm), O2 (1
(sccm) gas, and anisotropic etching is performed until the film thickness of the polycrystalline silicon 3 reaches R (nm). Next, as shown in FIG. 1D, the natural oxide film 4 is anisotropically etched under the same conditions as in FIG. At this time,
The natural oxide film 4 which could not be removed in FIG. 1B, particularly the natural oxide film 4a formed on the surface of the crystal grain of the polycrystalline silicon 3 on the side of the silicon substrate 1 is the polycrystalline oxide of FIG. 1C. Since the silicon 3 is exposed by being etched, it can be easily removed by a gas system similar to that shown in FIG. However, in the etching shown in FIG. 1D, before the etching base 5 (normal silicon oxide film) is exposed, specifically, the residual film of the polycrystalline silicon 3; R>
(Etching rate of polycrystalline silicon 3 in FIG. 1 (d))
It has to be performed under the condition that x (etching time) is satisfied. This is because the etching base 5 is etched from the middle of the step of FIG. 1D, causing a defect. As a result of the above, subsequently, the etching step of FIG. 1C is performed again, so that the polycrystalline silicon 3 patterned by the photoresist 6 is maintained in the shape as shown in FIG. 1E. It is possible to prevent generation of etching residue while protecting the etching base 5.

In the case of a metal film containing aluminum, as in the case of polycrystalline silicon, by adding an etching step using a chlorine-based gas in the middle of the etching step of the metal film, a residue is generated while protecting the etching base. Can be prevented.

[0013]

As described above, according to the dry etching method of the present invention, the first etching step of dry etching a crystallized silicon or amorphous silicon or a metal film containing at least aluminum, and then the crystallized silicon or A natural oxide film formed on the surface of the crystallized silicon or the amorphous silicon or the metal film by a gas containing at least fluorine in the case of the amorphous silicon and a gas containing at least chlorine in the case of the metal film. Or a second etching step of etching the deposit generated by the etching step, and a third etching step of dry etching the crystallized silicon, the amorphous silicon or the metal film again. The steps are performed in the order described and the second etching step is performed on the crystal. The natural oxide film or the deposit can be removed by performing before the remaining film of silicon, the amorphous silicon, or the metal film reaches the film thickness to be etched in the second etching step, and the throughput is reduced. It is possible to prevent the occurrence of etching residues while protecting the base film without doing so.

[Brief description of drawings]

FIG. 1 is a process sectional view of a dry etching method according to an embodiment of the present invention.

FIG. 2 is a process sectional view of a conventional dry etching method.

[Description of Reference Signs] 1 semiconductor substrate (silicon substrate) 2 step pattern 3 crystallized silicon (polycrystalline silicon) 4 natural oxide film 4a natural oxide film formed on the silicon substrate side

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Imai 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A first etching step of dry-etching crystalline silicon or amorphous silicon, and then a gas containing at least fluorine is formed on the surface of the crystalline silicon or amorphous silicon. The second etching step of etching the natural oxide film or the deposit generated by the etching step, and the third etching step of dry etching the crystallized silicon or the amorphous silicon again. A dry etching method characterized in that the steps are performed in order. 2. The second etching step according to claim 1,
The dry etching method is performed before the remaining film of the crystallized silicon or the amorphous silicon reaches a film thickness to be etched by the second etching step. 3. A dry etching method according to claim 1, wherein the gas containing at least fluorine is a gas containing sulfur hexafluoride. 4. A fourth etching step of dry-etching a metal film containing at least aluminum, and then a natural oxide film formed on the surface of the metal film by a gas containing at least chlorine, or the etching. A dry etching method comprising: performing a fifth etching step of etching the deposit generated by the step and a sixth etching step of subsequently dry etching the metal film again in the order described above. 5. The fifth etching step according to claim 4,
The dry etching method is performed before the remaining film of the metal film reaches the film thickness to be etched by the fifth etching step. 6. A dry etching method according to claim 4, wherein the gas containing at least chlorine is a gas containing silicon tetrachloride.