JPH1012734A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a contact hole in an excellent shape by uniformly depositing a protection film on the side wall of the contact hole. SOLUTION: On a semiconductor substrate 51, an infer-layer insulating film 52 is formed of an SiO2 film and on the infer-layer insulating film 52, an Al film and a TIN film are formed in order. After those films are patterned to form Al wiring 53 and a TIN film 54 in specific shapes, an infer-layer insulating film 55 is formed of an SiO2 film over the entire surface. After a resist pattern 56 in a specific shape is formed on the infer-layer insulating film 55, the infer- layer insulating film 55 is etched by a dry etching method by using the resist pattern 56 as a mask to form the contact hole C. A mixed gas of halogen-based gas and gas containing nitrogen atoms is used as etching gas and the infer-layer insulating film 55 is etched while the protection film 57 containing nitrogen atoms is deposited on the side wall of the contact hole C.

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 method suitable for forming a contact hole.

[0002]

2. Description of the Related Art As the integration density of semiconductor integrated circuits increases,
Wiring is becoming finer. Contact holes have also been miniaturized to achieve finer wiring. In order to process a fine contact hole with a high aspect ratio in an anisotropic shape while maintaining the selectivity with the underlying film, various techniques have been attempted in the contact hole processing technology. . Recently, as a contact hole processing technology, the reaction between the film to be processed and the etching gas, the decomposition of the resist, and the recombination of ions and radicals decomposed in the plasma are used to form the contact hole side wall. A method of performing processing while depositing a protective film has become mainstream.

A method of manufacturing a conventional semiconductor device in which an interlayer insulating film is etched while depositing a protective film on the side wall of a contact hole will be described. here,
A case will be described as an example where a contact hole is formed in the interlayer insulating film in order to make contact with an aluminum (Al) wiring under the interlayer insulating film. That is, a first layer of a silicon dioxide (SiO ₂ ) film is formed on a semiconductor substrate such as a silicon (Si) substrate on which a diffusion layer (not shown) and the like are formed according to a normal manufacturing process of a semiconductor device. An interlayer insulating film is formed. Next, an Al film and a titanium nitride (TiN) film as an antireflection film are sequentially formed on the interlayer insulating film, and then these are patterned into a predetermined shape to form an Al wiring. Next, after a second interlayer insulating film made of a SiO ₂ film is formed on the entire surface by a chemical vapor deposition (CVD) method, a resist pattern having a predetermined shape for forming a contact hole is formed on the interlayer insulating film. I do.

Next, using the resist pattern as a mask, the second interlayer insulating film is etched by dry etching. The etching conditions at this time are, for example, CHF ₃ / CF ₄ / Ar = 2 as an etching gas.
Using a mixed gas of 0/40/300 sccm, the reaction pressure is 33.3 Pa, and the high frequency power is 800 W. At this time, the resist pattern used as the etching mask or the carbon electrode attached to the electrode of the dry etching apparatus reacts with the etching gas to form a compound comprising carbon (C), hydrogen (H) and fluorine (F). _{C x H y F z (x} , y, z is an arbitrary number) is generated in the reactor of the dry etching apparatus. Then, while the compound is deposited as a protective film on the side wall of the contact hole formed in the interlayer insulating film, the etching of the interlayer insulating film proceeds. As a result, a contact hole having a protective film formed on a side wall is formed at a predetermined position of the interlayer insulating film. Thereafter, the resist pattern used as the etching mask is removed.

In this conventional method for manufacturing a semiconductor device, the contact hole can be finely processed by forming the protective film on the side wall of the contact hole as described above. Therefore, it is important how to control the deposition of the protective film on the side wall of the contact hole.

[0006]

However, in the above-described conventional method for manufacturing a semiconductor device, the reaction between the resist pattern and the etching gas is involved in the formation of the protective film deposited on the side wall of the contact hole. There is a problem that the state of deposition of the protective film changes depending on the shape and material of the resist pattern. FIG. 6 schematically shows a state when a contact hole actually formed is observed by a scanning electron microscope (SEM). Here, FIG. 6A is a plan view, and FIG. 6B is a sectional view taken along line BB of FIG. 6A. In FIG. 6, reference numeral 101 denotes an Al wiring, and 102 denotes T wiring.
An iN film, 103 is an interlayer insulating film, 104 is a protective film, and C ′ is a contact hole. As shown in FIG.
When the contact hole C ′ is formed by etching the interlayer insulating film 103 by the conventional manufacturing method, it is difficult to optimize the etching conditions because the protective film 104 is not formed uniformly on the side wall of the contact hole C ′. Yes,
As a result, the side wall of the contact hole C ′ has a rough shape. In addition, since the shape of the contact hole C ′ is distorted, there is a problem that the resistance between the wirings at the contact hole C ′ increases, and a problem occurs in an inspection after processing.

Accordingly, it is an object of the present invention to provide a method of manufacturing a semiconductor device capable of forming a contact hole having a good shape by making the deposition of a protective film uniform on the side wall of an opening. is there.

[0008]

According to the present invention, when an opening is formed by selectively etching an insulating film, etching is performed while depositing a protective film on a side wall of the opening. In a method for manufacturing a semiconductor device having a step, a mixed gas of at least a halogen-based gas and a gas containing a nitrogen atom is used for etching.

According to the present invention having the above-described structure, the insulating film is etched with the etching gas containing the gas containing nitrogen atoms, so that the protective film containing nitrogen atoms is uniformly formed on the side wall of the opening. Therefore, the shape of the opening can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, a dry etching apparatus used for forming a contact hole in this embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of this dry etching apparatus. As shown in FIG. 1, in this dry etching apparatus, an upper electrode 2 and a lower electrode 3 are provided in a reactor 1 so as to face each other. The upper electrode 2 has a carbon electrode 4
Is attached. Further, high-frequency power sources 7 and 8 are connected to the upper electrode 2 and the lower electrode 3 via capacitors 5 and 6, respectively. Reference numeral 9 denotes an exhaust port, 10 denotes a gas supply port, and 11 denotes a mass flow controller.

When etching is performed using this dry etching apparatus, a wafer 12 is placed on the lower electrode 3. On this wafer 12, an interlayer insulating film (not shown) is formed as a film to be etched in which a contact hole is formed. Then, after evacuating the inside of the reactor 1 through the exhaust port 9, an etching gas whose flow rate is controlled by the mass flow controller 11 is introduced into the reactor 1 from the gas supply port 10, and the pressure inside the reactor 1 is kept constant. To hold. Then, between the lower electrode 3 and the upper electrode 2, a high frequency is applied by a high frequency power supply 8 to discharge and excite an etching gas, thereby etching the interlayer insulating film on the wafer 12 to form a contact hole. I do. In this dry etching apparatus, when etching the interlayer insulating film on the wafer 12, a high frequency is applied to the carbon electrode 4 attached to the upper electrode 2 by the high frequency power supply 7, and the carbon electrode 4 is etched. As a result, the carbon electrode 4 serves as a source of carbon atoms, and etching of the interlayer insulating film proceeds while depositing a compound containing carbon atoms on the side wall of the contact hole as a protective film.

Next, a method of manufacturing the semiconductor device according to the embodiment will be described. 2 to 4 show a method of manufacturing the semiconductor device according to the embodiment. Here, a case will be described as an example where a contact hole is formed in the interlayer insulating film in order to make contact with the Al wiring under the interlayer insulating film. That is, in this method of manufacturing a semiconductor device, first, as shown in FIG. 2, a semiconductor substrate 51 such as a Si substrate on which a diffusion layer (not shown) and the like are formed according to a normal semiconductor device manufacturing process. A first-layer interlayer insulating film 52 made of a SiO ₂ film is formed by, for example, a CVD method or the like. Next, an Al film and a TiN film as an antireflection film are sequentially formed on the entire surface of the interlayer insulating film 52 by, for example, a sputtering method. Next, after a resist pattern (not shown) having a predetermined shape for forming a wiring is formed on the TiN film by lithography, the TiN film and the Al film are etched using the resist pattern as a mask. Thus, an Al wiring 53 is formed on the interlayer insulating film 52. Reference numeral 54 denotes a TiN film. Next, a second-layer interlayer insulating film 55 made of a SiO ₂ film is formed on the entire surface by, eg, CVD.

Next, as shown in FIG. 3, a resist pattern 56 having a predetermined shape for forming a contact hole is formed on the interlayer insulating film 55 by lithography. Code 56
“a” indicates an opening formed in the resist pattern 56.

Next, as shown in FIG. 4, the interlayer insulating film 55 is etched by a dry etching method using the resist pattern 56 as a mask. For this etching, the dry etching apparatus shown in FIG. 1 is used. Also,
In the etching at this time, a mixed gas of a gas containing at least a halogen-based gas and a nitrogen (N) atom is used as an etching gas. Here, as the halogen-based gas, a fluorine (F) -based gas is preferably used, and typically, a fluorocarbon (C _x F _y , where y ≧ 1) -based gas is used. As the gas containing a nitrogen atom, for example, N ₂ gas is used. In this case, specifically, for example, CHF ₃ / CF ₄ /
Using a mixed gas of Ar / N ₂ = 20/40/300/20 sccm, a reaction pressure of 33.3 Pa and a high frequency power of 8
00W. As a result, a contact hole C is formed in the portion of the interlayer insulating film 55 corresponding to the opening 56a.
At this time, a protective film 57 containing nitrogen atoms is formed on the side wall of the contact hole C as described later.

Thereafter, although not shown, the resist pattern 56 used as an etching mask is removed, an upper Al wiring is formed, and an insulating film is formed so as to cover the Al wiring. A semiconductor device is manufactured.

FIG. 5 schematically shows a state when a contact hole C actually formed in the interlayer insulating film 55 is observed by SEM in this method of manufacturing a semiconductor device. Here, FIG. 5A is a plan view, and FIG. 5B is BB of FIG. 4A.
It is sectional drawing along a line. When FIG. 5 is compared with FIG. 6, in FIG. 6, the protection film 104 is formed unevenly and the shape of the side wall of the contact hole C ′ is rough, whereas in FIG. Is improved and uniform. It can be seen that the shape of the contact hole C is good. Incidentally, the protective film 57 is formed by a resist pattern 56 used as an etching mask or a compound generated by a reaction of the carbon electrode 4 attached to the upper electrode 2 of the dry etching apparatus with an etching gas. It is formed by depositing on the side wall. In this case, since the etching gas used for etching the interlayer insulating film 55 contains N ₂ gas, the generated compound has a composition C _x H _y F _z N containing nitrogen (N) atoms.
_w (x, y, z, and w are arbitrary numbers). Thus, it is considered that the protective film 57 containing nitrogen atoms is uniformly formed on the side wall of the contact hole C.

As described above, according to this embodiment,
When forming the contact hole C in the interlayer insulating film 55,
By etching the interlayer insulating film 55 with an etching gas containing N ₂ gas, a protective film 57 containing nitrogen atoms is formed on the side wall of the contact hole C. Thereby, the protective film 7 can be uniformly deposited on the side wall of the contact hole C, and the shape of the contact hole C can be improved. Further, thereby, the fine contact hole C can be stably processed.

Although one embodiment of the present invention has been specifically described above, the present invention is not limited to the above embodiment, and various modifications based on the technical idea of the present invention are possible. For example, the numerical values, materials, and the like described in the above-described embodiment are merely examples, and the present invention is not limited thereto. In the above-described embodiment, a fluorine-based gas such as SF ₆ gas or NF ₃ gas may be used as the halogen-based gas used for the etching gas. As the gas containing nitrogen atoms used for etching gas, in addition to the N ₂ gas, NH ₃ gas,
NO ₂ gas or N ₂ O gas may be used. In the above-described embodiment, the dry etching device used for forming the contact hole C is merely an example, and another dry etching device may be used.

[0019]

As described above, according to the present invention, by using a mixed gas of at least a halogen-based gas and a gas containing a nitrogen atom for etching, the deposition of the protective film on the side wall of the contact hole can be made uniform. And the shape of the contact hole can be made favorable.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a dry etching apparatus used for forming a contact hole in a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the method for manufacturing a semiconductor device according to one embodiment of the present invention;

FIG. 3 is a cross-sectional view for explaining the method for manufacturing the semiconductor device according to one embodiment of the present invention;

FIG. 4 is a cross-sectional view for explaining the method for manufacturing a semiconductor device according to one embodiment of the present invention;

5A and 5B are a plan view and a sectional view schematically showing the shape of a contact hole formed by the method for manufacturing a semiconductor device according to one embodiment of the present invention;

6A and 6B are a plan view and a sectional view schematically showing the shape of a contact hole formed by a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

51: semiconductor substrate, 52, 55: interlayer insulating film,
53 ... Al wiring, 54 ... TiN film, 56 ...
Resist pattern, 57: protective film, C: contact hole

Claims (5)

[Claims] 1. A method for manufacturing a semiconductor device, comprising the steps of: performing etching while depositing a protective film on a side wall of the opening when forming an opening by selectively etching an insulating film; A method for manufacturing a semiconductor device, comprising using a mixed gas of a system gas and a gas containing a nitrogen atom. _{2. The} gas containing a nitrogen atom is N ₂ gas,
_{2. The} method according to claim 1, wherein the gas is NH ₃ gas, NO ₂ gas, or N ₂ O gas. 3. The method according to claim 1, wherein the halogen-based gas is a fluorine-based gas. 4. The method according to claim 1, wherein the halogen-based gas is a fluorocarbon-based gas. 5. The method according to claim 1, wherein the etching is performed using CHF ₃ gas or CF ₄ gas.
_{2. The} method according to claim 1, wherein a mixed gas of a gas, an Ar gas and a N ₂ gas is used.