JP2725695B2 - Method for manufacturing semiconductor device - Google Patents

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 for dry-etching a composite film of a polycrystalline silicon film and a metal silicide film, that is, a so-called polycide film.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device, as a material for a gate electrode and its wiring, polycrystalline silicon capable of forming a transistor having stable characteristics has been used. However, as semiconductor devices are miniaturized, it is required to reduce the resistance of gates and wiring materials. Therefore, the sheet resistance is lower by one digit than that of polycrystalline silicon, and the polycrystalline silicon gate and There is a tendency to use a polycide film that can form a transistor having similar stable characteristics.

[0003] In recent years, the miniaturization of semiconductor integrated circuit devices has been further advanced, and as a result, the polycide film and the oxide film serving as a base film thereof have also been reduced in thickness, resulting in high precision and high selection. There is a demand for an etching method having a property.

As a conventional polycide etching technique,
For example, a method described in Japanese Patent Application No. 4-126798 is known.

Here, a conventional polycide etching method will be outlined with reference to FIG.

First, a polycrystalline silicon film 703 and a tungsten silicide film 704 are sequentially laminated on a silicon oxide film 702 formed on a silicon substrate 701, and a photoresist 705 is applied on the tungsten silicide film 704. To form a processed substrate (FIG. 7A).

[0007] The tungsten silicide film 704 is etched by using a mixed gas of sulfur hexafluoride (SF ₆ ) and hydrogen bromide (HBr) by using a general dry etching apparatus such as a parallel plate type RIE. I do. Subsequently, the polycrystalline silicon film 703 is etched with a mixed gas of chlorine (Cl ₂ ) and HBr,
A gate electrode having a polycide structure is formed (FIG. 7)
(B)).

[0008]

However, in the above-described etching method, the gate width is reduced and the polycide film is made thinner.
If the polycrystalline silicon film is Angstrom and the polycrystalline silicon film is 1000 Angstrom, there is a problem that the silicon substrate itself is etched.

Referring to FIG. 8, first, at the stage where etching of metal silicide film 801 (for example, tungsten silicide film 704) is completed, polycrystalline silicon film 703 is already etched in a portion having a large opening area. (FIG. 8A). That is, in etching with a gas containing fluorine, such as SF ₆ , the etching rate of the polycrystalline silicon film 703 is twice or more the etching rate of the metal silicide film. Fluorine is supplied, and as a result, the polycrystalline silicon film 703 is etched in a portion having a large opening area.

As described above, after etching the metal silicide film, the polycrystalline silicon film 703 is etched by Cl ₂ and HBr, but fluorine of SF ₆ used for etching the metal silicide film remains. Therefore, the residual fluorine (fluorine atom 802) contributes to the etching of the polycrystalline silicon film 703.

The etching rate is particularly high in a portion having a large opening area. Therefore, as shown in FIG. 8B, not only the polycrystalline silicon film 703 and the silicon oxide film 702 are etched, but also in the worst case. Has a problem that the silicon substrate 701 is etched.

In order to prevent the above problems,
After the metal silicide film is etched, residual fluorine is removed, and a gas containing no fluorine is used for etching the metal silicide film.

When removing residual fluorine, generally, after etching the metal silicide film, the inside of the chamber is evacuated. However, this method has a problem that it takes a lot of time to remove fluorine until the silicon substrate is not etched so that productivity is impaired.

On the other hand, a method described in Japanese Patent Application Laid-Open No. 4-105321 is known as a method of using a gas containing no fluorine when etching a metal silicide film. Here, a method of etching the metal silicide film with Cl ₂ and O ₂ is described. In this method, since O ₂ is used as an etching gas, FIG.
As shown in (1), there is a problem that an oxide film-based reaction product 803 is hardly removed on the side wall after etching.

In addition, as a method of using a gas containing no fluorine when etching a metal silicide film, a method described in Japanese Patent Application Laid-Open No. 5-136102 is known. Here, the metal silicide film is etched only by carbon monoxide (CO).
There is a problem that the etching rate is low and the productivity is low.

An object of the present invention is to provide a method of manufacturing a semiconductor device in which a silicon substrate is not etched particularly in dry etching of a polycide film.

[0017]

According to the present invention, there is provided a first step of forming a polycide film comprising a polycrystalline silicon film and a metal silicide film on a semiconductor substrate, and selectively masking the polycide film on the polycide film. A second step of forming a material, and a third step of introducing a mixed gas containing sulfur hexafluoride and hydrogen bromide into the chamber, setting the mixed gas in a plasma state, and dry-etching the metal silicide film to form an etching substrate.
And a fourth step of processing the etching substrate by evacuating the chamber and then introducing a CO gas into the chamber to make the CO gas a plasma state. A method is obtained.

That is, after the metal silicide film is etched using a gas containing fluorine such as SF _{6 and the} like, when fluorine is to be efficiently removed, fluorine may be chemically adsorbed and exhausted. Therefore, in the present invention, after the metal silicide film is etched, vacuum evacuation is performed, and subsequently, plasma is generated using a CO gas. By this, 2F + CO →
The chemical reaction of COF ₂ enables fluorine to be removed more efficiently than vacuum evacuation.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining an example of a method for manufacturing a semiconductor device according to the present invention. Referring to FIG. 1, first, as shown in FIG. 1A, a silicon oxide film 102 is formed on a silicon substrate 101, which is a semiconductor substrate, and then a polycrystalline silicon film 103 having a thickness of 1000 Å is formed. A 1000 angstrom thick tungsten silicide film 104 is formed. Then, after a photoresist 105 is applied on the tungsten silicide film 104, a pattern is formed using a lithography technique to obtain a processing substrate.

Next, the processing substrate is subjected to an etching process using a dry etching apparatus shown in FIG.

Referring to FIG. 2, the illustrated dry etching apparatus includes a chamber 201 and a gas supply mechanism 201a for supplying an etching gas into the chamber 201. The upper electrode 2 is opposed to each other in the chamber 201.
02 and the lower electrode 203 are disposed, and the lower electrode 2
03 is the RF power supply 20 via the matching box 204.
5 (RF frequency 13.56 MHz) is connected.
Then, the processing substrate 206 described above is mounted on the lower electrode 203.

Here, referring to FIGS. 1 and 2, SF ₆ is applied at ₆₀ sc using the dry etching apparatus shown in FIG.
cm, HBr 80 sccm, pressure (in-chamber pressure) 0.04 Torr, RF power density 1.1 W /
cm ² and the tungsten silicide film 104 is etched (FIG. 1B: tungsten silicide film 1).
The substrate after etching the substrate 04 is called an etching substrate.)

Next, after evacuation is performed for 30 seconds, CO is introduced into the chamber 201. And CO is 400
Discharge is performed for 30 seconds at a sccm, a pressure of 0.1 Torr and an RF power density of 1.1 W / cm ² .

Finally, Cl ₂ is 30 sccm, HBr is 30 sccm, O ₂ is 4 sccm, and the pressure is 0.1 Torr.
r, the RF power density is set to 0.82 W / cm ² , and the polycrystalline silicon 103 is etched (FIG. 1C).

As a result, a gate electrode in which the silicon substrate 101 was not etched and the silicon oxide film 102 was maintained was completed.

FIG. 3 shows the state of the silicon substrate and the remaining silicon oxide film when the discharge time by CO is changed. FIG. 4 shows the state of the silicon substrate and the silicon when the flow rate of CO is changed. The remaining oxide film is shown. Further, FIG. 5 shows the state of the silicon substrate and the remaining silicon oxide film when the pressure (in-chamber pressure) is changed.

As can be easily understood from the results shown in FIGS. 3 to 5, CO is 300 sccm or more and the pressure is 0.1 Torr.
When etching is performed under the condition of not more than r and discharge time of 30 seconds or more, not only etching of the silicon substrate can be prevented, but also the silicon oxide film can be maintained.

Further, when a high frequency such as a microwave is used when discharging by CO, CO is separated from C and O, and as a result, the photoresist which is a mask is ashed by O (oxygen atom). In some cases.

According to the evaluation of the inventor, the RF frequency was 27.12M.
It was confirmed that CO was dissociated into C and O at a very high rate even at a discharge at Hz. Therefore, when performing discharge by CO, it is desirable to perform at an RF frequency of 13.56 MHz or less.

FIG. 6 is a view for explaining another example of the semiconductor manufacturing method according to the present invention. Referring to FIG. 6, first, as shown in FIG. 6A, a Ti film 602 and a TiN film are formed on a silicon oxide film 601 by a sputtering technique.
Film 603, Al—Si—Cu film 604, and TiN film 6
05 are sequentially formed.

Then, after a photoresist 606 is applied on the TiN film 605, a pattern is formed using a lithography technique to obtain a processing substrate.

Subsequently, using the photoresist 606 as a mask, the dry etching apparatus shown in FIG.
TiN film 605 by using the _2, BCl ₃ or the like gas, Al-
The Si-Cu film 604, the TiN film 603, and the Ti film 602 are etched to form a metal wiring (first metal wiring: the first metal wiring is a TiN film 605, an Al-Si-Cu film 604,
an iN film 603 and a Ti film 602).

After removing the photoresist 606, FIG.
As shown in (b), after forming a silicon oxide film 607, a photoresist 60 is formed on the silicon oxide film 607.
8 is applied, and a pattern is formed using a lithography technique.

Thereafter, via holes are formed again using the dry etching apparatus shown in FIG.

For example, as the first stage etching, C
The F ₄ 20 sccm, a CHF ₃ 40 sccm, 0.05 Torr pressure, RF power density 8.77W / cm
^Second , the silicon oxide film 607 is etched.

Next, in the second stage etching, SF
₆ at 20 sccm, CF ₄ at 40 sccm, pressure at 0.
2 Torr, RF power density is 3.3 W / cm ² ,
Etching of the TiN film 605 is performed to form the via holes 6.
09 is formed.

Next, after evacuation is performed for 30 seconds, CO is introduced into the chamber 201 (FIG. 2). And CO
At a pressure of 0.1 Torr and an RF power density of 1.1 W / cm ² for 30 seconds.

Subsequently, after removing the photoresist 608, a second metal wiring 610 is formed in the same manner as in the above-described method of forming the first metal wiring.

By the way, metal wiring (Al-Si-Cu)
It is known that when fluorine remains on the surface, poor adhesion between metal wirings and the like occurs, which causes a reduction in the reliability of the wirings.

In the present invention, the Al—Si—Cu film 60 is formed by SF ₆ used for etching the TiN film 605.
The fluorine remaining on the surface of No. 4 is removed by the discharge with the CO gas, and as a result, the reliability of the metal wiring can be improved.

[0042]

As described above, according to the present invention, there is an effect that etching of a silicon substrate can be prevented in a method of manufacturing a semiconductor device, in particular, in dry etching of a polycide film.

Further, there is an effect that the reliability of the metal wiring can be improved when forming the via hole which is a conduction hole between the metal wirings.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a method for manufacturing a semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a dry etching apparatus used in the method for manufacturing a semiconductor device according to the present invention.

FIG. 3 illustrates a method of manufacturing the semiconductor device shown in FIG.
FIG. 4 is a diagram illustrating a relationship between a discharge time due to O gas and a state of a silicon substrate.

FIG. 4 is a cross-sectional view of the method of manufacturing the semiconductor device shown in FIG.
FIG. 4 is a diagram showing a relationship between an O gas flow rate and a state of a silicon substrate.

FIG. 5 is a cross-sectional view of the method of manufacturing the semiconductor device shown in FIG.
FIG. 4 is a diagram showing a relationship between a pressure condition of discharge by O gas and a state of a silicon substrate.

FIG. 6 is a drawing for explaining another example of the method for manufacturing a semiconductor device according to the present invention.

FIG. 7 is a cross-sectional view for explaining a conventional method for manufacturing a semiconductor device.

FIG. 8 is a cross-sectional view for explaining a cause of etching a silicon substrate in a conventional method of manufacturing a semiconductor device.

FIG. 9 is a cross-sectional view for describing a problem that occurs in a conventional method of manufacturing a semiconductor device.

[Explanation of symbols]

 101,701 Silicon substrate 102,601,607,702 Silicon oxide film 103,703 Polycrystalline silicon film 104,704 Tungsten silicide film 105,606,608,705 Photoresist 201 Chamber 202 Upper electrode 203 Lower electrode 204 Matching box 205 RF Power supply 602 Ti film 603, 605 TiN film 604 Al-Si-Cu film 609 Via hole

Claims (8)

(57) [Claims] A first step of forming a polycide film composed of a polycrystalline silicon film and a metal silicide film on a semiconductor substrate; and a second step of selectively forming a mask material on the polycide film. A third step of introducing a mixed gas containing sulfur hexafluoride and hydrogen bromide into the chamber, making the mixed gas into a plasma state, dry-etching the metal silicide film to form an etching substrate, and evacuating the chamber. And then introducing a CO gas into the chamber and treating the etching substrate with the CO gas in a plasma state. 2. The method of manufacturing a semiconductor device according to claim 1, wherein when the CO gas is brought into a plasma state,
A method of manufacturing a semiconductor device, wherein a flow rate of the CO gas is 300 sccm or more. 3. The method of manufacturing a semiconductor device according to claim 1, wherein when the CO gas is brought into a plasma state, the pressure of the CO gas is 0.1 Torr or less. Manufacturing method. 4. The method of manufacturing a semiconductor device according to claim 1, further comprising a fifth step of etching said polycrystalline silicon film following said fourth step. Production method. 5. The method of manufacturing a semiconductor device according to claim 4, wherein in the fifth step, chlorine, hydrogen bromide,
And a mixed gas containing oxygen and oxygen, and etching the polycrystalline silicon film with the mixed gas in a plasma state. 6. The method of manufacturing a semiconductor device according to claim 1, wherein said mask material is a photoresist film. 7. The method for manufacturing a semiconductor device according to claim 1, wherein the frequency of the RF power supply used to bring the CO gas into a plasma state is 13.56.
MHz or less. 8. A first step of forming a first metal wiring on a first insulating film, and forming a second insulating film on the first metal wiring and then forming the first metal wiring on the first metal wiring. A second step of forming a hole to be reached in the second insulating film to obtain an etching substrate, a third step of treating the etching substrate with a CO gas in a plasma state, and conducting with the first metal wiring. And a fourth step of forming a second metal wiring.