JP3323264B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to a method of manufacturing a semiconductor equipment forming a Cu wiring having a low resistance.

[0002]

2. Description of the Related Art An example of a manufacturing method for forming a wiring layer mainly made of copper on a semiconductor substrate using a conventional technique will be described with reference to FIGS. 4 (a) to 4 (e). I do. In addition,
In this description, a transistor forming step is omitted for simplification. First, as shown in FIG. 4A, an insulating film 2 made of a silicon oxide film is formed on a silicon substrate 1 by a CVD method so as to be electrically and physically separated from a wiring layer. Next, a Ti film 3 is formed on the insulating film 2 by sputtering.
A TiN film 4 and a Cu film 5 are deposited. The thicknesses of the Ti film 3, TiN film 4, and Cu film 5 are 200 ° and 1000 °, respectively.
5000 $.

[0005] Next, as shown in FIG. 4 (b), a wiring pattern is formed on the Cu film 5 by a photoresist film 7 having a thickness of 1.5 μm. Next, to improve heat resistance,
Ultraviolet ray irradiation and hard baking at 260 ° C. are performed. Thereafter, as shown in FIG.
By a reactive ion etching method using l ₄ and N ₂ , a portion of Cu not covered with the photoresist film 7
The film 5, the TiN film 4, and the Ti film 3 are removed. The temperature of the silicon substrate 1 at the time of etching is 270 ° C.

Subsequently, as shown in FIG. 4D, the photoresist film 7 used as an etching mask is removed by oxygen ashing. Finally, to protect the patterned wiring, a PSG film 9 and a plasma nitride film 10 are formed as shown in FIG.

[0005]

When a copper wiring is formed using such a conventional manufacturing method, first, when the photoresist film 7 used as an etching mask is removed by oxygen ashing, FIG. 2), the surface of the Cu film 5 is oxidized by oxygen plasma, and a Cu ₂ O or CuO film which is a copper oxide film 13 is formed on the Cu film surface and side walls. For example, a 500 ° Cu film is oxidized only by ashing at a temperature of 200 ° C. for 5 minutes. When the Cu film thickness is sufficiently large and the wiring width is sufficiently large, the decrease in the effective cross-sectional area of the wiring due to oxidation does not significantly affect the increase in the wiring resistance. When the wiring width is as thin as 0.5 μm, both sides of the wiring are oxidized, so that the wiring width is reduced by 20%. Since the effective area is reduced by about 30%, the wiring resistance is about 1.
5 times. Therefore, the effect of using a low-resistance Cu film having a specific resistance of about two-thirds of that of Al for the wiring is completely lost. Since the wiring resistance increases as the wiring width becomes narrower, it cannot be used for fine wiring.

Further, the adhesion between oxide film 13 and PSG film 9 on the surface and side wall of oxidized Cu film 5 is poor.
Therefore, as shown in FIG.
The floating 14 of the PSG film 9 formed on the u film 5 occurs, and further, the film peels off, which is a very serious problem in reliability. Also, the same problem occurs when a plasma oxide film is formed as interlayer insulation of a multilayer wiring,
It could not be used for multilayer wiring.

The present invention solves the above problems,
Cu that prevents oxidation of the Cu film surface and has good adhesion of the protective film
And to provide a method of manufacturing a semiconductor equipment which it is possible to form a wiring.

[0008]

According to the present invention, there is provided a semiconductor device comprising :
The manufacturing method includes a step of forming an insulating film on the semiconductor substrate,
A first refractory metal film and a copper film and a second refractory metal film on the insulating film;
Forming a conductive film by sequentially depositing a point metal film;
Forming a wiring pattern with a photoresist on the conductive film
Process and using a photoresist as a mask to form a conductive film of NH ₃
Etching with etching gas composed of silicon and silicon compound
And forming a wiring layer by covering the wiring layer with a protective film.
And a step of

[0009]

According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: forming an insulating film on a semiconductor substrate; and forming a conductive film by sequentially depositing a refractory metal film and a copper film on the insulating film. Immersing a copper film in a water or alcohol solution containing benzotriazole, forming a chelate compound film on the copper film, forming a wiring pattern with a photoresist on the chelate compound film, and masking the photoresist Forming a wiring layer by etching the chelate compound film and the conductive film with an etching gas comprising NH ₃ and a silicon compound; and covering the wiring layer with a protective film.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein an insulating film is formed on a semiconductor substrate, and a first high melting point metal film, a copper film, and a second high melting point metal film are sequentially formed on the insulating film. A step of forming a deposited conductive film, a step of forming a film without oxygen as a constituent element on the conductive film, a step of forming a wiring pattern with a film without oxygen as a constituent element, and a step of forming oxygen as a constituent element The method includes a step of forming a wiring layer by etching the conductive film with an etching gas containing NH ₃ and a silicon compound using a film that is not used as a mask, and a step of covering the wiring layer with a protective film.

The silicon compound is SiCl ₄ , SiH ₂
It is made of any one of Cl ₂ , SiHCl ₃ and SiH ₄ .

[0013]

According to the structure of the present invention, since the second refractory metal film or the chelate compound film is formed on the surface of the copper film, the photoresist film is etched using the mask, and then the photoresist film is removed by oxygen ashing. At this time, oxidation of the copper film surface can be prevented. Further, since etching is performed using an etching gas composed of NH ₃ and a silicon compound, a nitride film is formed on the side wall of the copper film at the time of etching, so that oxidation of the side wall of the copper film when removing the photoresist film can be prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A method of forming a wiring layer mainly composed of Cu on a semiconductor substrate using a technique for preventing a film formed on a Cu film from oxidizing the Cu film will be described as an example. This will be described with reference to the cross-sectional views in the order of steps shown in FIGS. Note that in this description, a transistor formation step is omitted for simplicity.

First, as shown in FIG. 1 (a), a silicon oxide film is formed on a silicon substrate 1 by a CVD method in order to electrically and physically separate it from a wiring layer at a position other than a predetermined position. An insulating film 2 is formed. A Ti film 3, a TiN film 4, a Cu film 5, and a TiN film 6 are deposited on the insulating film 2 by a sputtering method to form a conductive film. Ti film 3, T
The thicknesses of the iN film 4, the Cu film 5, and the TiN film 6 are 200, 1000, 5000, and 1000, respectively. The Ti film 3 and the TiN film 4 form a first refractory metal film, and the TiN film 6 forms a second refractory metal film.
The TiN film 4 and the TiN film 6 are formed by sputtering in a mixed gas obtained by adding N ₂ to Ar.

Next, as shown in FIG. 1 (b), in order to form a wiring at a predetermined position, a photoresist film 7 having a thickness of 1.5 .mu.m is applied, and then exposed, and the photoresist in an unexposed portion is exposed. The film is removed with a developer to form a wiring pattern. Thereafter, in order to improve heat resistance, irradiation with ultraviolet rays is performed, followed by baking at 250 ° C. for 15 minutes. Next, as shown in FIG. 1 (c), using the photoresist film 7 as an etching mask,
₄ , reactive ion etching (RIE) using N ₂ , Cl ₂ and NH ₃ , the TiN film 6, Cu film 5, Ti
The N film 4 and the Ti film 3 are removed. For the etching, a single-wafer-processed cathode-coupling parallel plate type RIE apparatus in which a high frequency of 13.56 MHz is applied to a cathode electrode is used. The temperature of the silicon substrate 1 at the time of etching is 270 ° C.
The pressure during etching is 3 Pa. SiCl ₄ ,
The flow rates of N ₂ , Cl ₂ and NH ₃ are each 100 SCC
M, 30 SCCM, 10 SCCM, and 20 SCCM. Since SiCl ₄ and NH ₃ are used as the etching gas, the SiN-based nitride film 8 is formed on the side wall of the Cu film 5 as the etching proceeds. The thickness of the nitride film 8 is from several tens to several
00 °.

Thereafter, as shown in FIG. 1D, the photoresist film 7 is removed by oxygen ashing. Finally,
As shown in FIG. 1 (e), a PSG containing 4 wt% of P is formed by APCVD to protect the patterned wiring.
After depositing the film 9 at a thickness of 1000 プ ラ ズ マ, a plasma nitride film 10 having a thickness of 9000 に よ り is formed by a plasma CVD method.

According to the semiconductor device and the method of manufacturing the same, the surface of the Cu film 5 is covered with the TiN film 6 and the side wall of the Cu film 5 is covered with the nitride film 8. Oxidation of the Cu film 5 by oxygen plasma when removing the film 7 can be prevented. Although two layers of the Ti film 3 and the TiN film 4 are used as the first refractory metal film below the Cu film 5 and the TiN film 6 is used as the second refractory metal film above the Cu film 5. , W film or TiW
A high melting point metal such as a film may be used for the lower layer and the upper layer of the Cu film 5. Further, in order to improve characteristics such as heat resistance without significantly lowering the resistivity of the Cu film 5, a Cu film to which an impurity such as Ag of 0.01% is added may be used.

Although SiCl ₄ is used as a silicon compound, SiH ₂ Cl is used by optimizing etching conditions.
₂ , SiHCl ₃ or SiH ₄ may be used as an etching gas. Second Embodiment FIG. 2 (A) shows an example of a manufacturing method in which a protective layer formed on a Cu film uses a technique for preventing oxidation of the Cu film and a wiring layer mainly composed of Cu is formed on a semiconductor substrate. A description will be given with reference to sectional views in the order of steps a) to (f). Note that in this description, a transistor formation step is omitted for simplicity.

First, as shown in FIG. 2A, a silicon oxide film is formed on a silicon substrate 1 by a CVD method so as to be electrically and physically separated from a wiring layer at a position other than a predetermined position. An insulating film 2 is formed. A Ti film 3, a TiN film 4, and a Cu film 5 are deposited on the insulating film 2 by a sputtering method to form a conductive film. The thicknesses of the Ti film 3, TiN film 4 and Cu film 5 are 200, 1000 and 5, respectively.
000. A refractory metal film is formed by the Ti film 3 and the TiN film 4. Further, the TiN film 4 is formed by sputtering in a mixed gas obtained by adding N ₂ to Ar.

Next, as shown in FIG. 2 (b), alcohol and benzotriazole were mixed at a ratio of 1: 1 at 30.degree.
The silicon substrate 1 is immersed in the above solution for 1 minute to form a chelate compound film 11 having a thickness of 500 ° on the surface of the Cu film.
Thereafter, as shown in FIG. 2 (c), in order to form a wiring at a predetermined position, a photoresist film 7 having a thickness of 1.5 μm is applied, and then exposed, and an unexposed portion is removed with a developing solution.
A wiring pattern is formed. Thereafter, in order to improve heat resistance, irradiation with ultraviolet rays is performed, followed by baking at 250 ° C. for 15 minutes.

Next, as shown in FIG.
Etching using the strike film 7 as an etching mask
SiCl for gas_Four, N_Two, Cl_TwoAnd NH_ThreeUsing
The reactive ion etching (RIE) method
Chelate compound of the part not covered with the photoresist film 7
The object film 11, the Cu film 5, the TiN film 4, and the Ti film 3 are removed.
I do. 13.56 MHz for cathode electrode for etching
Single-wafer processing cathode coupling with high frequency applied
A flat plate type RIE apparatus is used. Silicon base during etching
The temperature of the plate 1 was 270 ° C., and the pressure during etching was 3 Pa.
is there. SiCl _Four, N_Two, Cl_TwoAnd NH_ThreeThe flow rate of
100 SCCM, 30 SCCM, 10 SCCM, 20 SCCM respectively
It is. SiCl for etching gas_FourAnd NH_ThreeFor
The side of the Cu film 5 with the progress of etching.
A SiN-based nitride film 8 is formed on the wall. Thickness of nitride film 8
The length is several tens to several hundreds degrees.

Thereafter, as shown in FIG. 2E, the photoresist film 7 is removed by oxygen ashing. Finally,
As shown in FIG. 2 (f), a PSG containing 4 wt% of P is formed by APCVD to protect the patterned wiring.
After depositing the film 9 at a thickness of 1000 プ ラ ズ マ, a plasma nitride film 10 having a thickness of 9000 に よ り is formed by a plasma CVD method.

According to the semiconductor device and the method of manufacturing the same, the surface of the Cu film 5 is covered with the chelate compound film 11 and the side wall of the Cu film 5 is covered with the nitride film 8. Therefore, it is possible to prevent the Cu film 5 from being oxidized by the oxygen plasma when the photoresist film 7 is removed. Although two layers of the Ti film 3 and the TiN film 4 are used as the first refractory metal film below the Cu film 5, a refractory metal such as a W film or a TiW film is used as the lower layer of the Cu film 5. You may. Further, in order to improve characteristics such as heat resistance without significantly lowering the resistivity of the Cu film 5, a Cu film to which an impurity such as Ag of 0.01% is added may be used.

Although SiCl ₄ is used as a silicon compound, SiH ₂ Cl is used by optimizing etching conditions.
₂ , SiHCl ₃ or SiH ₄ may be used as an etching gas. Further, when forming the chelate compound film 11, the semiconductor substrate 1 may be immersed in water containing benzotriazole.

Third Embodiment A two-layer film formed on an upper layer of a Cu film is used as a mask for preventing oxidation of the Cu film and etching the Cu film. FIG. 3 shows an example of a manufacturing method in which a wiring layer mainly composed of Cu is formed thereon.
This will be described with reference to the cross-sectional views in the order of steps (a) to (g). Note that in this description, a transistor formation step is omitted for simplicity.

First, as shown in FIG. 3A, a silicon oxide film is formed on a silicon substrate 1 by a CVD method in order to electrically and physically separate the wiring layer from a wiring layer other than at a predetermined position. An insulating film 2 is formed. A Ti film 3, a TiN film 4, a Cu film 5, and a TiN film 6 are deposited on the insulating film 2 by a sputtering method to form a conductive film. Ti film 3, T
The thicknesses of the iN film 4, the Cu film 5, and the TiN film 6 are 200, 1000, 5000, and 1000, respectively. A first refractory metal film is formed by the Ti film 3 and the TiN film 4, and a second refractory metal film is formed by the TiN film 6.
The TiN film 4 and the TiN film 6 are formed by sputtering in a mixed gas obtained by adding N ₂ to Ar.

Next, as shown in FIG.
A film having a thickness of 0.5 μm as a film not containing oxygen as a main element.
m of plasma nitride film 12 is deposited. The reaction gas includes S
iH _Four, NH_ThreeUse The temperature during deposition is 300 ° C
It is. Then, as shown in FIG.
1.5 μm thick photoresist for forming wiring
The film 7 is exposed, unexposed portions are removed with a developing solution, and the wiring pattern is removed.
Form a turn.

Next, as shown in FIG. 3D, using the photoresist film 7 as an etching mask, the plasma nitride film 12 is etched by a dry etching method using CHF ₃ and O ₂ as an etching gas. Then, FIG.
As shown in (e), the photoresist film 7 is removed by oxygen ashing.

Subsequently, as shown in FIG. 3F, reactive ion etching (RIE) using the plasma nitride film 12 as an etching mask and using SiCl ₄ , N ₂ , Cl ₂ and NH ₃ as etching gases. ) By law
The portions of the TiN film 6, Cu film 5, TiN film 4 and Ti film 3 not covered with the plasma nitride film 12 are removed.
For etching, a single-wafer-processed cathode-coupling parallel plate type RIE apparatus in which a high frequency of 13.56 MHz is applied to a cathode electrode is used. The temperature of the silicon substrate 1 during the etching is 270 ° C., and the pressure during the etching is 3 Pa.
The flow rates of SiCl ₄ , N ₂ , Cl ₂ and NH ₃ are 100 SCCM, 30 SCCM, 10 SCCM and 20 SCCM, respectively. Since SiCl ₄ and NH ₃ are used as the etching gas, the SiN-based nitride film 8 is formed on the side wall of the Cu film 5 as the etching proceeds. The thickness of the nitride film 8 is several tens to several hundreds degrees.

Finally, as shown in FIG. 3 (g), in order to protect the patterned wiring, 4 wt.
After depositing the PSG film 9 containing 1000% of P by 1000 .ANG., A plasma nitride film 10 having a thickness of 9000 .degree. According to the semiconductor device thus configured and the method of manufacturing the same, the surface of the Cu film 5 is
Therefore, when the photoresist film 7 is removed, the Cu film 5 can be prevented from being oxidized by oxygen plasma.

Further, using the photoresist film 7 as a mask, Cu
Since the film 5 is not etched, irradiation with ultraviolet rays for improving heat resistance and hard baking at 260 ° C. are not required. Therefore, the influence of dimensional conversion due to contraction, expansion or deformation of the photoresist film 7 due to hard baking can be avoided, and a fine pattern can be easily formed.

The Ti film 3 and the TiN film 4 are used as the first refractory metal film below the Cu film 5 and the TiN film 6 is used as the second refractory metal film above the Cu film 5. However, a refractory metal such as a W film or a TiW film may be used for the lower layer and the upper layer of the Cu film 5. Further, in order to improve characteristics such as heat resistance without significantly lowering the resistivity of the Cu film 5, a Cu film to which an impurity such as Ag of 0.01% is added may be used.

Although SiCl ₄ was used as the silicon compound, optimization of the etching conditions resulted in SiH ₂ Cl
₂ , SiHCl ₃ or SiH ₄ may be used as an etching gas.

[0035]

Effects of the Invention] According to the manufacturing method of the semiconductor equipment of the present invention, since the copper film was formed on the surface of the second refractory metal film or a chelating compound film, after etching the photoresist film as a mask, oxygen ashing Accordingly, when the photoresist film is removed, oxidation of the copper film surface can be prevented. Also, N
Since the etching by an etching gas composed of H ₃ and a silicon compound, a nitride film is formed on the sidewalls of the copper film during etching, thereby preventing oxidation of the copper film side wall for removing the photoresist film. Therefore, an increase in specific resistance due to oxidation can be prevented, and a semiconductor device having a low-resistance Cu wiring with good adhesion to the PSG film and excellent corrosion resistance can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a procedure of a manufacturing process when a low-resistance Cu wiring is formed using a first embodiment.

FIG. 2 is a cross-sectional view showing a procedure of a manufacturing process when a low-resistance Cu wiring is formed using the second embodiment.

FIG. 3 is a cross-sectional view showing a procedure of a manufacturing process when a low-resistance Cu wiring is formed using the third embodiment.

FIG. 4 is a cross-sectional view showing a procedure of a manufacturing process of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 insulating film 3 Ti film 4 TiN film 5 Cu film 6 TiN film 7 photoresist film 8 nitride film 9 PSG film 10 plasma nitride film 11 chelate compound film 12 plasma nitride film

Claims (4)

(57) [Claims] (1) Forming an insulating film on the semiconductor substrate; forming a conductive film by sequentially depositing a first high melting point metal film, a copper film, and a second high melting point metal film on the insulating film; Forming a wiring pattern on the conductive film with a photoresist, forming the wiring layer by etching the conductive film with an etching gas containing NH ₃ and a silicon compound using the photoresist as a mask,
Covering the wiring layer with a protective film. 2. A step of forming an insulating film on a semiconductor substrate, a step of forming a conductive film formed by sequentially depositing a refractory metal film and a copper film on the insulating film, Immersing the copper film in an alcohol solution to form a chelate compound film on the copper film; forming a wiring pattern on the chelate compound film with a photoresist; and forming the chelate using the photoresist as a mask. A method of manufacturing a semiconductor device, comprising: a step of forming a wiring layer by etching a compound film and the conductive film with an etching gas containing NH ₃ and a silicon compound; and a step of covering the wiring layer with a protective film. 3. A step of forming an insulating film on a semiconductor substrate, and forming a conductive film formed by sequentially depositing a first refractory metal film, a copper film, and a second refractory metal film on the insulating film. Forming a film on the conductive film that does not include oxygen, forming a wiring pattern using the film that does not include oxygen, and masking the film that does not include oxygen. Forming a wiring layer by etching the conductive film with an etching gas composed of NH ₃ and a silicon compound; and covering the wiring layer with a protective film. 4. The method according to claim 1, wherein the silicon compound is SiCl ₄ , SiH
₂ Cl _2, SiHCl _3, or the method of manufacturing the semiconductor device according to claim 1, wherein a substance of SiH _4.