JP3112832B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a wiring layer for patterning a laminated film including an aluminum alloy film and a titanium nitride film by plasma etching.

[0002]

2. Description of the Related Art Along with the high integration of semiconductor devices, the necessity of fine and high-precision wiring processing technology has been further increased. As an etching method for forming an aluminum-based wiring layer, a method using a resist film as an etching mask is widely used. However, the resist film has an etching rate selectivity to aluminum (Al /
PR selectivity) is not sufficient, and high-precision etching has become difficult with the miniaturization of wiring. Therefore, an etching method using a silicon oxide film as an etching mask has been proposed (JP-A-7-183298).
When a silicon oxide film is used as an etching mask, the selectivity to aluminum (Al / SiO ₂ selectivity) can be made larger than that when a resist film is used, which is effective for fine and highly accurate wiring processing. JP-A-7-183
In the etching using a silicon oxide film mask disclosed in Japanese Patent Publication No. 298, etching is performed using chlorine gas alone as an etching gas.

[0003]

Problems to be Solved by the Invention
In the technique disclosed in Japanese Patent Application Laid-Open No. 8 (1999) -86, chlorine gas alone is used as an etching gas. However, in etching using chlorine gas alone, shape control is very difficult, and side etching occurs in the wiring layer. FIG. 6 shows this state. FIG. 6A shows a state before etching.
A thermal oxide film 2 is formed to a thickness of 500 nm on a silicon substrate 1,
Further, the thickness of the Al—Si—Cu alloy film 3 for wiring is 900 nm.
Sputtered, thickness 300 as etching mask
The silicon oxide film 4 of nm is patterned. FIG. 6B shows a shape when etching is performed using chlorine gas alone as an etching gas, and side etching 5 occurs in the wiring layer 3a. This is because aluminum easily reacts with chlorine and the reaction product, aluminum chloride, is highly volatile. When a resist film is used as an etching mask, a decomposition product of the resist is re-adhered to the etched aluminum film side wall to form a protective film that suppresses side etching. However, when silicon oxide is used as an etching mask, Since a protective film is not formed by a reaction product accompanying such etching, severe side etching occurs. This side etching significantly lowers the reliability of the wiring layer.

In the case where a wiring layer is formed of a laminated film containing an aluminum alloy film and a titanium nitride film, an etching residue is generated when the titanium nitride film is etched by using chlorine gas alone simultaneously with aluminum. Occurs. This is shown in FIG. FIG. 7A shows a state before etching, in which a thermal oxide film 2 is formed on the silicon substrate 1 to a thickness of 500 nm, and subsequently, an Al-
Si-Cu alloy film 3-1 (500 nm) and TiN film 3
-2 (100 nm) are sequentially formed, and a 300 nm-thick silicon oxide film 4 is patterned as an etching mask. The shape when etching is performed using chlorine gas alone as an etching gas is shown continuously. FIG. 7B shows a shape of the upper TiN film 3-1 in the middle of etching. Asperities 6 are formed on the surface of the TiN film.
FIG. 7C shows the shape of the Al-Si-Cu film 3-1 during etching. The unevenness generated during the etching of the TiN film 3-2 serves as a micromask, and the columnar projection 7 is formed. FIG. 7D shows the shape after wiring etching. The state of FIG. 7C is directly reflected, and the etching residue 7 is reflected.
a has occurred. When the titanium nitride film is etched using chlorine gas alone, surface roughness (irregularities) occurs on the titanium nitride surface along with aluminum side etching, and the irregularities cause etching residues.
The degree of this surface unevenness becomes more remarkable as the titanium nitride film becomes thicker. The generation of an etching residue causes a problem of a short circuit between wirings.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress side etching and suppress the generation of etching residues when patterning a laminated film including an aluminum alloy film and a titanium nitride film, and to form a highly reliable fine wiring layer. An object of the present invention is to provide a method for manufacturing a device.

[0006]

According to a method of manufacturing a semiconductor device of the present invention, after a laminated film including an aluminum alloy film and a titanium nitride film is deposited on a first insulating film on a semiconductor substrate, a second insulating film is formed. Forming a film, patterning and then removing a resist film used for the patterning; and forming a wiring layer by patterning the laminated film by plasma etching using the patterned second insulating film as a mask. In the manufacturing method, BCl ₃ gas and C
The patterning of the laminated film is performed using an etching gas obtained by adding an N ₂ gas to a mixed gas of a l ₂ gas. Furthermore, it is preferable that the mixing ratio to the sum of the Cl ₂ gas and the BCl ₃ gas of the BCl ₃ gas in the etching gas at least 15%.

Further, BCl ₃ gas and BCl ₃ gas and Cl
_It is preferable that the mixing ratio with respect to the sum of the _two gases is 70% or less.

Further, etching can be performed using a parallel plate type high frequency plasma etching apparatus.

The second insulating film is preferably a silicon oxide film.

[0010] By adding a reducing etching gas to the Cl ₂ gas, the etching of the TiN film is facilitated and the surface roughness is suppressed.

Further, by adding N ₂ , aluminum nitride is re-adhered to the side wall to form a protective film.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an etching apparatus used for etching will be described. As the etching apparatus, a reactive ion etching (RIE) apparatus (parallel plate type high frequency plasma etching apparatus) shown in FIG. 4 was used.
The semiconductor wafer 100 is fixed to a wafer stage 101, and the etching container 103 is sufficiently evacuated from the exhaust port 102 to a vacuum. After the exhaust, an etching gas is supplied from the gas inlet 104, and the pressure is adjusted to a set value. afterwards,
13.56 MHz high frequency power from the RF power source 105
The wafer is supplied to the wafer stage 101 via the blocking capacitor 106 to generate plasma in the container 103 and perform etching.

Next, a first embodiment of the present invention will be described.

First, as shown in FIG. 1A, a thermal oxide film 2 is formed on a silicon substrate 1 to a thickness of 500 nm. After that, using a sputtering method, the titanium film is 100 nm and the TiN film is 30 nm.
0 nm sequentially to form a barrier film 8,
l-Si-Cu alloy film 3-1A (Si / 1%, Cu /
0.5%) is formed to a thickness of 900 nm. Next, plasma CVD
A silicon oxide film 9 is formed to a thickness of 300 nm by a method. Further, a resist film pattern 10 having a thickness of 1 μm is formed by photolithography. Next, resist film pattern 1
After etching the silicon oxide film 9 using 0 as an etching mask, the resist film pattern 10 is removed by ashing, thereby forming the silicon oxide film mask 4 (FIG. 1B). Next, Al-Si-Cu / Ti
The N / Ti three-layer film is etched using the silicon oxide film mask 4.

That is, the flow rates of the BCl ₃ gas, Cl ₂ gas and N ₂ gas are 15 SCCM and 60 SCCM, respectively.
And 10 SCCM, the pressure in the etching vessel was 0.13
By performing etching while adjusting the Pa and RF power to 150 W, as shown in FIG.
A wiring layer composed of a laminated film of the Cu alloy film 3-1Aa and the barrier film 8a is formed. A wiring layer having vertical side surfaces without side etching was able to be formed without generation of etching residues.

FIG. 2 shows a TiN film formed of BCl ₃ gas and Cl ₂ gas.
Surface roughness Rmax when plasma etching is performed using a gas mixture (maximum height in mechanical engineering)
4 is a graph showing the relationship between and BCl ₃ content. The horizontal axis is BCl ₃ / (BCl ₃ + Cl ₂₎ mixing ratio (mixing ratio to the sum of BCl ₃ gas and Cl ₂ gas BCl ₃ gas. Forth.). This graph shows a 500 nm thick Ti
This is data obtained when the entire surface of the N film is etched by about 300 nm. The pressure in the etching container was 0.13 Pa, and the RF power was 150 W.

The surface roughness Rmax is BCl ₃ (BCl ₃ +
Cl ₂ ) decreases with increasing mixing ratio. Accordingly, it is presumed that, when patterning the TiN film, the residue can be eliminated by performing the etching by setting the mixture ratio to a certain level or more. In fact, BCl ₃ /
By setting the (BCl ₃ + Cl ₂ ) mixture ratio to 15% or more, it was confirmed that a wiring layer can be formed without generating a residue. The surface roughness of the TiN film after etching tends to increase as the etching proceeds. TiN
The film is used for improving the anti-reflection film or barrier film or the resistance to stress migration when forming the wiring layer. However, it is not preferable to make the film too thick because of low electric conductivity. Therefore, FIG. 2 can be considered as the upper limit of the surface roughness as a guide when forming the fine wiring layer. That is, it is considered that the generation of the residue can be sufficiently suppressed by setting the mixture ratio of BCl ₃ / (BCl ₃ + Cl ₂ ) to 15% or more. On the other hand, even if the mixing ratio is 70% or more, the surface roughness does not decrease and the etching speed of aluminum decreases. Therefore, the mixing ratio is 15% or more,
It is good to make it 0% or less. In addition, BCl ₃ gas and Cl ₂
The addition of N ₂ gas to the gas has little effect on surface roughness.

FIG. 3 shows a 500 nm thick Al-Si-Cu
When the film is etched using a silicon oxide film mask (width 0.4 μm), the side etch depth d and N ₂ / (BC
13 is a graph showing the relationship of (l ₃ + Cl ₂ + N ₂ ) mixing ratio. However, the mixture ratio of BCl ₃ / (BCl ₃ + Cl ₂ ) is 20% (the flow rates of BCl ₃ gas and Cl ₂ gas are 15 SCCM and 60 SCCM, respectively), and the pressure in the etching vessel is about 0.1 Pa.

It can be seen that side etching occurs up to a N ₂ / (BCl ₃ + Cl ₂ + N ₂ ) mixing ratio of 5%. Therefore, N ₂ /
The mixing ratio of (BCl ₃ + Cl ₂ + N ₂ ) may be 5% or more. As the N ₂ / (BCl ₃ + Cl ₂ + N ₂ ) mixture ratio is further increased, the wiring has a conversely tapered cross section. The wiring layer having a tapered cross section is not necessarily excluded, but it cannot be denied that the processing dimensional accuracy is reduced. Therefore, the upper limit of the mixing ratio may be appropriately determined in consideration of the allowable value of the dimensional accuracy. For example, when the width of the wiring layer is 0.4 μm, it is appropriate to set the upper limit to 50%.

The reason why the cross-sectional shape of the wiring layer can be controlled by adding the N ₂ gas is that aluminum nitride is formed during the etching of the Al—Si—Cu alloy film and the aluminum film is re-adhered to form a protective film. It is considered that it is done. This protective film may be removed in the same manner as the silicon oxide film mask, but is not necessary. This is because it is considered that there is also an action of preventing the wiring layer from reacting with moisture or the like in the subsequent steps.

Incidentally, Japanese Patent Application Laid-Open No. 3-12087 discloses that
TiN using a mixed gas of BCl ₃ gas and Cl ₂ gas
It states that the film can be etched. This is a technique for forming a wiring layer using a photoresist film pattern as a mask, and does not describe controlling the cross-sectional shape of the wiring layer by adding N ₂ gas. Further, there is no description about the relationship between the mixture ratio of BCl ₃ / (BCl ₃ + Cl ₂ ) and the surface roughness. Also, JP-A-63-
Japanese Patent No. 289935 discloses that a TiN film can be etched with a mixed gas of BCl ₃ gas, SiCl ₄ gas and Cl ₂ gas. However, there is no description about controlling the cross-sectional shape or controlling the surface roughness. Absent.

Next, a second embodiment of the present invention will be described with reference to FIG.

First, a thermal oxide film 2 having a thickness of 500 nm is formed on a silicon substrate 1 as shown in FIG. Thereafter, a 500 nm thick Al-Si-Cu alloy film 3-1B and a 100 nm thick TiN film 3-2A are formed by sputtering. Next, the silicon oxide film 9 is
It is formed to a thickness of 00 nm. Further, a resist film pattern 10 having a thickness of 1 μm is formed by photolithography. Next, the silicon oxide film 9 is etched using the resist film pattern 10 as an etching mask, and the resist film pattern 10 is removed by ashing, thereby forming the silicon oxide film mask 4 (FIG. 5B). Next, the TiN / Al-Si-Cu two-layer film is etched using the silicon oxide film mask 4. A mixed gas of BCl ₃ / Cl ₂ / N ₂ is used as an etching gas, and gas flow rates of BCl ₃ , Cl ₂ and N ₂ are 20, 60 and 1, respectively.
5 SCCM. Etching is performed at a reaction pressure of 20 Pa and RF power of 150 W using the etching apparatus shown in FIG. FIG. 5C shows the shape of the upper TiN film during etching. The surface of the TiN film 3-24a is smooth. FIG. 5D shows the shape after wiring etching. Neither side etching nor etching residue is generated, and a wiring layer (two-layer film of the TiN film 3-2Ab and the Al-Si-Cu alloy film 3-1ba) having a good etching shape is obtained. In the case where a thick TiN film is formed in the upper layer as in this embodiment, surface irregularities generated during the etching of the TiN film are likely to cause etching residues, but BCl ₃ / (BCl ₃ +
The danger can be avoided by slightly increasing the Cl ₂ ) mixing ratio.

As described above, the case where the laminated film mainly including the Al-Si-Cu alloy film is etched has been described.
A wiring alloy film containing Al as a main component may be used. Although the case where a silicon oxide film is used as an etching mask has been described, other insulating films such as a silicon nitride film and a silicon oxynitride film may be used. In short, in plasma etching using a mixed gas of BCl ₃ gas and Cl ₂ gas, it is difficult to etch as compared with the TiN film and the aluminum alloy film and has a good masking property, and if it is an insulating film usually used for manufacturing a semiconductor device. Anything is fine.

[0025]

According to the present invention, when a laminated film including an aluminum alloy film and a titanium nitride film is etched using an insulating film mask, BCl ₃ / Cl is used as an etching gas.
_{Using a 2} / N ₂ mixed gas, BCl ₃ / (BCl ₃ + Cl
₂ ) By setting the mixing ratio to at least 15%, irregularities on the surface of the titanium nitride during etching of the titanium nitride film can be suppressed. As a result, it is possible to suppress the generation of an etching residue due to the titanium nitride surface unevenness, and to prevent a short circuit between wirings. Further, by adding N ₂ gas, side etching can be suppressed. Therefore, a semiconductor device having a highly reliable fine wiring layer can be provided.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views in the order of steps for explaining a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the surface roughness and the mixing ratio when a TiN film is etched using a mixed gas of BCl ₃ gas and Cl ₂ gas.

FIG. 3 shows an Al—Si—Cu alloy film formed of BCl ₃ gas and Cl.
₄ is a graph showing a relationship between a side etch depth and a mixing ratio when patterning is performed using a mixed gas of ₂ gas and N ₂ gas.

FIG. 4 is a schematic diagram showing a high-frequency plasma etching apparatus used in the present invention.

FIGS. 5A to 5D are cross-sectional views in the order of steps for explaining a second embodiment of the present invention.

FIGS. 6A and 6B are diagrams for explaining a first conventional example;
FIG. 4B is a sectional view illustrating a process order, which is separately illustrated in FIG.

FIGS. 7A to 7C are views for explaining a second conventional example.
FIG. 3D is a sectional view illustrating a process order, which is separately illustrated in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Thermal oxide film 3,3a, 3-1,3-1A, 3-1Aa Al-S
i-Cu alloy film 3-2, 3-2A, 3-2Aa, 3-2Ab TiN
Film 4 Silicon oxide film (mask) 5 Side etching 6 Unevenness 7, 7a Projection 8, 8a Barrier film 9 Silicon oxide film 10 Resist film pattern 100 Semiconductor wafer 101 Wafer stage 102 Exhaust port 103 Etching container 104 Gas inlet 105 RF power source 106 Blocking capacitor

Claims (8)

(57) [Claims] 1. A first insulating film on a semiconductor substrate is coated with a laminated film including an aluminum alloy film and a titanium nitride film, then a second insulating film is formed and patterned, and then a resist film used for the patterning is formed. And a method of manufacturing a semiconductor device in which a wiring layer is formed by patterning the laminated film by plasma etching using the patterned second insulating film as a mask, wherein a mixed gas of BCl ₃ gas and Cl ₂ gas is used. Patterning the stacked film using an etching gas obtained by adding an N ₂ gas to the semiconductor device. 2. The method according to claim 1, wherein the laminated film includes the aluminum alloy film provided on the first insulating film and the titanium nitride film provided on the aluminum alloy film. Of manufacturing a semiconductor device. 3. The laminated film according to claim 1, wherein the laminated film includes the titanium nitride film provided on the first insulating film and the aluminum alloy film provided on the titanium nitride film. Of manufacturing a semiconductor device. 4. The BCl in the etching gas
₃ The method of manufacturing a semiconductor device according to the BCl ₃ any one of claims 1 to 3, characterized in that at least 15% mixing ratio to the sum of the gas and the Cl ₂ gas in the gas. 5. The BCl in the etching gas
_The mixing ratio of the _three gases to the sum of the BCl ₃ gas and the Cl ₂ gas is 70% or less.
4. The method for manufacturing a semiconductor device according to claim 1. 6. In the plasma etching step,
4. The method of manufacturing a semiconductor device according to claim 1, wherein a parallel plate type high frequency plasma etching apparatus is used. 7. The method of manufacturing a semiconductor device according to claim 1, wherein the second insulating film is a silicon oxide film. 8. The method according to claim 1, wherein the resist film used for patterning the second insulating film is removed by ashing.