JPH0637041A - Forming method for wiring member - Google Patents

Abstract

PURPOSE:To improve a productive yield and shorten a processing time, by forming a tungsten film selectively using hexafluoride tungsten and organic silane having an electron donative substituent as a source gas in a CVD method. CONSTITUTION:A device-isolation insulating film 2 and a gate insulating film 3 are formed on a main face of p<->-type semiconductor substrate 1. A gate electrode 4 is formed on the gate insulating film 3. A pair of n<+>-type semiconductor regions 7 are formed, and an insulating film 6 is formed on the upper and side faces of the gate electrode 4. A connection hole 11 for exposing an interlayer insulating film 10 and a main face of the n<+>-type semiconductor region 7 is formed, and a tungsten film 12 is formed in the connection hole 11 using hexafluoride tungsten and a monomethylsilane gas as a source gas in a low-pressure CVD method. Then, a first-layer wiring 13 is formed. Similarly as the first layer, an interlayer insulating film 14, an insulating hole 15, and a tungsten film 16, and a second layer wiring 17 are formed above the first-layer wiring 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming technique,
In particular, the present invention relates to a technique effective when applied to a wiring forming technique using the selective CVD method.

[0002]

2. Description of the Related Art In a semiconductor device, a method is used in which a tungsten film is selectively formed by a CVD method so as to be buried in a fine connection hole formed in an interlayer insulating film. In this case, for example, the tungsten film is connected to the main surface of the lower semiconductor substrate exposed in the connection hole of the interlayer insulating film. The interlayer insulating film is composed of a silicon oxide film.
The wiring in the upper layer of the interlayer insulating film is composed of a tungsten film. The semiconductor substrate is composed of single crystal silicon. According to this technique, the wiring in the upper layer of the interlayer insulating film and the main surface of the semiconductor substrate in the lower layer can be connected through the connection hole having a large aspect ratio (aspect ratio).

The tungsten film is formed by a selective CVD method using tungsten hexafluoride gas and hydrogen gas or monosilane gas as a source gas.

[0004]

However, as a result of examining the above-mentioned prior art, the present inventor found the following problems.

When a tungsten film is formed by using the above-mentioned tungsten hexafluoride gas and hydrogen gas as source gases, since the reducing power of hydrogen to tungsten hexafluoride is weaker than that of silicon, the penetration of tungsten into a semiconductor substrate called encroachment. Is formed. As a result, when the tungsten film is connected to the semiconductor region forming the source or drain region of the MOSFET, the semiconductor regions forming the source and drain regions are short-circuited due to encroachment, and the yield of the semiconductor device is reduced. There's a problem. Or the encroachment is MO
There is a problem in that the tungsten film penetrates through the semiconductor region that constitutes the source or drain region and short-circuits between the tungsten film and the main surface portion of the semiconductor substrate due to encroachment (junction breakdown occurs) and the yield of the semiconductor device decreases. is there. Further, since the reducing power of hydrogen to tungsten hexafluoride is weaker than that of silicon, the deposition rate of the tungsten film is slower than that when the tungsten hexafluoride film and monosilane gas are used as the source gas, and the completion time of the semiconductor device becomes longer. There is a problem.

When the tungsten film is formed by using the tungsten hexafluoride gas and the monosilane gas as source gases, since the reducing power of monosilane with respect to tungsten hexafluoride is stronger than that of silicon, no encroachment is formed. In addition, since the reducing power of monosilane with respect to tungsten hexafluoride is stronger than that of silicon, the vapor deposition rate is faster than when tungsten hexafluoride gas and hydrogen gas are used as the source gas. However, since the hydrogen-silicon bond in monosilane is weak and easily broken, silicon is taken into the formed tungsten film and the resistivity of the tungsten film increases. As a result, there is a problem that the operation speed of the semiconductor device is reduced. Further, when silicon is taken into the tungsten film, the shrinking stress inside the tungsten film increases,
There is a problem that the tungsten film peels off during the manufacturing process of the semiconductor device and the yield decreases.

Therefore, in order to prevent the encroachment by the tungsten and the incorporation of silicon into the tungsten film, a method of forming a tungsten film using tungsten hexafluoride gas and difluorosilane gas as source gases has been developed. In this case, since difluorosilane has a stronger reducing power for tungsten hexafluoride than hydrogen, encroachment does not occur. Further, since the bond between silicon and fluorine is stronger than the bond between silicon and hydrogen, silicon is not incorporated in the tungsten film. However, there is a problem that the formation rate of the tungsten film is slower than the case where the tungsten hexafluoride gas and the monosilane gas are used as the source gas.

An object of the present invention is to provide a technique capable of improving the yield in a method for forming a wiring member.

Another object of the present invention is to provide a technique capable of shortening the process completion time in the method for forming a wiring member.

Another object of the present invention is to provide a technique capable of increasing the operating speed in the method for forming a wiring member.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0012]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

(1) A step of forming an opening for exposing the main surface of the semiconductor substrate in an insulating film on the main surface of the semiconductor substrate made of silicon, and tungsten hexafluoride and electron donating in the opening. Selectively forming a tungsten film by a CVD method using an organic silane having a reactive substituent as a source gas.

(2) The organosilane is an alkyl or phenyl derivative of monosilane.

(3) The organic silane is monomethylsilane or dimethylsilane.

[0016]

According to the above-mentioned means (1) to (3), the electron-donating substituent (alkyl or phenyl group) increases the reducing power of the organic silane (monosilane) for tungsten hexafluoride. The reducing power of silane for tungsten hexafluoride is larger than that of silicon and hydrogen. Therefore, in the step of forming the tungsten film,
Since the encroachment is not formed, it is possible to prevent the yield of the semiconductor device from lowering due to the encroachment.
That is, the yield of semiconductor devices can be improved.

Further, since the reducing power of the organosilane (monosilane) having the electron-donating substituent (alkyl or phenyl group) with respect to tungsten hexafluoride is larger than that of hydrogen and difluorosilane, the deposition rate of the tungsten film can be increased. As a result, the completion time of the semiconductor device can be shortened.

Since the bond between silicon and carbon in the organosilane (monosilane) having the electron-donating substituent (alkyl or phenyl group) is stronger than the bond between silicon and hydrogen in monosilane, the bond in the tungsten film is It is possible to prevent silicon from being taken in. As a result, the resistance value of the tungsten film can be prevented from increasing, so that the operating speed of the semiconductor device can be increased. In addition, since the incorporation of silicon into the tungsten film can be prevented, the tungsten film can be prevented from peeling off during the manufacturing process of the semiconductor device, so that the yield of the semiconductor device can be improved.

[0019]

Embodiments of the present invention will be specifically described below with reference to the drawings. In all the drawings for explaining the embodiments, parts having the same functions are designated by the same reference numerals, and repeated description thereof will be omitted.

First, the structure of a semiconductor device according to an embodiment of the present invention will be described with reference to FIG. 1 (main part sectional view).

As shown in FIG. 1, the semiconductor device comprises a p--type semiconductor substrate 1. The p − type semiconductor substrate 1 is made of, for example, single crystal silicon. This p-
N-channel MISFET is provided on the main surface of the semiconductor substrate 1.
Qn is provided.

The n-channel MISFET Qn is provided on the main surface of the active region whose periphery is defined by the element isolation insulating film 2 on the main surface of the non-active region of the p − type semiconductor substrate 1. The element isolation insulating film 2 is made of, for example, a silicon oxide film.

The n-channel MISFET Qn has a gate insulating film 3 provided on the main surface of the p − type semiconductor substrate 1, a gate electrode 4 provided on the gate insulating film 3,
Each of the pair of n + type semiconductor regions 7 forming the source region and the drain region is mainly constituted. The gate insulating film 3 is composed of, for example, a silicon oxide film. The gate electrode 4 is composed of, for example, a polycrystalline silicon film.
An insulating film 6 is provided on the upper surface and the side wall of the gate electrode 4. The insulating film 6 is composed of, for example, a silicon oxide film.

An interlayer insulating film 10 is formed on the insulating film 6.
Is provided. The interlayer insulating film 10 has, for example,
00nm approximately the thickness of the silicon oxide film and 800nm a film thickness of about BPSG (B oron P hospho S ilicate G lass) is composed of a stacked film of film.

A connection hole 11 is formed in the interlayer insulating film 10 so as to expose the main surfaces of the pair of n + type semiconductor regions 7 forming the source region and the drain region, respectively.
The diameter of the connection hole 11 is, for example, about 0.7 μm. The inside of this connection hole 11 is filled with a tungsten film 12. The tungsten film 12 connects between the wiring 13 of the first layer, which is the upper layer of the interlayer insulating film 10, and the main surface of the n + type semiconductor region 7.

The wiring 13 of the first layer is made of, for example, a tungsten film.

An interlayer insulating film 14 is provided on the first-layer wiring 13. The interlayer insulating film 14 is, for example, a silicon oxide film from the lower side, SOG (S pin O n G la
The ss) film and the silicon oxide film are laminated. A connection hole 15 exposing the surface of the first layer wiring 13 is formed in the interlayer insulating film 14. Similar to the inside of the connection hole 11, the inside of the connection hole 15 is filled with the tungsten film 16. This tungsten film 1
6 is a second layer wiring 17 which is an upper layer of the interlayer insulating film 14.
And the wiring 13 of the first layer are connected. The second-layer wiring 17 is composed of, for example, a laminated film of a titanium nitride film, an aluminum film, and a titanium tungsten film. A surface protective film (not shown) is provided on the upper layer of the wiring 17 of the second layer.

Next, a method of forming the semiconductor device will be described with reference to FIG.
3 and FIG. 3 (a main part sectional view showing the region shown in FIG. 1 as part of the manufacturing process).

First, the main surface of the inactive region of the p--type semiconductor substrate 1 is oxidized by the selective oxidation method to form the element isolation insulating film 2. The element isolation insulating film 2 is formed to have a film thickness of, for example, about 550 nm.

Next, in the region where the n-channel MISFETQn is formed, the main surface of the active region of which the periphery is defined by the element isolation insulating film 2 of the p-type semiconductor substrate 1 is exposed. Thereafter, the gate insulating film 3 is formed on the exposed main surface of the p − type semiconductor substrate 1 by a thermal oxidation method.

Next, a polycrystalline silicon film is deposited on the gate insulating film 3 and then patterned by photolithography and etching to form a gate electrode 4.

Next, in the region where the n-channel MISFETQn is formed, an n-type impurity such as arsenic is introduced into the main surface portion of the p--type semiconductor substrate 1 by ion implantation mainly using the gate electrode 4 as a mask. After this, 90
A heat treatment is performed at a temperature of about 0 ° C. for about 10 minutes to activate the introduced n-type impurities and form a pair of n + -type semiconductor regions 7. By forming the n + type semiconductor region 7, the n channel MISFET Qn is completed.

Next, the insulating film 6 is formed on each of the upper surface and the side surface of the gate electrode 4.

Next, a silicon oxide film is deposited to a thickness of about 100 nm under conditions of high temperature and low pressure, for example. After that, a B layer having a film thickness of, for example, about 800 nm is formed on the upper layer of the silicon oxide film.
A PSG film is formed. This BPSG film is formed by, for example, a CVD method using diborane, phosphine, monosilane, and oxygen as source gases. After the film deposition, the BPSG film is subjected to a reflow process by a heat treatment at a temperature of about 900 ° C. for about 10 minutes.

Next, by using, for example, a photolithography technique and an etching technique, as shown in FIG. 2, a connection hole 11 for exposing the main surfaces of the pair of n + type semiconductor regions 7 is formed in the interlayer insulating film 10. Form. This connection hole 11 is
For example, it is formed with a diameter of about 0.7 μm.

Next, as shown in FIG. 3, a tungsten film 12 is formed on the main surface of the n + type semiconductor region 7 exposed in the connection hole 11. This tungsten film 12
Is formed by a low pressure CVD method using tungsten hexafluoride gas and monomethylsilane gas as source gases. The tungsten film 12 is formed to have a film thickness of about 800 nm, for example. The conditions for forming the tungsten film 12 are, for example, that nitrogen is used as a carrier gas, the partial pressure of the tungsten hexafluoride gas is about 5.33 Pa, the partial pressure of the monomethylsilane gas is about 5.33 Pa, and the total pressure is Four
It is about 6.66 Pa. The substrate temperature is, for example, 2
It is about 50 ° C.

When the tungsten film 12 is formed under such conditions, methyl, which is an electron-donating substituent in monomethylsilane, increases the reducing power of organosilane (monosilane) for tungsten hexafluoride, and therefore monomethylsilane. The reducing power of tungsten hexafluoride is larger than that of silicon and hydrogen. Therefore, the tungsten film 1
Since no encroachment is formed in the step of forming 2, it is possible to prevent the yield of the semiconductor device from being lowered due to the encroachment. That is, the yield of semiconductor devices can be improved.

Since the reducing power of monomethylsilane for tungsten hexafluoride is larger than that of hydrogen and difluorosilane, the deposition rate of the tungsten film can be increased.
For example, when the tungsten film 12 is formed under the above-described conditions, the vapor deposition rate is about 100 nm / min, which is higher than that when tungsten hexafluoride gas and hydrogen or tungsten hexafluoride and difluorosila gas are used as the source gas. Since the speed is increased, the time required for completing the semiconductor device can be shortened. In addition, the tungsten film 1 is selectively formed in the connection hole 11.
2 can be formed.

Since the silicon-carbon bond in monomethylsilane is stronger than the silicon-hydrogen bond in monosilane, it is possible to prevent silicon from being taken into the tungsten film 12. For example, under the above-mentioned conditions, the tungsten film 1
In the case where No. 2 is formed, the resistance value of the tungsten film 12 is 10 μ regardless of the substrate temperature even if the tungsten film 12 is formed by changing the substrate temperature from 180 ° C. to 350 ° C.
There is about Ω · cm. That is, since the resistance value of the tungsten film 12 can be reduced, the operation speed of the semiconductor device can be increased.

Further, by preventing the incorporation of silicon into the tungsten film 12, it is possible to prevent the tungsten film 12 from peeling off during the manufacturing process of the semiconductor device, so that the yield of the semiconductor device can be improved.

Next, a tungsten film is deposited on the upper layer of the interlayer insulating film 10 and then patterned by photolithography and etching techniques to form the wiring 13 of the first layer. After that, an interlayer insulating film 14 is formed on the upper layer of the wiring 13 of the first layer. The interlayer insulating film 14 is formed of a laminated film in which a silicon oxide film, an SOG film, and a silicon oxide film are laminated from the lower layer side. The upper and lower silicon oxide films of the interlayer insulating film 14 are deposited by, for example, a plasma CVD method. The SOG film is formed by a coating method.

Next, a connection hole 15 exposing the surface of the wiring 13 of the first layer is formed in the interlayer insulating film 14.
Thereafter, similar to the tungsten film 12, low pressure CVD is performed.
Then, the tungsten film 16 is formed by the method, and the inside of the connection hole 15 is filled with the tungsten film 16. As described above, when the connection hole 15 that exposes the surface of the first-layer wiring 13 formed of the tungsten film is formed in the interlayer insulating film 14 and the inside of the connection hole 15 is filled with the tungsten film 16, a monosilane gas In this case, there is a possibility that decomposition will occur on the surface of the tungsten forming the wiring 13 of the first layer, but according to the structure of this embodiment,
Since the decomposition of the organic silane gas can be prevented, the connection hole 1
The tungsten film 16 can be formed in the film 6 with good selectivity. Further, in this case, the same effect can be obtained even when the first-layer wiring 13 is made of titanium nitride, tungsten silicide, molybdenum silicide, or the like.

Next, after forming a laminated film of a titanium nitride film, an aluminum film, and a titanium tungsten film on the interlayer insulating film 14, the laminated film is patterned by a photolithography technique and an etching technique to form a second layer. Eye wiring 17
To form. Thereafter, a surface protective film (not shown) is formed on the second-layer wiring 17 to complete the semiconductor device of this embodiment shown in FIG.

As described above, in this embodiment, n
On the interlayer insulating film 10 on the main surface of the + type semiconductor region 7, the n +
A step of forming a connection hole 11 exposing the main surface of the type semiconductor region 7, and depressurizing the connection hole 11 using tungsten hexafluoride and monomethylsilane gas which is an organic silane having an electron donating substituent as a source gas. And a step of selectively forming the tungsten film 12 by the CVD method. According to this configuration, the methyl group that is the electron-donating substituent increases the reducing power of the organosilane monosilane for tungsten hexafluoride, so that the reducing power of the monomethylsilane for tungsten hexafluoride is silicon and It becomes larger than hydrogen. Therefore, since the encroachment is not formed in the step of forming the tungsten film 12, it is possible to prevent the yield of the semiconductor device from lowering due to the encroachment. That is, the yield of semiconductor devices can be improved.

Since the reducing power of monomethylsilane having a methyl group for tungsten hexafluoride is larger than that of hydrogen and difluorosilane, the tungsten film 12
The deposition rate can be increased. As a result, the completion time of the semiconductor device can be shortened.

The silicon-carbon bond in the monomethylsilane having a methyl group is the same as the silicon-carbon bond in the monosilane.
Since it is stronger than the bond between hydrogen, it is possible to prevent silicon from being taken into the tungsten film 12. As a result, the resistance value of the tungsten film 12 can be prevented from increasing, so that the operating speed of the semiconductor device can be increased. Further, since it is possible to prevent silicon from being taken into the tungsten film 12, it is possible to prevent the tungsten film 12 from peeling off during the manufacturing process of the semiconductor device. As a result, the yield of semiconductor devices can be improved.

The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments.
It goes without saying that various changes can be made.

For example, in the above-mentioned embodiment, an example in which monomethylsilane gas having a methyl group as an atom-donating substituent is used as a source gas has been shown, but the present invention can also use dimethylsilane gas as a source gas. . Further, an organic silane gas having another alkyl group or phenyl group instead of the methyl group can be used as the source gas. Since the reactivity decreases when the carbon chain of the alkyl group and the carbon chain of the functional group of the phenyl group are long, it is preferable to use an organosilane derivative having a short carbon chain of the alkyl group and the phenyl group.

Further, if a tungsten film is formed on the entire surface of the substrate by, for example, a sputtering method and then a tungsten film is formed in the same manner as in the above-mentioned embodiment, the tungsten film can be formed on the entire surface of the substrate.

[0050]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

In the method of forming the wiring member, the yield can be improved.

In the method for forming the wiring member, the work completion time can be shortened.

In the method of forming the wiring member, the operating speed can be increased.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an essential part showing the region shown in FIG. 1 as part of a manufacturing process.

FIG. 3 is a cross-sectional view of an essential part showing the region shown in FIG. 1 as part of a manufacturing process.

[Explanation of symbols]

1 ... p-type semiconductor substrate, 2 ... element isolation insulating film, 3 ... gate insulating film, 4 ... gate electrode, 7 ... n + type semiconductor region,
10, 14 ... Interlayer insulating film, 11, 15 ... Connection hole, 12, 1
6 ... Tungsten film, 13 ... First layer wiring, ... 17 ...
Second layer wiring.

Claims (3)

[Claims] 1. A step of forming an opening for exposing the main surface of the semiconductor substrate in an insulating film on the main surface of the semiconductor substrate made of silicon, and tungsten hexafluoride and an electron donating property in the opening. C using an organic silane having a substituent as a source gas
And a step of selectively forming a tungsten film by a VD method. 2. The method for forming a wiring member according to claim 1, wherein the organic silane is an alkyl or phenyl derivative of monosilane. 3. The method for forming a wiring member according to claim 2, wherein the organic silane is monomethylsilane or dimethylsilane.