KR20010104964A - Amorphous silicon carbide film and method of forming the same - Google Patents

Abstract

An amorphous silicon carbide composition having a low dielectric constant and a method for forming the same are provided. The composition comprises silicon (Si), carbon (C), hydrogen (H) and nitrogen (N), the composition ratio of nitrogen being 2 to 10 atomic weights based on the total atomic weight of silicon, carbon, hydrogen and nitrogen And Si-CH ₃ bonds and Si-C bonds. The method for forming the composition comprises the steps of loading a semiconductor substrate on a chuck in a closed process chamber, controlling the pressure in the process chamber to a lower pressure than atmospheric pressure and simultaneously adjusting the temperature of the chuck to a temperature of 300 ° C to 450 ° C. And injecting nitrogen gas as a precursor gas and a carrier gas such as tri-methyl-silane (SiH (CH ₃ ) ₃ ) gas into the process chamber. Applying a radio frequency power source as a plasma source to the electrodes in the substrate, thereby forming an amorphous silicon carbide film on the semiconductor substrate.

Description

Amorphous silicon carbide film and method of forming the same

The present invention relates to an amorphous silicon carbide composition used in the manufacture of a semiconductor device and a method of forming the same.

As the degree of integration of semiconductor devices increases, the width and thickness of metal wirings gradually decrease. Accordingly, the cross-sectional area of the metal wiring is also reduced, thereby increasing the electrical resistance of the metal wiring, and as a result, it is difficult to improve the operation speed of the highly integrated semiconductor device.

Recently, a technique of applying a low resistance material such as copper to the metal wiring has been proposed to reduce the resistance of the metal wiring. Moreover, copper is known to be a very suitable material for next-generation metal wiring technology due to its high melting point and excellent electro-migration (E / M) characteristics, compared to aluminum, which has been widely used as a metal wiring material.

However, when the low resistance metal wiring formed of the copper film and the oxide film widely used as the interlayer insulating film are in direct contact, the copper atoms in the copper film diffuse in the oxide film. Accordingly, a diffusion barrier layer is essentially required between the copper wiring and the oxide film. In this case, a barrier metal film such as a tantalum nitride film (TaN) and / or a diffusion barrier insulating film such as an amorphous silicon carbide film (a-SiC) is widely used as the diffusion barrier.

U.S. Patent No. 5,818,071 discloses a technique of adopting an amorphous silicon carbide film as a diffusion barrier insulating film in forming a multilayer metal wiring.

According to U.S. Patent No. 5,818,071, an amorphous silicon carbide film is interposed between the metal wiring and the metal interlayer insulating film to prevent the diffusion of metal atoms into the metal interlayer insulating film between adjacent metal wirings. Therefore, the parasitic capacitance between the metal wirings is determined by the dielectric constants of the intermetallic insulating film and the diffusion preventing insulating film. As a result, an amorphous silicon carbide film having a low dielectric constant is required to improve the transmission speed of the electrical signal through the metallization.

It is an object of the present invention to provide an amorphous silicon carbide composition having a low dielectric constant suitable for high speed semiconductor devices.

Another object of the present invention is to provide a method of forming an amorphous silicon carbide film having a low dielectric constant.

1 is a cross-sectional view of a general semiconductor device employing an amorphous silicon carbide film in metallization technology.

FIG. 2 is a graph showing a change in dielectric constant of an amorphous silicon carbide film with respect to the flow rate of a precursor according to the type of transport gas used in the present invention and the prior art,

3 is a graph showing the correlation between the dielectric constant of the amorphous silicon carbide film and the bonding ratio of the methyl group (CH _3- ) according to the type of transport gas used in the present invention and the prior art,

Figure 4 is a graph showing the mass of the dielectric constant of the amorphous silicon carbide film according to the type of transport gas used in the present invention and the prior art,

5 is a process flowchart illustrating a method of forming an amorphous silicon carbide film according to the present invention.

In order to achieve the above technical problem, the amorphous silicon carbide composition according to the present invention includes silicon (Si), carbon (C), hydrogen (H) and nitrogen (N), wherein the composition ratio of the nitrogen is the silicon, the carbon, It is 2 to 10 atomic weight (atomic) based on the total atomic weight of the hydrogen and the nitrogen, it characterized in that it comprises a Si-CH ₃ bond and a Si-C bond.

In order to achieve the above technical problem, the method of forming an amorphous silicon carbide composition according to the present invention comprises the steps of loading a semiconductor substrate on a chuck in a closed process chamber, and the pressure in the process chamber lower than 12 Torr lower than atmospheric pressure Controlling the temperature of the chuck to a temperature of 300 ° C. to 450 ° C., and a process gas, such as tri-methyl-silane (SiH (CH ₃ ) ₃ ) gas, into the process chamber. Forming a amorphous silicon carbide film on the semiconductor substrate by injecting nitrogen gas as a precursor and a carrier gas, and applying a radio frequency power source as a plasma source to an electrode in the process chamber. Include.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a semiconductor device employing an amorphous silicon carbide film according to the present invention as a diffusion barrier insulating film.

Referring to FIG. 1, a first interlayer insulating film 3, an etch stop film 5, and a second interlayer insulating film 7 are sequentially formed on the semiconductor substrate 1. The first and second interlayer insulating films 3 and 7 may be formed of a silicon oxide film such as a fluorinated silicate glass (FSG) film or an undoped silicate glass (USG) film, and the etch stop film 5 may be formed of the first and second interlayer insulating films 3 and 7. The interlayer insulating film is formed of an insulating film having an etching selectivity, for example, a silicon nitride film. The groove 9 is formed by selectively etching the predetermined region of the second interlayer insulating layer 7 until the predetermined region of the etch stop layer 5 is exposed. The metal contact hole 11 exposing the predetermined region of the semiconductor substrate 1 by continuously etching the predetermined region of the etch stop layer 5 exposed by the groove 9 and the first interlayer insulating layer 3 is formed. Form. The barrier metal film 13 and the first metal wiring 15 are formed in the metal contact hole 11 and the groove 9 using a conventional damascene process. The barrier metal film 13 is formed of a tantalum nitride film or a titanium nitride film, and the first metal wire is formed of a copper, gold, silver, or superconducting metal film having a lower specific resistance than an aluminum film.

As shown in FIG. 1, a barrier metal film 13 is interposed between the first metal wiring 15 and the interlayer insulating film (the first interlayer insulating film and / or the second interlayer insulating film). Accordingly, the barrier metal film 13 prevents the metal atoms in the first metal wire 15 from being diffused into the interlayer insulating films 3 and 5 through the side surfaces of the first metal wire 15.

Referring to FIG. 1 again, an amorphous silicon carbide film 17 and an intermetallic insulating film 19 are sequentially formed on the entire surface of the resultant product on which the first metal wiring 15 is formed. Here, the amorphous silicon carbide film 17 is formed as a diffusion preventing insulating film to prevent the metal atoms in the first metal wiring 15 from being diffused into the interlayer insulating film 19. Subsequently, the metal interlayer insulating film 19 and the amorphous silicon carbide film 17 are patterned to form via holes (not shown) that expose predetermined regions of the first metal wire 15. A second metal wiring 21 is formed on the metal interlayer insulating film 19 to cover the via hole.

As described above, since the first metal wiring 15 is formed to be surrounded by the barrier metal film 13 and the amorphous silicon carbide film 17, the metal atoms in the first metal wiring 15 are interlayer insulating films 3 and 7. And diffusion into the metal interlayer insulating film 19 can be prevented. In this case, when the amorphous silicon carbide film 17 is formed by a conventional plasma chemical vapor deposition method (PE-CVD) using helium (He) gas or hydrogen (H) gas as a transport gas, the amorphous silicon carbide film The film 17 exhibits a dielectric constant on the order of 5-6. Further, the interlayer insulating films 3 and 7 and the metal interlayer insulating film 19 are formed of a conventional silicon oxide film having a dielectric constant of 4 or less. Therefore, in order to reduce the parasitic capacitance between the adjacent first metal wires 15 or the parasitic capacitance between the first and second metal wires 15 and 21, the dielectric constant of the amorphous silicon carbide film 17 is reduced. It is required to further reduce.

5 is a flowchart illustrating a method of forming an amorphous silicon carbide film according to the present invention.

Referring to FIG. 5, the semiconductor substrate is loaded onto a chuck inside the process chamber of the plasma chemical vapor deposition apparatus (51). Subsequently, the pressure in the process chamber is adjusted to a low pressure lower than atmospheric pressure, for example, 12 Torr or lower, and the temperature of the chuck is adjusted to a temperature of 300 ° C. to 450 ° C. (53). Subsequently, a process gas, for example, a precursor gas such as tri-methyl-silane (SiH (CH ₃ ) ₃ ) gas and a carrier gas, are injected into the process chamber. An amorphous silicon carbide film is formed on the substrate (55). Here, it is preferable to use nitrogen gas as the transport gas. The trimethyl silane gas is preferably injected at a flow rate of 100 to 500 sccm (standard cubic centimeter per minute), and the transport gas, that is, nitrogen gas, is preferably injected at a flow rate of 500 to 1000 sccm.

2 to 4 are graphs showing the measured physical properties of the amorphous silicon carbide film formed according to the present invention and the prior art. Here, the amorphous silicon carbide film according to the present invention and the prior art was formed using a plasma chemical vapor deposition process using tri-methyl silane (SiH (CH ₃ )) gas as a precursor. In addition, a 13.56 MHz radio frequency power source (RF power source) was used as a plasma power source for the plasma chemical vapor deposition process equipment. On the other hand, in the present invention and the prior art, the temperature of the chuck was heated to 400 ℃, the pressure inside the process chamber was adjusted to have a stable value of 9 Torr while the process gas and transport gas is injected. At this time, the flow rates of the transport gases, that is, hydrogen gas and helium gas, used in the prior art were 1200sccm and 800sccm, respectively, and the flow rate of the transport gas, that is, nitrogen gas, used in the present invention was 800sccm.

Specifically, FIG. 2 is a graph showing dielectric constants according to the formation conditions of the amorphous silicon carbide film 17 according to the present invention and the prior art. Here, the horizontal axis shows the flow rate of trimethyl silane (3MS) gas which is a process gas, and the vertical axis shows the dielectric constant.

From FIG. 2, the prior art using hydrogen gas or helium gas as a transport gas has a tendency that the dielectric constant of the amorphous silicon carbide film decreases from about 7 to 4.6 as the flow rate of trimethyl silane gas increases from 100 sccm to 400 sccm. On the other hand, the present invention using nitrogen gas as the transport gas showed a uniform value of about 4.5 to 4.1 regardless of the flow rate of trimethyl silane gas.

3 is a graph showing the correlation between the dielectric constant of the amorphous silicon carbide film formed according to the present invention and the prior art and the bonding ratio of the methyl group (CH ₃ −). Here, the horizontal axis represents the dielectric constant of the amorphous silicon carbide film, and the vertical axis represents the ratio of the Si—CH ₃ bond number to the Si—C bond number in the amorphous silicon carbide film. At this time, trimethyl silane gas used as a precursor was injected into the process chamber at a flow rate of 350sccm.

As can be seen from FIG. 3, it can be seen that the dielectric constant tends to decrease as the number of Si—CH ₃ bonds present in the amorphous silicon carbide film increases. From this, helium gas or hydrogen gas used as a transport gas in the prior art was evaluated to have an excellent ability to decompose the Si-CH ₃ bond of trimethyl silane gas as compared to the nitrogen gas used as the transport gas in the present invention. . As a result, the present invention showed the effect of reducing the dielectric constant of the amorphous silicon carbide film by increasing the number of Si—CH ₃ bonds relative to the prior art by using nitrogen gas as the transport gas.

4 is a graph showing a correlation between dielectric constant and density of an amorphous silicon carbide film obtained according to the present invention and the prior art. At this time, trimethyl silane gas used as a precursor was injected into the process chamber at a flow rate of 350sccm.

Referring to FIG. 4, the density of the amorphous silicon carbide film formed according to the present invention using nitrogen gas as the transport gas is about 1.6 gram / cm 3, whereas the helium or hydrogen gas is used as the transport gas according to the prior art. The density of the formed amorphous silicon carbide film showed a value of 1.6 to 1.9 gram / cm 3.

On the other hand, as a result of measuring the composition ratio of the amorphous silicon carbide composition formed according to the present invention and the prior art as shown in the following table. Here, the flow rates of helium gas, nitrogen gas, and hydrogen gas used as transport gas were 800sccm, 800sccm and 1200sccm, respectively.

Table Atomic Compositions of Amorphous Silicon Carbide Compositions Formed According to the Present Invention and the Prior Art

SiH (CH ₃ ) ₃ flow rate (sccm) Type of transportation gas Si C H N Dielectric constant 200 He 33.3 33.3 33.3 5.5 300 35.7 35.7 28.6 5.2 400 33.3 33.3 33.3 4.7 350 N ₂ 29.9 32.8 29.9 4.5 4.2 350 H ₂ 32.4 32.4 32.4 1.5 5.7

From the table, the amorphous silicon carbide composition obtained according to the present invention using nitrogen gas as the transport gas has a dielectric constant of 4.2 lower than that of the prior art. At this time, the nitrogen composition ratio of the amorphous silicon carbide composition according to the prior art using helium gas and hydrogen gas as the transport gas is 0 atomic and 1.5 atomic, respectively, whereas the amorphous silicon according to the present invention using nitrogen gas as the transport gas The nitrogen composition ratio of the carbide composition was 4.5 atomic.

As described above, according to the present invention, by using nitrogen as the transport gas, it is possible to form an amorphous silicon carbide film showing a lower dielectric constant than in the prior art. Accordingly, when the amorphous silicon carbide film according to the present invention is used as the diffusion barrier insulating film in the metal wiring technology of a semiconductor device using a low resistance metal film such as a copper film having high reliability and low resistivity compared to an aluminum film, Parasitic capacitances between metal lines can be significantly reduced.

Claims (1)

Silicon (Si), carbon (C), hydrogen (H) and nitrogen (N), and the composition ratio of the nitrogen is 2 to 10 atomic weights (based on the total atomic weight of the silicon, the carbon, the hydrogen and the nitrogen ( atomic) and comprises an Si—CH ₃ bond and an Si—C bond.