Method of forming interlayer insulating film

Abstract: A material containing, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x (where R 1 is a phenyl group or a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3) is caused to undergo plasma polymerization or react with an oxidizing agent to form an interlayer insulating film composed of a silicon oxide film containing an organic component. As the organic silicon compound where R 1 is a phenyl group, there can be listed phenyltrimethoxysilane or diphenyldimethoxysilane. As the organic silicon compound where R 1 is a vinyl group, there can be listed vinyltrimethoxysilane or divinyldimethoxysilane.

Description: The present invention relates to a method of forming an interlayer insulating film in a semiconductor device. Known interlayer insulating films formed in semiconductor devices include a silicon oxide film, a silicon oxide film composed of an organic SOG (Spin-On-Glass) containing an organic component, and an organic polymer film. In general, an interlayer insulating film formed in a semiconductor device is required to have a sufficiently low dielectric constant to achieve lower wiring capacitance and sufficiently high heat resistance to withstand a semiconductor manufacturing process. With the increasing miniaturization of an LSI formed on a semiconductor substrate, wiring capacitance which is parasitic capacitance between metal wires has remarkably increased, while degraded performance of the LSI due to a wiring delay caused thereby has presented a serious problem. The wiring capacitance is determined by the size of a space between the metal wires and by the magnitude of the dielectric constant of an interlayer insulating film present in the space. To reduce the wiring capacitance, therefore, it is important to reduce the dielectric constant of the interlayer insulating film. If an interlayer insulating film with low heat resistance is used, a thermal treatment at about 400 °C performed in a semiconductor manufacturing process will soften the interlayer insulating film and undulate wiring, which may cause a fatal failure such as a disconnection or short circuit. This is why the interlayer insulating film is required to have sufficiently high heat resistance to withstand the thermal treatment at about 400 °C. Since an interlayer insulating film composed of a silicon oxide film has an undesirably high dielectric constant, there has been proposed a fluorine-doped silicon oxide film made of silicon oxide doped with fluorine. Although the dielectric constant of the fluorine-doped silicon oxide film has been lowered by bonding a fluorine atom having low polarizability to a silicon atom composing the oxide film, the moisture absorbing property thereof increases with an increase in the amount of fluorine added thereto, so that a minimum dielectric constant attainable is about 3.5. Hence, it is difficult to use silicon oxide films including the fluorine-doped silicon oxide film as interlayer insulating films in an extremely miniaturized LSI. In place of silicon oxide films, the use of an organic SOG film or organic polymer film as an interlayer insulating film in an extremely miniaturized LSI is under consideration because of its low dielectric constant. The organic SOG film is formed by thermally curing a solution containing silica or siloxane each having an organic component such as a methyl group or a phenyl group. Since the organic component remains in the film even after thermal curing, a low dielectric constant of about 3.0 is attained. As a first conventional embodiment, a method of forming an interlayer insulating film composed of an organic SOG film will be described with reference to FIGS. 6(a) to 6(d). First, as shown in FIG. 6(a), first-level metal wires 2 are formed on a semiconductor substrate 1, followed by a first silicon oxide film 3 formed over the entire surface of the semiconductor substrate 1 including the first-level metal wires 2 by plasma CVD using a gas mixture of, e.g., tetraethoxysilane and oxygen as a raw material. Thereafter, an organic SOG agent is applied onto the first silicon oxide film 3 by spin coating and thermally cured to form an organic SOG film 4. Then, as shown in FIG. 6(b), the entire surface of the organic SOG film 4 is etched back such that the portions thereof overlying the first-level metal wires 2 are removed. Next, as shown in FIG. 6(c), a second silicon oxide film 5 is formed over the entire surface of the silicon oxide film 3 including the remaining organic SOG film 4 by, e.g., plasma CVD using a gas mixture of, e.g., tetraethoxysilane and oxygen as a raw material. Next, as shown in FIG. 6(d), contact holes are formed in the first and second silicon oxide films 3 and 5 by using a resist pattern as a mask, which is then removed by using an oxygen plasma. Subsequently, a metal material is filled in the contact holes to form contacts. After that, second-level metal wires 7 are formed on the second silicon oxide film 5, resulting in a structure having an interlayer insulating film consisting of the first silicon oxide film 3, the organic SOG film 4, and the second silicon oxide film 5 between the first- and second-level metal wires 2 and 7. As a second conventional embodiment, a method of forming an interlayer insulating film composed of a fluorinated amorphous carbon film, which is an organic polymer film, will be described. As disclosed in a technical report (Extended Abstracts of the 1995 International Conference on Solid State Devices and Materials, Osaka, 1995, pp.177-179), a fluorinated amorphous carbon film is formed by plasma CVD using, as a raw material, a mixture of a hydrocarbon-based component such as CH 4 and a fluorine-containing component such as CF 4 . After the gas mixture is introduced into a reaction chamber of a parallel-plate plasma CVD apparatus, the pressure inside the reaction chamber is held at several hundreds of Torr. When RF power on the order of 100 to 300 W at 13.56 MHz is applied to parallel-plate electrodes in the reaction chamber, the gas mixture is partially decomposed to generate monomers, ions, and radicals, which undergo plasma polymerization, resulting in a fluorinated amorphous carbon film as a plasma polymerization film deposited on a semiconductor substrate. The fluorinated amorphous carbon film thus formed has a low dielectric constant of 2.0 to 2.5 immediately after deposition. However, since the foregoing organic SOG film is formed by repeatedly performing the steps of applying the organic SOG agent and thermally curing the applied organic SOG agent several times, it has the disadvantages of poor film formability resulting from a large amount of time required by the formation of the organic SOG film and high cost resulting from the major portion of the agent wasted during the spin coating. In the case where the etch-back process, as illustrated in FIG. 6(b), is not performed with respect to the entire surface of the organic film 4 before contact holes are formed in the organic SOG film 4 and in the first silicon oxide film 3 by using the resist pattern as a mask, which is then removed by using an oxygen plasma, and contacts are formed by filling the metal material in the contact holes, the following problems arise. In the step of removing the resist pattern by using the oxygen plasma, SiCH 3 contained in the organic SOG films 4 exposed at the sidewalls of the contact holes reacts with the oxygen plasma to generate SiOH, which is condensed by dehydration to generate H 2 O in the step of filling the metal material in the contact holes. The resulting H 2 O causes the oxidization and contamination of the metal forming the contacts, leading to faulty conduction at a contact. As for the organic polymer film composed of the fluorinated amorphous carbon film, it has the advantage of an extremely low dielectric constant over the organic SOG film but is inferior thereto in heat resistance because of its low glass transition temperature. When the conventional fluorinated amorphous carbon film is subjected to a thermal treatment at a temperature of 300 °C or more, the thickness of the film is significantly reduced, while the dielectric constant thereof is greatly increased. For example, if a fluorinated amorphous carbon film made from CH 4 and CF 4 and having a dielectric constant of 2.2 immediately after deposition is subjected to a thermal treatment at a temperature of 300 °C for 1 hour, the film contracts till the thickness thereof is reduced to about 65% of the original thickness immediately after deposition, which is a 35% reduction, while the dielectric constant thereof is increased to about 2.8. It is to be noted that the foregoing problems are not limited to the interlayer insulating film formed between upper and lower metallization layers but also arise in an interlayer insulating film between metal wires included in a single metallization layer. EP-A-560617 discloses a method of manufacturing an insulating film of a semiconductor device comprising the steps of (a) preparing a semiconductor substrate, (b) treating a surface of said semiconductor substrate with a treating fluid comprising at least one organic compound, and (c) forming an insulating film on the thus treated surface of the semiconductor substrate by a chemical vapor deposition. EP-A-560617 further describes a method according to which a chemical vapor deposition is conducted on the semiconductor substrate by supplying a raw material gas, a reaction gas and an organic compound gas onto the semiconductor substrate to form a CVD insulating film. EP-A-212691 describes a method for low temperature chemical vapor deposition of a silicon dioxide-based film on a semiconductor structure using specific alkoxysilanes such as vinyltrialkoxysilanes. In view of the foregoing, the object of the present invention is to improve the film formability, cost efficiency, and processability of an interlayer insulating film composed of an organic SOG film. In order to solve the above object, the present invention provides a method of forming an interlayer insulating film, wherein a material containing, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x , wherein R 1 is a phenyl group; R 2 is an alkyl group; and x is an integer of 1 to 3, is caused to undergo plasma polymerization or react with an oxidizing agent to form an interlayer insulating film composed of a silicon oxide film containing an organic component. The present invention further provides a method of forming an interlayer insulating film, wherein a material containing, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x , wherein R 1 is a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3, is caused to undergo plasma polymerization to form an interlayer insulating film composed of a silicon oxide film containing an organic component. Since the resulting interlayer insulating film contains, as a main component, the organic silicon compound as defined above, the proportion of SiCH 3 contained in the interlayer insulating film is much lower than contained in a conventional organic SOG film, though the dielectric constant thereof is equal to that of the conventional organic SOG film. Accordingly, even when the interlayer insulating film is exposed to an oxygen plasma, only a small amount of SiOH is generated and the dehydration condensation of SiOH does not occur in the step of filling a metal material in contact holes. As a result, H 2 O is not generated and hence the problem of faulty conduction at a contact does not occur. Moreover, since the silicon oxide film containing the organic component is formed by causing the material containing the organic silicon compound as the main component to undergo plasma polymerization or react with an oxidizing agent, it is no more necessary to perform the steps of applying an organic SOG agent and curing the applied organic SOG agent, resulting in excellent film formability. In the above first method of forming an interlayer insulating film, the organic silicon compound represented by the general formula: R 1 x Si(OR 2 ) 4-x is preferably phenyltrimethoxysilane or diphenyldimethoxysilane. In the above second method of forming an interlayer insulating film, the organic silicon compound represented by the general formula: R 1 x Si(OR 2 ) 4-x is preferably vinyltrimethoxysilane or divinyldimethoxysilane. In a preferred method of forming an interlayer insulating film according to the present invention, a material containing, as a main component, a gas mixture of an organic silicon compound composed of a compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x (where R 1 is a phenyl group or a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3) and a fluorinated carbon compound is caused to undergo plasma polymerization or react with an oxidizing agent to form an interlayer insulating film composed of a silicon oxide film containing a fluorinated carbon. In accordance with this method of forming an interlayer insulating film, the silicon oxide film containing a fluorinated carbon is formed by causing the material containing, as the main components, the organic silicon compound and the fluorinated carbon compound to undergo plasma polymerization or react with the oxidizing agent so that the resulting interlayer insulating film contains the organic silicon compound and the fluorinated carbon compound, which significantly lowers the dielectric constant of the interlayer insulating film. Moreover, since the steps of applying the organic SOG agent and curing the applied organic SOG agent, which have been necessary to form the conventional organic SOG film, are no more necessary, similarly to the above first and second method of forming an interlayer insulating film, excellent film formability is achieved. FIG. 1 is a schematic view of a plasma CVD apparatus for use in a method of forming an interlayer insulating film according to the present invention; FIGS. 2(a) to 2(d) are cross-sectional views illustrating individual process steps in accordance with a method of manufacturing a semiconductor device to which the method of forming an interlayer insulating film according to the present invention is applied; FIGS. 3(a) to 3(d) are cross-sectional views illustrating individual process steps in accordance with another method of manufacturing a semiconductor device to which the method of forming an interlayer insulating film according to the present invention is applied; FIG. 4 shows the result of analysis when Fourier transform infrared spectroscopy was performed with respect to an interlayer insulating film prepared according to the present invention and to a conventional organic SOG film; FIG. 5 shows the result of analysis when Fourier transform infrared spectroscopy was performed with respect to interlayer insulating films prepared according to the present invention, which had undergone no thermal treatment, a thermal treatment at 450 °C, and a thermal treatment at 500 °C; and FIGS. 6(a) to 6(d) are cross-sectional views illustrating individual process steps in accordance with a conventional method of forming an interlayer insulating film. Referring now to FIG. 1, a description will be given first to a CVD apparatus for use in a method of forming an interlayer insulating film according to the present invention, which will be described later. FIG. 1 schematically shows the structure of a parallel-plate plasma CVD apparatus. As shown in the drawing, a semiconductor substrate 12 made of silicon and a sample stage 13, which is to serve as a lower electrode, are disposed in a hermetic reaction chamber 11. The sample stage 13 is connected to a first RF power source 15 or to the ground via a change-over switch 14. The sample stage 13 is internally provided with a heater (not shown) for heating the semiconductor substrate 12 placed on the sample stage 13 to a specified temperature. In a position opposing the sample stage 13 in the reaction chamber 11, there is provided a shower head 16, which is to serve as an upper electrode. The shower head 16 is connected to a second RF power source 17 for supplying RF power at 13.56 MHz. The reaction chamber 11 is provided with first, second, and third gas supply lines 21, 22, and 23 for introducing a gas into the reaction chamber 11. The first gas supply line 21 is provided with a first container 24 for containing a liquid raw material therein. When the first container 24 is supplied with carrier gas at a flow rate controlled by a mass flow controller (not shown), the bubbled gas is introduced from the first container 24 into the reaction chamber 11. The second gas supply line 22 is provided with a second container 25 for containing a liquid raw material therein. When the second container 25 is supplied with carrier gas at a flow rate controlled by a mass flow controller (not shown), the bubbled gas is introduced from the second container 25 into the reaction chamber 11. Since the reaction chamber 11 is connected to a vacuum pump 26, the reaction chamber 11 can be evacuated by driving the vacuum pump 26 so that the gases are exhausted from the reaction chamber 11. Below, a method of manufacturing a semiconductor device to which the method of forming an interlayer insulating film according to the present invention is applied will be described with reference to FIGS. 2(a) to 2(d). First, as shown in FIG. 2(a), first metal wires 101 made of, e.g., aluminum are formed on a semiconductor substrate 100. Then, as shown in FIG. 2(b), an interlayer insulating film 102 is deposited over the semiconductor substrate 100 including the first metal wires 101. As for a method of forming the interlayer insulating film 102, it will be described later. Next, as shown in FIG. 2(c), the interlayer insulating film 102 is subjected to planarization. Thereafter, as shown in FIG. 2(d), a contact 103 is formed in the interlayer insulating film 102, followed by second metal wires 104 made of, e.g., aluminum which are formed on the interlayer insulating film 102. Below, another method of manufacturing a semiconductor device to which the method of forming an interlayer insulating film according to the present invention is applied will be described with reference to FIGS. 3(a) to 3(d). First, as shown in FIG. 3(a), a first silicon nitride film 201, a first interlayer insulating film 202, a second silicon nitride film 203, and a second interlayer insulating film 204 are sequentially deposited on a semiconductor substrate 200. As for a method of forming the first and second interlayer insulating films 202 and 204, it will be described later. Next, as shown in FIG. 3(b), the second silicon nitride film 203 and the second interlayer insulating film 204 are patterned by photolithography to form openings 205 for forming a wiring pattern. Then, the first silicon nitride film 201 and the first interlayer insulating film 202 are patterned by photolithography to form openings for contacts. In this case, the second silicon nitride film 203 serves as an etching stopper against etching performed with respect to the second interlayer insulating film 204, while the first silicon nitride film 201 serves as an etching stopper against etching performed with respect to the first interlayer insulating film 202. Next, as shown in FIG. 3(c), a metal film 207 made of, e.g., copper is deposited over the entire surface of the semiconductor substrate 200 by sputtering or CVD and caused to reflow by a thermal treatment to be filled in the openings 205 for forming a wiring pattern and in the openings 206 for contacts. The metal film 207 is then subjected to CMP to form metal wires 208 and contacts 209 as shown in FIG. 3(d), resulting in buried wiring having a dual damascene structure. (First Embodiment) An interlayer insulating film prepared according to a first embodiment is a plasma polymerization film formed by inducing plasma polymerization of a material containing, as a main component, e.g. phenyltrimethoxysilane which is an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x (where R 1 is a phenyl group or a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3). A description will be given to a method of forming the interlayer insulating film prepared according to the first embodiment. First, the semiconductor substrate 12 is placed on the sample stage 13 heated to, e.g., 400 °C and grounded by the change-over switch 14 and then the reaction chamber 11 is evacuated by the vacuum pump 26. Next, phenyltrimethoxysilane represented by the following Chemical Formula 1: is contained in the first container 24, while carrier gas composed of, e.g., argon is supplied at a flow rate of 480 ml/min to the first container 24 so that bubbled phenyltrimethoxysilane is introduced into the reaction chamber 11. Next, the pressure inside the reaction chamber 11 is set to about 1.0 Torr and RF power of 250 W at a frequency of 13.56 MHz is applied from the second RF power source 17 to the shower head 16 serving as the upper electrode. During the process, phenyltrimethoxysilane gas is partially decomposed to generate monomers, ions, and radicals as decomposition products, which are polymerized to form the interlayer insulating film made of the plasma polymerization film on the semiconductor substrate 12. The structure of the plasma polymerization film is diagrammatically shown by the following Chemical Formula 2: Since the interlayer insulating film prepared according to the first embodiment is formed by plasma CVD, it is unnecessary to repeatedly perform the steps of applying the organic SOG agent and thermally curing the applied SOG agent several times, resulting in improved film formability and lower cost. In addition, since the interlayer insulating film prepared according to the first embodiment contains SiCH 3 in an amount much smaller than in the conventional organic SOG film, a minimum amount of SiOH is generated even when the interlayer insulating film is etched by using an oxygen plasma. Consequently, the step of filling metal in contact holes is free from the phenomenon that SiOH is condensed by dehydration to generate H 2 O and cause faulty conduction at a contact. FIG. 4 shows the result of analysis when Fourier transform infrared spectroscopy (hereinafter referred to as FT-IR) was performed with respect to the interlayer insulating film prepared according to the first embodiment and to the conventional organic SOG film. In contrast to the spectrum obtained from the conventional organic SOG film which exhibits a distinct peak of absorbance in the vicinity of a wave number of 1300 cm -1 , the spectrum obtained from the interlayer insulating film prepared according to the first embodiment exhibits only a small peak of absorbance in the vicinity of a wave number of 1300 cm -1 , which indicates that the interlayer insulating film prepared according to the first embodiment contains a smaller amount of SiCH 3 than the conventional organic SOG film. FIG. 5 shows the result of analysis when FT-IR was performed with respect to interlayer insulating films which had undergone no thermal treatment, a thermal treatment at 450 °C in a nitrogen atmosphere, and a thermal treatment at 500 °C in a nitrogen atmosphere. Since no difference is observed between the FT-IR spectra obtained from the interlayer insulating films with no thermal treatment and with the thermal treatments at 450 °C and 500 °C, it will be understood that the interlayer insulating film prepared according to the first embodiment has sufficiently high heat resistance to withstand an LSI manufacturing process. The dielectric constant of the interlayer insulating film prepared according to the first embodiment was about 3.0. After the interlayer insulating film was allowed to stand at room temperature for about 2 weeks, the dielectric constant thereof was measured again to be about 3.1. This indicates that the interlayer insulating film prepared according to the first embodiment has stable film quality scarcely varying with time. The density of leakage currents was also measured to be about 4.5 x 10 -8 A/cm 2 at 5 MV/cm, which was satisfactory. Although the pressure inside the reaction chamber 11 has been set to about 1.0 Torr, it is not limited thereto but may be set at any value within the range of 100 mTorr to 20 Torr. More preferably, the pressure inside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr. Although the semiconductor substrate 12 has been heated to 400 °C, it is not limited thereto but may be heated to any temperature within the range of 25 to 500 °C. If the semiconductor substrate 12 is heated to a temperature over 400 °C, however, aluminum composing the metal wires formed on the semiconductor substrate 12 will lose heat resistance, so that the semiconductor substrate 12 is preferably heated to a temperature equal to or lower than 400 °C. If the temperature of the semiconductor substrate 12 is less than 200 °C, on the other hand, an undesired component may be contained in the interlayer insulating film being formed, so that the semiconductor substrate 12 is preferably heated to a temperature of 200 °C or more. The RF power applied to the shower head 16 as the upper electrode may have any value within the range of 100 to 1000 W. More preferably, the RF power has a value within the range of 250 to 500 W. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a phenyl group, there can be listed diphenyldimethoxysilane (Ph 2 -Si-(OCH 3 ) 2 ) in addition to phenyltrimethoxysilane. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a vinyl group, there can be listed vinyltrimethoxysilane (CH 2 =CH-Si-(OCH 3 ) 3 ) and divinyldimethoxysilane ((CH 2 =CH) 2 -Si-(OCH 3 ) 2 ). In addition to the above process, the interlayer insulating film may also be formed by causing the material having, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x , wherein R 1 is a phenyl group; R 2 is an alkyl group; and x is an integer of 1 to 3, to react with an oxidizing agent made of, e.g., O 2 or H 2 O. In this case, O 2 gas, H 2 O gas, or the like is introduced into the reaction chamber 11 through the third gas supply line 23 in the CVD apparatus shown in FIG. 1. (Second Embodiment) An interlayer insulating film prepared according to a second embodiment is a silicon oxide film containing a fluorinated carbon formed by inducing plasma polymerization of a material containing, as a main component, a gas mixture of e.g. phenyltrimethoxysilane which is an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x (where R 1 is a phenyl group or a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3) and a benzene derivative having a F-C bond which is a fluorinated carbon compound. A description will be given to a method of forming the interlayer insulating film prepared according to the second embodiment. First, the semiconductor substrate 12 is placed on the sample stage 13 heated to, e.g., 400 °C and grounded by the change-over switch 14 and then the reaction chamber 11 is evacuated by the vacuum pump 26. Next, carrier gas composed of, e.g., argon is supplied at a flow rate of 200 ml/min to the first container 24 containing therein phenyltrimethoxysilane represented by the foregoing Chemical Formula 1, so that bubbled phenyltrimethoxysilane is introduced into the reaction chamber 11. Meanwhile, carrier gas composed of, e.g., argon is supplied at a flow rate of 200 ml/min to the second container 25 containing therein difluorobenzene which is a benzene derivative having a F-C bond represented by the following Chemical Formula 3 so that bubbled difluorobenzene is introduced into the reaction chamber 11: Next, the pressure inside the reaction chamber 11 is set to about 1.0 Torr and RF power of 600 W at a frequency of 13.56 MHz is applied from the second RF power source 17 to the shower head 16 serving as the upper electrode. During the process, phenyltrimethoxysilane gas and difluorobenzene are partially decomposed to generate monomers, ions, and radicals as decomposition products, which are polymerized to form the interlayer insulating film composed of the plasma polymerization film on the semiconductor substrate 12. The structure of the plasma polymerization film is diagrammatically shown by the following Chemical Formula 4: Since the interlayer insulating film prepared according to the second embodiment is formed by plasma CVD, it is unnecessary to repeatedly perform the steps of applying the organic SOG agent and thermally curing the applied SOG agent several times, resulting in improved film formability and lower cost. The dielectric constant of the interlayer insulating film prepared according to the second embodiment was as low as about 2.5. After the interlayer insulating film was allowed to stand at room temperature for about 2 weeks, the dielectric constant thereof was measured again to be about 2.7, which indicates stable film quality scarcely varying with time. Thus, according to the second embodiment, there can be formed the interlayer insulating film with improved film formability and a reduced dielectric constant. The density of leakage currents was also measured to be about 4.5 x 10 -8 A/cm 2 at 5 MV/cm, which was satisfactory. Although the pressure inside the reaction chamber 11 has been set to about 1.0 Torr, it is not limited thereto but may be set at any value within the range of 100 mTorr to 20 Torr. More preferably, the pressure inside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr. The RF power applied to the shower head 16 as the upper electrode may have any value within the range of 100 to 1000 W. More preferably, the RF power has a value within the range of 250 to 500 W. Although the semiconductor substrate 12 may be heated to any temperature within the range of 25 to 500 °C, similarly to the first embodiment, it is preferably heated to a temperature within the range of 200 to 400 °C. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a phenyl group, there can be listed diphenyldimethoxysilane in addition to phenyltrimethoxysilane. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a vinyl group, there can be listed vinyltrimethoxysilane and divinyldimethoxysilane. As the benzene derivative having a F-C bond which is a fluorinated carbon compound, benzene fluoride such as fluorobenzene or hexafluorobenzene may be used instead of difluorobenzene. (Third Embodiment) An interlayer insulating film prepared according to a third embodiment is a silicon oxide film containing a fluorinated carbon formed by inducing plasma polymerization of a material containing, as a main component, a gas mixture of e.g. phenyltrimethoxysilane which is an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x (where R 1 is a phenyl group or a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3) and C 2 F 6 which is a fluorinated carbon compound. A description will be given to a method of forming the interlayer insulating film prepared according to the third embodiment. First, the semiconductor substrate 12 is placed on the sample stage 13 heated to, e.g., 400 °C and grounded by the change-over switch 14 and then the reaction chamber 11 is evacuated by the vacuum pump 26. Next, carrier gas composed of, e.g., argon is supplied at a flow rate of 200 ml/min to the first container 24 containing therein phenyltrimethoxysilane so that bubbled phenyltrimethoxysilane is introduced into the reaction chamber 11, while C 2 F 6 gas is introduced into the reaction chamber 11 through the third gas supply line 23. Next, the pressure inside the reaction chamber 11 is set to about 1.0 Torr and RF power of 700 W at a frequency of 13.56 MHz is applied from the second RF power source 17 to the shower head 16 serving as the upper electrode. During the process, phenyltrimethoxysilane gas and C 2 F 6 are partially decomposed to generate monomers, ions, and radicals as decomposition products, which are polymerized to form the interlayer insulating film composed of the plasma polymerization film on the semiconductor substrate 12. The structure of the plasma polymerization film is diagrammatically shown by the following Chemical Formula 5: Since the interlayer insulating film prepared according to the third embodiment is formed by plasma CVD, it is unnecessary to repeatedly perform the steps of applying the organic SOG agent and thermally curing the applied SOG agent several times, resulting in improved film formability and lower cost. The dielectric constant of the interlayer insulating film prepared according to the third embodiment was as low as about 2.9. After the interlayer insulating film was allowed to stand at room temperature for about 2 weeks, the dielectric constant thereof was measured again to be about 3.0, which indicates stable film quality scarcely varying with time. Thus, according to the third embodiment, there can be formed the interlayer insulating film with improved film formability and a reduced dielectric constant. The density of leakage currents was also measured to be about 5.5 x 10 -8 A/cm 2 at 5 MV/cm, which was satisfactory. Although the pressure inside the reaction chamber 11 has been set to about 1.0 Torr (133,32 Pa), it is not limited thereto but may be set at any value within the range of 100 mTorr (13,32 Pa) to 20 Torr (2666,4 Pa). More preferably, the pressure inside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr (66,66 to 666,6 Pa). The RF power applied to the shower head 16 as the upper electrode may have any value within the range of 100 to 2000 W. More preferably, the RF power has a value within the range of 300 to 750 W. Although the semiconductor substrate 12 may be heated to any temperature within the range of 25 to 500 °C, it is preferably heated to a temperature within the range of 200 to 400 °C. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a phenyl group, there can be listed diphenyldimethoxysilane in addition to phenyltrimethoxysilane. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a vinyl group, there can be listed vinyltrimethoxysilane and divinyldimethoxysilane. As the fluorinated carbon compound, CF 4 , C 4 F 8 , or the like may be used instead of C 2 F 6 . In addition to the above process, the interlayer insulating film may also be formed by causing the material having, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x , wherein R 1 is a phenyl group; R 2 is an alkyl group; and x is an integer of 1 to 3, to react with an oxidizing agent made of, e.g., O 2 or H 2 O. In this case, O 2 gas or H 2 O gas as well as C 2 F 6 gas is introduced into the reaction chamber 11 through the third gas supply line 23. (Fourth Embodiment) An interlayer insulating film prepared according to a fourth embodiment is a silicon oxide film containing a fluorinated carbon formed by inducing plasma polymerization of a material containing, as a main component, a gas mixture of e.g. phenyltrimethoxysilane which is an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x (where R 1 is a phenyl group or a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3) and perfluorodecalin which is a fluorinated carbon compound represented by the following Chemical Formula 6. A description will be given to a method of forming the interlayer insulating film prepared according to the fourth embodiment. First, the semiconductor substrate 12 is placed on the sample stage 13 heated to, e.g., 400 °C and grounded by the change-over switch 14 and then the reaction chamber 11 is evacuated by the vacuum pump 26. Next, carrier gas composed of, e.g., argon is supplied at a flow rate of 280 ml/min to the first container 24 containing therein phenyltrimethoxysilane so that bubbled phenyltrimethoxysilane is introduced into the reaction chamber 11. Meanwhile, carrier gas composed of, e.g., argon is supplied at a flow rate of 42 ml/min to the second container 25 containing therein perfluorodecalin so that bubbled perfluorodecalin is introduced into the reaction chamber 11. Next, the pressure inside the reaction chamber 11 is set to about 2.0 Torr and RF power of 500 W at a frequency of 13.56 MHz is applied from the second RF power source 17 to the shower head 16 serving as the upper electrode. During the process, phenyltrimethoxysilane gas and perfluorodecalin are partially decomposed to generate monomers, ions, and radicals as decomposition products, which are polymerized to form the interlayer insulating film made of the plasma polymerization film on the semiconductor substrate 12. Since the interlayer insulating film prepared according to the fourth embodiment is formed by plasma CVD, it is unnecessary to repeatedly perform the steps of applying the organic SOG agent and thermally curing the applied SOG agent several times, resulting in improved film formability and lower cost. The dielectric constant of the interlayer insulating film prepared according to the fourth embodiment was as low as about 2.6. After the interlayer insulating film was allowed to stand at room temperature for about 2 weeks, the dielectric constant thereof was measured again to be about 2.7, which indicates stable film quality scarcely varying with time. Thus, according to the fourth embodiment, there can be formed the interlayer insulating film with improved film formability and a reduced dielectric constant. Moreover, the interlayer insulating film had a glass transition temperature of 430 °C or more, which indicates excellent heat resistance. Although the pressure inside the reaction chamber 11 has been set to about 1.0 Torr (133,32 Pa), it is not limited thereto but may be set at any value within the range of 100 mTorr (13,32 Pa) to 20 Torr (2666,4 Pa). More preferably, the pressure inside the reaction chamber 11 is within the range of 0.5 to 5.0 Torr (66,66 to 666,6 Pa). The RF power applied to the shower head 16 as the upper electrode may have any value within the range of 100 to 1000 W. More preferably, the RF power has a value within the range of 250 to 500 W. Although the semiconductor substrate 12 may be heated to any temperature within the range of 25 to 500 °C, similarly to the first embodiment, it is preferably heated to a temperature within the range of 200 to 400 °C. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a phenyl group, there may be listed diphenyldimethoxysilane in addition to phenyltrimethoxysilane. As compounds represented by the foregoing general formula: R 1 x Si(OR 2 ) 4-x where R 1 is a vinyl group, there may be listed vinyltrimethoxysilane and divinyldimethoxysilane.

Claims: A method of forming an interlayer insulating film, wherein a material containing, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x , wherein R 1 is a phenyl group; R 2 is an alkyl group; and x is an integer of 1 to 3, is caused to undergo plasma polymerization or react with an oxidizing agent to form an interlayer insulating film composed of a silicon oxide film containing an organic component. A method of forming an interlayer insulating film, wherein a material containing, as a main component, an organic silicon compound represented by the following general formula: R 1 x Si(OR 2 ) 4-x , wherein R 1 is a vinyl group; R 2 is an alkyl group; and x is an integer of 1 to 3, is caused to undergo plasma polymerization to form an interlayer insulating film composed of a silicon oxide film containing an organic component. The method of claim 1, wherein said organic silicon compound is phenyltrimethoxysilane or diphenyldimethoxysilane. The method of claim 2, wherein said organic silicon compound is vinyltrimethoxysilane or divinyldimethoxysilane.

Inventors: AOI NOBUO, ARAI KOJI, SAWADA KAZUYUKI, SUGAHARA GAKU, AOI, NOBUO, ARAI, KOJI, SAWADA, KAZUYUKI, SUGAHARA, GAKU
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1997
Main classification: C23C16
IPC codes: H01L21, C23C16