JP3633821B2 - Method for forming low dielectric constant porous silica film from gas phase - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a low dielectric constant porous silica film on a substrate at a low temperature and used for reducing the parasitic capacitance between wirings in multilayer wiring of a large scale integrated circuit device such as logic processing and memory, and the silica. The present invention relates to a semiconductor device having a film as an interlayer insulating film.
[0002]
[Prior art]
A low dielectric constant silicon-based insulating film used to reduce parasitic capacitance between wirings in a multilayer wiring of a large scale integrated circuit device is, for example, silica by oxidizing TEOS [Si (OC ₂ H ₅ ) ₄ ] with ozone. A CVD method for depositing a film from the gas phase is frequently used. The reason for this is that, in the CVD method, fine and deep grooves and holes generated on the LSI chip surface due to wiring, contacts, element isolation, etc. are filled with a silica film having excellent insulating properties. However, the silica film has a high relative dielectric constant of about 4.
[0003]
One common method for realizing a low dielectric constant film is an SOG film forming method called a spin-on-glass method using a solution containing an organosilane. A conventional SOG film is considered to be a low dielectric constant film due to electronic polarization and a decrease in density of the film itself due to the silicon-carbon bond therein. However, when the content of methyl group or the like increases, oxygen plasma resistance and adhesion become problems, and it is necessary to devise such as using a protective film. Therefore, a dielectric constant of about 3 has been practical.
[0004]
It has been reported that a relative dielectric constant of about 2 can be achieved by a carbon film called fluorocarbon bonded to fluorine (for example, Japanese Patent Laid-Open No. 10-209148). It is necessary to introduce a layer for improvement, and there is a problem of oxygen plasma resistance because it is a material close to a resist because it is basically a carbon film. Japanese Patent Application Laid-Open No. 11-31690 discloses that the pore size of the porous film formed by treating the SOG film with a gaseous basic compound or drying under reduced pressure is reduced to make the dielectric constant about 2.3. The method of making it low is disclosed.
[0005]
[Problems to be solved by the invention]
The conventional method for forming a porous silica film is to form pores in the film by evaporating the solvent component contained in the film using an organic silica liquid as described above, or particles having a small diameter. Is formed into a film. In these methods, it is difficult to fill fine holes of 1 micron or less existing on an LSI due to the influence of surface tension and the like. Furthermore, OH groups were contained in the film, which caused the characteristics to become unstable.
[0006]
For this reason, on LSIs having a fine structure and the like, restrictions are imposed as circuit miniaturization progresses, and the relative dielectric constant is required to be 2 or less, and it is highly possible to control the relative dielectric constant. Development of a means for forming a porous silica film is required.
[0007]
[Means for Solving the Problems]
The present invention is realized by a method (CVD method) in which a low dielectric constant silicon-based insulating film containing no OH group and hydrogen is deposited from a vapor phase at a low deposition temperature without using a liquid.
[0008]
That is, the present invention relates to a method for depositing a silicon-based insulating film on a substrate by chemical vapor deposition, a silicon-based material having a cyanate group, a silicon-based material having at least an alkyl group other than a methyl group or a phenyl group , and Gases derived from three kinds of amines are introduced into the reaction chamber and reacted to deposit a silicon-based insulating film on the substrate, and the silicon-based insulating film is heat-treated to remove an alkyl group having a desorption temperature lower than that of the methyl group or This is a method for forming a low dielectric constant porous silica film, wherein the phenyl group is removed from the insulating film.
[0009]
The presence of a methyl group in a silicon-based insulating film containing an organic component such as an alkyl group has an effect as described later, and the component to be eliminated is more effective as the molecular weight is larger. It is necessary to use a raw material having at least an alkyl group or a phenyl group other than a methyl group that can be eliminated at a low temperature.
[0010]
Preferably, the silicon-based material having a cyanate group is tetraisocyanate silane, the silicon-based material having at least a phenyl group other than a methyl group is bisdimethylaminodiphenylsilane, and the silicon-based insulating film deposited on the substrate is It is a film containing a phenyl group and no hydroxyl group.
[0011]
Preferably, the silicon-based material having a cyanate group and the silicon-based material having at least an alkyl group other than a methyl group are alkylsilyl isocyanate silanes having a cyanate group and simultaneously having at least an alkyl group other than a methyl group. .
[0012]
Since tetraisocyanate silane does not contain hydrogen in the raw material, a film containing no hydrogen can be deposited in principle, and has a dipole moment with a strong N—C bond existing in the structure. High quality organic silica films can be deposited by reacting with seed amines (alkylamines such as trimethylamine) at low temperatures.
[0013]
Bisdimethylaminodiphenylsilane has a structure in which two benzene rings and two dimethylamino groups are attached to a silicon atom. By flowing the above bisdimethylaminodiphenylsilane during the deposition of tetraisocyanate silane and the third type amine, an organic silica film containing a phenyl group in the film can be deposited.
[0014]
As the third type amine, for example, a trialkylamine such as trimethylamine, dimethylmonoethylamine, monomethyldiethylamine, triethylamine or the like, or a hydrogen of a trialkylamine such as trifluoromethylamine or trifluoroethylamine substituted with a halogen is used. it can.
[0015]
In the method of the present invention described in claims 1 to 4, a preferable deposition temperature is 200 ° C. or lower in order to include an alkyl group or a phenyl group other than a methyl group in the film. Further, if it is lower than 100 ° C., H ₂ O or OH may enter the film, so that it is preferably 100 ° C. or higher.
[0016]
In the method of the present invention, when a methyl group is contained in the film, the methyl group has a water repellency and has an effect such as good stability after film formation. For example, methylsilyl isocyanate silane and dimethyl diisocyanate silane having a cyanate group and a methyl group at the same time may be used as a raw material or mixed with the raw material.
[0017]
The organosilica film formed by the film-forming method according to claim 2 contains a phenyl group, which is preferably 300 ° C. or higher, more preferably 400 ° C. to 450 ° C. in an inert atmosphere or vacuum. On the other hand, when annealed for about 30 minutes, the phenyl group is detached from the organic silica film to form fine pores in the insulating film. When aluminum wiring is used on the substrate, the upper limit is preferably set to 450 ° C. because the aluminum and silicon in the insulating film react when the annealing temperature is high.
[0018]
Moreover, this invention is a formation method characterized by carrying out the silylation process to the low dielectric constant porous silica film formed by said method.
[0019]
Since the pores are dangling bonds of silicon, they react with moisture in the atmosphere to generate OH bonds. In order to prevent this, silylation treatment is more preferably performed using hexamethyldisilazane. The silylation treatment is preferably performed in an atmospheric pressure of about 250 ° C. Some pores are blocked by methyl groups, but are necessary for stability.
[0020]
The present invention further provides a semiconductor device characterized by having a low dielectric constant porous silica film formed by the above method as an interlayer insulating film.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the method of the present invention using a schematic side view of a CVD apparatus.
According to the present invention, it can be deposited organic silica film at a low temperature of about deposition temperature 100 to 150 ° C. using an atmospheric hot-wall type CVD apparatus.
[0022]
In a reaction chamber (reaction vessel) 1, a silicon raw material having a cyanate group containing no hydrogen, a third type amine, and a silicon-based raw material containing an alkyl group other than a methyl group or a phenyl group are reacted to form a methyl group on the substrate 5. alkyl group or an organic component such as a phenyl group other than to deposit the silicon dielectric film contained. The third type amine is supplied from the A supply pipe 2. The raw material gas is introduced into the reaction chamber 1 from the B supply pipe 3 directly or using the carrier gas. The third type amine supplied from the A supply pipe 2 reacts with the silicon raw material supplied from the B supply pipe 3 in the reaction chamber 1 to form a reaction product 7 at a low temperature.
[0023]
A silicon-based raw material having a cyanate group and a silicon-based raw material having an alkyl group other than a methyl group or a phenyl group, or a silicon-based raw material simultaneously containing a cyanate group and an alkyl group or a phenyl group other than a methyl group are: Supply from. For example, tetraisocyanate silane, bisdimethylaminodiphenyl silane, and phenyl triisocyanate silane are supplied. The amount of alkyl groups other than methyl groups or phenyl groups remaining in silicon-based insulating films containing organic components such as alkyl groups other than methyl groups or phenyl groups by changing film formation conditions such as gas mixing ratio Can be adjusted. The reaction product 7 generated in the reaction chamber 1 is deposited on the substrate 5 to form a silicon-based low dielectric constant insulating film 6 containing an organic component such as an alkyl group other than a methyl group or a phenyl group . The remaining reaction gas is exhausted from the exhaust pipe 4.
[0024]
【Example】
Example 1
FIG. 2 is a schematic flow diagram of Example 1 for producing the low dielectric constant porous silica film of the present invention.
A gas such as trimethylamine is supplied to the supply pipe 2 of A as the third type amine. Nitrogen gas is introduced as a carrier gas from the B supply pipe 3 and the liquid tetraisocyanate silane 22 gas contained in the container is carried to the reaction chamber 1 as a silicon-based material having a cyanate group. Also, nitrogen gas is introduced from the C supply pipe 4 as a carrier gas, and the liquid bisdimethylaminodiphenylsilane 23 gas contained in the container is conveyed to the reaction chamber 1 as a silicon-based material having a phenyl group.
[0025]
The flow rate of the amine gas is adjusted by the flow control device 11. The flow rate of the carrier gas carrying the tetraisocyanate silane gas is adjusted by the flow rate control device 12. The flow rate of the carrier gas carrying the bisdimethylaminodiphenylsilane gas is adjusted by the flow rate control device 13. The supply pipe 2 of A is provided with valves 14 and 15. Valves 16, 17, and 18 are provided in the B supply pipe 3. Valves 19, 20, and 21 are provided in the C supply pipe 4. The temperature of the reaction chamber 1 and the substrate 6 is adjusted by a heater 24 surrounding the reaction chamber 1.
[0026]
In FIG. 2, the third type amine-based gas is directly introduced into the reaction chamber 1 through the A supply pipe 2. The flow rate is controlled by the flow rate control device 11. A carrier gas is introduced through the B supply pipe 3, passes through the liquid tetraisocyanate silane 22, and is introduced into the reaction chamber 1 together with the tetraisocyanate silane gas. The flow rate is controlled by the flow rate control device 12. A carrier gas is introduced through the C supply pipe 4, passes through the liquid bisdimethylaminodiphenylsilane 23, and is introduced into the reaction chamber 1 together with the gas of bisdimethylaminodiphenylsilane. The flow rate is controlled by the flow rate control device 13.
[0027]
In the reaction chamber 1, an amine-based gas, a tetraisocyanate silane, and a bisdimethylaminodiphenylsilane gas are reacted and thermally decomposed at normal pressure or reduced pressure, and an organic silica film containing a phenyl group is deposited on the substrate 6. .
[0028]
According to the method described above, the flow rate of the amine-based raw material was flowed into the reaction chamber 1 at a flow rate of 60 sccm, TICS at 0.007 sccm (nitrogen carrier gas 10 sccm), and bisphenyldimethylaminodiphenylsilane at a flow rate of 0.007 sccm (nitrogen carrier gas 133 sccm). Then, an organic silica film was deposited on the substrate 6. The deposition temperature was 100 ° C., 150 ° C., and 200 ° C. The organic silica film deposited on the substrate 6 was heat-annealed in vacuum to remove the phenyl group from the film.
[0029]
FIG. 4 is a graph showing the results of measuring the deposition rate with respect to the flow rate of bisdimethylaminodiphenylsilane and the amount of carbon in the film by Auger photoelectron spectroscopy. In the silica film produced by the method of the present invention, it was confirmed that the carbon in the film was about 10 atomic weight% with respect to silicon.
[0030]
FIG. 5 is a graph showing the results (C6H5: phenyl group, temperature-programmed desorption spectrum having a mass number of 75) measured by the temperature-programmed thermal desorption method. It can be seen that the phenyl group is eliminated at 250 ° C. or higher, and heat treatment at about 400 ° C. or higher is preferable. FIG. 6 is a graph showing the results of determining the porosity with respect to the deposition temperature by an alcohol immersion method. Immediately after the deposition, annealing is performed in a vacuum at 400 ° C. for 30 minutes. From 100 ° C. to 150 ° C., the porosity is almost constant. It decreases at 200 ° C., and at 250 ° C. or higher, the deposited film does not contain phenyl groups, and no pores are produced even when annealing is performed in vacuum. Therefore, the deposition temperature is preferably a low temperature of 200 ° C. or lower.
[0031]
Example 2
FIG. 3 is a flow chart of an apparatus for performing silylation on a silica film deposited on a substrate 4, and valves 7, 8 and 9 are provided in the supply pipe system. The remaining gas in the reaction chamber 1 is exhausted from the exhaust port 6. A carrier gas was introduced from the supply pipe 2 and the liquid hexamethyldisilazane 10 gas contained in the container was carried into the reaction chamber 1 as a silylating agent. The flow rate of the carrier gas 3 was controlled by the flow rate control device 3. After deposition of the organic silica film, annealing in a vacuum at 400 ° C. was performed, and the substrate 4 having a porous silica film from which phenyl groups were eliminated was heated to 250 ° C. with a heater 5 to react methyl groups.
[0032]
FIG. 7 is a graph showing the change in relative dielectric constant with respect to the annealing temperature in vacuum. All samples are subjected to silylation treatment. The porous silica film annealed at 400 ° C. has a relative dielectric constant of 2.8, which indicates that the relative dielectric constant is smaller than those annealed at 300 ° C. and 350 ° C.
[0033]
【The invention's effect】
According to the present invention, a low-permittivity porous silica film suitable for use in reducing the inter-wiring parasitic capacitance is formed on a substrate at a low temperature by the above-described method in multilayer wiring of a large scale integrated circuit device. Therefore, it is more familiar with the existing device manufacturing process and contributes to solving the problem of high integration.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a CVD apparatus showing an embodiment of the method of the present invention.
FIG. 2 is a schematic flow diagram of a process of generating a silicon-based insulating film according to the first embodiment of the present invention.
FIG. 3 is a flow diagram of an apparatus for silylating a porous silica film.
FIG. 4 is a graph of the deposition rate and the amount of carbon in the film against the flow rate of bisdimethylaminodiphenylsilane.
FIG. 5 is a graph showing the results of measuring a porous silica film by a temperature rising thermal desorption method.
FIG. 6 is a graph of porosity versus deposition temperature of a silicon-based insulating film.
FIG. 7 is a graph showing the relative dielectric constant of a porous silica film with respect to the annealing temperature in vacuum.

Claims (6)

In a method of depositing a silicon-based insulating film on a substrate by chemical vapor deposition, a silicon-based material having a cyanate group, a silicon-based material having at least an alkyl group other than a methyl group or a phenyl group , and a third type amine as a material A silicon-based insulating film is deposited on the substrate by introducing a gas to be reacted into the reaction chamber, and the silicon-based insulating film is heat-treated to remove an alkyl group or a phenyl group having a desorption temperature lower than that of the methyl group from the insulating film. A method for forming a low-dielectric-constant porous silica film comprising removing the porous silica film. The silicon-based material having a cyanate group is tetraisocyanate silane, the silicon-based material having at least a phenyl group other than a methyl group is bisdimethylaminodiphenylsilane, and the silicon-based insulating film deposited on the substrate has a phenyl group. The method for forming a low dielectric constant porous silica film according to claim 1, wherein the film contains no hydroxyl group. The silicon-based raw material having a cyanate group and the silicon-based raw material having at least an alkyl group other than a methyl group are alkylsilyl isocyanate silanes having a cyanate group and at the same time having at least an alkyl group other than a methyl group. The method for forming a low dielectric constant porous silica film according to claim 1. The method for forming a low dielectric constant porous silica film according to any one of claims 1 to 3, wherein a raw material containing a methyl group is used in the film. A method for forming a low dielectric constant porous silica film, comprising subjecting the low dielectric constant porous silica film formed by the method according to claim 1 to silylation treatment. The semiconductor device characterized by having a low dielectric constant porous silica film formed by the method according to any one of claims 1 to 5 as an interlayer insulating film.

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