JP2000340651A - Manufacture of film having low dielectric constant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make low the dielectric constant of a composite film and improve its heat resistance, by adopting an echant whose etching speed relative to its component B is made not smaller than the etching speed being specific times as large as the etching speed relative to its component A, and by etching through the etchant the composite film made of the components A, B. SOLUTION: By using an etchant including hydrogen fluoride whose etching speed relative to a component B of SiO2 is made not smaller than the etching speed being ten times as large as the etching speed relative to a component A or polysiloxane made to the unit structure represented by RnSiO(4-n)/2, the composite film made of the components A, B is etched, where each of n pieces of R in the equation represents independently of others an organic group having one to six carbon atoms and (n) is a positive integer of one to three. Also, the sum of the numbers of the carbon atoms of the organic groups R bonded to a single Si atom is made not larger than eight. As a result, a high-quality composite film having a low dielectric constant and a high heat resistance can be manufactured with a good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a low dielectric constant film.

[0002]

2. Description of the Related Art With the miniaturization of wiring due to the high integration of LSIs, an increase in signal delay time due to an increase in capacitance between wirings has become a problem. Conventionally, a SiO ₂ film formed by a CVD method having a relative dielectric constant of about 4.2 has been used as an interlayer insulating film.
In order to improve the operation speed of the device, a film having a lower dielectric constant is required. As the low dielectric constant film, an SiOF film having a relative dielectric constant of about 3.5 (CVD method), an organic SOG (Spin On Glass) having a relative dielectric constant of 2.5 to 3.0, an organic polymer, etc. are currently in practical use. I'm coming. On the other hand, fluororesins and porous films have been proposed for materials having a relative dielectric constant of 2.5 or less which will be required in the future, but materials having sufficient properties as interlayer insulating films for LSIs have been developed. There is no present.

[0003] Fluororesins are expected as low dielectric constant materials because they have a relative dielectric constant of about 2, but Tg
Is not more than 300 ° C., it is difficult to apply it to the interlayer insulating film of the LSI as it is. As a method for solving this problem, a composite film of a fluororesin and polysiloxane as disclosed in Japanese Patent Application Laid-Open No. 9-144420 has been proposed. However, since the thermal decomposition onset temperature of the fluororesin is 400 ° C. or less, There is a problem that there is not enough margin even if the process temperature of the LSI is lowered.

[0004] Porous films are attracting attention as a technology capable of achieving a relative dielectric constant of 2 or less. As a method for forming a porous film, JP-A-8-162450, JP-A-8-593
No. 62, etc., a method of applying a polysiloxane solution and drying a gelled product, Japanese Patent Publication No. 6-1
No. 2790 discloses a method in which an organic polysiloxane-based coating solution containing an organic polymer such as polystyrene or polyethylene is applied and the organic polymer is decomposed by heat treatment.

However, the method of gelling and drying the polysiloxane solution has a problem that the process is complicated and the characteristics of the obtained film tend to vary. Further, in the method of thermally decomposing an organic polymer, a long-time heat treatment at a high temperature (about 450 ° C.) is required in order to completely decompose the organic polymer. (400 ° C. or lower), it is considered that application is difficult. In a miniaturized LSI, the diameter of the hole in the porous film is required to be controlled to 20 nm or less, which is about one tenth of the wiring interval and the wiring width. Cannot be controlled to a diameter of 20 nm or less.

[0006]

The inventions according to the first to sixth aspects of the present invention have a low relative dielectric constant (2.5 or less is possible) and a high heat resistance (450.degree. It is an object of the present invention to provide a method for producing a low-dielectric-constant film which can easily produce a high-quality film with high yield, is easy in quality control, and has an excellent effect of suppressing costs.

[0007]

According to the present invention, the etching rate for component B is one of the etching rate for component A.
The present invention relates to a method for producing a low dielectric constant film including a step of etching a composite film composed of a component A and a component B using an etching solution that is 0 times or more. In the present invention, the component A is represented by the following general formula (I)

Embedded image (In the general formula (I), n Rs each independently have 1 to 6 carbon atoms.
Wherein n is an integer of 1 to 3. However, the total number of carbon atoms of the organic group R bonded to one Si atom is 8 or less), the component B is SiO ₂ , and the etching solution is The present invention relates to a method for producing the low dielectric constant film, which is an etching solution containing hydrogen fluoride.

[0008] The present invention also relates to the method for producing a low dielectric constant film, wherein the composition of the composite film is 1.2 to 2.0 mol of Si with respect to 1.0 mol of carbon atoms. Also, the present invention
The present invention relates to the method for producing a low dielectric constant film, wherein the etching solution containing fluorine is 0.1 to 5% by weight of hydrofluoric acid.
Further, the present invention relates to the method for producing the low dielectric constant film, wherein the size of the space formed in the low dielectric constant film is 20 nm or less in diameter. Further, according to the present invention, the relative dielectric constant of the low dielectric constant film is 2.
The present invention relates to a method for producing the low dielectric constant film having a thickness of 5 or less.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the composite film comprising the components A and B and the etching solution is etched at a rate at which the etching rate for the component B is at least 10 times the etching rate for the component A. If so, various materials can be used without any particular limitation. In the present invention, it is necessary to select an appropriate combination of materials for the component A, the component B, and the etching solution.
It is desirable that the etching rate of the component B be high, and the etching rate of the component B with respect to the component A be 10 times or more.

As such a combination, for example,
The following combinations are mentioned. (1) Component A: General formula (I),

Embedded image(In the general formula (I), n Rs each independently have 1 to 6 carbon atoms.
Wherein n is an integer of 1 to 3. However, one
The total number of carbon atoms of the organic group R bonded to the Si atom is 8 or less
Polysiloxane having a unit structure represented by the following: Component B: SiO₂  Etching solution: Etching solution containing hydrogen fluoride

(2) Component A: organic polymer such as polyimide, polyquinoline, polyallyl ether, etc. Component B: SiO ₂ etching solution: etching solution containing hydrogen fluoride

(3) Component A: General formula (I)

Embedded image (In the general formula (I), n Rs each independently have 1 to 6 carbon atoms.
Wherein n is an integer of 1 to 3. However, the total number of carbon atoms of the organic group R bonded to one Si atom is 8 or less.) Polysiloxane having a unit structure represented by: Component B: Organic polymer soluble in solvent Etchant: Solvent ( Organic solvent, water, etc.)

[0013] SiO ₂ formed by SOG or CVD
When the film is etched with hydrofluoric acid, the etch rate of 0.1 to 5% by weight of hydrofluoric acid is about 100 to 10000 ° / min, depending on the film quality. On the other hand, the polysiloxane having an organic group as the component A of the combination (1) is hardly etched by about 0.1 to 5% by weight of hydrofluoric acid. Therefore, in the combination of (1), the etching selectivity of the component A and the component B is sufficient. Also in the case of the combination (2), since the organic polymer is not etched by hydrofluoric acid, the etching selectivity is also sufficient in this case. In the combination (3), the cured polysiloxane does not dissolve in the organic solvent, so that if the organic solvent that dissolves the organic polymer is selected, the etching selectivity is sufficient.

The combination (1) is excellent in heat resistance and mechanical strength at high temperatures since the component A is an organic group-containing polysiloxane. Further, since the organic-containing polysiloxane has little moisture absorption when left in the air, it is possible to avoid problems such as an increase in dielectric constant due to moisture absorption and degassing from the film, which are problems of the porous film. Further, since the component B is a polysiloxane containing no organic group and is of the same material, a composite film having a uniform film quality in which the component B is finely dispersed can be easily formed. As the component B is finely dispersed, the space formed by etching the component B is finely dispersed, the size of each space is reduced, and the mechanical strength and insulation of the film are improved. Also, as the size of each space is smaller, an LSI having finer wiring
Can be applied as an insulating film.

Regarding the combination (2), since the component A is an organic polymer, Tg (glass transition point) is determined in a step after the component B is etched to form a low dielectric film.
If the heat exceeding the temperature is applied, the film may be densified and the low dielectric property may be lost.

The combination of (3) is excellent in heat resistance and mechanical strength at high temperature, like the combination of (1). However, since etching is performed with a solvent, SiO ₂ is decomposed with hydrofluoric acid (1). And (2), the etching time is longer than that of the combination of (2). Further, since the combination of (2) and (3) is a combination of materials having different properties of polysiloxane and organic polymer, it is difficult to obtain a composite film having a uniform film quality in which the component B is finely dispersed.

In view of the compatibility with the LSI process, the combination (1) is most suitable for manufacturing the low dielectric constant film according to the present invention. Here, as a method of forming the composite film, CV
Although the D method and the SOG method can be used, a composite film in which the component B is appropriately dispersed in the component A is obtained, and the etching rate of the component B with respect to the component A is increased.
The OG method is more suitable. In addition, the SOG method has been conventionally used as a method for forming an organic group-containing polysiloxane, and is excellent in terms of simplicity of steps and reproducibility of film characteristics.

In the SOG method, a coating liquid (polysiloxane coating liquid) in which a polysiloxane oligomer is dissolved in a solvent is used to coat the substrate by spin coating. In order to obtain a cured film, the solvent is volatilized on a hot plate, and then heated at a temperature of about 350 ° C. to 450 ° C. using a furnace.

The polysiloxane coating solution can be obtained, for example, by subjecting an alkoxysilane monomer to hydrolysis and condensation by adding water in the presence of a solvent and a catalyst. At this time,
The molecular weight of the resulting polysiloxane is desirably in the range of 500 to 10,000 in terms of polystyrene. As the catalyst, inorganic acids such as nitric acid and phosphoric acid, and organic acids such as acetic acid and maleic acid can be used. As the solvent, an organic solvent can be used. Examples include alcohols such as methanol, ethanol, propanol and butanol, CF ₃ CH ₂ OH, CF ₃ CF ₂ CHOH, CF ₃ (CF _3
2 ) Fluorine-containing alcohol such as ₃ CH ₂ CH ₂ OH, acetate such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethylene glycol monomethyl acetate,
Various solvents such as glycol acetate solvents such as ethylene glycol diacetate, amide solvents such as N, N-methyl-2-pyrrolidone, and glycol ether solvents can be used.

As the alkoxysilane monomer for obtaining the polysiloxane coating solution, general formula (II):

Embedded image (In the general formula (II), n Rs each independently have 1 to 6 carbon atoms.
R ′ represents an alkyl group having 1 to 3 carbon atoms, and n is an integer of 0 to 3. However, the total number of carbon atoms of the organic group R bonded to one Si atom is 8 or less.)
Can be used, and these can be used in combination of two or more.

Examples of such alkoxysilane monomers include the following. Tetramethoxysilane, tetraethoxysilane, tetraalkoxysilanes such as tetrapropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, monoalkyl trialkoxysilanes such as hexyltrimethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, Dialkyldialkoxysilanes such as dimethyldiethoxysilane, etc .; alkoxysilanes having an aromatic ring such as phenyltrimethoxysilane, phenyltriethoxysilane and methylphenyltrimethoxysilane; trialkylmono such as trimethylmonomethoxysilane and triethylmonomethoxysilane Fluoroalkylsilanes such as alkoxysilanes, trifluoropropyltrimethoxysilane and pentafluorobutyltrimethoxysilane;

Among these alkoxysilanes, trialkylmonoalkoxysilanes are useful for increasing the etching selectivity of component A and component B. However, if too much is added, the adhesion of the composite film to the substrate will increase. Is reduced,
It is preferable that the content be 5 mol% or less of the entire alkoxysilane used to obtain the polysiloxane coating solution.

The general formula (I) as the component A

Embedded image (In the general formula (I), n Rs each independently have 1 to 6 carbon atoms.
Wherein n is an integer of 1 to 3. However, in order to form a polysiloxane consisting of unit structure represented by the total number of carbon atoms of the organic group R is bonded to one Si atom is 8 or less), a composite film made of SiO ₂ of component B As a method for obtaining a polysiloxane coating solution of the following, the alkoxysilanes (alkoxysilane monomer:
In the alkoxysilane represented by the general formula (II), n is 0
And a method of separately hydrolyzing and condensing the tetraalkoxysilanes necessary for the component B, and then mixing the two. The alkoxysilanes required for the component A and the tetraalkoxysilanes required for the component B Are mixed and simultaneously hydrolyzed and condensed.

In the latter method, the reaction is carried out under mild reaction conditions, and the oligomer containing a large amount of component A and the oligomer containing a large amount of component B are utilized by utilizing the difference in reactivity between the alkoxysilanes of component A and component B. Is preferably formed. Under the reaction conditions usually used, since the reactivity of the tetraalkoxysilanes of the component B is higher than the reactivity of the alkoxysilanes of the component A, the reaction of the alkoxysilanes of the component B easily occurs in the initial stage of the reaction,
An oligomer rich in component B is formed. In this method, a composite film in which the component B is finely dispersed is obtained as compared with a method in which the reaction of the component A and the component B are separately performed. Therefore, the space formed by etching the component B has a finer dispersed low dielectric constant. A film is obtained. In this method, the size of the space can be controlled to a diameter of 20 nm or less, which is a more preferable range for application as an interlayer film of an LSI.

The method for obtaining the low dielectric constant film of the present invention using the obtained polysiloxane coating solution is as follows.
1000-5000 rpm using polysiloxane coating solution
To form a coating film on the substrate by spin coating. Thereafter, the solvent is volatilized on a hot plate, and the temperature is set to 350 ° C. to 450 ° C. in a nitrogen atmosphere using a furnace for 0.5 hr to 2.0 hr.
To obtain a cured film (composite film). At this time, 400 ° C
When the above heating cannot be performed, heating at 350 ° C. to 400 ° C. may be performed.

Next, the cured film is etched with an etching solution containing fluorinated water. The temperature at this time is 20-30
There is no particular limitation as long as it is between ° C., but it is desirable to maintain a constant temperature in terms of reproducibility. The concentration in the case of using hydrofluoric acid may be determined between 0.1 and 5% by weight so that the treatment time becomes an appropriate length. May be impaired. Further, instead of hydrofluoric acid, a 0.1 to 10% by weight aqueous solution of ammonium fluoride which can provide an appropriate treatment time may be used.

The etching time is determined based on the stress of the cured film and the change in the refractive index. Examination of the relationship between the etching time, the stress, and the refractive index reveals that as the etching time becomes longer, the stress and the refractive index decrease and eventually become constant. The time during which the stress and the refractive index do not change is preferably set as the etching time. If the etching is continued even after the stress and the refractive index have become constant, the film may be peeled off from the substrate. Therefore, it is not preferable to make the etching time too long. The refractive index of the film can be measured with an ellipsometer, and the stress can be determined by measuring the warpage of the wafer.

The synthesis conditions and composition of the polysiloxane coating solution,
Depending on the conditions for forming the cured film, the low dielectric constant film obtained after etching the component B may have many Si-OH terminals. In that case, the moisture absorption of the film increases,
When the low dielectric property of the film is impaired, or when a multilayer wiring of the LSI is formed, problems such as poor conduction of the wiring occur due to the influence of degassing. In that case, by treating with hexamethyldisilazane (HMDS), Si-OH
By converting the terminal to Si—OH (CH ₃ ) ₃ , it is possible to reduce moisture absorption of the film. As a processing method, a method of exposing the wafer to HMDS vapor while heating the wafer to about 80 ° C. to 120 ° C. on a hot plate can be used. After exposing the wafer to the HMDS vapor, 150 ° C. is used to accelerate the HMDS reaction and remove excess HMDS.
Heating is performed at about 200 ° C.

Finally, in order to remove moisture adsorbed on the film during the etching, a furnace is used at 350.degree.
Heating is performed at 50 ° C. for 0.5 hr to 1.0 hr. At this time, if heating at 400 ° C. or more cannot be performed, 350 ° C. to 40 ° C.
Heating at 0 ° C. is sufficient.

According to the above method, the composition of the composite film composed of the component A and the component B is such that the content of Si is 1.2 to 1.0 mol per carbon atom (derived from the organic group R in the general formula (I)).
Preferably it is 2.0 moles. Adjustment to this range can be performed by adjusting the mixing ratio of the raw materials. The composition of the composite film can be confirmed by an FT-IR method, an elemental analysis method, or the like.

Si is added to 1.0 mole of C (carbon atom).
If (silicon atoms) is less than 1.2 mol, the component B tends to be hardly etched. On the other hand, if the content of Si exceeds 2.0 moles with respect to 1.0 mole of C, the density of the obtained low dielectric constant film is too low, so that the mechanical strength is significantly reduced or the entire composite film tends to be etched. There is. A particularly preferable range in terms of achieving both a low dielectric constant and mechanical strength is that Si is 1.2 to 1.0 mol C.
1.8 mol. Further, as an insulating film of an LSI having fine wiring, a preferable range for obtaining a film in which the size of each space in the film is 20 nm or less and the dielectric constant is 2.5 or less is C1.0 mol. On the other hand, Si is 1.3 to 1.6.
Is a mole. In addition, the size of each space in a film particularly suitable as an insulating film of an LSI having finer wiring is 1
A preferable range for obtaining a film having a dielectric constant of 2.5 nm or less is 0 nm or less.
1.5 mol.

A carbon atom (organic group R in the general formula (I)
If the amount of Si is in the range of 1.2 to 2.0 moles with respect to 1.0 mole, Si derived from component A and Si derived from component B
Is not particularly limited, but when the ratio of Si to C in the composite film is constant, the component B tends to be more easily etched when the molar ratio of the component B-derived Si to the component A-derived Si is larger. There is. A particularly desirable range for the amount of Si derived from component B relative to 1 mol of Si derived from component A is 0.4 mol or more.

When the component B is etched with an etching solution containing fluorinated water, if the etching time is too long, the film may peel off from the base. Further, if the etching time is too short, the dielectric constant of the obtained film may be high, so that the margin of the optimum etching time may be small. In such a case, the content of Si relative to 1.0 mol of C is from 0 to 1.
It is effective to form a 2 mol composite film in the lower layer. This film is hardly etched by the etchant used here, and since it is of the same type of material as the upper film and has good adhesion, peeling of the film during etching can be prevented. C1.
Since the relative dielectric constant of the composite film in which Si is 0 to 1.2 mol with respect to 0 mol is 3 or less, if the film thickness is small, the effect on the effective dielectric constant of the entire laminated film is small.

When the low dielectric constant insulating film according to the present invention is applied to a multilayer wiring of an LSI, it is preferable to use a damascene process. However, a metal wiring is formed first, and a space between the wirings is filled with a polysiloxane solution according to the present invention. It is also possible to lower the dielectric constant by etching a narrow portion between the wirings.

[0035]

The present invention will be described below with reference to examples. Examples 1 to 8 With respect to 1 mol of monomethyltrimethoxysilane, 0 mol, 0.2 mol, 0.4 mol, 0.1 mol of tetramethoxysilane was used.
The polysiloxane coating solution was adjusted by adding 6 mol thereof to obtain a polysiloxane coating solution. Adjustment is
In a flask, monomethyltrimethoxysilane, tetramethoxysilane and propylene glycol monopropyl ether as a solvent were mixed, and water with maleic acid as a catalyst dissolved therein was added dropwise with stirring. At this time, the temperature of the laboratory was 23 ° C., and temperature control by the flask bath was not performed. The amount of water added was equimolar to the alkoxy group of the alkoxysilane used, and the amount of maleic acid was 0.01 mol per 1.0 mol of alkoxysilane. The concentration of the coating solution was such that the non-volatile matter concentration calculated assuming that all of the alkoxysilane was hydrolyzed and condensed was 18% by weight.

After completion of the dropwise addition of the water and the catalyst, the mixture was stirred for about 2 hours, transferred to a sealed container and left at 23 ° C. for 5 days. At that time, the number average molecular weight (measured by gel permeation chromatography and converted to polystyrene, the same applies hereinafter) was between 800 and 2,000. Thereafter, it was stored in a freezer (−18 ° C.).

A polysiloxane solution A using only monomethyltrimethoxysilane and a polysiloxane solution B using only tetramethoxysilane were synthesized. 22 mol, 0.45 mol and 0.67 mol were mixed at a ratio to give a polysiloxane coating solution,
I got Polysiloxane solution A and polysiloxane solution B
Was adjusted in the same manner and under the same conditions except for the polysiloxane coating solution and the following proviso. However,
After completion of the water and catalyst dropping, after stirring for about 5 hours,
The polysiloxane solution A and the polysiloxane solution B were mixed to prepare a polysiloxane coating solution.

At this time, the number average molecular weight of the polysiloxane solution A was 500, and the number average molecular weight of the polysiloxane solution B was 900. After the adjustment, the mixture was stirred for about 30 minutes, transferred to a closed container, and left at 23 ° C. for 5 days. At this time, the number average molecular weight of the polysiloxane coating solution was 8
It was between 00 and 2000. After that, the freezer (-18
C).

A polysiloxane coating solution was prepared by adding 0.5 mol of tetramethoxysilane to 1 mol of monomethyltrimethoxysilane and 0.2 mol of dimethyldimethoxysilane to obtain a polysiloxane coating solution. The adjustment was carried out in the same manner as in the case of the coating solution and the number average molecular weight after leaving for 5 days was 1200.

A film was formed by spin coating using the polysiloxane coating solution. The substrate used was a bare silicon wafer. The coating rotation speed was adjusted for each coating liquid so that the film thickness after curing at 400 ° C. was about 4500 to 5000 °. After the spin coating, baking was continuously performed at 150 ° C./30 sec and 250 ° C./80 sec on a hot plate. The final curing was performed at 400 ° C. for 1 hour in a nitrogen atmosphere using a vertical furnace. Table 1 shows the measurement results of the stress and the refractive index of the cured film.

The cured film was etched using 1.0% by weight of hydrofluoric acid. Polysiloxane coating solution,
Was etched for 4 minutes, but the stress and the refractive index did not change. On the other hand, the stress and the refractive index of the films of the polysiloxane coating liquids 1 and 2 were reduced by the etching. As a result of examining the relationship between the etching time, the stress, and the change in the refractive index, a polysiloxane coating solution,
The stress and the refractive index of the film of Example 2 settled to constant values by etching for 2 to 3 minutes. The polysiloxane coating solution is
The stress and the refractive index became constant in 30 to 40 seconds. Etching of the film from the polysiloxane coating solution to the coating was terminated when the stress and the refractive index became constant. The refractive index and the film thickness of all of the films of the coating solution to were measured simultaneously by an ellipsometer, but the film thickness did not decrease even when hydrofluoric acid etching was performed.

Two wafers each having been subjected to hydrofluoric acid etching were produced, and one of them was treated with HMDS.
Using a hot plate with a function of introducing HMDS into the inside of the cover surrounding the hot plate, a treatment is performed at 100 ° C./2 minutes in an HMDS atmosphere, and then a treatment is performed at 160 ° C./2 minutes on a hot plate in a nitrogen atmosphere. went. H
No change in the refractive index was observed in the MDS treatment.

Etching with hydrofluoric acid or H
After the MDS treatment, the film of the polysiloxane coating solution is
Using a vertical furnace, nitrogen was treated at 400 ° C. for 1 hour. The stress, the refractive index and the film thickness after the heat treatment were the same as the stress, the refractive index and the film thickness after the etching or the HMDS treatment. Table 1 shows the stress refractive index after the second heat treatment.

One day after the second heat treatment, the dielectric constant was measured. A with a thickness of about 1500mm and a diameter of 2mm on the film
One electrode was formed, and the capacity of the capacitor formed by the Al electrode and the Si substrate was measured. Table 1 shows the results of the dielectric constant measurement.

[0045]

[Table 1]

The relative permittivity of a film obtained by curing a coating solution formed by spin coating using a polysiloxane coating solution in a nitrogen atmosphere at 400 ° C. for 1 hour in a vertical furnace was measured. 2.7, and the cured film of the coating solution was 2.9. When compared with the results in Table 1, the coating solution,
It can be seen that the cured film obtained from the above does not cause a decrease in the relative dielectric constant due to the hydrofluoric acid etching. Also,
It can be seen that stress and refractive index of these films did not change due to etching. It is considered that the SiO ₂ component was not etched because the film obtained from the coating solution had no or little SiO ₂ component having no organic group.

The film obtained from the polysiloxane coating solution is considered to have been etched with the SiO ₂ component having no organic group since the stress and the refractive index were reduced by the etching. The composition of the film remaining after etching is considered to be close to the composition of the film obtained from the coating solution, but the relative dielectric constant after etching is 2.2 to 2.2.
Since it is as low as 2.3, it is considered that the density of the film is lower than that of the film obtained from the coating solution.

The IR spectrum of the film obtained from the polysiloxane coating solution was measured before and after etching. The intensity of the absorption peak derived from the organic group of the cured film obtained from the coating solution did not change before and after the etching. On the other hand, the intensity of the absorption peak derived from the organic group after the etching of the coating solution was almost the same as the intensity of the absorption peak derived from the organic group of the cured film obtained from the coating solution.

Regarding the film after etching obtained from the polysiloxane coating solution, a dielectric constant of 2.2 was obtained regardless of the presence or absence of the HMDS treatment.
It is considered that good film quality with little OH terminal and little moisture absorption was obtained. In addition, the dielectric constant of the film of the polysiloxane coating liquid shows a low value of 2.3 without HMDS treatment, but the dielectric constant is further lowered by performing HMDS treatment. This is presumably because in the state without the HMDS treatment, Si-OH terminals were present in the film, and the dielectric constant increased due to moisture absorption.

With respect to the film of the polysiloxane coating solution to, the stress and the refractive index are reduced by etching, and the HMDS
In the case where the treatment was performed, the relative dielectric constant also decreased as compared with 2.9 of the coating solution. It is considered that the reason why the relative dielectric constant is high without the HMDS treatment is that the dielectric constant increased due to moisture absorption due to the presence of Si-OH terminals in the film. Further, the coating liquid film is made of SiO ₂ having no organic group similarly to the coating liquid film.
It is considered that the obtained component has a relatively high relative dielectric constant due to a small amount of the component.

The cross section of the film obtained from the polysiloxane coating liquid and not subjected to the HMDS treatment after the second curing was observed by SEM. As a result of taking a photograph at a magnification of 100,000, it was observed that the coating solution and the film had pores having a diameter of 20 nm or less in the cross section. The number of holes was the largest in the samples, and was similar. The size of the pores was 10 nm or less in diameter in all of the coating liquid films. Coating liquid,
, The pore diameter is almost 10 nm or less and 1
Very few (0 to 20 nm cross sections of 10 or less) were found to have a diameter of 0 to 20 nm, and no diameters larger than 20 nm were observed. In the case of the coating liquid, the magnification is 1
At a magnification of 0,000, no holes were observed in the cross section.

When applied as an insulating film of a miniaturized LSI, the pore size in the film is preferably 20 nm or less, particularly preferably 10 nm or less. The low dielectric constant film can be applied as an interlayer insulating film of an LSI.

The obtained low dielectric constant film can be formed at a curing temperature of 400 ° C.
Since it has a heat resistance of not less than ° C., it is suitable for combination with either an Al wiring having a high process temperature or a Cu wiring having a low process temperature. In fact, the coating solution
The low dielectric constant film obtained from the above was placed in a vertical furnace in a nitrogen atmosphere for 45 minutes.
The film thickness and the refractive index did not change even after the treatment at 0 ° C. for 1 hour.

[0054]

According to the method for producing a low dielectric constant film according to the first to sixth aspects, the relative dielectric constant is low (2.5 or less is possible) and the heat resistance is high, which is suitable as an interlayer insulating film of an LSI. (450 ° C. or higher is possible), and a high-quality film can be easily manufactured with good yield, quality control is easy, and cost is excellent.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/312 H01L 21/306 D 21/90 Q (72) Inventor Nobuko Terada 4-chome Higashimachi, Hitachi City, Ibaraki Prefecture No. 13-1 Hitachi Chemical Co., Ltd. Yamazaki Plant F term (reference) 4J002 CP031 DJ016 GQ00 5F033 QQ09 QQ20 RR20 RR23 RR29 SS22 WW00 WW01 WW04 WW09 XX23 5F043 AA31 BB22 DD07 EE22 EE23 GG03 5F004 AA01 A0101

Claims (6)

[Claims] An etching rate for a component B is as follows:
A method for producing a low dielectric constant film, comprising a step of etching a composite film composed of a component A and a component B using an etching solution having an etching rate which is 10 times or more the etching rate of the composite film. 2. Component A is represented by the following general formula (I): (In the general formula (I), n Rs each independently have 1 to 6 carbon atoms.
Wherein n is an integer of 1 to 3. However, the total number of carbon atoms of the organic group R bonded to one Si atom is 8 or less), the component B is SiO ₂ , and the etching solution is 2. The method for producing a low dielectric constant film according to claim 1, wherein the etching solution is an etching solution containing hydrogen fluoride. 3. The composition of the composite film according to claim 1, wherein the composition of Si is 1.2 to 2.0 mol per 1.0 mol of carbon atoms.
The method for producing a low dielectric constant film described in the above. 4. An etching solution containing fluorine containing 0.1%.
4. The method for producing a low dielectric constant film according to claim 2, wherein the amount of the hydrofluoric acid is from 5 to 5% by weight. 5. The method according to claim 1, wherein the size of the space formed in the low dielectric constant film is 20 nm or less in diameter. 6. The method for producing a low dielectric constant film according to claim 1, wherein the relative dielectric constant of the low dielectric constant film is 2.5 or less.