JPH06181202A - Insulating film of semiconductor device - Google Patents

Abstract

PURPOSE:To provide an insulating film for semiconductor devices having a low rate of moisture absorption, a low dielectric constant, and high planarization ability by forming the film using a material containing an organopolysiloxane, which includes an alkyl radical containing fluorine, as the film between SOG layers. CONSTITUTION:The alkylpolysiloxane which is an essential component of insulating films is expressed by a unit compositional formula. Here, R<1> is an alkyl radical containing fluorine, n is a natural number, x is a number in the range 0.1 to 1.0, y is a number in the range 0<=y<4, and 0<x+y<4. Some typical examples of the alkyl radical containing fluorine R<1> are the trifluoromethyl radical, the bifluoroethyl radical, the gamma-trifluoropropyl radical, etc. The usual amount of the alkyl radical containing fluorine is preferably 5 to 50% The amount of the alkylpolysiloxane containing an alkyl radical containing fluorine in the insulating film is normaly adjusted to be in the range 5 to 50% and preferably, in the range 10 to 30%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating film for a semiconductor device, and more particularly to an insulating film for a semiconductor device which is effective for flattening a wiring layer in a multi-layer wiring.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, it has become increasingly necessary to flatten the steps between wiring layers as much as possible due to the increase in the number of wiring layers and the cross-sectional aspect ratio of metal wiring layers. In particular, if the surface of the interlayer insulating film on the first aluminum wiring layer is not sufficiently flattened, the wiring layer above it may be broken or a failure in the reliability test may be caused. On the other hand, since the melting point of aluminum is low, the formation temperature of the interlayer insulating film must be 400 ° C. or lower.
There is a constraint.

Therefore, conventionally, as the interlayer insulating film, a plasma CVD oxide film (Jour.
nal of Electrochemical Society Vol.128 (1981) p154
5), plasma CV with tetraethoxysilane and oxygen
D oxide film (Extended Abstracts of 19th Conference on
Solid State Devices and Materials (1987) p451), normal pressure / low pressure CVD oxide film by tetraethoxysilane and ozone (Journal of Vacuum Scince and Technology Vol.
B4 (1986) p732; Journal of Electrochemical Society Vo
l.132 (1985) p950), and SOG (Spin-on-Glass) film by spin coating and thermal polycondensation of siloxane oligomer (JP-A-59-109565; Journal of Electroch).
Emical Society Vol.126 (1979) p1531) has been used.

However, in general, any of the oxide films formed by the plasma CVD method has a poor ability to flatten a step, and there is a problem that a void is generated between wirings. Further, although the CVD film and the SOG film made of tetraethoxysilane and ozone are excellent in flattening ability, water is likely to remain in the obtained film and water is strongly absorbed from the ambient atmosphere, so that the dielectric constant is Getting higher,
Moreover, there is a possibility that the aluminum wiring layer may be corroded and the hot carrier resistance of the MOS transistor may be deteriorated.

If the capacitance between the wiring patterns and between the wiring layers is large, the time constant becomes large, which may cause a signal delay. It has been pointed out that the influence of the capacitance of the wiring due to the dielectric constant of the interlayer film cannot be ignored as the density of the semiconductor device increases and the distance between the wirings shrinks, which causes a decrease in the operating speed of the semiconductor integrated circuit. There is. Therefore, since the dielectric constant of the interlayer insulating film is increased mainly by the absorbed water, an insulating film having a small water absorption amount is required.

[0006]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an insulating film for a semiconductor device which has a low water absorption, a low dielectric constant and a high leveling ability.

[0007]

The present inventors have made diligent efforts to solve the above-mentioned problems, and as a result, as a SOG interlayer film material, a film containing an organopolysiloxane containing a fluorine-containing alkyl group was used to form a film. The present inventors have found that the formation of an insulating film can provide an insulating film having a low water absorption, a low dielectric constant, and a high leveling ability, and thus reached the present invention.

That is, the present invention provides a unit composition formula (a): (R ^f ) _x (CH ₃ ) _y SiO _{2-(x + y) / 2} ) _n (a) [wherein R ^f is a fluorine-containing alkyl group]. A group, n is a natural number, x is a number from 0.1 to 1.0, and y is 0 ≦
and y <4 and 0 <x + y <4]. The present invention provides an insulating film of a semiconductor device containing an alkylpolysiloxane represented by the formula: 0 <x + y <4.

The insulating film of the semiconductor device of the present invention (hereinafter referred to as "insulating film of the present invention") will be described in detail below.

The alkylpolysiloxane which is an essential component of the insulating film of the present invention is represented by the unit composition formula (a). In this unit composition formula (a), R ^f is a fluorine-containing alkyl group, for example, the following formula (b): —C _p H _q F _r (b) [In the formula, p is an integer of 0 <p <8. And q and r are not 0 at the same time, an integer 0 ≦ q <15, and 0 <r ≦ 1
An integer of 5 and q + r = 2p + 1], which is a linear or branched alkyl group partially or wholly substituted with fluorine. Specific examples of the fluorine-containing alkyl group R ^f include a trifluoromethyl group, a perfluoroethyl group, a γ-trifluoropropyl group and the like.

The content of the fluorine-containing alkyl group in the alkylpolysiloxane, which is an essential component of the insulating film of the present invention, is usually preferably about 5 to 50%.

The content of the alkylpolysiloxane having a fluorine-containing alkyl group in the insulating film of the present invention is usually adjusted to about 5 to 50%, preferably about 10 to 30%.

Further, the insulating film of the present invention may contain a component made of another organopolysiloxane in addition to the alkylpolysiloxane having a fluorine-containing alkyl group represented by the unit composition formula (a). The organopolysiloxane is, for example, a polycondensation product of an organoalkoxysilane having at least one alkoxyl group in the molecule.

The formation of the insulating film of the present invention is carried out by fluorine-containing alkoxysilanes having a fluorine-containing alkyl group R ^f represented by the above formula (b) directly bonded to Si and further having at least one alkoxyl group in the molecule. (A) and then
By reacting a composition containing an alkoxysilane (B) for forming another organopolysiloxane, fluorine-containing alkoxysilanes (A) with each other, alkoxysilanes (B) with each other, or fluorine-containing alkoxysilanes ( A) and the alkoxysilane (B) are polycondensed to prepare a coating solution composed of a solution of an oligomer containing an alkylpolysiloxane represented by the unit composition formula (a), and the coating solution is applied to a substrate. Further, it can be carried out by a method of crosslinking and curing the oligomer to form a cured product.

Fluorine-containing alkoxysilanes (A) having the fluorine-containing alkyl group R ^f represented by the formula (b) directly bonded to Si and further having at least one alkoxyl group in the molecule include, for example, compounds represented by the following formula: (a-1): (R f) a Si (OR 1) b (a-1) wherein, R ^f is a fluorine-containing alkyl group represented by the formula (b), R ¹ is an alkyl group And a and b are positive integers and a + b = 4], such as (fluoroalkyl) trialkoxysilane, bis (fluoroalkyl) dialkoxysilane, and perfluorotrialkoxysilane. It is a kind. In formula (a-1), examples of the alkyl group represented by R ¹ include a methyl group, an ethyl group, and a butyl group.

Specific examples of the fluoroalkylalkoxysilanes include trifluoromethyltrimethoxysilane, γ-trifluoropropyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane and heptadecafluoro. Decylmethyldimethoxysilane and the like can be mentioned.

In the present invention, the fluoroalkylalkoxysilanes (A) represented by the above formula (a-1) may be used alone or in combination of two or more.

As the alkoxysilane (B),
For example, the following formulas (c), (d), (e) or (f): Si (OR ² ) ₄ (c) (R ³ ) Si (OR ² ) ₃ (d) (R ³ ) (R ⁴ ) Si (OR ² ) ₂ (e) (R ³ ) (R ⁴ ) (R ⁵ ) Si (OR ² ) (f) [in the formula (a), (b), (c) or (d), R
² , R ³ , R ⁴ and R ⁵ may be the same or different and each is an alkyl group or an aryl group.] Tetraalkoxysilane, monoalkyltrialkoxysilane, dialkyldialkoxysilane or trialkylalkoxysilane Is. R ² , R ³ , R ⁴ and R
Examples of the alkyl group of ⁵ include a methyl group, ethyl group, isopropyl group, butyl group, vinyl group and the like, and examples of the aryl group include a phenyl group and a diphenyl group. Of these, a methyl group or an ethyl group is preferable as R ² .

In the present invention, the above formulas (c), (d),
Alkoxysilane (B) represented by (e) or (f)
Can be used alone or in combination of two or more.

Specific examples of the alkoxysilane (B) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetraphenoxysilane,
Methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltriphenoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltriphenoxysilane, phenyltrimethoxysilane, phenyltriethoxy Silane, phenyltriisopropoxysilane, phenyltriphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiisopropoxysilane, dimethyldiphenoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldiisopropoxysilane, diethyldi Phenoxysilane, diisopropoxydimethoxysilane, diisopropoxydiethoxysilane, diisopropoxydiisopropoxy Silane, diisopropoxy di phenoxy, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyl diisopropoxy silane, diphenyl phenoxy silane, and vinyl trimethoxy silane and the like.

The coating liquid for forming the insulating film of the present invention comprises fluoroalkylalkoxysilanes (A) alone or oligomers obtained by polycondensing fluoroalkoxysilanes (A) and alkoxysilanes (B). It is the main component.

In this condensation polymerization, fluoroalkylalkoxysilanes (A) alone or fluoroalkylalkoxysilanes (A) and alkoxysilanes (B) are used with or without a reaction catalyst. Then, the reaction mixture can be charged into a reaction vessel together with a reaction solvent and the like, and reacted with stirring or heating under reflux at room temperature, and when the predetermined number average molecular weight is reached, the reaction mixture can be concentrated under reduced pressure. The number average molecular weight can be measured by, for example, a method of sequentially collecting samples from the reaction mixture and measuring by GPC.

The ratio of the fluoroalkylalkoxysilane (A) / alkoxysilane (B) used in the condensation polymerization is usually adjusted to about 100/0 to 5/95. In particular, a brittleness in the obtained insulating film does not decrease, cracks are less likely to occur, and an insulating film having high surface energy and excellent adhesion can be obtained. It is preferable that the total number of moles of the dialkyldialkoxysilane and the fluoroalkylalkoxysilane (A) is 0.1 to 0.5 mole. Further, the mutual ratio of the monoalkyltrialkoxysilane, the dialkyldialkoxysilane and the fluoroalkylalkoxysilane (A) is not particularly limited, but in general, when the amount of the dialkyldialkoxysilane and the bis (fluoroalkyl) dialkoxysilane is large. The flexibility of the obtained insulating film is increased, but the adhesiveness is reduced. Further, when the ratio of (fluoroalkyl) trialkoxysilane, bis (fluoroalkyl) dialkoxysilane, and perfluorotrisiloxane is high,
Although the amount of water absorption of the obtained insulating film decreases, it becomes difficult to dissolve the coating liquid described later, and the adhesion of the insulating film tends to decrease. Therefore, the usage ratio of each component can be appropriately selected according to the application of the insulating film, the pattern shape, etc. in consideration of this tendency.

When a reaction catalyst is used in this polycondensation, examples of the reaction catalyst used include hydrochloric acid, acetic acid, formic acid,
Examples thereof include acid-base catalysts such as phosphoric acid, ammonia, TMAH. Examples of the reaction solvent include alcohols such as methanol, ethanol and isopropyl alcohol, TH
F, dioxane, xylene and the like can be mentioned.

The reaction temperature for the polycondensation is usually 10 to 10.
It is about 100 ° C. Furthermore, the reaction time is usually 2 to
It is about 100 hours.

This oligomer has a number average molecular weight of 800.
It is preferable to adjust to about 20,000, more preferably 1500 to 5000. When the number average molecular weight is too small, it volatilizes during coating or baking or volatilizes without polycondensation during the subsequent crosslinking and curing, and a good film cannot be formed. If the number average molecular weight of the oligomer is too high, it may be difficult to dissolve it in the solvent.

The coating liquid for forming the insulating film can be prepared by dissolving this oligomer in a solvent. The solvent to be used is not particularly limited, but 2-propanol, butyl acetate and the like are preferable in that they dissolve the oligomer well, have a low viscosity, and have an appropriate drying rate.

The concentration of the oligomer in the coating solution is usually adjusted to about 5 to 15% in that it is within the range that a sufficient film thickness can be secured by one coating and the solid content can be dissolved. .

In addition to the above-mentioned oligomer, a surfactant, a dryness adjusting agent and the like may be added to the coating solution, if necessary.

To form the insulating film of the present invention, the coating solution is applied to a substrate of a semiconductor device by a spin coating method to a predetermined film thickness, the substrate is heated to about 200 ° C. to dry and remove the solvent, 300-50 in non-oxidizing atmosphere or air
It can be carried out by heating to about 0 ° C, preferably about 350 to 450 ° C to crosslink and cure the oligomer to form a cured product.

[0031]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples of the present invention.

(Example) In a reaction vessel having an internal volume of 1 liter, Table 1
300 ml of methanol in the proportions shown in Table 1
After charging with, add 0.5 g of 1% hydrochloric acid,
The mixture was heated to reflux at 0 ° C. for reaction. The reaction mixture was sampled by GPC and the number average molecular weight was measured. When the number average molecular weight reached about 2000, the reaction mixture was rapidly cooled in an ice bath and concentrated under reduced pressure at room temperature. %, Further deionized through a column of ion exchange resin, and filtered through a microfilter having a diameter of 0.1 μm to prepare an insulating film forming coating solution.

This insulating film forming coating solution was applied on a φ5-inch silicon substrate by a spin coater, dried at 200 ° C., and then cured at 400 ° C. for 30 minutes in an N ₂ atmosphere to form a film. At this time, the rotation speed of the spin coater is
The film thickness after drying was adjusted to be 5000Å. With respect to the obtained film, the water absorption amount and the relative dielectric constant were measured and the crack resistance was evaluated according to the following methods. The results are shown in Table 1.

Water absorption amount The film was heated to 400 ° C. together with the substrate, and the desorbed water was measured by the Karl Fischer titration method.

Dielectric constant After standing at 110 ° C. for 2 hours, at room temperature in N ₂ stream at 1 kHz
The Al pad was used as an electrode for measurement at the frequency of.

Crack resistance Visual determination was made.

[0037]

[Table 1]

As is clear from Table 1, the insulating film of the present invention
Has a water absorption of 1 μg / cm ²Less than or less, ratio
The dielectric constant is as low as 3.1 or less. Also crack
No defects such as peeling and peeling were observed.

[0039]

The insulating film of the present invention has a low water absorption and a low dielectric constant. Therefore, in recent years, the insulating film of the present invention is applied to a semiconductor device which is further miniaturized and has a higher density, and its industrial utility value is extremely large as a flattening film which enables its high speed operation.

Claims (1)

[Claims] 1. A unit composition formula (a): (R ^f ) _x (CH ₃ ) _y SiO _{2-(x + y) / 2} ) _n (a) [wherein R ^f is a fluorine-containing alkyl group, n is a natural number, x is a number of 0.1 to 1.0, and y is 0 ≦.
The number is y <4 and 0 <x + y <4].