JPH06181201A - Insulating film for semiconductor device and liquid applied for growing that insulating film - Google Patents

Abstract

PURPOSE:To provide an insulating film for semiconductor devices having a low rate of moisture absorption and superior adhesion and crack resistance characteristics by including additionally at least one element among titanium, zirconium, niobium, and tantalum to the conventional film material between SOG layers. CONSTITUTION:The insulating film includes at least one element among titanium, zirconium, niobium, and tantalum in addition to silicon, oxygen, and preferably carbon. Further, the insulating film is formed using the application of a liquid whose main component is an olygomer of an average molecular weight of 500 or more and which is a reduced compound of an organic metal compound containing at least one element among titanium, zirconium, niobium, and tantalum, and an organic silicon compound having at least one alcoxyl radical in its molecular structure. The organic metal compound can be anything as long as it includes titanium or other element and can be condensation- polymerized with alcoxyl silane using a catalyst such as water.

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 a coating liquid for forming the insulating film.
The present invention relates to an insulating film of a semiconductor device having excellent crack resistance and an insulating film forming coating solution for forming the insulating film.

[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, there is a constraint that the formation temperature of the interlayer insulating film must be 500 ° C. or lower, preferably 400 ° C. or lower.

Therefore, conventionally, in forming an interlayer insulating film, a solution of an oligomer of an organosilicon compound having a siloxane bond is spin-coated on a substrate and subjected to heat polycondensation to form a silicon oxide insulating film, so-called SOG. (Spin-on-Glass)
Has been used. Since this SOG is a process that uses a solution, the liquid also enters into the fine gaps, and it is possible to satisfactorily fill the steps and cover, and to perform polycondensation at 400 ° C.
Since the process proceeds below, it is possible to lower the temperature of the process, and since the obtained insulating film is made of silicon oxide, processing techniques such as conventional etching can be applied. is there.

However, since the silicon oxide film formed by this SOG is not in the form of perfect SiO ₂ , a large amount of SiOH groups remain on the film surface and the film quality is poor, so Has the property of absorbing water from the environment. Then, the water absorbed in the film is re-emitted in the subsequent process, causing the corrosion of the aluminum wiring layer and deteriorating the hot carrier resistance of the MOS transistor. In addition, the SOG film has a problem that the adhesion to the lower layer and the upper layer is poor, and peeling occurs between the layers due to thermal stress or internal stress of the film. Further, there is also a problem that cracks are likely to occur when applied thickly because a remarkable volume shrinkage occurs during heat condensation polymerization.

The above-mentioned problems seriously impair the reliability of the semiconductor device and reduce the yield, and a solution to the problem has been demanded. By the way, absorption and re-release of water by the SOG film poses a problem especially in the cross section after the via opening. Therefore, the literature (Microelectronic Manufacturin
As described in g and Testing Vol.12 No.5 (1989) p 10), a method of deeply etching back the SOG film so that it does not appear in the via cross section is generally adopted.
However, in this method, it is difficult to optimally set the film thickness and the conditions of reactive ion etching (RIE), the stability of etching depth control is lacking, and the process becomes complicated, which causes a cost increase. ing.

On the other hand, in order to improve the adhesion between the SOG film and the upper layer, a method of improving the adhesion between the SOG film and the upper layer by plasma is also proposed. (Journa
l ofVacuum Science and Technology Vol.B3 No.5 (198
5) p1352; Journal of Electrical Materials Vol.20 No.
4 (1991) p299) However, this method is not sufficiently effective, there is a risk of cracking of the film, and the adhesiveness to the upper layer and the lower layer of the SOG film cannot be improved at the same time.

As a method for preventing crack formation during heat polymerization in the SOG film formation step, a method of repeating thin coating and heating is known, but this method causes a large increase in process cost. In addition, there is a problem that a thick insulating film having a thickness of 1 μm or more cannot be formed. Further, as a method of forming a thick film, a so-called organic SOG coating liquid (Journal of Vacuum Science and Tech) in which an alkyl-substituted alkoxysilane is used as a part of a raw material component of SOG is used.
nology Vol.A9 No.5 (1991) p2696; 1986 VLSI Multilev
el Interconnection Conference (1986) p102; JP-A-62-230828) has also been developed. However, this method has a problem that the film quality and the adhesiveness of the obtained film are rather deteriorated.

[0008]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an insulating film of a semiconductor device which has low water absorption, excellent adhesion and crack resistance, and an insulating film forming film capable of forming the insulating film. To provide a coating solution.

[0009]

The inventors of the present invention have made diligent efforts to solve the above problems, and as a result, at least one selected from titanium, zirconium, niobium and tantalum is newly added to the conventional SOG interlayer film material. The inventors have found that the inclusion of an element makes it possible to obtain an interlayer film having low water absorption, high adhesiveness and high crack resistance, and arrived at the present invention.

That is, the present invention provides an insulating film of a semiconductor device containing at least one element selected from titanium, zirconium, niobium and tantalum, and silicon and oxygen.

The present invention also provides titanium, zirconium,
The present invention provides an insulating film for a semiconductor device containing at least one element selected from niobium and tantalum and silicon, carbon and oxygen.

Further, according to the present invention, an organic metal compound containing at least one element selected from titanium, zirconium, niobium and tantalum as an application liquid for forming an insulating film of the semiconductor device, and an alkoxyl group in the molecule. The present invention also provides a coating liquid for forming an insulating film, which comprises an oligomer having a number average molecular weight of 500 or more as a main component, which is obtained by polycondensing an organosilicon compound having at least one group.

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

The insulating film of the present invention contains at least one element selected from titanium, zirconium, niobium and tantalum, silicon and oxygen, and preferably carbon, and is composed of titanium, zirconium, niobium and tantalum. It is formed from an oligomer cured product obtained by polycondensing an organometallic compound containing at least one selected element and an organosilicon compound having at least one alkoxyl group in the molecule.

The organometallic compound containing at least one element selected from titanium, zirconium, niobium and tantalum as long as it contains these elements and can be polycondensed with alkoxylsilane by a catalyst such as water,
There is no particular limitation. For example, the following formula (A): M (OR ¹ ) _m (A) [In the formula, M is titanium, zirconium, niobium, or tantalum, and R ¹ is an alkyl group or an aryl group.]
Or a trisacetylacetonato titanium salt [Ti (CH ₃ COCHCOC
H ₃ ) ₃ ] X (X: a valent anion), tetrakis acetylacetonato zirconium [Zr (CH ₃ COCH
COCH ₃ ) ₄ ], diisopropyldiacetylacetonato titanium Ti (OC ₃ H ₇ ) ₂ (CH ₃ COCHCOC
H ₃ ) _{2 and} other metal complex compounds; titanium, zirconium,
Examples thereof include lactate or stearate of niobium or tantalum. These may be used alone or in combination of two or more. Among these, metal alkoxides having 3 to 4 carbon atoms are preferable because they have high solubility in organic solvents, are stable, and are easy to handle.

The organosilicon compound is a silicon compound having at least one alkoxyl group in the molecule, and is represented by the following formula (a), (b), (c) or (d): Si (OR ² ). ₄ (a) (R ³ ) Si (OR ² ) ₃ (b) (R ³ ) (R ⁴ ) Si (OR ² ) ₂ (c) (R ³ ) (R ⁴ ) (R ⁵ ) Si (OR ² ) (D) [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.

Specific examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetraphenoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltriphenoxysilane and ethyl. Trimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltriphenoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltriphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, Dimethyldiisopropoxysilane, dimethyldiphenoxysilane,
Diethyldimethoxysilane, diethyldiethoxysilane, diethyldiisopropoxysilane, diethyldiphenoxysilane, diisopropoxydimethoxysilane, diisopropoxydiethoxysilane, diisopropoxydiisopropoxysilane, diisopropoxydiphenoxysilane, diphenyldimethoxy Examples thereof include silane, diphenyldiethoxysilane, diphenyldiisopropoxysilane, diphenyldiphenoxysilane, vinyltrimethoxysilane, and γ-trifluoropropyltrimethoxysilane.

The insulating film of the present invention comprises, for example, an organometallic compound containing at least one element selected from the above-mentioned titanium, zirconium, niobium and tantalum, and an organosilicon compound having at least one alkoxyl group in the molecule. It is formed by using an insulating film forming coating liquid containing an oligomer obtained by polycondensation of as a main component.

The oligomer, which is the main component of the insulating film forming coating solution, is obtained by polycondensing the organometallic compound and the organosilicon compound. In this polycondensation, an organometallic compound and an organosilicon compound are charged with or without a reaction catalyst into a reaction vessel together with a reaction solvent and the like, and reacted at room temperature or while heating under reflux to give a predetermined reaction. When the number average molecular weight is reached, the reaction mixture can be concentrated under reduced pressure. To measure the number average molecular weight, the reaction mixture was sampled sequentially and GPC
The number average molecular weight may be measured by the method described above.

The ratio of the organometallic compound / organosilicon compound used in the polycondensation is usually adjusted to about 5/95 to 50/50.

When a reaction catalyst is used in this polycondensation, examples of the reaction catalyst used include acid-base catalysts such as hydrochloric acid, formic acid, phosphoric acid, acetic acid, ammonia and TMAH. Examples of the reaction solvent include alcohols such as methanol, ethanol and 2-propanol, THF,
Examples thereof include dioxane and diethylene glycol monomethyl ether acetate.

The reaction temperature of the polycondensation is usually 20 to 20.
It is about 100 ° C. Furthermore, the reaction time varies depending on the reaction temperature, but is usually about 2 to 100 hours.

This oligomer has a number average molecular weight of 500.
Above, it is preferably adjusted to be 1000 to 5000. The oligomer having a number average molecular weight of 500 or less volatilizes during coating or baking or volatilizes without polycondensation during the subsequent crosslinking and curing, and a good film cannot be formed. Further, the upper limit of the number average molecular weight of the oligomer is not particularly limited, but if the number average molecular weight is too high, it will be difficult to dissolve in the solvent, and even if dissolved, the viscosity of the solution will be too high, making it difficult to control the film thickness. There is a risk that

The insulating film-forming coating solution of the present invention 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 insulating film-forming coating liquid is appropriately adjusted according to the intended final film thickness, but is usually adjusted to about 5 to 12% by weight.

In addition to the above-mentioned oligomer, a surfactant, a drying conditioner and the like can be added to the coating solution for forming an insulating film, if necessary.

In order to form the insulating film of the present invention, the above-mentioned coating liquid for forming an insulating film is applied to a substrate of a semiconductor device to a predetermined film thickness by a spin coating method, and the substrate is heated to about 200 ° C. to dry the solvent, After the removal, it can be carried out by heating to about 300 to 500 ° C., preferably about 350 to 400 ° C. in a non-oxidizing atmosphere or air to crosslink and cure the oligomer to form a cured product.

The insulating film of the present invention thus formed contains at least one element selected from titanium, zirconium, niobium and tantalum, which is derived from the organometallic compound and the organosilicon compound which are the components of the oligomer. And a cured product containing silicon and oxygen. When an alkyl-substituted alkoxysilane such as monoalkyltrialkoxysilane or dialkyldialkoxysilane is used as the organosilicon compound, Si-R derived from the alkyl-substituted alkoxysilane is contained in the cured film.
As (R: alkyl group), carbon is contained, which is preferable in that an insulating film having excellent flexibility can be obtained while maintaining insulating properties.

[0029]

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
The organometallic compound and the organosilicon compound were charged together with 300 ml of methanol at the ratio shown in 1), 0.5 g of 1% hydrochloric acid was added, and the mixture was heated to reflux at the boiling point to react. The reaction mixture was sampled by GPC to measure the number average molecular weight. When the number average molecular weight reached about 2000, the reaction mixture was rapidly cooled in an ice bath to stop the reaction. After concentration under reduced pressure at room temperature, it is rediluted with 2-propanol to a solid content of 10%, further deionized through a column of ion exchange resin, and filtered through a microfilter of 0.1 μm diameter to form an insulating film. A coating liquid was prepared.

This insulating film forming coating solution was applied on a φ6 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 cured film, the adhesion strength and the water absorption amount were measured and the crack resistance was evaluated according to the following methods. The results are shown in Table 1.

Adhesion Strength The substrate was cut into a size of 10 mm × 10 mm, a φ4 mm rod was adhered, and the measurement was carried out by the Sebastian method.

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

Crack resistance The presence or absence of cracks was visually observed.

[0035]

[Table 1]

As is clear from Table 1, the insulating film of the present invention does not generate any cracks, has excellent crack resistance, has excellent adhesion strength, and has a water absorption of 1 μg / c.
As small as m ² or less. On the other hand, the film of Comparative Example had cracks, the water absorption amount was extremely large, and the adhesion strength was poor.

[0037]

EFFECT OF THE INVENTION The insulating film of the present invention is a film having low water absorption and excellent adhesion and crack resistance. Therefore, the insulating film of the present invention has a great industrial utility value as a highly reliable flattening film which can be applied to a semiconductor device whose density is becoming higher and higher in recent years. Moreover, the coating liquid for forming an insulating film of the present invention is suitable for forming the insulating film of the present invention.

Claims (3)

[Claims] 1. An insulating film for a semiconductor device containing at least one element selected from titanium, zirconium, niobium and tantalum, and silicon and oxygen. 2. An insulating film for a semiconductor device containing at least one element selected from titanium, zirconium, niobium and tantalum, and silicon, carbon and oxygen. 3. A number average obtained by polycondensing an organometallic compound containing at least one element selected from titanium, zirconium, niobium and tantalum and an organosilicon compound having at least one alkoxyl group in the molecule. A coating liquid for forming an insulating film, which contains an oligomer having a molecular weight of 500 or more as a main component.