JPS6366418B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for forming a silicon oxide film, and more specifically to a method for coating a resin on a substrate and thermally decomposing it to form a silicon oxide film.

(2) Conventional technology and problems Traditionally, element isolation in large-scale integrated circuits (LSIs) and interlayer insulation in devices with fine patterns such as LSIs, JJs, and bubble memories have been performed using silicon oxide (SiO) produced by thermal oxidation of silicon substrates. ₂ ) Film, _SiO2 -based insulating material grown by vapor phase growth using silane-based gas,
Alternatively, organic insulating materials such as polyimide and silicone resin are used, but these have advantages and disadvantages in terms of miniaturization and reliability. In other words, thermal oxidation methods for element isolation are reaching their limits in terms of miniaturization, while interlayer insulation has a flattening function, heat resistance (400 to 1000°C in air), reliability (adhesion, electrolytic corrosion resistance, There is no material that satisfies all of the requirements (thick film forming properties, etc.).

Currently, _SiO
Focusing on film formation, polydialkoxysilane
RO[-(RO) _2SiO ] _-oR where R is a monovalent hydrocarbon, such as _CH3 , _C2H5 , or _hydrogen , and at least 1/3 of OR is an alkoxy group. ] is known to be thermally decomposed into SiO ₂ . The reason why alkoxy groups are left in the molecule is that if all of them are OH, the storage stability will be very poor. When this polydialkoxysilane is thermally decomposed after being applied, it leaves distortions and pinholes in the paint film as the alkoxy groups scatter, so if it is applied to a film thickness of 0.2 to 0.5 μm or more, it will cause cracks in the paint film. enters,
Even if it is applied to a film thickness less than that, it will cause electrolytic corrosion defects. Therefore, if a silicone resin with very small atoms or atomic groups scattered during thermal decomposition is present, it should be possible to form an insulating film with excellent flattening function, heat resistance, and reliability.

(3) Purpose of the Invention Therefore, the purpose of the present invention is to provide an excellent insulating film that has not only flattening function and heat resistance but also reliability.

(4) Structure of the Invention In order to achieve the above object, the present invention provides a substrate with a general formula: R ² O(−R′ ₂ SiO)− _o R ² [wherein,
R' is all H, or at least half is H and the remainder is -OSiH ₃ , -
OSiH ₂ CH ₃ , −OSiH(CH ₃ ), or −OSi
( _CH3 ); ^R2 _{is -SiH3} , _-SiH2CH3 , -
SiH( _CH3 ) ₂ or -Si( _CH3 ) ₃ ; n is
It is a natural number between 2 and 1000. ] A silicon oxide film is formed by applying a silicone resin represented by the following, using a solvent if necessary, and then heating.

The basic principle of the invention is that the formula: H ₃ SiO (−H ₂ SiO
) − _o If a SiO _x film is formed using a silicone resin consisting of SiH ₃ , H is easily decomposed during thermal decomposition, so the amount of impurities in the SiO _x film is small, and H has a small volume, so after H scatters. The volumetric shrinkage strain of is small, the pinholes are minute, and the increase in volume due to oxidation of SiO alleviates the strain and fills the pinholes, so finally the strain is small, dense, and pure SiO _x (x=
1-2) A film can be obtained. As mentioned above, HO( _-H2SiO ) _-oH is unstable, but it becomes stable when the terminal is silylated, which makes the method of the present invention practical. The advantage of this basic principle is not lost even if the molecule contains some amount of CH ₃ in addition to Si, O, and H. However, it is preferable that substantially all of R′ in the molecule of the silicone resin used in the present invention is H,
The proportion of substituents other than H should normally be up to about 10%, and at most less than half.

Silicone resin R ² O (−R′ ₂ SiO
) - _o R ² is liquid when n = 1 to 2 or 3, and powder when n≧3. If it is liquid, it can be applied as it is, but if it is powder, it can be applied to the substrate by spin coating, for example. When applying it, it is dissolved in an organic solvent such as toluene and then applied. In the case of spin coating, the film thickness can be adjusted by adjusting the molecular weight, type of solvent, resin concentration, and rotation speed.

Silicone resin R ² O (−R′ ₂ SiO) − _o R ² can be coated by spin coating, spraying, or other methods, so it can be applied to uneven substrates and has the function of flattening the surface. There is. Therefore, it is suitable for isolation between elements of a semiconductor device in which the method is applied to a silicon substrate with holes, preheated at 60 to 350°C, and then heat treated at 350 to 1000°C to form SiO ₂ and fill the holes. It is also suitable for use as an interlayer insulating material for semiconductor devices with fine wiring or bubble memories, etc., by preheating at 60 to 300°C and heat treatment at 300 to 500°C to form SiO _x . Note that materials with CH ₃ groups at the end do not change to complete _SiO can. Thermal decomposition of Si--CH ₃ bonds occurs at temperatures above 300 to 350° C., and the reaction can be confirmed, for example, by tracking the content of CH ₃ groups or Si--C bonds by infrared absorption measurement. On the other hand, when used as isolation between elements, it does not contain any CH ₃ groups.
H ₃ Si (−H ₂ SiO) − _o SiH ₃ is suitable. By repeating coating and heat treatment to form _SiOx , a thick film can be obtained, or by filling deep holes and grooves, the flattening function can be emphasized and a dense film can be obtained.

(5) Examples (a) Preparation of resin 108 g of MIBK was placed in a four-necked flask equipped with a stirring bar, reflux condenser, thermometer and coat, and the flask was cooled to -30°C. Then diethoxysilane
After dropping 12 g (0.1 mol) from the funnel, add water 18
g (1 mol) was added dropwise from the funnel. The dropping rate was approximately 0.2 drops/second so that the liquid temperature did not rise above -10°C. The flask was then transferred to a 35°C water bath. The ice droplets melted and both the aqueous and organic layers became slightly cloudy, but they became transparent within 1 hour. After being kept at 35°C for 22 hours, the solution was transferred to a separatory funnel, washed three times with cold water, the aqueous layer was separated, the organic layer was transferred to an eggplant-shaped flask, and water was removed by evaporation under reduced pressure of 50 mmHg.
The liquid was placed in a three-necked flask, and while bubbling N ₂ gas, 5 g of dimethylchlorosilane was added and left for 10 minutes. Then, the liquid was transferred to an eggplant-shaped flask and concentrated under reduced pressure to obtain 4.1 g of a relatively viscous liquid. Acetonitrile was added to this liquid, and the resulting precipitate was dried to obtain a powdered resin.

Then, it was dissolved in toluene to make a 30% by weight solution. This resin liquid was applied to a KB _r crystal plate by spinning at 2000 rpm for 30 seconds, and the infrared absorption was measured.
A large absorption at 2250 cm ^-1 attributed to H in H ₂ SiO and a small absorption at 2140 cm ^-1 attributed to H in H(CH ₃ ) ₂ SiO _0.5 were observed. At 2140cm ^-1, only a small amount of absorption was observed as a shoulder. Also 2890cm ^-1 and 1250cm
^-1 , a small absorption thought to be attributable to CH ₃ in H(CH ₃ ) ₂ SiO _0.5 and a large broad absorption of Si-O at 1000 to 1200 cm ^-1 were observed, indicating that this material
It was found that it could be expressed as ( _CH3 ) ₂ -Si( _-H2SiO ) _-oSi ( _CH3 ) _2H , and the average value of n was 5.

(B) Example 1 The powdered resin prepared as described above was dissolved in toluene to prepare a 43% by weight resin liquid. Next, a bipolar element is formed in the silicon substrate,
A first layer of aluminum wiring was formed thereon.
The thickness of the aluminum wiring is 0.9μm, the minimum line width is 3μm,
The minimum line spacing is 2 μm. The above resin liquid
Spin coating was performed at 6000 rpm for 20 seconds, followed by solvent drying at 80°C for 30 minutes and heat treatment at 450°C for 60 minutes.
The film thickness obtained by coating on a flat plate under the same conditions is 1.0μ
The thickness was 0.4 μm on the aluminum wiring, 1.1 μm in the space, and the height difference was 0.2 μm. Next, 1.0 μm PSG is formed using a known method, through holes are formed, second layer aluminum wiring is formed,
Furthermore, a 1.3 μm PSG layer was formed as a protective layer, and a window for taking out the electrodes was opened to obtain a bipolar element device. This device has undergone a heating test in air at 500℃ for 1 hour, a thermal shock test of -65℃←→150℃ 10 times, and a 90% thermal shock test at 85℃.
There were no abnormalities or defects after 1000 hours of 6V application under RH and a combination test of these tests.

(C) Comparative Example 1 An attempt was made to obtain a bipolar element device in the same manner as in Example 1, except that polyimide was applied to the same thickness instead of the resin liquid and cured at 350°C for 30 minutes. At the stage when the PSG film was formed on the polyimide film, the PSG film peeled off.

(iv) Comparative Example 2 A bipolar element device was obtained in the same manner as in Example 1, except that the interlayer insulating layer and the protective layer were formed of polyimide. When this was subjected to a heat resistance test at 500°C for 1 hour in nitrogen, the polyimide layer turned brown. Furthermore, when a 6V application test was conducted at 85°C and 90%RH, a large leakage current flowed and a portion of the polyimide layer peeled off.

(E) Comparative Example 3 A bipolar element was obtained in the same manner as in Example 1, except that ladder-type methylpolysilsesquioxane was applied instead of the resin liquid and cured in nitrogen at 450°C for 1 hour. Ta. This was subjected to a heat resistance test in nitrogen at 500°C for 1 hour and a 6V application test at 85°C and 90% RH, but no defects were found. However, when a heat resistance test was conducted in air at 500°C for 1 hour, a crack occurred in a part of the electrode window opening.

(f) Example 2 A resin liquid was used in the same manner as in Example 1, except that the resin liquid was applied on the first layer of aluminum wiring and cured, and then the resin liquid was applied again and cured.
After forming through holes, the second layer of aluminum wiring was then formed. A protective layer thereon was also formed using a resin liquid, an electrode extraction window was formed, and a bipolar element was obtained. This semiconductor device was subjected to the test described in Example 1, but no abnormalities or defects were found.

(G) Example 3 Dichlorosilane was placed in a four-necked quartz flask in which an interface was formed between methyl isobutyl ketone and water.
H ₂ SiCl ₂ was introduced into the organic layer, and after hydrolysis, polymerization was carried out at 30° C. for 20 hours. After that, wash with water 5 times and after separating the aqueous layer, chlorosilane
H ₃ SiCl was introduced to perform silylation. After concentration under reduced pressure, sufficiently dehydrated acetonitrile was added to obtain a powder.
This powder was dissolved in toluene to form a 25% by weight coating liquid (resin liquid).

On the other hand, on the silicon wafer, a depth of 3 μm and a width of 1~
Grooves of 10 μm were formed using a parallel plate type dry etching device, and the surface layer was oxidized by thermal oxidation at 900° C. for 60 minutes.

A resin liquid was applied onto this substrate by spin coating, and after preheating at 150°C for 10 minutes, heat treatment was performed at 750°C for 30 minutes in oxygen. In this state, the 10 μm wide groove had a depth of 0.6 μm, and the 1 μm wide groove had a depth of 0.1 μm. Furthermore, as a result of applying the resin liquid in the same manner and curing it, the 10 μm width groove was formed.
The groove portion, which had a depth of just under 0.1 μm and a width of 8 μm or less, was almost flat. Next, the entire surface of this substrate was etched using CF ₄ gas to expose the silicon layer in areas other than the grooves. As a result, it was found that only the trench portion could be filled with SiO ₂ and could be applied to isolation between elements.

(6) Effects of the invention As is clear from the above explanation, the present invention makes it possible to obtain a reliable insulating film that is dense and has little distortion when coating an SiO _x film with a planarization function. Become.

Claims (1)

[Claims] 1. General formula: R ² O (−R′ ₂ SiO) − _o R ² [in the formula,
R' is all H, or at least half is H and the remainder is -OSiH ₃ , -
OSiH ₂ CH ₃ , −OSiH(CH ₃ ) ₂ , or −OSi
( _CH3 ) ₃ ; ^R2 _{is -SiH3} , _-SiH2CH3 , -
SiH( _CH3 ) ₂ or -Si( _CH3 ) ₃ ; n is
It is a natural number between 2 and 1000. ]A silicone resin represented by is applied using a solvent as necessary,
A method for forming a silicon oxide film, the method comprising: subsequent heat treatment.