JPH098029A - Insulation film containing fluorine and formation thereof - Google Patents

Abstract

PURPOSE: To obtain an insulation film which has both characteristics of a low dielectric coefficient and low hygroscopicity and is also excellent in flatness by making such a constitution that both Si-H coupling and Si-F coupling are included wherein SiH(OR)3 and fluorine-containing substance are simultaneously made into plasma, reacted and deposited. CONSTITUTION: Vapor of SiH(OR)3 having an arbitrary alkyl radical with R as a silicon source is used, and the silicon source is made into plasma simultaneously with gas containing fluorine to have them reacted and deposited. Such an insulation film is to include both Si-H coupling and Si-F coupling. For example, a substrate 7 is fixed to a heater 5 in a reduced pressure chamber 1 and heated while exhaustion is made from an exhaust port 6. Then while process gas 10 (O2 ), the silicon source (SiH(C2 H5 )3 +N2 ) and a fluorine source 9 (C2 F6 ) are supplied to parallel plate electrode 2 which also serves as a gas supply shower nozzle, RF is applied simultaneously from a plasma power source 3 to generate plasma.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to an insulating film containing fluorine used for a wiring interlayer insulating film and a surface protective film of a VLSI semiconductor device and a method of forming the same.

[0002]

2. Description of the Related Art In a process of forming a wiring interlayer insulating film and a surface protective film in the manufacture of a semiconductor device, a plasma CVD method of placing a semiconductor substrate in plasma and forming an insulating film by using a gas phase reaction is often used. There is. Above all, TEO as a silicon source
The so-called PE (Plasma enhanced) -TEOS-CVD process using S (tetraethoxysilane; Si (OC ₂ H ₅ ) ₄ ) uses conventional silane (SiH ₄ ) in view of the filling property of the underlying step. Since it is superior to the method used, it is widely used today.

However, as semiconductor devices have been miniaturized in recent years, the operation delay of the device itself has decreased, whereas the wiring delay due to the resistance and capacitance of the wiring tends to increase, and in the near future. There was a fear that wiring delay would limit the operating speed of semiconductor devices. As a means for avoiding this, it is known to reduce the dielectric constant of the interlayer insulating film. One of them is a method of forming a SiOF film by introducing fluorine into a conventionally used Si-O insulating film, for example, C ₂ as disclosed in Applied Physics Society '94 Spring 29p-Xv-14. A gas containing fluorine such as F _{6 is used} for PE-TEO
This is a method of introducing F atoms into the insulating film by introducing it into the S-CVD process. According to this, a high buried step difference can be obtained, and the relative permittivity can be reduced.
The reason why the dielectric constant is reduced by forming the insulating film into a SiOF film in this manner is that the introduced F atoms and Si atoms are combined to form Si-F.
It is believed to create bonds, which change the polarization of the molecule. Regarding the introduction of fluorine into the insulating film, there is also a method in which SiF ₄ is used as a silicon source and plasma CVD is performed in a mixed atmosphere with O ₂ or N ₂ O (JP-A-6-
(See Japanese Patent No. 333919).

[0004]

However, on the other hand, the Si-F bond also has the property of enhancing the hygroscopicity of the insulating film, and fluorine is released from the insulating film as a result of moisture absorption, so that the dielectric constant is lowered. The rate will rise again. Further, at this time, when free fluorine or adsorbed moisture diffuses in the insulating film and reaches the lower semiconductor element, its electrical characteristics deteriorate. Since the SiOF film is lower in film stress and denseness than the SiO ₂ film, such deterioration of electrical characteristics is more likely to occur. Conventional measures to prevent this adverse effect are only moisture absorption prevention measures such as stacking a film that does not allow water to easily pass through.To implement these measures, an extra moisture absorption prevention film that should be omitted if possible. There is a problem in that a lamination process must be added.

In view of the above-mentioned problems, it is an object of the present invention to provide an insulating film having both low dielectric constant and low hygroscopicity and excellent flatness, and a method for forming the insulating film.

[0006]

As a result of intensive investigations by the present inventors, the above-mentioned object is to provide an insulating film having a structure containing both Si—H bond and Si—F bond, and It was found that the film can be optimally formed by simultaneously converting SiH (OR) ₃ and a fluorine-containing substance into plasma and reacting them, and depositing them, and based on this, the present invention was completed.

That is, according to the present invention, a vapor of SiH (OR) ₃ having R as an arbitrary alkyl group is used as a silicon source, and the silicon source is plasma-reacted at the same time as a fluorine-containing gas to be reacted and deposited. Insulating film, Si-H bond and Si-F
It is an insulating film containing fluorine, which is characterized by containing both bonds. The present invention also provides a method for forming a fluorine-containing silicon oxide insulating film on a semiconductor substrate surface, wherein SiH containing R as an arbitrary alkyl group as a silicon source is used.
A method for forming a fluorine-containing insulating film, characterized in that the vapor of (OR) ₃ is used and the silicon source is made into plasma and reacted at the same time as a fluorine-containing gas to be deposited.

In carrying out the method of the present invention, it is not necessary to prepare any new material or apparatus except that a compound of SiH (OR) ₃ (trialkoxysilane) having R as an arbitrary alkyl group is used as a silicon source. For example, a known plasma CVD apparatus having parallel plate electrodes can be used. Then, in order to obtain desired film characteristics such as dielectric constant, hygroscopicity, film stress, etching rate, and step filling property, the gas supply amount, the pressure in the chamber, the distance between the electrodes, the plasma intensity, etc. are adjusted, The material gas concentration and reaction energy, which are factors affecting the film formation reaction, and their distribution may be controlled. The power source used for plasma generation may be one that can apply RF of 13.56 MHz between the parallel plate electrodes.
A combination of an applied power source and a low frequency power source of about several hundred kHz may be used. Further, in order to control the film densification and water permeability, it is effective to use a system other than such a plasma system, for example, ECR (electron cyclotron resonance), helicon wave, or ICP (Inductively Coupled Plasma). .

The alkyl group R of the silicon source SiH (OR) ₃ is not particularly limited, but from the viewpoint of the characteristics of the obtained insulating film (film characteristics), the cost of the material and the ease of handling,
Those having 1 to 5 carbon atoms are preferable, and CH ₃ and C ₂ H ₅ are particularly preferable. Since the silicon source SiH (OR) ₃ is a liquid at room temperature, it may be vaporized and supplied by a known bubbler, or a supply system other than the bubbler, for example, a known liquid injection system may be used. The carrier gas is preferably an inert gas such as N ₂ , Ar, He.

[0010] A professional that is mixed with the silicon source to react
Seth Gas is O₂, N₂O, NH_Three, H₂ Etc. individually or in appropriate groups
Can be used in combination, but to obtain a good insulating film,
O₂, N₂O is preferred. A film for introducing fluorine into the insulating film.
Fluorine gas is F₂, NF_Three, CF_Four, C₂F₆, C_ThreeF₈, CHF _Three,SCIENCE FICTION₆, SiF_Four, C
lF_Three Any gas containing fluorine can be used
However, from the perspective of safety and effectiveness, CF_FourAnd C₂F₆Is preferred.

Film formation is possible if a substrate temperature of 200 ° C. or higher can be secured, but good film characteristics can be obtained in 300 to
It is 400 ℃.

[0012]

[Function] A source gas SiH (OR) _{3 as} a silicon source and a fluorine-based gas as a fluorine source are simultaneously plasmatized and reacted,
The deposited insulating film of the present invention is Si-F derived from a fluorine source.
Both the bond and the Si—H bond derived from the source gas are uniformly contained throughout the film thickness. Therefore, in the insulating film, the water trapping property and hydrophobicity peculiar to the Si-H bond are uniformly expressed over the entire film thickness, and as a result, the Si-F bond introduced into the film for the purpose of reducing the dielectric constant. The effect of increasing the hygroscopicity due to is canceled out, and the hygroscopicity of the insulating film is dramatically reduced. That is, by coexisting Si—H bonds and Si—F bonds in the insulating film, it is possible to sufficiently exhibit the effect of reducing the dielectric constant while suppressing an increase in hygroscopicity which is a harmful side effect of Si—F bonds. The reason why it is essential to simultaneously react the raw material gas SiH (OR) ₃ and the fluorine-based gas is that, for example, if the gas composition that reacts at the same time is changed by changing the supply timing of them, Si-H bond and This is because the distribution of Si—F bonds becomes uneven, and the effect of the present invention exerted by having these at the same time is impaired, resulting in undesired results such as an increase in the dielectric constant. It should be noted that the excellent underlying step embedding property and covering property, which are the unique advantages of the organosilane compound-based raw material, are maintained as they are conventionally due to the presence of the Si (OR) atomic group. Therefore, the insulating film of the present invention has both low dielectric constant and low hygroscopicity and is excellent in flatness.

From the viewpoint of the film forming process, the film forming method of the present invention is different from the conventional one only in that SiH (OR) ₃ is used as the silicon source instead of the conventional TEOS. Therefore, the existing manufacturing apparatus can be used as it is when performing the film forming method of the present invention. Since SiH (OR) ₃ has a higher vapor pressure than TEOS, there is an advantage that the time required for film growth can be shortened. Furthermore, since the insulating film after film formation has both the characteristics of low dielectric constant and low hygroscopicity and is excellent in flatness, it is not necessary to add an extra film laminating step for moisture absorption prevention or flattening. .

[0014]

EXAMPLE FIG. 1 is a sectional view of a film forming apparatus suitable for carrying out the present invention. In FIG. 1, 1 is a decompression chamber, 2 is a parallel plate electrode and gas supply shower nozzle, 3 is a plasma power supply, 4 is a gas supply pipe, 5 is a heater, 6 is an exhaust port, 7 is a substrate, 8 is a silicon source, 9 Is a fluorine source and 10 is a process gas. (Embodiment 1) A substrate 7 is formed by using the film forming apparatus shown in FIG.
Using a 6-inch Si wafer as the silicon source 8 and trialkoxysilane (SiH (C ₂ H ₅ ) ₃ ) as the silicon source 8, the method of the present invention was carried out in the following manner to obtain an insulating film of the present invention.

That is, first, the substrate 7 was fixed to the heater 5 in the decompression chamber 1, exhausted from the exhaust port 6, and heated to 350 ° C. while maintaining the internal pressure of the decompression chamber 1 at 100 Pa. Next, the gas supply pipe 4 is connected to the parallel plate electrode / gas supply shower nozzle 2 facing the substrate 7 at a position of 25 mm.
To process gas 10 (O _{2 in} this example), silicon source 8
(SiH (C ₂ H ₅ ) ₃ , carrier gas: N ₂ , a bubbler (not shown) is used in this embodiment) and a fluorine source 9 (C ₂ F ₆ in this embodiment) are supplied at the same time from the plasma power supply 3 to 13.56 MHz. RF was applied to obtain a mixed plasma of these gases on the surface of the substrate 7.
At this time, as target values of the process factors that influence the film characteristics, the RF applied power is 100 W and the flow rate ratio of the carrier gas, the process gas and the fluorine-based gas is N ₂ : O ₂ : C ₂ F ₆
= 2: 3: 2. The insulating film thus formed was designated as Inventive Example A. An insulating film formed in the same manner as in the example of the present invention except that TEOS was used as the silicon source 8 was used as Comparative Example C, and C ₂ F was used in the initial stage of the reaction in the example of the present invention. ₆ without supply of a sample of Comparative example D with the formed insulating film in the flow rate by supplying the C ₂ F ₆ after 40% of the film forming process has elapsed. (Example 2) except for using tri-isobutoxy silane as the silicon source _{8 (SiH (OC 4 H 9} ) 3) is to carry out the present invention method in the same manner as in Example 1, the insulating film of the present invention Example B Got

With respect to the insulating films of the present invention example and the comparative example, the relative dielectric constant during drying and that after moisture absorption treatment (moisture absorption condition: the substrate was immersed in ultrapure water and left for 1 hour) were evaluated, and FT- The presence or absence of Si-H bond and Si-F bond in the film was investigated by IR method. Table 1 shows the results.

[0017]

[Table 1]

As shown in Table 1, the dielectric constant of the insulating film of the present invention is lower than that of the comparative example in the dry state,
Moreover, it can be seen that the rise after the moisture absorption treatment is significantly suppressed.

[0019]

As described above, SiH (OR) _{3 in} which R is an arbitrary alkyl group is used as the organosilane compound of the raw material gas in place of the conventional TEOS, under the coexisting environment with the fluorine-containing gas. According to the present invention in which plasma CVD is performed to form an insulating film, it is possible to obtain a high-quality interlayer insulating film having a low dielectric constant and low hygroscopicity with good compatibility with existing processes, easily and at low cost. It has an extremely beneficial effect on the industry.

[Brief description of drawings]

FIG. 1 is a sectional view of a film forming apparatus suitable for implementing the present invention.

[Explanation of symbols]

1 Decompression chamber 2 Parallel plate electrode / gas supply shower nozzle 3 Plasma power supply 4 Gas supply pipe 5 Heater 6 Exhaust port 7 Substrate (Si wafer) 8 Silicon source (SiH (OR) ₃ gas and carrier gas) 9 Fluorine source (fluorine-based) Gas) 10 process gas

Claims (2)

[Claims] 1. An insulating film deposited by using SiH (OR) ₃ vapor in which R is an arbitrary alkyl group as a silicon source, and simultaneously reacting the silicon source with a gas containing fluorine to form a plasma. An insulating film containing fluorine, which contains both Si—H bond and Si—F bond. 2. A method for forming a fluorine-containing silicon oxide insulating film on a surface of a semiconductor substrate, wherein SiH (OR) ₃ vapor containing R as an arbitrary alkyl group is used as a silicon source, A method for forming an insulating film containing fluorine, which comprises simultaneously forming a plasma containing a gas containing fluorine, causing the reaction, and depositing the plasma.