JPH09232308A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a silicon oxide based insulating film with a practical deposition rate which film is free from contamination and contains fluorine, by using a CVD method material gas whose main component is compound composed of silane based gas, oxidizing gas, rare gas atoms and fluorine atoms. SOLUTION: A substrate 11 to be treated is constituted by forming a wiring layer 3 composed of Al based metal constituted of line and space of specified width, on an interlayer insulating film 2 on a semiconductor substrate 1 of Si or the like. The substrate 11 is mounted on the stage of a CVD equipment. A silicon oxide based insulating film(SIOF) containing fluorine is formed on the substrate 11 to be treated, by a CVD method using material gas whose main component is compound composed of silane based gas, oxydizing gas, rare gas atoms and fluorine atoms. Thereby an interlayer insulating film 4 is formed with a practical deposition rate which film is excellent in step coverage and composed of SiOF free from contamination of carbon and sulfur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device having a step of forming a low dielectric constant silicon oxide insulating film containing fluorine.

[0002]

2. Description of the Related Art With the progress of high integration of semiconductor devices such as LSI, in a multi-layer wiring structure, the width of an interlayer insulating film between adjacent wirings in the same wiring layer is narrowed, and the interlayer insulation between different wiring layers is also increased. The film is also thin. Due to the reduction of the wiring interval, an increase in inter-wiring capacitance is becoming a problem. Therefore, the actual operating speed of the semiconductor device is 1 / K
Since the scaling rule of (K is a reduction ratio) is not met, the merit of high integration cannot be fully enjoyed. Preventing the increase in inter-wiring capacitance is for high-speed operation of highly integrated semiconductor
To meet various demands such as low power consumption and low heat generation,
It is one of the elemental technologies that must be resolved by all means.

As a method of reducing the capacitance between wirings of a highly integrated semiconductor device, for example, as disclosed in Japanese Patent Application Laid-Open No. 63-7650, it is effective to use a low dielectric constant material for an interlayer insulating film. As the low dielectric constant material, an inorganic material such as a silicon oxide insulating film containing fluorine (hereinafter referred to as SiOF) is representative, but in addition to this, an organic SOG (Spin On Glass) having a siloxane bond, polyimide , Polyparaxylylene (trade name parylene), polynaphthalene and other organic polymer materials, flare (trade name of Allied Signal Co.), perfluoro group-containing polyimide, fluororesin organic polymers such as fluorinated polyallyl ether There is material. For these low dielectric constant materials, see, for example, Nikkei Microdevice Magazine, July 1995 issue, p. 105
Has been introduced.

[0004] These low dielectric constant material layers having a relative dielectric constant of 3.5 or less are applied not only between adjacent wirings but also between wiring layers of different levels.
₂ (dielectric constant 4), SiON (dielectric constant 4 to 6), Si
_The applicant of the present invention applied for a laminated insulating film having a structure sandwiched between insulating films having excellent film quality such as ₃ N ₄ (relative dielectric constant 6) by the applicant of the present invention.
No. 727, the possibility of a semiconductor device having an interlayer insulating film having both low dielectric constant and high reliability was shown.

Of the low dielectric constant materials, SiOF has attracted attention because its film formation process is compatible with the film formation process of conventional inorganic interlayer insulating films such as SiO _2, and can be easily adopted even in current production equipment. Have been. That is, generally, as disclosed in Japanese Patent Laid-Open No. 6-333919, the source gas such as SiH ₄ for forming the silicon oxide based insulating film is changed to a fluorosilane based gas such as SiF ₄ to perform the CVD. By doing so, Si—F bonds can be incorporated into the silicon oxide insulating film to form SiOF. However, since SiF ₄ has a small dissociation rate in plasma, it is difficult to sufficiently incorporate Si—F bonds.

On the other hand, the applicant of the present application disclosed a method of adding a basic gas such as NH ₃ to accelerate the dissociation of the raw material gas in the plasma in Japanese Patent Laid-Open No. 6-295907. According to this method, an excellent effect can be seen in reducing the hydroxyl group concentration in the silicon oxide-based insulating film, but the effect of reducing the relative dielectric constant is small.

As a source of fluorine atoms, for example, as disclosed in JP-A-7-90589, CF
_If a fluorocarbon-based gas such as ₄ or C ₂ F ₆ is used, the effect of reducing the specific inductivity can be obtained, but the contamination problem due to the mixing of carbon atoms remains.

Therefore, an attempt to eliminate unnecessary carbon atoms from the CVD reaction system by using SF ₆ gas as a source of fluorine atoms has been conducted in the proceedings of the 56th Annual Meeting of the Society of Applied Physics (Autumn Annual Meeting 1995) p590. , Presentation number 26p-ZB-
2 reported. This is TEOS (Tetra
And from Ethyl Ortho Silicate) and an oxidizing agent as a raw material gas, was added to SF ₆ to the plasma C
SiOF is formed by VD. As a result,
The specific induction rate drops to 3.3. However, SF ₆
Since a large amount of F ^* (F radicals) is generated in the plasma due to the dissociation of Al, an etching reaction occurs in competition with the deposition, so that the phenomenon that the deposition rate is saturated and the contamination by sulfur are seen.

[0009]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention is a method of manufacturing a semiconductor device including a step of forming a low dielectric constant silicon oxide insulating film containing fluorine. An object of the present invention is to provide a method of manufacturing a semiconductor device having a step of forming a silicon oxide-based insulating film containing fluorine that has a sufficiently reduced rate and is free from contamination by an added gas.

[0010]

A method of manufacturing a semiconductor device of the present invention is proposed to solve the above-mentioned problems, and is composed of a silane-based gas, an oxidizing gas, and a rare gas atom and a fluorine atom. The method is characterized by including a step of forming a silicon oxide insulating film containing fluorine on the substrate to be processed by a CVD method using a source gas mainly containing the compound described above.

Examples of the compound composed of a rare gas atom and a fluorine atom used in the present invention include ArF, KrF, XeF ₂ and NeF. As is well known, these gases include rare gas and F _{2 which} are excited in at least one of them.
It is a compound obtained by binding to
F ₄ , XeF ₆ , KrF _{2 and the} like are known, but these compounds may be adopted. The silane-based gas may be either an inorganic silane-based gas or an organic silane-based gas. In one embodiment of the present invention, it is desirable to form a silicon oxide-based insulating film containing fluorine while applying ultrasonic waves to a substrate to be processed.

Next, the operation will be described. In the present invention, the fluorine supply source gas in the film formation by the CVD method of SiOF does not contain an element which becomes contamination,
As a fluorine compound which is also excellent in dissociation in plasma, a compound composed of a rare gas atom and a fluorine atom is adopted. Noble gases such as Ar, Kr, and Xe are inert elements, and unlike active elements such as carbon and sulfur, they are less likely to be incorporated into SiOF. Further, since the amount of the fluorine-based chemical species supplied per molecule of these fluorine compounds is 1 atom or 2 atoms in terms of fluorine atom, SF
_{As in} the case of ₆ , the excess F ^* does not promote the etching reaction and saturate the deposition rate.

Further, by applying ultrasonic vibration to the CVD reaction system, the vibration energy of the substrate to be processed and the vibration energy level such as translation or rotation of the raw material gas molecules are increased, and the dissociation reaction of the raw material gas and intermediate generation Migration of an object on a substrate to be processed is activated. For this reason, it is possible to efficiently form a film with good step coverage even at a lower temperature than before.

Due to these actions, it is possible to form SiOF without contamination at a practical deposition rate.

As a prior application similar to the present invention, SiO 2 is applied while applying ultrasonic vibration to the substrate support or the reaction space.
A method for forming _two films is disclosed in Japanese Patent Application Laid-Open No. 5-44037. This is the thermal decomposition C by O ₃ / TEOS system.
No specific description can be found for the formation of a low dielectric constant silicon oxide-based insulating film due to VD and without contamination.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. First, a configuration example and operation of a single-wafer plasma CVD apparatus used as an example in each embodiment of the present invention will be described with reference to a schematic sectional view shown in FIG.

The apparatus shown in FIG. 2 has a basic configuration of a parallel plate type plasma CVD apparatus. That is, the substrate 11 on which SiOF is to be formed is set on the substrate stage 12 having a built-in heater 13 at a ground potential. The raw material gas introduced into the gas introduction holes 16 is diffused by the gas diffusion plate 15, and passes through the gas shower head 14 having a perforated plate-shaped gas blowout hole facing the substrate 11 to be processed. Spouts evenly. Reference numeral 17 denotes a gas ring disposed on the outer peripheral upper surface of the substrate to be processed, which is a hollow annular nozzle member having a large number of gas ejection holes, and a part of the raw material gas, a diluent gas or the like is added as necessary. It is a thing. Reference numeral 18 denotes a gas exhaust hole connected to a vacuum pump (not shown), and reference numeral 19 denotes an RF power supply for supplying RF power to the gas shower head 14 also serving as an upper electrode. If the vertical relationship between the gas shower head 14 and the substrate stage 12 is reversed, that is, if the face-down structure in which the substrate 11 to be processed is held downward on the back surface, the substrate 11 to be processed is
Particles are prevented from adhering to the surface.

Characteristic portions of the present plasma CVD apparatus are ultrasonic vibration applying means 20A, 20B and 20C. Among them, the ultrasonic vibration applying means 20A is provided on the substrate stage 12
And directly excites the substrate 11 to be processed. The ultrasonic vibration applying means 20B is incorporated in the gas diffusion plate 15, and excites the raw material gas ejected from the gas shower head 14. The ultrasonic vibration applying means 20B includes the gas shower head 14, the gas introduction hole 16, or the gas ring 1
7 may be attached. Also, the ultrasonic vibration applying means 20C
Is mounted on the inner wall of the CVD chamber to excite the source gas on the upper surface of the substrate 11 to be processed. The ultrasonic vibration applying means 20C is provided with a horn to enhance the directivity of the ultrasonic wave in order to effectively excite the source gas near the substrate 11 to be processed. This is like a horn tweeter in a speaker system. It is desirable that a plurality of ultrasonic vibration applying means 20C be attached to the inner wall of the etching chamber. As the ultrasonic vibration applying means, various electric / acoustic converters such as a piezoelectric element, a magnetostrictive element, and an electrodynamic type using a magnetic circuit and a coil may be arbitrarily used.

Example 1 Next, a specific example of the step of forming SiOF will be described.
This embodiment is an example in which a low dielectric constant interlayer insulating film made of SiOF is formed on an Al-based metal wiring by plasma CVD using SiH ₄ , O ₂ and ArF as source gases, and this is shown in FIG. This will be described with reference to (b).

First, a wiring layer 3 made of an Al-based metal having a line-and-space width of 0.35 μm, for example, is formed on the interlayer insulating film 2 on the semiconductor substrate 1 made of Si or the like, and is used as a substrate to be processed. This is shown in FIG.

Then, a thin lower insulating film (not shown) is conformally formed by ordinary plasma CVD using SiH ₄ and N ₂ O as source gases. This lower insulating film is formed to complement the quality of the SiOF film deposited in the next step, but the film formation may be omitted if not necessary.

Subsequently, the substrate 11 to be processed is placed on the substrate stage 12 of the CVD apparatus shown in FIG. 2 and the plasma CVD of SiOF, which is the essential part of this embodiment, is performed under the following conditions. SiH ₄ 50 sccm O ₂ 50 sccm ArF 30 sccm Gas pressure 27 Pa RF power supply power 0.08 W / cm ² (13.56 MHz) Substrate temperature 300 ° C.

The SiOF film was formed to a thickness of, for example, 0.3 μm above the Al-based metal wiring. As a result, as shown in FIG. 1 (b), SiOF has good step coverage and no carbon or sulfur contamination.
The inter-layer insulating film 4 made of was formed at a practical deposition rate. The relative dielectric constant of the interlayer insulating film 4 was 3.3. After that, a thin upper layer insulating film (not shown) may be formed again as required by ordinary plasma CVD using SiH ₄ and N ₂ O as source gases. By adopting such a laminated structure, it is possible to obtain a highly reliable interlayer insulating film having a low dielectric constant and excellent moisture resistance.

Example 2 This example is the same as Example 1 except that KrF was used instead of ArF. Also in this example, SiOF having a specific dielectric constant of 3.3 was formed at a practical film formation rate with good step coverage and without contamination.

Embodiment 3 In this embodiment, SiOF is applied to a substrate to be processed while applying ultrasonic waves.
This is an example in which is formed. Since the substrate to be processed used in this example is the same as that shown in FIG. 1A in Example 1, duplicate description will be omitted. This substrate 1 to be processed
1 is placed on the substrate stage 12 of the CVD apparatus shown in FIG. 2, and plasma CVD of SiOF is performed under the following conditions as an example. The ultrasonic vibration was applied using the ultrasonic vibration applying means 20A incorporated in the substrate stage 12. The power for excitation was set to 100 W as an example, but the optimum value varies depending on the diameter and weight of the substrate 11 to be processed and the conversion efficiency of the electric / acoustic converter. SiH ₄ 50 sccm O ₂ 50 sccm XeF ₂ 30 sccm Gas pressure 27 Pa RF power supply power 0.08 W / cm ² (13.56 MHz) Ultrasonic vibration (continuous) 100 W (200 kHz) Substrate temperature 300 ° C.

The SiOF film was formed to a thickness of 0.3 μm above the Al-based metal wiring. As a result, as shown in FIG. 1B, the step coverage was good, and the interlayer insulating film 4 made of SiOF free from carbon or sulfur contamination was formed at a practical deposition rate. The relative dielectric constant of the interlayer insulating film 4 was 3.2 because the dissociation of XeF ₂ was improved by the application of ultrasonic waves and the fluorine atoms were efficiently incorporated into the film.

Embodiment 4 This embodiment is an example in which SiOF is formed while applying ultrasonic waves to the raw material gas ejected from the gas shower head 14. With this configuration, ultrasonic vibration energy can be applied to both the plasma space and the substrate to be processed. The substrate to be processed used in this example is the same as that shown in FIG. 1A in Example 1, and duplicate description is omitted. The substrate 11 to be processed is referred to as C shown in FIG.
The substrate is placed on the substrate stage 12 of the VD apparatus, and plasma CVD of SiOF is performed under the following conditions as an example. The ultrasonic vibration is generated by the gas diffusion plate 15 in the gas shower head 14.
It was applied using the ultrasonic vibration applying means 20B incorporated in. The power for excitation was 100 W as an example, but the optimum value varies depending on the diameter and weight of the gas diffusion plate 15, the conversion efficiency of the electric / acoustic converter, the gas flow rate, and the like. SiH ₄ 50 sccm O ₂ 50 sccm KrF 30 sccm Gas pressure 27 Pa RF power supply power 0.08 W / cm ² (13.56 MHz) Ultrasonic vibration (continuous) 100 W (200 kHz) Substrate temperature 300 ° C.

The SiOF film was formed to a thickness of 0.3 μm above the Al-based metal wiring. As a result, as shown in FIG. 1B, the step coverage was good, and the interlayer insulating film 4 made of SiOF free from carbon or sulfur contamination was formed at a practical deposition rate. The specific dielectric constant of the interlayer insulating film 4 was 3.2 because the dissociation of KrF was improved by the application of ultrasonic waves and the fluorine atoms were efficiently incorporated into the film.

Although the present invention has been described above with reference to the four examples, the present invention is not limited to these examples.

For example, SiH ₄ is used as the silane-based gas, but an inorganic high-order silane-based gas such as Si ₂ H ₆ may be used. In addition, TEOS is used as an organic silane-based gas, and Octa Methyl Cyclo Tetra
Siloxane (OMCTS), Tetra Pr
opoxy Silane (TPOS), TetraM
Ethyl Cyclo Tetra Siloxan
e (TMCTS), Tetramethyl Orth
Oscillate (TMOS), Diacetoxy
Dietarybutyxy Silane
(DADBS), Tetraethyl Silane
(TES), TetramethylSilane (T
Other organic silane-based gases such as MS) can be used as appropriate. In addition, SiH ₄ , Si
_An inorganic silane gas such as ₂ H ₆ may be mixed and used.

Although O ₂ is used as the oxidizing gas, other oxidizing gases such as O ₃ , N ₂ O, NO ₂ , H ₂ O and H are of course used.
₂ O ₂ may be used or mixed. In addition, a rare gas such as He, Ar, or Xe or N ₂ may be mixed and used as a diluent gas.

In the embodiment, ultrasonic waves are applied using the ultrasonic vibration applying means 20A incorporated in the substrate stage 12 and the ultrasonic applying means 20B incorporated in the gas diffusion plate 15, but the ultrasonic waves directly attached to the chamber wall. Applying means 20
C may be used. The ultrasonic wave may be applied intermittently. The frequency may be other than 200 kHz, and a plurality of frequencies may be switched and applied, or the frequency or output may be swept and applied.

In the case of using the plasma CVD method, in addition to the parallel plate type apparatus used in the above embodiment, the microwave C
It is also possible to use a VD apparatus, an ECR-CVD apparatus, or a high density plasma source such as helicon wave plasma or inductively coupled plasma (ICP). Further, the use of UV rays such as a low pressure Hg lamp is useful for promoting dissociation of raw material gas and reducing substrate damage. LP-CVD and atmospheric pressure C
It is also possible to adopt the VD method. In this case, ultrasonic wave applying means may be appropriately attached to the substrate stage, gas nozzle, CVD chamber, or the like of these conventional CVD apparatuses.

In each of the above-mentioned embodiments, the case of forming the interlayer insulating film on the Al-based metal wiring has been exemplified. However, the case of using another wiring material layer, the case of using it as the final passivation film, and the trench isolation. It is needless to say that the above can also be applied to the case where the above is buried flat without generating voids.

[0035]

As is apparent from the above description, according to the present invention, the low dielectric constant of SiOF, which is free from contamination by carbon, sulfur, etc., which are the constituents of the raw material gas, can be achieved at a practical deposition rate. Can be formed. Therefore, it is possible to reliably manufacture a semiconductor device such as a microprocessor or a highly integrated memory in which signal delay due to the capacitance between wirings becomes a problem.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating a plasma CVD process of Examples 1 to 3 of the present invention, in which (a) is a state in which a wiring layer is formed on an interlayer insulating film, and (b) is a low dielectric constant silicon oxide. This is a state in which an interlayer insulating film made of a system insulating film is formed.

FIG. 2 is a schematic cross-sectional view showing a configuration example of a single-wafer plasma CVD apparatus used in Examples 1 to 3 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Interlayer insulating film, 3 ... Wiring layer, 4 ... Interlayer insulating film 11 ... Substrate to be processed, 12 ... Substrate stage, 13 ... Heater, 14 ... Gas shower head, 15 ... Gas diffusion plate, 1
6 gas introduction hole, 17 gas ring, 18 gas discharge hole, 19 RF power supply, 20A, 20B, 20C ultrasonic wave applying means

Claims (4)

[Claims] 1. A silicon oxide insulating material containing fluorine on a substrate to be processed by a CVD method using a silane-based gas, an oxidizing gas, and a source gas mainly containing a compound composed of a rare gas atom and a fluorine atom. A method of manufacturing a semiconductor device, comprising the step of forming a film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the compound composed of a rare gas atom and a fluorine atom is at least one of ArF, KrF, XeF ₂ and NeF. . 3. The method of manufacturing a semiconductor device according to claim 1, wherein the silane-based gas is at least one of an inorganic silane-based gas and an organic silane-based gas. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the silicon oxide insulating film containing fluorine is formed while applying ultrasonic waves to the substrate to be processed.