JPH09162184A - Fabrication of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the permittivity sufficiently by depositing a silicon oxide based insulation film containing fluorine on a substrate to be processed by CVD using a material gas principally comprising a silane based gas, an oxidizing gas and thiocarbonyl fluoride. SOLUTION: A substrate 11 to be processed is mounted on the substrate stage 12 of a CVD system. A silicon oxide based insulation film containing fluorine is then deposited on a substrate to be processed by CVD using a material gas principally comprising a silane based gas, an oxidizing gas and thiocarbonyl fluoride. Consequently, an interlayer insulation film composed of SiOF free from contamination with carbon or sulfur can be deposited with high step coverage at a practical deposition rate. In other words, contamination free SiOF having low permittivity can be deposited at a practical deposition rate.

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 decrease in the wiring interval, an increase in inter-wiring capacitance is becoming a problem. Preventing an increase in the capacitance between wirings is one of the elemental technologies that must be solved in order to respond to various demands such as high-speed operation, low power consumption, and low heat generation of a highly integrated semiconductor device.

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, in general, by adding SiF ₄ to the source gas for forming the silicon oxide type insulating film by the plasma CVD method, S
Incorporating i-F bond into the silicon oxide insulating film,
Form OF. 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.

CF ₄ and C _{2 are} used as a source of fluorine atoms.
If a fluorocarbon-based gas such as F ₆ is used, the effect of reducing the specific induction can be obtained, but the problem of contamination due to the incorporation of carbon atoms remains.

Therefore, an attempt has been made to exclude carbon atoms from the CVD reaction system by using SF ₆ gas as a supply source of fluorine atoms.
It is reported in Proceedings p590, Lecture No. 26p-ZB-2 of the 56th Academic Meeting of Japan Society of Applied Physics (Autumn Annual Meeting 1995). This is TEOS (Tetra Et
hyl Ortho Silicate) and an oxidizing agent as raw material gases, plasma CVD by adding SF ₆ to
To form SiOF. As a result, the specific induction rate drops to 3.3. However, there is a phenomenon in which the deposition rate is saturated because an etching reaction due to F ^* (F radicals) generated in large quantity in plasma due to dissociation of SF ₆ competes with the deposition.

[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 a raw material mainly containing a silane-based gas, an oxidizing gas and thiocarbonyl fluoride. By the CVD method using gas,
The method is characterized by including a step of forming a silicon oxide insulating film containing fluorine on the substrate to be processed.

The thiocarbonyl fluoride used in the present invention is at least one of CSF ₂ and CSF ₄ , and these are used alone or in combination.

The silane-based gas used in the present invention is at least one of an inorganic silane-based gas and an organic silane-based gas, and these are used alone or in combination.

A preferred embodiment of the present invention is characterized in that a silicon oxide type insulating film containing fluorine is formed while applying ultrasonic waves to the substrate to be processed. The method of applying the ultrasonic wave is not particularly limited, but a method of directly exciting the substrate to be processed from the substrate stage, a method of exciting the material gas introduction hole and the vicinity of the gas shower head, or a reaction space in the chamber By exciting, it is possible to arbitrarily adopt a method of indirectly exciting the substrate to be processed.

Next, the operation will be described. CSF ₂ or C
A thiocarbonyl fluoride compound such as SF ₄ is dissociated to supply a fluorine-based chemical species into the plasma, and this is efficiently incorporated as a Si—F bond in the silicon oxide network. Since the amount of the fluorine-based chemical species supplied per molecule of the thiocarbonyl fluoride compound is 2 or 4 atoms in terms of fluorine atoms, the etching reaction proceeds due to excess F ^* as in the case of SF _6. The deposition rate never saturates.

The other dissociation product, the thiocarbonyl residue, is oxidized by an oxidizing gas to produce CO _x and SO _x.
Is exhausted from the CVD chamber. The same applies when the carbonyl residue is further dissociated into a carbon-based chemical species or a sulfur-based chemical species. Even if free sulfur atoms are generated, they are excluded from the CVD chamber because they are sublimable substances and do not remain in the SiOF film. Therefore, there is no risk that any dissociation products other than fluorine will remain as contamination in the silicon oxide insulating film.

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 source gas molecules are increased, and the dissociation reaction of the source gas is activated. It 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.

[0019]

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

The target substrate 11 on which SiOF is to be formed is
The heater 13 is set on the substrate stage 12 having 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 is a gas ring disposed on the outer peripheral upper surface of the substrate to be processed, which is a hollow annular 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 if necessary. Is. The raw material gas nozzle referred to in claim 3 of the present invention refers to the members of the gas shower head 14, the gas diffusion plate 15, the gas introduction hole 16 and the gas ring 17. Reference numeral 18 is a gas discharge hole connected to a vacuum pump (not shown), and reference numeral 19 is an RF power source for supplying RF power to the gas shower head 14 also serving as an upper electrode. The gas shower head 14 and the substrate stage 12
If the upper and lower sides of the above are reversed, that is, if the substrate 11 to be processed is held downward on the back surface, particles are prevented from adhering to the surface of the substrate 11 to be processed.

Characteristic parts of this 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 example 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 CSF ₂ as source gases.
This will be described with reference to FIGS.

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 this 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 main part of this embodiment, is performed under the following conditions. SiH ₄ 50 sccm O ₂ 50 sccm CSF ₂ 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 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 3.3.

Example 2 This example is the same as Example 1 except that CSF ₄ was used as thiocarbonyl fluoride instead of CSF ₂ . Also in this example, although the deposition rate was slightly lower than that in Example 1, SiOF having a specific induction of 3.25 had a good step coverage at a sufficiently practical speed,
Also, it was formed without contamination.

Example 3 In this example, SiOF was applied to the substrate to be processed while applying ultrasonic waves.
This is an example in which is formed. The substrate to be processed used in this example is the same as that shown in FIG. The substrate 11 to be processed is placed on the substrate stage 12 of the CVD apparatus shown in FIG.
As an example, OF plasma CVD is performed under the following conditions. 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 CSF 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 thickness of 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 lowered to 3.2 because dissociation of CSF ₂ was improved by application of ultrasonic waves and fluorine atoms were efficiently incorporated into the film.

In this embodiment, ultrasonic waves are applied using the ultrasonic vibration applying means 20A incorporated in the substrate stage 12, but the ultrasonic wave applying means 20B incorporated in the gas diffusion plate 15 is applied.
Or ultrasonic wave applying means 20C directly attached to the chamber wall
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.

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

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 added.

O ₂ was used as the oxidizing gas, but 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, He, Ar and Xe are used as diluent gases.
It may be mixed and used noble gas or N ₂ and the like.

When plasma CVD is used, in addition to the parallel plate type apparatus used in the above-mentioned embodiment, a microwave CV is used.
It is also possible to use a D apparatus, an ECR-CVD apparatus, and 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. In addition, LP-CVD and atmospheric pressure CV
It is also possible to adopt the D 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-described embodiments, the case of forming the interlayer insulating film on the Al-based metal wiring has been exemplified, but the case of using another wiring material layer, the case of using as the final passivation film, and the trench isolation. It is needless to say that the present invention can be applied to the case where the layer is embedded flat without generating voids.

[0037]

As is apparent from the above description, according to the present invention, it is possible to form a low dielectric constant made of SiOF, which has no contamination due to the constituent components of the raw material gas, at a practical deposition rate. Become. 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 poses a problem.

[Brief description of the 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]

 1 Semiconductor Substrate 2 Interlayer Insulation Film 3 Wiring Layer 4 Interlayer Insulation Film 11 Substrate 12 Substrate Stage 13 Heater 14 Gas Shower Head 15 Gas Diffusion Plate 16 Gas Introduction Hole 17 Gas Ring 18 Gas Exhaust Hole 19 RF Power Supply 20A, 20B, 20C Ultrasonic vibration applying means

Claims (4)

[Claims] 1. A step of forming a silicon oxide-based insulating film containing fluorine on a substrate to be processed by a CVD method using a raw material gas mainly containing a silane-based gas, an oxidizing gas and thiocarbonyl fluoride. A method for manufacturing a semiconductor device, comprising: 2. The method for manufacturing a semiconductor device according to claim 1, wherein the thiocarbonyl fluoride is at least one of CSF ₂ and CSF ₄ . 3. The method for 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.