JPH08227888A - Forming method of dielectric film - Google Patents

Abstract

PURPOSE: To obtain a dielectric film which is enhanced in filling performance and lessened in dielectric constant by a method wherein material gas used in a chemical vapor growth process where dielectric film is formed is composed of silane gas such as monosilane or polysilaxae, specific hydrocarbon, and oxidizing agent of oxygen atom-containing gas. CONSTITUTION: A wiring 13 is formed on a semiconductor board 11 through the intermediary of an insulating film 12, and a protective film 14 is formed on the surface of the wiring 13. Then, a dielectric film 15 of low dielectric constant is formed on the protective film 14. The dielectric film 15 is formed through a vacuum CVD device 201, and material gas is introduced into the reaction chamber 211 of the vacuum CVD device 201 through the intermediary of gas inlet sections 212 and 213 and a diffusion section 216. The material gas is composed of silane gas such as monosilane or polysilane, specific hydrocarbon represented by a formula, Cn H2n+2 (n denote positive integer), and oxidizing agent of oxygen atom-containing gas. By this setup, the dielectric film 15 which has a high filling performance and a low dielectric constant is capable of being realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a dielectric film having a low dielectric constant used in a semiconductor device, particularly a dielectric film used as an interlayer insulating film of a semiconductor device having a design rule of 0.25 μm or less. It is about.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices, lower power consumption, and higher speed operation, reduction of the dielectric constant of an interlayer insulating film has been studied. The currently disclosed dielectric film having a low dielectric constant (hereinafter referred to as a low dielectric film) has a low dielectric constant by containing carbon atoms or fluorine atoms. At present, a low dielectric film having a dielectric constant of about 1.5 to 2.5 has been realized.

Low dielectric materials containing carbon atoms are organic SO
G (Spin on glass), polyimide, polyparaxylylene, etc. are known. It is said that these materials have a low dielectric constant by containing a carbon atom, a so-called alkyl group, to reduce the density of the material and to lower the polarizability of the atom itself. Further, these materials not only have a low dielectric constant but also have heat resistance which is indispensable as a material for a semiconductor device. The organic SOG has a siloxane structure, the polyimide has an imide bond, and the polyparaxylylene is a polymer having a benzene ring, so that each has heat resistance.

Silicon oxyfluoride [SiOF] is known as a low dielectric material containing a fluorine atom. This material is S
By terminating the i-O-Si bond with a fluorine atom,
The dielectric constant is lowered due to the decrease in density and the low polarizability of fluorine atoms themselves. Naturally, this material also has excellent heat resistance.

Further, not only the low dielectric film but also the insulating film is required to be embedded between wirings, and it is necessary to have an embedding ability and an ability to flatten a large area (hereinafter referred to as global flattening). As the method, the APL technology is drawing attention. This APL technology is an abbreviation for Advanced Planarization Layer developed by ETE in the UK, and is a technology having an embedding capability and a certain level of global planarization capability. This technique uses monosilane [SiH ₄ ] and hydrogen peroxide [H ₂ O ₂ ] as raw materials, cools the substrate to around 0 ° C., and performs chemical vapor deposition (hereinafter referred to as CVD) to obtain a substrate. It is a method of forming an insulating film (SiO ₂ film) on the surface in a shape like a liquid dropped and cured. Regarding the embedding ability, an aspect ratio of up to about 4 is possible. The global leveling capability is 10 μm
It is possible to embed approximately square. In this technique, it is known that when the substrate temperature is raised to 10 ° C. or higher, the film does not behave like a liquid during film formation, and the above capability gradually disappears.

[0006]

[Problems to be Solved by the Invention] However, the APL
In the technology, the dielectric constant of the formed insulating film is about 4 to 5,
SOG film, ozone-tetraethoxysilane [O ₃ -TE
OS] film and the like, and has a low dielectric constant (dielectric constant of 1.5 to
A film of about 2.5) cannot be formed. that is,
The film formed by the APL technique is a silicon oxide film, and even if the dielectric constant is ideally lowered, the dielectric constant of 3.8 is the limit. Moreover, since the insulating film formed by the APL technique contains a hydroxyl group [—OH ⁻ ] having an effect of increasing the dielectric constant, the dielectric constant becomes higher than that of the silicon oxide film.

Therefore, an object of the present invention is to provide a method for forming a dielectric film having a high embedding ability and a low dielectric constant.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for forming a dielectric film, which has been made to achieve the above object. That is, in a method of forming a dielectric film for forming a silicon oxide film containing an organic component by a chemical vapor deposition method, at least a silane-based gas of monosilane or polysilane and C _n H _{2n + 2} [n is positive Represents an integer of], and by forming a dielectric film by chemical vapor deposition using a source gas composed of a hydrocarbon and an oxidizing agent consisting of a gas containing oxygen atoms, Solve.

[0009]

In the above method of forming the dielectric film, at least a silane-based gas, a hydrocarbon represented by C _n H _{2n + 2} [n represents a positive integer], and an oxidation gas containing an oxygen atom are used. Since a dielectric film is formed by chemical vapor deposition using a raw material gas composed of an agent and a silane-based gas and an oxidizing agent are condensed, silanol is generated, and this silanol and hydrocarbon are formed. The reaction produces a precursor having a bond between an organic component (for example, an alkyl group) and Si. Then, the precursor and silanol react with each other to form a dielectric film made of silicon oxide having a bond between an organic component (for example, an alkyl group) and Si.

As described above, by attaching an alkyl group to a silicon atom, the bond network is cut off at that point, so that electrons do not flow between molecules. That is, as the electronic polarizability decreases, the dielectric constant decreases.
In addition, since the chemical bond is broken, the density of the film is reduced. That is, since the number of polarized molecules per unit volume decreases, the dielectric constant decreases.

Since the polymerization reaction in the above forming method is relatively slow, the formed film behaves like a liquid on the film forming surface while the polymerization reaction does not proceed. Therefore, it has an embedding capability and a global planarization capability.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the schematic configuration diagram of the forming method of FIG. 1, the capacitive coupling type plasma CVD apparatus of FIG. 2 and the low pressure CVD (hereinafter referred to as LPCVD) apparatus of FIG. Further, in the first embodiment, an example applied to the interlayer insulating film will be shown.

First, the capacitively coupled plasma CVD apparatus (hereinafter referred to as plasma CVD apparatus) 101 shown in FIG.
Will be briefly described. This plasma CVD apparatus 101 is
A reaction chamber 111 is provided, and a gas introduction part 112 for introducing a source gas and an exhaust part 113 are connected to the reaction chamber 111. Further, the upper electrode 114 and the lower electrode 115 on which the semiconductor substrate 11 is mounted are provided in the reaction chamber 111 so as to face each other.
14 has a structure in which a high frequency power source 116 for applying high frequency power is connected.

Next, the low pressure CVD (hereinafter LPC) shown in FIG.
A device 201 (referred to as VD) will be briefly described. This LPC
The VD device 201 is provided with a reaction chamber 211, and gas introduction units 212 and 213 for introducing a raw material gas and an exhaust unit 214 are connected to the reaction chamber 211. The reaction chamber 211 has a structure in which a substrate mounting portion 215 on which the semiconductor substrate 11 is mounted and a diffusion portion 216 are provided so as to face each other.

Next, the first embodiment will be described. As shown in (1) of FIG. 1, a wiring 13 is formed on a semiconductor substrate 11 as a base with an insulating film 12 interposed therebetween.
A protective film 14 is formed on the surface of No. 3.

The protective film 14 is formed by the plasma CVD apparatus 101 described with reference to FIG. In the reaction chamber 111 of the plasma CVD apparatus 101, the gas introduction unit 11
A gas obtained by mixing, for example, monosilane [SiH ₄ ], oxygen [O ₂ ] and helium [He] as a diluent gas (carrier gas) was introduced through 2. And the exhaust part 11
The pressure in the reaction chamber 111 was adjusted to 100 Pa, for example, by exhausting air from No. 3. Further, the temperature of the lower electrode 115 on which the semiconductor substrate 11 is mounted is set to, for example, 350 ° C., and high frequency power of, for example, 1.0 W / cm ² is supplied from the high frequency power supply 116 between the upper electrode 112 and the lower electrode 113. . Then, as shown in (1) of FIG.
A protective film 14 made of SiO ₂ and having a thickness of 50 nm was formed on the semiconductor substrate 11 arranged in the No. 1 structure.

Next, as shown in (2) of FIG.
A low dielectric film 15 having a dielectric constant of 2.5 to 3.5 is formed on the protective film 14.
Form a film. The low dielectric film 15 has a structure as shown in FIG.
The film is formed by the low pressure CVD apparatus 201. The above LPCVD equipment
In the reaction chamber 211 of the apparatus 201, gas introduction parts 212, 21
3, the raw material gas was introduced through the diffusion section 216. this
The raw material gas is a silane-based gas (monosilane or polysilica).
For example, monosilane [SiH_Four], And C_nH
_{2n + 2}[Wherein n represents a positive integer]
Then, for example, ethane [C₂H₆], And a gas containing oxygen atoms
As an oxidant composed of, for example, hydrogen peroxide [H₂O ₂〕When
It is composed of. The gas flow rate at this time is SiH_FourBut
50 sccm, C ₂H₆Is 25 sccm, H₂O₂Is 2
It was set to 00 sccm. Then, the exhaust from the exhaust unit 214
Adjust the amount to keep the pressure in the reaction chamber 211 at 100 Pa.
Was. In addition, the semiconductor substrate 11 mounted on the substrate mounting portion 215
The temperature is kept at 0 ° C. and further provided above the semiconductor substrate 11.
The temperature of the diffusion part 216 is kept at 100 ° C. Up
The numerical value conditions are an example, and are not limited to the numerical values shown here.
It will not be done. Under the above conditions, the semiconductor substrate 11
Si containing 800 nm thick organic component (ethyl group) on top
O₂A low dielectric film 15 of was formed.

Next, as shown in FIG. 1C, an insulating film 16 was formed on the low dielectric film 15 by the CVD method. The insulating film 16 is a silicon oxide [SiO ₂ ] film having a thickness of 0.3 μm. As a method for forming the insulating film 16, there are sputtering, spin coating, and the like, in addition to the CVD method.

Next, in order to remove the moisture in the low dielectric film 15, annealing was performed. This annealing is carried out by using, for example, a general diffusion furnace, and nitrogen (N
₂ ) By leaving in the atmosphere for 15 minutes.

In the case of further forming an upper layer wiring, as shown in FIG. 4, after forming a contact hole 17 in the insulating film 16, the low dielectric film 15 and the protective film 14, a plug 18 is formed in the contact hole 17. To form. Further, the step of forming the upper layer wiring 19 is performed. Further, a protective film 20 is formed by a method similar to that of the protective film 14 described in (1) of FIG. 1 described above, and then a protective film 20 is formed by a method similar to that of the low dielectric film 15 described in (2) of FIG. Dielectric film 21
To form. Further, the insulating film 22 is formed by the same method as the insulating film 16 described in (3) of FIG. In this way, a multilayer wiring structure is formed.

In the reaction for forming the low dielectric film 15 in the first embodiment, the following reaction is considered to occur in the reaction chamber 211. First,

Embedded image The reaction of SiH ₄ + 2H ₂ O ₂ → Si (OH) ₄ + 2H ₂ ↑ [1] produces silanol represented by Si (OH) ₄ . And

Embedded image In the reaction of Si (OH) ₄ + C ₂ H ₆ → Si (OH) ₃ (C ₂ H ₅ ) + H ₂ O ↑, a precursor represented by Si (OH) ₃ (C ₂ H ₅ ) Is generated,

Embedded image Si (OH) ₃ (C ₂ H ₅ ) + Si (OH) ₄ → (OH) ₃ SiOSi (OH) ₂ (C ₂ H ₅ ) + H ₂ O ↑ Silicon oxide having bonds is produced. In this way, the low dielectric constant film 15 of silicon oxide having a bond between the organic component (for example, one kind of alkyl group, ethyl group) and Si is formed.

In the low dielectric film 15, when an ethyl group is attached to a silicon atom, the bond network is cut off there, so that electrons do not pass between molecules. That is, as the electronic polarizability decreases, the dielectric constant decreases. In addition, since the chemical bond is broken, the density of the film is reduced. That is, since the number of polarized molecules per unit volume is reduced, the dielectric constant is 2.5 to 3.
It becomes as low as 5.

Since the polymerization reaction in the above-mentioned forming method is relatively slow, the formed film behaves like a liquid on the film forming surface while the polymerization reaction does not proceed. Therefore, the embedding ability can be up to an aspect ratio of 4, and the global flattening degree kept a substantially flat shape up to a wiring interval of 10 μm.

Next, a second embodiment will be described. The second embodiment is the same as the first embodiment except that the low dielectric film 15 is formed. Therefore, here, an example of a method of forming the low dielectric film 15 will be described by giving the same reference numerals as those in the first embodiment. Since the drawing of the forming method is the same as that of FIG. 1, it is omitted here.

The low dielectric film 15 of the second embodiment is the same as that shown in FIG.
The film is formed by the LPCVD apparatus 201 shown in FIG. This LP
In the reaction chamber 211 of the CVD apparatus 201, monosilane [SiH ₄ ] which is a silane-based gas and methane [C which is a hydrocarbon]
A raw material gas formed by mixing H ₄ ], oxidant water [H ₂ O] and ozone [O ₃ ] was introduced. An example of film forming conditions at this time will be described below. The flow rates of the raw material gases are 50 sccm for SiH ₄ , 100 sccm for CH ₄ , and 20 for H ₂ O.
0 sccm and O ₃ were 30 sccm. Then, the pressure inside the reaction chamber 211 was set to 200 Pa, and the temperature of the semiconductor substrate 11 mounted on the substrate mounting part 215 was set to −50 ° C.
The temperature of the diffusion part 216 was kept at 100 ° C. The above numerical conditions are examples, and each numerical value is not limited.
Then, under the above conditions, a thickness of 8 is formed on the semiconductor substrate 11.
A low dielectric film 15 made of SiO ₂ containing an organic component (methyl group) of 00 nm was formed.

Then, after the silicon oxide [SiO ₂ ] film 16 is formed in the same manner as described in the first embodiment,
Water was removed from the low dielectric film 15 by annealing in a nitrogen (N ₂ ) atmosphere at 400 ° C. for 15 minutes.

The low dielectric film 15 in the second embodiment.
When a methyl group is attached to a silicon atom, the bond network is cut off there, and the transfer of electrons between molecules disappears. That is, as the electronic polarizability decreases, the dielectric constant decreases. In addition, since the chemical bond is broken, the density of the film is reduced. That is, by reducing the number of polarized molecules per unit volume,
The dielectric constant is as low as 2.5 to 3.5.

Since the polymerization reaction in the above forming method is relatively slow, the formed film behaves like a liquid on the film forming surface while the polymerization reaction does not proceed. Therefore, the embedding ability can be up to an aspect ratio of 4, and the global flattening degree kept a substantially flat shape up to a wiring interval of 10 μm.

Next, a third embodiment will be described. The third embodiment is the same as the first embodiment except that the low dielectric film 15 is formed. Therefore, here, an example of a method of forming the low dielectric film 15 will be described by giving the same reference numerals as those in the first embodiment. Since the drawing of the forming method is the same as that of FIG. 1, it is omitted here.

The low dielectric film 15 of the third embodiment is the same as that shown in FIG.
High density plasma enhanced CVD (hereinafter referred to as HDCVD, HDCVD is referred to as High Dencity Plasma Enhanced
The film is formed by an apparatus 301 (abbreviation of Chemical Vapor Deposition).

First, the HDCVD apparatus 30 shown in FIG.
1 will be briefly described. In this HDCVD device 301,
A plasma generation chamber 311 and a reaction chamber 312 connected to the plasma generation chamber 311 are provided. A coil 314 connected to a high frequency power supply 313 is provided on the outer circumference of the plasma generation chamber 311, and a magnet 315 for generating a magnetic field is further installed. Also, the plasma generation chamber 311
The gas introduction part 316 for introducing the gas to be turned into plasma
Is connected. On the other hand, the reaction chamber 312 is connected to a gas introduction section 317 for introducing the raw material gas and an exhaust section 318 for adjusting the internal pressure. Further, inside the reaction chamber 312, a gas diffusion part 319 connected to the gas introduction part 317 and a substrate mounting part 320 on which the semiconductor substrate 11 is mounted are provided. Further reaction chamber 3
The outer circumference of 12 has a structure in which a magnet 321 is installed.

To form the low dielectric film 15, the above HD is used.
In the reaction chamber 312 of the CVD device 301, the silane-based gas
Disilane, which is one of the polysilanes [Si₂H₆], And charcoal
Hydrogen ethane [C₂H₆] And the oxidizer hydrogen peroxide
[H₂O₂] The raw material gas obtained by mixing
It was introduced through 317 and the gas diffusion section 319. That
At the same time, the gas introduction part 316 is provided in the plasma generation chamber 311.
Through nitrous oxide [N ₂O] was introduced. Qi at this time
Body flow rate is Si₂H₆Is 50 sccm, C₂H₆Is 10
0 sccm, H₂O₂Is 200 sccm, N₂O is 30
It was set to sccm. Then, the pressure in the reaction chamber 312 is
The exhaust amount of the air part 318 was adjusted and maintained at 200 Pa. Well
The temperature of the semiconductor substrate 11 mounted on the substrate mounting portion 320 is
Hold at -50 ° C. The above numerical conditions are examples.
Therefore, the values are not limited to those shown here. And
Under the above conditions, a thickness of 800 n is formed on the semiconductor substrate 11.
SiO containing m organic component (ethyl group)₂Low invitation consisting of
The electric film 15 was formed.

Next, after the silicon oxide [SiO ₂ ] film 16 is formed in the same manner as described in the first embodiment,
The moisture in the low dielectric film was removed by annealing in a nitrogen (N ₂ ) atmosphere at 400 ° C. for 15 minutes.

The above-mentioned low dielectric film 1 thus formed
In No. 5, the dielectric constant was 2.5 to 3.5, the embedding ability was possible up to the aspect ratio of 4, and the global flatness was kept substantially flat until the wiring interval was 10 μm.

In the third embodiment, the oxidizing agents are N ₂ O and H.
It was used and ₂ O _2, for example, N ₂ O oxygen instead of [O
₂ ] can also be used.

The silane-based gas in the first to third embodiments is the monosilane [SiH ₄ ] or disilane [Si ₂
In addition to H ₆ ], trisilane [Si ₃ H ₈ ], polysilane [SiH ₆ ] and the like can be used. The oxidizing agent is selected from at least one of oxygen [O ₂ ], ozone [O ₃ ], water [H ₂ O], hydrogen peroxide [H ₂ O ₂ ] and dinitrogen oxide [N ₂ O]. To be done. Further, the hydrocarbon is C such as methane [CH ₄ ] or ethane [C ₂ H ₆ ] described above.
_n H _{2n +2} [wherein n represents a positive integer] may be used.

The temperature of the semiconductor substrate 11 at the time of forming the low dielectric film 15 is equal to or higher than the higher of the melting points of the silane-based gas and the oxidant in the film-forming atmosphere, and the silane-based gas. It may be set within a temperature range not higher than the higher boiling point of the boiling point of the gas and the boiling point of the oxidizing agent.

[0038]

As described above, according to the present invention,
At least silane-based gas and C_nH _{2n + 2}Carbonization
Consisting of hydrogen and an oxidizer consisting of a gas containing oxygen atoms
Dielectric film by chemical vapor deposition using source gas
The dielectric film is formed by the alkyl group of the organic component.
And becomes silicon oxide having a bond between Si and Si. For this reason,
Since the electronic polarizability becomes smaller, it is possible to lower the dielectric constant.
It will be possible. Also, since the density of the dielectric film becomes smaller,
To reduce the number of polarized molecules per unit volume
Therefore, the dielectric constant can be lowered. Further, the chemical vapor phase of the present invention
In the growth method, the polymerization reaction proceeds relatively slowly
The film can behave like a liquid on the film formation surface.
Therefore, it is possible to embed a step with a high aspect ratio.
And global flattening becomes possible.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a forming method according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a capacitively coupled plasma CVD apparatus.

FIG. 3 is a schematic configuration diagram of a low pressure CVD apparatus.

FIG. 4 is an explanatory diagram of a method for forming a multilayer wiring structure.

FIG. 5 is a schematic configuration diagram of a high-density plasma CVD apparatus.

[Explanation of symbols]

 15 Low dielectric film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 21/3205 H01L 21/88 K 21/768 21/90 K

Claims (4)

[Claims] 1. In a method for forming a dielectric film for forming a silicon oxide film containing an organic component by a chemical vapor deposition method, a raw material gas used for chemical vapor deposition is at least monosilane or polysilane silane. System gas and C _n H _{2n + 2}
A method for forming a dielectric film, comprising: a hydrocarbon represented by [n represents a positive integer] and an oxidant composed of a gas containing an oxygen atom. 2. The method for forming a dielectric film according to claim 1, wherein the oxidizing agent is at least one of oxygen, ozone, water, hydrogen peroxide and dinitrogen oxide. Method for forming body membrane. 3. The method for forming a dielectric film according to claim 1, wherein the substrate temperature is equal to or higher than a higher one of a melting point of the silane-based gas and a melting point of the oxidant in a film forming atmosphere, and the silane. A method for forming a dielectric film, characterized in that the temperature is within a temperature range not higher than the boiling point of the system gas and the boiling point of the oxidizing agent. 4. The method for forming a dielectric film according to claim 2, wherein the substrate temperature is equal to or higher than a melting point of a melting point of the silane-based gas and a melting point of the oxidizing agent, whichever is higher in a film forming atmosphere, and the silane. A method for forming a dielectric film, characterized in that the temperature is within a temperature range not higher than the boiling point of the system gas and the boiling point of the oxidizing agent.