JP2748879B2 - Method for producing fluorinated amorphous carbon film material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an insulating material for use in an interlayer insulating film of a semiconductor device, in particular, a low dielectric constant insulating material and a method for manufacturing the same, and a wiring delay is reduced by using a low dielectric constant insulating material. The present invention relates to a high-speed semiconductor device.

[0002]

2. Description of the Related Art As the wiring width and the wiring interval of a semiconductor device and its mounting substrate decrease in the future, the wiring stray capacitance and the wiring resistance will increase. As a result, an increase in wiring delay causes a problem in high-speed operation of the semiconductor device. In general, the wiring delay is proportional to the square root of the dielectric constant of the insulating material, so it is possible to reduce the wiring delay by using an insulating material having a low relative dielectric constant. Has been done. Conventionally, SiO ₂ has been mainly used for an interlayer insulating film of a semiconductor device, and a method of manufacturing by plasma CVD has been established. However, the relative dielectric constant of the SiO ₂ film manufactured by this method is about 4, and the development of a method for depositing a film having a relative dielectric constant of less than that is desired. Therefore, as a next-generation low dielectric constant interlayer insulating material, a fluorinated amorphous carbon material having a relative dielectric constant of 3 or less is considered promising.

[0003] This fluorinated amorphous carbon material has conventionally been formed by plasma deposition.
-217470, mainly CxF
a fluorocarbon gas such as y (x = 1-4, y = 4-8);
Further, those obtained by adding a hydrogen-based gas to them are used.

[0004]

The conventional fluorinated amorphous carbon film has a relative dielectric constant of about 2.1 and has a low dielectric constant, but has a heat resistant temperature higher than that of SiO _2. Because of its low value, its use is limited. For example, Japanese Patent Application No. 06-2
In the case of No. 17470, decomposition of the film starts at about 420 ° C., and a decrease in the film thickness and generation of gas accompanying the film are observed.
When using this low dielectric constant material, the heat treatment temperature is set to 420
It was necessary to keep the temperature below ° C. When this amorphous carbon material is applied to an inter-wire insulating material, patterning by a known lithographic technique is required, but since the amorphous carbon material is a carbon material similar to a resist material used for lithography, , when etched with CF ₄ or CHF ₃ gas, it is impossible to increase the etching selectivity of the resist, for example, and patterning the amorphous carbon film is 1μm deposited, the resist on the amorphous carbon film-like Must be applied at least about 2 μm. When the resist is removed, the resist is usually ashed by oxygen plasma. However, since the amorphous carbon film is also ashed at that time, a non-amorphous structure having a structure that is hardly etched by oxygen plasma is obtained. There is a need for a crystalline carbon film material.

An object of the present invention is to provide a low-dielectric-constant insulating material having excellent heat resistance and etching characteristics, a method of manufacturing the same, and a semiconductor device using the same as an interlayer insulating film, instead of a conventional amorphous carbon film material. Is to provide.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by introducing another atom into a conventional fluorinated amorphous carbon film. As a usual fluorinated amorphous carbon film, a fluorocarbon-based gas or a gas obtained by adding a hydrogen gas to a fluorine-based gas is used as a raw material. , And a hydrogen atom. Of these, carbon atoms form a carbon-carbon bond in the film, that is, form a structure serving as a skeleton of the film, and fluorine atoms play a role in lowering the dielectric constant of the film. In addition, hydrogen atoms play a role in terminating unbonded orbitals in the film. In the present invention, by introducing nitrogen atoms or silicon atoms into this film,
A strong bond such as a carbon-nitrogen bond or a carbon-silicon bond appears in the film to increase the degree of cross-linking in the film, thereby improving heat resistance and etching resistance.

[0007]

In general, in the case of a carbon-based material, the factor that determines the heat resistance of a film is the crosslinked structure of the film. The crosslinked structure is a structure in which carbon-carbon bonds are randomly present in a film. The conventional fluororesin has a structure of (CF ₂ ) _n , that is, a structure in which carbon-carbon bonds extend in a chain shape. In this case, the bonds between the chain molecules are maintained by Van der Waals force, and the membrane has a cross-linked structure. I do not have. About 300 ℃
Starts decomposition, and the heat resistance of the film is low. However, in a normal amorphous carbon film, since a film is formed by dissociating the gas with plasma using a hydrogen fluoride-based gas, carbon-carbon bonds are randomly distributed in the film, and the film has a crosslinked structure. Have. Therefore, the heat resistance becomes higher than that of the fluororesin, and the desorption of the membrane components starts at about 420 ° C. Desorption of film components from the fluorinated amorphous carbon film is caused by the presence of -CF ₃ or-
Bonding of side chain such as (CF ₂ ) _n -CF ₃ is about 420 ° C
It is thought to be caused by cutting to the extent.

If the degree of crosslinking is increased by bundling these side chains with a new bond, the desorption temperature can be increased. In the present invention, another atom for increasing the degree of crosslinking is contained in the film, and these side chains are bundled. The atom that increases the degree of crosslinking may be any as long as it can be supplied as a gas and can form a covalent bond with a carbon atom, and the resulting material maintains insulation. In the present invention, a three-coordinate nitrogen atom or a four-coordinate silicon atom is contained in an amorphous carbon film, and these atoms are combined with carbon atoms to form a side chain having a particularly low degree of crosslinking in the film. To form a new crosslinked structure. Further, by utilizing the fact that these carbon-silicon bonds or carbon-nitrogen bonds are stronger than conventional carbon-carbon bonds, the etching rate by oxygen plasma is reduced as compared with a normal amorphous carbon film. Even if the resist is ashed, the amorphous carbon film is not ashed. In addition, when etching an amorphous carbon film with a fluorocarbon-based gas during patterning, silicon is contained in the film, thereby increasing the etching rate as compared with a resist, similarly to the etching of normal SiO ₂ . The same patterning process as for SiO ₂ can be used.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a schematic view of an apparatus for forming a fluorine-containing amorphous carbon film. In the apparatus, electrodes 105 and 107 are provided in a vacuum chamber installed on a support 101, and between them, DC and AC power can be applied from a high voltage power supply 108. The lower electrode is provided with a sample heating device, and can heat the sample to an arbitrary temperature. In order to form an amorphous carbon film using this apparatus, a sample 106 such as a silicon substrate is placed on the lower electrode. Since a high frequency is applied to the lower electrode, a negative bias of about several hundred volts is applied to the electrode, and ions accelerated by the bias are applied to the sample to obtain a crosslinked amorphous carbon film.

After placing the sample on the electrode, CF ₄ , SF ₆ , C
₂ and F _4, NF _3, fluorine-based gas such as _{C 2 F 6, C 3 F} 8, C 4 F 8, a hydrocarbon or hydrogen gas, such as CH ₄ was introduced, the degree of vacuum 0.01-0.5Torr Then, a high frequency or DC power is applied between the electrodes to cause glow discharge to generate plasma of carbon fluoride. A fluorinated amorphous carbon film is deposited by this fluorocarbon plasma.
In addition to the plasma generation method using the high frequency, a high-density plasma using a microwave, a helicon wave, or the like can also be used. In the above case, a normal fluorinated amorphous carbon film is deposited, but in the present invention, a nitrogen gas or a silicon gas is caused to flow in at the same time to contain fluorine atoms or silicon atoms in the film to control the film quality. N as nitrogen gas
₂ , NH ₃ , NF ₃ , and silicon gas as Si
H ₄ and Si ₂ H ₆ can be used.

First, an embodiment in which nitrogen atoms are contained in a fluorinated amorphous carbon film will be described. A case where a film is formed by using the high-frequency discharge shown in FIG. 1 will be described. C
Film formation was performed using F ₄ , CH ₄ and N ₂ gases as raw materials. Substrates were made of SiO ₂ / Si (100) and P ⁺ Si (1).
00), a film was attached to an electrode to which a high frequency was applied. The total gas flow rate was fixed at 50 sccm, the high frequency power was fixed at 200 W, and the CF ₄ / CH ₄ flow ratio was fixed at 16,
Film formation was performed while changing the N ₂ flow rate.

The obtained film was heated to 500 ° C. in a vacuum, and the heat resistance was evaluated by estimating the degree of decrease in the film thickness. The nitrogen content in the film was determined using X-ray photoelectron spectroscopy.
The area ratio of the C _1s , F _1s , and N _1s peaks of the obtained signal was calculated and obtained. Further, a capacitor was formed from Al / amorphous carbon film / p ⁺ Si, and the relative permittivity of the film was obtained by measuring the capacitance (1 MHz). FIG. 2 shows the change in the nitrogen content in the film with respect to the N ₂ gas flow ratio in the total flow. It can be seen that the nitrogen content in the film increases as the gas flow rate increases. Next, FIG. 3 shows a change in heat resistance with respect to the N ₂ gas flow ratio in the total flow. In this case, the heat resistance is evaluated based on the degree of decrease in film thickness, and indicates how much the film thickness after heating has decreased before heating. The heating was performed by heating the sample in a vacuum at the temperature shown in the figure for one hour. As shown in FIGS. 2 and 3, nitrogen is added to the film by adding N ₂ gas, and the heat resistance is improved as compared with the amorphous carbon film not containing nitrogen. %, It was found that a film having high heat resistance, whose thickness did not decrease even when heated to 470 ° C., was formed.

Next, the relative dielectric constant of the nitrogen-containing amorphous carbon film calculated from the capacitance is shown by a curve 1 in FIG.
As shown in the figure, it was found that as the nitrogen content in the film increased, the relative dielectric constant monotonously increased. As described above, it was found that the relative dielectric constant increased due to the nitrogen content, but the relative dielectric constant remained at 3 or less. Curve 2 shows the change in the relative dielectric constant of the amorphous carbon film due to heat treatment at 300 ° C. for 1 hour in vacuum. A conventional amorphous carbon film containing no nitrogen or a film having a small content raises the relative dielectric constant by heat treatment at 300 ° C. It was found that the increase in the relative dielectric constant due to the heat treatment was suppressed. The reason why the film thickness did not decrease and the relative dielectric constant did not increase due to the heat treatment in this manner is considered to be due to the formation of a new network of CN in the film. The bond energy of the C—N bond is 1
75 kcal / mol, the bond energy of the CC bond is 145 kcal / mol, and it is considered that the heat resistance of the film is improved because the CN bond is more stable than the CC bond. In addition, when the bonding state in the film was examined by X-ray photoelectron spectroscopy and infrared absorption spectroscopy, all the nitrogen in the film was present in the form of CN bonds, and the NF bond was found in the film. Did not exist. That is, it is considered that all of the nitrogen is bonded to the carbon atoms and exists in the film, thereby increasing the degree of crosslinking of the film.

Next, an embodiment in which silicon is contained in the film will be described. The gas used was SiH ₄ . Similarly, a case where a film is formed using the high-frequency discharge device shown in FIG. 1 will be described. The substrate was formed using SiO ₂ / Si (100) and P ⁺ Si (100) by attaching it to an electrode to which a high frequency was applied. The film was formed by changing the flow rate of the silicon gas while fixing the total flow rate of the gas at 50 sccm, the high-frequency power at 200 W, and the CF ₄ / CH ₄ flow rate ratio at 16, and changing the flow rate of the silicon gas.

The resulting film is heated at 500 ° C. in vacuum,
The heat resistance was evaluated by estimating the degree of decrease in the film thickness.
The silicon content in the film was determined by using X-ray photoelectron spectroscopy and calculating the area ratio of the C _1s , F _1s , and Si _1s peaks of the obtained signal. Further, a capacitor was formed from Al / amorphous carbon film / p ⁺ Si, and the relative permittivity of the film was obtained by measuring the capacitance (1 MHz). FIG. 5 shows a change in the silicon content in the film with respect to the flow rate of the SiH ₄ gas. Thus, it was found that silicon was contained in the film only by adding the SiH ₄ gas during the film formation. FIG. 6 shows the change in heat resistance.
The heat resistance in this case also indicates how much the film thickness has decreased after the heat treatment for one hour and before the heat treatment. As shown in FIGS. 5 and 6, by adding SiH ₄ gas at the time of film formation, silicon is contained in the film, and the heat resistance is improved as compared with the amorphous carbon film not containing silicon. It was found that a film containing 20% or more of silicon can have heat resistance up to 470 ° C.

The curve 1 in FIG. 7 shows the relative dielectric constant of the silicon-containing amorphous carbon film calculated from the capacitance.
The relative permittivity monotonically increased as the silicon content in the film increased. It was an amorphous carbon film containing 20% silicon and had a relative dielectric constant of 2.8. As described above, it has been found that the relative dielectric constant increases with the inclusion of silicon as in the case with the inclusion of nitrogen, but the relative dielectric constant remains at 3 or less. Curve 2 shows the change in the relative dielectric constant of the amorphous carbon film due to heat treatment at 300 ° C. for 1 hour in vacuum. As shown in the figure, in the case of an amorphous carbon film having a small silicon content, the relative dielectric constant increases due to heat treatment after film formation, but the relative dielectric constant increases due to the heat treatment when silicon is contained in the amorphous carbon film. Was found to be suppressed. The bonding state of the silicon-containing amorphous carbon film was examined. According to X-ray photoelectron spectroscopy and infrared absorption spectroscopy, silicon was found to be present in the film as Si-
It turned out that it exists only by C bond. In other words, it is considered that the silicon atoms contained in the film form a strong bond of Si—C to increase the heat resistance of the film.

Subsequently, the etching characteristics were examined. First, O ₂ gas was flowed at 100 sccm into the apparatus shown in FIG. 1, and the obtained film was etched with high-frequency power of 200 W to examine the oxygen-resistant plasma characteristics. FIG. 8 shows the etching rates of the fluorinated amorphous carbon film containing nitrogen and the fluorinated amorphous carbon film containing silicon by oxygen plasma with respect to the respective contents. By adding nitrogen or silicon to the film, an amorphous carbon film having oxygen-resistant plasma characteristics was obtained.

Next, the etching characteristics with CF ₄ gas were examined. Similarly to the apparatus of FIG. 1, a CF ₄ gas 100
The cell was etched by flowing a flow of sccm and applying a high frequency of 200 W to generate plasma. FIG. 9 shows the etching rate by CF ₄ plasma. In the case of this gas, when silicon was contained in the film, the etching rate could be increased as compared with a normal amorphous carbon film. This is because, in a fluorocarbon plasma such as CF ₄ , silicon atoms are more easily etched than carbon atoms, so silicon atoms in the amorphous carbon film are etched first, and an etching substance is further removed where the silicon component is removed. It is considered that the etching of the film proceeds due to the adsorption of fluorine.

Instead of the above-described embodiment using N ₂ and SiH ₄ , a fluorinated amorphous carbon film containing nitrogen and silicon was formed using another gas as a raw material. CF ₄ or NO in the gas it was added _{CH 4, NO 2, NH 3} , N
When a nitrogen-containing film was formed by adding F ₃ as nitrogen gas, a nitrogen-containing amorphous carbon film having the same heat resistance and etching characteristics as those obtained by adding N ₂ was obtained. In addition, fluorocarbon gas is used for C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ , CH
F _3, and the hydrogen-based gas added to them is H ₂ , C ₂ H
₆ , C ₂ H ₄ , C ₂ H ₂ , and C ₃ H ₈ were formed by adding N ₂ , NO, NO ₂ , NH ₃ , and NF ₃ , respectively, and these films also had the same heat resistance. And etching characteristics. For silicon-containing films, CF
_When Si ₂ H ₆ and SiF ₄ were added as a silicon gas to a gas to which CH ₄ was added or a gas containing CH ₄ was added, a silicon-containing amorphous material having the same heat resistance and etching characteristics as those when SiH ₄ was added. A carbonaceous film was obtained. Also, fluorocarbon gas is used as C ₂ F ₆ , C ₃ F ₈ , C ₄ F
₈ , CHF ₃ , and hydrogen-based gases added to them are H ₂ , C ₂ H ₆ , C ₂ H ₄ , C ₂ H ₂ , and C ₃ H ₈ , each of which is SiH ₄ , Si ₂ H ₆ , SiF ₄
When these were added to form films, these films also exhibited the same heat resistance and etching characteristics. Since the film forming method of the present invention uses plasma, any gas containing nitrogen or silicon can be used. Further, it was confirmed that the same effect as the high-frequency discharge was obtained even when the film was formed using high-density plasma generated by microwave and helicon wave discharge.

As described above, an amorphous carbon film having high heat resistance and excellent etching characteristics was obtained. Then, the amorphous carbon film having the structure shown in FIG.
A type FET semiconductor device was manufactured. A known lithography technique was used for patterning the wiring. MOS FET
First layer aluminum 1003 and second layer aluminum 1
The amorphous carbon film 100 of the present invention is used as an insulating film during the period 002.
1 was used. In a conventional semiconductor device using an amorphous carbon film, a gas is generated from the amorphous carbon film.
Although only the heat resistance up to ℃ was obtained, when the amorphous carbon film of the present invention was used, 470 ° C.
Up to about 5% of the signal propagation of the wiring compared to a conventional semiconductor device using an amorphous carbon film because the contact resistance of the wiring can be reduced. The speed could be increased. Also available are similar gas and the resist and conventional in the SiO ₂ etching the etching in patterning, the conventional method for removing resist also by oxygen plasma can be used, similar to the case of using SiO ₂ interlayer insulating film By using the patterning process, a semiconductor device having an amorphous carbon film as an interlayer insulating film could be formed. FIG. 10 shows M
Although the embodiment is applied to a semiconductor device constituted by an OS type field effect transistor, in addition to the semiconductor device constituted by a bipolar transistor,
The same effect was obtained.

[0021]

As described above, the present invention provides an amorphous carbon film containing silicon or nitrogen and having excellent heat resistance and etching characteristics, and a method for producing the same. Further, by using this amorphous carbon film as an interlayer insulating film of a semiconductor device, a semiconductor device capable of increasing the speed of a semiconductor device without deteriorating reliability has been realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for producing a fluorinated amorphous carbon film containing nitrogen or silicon.

FIG. 2 is a diagram showing a change in a nitrogen content in a film with respect to an N ₂ gas flow ratio in a total gas flow.

FIG. 3 is a diagram showing a change in heat resistance with respect to a N ₂ gas flow ratio in the entire gas flow.

FIG. 4 is a view showing the relative dielectric constant of a fluorinated amorphous carbon film containing nitrogen.

FIG. 5 is a diagram showing a change in a silicon content in a film with respect to a SiH ₄ gas flow ratio in a total gas flow.

FIG. 6 is a diagram showing a change in heat resistance with respect to a SiH ₄ gas flow ratio in the entire gas flow.

FIG. 7 is a view showing the relative dielectric constant of a fluorinated amorphous carbon film containing silicon.

FIG. 8 is a diagram showing an etching rate of an amorphous carbon film by O ₂ plasma.

FIG. 9 is a diagram showing an etching rate of an amorphous carbon film by CF ₄ plasma.

FIG. 10 is a sectional view of a semiconductor device using the amorphous carbon film of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 101 support base 102 vacuum pump 103 gas cylinder 104 vacuum vessel 105 upper electrode 106 sample 107 lower electrode 108 high frequency power supply 109 upper lid 1001 amorphous carbon film 1002 second layer aluminum 1003 first layer aluminum 1004 SiO ₂ 1005 silicon substrate

Claims (2)

(57) [Claims] 1. Fluorocarbon gases CF ₄ , C ₂ F ₆ ,
At least one of C ₃ F ₈ , C ₄ F ₈ , CHF ₃ ,
Alternatively, hydrogen gas H ₂ or hydrocarbon gas C
_{H 4, C 2 H 6,} C 2 H 4, C 2 H 2, C 3 H
A gas prepared by adding at least one of _8, further N ₂ or NO, NO _2, NH _3, at least one of NF ₃
It is characterized by forming a film by chemical vapor deposition (plasma CVD) using plasma from a gas to which one is added.
A method for producing a fluorinated amorphous carbon film material containing nitrogen . 2. Fluorocarbon gases CF ₄ , C ₂ F ₆ ,
At least one of C ₃ F ₈ , C ₄ F ₈ , CHF ₃ ,
Alternatively, hydrogen gas H ₂ or hydrocarbon gas C
_{H 4, C 2 H 6,} C 2 H 4, C 2 H 2, C 3 H
A gas prepared by adding at least one of _8, further SiH ₄
The gas added at least one gas of Si ₂ H _6, SiF ₄ as a raw material, the production method of the fluorine amorphous carbon film material is silicon, wherein are contained be formed by a plasma CVD .