JP3348263B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method suitable for manufacturing a semiconductor device having a multilayer wiring with an insulating film having a low dielectric constant.

[0002] At present, reexamination of an insulating film in a multilayer wiring is being actively conducted in order to realize high integration or high speed of a semiconductor device. For example, SiO ₂ is an insulating material that has been frequently used in semiconductor devices.
Since the dielectric constant is as high as 4.1, the parasitic capacitance between the wirings increases, which causes the signal propagation delay to increase.

This signal propagation delay is a major factor in lowering the operation speed of the semiconductor device. In the future, as the miniaturization of the semiconductor device progresses and the distance between wirings becomes shorter, the parasitic capacitance further increases and the signal propagation delay increases. Since the delay time should be long, it is necessary to improve this point, and the present invention can contribute to solving this problem.

[0004]

2. Description of the Related Art The use of a material having a small dielectric constant as an insulating material in a semiconductor device makes it possible to reduce the parasitic capacitance between wirings and shorten the signal propagation delay time.

In recent years, plasma enhanced chemical vapor deposition (plasm
a chemical vapor deposition
ion: when p-CVD) method using the formation of the SiO ₂ film, in the process, depending on the addition of gas containing fluorine atoms in the source gas, SiO ₂ containing fluorine
(Hereinafter referred to as SiOF) has been reported that a film can be formed (if necessary, “Extended Abst”).
fracts of the 1993 Interna
temporal Conference on Solid
State Devices and Materi
als, Makuhari, 1993, pp158-1.
60. "," Extended Abstracts "
of the 1993 International
Conference on Solid Stat
e Devices and Materials, Ma
kuhari, 1993, pp161-163. "
"Extended Abstracts of the
e 1993 International Conf
erence on Solid StateDevi
ces and Materials, Makuhar
i, 1993, pp 510-512. Etc.).

The SiOF film has a dielectric constant of 3.6,
Since it is lower than SiO ₂ , it is advantageous for high-speed operation of a semiconductor device, and is attracting attention as an interlayer insulating film in a next-generation semiconductor device.

[0007]

When an SiOF film is used as an interlayer insulating film, for example, an AlF
A step of applying a heat treatment of 400 ° C. or more, such as sputtering or wiring annealing, is essential.

At this time, fluorine escapes from the SiOF film, and the fluorine causes problems such as deterioration of transistor characteristics or corrosion of Al wiring.

The present invention makes it possible to obtain a stable SiOF film in which fluorine is not released from the film even when heat treatment is applied.

[0010]

According to the present invention, a CVD method,
For example, it is fundamental to form a SiOF film on a substrate by applying a p-CVD method and then expose the substrate to a plasma atmosphere using N ₂ gas.

[0011]

According to the above-mentioned means, even if a heat treatment is applied after the formation of the SiOF film, fluorine is not released from the film, and a stable film is maintained.

The reason for suppressing the release of fluorine and the reason why the above-mentioned gas is preferable as a gas for generating a plasma atmosphere have not yet been confirmed. However, it is easy to confirm experimentally.

[0013]

FIG. 1 shows an improved SiOF according to the present invention.
FIG. 3 is an explanatory view of a main part of a plasma film forming apparatus used for growing a film.

In the drawing, 1 is a reaction chamber, 2 is a vacuum pipe, 3 is a vacuum pump, 4 is a plate, 5 is a shower head, 6 is a fluorine source, for example, a tank of C ₂ F ₆ gas, and 6A is Pipe, 7 is a tank of O ₂ gas, 7A is a pipe, 8 is a tank for plasma processing gas after film formation, 8A is a pipe, 9 is a tank for plasma processing gas after film formation, 9
A is a pipe, 10 is a tank of He gas, 10A is a pipe, 11 is a container of tetraethoxysilane (TEOS),
11A is a pipe, 12 is a pipe, 13 is a high frequency power supply, 1
Reference numeral 4 denotes a low-frequency power supply, and reference numeral 15 denotes a wafer.

The case where a SiOF film is formed and plasma processing is performed using the illustrated film forming apparatus will be described.

A wafer 15 on which a film is to be formed is placed on a plate 4 in the reaction chamber 1. Thereafter, the reaction chamber 1 is sealed, and a vacuum pump 3 is used to close the reaction chamber 1.
It is exhausted to about 01 [Torr].

The plate 4 on which the wafer 15 is placed is heated by a lamp (not shown).

The shower head 5 is arranged so that a source gas can be jetted to the wafer 15 and is connected to a high frequency power supply 13 and a low frequency power supply 14 which are energy sources for generating plasma. It is said that a film to be formed can be made denser by using both a high frequency and a low frequency.

C ₂ F ₆ gas, which is a fluorine source, is supplied from the tank 6 to the shower head 5 via pipes 6 A and 12.

O ₂ gas is supplied from the tank 7 to the pipes 7A and 1A.
2 to a shower head 5.

He gas is supplied from the tank 10 to the container 11 via the pipe 10A, and the contained liquid TE
OS is bubbled and vaporized, and the vaporized TEOS
In the shower head 5 through the pipes 11A and 12A. Therefore, the container 11 functions as a bubbler.

In the shower head 5, the vaporized TEOS, C ₂ F ₆ gas and O ₂ gas are mixed, and the mixture gas is injected toward the wafer 15 as shown by the arrow in the drawing. An SiOF film is formed.

At this time, of course, a plasma appears between the shower head 5 and the wafer 15 due to the high-frequency energy and the low-frequency energy applied to the shower head 5.

After the formation of the SiOF film is completed, the reaction chamber 1
The inside is evacuated as described above, and then the tank 8 or 9,
Alternatively, plasma processing is performed by supplying a plasma processing gas from both of them.

In this case, the tank 8 contains CO or NO ₂
Or O ₃ etc., and N ₂ or N
₂ O or CO ₂ or the like may be accommodated, and may be appropriately used or mixed for use, or a tank may be added as necessary.

The main conditions for forming a SiOF film using the above-mentioned plasma film forming apparatus are as follows.

Low frequency (350 [kHz]): 0.5 [W / cm ² ] High frequency (13.56 [MHz]): 0.4 [W / cm ² ] Gas flow rate He: 500 [sccm] (TEOS O ₂ : 700 [sccm] C ₂ F ₆ : 300 [sccm] Pressure: 5.0 [Torr] Plate temperature: 400 [° C]

In the plasma film forming apparatus, the formed SiOF film is converted into various gases, for example, O ₂ , N ₂ O, NO
Plasma treatment was performed using the following conditions by using N ₂ , N ₂ , CO, CO ₂ , O _{3, and the} like.

Low frequency (350 [kHz]): 0 [W / cm ² ] High frequency (13.56 [MHz]): 2.4 [W / c]
m ² ] Flow rate of various gases: 300 [sccm] Pressure: 5.0 [Torr] Plate temperature: 400 [° C] Processing time: 1 [min]

The plasma treated S
Since the amount of fluorine released from the iOF film was examined, the result will be described in comparison with other examples.

The amount of fluorine released from the SiOF film is:
The measurement was performed using a degassing analyzer (TDS). TDS
Is an analyzer that arranges a sample in a vacuum container, and specifies and quantifies molecules and atoms released from the sample while heating the sample by lamp heating.

FIG. 2 is a graph summarizing data obtained by measuring the amount of fluorine released from the SiOF film using a degassing analyzer, and the vertical axis represents the amount of degassed fluorine [T
orr] and the temperature [° C.] on the horizontal axis.

In the figure, the solid line is the characteristic line of the SiOF film not subjected to the plasma treatment, the broken line is the characteristic line of the SiOF film thermally annealed in the O ₂ atmosphere, and the dashed line is the characteristic line of the SiOF film subjected to the O ₂ plasma treatment. Each is shown.

The thermal annealing of the SiOF film having the broken characteristic line was performed under the conditions of a temperature of 450 ° C. and a time of 30 minutes, and in the case of the embodiment of the present invention shown by the dashed line. Is, of course, plasma-treated under the conditions described above.

[0035] As is perceiving from the results seen in Figure 2, the SiOF film O ₂ plasma treatment, the untreated S
The amount of released fluorine is smaller than that of the iOF film or the thermally annealed SiOF film.

That is, the total amount of fluorine released from the O ₂ plasma-treated SiOF film is about 1/100 of that of the untreated SiOF film.
10 and thermally annealed in an O ₂ atmosphere
The total amount of fluorine released from the OF film is almost the same as that of the untreated SiOF film.

The present inventors have been concerned that, by performing the plasma treatment, fluorine was released, and the amount of released fluorine was reduced during TDS analysis.
The amount of fluorine in the SiOF film before and after the O ₂ plasma treatment was examined from the absorption intensity of the Si—F bond based on the infrared absorption spectrum, but no change was observed in the absorption intensity. Therefore, it is determined that the amount of fluorine existing in the SiOF film does not change even if the plasma processing is performed.

FIG. 3 is a graph summarizing data obtained by measuring the amount of fluorine released from the SiOF film subjected to plasma treatment using various gases using TDS, and the vertical axis represents the desorption of fluorine. The gas amount [Torr] is plotted, and the temperature [° C.] is plotted on the horizontal axis.

In the figure, the solid line is the characteristic line of the SiOF film not subjected to the plasma treatment, the broken line is the characteristic line of the SiOF film treated with the CO plasma, the dashed line is the characteristic line of the SiOF film treated with the CO ₂ plasma, and the three-dot chain line. Represents the characteristic line of the SiOF film treated with O ₃ plasma, the solid line represents the characteristic line of the SiOF film treated with N ₂ plasma, the two-dot chain line represents the characteristic line of the SiOF film treated with N ₂ O plasma, and the dotted line represents the SiOF film treated with NO ₂ plasma. Are shown respectively.

Si gas plasma-treated using any gas
Even in the case of the OF film, it is remarkably observed that the amount of fluorine is reduced as compared with the SiOF film not subjected to the plasma treatment, and it is clear that N ₂ O and N ₂ are particularly effective. is there.

In the present invention, many other modifications can be realized without being limited to the above-described embodiment.

For example, in the embodiment, a parallel plate type apparatus is used as a plasma film forming apparatus.
R (electron cyclotron reso
nonce) type can be used.

In the embodiment, the plasma processing was performed in the film forming apparatus immediately after the film formation. However, if necessary, the film is formed and then taken out to the atmosphere. Similar good results can be obtained.

Furthermore, although TEOS, O ₂ , and C ₂ F ₆ are used as source gases for forming a SiOF film, the present invention is applied to a SiOF film formed using another source gas. It is also possible to perform a plasma treatment.

[0045]

According to the method of manufacturing a semiconductor device according to the present invention, a fluorine-containing silicon oxide film is formed on a substrate by applying a chemical vapor deposition method. The oxide film is exposed to a plasma atmosphere using N ₂ gas.

By adopting the above configuration, even if a heat treatment is applied after the formation of the fluorine-containing silicon oxide film, fluorine is not released from the film, and a stable film can be maintained. Therefore, there is no danger that the characteristics of the transistor will be degraded or the electrodes and wirings made of metal such as Al will be corroded by fluorine, and the fluorine is suitable for application when forming a multilayer wiring. Thus, the advantage that the dielectric constant of the fluorine-containing silicon oxide film is low can be enjoyed without any risk, and it can contribute to an increase in the speed and reliability of the semiconductor device.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a main part of a plasma film forming apparatus used for growing an improved SiOF film according to the present invention.

FIG. 2 shows the amount of fluorine released from the SiOF film by TDS.
FIG. 4 is a diagram summarizing data obtained by measuring according to FIG.

FIG. 3 is a diagram summarizing data obtained by measuring the amount of fluorine released from a SiOF film plasma-treated using various gases by using TDS.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reaction chamber 2 Vacuum pipe 3 Vacuum pump 4 Plate 5 Shower head 6 Tank of fluorine source, for example, C ₂ F ₆ gas 6A Pipe 7 Tank of O ₂ gas 7A Pipe 8 Tank of plasma processing gas after film formation 8A Pipe 9 Plasma treatment gas tank after film formation 9A pipe 10 He gas tank 10A pipe 11 Tetraethoxysilane (TEOS) container 11A pipe 12 pipe 13 High frequency power supply 14 Low frequency power supply 15 Wafer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-203890 (JP, A) JP-A-6-333919 (JP, A) JP-A-8-148562 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/316 H01L 21/768

Claims (2)

(57) [Claims] 1. A step of forming a fluorine-containing silicon oxide film on a substrate by applying a chemical vapor deposition method, and thereafter, converting the fluorine-containing silicon oxide film into a plasma atmosphere using N ₂ gas. And b. Exposing the semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of forming an electrode and a wiring made of metal on the fluorine-containing silicon oxide film.