JPH11111716A - Insulation film for semiconductor element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a silicon oxide film having a high characteristic capacity of being embedded and a low hygroscopic property. SOLUTION: A silicon oxide film for highly integrated devices and a method for manufacturing the film are provided. This silicon-based insulating film is formed by using a mixed gas of at least alkoxyfluorosilane (TEFS) and oxygen as a source gas and causing a polymerization reaction in an evacuated reaction chamber by using first RF power, and then subjecting the deposit of the obtained alkoxysilane-based polymer (oligomer) to a condensation reaction by using a second RF power. TEOS and/or TRIES and an inert gas may also be added to the source gas. In addition, an alkoxydilane gas having a benzene ring may be used in place of the TEFS.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of semiconductor devices, and more particularly to a silicon oxide film for use as an interlayer insulating film of a multilayer wiring and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, the TEOS-O ₃ method has been widely used as a technique for forming a silicon oxide film of a semiconductor device. T
The EOS-O ₃ method uses TEOS and ozone (O ₃ ) as source gases and uses TEOS with ozone in a normal-pressure CVD device at around 400 ° C.
The polymerization reaction of S results in oligomers ((C ₂ H ₅ O) ₃ SiOSi
(OC ₂ H ₅ ) ₃ ) and silanol ((C ₂ H ₅ O) ₃ SiOH)
The oligomer is gradually oxidized to form Si on the silicon (Si) substrate.
An O ₂ (TEOS.O ₃ —SiO ₂ ) film is formed. T
The EOS-O ₃ film has a gentle reflow shape and high embedding performance, but has the disadvantage of low film stability and high moisture absorption.

As a countermeasure against the hygroscopicity of a TEOS-O ₃ film, a method of heating the film surface after film formation (for example, a FAST process) is known. The method uses an alkoxyfluorsilane (FSi
(OC ₂ H ₅ ) ₃ ) The film surface after film formation in steam is separately heat-treated in an annealing furnace. As a result of the heat treatment, the alkoxyfluorsilane is diffused into the film, and the Si-OH, which causes the hygroscopicity, is dehydrated and condensed to decrease, so that the hygroscopicity of the film is somewhat improved, but the effect is not sufficient.

Another known method for forming a silicon oxide film is a plasma CVD method. The method involves the use of alkoxysilane based gases (eg, TEOS and TEFS) and O ₂ or N _2.
Using a mixed gas of an oxidant such as ₂ O as a source gas,
In the evacuated reaction chamber, plasma is generally generated by RF power of 0.8 W / cm ² or more, and the source gas is decomposed by the plasma. As a result, a high quality silicon oxide film is formed.
It is to be plasma grown on a substrate.

[0005] The plasma CVD film is compared with the TEOS-O ₃ film, there is a stable and characterized in that the low moisture absorption, has the disadvantage that the embedded performance is low. However. FIG. 1 shows a cross-sectional SEM photograph of a silicon oxide film formed by a plasma CVD method. Since the step portion has a conformal shape as shown in FIG. 1, it can be seen that there is no reflow property and the embedding performance is low.

[0006]

[Problems to be Solved by the Invention] Conventional TEOS-O ₃ normal pressure C
VD films have a problem in that they have high hygroscopicity.
When (F) is added, the chemical stability of the film decreases.
In addition, an ozone generator and an annealing furnace for post-processing are additionally required, which is problematic in terms of equipment space. further,
There is also the problem of particle contamination when moving between devices for post-treatment.

On the other hand, the plasma CVD film is problematic in that it has a low filling performance and is difficult to apply to a highly integrated device.

Accordingly, it is an object of the present invention to provide a silicon insulating film having low hygroscopicity and high chemical stability of the film.

Another object of the present invention is to provide a semiconductor device having a wiring interval of 0.35
An object of the present invention is to provide a silicon insulating film excellent in embedding performance such as embedding a highly integrated device wiring of μm or less flat without voids.

It is still another object of the present invention to provide an efficient and reliable method of forming an insulating film without increasing the device space and without moving between devices.

[0011]

To achieve the above object, the present invention comprises the following means.

The silicon-based insulating film according to the present invention uses a mixed gas comprising at least an alkoxysilane-based organic silicon gas and oxygen as a source gas, and performs a polymerization reaction using a first RF power in an exhausted reaction chamber. Causes
It is obtained by further subjecting the resulting polymer deposit to a condensation reaction with a second RF power.

Here, preferably, the second RF power has a higher energy density than the first RF power.

Preferably, the alkoxysilane-based organosilicon gas is an alkoxyfluorosilane (TEF).
S).

Further, TEOS can be included as a source gas.

Further, an inert gas may be contained as a source gas.

On the other hand, a method of forming a silicon-based insulating film according to the present invention uses a mixed gas comprising at least an alkoxysilane-based organic silicon gas and oxygen as a source gas and uses a first RF power in a reaction chamber. And a step of further causing a condensation reaction on the polymer deposit obtained by the polymerization reaction by using a second RF power.

In this method, the second RF power has a higher energy density than the first RF power.

A feature of this method is that the step of the polymerization reaction and the step of the condensation reaction can be continuously performed in the same reaction chamber.

In this method, the alkoxysilane-based organosilicon gas is preferably alkoxyfluorosilane (TEFS).

In this method, the source gas
It can also include TEOS.

Further, in this method, an inert gas may be included as a source gas.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 schematically shows an apparatus for manufacturing a SiOF film which is a silicon-based insulating film according to the present invention. The apparatus includes a plasma processing apparatus 1 and a gas supply apparatus 12. The plasma processing apparatus 1 is of a parallel plate type as in the prior art, and includes a vacuum chamber 6, a gas supply head 5 installed in the upper inside of the vacuum chamber, and a silicon wafer disposed in parallel to the gas supply head. It comprises a susceptor 3 for holding a substrate and a heater 2 for heating and holding the susceptor. The gas supply head 5 and the susceptor 3 function as high-frequency electrodes, and one of them is connected to a high-frequency RF power supply (not shown). The processed reaction gas is exhausted from the exhaust port 11. On the other hand, the gas supply device 12
And a flow controller 7 for controlling the opening / closing of each valve and the gas flow rate.

SiOF which is a silicon-based insulating film according to the present invention
The film is formed by using a mixed gas comprising at least an alkoxysilane-based organosilicon gas and oxygen as a source gas, causing a polymerization reaction using a first RF power in an evacuated reaction chamber, and obtaining a polymerization reaction. It is obtained by subjecting the coalesced deposit to a condensation reaction with a second RF power. Thus, the SiOF film of the present invention is formed through two reaction steps.

First, the polymer forming reaction, which is the first step, will be described. The alkoxysilane-based organosilicon gas required for the reaction is preferably an alkoxyfluorosilane (T
EFS): FSi (OC ₂ H ₅ ) ₃ , but an alkoxysilane gas having a benzene ring as a bonding species can also be used. oxygen
(O ₂ ) is used to generate ozone (O ₃ ). In addition, an inert gas may be included as a source gas in order to improve plasma stability. In the example, helium (He) was used as an inert gas. Further, as a source gas, an alkoxysilane gas containing no fluorine, such as TEOS or TRIES, may be included. These gases are Si
It has the function of adjusting the fluorine content in the OF film.

Each of the above gases is preferably supplied to the flow controller 7 by TEFS: 70 sccm, TEOS: 70 sccm, O ₂ : 2000 sccm and He: 2000 sccm.
The gas is mixed at a flow rate of cm and introduced into the reaction region of the vacuum chamber 6 through the fine holes 10 of the gas supply head 5. The pressure in the vacuum chamber 6 is maintained at 1 to 10 Torr, preferably 6 Torr. The temperature of the susceptor 3 is maintained at 150 to 550C, preferably 400C. The frequency of the first RF power applied to the mixed gas is
10-20 MHz and / or 300-500 kHz, preferably 1
3.4 MHz. Also the energy density 0.1W / cm ² ~0.
It is 6 W / cm ² , preferably 0.4 W / cm ² . This is a lower energy density than the second RF power described below.

The polymerization reaction, which is the first reaction, occurs as follows. Ozone O ₃ is generated from the O ₂ plasma by the first RF power. The ozone reacts with TEFS to form a TEFS polymer (oligomer). It deposits on the silicon substrate. Since this polymer is gradually oxidized, it exhibits a quasi-liquid behavior (reflow effect) and has extremely high embedding characteristics.

Here, in the step of the polymer formation reaction, 0.1.
It should be noted that when RF with a high energy density of 8 W / cm ² or more is applied, the decomposition of TEFS proceeds, the polymerization reaction does not proceed, and no oligomer is formed.
In such a case, the formed film no longer has a reflow effect, and has a conventional conformal shape as shown in FIG.

Next, the condensation reaction which is the second reaction will be described. The first reaction and the second reaction can be continuously performed in the same vacuum chamber 6. First, after the completion of the first reaction, the unreacted mixed gas is exhausted through the exhaust port 11.
Next, a mixed gas of a predetermined flow rate of O ₂ and He (O ₂ : 2000 sccm, H
e: 2000 sccm) is introduced into the vacuum chamber 6. The pressure in the vacuum chamber 6 is maintained at 1 to 10 Torr, preferably 3 Torr. The temperature of the susceptor 3 is maintained at 150 to 550C, preferably 400C. The frequency of the second RF power applied to the mixed gas is
10-20 MHz and / or 300-500 kHz, preferably 1
3.4 MHz and 430 kHz. Its energy density is 0.
^{5W / cm 2 ~4.0W / cm 2} , preferably 13.4MHz: 1.0W / cm ² and 430
kHz: 0.8 W / cm ² . The energy density of this second RF power is substantially equal to that of the first RF power when compared at 13.4 MHz.
2.5 times the F power. The treatment time t for performing the condensation reaction varies depending on the conditions of the applied RF power, the film thickness, and the like, but was set to 60 seconds in the examples. The processing time t must be a time sufficient for the condensation reaction to proceed from the film surface to the depth direction.

Finally, an evaluation experiment of the SiOF film according to the present invention will be described. First, FIG. 3 shows the SiOF according to the embodiment of the present invention.
4 is a cross-sectional SEM photograph showing the film filling characteristics. Referring to FIG. 3, it can be seen that the step portion is not a conformal shape but a reflow shape as compared with the conventional plasma CVD film (FIG. 1). In addition, it can be seen that there is no step between the wirings and flattening has been achieved. This is because the SiOF film according to the present invention has a pseudo-liquid behavior (reflow effect). As described above, the silicon oxide film according to the present invention has very high filling characteristics.

Next, the evaluation of the hygroscopicity of the SiOF film according to the present invention will be described. The following table shows the Si values of the examples according to the invention.
Si-F and Si- in FT-IR absorption intensity distribution for OF film
3 shows the results of measuring the OH concentration in the film before and after the condensation treatment.

[0032] From this measurement result, it can be seen that the unstable bond Si-F or Si-OH, which causes hygroscopicity, is effectively reduced by the condensation treatment. This is because, in the second step, the plasma heat treatment is performed, so that the Si-F or
This is probably because unstable bonds such as Si-OH were condensed and changed into stable Si-O-Si bonds.

FIG. 4 shows a comparison of the FT-IR absorption spectrum profiles of the Si-F bond before and after the condensation treatment with the SiOF film of the embodiment according to the present invention. The graph shows that the width of the absorption peak near the wave number of 940 (cm ^-1 ) is narrower after the plasma heating treatment. This is because the stable O ₃ SiF bond is not affected by the plasma treatment, only the unstable O ₂ Si-F ₂ bond and the Si—OH bond undergo a condensation reaction to change to a stable O—Si—O bond. This is probably because the number of unstable O ₂ Si—F ₂ bonds decreased. From this,
It can be seen that the plasma heating treatment improved the chemical stability of the SiOF film.

FIG. 5 is a schematic diagram showing a SiOF according to an embodiment of the present invention.
This shows the moisture absorption performance of the film by FT-IR. The measurement was performed at 80 ° C, 1 atm, and humidity of 80% for the SiOF film of the example.
This was performed after standing for 20 hours under humidified conditions. From the graph, it can be seen that near the wave number of 3700 to 3100 (cm ^-1 ), the amount of infrared absorption decreases after the plasma condensation treatment.
These results indicate that the silicon oxide film according to the present invention has very low hygroscopicity.

From the above evaluation results, it has been proved that the silicon oxide film according to the present invention has high filling performance, high chemical stability and low moisture absorption.

[0036]

According to the present invention, a silicon oxide film having high filling performance, high chemical stability, and low hygroscopicity can be formed.

Further, according to the present invention, an additional device is not required, and the device space can be greatly reduced.

Further, according to the present invention, a highly reliable device with less particle contamination can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional SEM photograph of a silicon oxide film formed on an aluminum wiring by a conventional plasma CVD method.

FIG. 2 is a schematic view of an apparatus used for manufacturing a silicon oxide film according to the present invention.

FIG. 3 is a cross-sectional SEM photograph of a SiOF film formed on an aluminum wiring according to the present invention.

FIG. 4 is a graph showing an FT-IR profile of a Si—F bond of an SiOF film of an example according to the present invention.

FIG. 5 is a graph showing the FT-IR absorption profile of the SiOF film of the example according to the present invention after humidification.

[Explanation of symbols]

 1 Plasma processing device 2 Heater 3 Susceptor 4 Semiconductor wafer 5 Gas supply head 6 Vacuum chamber 7 Gas flow controller 8 Valve 9 Gas tank 10 Pores 11 Exhaust port 12 Gas supply device 13 Piping

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Johannes Bad Conelis van der Hirst 6-23-1, Nagayama, Tama-shi, Tokyo Inside ASM Japan

Claims (11)

[Claims] A mixed gas comprising at least an alkoxysilane-based organosilicon gas and oxygen is used as a source gas, and a polymerization reaction is caused by using a first RF power in an exhausted reaction chamber to obtain a polymerization reaction. A silicon-based insulating film obtained by further subjecting the polymer deposit to a condensation reaction with a second RF power. 2. The insulating film according to claim 1, wherein the second RF power has a higher energy density than the first RF power. 3. The insulating film according to claim 1, wherein said alkoxysilane-based organic silicon gas is alkoxyfluorosilane (TEFS). 4. The silicon-based insulating film according to claim 3, further comprising TEOS as a source gas. 5. The silicon-based insulating film according to claim 4, further comprising an inert gas as a source gas. 6. A method for forming a silicon-based insulating film, wherein a mixed gas comprising at least an alkoxysilane-based organic silicon gas and oxygen is used as a source gas.
A step of causing a polymerization reaction in the evacuated reaction chamber using the first RF power, and a step of causing a condensation reaction in the polymer deposit obtained by the plasma polymerization reaction by further using the second RF power. And b. 7. The method according to claim 6, wherein the second
Wherein the RF power has a higher energy density than the first RF power. 8. The method according to claim 6 or 7, wherein
A method characterized in that the step of the polymerization reaction and the step of the condensation reaction are continuously performed in the same reaction chamber. 9. The method according to claim 8, wherein the alkoxysilane-based organosilicon gas is alkoxyfluorosilane (TEFS). 10. The method of claim 9, further comprising TEOS as a source gas. 11. The method according to claim 10, further comprising an inert gas as a source gas.