JPH09330925A - Formation of low dielectric-constant silicon oxide insulating film and semiconductor device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the specific dielectric constant of a silicon oxide insulating film and to prevent contamination due to additional gas and the deterioration of a hot carrier resistance from being generated in a semiconductor device by a method wherein the fluorine-containing silicon oxide insulating film is formed on a substrate to be treated by a CVD method using a compound consisting of a tetraisocyanate silane, rare gas element and fluorine. SOLUTION: A fluorine-containing silicon oxide insulating film is formed on a substrate 11 to be treated by a CVD method using a compound consisting of a tetraisocyanate silane, rare gas and fluorine. The substrate 11 is set on a substrate stage 12, which is provided with a built-in heater 13 and has a grounding potential. Raw gas, which is introduced in a gas introducing hole 16, is diffused by a gas diffusion plate 15 and is uniformly jetted on the surface of the substrate 11 through a gas shower head 14 opposing to the substrate 11. An ultrasonic vibration applying means 20A directly excites the substrate 11 and an ultraviolet vibration applying means 20B excites the raw gas which is jetted through the head 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a low dielectric constant silicon oxide based insulating film and a semiconductor device using the same, and more particularly, to a method for forming a low dielectric constant silicon oxide based insulating film containing fluorine. The present invention relates to a method for forming a low dielectric constant silicon oxide-based insulating film with reduced impurities in the film and a semiconductor device using the same.

[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 reduction of the wiring interval, an increase in inter-wiring capacitance is becoming a problem. Therefore, the actual operating speed of the semiconductor device is 1 / K
(K is a reduction ratio) does not meet the scaling rule, and the merit of high integration cannot be fully enjoyed. 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-based insulating film containing fluorine (hereinafter referred to as SiOF) is typical. In addition, organic SOG (Spin On Glass) having a siloxane bond, polyimide , Organic polymer materials such as polyparaxylylene (trade name: parylene), benzocyclobutene, polynaphthalene,
There is a flare (trade name of Allied Signal Co., Ltd.) or a fluororesin-based organic polymer material such as perfluoro group-containing polyimide or fluorinated polyallyl ether. These low dielectric constant materials are described in, for example, Nikkei Microdevice Magazine 199.
July, 5 issue p. 105, and regarding the SiOF low dielectric constant interlayer insulating film, see, for example, Monthly Semiconductor World Magazine (Press Journal), March 1996, p. 76
Have 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, as disclosed in JP-A-6-333919, a silicon source gas such as SiH ₄ for forming a silicon oxide-based insulating film is generally changed to a fluorosilane-based gas such as SiF ₄ , Alternatively, by adding SiF ₄ or the like to SiH ₄ or the like and performing CVD, Si—F bonds can be incorporated into the silicon oxide-based insulating film to form SiOF. However, since SiF ₄ has a low dissociation rate in plasma, it is difficult to sufficiently incorporate Si—F bonds and reduce the relative dielectric constant. In some cases, TEOS (Tetraethylorthosilicate) or a derivative thereof is used as the silicon source gas. However, TE
Since OS and SiH ₄ are compounds containing hydrogen, SiO
H atoms may be taken into F to induce a Si—OH bond, which may degrade the hot carrier resistance of the transistor.

Further, the applicant of the present application has disclosed a method of promoting the dissociation of a source gas in plasma by adding a basic gas such as NH _{3 to} Japanese Patent Application 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.

As a source of fluorine atoms, for example, as disclosed in JP-A-7-90589, CF
_If a fluorocarbon-based gas such as ₄ or C ₂ F ₆ is used, the effect of reducing the specific inductivity can be obtained, but the contamination problem due to the mixing of carbon atoms remains.

On the other hand, as a raw material compound for silicon, tetraisocyanate silane (S
Attempts to eliminate Si—OH bonds in an insulating film that degrades the hot carrier resistance of a transistor by employing i (NCO) ₄ ) have been made, for example, in the IEICE, December 1995.
Monthly issue p. 35 (SDM95-179). In this report, a SiOF film is formed by mixing SiF ₄ and Ar in addition to tetraisocyanate silane. Therefore, the above-mentioned problem of using SiF ₄ as a source of fluorine atoms still remains.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a sufficiently reduced relative dielectric constant. An object of the present invention is to provide a method for forming a silicon oxide-based insulating film having a low dielectric constant, which forms a silicon oxide-based insulating film containing fluorine. Another object of the present invention is to provide a semiconductor device using a low-dielectric-constant silicon oxide-based insulating film formed by such a method, having improved hot carrier resistance, operating at high speed, and consuming low power.

[0010]

A method of manufacturing a semiconductor device according to the present invention is proposed to solve the above-mentioned problems, and a tetraisocyanate silane and a compound composed of a rare gas element and a fluorine element are used. A silicon oxide insulating film containing fluorine is formed over the substrate to be processed by the CVD method used.

Compounds composed of a rare gas element and a fluorine element used in the present invention include ArF, KrF and X.
Examples thereof include eF ₂ and NeF, and these compounds can be used alone or in combination. As is well known, these compounds are gases obtained by a chemical reaction between a rare gas and fluorine. In addition to these, XeF ₄ , Xe
The existence of F ₆ , KrF _2, etc. is also known, but these may be adopted. In addition to tetraisocyanate silane, a compound composed of a rare gas element and a fluorine element, an oxidizing agent such as O ₂ or N ₂ O may be added. In one embodiment of the present invention, it is desirable to form a silicon oxide-based insulating film containing fluorine while applying ultrasonic waves to a substrate to be processed.

A semiconductor device according to the present invention is characterized in that it has a low dielectric constant silicon oxide-based insulating film formed by such a forming method as an insulating film such as an interlayer insulating film.

Next, the operation will be described. In the present invention, by employing tetraisocyanate silane as a source gas in the formation of a SiOF film by the CVD method, hydrogen atoms are eliminated as much as possible from the reaction system, and S in the film is removed.
Reduce i-OH bond and improve hot carrier resistance. On the other hand, as a fluorine source gas, a compound composed of a rare gas element and a fluorine element is adopted as a fluorine compound which does not contain an element remaining as contamination and is excellent in dissociation in plasma. The compound composed of the rare gas element and the elemental fluorine easily dissociates in the excited state to serve as a source of supplying fluorine atoms. The other rare gas generated by dissociation is an inert element, and unlike hydrogen atoms and carbon atoms, is unlikely to be taken into SiOF. Even if it is taken into the SiOF film, it can be easily removed by annealing after film formation.

Further, as compared with the case where SiF ₄ is used as an F supply source, since SiOF formed does not have Si, it does not have a Si-rich composition. Further, the F atom supplied by the dissociation of one molecule is 1 or 2, which is an appropriate amount, and the deposition rate is not saturated by the etching reaction of excess F ^* (F radical).

Further, by applying ultrasonic vibration to the CVD reaction system, the vibration energy of the substrate to be processed and the internal energy level such as the translation or rotation and vibration of the source gas molecules are increased, and the dissociation reaction of the source gas, The migration of the intermediate product on the substrate to be processed is activated. For this reason, it is possible to efficiently form a film with good step coverage even at a lower temperature than before.

By these effects, it becomes possible to form a contamination-free SiOF film with good step coverage. In addition, by using such SiOF for an interlayer insulating film or the like of a highly integrated semiconductor device, a semiconductor device with improved hot carrier resistance and high speed and low power consumption can be provided.

[0017] As a prior application similar to the present invention, SiO 2 is applied while applying ultrasonic vibration to a substrate support or a 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.

[0018]

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

The apparatus shown in FIG. 2 is basically a parallel plate type plasma CVD apparatus. That is, the substrate 11 on which SiOF is to be formed is set on the substrate stage 12 having a built-in heater 13 at 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 denotes a gas ring disposed on the outer peripheral upper surface of the substrate 11 to be processed, which is a hollow annular nozzle member having a large number of gas ejection holes, and a part of the raw material gas, a diluting gas or the like is added if necessary. To do. Reference numeral 18 denotes a gas exhaust hole connected to a vacuum pump (not shown), and reference numeral 19 denotes an RF power supply for supplying RF power to the gas shower head 14 also serving as an upper electrode. Note that if the gas shower head 14 and the substrate stage 12 are configured to have an inverted vertical relationship, that is, a face-down configuration in which the substrate 11 to be processed is held downward, the substrate 1
Particle adhesion to one surface is prevented.

The features of the present 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.

Embodiment 1 Next, a specific embodiment of a process of forming SiOF will be described.
In this embodiment, a low dielectric constant interlayer insulating film made of SiOF is formed on an Al-based metal wiring by using tetraisocyanatesilane and Ar.
This is an example of plasma CVD using F as a source gas, which 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, for example, 0.35 μm is formed on an interlayer insulating film 2 on a semiconductor substrate 1 made of Si or the like. This is shown in FIG.

Next, as an example, a thin lower insulating film (not shown) is formed conformally by ordinary plasma CVD using SiH ₄ and N ₂ O as source gases. This lower insulating film is formed to complement the film quality of the SiOF film deposited in the next step, but may be omitted if not necessary.

Subsequently, the substrate 11 is placed on the substrate stage 12 of the CVD apparatus shown in FIG. 2, and plasma CVD of a SiOF film, which is a main part of the present embodiment, is performed under the following conditions as an example. Si (NCO) ₄ 50 sccm ArF 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, for example, 0.3 μm above the Al-based metal wiring. As a result, as shown in FIG. 1B, an interlayer insulating film 4 made of SiOF with good step coverage and no hydrogen contamination was formed at a practical deposition rate. The relative dielectric constant of the interlayer insulating film 4 was 3.3. Although the interlayer insulating film 4 has a relatively flat surface, it may be further flattened by chemical mechanical polishing or the like at this stage. After this,
Again, a thin upper insulating film (not shown) made of SiO ₂ is formed as necessary by normal plasma CVD using SiH ₄ and N ₂ O as source gases. Alternatively, the upper insulating film may be formed thick and planarized by CMP. With such a laminated structure, a highly reliable low dielectric constant interlayer insulating film having excellent moisture resistance and flatness can be obtained. Further, the semiconductor device having the low dielectric constant silicon oxide based insulating film formed as the interlayer insulating film according to the present embodiment is different from the semiconductor device having SiOF having hydrogen atoms in the film formed by the conventional method as the interlayer insulating film. In comparison, hot carrier resistance was improved by one digit.

Example 2 This example is similar to Example 1 except that a little O ₂ was further added to the raw material gas of Example 1 as an oxidizing agent. An example of the CVD conditions is shown below. Si (NCO) ₄ 50 sccm ArF 30 sccm O ₂ 20 sccm Gas pressure 27 Pa RF power supply power 0.08 W / cm ² (13.56 MHz) Substrate temperature 300 ° C. Specific induction rate 3.
The interlayer insulating film 4 made of SiOF having No. 3 was formed with good step coverage and without contamination of hydrogen or carbon.

Example 3 This example is an example in which KrF is used instead of ArF as a compound composed of a rare gas element and a fluorine element.
The others are the same as those in Example 2. An example of the CVD conditions is shown below. Si (NCO) ₄ 50 sccm KrF 30 sccm O ₂ 20 sccm Gas pressure 27 Pa RF power supply power 0.08 W / cm ² (13.56 MHz) Substrate temperature 300 ° C. Specific induction rate 3.
The interlayer insulating film 4 made of SiOF having No. 3 was formed with good step coverage and without contamination of hydrogen or carbon.

Example 4 This example is an example in which XeF ₂ was adopted in place of ArF as a compound composed of a rare gas element and a fluorine element.
The others are the same as those in Example 2. An example of CVD conditions is shown below. Si (NCO) ₄ 50 sccm XeF ₂ 30 sccm O ₂ 20 sccm Gas pressure 27 Pa RF power supply power 0.08 W / cm ² (13.56 MHz) Substrate temperature 300 ° C. In this embodiment, from one molecule of XeF ₂ Since two fluorine atoms are supplied, the interlayer insulating film 4 made of SiOF having a specific dielectric constant of 3.2 was formed with good step coverage at a practical film formation rate. There was also no carbon contamination, not to mention hydrogen.

Example 5 This example is an example in which 20 sccm of O ₂ was further added to the raw material gas of tetraisocyanate silane and KrF, and SiOF was formed while applying ultrasonic waves to the substrate to be treated. That is, based on the previous Example 3, this CVD
This is a combination of conditions and ultrasonic wave application. The substrate 11 to be processed adopted in the present embodiment is the same as that shown in FIG. 1A in the first embodiment, and the duplicated description will be omitted. This processed substrate 11 is the CV shown in FIG.
It is mounted on the substrate stage 12 of the D device, and the plasma CVD of SiOF is performed under the following conditions as an example. 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. Si (NCO) ₄ 50 sccm KrF 30 sccm O ₂ 20 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 SiOF film was formed to a thickness of 0.3 μm above the Al-based metal wiring. As a result, as shown in FIG. 1 (b), an interlayer insulating film 4 made of SiOF having good step coverage and no contamination of carbon or hydrogen was formed at a practical deposition rate. The specific induction ratio of the interlayer insulating film 4 was 3.1 because the dissociation of the source gas was improved by the application of ultrasonic waves and fluorine atoms were efficiently incorporated into the film.

Although the present invention has been described with reference to the five examples, the present invention is not limited to these examples.

For example, ArF, KrF, and XeF ₂ were used as the compound composed of the rare gas element and the fluorine element, but NeF, XeF ₄ , XeF ₆ , and KrF may also be used.
Compounds such as ₂ can be used. O ₂ was used as the oxidizing gas, but other oxidizing gases such as O ₃ and N ₂ are of course used.
O, NO ₂ , and NO may be used or mixed. A nitriding gas or an impurity source gas may be mixed to form a SiON film containing F or the like. In addition, He and A as diluent gas
A rare gas such as r or Xe or N ₂ may be mixed and used.

In the embodiment, ultrasonic waves are applied using the ultrasonic vibration applying means 20A incorporated in the substrate stage 12, but the ultrasonic vibration applying means 2 incorporated in the gas diffusion plate 15 is used.
0B or the ultrasonic vibration applying means 20C directly attached to the chamber wall. 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.

When the plasma CVD method is used, in addition to the parallel plate type apparatus used in the above embodiment, the microwave C
It is also preferable to use a VD apparatus, an ECR-CVD apparatus, or a high-density plasma source such as helicon wave plasma or inductively coupled plasma (ICP), particularly for a large-diameter substrate to be processed. Utilization of UV light such as a low-pressure Hg lamp or an excimer laser is useful for accelerating the dissociation of a source gas and reducing substrate damage. If there is no low melting point Al-based metal wiring in the lower structure of the SiOF film, LP-CVD
Alternatively, a normal pressure CVD method can be employed. In this case, an ultrasonic vibration applying means may be appropriately attached to a substrate stage, a gas nozzle or a CVD chamber of the conventional CVD apparatus.

In each of the above-mentioned embodiments, the case of forming the interlayer insulating film on the Al-based metal wiring is exemplified, but other wiring material layers may be used. Also, a groove is formed in the interlayer insulating film,
The present invention may be applied to a semiconductor device structure in which a buried wiring is formed in a groove by etching back or polishing. Further, the present invention can be applied to the case where it is used as a final passivation film, and the case where trench isolation or the like is buried flat without generating voids. In addition to the semiconductor device, it goes without saying that the invention can be applied to various electronic devices such as a thin film head and a thin film inductor.

[0036]

As is apparent from the above description, fluorine atoms are effectively incorporated into the SiOF film by eliminating hydrogen atoms from the raw material gas system and employing a fluorine compound having high dissociation efficiency. In addition, contamination such as hydrogen atoms and carbon atoms in the SiOF film is reduced. Therefore, it is possible to improve the hot carrier resistance and to provide a semiconductor device such as a logic IC or a highly-integrated memory, in which signal delay due to the capacitance between wirings becomes a problem, with high reliability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view illustrating a plasma CVD process according to Examples 1 to 5 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 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 5 of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Interlayer insulating film, 3 ... Wiring layer, 4 ... Interlayer insulating film 11 ... Substrate to be processed, 12 ... Substrate stage, 13 ... Heater, 14 ... Gas shower head, 15 ... Gas diffusion plate, 1
6 gas introduction hole, 17 gas ring, 18 gas discharge hole, 19 RF power supply, 20A, 20B, 20C ultrasonic wave applying means

Claims (4)

[Claims] 1. A CV using tetraisocyanate silane and a compound composed of a rare gas element and a fluorine element.
A method for forming a silicon oxide-based insulating film having a low dielectric constant, comprising forming a silicon oxide-based insulating film containing fluorine on a substrate to be processed by Method D. 2. The low dielectric constant silicon oxide according to claim 1, wherein the compound composed of the rare gas element and the fluorine element is at least one of ArF, KrF, XeF ₂ and NeF. Method of forming a system insulating film. 3. The method for forming a silicon oxide-based insulating film having a low dielectric constant according to claim 1, wherein the silicon oxide-based insulating film containing fluorine is formed while applying ultrasonic waves to the substrate to be processed. . 4. A semiconductor device comprising a fluorine-containing silicon oxide insulating film formed by the method for forming a silicon oxide-based low dielectric constant insulating film according to claim 1.