JPH09181176A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor device in which the permittivity of an interlayer insulating film is reduced and in which there is no fear that a contamination due to an additive gas is left by using a compound of fluorine and oxygen as at least one gas used for chemical vapor growth to form an insulator thin film. SOLUTION: When at least one layer of an insulator thin film 14 is formed, by a chemical vapor growth method, on a substrate 11 on which an electronic circuit is formed, a compound of fluorine and oxygen as at least one gas used for a chemical vapor growth operation is used. For example, an interlayer insulating film 12 and an Al interconnection layer 13 are formed sequentially on a semiconductor substrate 11, and an interlayer insulating film 14 is formed on them by a CVD operation. At this time, the temperature of the substrate 11 is set to about 300 deg.C, SiH4 is introduced as a compound which contains silane, and O2 and COF2 are introduced as oxidizing agents. Then, the pressure inside a reaction container is lowered to a prescribed pressure, a high frequency is applied, and a silicon oxide film which contains F much is formed as the interlayer insulating film 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing method, and is particularly suitable for application to an insulating film forming method.

[0002]

2. Description of the Related Art Today, semiconductor integrated circuits such as memory devices and logical operation devices tend to have higher densities, and wiring technologies are becoming finer and more multilayered. Along with this, the so-called multi-layer wiring technology in the manufacturing process of semiconductor integrated circuits has become more and more important.

This is because as the wiring becomes finer and the number of layers increases, the step of the interlayer insulating film becomes larger and steeper, which makes it difficult to form a metal wiring pattern on the interlayer insulating film. Further, in the wiring that has been miniaturized and multilayered, the resistance of the wiring and the capacitance between the wirings start to become a problem, and the so-called scaling law cannot be met. To put it simply, the scaling rule is satisfied at the transistor level and the simple ring oscillator level, but at the actual device level, the problem is to lower the dielectric constant of the interlayer insulating film itself in order to reduce the capacitance between wirings. .

[0004]

Therefore, each semiconductor device maker has attempted to realize a low capacitance by doping a silicon oxide film (SiO ₂ ) with a fluorine (F) element to form SiOF. This is because silicon (Si) and fluorine (F) are contained in the silicon oxide film (SiO ₂ ).
By making a bond with, the dielectric constant is lowered by a method of eliminating the OH group, which is one of the factors that increase the dielectric constant. For the SiOF treatment, a method of adding SiF ₄ gas to the generated gas of the silicon oxide film (SiO ₂ ) is generally adopted.

However, these methods also have various problems to be solved. For example, when SiF ₄ gas is added, the dissociation in plasma is so low that fluorine (F) cannot be taken in sufficiently. Moreover, the dielectric constant does not decrease so much in the system to which NH ₃ gas is added. On the other hand, if CF ₄ gas or C ₂ F ₆ gas is added, the dielectric constant can be reduced, but there is a problem that carbon (C) remains as a contaminant. Therefore, at the 56th Annual Meeting of the Japan Society of Applied Physics held in August 1995, a technique of adding SF ₆ gas was reported (lecture number 26P-ZB-2).
However, although using this gas can reduce the relative dielectric constant to about 3.3, there was a problem that sulfur (S) remained as a contaminant when too much SF ₆ gas was added.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a method of manufacturing a semiconductor device in which the dielectric constant of an interlayer insulating film is not reduced and contaminants due to an added gas are not likely to remain.

[0007]

In order to solve the above problems, the present invention provides a method of forming at least one insulating thin film on a substrate having an electronic circuit formed thereon by chemical vapor deposition. A compound of fluorine and oxygen is used as at least one gas used for chemical vapor deposition. This makes it possible to generate reactive species having an OF bond from the chemical vapor deposition gas dissociated in plasma. Further, at this time, O existing alone in the plasma forms an oxide with other constituent molecules of the gas and is exhausted from the reaction system, so that the constituent molecules can be prevented from remaining as contaminants in the produced film. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

(1) Structure of Film Forming Apparatus FIG. 1 shows a plasma CVD (Chemic) used for carrying out the present invention.
al Vapor Deposition) shows a schematic sectional structure of the device. It should be noted that the configuration of the wafer mounting and the devising of the usage method are not particularly limited as long as they are related to the essence of the present invention. A reaction vessel 1 serving as a reaction chamber is provided with an introduction pipe 2 above which a silane-containing compound (for example, SiH ₄ or TEOS) and an oxidizing agent (for example, a compound gas of oxygen and fluorine) are introduced from the direction of arrow A. Has been.

Here, a dispersion plate 3 and a shower head 4 are arranged near the opening of the introduction pipe 2 so as to face the opening, and the introduced gas can be uniformly dispersed while ensuring high in-plane uniformity. It is done like this. The introduced gases are mixed just before the shower head 4. The shower head 4 also serves as an upper electrode, and a high frequency of 13.56 [MHz] is applied from the high frequency power source 5.

A susceptor 7 on which a wafer 6 as a substrate to be processed is placed is accommodated in the lower portion of the shower head 4 and is kept at a constant temperature by an embedded heater 8. This allows the reaction to proceed at a predetermined temperature. An ultrasonic wave applying device 9 for applying ultrasonic waves is incorporated in the susceptor 7 so that ultrasonic waves can be applied from an ultrasonic wave source 10. When this ultrasonic wave applying device 9 is used, the dissociation of the compound gas composed of fluorine and oxygen can be further promoted, and OF
Fluorine can be efficiently incorporated into the film as a reaction film having a bond. Further, when the ultrasonic wave applying device 9 is used, contaminants can be efficiently removed at the same time.

(2) Example of Film Forming Conditions (2-1) First Example Here, the case of flattening the Al wiring layers will be described. Note that FIG. 2A shows the sectional structure of the wafer 6 before the CVD film is formed, and FIG. 2B shows the sectional structure of the wafer 6 after the film is formed. The wafer 6 shown in FIG.
Is formed by sequentially stacking an interlayer insulating film 12 made of silicon oxide or the like and an Al wiring layer 13 on a semiconductor substrate 11 made of silicon or the like. Further, the CVD film stacked under the following film forming conditions is the interlayer insulating film 14.

First, the temperature of the wafer 6 is set to about 300 ° C. by heating the heater 8. Then, the inside of the reaction vessel 1 is evacuated to reduce the pressure inside the chamber, and the silane-containing compound and the oxidizing agent are introduced from the introduction pipe 2. In this example, SiH ₄ is introduced as a silane-containing compound, and O ₂ and COF ₂ are introduced as oxidizing agents. At this time, SiH ₄ and O ₂ are 50 [SCCM]
COF ₂ is introduced at 30 [SCCM]. After that, the pressure in the reaction vessel 1 is adjusted to a predetermined pressure (for example, 27 [P
a)) and apply a high frequency with an output of 0.08 [W / cm ² ].

Plasma is generated by this high frequency, and O ₂ and COF ₂ introduced into the reaction vessel 1 are separated. O in this plasma reacts with F, and most of it is O-
It becomes a reactive species containing an F bond. Subsequently, the reactive species containing the O—F bond activates SiH ₄ and bonds to form a silicon oxide film containing a large amount of F as the interlayer insulating film 14.
At this time, the main composition of the interlayer insulating film 14 is SiOF.
It should be noted that in plasma, the state where the bond between O and F is broken, that is, even O alone can exist, but this O forms carbon (C) and oxide (that is, CO) in the plasma, Since the air is exhausted, it is possible to eliminate the possibility that carbon remains in the interlayer insulating film 14 as a contaminant.

By using COF ₂ as the compound gas of oxygen and fluorine as the introduction gas in this way, it is possible to grow an interlayer insulating film in a good film formation state without lowering the growth rate. The relative dielectric constant of the interlayer insulating film 14 is
It was as low as 3.3. That is, if this film forming condition is adopted, the interlayer dielectric film 14 having a low dielectric constant and no contamination can be realized.

(2-2) Second Embodiment Next, the film forming conditions of the second embodiment will be described. This example is also an example in which the Al wiring layers are flattened. Incidentally, in this embodiment, the other introduction conditions are the same as those in the first embodiment except that O ₂ and NOF ₂ are used as the oxidizing agents to be introduced. Therefore, the interlayer insulating film 14 is the same as in the case of the first embodiment.
It is possible to grow an interlayer insulating film having a good film formation state without lowering the growth rate. In this case as well, the relative dielectric constant of the interlayer insulating film 14 was 3.3. In the case of this example, O existing in the plasma is nitrogen (N) and oxide (that is, NO).
And is exhausted from inside the reaction vessel 1.

(2-3) Third Example Next, the film forming conditions of the third example will be described. This example is also an example of flattening the Al wiring layers. In this example, the other introducing conditions were the same as those in the first example except that O ₂ and SOF ₂ were used as the oxidizing agents to be introduced.
However, in the case of this embodiment, the ultrasonic wave applying device 9
200 [kHz] ultrasonic waves from the ultrasonic source 10 to the reaction vessel 1
Apply within. As a result, the dissociation of SOF _{2 in} the plasma is further promoted, more reactive species having OF bonds are generated, and are taken into the interlayer insulating film 14. That is, the amount of fluorine taken in the interlayer insulating film 14 can be increased. As a result, the relative dielectric constant of the interlayer insulating film 14 formed under the present film forming conditions becomes a lower value of 3.2.

(3) Other Embodiments In the above embodiment, the type, flow rate, pressure, temperature, applied RF, and ultrasonic output of the gas introduced into the reaction vessel 1 are set to the first, second and third, respectively. Although the case of setting the conditions described in the embodiment is described, the present invention is not limited to this,
Modifications can be made without departing from these spirits. For example, SiH ₄ was used as the silane-containing compound, but higher order silane or an organic metal alkoxide capable of forming an insulating film may be used. In addition, TEOS (tetraethoxysilane)
), OMCTS (octa methyl cyclo siloxane), T
POS (tetra propoxy silane), TMCTS (tetra
methyl cyclo tetra siloxane) or the like. In addition to oxygen, ozone, water, nitric oxide or the like may be used as the oxidizing agent. Further, in each of the above-described embodiments, the plasma CVD apparatus having the configuration shown in FIG. 1 has been described, but the present invention is not limited to this and can be widely applied to the plasma CVD apparatuses having other configurations.

[0019]

As described above, according to the present invention, in a method of forming at least one insulating thin film on a substrate having an electronic circuit formed thereon by chemical vapor deposition, chemical vapor deposition By using a compound of fluorine and oxygen as at least one gas used for the above, a semiconductor device manufacturing method capable of easily forming a film having a low relative dielectric constant and no contamination by gas constituent molecules is provided. Can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a semiconductor manufacturing apparatus using a semiconductor manufacturing method according to the present invention.

FIG. 2 is a schematic diagram showing processing steps of a semiconductor manufacturing method according to the present invention.

[Explanation of symbols]

1 ... Reaction container, 2 ... Introduction tube, 3 ... Dispersion plate, 4 ...
Shower head, 5 ... High frequency power supply, 6 ... Wafer, 7
...... Susceptor, 8 ... Heater, 9 ... Ultrasonic wave applying device,
10 ... Ultrasonic source.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/95

Claims (3)

[Claims] 1. At least one substrate on which an electronic circuit is formed.
A method for forming an insulating thin film having a number of layers or more by a chemical vapor deposition method, characterized in that a compound of fluorine and oxygen is used as at least one gas used for the chemical vapor deposition, . 2. The compound of fluorine and oxygen is COF ₂ ,
_2. The method of manufacturing a semiconductor device according to claim 1, wherein the gas is at least one gas selected from the group consisting of NOF, NOF ₂ , SO ₂ F ₂ , and SOF ₂ . 3. The method of manufacturing a semiconductor device according to claim 1, wherein ultrasonic waves are applied during the chemical vapor deposition.