JPH07111261A - Apparatus and method for film forming - Google Patents

Abstract

PURPOSE:To form a high quality insulating film by a method wherein a helicon mode plasma made of first reactive gas is generated and second reactive gas is activated by the plasma and a bias voltage is applied to a substrate and the activated first and second reactive gases are reacted with each other to form a film on the substrate. CONSTITUTION:Oxygen gas is introduced into a depressurized plasma generating chamber 1 and, by supplying a power with a frequency of 13. 56 MHz to an outer antenna 2 from an RF power supply 4 through a matching network 3, a helicon wave is excited and the oxygen gas is activated and a high density plasma is generated. The generated plasma is transferred to a film forming chamber 7 to activate SiH. gas supplied onto a wafer 15. By this, the activated SiH. gas and the oxygen plasma are reacted with each other to deposit a silicon oxide film on the wafer 15. As the introducing pipe 8 of the oxygen gas and the introducing pipe 9 of the Sill. gas are separated from each other, particles are not produced while the film is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method, and more specifically, a film forming method for forming an insulating film or the like by a CVD method (chemical vapor deposition method) by activating a reactive gas by converting it into plasma. Regarding the method.

[0002]

_2. Description of the Related Art The CVD method is used in the manufacture of semiconductor devices, such as SiO ₂ film, PSG film, BSG film, BPSG film, Si ₃ N ₄ film, amorphous Si film, polycrystalline Si film, W film and Mo film. , WSi ₂ film, MoSi ₂ film,
This is a useful technique when forming an Al film or the like. Conventional example C
When the VD method is classified by means for activating the reaction gas, the main ones are the thermal CVD method, the photo CVD method and the plasma CVD method.

The thermal CVD method uses a method of activating the reaction gas depending on the temperature, and is classified into low pressure and normal pressure depending on the pressure used. Further, it is classified into low temperature and high temperature depending on the substrate temperature, and further classified into resistance heating, induction heating and lamp heating depending on the heating method. Further, depending on the installation location of the heating means, it is classified into a hot wall type and a cold wall type.

The photo-CVD method uses a method of activating the reaction gas by irradiating the reaction gas with ultraviolet rays to activate the reaction gas, and it is possible to form a film at a low pressure or a high pressure and at a low temperature. Is. Further, the plasma CVD method uses a method of activating the reaction gas directly or indirectly by using AC power or a magnetic field, and is generally performed at low pressure and low temperature. The plasma generation means gives energy to the electrons by the parallel plate type which directly activates the reaction gas by the radiation of the high frequency power, the high frequency power and the magnetic field,
It is classified into the ECR method in which the reaction gas is indirectly activated by the electrons.

[0005]

The above-mentioned thermal CVD method is sometimes unfavorable in that the temperature of the substrate becomes high. Furthermore, there is room for improvement in terms of film quality such as compactness. Further, in the photo CVD method, a film is formed in an unnecessary place,
It causes the generation of particles. Further, the deposit rate is slow, and there is room for improvement in practical use.

Further, the plasma CVD method, especially the parallel plate type, causes damage to the substrate due to plasma irradiation.
For this reason, the plasma CVD method by the ECR method is used especially when the substrate damage is a problem. In this case, it is effective in terms of preventing substrate damage and forming a dense film, but it uses an ultrahigh frequency of 2.45 GHz, which requires a large-scale device.

The present invention was created in view of the problems of the conventional example, and an object of the present invention is to provide a film forming method capable of forming an insulating film having a good film quality with a simple device configuration. .

[0008]

[Means for Solving the Problems] The above-mentioned problems are, firstly, a plasma generation chamber for generating helicon mode plasma;
A first reaction gas introduction pipe for introducing a first reaction gas into the plasma generation chamber, and a periphery of the plasma generation chamber for radiating electromagnetic waves into the plasma generation chamber to activate the first reaction gas. An antenna provided, a source solenoid that forms a magnetic field in the plasma generation chamber, is provided around the plasma generation chamber, a film formation chamber connected to the plasma generation chamber, the plasma generation chamber, and the plasma generation chamber. An exhaust port for exhausting the inside of the film chamber, a substrate holder provided in the film forming chamber for holding a substrate on which a film is to be formed, and a second reaction gas introduced above the substrate holder to introduce the second reaction gas. And a second reaction gas introducing pipe for discharging the reaction gas onto the surface of the substrate on the substrate holder.
In the film forming apparatus according to the first invention, a high-frequency power source of 13.56 MHz is connected to the antenna. Thirdly, the second reaction gas introducing pipe is
The present invention is achieved by the film forming apparatus according to the first or second aspect of the present invention, which has a gas discharge part formed of a ring-shaped tube having a plurality of gas discharge holes formed therein. Fourthly, the substrate holder. A high-frequency power source for supplying a high-frequency power of 13.56 MHz or 100 kHz is connected to the film forming apparatus according to the first, second or third invention, and fifth and first Electromagnetic wave is radiated to the reaction gas and the magnetic field is applied to generate a helicon mode plasma composed of the first reaction gas, the second reaction gas is activated by the plasma, and the substrate is biased by a voltage,
This is achieved by a film forming method characterized in that a film is formed on the substrate by reacting the plasma-converted first reaction gas with the activated second reaction gas.
A fifth aspect characterized in that the second reaction gas is released downstream from the plasma generation part, and the plasma-converted first reaction gas is guided downstream to activate the second reaction gas. Which is achieved by the film forming method described in
And the first reaction gas is oxygen gas, and the second reaction gas is a gas containing TEOS, which is achieved by the film forming method according to the fifth or sixth invention. In the eighth aspect, the first reaction gas is oxygen gas and the second reaction gas is SiH ₄ gas, which is achieved by the film forming method according to the fifth or sixth invention.
Ninth, the frequency of the electromagnetic wave radiated to the first reaction gas is 13.56 MHz, which is achieved by the film forming method according to the fifth, sixth, seventh or eighth invention. 1
In order to bias the substrate with a voltage of 0, a high frequency power having a frequency of 13.56 MHz or 100 kHz is applied to the substrate according to the fifth, sixth, seventh, eighth or ninth invention. It is achieved by the film forming method.

[0009]

[Operation] In the film forming apparatus according to the present invention, since the plasma generation chamber has an antenna that radiates electromagnetic waves, for example, high-frequency power having a frequency of 13.56 MHz, and a source solenoid that forms a magnetic field in the plasma generation chamber, It is possible to generate high density plasma in the helicon mode in the room.

Further, since the frequency of the high frequency power applied to the antenna is 13.56 MHz, the equipment such as a waveguide for generating the microwave power of the extremely high frequency of 2.45 GHz is not required as in the case of the ECR method. The device configuration is simple. Further, the first reaction gas introducing pipe for introducing the helicon mode plasma into the plasma generation chamber is separated from the first reaction gas introducing pipe, and the second reaction gas introducing pipe for releasing the second reaction gas is formed on the substrate surface. It is provided above. Therefore, it is possible to prevent the reaction gas from reacting while the reaction gas is being introduced onto the substrate, thereby preventing the generation of particles.

Further, the substrate holder has a frequency of 13.56 MHz or 1
Since a high frequency power supply for supplying a high frequency power of 00 kHz is connected, the negative DC voltage applied to the substrate can be adjusted to optimize the film quality such as the density and stress of the film. In the film formation method according to the present invention, for example, an electromagnetic wave having a frequency of 13.56 MHz is radiated, and a magnetic field is applied to generate a first reaction gas, for example, helicon mode plasma composed of oxygen (O ₂ ) gas, Second by the plasma moved downstream
Of the reaction gas such as TEOS or monosilane (SiH ₄ ) gas is activated and the first reaction gas and the second reaction gas are reacted to form a film on the substrate.

The above helicon mode plasma is
Higher density than the case (1 x 10 ¹²cm^-3Or more)
Therefore, the denseness of the formed film is further improved,
It approaches the quality of the thermal oxide film. Moreover, the voltage on the substrate
Since it is biased, the density of the film formed on the substrate
The power can be optimized.

In particular, when using a helicon mode plasma of oxygen gas and monosilane, it is preferable to apply a high frequency power of 100 kHz and bias the substrate with a voltage in order to improve the quality of the formed film. It was confirmed by experiments. Further, the plasma of the first reaction gas is moved downstream to activate the second reaction gas released immediately before the substrate on which the film is to be formed, whereby the first reaction gas and the second reaction gas are activated. Since the reaction is performed, most of the reaction products are deposited on the surface of the substrate. Therefore, it is possible to prevent the reaction products from adhering to the inner wall of the reaction chamber around the substrate,
This can prevent the generation of particles.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. (1) CV applied to the film forming method according to the embodiment of the present invention
D Description of Film Forming Apparatus FIG. 1A is a configuration diagram illustrating a CVD film forming apparatus applied to a film forming method using helicon mode plasma according to an embodiment of the present invention.

In FIG. 1A, 1 is a diameter of 15 cm ×
A first reaction gas introduced from the first reaction gas introduction pipe 8, for example, oxygen gas (O ₂ gas) is activated in a plasma generation chamber made of quartz having a length of 25 cm. Then, the first reaction gas introduction pipe 8 is arranged so that the gas ejection port of the first reaction gas introduction pipe 8 comes to the central portion of the plasma generation chamber 1. The first reaction gas introduction pipe 8 may be connected to the upper part of the plasma generation chamber 1 to introduce the reaction gas into the plasma generation chamber 1.

Reference numeral 2 is an external antenna mounted around the plasma generating chamber 1. Two ring-shaped conductors circulate around the upper and lower peripheral portions of the cylindrical plasma generation chamber 1 at a predetermined interval. The interval between the two ring-shaped conductors is important for adjusting the wave number of the helicon wave, that is, the plasma density. An example of the shape of the external antenna 2 is shown in FIG.
In this case, RF is applied to the two ring-shaped conductors in opposite directions.
A current flows so that a zero-mode helicon wave is formed. By changing the shape of the external antenna, it is possible to form a helicon wave of higher order mode.

Reference numeral 3 is a matching network connected to the external antenna 2, and reference numeral 4 is an RF power source for supplying RF power having a frequency of 13.56 MHz to the external antenna 2 via the matching network 3. RF power is an energy source for plasma generation. Reference numeral 5 denotes a cylindrical inner source solenoid provided around the plasma generation chamber 1, 6 denotes a cylindrical outer source solenoid provided around the inner source solenoid 5, and the inner source solenoid 5 and the outer source solenoid 6 are A magnetic field is formed in the plasma generation chamber 1 in the axial direction.
Such a magnetic field is required to form a helicon wave and adjust the plasma density. The relationship between the current flowing through the inner source solenoid 5 and the outer source solenoid 6 and the generated magnetic field is shown in FIG. In the figure, I _IS represents the inner source solenoid current and I _OS represents the outer source solenoid current.

The above is the high density of the helicon mode (10 ¹² cm ^-3
Plasma generation chamber 1 required for plasma generation (above)
And the device configuration of its peripheral part, especially, RF power,
The magnetic field and the distance between the two ring-shaped conductors of the external antenna 2 are important parameters. Reference numeral 7 denotes a film forming chamber connected to the downstream side of the plasma generating chamber 1 and made of a metal such as quartz or aluminum in a cylindrical shape having a diameter of 30 cm and a length of 22.5 cm. The helicon mode plasma composed of the first reaction gas generated in the plasma generation chamber 1 is supplied, and the second reaction gas introduction pipe 9 supplies the second reaction gas, for example, Si.
H ₄ gas is introduced.

As shown in FIG. 1 (b), the second reaction gas introducing pipe 9 has a gas releasing portion 9a made of a ring-shaped quartz pipe having a diameter of about 200 cm. A plurality of gas discharge holes for discharging the reaction gas are formed. They are arranged on the wafer 15 at a predetermined distance. Reference numeral 10 denotes a chamber solenoid that is provided around the film forming chamber 7 and is composed of a cylindrical permanent magnet. An appropriate magnetic field can be applied to the film forming chamber 7. As a result, the plasma is guided from the plasma generation chamber 1 to the film formation chamber 7, and the shape of the flowing plasma is adjusted.

Reference numeral 11 denotes an exhaust port connected to an exhaust device for exhausting unnecessary reaction gas and reducing the pressure in the plasma generation chamber 1 and the film forming chamber 7, and is provided in the film forming chamber 7. Reference numeral 12 denotes a wafer holder (substrate holder) on which the wafer 15 is placed, which has a built-in heater for heating the wafer 15 and can move up and down. Further, an RF power source 14 for supplying electric power having a frequency of 13.56 MHz or 100 kHz is connected to the wafer holder 12 via a matching network 13. By applying electric power of 13.56 MHz or 100 kHz to the wafer 15, a negative self-bias DC voltage is applied to the wafer 15 to optimize the film quality such as the density and stress of the formed film.

Next, the operation of the above CVD apparatus will be briefly described. First, oxygen gas is introduced into the depressurized plasma generation chamber 1. In addition, the RF power supply 4 supplies electric power having a frequency of 13.56 MHz to the external antenna 2 via the matching network 3. As a result, the external antenna 2
Plasma generation chamber 1 in each of the two ring-shaped conductors in opposite directions
An RF current that circulates in the direction of current is flowed to radiate an electromagnetic wave. Furthermore,
A current is supplied to the inner source solenoid 5 and the outer source solenoid 6 to generate a magnetic field in the axial direction.

As described above, the helicon wave is excited, the oxygen gas in the plasma generation chamber 1 is activated, and high-density (10 ¹² cm ⁻³ or more) plasma in the helicon mode is generated. The generated plasma moves to the downstream film forming chamber 7 whose pressure has been reduced by a magnetic field and activates the SiH ₄ gas supplied onto the wafer 15. As a result, the activated SiH ₄ gas and oxygen plasma react with each other to deposit a silicon oxide film on the wafer 15.

According to the above CVD apparatus, the external antenna 2 to which the RF power source 4 and the like are connected is provided, and the frequency is 13.56.
A plasma is generated by supplying RF power of MHz. Therefore, equipment such as a waveguide, which is required in the case of the ECR method, is unnecessary, and the device configuration is simplified. Also, EC
Since it is possible to use a frequency lower than the frequency of 2.45 GHz in the case of the R method, it is easy to generate high frequency power.

Further, since the oxygen gas introduction pipe 8 and the SiH ₄ gas introduction pipe 9 are separated from each other, the reaction between the reaction gases during the supply is prevented and the generation of particles is prevented. However, if necessary, all the gas may be introduced through the first reaction gas introduction pipe 8. The dimensions of the plasma generating chamber 1 and the film forming chamber 7 can be appropriately changed. (2) Description of a film forming method by a CVD method using helicon mode plasma according to an embodiment of the present invention (A) Description of an embodiment according to a first film forming method (i) First film forming method Next, a method of forming a silicon oxide film using the CVD film forming apparatus of FIG. 1 according to an example of the first film forming method of the present invention will be described. O ₂ gas and TEOS as reaction gas
(N ₂ ) gas is used. TEOS (N ₂ ) gas is N ₂
It is obtained by bubbling in a TEOS solution at room temperature using gas as a carrier gas. In addition, TEOS
Is represented by Si (OC ₂ H ₅ ) ₄ (4 ethoxysilane).

As film forming conditions, (a) O ₂ / TEOS (N ₂ ) flow rate ratio (standard value = 3) (b) Total gas flow rate (total gas flow rate standard value = 1.75 SLM, O ₂ gas flow rate standard) Value = 1.31SLM, TEOS (N ₂ ) gas flow rate standard value = 0.44SLM) (c) Gas pressure (standard value = 0.2Torr) (d) Substrate temperature (standard value = 350 ° C) (e) Wafer position (deposition The lower end of the chamber 7 is zero, the upper side is positive and the lower side is negative.Standard value = + 45 mm) (f) RF power [P _RF ] applied to the external antenna 2 (standard value = 1.5 kW) (g ) Inside source solenoid current [I _IS ] (standard value = 20
A) (f) Outside source solenoid current [I _OS ] (standard value = 60
A) is mentioned. In this example, in order to investigate the characteristics of the formed film, various parameters were changed to prepare various samples. The standard value is a fixed value of another parameter when the parameter is being changed.

First, the plasma generating chamber 1 and the film forming chamber 7 are evacuated by a turbo molecular pump and maintained at 1 × 10 ⁻³ Torr or less. Next, the wafer holder 3 on which the wafer 15 is placed
Is moved upward and placed at a predetermined position in the film forming chamber 7. Subsequently, the wafer 15 is heated by a heater (not shown) built in the wafer holder 3 to hold the wafer 15 at a predetermined temperature.

Next, a predetermined flow rate of O ₂ gas is introduced into the plasma generation chamber 1 through the first reaction gas introduction pipe 8, and a predetermined flow rate of T 2 is introduced through the second reaction gas introduction pipe 9.
EOS (N ₂ ) gas is introduced into the film forming chamber 7. Then, the gas pressure in the film forming chamber 7 is adjusted and maintained at a predetermined pressure.
Next, a predetermined current is applied to the inner source solenoid 5 and the outer source solenoid 6 to generate a magnetic field, and a predetermined RF power is applied to the external antenna 2 via the matching network 3. As a result, O ₂
The gas is activated and helicon mode plasma is generated. Further, this helicon mode plasma flows into the film forming chamber 7 downstream, and the TEOS gas is activated. Then, the activated TEOS gas and oxygen plasma react with each other to start depositing a silicon oxide film on the wafer 15 at a predetermined deposition rate.

By holding this state for a predetermined time, a silicon oxide film having a predetermined thickness is formed. (Ii) Description of Investigation Results of Characteristics of Silicon Oxide Film According to Example of First Film Forming Method Next, with respect to the silicon oxide film formed as described above, film deposition rate (deposition) and formation The results of investigating the etching rate (etch rate) of the film and the stress of the formed film will be described.

Deposition of Silicon Oxide Film Dependency of the deposition rate of the silicon oxide film in a predetermined range of each parameter is shown in FIGS. 4 (a) to 4 (d) and 5 (a).
It shows in (d). 4 (a) _{is, O 2 / TEOS (N 2} )
It is a characteristic view which shows the dependency of the deposit rate in the range of 1-3 of a flow rate ratio. As shown in the figure, the deposition rate is O ₂
/ TEOS (N ₂ ) becomes smaller as the flow ratio increases,
It varies from 450 Å / min to 350 Å / min.

FIG. 4B shows a total gas flow rate of 0.75 SLM-1.
It is a characteristic view which shows the dependency of the deposit rate in the range of 75 SLM. As shown in the figure, the deposition rate is O ₂ + TEO.
It increases as the total flow rate of S (N ₂ ) increases to 200 Å
It changes in the range of / min to 600 Å / min. FIG. 4C is a characteristic diagram showing the dependency of the deposit rate in the gas pressure range of 0.2 Torr to 0.6 Torr. As shown in the figure, the deposit has a maximum value of 460 Å / min at a total gas pressure of O ₂ + TEOS (N ₂ ) of 0.4 Torr, and varies from 380 Å / min to 460 Å / min.

FIG. 4D is a characteristic diagram showing the dependency of the deposit rate in the range of the substrate temperature of 250 ° C. to 350 ° C.
As shown in the figure, the deposition rate decreases as the substrate temperature increases, and changes in the range of 500 Å / min to 300 Å / min. FIG. 5A is a characteristic diagram showing the dependency of the deposition rate in the range of the wafer position −45 mm to +45 mm. As shown in the figure, the deposition rate increases as the wafer position rises, and changes in the range of 500Å / min to 300Å / min.

FIG. 5B is a characteristic diagram showing the dependency of the deposit rate in the RF power range of 1 kW to 2 kW. As shown in the figure, the depo rate is RF power 1.5 kW and the minimum value is 30.
It has 0 Å / min and varies from 300 Å / min to 460 Å / min. FIG. 5C shows the inner source solenoid current 20A.
It is a characteristic view which shows the dependency of the deposit rate in the range of -80A. As shown in the figure, the deposition rate decreases as the inner source solenoid current increases, and changes in the range of 500 Å / min to 300 Å / min.

FIG. 5D is a characteristic diagram showing the dependency of the deposit rate in the range of the outer source solenoid currents 20A to 80A. The deposit has a minimum value of 380 Å / min at an outer source solenoid current of 60 A, 380 Å / min ~ 440
Changes in the range of Å / minute. According to the film forming method of the embodiment of the present invention, although the deposition rate is small, the CV by the ECR method is used.
Compared to the case of D, it is almost the same and there is no practical inconvenience.

Etching Rate of Formed Film Dependence of the etch rate of the formed film in a predetermined range of each parameter is shown in FIGS. 6 (a) to 6 (d) and 7 (a) to 7 (d).
Shown in. The etching rate was measured using a 1.2% HF aqueous solution. The smaller the etching rate is, the denser the silicon oxide film is, which is preferable as an insulating film used in a semiconductor device, for example. The etching rate of the silicon oxide film formed by thermal oxidation is 98Å / min.

FIG. 6A is a characteristic diagram showing the dependence of the etch rate in the range of 1 to 3 of the O ₂ / TEOS (N ₂ ) flow rate ratio. As shown in the figure, the etch rate is O
_It decreases with an increase in the ₂ / TEOS (N ₂ ) flow rate ratio, and changes in the range of 625 Å / min to 525 Å / min. Figure 6
(B) is a characteristic diagram showing the dependence of the etch rate in the range of 0.75 SLM to 1.75 SLM of the total gas flow rate. As shown in the figure, the etch rate increases as the total flow rate of O ₂ + TEOS (N ₂ ) increases, and is 525 Å / min to 610 Å
It changes within the range of / minute.

FIG. 6C shows a gas pressure of 0.2 Torr to 0.6 Torr.
It is a characteristic view which shows the dependence of the etching rate in the range of r. As shown in the figure, the etch rate is O ₂ + TEO
It increases as the total gas pressure of S (N ₂ ) increases, and
It varies from 0 Å / min to 650 Å / min. Figure 6 (d)
FIG. 3 is a characteristic diagram showing the dependence of the etch rate in the substrate temperature range of 250 ° C. to 350 ° C. As shown in the figure, the etch rate decreases with increasing substrate temperature,
Varies in the range of Å / min to 480 Å / min.

FIG. 7A shows a wafer position of −45 mm to +45 mm.
It is a characteristic view which shows the dependence of the etching rate in the range of m. As shown in the figure, the etch rate has a minimum value of 540 Å / min at 0 mm at the wafer position, and 540 Å / min to 610 Å / min.
Varies in the range of minutes. FIG. 7B shows RF power of 1 kW to 2 kW.
It is a characteristic view which shows the dependence of the etching rate in the range of kW. As shown in the figure, the etch rate decreases as the RF power increases and changes in the range of 675 Å / min to 500 Å / min.

FIG. 7C is a characteristic diagram showing the dependence of the etch rate in the range of the inner source solenoid currents 20A to 80A. As shown in the figure, the etch rate has a maximum value of 600 Å / min at an inner source solenoid current of 50 A, and varies in the range of 550 Å / min to 600 Å / min. Figure 7
(D) is a characteristic diagram showing the dependence of the etch rate in the range of the outer source solenoid current 20A to 80A. The etch rate has a maximum value of 640 Å / min at an outer source solenoid current of 60 A and varies from 530 Å / min to 640 Å / min.

As described above, the etching rate of the silicon oxide film formed by the film forming method of the embodiment of the present invention is E
Compared with the etching rate of the silicon oxide film formed by CVD using the CR method. It is considered that this is because the film formation was performed by high-density plasma as in the CVD using the ECR method. Judging from the above etching rate, it can be said that the film quality is sufficiently good as an insulating film used for a semiconductor device.

Stress of Formed Film The dependence of the stress of the formed film in a predetermined range of each parameter is shown in FIGS. 8 (a) to 8 (d) and 9 (a) to 9 (d).
The stress measurement was calculated from the amount of warpage of the substrate, as is commonly done. Positive signs indicate tensile stress, negative signs indicate compressive stress.

FIG. 8A is a characteristic diagram showing the stress dependence in the range of 1 to 3 of the O ₂ / TEOS (N ₂ ) flow rate ratio. As shown in the figure, the stress is O ₂ / TEOS (N
₂ ) A minimum value of +0.1 × 10 ⁹ dyne / cm ² at a flow rate ratio of 2
It varies in the range of 0.1 × 10 ⁹ dyne / cm ² to + 0.35 × 10 ⁹ dyne / cm ² . Fig. 8 (b) shows 0.75 SLM to 1.75 S of the total gas flow rate.
It is a characteristic view showing the dependence of stress in the range of LM. As shown in the figure, the stress becomes smaller as the total flow rate of O ₂ + TEOS (N ₂ ) increases, and the stress becomes + 0.5 × 10 ⁹ dyne / cm ² ~
It varies in the range of 0 dyne / cm ² .

FIG. 8C shows a gas pressure of 0.2 Torr to 0.6 Tor.
It is a characteristic view which shows the dependence of the stress in the range of r. The stress gradually decreases from a negative value to zero as the total gas pressure of O ₂ + TEOS (N ₂ ) increases, and further increases toward a positive value. The stress value is −0.5 × 10
It varies within the range of ⁹ dyne / cm ² to + 0.8 × 10 ⁹ dyne / cm ² .

FIG. 8D is a characteristic diagram showing the stress dependence in the substrate temperature range of 250 ° C. to 350 ° C. The stress has a minimum value of 0 dyne / cm ² at a substrate temperature of 300 ℃,
It varies within the range of m ² to +0.6 × 10 ⁹ dyne / cm ² . Figure 9
(A) is a characteristic view showing the dependency of stress in the range of wafer position -45 mm to +45 mm. The stress gradually decreases from positive to zero as the wafer position increases,
The more negative the value, the larger the negative value. The stress value varies from ^{+0.7 × 10 9 dyne / cm 2} ~-0.1 × 10 9 dyne / cm 2.

FIG. 9B is a characteristic diagram showing the dependence of stress in the range of RF power of 1 kW to 2 kW. The stress is RF
As the electric power increases, the value gradually decreases from positive to zero, and when the value further shifts to negative, the negative value gradually increases. The stress value is +0.7 × 10 ⁹ dyne / cm ² to −0.65 × 10 ⁹ d
It varies within the range of yne / cm ² . FIG. 9C is a characteristic diagram showing the dependency of stress in the range of the inner source solenoid currents 20A to 80A. The stress increases as the inner source solenoid current increases, and becomes +0.1 × 10 ⁹ dyne / cm ²
It varies within the range of +0.4 × 10 ⁹ dyne / cm ² .

FIG. 9 (d) is a characteristic diagram showing the stress dependence in the range of the outer source solenoid currents 20A to 80A. The stress has a maximum value of +0.5 × 10 ⁹ dyne / cm ² at an outer source solenoid current of 60 A, and +0.0 × 10 ⁹ dyne / cm 2.
It varies from ^{2 ~ + 0.5 × 10 9 dyne} / cm 2. As described above, the stress of the silicon oxide film formed by the film forming method of the embodiment of the present invention is small, and it is sufficient as an insulating film used for a semiconductor device.

Refractive Index of Formed Film All the above parameters were set to standard values, and the refractive index of the formed silicon oxide film was obtained. The refractive index was measured using an ellipsometer. The refractive index is also an important evaluation item for evaluating the denseness, and the larger the refractive index, the denser the film.

The result was 1.452. It can be said that the refractive index is about the same as that of the thermal oxide film, and that the film quality is sufficiently good as an insulating film used for a semiconductor device. Although the silicon oxide film is formed by using O ₂ + TEOS (N ₂ ) gas in the above embodiment, SiH ₄ + O ₂ gas may be used. Further, it is possible to form a PSG film, a BSG film, a BPSG film and the like by adding a dopant to these gases. Further, a silicon nitride film can be formed by using N ₂ , NH ₃ , and H ₂ NNH ₂ as a reaction gas for supplying nitrogen. (B) Description of Example Related to Second Film Forming Method (i) Example Related to Second Film Forming Method Next, referring to FIG. 1 according to an example of the second film forming method of the present invention. A method for forming a silicon oxide film using a CVD film forming apparatus will be described. O ₂ gas is used as the first reaction gas,
SiH ₄ gas is used as the second reaction gas.

As film forming conditions, (a) O ₂ / SiH ₄ flow rate ratio (standard value = 1) (b) Reactant gas flow rates and total gas flow rate (O ₂ gas flow rate standard value = 30 SCCM, SiH ₄ gas flow rate) Standard value = 30 SCCM, total gas flow rate standard value = 60 SCCM) (c) Gas pressure (standard value = 20 mTorr) (e) Wafer position (the lower end of the film forming chamber 7 is zero and the position above this is shown. = 161mm) (f) Substrate bias [P _B ] (standard frequency = 100kHz)
, Power standard value = 200 W) (g) RF power applied to the external antenna 2 [P _RF ] (frequency standard value = 13.56 MHz, power standard value = 1.0 kW) (h) inner source solenoid current [I _IS ] (standard) Value = 50
A) (i) Outer source solenoid current [I _OS ] (standard value = 60
A) In this example, in order to investigate the characteristics of the formed film, various conditions are changed to prepare various samples. The above standard value refers to a fixed value of another condition when the condition is being changed.

In the embodiment, the gas releasing portion 9a is fixedly installed at about 230 mm above the lower end of the film forming chamber 7 as measured. Therefore, the standard value of the wafer position is 1
At 61 mm, the gas discharge portion 9a is located at about 70 mm on the surface of the wafer 15. Although the wafer 15 is not particularly heated, it is heated to some extent by plasma irradiation.

First, the plasma generating chamber 1 and the film forming chamber 7 are evacuated by a turbo molecular pump and the pressure is kept at 10 ^-3 Torr or less. Next, the wafer holder 3 on which the wafer 15 is placed
Is moved upward and placed at a predetermined position in the film forming chamber 7. next,
A predetermined flow rate of O ₂ gas is introduced into the plasma generation chamber 1 through the first reaction gas introduction pipe 8, and a predetermined flow rate of SiH ₄ gas is introduced through the second reaction gas introduction pipe 9. Introduce to 7. Then, the gas pressure in the film forming chamber 7 is adjusted and maintained at a predetermined pressure.

Next, a predetermined current is applied to each of the inner source solenoid 5 and the outer source solenoid 6 to generate a magnetic field, and a predetermined RF power is applied to the external antenna 2 via the matching network 3. As a result, O ₂ gas is activated and helicon mode plasma is generated. Further, this helicon mode plasma flows into the film forming chamber 7 and the SiH ₄ gas is activated. continue,
The activated SiH ₄ gas and oxygen plasma react with each other to start depositing a silicon oxide film on the wafer 15 at a predetermined deposition rate.

By holding this state for a predetermined time, a silicon oxide film having a predetermined thickness is formed. In addition,
In the film forming method of the above embodiment, the wafer 15 is not heated, but by appropriately heating the substrate at a temperature of about 200 to 300 ° C., the quality of the formed silicon oxide film can be adjusted.

(Ii) Description of Investigation Results of Characteristics of Silicon Oxide Film According to Example of Second Film Forming Method Next, with respect to the silicon oxide film formed as described above, the deposition rate of the film (deposition rate) ), The deposition rate, the hydrogen bond and moisture in the film, the SiO peak wave number in the film, the etching rate ratio of the film, the refractive index, and the results of investigation of stress will be described. The results are shown in FIGS.

Film Deporate The silicon oxide film deporate (Å / min) was investigated in a predetermined range of each parameter. It was directly formed on a silicon substrate having a diameter of 150 mm. The result is shown in FIG.
It shows in (g). FIG. 10A shows the O ₂ / SiH ₄ flow rate ratio of 0.
It is a characteristic view which shows the dependency of the deposit rate in the range of 8 to 3. As shown in the figure, when the O ₂ / SiH ₄ flow rate ratio is about 1, the depo rate has a minimum value of 800 Å / min, and the depo rate increases as the flow rate increases thereafter. Flow rate ratio approx.
At 1.8, the maximum value is 1250 Å / min, and as the flow rate increases thereafter, the deporate decreases, and at the flow rate of 3
950Å / min.

In FIG. 10B, the total flow rate of the reaction gas is 0 sc
Dependence of depo rate in the range of cm-100sccm
It is a characteristic diagram. As shown in the figure, the deposit rate is O₂+
SiH_FourMonotonically increases as the total gas flow in
When the gas flow rate is 100 sccm, the range is approximately 1600Å / min.
It FIG. 10C shows a gas pressure in the film forming chamber 7 of 10 mTorr.
Dependency of deposition rate in the range of -40 mTorr
It is a characteristic diagram. As shown in the figure, the deposit rate is O ₂+
SiH_FourIt does not depend so much on the gas pressure of. Gas pressure 10mTorr
Was 1000Å / min, but as the gas pressure increased
And a slight decrease, 800 Å when the gas pressure is 40 mTorr
/ Minute.

FIG. 10D shows a wafer position of 20 mm to 16 mm.
It is a characteristic view which shows the dependency of the deposition rate in the range of 1 mm. As shown in the figure, the deposition rate increases as the wafer position rises, that is, as the wafer 15 approaches the gas discharge portion 9a, and changes in the range of 300Å / min to 900Å / min. FIG. 10E shows the substrate bias [P
_B ] A characteristic diagram showing the dependency of the deposition rate in the range of 0 W to 200 W. As shown in the figure, the depo rate has about 1000Å / min when the substrate bias is zero, the depo rate decreases as the substrate bias increases thereafter, and becomes about 900Å / min when the substrate bias is 200W.

FIG. 10 (f) shows the RF power [P_RF] 0.5k
Characteristic showing dependency of deposition rate in the range of W to 2kW
It is a figure. As shown in the figure, the deposition rate is RF power.
It has about 650Å / min at 0.5kW, and the RF power after that
It increases as it increases, and when RF power is 1.5kW, it is about
1100Å / min. Figure 10 (g) shows the inside source Soleno
Id current [I_IS] Depot in the range of 20A-80A
It is a characteristic diagram showing the dependence of the table. Outside sauce solenoy
Current [I _OS] Adjusted under 3 conditions of 20A, 60A, 100A
Sticky.

As shown in FIG._OS= 20A
(Indicated by a square mark), the deposit is I _IS= 50A
Has a maximum value of approximately 900Å / min, 700Å / min to 900Å
It changes within the range of / minute. Also, I_OS= 60A (Three
Indicated by square marks. ), The deposit is I_ISMaximum when = 50A
Has a value of about 820Å / min, 600Å / min to 820Å / min
Changes in the range of.

Further, when I _OS = 100 A (shown by a circle), the minimum value of the deposit is about 70 when I _IS = 50 A.
It has 0Å / min and varies from 700Å / min to 900Å / min. As described above, according to the film forming method of the embodiment of the present invention, the deposition rate is large and is practically sufficient.

Deposition Ratio of Silicon Oxide Film The deposition ratio of the silicon oxide film in a predetermined range of each parameter was investigated. The result is shown in FIG.
~ (G). The deposit ratio is defined as follows. That is, on the silicon oxide film formed by the plasma CVD method using the mixed gas of O ₂ + SiH ₄ against the deposition rate of the silicon oxide film formed directly by the thermal CVD method using the mixed gas of TEOS + O ₃ on the silicon substrate. It is the ratio of the deposition rate of the silicon oxide film formed by the thermal CVD method using a mixed gas of TEOS + O ₃ . The above-mentioned deposition rate is the thermal CV using a mixed gas of TEOS + O _3.
The quality of the film is judged from the aspect of compatibility with the silicon oxide film by the D method. The closer the value is to 1, the better the compatibility is judged to be.

Here, the film forming conditions of the thermal CVD method using the mixed gas of TEOS + O ₃ are as follows. (a) TEOS temperature: 65 ° C. (b) TEOS carrier gas: N ₂ gas, flow rate: 1.5 slm (c) Ozone-containing oxygen gas: O ₃ content 5 vol%, flow rate: 7.5 slm (d) Wafer temperature: 400 ° C. Figure 11 (a) is a characteristic diagram showing the dependence of the deposition rate ratio in the range 0.8 to 3 of O ₂ / SiH ₄ flow ratio. As shown in the figure, the O ₂ / SiH ₄ flow rate ratio was 0.8.
Approximately 1 is obtained at ~ 1, and the compatibility is the best. After that, when the flow rate ratio increased, the depo rate ratio suddenly decreased to about 0.5.
Falls down. After that, it becomes almost constant even if the flow rate ratio increases.

In FIG. 11B, the total flow rate of the reaction gas is 60.
It is a characteristic view which shows the dependency of the depo rate in the range of sccm-100sccm. As shown in the figure, when the total gas flow rate of O ₂ + SiH ₄ is 60 sccm, the deporate ratio has a value of about 0.85. As the total gas flow rate increases thereafter, it approaches 1 monotonously, and when the total gas flow rate is 100 sccm, It will be about 0.93. Figure 1
1 (c) is a gas pressure in the film forming chamber 7 of 10 mTorr to 40 mT
It is a characteristic view which shows the dependency of the depo rate in the range of orr. As shown in the figure, the deposition rate is O ₂ + SiH ₄
Has a value of about 0.8 when the gas pressure is 10 mTorr, and approaches 1 as the gas pressure increases thereafter, and the gas pressure is 40 mTorr.
It becomes about 0.95.

FIG. 11D shows a wafer position of 20 mm to 16 mm.
It is a characteristic view which shows the dependency of the deposition rate in the range of 1 mm. As shown in the figure, the deposition rate has a value of 1.1 at the wafer position of 20 mm, and becomes smaller as the wafer position rises. Then, after passing around 40 mm which is about 1 and further descending, the minimum value is about 0.75 near 100 mm.
After that, it becomes larger again as the wafer position rises, 161
It becomes 0.85 in mm.

FIG. 11E shows the substrate bias [P _B ] 0.
It is a characteristic view which shows the dependency of the deposition rate in the range of W-200W. As shown in the figure, the depo rate is about 0.75 when the substrate bias is zero, and as the substrate bias increases thereafter, the depo rate increases to about 1. 8
Substrate bias 100
When W, the maximum value is about 1.05. After that, as the substrate bias increases, the deposition rate decreases,
It becomes 0.85.

FIG. 11 (f) shows the RF power [P _RF ] 0.5k.
It is a characteristic view which shows the dependency of the deposition rate ratio in the range of W-2kW. As shown in the figure, the deposition rate has a value of about 0.95 when the RF power is 0.5 kW, decreases monotonically as the RF power increases thereafter, and becomes about 0.63 when the RF power is 2 kW. FIG. 11 (g) shows the inner source solenoid current [I
_IS ] A characteristic diagram showing the dependency of the deposition rate in the range of 20A to 80A. Outside source solenoid current [I
_OS ] It was examined under three conditions of 20A, 60A and 100A.

As shown in FIG._OS= 20A
(Indicated by a square mark), the deposition rate is 0.85 to 0.9.
To increase. Also, I_OS= 60A (indicated by a triangle
You ), The deposition rate increases monotonically from 0.8 to 0.85.
It Furthermore, I_OS= 100 A (indicated by a circle), I
_IS== 20 A, the deposition rate has about 1. Below
Descend, I_IS= 50A, the minimum value is about 0.77. I _ISBut
As it gets bigger, it rises again and I_IS= 80A approx.
It becomes 0.97.

As described above, according to the film forming method of the embodiment of the present invention, as shown in FIG. 11A, the flow rate ratio is preferably about 1 in terms of compatibility. Further, the deposition rate can be controlled by adjusting the wafer position and the substrate bias in addition to the flow rate ratio, and the deposition rate of 1 can be realized by appropriately adjusting these parameters.

SiOH, SiH bond and SiO bond in the film Four kinds of silicon oxide films in which the O ₂ / SiH ₄ flow rate ratio was changed in the range of 0.88 to 3.00 were analyzed by Fourier transform infrared spectroscopy (FTIR). SiOH, SiH bond and S
The iO binding was investigated. The result is shown in FIG. 12
, The vertical axis represents the absorption intensity and the horizontal axis represents the wave number (c
m ^-1 ).

By the way, SiOH bond has an absorption peak in the vicinity of the 3600 cm ^-1, also SiH bonds are known to have absorption peak near the 2000 cm ^-1. When the silicon oxide film according to an embodiment of the present invention, as shown in FIG. 12, the absorption peak near 3600 cm ^-1 and 2000 cm ^-1 in either case the flow rate ratio was observed. This shows that neither SiOH bond nor SiH bond exists in the formed silicon oxide film, and SiH ₄ is sufficiently oxidized. Therefore, it is possible to form a dense and good-quality silicon oxide film containing no water.

The absorption peak appearing near 1080 cm ^-1 indicates SiO bond. It is shown that the closer the wave number of this absorption peak is to 1080 cm ⁻¹ , the closer the composition of the thermal oxide film and the denser SiO ₂ is generated. Si0 peak wave number in the film and etching rate ratio of the film S of the silicon oxide film in a predetermined range of each parameter
The i0 peak wavenumber ν _SIO (cm ⁻¹ ) was investigated. ν _SIO indicates the bonding state of SiO in the silicon oxide film, and ν _SIO is
It is shown that the closer to 1080 cm ⁻¹ , the closer the composition of the thermal oxide film and the denser SiO ₂ is generated. The investigation was conducted by FTIR. The result is shown in FIG.
~ (G).

Further, in FIG. 13 (h), the O ₂ / SiH ₄ flow rate ratio of 0.
The result of having investigated the dependence of the etching rate ratio in the range of 8 to 3 is shown. The etching rate ratio is the ratio of the etching rate of the silicon oxide film formed by the plasma CVD method of the embodiment to the etching rate of the silicon oxide film formed by thermal oxidation.
The etching rate was measured using a 1.2% HF aqueous solution. The closer the etch rate ratio is to 1, the closer the quality of the thermal oxide film is to that of the formed silicon oxide film, which is preferable, for example, as an insulating film used in a semiconductor device. The etching rate of the silicon oxide film formed by thermal oxidation is about 98Å / min.

The survey results will be described below. FIG.
(A) is O₂/ SiH_FourIn the range of 0.8 to 3 of flow rate ratio
ν_SIOIt is a characteristic view which shows the dependency of. As shown in the figure
, Ν _SIOIs 1050 cm when the flow ratio is 0.8^-1And has
When the flow rate ratio increases, it rapidly increases to 1080 cm^-1Approach. Flow rate is
1080 cm near 1.03^-1Is reached and the flow ratio increases thereafter
Fixed 1080cm^-1Becomes O₂/ SiH_FourWhere the flow rate is low
ν_SIOIs small because there is more Si than oxygen in the formed film.
It is thought that this is because the film exists, and as a result, the film is
It shows that it is dense.

When the silicon oxide film produced above is etched, it has a value closer to the etching rate of the silicon oxide film formed by thermal oxidation at a small flow rate ratio, as shown in FIG. 13 (h). It can be proved from that. FIG. 13B is a characteristic diagram showing the dependency of ν _{SI O} when the total flow rate of the reaction gas is in the range of 60 sccm to 100 sccm. As shown in the figure, ν _SIO has about 1060 cm ⁻¹ when the total gas flow rate of O ₂ + SiH ₄ is 60 sccm. After that, it decreases monotonically as the total gas flow rate increases, and becomes about 1045 cm ^{-1 at} 100 sccm.

FIG. 13C shows the gas pressure 1 in the film forming chamber 7.
It is a characteristic view which shows the dependency of ν _SIO in the range of 0 mTorr to 40 mTorr. As shown in the figure, ν _SIO has a value of about 1060 cm ⁻¹ with respect to the change of the gas pressure of O ₂ + SiH ₄ ,
It doesn't change much. FIG. 13D shows a wafer position of 20 mm.
It is a characteristic view which shows the dependence of (nu) _SIO in the range of -161 mmm. As shown in the figure, ν _SIO is the wafer position 20.
It has a diameter of about 1050 cm ⁻¹ and increases monotonically with increasing wafer position. And it becomes about 1060 cm ^{-1 at} 161 mm.

FIG. 13E shows the substrate bias [P _B ] 0.
It is a characteristic view which shows the dependence of (nu) _SIO in the range of W-200W. As shown in the drawing, [nu _SIO has about 1065 cm ^-1 in the substrate bias zero, the [nu _SIO as later substrate bias increases monotonously decreases from about the time of 200W 1055cm ^-1
Becomes FIG. 13 (f) shows RF power [P _RF ] 0.5kW
It is a characteristic view which shows the dependence of ν _SIO in the range of 2 kW. As shown in the figure, ν _SIO is about 0.5kW with RF power.
It has 1050 cm ^-1 , and thereafter increases as the RF power increases, and becomes about 1065 cm ^-1 when the RF power is 2 kW.

FIG. 13 (g) is a characteristic diagram showing the dependency of ν _SIO in the range of the inner source solenoid current [I _IS ] 20A to 80A. Outside source solenoid current [I
_OS ] It was examined under three conditions of 20A, 60A and 100A. As shown in the figure, when I _OS = 20 A (indicated by a square mark), ν _SIO monotonically decreases from about 1065 cm ⁻¹ to about 1055 cm ⁻¹ .

When I _OS = 60 A (indicated by a triangle mark), ν _SIO changes in the range of about 1055 cm ⁻¹ to about 1058 cm ⁻¹ . Further, when I _OS = 100 A (shown by a circle), ν _SIO changes in the range of about 1058 cm ⁻¹ to about 1063 cm ⁻¹ . As described above, according to the film forming method of the example of the present invention, as shown in FIG. 13A, v _{SIO of} about 1080 cm ⁻¹ was obtained at a flow rate ratio of about 1.03 or more. When setting the CVD conditions, it is preferable to make ν _SIO as close as possible to 1080 cm ⁻¹ . From the graph of the etching rate ratio shown in FIG. 13 (h), there are cases where ν _SIO is smaller than 1080 cm ^−1, where there is a high density,
It is necessary to make a comprehensive judgment in consideration of other parameters.

Refractive Index of Film The refractive index of the silicon oxide film in a predetermined range of each parameter was investigated. The refractive index was measured using an ellipsometer. The results are shown in FIGS.
Shown in. FIG. 14A shows that the O ₂ / SiH ₄ flow rate ratio is 0.8 to 3.
It is a characteristic view showing the dependence of the refractive index in the range of. As shown in the figure, the flow ratio is 0.8 and the refractive index is 1.63.
After that, when the flow rate ratio becomes higher, it decreases sharply and 1.49 at flow rate ratio 1.
To a certain extent. It slightly decreases when the flow rate ratio is 1 or more, and becomes 1.45 when the flow rate ratio is 3. The high refractive index at a flow rate ratio of 0.8 is shown in Fig. 1.
It is considered to be the same as the reason why the ν _{SIO of} 3 (a) is low. That is, it is considered that silicon is excessively present in the silicon oxide film.

In FIG. 14B, the total flow rate of the reaction gas is 60.
It is a characteristic view which shows the dependence of the refractive index in the range of sccm-100sccm. As shown in the figure, the refractive index is about 1.52 when the total gas flow rate of O ₂ + SiH ₄ is 60 sccm. After that, it increases monotonically as the total gas flow rate increases to about 1.58 at 100 sccm. FIG. 14C is a characteristic diagram showing the dependence of the refractive index in the gas pressure range of 10 mTorr to 40 mTorr in the film forming chamber 7. As shown in the figure, O ₂ + SiH ₄
The refractive index is around 1.50 with respect to the change of the gas pressure of, and does not change much.

FIG. 14D shows the wafer positions 20 mm to 16 mm.
It is a characteristic view which shows the dependence of the refractive index in the range of 1 mm. As shown in the figure, the refractive index is about 1.52 with respect to the change of the wafer position, and does not change much. 14
(E) is a characteristic diagram showing the dependence of the refractive index in the range of the substrate bias [P _B ] 0 W to 200 W. As shown in the figure, the refractive index has a value of about 1.52 when the substrate bias is zero and decreases monotonically as the substrate bias increases thereafter.
It becomes about 1.5 at 0W.

FIG. 14 (f) shows the RF power [P _RF ] 0.5k.
It is a characteristic view which shows the dependency of the refractive index in the range of W-2kW. As shown in the figure, the refractive index is about 1.53 when the RF power is 0.5 kW, decreases as the RF power increases thereafter, and becomes about 1.48 when the RF power is 2 kW. Figure 14 (g)
Is the inner source solenoid current [I _IS ] 20A-80A
It is a characteristic view showing the dependence of the refractive index in the range of. Outer source solenoid current [I _OS ] 20A, 60A, 10
It was examined under three conditions of 0A.

As shown in the figure, when I _OS = 20 A (indicated by a square mark), the refractive index is about 1. when I _IS is 20 A.
It has 47 and rises to about 1.5 at 50A and 50 at 80A.
Almost the same as in case A. When I _OS = 60 A (indicated by a triangle), the refractive index monotonically decreases from about 1.52 to about 1.5.

Further, when I _OS = 100 A (indicated by a circle), the refractive index changes within the range of about 1.5 to about 1.49.
As described above, according to the film forming method of the embodiment of the present invention, the refractive index can be controlled mainly by adjusting the total gas flow rate and the RF power, and the semiconductor can be controlled from the adjusted refractive index value. It can be said that the film quality is sufficiently good as an insulating film used in the device.

Film Stress The dependence of the film stress on the prescribed range of each parameter was investigated. The stress measurement was calculated from the amount of warpage of the wafer 15, as is commonly done. The result is shown in Figure 1.
5 (a) to (d) and FIGS. 15 (a) to (g). The vertical axis represents stress (× 10 ⁹ dyne / cm ² ) and the horizontal axis represents the range of change in each parameter. In the figure, positive signs indicate tensile stress, and negative signs indicate compressive stress. The white circles represent the values measured immediately after the film formation, and the black circles represent the values measured after being left in the atmosphere having a humidity of 50 to 60% for 3 weeks.

Here, it is possible to judge the film quality by the type of stress and the state of the change of stress over time. That is, the densified film has compressive stress. However, even a film that has a compressive stress and appears dense may absorb moisture in the atmosphere or the stress may change due to heat treatment. The stability is evaluated by observing the change with time of stress due to being left in the atmosphere.

FIG. 15A shows the O ₂ / SiH ₄ flow rate ratio of 0.8.
It is a characteristic view which shows the dependence of the stress in the range of ~ 3.
As shown in the figure, the stress has + 1.8 × 10 ⁹ dyne / cm ² when the O ₂ / SiH ₄ flow ratio is 0.8, and tends to decrease as the flow ratio increases, and becomes + 1.25 × 10 9. ⁹ dyne / cm ² ~ +1.8
It varies in the range of × 10 ⁹ dyne / cm ² . When left for 3 weeks, the stress changes somewhat.

FIG. 15B shows the total flow rate of the reaction gas of 60 sc.
It is a characteristic view which shows the dependence of the stress in the range of 100 cm to 100 sccm. As shown in the figure, the stress tends to decrease as the total flow rate of O ₂ + SiH ₄ increases, and the stress becomes +0.3 × 10 ⁹ d
It varies within the range of yne / cm ² to −1.8 × 10 ⁹ dyne / cm ² . Three
If left for a week, the stress will fluctuate somewhat. FIG. 15 (c)
[Fig. 4] is a characteristic diagram showing stress dependence in a gas pressure range of 10 mTorr to 40 mTorr. The stress does not fluctuate much with changes in the gas pressure of O ₂ + SiH _{4, and} the stress is almost −1.5.
It has × 10 ⁹ dyne / cm ² . The stress does not change even when left for 3 weeks.

FIG. 15D shows a wafer position of 20 mm to 16 mm.
It is a characteristic view which shows the dependence of the stress in the range of 1 mm.
The stress has a value of −1.0 × 10 ⁹ dyne / cm ² at a wafer position of 20 mm, and increases in the negative direction as the wafer position rises.
Maximum negative value when wafer position is about 90 mm −2.0 × 10 ⁹ d
It becomes yne / cm ² . Further, as the wafer position rises, the negative becomes smaller, and when the wafer position is 161 mm, it is -1.4 x 10
It becomes ⁹ dyne / cm ² . The stress does not change even when left for 3 weeks.

FIG. 15E shows the substrate bias 0 W to 20 W.
It is a characteristic view which shows the dependence of the stress in the range of 0W.
The stress has about + 0.4 × 10 ⁹ dyne / cm ² when the substrate bias is zero, and changes to a negative stress as the substrate bias increases, passing through a point where the stress is zero near 10 W. Further, it increases in the negative direction as the substrate bias increases, and becomes about −1.1 × 10 ⁹ dyne / cm ^{2 at} 100 W. Furthermore, as the substrate bias increases, it becomes slightly negative and becomes about −1.5 × 10 ⁹ dyne / cm ^{2 at} 200 W.

When left for 3 weeks, the stress in the case of zero substrate bias fluctuates drastically to about + 0.4 × 10 ⁹ dyne /
From cm ² is about ^{-1.1 × 10 9 dyne / cm 2} . This is stress relaxation due to absorption of moisture in the atmosphere, and a large value indicates that the film has hygroscopicity and is not dense. Therefore, the effect of applying the substrate bias in order to improve the denseness of the film is great.

FIG. 15 (f) shows an RF power of 0.5 kW to 2 kW.
It is a characteristic view which shows the dependence of the stress in the range of. The stress has about −1.0 × 10 ⁹ dyne / cm ² when the RF power is 0.5 kW, and gradually increases in the negative direction as the RF power increases, and about −1.5 × 10 ⁹ dyne / cm ² when the RF power is 1 kW. Becomes Furthermore, the negative value becomes smaller as the RF power increases, and when the RF power is 2 kW, it is approximately −0.5 × 10 ⁹ dyne /
It becomes cm ² . The stress does not change even when left for 3 weeks.

FIG. 15G is a characteristic diagram showing the dependence of the film stress on the inner source solenoid current [I _IS ] 20A to 80A. The outer source solenoid current [I _OS ] was examined under three conditions of 20 A, 60 A and 100 A.
As shown in the figure, when I _OS = 20 A (indicated by a square mark), the negative value of the stress becomes smaller as I _IS increases, and −1.45 × 10 ⁹ dyne / cm ² to −1.1 × 10 ^{9 is obtained.} It varies within the range of dyne / cm ² .

When I _OS = 60 A (indicated by triangles), the stress is −1.4 × 10 ⁹ dyne / cm when I _IS is 20 A.
² and I _IS hardly fluctuates up to 50A. Further I _IS
The negative value increases as I increases, and I _IS 80A.
In this case, -1.75 × 10 ⁹ dyne / cm ² is obtained. Furthermore, I _OS = 10
In the case of 0 A (indicated by a circle), the stress does not fluctuate significantly with changes in I _IS , and has approximately −1.30 × 10 ⁹ dyne / cm ² .

As described above, according to the film forming method of the embodiment of the present invention, the stress of the formed silicon oxide film can be controlled mainly by adjusting the O ₂ / SiH ₄ flow rate ratio and the substrate bias. In particular, it is possible to form a dense and stable insulating film having a compressive stress. (C) Comparative Example of Example of Film Forming Method of Present Invention For comparison, characteristics of a silicon oxide film formed by a parallel plate plasma CVD method using SiH ₄ + N ₂ O gas will be described.

(I) Preparation of Sample of Comparative Example The film forming conditions of the comparative example are as follows. (a) N ₂ O / SiH ₄ flow rate ratio (standard value = 11) (b) Reactant gas flow rate and total gas flow rate (N ₂ O = 220 sccm, S
iH ₄ = 20 sccm, standard value = 240 sccm) (c) Gas pressure (standard value = 1 Torr) (d) Substrate temperature (standard value = 350 ° C) (e) RF power [P _RF ] (frequency standard value = 13.56 MHz) ，
Electric power standard value = 200 W) In this comparative example, various samples were prepared by changing each condition for comparison with the above-mentioned example. The above standard value refers to a fixed value of another condition when the condition is being changed.

The film forming conditions of the comparative example are characterized by a higher flow rate ratio and a higher gas pressure than the film forming conditions of the example. Incidentally, as in the embodiment according to the second film forming method, the reason for using a SiH ₄ + N ₂ O gas without using the SiH ₄ + O ₂ gas, SiH ₄ is highly reactive is used with O ₂ This is because a large amount of powder is generated, which is unsuitable as a gas used in the parallel plate plasma CVD method.

(Ii) Description of the investigation result of the film quality of the formed film In the same manner as in the example of the second film forming method described above,
For the silicon-containing insulating film formed under the condition (i), the refractive index and etching rate ratio of the film such as ν _SIO , SIOH bond and SiH bond in the film were investigated. The results are shown in FIGS. 9 to 12, respectively.

Si0 peak wavenumber ν _{SIO of the} film S of the silicon oxide film in a predetermined range of each parameter
The i0 peak wavenumber ν _SIO (cm ⁻¹ ) was investigated. The survey is F
By TIR. The result is shown in FIG.
It shows in (c). FIG. 16 (a) shows a flow rate ratio of N ₂ O / SiH ₄ of 5
It is a characteristic view which shows the dependence of (nu) _SIO in the range of _-23 . As shown in the figure, ν _SIO is when the flow rate is 5
It has 1035 cm ^-1 and has 1065 cm ^-1 when the flow ratio is 10. When the flow rate ratio is changed from 10 to 23, ν _SIO is 10
It will be slightly higher at 70 cm ^-1 .

As described above, in order to form a silicon-containing insulating film containing a large amount of bonds which become stoichiometrically SiO ₂ , the flow rate of N ₂ O should be changed relative to the flow rate of SiH ₄ as compared with the embodiment. It is necessary to increase considerably. FIG. 16B shows ν in the total gas flow rate range of 180 sccm to 650 sccm of N ₂ O / SiH _4.
It is a characteristic view which shows the dependency of _SIO . As shown in the figure, ν _SIO monotonically decreases with changes in the total gas flow rate, and changes in the range of 1068 cm ^{−1 to} 1042 cm ⁻¹ .

FIG. 16C shows the RF power [P _RF ] 10
Is a characteristic diagram showing the dependence of [nu _{SI O} in the range of 0W～300W. As shown in the figure, ν _SIO decreases monotonically with changes in RF power, and is 1068 cm ^{−1 to} 1042c.
It varies in the range of m ^-1 . Content of SIOH bond, SiH bond and NH bond in the film The SIOH bond, SiH bond and NH bond in the silicon oxide film in a predetermined range of each parameter were investigated. The investigation was conducted by FTIR. The result is shown in FIG.
It shows in (a)-(c). In the figure, white triangles indicate NH bonds, black triangles indicate SiH bonds, and squares indicate SiO.
Shows H-bonds.

FIG. 17A shows a flow rate ratio of N ₂ O / SiH ₄ of 5 to 5.
Content of SIOH bond, etc. in the range of 23 (μm ⁻¹ )
It is a characteristic view which shows the dependency of. As shown in the figure, in the case of NH bond, the content is 0.09 μm ⁻¹ when the flow rate ratio is 5.
However, it disappears at a flow rate ratio of 11 or more. Also, SiH
In the case of combination, when the flow rate ratio is 5, the content is 0.03 μm ⁻¹ ,
When the flow rate ratio is 11, the content decreases to 0.01 μm ⁻¹ but does not completely disappear. It completely disappears when the flow rate ratio is 23. Further, in the case of SIOH bond, the content is zero when the flow rate ratio is 5, but in the case of flow rate ratios 11 and 23, the content is 0.03 μm.
^-1 , and the SIOH bond remains.

FIG. 17B is a characteristic diagram showing the dependency of the content (μm ⁻¹ ) of SIOH bonds and the like in the total gas flow rate range of 180 sccm to 650 sccm of N ₂ O / SiH ₄ . As shown in the figure, in the case of NH coupling, the total gas flow rate is 1
At 80 sccm, NH bonds do not remain in the film, but at 230 sccm
The above remains. In the case of SiH bond, the total gas flow rate is 2
SiH bonds do not remain in the film at 50 sccm or less, but remain at the total gas flow rate of 250 sccm or more. Further, in the case of SIOH bond, the SIOH bond remains in the film although it decreases with an increase in the total gas flow rate.

FIG. 17C shows the RF power [P _RF ] 10
It is a characteristic view which shows the dependence of the content rate (%) of SIOH bond, SiH bond, and NH bond in the range of 0W-300W. As shown in the figure, in the case of NH bond, RF
When the power is 200 W, NH bonds do not remain in the film, but in other cases, 1% or more remains. In the case of SiH bond, RF
When the power is 200 W, SiH bonds do not remain in the film, but in other cases, about 1% to 4% remains. Further, in the case of SIOH bond, the SIOH bond remains in the film at any time.

As described above, in the comparative example, SIOH bonds, SiH bonds and N atoms are formed in the formed silicon-containing insulating film.
Since a considerable amount of H bonds are included, the film quality is inferior to that in the example. Refractive Index of Film The refractive index of the silicon oxide film in a predetermined range of each parameter was investigated. The results are shown in FIGS. 18 (a) to 18 (c).

FIG. 18A shows a flow rate ratio of N ₂ O / SiH ₄ of 5 to 5.
It is a characteristic view which shows the dependence of the refractive index in the range of 23. As shown in the figure, the refractive index is 1.
It has a flow rate of 58, and when the flow rate ratio is 11, it drops sharply to 1.47. When the flow rate ratio is changed from 11 to 23, the refractive index is 1.
48 and slightly higher. FIG. 18B is a characteristic diagram showing the dependence of the refractive index on the total gas flow rate of N ₂ O / SiH ₄ in the range of 180 sccm to 650 sccm. As shown in the figure, the refractive index increases as the total gas flow rate increases, and
It varies in the range of ~ 1.5.

FIG. 18C shows the RF power [P _RF ] 10
It is a characteristic view which shows the dependence of the refractive index in the range of 0W-300W. As shown in the figure, the refractive index is 1.54 at the RF power of 100 W, sharply decreases at the RF power of 200 W, and is 1.50 from the RF power of 200 W to 300 W.
It does not change much from 47 to 1.48. Etching rate ratio of film The etching rate ratio of the silicon oxide film in a predetermined range of each parameter was investigated. The etching rate ratio is the same as the definition described in (ii) of (B) above. The results are shown in FIGS. 19 (a) to (c).

FIG. 19A shows a flow rate ratio of N ₂ O / SiH ₄ of 5 to 5.
It is a characteristic view which shows the dependence of the refractive index in the range of 23. As shown in the figure, the etching rate ratio has 19 when the flow rate ratio is 5, and sharply decreases to 7 when the flow rate ratio is 11. When the flow rate ratio is changed from 11 to 23,
The etching rate ratio is slightly reduced to 6. When the flow rate ratio is small, the etching rate ratio is large as shown in FIG.
This corresponds to the tendency of (a), FIG. 17 (a), and FIG. 18 (a). That is, it is considered that since the SiH bond and the NH bond remain in the film, the formed silicon oxide film is porous and therefore the etching rate ratio is also high.

FIG. 19B is a characteristic diagram showing the dependence of the etching rate ratio on the total gas flow rate of N ₂ O / SiH ₄ in the range of 180 sccm to 650 sccm. As shown in the figure, the etching rate ratio increases as the total gas flow rate increases, and changes in the range of 6 to 12. FIG. 19C shows
It is a characteristic diagram showing the dependency of the etching rate ratio in the range of RF power [P _RF] 100W～300W. As shown in the figure, the etching rate ratio is 7 to 12
Fluctuates in the range of.

As described above, in the comparative example, the etching rate ratio is large, and the denseness is considerably inferior to that of the thermal oxide film.

[0110]

As described above, in the film forming apparatus according to the present invention, since the plasma generating chamber has the antenna for radiating electromagnetic waves and the plasma generating chamber having the source solenoid, the plasma generating chamber is provided. It is possible to generate high density plasma in helicon mode.

Further, since the frequency of the high frequency power applied to the antenna is low at 13.56 MHz, there is no need for equipment such as a waveguide for generating microwave power as in the case of the ECR method, and the device configuration is simple. is there. Further, the first reaction gas introducing pipe for introducing the helicon mode plasma into the plasma generation chamber is separated from the first reaction gas introducing pipe, and the second reaction gas introducing pipe for releasing the second reaction gas is formed on the substrate surface. It is provided above. Therefore, it is possible to prevent the reaction gas from reacting while the reaction gas is being introduced onto the substrate, thereby preventing the generation of particles.

Further, the substrate holder has a frequency of 13.56 MHz or 1
Since a high frequency power source for supplying a high frequency power of 00 kHz is connected, it is possible to bias the substrate with a voltage. In the film formation method according to the present invention, the helicon mode plasma composed of the first reaction gas is reacted with the second reaction gas activated by the plasma to form a film on the substrate. Therefore, since the film is formed by the high density plasma, the denseness of the film is improved, and the composition of the thermal oxide film approaches.

Since the substrate is biased by the voltage, the density and stress of the film formed on the substrate can be optimized. Especially, when the helicon mode plasma of oxygen gas and monosilane is used, the frequency is 100 kHz.
It is preferable to apply the high-frequency power and to bias the substrate with a voltage in order to improve the quality of the formed film.

Further, the plasma of the first reaction gas is moved to the downstream side to activate the second reaction gas released immediately before the substrate on which the film is formed, and the first reaction gas and the second reaction gas are activated. Is reacting. Therefore, most of the reaction products are deposited on the surface of the substrate and can be prevented from adhering to other parts of the apparatus, so that generation of particles and the like can be prevented.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a CVD film forming apparatus used in a film forming method using helicon mode plasma according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a detailed configuration of an external antenna in a CVD film forming apparatus using helicon mode plasma according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relation of a vertical magnetic field with respect to a source solenoid current in a CVD film forming apparatus using helicon mode plasma according to an embodiment of the first film forming method of the present invention.

FIG. 4 is a characteristic diagram (No. 1) for explaining deposition of a silicon oxide film by a CVD method using helicon mode plasma according to an example of the first film forming method of the present invention.

FIG. 5 is a characteristic diagram (No. 2) for explaining the deposition of the silicon oxide film by the CVD method using the helicon mode plasma according to the example of the first film forming method of the present invention.

FIG. 6 is a characteristic diagram (No. 1) for explaining the examination result of the etching rate of the silicon oxide film formed by the CVD method using the helicon mode plasma according to the example of the first film forming method of the present invention. is there.

FIG. 7 is a characteristic diagram (No. 2) for explaining the examination result of the etching rate of the silicon oxide film formed by the CVD method using the helicon mode plasma according to the example of the first film forming method of the present invention. is there.

FIG. 8 is a characteristic diagram (No. 1) for explaining the results of investigation of stress in a silicon oxide film formed by a CVD method using helicon mode plasma according to an example of the first film forming method of the present invention. .

FIG. 9 is a characteristic diagram (No. 2) for explaining the results of investigating the stress of the silicon oxide film formed by the CVD method using the helicon mode plasma according to the example of the first film forming method of the present invention. .

FIG. 10 is a characteristic diagram showing deposition of a silicon oxide film by a CVD method using helicon mode plasma according to an example of a second film forming method of the present invention.

FIG. 11 is a characteristic diagram showing a deposition rate of a silicon oxide film formed by a CVD method using helicon mode plasma according to an example of a second film forming method of the present invention.

FIG. 12 is a characteristic diagram showing the results of investigating the etching rate of a silicon oxide film formed by a CVD method using helicon mode plasma according to an example of the second film forming method of the present invention.

FIG. 13 shows the SiO peak wave number ν _SIO and the etching rate ratio of the silicon oxide film in the silicon oxide film formed by the CVD method using helicon mode plasma according to the second film forming method of the present invention. It is a characteristic view shown about an investigation result.

FIG. 14 is a characteristic diagram showing the results of investigation of the refractive index of a silicon oxide film formed by a CVD method using helicon mode plasma according to an example of the second film forming method of the present invention.

FIG. 15 is a characteristic diagram showing the results of investigation of stress in a silicon oxide film formed by a CVD method using helicon mode plasma according to an example of a second film forming method of the present invention.

FIG. 16 is a characteristic diagram showing the results of investigation of SiO peak wavenumber ν _SIO in a silicon-containing insulating film formed by a parallel plate plasma CVD method according to a comparative example.

FIG. 17 is a characteristic diagram showing the results of investigating the contents of SiOH bonds, SiH bonds and NH bonds in a silicon-containing insulating film formed by a parallel plate plasma CVD method according to a comparative example.

FIG. 18 is a characteristic diagram showing the results of investigation of the refractive index of a silicon oxide film formed by a parallel plate plasma CVD method according to a comparative example.

FIG. 19 is a characteristic diagram showing the results of investigation of the etching rate ratio of the silicon oxide film formed by the parallel plate plasma CVD method according to the comparative example.

[Explanation of symbols]

 1 plasma generation chamber, 2 external antenna, 3,13 matching network, 4,14 RF power supply, 5 inner source solenoid, 6 outer source solenoid, 7 film forming chamber, 8 first reaction gas introduction pipe, 9 second reaction Gas introduction pipe, 9a gas discharge part, 10 chamber solenoid, 11 exhaust port, 12 wafer holder, 15 wafer (substrate).

Front Page Continuation (72) Inventor Koichi Ohira 2-13-29 Konan, Minato-ku, Tokyo Semiconductor Process Laboratory Co., Ltd. (72) Inventor Yuko Nishimoto 2-13-29 Konan, Minato-ku, Tokyo Semiconductor Process Laboratory Co., Ltd.

Claims (10)

[Claims] 1. A plasma generation chamber for generating helicon mode plasma, a first reaction gas introduction pipe for introducing a first reaction gas into the plasma generation chamber, and an electromagnetic wave radiated into the plasma generation chamber to generate the plasma. An antenna provided around the plasma generation chamber for activating a first reaction gas, a source solenoid provided around the plasma generation chamber for forming a magnetic field in the plasma generation chamber, and the plasma generation A film forming chamber connected to the chamber, an exhaust port for exhausting the plasma generation chamber and the film forming chamber, a substrate holder provided in the film forming chamber for holding a substrate on which a film is to be formed, and the substrate A second reaction gas is introduced above the holder, and the second reaction gas is discharged to the substrate surface on the substrate holder.
And a reaction gas introduction pipe of 2. The film forming apparatus according to claim 1, wherein a high frequency power supply of 13.56 MHz is connected to the antenna. 3. The composition according to claim 1, wherein the second reaction gas introduction pipe has a gas discharge portion formed of a ring-shaped pipe having a plurality of gas discharge holes formed therein. Membrane device. 4. The substrate holder has a frequency of 13.56 MHz or 1
A high-frequency power source for supplying a high-frequency power of 00 kHz is connected, and the film forming apparatus according to claim 1, claim 2 or claim 3. 5. A helicon mode plasma composed of the first reaction gas is generated by radiating an electromagnetic wave to the first reaction gas and applying a magnetic field to activate the second reaction gas by the plasma. A film forming method comprising forming a film on the substrate by biasing the substrate with a voltage and reacting the plasma-converted first reaction gas with the activated second reaction gas. 6. The second reaction gas is released downstream of the plasma generation part, and the first reaction gas that has been turned into plasma is guided downstream to activate the second reaction gas. The film forming method according to claim 5, which is characterized in that. 7. The first reaction gas is oxygen gas,
7. The film forming method according to claim 5, wherein the second reaction gas is a gas containing TEOS. 8. The first reaction gas is oxygen gas,
The film forming method according to claim 5 or 6, wherein the second reaction gas is SiH ₄ gas. 9. The film forming method according to claim 5, wherein the frequency of the electromagnetic wave radiated to the first reaction gas is 13.56 MHz. 10. A high frequency power having a frequency of 13.56 MHz or 100 kHz is applied to the substrate in order to bias the substrate with a voltage. The film forming method according to claim 9.