JP3094688B2 - Manufacturing method of insulating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an insulating film typified by an interlayer insulating film or a surface protective film in a semiconductor integrated device, and more particularly, to a method for providing a microwave transmission window on one end face and generating plasma. The electron cyclotron resonance of a cylindrical plasma generation chamber into which the application gas is introduced, and microwaves arranged coaxially with the plasma generation chamber outside the plasma generation chamber and introduced through the micro transmission window into the plasma generation chamber. A main coil for forming a magnetic field region to be generated, a reaction chamber in which a substrate on which a film is to be formed is placed in communication with a plasma generation chamber on the side facing the microwave transmission window and a reactive gas is introduced, An electron cyclotron resonance plate including a high-frequency power supply for supplying power and an auxiliary coil disposed coaxially with the main coil on the back side of the substrate on which the film is to be formed. CVD apparatus (hereinafter ECR plasma C
VD apparatus), O ₂ is used as a plasma generation gas to be introduced into the plasma generation chamber, and SiH ₄ is used as a reactive gas to be introduced into the reaction chamber.
_{(2) The present} invention relates to an insulating film manufacturing method for forming an insulating film.

[0002]

2. Description of the Related Art Generally, as an interlayer insulating film or a surface protective film of a semiconductor integrated circuit, gas molecules are excited by a thermal CVD method using thermal energy to excite gas molecules as a raw material of the insulating film or a plasma discharge by a high frequency voltage. An oxide film, a nitride film, or the like formed by a high-frequency plasma CVD method is used. However, in recent years, the integration and density of semiconductor devices have been advanced, and as the structural dimensions such as wiring intervals and wiring widths have shifted to the submicron region, higher quality insulating films have been required, Various methods other than the above-described film forming method have been tried. As one of them, an ECR plasma CVD method capable of forming an insulating film having excellent acid resistance and denseness has been developed.

[0003]

SUMMARY OF THE INVENTION Among the above film forming methods,
Since the high-frequency plasma CVD method raises the film forming temperature to about 350 ° C., the thermal stress damage to electrodes, wirings, etc. (particularly aluminum wirings) formed on the substrate is large, which is a factor to shorten the life of the device. Was. Also, ECR
When the film formation temperature is set to a room temperature to 150 ° C. using a plasma CVD method, the problem of thermal stress damage is eliminated,
Since the fluctuation between the film stress before the annealing after the film formation and the film stress after the annealing is large, there is a problem of causing damage due to the stress and a problem of lack of water permeability.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide an insulating film manufacturing method capable of manufacturing a high-quality insulating film having high water resistance and no damage to electrodes and wiring due to thermal stress damage and stress fluctuation before and after annealing.

[0005]

In order to solve the above-mentioned problems, as an SiO ₂ insulating film manufacturing method using an insulating film manufacturing apparatus having the configuration described at the outset and a raw material gas, a method of forming an SiO ₂ insulating film using a main coil and an auxiliary coil is described. The magnetic field is a mirror magnetic field, and after depositing the film-forming substrate at a position within ± 20 mm in the axial direction from the axial position of the cross section where the magnetic flux density in the cross section perpendicular to the central axis of the mirror magnetic field is minimum, It is assumed that a method for manufacturing an insulating film that enters a film forming process is employed.

Further , the axial position of the cross section perpendicular to the central axis of the mirror magnetic field, at which the magnetic flux density is minimized, is 350 to 400 mm from the position on the central axis of the electron cyclotron resonance magnetic field region formed by the main coil. you with controlling the main coil current and or auxiliary coil current to lie within the range of. After the start of the film formation process, the substrate is placed on a stage formed so as to be capable of heating and cooling, the substrate temperature during film formation is kept within the range of 200 to 300 ° C., and the gas flow ratio is set to SiH ₄ / O. ₂ = 0.72-0.9
2. Film formation at a gas pressure of 1 × 10 ^{-4 to} 5 × 10 ^-3 Torr, a microwave power of 200 to 1200 W, and a high frequency power of 2.0 to 4.0 W / cm ² per unit area of the substrate on which the film is to be formed. I do.

In this case, it is preferable that the film is formed by setting the ratio between the microwave power and the flow rate of the SiH ₄ gas to 1 to 2 cc / s / 200 W. When the substrate temperature is 200
Before entering the film forming process held in the range of 300 ° C. to 300 ° C., the substrate is irradiated with O ₂ plasma generated in the plasma generation chamber as a pretreatment heating step of the substrate, thereby reducing the initial temperature due to the heating of the substrate stage. It is preferable to increase the substrate temperature within the range of 200 to 300 ° C.

Further, by controlling the microwave power and the main coil current, the plasma density in the plasma generation chamber is reduced to 1 × 10 ¹¹
It is more preferable that the film is formed at a thickness of about 1 × 10 ¹² cm ⁻³ .

[0009]

According to a method of manufacturing an SiO ₂ insulating film, a magnetic field formed by a main coil and an auxiliary coil is used as a mirror magnetic field,
Insulating film production which starts the film forming process after arranging the film forming substrate at a position within ± 20 mm in the axial direction from the axial position of the cross section where the magnetic flux density in the cross section perpendicular to the center axis of the mirror magnetic field is minimum. According to the method, the axial position of the cross section where the magnetic flux density in the cross section perpendicular to the central axis of the magnetic field is minimum is the position where the magnetic flux passing inside the main coil and the auxiliary coil expands to the maximum, The position where the magnetic flux density distribution has the highest uniformity compared to other positions on the central axis, and the plasma generated in the plasma generation chamber moves along the lines of magnetic force. At a position of ± 20 mm or less, the plasma density distribution becomes substantially uniform, the film thickness distribution becomes uniform, and a film having a uniform film characteristic distribution such as intra-film stress and water resistance can be obtained. Therefore, residual stress after film formation and stress fluctuation due to annealing are not locally concentrated on the substrate, and wiring and the like are less likely to be damaged.
Further, even if the magnetic flux density at the above position is minimum in the mirror magnetic field, the magnetic flux density due to the divergent magnetic field generated only by the main coil is larger than the magnetic flux density at the substrate position, so the plasma density at the substrate position is large, A denser film is formed, and as a result, a dense film in which stress damage to wiring and the like does not easily occur is formed.

If the position of the minimum magnetic flux density is 350 to 400 mm from the position on the central axis of the ECR magnetic field region,
This position is sufficiently away from the dome-shaped ECR magnetic field region from the substrate-side end surface of the main coil to the inside of the main coil, and is set by placing the substrate near the minimum magnetic flux density position in the mirror magnetic field. The effect of uniform film characteristics
A film can be formed without loss .

Low temperature film formation by ECR plasma CVD
In case, SiH_FourAnd O_TwoH generated during the reaction with_TwoO and H
_TwoAre taken into the film at a certain rate. others
Therefore, when the film is formed at a low temperature, the generated gas is mixed with the film composition in the film.
And Si-H, O-H or H _TwoCaptured in the form of O
Have been. This has an adverse effect on membrane stress and water resistance.
As a result, a film quality that lacks stress fluctuation and water resistance is obtained. There
During the film formation, the substrate temperature is maintained at 200 to 300 ° C.
And the H on the substrate_TwoO molecules gain thermal energy and separate
The amount that is removed and taken into the membrane decreases, and the water resistance of the membrane is improved.
Up.

Further, the gas flow ratio is set to SiH ₄ / O ₂ = 0.
If it is 85 to 0.92, the refractive index is 1.46 to 1.50.
And a proper composition ratio of Si and O can be obtained. When the gas flow ratio is out of the range, for example, if the flow ratio is 0.85 or less, the film becomes an oxygen-excessive film, and if the gas flow ratio is 0.92 or more, the film becomes a silicon-excessive film. On the other hand, the gas flow ratio is set to 0.72-0.
If it is set to 95, Si-H and O-H fall within a range in which damage due to stress fluctuation during annealing can be avoided. Therefore, by setting the gas flow ratio to 0.72 to 0.95,
In practice, a film that is satisfactory in both stress and water resistance can be obtained.

By increasing the microwave power to 200 W or more, the plasma density can be increased, and the activation of the reactive gas can be enhanced by increasing the decomposition efficiency of the reactive gas. It is formed. In addition, when increasing the microwave power, it is necessary to supply a reactive gas corresponding to this power, but there is an optimum power required for the reaction. Efficiency and response are better.

Before the film formation process in which the substrate temperature is kept in the range of 200 to 300 ° C., the substrate is irradiated with O ₂ plasma generated in a plasma generation chamber as a pretreatment and heating step of the substrate. By increasing the substrate temperature within a range of 200 to 300 ° C. from the initial temperature due to the heating of the substrate stage, a substance having a relatively low boiling point can be used as a heat medium, and the heating system can be easily formed. become.

Further, by controlling the microwave power and the main coil current, the plasma density of the plasma generation chamber is set to 1 × 10 ¹¹ to
By increasing the plasma density to 1 × 10 ¹² cm ⁻³ , the decomposition efficiency of the reactive gas is increased, the reaction is activated, and a high-quality film is formed. In this case, the control of the microwave power and the main coil current includes controlling the magnitude of the microwave power, controlling the relative position of the ECR magnetic field region with respect to the microwave electric field by controlling the magnitude of the main coil current, and controlling the microwave. There is control of how to output the power. For example, it is also possible to increase the absolute value of the output by outputting microwave power in a pulse form to increase the plasma density. In this case, of course, the high-frequency power is also pulsed in accordance with the method of outputting the microwave power, synchronized with the microwave power, and the plasma generated by the microwave is efficiently driven into the substrate to provide a good film quality. You will get

[0016]

FIG. 1 shows an outline of an ECR plasma CVD apparatus to which the present invention is applied. A waveguide 1 for transmitting microwaves from a microwave source (not shown) to the plasma generation chamber 5 is connected to the plasma generation chamber 5 having the microwave transmission chamber 2 on one end surface. A main coil 4 is arranged outside of 5 coaxially with the plasma generation chamber 5. A reaction chamber 6 in which a substrate 9 is placed is connected to a side of the plasma generation chamber 5 facing the microwave transmission window 2 through a plasma extraction window 5a.
The substrate 9 is mounted on a sample stage 10, and a high frequency power source, a so-called RF power source 12 is connected to the sample stage 10 via a capacitor 13.
Is connected. On the back side of the substrate 9, an auxiliary coil 11 is provided coaxially with the main coil 4.

To form a thin film on the substrate 9, the main coil 4
And a magnetic field of 875 gauss is formed in the plasma generation chamber 5 to introduce O ₂ gas from the first gas introduction system 3, and a microwave having a frequency of 2.45 GHz is transmitted through the microwave transmission window. Plasma generation chamber 5 through 2
When introduced into the O ₂ gas, the O ₂ gas resonates and absorbs microwave energy in a magnetic field region of 875 gauss, and becomes a high-density plasma. The O ₂ plasma is generated by the main coil 4 and the auxiliary coil 1
1 is drawn out into the reaction chamber 6 along the magnetic field lines of the mirror magnetic field formed by the mirror 1. At this time, when the SiH ₄ gas is introduced from the second gas introduction system 7, the SiH ₄ gas is decomposed by the energy of the O ₂ plasma, and an SiO ₂ film is formed on the surface of the substrate 9 placed on the sample stage 10. .

A mirror magnetic field formed by the main coil 4 and the auxiliary coil 11 is formed between both coils as shown in FIG. The divergent magnetic field formed by the main coil 4 is converged by the magnetic field formed in the same direction as the main coil 4 by the auxiliary coil 11. It is formed. As shown in the figure, this magnetic flux has the minimum magnetic flux density at the center, but has the most uniform magnetic flux density distribution, and the magnetic flux density distribution is substantially uniform within a range of ± 20 mm in the axial direction from this position. Accordingly, the density distribution of the plasma moving along the lines of magnetic force also becomes uniform at the substrate position, and the film thickness distribution of the thin film formed on the substrate 9 and the film characteristic distribution such as film stress and water resistance become uniform. Then, the current of the main coil 4 and / or the auxiliary coil 11 is adjusted so that the position where the magnetic flux density is minimum is E.
If the ECR magnetic field region is located within a range of 350 to 40 mm from the position on the central axis of the CR magnetic field region, the ECR magnetic field region is considerably separated from the substrate position. A thin film can be formed without deteriorating the uniformity of film characteristics.

Further, in this apparatus, piping for heating and cooling is provided so that the substrate temperature can be controlled, a fluorocarbon-based substance (boiling point: 174 ° C.) is used as a heat medium, and this substance is heated to about 170 ° C. in the heating system. And transported to the heat exchange holder 17 (FIG. 1) to heat the electrostatic chuck forming the sample stage 10. At this time, the temperature of the electrostatic chuck becomes 150 ° C., and the substrate temperature at the start of film formation also becomes 150 ° C. After reaching this initial temperature, O generated in the plasma generation chamber 5
_{2 The} substrate 9 is irradiated with plasma, and the substrate 9 is further heated by the plasma irradiation. When the substrate 9 reaches a predetermined temperature range, a cooling system is activated to keep the substrate temperature within the predetermined range. SiH ₄ gas is introduced into the inside. Table 1 shows the film forming conditions when a SiO ₂ film was formed on the substrate 9 using the apparatus shown in FIG.

[0020]

[Table 1] The film characteristics obtained from Table 1 are shown in FIGS. 3 and 4 show that the film stress, the refractive index, the film formation rate and the film thickness distribution depend on the microwave power and the RF power at a gas flow ratio of SiH ₄ / O ₂ = 0.9, respectively. An example of the results obtained by measuring the properties under various conditions other than the gas flow rate ratio is shown. FIG. 5 shows the gas flow ratio dependence of the film stress after film formation and before and after annealing. FIG. 6 shows a comparison between the water permeability of the SiO ₂ film (P-SiO film) by the RF plasma CVD method and the water permeability of the SiO ₂ film (ECR-SiO film) by the ECR plasma CVD method. In the water resistance test, a PSG film (phosphorized glass film) was formed on a substrate as an evaluation film, and this was placed in an atmosphere at a temperature of 120 ° C., a humidity of 100%, and a pressure (gauge) of 1 atm. This shows the time change of the area of (oxygen double bond), and it can be seen that the water resistance of the ECR-SiO film is remarkably superior to that of the P-SiO film. Then, by combining each item within the setting range of each item in Table 1, as a film characteristic, a film formation rate ≧
At 850 ° / min, a film having a forward taper, that is, a film having a thicker side wall from the top surface to the bottom surface of the uneven portion of the substrate surface is formed, and the residual stress after film formation is also -1.0 × 10 ⁹ dyne /
A film having a low trace of less than ² cm ² is obtained, and the amount of change in film stress due to heat treatment after film formation is also 0.5 × 10 ⁹ dyne / cm ^2.
The results below show that stress damage to wiring and the like is reduced and that a film having excellent water resistance can be obtained.

[0021]

As described above, according to the insulating film manufacturing method of the present invention, the magnetic field formed by the main coil and the auxiliary coil is used as the mirror magnetic field, and the magnetic field formed in the cross section perpendicular to the central axis of the mirror magnetic field. After the substrate is placed at a position within ± 20 mm in the axial direction from the axial position of the cross-section where the magnetic flux density of the cross-section becomes minimum, the film-forming process is started. Performed in a region with uniform density, it is possible to obtain a film with uniform film characteristics such as film thickness distribution, stress, and water permeability. Residual stress after film formation and stress fluctuation due to annealing are localized on the substrate. It is possible to obtain a film that is not concentrated and hardly causes stress damage such as wiring.

The position where the magnetic flux density distribution is uniform is defined as E
Since it is formed at a distance of 350 to 400 mm from the position on the axis of the CR magnetic field region, the effect of making the plasma density non-uniformity of the ECR magnetic field region which usually has a dome shape does not reach, and the uniformity of film characteristics is maintained. Has become possible. Therefore, by forming a film by combining each item within the setting range of each item under the film forming conditions described in claim 2 , a film having small residual stress and small stress fluctuation due to annealing can be obtained. A film with excellent properties has been obtained.

Further, since the ratio between the microwave power and the flow rate of the SiH ₄ gas is set to 1 to 2 cc / s / 200 W, the film is formed with high reaction efficiency, and a high quality film can be obtained. further,
Since the initial temperature is relatively low and the temperature is increased by plasma irradiation in order to raise the substrate temperature to 200 to 300 ° C., the configuration of the heating system is simplified, and the cost of the apparatus is reduced slightly. .

Further, when the film is formed under the conditions described in claim 2, the film is formed at a high density of 1 × 10 ¹¹ to 1 × 10 ¹² cm ^-3 , so that the efficiency of decomposition of the reactive gas is increased. , The reaction is activated, a high quality film is obtained, and the life of the semiconductor device can be extended.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an insulating film manufacturing apparatus configuration to which the present invention is directed.

FIG. 2 is an explanatory view showing the shape of a mirror magnetic field formed according to the method of manufacturing an insulating film of the present invention and the position of a substrate in the mirror magnetic field.

FIG. 3 shows a microwave power showing an example of a microwave power dependency of a film stress, a refractive index, a film forming speed, and a film thickness distribution when a film is formed according to film forming conditions in the insulating film manufacturing method of the present invention. Characteristic diagram

FIG. 4 is an RF power characteristic diagram showing an example of the RF power dependence of a film stress, a refractive index, a film forming speed, and a film thickness distribution when a film is formed according to the film forming conditions in the insulating film manufacturing method of the present invention.

FIG. 5 is a gas flow ratio characteristic diagram of film stress showing the dependence of film stress on gas flow ratio after film formation and before and after annealing when the film is formed according to the film forming conditions in the insulating film manufacturing method of the present invention.

FIG. 6 is a water resistance characteristic diagram showing a comparison of water resistance between an insulating film manufactured by an insulating film manufacturing apparatus to which the present invention is applied and an insulating film manufactured by an RF plasma CVD method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waveguide 2 Microwave transmission window 3 1st gas introduction system 4 Main coil 5 Plasma generation room 6 Reaction room 7 2nd gas introduction system 9 Substrate 10 Sample stand 11 Auxiliary coil 12 RF power supply (high frequency power supply) 14 Heater 15 Cooler 17 Heat exchange holder

Claims (5)

(57) [Claims] 1. A cylindrical plasma generation chamber having a microwave transmission window on one end face and into which a plasma generation gas is introduced, and a plasma disposed outside the plasma generation chamber and coaxial with the plasma generation chamber. A main coil that forms a magnetic field region that generates electron cyclotron resonance with microwaves introduced through the microwave transmission window into the generation chamber, and a substrate on which the film is to be formed are placed in communication with the plasma generation chamber on the side facing the microwave transmission window. A reaction chamber into which a reactive gas is introduced and a high-frequency power supply for supplying high-frequency power to a substrate on which a film is to be formed;
An electron cyclotron resonance plasma C comprising a main coil and an auxiliary coil disposed coaxially on the back side of the substrate on which the film is to be formed.
With VD device, the O ₂ as the plasma generation gas introduced into the plasma generation chamber, the insulating film manufacture to form an SiO ₂ insulating film on the target substrate surface using SiH ₄ as a reactive gas to be introduced into the reaction chamber In the method, a magnetic field formed by the main coil and the auxiliary coil is a mirror magnetic field, and is within ± 20 mm in an axial direction from an axial position of the cross section where a magnetic flux density in a cross section perpendicular to a central axis of the mirror magnetic field is minimum. with placing a deposition target substrate to a position of the magnetic flux density in the perpendicular cross section to the central axis of the mirror magnetic field minimum
The position of the cross section in the axial direction is determined by the electronic sensor formed by the main coil.
350 from the center axis of the cyclotron resonance magnetic field region
Main coil current and
And / or controlling an auxiliary coil current . 2. A method according to claim 1, wherein the stage on which the substrate on which the film is to be formed is placed is formed so as to be capable of being heated and cooled, and the substrate temperature during the film formation is kept in the range of 200 to 300 ° C. And the gas flow rate ratio was set to SiH ₄ / O ₂ = 0.72-
0.92, gas pressure 1 × 10 ^{-4 to} 5 × 10 ^-3 Torr
r, microwave power of 200 to 1200 W and high frequency power of 2.0 to 4.0 W / cm ² per unit area of the substrate on which the film is to be formed.
A method of manufacturing an insulating film. 3. The method according to claim 2 , wherein the ratio between the microwave power and the flow rate of the SiH ₄ gas is 1 to 2 cc /.
s / 200W, a method for manufacturing an insulating film. 4. The method according to the second claims, prior to entering the deposition process holding the substrate temperature within the range of 200 to 300 [° C., as a pretreatment pressurized thermal process of the substrate, in the plasma generating chamber By irradiating the substrate with the generated O ₂ plasma, the temperature from the initial temperature by heating the substrate stage to 200 to
A method of manufacturing an insulating film, wherein the temperature of a substrate is increased within a range of 300 ° C. 5. The method according to claim 2 , wherein the microwave power and the main coil current are controlled to make the plasma density in the plasma generation chamber 1 × 10 ¹¹ to 1 × 10 ¹² cm ^-3. A method for manufacturing an insulating film, comprising: