JPH08111412A - Manufacturing for semiconductor device - Google Patents

Abstract

PURPOSE: To form a flat silicon oxide film at a relatively low temperature, by carrying out plasma discharging in a reaction chamber and growing a silicon oxide film in reaction of a silane-based gas, water vapor, and an oxidizing material. CONSTITUTION: A mixed gas of silane-based water gas, water vapor, and an oxidizing material at an adjusted flow rate is conducted into a reactive chamber 3 from a gas supply system A, and plasma is discharged while power from a high-frequency power supply 8 is applied across a gas feeding board 5 and a substrate mounting stage 4. In this case, water vapor with good fluidity almost equal to a liquid phase is applied to a surface of a substrate and reacted with the silane-based gas to grow an oxide film. An intermediate product of oxide film formed on the surface is well fluidized, the oxide film is grown more at a recessed part than a projected part, so a flat oxide film can be formed. After all, a flat oxide film is formed at a lower temperature.

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 a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a step of forming an insulating film by a plasma CVD method.

[0002]

2. Description of the Related Art As a method of forming an insulating film indispensable for manufacturing a semiconductor device, there are, for example, a thermal CVD method and a plasma CVD method. The thermal CVD method has good film productivity and can grow an insulating film flat regardless of the surface shape of the base. However, since the thermal CVD method generally requires a high temperature of 700 ° C. or higher when forming a film,
For example, it is not suitable for use when growing an interlayer insulating film having a multilayer wiring structure having an aluminum wiring layer having a low melting point.

On the other hand, in the plasma CVD method, the plasma is introduced into the reaction chamber under normal pressure or reduced pressure to activate the reaction gas to grow the film, so that the film can be grown at a relatively low temperature and the layer having a low melting point as the base layer. Does not cause damage even if present.

[0004]

However, when the insulating film is grown by the plasma CVD method, the flatness of the grown insulating film is poor. For example, as shown in FIG. 3, an interlayer insulating film 15 covering the aluminum wiring 13 is formed on the silicon dioxide oxide film 12 on the surface of the Si substrate 11 while the aluminum wiring 13 is formed in a convex shape at intervals. It is formed by plasma CVD. According to this, since the interlayer insulating film 15 grows almost uniformly along the surfaces of the aluminum wiring 13 and the insulating film 12, the surface of the interlayer insulating film 15 is uneven.

When an interconnection layer is to be further formed on such an interlayer insulating film 15, the interlayer insulating film 1
Due to the unevenness of No. 5, the wiring formed on the insulating film is broken, or the exposure focus at the time of photolithography is blurred, and the patterning accuracy of the wiring is deteriorated to hinder high-density wiring. It was On the other hand, when the plasma power is reduced to increase the amount of silanol produced, the flatness of the interlayer insulating film 15 is improved to some extent, but the growth rate of the silicon oxide film is reduced and the growth rate is reduced. Occurs.

The present invention has been made in view of the above problems, and an object thereof is to provide a method of manufacturing a semiconductor device for forming silicon oxide flat at a relatively low temperature.

[0007]

[Means for Solving the Problems]
2, a step of introducing at least one of an oxidant and an acid, a silane-based gas and steam into the reaction chamber, and a plasma discharge in the reaction chamber to react the silane-based gas, the steam and the oxidant with each other. And a step of growing a silicon oxide film by the method of manufacturing a semiconductor device.

Alternatively, the method of manufacturing a semiconductor device is characterized in that the flow rate of the water vapor when being introduced into the reaction chamber is 10 times or more the flow rate of the silane-based gas. Alternatively, the oxidant is any one of hydrogen peroxide, nitric acid, and ammonium hydroxide, which is solved by a method for manufacturing a semiconductor device.

Alternatively, the acid is any one of nitric acid, hydrochloric acid and sulfuric acid, which is solved by a method for manufacturing a semiconductor device. Alternatively, it is solved by a method for manufacturing a semiconductor device, which is characterized in that a halogen-based gas is introduced into the reaction chamber. Alternatively, at least the introduction of the silane-based gas and the water vapor into the reaction chamber and the plasma discharge corresponding thereto are intermittently performed to grow the insulating film in a stepwise manner. To solve.

Alternatively, the problem can be solved by a method for manufacturing a semiconductor device, wherein the pressure in the reaction chamber during the plasma discharge is 10 Torr or more.

[0011]

[Operation] According to the present invention, a silane-based gas, water vapor and an oxidant are introduced into the reaction chamber in a gas state, and plasma discharge is performed in the reaction chamber to grow an insulating film on the substrate surface. It adheres to the surface in a state of high fluidity, which is almost like a liquid phase, and the steam and the silane-based gas in a state close to the liquid phase react with each other to grow an oxide film. At this time, the oxidant promotes the oxidation to accelerate the deposition rate, and the oxide film is formed by the plasma discharge with low excitation energy, so that the production of silanol having high fluidity is promoted. Therefore, since the intermediate product of the oxide film that grows on the surface of the substrate easily flows on the surface of the substrate, the oxide film grows more in the concave portions than in the convex portions on the substrate surface and becomes flat. in this case,
An acid may be used instead of the oxidizing agent, or an acid may be added to the oxidizing agent. This is because the acid acts as a catalyst for oxidation and promotes the oxidation.

Further, by making the flow rate of the water vapor including the oxidizing agent introduced into the reaction chamber 10 times or more the flow rate of the silane-based gas, the water vapor in the vicinity of the substrate surface becomes closer to the liquid phase and the oxide film The fluidity of the intermediate product is increased, and the flattening is promoted. Further, by setting the pressure in the reaction chamber at the time of plasma discharge to 10 Torr or more, the excitation energy in the reaction chamber becomes low and a weak excitation state is obtained, so that the production of silanol is promoted and the oxide film is flattened.

Furthermore, by introducing silane-based gas, water vapor, and halogen-based gas into the reaction chamber and performing plasma discharge, the halogen-based gas reacts with the silane-based gas and water vapor, and hydrofluoric acid, which is an etchant for the oxide film. Is generated. Since this hydrofluoric acid etches the convex portions of the growing oxide film, the surface of the oxide film is flattened. Further, by intermittently repeating at least introduction of silane-based gas, water vapor and oxidant and plasma discharge, water vapor in a state close to a liquid phase is always present on the surface on which the oxide film grows, and the oxide film is formed. The rate of fluid growth increases and the oxide film becomes flat.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a plasma C used for carrying out a method of manufacturing a semiconductor device according to a first embodiment of the present invention.
1 schematically shows a VD device and its gas supply system.

The plasma CVD apparatus 1 shown in FIG. 1 includes a chamber 2, a substrate mounting table 4 arranged in a reaction chamber 3 in the chamber 2, and a gas supply board 5 arranged so as to face the substrate mounting table 4. Have The substrate mounting table 4 is grounded, a Si substrate 6 on which a film is deposited is mounted on the substrate mounting table 4, and a heater 7 for heating the silicon (Si) substrate 6 is incorporated therein. . Since the gas supply board 5 also serves as gas supply, it has a hollow interior and has a number of small holes formed in the lower surface, and is configured to inject gas supplied from outside from the many holes in a shower shape. There is.

The gas supply board 5 also serves as a discharge electrode, and a high frequency power source 8 is connected thereto. Further, the chamber 2 is provided with an exhaust port 2a. Gas necessary for forming a silicon oxide film is supplied to the gas supply board 5 of the plasma CVD apparatus 1 from a gas supply system A surrounded by a broken line in FIG. A first gas cylinder 21, a first constant temperature tank 22, a second constant temperature tank 23, and a second gas cylinder 24 are provided as a reaction gas supplier for forming a silicon oxide film. Water (H ₂ O
) Is stored, and hydrogen peroxide solution (H
It contains an oxidizer such as ₂ O ₂ ). A silane-based gas such as silane (SiH ₄ ) is stored in the first gas cylinder, and a halogen-based gas such as fluorine (F ₂ ) is stored in the second gas cylinder 24.

The amount of vaporization of the liquid in the first and second constant temperature baths 22 and 23 may be adjusted by bubbling. The solution stored in each of the first constant temperature tank 22 and the second constant temperature tank 23 becomes vapor by heating, and the gas pipe 2
The gas is supplied into the gas supply board 5 through 6a and 26b. These flow rates are determined by the mass flow controllers 25a and 25b.
Adjusted by The temperatures of the first constant temperature bath 22 and the second constant temperature bath 23 are adjusted by a controller (not shown).

Further, the first and second gas cylinders 21 and 2
The gas in 4 is supplied to the gas supply board 5 through the gas pipes 26c and 26d, respectively, and the flow rates thereof are adjusted by the mass flow controllers 25c and 25d. Next, the step of growing a silicon oxide film as an insulating film using the plasma CVD apparatus described above will be specifically described.

A gas whose flow rate is appropriately controlled is introduced from the gas supply system A into the reaction chamber 3, and the power of the high frequency power source 8 is supplied between the gas supply plate 5 and the substrate mounting table 4, and plasma is supplied between them. Is generated, whereby SiO ₂ is grown on the Si substrate 6. 2A and 2B show Si on a Si substrate 6 placed on a substrate mounting table 4 in a reaction chamber 3 of a plasma CVD apparatus.
The process of growing O ₂ is shown.

In the initial state, as shown in FIG. 2 (a),
A first insulating film 12 made of silicon oxide is formed on a Si semiconductor substrate 11, and a plurality of wirings 13 made of aluminum are further formed on the first insulating film 12. The wirings 13 form a wiring on the first insulating film 12. There are irregularities. In the gas supply system, water heated to 40 to 70 ° C. is stored in the first constant temperature tank 22, and 4 to 80 is stored in the second constant temperature tank 23.
Hydrogen peroxide solution kept at ℃ is stored, SiH ₄ is sealed in the first gas cylinder, and fluorine is sealed in the second gas cylinder. Further, the gas pipes 26a to 26d are 30
The temperature is kept above ℃.

Then, the mass flow controllers 25a-
By adjusting 25d, silane gas, water vapor, hydrogen peroxide gas, and fluorine gas are supplied into the reaction chamber 3 through the gas supply plate 5 and turned into plasma. At this time, the ratio of the flow rates of supplying the silane gas and the steam is important, and the flow rate of the steam is preferably 10 times or more the flow rate of the silane gas.
Specifically, the flow rate of water vapor was 200 sccm for 10 sccm of silane gas.

The flow rate of the fluorine gas is preferably higher than the flow rate of the silane gas and lower than the flow rate of the water vapor, and here it is set to 30 sccm. The flow rate of the hydrogen peroxide solution is 15 sccm, and it is desirable that the flow rate is more than half the flow rate of the silane gas. These silane, water vapor, hydrogen peroxide gas and fluorine gas are mixed at once and introduced into the reaction chamber 3 from the gas supply board 5, and plasma discharge is performed. When the excitation energy of plasma discharge is large, the amount of silanol produced is small, and the flatness of the insulating film is impaired. One of the methods for reducing the excitation energy is to reduce the power of the high frequency power source 8, and
00W is preferable, and in this embodiment, 100W
It was discharged continuously.

By this plasma discharge, silane gas and water vapor react to generate silicon oxide. At this time,
By introducing a large amount of water vapor into the reaction chamber at the same time as the silane gas, as shown in FIG. 2 (a), a large amount of water vapor adheres to the surfaces of the insulating film 12 and the wiring 13 and becomes a state close to a liquid phase. Moreover, hydrogen peroxide, which is an oxidant, is dissolved in it.

As a result, a large amount of silanol is generated under the low plasma excitation, and the first insulating film 1 is caused by its fluidity.
2 and the silicon oxide film formed on the wiring 13 are planarized. In this case, oxidation is promoted by hydrogen peroxide, and the growth rate of silicon oxide is maintained at 1000 Å / min even under low plasma excitation and is not reduced. In addition, the reaction of SiH ₄ with water vapor and hydrogen peroxide solution on the surfaces of the first insulation film 12 and the wiring 13 is closer to the liquid phase than the gas phase due to the water vapor supplied onto the first insulation film 12. And the migration of surface molecules is promoted. As described above, since the fluidity of the reactive molecules is high on the first insulating film 12, the grown silicon oxide film has a recessed portion between the electrodes 13 on the substrate surface, as shown in FIG. 2 (b). Thick on the electrode 13
The convex portion formed with is grown thin and becomes flat, and the growth rate does not decrease. The reaction in this case is as shown in equation (1).

2SiH ₄ + 2H ₂ O + H ₂ O ₂ → 2SiO ₂ + 7H ₂ (1) It should be noted that silanol is a combination of silicon and a hydroxyl group generated in the process of forming a silicon oxide film, and is a fluid. It has a sex. On the other hand, fluorine gas reacts as in the following formula (2) to generate hydrofluoric acid. SiH ₄ + F ₂ + 2H ₂ O → SiO ₂ + 2HF + 3H ₂ (2) This hydrofluoric acid serves as an etchant for silicon oxide and etches the protrusions of the grown silicon oxide.
The surface of the oxide film is flattened.

In the reactions of the above reaction formulas (1) and (2), the ratio thereof changes depending on the amount of the fluorine gas added, and if the amount of the fluorine gas added is too large, the amount of hydrofluoric acid becomes large, resulting in etching. Occurs violently, which hinders the growth of the oxide film. Therefore, the amount of fluorine added must be set to an appropriate amount. Further, the added fluorine gas is combined with silicon and taken into silicon oxide to lower the dielectric constant of silicon oxide, which also has the effect of reducing the parasitic capacitance of the semiconductor device. Since halogen such as chlorine and bromine, or a compound thereof, or a fluorine compound serves as an etching gas for silicon oxide, the gas may be used instead of fluorine.

In order to reduce the plasma excitation energy, in addition to reducing the amount of power from the high frequency power source 8, there is also a method of increasing the pressure in the reaction chamber 3 to reduce the kinetic distance of electrons in the plasma. However, there is also a method of increasing the flow rate of the reaction gas to shorten the time of exposure to plasma, which can accelerate the production of silanol.

The flatness of the silicon oxide film 14 grown under the above conditions is greatly improved as shown in FIG. 2 (b). Therefore, even if a wiring is further formed on the silicon oxide film 14, the upper surface of the silicon oxide film is substantially flat, so that the patterning accuracy of the wiring becomes high and the disconnection of the wiring can be avoided. (Other Examples) In the first example, an oxide film was grown by adding both hydrogen peroxide gas and fluorine gas to silane gas and water vapor, but flattening and growth rate increase were achieved with hydrogen peroxide alone. It is possible.

In the first embodiment, silane is used as the silane-based gas, but disilane, trisilane or the like can be used to obtain the same effect. Further, nitric acid or ammonium hydroxide may be used instead of the oxidizing agent, or nitric acid, sulfuric acid, hydrochloric acid or the like may be added to the oxidizing agent. These acids act as a catalyst during the growth of the oxide film to accelerate the oxidation and increase the growth rate of silicon oxide.

In addition to the above, examples of combinations of water vapor, oxidizing agent and acid include ammonium hydroxide, hydrogen peroxide and water vapor, or sulfuric acid, hydrogen peroxide solution and water vapor. Further, in the first embodiment, the plasma discharge was continuously performed, but the supply of water vapor and oxidant, the supply of silane, and the plasma discharge are sequentially repeated, or the water vapor,
The plasma excitation energy may be substantially reduced by alternately supplying the reaction gas such as silane and the plasma discharge.

[0031]

As described above, according to the present invention, since an oxide film is grown by plasma discharge from, for example, silane gas vapor and hydrogen peroxide gas, a high quality oxidation can be performed by a plasma CVD method at a relatively low temperature. The film can be planarized and formed. Further, by introducing fluorine gas or the like together with water vapor, the oxide film surface is etched, and the oxide film surface is further flattened.

Further, by making the flow rate of the steam introduced into the reaction chamber 10 times or more the flow rate of the silane gas, the steam in the vicinity of the substrate surface becomes closer to the liquid phase and the oxide film is fluidized. , The surface of the oxide film is further flattened. The pressure in the reaction chamber during plasma discharge is 10
By setting it to Torr or more, the oxide film can be grown in a weakly excited state, and the oxide film is further flattened.

By introducing gas into the reaction chamber and performing plasma discharge intermittently, an oxide film having a flatter surface can be formed.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a plasma CVD apparatus for carrying out a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the method of manufacturing the semiconductor device according to the embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a semiconductor device having an oxide film formed by a conventional plasma CVD method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma CVD apparatus 2 Chamber 3 Reaction chamber 4 Substrate mounting table 5 Gas supply board 6 Si substrate 7 Heater 8 High frequency power supply 9 High frequency power supply device 11 Si substrate 12 Insulation layer 13 Electrode station 14, 15 Interlayer insulation film 21 Silane gas 22 Water 23 Halogen-based gas 24 Hydrogen peroxide 25 Mass flow controller 26 Gas pipe A Gas supply system

Claims (7)

[Claims] 1. A step of introducing at least one of an oxidant and an acid, a silane-based gas and water vapor into a reaction chamber, and performing plasma discharge in the reaction chamber to oxidize by a reaction of the silane-based gas, the water vapor and the oxidant. And a step of growing a silicon film. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the flow rate of the water vapor when being introduced into the reaction chamber is 10 times or more the flow rate of the silane-based gas. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the oxidizing agent is any one of hydrogen peroxide, nitric acid, and ammonium hydroxide. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the acid is any one of nitric acid, hydrochloric acid and sulfuric acid. 5. The method of manufacturing a semiconductor device according to claim 1, wherein a halogen-based gas is introduced into the reaction chamber. 6. The insulating film is grown stepwise by introducing at least the silane-based gas and the water vapor into the reaction chamber and corresponding plasma discharge intermittently. 1. The method for manufacturing a semiconductor device according to 1. 7. The pressure in the reaction chamber during the plasma discharge is 10 Torr or more.
A method of manufacturing a semiconductor device according to item 1.