JP3235095B2 - Method of forming silicon oxide 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 of forming a silicon oxide film by a plasma CVD method, and more particularly, to a method of forming a silicon oxide film having a good uniformity of film thickness in a wafer surface by a plasma CVD method. How to do it.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, conventionally,
The formation of a silicon oxide film by a plasma CVD method is frequently used. For example, in the wiring structure of a semiconductor integrated circuit,
As shown in FIG. 1, a wiring (hereinafter abbreviated as Al wiring) 2 (a) and aluminum wiring (b) made of aluminum or an aluminum alloy and between the Al wiring 4 or the Al wiring 2
Between (a) and the Al wiring 2 (b), a silicon oxide film 3 is formed for the purpose of electrical insulation by a plasma CVD method.

Hereinafter, a conventional method for forming a silicon oxide film with the formation of the above-described wiring structure will be described. First, an Al alloy is deposited to a thickness of 500 to 800 nm on a silicon wafer substrate or a silicon oxide film for manufacturing a semiconductor integrated circuit by a sputtering method, and then a photoresist film is applied on the Al alloy layer. After performing a photolithography process on the photoresist film to form an etching mask, patterning of the Al alloy layer is performed by a plasma etching method to form an Al wiring. After the patterning of the Al alloy layer is completed, the unnecessary photoresist is removed to form the Al wiring 2 (a) and the Al wiring 2 (b) as shown in FIG. )
Then, a silicon oxide film 3 is formed on the Al wiring 2 (b) by a plasma CVD method.

[0004]

However, in the above-mentioned conventional method of forming a silicon oxide film by the plasma CVD method, the thickness of the silicon oxide film is limited to the state of the surface of the silicon wafer before the formation of the silicon oxide film. In particular, there is a problem that it fluctuates depending on organic impurity contamination on the surface of the wafer,
It has been difficult to improve the in-plane uniformity of the thickness of the silicon oxide film. This is because in the process of manufacturing a semiconductor integrated circuit, organic impurities adhere to the wafer surface, and the initial film formation rate of a silicon oxide film formed on the wafer is affected by the impurities and fluctuates. This is because the thickness of the formed silicon oxide film varies.

Method for removing organic impurities on wafer surface
Conventionally, O_TwoOr CO _Two, N_TwoO, H_TwoO
Plasma treatment using an oxygen compound gas such as
Silicon oxidation to remove organic impurities on the surface of eha
A film formation pretreatment method is known. But this way
Now, the electrons and ions in the plasma are
And charge the semiconductor integrated circuit, causing malfunction.
There was a problem of getting up. Also, for that,
There is also a risk of damaging the semiconductor integrated circuit fabricated on c
there were.

Accordingly, an object of the present invention is to provide a method of processing a wafer surface by a method instead of plasma processing, and forming a silicon oxide film having good uniformity of film thickness within the wafer surface by a plasma CVD method. It is.

[0007]

In order to achieve the above object, a method of forming a silicon oxide film according to the present invention comprises a method of forming a source gas on a surface of a wafer by using TEOS (Tetra Ethoxy Silan) as a source gas.
In a method of forming a silicon oxide film on a wafer by a plasma CVD method by supplying a gas containing a gas, an O ₂ gas, and a He gas, before the silicon oxide film is formed by the plasma CVD method, In addition, a heat treatment is performed on the wafer in an O ₂ atmosphere.

In another method of forming a silicon oxide film according to the present invention, a TEOS (TOS
(Etra Ethoxy Silan) A method of forming a silicon oxide film on a wafer by supplying a gas including an O ₂ gas and a He gas to form a silicon oxide film on a wafer by a plasma CVD method. Before film formation, the wafer is subjected to a heat treatment in an N ₂ O (nitrous oxide) atmosphere.

In the method of the present invention, before the silicon oxide film is formed by the plasma CVD method, the organic impurities on the wafer surface are oxidized by heat treatment in an O ₂ atmosphere or an N ₂ O atmosphere.
Since the silicon oxide film is removed, the film formation rate in the initial stage of the growth of the silicon oxide film becomes uniform in the wafer surface, and the uniformity of the film thickness of the silicon oxide film formed on the wafer is improved. Also, since organic impurities on the wafer are removed by heat treatment instead of plasma treatment,
As in the conventional plasma processing, ions and electrons in the plasma are not accumulated in the semiconductor integrated circuit and are not charged, so that the semiconductor integrated circuit formed on the wafer can be prevented from being damaged by the plasma.

In the method of the present invention, the heat treatment of the wafer is performed by silicon.
This is performed in the same chamber as the oxide film formation chamber. Ma
Also, the heat treatment of the wafer_TwoO in the atmosphere_TwoGas partial pressure,
Or N _TwoN in O atmosphere_TwoO gas partial pressure of 250 Torr or less
Do above. Furthermore, the heat treatment of the wafer is performed at
It is performed at a temperature in the range of 0 ° C. or less. Furthermore, heat treatment of the wafer
For a heat treatment time in the range from 60 seconds to 300 seconds.

According to the method of the present invention, when a silicon oxide film is formed by a plasma CVD method, before forming the silicon oxide film, an O ₂ atmosphere or a N ₂ atmosphere having a pressure (partial pressure) of 250 Torr or more is used.
After subjecting the wafer to heat treatment at a temperature of 350 to 450 ° C. in a ₂ O atmosphere, a silicon oxide film is formed by a plasma CVD method.

In a manufacturing process of a semiconductor integrated circuit, as shown in FIG.
For the purpose of electrical insulation between the 1 wiring 2 (a) and the Al wiring 2 (b) and the Al wiring 4 or between the Al wiring 2 (a) and the Al wiring 2 (b), silicon oxide is applied by a high-frequency plasma CVD method. The film 3 is often formed. Various organic impurities adhere to the substrate or the silicon oxide film 1 on which the silicon oxide film 3 is formed during the manufacturing process of the semiconductor integrated circuit.
Is affected by the initial film formation speed. Therefore, the thickness uniformity of the silicon oxide film 3 in the wafer surface varies depending on the organic impurities. Therefore, in the method of the present invention,
By subjecting the wafer to heat treatment at a predetermined temperature in an O ₂ atmosphere or a N ₂ O atmosphere at a pressure (partial pressure) of 250 Torr or more,
Organic impurities have been removed. Thereby, the uniformity of the thickness of the silicon oxide film 3 can be improved, and the plasma does not adversely affect the semiconductor integrated circuit.

[0013]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment of a method for forming a silicon oxide film according to the present invention, and FIG. 2 shows an apparatus for performing the method for forming a silicon oxide film according to this embodiment. It is a flow sheet showing a configuration. First, with reference to FIG. 2, the configuration of a plasma CVD film forming apparatus that performs the method of the present embodiment will be described. As shown in FIG. 2, the plasma CVD film forming apparatus 20 includes a film forming chamber 29 for generating a plasma to form a silicon oxide film on a wafer, and a high frequency for applying a high frequency voltage between the electrodes of the film forming chamber 29. Oscillation mechanisms 24, 25
A gas supply system for supplying various gases to the film formation chamber 29; and an exhaust system for exhausting the film formation chamber 29.

The film forming chamber 29 has a susceptor 22 on which a wafer 21 for manufacturing a semiconductor integrated circuit is mounted, and a gas supply unit 23 on the upper part. Susceptor 2
Reference numeral 2 has a heating means, and can maintain the wafer 21 at a constant temperature. A gas serving as a raw material is supplied into a film forming chamber 29 from a gas supply unit 23 above the wafer 21.

The susceptor 22 and the gas supply unit 23
It is formed of a conductive material and functions as a lower electrode and an upper electrode, respectively. By applying a high-frequency voltage between the electrodes of the susceptor 22 and the gas supply unit 23 by the high-frequency oscillation mechanisms 24 and 25, the film forming chamber 29 is formed.
The source gas molecules inside are excited to generate plasma.
The excited and activated source gas molecules are fixed on the wafer 21, and a thin film is formed on the wafer 21. The high-frequency voltage is oscillated by a high-frequency oscillator 24 and applied between the electrodes via a composite device 25.

An exhaust port 26 is provided in the film forming chamber 29, and is evacuated by a vacuum exhaust device 27 connected to the exhaust port 26. The exhaust port 26 is provided with a valve 28. By adjusting the valve opening of the valve 28, the pressure in the film forming chamber 29 can be adjusted and maintained at a predetermined pressure. O ₂ gas, source gas, inert gas, and N ₂ O gas are supplied to the gas supply unit 23 from the O ₂ gas source 30, the source gas source 31, the inert gas source 32, and the N ₂ O gas source 33, respectively. A desired gas is supplied to the gas supply unit 23 via a mass flow controller.

Next, the operation of the plasma film forming apparatus 10 will be described with reference to FIGS. In the present embodiment, as shown in FIG. 1, the Al wiring 2 (a) and the Al wiring 2
(B) A silicon oxide film 3 is formed thereon. First, an Al alloy is deposited to a thickness of 500 to 800 nm on the wafer substrate or the silicon oxide film 1 by a sputtering method, and then a photoresist film is applied. Photolithography is performed on the photoresist film to perform patterning, thereby forming an etching mask. The Al alloy layer is patterned by a plasma etching method using an etching mask, and then the etching mask is removed. As shown in FIG. 1, the Al wiring 2 (a) and the Al wiring 2 (b) are It is formed on the silicon oxide film 1.

Next, as shown in FIG. 2, on the susceptor 22 in the film forming chamber 29 of the plasma film forming apparatus 10, the Al wiring 2 (a) and the Al wiring 2 (a) are formed on the substrate or the silicon oxide film 1 through the above-described steps. Wafer 2 on which Al wiring 2 (b) is formed
Transfer 1 At this time, the pressure in the film forming chamber 29 is maintained at 0.005 Torr or less by adjusting the valve opening of the valve 28 provided at the tip of the exhaust port 26.

The susceptor 22 is maintained at a temperature in the range of 350.degree. After the wafer 21 is placed on the susceptor 22, O ₂ gas is supplied from the gas supply unit 23 into the film forming chamber 29. At this time, the flow rate of the O ₂ gas from the O ₂ gas source 30 is controlled by a mass flow controller (MFC) to a flow rate range of 800 sccm to 2000 sccm. The partial pressure of the O ₂ gas in the film forming chamber 29 is maintained at 250 Torr or more by adjusting the valve opening of the valve 28 provided at the end of the exhaust port 26.

A temperature in the range 350 ° C. to 450 ° C. and 2
The wafer 21 is maintained in the film forming chamber 29 at a pressure of 50 Torr or more for a time in a range of 60 seconds to 300 seconds.
Next, the supply of the O ₂ gas is temporarily stopped, and the film forming chamber 29 is evacuated by adjusting the valve opening of the valve 28 so that the pressure in the film forming chamber 29 becomes 0.005 Torr or less. Thereafter, a source gas, an O ₂ gas, and an inert gas are introduced from the gas supply unit 23, and the film forming chamber 2
After controlling the pressure in 9 to 2.0 to 5.0 Torr, a high frequency voltage is applied, and the process shifts to a silicon oxide film forming process by a plasma CVD method.

In the step of forming a silicon oxide film, the flow rates of the source gases are respectively controlled by a mass flow controller, the flow rate of a TEOS gas is 100 to 300 sccm, the flow rate of an O ₂ gas is 600 to 1500 sccm, and the flow rate of a carrier gas is He.
The gas is mixed with 100 to 400 sccm immediately before the film forming chamber 29 and then supplied into the film forming chamber 29.

At the same time as supplying the raw material gas, 13.56 MH
A high frequency voltage having a frequency of z and a frequency of 250 to 450 KHz is oscillated by a high frequency oscillator 24, combined by a combiner 25 immediately before a film forming chamber 29, and applied between a susceptor 22 and a gas supply unit 23. At this time, the high frequency power is 0
Variable up to 1000W. The source gas molecules introduced from the gas supply unit 23 are excited by the applied high frequency, and plasma is generated. The excited and activated source gas molecules are fixed on the surface of the wafer 21 to form a silicon oxide film. After forming the silicon oxide film, the wafer 21 is carried out of the film forming chamber 29.

The first effect of the method for forming a silicon oxide film of this embodiment is that the uniformity of the thickness of the silicon oxide film formed on the wafer is improved. Organic impurities attached to the wafer surface before the formation of the silicon oxide film are oxidized and removed by a heat treatment in an O ₂ atmosphere, so that the film formation rate in the initial growth of the silicon oxide film becomes uniform within the wafer surface. Because. The second effect is that the semiconductor integrated circuit formed on the wafer can be prevented from being damaged by plasma. Since the removal of organic impurities on the wafer is performed not by plasma processing but by heat treatment, ions and electrons in the plasma accumulate in the semiconductor integrated circuit as in conventional plasma processing.
This is because there is no charge.

Embodiment 2 The present embodiment is an embodiment of the plasma CV used in Embodiment 1.
This is another example of the embodiment in which the method for forming a silicon oxide film according to the present invention is applied when a silicon oxide film is formed on a wafer using the D film forming apparatus 20. First, Embodiment 1
Similarly, as shown in FIG. 1, an Al wiring 2 (a) and an Al wiring 2 (b) are formed on the substrate or the silicon oxide film 1.

Next, as shown in FIG. 2, the Al wiring 2 (a) and the Al wiring 2 (a) are formed on the substrate or the silicon oxide film 1 on the susceptor 22 in the film forming chamber 29 of the plasma film forming apparatus 10 through the above-described steps. Wafer 2 on which Al wiring 2 (b) is formed
Transfer 1 At this time, the pressure in the film forming chamber 29 is maintained at 0.005 Torr or less by adjusting the valve opening of the valve 28 provided at the tip of the exhaust port 26.

The susceptor 22 is maintained at a temperature in the range of 350.degree. After placing the wafer 21 on the susceptor 22, N ₂ O gas is supplied from the gas supply unit 23 into the chamber. At this time, the N ₂ O gas source 3
The flow rate of the N ₂ O gas from Step 3 is controlled by a mass flow controller (MFC) in a flow rate range of 500 sccm to 3000 sccm. The partial pressure of the O ₂ gas in the film forming chamber 29 is maintained at 250 Torr or more by adjusting the valve opening of the valve 28 provided at the end of the exhaust port 26.

Temperature in the range of 350 ° C. to 450 ° C. and 2
The wafer 21 is maintained in the film forming chamber 29 at a pressure of 50 Torr or more for a time in a range of 60 to 300 seconds.
Next, the supply of the N ₂ O gas is temporarily stopped, and the film forming chamber 29 is evacuated by adjusting the valve opening of the valve 28 so that the pressure in the film forming chamber 29 becomes 0.005 Torr or less. . Then, the raw material gas, O ₂ gas,
After an inert gas is introduced from the gas supply unit 23 and the pressure in the film forming chamber 29 is controlled at 2.0 to 5.0 Torr, a high frequency voltage is applied, and the process proceeds to the step of forming a silicon oxide film by plasma CVD. Transition.

In the step of forming the silicon oxide film, the flow rates of the source gases are respectively controlled by a mass flow controller, the flow rate of the TEOS gas is 100 to 300 sccm, the flow rate of the O ₂ gas is 600 to 1500 sccm, and the flow rate of the carrier gas is He.
The gas is mixed with 100 to 400 sccm immediately before the film forming chamber 29 and then supplied into the film forming chamber 29.

At the same time as supplying the raw material gas, 13.56 MH
A high frequency voltage having z and a frequency of 250 to 450 KHz is oscillated by a high frequency oscillator 24, combined by a complex device 25 immediately before a film forming chamber 29, and applied between a susceptor 22 and a gas supply unit 23. At this time, the high frequency power is 0
Variable up to 1000W. The source gas molecules introduced from the gas supply unit 23 are excited by the applied high frequency, and plasma is generated. The excited and activated source gas molecules are fixed on the surface of the wafer 21 to form a silicon oxide film. After forming the silicon oxide film, the wafer 21 is carried out of the film forming chamber 29.

In order to evaluate the method of the present invention, the film thickness uniformity of the silicon oxide film formed by the plasma CVD method after heat treatment in an O ₂ gas atmosphere according to the method of the first and second embodiments. And the film thickness uniformity of the silicon oxide film formed by the plasma CVD method without performing the heat treatment in the O ₂ gas atmosphere.
It was shown to. As it can be seen from FIG. 3, the film thickness uniformity when subjected to heat treatment in O ₂ gas atmosphere, as compared with the film thickness uniformity when not heat-treated in an O ₂ gas atmosphere, are significantly better.

[0031]

According to the structure of the present invention, plasma CVD
Before the formation of the silicon oxide film by the method, the organic impurities on the wafer surface are oxidized and removed by a heat treatment in an O ₂ atmosphere or an N ₂ O atmosphere. The surface becomes uniform, and the uniformity of the thickness of the silicon oxide film formed on the wafer is improved. Also, since the removal of organic impurities on the wafer is performed by heat treatment instead of plasma treatment, ions and electrons in the plasma are not accumulated in the semiconductor integrated circuit and charged on the wafer, unlike conventional plasma treatment. Damage to the semiconductor integrated circuit formed by the plasma can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wafer on which a silicon oxide film is formed.

FIG. 2 is a flow sheet showing a configuration of a plasma CVD film forming apparatus.

[3] and the film thickness uniformity when subjected to heat treatment in O ₂ gas atmosphere is a graph showing a comparison of the film thickness uniformity when not heat-treated in an O ₂ gas atmosphere.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate or silicon oxide film 2 (a), 2 (b) Al wiring 3 Silicon oxide film 4 Al wiring 20 Plasma CVD film-forming apparatus 21 Wafer 22 Susceptor 23 Source gas supply unit 24 High frequency oscillator 25 Composite device 26 Exhaust port 27 Vacuum exhaust device 28 Valve 29 Film forming chamber 30 O ₂ gas source 31 Raw material gas source 32 Inert gas source 33 N ₂ O gas source

Claims (6)

(57) [Claims] 1. A method for forming a silicon oxide film on a wafer by supplying a gas containing a TEOS gas, an O ₂ gas, and a He gas as a source gas to a film forming chamber and forming a silicon oxide film on a wafer by a plasma CVD method. A method for forming a silicon oxide film, comprising: performing a heat treatment on a wafer in an N ₂ O (nitrous oxide) atmosphere before forming the silicon oxide film by a plasma CVD method. 2. A method of forming a silicon oxide film according to claim 1, characterized in that the heat treatment to the wafer in a deposition chamber of the same chamber for depositing the silicon oxide film. Wherein the partial pressure of N ₂ O gas in N ₂ O atmosphere 2
3. The method for forming a silicon oxide film according to claim 1, wherein the heat treatment of the wafer is performed at 50 Torr or more. 4. A heat treatment of the wafer is performed at 350 ° C. or more and 450 ° C.
2. The method according to claim 1, wherein the heating is performed at a temperature in the following range.
4. The method for forming a silicon oxide film according to any one of 3 . 5. The heat treatment of a wafer is performed for a heat treatment time in a range of 60 seconds or more and 300 seconds or less.
5. The method for forming a silicon oxide film according to any one of items 4 to 4 . 6. The method according to claim 1, wherein a silicon oxide film is formed on a wafer on which the integrated circuit is formed.
6. The method for forming a silicon oxide film according to any one of the items 5 .