JP2002329721A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method which can reduce leakage current and slow the rise of the absolute flat band voltage including an annealing method capable of reducing lost boron. SOLUTION: This semiconductor device manufacturing method comprises a CVD film forming process for forming a CVD film with a nitriding treatment or an oxynitriding treatment by CVD method after a silicon oxide film is formed on a silicon substrate, and a CVD film annealing process for annealing the CVD film in the atmosphere of gaseous ozone. A semiconductor device manufacturing apparatus 10 comprises a means for forming a CVD film and a means for annealing a CVD film. In the manufacturing apparatus 10, a plurality of silicon substrates 20 are mounted on a stepped wafer port 18, and the process gas is fed from a gas feeder tube 24 toward the upper part of a reactive tube 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for forming a silicon nitride film or a silicon oxynitride film and a method for annealing the same.

[0002]

2. Description of the Related Art A thermal oxide film of silicon is used for an MO for a memory.
It is used for a gate insulating film of an SFET, a capacitor insulating film of a DRAM, and the like. As the degree of integration of semiconductor devices has increased in recent years, it is necessary to reduce the area occupied by MOSFETs and the like. To achieve this, the thickness of the silicon thermal oxide film must be reduced in order to maintain a constant capacitance. In addition, due to the demand for scaling accompanying miniaturization of elements, the thickness of the thermal oxide film has recently been required to be reduced to about several tens of kilometers. The same applies when forming a thermal oxynitride film instead of a thermal oxide film.

[0003] Such thinning of the thermal oxide film or thermal oxynitride film of silicon directly increases the tunnel current,
This causes a leakage current when the gate is off,
There have been problems such as that the circuit of the semiconductor device does not operate normally or power consumption increases.

[0004] For this reason, for example, a silicon nitride film or oxynitride film having a dense structure has been studied as a good insulating film in place of the thermal oxide film or thermal oxynitride film of silicon.

The silicon nitride film or oxynitride film is formed by nitriding or oxynitriding a thermal oxide film or thermal oxynitride film of silicon. The nitride film or oxynitride film has the same capacitance as the silicon thermal oxide film that maintains a constant capacitance by increasing the capacitance with the relatively large dielectric constant of the nitride film or oxynitride film. The film thickness (physical film thickness) can be increased, thereby reducing leakage current. Hereinafter, in the present specification, a value obtained by converting the thickness of a silicon nitride film or an oxynitride film into the thickness of a silicon thermal oxide film that provides equivalent capacitance is referred to as an electrical film thickness.

As described above, it is difficult for the silicon nitride film or the oxynitride film to sufficiently reduce the leak current. On the other hand, in the case of the MOS capacitor using the oxynitride film as the insulating film, the flat band voltage Shift, and the absolute value increases.

The phenomenon that the absolute value of the flat band voltage increases is caused by an increase in positive fixed charges in the film, and changes the threshold value of the operation voltage, which causes a device operation failure.

Further, even when a silicon nitride film or an oxynitride film is formed, a further reduction in leak current is required.

Therefore, it has been studied to further anneal the silicon nitride film or oxynitride film to improve the film quality.

For example, as an annealing method, it has been proposed to treat the silicon nitride film or oxynitride film at a high temperature of about 1000 ° C. in an atmosphere of ammonia gas or nitrogen monoxide gas.

[0011]

However, the above-described annealing method using ammonia gas or nitric oxide gas has little effect on reducing the leak current. Further, the phenomenon that the absolute value of the flat band voltage increases has not been solved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a semiconductor device including an annealing method capable of further reducing a leak current and reducing an increase in an absolute value of a flat band voltage. It is an object of the present invention to provide a method for producing the same.

[0013]

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate;
A step of forming a second film made of a silicon nitride film or a silicon oxynitride film on the first film; and a step of annealing the second film in an ozone gas atmosphere.

In this case, in the step of annealing the second film, it is more preferable that the ozone concentration is 0.1 to 15% by volume and the processing temperature is 500 to 850 ° C. The processing pressure was 0.4 to 920 Pa, and the processing time was 1 to 1
A time of 0 minutes is more preferable.

According to the above configuration of the present invention, the positive fixed charges of the silicon oxide film or the silicon oxynitride film are reduced by reacting with ozone, and the increase of the absolute value of the flat band voltage is reduced. Also, the leak current decreases due to the decrease in traps in the film.

Further, the method of manufacturing a semiconductor device according to the present invention is characterized in that the second film is treated with oxygen plasma.

Thus, the same function and effect as when annealing is performed in the above-described ozone gas atmosphere can be obtained.

Further, a method of manufacturing a semiconductor device according to the present invention is characterized in that the second film is treated with hydrogen plasma.

As a result, dangling bonds (unbonded hands), that is, irregularities at the film interface and crystal defects in the film can be reduced, and an increase in the absolute value of the flat band voltage can be reduced. Also, the leak current decreases.

Further, a method of manufacturing a semiconductor device according to the present invention is characterized in that the second film is treated with nitrogen plasma.

As a result, the portion of the second film where the nitriding treatment is insufficient is sufficiently nitrided, and the leakage current is reduced.

Further, a method of manufacturing a semiconductor device according to the present invention is characterized in that the second film is treated with nitrogen plasma, and subsequently, the second film is treated with oxygen plasma.

As a result, the portion of the second film where the nitriding treatment is insufficient is sufficiently nitrided to reduce the leak current, and react with the oxygen plasma to correct the silicon oxide film or the silicon oxynitride film. And the increase in the absolute value of the flat band voltage is alleviated.

Further, the method of manufacturing a semiconductor device according to the present invention is characterized in that the above-mentioned oxygen plasma, hydrogen plasma, nitrogen plasma or nitrogen plasma and oxygen plasma are generated by a planar antenna member having a plurality of slits. I do.

As a result, a low plasma sheath voltage can significantly reduce plasma damage to the film.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a method of manufacturing a semiconductor device according to the present invention (hereinafter, referred to as an embodiment) will be described below with reference to the drawings.

First, an apparatus for manufacturing a semiconductor device according to this embodiment will be described with reference to FIG.

A manufacturing apparatus 10 shown in FIG. 1 is a rapid thermal processing system (FTPS).
m) is a kind of.

The manufacturing apparatus 10 includes a reaction tube 12 made of, for example, quartz and formed in a cylindrical shape with a ceiling whose longitudinal direction is directed vertically. Below the reaction tube 12, a manifold 14 formed of a stainless steel tube formed in a cylindrical shape is used.
Are arranged so as to be airtight with the lower end of the reaction tube 12.
A lid 16 is disposed below the manifold 14 so as to be movable up and down.
4 is configured to be closed.

The reaction tube 12, the manifold 14, and the lid 16 constitute a processing chamber.

The lid 16 is provided with a shelf-like wafer port 18 made of quartz. A plurality of silicon substrates 20 are accommodated in the wafer port 18 at predetermined intervals in the vertical direction.

Surrounding the reaction tube 12 is provided a heater 22 for increasing the temperature, for example, composed of a resistance heating element.

A process gas supply pipe 24 is inserted through a side surface of the manifold 14. The process gas supply pipe 24 is bent so that the tip portion 24a faces upward.
For this reason, the process gas supplied from the process gas supply pipe 24 is ejected above the reaction tube 12. Reference numeral 26 indicates an exhaust pipe.

Since the manufacturing apparatus 10 described above is configured so that the process gas reaches above the reaction tube, it is supplied at a high speed and a large flow rate. Further, since the process gas is configured to reach the ceiling of the reaction tube, and a predetermined gap is provided in the reaction tube, the process gas is uniformly supplied to the processing region, and the silicon substrate is uniformly formed. It is processed.

A method of manufacturing a semiconductor device according to the present embodiment using the above-described manufacturing apparatus 10 will be described below.

The method of manufacturing a semiconductor device includes a first method of forming a silicon oxide film or a silicon oxynitride film on a silicon substrate.
Forming a second film made of a silicon nitride film or a silicon oxynitride film on the first film, and annealing the second film in an ozone gas atmosphere.

In the method of manufacturing a semiconductor device according to the present embodiment, a method of forming a first film made of a silicon oxide film or a silicon oxynitride film and a method of forming a second film made of a silicon nitride film or a silicon oxynitride film are as follows. However, neither is particularly limited. For example, a thermal oxidation method may be used, or a deposition method such as CVD may be used. In this case, when using the CVD method, thermal CVD, plasma CV
It can be used by appropriately selecting from various CVD methods such as D or photo-CVD.

Here, the following method, which is preferable from the viewpoint of the leakage current reduction effect, is used.

That is, a silicon oxide film as a first film is formed on a silicon substrate by a thermal oxidation method. Next, this silicon oxide film is heat-treated in an ammonia gas atmosphere. Further, a silicon nitride film as a second film is deposited and formed. In the thermal oxide film forming step, a silicon oxynitride film may be formed instead of the silicon oxide film.

In the step of forming the thermal oxide film, a mixed gas having a flow ratio of about O ₂ / N ₂ = 8/2 (slm ratio) is used as a process gas under a pressure of about 1.3 kPa and a pressure of about 850.
The treatment is performed at a temperature of about ° C for a time of about 60 s (second). Thereby, a silicon oxide film (SiO ₂ film) having a thickness of, for example, about 1.0 nm is formed on the silicon substrate.

In the heat treatment step, ammonia gas (NH ₃ ) having a flow rate of about 2 (slm) is used as a process gas under a pressure of about 1.1 kPa, at a temperature of about 850 to 900 ° C., for about 10 minutes (minutes). Time to process. This heat treatment step is an in-situ cleaning (ISC) step, whereby the surface of the silicon oxide film is nitrided in preparation for the next step of forming a nitride film.

In the step of forming a silicon nitride film, TCS / NH ₃ = 50/50 (sccm) is used as a process gas.
The mixture is processed at a temperature of about 550 to 650 ° C. for about 120 s under a pressure of about 35 Pa using a mixed gas having a flow ratio of about (ratio). Thereby, for example, 1.0 to 1.5 nm
A silicon nitride film (SiN film) having a moderate thickness is formed on the silicon oxide film. Here, TCS refers to tetrachlorosilane.

The silicon nitride film formed as described above can obtain a leak current reducing effect more than other conventional methods. However, the phenomenon of an increase in positive fixed charges in the film occurs to the same degree as in other conventional methods.

Therefore, in the method of manufacturing a semiconductor device according to the present embodiment, the formed silicon nitride film is further annealed in an ozone gas atmosphere.

The ozone gas is O ₃ / O ₂ = 10/90
Using a gas having a volume ratio of about (volume% ratio), the treatment is performed under a pressure of about 18 Pa at a temperature of about 850 ° C. for about 60 s.

FIGS. 2 and 3 show characteristics evaluation results when the silicon nitride film formed by the above method is used as an insulating film of an nMOS capacitor.

FIG. 2 shows the result of the gate leakage current evaluation. Here, the vertical axis (Ig) is-from the flat band voltage.
The leak current at the time of 0.6 V accumulation is shown, and the horizontal axis (Teq) shows the electric film thickness.

In the figure, the case where POA-C is the embodiment is shown. In the figure, Ref. Pure SiO ₂ indicates a case of a silicon oxide film, None-POA indicates a case where only the above-described silicon nitride film forming process is performed, and no annealing process is performed, and POA-A indicates a temperature of 900 ° C. in an oxygen gas atmosphere. Shows the case of annealing with
POA-B shows the case where annealing was performed at a temperature of 850 ° C. in a nitrogen monoxide gas atmosphere.

As is apparent from FIG. 2, the effect of the conventional annealing using oxygen gas or nitric oxide gas does not show a reduction effect of the leak current as compared with the case where the annealing is not performed. However, in the case of the present embodiment, in addition to the leakage current reduction effect (to the silicon oxide film) by the silicon nitride film forming process, a still further leakage current reduction effect is obtained.

FIG. 3 shows the evaluation results of the flat band voltage. Here, the vertical axis (Vfb) indicates the flat band voltage, and the horizontal axis (Teq) indicates the electrical film thickness. POA in the figure
Reference numerals such as -A indicate the same as those in FIG.

As apparent from FIG. 3, when only the silicon nitride film forming process is performed and the annealing process is not performed, the absolute value of the flat band voltage is greatly increased as compared with the case of the silicon oxide film. On the other hand, in the case of the present embodiment, an increase in the absolute value of the flat band voltage is greatly suppressed.

As described above, according to the method of manufacturing the semiconductor device according to the present embodiment, the leak current can be further reduced, and the increase in the absolute value of the flat band voltage is reduced.

In the method of manufacturing a semiconductor device according to the present embodiment, ozone gas is used in the annealing step of the second film. Alternatively, oxygen plasma, nitrogen plasma, or hydrogen plasma may be used instead. Well, also
Nitrogen plasma and oxygen plasma may be used sequentially.

As a manufacturing apparatus used in the method of manufacturing a semiconductor device according to the present embodiment, a vertical rapid thermal processing apparatus capable of processing a large number of silicon substrates as described above was used. Not limited to this, a single-wafer-type device may be used.

In the manufacturing apparatus, the vertical rapid thermal processing apparatus was used in the step of forming the silicon oxide film and the silicon nitride film and also in the step of annealing the silicon nitride film in an ozone gas atmosphere. When a silicon nitride film is treated with plasma, a plasma processing apparatus is used.

It is preferable to use a plasma processing apparatus described below as the plasma processing apparatus.

The plasma processing apparatus 28 shown in FIG. 4 has a processing vessel 30 and a microwave generator 32.

The processing container 30 has, for example, a side wall and a bottom portion made of a conductor such as aluminum, is formed in a cylindrical shape as a whole, and has a shape in which an upper portion is reduced in a stepped shape. A mounting table 33 on which a silicon substrate is mounted is provided inside the processing container 30, and a closed processing space S is formed. Above the processing space S, a plasma generation space S1 is formed. Further, a gas supply nozzle 34 for supplying a process gas whose flow rate is controlled is provided on a side wall of the processing container 30. An exhaust port 36 is provided at the bottom of the processing container 30.

A microwave transmission window 38 is provided on the ceiling of the processing container 30. Then, the microwave transmission window 38
A disc-shaped planar antenna member 40 in which a plurality of slits (not shown) are formed is disposed on the upper surface side of the antenna. A slow-wave member 42 is disposed on the upper surface of the planar antenna member 40.

The microwave generator 32 has, for example, 2.4
It generates a 5 GHz microwave and is connected to the planar antenna member 40 via a rectangular waveguide 48 or the like.

In the processing device 28 configured as described above, the microwave generated by the microwave generator 32 propagates through the waveguide 48 and reaches the planar antenna member 40. Further, during the microwave propagation from the center of the planar antenna member 40 to the peripheral portion thereof, an electrostatic field is generated between a large number of concentrically formed slits in the planar antenna member 40. , An electrostatic field is formed. The process gas excited by the electrostatic field is turned into plasma, and the surface of the silicon substrate is processed.

When the above-described plasma processing apparatus 28 is used,
Since the electron temperature is about 1 eV or less and the plasma sheath voltage is also several volts or less, plasma damage can be significantly reduced with respect to conventional plasma having a plasma sheath voltage of about 50 V.

[0063]

According to the method of manufacturing a semiconductor device of the present invention, since the method includes the step of annealing a second film made of a silicon nitride film or a silicon oxynitride film in an ozone gas atmosphere, the absolute value of the flat band voltage is reduced. Is reduced, and the leak current is reduced.

The same effect as described above can be obtained by using any one of oxygen plasma, nitrogen plasma, and hydrogen plasma instead of ozone gas, or by using nitrogen plasma and oxygen plasma sequentially.

Further, according to the method of manufacturing a semiconductor device according to the present invention, plasma is generated by the planar antenna member having the plurality of slits, so that plasma damage to the film can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a graph for explaining a characteristic evaluation result when a silicon nitride film formed by the method for manufacturing a semiconductor device according to the present embodiment is used as an insulating film of an nMOS capacitor; The results are shown.

FIG. 3 is a graph for explaining a characteristic evaluation result when a silicon nitride film formed by the method for manufacturing a semiconductor device according to the present embodiment is used as an insulating film of an nMOS capacitor; The evaluation results are shown.

FIG. 4 is a schematic view of a plasma processing apparatus as another example of the apparatus for manufacturing a semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 12 Reaction tube 14 Manifold 16 Lid 18 Wafer port 20 Silicon substrate 22 Heating heater 24 Process gas supply pipe 26 Exhaust pipe 28 Plasma processing apparatus 30 Processing vessel 32 Microwave generator 33 Mounting table 34 Gas supply nozzle 36 Exhaust port 40 Planar antenna member 42 Slow wave material

Continuation of the front page (72) Inventor Masayuki Imai 5-3-6 Akasaka, Minato-ku, Tokyo TBS Release Center Inside Tokyo Electron Limited (72) Inventor Shingo Hishiya 5-6-1 Akasaka, Minato-ku, Tokyo TBS (72) Inventor Takuya Sugawara 5-3-6 Akasaka, Minato-ku, Tokyo TBS Release Center Tokyo Electron Limited F-term (reference) 5F058 BA01 BD02 BD04 BD09 BD15 BF02 BF55 BH03 BH05 BH16 BJ02

Claims (12)

[Claims] 1. A step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a second film made of a silicon nitride film or a silicon oxynitride film on the first film Forming a semiconductor device, and annealing the second film in an ozone gas atmosphere. 2. The method of manufacturing a semiconductor device according to claim 2, wherein said annealing step has an ozone concentration of 0.1 to 15% by volume. 3. The method according to claim 1, wherein in the annealing step, a processing temperature is 500 to 850 ° C. 4. A step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a second film made of a silicon nitride film or a silicon oxynitride film on the first film Forming a semiconductor device and a process of treating the second film with oxygen plasma. 5. A step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a second film made of a silicon nitride film or a silicon oxynitride film on the first film Forming a semiconductor device, and a step of treating the second film with hydrogen plasma. 6. A step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a second film made of a silicon nitride film or a silicon oxynitride film on the first film Forming a semiconductor device, and treating the second film with nitrogen plasma. 7. A step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a second film made of a silicon nitride film or a silicon oxynitride film on the first film Forming a second film, treating the second film with nitrogen plasma, and subsequently treating the second film with oxygen plasma. 8. The method according to claim 4, wherein the oxygen plasma is generated by a planar antenna member having a plurality of slits. 9. The method according to claim 5, wherein the hydrogen plasma is generated by a planar antenna member having a plurality of slits. 10. The method according to claim 6, wherein the nitrogen plasma is generated by a planar antenna member having a plurality of slits. 11. The method according to claim 7, wherein the nitrogen plasma and the oxygen plasma are generated by a planar antenna member having a plurality of slits. 12. The method according to claim 12, further comprising a step of heat-treating the first film in an ammonia gas atmosphere between the step of forming the first film and the step of forming the second film. A method for manufacturing a semiconductor device according to claim 1.