JP2003273103A - Method and apparatus for manufacturing semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the degradation of the performance of a transistor caused by interface level rising due to the entry of nitrogen atoms that have been implanted in a silicon oxide film, reaching an interface between the film and a silicon substrate. <P>SOLUTION: A substrate with a silicon oxide film formed thereon as a wafer is heated for a millisecond to centisecond by using a flash lamp, while supplying thereto gas that has been composed so as to contain nitrogen radicals by plasma irradiation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method and thin film modifying method and apparatus used in semiconductor manufacturing.

[0002]

2. Description of the Related Art In recent CMOS, boron (B) is used as a gate electrode in PMOS to improve transistor performance.
The polycrystalline silicon containing is used for NMOS, and the polycrystalline silicon containing phosphorus (P) or arsenic (As) is used for NMOS. This is a so-called Dual Poly-Si Gate technology. In the transistor manufacturing process, usually, a polycrystalline silicon film containing no dopant is formed, and after the gate electrode is processed, ions are simultaneously implanted at the time of forming the source and drain portions. Subsequently, the dopant is activated by heat treatment. During this heat treatment, B implanted into the polycrystalline silicon film thermally diffuses and reaches the silicon substrate across the gate oxide film. As a result, there arises a problem that the performance of the transistor is impaired such that the threshold voltage changes.

In order to prevent this so-called "penetration of B", several atm% of nitrogen is introduced into the gate oxide film to make the film a dense structure to serve as a barrier against B diffusion. Initially, the method for introducing nitrogen into the gate oxide film was NO gas or NH.
_Three gases were used, but in each case nitrogen reached the interface with the silicon substrate. When nitrogen reaches the interface of the silicon substrate, it increases the interface level near the interface,
Impairs transistor performance.

As a method for solving this problem, plasma nitriding is drawing attention as a method for introducing nitrogen only to the vicinity of the surface of the gate oxide film without reaching the interface of the silicon substrate. However, it has been found that this method also has a limit when the gate oxide film thickness becomes as thin as 2 nm these days. That is, even in plasma nitriding, it takes some time to introduce nitrogen. During this time, nitrogen atoms diffuse in the gate oxide film and reach the interface with silicon. As a result, the interface state is increased and the carrier mobility is lowered, so that the performance of the transistor is significantly impaired.

[0005]

As described above, even if the method of plasma nitriding, which has recently been attracting attention, is applied to a gate oxide film having a film thickness of 2 nm or less, which is required in the future, it is introduced into the film. There is a problem that the generated nitrogen atoms reach the interface with the silicon substrate to increase the interface state and impair the performance of the transistor.

The present invention has been made in view of the above circumstances, and its purpose is to introduce nitrogen only into the surface of a gate oxide film having a thickness of 2 nm or less without allowing nitrogen to reach the interface with a silicon substrate. , And to provide a method for introducing nitrogen that maintains the interface state at a low level. And such an objective is achieved by the following means.

[0007]

According to the method of manufacturing a semiconductor device of the present invention, the substrate to be processed is supplied to the substrate to be temperature-controlled at 1 / 1000th while supplying the activated gas to the substrate.
The heating is for one second to one hundredth of a second.

Further, in the method of manufacturing a semiconductor device of the present invention, the heating is performed by irradiation with a flash lamp.

Further, in the method for manufacturing a semiconductor device according to the present invention, the irradiation with the flash lamp is intermittently performed twice or more so that the total irradiation time is 1/1000 second to 1/100 second. It is a thing.

Further, the method for manufacturing a semiconductor device of the present invention uses a gas containing nitrogen radicals as the activated gas.

Further, according to the method of manufacturing a semiconductor device of the present invention, a gas containing nitrogen radicals is made to act on a silicon wafer on which a silicon oxide film is formed, and the silicon wafer is irradiated with a flash lamp for 1/1000 second to 100 minutes. Is heated for 1 second.

Further, the semiconductor manufacturing apparatus of the present invention includes a vacuum container, a sample table which is placed in the vacuum container and on which a substrate to be processed is mounted, a means for adjusting the temperature of the sample table, and the vacuum container. A means for supplying an activated gas and a means for exhausting the gas;
And means for heating for 1/100 second.

Further, in the semiconductor manufacturing apparatus of the present invention, the means for supplying the activated gas has a plasma generating means for applying microwave or high frequency power.

Further, in the semiconductor manufacturing apparatus of the present invention, the means for supplying the activated gas supplies a gas containing radicals.

In the semiconductor manufacturing apparatus of the present invention, the means for heating the substrate to be processed is a flash lamp.

Further, the semiconductor manufacturing apparatus of the present invention includes a vacuum container, a sample table placed in the vacuum container for mounting a substrate to be processed, a means for adjusting the temperature of the sample table, and nitrogen gas activation. Of the microwave discharge plasma generator introduced into the vacuum vessel and the substrate to be treated by 1/1000.
And a flash lamp for heating for 1/100 second.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, the basic concept of the invention will be described. First, the mechanism of introducing nitrogen into the silicon oxide film will be briefly described. When nitrogen is introduced using NO gas, the introduced nitrogen atoms are mainly distributed at the interface with silicon. NO gas is stable and does not dissociate in the silicon oxide film, and dissociates only when it reaches the interface with silicon and receives electrons from the silicon substrate. Therefore, the vicinity of the interface between the silicon oxide film and the silicon substrate is mainly nitrided.

On the other hand, in the case of NH ₃ , since a high temperature of about 800 ° C. is usually used, it has already been decomposed in the gas to generate active chemical species such as NH 2 and NH. Since these chemical species are radicals and are active, they are nitrided from the surface of the silicon oxide film.
However, since the nitriding temperature is high and the time is long, it diffuses in the silicon oxide film to reach the interface with the substrate, and nitriding proceeds even near the interface.

On the other hand, plasma nitriding is characterized in that nitrogen radicals generated by electric discharge are active species, and that nitriding time is short and temperature is low. Since the temperature is low, the distance by which nitrogen radicals diffuse in the silicon oxide film is short and cannot reach the interface with the substrate. Therefore, a good interface is maintained with few interface states. However, when the silicon oxide film itself becomes thin, nitrogen atoms reach the interface with the substrate, no matter how low the temperature is and the time is short. This is a matter of course because if it diffuses a little, it will be the interface with the substrate.

The present invention is based on consideration of the above mechanism. That is, in order to maintain a good interface, the diffusion of nitrogen should be suppressed. One way to do this is to use nitrogen radicals as the active species and shorten the nitriding time so that the nitrogen atoms cannot diffuse.

As a method for realizing this idea, in the present invention, a flash lamp is used and the ratio is 1/1000 to 1/100.
It is characterized in that the wafer to be treated is heated only for a second.
Since the time to heat the wafer to be processed is extremely short,
Nitrogen radicals react on the surface of the silicon oxide film, but do not diffuse into the inside of the film, and the interface with the substrate maintains a good interface free of nitrogen atoms.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a semiconductor manufacturing apparatus according to an embodiment of the present invention. Since this device is a vacuum device, it naturally has an exhaust system such as a vacuum pump, but for simplicity, these devices are omitted in this figure, and only the main parts are shown. In this apparatus, a sample stage 3 is installed in a vacuum container 1, and a heater 2 or a pipe (not shown) for flowing a cooling refrigerant is incorporated in the sample stage 3. A sample wafer 4 as a substrate to be processed is placed on the sample table 3. A discharge tube 5 is connected to the vacuum container 1 to supply radicals as an activating gas. The discharge tube 5 is a tube made of quartz, and a microwave is applied through the microwave cavity resonator 6 to generate plasma. The discharge tube 5, the microwave cavity resonator 6, the coaxial cable 11 and the like constitute plasma generating means. Reference numeral 10 is an exhaust port for gas.

A quartz window 7 is provided in the upper part of the vacuum container 1, and a flash lamp 8 and its reflector 9 are installed in this upper part. A condenser for supplying electric power and a power source are connected to the flash lamp, but these are facilities for making the flash lamp emit light, and are not shown in the figure because they are self-explanatory.
With the above equipment, it is possible to heat the sample wafer 4 for an extremely short time by irradiating the flash lamp 8 while supplying the radicals generated in the discharge tube 5 onto the sample wafer 4.

As described above, in the semiconductor manufacturing apparatus of this embodiment, the temperature control of the vacuum stage 1 such as the sample stage 3 on which the substrate to be processed is placed and the heater 2 for adjusting the temperature of the sample stage 3 is performed. Equipped with means. Further, the discharge tube 5 serves as a passage for supplying gas from the outside, the microwave cavity resonator 6 that activates the gas from the discharge tube 5 by plasma, the discharge tube 5, the microwave cavity resonator 6, and the like. 5
It is provided with a plasma generating means for generating plasma by applying microwave or high-frequency power to the gas from the above, an activated gas supplying means, an exhaust port 10 as a gas exhausting means, and a flash lamp 8 as a heating means.

Next, the characteristics of the gate oxide film formed by using the semiconductor manufacturing apparatus shown in FIG. 1 will be described with reference to FIG. FIG. 2 shows a cross-sectional view of a sample prepared for carrying out the present invention. As shown in FIG. 2, the P-type (100) silicon substrate 21 was oxidized at 750 ° C. to obtain film thicknesses of 2.0, 2.5,
A 3.0 nm silicon oxide film 22 was formed. This sample is placed in the semiconductor manufacturing apparatus shown in FIG. 1 and nitrogen is caused to flow at 100 sccm to maintain the pressure at 1 Torr. Next, a frequency of 2.
Nitrogen gas was discharged by applying a microwave of 45 GHz and 1 kW, and nitriding of the silicon oxide film 22 was tried. At this time,
The concentration and distribution of nitrogen atoms in the silicon oxide film were investigated in detail using the temperature of the sample and the time for which the nitrogen radicals act as parameters.

Next, for comparison with the present invention, an experiment according to the prior art was first conducted. First, the temperature of the sample table 3 on which the sample wafer 22 is placed was set to 700 ° C., and the time for causing the nitrogen radicals to act was 10 minutes. In addition, fix the nitrogen radical irradiation time to 10 minutes and set the temperature of the sample table to 400
The data was changed to ℃ and 500 ℃. Next, the present invention was carried out under the following conditions. While maintaining the temperature of the sample table 3 at room temperature, the flash lamp 8 was irradiated once every 30 seconds, that is, 10 shots at 2 Hz, while making nitrogen radicals act. SIMS analysis was performed on these silicon oxide films to examine the concentration and distribution of nitrogen atoms in the silicon oxide film.

The results are shown in FIG. In FIG. 3, the horizontal axis represents the depth from the film surface to the right, and the vertical axis represents the concentration. The symbol O indicates the oxygen concentration distribution, and the symbol N indicates the nitrogen concentration distribution. FIG. 3A shows the result of introducing nitrogen under typical conditions according to the conventional technique. Average nitrogen concentration in the film is 3-4%
Since the nitridation occurs from the surface of the silicon oxide film, the nitrogen concentration is high on the surface, but the nitrogen atoms reach the interface with the silicon substrate. This is because the temperature is high and the processing time is long, so that nitrogen atoms diffuse in the silicon oxide film. 3 (b) and 3 (c) show that the temperature of the sample table 3 is 400 ° C.
This is the result when the temperature is lowered to 00 ° C. Since the temperature is low, diffusion is slow and nitrogen atoms have not reached the interface with the silicon substrate, but the nitrogen concentration in the film is low. This cannot prevent the diffusion of boron.

FIG. 3 (d) shows the result of carrying out the present invention.
Nitrogen radicals are allowed to act at room temperature, and the heating time with a flash lamp is about 1 msec, which is extremely short compared to conventional techniques, so nitrogen atoms do not diffuse in the film and do not reach the interface with the silicon substrate. . However, since the lamp was irradiated 5 times, that is, 5 shots were repeated, the nitrogen concentration on the film surface was sufficiently high.
Therefore, it is possible to suppress the diffusion of boron.

Actually, a polycrystalline silicon film was deposited on these samples, boron was ion-implanted, and then heat treatment was performed at 1015 ° C. for 10 seconds to form a capacitor, and a flat band voltage and an interface state were measured. When the influence of nitrogen on the interface was evaluated by the diffusion of boron, the results shown in Table 1 were obtained.

[0030]

[Table 1]

In Table 1, (a), (b), (c), and FIG.
Under the conditions a, b, c, and d corresponding to (d), the amount of change from the flat band voltage Vfb before heat treatment and the interface state are shown. In the case of the condition d, the interface state is remarkably improved. As can be seen from the above experiments, it is clear that the present invention can suppress the diffusion of boron and realize a good interface.

As described above, in this embodiment, the substrate 4 to be processed is supplied to the substrate 4 to be temperature-adjusted while the activated gas is supplied, for 1/1000 second to 100 seconds.
Heat for a second. Then, preferably, this heating is performed by irradiation with a flash lamp. Irradiation with a flash lamp is intermittently performed twice or more within a predetermined time so that the total irradiation time is 1/1000 second to 1/100 second. A preferred embodiment is a mode in which a gas containing nitrogen radicals is made to act on a silicon wafer on which a silicon oxide film is formed, and the silicon wafer is irradiated with a flash lamp and heated for 1/1000 second to 1/100 second. As a result, nitrogen is introduced only into the surface of a silicon oxide film that does not exceed a thickness of 2 nm, and nitrogen is not allowed to reach the interface with the underlying silicon substrate, and the interface state is maintained at a low level. be able to.

[0033]

As described above, according to the present invention, it is possible to introduce nitrogen only into the vicinity of the surface of a very thin silicon oxide film having a film thickness of 2 nm or less, and to increase B without increasing the interface state. B from doped polycrystalline silicon gate electrode
Can be prevented from spreading.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of a semiconductor manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a sample prepared for carrying out the present invention.

FIG. 3 is a diagram showing an experimental result of carrying out the present invention together with a comparative example.

[Explanation of symbols]

1 vacuum container, 2 heaters 3 sample table, 4 samples, 5 discharge tubes, 6 Microwave cavity resonator, 7 quartz plate, 8 flash lamps, 9 reflector, 10 exhaust port, 11 coaxial cable.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4M104 CC05 EE03 GG09 GG10 GG14                 5F045 AA20 AB33 AB34 AF08 BB17                       CA05 DC55 DP01 EH18 EK12                       EK29                 5F058 BA06 BC02 BH04 BH07 BH20                 5F140 AA28 BA01 BD06 BD09 BD17                       BE07 BE17 BE19 BF01 BF04                       BG27 BG43

Claims (10)

[Claims] 1. A semiconductor device comprising: a substrate to be temperature-controlled, which is heated for 1/1000 second to 1/100 second while the activated gas is being supplied to the substrate. Production method. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the heating is performed by irradiation with a flash lamp. 3. The irradiation with the flash lamp is intermittently performed twice or more, and the total irradiation time is 1/1000 second to 10 seconds.
The method of manufacturing a semiconductor device according to claim 2, wherein the time is set to 1/0 second. 4. The method of manufacturing a semiconductor device according to claim 1, wherein a gas containing nitrogen radicals is used as the activated gas. 5. A silicon wafer having a silicon oxide film formed thereon is treated with a gas containing nitrogen radicals, irradiated with a flash lamp, and heated for 1/1000 second to 1/100 second. Manufacturing method of semiconductor device. 6. A vacuum container, a sample table placed in the vacuum container for mounting a substrate to be processed, a means for adjusting the temperature of the sample table, and a means for supplying an activated gas into the vacuum container. And a means for exhausting the gas and a means for heating the gas to be treated for 1/1000 second to 1/100 second. 7. The semiconductor manufacturing apparatus according to claim 6, wherein the means for supplying the activated gas has a plasma generating means for applying microwave or high frequency power. 8. The means for supplying the activated gas supplies a gas containing radicals.
The semiconductor manufacturing apparatus according to. 9. The semiconductor manufacturing apparatus according to claim 6, wherein the means for heating the substrate to be processed is a flash lamp. 10. A vacuum container, a sample table which is placed in the vacuum container and on which a substrate to be processed is mounted, a means for adjusting the temperature of the sample table, and nitrogen gas is activated and introduced into the vacuum container. A semiconductor manufacturing apparatus comprising: a microwave discharge plasma generator and a flash lamp for heating the substrate to be treated for 1 / 1000th to 1 / 100th of a second.