JP2001044193A - Method of forming silicon oxide film and silicon nitride oxide film, and silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can form an insulating film, which is ultrathin and is high in electrical reliability and is superior in equality of thickness under the water face, simply without using special facilities or processes. SOLUTION: In this formation method, a silicon oxide film is made on the surface of a silicon wafer by heat-treating the silicon wafer under oxidative atmosphere, using a quick heating and quick cooling device. In this case, a silicon oxide film 15 nm or smaller in thickness is formed, by making the oxidative atmosphere the mixed gas between argon and oxygen, and making the beat treatment of the heat treatment 1,000 deg.C or over.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rapid heating and rapid cooling (RTA).
The present invention relates to a method for forming an ultra-thin silicon oxide film and a silicon oxynitride film using a ling apparatus.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of devices has increased, the thickness of a gate oxide film has been reduced.
A film thickness of about nm is required, and a silicon oxide film as thin as 5 nm or less is also required. In addition, a silicon oxynitride film has been used as an insulating film instead of a silicon oxide film. As a general method of forming a silicon oxide film, there are wet oxidation (hereinafter sometimes referred to as pyrogenic oxidation) in which heat treatment is performed in an atmosphere containing water vapor, and dry oxidation in a dry oxygen atmosphere. It is known that an oxide film having high electrical reliability can be obtained. With respect to the oxidation temperature, it is known that an oxide film grown at a low temperature has worse quality than a film grown at a high temperature. Therefore, in order to obtain an oxide film having reliable electric characteristics, it can be said that it is preferable to use wet oxidation at a high temperature.

However, in order to uniformly form such an ultra-thin silicon oxide film as described above, it is necessary to reduce the growth rate of the oxide film, so that wet oxidation at a high temperature has been extremely difficult. That is, if a very high growth rate is used to form an extremely thin oxide film, the film thickness cannot be controlled. For this reason, in the method described in Japanese Patent Application Laid-Open No. 9-283750, a relatively low temperature (850 mm) is obtained by diluting a hydrogen / oxygen mixed gas with nitrogen to slow the oxidation rate.
C), but a 5 nm gate oxide film is formed by pyrogenic oxidation. In this method, a normal resistance heating type heat treatment furnace (hereinafter, referred to as a batch furnace) is used.

On the other hand, a method using an RTA apparatus as a heat treatment furnace for forming an extremely thin oxide film (RTO: Ra)
However, when wet oxidation is performed with such an RTA apparatus, there is a problem that water vapor is condensed when the temperature inside the apparatus is reduced because the chamber is a cold wall. To solve this problem, Japanese Patent Application Laid-Open No. Hei 7-297178 solves this problem by using an external combustion system in which a combustion device for generating water vapor is installed outside the heat treatment chamber. A technique for forming a gate oxide film of 5 nm by the addition is disclosed.

In Japanese Patent Application Laid-Open No. 9-106971, a process of radiating ultraviolet rays in a chlorine gas flow before oxidation is performed, so that a temperature of 1000.degree.
It is described that a 5.5-nm oxide film with good film quality can be obtained by dry oxidation for 30 seconds.

[0006]

However, the above three methods have the following disadvantages. That is, in the method described in JP-A-9-283750, since an extremely thin oxide film is formed using a batch furnace, the in-plane uniformity of the formed oxide film is not sufficient.
In particular, as the diameter of the wafer becomes larger, it takes more time to obtain a uniform temperature distribution in the plane in the batch furnace, and the effect becomes more remarkable. In addition, in order to perform pyrogenic oxidation,
Equipment for supplying and exhausting explosive hydrogen gas was required.

On the other hand, the method described in Japanese Patent Application Laid-Open No. 7-297178 is an RTA apparatus, so that uniformity of the film thickness can be expected even if the wafer has a large diameter. In order to avoid the problem of condensation of water vapor inside the apparatus, an external combustion system is required, and equipment for supplying and exhausting hydrogen gas is required. In addition, although the oxidation is performed at a relatively low temperature, the wet oxidation is performed, so that the oxidation rate is high, and it is difficult to accurately control the film thickness.

On the other hand, the method described in Japanese Patent Application Laid-Open No. 9-106971 is a dry oxidation method using an RTA apparatus, so that equipment related to hydrogen is not required. To perform ultraviolet radiation in a chlorine gas stream, special equipment related to these was required.

The present invention has been made in order to solve the above-mentioned problems, and has an extremely thin electrical reliability (in particular,
The main object of the present invention is to provide a method capable of easily forming an oxide film having high withstand voltage characteristics of an oxide film and excellent uniformity of film thickness in a wafer surface without using any special equipment or process. I do. Further, it is another object of the present invention to form a nitrided oxide film having excellent electrical reliability by a simple method using the formed oxide film.

[0010]

According to a first aspect of the present invention, a silicon wafer is heat-treated in an oxidizing atmosphere using a rapid heating / cooling apparatus. In the method of forming a silicon oxide film on the surface of a silicon wafer, the oxidizing atmosphere is a mixed gas of argon and oxygen, and the heat treatment temperature of the heat treatment is set to 1000 ° C. or more, so that the film thickness becomes 15
A method for forming a silicon oxide film, characterized in that a silicon oxide film having a thickness of not more than nm is formed.

As described above, since the oxidizing atmosphere is a mixed gas of argon and oxygen, not only the oxygen diluting effect of argon but also the etching effect of the oxide film by argon is provided. It has become possible to suppress the growth rate of the film. That is, R
A high-temperature, dry oxidation can be performed at a low growth rate by a TA apparatus, whereby a silicon oxide film having a film thickness of 15 nm or less, good film thickness uniformity, and excellent electrical characteristics (oxide film breakdown voltage characteristics) can be obtained. Can be formed.

In this case, as described in claim 2, the ratio of the argon gas in the mixed gas of argon and oxygen is set to 10%.
To 80%. As described above, when the ratio of the argon gas is increased, the change in the oxidation rate is very small in this range. Therefore, the oxide film thickness can be accurately controlled by controlling the oxidation time.

In this case, it is desirable that the heat treatment temperature of the heat treatment be 1100 ° C. to 1300 ° C. If the temperature is 1100 ° C. or more, the film quality becomes good, and if the temperature exceeds 1300 ° C., slip dislocation or the like may occur on the wafer, and the wafer strength may be reduced. This is because there is a possibility that it may have an adverse effect.

Further, in this case, after the natural oxide film on the surface of the silicon wafer is removed,
It is desirable to perform the heat treatment. The reason for this is that the natural oxide film is a film with low density, and contaminants may be taken into the film.

According to a fifth aspect of the present invention, after the silicon oxide film is formed, the silicon nitride oxide film is formed by further performing a heat treatment in a nitriding atmosphere using a rapid heating / cooling device. Can also. According to such a method, a silicon oxynitride film having excellent electric characteristics can be formed relatively easily without impairing the uniformity of the thickness of the silicon oxide film formed first.

Next, a sixth aspect of the present invention is a silicon wafer having on its surface a silicon oxide film formed by the method according to the first to fourth aspects. The silicon oxide film thus formed is a dense thin film having a uniform thickness of 15 nm or less and has excellent electrical characteristics. Therefore, if a silicon wafer having such an oxide film is used, MO with excellent device characteristics
An S device can be manufactured.

According to a seventh aspect of the present invention, there is provided a silicon wafer having on its surface a silicon oxynitride film formed by the method of the fifth aspect. Since the silicon oxynitride film thus formed exhibits electrical characteristics equal to or higher than that of the silicon oxide film, the electrical characteristics are extremely excellent by using a silicon wafer having such a silicon oxynitride film. A device can be manufactured.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. The present inventors have conducted dry oxidation using an RTA apparatus without using hydrogen gas or explosive danger of hydrogen gas or corrosive hydrogen chloride gas, etc. As a result of intensive studies to obtain an oxide film having a high uniformity in film thickness on the wafer surface, the present inventors have completed the present invention based on the idea of performing thermal oxidation in a mixed atmosphere of argon gas and oxygen gas.

That is, in order to obtain an oxide film having good electrical characteristics by dry oxidation, it is essential to oxidize at a high temperature. However, when oxidized at a high temperature, dry oxidation can be said to be a very rapid oxidation. It becomes difficult to control the film thickness of 15 nm or less by the heat treatment time. Thus, the present inventors have conceived of diluting oxygen gas with argon gas to lower the oxidation rate.

FIG. 1 shows the relationship between the oxide film thickness at 1200 ° C. and 1100 ° C. and the argon concentration in an oxygen atmosphere. The oxidation treatment was performed for 60 seconds using an RTA apparatus as an annealing furnace and a mixed gas of oxygen and argon as an atmosphere. High-temperature annealing with a mixed gas of argon and oxygen not only has the effect of diluting oxygen to lower the oxidation rate, but also has a special effect of etching an oxide film with argon, which is not seen with nitrogen gas or the like.

Therefore, as shown in FIG. 1, it can be seen that as the ratio of argon increases, the thickness of the formed oxide film decreases exponentially. Moreover, it can be seen from FIG. 1 that this phenomenon is more remarkable at higher temperatures. Due to this effect, the growth rate of the oxide film can be suppressed at a high temperature, and the change in the oxidation rate is very small particularly when the argon concentration is in the range of 10 to 80%. Therefore, in this concentration range, fine control of the film thickness can be easily performed by controlling the oxidation time. Therefore, even at a high temperature, for example, an oxide film having a thickness of 5 nm or less can be sufficiently formed with good film thickness uniformity.

In order to form an oxide film by such dry oxidation and to obtain electrical characteristics comparable to those of an ultra-thin oxide film formed by low-temperature wet oxidation, the oxidation temperature must be 1000 ° C. Or more, preferably 1100
C. to 1300 C. When the temperature is 1000 ° C. or higher, particularly 1100 ° C. or higher, the film is dense and has good film quality. At a temperature higher than 1300 ° C., slip dislocations and the like may occur in the wafer, and the wafer strength may be reduced. In addition, the thermal load on the RTA apparatus may be large, and the life of the apparatus may be adversely affected. This is because there is a risk of contamination.

Further, it is preferable that the natural oxide film on the wafer surface is removed from the wafer before the heat treatment by using a low concentration hydrofluoric acid aqueous solution or the like. This is because the natural oxide film is a film having low density, and contaminants may be taken into the film. Therefore, if an ultrathin oxide film is formed by the method of the present invention after removing the oxide film, the entire oxide film can have extremely good film quality.

As described above, the silicon oxide film formed by the method of the present invention, whose thickness is 15 nm or less and whose thickness is accurately controlled, has good electrical characteristics while being a thin film, and has excellent film thickness uniformity. Therefore, if a silicon wafer having such an oxide film is used, an MO having excellent device characteristics can be obtained.
An S device can be manufactured.

Further, the same R is applied to the silicon wafer having the silicon oxide film formed as described above.
By performing heat treatment in a nitriding atmosphere (for example, a nitrogen oxide gas such as nitrogen monoxide) using a TA device, nitrogen is introduced into the silicon oxide film, so that a silicon nitride oxide film can be formed.

Here, a heat treatment apparatus used for heat-treating the silicon wafer of the present invention will be described. First, as a rapid heating / cooling device for a silicon wafer used in the present invention, a device such as a lamp heater using heat radiation can be mentioned. Also, as commercially available,
For example, an apparatus such as SHS-2800 manufactured by Stiac Microtech International Co., Ltd., which is not particularly complicated and not expensive.

Here, an example of a rapid heating / cooling apparatus (RTA apparatus) for a silicon single crystal wafer used in the present invention will be described. FIG. 4 is a schematic diagram of an RTA apparatus. The heat treatment apparatus 10 shown in FIG. 4 has a chamber 1 made of quartz, and heats a wafer in the chamber 1. Heating is performed by a heating lamp 2 arranged so as to surround the chamber 1 from above, below, left and right. The lamps can independently control the power supplied.

The gas exhaust side is equipped with an automatic shutter 3 to block outside air. Auto shutter 3
A wafer insertion port (not shown) configured to be opened and closed by a gate valve is provided. The auto shutter 3 is provided with a gas exhaust port so that the atmosphere in the furnace can be adjusted.

Then, the wafer 8 is placed on the three-point support 5 formed on the quartz tray 4. A buffer 6 made of quartz is provided on the gas inlet side of the tray 4.
It is possible to prevent the introduced gas from directly hitting the wafer. The chamber 1 is provided with a special window for temperature measurement (not shown), and the temperature of the wafer 8 can be measured through the special window by a pyrometer 7 installed outside the chamber 1.

The thermal oxidation treatment for rapidly heating / cooling the wafer by the heat treatment apparatus 10 as described above is performed as follows. First, the wafer 8 is put into the chamber 1 through the insertion port by a wafer handling device (not shown) arranged adjacent to the heat treatment device 10, placed on the tray 4, and then the automatic shutter 3 is closed.

After sufficiently purging with nitrogen gas, the atmosphere gas is switched to a mixed gas of oxygen and Ar, electric power is supplied to the heating lamp 2 and the wafer 8 is moved to, for example, 1100-1.
The temperature is raised to a predetermined temperature of 300 ° C. At this time, the time required to reach the target temperature is, for example, about 20 seconds. Next, by holding the wafer at that temperature for a predetermined time, the wafer 8 can be subjected to a high-temperature heat treatment. When a predetermined time has elapsed and the high-temperature heat treatment has been completed, the output of the lamp is reduced to lower the temperature of the wafer. This cooling can be performed in about 20 seconds, for example. Finally, the wafer is taken out by the wafer handling device to complete the thermal oxidation treatment. Further, when there is a wafer to be subjected to the thermal oxidation treatment, the wafers can be successively charged and the RTA treatment can be continuously performed.

[0032]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. (Example) As the RTA apparatus for thermal oxidation treatment, SHS-2800 manufactured by STEACH MICROTECH INTERNATIONAL CORPORATION was used, and the thermal oxidation treatment condition was 1200.
60 ° C., atmosphere: Ar 15% (capacity), O ₂ 85%
And As the silicon wafer, two mirror-polished products having a diameter of 200 mm were used (sample numbers A and B).

With respect to the sample after the thermal oxidation treatment, TZDB (dielectric breakdown voltage) and TDDB (time-dependent dielectric breakdown voltage) were measured as an oxide film thickness and electrical characteristics (oxide film breakdown voltage). The thickness of the oxide thin film is 5.0 nm for both A and B. An ellipsometer for measuring oxide film thickness is L11 manufactured by Gartner.
5C was used.

FIGS. 2 and 3 show the measurement results of TZDB and TDDB.
3 is shown. The non-defective rate of TZDB here is the gate
Oxide film thickness 5.0 nm, gate area 8 mm^Two , Judgment current value
1mA / cm^Two The oxide film breakdown voltage is 8 MV at room temperature.
/ Cm or more. In addition, TDDB
The non-defective rate means that the gate oxide film thickness is 5.0 nm and the gate area is 4
mm ^Two , Stress current value 0.01 A / cm^Two , Room temperature
The oxide film breakdown voltage is 1C / cm^Two Although having the above
Rate.

TZD of oxide thin film formed by the method of the present invention
The non-defective rate in the B characteristic is almost 100% (see FIG. 2), and the non-defective rate in the TDDB characteristic is as good as about 90%. In addition, 5.0 grown in the example was used.
The in-plane film thickness distribution of the oxide thin film of nm is 5.0 ± 0.1 n
m, and it was found that the variation in the film thickness was also kept low.

Next, another wafer on which a 5-nm oxide film was formed by the above method was used by using the same RTA apparatus as above.
Heat treatment is performed at 1100 ° C. for 60 seconds in a nitrogen monoxide gas atmosphere to form a nitrided oxide film, and the same TZDB as the oxide film is formed.
And TDDB were measured. As a result, the non-defective rate in the TZDB characteristic was almost 100%, and the non-defective rate in the TDDB characteristic was 90% or more.

Comparative Example As a comparative example, two silicon wafers (sample numbers C and D) were grown in a normal vertical batch furnace at 850 ° C. for 15 minutes in a dry oxygen atmosphere. Was processed in the same manner as in the example, and the oxide film thickness and the oxide film breakdown voltage were measured. The thickness of the oxide thin film is 5.0 nm for both C and D.

The TZDB conforming rate of an oxide thin film formed by a normal batch furnace is only about 70% (see FIG. 2).
In addition, the TDDB non-defective rate was only about 20% (see FIG. 3).

In the above measurement of the constant current TDDB,
_Qbd (total charge injected until destruction) defined below was determined, and the examples and comparative examples were compared. Q _bd (C / cm ² ) = J (A / cm ² ) × T (sec) where J: stress current, T: time required for 50% of the device to be destroyed. As a result, Q _bd whereas was about 0.7 C / cm ² in Comparative Example showed good values as in Example (oxide film) at about 2.3C / cm ^2.

From the above test results, it was found that the withstand voltage characteristics of the insulating film, especially the TDDB characteristics, were remarkably improved, and it was revealed that the method of the present invention is effective for forming an insulating thin film having high reliability. .

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

For example, in the embodiment of the present invention, the diameter is 200 m.
An oxide film is formed on a silicon wafer of m (8 inches), but in recent years 250 mm (10 inches) to 400 mm
(16 inches) or more.

[0043]

As described above in detail, according to the present invention, an oxide film or an oxynitride film which is extremely thin, has high electrical reliability, and is excellent in uniformity of the film thickness on the wafer surface can be obtained. It can be formed by a very simple method without using equipment and steps. Therefore, a silicon wafer having a high-quality insulating film can be manufactured with high yield and high productivity, and cost can be reduced. Also, by using this silicon wafer with an insulating film, a MOS device having excellent device characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 is a result diagram showing the effect of argon concentration on oxide film thickness during annealing at 1200 ° C. or 1100 ° C. for 60 seconds.

FIG. 2 is a comparison diagram of non-defective products (%) by TZDB evaluation of oxide films grown by the present invention and a conventional method.

FIG. 3 is a comparison diagram of non-defective rate (%) by TDDB evaluation of an oxide film grown according to the present invention and a conventional method.

FIG. 4 is a schematic view showing an example of a rapid heating / rapid cooling device used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chamber, 2 ... Heating lamp, 3 ... Auto shutter, 4 ... Quartz tray, 5 ... 3-point support part, 6 ... Buffer, 7 ... Pyrometer, 8 ... Wafer, 10 ...
Heat treatment equipment.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tsuyoshi Otsuki 2-13-1 Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Semiconductor Isobe Laboratory F-term (reference) 5F040 DA19 DC01 ED03 FC00 5F045 AA20 AB32 AB34 AC11 AC16 AD14 AD15 AD16 AF03 BB02 BB08 BB16 DP04 EK12 GB13 HA16 HA25 5F058 BA06 BC02 BC11 BE03 BF56 BF62 BH04 BJ01

Claims (7)

[Claims] 1. A silicon wafer is heat-treated in an oxidizing atmosphere by using a rapid heating / cooling device,
In the method of forming a silicon oxide film on the surface of a silicon wafer, a silicon oxide film having a thickness of 15 nm or less is obtained by setting the oxidizing atmosphere to a mixed gas of argon and oxygen and setting the heat treatment temperature to 1000 ° C. or more. Forming a silicon oxide film. 2. The method according to claim 1, wherein the ratio of the argon gas in the mixed gas of argon and oxygen is 10 to 80%. 3. The heat treatment temperature of the heat treatment is 1100 ° C.
The method for forming a silicon oxide film according to claim 1, wherein the temperature is set to 1300 ° C. 4. 4. The method for forming a silicon oxide film according to claim 1, wherein the heat treatment is performed after removing a natural oxide film on the surface of the silicon wafer. 5. The method according to claim 1, wherein after the formation of the silicon oxide film, the silicon nitride oxide film is formed by heat treatment in a nitriding atmosphere using a rapid heating / cooling device. Item 5. The method for forming a silicon oxynitride film according to any one of Items 4. 6. A silicon wafer having on its surface a silicon oxide film formed by the method according to claim 1. 7. A silicon wafer having on its surface a silicon oxynitride film formed by the method according to claim 5.