JP3534001B2 - Method for forming silicon oxide film and silicon oxynitride film, and silicon wafer - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to rapid heating / rapid cooling (RTA: Rapid Thermal Anneal).
ing) apparatus for forming an extremely thin silicon oxide film and a silicon oxynitride film.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of devices has increased, the gate oxide film has been made thinner, and the thickness is 10 to 15
A film thickness of about nm is required, and an ultrathin silicon oxide film having a thickness of 5 nm or less is also required. Further, a silicon oxynitride film has come to be used as an insulating film replacing the silicon oxide film. By the way, as a general method for forming a silicon oxide film, there are wet oxidation (hereinafter also referred to as pyrogenic oxidation) in which heat treatment is performed in an atmosphere containing water vapor, and dry oxidation in which a dry oxygen atmosphere is used. However, it is known that an oxide film having high electrical reliability can be obtained. Regarding the oxidation temperature, it is known that the oxide film grown at a low temperature is inferior in film quality to the 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 high temperature.

However, in order to uniformly form the ultrathin silicon oxide film as described above, it is necessary to slow down the growth rate of the oxide film, so that wet oxidation at high temperature is very difficult. That is, if a high growth rate is used to form an ultrathin oxide film, the film thickness cannot be controlled. Therefore, in the method described in Japanese Patent Application Laid-Open No. 9-283750, the hydrogen / oxygen mixed gas is diluted with nitrogen to slow the oxidation rate, so that a relatively low temperature (850
However, a gate oxide film of 5 nm 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 ultrathin oxide film (RTO: Ra).
pid Thermal Oxidation), but when performing wet oxidation in such an RTA apparatus, there is a problem that water vapor is condensed when the temperature inside the apparatus is lowered because the chamber is a cold wall. Therefore, in Japanese Patent Laid-Open No. 7-297178, this problem is solved by using an external combustion method in which a combustion device that generates steam is installed outside the heat treatment chamber, and a pyrogenic oxidation (HCl is performed at 1000 ° C. for 30 seconds is used). Addition) to form a 5 nm gate oxide film is disclosed.

Further, Japanese Patent Laid-Open No. 9-106971 incorporates a treatment of radiating ultraviolet rays in a chlorine gas stream before oxidation, whereby 1000 ° C. using an RTA apparatus,
It is described that a dry oxidation for 30 seconds can provide a 5.5 nm oxide film with good film quality.

[0006]

However, the above-mentioned three methods have the following drawbacks. That is, in the method described in Japanese Patent Application Laid-Open No. 9-283750, since a very thin oxide film is formed using a batch furnace, the in-plane uniformity of the formed oxide film is not sufficient,
In particular, the larger the diameter of the wafer, the more time it takes for the in-plane temperature distribution to be uniform in the batch furnace. Also, because of the pyrogenic oxidation,
Equipment for supplying and exhausting explosive hydrogen gas was required.

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

On the other hand, the method described in Japanese Patent Application Laid-Open No. 9-106971 does not require hydrogen-related equipment because it is a dry oxidation using an RTA apparatus, but in order to improve the quality of the oxide film, it is necessary to perform the oxidation before the oxidation. Because of the ultraviolet radiation in the chlorine gas stream, special equipment related to these was required.

Therefore, the present invention has been made to solve the above problems, and is extremely thin and has high electrical reliability (particularly,
Its main purpose is to provide a method capable of easily forming an oxide film having a high oxide film withstand voltage characteristic) and excellent in film thickness uniformity within the wafer surface without using special equipment or processes. To do. Further, it is an object of the present invention to form a nitrided oxide film having excellent electrical reliability by a simple method by using the formed oxide film.

[0010]

In order to solve the above problems SUMMARY OF THE INVENTION The present onset Ming, by heat treatment in an oxidizing atmosphere to a silicon wafer using a rapid heating-rapid cooling apparatus,
In the method for 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 1000 ° C. or higher, whereby a silicon oxide film having a thickness of 15 nm or less is obtained. Is a method of forming a silicon oxide film.

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 exerted, so that the oxidation at a high temperature of 1000 ° C. or higher is performed. It became possible to suppress the growth rate of the film. That is, R
A high-temperature, dry oxidation can be performed with a TA device at a low growth rate, whereby a silicon oxide film having a film thickness of 15 nm or less, good film thickness uniformity, and excellent electrical characteristics (oxide film withstand voltage characteristics). Can be formed.

In this case , the ratio of argon gas in the mixed gas of argon and oxygen can be set to 10 to 80%. In this way, if you increase the ratio of argon gas,
Since the change in the oxidation rate is very small in this range, 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. 110
If the temperature is 0 ° C or higher, the film quality will be good, and 1300
This is because, at a temperature higher than 0 ° C., a slip dislocation or the like may occur in the wafer to reduce the strength of the wafer, and the heat load on the RTA device is large, which may adversely affect the life of the device.

Further, in this case , it is desirable to perform the heat treatment after removing the natural oxide film on the surface of the silicon wafer. The reason for doing this is that the natural oxide film is a film having a low density and there is a possibility that contaminants may be taken into the film.

Further, after forming the silicon oxide film,
Further, the silicon oxynitride film can be formed by heat treatment in a nitriding atmosphere using a rapid heating / cooling device. With such a method, a silicon oxynitride film having excellent electrical characteristics can be formed relatively easily without impairing the film thickness uniformity of the silicon oxide film formed first.

Next, the present invention is a silicon wafer having a silicon oxide film formed by the above method on its surface. The silicon oxide film thus formed is a dense thin film having a thickness uniformity of 15 nm or less and excellent electrical characteristics. Therefore, if a silicon wafer having such an oxide film is used, MO with excellent device characteristics
S-devices can be made.

A silicon wafer having a silicon oxynitride film formed by the above method on its surface.
The silicon oxynitride film thus formed exhibits electrical characteristics equal to or higher than those of the silicon oxide film. Therefore, by using a silicon wafer having such a silicon oxynitride film, the electrical characteristics are extremely excellent. It becomes possible to manufacture a device.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The embodiments of the present invention will be described below, but the present invention is not limited thereto. The inventors of the present invention have achieved ultrathin electrical reliability (oxide film withstand voltage characteristics) by dry oxidation using an RTA device without using hydrogen gas, which has a risk of explosion, or hydrogen chloride gas, which has corrosive properties for metals. ) Is high, and as a result of earnest research to obtain an oxide film excellent in film thickness uniformity on the wafer surface, the present invention has been completed based on the idea of thermal oxidation in a mixed atmosphere of argon gas and oxygen gas.

That is, in order to obtain an oxide film having good electric characteristics by dry oxidation, it is indispensable to oxidize it at a high temperature, but if it is oxidized at a high temperature, it is a dry oxidation, but its oxidation rate is considerably high. Therefore, it becomes difficult to control the film thickness of 15 nm or less by the heat treatment time. Therefore, it has been conceived to dilute the oxygen gas with argon gas to reduce the oxidation rate.

FIG. 1 shows the relationship between the oxide film thickness at 1200 ° C. and 1100 ° C. and the argon concentration in the oxygen atmosphere. An RTA apparatus was used as an annealing furnace, and a mixed gas of oxygen and argon was used as an atmosphere to perform an oxidation treatment for 60 seconds. The high-temperature annealing with a mixed gas of argon and oxygen not only has the effect of diluting oxygen to reduce the oxidation rate, but also has a special effect not found in nitrogen gas, such as the effect of etching an oxide film with argon.

Therefore, as shown in FIG. 1, it can be seen that the oxide film thickness formed decreases exponentially as the ratio of argon increases. Moreover, it can be seen from FIG. 1 that this phenomenon is more remarkable at higher temperatures. Due to this effect, it becomes possible to suppress the growth rate of the oxide film under high temperature, and the change of the oxidation rate is very small especially in the range of the argon concentration of 10 to 80%. Therefore, in this concentration range, it is easy to perform delicate film thickness control by controlling the oxidation time. Therefore, even at high temperature, it is possible to sufficiently form an oxide film having a thickness of 5 nm or less with good film thickness uniformity.

In order to form an oxide film by such dry oxidation and to obtain the same electrical characteristics as the ultrathin oxide film formed by low temperature wet oxidation, the oxidation temperature is 1000 ° C. It is necessary to be above, preferably 1100
C. to 1300.degree. C. is preferable. When the temperature is 1000 ° C. or higher, and particularly 1100 ° C. or higher, the film becomes dense and has good film quality. Further, at temperatures above 1300 ° C., slip dislocations and the like may occur in the wafer and the strength of the wafer may decrease, and the heat load on the RTA equipment may be large, which may adversely affect the life of the equipment. This is because there is a risk of contamination.

Further, it is preferable to remove the natural oxide film on the surface of the wafer before the heat treatment with a hydrofluoric acid solution having a low concentration. This is because the natural oxide film is a film having a low density and contaminants may be taken into the film. Therefore, if this is removed and then an extremely thin oxide film is formed by the method of the present invention, the entire oxide film can be made to have extremely good quality.

As described above, the silicon oxide film formed by the method of the present invention and having a thickness of 15 nm or less and the thickness of which is accurately controlled is excellent in electrical characteristics and excellent in film thickness uniformity even though it is a thin film. Therefore, if a silicon wafer having such an oxide film is used, it is possible to obtain an MO device having excellent device characteristics.
S-devices can be made.

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

The heat treatment apparatus used for heat treating the silicon wafer of the present invention will be described below. First, as a rapid heating / quick cooling device for a silicon wafer used in the present invention, a device such as a lamp heater by heat radiation can be mentioned. Also, as commercially available,
For example, a device such as SHS-2800 manufactured by Stiac Microtech International can be mentioned, which is neither particularly complicated nor expensive.

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

An auto shutter 3 is provided on the gas exhaust side to block outside air. The auto shutter 3
A wafer insertion opening (not shown) that can be opened and closed by a gate valve is provided. Further, 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 supporting portion 5 formed on the quartz tray 4. A quartz buffer 6 is provided on the gas inlet side of the tray 4,
It is possible to prevent the introduced gas from directly hitting the wafer. Further, a special window for temperature measurement (not shown) is provided in the chamber 1, and the temperature of the wafer 8 can be measured through the special window by a pyrometer 7 installed outside the chamber 1.

With the heat treatment apparatus 10 as described above, the thermal oxidation treatment for rapidly heating and cooling the wafer is performed as follows. First, a wafer handling device (not shown) disposed adjacent to the heat treatment device 10 puts the wafer 8 into the chamber 1 through the insertion port, places it on the tray 4, and then closes the auto shutter 3.

Then, after sufficiently purging with nitrogen gas, the atmosphere gas is switched to a mixed gas of oxygen and Ar, power is supplied to the heating lamp 2, and the wafer 8 is, 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, the wafer 8 can be subjected to high-temperature heat treatment by holding at that temperature for a predetermined time. When the high temperature heat treatment is completed after a lapse of a predetermined time, the lamp output is decreased and the wafer temperature is decreased. This temperature drop can also 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 thermal oxidation treatment, the wafers can be successively loaded and the RTA treatment can be continuously performed.

[0032]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these. (Example) As the RTA device for thermal oxidation treatment, the above-mentioned SHS-2800 manufactured by Steak Microtech International was used, and the thermal oxidation treatment condition was 1200.
℃, 60 seconds, atmosphere 15% Ar (capacity), 85% O ₂
And As the silicon wafer, two mirror-polished products having a diameter of 200 mm were used (the sample numbers are A and B).

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

The measurement results of TZDB and TDDB are shown in FIG. 2 and FIG.
Shown in 3. The non-defective rate of TZDB here is the gate
Oxide film thickness 5.0nm, Gate area 8mm² , Judgment current value
1 mA / cm² The oxide film withstand voltage is 8 MV at room temperature
/ Cm or more. Also, in TDDB
The non-defective rate is a gate oxide film thickness of 5.0 nm and a gate area of 4
mm ² , Stress current value 0.01A / cm² Room temperature
Under conditions, oxide film withstand voltage is 1C / cm² Although having the above
Is the 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 about 90%, which is a good value. Also, 5.0 grown in the example
nm in-plane film thickness distribution is 5.0 ± 0.1n
It was found that the thickness was m and the variation in the film thickness was suppressed to a low level.

Next, another wafer on which a 5 nm oxide film was formed by the above method was used, using the same RTA apparatus as above.
In a nitrogen monoxide gas atmosphere, heat treatment is performed at 1100 ° C. for 60 seconds to form a nitride oxide film, and TZDB identical to 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 an ordinary vertical batch furnace except that oxide thin films were grown at 850 ° C. for 15 minutes in a dry oxygen atmosphere. Was processed in the same manner as in Example to measure the oxide film thickness and the oxide film breakdown voltage. The thickness of the oxide thin film is 5.0 nm for both C and D.

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

Further, in the above measurement of the constant current TDDB,
_Qbd (total amount of charge injected until destruction) defined below was obtained, and the examples and the comparative examples were compared. Q _bd (C / cm ² ) = J (A / cm ² ) × T (sec) where J: stress current, T: 50% of the time required to break the element. 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 characteristic of the insulating film, especially the TDDB characteristic, was dramatically improved, and it became clear 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-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has any similar effect to 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 larger diameter can be sufficiently dealt with.

[0043]

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

[Brief description of drawings]

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

FIG. 2 is a comparison diagram of non-defective rate (%) 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 oxide films grown by 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.

─────────────────────────────────────────────────── --- Continuation of front page (56) Reference JP-A-7-335876 (JP, A) JP-A-8-288283 (JP, A) JP-A-10-32328 (JP, A) JP-A-10- 92812 (JP, A) JP 10-270434 (JP, A) JP 10-74922 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/31 H01L 21 / 312 H01L 21/314 H01L 21/316 H01L 21/318 H01L 29/78

Claims (7)

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