JPH11162977A - Method of forming silicon oxide film - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention provides a highly clean oxidizing atmosphere.
Another object is to form a highly reliable silicon oxide film by performing a heat treatment after the oxidation treatment to modify the oxide film. SOLUTION: The method for forming a silicon oxide film of the present invention comprises:
Moisture is generated from oxygen and hydrogen by a catalytic action and is brought into contact with silicon kept at a high temperature to form a silicon oxide film. In the method for forming a silicon oxide film of the present invention, a silicon oxide film is formed by generating water from oxygen and hydrogen by a catalytic action, adding a diluent gas, and contacting the silicon kept at a high temperature. It is characterized by the following. According to the transport method of the present invention, after the above-described silicon oxide film is formed, the water as an impurity is 100 ppb or less and the hydrocarbon is 1
It is characterized in that it is transferred to a processing chamber in the next step in a clean nitrogen or clean nitrogen / oxygen atmosphere of 00 ppb or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a highly reliable oxide film in oxidizing silicon in semiconductor manufacturing.

[0002]

BACKGROUND OF THE INVENTION In the manufacture of semiconductors, the device size is currently being reduced in order to increase the speed of an MPU or the like.
With miniaturization, the thickness of the gate oxide film is also reduced, and a highly reliable ultra-thin gate oxide film is required.

In particular, in a flash memory, a high electric field is applied to a gate oxide film, and a tunnel current flows to write and erase information. Therefore, it is important to establish a technology for forming a highly reliable oxide film that does not deteriorate even in high electrolysis.

Conventionally, a pyrogenic oxide film forming technique has been introduced for forming an oxide film. The pyrogenic method is a method in which hydrogen is introduced into an excess oxygen atmosphere, ignited at the inlet, and moisture is generated.In this method, the moisture concentration is not flexible and the temperature at the time of moisture generation is high. Therefore, it is difficult to maintain a uniform temperature in the plane of the silicon substrate, and it is difficult to obtain a highly reliable oxide film due to problems such as deterioration of the oxidizing atmosphere due to elution of the material at the ignition point.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to form a highly reliable silicon oxide film in an oxidizing atmosphere with high cleanliness.

SUMMARY OF THE INVENTION It is an object of the present invention to reform an oxide film by performing a heat treatment after an oxidation process to form a highly reliable silicon oxide film.

[0007]

According to the method of forming a silicon oxide film of the present invention, water is generated by catalytic action from oxygen and hydrogen, and the silicon oxide film is formed by contacting the silicon kept at a high temperature. It is characterized by the following.

The method of forming a silicon oxide film according to the present invention is characterized in that a water is generated from oxygen and hydrogen by a catalytic action, a diluent gas is added, and the silicon oxide film is brought into contact with silicon kept at a high temperature. Is formed.

In the present invention, the volume ratio of hydrogen to oxygen is preferably such that oxygen / hydrogen is at least 1/3 to 1/1.

In the present invention, the volume ratio of hydrogen to oxygen is preferably about 1/2.

In the present invention, the diluent gas is preferably argon or nitrogen.

In the present invention, it is preferable to perform a heat treatment with argon or nitrogen after the oxidation with moisture.

In the present invention, it is preferable to form an oxide film with a gas containing oxygen after the oxidation with moisture.

In the present invention, the gas containing oxygen is preferably a gas obtained by diluting oxygen with argon or nitrogen.

According to the transfer method of the present invention, after the formation of the silicon oxide film, the transfer of the silicon oxide film to the processing chamber of the next step is performed in a clean nitrogen or clean nitrogen / oxygen atmosphere in which the water content of impurities is 100 ppb or less and the hydrocarbon is 100 ppb or less. It is characterized by doing.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is characterized in that water is generated by catalytic action from oxygen and hydrogen to form a silicon oxide film. Due to the catalysis, water generation at high temperatures (about 2000 ° C.) in the prior art is reduced to low temperatures (about 45
0 ° C), temperature control during oxidation formation is easy, it is easy to keep the temperature in the silicon substrate surface uniform, and by preventing material elution in the reaction furnace, a highly clean oxidizing atmosphere can be formed. The oxide film can be formed and a highly reliable oxide film can be formed.

Under oxidizing conditions, the volume ratio of oxygen to hydrogen used is from oxygen / hydrogen of 1/3 or more (hydrogen excess state) to 1/1 or less (oxygen excess state), preferably 1/2. Yes, it is possible to form an oxide film with various oxidizing species, which was not possible in the past. In an oxidizing atmosphere, it is preferable to use argon or nitrogen as a gas for diluting moisture.

In the present invention, after oxidation with water,
Heat treatment using argon or nitrogen removes moisture adsorbed at the time of oxide film formation and hydrogen-silicon bonds or hydroxyl-silicon bonds, which can cause defects in electrical characteristics, thereby improving reliability. A high oxide film can be formed.

Further, after the above-described oxidation, silicon which is not bonded to oxygen is oxidized, so that a heat treatment is performed with oxygen, whereby a highly reliable oxide film can be obtained. Argon, as a diluent gas in the oxygen heat treatment described above,
Alternatively, nitrogen may be used.

After the oxidation according to the present invention, in order to prevent adhesion of moisture, hydrocarbons and the like to the silicon oxide film, the silicon oxide film is transported to the next step in a clean nitrogen or clean nitrogen / oxygen atmosphere. For example, the box is filled with clean nitrogen or clean nitrogen / oxygen, and a substrate having a silicon oxide film formed therein is accommodated and transported. Here, clean nitrogen or clean nitrogen / oxygen means that the water content is 100 ppb or less (preferably 10 ppb or less) and the hydrocarbon content is 100 ppb or less (preferably 10 ppb or less).
pb or less) of nitrogen or nitrogen / oxygen.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A technique for forming a highly reliable oxide film in the oxidation of silicon in semiconductor manufacturing according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to these examples. Not something.

In this case, silicon was oxidized by generating water by a catalytic action in a reactor coated with about 2 μm of platinum. The metal catalyst effective for generating moisture may be nickel, palladium, gold, copper, or the like.

(Example 1) In order to compare the amount of contamination of the water generated by the pyrogenic method with the amount of water generated by the water generator by the catalytic action, 1 L / min of oxygen and 500 cc / min of hydrogen were introduced, respectively. The obtained water was applied to an amorphous carbon substrate for 3 hours, and the amount of metal contamination was measured by total reflection X-ray fluorescence spectroscopy using TREX610 of TECNOS.

[0024]

[Table 1] From Table 1, in the pyrogenic water generation method,
Due to the elution of the reaction furnace material (silicon glass) at the time of ignition,
Although water was contaminated, no water contamination was observed in the catalytic water generator.

The amount of water contamination indicates the cleanliness at the time of forming the oxide film, and the method of generating water by the catalytic action capable of creating an oxidizing atmosphere with high cleanliness forms a highly reliable oxide film. It is possible to

(Example 2) By the moisture generator used in Example 1, the volume ratio of oxygen to hydrogen was changed from 1/3 or more (hydrogen excess state) to 1/1 or less (oxygen excess state). ), A moisture is generated and brought into contact with a silicon substrate held at 900 ° C. to form an oxide film with a thickness of about 6 nm;
A MOS capacitor (an n ⁺ poly-Si / SiO ₂ / n-Si structure in which polycrystalline silicon (polysilicon) doped with phosphorus is formed as a gate electrode on an oxide film) is formed, and an electrical connection at that time is formed. The characteristics were measured for oxidized species dependence using 4156B manufactured by Hewlett-Packard Company. The measurement conditions at that time are shown in FIG. 1 when the voltage of the gate electrode was made positive and a constant current stress (1 A / cm ² ) was applied.

FIG. 1 shows the dielectric breakdown characteristics over time.
The vertical axis represents the cumulative failure rate, and the horizontal axis represents the charge injection amount up to the dielectric breakdown. The charge injection amount is a constant current stress of 1 A
In the case where / cm ² = 1C (second · cm ² ), the dielectric constant is 10 C / cm ² when the oxide film is broken down due to the stress caused by the constant current in 10 seconds. Good oxide film quality means that dielectric breakdown is unlikely to occur, that is, it is sufficient that the injected charge amount is large. Therefore, those on the right side of the graph have better characteristics. In a flash memory, the stress condition (1 A / cm ² )
When charge can be injected into the oxide film at 0 C / cm ² , writing and erasing can be performed one million times.

From FIG. 1, it can be seen from FIG. 1 that in the excess oxygen state, the oxidation occurs simultaneously with the moisture oxidation and the dry oxidation, and is located between the characteristics of the moisture oxidation and the dry oxide film. Completely SiO ₂ by action
It can be seen that good results were not obtained, and good results were obtained when the volume ratio of oxygen to hydrogen was 1/2. From this, the conditions at the time of forming the oxide film are as follows:
It can be seen that the volume ratio of oxygen to hydrogen used is from 1/3 or more (hydrogen excess state) to 1/1 or less (oxygen excess state), preferably 1/2.

In this case, argon was used as the diluent gas,
The water content was 2%. If the water concentration is increased, the oxidation rate is increased, and the formation temperature can be lowered in order to obtain the same acid acceleration. Therefore, it is presumed that contamination from an electric furnace or the like can be reduced, and better results can be obtained. . Further, nitrogen may be used as the dilution gas.

Example 3 As in Example 2, the volume ratio of oxygen and hydrogen used was 1/2 oxygen / hydrogen, an oxide film was formed, and after forming the oxide film, argon was used while maintaining the temperature. A heat treatment is applied to form a MOS capacitor, the electrical characteristics are measured, and the results of the effect of the heat treatment after oxidation are shown in FIG. The measurement conditions were the same as in Example 2, except that the gate electrode voltage was made positive and a constant current stress (1 A / cm ₂ ) was applied.

In FIG. 2, the abscissa axis indicates the application time of the stress, and the ordinate axis indicates the amount of change in the gate voltage. The voltage of the gate electrode is applied so that a constant stress current flows in the oxide film. However, when electrons or holes are trapped in an incomplete portion of the gate oxide film, the gate voltage changes to flow a constant current. Therefore, in the case of a complete gate oxide film, the gate voltage does not change when a constant current stress is applied. In other words, the better the oxide film, the smaller the amount of change in the gate voltage.

As shown in FIG. 2, the amount of shift of the gate voltage is reduced by performing a heat treatment using argon after the oxidation with moisture. That is, by performing a heat treatment after the gate oxidation using argon, moisture adsorbed at the time of forming the oxide film and hydrogen which can be a defect in electrical characteristics are obtained.
It is understood that a highly reliable oxide film is formed by removing a silicon bond or a hydroxyl-silicon bond. The optimal time is estimated to be about one hour.
Further, nitrogen may be used as a heat treatment gas.

Example 4 As in Example 3, the volume ratio of oxygen and hydrogen used was 1/2 oxygen / hydrogen, an oxide film was formed, and after forming the oxide film, argon was used while maintaining the temperature. Heat treatment with 10% oxygen mixed gas diluted with
An S capacitor was prepared, its electrical characteristics were measured, and the results of the effect of the heat treatment after oxidation are shown in FIG.

FIG. 3 shows the time-dependent dielectric breakdown characteristics. The measurement conditions are a constant current stress (0.1 A / cm ² ) with a negative gate electrode voltage. When the voltage of the gate electrode is negative, it is used at the time of erasing in the flash memory. An oxide film having a characteristic of 10 C / cm ^{2 at} a stress current (1 A / cm ² ) in order to be able to erase one million times. At present, generally, the time-dependent dielectric breakdown characteristics when the applied voltage of the gate electrode is negative are poor, and improvement of the characteristics is required.

From FIG. 3, it can be seen from FIG. 3 that, after oxidation with moisture, silicon not bonded to oxygen is oxidized, so that heat treatment with oxygen increases the charge injection amount up to dielectric breakdown, thereby increasing the reliability of the oxide film. It is possible to get.

With a 10% oxygen / argon mixed gas, the heat treatment time of one minute is the most optimal, but it is considered that the heat treatment time can be shortened by increasing the oxygen concentration. Also, this time, argon was used as a diluent gas, but 100% oxygen may be used without dilution.
Further, nitrogen may be used as the diluent gas.

(Example 5) As in Example 2, the volume ratio of oxygen and hydrogen used was 1/2 oxygen / hydrogen. After an oxide film was formed, moisture, hydrocarbon, etc. were added to the silicon oxide film. In order to prevent the adhesion of ash, the wafer was transferred in a transfer container capable of holding a clean nitrogen atmosphere, a MOS capacitor was prepared, the electrical characteristics were measured, and the results of the effect of the transfer in a clean nitrogen atmosphere are shown in FIG. Show. FIG. 4A shows a case in which clean nitrogen transfer is not performed, and FIG. 4B shows a case in which clean nitrogen transfer is performed.

4 (a) and 4 (b), when the clean nitrogen transport was not performed, the dielectric breakdown electric field varied, but when the clean nitrogen transport was performed, the dielectric breakdown electric field did not vary. By performing clean nitrogen transport, a highly reliable oxide film can be obtained.

In this embodiment, the transfer atmosphere is clean nitrogen, but the transfer may be performed in a clean nitrogen / oxygen atmosphere.

[0040]

According to the present invention, it is possible to form a highly reliable silicon oxide film in an oxidizing atmosphere with high cleanliness.

According to the present invention, by performing a heat treatment after the oxidation treatment, the oxide film is reformed, and a silicon oxide film with higher reliability can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing electrical characteristics (oxidation species dependence) of an oxide film by various oxidation species.

FIG. 2 shows the effect of heat treatment after oxidation (heat treatment dependence).

FIG. 3 shows the effect of oxygen heat treatment after oxidation (dependence on oxygen heat treatment).

FIG. 4 shows the effect of clean nitrogen transport after forming an oxide film.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuhisa Nitta 4-1-1 Hongo, Bunkyo-ku, Tokyo Inside Ultra Clean Technology Development Laboratory Co., Ltd. (72) Inventor Toshiyuki Iwamoto Aramaki Aoba-ku, Aoba-ku, Sendai, Miyagi Aoba (unnumbered) Tohoku University

Claims (9)

[Claims] 1. A method for forming a silicon oxide film, comprising generating moisture from oxygen and hydrogen by a catalytic action and bringing the silicon into contact with silicon kept at a high temperature to form a silicon oxide film. 2. A silicon oxide film comprising forming a silicon oxide film by generating water from oxygen and hydrogen by a catalytic action, adding a diluent gas, and bringing it into contact with silicon kept at a high temperature. Method of forming a film. 3. The method for forming a silicon oxide film according to claim 2, wherein the volume ratio of hydrogen to oxygen is such that oxygen / hydrogen is at least １ ／ to 1/1. 4. The volume ratio of hydrogen to oxygen is approximately 1
4. The method of claim 3, wherein the ratio is / 2. 5. The method according to claim 2, wherein the dilution gas is argon or nitrogen. 6. A method for forming an oxide film, comprising performing a heat treatment with argon or nitrogen after oxidation with water. 7. An oxide film is formed by a gas containing oxygen after oxidation by water.
5. The method for forming a silicon oxide film according to claim 1. 8. The method according to claim 7, wherein the gas containing oxygen is a gas obtained by diluting oxygen with argon or nitrogen. 9. After the formation of the silicon oxide film according to claim 1, 100% of water as an impurity is removed.
A transfer method, wherein the transfer is carried out to a processing chamber of the next step in a clean nitrogen or clean nitrogen / oxygen atmosphere of ppb or less and hydrocarbons of 100 ppb or less.