JPH0855847A - Method and apparatus for heat treatment of silicon oxide film - Google Patents

Abstract

PURPOSE:To denature a silicon oxide film which is sufficient for use as a gate insulating film by a method wherein the silicon oxide film heated to a temperature in a specific temperature range is irradiated with ultraviolet rays in a hydrogen nitride atmosphere. CONSTITUTION:A silicon oxide film as a substratum is formed on a substrate 105, and an amorphous silicon film is formed. After that, a heating treatment is executed in an N2 atmosphere, and the amorphous silicon film is crystallized. The crystallized silicon film is etched, an island-shaped region is formed, and a silicon oxide film as a gate insulating film is formed. The substrate 105 is placed on a substrate holder 104 in which a heater has been installed at the lower part. Then, NH3 is introduced into a chamber 101 from a gas introduction system 107, and a heating treatment is executed at a temperature of 300 to 700 deg.C while ultraviolet rays are being emitted from an ultraviolet light source 106 in a substantially 100-% NH, atmosphere in which the pressure at the inside of the chamber is set at atmospheric pressure. Thereby, it is possible to obtain the silicon oxide film whose durability is good, which is not degraded and which is excellent in a characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an insulating substrate such as glass,
Alternatively, a semiconductor device using a silicon oxide film formed by a PVD method or a CVD method as a gate insulating film provided on an insulating coating formed on various substrates, for example, a thin film transistor (TFT) or a thin film to which the thin film is applied The present invention relates to a method for manufacturing an integrated circuit, in particular, a thin film integrated circuit for an active liquid crystal display device (liquid crystal display), and more particularly to a heat treatment method and a heat treatment apparatus for a gate insulating film to obtain a gate insulating film having good characteristics.

[0002]

2. Description of the Related Art In recent years, semiconductor devices having TFTs on an insulating substrate such as glass, for example, active type liquid crystal display devices using TFTs for driving pixels and image sensors have been developed. TFTs used in these devices include
Generally, a thin film silicon semiconductor is used. The thin film silicon semiconductor is roughly classified into two types, that is, an amorphous silicon semiconductor and a crystalline silicon semiconductor. Amorphous silicon semiconductors have a low production temperature, can be produced relatively easily by the vapor phase method, and have high mass productivity.
Although most commonly used, the physical properties such as conductivity are inferior to those of crystalline silicon semiconductors. Therefore, in order to obtain higher speed in the future, a method of manufacturing a TFT made of crystalline silicon semiconductors. There is a strong demand for establishment.

TFT using amorphous silicon having low mobility
In this case, the characteristics of the gate insulating film did not pose a problem. For example, in a TFT using amorphous silicon, a silicon nitride film having electric characteristics inferior to that of silicon oxide is used as a gate insulating film. However, in a TFT using a crystalline silicon film having a high mobility, the characteristics of the gate insulating film are a big problem as much as the characteristics of the silicon film itself. A thermal oxide film is preferable as the gate insulating film. For example, a gate insulating film could be obtained by using a thermal oxidation method on a substrate such as a quartz substrate that can withstand high temperatures. (For example, Japanese Patent Publication No. 3-71793)

A high temperature of 950 ° C. or higher is required to obtain a silicon oxide film that can be used as a gate insulating film by the thermal oxidation method. However, there is a substrate material other than quartz that can withstand such a high-temperature treatment, and the quartz substrate is expensive and has a problem that it is difficult to increase the area because it has a high melting point. However, the cheaper glass substrate materials have a strain point of 750 ° C. or lower, generally 550 to 6
There has been a problem that the substrate cannot withstand the high temperature at 50 ° C. for obtaining a thermal oxide film by a usual method. Therefore, the gate insulating film is formed by a physical vapor deposition method (PVD method, for example, sputtering method) or a chemical vapor deposition method (CVD method, for example, plasma CVD method, optical CVD method) that can be formed at a lower temperature. .

[0005]

[Problems to be Solved by the Invention] However, PVD
The insulating film formed by the CVD method or the CVD method had a high concentration of dangling bonds or hydrogen, and had poor interface characteristics. Therefore, it is weak against injection of hot carriers and the like, and is likely to form charge trap centers due to dangling bonds and hydrogen. Therefore, when it is used as a gate insulating film of a TFT, the electric field mobility and the subthreshold characteristic value (S
Value) is not good, or the leak current of the gate electrode is large, and the ON current decreases (deterioration / aging)
However, there was a problem that it was huge.

For example, in the case of using the sputtering method which is the PVD method, if synthetic quartz composed of high-purity oxygen and silicon is used as a target, in principle only a film of a compound of oxygen and silicon is formed. However, it was extremely difficult to obtain a silicon oxide film in which the ratio of oxygen to silicon in the obtained coating is close to the stoichiometric ratio and the number of dangling bonds is small. For example,
Oxygen was the preferred sputter gas. However, oxygen has a small atomic weight and a low sputtering rate (deposition rate), and is unsuitable as a sputtering gas in consideration of mass production. Further, in an atmosphere of argon or the like, although a sufficient film formation rate was obtained, the ratio of oxygen and silicon was different from the stoichiometric ratio, and it was extremely inappropriate as a gate insulating film.

Further, it is difficult to reduce the dangling bonds of silicon whatever the sputtering atmosphere is, and by performing a heat treatment in a hydrogen atmosphere after the film formation, the dangling bonds of silicon Si.・ Si-H, Si
It was necessary to stabilize it as -OH. However, the Si-H and Si-OH bonds are unstable, and are easily broken by the accelerated electrons and converted into the original dangling bonds of silicon. Such weak bond Si-
The presence of H and Si—OH is a factor that causes the deterioration due to the hot carrier injection. Similarly, plasma CV
The silicon oxide film formed by the D method also has Si-H and Si.
Since a large amount of hydrogen was contained in the form of -OH and there were many unpaired bonds, it was a source of the above problems. The present invention provides means for solving the above problems.

[0008]

A silicon oxide film, for example, a silicon oxide film formed by a thermal oxidation method is replaced with ammonia (N
H ₃ ), hydrazine (N ₂ H ₄ ) and the like are subjected to heat treatment at a temperature of 900 ° C. or higher in an atmosphere of hydrogen nitride to reduce nitridation and reduce unpaired bonds. It is known that the silicon oxide film becomes higher and an ideal silicon oxide film can be obtained as a gate insulating film.

However, the heat treatment performed at this time is a process that can be performed only on a substrate having a high strain point such as a quartz substrate because the temperature is as high as 900 ° C. or higher. Therefore, the strain point is 750 ° C or lower, typically 55
This heat treatment could not be introduced in the low temperature process of forming a TFT using various glass substrates at 0 to 650 ° C.

The inventors of the present invention proceeded with research on lowering the temperature of this reaction, and by irradiating with ultraviolet light during the heat treatment in an NH ₃ or N ₂ H ₄ atmosphere, 300
It was found that the same effect as the heat treatment at 900 ° C. or higher can be obtained by the heat treatment at −700 ° C., preferably 500 to 600 ° C. At this time, the wavelength of the ultraviolet light used is 100 to 350 nm, preferably 15
It is set to 0 to 300 nm.

The first aspect of the present invention is the PVD method or CVD.
The silicon oxide film formed by the method is subjected to 300 to 7 in a hydrogen nitride atmosphere such as NH ₃ or N ₂ H _4.
A heat treatment is performed at 00 ° C., preferably 500 to 600 ° C., and at the same time, irradiation with ultraviolet light is performed to modify the silicon oxide film to be sufficient as a gate insulating film.

The time of the heat treatment in the hydrogen nitride atmosphere depends on the characteristics of the silicon oxide film, the heat treatment temperature, the intensity of the ultraviolet light, etc., but it is preferably 30 minutes to 6 hours in consideration of mass productivity. In addition, the rate of rise or fall of the substrate temperature in the heat treatment step may be determined depending on the embodiment of the present invention.
It is desirable to raise or cool the temperature at a rate of -30 ° C / min. Further, the temperature raising / cooling may be performed in a nitrogen atmosphere.

In the present invention, for example, the PVD method is a sputtering method, and the CVD method is a plasma CVD method.
Method, low pressure CVD method, or atmospheric pressure CVD method may be used. Other film forming methods can also be used. Further, as the plasma CVD method or the low pressure CVD method, TEOS is used.
You may use the method made from. In the former case, the substrate temperature is 200 to 50 using TEOS and oxygen as raw materials.
It may be deposited at 0 ° C. In the latter case, TE
Using OS and ozone as raw materials, the temperature is relatively low (for example, 37
At 5 ° C. ± 20 ° C.), a silicon oxide film free from plasma damage can be obtained. Similarly, by using the low pressure CVD method, even when monosilane (SiH ₄ ) and oxygen gas (O ₂ ) are the main raw materials, a silicon oxide film can be obtained without causing plasma damage to the active layer. Among plasma CVD methods, ECR (electron cyclotron resonance)
Since the ECR-CVD method using discharge under the condition causes less damage due to plasma, a better gate insulating film can be formed.

A second aspect of the present invention relates to a heat treatment apparatus suitable for performing the above-mentioned steps, which is a chamber for heat treatment, and a preparatory chamber for setting a substrate before heat treatment and a substrate after heat treatment. And a front chamber provided with a carrier for transferring the substrate, the chamber is provided with a substrate holder provided with a heater for heating the substrate, and a chamber for heating the substrate is provided. The heat treatment apparatus is characterized in that a light source for irradiating the substrate with ultraviolet light is attached to the outside or inside.

In this apparatus, in order to further improve the productivity, the substrate holder inside the chamber is made into a roughly conveyor-shaped carrier made of heat-resistant metal, and the heat treatment can be performed while moving the substrate. You may do it. Further, the substrate holder inside the chamber for heating the substrates may be a conveyor-like transfer device made of heat-resistant metal so that a plurality of substrates can be attached and heat treatment can be performed at once. . Further, a heater may be provided below the roughly conveyor-shaped transport device.

Another apparatus of the present invention has a cylindrical chamber, and a heater for heating a substrate is provided around the cylindrical chamber, and the central portion of the cylindrical chamber is provided. Is provided with a light source for irradiating the substrate with ultraviolet light, and has a structure for mounting the substrate along the inner wall of the cylindrical chamber. By doing so, the ultraviolet light can be effectively used and the productivity can be improved.

[0017]

[Function] A silicon oxide film formed by a CVD method or a PVD method is heated to 900 ° C. in an NH ₃ or N ₂ H ₄ atmosphere.
When the above heat treatment is carried out, the unpaired bonds are filled with nitrogen, Si--H bonds in the silicon oxide film and Si--
When the OH bond is nitrided, Si≡N or Si ₂ ═N−
The H-bond is changed to increase nitrogen in the silicon oxide film. In particular, this reaction easily proceeds at the interface between silicon oxide and silicon, and as a result, nitrogen is concentrated at the silicon oxide-silicon interface. The amount of nitrogen concentratedly added near the interface by such means is 10 times or more the average concentration of the silicon oxide film. It is preferable for the gate insulating film to contain 0.1 to 10 atomic%, typically 1 to 5 atomic% of nitrogen in silicon oxide.

As a result, an unpaired bond at the interface between the gate insulating film and the active layer, or a Si—H bond or a Si—OH bond that is weakly bonded and easily broken by hot carriers, has a strong bond. It is replaced with N bond, Si ₂ ═N—O bond, etc., and the change in chemical state due to hot carriers becomes extremely small.

As described above, in the silicon oxide film, especially in the vicinity of the interface with the silicon film, dangling bonds, Si--H bonds and Si--OH.
By nitriding the bond, the resistance to hot carriers is improved, the electric field mobility and the subthreshold characteristic value (S value) when used as a gate insulating film of a TFT are improved, and the on-current decreases (deterioration / deterioration). A significant effect was brought about in preventing (change with time).

The above reaction proceeded only in the heat treatment at 900 ° C. or higher. It is estimated that this is because the temperature required for decomposing NH ₃ and N ₂ H ₄ is 900 ° C. or higher. However, it was possible to lower the temperature by using UV irradiation together. At this time, the wavelength of the ultraviolet light used is 100 to 350 nm, preferably 150 to 300 nm. This is because NH ₃ and N ₂ H ₄ are decomposed by ultraviolet light, and thus 300 to 700 ° C., preferably 500 to 600 ° C.
It is presumed that even in the heat treatment of 1, the reaction equivalent to the above became possible. Further, in the silicon oxide film irradiated with ultraviolet light, particularly, dangling bonds, Si-H bonds, Si-
It is also considered that the OH bond easily absorbs the ultraviolet light, and as a result, such a portion is chemically excited and the chemical reaction is promoted.

A silicon oxide film formed according to the present invention by a sputtering method (particularly, a silicon oxide film having an oxygen concentration lower than a stoichiometric ratio by using argon or the like as a sputtering atmosphere).
The effect is particularly remarkable when applied to. That is,
Although such a film has many unpaired bonds, NH ₃ ,
In an atmosphere of hydrogen nitride such as N ₂ H ₄ , 300 to 700 ° C., preferably 500 to 60, while irradiating with ultraviolet light.
By heat treatment at 0 ° C, nitriding dangling bonds,
Nitrogen can be bonded instead of oxygen, which is insufficient with respect to the stoichiometric ratio, to form an oxynitride film with few unpaired bonds.

The above shows that the formation of the silicon oxide film by the sputtering method is not disadvantageous. That is,
Conventionally, to form a silicon oxide film by a sputtering method,
In order to bring the composition close to the stoichiometric ratio, it was performed only in an atmosphere of limited conditions. For example, considering a system of a mixed atmosphere of oxygen and argon as the atmosphere, it is necessary to satisfy the condition of oxygen / argon> 1, and preferably,
It was desired to do it in a pure oxygen atmosphere. Therefore, the film forming rate was low and it was not suitable for mass production. Further, oxygen is a reactive gas, and there is a problem that the vacuum device, the chamber and the like are oxidized.

However, according to the present invention, even a silicon oxide film having a composition deviating from the stoichiometric composition can be converted into a silicon oxide film suitable for use as a gate insulating film, so that the same mixed atmosphere system of oxygen and argon is used. Even in
It can be carried out under more favorable conditions with respect to the film formation rate, such as oxygen / argon ≦ 1. For example, it is possible to form a film under stable conditions with a very high film forming rate as in a pure argon atmosphere.

Such an effect is obtained by PVD other than the sputtering method.
Method or a silicon oxide film formed by various CVD methods. As described above, by using the present invention, although the temperature is as low as 300 to 700 ° C.,
The dangling bonds in the silicon oxide film formed by the PVD method or the CVD method can be reduced and the concentration of nitrogen can be increased. The TFT using this silicon oxide film as a gate insulating film exhibits excellent characteristics and high reliability.

[0025]

【Example】

[Embodiment 1] In this embodiment, a silicon oxide film formed by a plasma CVD method is irradiated with ultraviolet light simultaneously with NH ₃ heat treatment for modification, and an N channel type TFT is formed using this as a gate insulating film. It is an example. FIG. 7 shows the manufacturing process of the TFT of this embodiment, and FIG. 1 shows an outline of the apparatus used for the heating / ultraviolet light irradiation treatment of the silicon oxide film.

First, the underlying silicon oxide film 7 is formed on the substrate 701.
02 was formed to 3000 Å by the plasma CVD method. Then, an amorphous silicon film was formed to a thickness of 500 Å by the plasma CVD method. Then, heat treatment was performed in an N ₂ atmosphere to crystallize the amorphous silicon film. At this time, in order to promote the crystallization of the amorphous silicon film, a trace amount of an element such as nickel that promotes the crystallization of the amorphous silicon may be added. Further, laser annealing may be performed to improve crystallization. (Figure 7 (A))

Next, the crystallized silicon film 703 was etched to form island regions 704. This island region 70
Reference numeral 4 is an active layer of the TFT. Then, a 1000 Å silicon oxide film 705 was formed as a gate insulating film. In this example, a silicon oxide film was produced by the following first to third different methods. (FIG. 7 (B)) The first is a plasma CVD method using TEOS as a raw material. In this method, TEOS and oxygen vaporized by a vaporizer are introduced into a chamber having parallel plate type electrodes, and RF
Electric power (for example, 13.56 MHz) was introduced to generate plasma, and the plasma was deposited at a substrate temperature of 200 to 500 ° C, preferably 250 to 400 ° C. In this embodiment, the reaction pressure is 4 Pa, the input power is 150 W, and the substrate temperature is 350 ° C.
And

The second method is the sputtering method. This uses synthetic quartz as a target, oxygen 100%,
A film was formed by sputtering in an atmosphere of 1 Pa. Input power was 350 W and substrate temperature was 200 ° C. The third is by the ECR-CVD method, which uses monosilane (SiH ₄ ) and oxygen as source gases. Nitrogen oxide gas such as N ₂ O, NO, NO ₂ may be used instead of oxygen. In addition, as film forming conditions at this time, the substrate was not heated, and the input power of microwave (frequency: 2.45 MHz) was 400 W.

After that, the heat treatment apparatus shown in FIG. 1 was used to perform heat treatment in an NH ₃ atmosphere. As shown in FIG. 1, the heat treatment apparatus used in this embodiment includes a chamber 101 for performing heat treatment, a preparatory chamber 102 for storing unprocessed substrates, and a reserve chamber for storing processed substrates. It is composed of a chamber 103 and a front chamber 109 having a carrier 110, and the substrate 111 is transferred by the carrier 110 between these chambers. In this embodiment, the chamber 101 is of a single-wafer type that can perform one heat treatment at a time.

The chamber 101 also has a substrate holder 104 having a heater for heating the substrate 105 at the bottom. Further, an ultraviolet light source 106 is provided outside the chamber 101. In this embodiment, a low pressure mercury lamp (center wavelength 24
6 nm, and 185 nm) were used. Chamber 1
In the upper part of 01 where the ultraviolet light source 106 is attached, a window is formed by a material such as quartz that does not absorb the ultraviolet light in order to take in the ultraviolet light. Although the ultraviolet light source is installed outside the chamber in this embodiment, it may be installed inside the chamber.

Further, the chamber 101 and the antechamber 109 are provided with an exhaust system 108 for exhausting gas and a gas introducing system 107 for introducing gas. First, a plurality of unprocessed substrates are set in a cassette, and the preliminary chamber 10
I set it to 2. Then, the substrate is transferred to the front chamber 109 by the carrier 110, and the exhaust system evacuates the front chamber to reduce the pressure in the front chamber 109. Then, the substrate is transferred to the already-decompressed heat treatment chamber 101 and is transferred to the substrate holder 104. It was installed.

Then, NH ₃ is introduced into the chamber 101 from the gas introduction system 107, and in a substantially 100% NH ₃ atmosphere in which the pressure inside the chamber is atmospheric pressure,
The heat treatment was performed while irradiating with ultraviolet light. On this occasion,
The heating temperature was 350 to 600 ° C., for example 500 ° C.
The processing time was 30 minutes to 6 hours, for example, 3 hours.

After the heat treatment as described above, the processed substrate is transferred to the front chamber 109 by the carrier 110, and then set in the cassette in the preliminary chamber 103 in which the processed substrate is set, The process of processing one substrate is completed. After that, the same process was repeated. The heat treatment of the present invention was performed as described above.
The same effect as that obtained when the heat treatment at 900 ° C. was performed in the H ₃ atmosphere was obtained at the heat treatment at 500 ° C.

That is, as a result of analyzing the sample which was subjected to the heat treatment combined with the ultraviolet light by the secondary ion mass spectrometry (SIMS), it was found in the silicon oxide film that the above first method (TEOS plasma CVD method) was used. It was confirmed that the amount of nitrogen (N) increased at the interface with the silicon film in the silicon oxide film manufactured by. The same applies to the silicon oxide film formed by the second method (sputtering method) and the third method (ECR-CVD method). The silicon oxide film having such a composition was preferable as the gate insulating film. For comparison, the silicon oxide film formed by the above first to third methods is used in the device of FIG.
No change in the concentration of nitrogen was observed when heating under the same temperature conditions in a nitrogen atmosphere instead of NH ₃ .

Then, aluminum with a thickness of 5000 Å (1 wt% Si, or 0.1-0.3 wt% S
A film (including c) was formed by a sputtering method, and this was etched to form a gate electrode 706. Next, the substrate was immersed in a 1% to 3% ethylene glycol solution of tartaric acid adjusted to pH≈7 with ammonia, and anodization was performed using platinum as a cathode and this aluminum gate electrode as an anode. The anodization was completed by first increasing the voltage to 120 V with a constant current and maintaining the state for 1 hour. Thus, an anodic oxide having a thickness of 1500 Å was formed.

After that, impurities (phosphorus in this case) are implanted in the island-shaped silicon film 704 in a self-aligned manner by the ion doping method using the gate electrode 706 as a mask. In this case, the dose amount is 1 × 10 ^{14 to} 5 × 10 ¹⁵ atoms / cm ² , the accelerating voltage is 10 to 90 kV, for example, the dose amount is 1 × 10 ^15.
The atom / cm ² and the acceleration voltage were 80 kV. As a result,
N-type impurity region 707 was formed. (FIG. 7C) Further, a KrF excimer laser (wavelength 248 nm, pulse width 20 nsec) was irradiated to activate the doped impurity region 707. The energy density of the laser was 200 to 400 mJ / cm ² , preferably 250 to 300 mJ / cm ² . This step may be performed by heat treatment.

Next, as the interlayer insulating film 708, a silicon oxide film was formed to a thickness of 4000 Å by the plasma CVD method. (FIG. 7D) Then, the interlayer insulating film 708 and the gate insulating film 705 were etched to form contact holes in the source / drain. After that, an aluminum film is formed by a sputtering method and patterned to form a source / drain electrode 709, and an N-channel TFT.
Was produced.

The deterioration of the TFT manufactured in this example was evaluated. The TFT manufacturing method includes a gate insulating film manufacturing method (any one of the first to third methods) and a gate insulating film heat treatment method (NH ₃ atmosphere / ultraviolet light irradiation / 500 ° C./3).
Time (either of the above conditions is referred to as "NH ₃ atmosphere") or N ₂ atmosphere / no ultraviolet light irradiation / 500 ° C / 3 hours (the above conditions are referred to as "N ₂ atmosphere") All were the same except that they were changed as shown in the table. The drain voltage of the obtained TFT was fixed at +14 V, and the gate voltage was changed from -17 V to +17 V, and the drain current was measured. This measurement was measured 10 times, and the field-effect mobility μ ₀ obtained by the first measurement was compared with the field-effect mobility μ ₁₀ obtained by the 10th measurement, and 1- (μ ₁₀ / μ
₀ ) was defined as the deterioration rate. The results are shown in the table below.
(The negative sign of the deterioration rate means that the mobility has increased)

Sample name Gate insulating film forming method Heat treatment method Deterioration rate A-1 1st (TEOS plasma CVD) NH ₃ atmosphere 4.3% A-2 1st (TEOS plasma CVD) N ₂ atmosphere 50. 6% B-1 2nd (sputtering method) NH ₃ atmosphere -0.8% B-2 2nd (sputtering method) N ₂ atmosphere 12.5% C-1 3rd (ECR-CVD method) NH ₃ atmosphere 1 .2% C-2 a 3 (ECR-CVD method) N ₂ atmosphere 21.6 percent

As described above, it was clarified that the deterioration rate was remarkably reduced by irradiating the sample with ultraviolet light during the heat treatment in the NH ₃ atmosphere of the present invention in all the samples. Further, from the same experiment, it was also clarified that no improvement was observed in the deterioration rate unless UV light was irradiated during the heat treatment in an NH ₃ atmosphere.

Although the TFT manufactured in this example uses a silicon oxide film manufactured by the PVD method or the CVD method for the gate insulating film, it has good durability and little deterioration, and , The one with excellent characteristics was obtained. This is because the dangling bonds, Si-H, and Si-OH bonds were nitrided by the heat treatment of the present invention combined with ultraviolet light irradiation in the NH ₃ atmosphere, and the nitrogen in the silicon oxide film increased. This is due to the fact.

[Embodiment 2] In this embodiment, a silicon oxide film formed on a silicon film is subjected to a heat treatment by a plasma CVD method using TEOS as a raw material by using the heat treatment apparatus shown in FIG. Here is an example. The silicon oxide film used in this embodiment was formed by the first method of the silicon oxide film 705 (see FIG. 7B) of the embodiment. As shown in FIG. 2, the heat treatment apparatus used in this example is different from the single-wafer type chamber shown in the first example, and is composed of only a chamber for performing heat treatment, and a plurality of chambers are provided at one time. It has a batch type structure that can process one substrate.

The chamber 201 of this embodiment has a columnar shape so that the substrate 203 can be placed along the inner wall thereof. The substrate 203 is heated by a heater 202 provided around the chamber 201. Further, an ultraviolet light source 204 is provided in the center of the chamber 201 so that all the substrates are uniformly irradiated with the ultraviolet light. In this example, a low-pressure mercury lamp (center wavelength: 246 nm and 185 nm) was used as an ultraviolet light source.

In addition, an exhaust system 206 for exhausting gas and a gas introducing system 2 for introducing gas are provided in the chamber.
05 is provided. An example of processing using this processing apparatus will be described. The substrate 203 was set along the inner wall of the chamber 201 so as to surround the ultraviolet light source 204. Then, N _{2 is} introduced into the chamber 201 from the gas introduction system.
Was introduced to replace the inside of the chamber with N ₂ . At this time, air was exhausted from the exhaust system 206 so that the inside of the chamber always maintained a constant pressure.

Next, when the inside of the chamber was replaced with N ₂ , the heater was heated and ultraviolet irradiation was performed. At this time, the heating temperature was 300 to 700 ° C., for example, 500 ° C. When the substrate is heated to a predetermined temperature, N ₂ is added to N ₂ H ₄
It was replaced with and irradiated with ultraviolet light. At this time, the processing time was 30 minutes to 6 hours, for example, 4 hours. The silicon oxide film that has been subjected to the above-mentioned treatment is subjected to secondary ion mass spectrometry (SIM
When analyzed by S), the nitrogen concentration was higher than the nitrogen concentration contained in the initial silicon oxide film, and in particular, the accumulation of nitrogen was observed at the interface with the silicon film.

[Embodiment 3] In this embodiment, a synthetic quartz is used as a target, a silicon oxide film formed on a silicon film by a sputtering method in an atmosphere of 100% oxygen is used, and the heat treatment apparatus shown in FIG. 3 is used. In this example, heat treatment is performed. The silicon oxide film used in this example was formed by the second method of the silicon oxide film 705 (see FIG. 7B) of the example.

As shown in FIG. 3, the heat treatment apparatus used in this embodiment has a chamber 30 for performing heat treatment.
1, a preliminary chamber 302 for storing unprocessed substrates, a preliminary chamber 303 for storing processed substrates, and a carrier 306.
It comprises front chambers 304 and 305 provided with 307, and substrates 308 and 309 are transferred between these chambers by transfer machines 306 and 307. In this example, the chamber for performing the heat treatment was
It is a batch type in which multiple substrates can be moved at one time by a conveyor and heat treatment can be performed.

FIGS. 4A and 4B show the internal structure of the chamber 301. The chamber 301 is provided with a conveyer 401 made of heat-resistant metal so that heat treatment can be performed while moving the substrate. Further, heaters 406, 407, and 408 for heating the substrate 402 are provided below the conveyor 401. In addition, the heater is the part 4 that raises the temperature of the substrate.
06, a part 407 for heating at a constant temperature, and a part 408 for cooling, which are composed of three different zones.
Further, an ultraviolet light source 409 is provided on the upper portion of the conveyor which is heated at a constant temperature. In this embodiment, a low-pressure mercury lamp (center wavelength: 246n) is used as an ultraviolet light source.
m, and 185 nm) were used.

Further, the chamber 301 is provided with exhaust systems 412, 413 for exhausting gas and gas introducing systems 409, 410, 411 for introducing gas. In the present embodiment, the portions 403 and 405 for heating and cooling the substrate are in the N ₂ atmosphere, and the portion 404 for heating at a constant temperature while irradiating ultraviolet light is in the NH ₃ atmosphere. Therefore, each part is equipped with a gas introduction system. In addition, exhaust systems 412 and 413 for exhausting the introduced gas are provided near the boundary of each zone. By providing the exhaust systems 412 and 413 at this boundary portion, gas mixture in each zone is prevented.

Next, working steps will be described. First, a plurality of unprocessed substrates were set in a cassette and set in the preliminary chamber 302. Here, in this embodiment, there are two preparatory chambers for setting the unprocessed substrate and two preparatory chambers for setting the treated substrate, respectively. This is because the substrate can be exchanged without stopping the apparatus and the work efficiency is improved. After that, the substrate was transferred to the front chamber 304 by the carrier 306, further transferred to the chamber 301 for heat treatment, and set on the conveyor 401. At this time, two substrates 402 are arranged side by side on the conveyor 401.

Then, in the heating step, the conveyor 4
The temperature gradient on 01 is shown in FIG. First, in the heating zone 403, the substrate is heated at a rate of 5 to 30 ° C./min, for example, 10 ° C./min. At this time,
N ₂ was introduced from the gas introduction system 409, and heating was performed in an N ₂ atmosphere.

The substrate was then moved to zone 404 where it was heated at a constant temperature. Here, the heat treatment was performed while irradiating ultraviolet light from an ultraviolet light source provided on the conveyor. The heating temperature is 500 to 600 ° C., for example, 5
It was set to 50 ° C. At this time, NH ₃ is supplied from the gas introduction system 410.
Was introduced to create an NH ₃ atmosphere. In the zone 404, 20 substrates can be processed at one time. The time required for one substrate to pass through this zone, that is, the time required for one substrate to be heat-treated was 30 minutes to 6 hours, for example, 3 hours.

After such heat treatment, the material is cooled to 250 ° C. by the cooling zone 405. The cooling rate at this time is 5 to 30 ° C./min as in the case of heating,
For example, it was set to 10 ° C./min. At this time, N ₂ was introduced from the gas introduction system 411 to create an N ₂ atmosphere. Then, the processed substrate is transferred to the front chamber 305 by the transfer system 307.
Preliminary chamber 3 where the processed substrate is transferred to
It was set in the cassette in No. 03, and the substrate processing step was completed.

In this way, N which is used in combination with ultraviolet light irradiation
Although the heat treatment was performed in an H ₃ atmosphere, Example 1
In the equipment shown in Fig. 4, it takes 4 substrates to process one substrate.
Although it took about a time, the use of the apparatus shown in this example improved the productivity to 10 minutes or more. The heat treatment of the present invention was performed as described above. As a result of analysis by secondary ion mass spectrometry (SIMS), it was observed that the amount of nitrogen was increased in the silicon oxide film, particularly at the interface with the silicon film, as a result of heat treatment using ultraviolet light in combination. This was the same as when the heat treatment was performed at 900 ° C. in the NH ₃ atmosphere.

Example 4 In this example, ECR-CVD using monosilane (SiH ₄ ) and oxygen as source gases.
In this example, the silicon oxide film formed on the silicon film by the method is subjected to heat treatment using the heat treatment apparatus shown in FIG. The silicon oxide film used in this embodiment was formed by the third method of the silicon oxide film 705 (see FIG. 7B) of the embodiment.

As shown in FIG. 5, the heat treatment apparatus used in this embodiment has a chamber 50 for performing heat treatment.
1, a preparatory chamber 502 in which pre-processed substrates are stored, a preparatory chamber 503 in which post-processed substrates are stored, and a pre-chamber 504 provided with a carrier 505. The substrate 506 is these chambers. It is transferred by a carrier 505. In the present embodiment, the chamber 501 is
It is a batch type in which multiple substrates can be moved at one time by a conveyor and heat treatment can be performed.

FIGS. 6A and 6B show the internal structure of the chamber 501. The chamber 501 is provided with a conveyor 601 made of heat-resistant metal for installing the substrate 602. Also, the conveyor 601
A heater 603 for heating the substrate is provided in the lower part of the. Furthermore, on the upper part of the conveyor 601,
An ultraviolet light source 604 is provided. In this embodiment, a low-pressure mercury lamp (center wavelength 246 nm,
And 185 nm) were used.

Further, the chamber 501 is provided with a gas introduction system 605 in order to create an N ₂ atmosphere when heating and cooling the substrate and an N ₂ H ₄ atmosphere when heating the substrate at a constant temperature. Further, an exhaust system 606 for exhausting the introduced gas is provided. Also,
A light source 605 for irradiating the substrate with ultraviolet light is provided.

Next, the processing steps will be described. A plurality of unprocessed substrates were set in the cassette and set in the preliminary chamber 502. Then, the substrate is transferred to the front chamber 5 by the carrier 505.
04, and a chamber 50 for heat treatment.
1 and was installed on the conveyor 601. At this time, the substrate 602 is sent on the conveyor 601 and is moved to the side by 2
They are arranged one by one and stopped when a total of 20 sheets are installed. FIG. 6C shows how the temperature changes with time during the heat treatment. When the temperature is raised, the temperature of the substrate is 5 to 30 ° C./mi
n, for example, heated at a rate of 10 ° C./min. At this time, N ₂ was introduced from the gas introduction system 605, and heating was performed in the N ₂ atmosphere.

After that, when the temperature for heat treatment was reached, ultraviolet light was emitted from an ultraviolet light source 604 provided on the conveyor 601. The heating temperature is 500-600 ° C,
For example, heating was performed at 550 ° C. At this time, immediately before the temperature reaches the temperature at which the heat treatment is performed, the gas introduction system 60
It is also possible to introduce N ₂ H ₄ from No. 5 and completely perform the heat treatment in the N ₂ H ₄ atmosphere when the temperature reaches the heat treatment temperature. At this time, the heat treatment time was 30 minutes to 6 hours, for example, 4 hours.

After performing such heat treatment, 25
Cooled to 0 ° C. The cooling rate at this time was 5 to 30 ° C./min, for example, 10 ° C./min, as in the heating. At this time, N ₂ was introduced from the gas introduction system 605 and the treatment was performed in an N ₂ atmosphere. After that, the processed substrate is transferred to the front chamber 504 by the carrier 505, and then set in the cassette in the preliminary chamber 503 in which the processed substrate is set, and the substrate processing step is completed.

The heat treatment of the present invention was performed as described above. By the above treatment, 900 ° C in N ₂ H ₄ atmosphere
It was confirmed by secondary ion mass spectrometry (SIMS) that the silicon oxide film contained the same amount of nitrogen as that obtained when the heat treatment was performed.

Example 5 In this example, monosilane (S
This is an example in which a silicon oxide film formed on a silicon film is subjected to heat treatment using a heat treatment apparatus shown in FIG. 5 by a low pressure CVD method using iH ₄ ) and oxygen gas (O ₂ ) as raw materials. . The conditions for forming the silicon oxide film used in this example are: substrate temperature of 300 to 500 ° C., chamber pressure of 0.1 to 10 torr, eg, 400 ° C., 1.5 to.
rr.

First, a plurality of unprocessed substrates were set in a cassette and set in a preliminary chamber 502. Then, the substrate is transferred to the front chamber 504 by the carrier 505, and further,
It was transferred to the chamber 501 for heat treatment and installed on the conveyor 601. FIG. 6C shows how the temperature changes with time during the heat treatment. When the temperature is raised, the substrate is 5 to 30
C./min, for example, heated at a rate of 10.degree. C./min. At this time, N ₂ was introduced from the gas introduction system 605, and heating was performed in the N ₂ atmosphere.

After that, when the temperature for heat treatment was reached, ultraviolet light (center wavelength 246 nm, 185 nm) was emitted from an ultraviolet light source 604 provided on the conveyor 601. The heating temperature is 500 to 600 ° C., for example, 550 ° C.
It was heated at. At this time, N ₂ H ₄ is introduced from the gas introduction system 605 immediately before the temperature reaches the temperature at which the heat treatment is performed, and when the temperature reaches the temperature at which the heat treatment is performed, the heat treatment is completely performed in the N ₂ H ₄ atmosphere. It may be like this. At this time, the heat treatment time is 3
It was set to 0 minutes to 6 hours, for example, 3 hours.

After performing such heat treatment, 25
Cooled to 0 ° C. The cooling rate at this time was 5 to 30 ° C./min, for example, 10 ° C./min, as in the heating. At this time, N ₂ was introduced from the gas introduction system 605 and the treatment was performed in an N ₂ atmosphere. After that, the processed substrate is transferred to the front chamber 504 by the carrier 505, and then set in the cassette in the preliminary chamber 503 in which the processed substrate is set, and the substrate processing step is completed.

The heat treatment of the present invention was performed as described above. By the above treatment, 900 ° C in N ₂ H ₄ atmosphere
It was confirmed by secondary ion mass spectrometry (SIMS) that the silicon oxide film contained the same amount of nitrogen as that obtained when the heat treatment was performed.

[0068]

INDUSTRIAL APPLICABILITY As in the present invention, the PVD method or the CV method is used.
The silicon oxide film formed by the D method is replaced with NH ₃ or N
_{In a 2} H ₄ atmosphere, while irradiating with ultraviolet light, 300
To 700 ° C., preferably about 500 to 600 ° C., by heat treatment at a low temperature, in the silicon oxide film,
It was possible to increase the nitrogen concentration at the interface between silicon oxide and silicon.

In the embodiment, a plasma CVD method using TEOS as a raw material, synthetic quartz as a target, and oxygen 1
The silicon oxide film by the sputtering method in the 00% atmosphere, the ECR-CVD method using monosilane (SiH ₄ ) and oxygen as the source gas and the low pressure CVD method has been described.
A silicon oxide film formed by another PVD method or a CVD method also contains dangling bonds and a large amount of hydrogen,
By carrying out the present invention, the number of dangling bonds is reduced,
It will be apparent that the effect of being able to modify the silicon oxide film, which is preferable as the gate insulating film, can be obtained by increasing the concentration of nitrogen. As described above, by using the silicon oxide film processed according to the present invention as the gate insulating film, it is possible to manufacture a TFT which is not easily deteriorated and has excellent characteristics, and the present invention is an industrially useful invention.

[Brief description of drawings]

FIG. 1 shows a heat treatment apparatus according to a first embodiment.

FIG. 2 shows a heat treatment apparatus according to a second embodiment.

FIG. 3 shows a heat treatment apparatus according to a third embodiment.

FIG. 4 shows the temperature gradient inside the chamber of the heat treatment apparatus according to Example 3 and during heating.

FIG. 5 shows a heat treatment apparatus according to Examples 4 and 5.

FIG. 6 shows the temperature gradient inside the chamber of the heat treatment apparatus according to Examples 4 and 5 and during heating.

FIG. 7 shows a process of manufacturing the TFT of Example 1.

[Explanation of symbols]

 101 ... Heat treatment chambers 102 and 103 ... Preliminary chamber 104 ... Substrate holder 105 ... Substrate 106 ... UV light source 107 ...・ Gas introduction system 108 ・ ・ ・ ・ ・ ・ Exhaust system 109 ・ ・ ・ ・ ・ Anterior chamber 110 ・ ・ ・ ・ ・ ・ Conveyor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location H01L 21/31 E 29/786 21/336 9056-4M H01L 29/78 617 V (72) Inventor Satoshi Teramoto 398 Hase, Atsugi City, Kanagawa Prefecture, Semiconducting Energy Laboratory Co., Ltd. (72) Inventor Yasuhiko Takemura, 398, Hase, Atsugi City, Kanagawa Prefecture, Semiconducting Energy Laboratory Ltd. (72) Inventor, Shigefumi Sakai, Hase, Atsugi City, Kanagawa No. 398 Inside Semiconductor Energy Laboratory Co., Ltd.

Claims (12)

[Claims] 1. A step of evacuating a chamber in which heat treatment is performed, and a step of introducing hydrogen nitride gas into the chamber after the step, wherein the hydrogen nitride atmosphere obtained in the step is 3
A heat treatment method for a silicon oxide film, which comprises irradiating a silicon oxide film heated to a temperature of 00 ° C to 700 ° C with ultraviolet light. 2. A step of introducing nitrogen into a chamber for heat treatment; a step of heating a silicon oxide film to a temperature of 300 ° C. or higher and 700 ° C. or lower while irradiating ultraviolet light in a nitrogen atmosphere; After heating to, the step of introducing hydrogen nitride gas into the chamber and substituting nitrogen with hydrogen nitride gas is performed, and the silicon oxide film is irradiated with ultraviolet light in the hydrogen nitride atmosphere obtained by the above step. A heat treatment method for a silicon oxide film, comprising: 3. The heat treatment method according to claim 1, wherein the silicon oxide film is formed by a low pressure CVD method using monosilane (SiH ₄ ) and oxygen gas (O ₂ ) as source gases. . 4. The heat treatment method according to claim 1, wherein the heating temperature of the silicon oxide film is 500 ° C. or higher and 600 ° C. or lower. 5. The heat treatment method according to claim 1, wherein the heating time of the silicon oxide film is 30 minutes or more and 6 hours or less. 6. The heat treatment method according to claim 1, wherein the substrate temperature is raised and cooled at a rate of 5 to 30 ° C./min during heating. 7. The heat treatment method according to claim 2, wherein the heating and the cooling of the substrate during heating are performed in a nitrogen atmosphere. 8. A chamber for heating a substrate, a preliminary chamber for setting the substrate before the heat treatment and the substrate after the heat treatment, and a front chamber provided with a carrier for transferring the substrate. The chamber for heating the substrate is provided with a substrate holder equipped with a heater for heating the substrate, and for irradiating the substrate with ultraviolet light outside or inside the chamber for heating the substrate. A heat treatment device, which is equipped with a light source. 9. A cylindrical chamber is provided, and a heater for heating the substrate is provided around the cylindrical chamber, and an ultraviolet light is applied to the substrate at the center of the cylindrical chamber. A heat treatment apparatus comprising a light source for irradiating light, wherein a substrate is attached around the inner wall of the cylindrical chamber. 10. The substrate holder in a chamber for heating a substrate according to claim 8, wherein the substrate holder is a substantially conveyor-shaped transfer device made of heat-resistant metal, and the heat treatment is performed while moving the substrate. A heat treatment device characterized by being able to perform. 11. The substrate holder inside the chamber for heating the substrate according to claim 8, wherein the substrate holder is a substantially conveyor-shaped transfer device made of heat-resistant metal, and a plurality of substrates are mounted once to be mounted. A heat treatment device, which is capable of performing heat treatment on. 12. The heat treatment apparatus according to claim 10 or 11, wherein a heater is provided at a lower portion of the substantially conveyor-shaped transfer device.