JPH06302525A - Vapor phase reactor - Google Patents

Abstract

PURPOSE:To raise the reaction efficiency and to prevent the production of snow flakes, unnecessary products. CONSTITUTION:An ultraviolet light source 2 is put in a light source chamber 3 keeping the atmospheric pressure. On the other hand, a reactor gas is supplied from a gas supplying facility 5, and preparatory excitation is performed by the ultraviolet rays from the ultraviolet light source 2, at a piping part 41 made of synthetic quartz. Then, the reactive gas excited preparatorily in 41 is brought into a reaction chamber 16, and plasma gas phase reaction takes place by using ultraviolet rays condensed through a synthetic quartz window 1, thermal energy from a near infrared ray source 14, and electromagnetic energy applied from a pair of electrodes 9 and 13.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a photochemical gas phase reaction and
The present invention relates to an apparatus capable of forming a thin film having high-quality physical properties on a substrate at high speed with good reproducibility under reduced pressure by a plasma chemical vapor reaction.

[0002]

2. Description of the Related Art Conventionally, there is known a technique of forming a thin film of a material by a gas phase reaction using a reactive gas containing a material forming the thin film. As a well-known method, a CVD method that activates a reactive gas by using light energy to cause a gas phase reaction, a thermal CVD method that activates a reactive gas by using heat energy and causes a gas phase reaction ,
An example is a plasma CVD method in which a reactive gas is activated by using electromagnetic energy (a high frequency of 13.56 MHz or a microwave of 2.45 GHz) to cause a gas phase reaction.

[0003]

The photo-CVD method has a problem that the film forming rate is extremely slow and it is not suitable for mass production. The thermal CVD method has problems such as damage to the substrate due to heating, a problem of productivity, and safety during manufacturing. In addition, the plasma CVD method is related to film quality, in particular, lowering of withstand voltage due to the influence of hydroxyl groups in the film, promotion of high dielectric constant, residual internal stress, and step coverage. At present, it is not possible to obtain a material that satisfies the requirements for flatness and flatness.

Further, in the conventional film forming method, snow flakes (reaction products due to insufficient reaction) are deposited in a region other than the reaction space, resulting in deterioration of reliability of the thin film, poor reproducibility, and pin formation in the thin film. The inconvenience of increasing the number of holes has occurred. The snow flakes are generated especially on the inner wall of the reaction chamber where heating is not performed or the portion where energy is not sufficiently supplied.

As described above, in the conventional film forming method, it is difficult to simultaneously satisfy various conditions such as low temperature film forming, high quality film forming, and high speed film forming, and further, especially energy is supplied to the inner wall of the reaction chamber or the reaction chamber. There was a problem of snowflake that occurs in the part that is not covered.

The present invention satisfies the above conditions while
Moreover, it is an object of the present invention to obtain a gas-phase reactor capable of forming a film without generation of snowflakes.

[0007]

According to the present invention, a light source chamber kept at atmospheric pressure, a reaction chamber kept at a predetermined pressure, and a reactive gas connected to the reaction chamber through the light source chamber are reacted. And a reactive gas introduction system for introducing into the chamber, light from the light source chamber is irradiated into the reaction chamber, in the light source chamber, the reactive gas introduction system is from the light source. It is made of a material that transmits light,
The reactive gas is activated by light from the light source in the light source chamber, and is also activated by light emitted from the light source chamber into the reaction chamber in the reaction chamber. The subject is a phase reactor.

In the above invention, it is effective to use light in the ultraviolet region as light for activating the reactive gas.

In the present invention, the light source chamber is set to atmospheric pressure in order to extend the life of the lamp which is the light source.
For example, when a low-pressure mercury lamp is used as a lamp for an ultraviolet light source, its life is greatly different between when it is used under reduced pressure and when it is used under atmospheric pressure. It is preferably used below. Further, it is important to cool the lamp of the ultraviolet light source, and there is a problem that effective cooling cannot be performed under reduced pressure. Therefore, in the present invention, the light source chamber in which the lamp of the ultraviolet light source, in which the life of the lamp is particularly problematic, is placed at the atmospheric pressure, and the atmospheric pressure is used, and the lamp can be cooled by the inert gas. Is.

Further, in the present invention, the reactive gas introducing system passes through the light source chamber, and the introducing system is made of a material such as quartz which transmits light from the light source.
When the reactive gas passes through this introduction system, the reactive gas is excited (pre-excited). Then, the reactive gas that is pre-excited when passing through the light source chamber is introduced into the reaction chamber, and this time it is activated by the light emitted from the light source chamber into the reaction chamber and the gas phase reaction is performed.

In the present invention, the reactive gas is pre-excited (pre-activated) in the introduction system, the pre-excited reactive gas is introduced into the reaction chamber where the gas phase reaction is carried out, and further activated. By irradiating the light energy for (excitation), the reactive gas is completely reacted in the gas phase to prevent the generation of snow flakes due to the incomplete gas phase reaction. Further, by increasing the efficiency of the gas phase reaction, the film forming rate and the film quality are improved.

In the present invention, the light emitted from the light source chamber into the reaction chamber is condensed in the reaction chamber to increase the efficiency of the gas phase reaction. In order to realize the above configuration, it is possible to connect the light source chamber and the reaction chamber through a synthetic quartz window formed in a convex shape on the light source chamber side, and irradiate light from the light source chamber into the reaction chamber. For example, the light from the light source chamber can be focused on the surface of the substrate (the glass substrate or the material having the formation surface) arranged in the reaction chamber, and the efficiency of the gas phase reaction can be increased.

To further increase the reaction efficiency, it is useful to heat the substrate. For this heating, the present invention has means for supplying thermal energy. As a means for supplying heat energy, it is useful to use an infrared lamp or a near infrared lamp. In the present invention,
By supplying thermal energy not only to the substrate but also to the entire inner wall of the reaction chamber, generation of snowflake on the inner wall of the reaction chamber is prevented.

Further, in the present invention, electromagnetic energy is applied to the reaction chamber in order to promote the gas phase reaction. It is preferable to use an AC waveform having a frequency of 1 MHz or less for this electromagnetic energy. When a frequency of 1 MHz or more is used, an electric field is generated due to almost no movement of ions, so that a sputtering effect on a substrate or a thin film surface is obtained. This is because it is generated, which adversely affects the quality of the formed film. According to experiments by the present inventors, the frequency to be used is 50
It has been found that using a frequency of KHz to 500 KHz is a frequency that does not affect the film quality and can increase the film formation rate.

The electromagnetic energy is generally supplied from a pair of parallel plate type electrodes. When this parallel plate type configuration is adopted, a base body having a surface to be formed is arranged on one electrode (generally grounded electrode) side,
A film is formed.

Further, when the parallel plate type structure is adopted, it is preferable that the electrode interval is within 20 mm. This is because when the film formation was performed while changing the electrode interval, good film quality was obtained when the electrode interval was within 20 mm. The electrode interval of 20 mm or less is limited by the size of the substrate, the method of introducing the reactive gas, and the like. For example, good film formation can be performed even if the interval is set so as not to introduce the reactive gas. is not.

As described above, according to the present invention, a pre-excitation step is provided in a part of the route of the introduction system of the source gas (reactive gas) to improve the efficiency of the gas phase reaction, and thus the film formation during film formation is improved. By lowering the temperature, a high quality thin film can be formed in the range of 230 to 340 ° C., for example.

[0018]

In the gas phase reaction apparatus of the present invention, the reactive gas is preexcited by ultraviolet rays in advance, and thereafter, the film formation is carried out by the plasma gas phase reaction in the reaction chamber, so that the reaction efficiency can be enhanced. Also, by keeping the ultraviolet light source at atmospheric pressure, the life of the ultraviolet light source can be extended.

Further, since the excitation by light and the excitation by electromagnetic energy are used together, the characteristic of tensile stress peculiar to the film formed by the photo-CVD method and the compression peculiar to the film formed by the plasma CVD method. The property of the generative stress and the property of the generative stress cancel each other out, and a thin film having a small internal stress can be formed.

Further, by controlling various parameters, it is possible to control the direction and absolute value of stress, and it is possible to form a thin film having a wide range of applications.

[0021]

【Example】

[Example 1] An example in which a silicon oxide film is formed using the cold wall type (type in which the reaction vessel is not particularly heated) vapor phase reactor of the present invention shown in FIG. 1 will be described below.
As a starting material reaction gas, TEOS (tetraethoxysilane) and oxygen are separately introduced into the light source chamber (3), which is a pre-excitation and air-cooled container, from the gas supply facility (5) via the gas introduction system (4). Then, the synthetic quartz pipe portion (41) formed in the coil shape is pre-excited with ultraviolet rays from the ultraviolet light source (2). The pipe part (41) is formed in a coil shape, and is configured so that the path of the reactive gas becomes long. In addition, direct excitation of outer shell electrons of the TEOS molecule is not expected here.

Oxygen molecules are emitted from the ultraviolet light source (2) at 20
It absorbs ultraviolet rays having a wavelength of 0 nm or less and becomes ozone (O ₃ ), which is 200 to 300 from the ultraviolet light source (2).
It absorbs UV rays of nm and becomes excited ozone. Excited ozone acts at the same time as active oxygen, giving oxygen to TEOS to generate O ₂
Therefore, it is inferred from the experimental results that the excitation and the reaction are promoted by the collision with other excited molecules.
In this embodiment, a low-safety and relatively inexpensive low-pressure mercury lamp is used as the ultraviolet light source (2), and the light source chamber (3) in which the low-pressure mercury lamp is disposed is a low-pressure mercury lamp ( to ensure the safety and service life of 2), held at atmospheric pressure, in order to facilitate cooling, flowing the N ₂ per minute 1l in N ₂ gas outlet from the N ₂ gas inlet (6) (7) I am purging at.

A reactive gas that has been pre-excited is introduced into the reaction chamber (16), which is a vacuum container, from the gas introduction system (42). Thermal energy is supplied to the pre-excited reaction gas from the near-infrared light source (14) through the lamp house (15). Further, from the ultraviolet light source (2), light energy of ultraviolet rays is irradiated through the synthetic quartz window (1) and the mesh electrode (9). Further mesh electrode (9)
Electromagnetic energy is supplied from the low-frequency power supply system (8) between the opposite ground electrode (13) and the ground electrode (13), and the distance between electrodes (1
A plasma reaction space (12) is formed in 0).

By this plasma vapor phase reaction, the substrate (1
1) A silicon oxide film is formed on top. Further, unnecessary gas is discharged to the outside of the system through the exhaust system (18).

A junction valve (17) is provided between the lamp house (15) on the near-infrared light source side and the reaction chamber (16) so as not to generate a pressure difference, and the junction house (15) is composed. It is constructed so that no pressure is applied to the quartz material. The pre-excitation and air-cooled container (3)
Since the inside is kept at atmospheric pressure, it is not necessary to provide a junction valve with the reaction chamber (16).

To selectively vibrationally excite the C—O bond of the TEOS molecule, an ultraviolet ray of 1000 to 1200 cm ⁻¹ is used.
It is said that irradiation with ultraviolet rays of 00 cm ^-1 is effective.

Since the low-pressure mercury lamp used as the ultraviolet light source (2) has the strongest emission line at 254 nm and has a relatively strong emission line at 185 nm, it is the most suitable light source for exciting the oxygen source gas. is there.

Further, the experimental results of this example show data suggesting that the C—H bond of the ethyl group C ₂ H _{5 in} the TEOS molecule may be broken.

The energy per mole is generally given by the following equation: E = Nhc / λ × 10 ⁵ KJ / mol h: Planck's constant 6.6 × 10 ⁻³⁴ J · sec C: Speed of light 3 × 10 ¹⁰ cm · sec ⁻¹ λ: Wavelength cm N: Avogadro's constant 6.0 × 10 ²³ mol ^{-1 From the} above, the 254 nm E of the low pressure mercury lamp is 472 KJ.
-Mol ^-1 , E of 185 nm is 647 KJ-mol ^-1 , so the interatomic bond energy of C-H bond is 413 KJ.
-It is considered that mol ^-1 can be easily dissociated. By the way, the interatomic bond energy of each molecule is as follows. O-O 139KJ / mol O-H 463KJ / mol C-C 348KJ / mol C = C 607KJ / mol C-O 351KJ / mol C = O 724KJ / mol

Further, as shown in FIG. 1, the synthetic quartz window (1) is specially designed so that the incident side of ultraviolet rays is formed in a convex shape, and the light emitted from the ultraviolet light source is projected on the convex side. By receiving the radiation, the radiation is focused on the surface of the substrate (12) in the reaction chamber (16). By doing so, the luminous flux becomes the largest on the surface of the substrate (16),
The activation efficiency of the reactive gas can be increased on the back surface of the substrate, the density of radicals near the surface of the formation surface can be increased, and the irradiation of ultraviolet rays to unnecessary areas can be suppressed. Generation of unnecessary reaction products in the phases can be suppressed.

Further, since the inner wall of the vacuum container (16) is processed with high precision by complex electropolishing, generation of snow flakes and lower oxides can be completely suppressed.

The reaction conditions in this example are shown below. Reaction conditions Reaction gas TEOS / O ₂ = 5 / 100SCCM Pressure 400Pa Low frequency power 80W (f: 200KHz) Substrate temperature 315 ℃ Electrode distance 18mm Reaction time 1min Substrate 8 inch Si wafer formation rate 0.1μm / min

The physical properties of the silicon oxide film formed under the above conditions are investigated and summarized below. Film thickness 1000 Å Refractive index 1.468 Density 2.37 g / cm ³ Withstand voltage 6.3 MV / cm (at 1 μA) Relative permittivity 3.97 Residual internal stress 5.3 × 10 ⁹ dyn / cm ² (compressed)

The above is one example, and the optimization of the parameters can achieve the forming rate of 0.5 μm / min. Needless to say, the conditions can be selected depending on the application.

In the case of the silicon oxide film, the space and the wall where light and heat energy do not contribute to the gas phase reaction essentially have a tendency to generate snowflake or lower oxide, but in this embodiment, , Reactive gas is activated in advance by the ultraviolet light from the ultraviolet light source (2) at (41) and is introduced into the plasma reaction space (12), so snowflake and lower oxides (not a thin film, a fragile film that is not rough) Of the vacuum vessel (1
6) A silicon oxide film is formed on the inner wall. Further, in this example, since the near infrared ray from the near infrared light source (14) is also applied to the inner wall of the vacuum container (16) through the lamp house (15) made of synthetic quartz, the reaction in the above (41) is performed. Combined with the pre-excitation of the reactive gas, the silicon oxide film is formed even in an unnecessary space other than the substrate, the formation of snowflakes and lower oxides is suppressed, and the silicon oxide film that does not affect the film formation is formed. Will be filmed.

[Embodiment 2] An example in which a silicon nitride film is formed using the same apparatus as in Embodiment 1 will be described below. In this example, Si ₂ H ₆ (disilane) and NH ₃ (ammonia) were used as the reactive gas as the source gas. The reaction conditions are shown below. At this time, only NH ₃ (ammonia) was pre-excited. That is, disilane was directly introduced into the vacuum container (16) without pre-excitation (the introduction system is not shown).

Reaction conditions Reaction gas Si ₂ H ₆ / NH ₃ = 15/500 SCCM Pressure 400 Pa Low frequency power supply 80 W (f: 200 KHz) Substrate temperature 250 ° C. Electrode distance 18 mm Reaction time 2 min Substrate 8 inch Si wafer formation rate 0.068 μm / Min

The physical properties of the silicon nitride film formed under the above conditions were examined and summarized below. Film thickness 1200Å Refractive index 2.03 Density 2.94g / cm ³ Pressure resistance 6.9MV / cm Dielectric constant 6.73 Residual internal stress 3.7 × 10 ⁹ dyn / cm ² (compressed)

When SiH ₄ (monosilane) was tried as the Si source, the formation rate was 0.043.
It was found that the same physical properties were obtained except that the value decreased to μm / min.

It is noteworthy that the above-mentioned high quality thin film was obtained in this example even though the substrate temperature was as low as 250 ° C. It is considered that this is because the ammonia gas is pre-excited and the concentrated ultraviolet rays are applied to the surface of the substrate to promote the activation of the ammonia gas, which effectively acts.

This is supported by Table 1 which compares the forming speeds (film forming speeds) when forming a silicon nitride film under the following four different conditions.

[0042]

[Table 1]

The data shown in Table 1 above is a summary of the results of film formation under the above-mentioned film formation conditions shown in the present embodiment under different conditions.
In Table 1 above, condition 1 is that, in the apparatus shown in FIG. 1, ammonia gas was directly introduced into the reaction chamber (16) in (41) without being pre-excited by ultraviolet rays and synthesized from the ultraviolet light source (2). The reactive gas is activated only by the ultraviolet rays irradiated through the quartz window (1), and the substrate (1
In this example, a silicon nitride film is formed on 1). That is, under the condition 1, the electromagnetic energy is not applied from the mesh electrode (9) and the counter ground electrode (13), and the heat energy is not supplied from the near infrared light source. This is an example of forming a film by energy.

The condition 2 is the same as the condition 1 except that the ammonia gas is pre-excited at (41) with the ultraviolet light from the ultraviolet light source (2) and introduced into the reaction chamber (16) which is a reaction space. This is an example in which a silicon nitride film is formed by being activated in the reaction chamber by ultraviolet rays from the light source (2).

Condition 3 is an example in which electromagnetic energy (200 KHz, 80 W) is applied from the mesh electrode (9) and the opposing ground electrode (13) to the plasma gas phase reaction in Condition 1 above. The condition 3 is an example in which the pre-excitation is not performed with ultraviolet rays in (41).

Condition 4 is an example of the condition 3 in which the reactive gas was pre-excited with ultraviolet rays at (41).

In the case of condition 1 and condition 2 in Table 1, S in the film
When the i / N ratio was examined, it became a Si Poor film, and the refractive index tended to decrease to 0.15 to 0.22.
In addition, in the case of Condition 3 and Condition 4, the decomposition and activation rates of the Si source system are improved, the film composition approaches the stoichiometric composition ratio, and the high quality ratio of the film tends to be promoted. Was confirmed.

As described above, the reactive gas is pre-excited by ultraviolet rays, and the photochemical gas phase reaction by ultraviolet rays and the plasma gas phase reaction by low frequency electromagnetic energy are used in combination to obtain 250 ° C. (substrate It was found that a high-quality silicon nitride film can be formed at a low temperature (temperature) with a high film formation rate, and the effectiveness of the present invention was confirmed.

[0049]

In the gas phase reactor, the reaction efficiency can be increased by using one light source system for both pre-excitation of the reactive gas and excitation on the substrate surface.
Further, since the heat energy is supplied to the entire inner wall of the reaction chamber where the gas phase reaction is performed, it is possible to realize a structure in which flakes and lower oxides are not formed in combination with the structure for increasing the reaction efficiency. It was

The effects of the present invention are summarized below. 1. The low-pressure mercury lamp, which is an ultraviolet light source, can be used at atmospheric pressure to improve the life of the low-pressure mercury lamp. 2. The light source was used for pre-excitation of the reaction gas to promote the gas phase reaction. 3. By introducing the light source into the reaction chamber through a synthetic quartz window having a convex surface, it was possible to improve the film formation rate and suppress the generation of unnecessary reaction products. 4. By using ultraviolet rays to accelerate the activation of the reaction positive gas, high-speed film formation, suppression of unnecessary flake generation,
We were able to solve various problems such as low temperature process and high quality film quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the internal structure of a gas phase reaction apparatus used in an example of the present invention.

[Explanation of symbols]

1 Synthetic Quartz Window 2 Ultraviolet Light Source 3 Light Source Chamber 4 Gas Introducing System (Synthetic Quartz Tube Inside 3) 5 Gas Supply Facility 6 N ₂ Gas Inlet 7 N ₂ Gas Outlet 8 Low Frequency Power Supply 9 Mesh Electrode 10 Electrode Distance 11 Substrate 12 Reaction space (plasma region) 13 Opposite ground electrode 14 Near infrared light source 15 Lamphouse 16 Reaction chamber 17 Junction valve 18 Exhaust system

Claims (8)

[Claims] 1. A light source chamber kept at atmospheric pressure, a reaction chamber kept at a predetermined pressure, and a reactivity for introducing a reactive gas connected to the reaction chamber through the light source chamber into the reaction chamber. A gas introduction system, and light from the light source chamber is irradiated into the reaction chamber, and in the light source chamber, the reactive gas introduction system is formed of a material that transmits light from the light source. The reactive gas is activated by the light from the light source in the light source chamber, and is activated by the light emitted from the light source chamber into the reaction chamber in the reaction chamber. Gas phase reactor. 2. The gas phase reaction apparatus according to claim 1, wherein an ultraviolet light source is used as the light source. 3. The reaction chamber according to claim 1, wherein the light emitted from the light source chamber into the reaction chamber is emitted into the reaction chamber through a synthetic quartz window formed in a convex shape toward the light source chamber. A gas-phase reaction device characterized by being condensed and irradiated. 4. The vapor phase reaction apparatus according to claim 1, wherein synthetic quartz is used as a material that transmits light from a light source that constitutes a reactive gas introduction system in the light source chamber. 5. The gas phase reaction apparatus according to claim 1, wherein thermal energy is applied to the entire inner wall of the reaction chamber. 6. The gas phase reaction apparatus according to claim 1, wherein electromagnetic energy is applied to the reaction chamber from a pair of electrodes. 7. The gas phase reaction apparatus according to claim 6, wherein the distance between the pair of electrodes is 20 mm or less, and the substrate having the formation surface is arranged on one of the electrodes. 8. The gas phase reactor according to claim 6, wherein electric energy of 50 to 500 KHz is used as electromagnetic energy.