JP5069082B2 - Silicon nitride film manufacturing method, gas barrier film, and thin film element - Google Patents

Description

  The present invention relates to a method of forming a silicon nitride film having a low water vapor transmission coefficient and a good gas barrier property on a substrate having a low heat resistant organic layer such as a resin substrate, and a silicon nitride formed by the method The present invention relates to a gas barrier film obtained by using a film, and a thin film element.

  In recent years, in fields such as liquid crystal display elements and organic EL elements used in flat panel displays (FPDs), the development of flexible displays employing lightweight and flexible resin substrates has been actively made. Since the resin substrate has inferior gas barrier properties compared to an inorganic substrate such as a glass substrate, a flexible device generally has a structure including a gas barrier film or the like for suppressing the mixing of air and water vapor on the resin substrate. Yes. Typical examples of the gas barrier film include a silicon nitride film represented by SiNx and a silicon nitride film such as silicon oxynitride represented by SiONx.

In applications of liquid crystal display elements, the size has been increasing in recent years, and in organic EL elements, organic solar cells, CIGS solar cells and the like, it is known that the element characteristics are easily affected by water vapor and oxygen. Therefore, a higher gas barrier property has been required for the gas barrier film. The gas barrier property can be evaluated by the water vapor transmission rate (Water Vapor Transmission Rate: WVTR). Currently, the organic EL element is required to have a water vapor transmission rate satisfying WVTR ≦ 10 ⁻⁶ g / m ² / day. As described above, in a field where high gas barrier properties are required, a configuration in which a desired water vapor transmission rate is achieved by laminating a plurality of silicon nitride films via an organic layer has been reported. Therefore, from the viewpoint of element configuration and miniaturization, it is preferable that the number of stacked layers is small. Currently, a gas barrier property of WVTR ≦ 10 ⁻³ g / m ² / day is required per layer.

  The silicon nitride film is amorphous and has properties such as high density, high relative permittivity, and high resistance to hydrofluoric acid etching. Therefore, not only the use of the gas barrier film described above but also a wide range of uses such as an interlayer insulating film such as a TFT element, a gate insulating film, a capacitor capacity film of a DRAM or a nonvolatile memory, and the like. Therefore, the film forming method and film forming conditions are optimized so that a silicon nitride film having good film characteristics can be obtained according to the application.

  One of the film forming methods often used for forming a silicon nitride film is a low pressure plasma CVD method. A silicon nitride film formed by such a method has high in-plane uniformity of film characteristics, and a high-quality film can be obtained. However, since the supply amount of the source gas must be limited in order to reduce the pressure, the chemical reaction necessary for forming a thin film is limited by the supply amount of the source gas in the low-pressure plasma CVD method, and the film formation rate is limited. . For this reason, it is not possible to expect a deposition rate of 1 μm / min or more per unit area.

Therefore, in recent years, a method for forming a high-quality silicon nitride film by a plasma CVD method under atmospheric pressure capable of increasing the supply amount of the source gas has been studied. Under atmospheric pressure, since the concentration of gas molecules can be increased, film formation can be performed at a good film formation rate. On the other hand, when the film formation rate is high, reaction rates such as unnecessary chemical reaction and gas molecule aggregation also increase, so that it is difficult to form a high-quality film.

Under such circumstances, a method of forming a high-quality silicon nitride film by using a source gas containing H ₂ gas in a plasma CVD method under atmospheric pressure has been studied. When H ₂ gas is included in the source gas, it is said that effects such as reduction of unnecessary reaction by-products and reduction of defects in the film can be obtained. Patent Document 1 discloses a method for forming a high-quality film by a plasma CVD method under a pressure much higher than a film formation pressure used in a low pressure plasma CVD method. In Patent Document 1, the ratio of NH _{3 in} the raw material gas to SiH ₄ is 2 or more, or 2 or more and 20 or less, and the ratio of hydrogen in the mixed gas is 5% or more. It is described that a silicon nitride film having a film quality almost comparable to the formed silicon nitride film can be formed (see paragraph [0024] and the like).
JP 2004-56152 A

  However, in Patent Document 1, a silicon nitride film is used for a gate insulating film of an electronic device such as a TFT element used in FPD or the like. In such a use, a glass substrate is usually used. Film formation at a relatively high substrate temperature is possible.

  As described in Journal of Plasma Fusion Society Vol.76, No.8, Journal of Plasma Fusion Society, Vol.77, No. 7, etc., the decomposition conditions of the source gas generally change as the substrate temperature changes. For this reason, it is considered that the ratio of generated gas changes and the film quality of the film to be formed changes.

  Furthermore, if the substrate temperature is low, flying particles decomposed from the source gas cannot migrate sufficiently on the substrate surface, and there is a high probability that the silicon nitride on the film surface is terminated with hydrogen atoms. Particle migration is further suppressed. For this reason, the particles are deposited on the substrate before reaching the site to be originally adsorbed, so that sufficient bonding cannot be achieved and the film is likely to be a low-density film. If the denseness is low, the film composition is likely to change with time and cannot be used as a gate insulating film of an electronic device. For this reason, in the said use, it is common to form into a film with the substrate temperature of 300-400 degreeC, and also in patent document 1, the substrate temperature described in the Example is 300 degreeC (Table 1-1). (See Table 3).

  As described above, the gas barrier film is used for a device having a resin substrate, and is also used for a device having an organic layer to suppress mixing of air and water vapor. The heat-resistant temperature of the resin substrate or the organic layer is lower than that of a glass substrate or the like, and a highly versatile and inexpensive PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) substrate is 150 ° C. or lower. Therefore, the substrate temperature at the time of film formation needs to be 150 ° C. or lower, and the film formation method of Patent Document 1 cannot be applied as it is.

  In the case of a glass substrate, since the function as a gas barrier film is unnecessary, Patent Document 1 does not evaluate any gas barrier properties such as a WVTR value. In Patent Document 1, studies focusing on the bond density have been made. However, as the bond density is increased, the film stress increases, and when the film stress increases excessively, partial peeling or cracks occur and gas barrier properties are reversed. Is considered to be low.

Actually, a silicon nitride film obtained by the method described in Patent Document 1 with a film formation temperature of room temperature and a hydrogen concentration in the source gas of 5% to 30% is formed at a hydrogen concentration of 5%. The inventor has confirmed for the first time that the composition changes after 12 hours in air storage after film formation. It was also confirmed that when the hydrogen concentration was 10%, the composition did not change even after 2 weeks in the air storage, but the composition changed in several weeks in the atmosphere of temperature 40 ° C and humidity 90%. If the hydrogen concentration is increased to 30%, it is possible to obtain a film characteristic that does not change the composition even when the film is formed at room temperature. On the other hand, the film formation rate decreases by about 40% due to an increase in the hydrogen concentration. Also confirmed.

The present invention has been made in view of the above circumstances, and is a silicon nitride film having a water vapor transmission rate of 10 ⁻³ g / m ² / day or less and having a good film quality, which is suitable as a gas barrier film of a thin film element. It is an object of the present invention to provide a method for forming a silicon nitride film that can be formed with high efficiency at a film forming temperature that is not higher than the heat resistant temperature of the organic layer.

The silicon nitride film forming method of the present invention is a method of forming a silicon nitride film on a substrate having at least one organic layer placed in a reaction vessel by chemical vapor deposition using plasma. In the reaction vessel, a source gas containing SiH ₄ , NH ₃ , H ₂ , and He is supplied so that the total gas pressure becomes atmospheric pressure, and an electric field is applied to the electrode installed above the substrate. A step of applying an electric field between the electrode and the substrate to generate a source gas between the electrode and the substrate by the electric field, and the source gas in a plasma state at a temperature lower than the heat resistant temperature of the organic layer. A step of forming a silicon nitride film on the substrate using the substrate, the ratio of H _{2 in} the source gas is 13% or more and 20% or less, and the ratio of NH ₃ to SiH ₄ in the source gas is 13% or more and 24% or less Is.

In this specification, the atmospheric pressure is defined as 100 to 1000 Torr (1 Torr = about 133.322 Pa).
In this specification, the silicon nitride film includes a silicon nitride film and a silicon oxynitride film generally represented by SiNx, and has a composition with a stoichiometric ratio and includes a hydrogen atom and the like. A composition other than the stoichiometric composition (for example, Si ₃ N _{4 in} the case of silicon nitride) is included.
In the present specification, the unit of the ratio of each component in the raw material gas is volume% unless otherwise specified.

In the silicon nitride film forming method of the present invention, the ratio of H _{2 in} the source gas is preferably 15% or more and 18% or less. The power density of the electric field applied to the electrode is preferably not more than 250 W / cm ³ Ultra 450 W / cm ^3.

In the method for forming a silicon nitride film of the present invention, a silicon nitride film having a water vapor transmission rate of 10 ⁻³ g / m ² / day or less at a film thickness of 200 nm or less can be formed.
In this specification, the gas barrier property is evaluated by the water vapor transmission rate. The water vapor transmission rate is a value at a measurement temperature of 40 ° C. and a relative humidity of 90%.

  Further, in the method for forming a silicon nitride film of the present invention, the film formation can be performed at a film formation speed of 1 μm / min or more.

The silicon nitride film of the present invention has a water vapor transmission rate of 10 ⁻³ g / m ² / day or less, and is formed by the silicon nitride film deposition method of the present invention. Is.

The gas barrier film of the present invention is characterized in that at least one layer of the silicon nitride film of the present invention and at least one layer of organic film are alternately laminated.
The gas barrier film of the present invention can have a water vapor transmission coefficient of 10 ⁻⁶ g / m ² / day or less.

 The thin film element of the present invention is characterized in that the gas barrier film of the present invention is provided on a substrate.

The silicon nitride film forming method of the present invention is a method of forming a silicon nitride film on a substrate having at least one organic layer by chemical vapor deposition using plasma under atmospheric pressure. ₄ , the ratio of H _{2 in} the source gas containing NH ₃ , H ₂ , and He is 13% or more and 20% or less, and the ratio of NH _{3 in} the source gas to SiH ₄ is 13% or more and 24% or less It is. According to such a film forming method, a silicon nitride film having a water vapor transmission rate of 10 ⁻³ g / m ² / day or less, which is suitable as a gas barrier film of a thin film element, and a good film quality is obtained. Film formation can be performed with high efficiency at a film formation temperature lower than the temperature.

According to the present invention, for example, a silicon nitride film having a water vapor transmission rate of 10 ⁻³ g / m ² / day or less can be formed even when the film thickness is 200 nm or less. In the gas barrier film in which the silicon nitride film and the organic film formed by the method are alternately laminated, a gas barrier property with a water vapor transmission rate of 10 ⁻⁶ g / m ² / day or less can be achieved.

"Method for forming silicon nitride film"
In the present invention, a substrate having at least one organic layer placed in a reaction vessel by a chemical vapor deposition method using plasma under atmospheric pressure (hereinafter referred to as atmospheric pressure plasma CVD (Chemical Vapor Deposition) method). Then, a silicon nitride film is formed. In general, in the atmospheric pressure plasma CVD method, a raw material gas component supplied into a reaction vessel in which a film formation target is installed is reacted in a plasma state under atmospheric pressure, and the constituent components of the source gas are formed on the film formation target. A functional film including the same is formed. FIG. 1 schematically shows a state during film formation by atmospheric pressure plasma CVD.

  In the present invention, the film formation target of the silicon nitride film is not particularly limited as long as it is a substrate having at least one organic layer, but here, a case where a film-like resin substrate is a film formation target will be described as an example. .

  In the present invention, the film forming apparatus is not particularly limited, but when a film-like resin substrate is used, a continuous film forming method called a roll-to-roll method is considered preferable in terms of productivity.

  FIG. 2 is a schematic view showing a configuration of a continuous film forming apparatus 300 using a roll-to-roll method. As described in the background section, in applications where gas barrier films are required, in a field where high gas barrier properties are required, a desired water vapor transmission rate is achieved by laminating a plurality of silicon nitride films via an organic layer. The structure to perform is common. The configuration shown in FIG. 2 is an example in the case where the silicon nitride film (inorganic layer) is continuously formed after the organic layer is formed. An embodiment of the gas barrier film will be described later.

  The film-shaped resin substrate 10 supplied from the film supply roll 310 is included in the precursor in the curing and drying unit 330 after the organic layer precursor is formed on the resin substrate 10 in the organic layer coating unit 320. An organic layer is formed by volatilizing an organic solvent or the like. Next, a silicon nitride film is formed in the inorganic layer film forming unit 340 and is taken up by the take-up roll 310. The organic layer coating unit 320, the curing and drying unit 330, and the inorganic layer film forming unit 340 may be appropriately set in number or configuration depending on the number of organic layers and inorganic layers.

  An atmospheric pressure plasma CVD apparatus is installed in the inorganic layer film forming unit 340 on which the silicon nitride film is formed. The apparatus configuration of the atmospheric pressure plasma CVD apparatus is not particularly limited, but in this embodiment, a rotating electrode type atmospheric pressure plasma CVD apparatus 100 is used. Atmospheric pressure plasma CVD apparatuses are roughly classified into two types, a rotating electrode system and a parallel plate electrode system, depending on the electrode configuration.

 The atmospheric pressure plasma CVD apparatus 100 shown in FIG. 3 is driven by a movable substrate stage 113 provided with a heater 114 and a high frequency power supply 116 in a reaction vessel 110 provided with a gas supply unit 117 and a gas exhaust unit 118. The cylindrical rotary electrode 111 is provided. The gas exhaust unit 118 is provided with a circulation line 119 including a powder removal filter 120 that functions by a circulation pump 121. In the atmospheric pressure plasma CVD apparatus 100, an electric field P is generated between the cylindrical rotary electrode 111 and the resin substrate 10 placed on the substrate stage 13 by applying a voltage, and the electric field P is supplied from the gas supply unit 117. The formed source gas G is turned into plasma, and a film containing the constituent elements of the source gas G can be formed on the resin substrate 10. By moving the movable substrate stage 113, the resin substrate 10 is moved in a state where a certain tension is applied, and film formation is continuously performed.

First, the source gas G containing SiH ₄ , NH ₃ , H ₂ and He is supplied to the reaction vessel 110 of the atmospheric pressure plasma CVD apparatus 100 so that the total gas pressure becomes atmospheric pressure. The source gas G may contain oxygen, nitrogen, or the like depending on the composition of the film to be formed.

  Next, an electric field is applied to the cylindrical rotating electrode 111 to generate an electric field P between the cylindrical rotating electrode 111 and the resin substrate 10, and the raw material gas between the cylindrical rotating electrode 111 and the resin substrate 10 is generated by this electric field. The silicon nitride film 1 is formed on the resin substrate 10 using the source gas G that is in a plasma state at a temperature equal to or lower than the heat resistance temperature of the resin substrate 10.

 FIG. 4 shows an example of a parallel plate electrode type atmospheric pressure plasma CVD apparatus. In the atmospheric pressure plasma CVD apparatus 200, a voltage is applied by a second parallel plate electrode 212 having a heater 214 and a high frequency power source 216 in a reaction vessel 210 having a gas supply unit 217 and a gas exhaust unit 218. 1 parallel plate electrode 211 is provided. Since the atmospheric pressure plasma CVD apparatus 200 has substantially the same structure as the rotating electrode system except that the structure of the electrodes is different, the silicon nitride film 1 can be formed in the same manner as the atmospheric pressure plasma CVD apparatus 100.

In the present invention, a silicon nitride film 1 having a water vapor transmission rate (hereinafter referred to as WVTR) of 10 ⁻³ g / m ² / day or less suitable as a gas barrier film of a thin film element is formed. Therefore, the film forming conditions for the silicon nitride film are determined so as to have such a WVTR value. The film forming conditions in the present invention are described in detail below.

(Deposition conditions)
The inventor first paid attention to the film thickness and the film density as film characteristics that affect the WVTR of the silicon nitride film 1 having good gas barrier properties. The film density is a factor that greatly affects the gas barrier property. If there are no defects such as cracks in the film, the gas barrier property is considered to be higher as the film thickness is higher and the film density is higher. However, as described above, since the silicon nitride film is an inorganic film and has low flexibility, cracks are likely to occur due to film stress such as bending as the film thickness increases. When cracks occur, the element characteristics such as being easily peeled and allowing air and water vapor to permeate through the cracks are deteriorated. Therefore, it is necessary to set the film thickness so that cracks do not easily occur due to film stress. In view of this point, the thickness of the silicon nitride film 1 is preferably 200 nm or less.

 If the film thickness is thin, there will be no problem of cracks and productivity will be improved. On the other hand, if it is too thin, the energy barrier will be small and water molecules in the air will be easily transmitted. The degree of the energy barrier varies depending on the film density, and the higher the film density, the higher the energy barrier even if the film thickness is the same.

As described in the background art section, the fact that the film has low density indicates that there are vacancies in the film, and the gas barrier property per unit film thickness is lowered, thereby obtaining an equivalent gas barrier property. It is necessary to make the film relatively thick. Further, the composition easily changes over time from SiN _x to SiO _z N _y, and when the composition changes, defects such as film peeling partially occur. For this reason, from the viewpoint of gas barrier properties, it is preferable that the film density is high. However, even if the film density is too high, cracks due to film stress easily occur. Therefore, it is preferable to determine the film thickness and the film density so that cracks due to film stress are difficult to occur and an energy barrier exhibiting good gas barrier properties is provided.

The inventor of the present invention studied a combination of a film thickness and a film density exhibiting good gas barrier properties in a silicon nitride film.
In this specification, the film thickness is measured by observing an ultrathin section of a film sample with a scanning electron microscope “S-900 type” manufactured by Hitachi, Ltd., and the film density is obtained by forming an inorganic layer on a Si wafer. Using the filmed sample for evaluation, it was calculated from the X-ray reflectivity using ATX-G manufactured by Rigaku Denki.

Further, the water vapor transmission rate (WVTR) was measured using “PERMATRAN-W3 / 31” (condition: 40 ° C., relative humidity 90%) manufactured by MOCON. Moreover, the value below 0.01 g / m < ² > / day which is the measurement limit of this MOCON apparatus is supplemented using the following method.
First, metal Ca is directly deposited on the gas barrier film, and the measurement sample is prepared by sealing the gas barrier film and the glass substrate with a commercially available organic EL sealing material so that the deposited Ca is inside. A WVTR value was calculated from the result of measuring the optical density change of metal Ca on the gas barrier film (utilizing that the metallic luster decreases due to hydroxylation or oxidation) while keeping this measurement sample at the above temperature and humidity conditions.

First, silicon nitride films having different film densities were produced, and the WVTR values were measured when the film thicknesses of the silicon nitride films having different film densities were varied. The film densities were 1.9 ± 0.1 g / cm ³ , 2.2 ± 0.1 g / cm ³ , and 2.5 ± 0.1 g / cm ³ . In consideration of the film density in which the film composition hardly changes, it is considered that the film density is preferably 1.9 g / cm ³ (which may include an error of ± 0.1) or more. In addition, when the film density exceeds 2.5 ± 0.1 g / cm ³ , the film cannot be measured because cracks occur during the WVTR value evaluation process when the film thickness exceeds 120 nm. It was judged that it was preferably ± 0.1 g / cm ³ or less. The results are shown in FIG.

 FIG. 5 shows a tendency that the WVTR value decreases as the film thickness increases at any film thickness, and conversely increases when the film thickness reaches a certain film thickness. This is because when the film thickness is too thin, the energy barrier becomes small and water molecules in the air tend to permeate, and stress increases as the film thickness increases, which tends to cause cracks. ing. Within the plotted film thickness range, cracks were not found in the film by visual observation using an optical microscope or the like, but a small void was formed in the film due to stress, and the WVTR value increased. Conceivable.

Next, based on the results shown in FIG. 5, the range of film thickness and film density where the WVTR value is 10 ⁻³ g / m ² / day or less was plotted (FIG. 6). FIG. 6 shows that in a silicon nitride film having a film thickness and a film density within the range indicated by hatching, the WVTR value is 10 ⁻³ g / m ² / day or less. In the range indicated by the oblique lines in FIG. 6, the film thickness t (nm) and the film density d (g / cm ³ ) satisfy the following expressions (1) and (2).
1.9 ≦ d ≦ 2.5 (1),
−700d + 1930 ≦ 6t ≦ −700d + 2530 (2)

  FIG. 6 shows that the allowable range of thin film thickness increases as the film density increases. Considering productivity and ease of occurrence of cracks, the thickness t is preferably smaller within the above range, and is preferably 100 nm or less.

In the silicon nitride film forming method of the present invention, H ₂ gas is added to the source gas. As described in the background section, when a silicon nitride film is formed by an atmospheric pressure plasma CVD method, if the source gas contains H ₂ gas, unnecessary reaction by-products are reduced. It is said that the film quality is improved by obtaining an effect such as reduction of medium defects. This is because hydrogen, which has been radicalized and increased in energy, collides with the surface during film formation, resulting in film formation particles that are physically adsorbed on unnecessary sites and by-products generated by unnecessary chemical reactions. It is considered that a dense film is formed by dissociating a substance that causes a film defect such as an object.

On the other hand, when the source gas contains H ₂ gas, it is known that the thickness of the obtained film becomes thinner than the thickness obtained when no H ₂ gas is contained. As described above, when the source gas contains H ₂ gas, it becomes a dense film, so the film thickness may be reduced accordingly, but the film thickness obtained by film formation under the same conditions is reduced, This means that the film formation rate decreases and the production efficiency deteriorates. Therefore, it is necessary to determine the H ₂ gas concentration in the source gas so that a desired WVTR value can be obtained at a good film formation rate.

Therefore, the inventor examined the influence on the film thickness and WVTR with respect to the H ₂ gas concentration in the raw material gas. The result is shown in FIG. In FIG. 7, the horizontal axis represents the H ₂ gas concentration (volume%) in the source gas, and the vertical axis represents the rate of change in film thickness due to the addition of H ₂ gas (film thickness / film thickness without addition of H ₂ gas × 100). ), The right side shows the WVTR value. In FIG. 7, the film formation temperature is RT, the input power density during film formation is 250 W / cm ^3, and the composition of the source gas other than the H ₂ gas concentration is SiH ₄ : 0.05%, NH ₃ : 1.0. %, The remainder was He gas.

FIG. 7 shows that a WVTR value of 10 ⁻³ g / m ² / day or less can be obtained near an H ₂ gas concentration of 14%. Therefore, from the viewpoint of WVTR, the H ₂ gas concentration may be 14% or more.

As the H ₂ gas concentration increases, the film thickness change rate increases and the film formation rate decreases. Therefore, the upper limit of the H ₂ gas concentration may be determined so as to have a film thickness change rate that maintains a good film formation rate. In view of production efficiency, the film forming speed is preferably 1 μm / min or more. Considering the film forming speed when no H ₂ gas is added, the film forming speed is the same as when no H ₂ gas is added. It is preferably 80% or more of the film formation rate. In order to achieve such a deposition rate, the H ₂ gas concentration may be 20% or less, and is preferably 18% or less in order to achieve better production efficiency.

As described above, the H ₂ gas concentration is 14% or more from the viewpoint of WVTR, and the H ₂ gas concentration is 20% or less, preferably 18% or less from the viewpoint of film formation speed. By the way, when the H ₂ gas concentration is 14%, the film formation rate is almost 90% of that when no H ₂ gas is added. Considering that the film formation rate may be 80% or more when H ₂ gas is not added, if WVTR is achieved by increasing the film thickness by the remaining 10%, the concentration is less than 15%. It may be. Tray such points into consideration and the result of examining the range of _{H 2} gas concentration, _{H 2} gas concentration WVTR values below ¹⁰ -3 ^g / m 2 / day in good deposition rate is obtained, 13% or more 20 %, Preferably 15% or more and 18% or less.

The optimization of the H ₂ gas concentration is performed at an input power density of 250 W / cm ³ , but can be applied regardless of the input power density as long as a stable plasma state can be formed. it can. 250 W / cm ³ is almost the minimum value of input power density that can form a stable plasma state in the current atmospheric pressure plasma CVD apparatus.

The input power density is a factor that changes the magnitude of the energy that the H ₂ gas has when radicalized, and the higher the input power density, the greater the energy. Therefore, the higher the input power density, the better the effect of adding a higher H ₂ gas even at the same H ₂ gas concentration, which is preferable. The upper limit of the input power density capable of forming a stable plasma state in the current atmospheric pressure plasma CVD apparatus is approximately 450 W / cm ³ .

FIG. 8 shows the concentration range of H ₂ gas that gives a WVTR value of 10 ⁻³ g / m ² / day or less at a good film formation rate when the input power density is 250 to 450 W / cm ^3. Shown with diagonal lines. A hatched portion indicates a preferable region. Here, the film forming conditions in FIG. 7 were set to the same conditions except that the input power was changed.

As shown in FIG. 8, the lower limit value of the H ₂ gas concentration range in which a WVTR value of 10 ⁻³ g / m ² / day or less can be obtained at a good film formation rate decreases as the input power density increases. It has spread. Therefore, FIG. 8 confirms that the concentration range of the H ₂ gas optimized under the condition of the input power density of 250 W / cm ³ is applicable in the range of the input power density of 250 to 450 W / cm ^3. .

Further, in all the studies on the film forming conditions described above, the composition of the source gas other than the H ₂ gas concentration in the source gas is SiH ₄ : 0.05%, NH ₃ : 1.0%, and the rest is He. Gas is used. Therefore, the mixing ratio of SiH ₄ and NH _{3 in} the source gas to which the above film forming conditions can be applied was further examined.

Conditions other than the mixing ratio of SiH ₄ and NH _3, as the effect of the _{H 2} gas is higher following condition, the input power density of SiH ₄ and NH ₃ as 450 W ^/ cm 3, _{H 2} gas concentration of 20% The influence on the WVTR by the compounding ratio was examined. The film forming conditions optimized under the condition that the effect of H ₂ gas is higher can be applied in a range where the effect of H ₂ gas is low.

The results are shown in FIG. FIG. 9 shows that the compounding ratio of SiH ₄ and NH ₃ at which a WVTR value of 10 ⁻³ g / m ² / day or less can be obtained at a good film formation rate is 14 or more and 24 or less.

As described above, in the method of forming a silicon nitride film on a substrate having at least one organic layer installed in a reaction vessel by chemical vapor deposition using plasma, H ₂ in a source gas is used. 10 to ³ g / m ² , which is suitable as a gas barrier film of a thin film element, by adjusting the ratio of NH ₃ to SiH ₄ in the raw material gas to 13% to 20% and 13% to 24%. A silicon nitride film having a water vapor permeability of not more than / day and good film quality can be formed with high efficiency at a film forming temperature not higher than the heat resistance temperature of the resin substrate.

"Silicon nitride film, gas barrier film"
With reference to FIG. 10, the gas barrier film provided with the silicon nitride film manufactured by the silicon nitride film manufacturing method of the present invention will be described. FIG. 10 is a sectional view in the thickness direction of the gas barrier film 3.

 As shown in FIG. 10, the gas barrier film 3 of the present embodiment is formed on a resin substrate 10, and is formed of at least one layer of the silicon nitride film 1 manufactured by the method of manufacturing a silicon nitride film of the present invention. And at least one organic film 2 are alternately laminated. In the present embodiment, the gas barrier film 3 is formed on the upper surface of the resin substrate 10. However, the gas barrier film 3 may be formed on the lower surface of the substrate, or may be configured on both the upper and lower surfaces. Good.

 In the gas barrier film 3, the silicon nitride film 1 and the organic film 2 may be alternately stacked, and the layer directly formed on the resin substrate 10 and the uppermost layer are not particularly limited, but the surface of the resin substrate 10 In the case where there is unevenness, it is preferable that the organic film 2 is directly formed in order to reduce the unevenness. The uppermost layer is preferably the organic film 2 in consideration of adhesion with a layer formed on the gas barrier film 3.

 As described above, since the silicon nitride film 1 has poor flexibility, the film thickness is limited so that cracks do not occur due to film stress. Therefore, although the obtained gas barrier property is also limited, as shown in the figure, by laminating via the organic film 2, it is equivalent to that having a film thickness equivalent to the number of layers of the silicon nitride film 1. Gas barrier properties can be realized.

The shearing force S (N / m ² ) acting on the interface between the organic film 2 and the silicon nitride film 1 is larger than that of the silicon nitride film 1 as in the present embodiment. If it is thick (the film thickness of the organic film 2 will be described later), its rigidity becomes the organic film 2 >> silicon nitride film 1, and the elongation of the gas barrier film 3 is determined by the organic film 2. For this reason, the shearing force acting on the boundary surface is determined only by the rigidity of the silicon nitride film 1, and if the sandwich structure having the organic film 2 above and below the silicon nitride film 1 is supported evenly at the top and bottom, The stress generated in the material film 1 is halved, and the stress applied to the silicon nitride film 1 can be reduced. From this point of view, it is preferable to form a laminate.

The number of layers of the silicon nitride film 1 constituting the cas barrier film 3 is not particularly limited, but typically 2 to 30 layers are preferable, and 3 to 20 layers are more preferable. The number of layers of the silicon nitride film 1 may be appropriately designed according to the required WVTR value. If the WVTR value of the silicon nitride film 1 is about 10 ⁻³ g / m ² / day, the silicon nitride film By providing about two layers of the film 1, it is possible to realize a WVTR value of 10 ⁻⁶ g / m ² / day that is currently required as a gas barrier film of an organic EL element.

 The resin substrate 10 is not particularly limited and can be appropriately selected depending on the purpose of use. Specifically, polyesters such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate), acrylic resins (including methacrylic resins), methacrylic acid-maleic acid copolymers, polystyrene, fluorine-containing resins, polyimides, fluorinated polyimides , Polyamide, Polyamideimide, Polyetherimide, Cellulose acylate, Polyurethane, Polyetherketone, Polycarbonate, Alicyclic polyolefin, Polyarylate, Polyethersulfone, Polysulfone, Fluorine ring modified polycarbonate, Alicyclic modified polycarbonate, Fluorine Examples thereof include thermoplastic resins such as ring-modified polyesters and acryloyl compounds.

 The thickness of the resin substrate 10 is appropriately selected according to the application and is not particularly limited. In the use of a thin film element, the typical thickness of the resin substrate 10 is 1 to 800 μm, preferably 10 to 200 μm.

 The resin substrate 10 may be provided with various functional layers such as a conductive layer and a primer layer on the upper surface and / or the lower surface. As the functional layer, a layer shown in paragraphs [0036] to [0038] of JP-A-2006-289627, a matting agent layer, a protective layer, an antistatic layer, a smoothing layer, an adhesion improving layer, a light shielding layer, an antireflection layer Examples include a layer, a hard coat layer, a stress relaxation layer, an antifogging layer, a mudproof layer, and a printing layer.

 The organic film 2 is a layer that relieves stress on the silicon nitride film 1 due to film stress such as bending. The organic film 2 is not particularly limited as long as it has such a function, and a resin layer is usually used. An example of the resin layer is a thermoplastic resin that can be easily formed. Examples of the thermoplastic resin include the same resins as those exemplified for the resin substrate 10.

 Examples of the method for forming the organic film 2 include a vacuum film forming method and a solution coating method. The vacuum film formation method is not particularly limited, and examples thereof include a vapor deposition method and a plasma CVD method.

 Examples of the solution coating method include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, and a slide coating method, and are described in US Pat. No. 2,681,294. For example, an extrusion coating method using a conventional hopper. In such a solution coating method, when the organic film 2 is a resin layer, a resin solution in which a resin is dissolved in an organic solvent may be applied and then dried to form the organic film 2, or a resin precursor. A solution containing (for example, an oligomer or a monomer) may be applied and then polymerized to form the organic film 2. The solution containing the resin precursor may contain a polymerization initiator, a chain transfer agent, or the like as necessary.

 Examples of the monomer capable of forming the organic film 2 by polymerizing after coating the monomer include various methacrylate monomers and various acrylate monomers. Suitable materials for the methacrylate and acrylate monomers include the compounds described in US Pat. No. 6,083,628 and US Pat. No. 6,214,422.

 The monomer polymerization method is not particularly limited, and examples thereof include heat polymerization, photopolymerization (including ultraviolet polymerization and visible light polymerization), electron beam polymerization, plasma polymerization, and combinations thereof. What is necessary is just to select a polymerization method suitably with an initiator according to the kind of monomer.

 For example, when performing photopolymerization, a photopolymerization initiator is used as a polymerization initiator. Examples of the photopolymerization initiator include Irgacure series (for example, Irgacure 651, Irgacure 754n Irgacure 184, Irgacure 2959, Irgacure 369, Irgacure 379, Irgacure 819, etc.), Darocur Series (manufactured by Ciba Specialty Chemicals) For example, Darocur TPO, Darocur 1173, etc.), QuantaCure PDO, Ethercure series manufactured by Sartomer (for example, Ezacure TZM, Ezacure TZT, etc.), and the like. When such a polymerization initiator is used, polymerization proceeds by irradiation with ultraviolet rays. A generally used high-pressure mercury lamp or low-pressure mercury lamp may be used for ultraviolet irradiation.

Since acrylate monomers and methacrylate monomers are subject to polymerization inhibition due to the presence of oxygen during polymerization, it is preferable to lower the oxygen concentration or oxygen partial pressure during polymerization. When the polymerization is insufficient, the organic film 2 is likely to deteriorate with time due to unreacted monomers remaining in the organic film 2. Therefore, the polymerization rate is preferably 80% or more, more preferably 85% or more, and still more preferably 90% or more. Here, the polymerization rate means the ratio of reacted polymerizable groups among all polymerizable groups in the monomer mixture (ac density is an acryloyl group for a related monomer and a methacryloyl group for a methacrylate monomer). infrared absorption spectrum in the vicinity of the absorption intensity and 810 cm ^-1 based on the carbonyl group in the vicinity of 1720 cm ^-1 of carbon atoms in the mixture - from the ratio of the absorption intensity based on the carbon double bonds can be calculated by equation 1 below.

(Calculation formula 1)
Curing rate (%) = {(a × d−b × c) / a × d} × 100
a: peak intensity of the cured film near 1720 cm ⁻¹ b: peak intensity of the cured film near 810 cm ⁻¹ c: peak intensity of the monomer mixture near 1720 cm ⁻¹ d: peak intensity of the monomer mixture near 810 cm ⁻¹

Examples of the method for lowering the oxygen concentration include a general nitrogen substitution method. In this case, the oxygen concentration is preferably 2% or less, and more preferably 0.5% or less. As a method for reducing the oxygen partial pressure, a general decompression method or the like can be used. In this case, the total pressure is preferably 1000 Pa or less, and more preferably 100 Pa or less. When photopolymerization is performed by a reduced pressure method, the energy of the irradiated light is preferably ² J / cm ² or more under reduced pressure conditions of 100 Pa or less.

The organic film 2 preferably has high smoothness, and the average surface roughness Ra is preferably 10 nm or less, more preferably 2 nm or less at a 10 μm square. Surface smoothness can be measured using an atomic force microscope (AFM). At this time, the smoothness was expressed by an average roughness Ra (unit: nm) with respect to a measurement range of 1 μm square. The apparatus used was SPI3800N / SPA400 (manufactured by SII NanoTechnology Co., Ltd.), the cantilever was SI-DF20, and the measurement conditions were an operating frequency of 1 Hz and a number of X and Y data of 256 lines.

 The organic film 2 preferably has a high film hardness, preferably has a pencil hardness of HB or higher, more preferably H or higher.

 The film thickness of the organic film 2 is not particularly limited, but if it is too thin, it will be difficult to obtain film thickness uniformity, and if it is too thick, cracks will occur due to film stress such as bending even if the organic film is highly flexible. Resulting in. From this viewpoint, the thickness of the organic film 2 is preferably 300 nm to 2 μm, and more preferably 500 nm to 1 μm.

The silicon nitride film 1 is formed by the silicon nitride film manufacturing method of the present invention. As described in the embodiment of the silicon nitride film manufacturing method, the silicon nitride film 1 has a water vapor transmission rate of 10 ⁻³ g / m ² / day or less at a film thickness of 200 nm or less suitable as a gas barrier film of a thin film element. It is a film having a good film quality.

 As already described, in the gas barrier film 3, the uppermost layer is preferably the organic film 2, but a configuration in which a functional layer is further provided on the upper surface of the uppermost organic film 2 may be employed. Examples of such a functional layer include the same functional layers that can be provided on the upper surface and / or the lower surface of the resin substrate 10.

The gas barrier film 3 of the present embodiment is obtained by alternately laminating the silicon nitride film 1 and the organic film 2 of the present invention on a resin substrate 10. Since the silicon nitride film 1 of the present invention has a water vapor transmission rate (WVTR) of 10 ⁻³ g / m ² / day or less, the gas barrier film 3 including the silicon nitride film 1 has good gas barrier properties. It will have. In the gas barrier film 3 of the present embodiment, it is possible to have a desired gas barrier property by designing the number of layers of the silicon nitride film 1. Therefore, according to the present embodiment, the WVTR is 10 ⁻⁶ g. The gas barrier film 3 having a gas barrier property of / m ² / day or less can be provided.

 In the present embodiment, the configuration in which the boundary between the organic film 2 and the silicon nitride film 1 is clear in the gas barrier film 3 as shown in FIG. 10 has been described. The boundary (interface) is not necessarily clear, and there may be a region where the organic compound constituting the organic film 2 and the inorganic compound constituting the silicon nitride film 1 are mixed.

 In such a configuration, since the functions of the silicon nitride film 1 and the organic film 2 are integrated, the gas barrier film 3 as a whole may be designed to have a desired WVTR value. For example, the ratio between the organic compound and the inorganic compound may change continuously in the film thickness direction. Examples include an embodiment described in “Journal of Vacuum Science and Technology A Vol. 23 p971-977 (2005 American Vacuum Society,”), or an organic layer and an inorganic layer disclosed in US Published Patent No. 2004-46497. In the case where a region where organic compounds and inorganic compounds are mixed is provided as described above, a region where the organic compound content is high and a region where the inorganic compound content is high. It is preferable to adopt a structure in which sapphire appears alternately in the film thickness direction.

"Thin film element"
With reference to FIG. 11, the structural example of the thin film element provided with the gas barrier film 3 of the said embodiment is demonstrated. Examples of the thin film element include an organic EL element, a liquid crystal display element, an image display element such as electronic paper, a dye-sensitized solar cell, and a touch panel. In the present embodiment, the organic EL element is described as an example. To do. FIG. 11 is a schematic cross-sectional view showing the configuration of the organic EL element of this embodiment.

  The organic EL element (thin film element) 4 of the present embodiment has a lower electrode 11, an organic EL layer 20, an upper electrode 12, an upper surface, The resin substrate 10 provided with the gas barrier film 3 of the above embodiment is provided on the lower surface, and an image or the like is displayed from below in the figure.

As described above, in the use of the organic EL element, the gas barrier film 3 preferably has a WVTR of 10 ⁻⁶ g / m ² / day or less. Therefore, the number of layers of the silicon nitride film 1 is designed so that the gas barrier film 3 of this embodiment has such a WVTR value.

  The materials and configurations of the lower electrode 11 and the upper electrode 12 are specifically described in detail in paragraphs [0042] to [0048] of JP-A-2006-289627.

  The organic EL layer 20 is specifically described as an organic compound layer in paragraphs [0049] to [0058] of JP-A-2006-289627.

Since the organic EL element 4 of the present embodiment includes the gas barrier film 3 having a WVTR of 10 ⁻⁶ g / m ² / day or less, the mixture of air and water vapor into the element is suppressed to a high level. Can do. Therefore, even in an organic EL element whose element characteristics are easily influenced by water vapor or oxygen, it is possible to realize good and highly reliable element characteristics that hardly cause characteristic deterioration due to mixing of water vapor or oxygen.

(Design changes)
In the above embodiment, the resin substrate has been described as an example of the substrate having at least one organic layer, but the substrate is not limited to this. For example, it can be preferably applied to a substrate in which an inorganic layer and an organic layer are laminated, a substrate having various functional layers, wirings, and the like.

Embodiments according to the present invention will be described.
Example 1
A silicon nitride film was formed on the PEN film substrate using the atmospheric pressure plasma CVD apparatus 100 shown in FIG. The film formation conditions are: input power density 250 W / cm ³ , RF frequency 150 MHz, pressure 760 Torr, source gas ratio (volume%): SiH ₄ : 0.05%, NH ₃ : 1.0%, H ₂ : 20%, He: 78.95%, substrate-electrode distance: 800 μm, film thickness 100 nm, substrate temperature was RT. Here, the substrate temperature is a temperature obtained by monitoring the substrate stage temperature with a K thermocouple, and RT is in the range of 25 ± 1 ° C. The film formation speed at this time was 6 to 7 μm / min.

Cracks and the like were not observed in the obtained silicon nitride film, and the film density was measured. As a result, the film density was 2.4 ± 0.1 g / cm ³ .

Next, WVTR measurement was performed on the silicon nitride film. As described in the above embodiment, the measurement of WVTR is performed using “PERMATRAN-W3 / 31” (condition: 40 ° C., relative humidity 90%) manufactured by MOCON, and complemented by changes in the optical density of metallic Ca. Calculated by going. As a result, the WVTR value was 2 × 10 ⁻⁴ g / m ² / day.

A silicon nitride film was formed on a PEN film substrate by changing the film formation conditions in Example 1. The film forming conditions are: input power density 450 W / cm ³ , RF frequency 150 MHz, pressure 760 torr, source gas ratio (volume%): SiH ₄ : 0.05%, NH ₃ : 1.0%, H ₂ : 15%, He: 83.95%, substrate-electrode distance: 800 μm, film thickness 100 nm, substrate temperature was RT. The film formation speed at this time was 6.5 to 7.5 μm / min.

Cracks and the like were not observed in the obtained silicon nitride film, and the film density was measured and found to be 2.3 ± 0.1 g / cm ³ . Moreover, as a result of measuring WVTR like Example 1 about the obtained silicon nitride film, WVTR value was 4 * 10 < ^-4 > g / m < ² > / day.

The film obtained in Example 1 and Example 2 is a film obtained at a good film formation rate, and has a good quality without cracks having a WVTR value of 10 ⁻³ g / m ² / day or less. It was a silicon nitride film. Therefore, the effectiveness of the present invention was shown.

  The silicon nitride film of the present invention is preferably applied to an organic EL element using a resin substrate, a liquid crystal display element, an image display element such as electronic paper, and a gas barrier film of a thin film element such as a dye-sensitized solar cell and a touch panel. be able to.

Schematic diagram showing the state of film formation in atmospheric pressure plasma CVD Schematic showing the configuration of a continuous film forming apparatus using the roll-to-roll method Schematic showing an example of a rotating electrode type atmospheric pressure plasma CVD apparatus used in the silicon nitride film forming method of the present invention. Schematic showing an example of a parallel plate type atmospheric pressure plasma CVD apparatus used in the silicon nitride film forming method of the present invention. The figure which shows the relationship between the film thickness and WVTR value in the silicon nitride film from which film | membrane density differs The figure which shows the range of the film thickness and film | membrane density from which water vapor permeability is 10 < ^-3 > g / m < ² > / day or less. Shows and H ₂ gas concentration in the raw material gas, the relationship between the film thickness of the resulting silicon nitride film and WVTR It shows a range of concentrations of input power density and the _{H 2} gas to be obtained WVTR value of less than 10 ^-3 g ^/ m 2 / day Diagram showing the relationship between WVTR of silicon nitride film obtained with the mixing ratio of SiH ₄ and NH ₃ in the feed gas 1 is a schematic cross-sectional view showing a configuration of a gas barrier film according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing the configuration of a thin film element (organic EL element) according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon nitride film 2 Organic film 3 Gas barrier film 4 Thin film element (organic EL element)
10 Resin substrate (base)

Claims (7)

A method of forming a silicon nitride film on a substrate having at least one organic layer placed in a reaction vessel by chemical vapor deposition using plasma,
Supplying a source gas containing SiH ₄ , NH ₃ , H ₂ and He into the reaction vessel so that the total gas pressure of the source gas becomes atmospheric pressure;
Upwards the installed electrodes of the substrate, by applying a power density of 250 W / cm ³ Ultra 450 W / cm ³ or less of the electric field is generated an electric field between the electrode and the substrate, the said electrode by electric field Bringing the source gas between the substrate into a plasma state;
Forming the silicon nitride film on the substrate using the source gas in a plasma state at a temperature lower than the heat resistant temperature of the organic layer,
The ratio of H ₂ in the source gas is 13% or more and 20% or less, and the ratio of NH ₃ to SiH ₄ in the source gas is 13% or more and 24% or less. Film forming method. The method for forming a silicon nitride film according to claim 1, wherein a ratio of H ₂ in the source gas is 15% or more and 18% or less.   The method for forming a silicon nitride film according to claim 1, wherein the film formation rate is 1 μm / min or more. Supplying a source gas containing SiH ₄ , NH ₃ , H ₂ and He into the reaction vessel so that the total gas pressure of the source gas becomes atmospheric pressure;
An electric field is applied to an electrode disposed above a substrate having at least one organic layer disposed in the reaction vessel to generate an electric field between the electrode and the substrate, and the electric field and the electrode Bringing the source gas between the substrate into a plasma state;
Forming the silicon nitride film on the substrate using the source gas in a plasma state at a temperature lower than the heat resistant temperature of the organic layer by a chemical vapor deposition method using plasma,
It is formed by a silicon nitride film forming method in which the ratio of H ₂ in the source gas is 13% to 20% and the ratio of NH ₃ to SiH ₄ in the source gas is 13% to 24%. A silicon nitride film formed,
A silicon nitride film having a water vapor transmission rate of 10 ⁻³ g / m ² / day or less. 5. A gas barrier film comprising at least one silicon nitride film according to claim 4 and at least one organic film laminated alternately. The gas barrier film according to claim 5 , wherein the water vapor transmission coefficient is 10 ⁻⁶ g / m ² / day or less. A thin film element comprising the gas barrier film according to claim 5 or 6 on a substrate.

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