JP2009041091A - Film deposition method and film deposition system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film deposition method and a film deposition system where, when a metal fluoride such as MgF<SB>2</SB>is used as a target, and film deposition is performed by a sputtering process, a thin film free from light absorption and also having sufficient mechanical strength can be produced with high film thickness reproducibility even if an erosion shape is changed by the repeated use of a target material. <P>SOLUTION: In the film deposition method where a material at least comprising a metal fluoride is used as a target 6, high frequency electric power is applied to the target while introducing a discharge gas into a film deposition chamber 2, and plasma 14 is generated, so as to deposit a film on a substrate 3 by a sputtering process, the method comprises: a stage where plasma light emission intensity is measured with a first measuring instrument 41, and the measured result is fed-back, and the introduction amount of the discharge gas to the film deposition chamber is regulated; and a stage where the film deposition rate of the sputtering particles in the film deposition chamber is measured with a second measuring instrument 42, and the measured result is fed-back, and the high frequency electric power applied to the target is regulated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a film forming method and a film forming apparatus for forming a thin film by a sputtering method, and more particularly to a film forming method and a film forming apparatus for forming an optical thin film such as an antireflection film by a sputtering method.

  Conventionally, when an optical thin film such as an antireflection film is formed on a substrate such as an optical component, a vacuum deposition method in which the material is heated and evaporated to adhere to the substrate has been mainly used. In contrast to this vacuum deposition method, sputtering is automated, labor-saving, applicable to large-area substrates, and the possibility of low-temperature film formation due to the energy of the sputtering particles being one to two orders of magnitude higher than the deposited particles. There are many advantages and it is widely applied in the coating field.

As a material constituting the antireflection film, a metal fluoride such as CaF ₂ or MgF ₂ is often used because of a low refractive index in addition to a metal oxide such as SiO ₂ or ZrO ₂ . Metal fluorides such as CaF ₂ or MgF _2, by vacuum deposition while heating the substrate about 300 ° C., while the light absorption is less mechanical high strength quality thin films of these by sputtering When a metal fluoride is used, fluorine is easily dissociated from the metal fluoride, and a film formed by this method has a problem that light absorption in the visible region is likely to occur.

Patent Document 1 discloses a film forming method in which film formation is performed while maintaining the plasma emission intensity of Mg atoms, MgF molecules, and discharge gas (atoms, molecules) in an appropriate range in the sputtering of MgF ₂ . According to this film formation method, it is said that a film having a low mechanical absorption and a high mechanical strength can be formed on the substrate.

In sputtering of MgF _2, types of targets in the form and the discharge gas, the gas pressure, depending on the conditions such as input power, emission of MgF molecules in the plasma (wavelength 359 nm) can be measured by a plasma emission monitor (PEM). The fact that MgF molecules emit light indicates that there are MgF ₂ molecules in the sputtered particles that are scattered. When the emission intensity of MgF molecules increases, the probability that MgF ₂ scatters in the molecular state as sputtered particles increases. Therefore, fluorine is less likely to dissociate, and as a result, the light absorption of the formed film is reduced.

However, it is not necessary that the emission intensity of the MgF molecule is strong. If the emission intensity of the MgF molecule is too high compared to the emission of Mg atoms, the light absorption of the film is reduced, but the mechanical strength of the film is low. I know it ’s easy to be. Under such conditions, the scattering rate of MgF ₂ molecules that evaporate when the target is heated is high. It is considered that the mechanical strength of the resulting film is lowered because the energy of particles scattered by heating is about 1 to 2 orders of magnitude lower than that of sputtered particles.

From the above, in order to obtain an MgF ₂ film having low light absorption and high mechanical strength without performing substrate heating, the ratio of the emission intensity of MgF molecules to the emission intensity of Mg atoms is set within a certain range. It is necessary to perform film formation while maintaining. Note that, as described above, the ratio of the emission intensity of MgF molecules to the emission intensity of Mg atoms varies depending on conditions such as the target form, the type of discharge gas, the flow rate of discharge gas, and the input power.
JP-A-9-104976

However, in the conventional film forming method and film forming apparatus disclosed in Patent Document 1, the target material is repeatedly used even if the plasma emission intensity and the plasma emission intensity ratio are controlled to be constant. Due to the erosion shape of the target surface caused by the above, there is a problem that the film thickness reproducibility is deteriorated.
Considering this reason, a magnet is disposed under the target, but the distance between the magnet and the target is non-uniform in the erosion portion. Even when the plasma emission intensity of the target is controlled to be constant, the plasma density at the time of sputtering increases because the distance between the target and the magnet is close at the portion of the target that is locally concave due to erosion. For this reason, it is considered that the deposition rate increases due to the local increase in plasma emission intensity, and the thickness of the film deposited on the substrate becomes unstable.

This tendency to become unstable becomes remarkable according to the number of times the target material is repeatedly used. This is because the target is dug deep every time sputtering is performed.
Moreover, the tendency to become unstable is remarkable also when a granular target is used instead of a plate target.

Furthermore, it has been found that the target temperature is raised to about 800 ° C. or higher due to the temperature rise caused by the plasma under the condition that the emission of MgF molecules appears in the sputtering of MgF ₂ . When the erosion shape changes by repeatedly using the target material, the plasma density on the target surface changes, and the temperature distribution on the target surface changes accordingly. When the target surface temperature is different, the film formation rate is also different. Therefore, even if the plasma emission intensity is kept at an appropriate value and film formation is performed at the same film formation time every time, the film thickness reproducibility of the produced thin film is lowered.

The present invention has been made in view of such problems, and in forming a film by sputtering using a metal fluoride such as MgF ₂ , a thin film that does not absorb light and has sufficient mechanical strength is provided. It is an object of the present invention to provide a film forming method and a film forming apparatus that can be manufactured with good film thickness reproducibility even when the erosion shape is changed by repeatedly using a target material.

In order to solve the above problems, the present invention proposes the following means.
In the film forming method of the present invention, a material containing at least a metal fluoride is used as a target, plasma is generated by introducing high-frequency power into the target while introducing a discharge gas into the film forming chamber, and a film is formed on a substrate by a sputtering method. In the film forming method, the step of measuring the emission intensity of the plasma with a first measuring device and feeding back the measurement result to adjust the introduction amount of the discharge gas into the film forming chamber; And measuring the film formation rate of the sputtered particles with a second measuring instrument, feeding back the measurement result, and adjusting the high-frequency power to be input to the target.

  The film forming apparatus of the present invention uses a material containing at least a metal fluoride as a target, generates a plasma by introducing high-frequency power into the target while introducing a discharge gas into the film forming chamber, and forms a substrate on the substrate by a sputtering method. In the film forming apparatus for forming a film, the first measuring means for measuring the emission intensity of the plasma, the second measuring means for measuring the film forming speed of the sputtering particles in the film forming chamber, and the first measuring means The first control means for adjusting the introduction amount of the discharge gas into the film forming chamber by feeding back the measurement result and the high-frequency power to be fed to the target by feeding back the measurement result of the second measurement means And a second control means.

  According to the film forming method and the film forming apparatus of the present invention, not only the plasma emission intensity is fed back to adjust the amount of discharge gas introduced into the film forming chamber, but also the film forming speed of the sputtered particles in the film forming chamber. Since the high-frequency power fed back to the target is adjusted, a thin film that does not absorb light and has sufficient mechanical strength can be heated even when the erosion shape of the target surface changes, with good film thickness reproducibility. It becomes possible to manufacture without performing.

  In the film forming method, the second measuring instrument measures the amount of the sputtered particles adhering to the surface of the crystal resonator in the film forming chamber, and the time variation of the amount of adhering It is more preferable that the film forming speed be calculated.

  In the film forming apparatus, the second measuring unit measures the amount of the sputtered particles adhering to the surface of the crystal resonator in the film forming chamber, and the time variation of the amount of adhering It is more preferable that the film forming speed be calculated.

  According to the film forming method and the film forming apparatus according to the present invention, the second measuring instrument and the second measuring means measure the amount of sputtered particles adhering to the surface of the crystal unit in the film forming chamber, Since the film forming speed is calculated from the temporal change in the amount of adhesion, the film forming speed can be accurately measured in units of 0.1 nm / sec, and the thickness of the film to be formed is stabilized.

  In the film forming method, the second measuring instrument is more preferably configured to measure the surface temperature of the target and calculate the film forming rate of the sputtered particles from the surface temperature. ing.

  In the film forming apparatus, the second measuring unit is preferably configured to measure the surface temperature of the target and calculate the film forming rate of the sputtered particles from the surface temperature. ing.

According to the film forming method and the film forming apparatus of the present invention, the second measuring instrument and the second measuring means are
Since the surface temperature of the target is measured and the film formation rate of the sputtering particles is calculated from the surface temperature, the surface temperature of the target is stabilized and the thickness of the film to be formed can be stabilized.

Furthermore, in the film forming method of the present invention, a material containing at least MgF ₂ (magnesium fluoride) is used as a target, high-frequency power is applied to the target while introducing a discharge gas into the film forming chamber, and plasma is generated. In the film forming method of forming a film on the substrate in step 1, the plasma emission intensity ratio, which is the ratio of the emission intensity of the plasma of Mg and the emission intensity of the plasma of MgF, is measured with a first measuring instrument, and the measurement result is fed back. Adjusting the amount of the discharge gas introduced into the film forming chamber so that the plasma emission intensity ratio becomes a constant value, and the film forming speed of the sputtering particles in the film forming chamber with a second measuring instrument. Measuring and feeding back the measurement result, and adjusting the high-frequency power to be input to the target so that the film formation rate becomes a constant value. To have.

According to the film forming method of the present invention, with a material containing at least MgF ₂ as a target, plasma is generated by introducing high-frequency power into the target while introducing a discharge gas into the film forming chamber, and the substrate is formed by sputtering. In the film forming method for forming a film, the measurement result of the plasma emission intensity ratio, which is the ratio of the Mg plasma emission intensity to the MgF plasma emission intensity, is fed back to form a discharge gas film so that the plasma emission intensity ratio becomes a constant value. The amount introduced into the chamber was adjusted, and the measurement result of the deposition rate of the sputtered particles in the deposition chamber was fed back to adjust the high-frequency power supplied to the target so that the deposition rate became a constant value. Therefore, a thin film of MgF ₂ that does not absorb light and has sufficient mechanical strength can be manufactured with good film thickness reproducibility and without heating the substrate even if the erosion shape of the target surface changes.

  In the film forming method, the amount of the discharge gas introduced into the film forming chamber is adjusted so that the plasma emission intensity ratio is a constant value of 1.5 or more and 3.5 or less. It is more preferable to adjust the high-frequency power input to the target so that the film speed becomes a constant value of not less than 0.5 nm / sec and not more than 5.0 nm / sec.

According to the film forming method of the present invention, the amount of discharge gas introduced into the film forming chamber is adjusted so that the measured plasma emission intensity ratio becomes a constant value of 1.5 or more and 3.5 or less. Since the high-frequency power input to the target was adjusted so that the speed became a constant value of not less than 0.5 nm / sec and not more than 5.0 nm / sec, a thin film of MgF ₂ having no mechanical absorption and no mechanical absorption was obtained. Even if the erosion shape of the target surface changes, the film thickness can be reproduced with good reproducibility without heating the substrate.

  According to the film forming method and the film forming apparatus of the present invention, a thin film that does not absorb light and has sufficient mechanical strength is heated with high film thickness reproducibility even if the erosion shape of the target surface changes. It becomes possible to produce without.

FIG. 1 is a cross-sectional view showing a configuration of a film forming apparatus according to a first embodiment of the present invention. A substrate 3 is rotatably disposed above the inside of the vacuum chamber 2 serving as a film forming chamber. In this embodiment, an optical glass made of BK7 (refractive index 1.52) is used as the substrate 3.
Below the substrate 3 in the vacuum chamber 2, a quartz dish 5 is placed on a magnetron cathode 4 having a diameter of 6 inches (about 152.4 mm). The dish 5 has a particle diameter of 0.1 to 10 mm. The target 6 which is a granule of MgF ₂ is filled. The magnetron cathode 4 is connected to a high frequency power source 7 for sputtering.
A discharge gas inlet 11 is formed on the side surface of the vacuum chamber 2. The flow rate of the discharge gas is controlled by the mass flow controller 12, and thereby the gas pressure in the vacuum chamber 2 is controlled.

Further, a plasma emission monitor 13 is disposed on the side of the target 6. The plasma emission monitor 13 is a device that measures the emission intensity of the generated plasma 14, and the measured plasma emission intensity is converted into an electrical signal by the plasma emission monitor control unit 15. Further, a shutter 16 is disposed above the target 6, and opening / closing of the shutter 16 is controlled by an opening / closing device 17 to which the shutter 16 is attached.
A crystal resonator 21 is disposed between the target 6 and the shutter 16. The quartz oscillator 21 can measure the amount of the sputtered particles in the vacuum chamber 2 from the change in the resonance frequency due to the deposition of the attached film. The crystal resonator control unit 22 to which the crystal resonator 21 is connected measures the adhesion amount of the sputtered particles by measuring the resonance frequency of the crystal resonator 21, and the sputtering in the film forming chamber is performed from the time change of the measured value. The particle deposition rate is calculated, and the calculation result is output as an electrical signal.
A sputtering high-frequency power source 7, a mass flow controller 12 for controlling the flow rate of the discharge gas, a plasma emission monitor control unit 15 for converting the emission intensity of plasma into an electric signal, and a crystal for converting the resonance frequency of the crystal resonator 21 into an electric signal The vibrator control unit 22 and the opening / closing device 17 that opens and closes the shutter 16 are connected to the device control unit 31 and controlled integrally.

Next, a procedure for forming a film using the film forming apparatus 1 of the first embodiment will be described.
First, the substrate 3 is placed in the vacuum chamber 2, and the vacuum chamber 2 is evacuated to 1 × 10 ⁻⁴ Pa by a vacuum pump (not shown). At this time, the substrate 3 is not heated.
Next, O ₂ gas as discharge gas is introduced into the vacuum chamber 2 from the gas inlet 11 while controlling the flow rate by the mass flow controller 12, and the gas pressure is adjusted to 4 × 10 ⁻¹ Pa. Then, high frequency power is supplied to the magnetron cathode 4 to generate plasma 14. The target 14 made of MgF ₂ is heated by the plasma 14, and simultaneously sputtered by the discharge gas ions in the plasma 14 and scattered in the vacuum chamber 2.

Light emitted from the plasma 14 is taken into a plasma emission monitor 13 disposed on the side of the target 6. The plasma emission monitor 13 spectrally separates light in the wavelength range of 200 nm to 850 nm, and the plasma emission intensity of each of MgF (wavelength 359 nm) and Mg (wavelength 518 nm), and the plasma emission intensity of MgF molecules relative to the plasma emission intensity of Mg atoms. (Hereinafter, referred to as “MgF / Mg plasma emission intensity ratio”) is calculated in real time.
The calculation result is sent to the plasma emission monitor control unit 15, and when the calculation result, that is, the MgF / Mg plasma emission intensity ratio becomes 3.0, the plasma emission monitor control unit 15 outputs a signal to the apparatus control unit 31. The device control unit 31, such that the plasma emission intensity ratio of MgF / Mg is maintained at 3.0, and controls the flow rate of _{O 2} gas flowing from the inlet 11 at a mass flow controller 12.

  As described above, the first measuring device (first measuring means) 41 for measuring the plasma emission intensity ratio of MgF / Mg described in the claims includes the plasma emission monitor 13 and the plasma emission monitor control unit 15. It is configured.

When the target 6 is sputtered and the particles are scattered in the vacuum chamber 2, the crystal oscillator control unit 22 measures the amount of the sputtered particles by measuring the resonance frequency of the crystal oscillator 21, and the measurement value changes with time. The film formation speed of the sputtering particles in the film formation chamber is calculated from the above, and the calculation result is output to the apparatus control unit 31. The apparatus control unit 31 controls the high frequency power applied to the high frequency power supply 7 so that the calculated film formation rate is maintained at 3.0 nm / sec.
As described above, the second measuring device (second measuring means) 42 for measuring the film forming speed of the sputtering particles in the film forming chamber described in the claims is the same as the crystal resonator 21 in the first embodiment. And a crystal resonator control unit 22.
Further, the first control means 51 for adjusting the amount of discharge gas introduced into the film forming chamber and the second control means 52 for adjusting the high frequency power to be supplied to the target 6 are both described in the claims. The control unit 31 also serves.

When the apparatus control unit 31 determines that the plasma emission intensity ratio of MgF / Mg is maintained at 3.0 and at the same time the film forming speed is maintained at 3.0 nm / sec, the apparatus controller 31 drives the opening / closing device 17 to open the shutter 16. As a result, an MgF ₂ film is formed on the substrate 3. During this time, the plasma emission monitor 13 measures the plasma emission intensity ratio of MgF / Mg, and the crystal oscillator 21 measures the film formation rate. The mass flow controller 12 adjusts the measured values to 3.0 and 3.0 nm / sec, respectively. And the high frequency power supply 7 is controlled. At this time, the high-frequency power was 1000 to 1050 W, and the flow rate of O ₂ gas as a discharge gas was about 20.0 to 22.0 sccm.

The material comprising MgF ₂ (magnesium fluoride) in the case of the target 6, the range of values of desired parameters, a constant value plasma emission intensity ratio is 1.5 to 3.5 of MgF / Mg, further growth This is a range in which the film speed is adjusted to a constant value between 0.5 nm / sec and 5.0 nm / sec. At this time, the amount of discharge gas introduced into the film formation chamber 2 in order to control the plasma emission intensity ratio is adjusted in the range of 10 to 50 sccm, and the high-frequency power input to control the film formation rate is 500. It is adjusted in the range of ~ 1500W.

  The reason for controlling the MgF / Mg plasma emission intensity ratio between 1.5 and 3.5 is that when the plasma emission intensity ratio is outside this range, fluorine dissociates from the metal fluoride and the energy of the sputtered particles is low. This is because the mechanical strength of the film decreases. Also, the reason for controlling the film formation speed between 0.5 nm / sec and 5.0 nm / sec is that if the film formation speed is out of this range, the film thickness is reproducibly affected by the erosion shape. It is.

FIG. 2 is a spectral reflectance characteristic diagram of the MgF ₂ film formed according to the first embodiment. For similarly low to that obtained in the refractive index is 1.39 and the vacuum deposition of MgF ₂ film, the reflectance as shown in FIG. 2 is not more than 2% in the visible range (wavelength 400 nm to 700 nm), antireflection It is effective as a membrane. Further, the light absorption of the film in the visible region (wavelength 400 nm to 700 nm) is less than 0.5%, which is as low as that obtained by the vacuum deposition method, and there is no optical problem. Furthermore, although the substrate 3 was not heated, the mechanical strength of the film such as adhesion and scratching was good, which was practically sufficient.

FIG. 3 shows changes in the values of the refractive index, light absorption, and film formation rate of the MgF ₂ film formed according to the first embodiment depending on the number of times the target 6 is used repeatedly. In this embodiment, the same MgF ₂ target 6 was repeatedly used up to 20 times to form a film.
FIG. 4 shows, as a comparative example, changes in the values of the refractive index, light absorption, and film formation speed of the MgF ₂ film formed under conditions different from those of the first embodiment, depending on the number of times the target 6 is used repeatedly. The condition different from the first embodiment is that the flow rate of O _{2 as} a discharge gas is kept constant at 20.0 sccm, the plasma emission monitor 13 measures the plasma emission intensity ratio of MgF / Mg, and the value is 3.0. It is a condition that is controlled by high frequency power so as to be constant. The film formation rate was calculated from the thickness of the thin film produced and the film formation time.

3 and 4, in the first embodiment of the present invention and the method in which only the plasma emission intensity ratio is controlled to a constant value, both the refractive index and light absorption of the produced film are not problematic in practical use. Recognize. This is because the film was formed under the control of the plasma emission monitor 13 so that the plasma emission intensity ratio would be optimal, so that the MgF ₂ molecules were scattered in the form of sputtered particles without the fluorine dissociating. .

However, in the method in which only the plasma emission intensity ratio shown in FIG. 4 is controlled to a constant value, the film forming speed is a relatively constant value from 1 to 7 times of repeated use. As the value increases, the deposition rate increases. This is because as the number of film formation increases, a concave portion is formed on the target surface, and the plasma density increases in the concave portion as it approaches a magnet disposed under the target. Even if the plasma emission intensity is controlled to be constant, the plasma emission intensity actually differs depending on the position of the target surface due to the erosion shape.
On the other hand, in the first embodiment, the film formation rate is measured using the crystal resonator 21, and the film formation rate is controlled from the first use to the 20th use by controlling the high frequency power so that the value is constant. Became almost equal.

As described above, in the first embodiment of the present invention, not only the plasma emission intensity is controlled by the discharge gas flow rate, but also the film formation speed is controlled by the high frequency power, so there is no light absorption and sufficient mechanical strength. Even if the erosion shape of the target surface changes, it is possible to produce a thin film with good film thickness reproducibility and without heating the substrate.
Further, as the second measuring instrument, a measuring instrument that measures the deposition amount of the target material adhering to the surface of the crystal unit and calculates the deposition rate of the sputtered particles in the deposition chamber from the temporal change of the deposition amount is used. Thus, the film forming speed can be measured with accuracy in units of 0.1 nm / sec, and the thickness of the film to be formed is stabilized.

As described above, the MgF / Mg plasma emission intensity ratio varies depending on conditions such as the target form, the type of discharge gas, the flow rate of discharge gas, and the input power.
In addition, when the high-frequency power changes to control the deposition rate, the plasma emission intensity ratio also changes, but the plasma emission intensity ratio is adjusted to a desired value by controlling with the O ₂ gas flow rate by the plasma emission monitor 13. can do.

  In the first embodiment, the crystal resonator 21 is used to measure the deposition rate of the sputtered particles in the deposition chamber. Instead, the deposition rate is measured by calculating a periodic change in reflectance. An optical monitoring meter may be used.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a cross-sectional view showing a configuration of a film forming apparatus according to the second embodiment of the present invention. For convenience of explanation, in the second embodiment of the present invention, the same components as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In regard to the configuration of the film forming apparatus, the second embodiment replaces the crystal resonator 21 and the crystal resonator control unit 22 used in the first embodiment, and in the second embodiment, a radiation is used to measure the surface temperature distribution of the target 6. A thermometer 26 is installed on the side of the vacuum chamber 2 so as to measure a two-dimensional temperature distribution on the surface of the target 6, and the radiation thermometer 26 is connected to a radiation thermometer control unit 27. Although the temperature of the surface of the target 6 rises in the erosion part, the radiation thermometer control part 27 weights and averages the measured two-dimensional temperature distribution in consideration of the influence of the erosion part. Calculate the surface temperature at which

Next, a procedure for forming a film by the film forming apparatus 1 of the second embodiment will be described.
The procedure up to the control by the mass flow controller 12 so that the MgF / Mg plasma emission intensity ratio is maintained at 3.0 is the same as that of the film forming apparatus 1 of the first embodiment, and thus the description thereof is omitted.

When the particles are scattered in the vacuum chamber 2 after being sputtered, the radiation thermometer control unit 27 calculates the deposition rate of the sputtering particles in the deposition chamber from the relationship between the surface temperature and the deposition rate stored in advance. The calculation result is output to the device control unit 31. From the relationship between the surface temperature and the film formation rate, it is known that the surface temperature should be 800 ° C. in order to achieve the film formation rate of 3.0 nm / sec. Therefore, the device control unit 31 controls the high-frequency power applied to the high-frequency power source 7 so that the calculated surface temperature is maintained at 800 ° C.
As described above, the second measuring instrument (second measuring means) 42 for measuring the deposition rate of the sputtered particles in the deposition chamber described in the claims is the radiation thermometer 26 in the second embodiment. It is comprised with the radiation thermometer control part 27. FIG.

When the apparatus controller 31 determines that the plasma emission intensity ratio of MgF / Mg is maintained at 3.0 and at the same time the surface temperature is maintained at 800 ° C., the apparatus controller 31 drives the opening / closing device 17 to open the shutter 16, thereby An MgF ₂ film is formed on 3. During this time, the plasma emission monitor 13 measures the MgF / Mg plasma emission intensity and the radiation thermometer 26 measures the surface temperature. The mass flow controller 12 and the high-frequency power source 7 are connected so that the measured values are 3.0 and 800 ° C., respectively. I have control. At this time, the high frequency power was 1000 to 1050 W, and the O ₂ gas flow rate was about 20.0 to 22.0 sccm.

FIG. 6 is a spectral reflectance characteristic diagram of the MgF ₂ film formed according to the second embodiment of the present invention. As shown in FIG. 6, the reflectance is 2% or less in the visible region (wavelength 400 nm to 700 nm), which is effective as an antireflection film. Further, the light absorption of the film in the visible region (wavelength 400 nm to 700 nm) is less than 0.5%, which is as low as that obtained by the vacuum deposition method, and there is no optical problem. Furthermore, although the substrate 3 was not heated, the mechanical strength of the film such as adhesion and scratching was good.

FIG. 7 shows changes in the values of the refractive index, light absorption, and film formation rate of the MgF ₂ film formed according to the second embodiment depending on the number of times the target 6 is used repeatedly. In this embodiment, the same MgF ₂ target 6 was repeatedly used up to 20 times to form a film.
Referring to FIG. 7, it can be confirmed that when the surface temperature is controlled to 800 ° C., the deposition rate becomes 3.0 nm / sec, and the refractive index and light absorption of the film fabricated in the second embodiment of the present invention are It turns out that there is no problem in practice.

Further, as a comparative example in FIG. 8 shows the MgF ₂ film formed under different conditions from the second embodiment, the change in the value of the target surface temperature and deposition rate due to the repeated number of uses of the target 6. The condition different from that of the second embodiment is that the flow rate of O _{2 as} a discharge gas is kept constant at 20.0 sccm, the plasma emission intensity ratio is measured by the plasma emission monitor 13, and the value becomes constant at 3.0. This is the condition controlled by the high frequency power.
Referring to FIG. 8, it can be seen that as the number of repeated uses of the target 6 increases, the target surface temperature rises and the film formation rate rises accordingly.

As described above, in the second embodiment of the present invention, not only the plasma emission intensity is controlled by the discharge gas flow rate but also the film formation rate is controlled by the high frequency power, so that there is no light absorption and sufficient mechanical strength. Even if the erosion shape of the target surface changes, it is possible to produce a thin film with good film thickness reproducibility and without heating the substrate.
Further, when controlling the film formation rate, the surface temperature of the target 6 is measured using the radiation thermometer 26, and the high-frequency power is applied so that the average surface temperature is constant by weighting in consideration of the influence of the erosion portion. By controlling the above, the target surface temperature becomes constant regardless of the erosion shape, and the film formation rate can be made constant.
When the high-frequency power is changed to control the target surface temperature, the plasma emission intensity ratio also changes. However, the plasma emission intensity ratio is adjusted to a desired value by controlling the plasma emission monitor 13 with the O ₂ gas flow rate. can do.

  Further, in the second embodiment, the radiation thermometer 26 is used to measure the surface temperature of the target 6, but a thermocouple may be used instead.

As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.
In the above-described embodiment, the example in which the present invention is applied to the antireflection film has been described. However, the present invention is not limited thereto, and the present invention can be applied to the production of other optical components such as edge filters and beam splitters. is there.

In the first embodiment and the second embodiment of the present invention, the plasma emission monitor 13 measures the plasma emission intensity ratio of MgF / Mg, and the mass flow controller 12 controls the amount of the measured discharge gas introduced into the film formation chamber. It was adjusted. However, in these embodiments, instead of measuring the MgF / Mg plasma emission intensity ratio, the MgF molecule plasma emission intensity, the Mg atom plasma emission intensity, the MgF molecule / Mg atom plasma emission intensity ratio, or the MgF molecule At least one value of the plasma emission intensity ratio of / O atoms (wavelength 777 nm) may be measured and adjusted by the mass flow controller 12.
When measuring the plasma emission intensity, a plasma emission monitor 13 or a spectrometer that measures the plasma emission intensity may be used as the first measuring instrument in the claims.

In the first embodiment and the second embodiment of the present invention, MgF ₂ is used as the target 6. However, in these embodiments, instead of MgF ₂ , the metal fluorides AlF ₃ , LiF, NaF, CaF ₂ , SrF ₂ , BaF ₂ , CeF ₃ , NdF ₃ , LaF ₃ , SmF ₃ , Na ₃ AlF ₆ , Na ₅ AlF ₁₄ may be used for film formation. Further, in these embodiments, a single-layer antireflection film is used, but a multilayer film combined with a thin film made of another high refractive index material such as TiO ₂ or Ta ₂ O ₅ or another low refractive index material such as SiO _2. It is good.

It is sectional drawing which shows the structure of the film-forming apparatus of 1st Embodiment of this invention. It is a spectral reflectance characteristic view of the MgF ₂ film formed according to the first embodiment of the present invention. The refractive index of MgF ₂ film formed by the first embodiment of the present invention, showing the light absorption and deposition rate. With respect to the first embodiment as a comparative example, the refractive index of MgF ₂ film only plasma emission intensity ratio was deposited in a controlled manner to a constant value, is a diagram showing an optical absorption and deposition rate. It is sectional drawing which shows the structure of the film-forming apparatus of 2nd Embodiment of this invention. The second embodiment of the present invention is a spectral reflectance characteristic diagram of MgF ₂ film formed. The refractive index of MgF ₂ film formed by the second embodiment of the present invention, showing the light absorption and deposition rate. With respect to the second embodiment as a comparative example, it illustrates the temperature and the deposition rate of the target surface of the MgF ₂ film only plasma emission intensity ratio was formed in a controlled manner to a predetermined value.

Explanation of symbols

1 Deposition device 2 Vacuum chamber (deposition chamber)
3 Substrate 6 Target 7 High-frequency power supply 12 Mass flow controller 14 Plasma 21 Crystal resonator 26 Radiation thermometer 41 First measuring instrument (first measuring means)
42 Second measuring instrument (second measuring means)
51 1st control means 52 2nd control means

Claims (8)

In a film forming method in which a material containing at least a metal fluoride is used as a target, plasma is generated by introducing high-frequency power into the target while introducing a discharge gas into the film forming chamber, and a film is formed on a substrate by a sputtering method.
Measuring the emission intensity of the plasma with a first measuring instrument, feeding back the measurement result, and adjusting the amount of the discharge gas introduced into the deposition chamber;
Measuring the deposition rate of the sputtered particles in the deposition chamber with a second measuring instrument, and feeding back the measurement result to adjust the high-frequency power to be input to the target. Membrane method. In the film-forming method of Claim 1,
The second measuring instrument is configured to measure the amount of the sputtered particles adhering to the surface of the crystal resonator in the film forming chamber and calculate the film forming speed from a temporal change in the amount of adhering. A film forming method characterized by the above. In the film-forming method of Claim 1,
The film forming method, wherein the second measuring instrument is configured to measure a surface temperature of the target and calculate the film forming speed of the sputtering particles from the surface temperature. A film forming method in which a material containing at least MgF ₂ (magnesium fluoride) is used as a target, plasma is generated by introducing high-frequency power into the target while introducing a discharge gas into the film forming chamber, and a film is formed on a substrate by a sputtering method In
The plasma emission intensity ratio, which is the ratio of the emission intensity of the Mg plasma and the emission intensity of the MgF plasma, is measured with a first measuring instrument, and the measurement result is fed back to make the plasma emission intensity ratio a constant value. Adjusting the amount of the discharge gas introduced into the film formation chamber,
The film forming speed of the sputtered particles in the film forming chamber is measured with a second measuring instrument, and the measurement result is fed back to adjust the high-frequency power supplied to the target so that the film forming speed becomes a constant value. The film-forming method characterized by including the process to perform. In the film-forming method of Claim 4,
The amount of the discharge gas introduced into the film formation chamber is adjusted so that the plasma emission intensity ratio is a constant value between 1.5 and 3.5, and the film formation rate is 0.5 nm / sec. A film forming method comprising adjusting the high-frequency power input to the target so as to have a constant value of 5.0 nm / sec or less. In a film forming apparatus that targets a material containing at least a metal fluoride, generates a plasma by introducing high-frequency power into the target while introducing a discharge gas into the film forming chamber, and forms a film on a substrate by a sputtering method.
First measuring means for measuring the emission intensity of the plasma;
A second measuring means for measuring a film forming speed of the sputtering particles in the film forming chamber;
A first control unit that feeds back a measurement result of the first measurement unit and adjusts an introduction amount of the discharge gas into the film forming chamber;
A film forming apparatus comprising: a second control unit that adjusts the high-frequency power to be fed to the target by feeding back a measurement result of the second measuring unit. In the film-forming apparatus of Claim 6,
The second measuring means is configured to measure the amount of the sputtered particles adhering to the surface of the crystal resonator in the film forming chamber and calculate the film forming speed from a temporal change in the amount of adhering. A film forming apparatus. In the film-forming apparatus of Claim 6,
The film forming apparatus characterized in that the second measuring means is configured to measure a surface temperature of the target and calculate the film forming speed of the sputtering particles from the surface temperature.

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