JP2012219281A - Film deposition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film deposition apparatus having an optical film thickness monitor capable of measuring the thickness of an optical thin film to be deposited with high accuracy without using any special light source with the increased quantity of light or any special detector of high sensitivity.SOLUTION: The film deposition apparatus is provided with an optical film thickness monitor including: a monitor substrate; a light emission means which is installed outside a vacuum chamber to emit the monitor light to the monitor substrate via a transparent window; a light receiving means for receiving the monitor light which is reflected by the monitor substrate and guided outside the vacuum chamber; and a means for calculating the film thickness of a thin film to be deposited on a member to be film-deposited from the change in intensity of the monitor light measured by the light receiving means. The monitor substrate has a first thin film consisting of a semiconductor with its film thickness being <100 nm on its plane surface.

Description

  The present invention relates to a thin film forming apparatus, and more particularly to a film forming apparatus having an optical film thickness monitor.

Optical parts such as lenses and mirrors are provided with an optical thin film on the surface in order to improve the transmittance and reflectance and sometimes control the polarization. An example of such an optical thin film is an AR coat of a spectacle lens.
Since the thickness of the optical thin film greatly affects the characteristics of the optical component provided with the optical thin film, it is important to control the film thickness to a desired thickness when forming the optical thin film. Measurement of the film thickness during film formation is indispensable.

As one of the means for forming an optical thin film, there is vacuum deposition, and various film thickness measuring means for forming a film by a vacuum deposition apparatus have been proposed.
For example, when a film thickness monitoring substrate (monitor glass) is installed in a vacuum vapor deposition apparatus, the reflectivity of the film thickness monitoring substrate accompanying the increase in the film thickness of the vapor deposition film formed on the film thickness monitoring substrate during film formation or There is a means for measuring the film thickness from the change in transmittance.

  This film thickness measuring means is adapted to increase the optical thickness of the thin film formed on the film thickness monitoring substrate so that the reflectance or transmittance of the film thickness monitoring substrate is the light used for measurement (referred to as measurement light). ) Of wavelength λ, that is, a periodic curve having a limit value at a position of an optical thickness that is an integral multiple of λ / 4, and the limit value A of reflectance or transmittance. And the ratio B / A between the reflectance or transmittance of a predetermined film thickness and the difference B between the limit value A (see, for example, Patent Document 1).

However, in the film thickness measurement means described in Patent Document 1, when the refractive index of the film thickness monitoring substrate and the refractive index of the optical thin film to be formed are close to the wavelength of the measurement light, the cycle of reflectance or transmittance Corresponding to the change, there is a problem that the amplitude of the intensity change of the detected reflected light or transmitted light becomes small and it becomes difficult to measure the film thickness.
As a film thickness measuring means for solving such problems, an optical film thickness monitor using a glass substrate provided with a metal film in advance and having a complex refractive index substantially larger than the refractive index of the optical thin film as the film thickness monitoring substrate. (See, for example, Patent Document 2).

Japanese Examined Patent Publication No. 57-024485 (2nd page, Fig. 3) Japanese Patent Laid-Open No. 01-178807 (2nd page, FIG. 2)

In order to measure the thickness of the optical thin film formed using the film thickness monitoring substrate, the measurement light needs to be transmitted or reflected through the optical thin film.
In the film thickness monitoring substrate of the optical film thickness monitor described in Patent Document 2, the measurement light passes through or reflects the optical thin film that is a film formation target after passing through the metal film provided on the glass substrate.
In general, when light, which is an electromagnetic wave, enters a metal, an oscillating electric field is generated in the metal and free electrons move. As a result, electric polarization occurs in the metal, and the light entering the metal is shielded by an electric field opposite to the electric field of the light itself.

Therefore, in the film thickness monitoring substrate formed of the glass substrate provided with the metal film described in Patent Document 2, the measurement light is shielded by the metal film, and the intensity of the measurement light transmitted or reflected by the optical thin film is reduced. In particular, in a film thickness monitoring substrate provided with a metal film having a thickness for obtaining a required complex refractive index, the light of a halogen lamp generally used in an optical film thickness monitor as a film thickness measuring means is approximately 100. % (> 99.9%) absorption and loss of permeability.
That is, in the optical film thickness monitor using the film thickness monitoring substrate described in Patent Document 2, there is a problem that it is necessary to use a special light source with increased light quantity and a special detector with high sensitivity.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to form an optical thin film without using a special light source with high light intensity or a special detector with high sensitivity. It is to obtain a film forming apparatus equipped with an optical film thickness monitor that measures the film thickness of the film with high accuracy.

  A first film forming apparatus according to the present invention includes a monitor substrate disposed in the vicinity of an installation portion of a film forming member in a vacuum chamber, and a transparent window disposed outside the vacuum chamber and provided in the vacuum chamber. A light emitting means for projecting monitor light onto the monitor substrate, a light receiving means for receiving the monitor light reflected from the monitor substrate and led out of the vacuum chamber through the transparent window, and the monitor light measured by the light receiving means A film forming apparatus having an optical film thickness monitor having means for calculating a film thickness of a thin film formed on a film forming member from a change in strength of the semiconductor substrate, wherein the monitor substrate is placed on at least one plane on the semiconductor The first thin film having a thickness of less than 100 nm is provided.

  A second film forming apparatus according to the present invention includes a monitor substrate disposed in the vicinity of a deposition portion of a film forming member in a vacuum chamber, and one transparent film disposed outside the vacuum chamber and disposed in the vacuum chamber. Light emitting means for projecting monitor light to the monitor substrate through the window, and light reception for receiving the monitor light transmitted through the monitor substrate and led out of the vacuum chamber through the other transparent window provided in the vacuum chamber A film forming apparatus comprising: an optical film thickness monitor having means for calculating a film thickness of a thin film formed on a film forming member from a change in intensity of monitor light measured by the light receiving means; The substrate is provided with a first thin film having a thickness of less than 100 nm made of a semiconductor on at least one plane.

  A first film forming apparatus according to the present invention includes a monitor substrate disposed in the vicinity of an installation portion of a film forming member in a vacuum chamber, and a transparent window disposed outside the vacuum chamber and provided in the vacuum chamber. A light emitting means for projecting monitor light onto the monitor substrate, a light receiving means for receiving the monitor light reflected from the monitor substrate and led out of the vacuum chamber through the transparent window, and the monitor light measured by the light receiving means A film forming apparatus having an optical film thickness monitor having means for calculating a film thickness of a thin film formed on a film forming member from a change in strength of the semiconductor substrate, wherein the monitor substrate is placed on at least one plane on the semiconductor The first thin film with a thickness of less than 100 nm is provided, and the change in reflectance of the monitor substrate is large and the attenuation of the monitor light is small. Without using a source and sensitive special detector, the thickness of the optical thin film formed can be controlled can be measured with high accuracy.

  A second film forming apparatus according to the present invention includes a monitor substrate disposed in the vicinity of a deposition portion of a film forming member in a vacuum chamber, and one transparent film disposed outside the vacuum chamber and disposed in the vacuum chamber. Light emitting means for projecting monitor light to the monitor substrate through the window, and light reception for receiving the monitor light transmitted through the monitor substrate and led out of the vacuum chamber through the other transparent window provided in the vacuum chamber A film forming apparatus comprising: an optical film thickness monitor having means for calculating a film thickness of a thin film formed on a film forming member from a change in intensity of monitor light measured by the light receiving means; The substrate is provided with the first thin film made of a semiconductor having a film thickness of less than 100 nm on at least one plane, and the monitor substrate has a large change in transmittance, which reduces monitor light. Since even small, without using a high specific detector of special light source and sensitivity enhanced light intensity, a thickness of the optical thin film formed can be controlled can be measured with high accuracy.

It is a schematic diagram which shows the structure of the film-forming apparatus concerning Embodiment 1 of this invention. It is a side surface cross-section schematic diagram of the monitor board | substrate used for the film-forming apparatus concerning Embodiment 1 of this invention. It is a schematic diagram which shows the relationship between the film thickness of the optical thin film formed in a transparent substrate, and the reflectance of the transparent substrate in which the optical thin film was formed. In the case of the YF ₃ film is formed without heating the substrate is a diagram showing an example of measurement of a reflection type optical film thickness monitor using a monitor substrate of Comparative Example 1. Obtained by depositing a YF ₃ film at a substrate temperature of 125 ° C., a diagram showing an example of measurement of a reflection type optical film thickness monitor using a monitor substrate of Comparative Example 1. In the case where the YbF ₃ film is formed without heating the substrate is a diagram showing an example of measurement of a reflection type optical film thickness monitor using a monitor substrate of Comparative Example 1. Obtained by depositing a YbF ₃ film at a substrate temperature of 125 ° C., a diagram showing an example of measurement of a reflection type optical film thickness monitor using a monitor substrate of Comparative Example 1. It is a figure which shows the characteristic of the reflectance and transmittance | permeability of the glass substrate which formed the metal film with a film thickness of 200 nm as a 1st thin film. It is a figure which shows the transmittance | permeability characteristic of the white plate glass substrate which formed Ge film | membrane as a 1st thin film. It is a figure which shows the transmittance | permeability characteristic of the white plate glass substrate which formed Si film | membrane as a 1st thin film. It is a figure which shows the reflectance characteristic and the transmittance | permeability characteristic in the glass substrate which formed the compound semiconductor film with a film thickness of 200 nm as a 1st thin film. It is a figure which shows the example of a measurement in the reflection type optical film thickness monitor which used the monitor glass which formed the Ge film | membrane with a film thickness of 50 nm as a 1st thin film of Example 1 for the monitor board | substrate.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing a configuration of a film forming apparatus according to Embodiment 1 of the present invention.
A film forming apparatus 100 according to the present embodiment shown in FIG. 1 is a configuration example based on a vacuum vapor deposition apparatus that is most commonly used for forming an optical thin film.

  As shown in FIG. 1, a film forming apparatus 100 according to the present embodiment includes a vacuum chamber (hereinafter referred to as a vacuum chamber) 1, and a hearth liner (a crucible and a crucible) into which a deposition material is placed below the vacuum chamber 1. 3 is installed, and an electron gun (hereinafter referred to as an EB gun) 2 that emits an electron beam 16 is disposed in the vicinity of the crucible 3, and is emitted from the EB gun 2 on one side of the crucible 3. A shutter that shields the electron beam 16 is provided. The shutter is formed by a shutter main body 5 that shields the electron beam 16 and a shutter shaft 4 that holds the shutter main body 5 and is rotatably installed at the bottom of the vacuum chamber 1.

In addition, a substrate dome 6 that holds a member (depicted as a film forming member) 7 on which an optical thin film such as a substrate is formed is disposed above the vacuum chamber 1 so as to face the crucible 3. A monitor substrate 10 used for obtaining the film thickness of the thin film to be formed is disposed at a substantially central position 6.
The monitor substrate 10 is held by the monitor substrate holder 9, and the end of the monitor substrate holder 9 opposite to the end holding the monitor substrate 10 is coupled to the monitor substrate holder rotation mechanism 8. .
A transparent window 11 is provided on the ceiling portion of the vacuum chamber 1 immediately above the monitor substrate 10.

In addition, a reflection mirror 15 is installed above the transparent window 11 outside the vacuum chamber 1, and the light emitting means 12 is installed at a position where the monitor light 18 can be projected onto one reflection mirror 15a. The other reflection mirror 15b The light receiving means 13 is disposed at a position where the reflected monitor light 18 can be received.
That is, the monitor substrate 10, the light emitting means 12, the reflecting mirror 15, the transparent window 11, and the light receiving means 13 form a reflective optical film thickness monitor.
Further, a film thickness control means 14 for inputting a film thickness signal detected by the light receiving means 13 and controlling the shutter is also provided.

FIG. 2 is a schematic side sectional view of a monitor substrate used in the film forming apparatus according to Embodiment 1 of the present invention.
As shown in FIG. 2, the monitor substrate 10 of the present embodiment is formed by a monitor substrate body 21 and a film (hereinafter referred to as a first thin film) 22 having a thickness of less than 100 nm formed on the plane of the monitor substrate body 21. Has been.
In the present embodiment, the first thin film is formed of a semiconductor. Examples of the semiconductor include a single element semiconductor such as Ge and Si, a compound semiconductor such as ZnSe and ZnS, or a combination of these semiconductors. A composite composed of at least two types is used.

A process of forming an optical thin film with the film forming apparatus 100 of the present embodiment will be described.
First, a predetermined vapor deposition material is supplied to the crucible 3 set in the vacuum chamber 1 and a film-forming member 7 (for example, a lens or mirror before film formation) is provided on the surface of the substrate dome 6 facing the crucible 3. Set.
Next, the vacuum chamber 1 is evacuated by a vacuum pump (not shown), and after reaching a predetermined degree of vacuum, the power source (not shown) of the EB gun 2 is turned on to emit the electron beam 16.

Next, the electron beam 16 is deflected 180 degrees or 270 degrees by a deflection coil (not shown), guided to the crucible 3, and the vapor deposition material set in the crucible 3 is heated by the electron beam 16 to be in a molten state. Evaporate.
In such a process, the vapor deposition material 17 that evaporates jumps upward from the crucible and is deposited on the surface of the film formation target member 7 set on the substrate dome 6 to form an optical thin film.

Next, a mechanism for measuring the film thickness of the deposited optical thin film and a mechanism for controlling the film thickness of the optical thin film based on the measured film thickness data in the film forming apparatus 100 of the present embodiment will be described.
In the film forming apparatus 100 of the present embodiment, in the vapor deposition process, the vapor deposition material 17 is not only deposited on the surface of the film formation target member 7 to form an optical thin film, but is also installed at a substantially central position of the substrate dome 6. The thin film (referred to as a second thin film) is also deposited on the surface of the monitor substrate 10.

Further, the monitor substrate 10 is irradiated with the monitor light 18 emitted from the light emitting means 12 provided outside the vacuum chamber 1 through the first reflection mirror 15a and the transparent window 11, and the monitor substrate 10 is irradiated with the monitor substrate 10. The light reflected from the light enters the light receiving means 13 through the transparent window 11 and the second reflecting mirror 15b.
The intensity of the monitor light 18 incident on the light receiving means 13 changes because the reflectance of the monitor substrate 10 changes as the second film is formed on the monitor substrate 10 by vapor deposition and the film thickness increases.

The light receiving means 13 to which the monitor light 18 is incident measures the intensity change of the monitor light 18 and obtains the film thickness by means of obtaining the film thickness from the intensity change signal of the monitor light incorporated therein. Input to the film thickness control means 14. The film thickness control means 14 controls the film thickness of the optical thin film formed on the film forming member 7 by controlling the shutter 4 based on the film thickness data signal from the light receiving means.
The light receiving means 13 measures the intensity change of the monitor light 18 and inputs the intensity change signal to the film thickness control means 14, and the film thickness control means 14 is deposited by the intensity change signal from the light receiving means. While determining the film thickness of the optical thin film, the film thickness of the optical thin film formed on the film forming member 7 may be controlled by controlling the shutter 4 from the film thickness data.

Next, means for obtaining the film thickness of the second film from the intensity change signal of the monitor light 18 measured by the light receiving means 13 corresponding to the change in the reflectance of the monitor substrate 10 due to the increase in the film thickness of the second film. Will be described.
FIG. 3 is a schematic diagram showing the relationship between the thickness of the optical thin film formed on the transparent substrate and the reflectance of the transparent substrate on which the optical thin film is formed.
In FIG. 3, the horizontal axis represents the optical film thickness nd which is the product of the physical thickness d of the optical thin film and the refractive index n, and the vertical axis represents the reflectance R of the transparent substrate on which the optical thin film is formed.

  As shown in FIG. 3, the reflectance R of the transparent substrate on which the optical thin film is formed is such that the optical film thickness nd is minimal at a quarter of the wavelength λ of the projected light, that is, a period of λ / 4. The valleys (denoted as the minimum reflectance Rmin) and the peaks (denoted as the maximum reflectance Rmax) are alternately repeated, and the intensity of the reflected light from the transparent substrate changes in a similar cycle.

The means for calculating the film thickness of the optical film thickness monitor of the present embodiment first obtains the monitoring light intensity repetition number C by the light receiving means 13 from the above principle. Also. In the light receiving means 13, a monitor light intensity difference signal (referred to as a first difference signal) Sa corresponding to the reflectance difference A between the maximum reflectance Rmax and the minimum reflectance Rmin of the monitor substrate 10, a predetermined film A monitor light intensity difference signal (referred to as a second difference signal) Sb corresponding to the reflectance difference B between the reflectance Rx and the minimum reflectance Rmin of the monitor substrate 10 on which the optical thin film of thickness X is formed is obtained.
Then, the optical film thickness nd is calculated from the wavelength λ of the monitor light, the repetition number C of the monitor light intensity, and the ratio Sb / Sa of the second difference signal Sa and the first difference signal Sa. .

In the reflective optical film thickness monitor of the present embodiment, the monitor light 18 reflected from the monitor substrate 10 is measured to determine the film thickness of the optical thin film.
However, since the vapor deposition substance is present in the optical path of the monitor light, the detection sensitivity is somewhat lowered. However, a transparent window is provided on the floor portion of the vacuum chamber 1 immediately below the monitor substrate 10, and a light receiving means is disposed outside the transparent window. Then, a transmissive optical film thickness monitor that measures monitor light transmitted through the monitor substrate 10 may be used.
In this case, the film thickness of the optical thin film is obtained from the change in the transmittance of the monitor substrate 10 that changes in the same manner as the reflectance shown in FIG.

An optical film thickness monitor that determines the thickness of the optical thin film to be measured by measuring the change in the intensity of the monitor light due to the change in the reflectance or transmittance of the monitor substrate as the thickness of the deposited material film increases. In the film forming apparatus provided, if the change in reflectance or transmittance of the monitor substrate due to the formation of the vapor deposition material film is small, it becomes difficult to measure the film thickness using the monitor substrate.
However, the optical film thickness monitor of the film forming apparatus of the present embodiment uses a substrate in which a semiconductor film having a film thickness of less than 100 nm is previously formed as the first thin film on the monitor substrate. The difference between the refractive index and the refractive index of the optical thin film to be formed is large, the change in the reflectivity or transmittance of the monitor substrate due to the formation of the vapor deposition material film is large, and the attenuation of the monitor light is also small. The thickness of the optical thin film to be formed can be measured and controlled with high accuracy without using a special light source or a highly sensitive special detector.

That is, the film forming apparatus of the present embodiment is a film forming apparatus that includes an optical film thickness monitor with high accuracy and high sensitivity, and enables advanced film thickness control.
Next, the effects of the film forming apparatus of this embodiment will be described with reference to examples and comparative examples.

Comparative Example 1
Comparative Example 1 is a case where a glass substrate is used as the monitor substrate.
Table 1 shows the refractive index between the glass substrate and the main substance and the difference in refractive index between the glass substrate and the main substance.

The refractive index of each material has a so-called wavelength dispersion characteristic that differs with respect to the wavelength, and the difference in refractive index between the glass substrate and the film forming material also varies depending on the wavelength.
As shown in Table 2, fluorides such as BaF ₂ , HfF ₄ , YF ₃ , and YbF ₃ have a particularly small difference in refractive index from the glass substrate. In the film formation of these substances, the reflectance of the monitor substrate or The change in transmittance is small and the film thickness cannot be measured accurately.
Furthermore, in YbF _3, in the case of 1000nm and when the wavelength of the monitor light is 600 nm, is reversed positive and negative refractive index difference, in advance between the wavelength 600Nm～1000nm, the refractive index difference between the glass substrate is zero It shows that there is a part. In such a case. Since the intensity change of reflected light or transmitted light from the monitor substrate becomes zero, the film thickness cannot be measured.

  The refractive indexes of various substances shown in Table 1 are examples. In the case of a thin film, it is known that the refractive index varies depending on the film forming conditions and the film forming apparatus. This is because the film density called the filling rate varies depending on the film forming conditions and the film forming apparatus. Usually, the thin film has some voids as compared with the bulk material and the filling rate is 100% or less. However, since the air or moisture enters the voids, the refractive index changes accordingly.

  In physical film formation such as vacuum deposition, substrate heating is performed for the purpose of improving film adhesion and crystallinity. However, depending on the substance, there is a material whose film characteristics change greatly at a relatively low temperature. For example, there is a substance in which the wavelength dispersion characteristic of the refractive index changes greatly at a substrate heating temperature of 100 ° C. to 200 ° C.

FIG. 4 is a diagram showing a measurement example with a reflective optical film thickness monitor using the monitor substrate of Comparative Example 1 when the YF ₃ film is formed without heating the substrate.
FIG. 5 is a diagram showing a measurement example with a reflective optical film thickness monitor using the monitor substrate of Comparative Example 1 when the YF ₃ film is formed at a substrate temperature of 125 ° C.
The wavelength of the monitor light used in the measurement examples shown in FIGS. 4 and 5 is 1000 nm.
FIG. 4 shows a reflected light amount change curve 31 of the monitor light when the film is formed without heating the substrate, and FIG. 5 shows a reflected light amount change curve 32 of the monitor light when the film is formed at the substrate temperature of 125 ° C. ing.
The change in the amount of reflected light shown in FIGS. 4 and 5 corresponds to the change in the reflectance of the monitor substrate.

In the reflected light amount change curve 31 shown in FIG. 4, a difference of about 20% was observed between the peak and the peak.
However, in the reflected light amount change curve 32 shown in FIG. 5, a maximum difference of about 5% is recognized between the peak and the valley peak, but the difference in reflected light amount is only about 2% at the initial stage of film formation. It shows that the reflectance characteristic of the substrate is very unstable.

FIG. 6 is a diagram illustrating a measurement example using a reflective optical film thickness monitor using the monitor substrate of Comparative Example 1 when the YbF ₃ film is formed without heating the substrate.
FIG. 7 is a diagram showing a measurement example with a reflective optical film thickness monitor using the monitor substrate of Comparative Example 1 when a YbF ₃ film is formed at a substrate temperature of 125 ° C.
The wavelength of the monitor light used in the measurement examples shown in FIGS. 6 and 7 is 1800 nm.
FIG. 6 shows a reflected light amount change curve 33 of the monitor light when the film is formed without heating the substrate, and FIG. 7 shows a reflected light amount change curve 34 of the monitor light when the film is formed at the substrate temperature of 125 ° C. ing.
The change in the amount of reflected light shown in FIGS. 6 and 7 corresponds to the change in the reflectance of the monitor substrate.

In the reflected light amount change curve 33 shown in FIG. 6, a difference of about 20% is recognized between the peak and the peak.
However, in the reflected light amount change curve 34 shown in FIG. 7, only a difference of about 1% at maximum is observed between the peak peak and the valley peak, and an increase in the reflected light amount is recognized at the initial stage of film formation. , Which is very unstable.
In addition, when the substrate is not heated in the formation of the YbF ₃ film, as is apparent from the reflected light amount change curve 33, the refractive index is maintained to be smaller than that of the glass substrate shown in Table 1. _In the formation of the _three films, when the substrate temperature is 125 ° C., as is apparent from the reflected light amount change curve 34, the refractive index is higher than that of the glass substrate at the initial stage of the film formation.

  That is, as in this comparative example, in the case of an optical film thickness monitor using a glass substrate alone as a monitor substrate, the change in reflectance of the monitor substrate is small in the film formation of a substance having a small refractive index difference from the glass substrate, In addition, the film thickness is unstable, an accurate film thickness cannot be measured, and it is difficult to perform stable film formation control.

Comparative Example 2
Comparative Example 2 is a case where a glass substrate in which a metal film is formed as a first thin film on a monitor substrate is used.
FIG. 8 is a diagram illustrating the characteristics of reflectance and transmittance of a glass substrate on which a metal film having a thickness of 200 nm is formed as the first thin film.
In FIG. 8, the left vertical axis represents the reflectance R, the right vertical axis represents the transmittance T, and the horizontal axis represents the wavelength λ.
In this comparative example, the transmittance of the glass substrate on which the metal film having a thickness of 200 nm is formed corresponds to the transmittance when the metal film having a thickness of 100 nm is formed on the monitor glass of the reflective optical film thickness monitor. .
FIG. 8 shows a reflectance change curve 41 and a transmittance change curve 43 when an Ag film is formed on a glass substrate, and a reflectance change curve 42 when an Al film is formed on a glass substrate. A transmittance change curve 44 is shown.

As is apparent from FIG. 8, when a metal film having a film thickness of 100 nm or more is provided on the monitor glass in the reflective optical film thickness monitor, the entire range of 400 nm to 2000 nm that is usually used as monitor light for the optical thin film is used. The transmittance is 0.1% or less at a wavelength of.
That is, if a metal film having a film thickness of 100 nm or more is provided on the monitor substrate of Comparative Example 2, light is blocked by a normal light source, so a special high-intensity lamp is used or a special detector with high sensitivity And the device becomes expensive.
In general, even when a high-intensity lamp is used, the amount of transmitted light is almost zero at a wavelength of 700 nm or more, and a change in the amount of monitor light cannot be detected.

  Also, almost 4% of reflected light is generated from the back glass surface of the monitor substrate over the entire wavelength range of 400 to 2000 nm, and 4% of the reflected monitor light is always incident on the monitor light receiving means. Will do. Accordingly, the S / N ratio of the monitor light is <1/40, and it is difficult to accurately monitor the change in the amount of reflected light even when a high-luminance light source is used.

Example 1.
Example 1 is a case where a glass substrate in which a single element semiconductor film is formed as a first thin film on a monitor substrate is used.
FIG. 9 is a diagram showing the transmittance characteristics of a white glass substrate on which a Ge film is formed as the first thin film.
In FIG. 9, the vertical axis represents the transmittance T, and the horizontal axis represents the wavelength λ.
In FIG. 9, transmittance change curves 51, 52, 53, 54 when the respective Ge films having a film thickness of 1 nm, 3 nm, 5 nm, 10 nm, 20 nm, 40 nm, 100 nm, and 200 nm are provided on a white glass substrate. 55, 56, 57, 58 are shown.

As is apparent from FIG. 9, when a white glass substrate on which a Ge film is formed is used as a monitor substrate, it is possible to use a substrate provided with a Ge thin film having a thickness of less than 100 nm in consideration of absorption. The film having the Ge thin film is suitable because the transmittance of the monitor light is ensured to be approximately 5% or more at all wavelengths of 400 nm or more.
Further, the refractive indexes of Ge at the monitor light wavelengths of 1000 nm and 2000 nm are 2.720 and 3.565, respectively, and the refractive indexes of the glass of the same wavelength are 1.508 and 1.494, respectively. Since the difference in refractive index between the film and the film is large, the change in reflectance or transmittance as a monitor substrate during film formation is large, the film thickness can be accurately measured, and the deposition film can be controlled stably. .

FIG. 10 is a diagram showing the transmittance characteristics of a white glass substrate on which a Si film is formed as the first thin film.
In FIG. 10, the vertical axis represents the transmittance T, and the horizontal axis represents the wavelength λ.
In FIG. 10, transmittance change curves 61, 62, 63, 64, when each Si film having a film thickness of 1 nm, 3 nm, 5 nm, 10 nm, 20 nm, 40 nm, 100 nm, and 200 nm is provided on a white glass substrate. 65, 66, 67 and 68 are shown.

As is apparent from FIG. 10, when a white glass substrate on which a Si film is formed is used as a monitor substrate, it is possible to use a substrate provided with a Si thin film having a thickness of less than 200 nm in consideration of absorption. A film provided with a Si thin film of this thickness is suitable because the transmittance of the monitor light is ensured to be approximately 5% or more at all wavelengths of 400 nm or more.
Moreover, the refractive indexes of Sie at wavelengths of 1000 nm and 2000 nm of the monitor light are 3.887 and 4.139, respectively, and the refractive indexes of the glass of the same wavelength are 1.508 and 1.494, and Si and glass Since the difference in refractive index between the film and the film is large, the change in reflectance or transmittance as a monitor substrate during film formation is large, the film thickness can be accurately measured, and the deposition film can be controlled stably. .

Example 2
Example 2 is a case where a glass substrate in which a compound semiconductor film is formed as a first thin film on a monitor substrate is used.
FIG. 11 is a diagram showing reflectance characteristics and transmittance characteristics in a glass substrate on which a compound semiconductor film having a thickness of 200 nm is formed as the first thin film.
In FIG. 11, the vertical axis on the left is the reflectance R, the vertical axis on the right is the transmittance T, and the horizontal axis is the wavelength λ.
In this example, the transmittance of the glass substrate on which the compound semiconductor film having a thickness of 200 nm is formed is the transmittance when the compound semiconductor film having a thickness of 100 nm is formed on the monitor glass of the reflective optical film thickness monitor. Equivalent to.

  FIG. 11 shows a reflectance change curve 71 and a transmittance change curve 73 when a ZnSe film is formed on a glass substrate, and a reflectance change curve 72 when a ZnS film is formed on a glass substrate. A transmittance change curve 74 is shown.

As is apparent from FIG. 11, when the film thickness of the ZnSe film or ZnS film provided on the monitor glass in the reflective optical film thickness monitor is less than 100 nm, 400 nm to 2000 nm used for the monitor light of the optical thin film. A transmittance of approximately 5% or more can be obtained at all wavelengths in the range.
That is, a special high-intensity lamp or a special detector with high sensitivity is used for a substrate in which ZnSe or ZnS, which is a compound semiconductor having a film thickness of less than 100 nm, is formed on the monitor glass of a reflective optical film thickness monitor. Therefore, the amount of monitor light can be stably obtained, and a highly accurate optical film thickness monitor can be realized at low cost.

Example 3
FIG. 12 is a diagram showing a measurement example of the reflective optical film thickness monitor using the monitor glass in which a Ge film having a film thickness of 50 nm is formed as the first thin film of Example 1 as a monitor substrate.
FIG. 12 shows a reflected light amount change curve 81 of the monitor light when the YbF ₃ film, which is the second thin film, is formed at the substrate temperature of 125 ° C.
The wavelength of the monitor light used in the measurement example shown in FIG. 12 is 1000 nm.
The change in the amount of reflected light shown in FIG. 12 corresponds to the change in the reflectance of the monitor substrate.
As is apparent from FIG. 12, the monitor substrate used in this example has a reflectance difference of 50% or more at the peak-to-peak, and the optical film thickness monitor using the monitor substrate of this example is The film thickness of the optical thin film can be accurately measured, and stable film thickness control of the deposited optical thin film becomes possible.

Example 4
Next, in the formation of an optical thin film of a substance having a small refractive index difference from the glass substrate, each of the monitor substrates in Example 1, Example 2 and Comparative Example 2, that is, the first thin films of different materials were formed. It was verified whether the glass substrate can be used in an optical film thickness monitor.
As the first thin film, the monitor substrate used is formed by forming a thin film of Ag, Al, Cu, which is a metal, Ge, Si, which is a single element semiconductor, ZnSe, ZnS, which is a compound semiconductor, on a glass substrate. It is a thing.
The wavelength of the monitor light used for the verification is 500 nm in the middle of the wavelength 400 nm to 600 nm, 700 nm in the middle of the wavelength 600 nm to 800 nm, 900 nm in the middle of the wavelength 800 nm to 1000 nm, and the middle of the wavelength 1000 nm to 1200 nm. 1100 nm and 1800 nm in the middle of wavelengths 1200 nm to 2500 nm.

Table 2 shows a case where a first thin film having a thickness of 300 nm is formed, Table 3 shows a case where a first thin film having a thickness of 200 nm is formed, and Table 4 shows a first thin film having a thickness of 150 nm. Table 5 shows the case where a first thin film having a thickness of 100 nm is formed, and Table 6 shows the case where a first thin film having a thickness of 50 nm is formed.
In each table, ○ indicates that the film thickness can be monitored stably, △ indicates that the film thickness can be monitored but is somewhat unstable, and × indicates that the film thickness cannot be monitored because there is little or no reflected light. It is shown that.

As shown in Tables 2 to 6, in the case of a monitor substrate in which a metal film of 100 nm or more is formed as a first thin film on a glass substrate, there is almost no change in the amount of light reflected from the monitor substrate due to light absorption by the film. No film thickness monitoring was possible.
In the case of a monitor substrate on which a metal film is formed, even if the metal film is 50 nm or less, it is only at a level that can be used in some wavelength regions.

Further, as shown in Tables 2 to 6, a monitor in which a thin film of either Ge or Si as a single element semiconductor or ZnSe or ZnS as a compound semiconductor is formed as a first thin film on a glass substrate. In the case of a substrate, if the thickness of the first thin film is 200 nm, a monitor substrate using Ge or Si for the first thin film is not applicable in a part of the wavelength range. The monitor substrate used for the first thin film is not applicable in a part of the wavelength range, but can be monitored in a considerable wavelength range.
In particular, a monitor substrate in which the first thin film made of a single element semiconductor or a compound semiconductor has a thickness of 100 nm or less can be monitored in all wavelength ranges of monitor light used for verification.

In the film forming apparatus having the optical film thickness monitor according to the present invention, the monitor substrate used in the optical film thickness monitor is a glass substrate, a single element semiconductor or compound semiconductor thin film having a film thickness of less than 100 nm, A conventional monitor light source and detector can be used even in the film formation of a substance having a small refractive index difference from the glass substrate, which is formed as the first thin film, and the cost of the film forming apparatus can be reduced. Note that the minimum film thickness that can be controlled by a vacuum deposition apparatus, which is a physical film formation apparatus, is determined by the shutter opening / closing operation above the electron gun, and is about 5 nm in the inventors' apparatus, which is the above-described single element semiconductor or compound semiconductor. This is the lower limit of the thickness of the thin film.
In addition, the film thickness can be measured with high accuracy for various materials without being limited by the refractive index of the glass substrate, and stable film thickness control can be realized.

  In the film forming apparatus according to the present invention, the optical film thickness monitor can detect the film thickness with high accuracy even in the film formation of a substance having a small refractive index difference from the glass substrate. Used when manufacturing.

1 vacuum chamber, 2 EB gun, 3 crucible, 4 shutter shaft,
5 Shutter body, 6 Substrate dome, 7 Film deposition member,
8 Monitor board holder rotation mechanism, 9 Monitor board holder, 10 Monitor board,
11 transparent window, 12 light emitting means, 13 light receiving means, 14 film thickness controlling means,
15 reflection mirror, 15a one reflection mirror, 15b the other reflection mirror,
16 Electron beam, 17 Vapor deposition material, 18 Monitor light, 21 Monitor substrate body,
22 First thin film, 100 Deposition apparatus.

Claims (4)

Monitor light is projected onto the monitor substrate via a monitor substrate disposed in the vacuum chamber in the vicinity of the part where the film-forming member is placed and a transparent window provided outside the vacuum chamber and provided in the vacuum chamber. Light receiving means for receiving monitor light reflected from the monitor substrate and led out of the vacuum chamber through the transparent window, and intensity change of the monitor light measured by the light receiving means. A film forming apparatus comprising an optical film thickness monitor having means for calculating a film thickness of a thin film formed on the film forming member,
The film forming apparatus, wherein the monitor substrate includes a first thin film having a thickness of less than 100 nm made of a semiconductor on at least one plane. Monitor light is placed on the monitor substrate through a transparent substrate provided outside the vacuum chamber and provided in the vacuum chamber, in the vicinity of the installation portion of the film forming member in the vacuum chamber. A light emitting means for projecting light, a light receiving means for receiving monitor light that is transmitted through the monitor substrate and led out of the vacuum chamber through the other transparent window provided in the vacuum chamber, and the light receiving means A film forming apparatus comprising an optical film thickness monitor having means for calculating the film thickness of the thin film formed on the film forming member from the intensity change of the monitor light measured in
The film forming apparatus, wherein the monitor substrate includes a first thin film having a thickness of less than 100 nm made of a semiconductor on at least one plane. The semiconductor forming the first thin film is Ge, Si, ZnSe, ZnS, or a composite composed of at least two of these semiconductors. 2. The film forming apparatus according to 2. The film forming apparatus according to claim 1, wherein the first thin film has a thickness of 50 nm or less.

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