JPH0689450B2 - Device for monitoring evaporation rate and film thickness in vacuum deposition equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a device for monitoring the evaporation rate and film thickness in a vacuum evaporation system, and in particular, for example, a thin film such as TiO ₂ or SiO ₂ which is an optical thin film on a lens or a glass substrate. The present invention relates to an evaporation rate and film thickness monitoring apparatus suitable for use in a vacuum vapor deposition apparatus for forming transparent insulating thin films in multiple layers.

<Prior Art> FIG. 3 shows a conventional vacuum deposition apparatus for forming such an optical multilayer thin film.

In FIG. 3, 1 is a bell jar, 2 is an evaporation source for evaporating an evaporation material toward a target by an electron beam,
3 is a product such as a lens or a glass substrate to be coated with an optical thin film. A rotary monitor holder 4 is provided with a large number of monitor glasses (transparent glass plates) 5 for film thickness monitoring, which are attached at equal intervals, and one of the monitor glasses 5 in the monitor glass group 5 is formed every time one optical thin film is formed. One of them is selectively positioned in the vapor deposition target area. 6 is a monitor glass 5 in the target area
The measurement light 6 is a measurement light having a constant wavelength, which is transmitted to the laser beam, is transmitted through the monitor glass 5 and then guided to the photodetector 8 via the mirror 7, and the output of the photodetector 8 is subjected to film thickness calculation via an amplifier as appropriate. The signal is sent to the circuit 9. That is, the film thickness of the transparent single layer film can be measured by utilizing optical interference as is known,
The output of the light receiver 8 draws a curve of sin ² θ as shown by the solid line in FIG. 2 when the optical film thickness is on the horizontal axis and the light intensity is on the vertical axis. Therefore, the output of this light receiver 8 is fetched, converted and stored. -The film thickness can be monitored by performing arithmetic processing.

Reference numeral 10 is a known AT-cut "thickness-shear vibration" quartz oscillator for evaporation (vapor deposition) rate monitor, which is proportional to the thickness of the deposited quartz crystal 10 within a predetermined range. The frequency is output, and the evaporation rate calculation circuit 11 monitors the evaporation (evaporation) rate by taking in, converting, storing and calculating the frequency. Reference numeral 12 denotes a process controller for controlling the vapor deposition process, which controls the vapor deposition rate, the vapor deposition timing, etc. based on the information from the film thickness computing circuit 9, the evaporation rate computing circuit 11 and the like. That is, the process controller 12 performs electron beam control via the evaporation source power source 13 to control the evaporation rate, and via the shutter drive source 14 controls the shutter 15 for opening / closing the evaporation source 2 to perform evaporation. It is designed to control the start / end timing.

Here, the reason why the vapor deposition rate is monitored in addition to the film thickness of each optical thin film deposited as described above is that the refractive index of the optical thin film depends on the vapor deposition (evaporation) speed as shown in FIG. Because it does.

<Problems to be Solved by the Invention> As described above, the optical monitoring accuracy of the film thickness performed by replacing the monitor glass 5 layer by layer is considerably good,
Practically sufficient film thickness control can be performed. However,
The monitor accuracy of the vapor deposition rate by the crystal oscillator 10 is apt to deteriorate when the optical thin film to be vapor deposited becomes a multilayer of about 10 layers or more, which makes it difficult to control the vapor deposition rate accurately.
Therefore, it is difficult to guarantee the desired refractive index of the optical thin film. This is because the oscillation frequency range that is guaranteed to be proportional to the deposited film thickness in the crystal oscillator 10 is within a certain fixed range. Therefore, as the optical thin films are deposited in multiple layers and the film thickness increases, the crystal vibration increases. Since the oscillation of the child 10 becomes unstable and it becomes impossible to accurately monitor the evaporation rate, the situation where the oscillation is finally stopped has also been brought about. Therefore, for example, it is a major obstacle to fully automatically forming an optical multilayer thin film with 20 to 50 layers. In order to solve this point, it is conceivable to provide a large number of the crystal oscillators 10 and switch and expose them in the target region, but it requires considerable modification of the vapor deposition device and is not preferable in terms of space factor. .

<Object of the Invention> Therefore, the technical problem to be solved by the present invention is to solve the above-mentioned conventional drawbacks, and an object thereof is that even if the number of film layers of an optical thin film to be produced / deposited is large. An object of the present invention is to provide a device for monitoring the evaporation rate and the film thickness in a vacuum evaporation system, which can measure and control the evaporation rate with high reliability and can achieve this with a relatively simple structure.

<Means for Solving the Problems> The above object of the present invention is to provide a product in which a plurality of optical thin films are to be deposited in a bell jar of a vacuum deposition apparatus, and a deposition target area for each formation of the optical thin film. A plurality of monitor glasses that are exposed by switching to, and a short-wavelength measuring light for film thickness monitoring, which is simultaneously irradiated to the monitor glass in the target area, and a measurement light of approximately several times the short-wavelength measuring light. A long-wavelength measuring light for monitoring the evaporation rate, which has a wavelength, and a short-wavelength measuring light for separating and receiving the short-wavelength measuring light and the long-wavelength measuring light transmitted through the monitor glass, respectively. Light receiving device and a second light receiving device for long wavelength, a first calculating means for calculating and monitoring the film thickness by the output of the first light receiving device, and an evaporation rate by the output of the second light receiving device. Second computing means for computing and monitoring It is achieved by a device for monitoring the evaporation rate and the film thickness in a vacuum evaporation system, which is provided with a process controller that controls the evaporation process by receiving the outputs of the first calculating device and the second calculating device.

<Operation> The monitor glass is irradiated with short-wavelength measurement light and long-wavelength measurement light at the same time, and one of the short-wavelength measurement lights is used to monitor the film thickness by the same method as before. Further, since the wavelength of the other long-wavelength measuring light is approximately several times that of the short-wavelength measuring light, the optical interference output of the second light receiver for selectively receiving the long-wavelength measuring light. The waveform (optical film thickness-light intensity) can be approximated to a straight line within a desired film thickness range by drawing a gentle curve having a period of about 1 / several minutes of the optical interference output waveform of the first light receiver. The evaporation rate is monitored by differentiating this.

<Example> The present invention will be described below with reference to the example shown in FIG.
In FIG. 1, the same or equivalent parts as those of the conventional structure are designated by the same reference numerals, and some of them will not be described to avoid duplication.

In FIG. 1, reference numeral 16 denotes a holder holding the products 3, ... Through the hole 16a, the rotary monitor holder 4
Only one of the plurality of monitor glasses 5 attached to the monitor glass 5 is selectively exposed to the target region by switching each time one layer of the optical thin film is formed (with respect to the evaporation source 2). Exposed). The number of the monitor glasses 5 is prepared so as to correspond to at least the number of optical thin film layers formed on the product 3, and the monitor glasses 5 exposed to the target region are substantially the same as the product 3 group. The position is set so that the optical thin film is deposited under the conditions.

17 and 18 are glass seals attached to the bell jar 1, 19 and 20 are half mirrors,
19, glass seal 17, hole 16a, monitor glass 5 in the target area, glass seal 18, half mirror 20,
They are positioned so as to be on a straight line (on the same optical path) from the bottom in the figure.

6 is a measuring light of a short wavelength for film thickness monitoring, which is equivalent to that of the conventional example, and 21 is an evaporation rate monitoring light set to a wavelength which is approximately several times (three times in the embodiment) the measuring light 6. With long-wavelength measuring light,
Both meter side lights 6 and 21 are irradiated to the half mirror 19 by appropriate light generation / irradiation means, one of which is reflected by the half mirror 19 and the other of which is transmitted through the half mirror 19, and both of the measurement light 6 and
21 passes through the hole 16a and the monitor glass 5 in the target area and is guided to the other half mirror 20 on the optical path.

Reference numeral 22 denotes a first filter, which selectively transmits only the measuring light 6 having a short wavelength of the measuring lights 6 and 21 transmitted through the half mirror 20. Reference numeral 8 is a first photodetector through which the short-wavelength measurement light 6 that has passed through the first filter 22 is guided, and is equivalent to the photodetector 8 of the conventional example described above, but in the present embodiment, it is the It is referred to as the No. 1 light receiver. Then, the output of the first photodetector 8 is supplied to the film thickness arithmetic circuit 9 equivalent to that of the conventional example through the amplifier 23, and the curve of sin ² θ is drawn as shown in the solid line in FIG. The film thickness is monitored by converting, storing, and processing the output of the first light receiver. That is,
The output level (light intensity) of the first light receiver 8 is digitally converted and stored at each time point, and the upper and lower peak values of the output waveform and the number thereof are also stored, and the acquisition information and the calculation program given in advance are stored. The optical film thickness at the latest point is sometimes recognized based on this.
The film thickness monitor information is supplied to the process controller 12, which is substantially equivalent to the above-mentioned conventional structure.

Reference numeral 24 denotes a second filter, which is the long-wavelength measuring light 21 of the two measuring lights 6 and 21 reflected by the half mirror 20.
Only the selective transmission is made. Reference numeral 25 is a second light receiver through which the long-wavelength measurement light 21 that has passed through the second filter 24 is guided. The output of the second light receiver 25 is an amplifier.
It is sent to the evaporation rate calculation circuit 27 via 26. Second above
The output of the light receiver 25 of the
Is set to be three times that of the measuring light 6, so that when the optical film thickness is plotted on the horizontal axis and the light intensity is plotted on the vertical axis, the above-mentioned first light reception is obtained as shown by the dotted line in FIG. Draw a gentle sin ² α curve with a period of about 1/3 of the output waveform of the unit 8. The output curve of the second optical receiver 25 can be approximated to a straight line within this range because the film thickness stop point of one layer of the optical thin film is usually 3 / 4λ or less of the optical film thickness, and therefore, The output of the second light receiver 25 is used as the evaporation rate calculation circuit.
27 takes in and differentiates to sometimes recognize the evaporation rate, and this evaporation rate monitor information is supplied to the process controller 12.

Then, the process controller 12 controls the evaporation source power supply 13 and the shutter drive source 14 based on information from the film thickness calculation circuit 9, the evaporation rate calculation circuit 27, various sensors (not shown) and the like, as in the conventional example. At the same time, the optical multilayer thin film is formed on the product 3 while controlling the film thickness and the evaporation rate to the desired values for each layer formation in accordance with the predetermined sequence.

As described above, the evaporation rate monitor information obtained by the optical detection method is switched every time one layer of the monitor glass 5 is formed. Therefore, even if the optical thin film on the product 3 has several tens of layers, the total film thickness increases. As a result, it is possible to always ensure that the accuracy is high, and thus it is possible to control the refractive index of each layer of the optical thin film to a desired value. Further, since the film thickness and the evaporation rate are measured by the same monitor glass 5, the vacuum evaporation apparatus need not be modified and the conventional apparatus can be used as it is. Furthermore, unlike the conventional example, since the crystal unit 10 and the monitor glass 5 are not installed in separate places, correction / comparison calculation considering the difference in installation place is also unnecessary.

<Effect> As described above, according to the present invention, it is possible to measure and control the evaporation rate with high reliability even when the number of optical thin films to be formed and deposited is large, and it is relatively simple. With such a configuration, it is possible to provide a device for monitoring the evaporation rate and film thickness in a vacuum vapor deposition device that can achieve this, and its industrial value is great.

[Brief description of drawings]

1 and 2 relate to an embodiment of the present invention. FIG. 1 is an explanatory view of a device for monitoring evaporation rate and film thickness in a vacuum vapor deposition apparatus, and FIG. FIG. 3 is an explanatory diagram of an output waveform, FIG. 3 is an explanatory diagram of a conventional configuration, and FIG. 4 is a graph showing a relationship between a vapor deposition rate and a refractive index. 1 …… Bell jar 2 …… Evaporation source 3 …… Product 4 …… Rotating monitor holder 5 …… Monitor glass 6 …… Short wavelength measuring light 8 …… First light receiver 9 …… Film thickness calculation circuit 12 …… Process controller 13 …… Evaporation drive source 14 …… Shutter drive source 15 …… Shutter 16 …… Holder 17, 18 …… Glass seal 19,20 …… Half mirror 21 …… Long wavelength measurement light 22 …… First Filter 23, 26 ...... Amplifier 24 ...... Second filter 25 ...... Second light receiver 27 ...... Evaporation rate calculation circuit

Claims (1)

[Claims] 1. A product to be coated with a plurality of optical thin films in a bell jar of a vacuum vapor deposition apparatus, and a plurality of monitor glasses exposed by switching to a vapor deposition target region for each formation of one optical thin film. , A short-wavelength measuring light for film thickness monitoring, which is simultaneously irradiated to the monitor glass in the target region, and a long-wavelength measuring light for evaporation rate monitoring, which has a wavelength of approximately several times the short-wavelength measuring light. A first light receiver for short wavelength and a second light receiver for long wavelength for separately receiving the measurement light, the measurement light of the short wavelength and the measurement light of the long wavelength that have passed through the monitor glass. A first calculating means for calculating and monitoring the film thickness by the output of the first light receiving device, a second calculating means for calculating and monitoring the evaporation rate by the output of the second light receiving device, First computing means and the second performance And a process controller for controlling the evaporation process receives the output means, the evaporation rate and the film thickness of the monitoring device in the vacuum vapor deposition apparatus characterized by comprising.