JPH0790583A - Thin film forming method - Google Patents

Abstract

PURPOSE:To form a thin film stabilized in refractive index and thickness on a large-sized substrate by measuring the refractive index or film thickness at the intermediate point of a thin film depositing zone and adjusting the refractive index or the thickness by feedback control. CONSTITUTION:A substrate 61 is continuously transferred in a vapor deposition chamber 11, the substrate 61 is irradiated with the lights from light emitting elements 21, 23, 25 and 27 consisting of the tip of an optical fiber, etc., the lights are received by light receiving elements 31, 33, 35 and 37, and the respective transmittances are measured by a transmission type film thickness monitoring device 41. The transmittance varies with an increase in the thickness of film formed on the substrate 61. The refractive index of the substrate 61 is obtained from the relation between the transmittance and film thickness and compared with a reference value, the difference is fed back, and a thin film having a specified thickness is formed at all times. Besides, an optical film thickness is obtained from the transmittance or reflectance and compared with a specified value, and a final film thickness correcting plate 19 is turned in the opening or closing direction in accordance with the difference to adjust the final film thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming method applied to a continuous mass production thin film forming apparatus, a thin film forming on a large substrate, a thin film forming on a long sheet or a film, etc. The present invention relates to a film thickness control method.

[0002]

2. Description of the Related Art Various functional thin films such as an antireflection film, a surface protection film, etc. are formed on a substrate by vacuum deposition, sputtering or the like.
Forming a transparent conductive film or the like has been conventionally performed in a wide variety of fields. Conventionally, a substrate such as glass or plastic is supported by a holder, and a thin film is formed on the substrate by vapor-depositing or sputtering while rotating (revolving) the holder. A thin film having a uniform film thickness was formed. In addition, in order to make the film thickness uniform, the holder is made into a dome shape and the distance from the evaporation source is made uniform, or a correction plate (baffle plate) is arranged between the evaporation source and the substrate, and It controlled the amount of vapor deposition material that flew to and reached. Furthermore, for the multi-layer anti-reflection film whose accuracy of the film thickness of each layer severely affects the final characteristics, an optical film thickness monitor is used.
High-precision film thickness control has been performed by utilizing the fact that the transmittance or reflectance exhibits a maximum value or a minimum value each time the optical film thickness becomes λ / 4.

On the other hand, a continuous thin film forming apparatus is under development, and a preliminary exhaust heating chamber-thin film forming chamber (may be one tank or multiple tanks) -post-treatment chamber (slow cooling, take-out chamber). Gate valves are provided in series between the chambers, and high-precision functional thin films such as multilayer antireflection films are continuously formed without breaking the vacuum atmosphere in the thin film forming chamber. As the evaporation source in the thin film forming chamber, a heating evaporation source such as an electron gun, a sputtering target, etc. are used.In either case, the substrate is temporarily stopped in the thin film forming chamber, or it is mounted and rotated in a holder to form a thin film. Are formed. Therefore, since a uniform thin film is deposited on one lot of substrates, the film thickness of the thin film formed on any one point of the substrate or a separate monitor substrate is detected by an optical film thickness monitoring device or the like. As a result, the film thickness could be controlled.

However, in recent years, there has been an increasing demand for forming a single-layer or multi-layer thin film whose thickness is controlled with high precision on a large-sized substrate, such as forming a multi-layer antireflection film on the front panel of a liquid crystal display. It is possible to mount these large-sized substrates on a dome-shaped holder as in the conventional case and rotate them to form a thin film, but this leads to an increase in the size of the apparatus and deteriorates production efficiency. In addition, when a rectangular substrate such as a front panel of a liquid crystal display is mounted on a rotating conical holder, an unnecessary portion is increased. Forming a thin film on a substrate while continuously conveying the substrate to a thin film forming zone is performed in the field of forming an aluminum thin film on a continuous plastic film.
However, the film thickness control in this case is rough, and it cannot be applied as it is to a field in which highly accurate film thickness control is required such as an optical thin film such as a multilayer antireflection film.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to control and adjust the refractive index and film thickness of a thin film formed on a substrate in a thin film deposition zone.

[0006]

According to the thin film forming method of the present invention, a thin film forming material is made to fly from an evaporation source onto a substrate while transferring the substrate from a starting point to an end point of the zone in the thin film deposition zone. Then, a thin film is deposited on the substrate, a plurality of intermediate measurement points having different positions in the transfer direction are provided between the starting point and the end point, and the transmittance or the recoil coefficient of the substrate on which the thin film is formed is set to It is characterized in that the measurement is performed at the same wavelength at an intermediate measurement point, the refractive index of the formed thin film is calculated, and the thin film deposition conditions are controlled so that the refractive index becomes a predetermined value.

Also, instead of measuring at a plurality of intermediate measurement points having different positions in the transfer direction, the transmittance or reflectance at a plurality of wavelengths at the same point may be measured to similarly obtain the refractive index and optical properties of the thin film. Film thickness can be controlled.

[0008]

EXAMPLE FIG. 1 is an explanatory view showing an example of the present invention, showing a case of forming a thin film by a vacuum vapor deposition method. A large, rectangular substrate 61 supported by a substrate holder (not shown) is continuously transferred into the vacuum-deposited deposition chamber 11, and the deposition chamber 1 does not stop in the deposition chamber 1 without being stopped.
The inside of 1 moves from left to right at a predetermined speed. Board 61
Are successively sent into the vapor deposition chamber 11 one after another, and a large amount of substrates 6
1 to continuously form a thin film.

As the substrate 61, a transparent substrate such as glass or plastic is used. Although FIG. 1 illustrates the case where the substrates 61 are transferred one by one, a large number of substrates may be mounted in one holder and transferred in holder units. In the case of a plastic sheet or film, it may be transported itself without using a holder.

An evaporation source 13, a crystal oscillator 15, a fixed film thickness regulating plate 17, and a final film thickness correcting plate 19 are provided in the vapor deposition chamber 11, and light emitting elements 21, 23, 25, 27 and a light receiving element are provided. 31, 33, 35, 37 and a transmission type film thickness detection device 41 are provided. Instead of this, it is also possible to use a reflection type film thickness detection device and a light emitting / light receiving element therefor, or a film thickness detection device of another principle.

The evaporation source 13 is assumed to be heated by an electron gun in FIG. 1, but may be a resistance heating type evaporation source, an induction heating type evaporation source, a sputtering target or the like. The crystal oscillator 15 detects the evaporation rate of the thin film forming substance from the evaporation source 13, and the controller 51 controls this rate. From the evaporation source 13,
When a thin film forming material such as MgF ₂ , SiO ₂ , TiO ₂ , ZrO ₂ is continuously vaporized without interruption and is transferred between the fixed correction plate 17 and the final film thickness correction plate 19, a thin film is formed on the substrate 61. Are deposited. That is, the right end of the fixed correction plate 17,
A thin film deposition zone is formed between the final film thickness correction plate 19 and the left end thereof, and the thickness of the thin film on the substrate 41 gradually increases.

Light from the light emitting elements 21, 23, 25, and 27, which are composed of the tip portions of the optical fibers, irradiate the substrate 61 on which the thin film is formed with light of the same specific wavelength, and the light is received by the light receiving elements 31, 33, and 35, respectively. , 37, and the transmission type film thickness monitoring device 41 measures the respective transmittances. Board 6
As 1 moves to the right, the optical film thickness n · d of the thin film formed on the substrate 61 increases. Along with this, the transmittance increases or decreases, and when a thin film having an optical film thickness of ¼ of the measurement wavelength λ is formed, the transmittance takes a maximum value or a minimum value. Now, considering the case of depositing MgF ₂ on glass, as shown in FIG.
The detected value of the transmittance by 5, 37 changes with the increase of n · d, and the graph of the transmittance / optical film thickness can be drawn by connecting them. Since the refractive index of the substrate 61 is known, the refractive index n of the formed thin film can be obtained from the transmittance value at λ / 4. In FIG. 2, measurement points are set on both sides of λ / 4, which enables accurate measurement, but it is not always necessary. In fact, since the refractive index of the thin film to be formed is almost known, the curve shown in FIG. 2 can be obtained even at a small number of measurement points.

[0013] In vacuum deposition, MgF _2, the refractive index hardly fluctuation of film deposition conditions are also formed fluctuates S
There are TiO ₂ , ZrO _{2 and the} like, which tend to fluctuate, such as iO ₂ , and when the mixture is vapor-deposited like a mixture of TiO ₂ and La ₂ O ₅ , the fluctuation is further large. Therefore, in the present invention, the refractive index is measured as described above, and when it changes from a predetermined set value, this is detected and feedback correction is performed to always form a thin film having a predetermined refractive index.

The refractive index can be adjusted by changing the vapor deposition rate from the evaporation source 13 or by changing the partial pressure of oxygen introduced into the vapor deposition chamber 11. Specifically, for example, in the case of TiO _2, it is possible to increase the refractive index of the thin film formed by increasing the vapor deposition rate or increasing the oxygen partial pressure. Further, if the refractive index is known, the optical film thickness of the thin film formed on the substrate 61 can be obtained from the measured transmittance or reflectance. Compare the calculated optical film thickness with the reference value,
If it is smaller than the reference value, the final film thickness correction plate 19 is opened according to the difference, and the distance of the thin film forming zone is increased. On the contrary, when the film thickness of the formed thin film is smaller than the reference value, the final film thickness correction plate 19 is rotated in the closing direction. The mechanism of the final film thickness correction plate 19 is not limited to the rotation type shown in FIG. 1, and may be a slide type that extends in the left-right direction in FIG.

In addition to changing the distance of the thin film forming zone, the final film thickness can be adjusted by the following method. The substrate transfer rate is adjusted to control the time the substrate dwells in the thin film deposition zone. Control the evaporation rate of the thin film forming material from the evaporation source.

FIG. 3 is an explanatory view showing another embodiment of the present invention, except that there is only one transmittance measuring point.
Is the same as. However, in the embodiment of FIG. 3, the transmittance is measured at a plurality of wavelengths at this measurement point.

Specifically, as shown in FIG. 4, the light from the light source 71 is guided to the optical fiber 73, the light emitting element 29 (the tip of the optical fiber) irradiates the substrate 61, and this is received by the light receiving element 39 (the tip of the optical fiber). Receive at. Since the optical fiber 75 is composed of a bundle of fine fibers, the optical fiber 75 is divided into four bundle groups 77a to 77d, and four wavelengths (for example, 400 nm, 500 nm, 600 nm, 700) are passed through the spectral filters 79a to 79d.
(nm) light is guided to the transmission type film thickness monitoring device 41, and each transmittance is measured. When this transmittance is plotted, a spectral wavelength curve is obtained as shown in FIG. From this, similarly to the above, the refractive index and the optical film thickness of the thin film formed on the substrate can be obtained. Therefore, these are compared with a reference value and feedback-controlled to obtain a thin film of a predetermined film thickness with a predetermined refractive index. It can be manufactured continuously. Further, although FIG. 3 shows the case where the film thickness measurement in the middle is performed at one point, the film thickness of the thin film may be detected at a plurality of points.

[0018]

According to the present invention, while the substrate is continuously transferred in the thin film deposition zone, the refractive index or the film thickness is measured at the midpoint and feedback control is performed to form a stable thin film. In particular, it is suitable for forming a thin film on a large panel, a flat panel or the like. Further, it is suitable for forming a thin film such as titanium oxide or zirconium oxide in which the refractive index of the thin film formed is easily changed due to changes in the vapor deposition conditions.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a thin film forming method of the present invention.

FIG. 2 is a graph showing the relationship between optical film thickness and transmittance.

FIG. 3 is an explanatory view showing another embodiment of the thin film forming method of the present invention.

4 is an explanatory view of a film thickness monitoring system in the embodiment of FIG.

FIG. 5 is a graph showing the relationship between wavelength and transmittance.

[Explanation of symbols]

 11 vapor deposition chamber 13 evaporation source 15 crystal oscillator 17 fixed correction plate 19 final film thickness correction plate 21, 23, 25, 27, 29 light emitting device 31, 33, 35, 37, 39 light receiving device 41 transmissive film thickness monitoring device 51 Control device 61 Substrate 71 Light source 73,75 Optical fiber 77a, 77b, 77c, 77d Bundle 79a, 79b, 79c, 79d Spectral filter

Claims (4)

[Claims] 1. A thin film forming material is jetted onto a substrate from an evaporation source while transferring the substrate from a starting point to an end point of the zone in the thin film deposition zone to deposit a thin film on the substrate. A plurality of intermediate measurement points with different positions in the transfer direction are provided between the point and the end point, and the transmittance or reflectance of the substrate on which the thin film is formed is measured at each intermediate measurement point at the same wavelength to form A method of forming a thin film, comprising: calculating a refractive index of the thin film thus formed, and controlling deposition conditions of the thin film so that the refractive index becomes a predetermined value. 2. Further, the optical film thickness of the thin film formed from the refractive index and the transmittance or the reflectance is calculated, and the deposition condition is set so that the optical film thickness of the thin film formed on the substrate becomes a predetermined value. The method for forming a thin film according to claim 1, which is controlled. 3. A thin film forming substance is jetted onto the substrate from an evaporation source while transferring the substrate from a starting point to an end point of the zone in the thin film deposition zone to deposit a thin film on the substrate. An intermediate measurement point is provided between the point and the end point, the transmittance or reflectance of the substrate on which the thin film is formed is measured at multiple wavelengths at the same point, and the refractive index of the formed thin film is calculated. A method of forming a thin film, which comprises controlling deposition conditions of the thin film so that the rate becomes a predetermined value. 4. Further, the optical film thickness of the thin film formed from the refractive index and the transmittance or the reflectance is obtained, and the deposition condition is set so that the optical film thickness of the thin film formed on the substrate becomes a predetermined value. The thin film forming method according to claim 3, which is controlled.