CN112553589A

CN112553589A - High-stability film monitoring method and film coating device

Info

Publication number: CN112553589A
Application number: CN202110188380.6A
Authority: CN
Inventors: 鲍刚华; 林兆文
Original assignee: Shanghai Mifeng Laser Technology Co ltd
Current assignee: Shanghai Mifeng Laser Technology Co ltd
Priority date: 2021-02-19
Filing date: 2021-02-19
Publication date: 2021-03-26
Anticipated expiration: 2041-02-19
Also published as: CN112553589B

Abstract

The invention provides a high-stability film monitoring method and a film coating device, wherein the method comprises the following steps: arranging a film thickness monitoring system at least three points on the umbrella stand of the film plating machine to obtain at least three instantaneous film thickness data; substituting the at least three instantaneous film thickness data into a film thickness distribution formula to obtain a material evaporation characteristic parameter n; and monitoring the thickness of the film and correcting the thickness in real time by monitoring the change of the evaporation characteristic parameter n value of the material. The invention can obtain the optical film with good uniformity, high repeatability and good stability in the film batch production process, and effectively improves the yield of high-precision coating.

Description

High-stability film monitoring method and film coating device

Technical Field

The disclosure relates to the technical field of optical film preparation, in particular to a high-stability film monitoring method and a film coating device.

Background

In the conventional coating equipment, no matter the coating equipment is in a spherical revolution umbrella structure or a planar revolution umbrella structure, the thickness monitoring is realized by placing a crystal oscillator film thickness control system or an optical control system at the center of an umbrella stand of a coating machine to monitor the thickness, the speed and the like of a coated film, and the structure of the coating machine is shown in figure 1. Fig. 2 shows two sample points, i.e., the innermost a1 point and the outermost a2 point, on the spherical revolute parachute, and ideally, when the repeatability is good, the film thickness ratio of the a1 point to the a2 point is constant. In the actual batch production process, although the process parameters are determined, the evaporation parameter n value between actual heats has a certain slight change, which causes the film thickness ratio of A1 to A2 to change. The change in the ratio of the film thicknesses at points a1 and a2 causes two problems: first, the spectral repeatability of the film between heats is poor. The film thickness error between the furnaces at the same position of the conventional coating equipment is usually more than 2 percent, which is not beneficial to continuously preparing the film with high precision requirement. Second, the spectral uniformity of the film may vary from run to run. The uniformity of the film thickness of the conventional film plating equipment in different positions among the furnaces can also change, which can reduce the yield of high-precision film plating, and the conventional single-point film thickness monitoring system cannot monitor the proportional change, so that the conventional film plating method and the conventional film plating equipment cannot solve the two problems.

Disclosure of Invention

In view of this, the embodiments of the present disclosure provide a high-stability film monitoring method and a film coating apparatus, where the film monitoring method is combined with the film coating apparatus to obtain an optical film with good uniformity, high repeatability and good stability in a film batch production process, so as to effectively improve the yield of high-precision film coating.

In order to achieve the above purpose, the invention provides the following technical scheme:

a high stability thin film monitoring method, the method comprising: arranging a film thickness monitoring system at least three points on the umbrella stand of the film plating machine to obtain at least three instantaneous film thickness data;

substituting the at least three instantaneous film thickness data into a film thickness distribution formula (1) to obtain a material evaporation characteristic parameter n;

（1）

wherein t is the film thickness, the index n is the evaporation characteristic parameter of the material, C is the proportionality constant,

in order to obtain the angle of evaporation,

r is the distance from the evaporation source to the measuring point as a deposition angle;

and monitoring the thickness of the film and correcting the thickness in real time by monitoring the change of the evaporation characteristic parameter n value of the material.

In a preferred embodiment, the method comprises the following steps: arranging a film thickness monitoring system at three points on the umbrella stand of the film plating machine to obtain three instantaneous film thickness data;

the first point position is positioned at the central vertex position of the umbrella stand of the film plating machine and marked as a point A; making an overhead projection view of the umbrella stand of the film plating machine, wherein the second point is the intersection point of an extension line of a connecting line of the point A and the evaporation source in the overhead projection view and the outermost ring edge of the umbrella stand of the film plating machine and is marked as a point B; on a top-view projection drawing, the third point is positioned at the outermost ring edge of the umbrella stand of the film plating machine, is marked as a point C, and meets the condition that the angle CAB is 60 degrees.

The invention also provides a coating device using the high-stability film monitoring method, the coating device comprises a coating machine umbrella stand arranged in the vacuum coating chamber, and a first film thickness monitoring system, a second film thickness monitoring system and a third film thickness monitoring system are arranged on the coating machine umbrella stand;

the first film thickness monitoring system is arranged at the central vertex position of the umbrella stand of the film plating machine and marked as a point A; making an overhead projection view of the umbrella stand of the film plating machine, wherein the second film thickness monitoring system is arranged at the intersection point of the extension line of the connecting line of the point A and the evaporation source and the outermost circle edge of the umbrella stand of the film plating machine in the overhead projection view and is marked as a point B; on a top-view projection diagram, the third film thickness monitoring system is arranged at the outermost ring edge of the film plating machine umbrella stand, is marked as a point C, and meets the condition that the angle CAB is 60 degrees.

In a preferred embodiment, the film thickness monitoring system is a crystal oscillator film thickness control system or an optical film thickness control system.

In a preferred embodiment, the coating machine umbrella stand is in a spherical revolution umbrella or planar revolution and rotation umbrella structure.

The invention discloses a high-stability film monitoring method and a film coating device, which have the beneficial effects that: the method can calculate the film thickness distribution of the film thickness on the whole spherical revolution umbrella, realizes the monitoring and control of the film thickness uniformity and repeatability, is a high-stability film thickness control method and a film coating device with good uniformity and ultrahigh repeatability, can effectively solve the problems of poor spectrum uniformity and spectrum repeatability of the film between heats in the traditional film coating process, and effectively improves the yield of high-precision film coating.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic structural view of a conventional coating apparatus;

FIG. 2 is a schematic view of a part of a spherical revolution umbrella of the conventional coating device shown in FIG. 1;

FIG. 3 is a schematic diagram of a non-cosine distribution structure of facet source electron beam evaporation;

FIG. 4 is a schematic diagram of the instant film thickness distribution corresponding to different positions of the film coating apparatus away from the center according to the embodiment of the present invention;

FIG. 5 is a schematic diagram of a point selection rule of three film thickness monitoring systems according to an embodiment of the present invention;

FIG. 6 is a schematic view of the uniformity of the first furnace of the coater A;

FIG. 7 is a schematic view of the uniformity of the second furnace of the coater A;

FIG. 8 is a schematic view of the uniformity of the first furnace of the B coater;

FIG. 9 is a schematic view of the uniformity of the second furnace of the B coater;

FIG. 10 is a schematic view of a point selection for three film thickness monitoring systems according to another embodiment of the present invention;

FIG. 11 is a schematic view of the spectral curves of the same positions of 3 furnaces of a coater (A coater) of the single film thickness monitoring system;

FIG. 12 is a schematic diagram of the spectral curves of the same position of the coater in 3 heats of the 90-degree three-point monitoring system;

FIG. 13 is a schematic diagram showing the spectral curves of the same positions of 3 furnaces of a coater (B coater) of the 60-degree three-point monitoring system according to the present invention;

FIG. 14 is a schematic view of film thickness uniformity in an embodiment of the present invention.

Detailed Description

The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

The embodiments of the present disclosure are described below with specific examples, and other advantages and effects of the present disclosure will be readily apparent to those skilled in the art from the disclosure in the specification. It is to be understood that the described embodiments are merely illustrative of some, and not restrictive, of the embodiments of the disclosure. The disclosure may be embodied or carried out in various other specific embodiments, and various modifications and changes may be made in the details within the description without departing from the spirit of the disclosure. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.

It is noted that various aspects of the embodiments are described below within the scope of the appended claims. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the disclosure, one skilled in the art should appreciate that one aspect described herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented and/or a method practiced using any number of the aspects set forth herein. Additionally, such an apparatus may be implemented and/or such a method may be practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.

It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present disclosure, and the drawings only show the components related to the present disclosure rather than the number, shape and size of the components in actual implementation, and the type, amount and ratio of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.

In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects may be practiced without these specific details.

Referring to fig. 1, fig. 1 is a schematic structural view of a conventional coating apparatus. As shown in fig. 1, the evaporation source 4 heats the film material to a vaporized state, and the gaseous film molecules are volatilized upwards and contact the glass substrate placed on the spherical revolution umbrella 1, and are condensed and deposited to form a film. Since the distribution of the thickness of the thin film deposited in this way is not uniform over the entire spherical umbrella, a film thickness correction plate 3 is usually added between the evaporation source 4 and the spherical revolution umbrella 1 to ensure uniformity.

And the monitoring probe 2 is positioned at the center of the machine and is used for monitoring and controlling the thickness of the film. The film thickness value obtained by the monitoring probe 2 does not represent the actual coating thickness, but forms a certain proportional relation with the film thickness coated on the spherical revolution umbrella 1, and the proportional relation is usually expressed by tolling, so that the film thickness repeatability of the coating can be reflected to a certain degree.

Fig. 2 is a schematic diagram of two sample points, namely an innermost point a1 and an outermost point a2, on the spherical revolving umbrella 1 in the conventional coating device of fig. 1, and ideally, when the repeatability is good, the film thickness ratio of the points a1 and a2 is constant. In the actual production process, the evaporation characteristics between heats have certain slight changes, which causes the film thickness ratio of A1 to A2 to change, thereby causing the uniformity change; after the film thickness distribution of A1 and A2 changes, the film thickness ratio to the position of the central monitoring probe changes, i.e. Tooling changes accordingly.

Under the condition, the conventional single-point film thickness monitoring system cannot monitor the two changes, and the uniformity and the repeatability are difficult to ensure.

In addition, the distribution of the film thickness on the whole spherical revolution umbrella is a function of the influence factors such as the machine structure, the coating process, the shape of the revolution umbrella and the like. Therefore, in the case of determining the machine structure and the coating process, the film thickness of A1 and A2 can be monitored simultaneously, so that the film thickness of points except A1 and A2, such as A3, can not be reflected, and the film thickness distribution of the film thickness on the whole spherical revolution umbrella can not be reflected.

Therefore, the two-point monitoring cannot solve the problem of poor uniformity and repeatability. The film thickness distribution of the film thickness on the whole spherical revolution umbrella can be calculated only by reasonably considering the number of the points and the positions of the points, and the uniformity and the repeatability can be really monitored and controlled.

Therefore, the invention provides a high-stability film monitoring method and a film coating device, wherein the method comprises the following steps: arranging a film thickness monitoring system at least three points on the umbrella stand of the film plating machine to obtain at least three instantaneous film thickness data;

（1）

in order to obtain the angle of evaporation,

The conventional evaporation coating machine is a single evaporation source evaporation mode, mainly uses the evaporation of a small-surface source as a main mode, the emission characteristic of the evaporation of an electron beam of the small-surface source follows non-cosine distribution, the specific structure of the conventional evaporation coating machine is shown in figure 3, and the film thickness distribution on a spherical umbrella can be represented by the formula (1).

The index n is a material evaporation characteristic parameter and is related to evaporation characteristics; c is a proportionality constant,

in order to obtain the angle of evaporation,

r is the distance from the evaporation source to the point S for the deposition angle. Consider that the film thickness measured by the monitoring probe is an instantaneous film thickness. Therefore, the parameters are substituted into the formula (1) to obtain the instantaneous film thickness distribution formula (2) at each position:

（2）

the film thickness distribution formula is mainly applied to the calculation of the uniformity of the whole umbrella of a film coating machine in the field. The material evaporation parameter n in the formula is used as a characteristic parameter of material evaporation, and can be used for evaluating the repeatability and stability of the coating. The value of n is fixed under ideal uniformity and repeatability conditions. The uniformity and repeatability change in the coating process can be mathematically simulated by the weak change of n.

In equation (2), the (h, r, θ) parameters are determined simultaneously for a location s on the umbrella, the film density μ and the evaporation parameter n are unknowns, and the film density μ is a function of the location s. This means that the instantaneous film thickness profile of at least 3 location points needs to be known in order to resolve a specific value of the evaporation parameter n. At least 3 monitoring points are needed to accurately detect and control the uniformity and repeatability of the coating equipment.

In a preferred embodiment, a film thickness monitoring system is arranged at three points on an umbrella stand of the film plating machine, so that three instantaneous film thickness data are obtained; next, a method of setting the three-point monitoring points described above will be described.

Equation (2) can be described more intuitively using polar plots after machine geometry and material determination. FIG. 4 shows 2700 the instantaneous film thickness distribution for different positions of the coater from the center, where the area of each circle in FIG. 4 is proportional to the thickness of the film deposited after one rotation of the position.

In FIG. 4, the polar diagram at the center point of the umbrella stand is a perfect circle and the distance from the S point to the rotating shaft

The polar diagram becomes elliptical. Each point on the polar coordinates shows the instantaneous film thickness information of the position, the center position of each circle or ellipse is known, and three points are needed to define an ellipse.

Region I: in order to achieve the instantaneous film thickness distribution at different positions on the umbrella near the center position on the left side of the umbrella, it can be seen from the figure that the instantaneous error at each position of the area I is the smallest compared with the other two areas, so that the overall film thickness distribution can be monitored by placing 1 film thickness monitoring point (monitoring point A) at the center position, and the control error is reduced.

Therefore, the position of the first film thickness monitoring system is positioned at the central vertex position of the umbrella stand of the film coating machine and marked as the point A.

And a second region: in order to obtain the film thickness distribution at different positions on the umbrella near the outermost position of the umbrella just above the evaporation source, it can be seen from the figure that the instantaneous error at each position of the second area is the largest compared with the other two areas, so the second film thickness monitoring point (monitoring point B) is arranged in the horizontal axial direction.

Therefore, as shown in fig. 5, when the coating machine umbrella stand is viewed from the top, the second point is the intersection point between the extension line of the connection line between the point a and the evaporation source and the outermost circle edge of the coating machine umbrella stand, and is marked as point B.

Zone III: in the area where the instantaneous film thickness on the umbrella is the same or close to each other, as can be seen from fig. 4, the film thickness distribution in this area is close to each other, and the angle formed by the connection line between the third area and the first area and the second area in fig. 4 is 60 °, so that the third film thickness monitoring point (monitoring point C) is placed on the outermost side of the extension line of the 60 ° angle.

Therefore, on the top projection view, the third point is positioned at the outermost ring edge of the umbrella stand of the film plating machine, is marked as a point C, and meets the condition that the angle CAB is 60 degrees.

The selection of three characteristic monitoring points selected by the point selection rule is shown in fig. 5, in the figure, the central point of the revolution umbrella 1 is a main monitoring point A, the other two points are a first auxiliary monitoring point B and a second auxiliary monitoring point C, the computer can reversely deduce the size of the n value of the material evaporation parameter through calculation by actually testing the real film thickness data of the three points, and write a program to monitor in real time, judge the n value through an algorithm and correct the n value through the modification of the process, so as to achieve the purpose of improving the uniformity and the repeatability of the film plating machine.

The invention will now be described in further detail with reference to the following examples, with reference to the accompanying figures 6-12: the film coating machine of a single film thickness monitoring system (hereinafter referred to as an A film coating machine) and the film coating machine of a three-point monitoring system with 60 DEG < CAB (B film coating machine) are used for verifying the uniformity and repeatability of the film, and in order to ensure that the experimental result is reliable, the two film coating machines have the same size and the same configuration except the monitoring system.

Example 1: film thickness uniformity verification

The high-stability vacuum coating machine is provided with a multi-point film thickness monitoring system, and compared with the traditional single-point film thickness monitoring system, the uniformity can be effectively improved.

The specific experimental verification mode is as follows: the uniformity of the 400-ion 700nm antireflection film is respectively adjusted by using A, B two coating machines. Fig. 6-9 are schematic diagrams of uniformity curves of A, B coater for respectively preparing two furnaces, where a1 in fig. 6 is the uniformity of the first furnace of the a coater, a2 in fig. 7 is the uniformity of the second furnace of the a coater, B1 in fig. 8 is the uniformity of the first furnace of the B coater, and B2 in fig. 9 is the uniformity of the second furnace of the B coater. As can be seen from the comparison of the enlarged images of FIG. 6 and FIG. 7, the uniformity of the whole umbrella between the two heats of the A coating machine is changed and irregular; as can be seen from the comparison of the enlarged images of FIGS. 8 and 9, the uniformity of the whole umbrella between two furnaces is hardly changed, and the three-point thickness control system in the coating machine of the invention is greatly helpful for improving the uniformity between each furnace.

Example 2: repeatability verification

The high-stability vacuum coating machine provided by the invention is provided with a three-point monitoring system, and has a good effect of improving the repeatability among heats compared with the traditional single-point film thickness monitoring system.

The specific experimental verification mode is as follows: a coating machine using a single-film thickness monitoring system, a coating machine of a three-point monitoring detection system with 90 DEG CAB as shown in fig. 10 and a coating machine of a three-point monitoring system with 60 DEG CAB as shown in fig. 5 are prepared into 400-plus 700nm antireflection films, 3 furnaces are respectively prepared, the spectrum conditions of samples at the same position and different times of furnaces are compared after preparation, the spectra are shown in fig. 11, fig. 12 and fig. 13, and fig. 11, fig. 12 and fig. 13 are respectively a single-film thickness monitoring system, a three-point monitoring system with 90 DEG CAB as well as three coating machines with 60 DEG CAB as shown in fig. 11, fig. 12 and fig. 13 are spectrum curves at the same position of 3 furnaces. Through statistical calculation, the repeatability error of a single-film-thickness monitoring system coating machine is 2.5%, the repeatability error of an angle CAB 90-degree three-point monitoring system coating machine is 1.25%, and the repeatability error of an angle CAB 60-degree three-point monitoring system coating machine is 0.8%. By comparing the monitoring system with 90 degrees of < CAB with the monitoring system with 60 degrees of < CAB, the coating machine with the three-point monitoring system with 60 degrees of < CAB has better repeatability and verifies theoretical calculation.

Example 3: monitoring and process adjustment of material evaporation characteristic parameter n

This example illustrates how the evaporation characteristic parameter n of the material is calculated from three-point film thickness data actually measured, and how the quality of the plated film is improved by process adjustment when n changes.

The n-value evaluation function of the three-point monitoring system is established as shown in formula (3):

（3）

wherein

The material parameter n is calculated according to the position of the central point of the umbrella stand,

、

the instantaneous film thicknesses measured at A, B, C points at this time point.

In the use of TiO₂/SiO₂In the process of preparing 400-700nm materials by two materials, data are summarized after monitoring for multiple times, and TiO is well repeated₂The material evaporation characteristic parameter n of the material is stabilized at about 2.4, and SiO₂The material evaporation characteristic parameter n of the material is stabilized to be about 2.0.

After evaporation to the third layer of TiO₂When, due to unknown external factors, TiO₂The evaporation parameter of the material is suddenly changed to 2.6, the computer judges the change of the evaporation parameter through algorithm analysis, the process is finely adjusted (the computer sets the n value to be 2.4, the error is +/-0.2, the sudden change is changed to 2.6 in the process, and the computer controls an electronic gun control system to automatically finely adjust the size and the position of a light spot so as to ensure that the TiO is subjected to fine adjustment₂The value of the evaporation parameter n tends to 2.4), and the evaporation characteristic parameter n of the material after process adjustment is stabilized to be near 2.4. The uniformity of the entire umbrella was tested after plating and the test pattern is shown in FIG. 14. From fig. 14, it can be seen that the repeatability of coating is effectively improved and the yield of the coating machine is improved by automatically regulating and controlling the n value.

The above description is only for the specific embodiments of the present disclosure, but the scope of the present disclosure is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present disclosure should be covered within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A method for monitoring a high stability thin film, the method comprising: arranging a film thickness monitoring system at least three points on the umbrella stand of the film plating machine to obtain at least three instantaneous film thickness data;

（1）

in order to obtain the angle of evaporation,

2. The high stability thin film monitoring method of claim 1, comprising: arranging a film thickness monitoring system at three points on the umbrella stand of the film plating machine to obtain three instantaneous film thickness data;

3. A coating apparatus using the high-stability thin film monitoring method according to claim 1 or 2, wherein the coating apparatus comprises a coating machine umbrella stand provided in a vacuum coating chamber, and the coating machine umbrella stand is provided with a first film thickness monitoring system, a second film thickness monitoring system and a third film thickness monitoring system;

4. The plating device according to claim 3, wherein the film-thickness monitoring system is a crystal-oscillator-film-thickness control system or an optical-film-thickness control system.

5. The coating device according to claim 3, wherein the coating machine umbrella stand is of a spherical revolution umbrella structure or a planar revolution and rotation umbrella structure.