HK1228965B - Thin film coating method and the manufacturing line for its implementation - Google Patents

Description

Thin film coating method and production line for implementing the method

Technical Field

The present invention relates to processing equipment for treating surfaces in large-scale production, in particular to vacuum processing equipment designed for thin film coatings with defined optical, electrical and other properties.

Background Art

From a technical perspective, there are various methods for applying thin film coatings to processed workpieces (substrates).

Patent US 4851095 published on July 25, 1989 describes a method for magnetron deposition of thin film coatings onto substrates placed on a rotating drum. The coating is deposited onto the substrate by operating an apparatus located around the drum in a vacuum chamber.

This solution suffers from low productivity and considerable production costs due to the need to repeat the processing steps in order to obtain the desired number of layers in the structure.

Patent US 6893544 published on May 17, 2005 discloses a combination of important features that is closest to the method proposed in the present invention. The patent discloses a method for applying a thin film coating, wherein the substrate is mounted on a vertical flat carriage that can be moved in a linear processing device (magnetron deposition cathode, linear plasma source, etc.).

The disadvantages of this approach are high cost and low productivity, especially when applying complex and precise coatings, due to the need to use complex control systems and setup (i.e., indirect time and material costs), high material consumption, due to the fact that the area of the processing zone within the processing equipment is higher than the uniform area, e.g., during magnetron deposition, 30%-50% of the target material does not reach the substrate, and a limited range of applicable processing equipment, as we can only use such equipment that can guarantee acceptable uniformity, which excludes many cutting-edge technologies.

From the state of the art, we also know a variety of devices for applying thin film coatings to processed workpieces (substrates).

In particular, in large-scale production, small-sized substrates are processed using periodically operated drum devices, such as the device described in US Pat. No. 4,851,095, published on July 25, 1989, which includes a cylindrical substrate holder around which the substrate is wound. The uniformity of the coating is ensured in one direction by the rotation of the drum, and in the other direction by using a linear processing device.

In the production of displays, linear equipment is used to process planar substrates. As an example of such equipment, in which the substrate is mounted on a carriage and moved through subsequent processing stages, we can refer to Utility Model Patent RU78785, published on December 10, 2008, which discloses an automated device for forming a thin-film coating. However, this equipment, like other known equipment to date, suffers from low operational reliability due to its reliance on a stable transport system for secure attachment to the substrate, as well as high costs due to the complex control system and setup required to ensure the desired uniformity of the coating applied to the surface.

From the perspective of overall important parameters, patent US6893544 published on May 17, 2005 discloses a processing line for depositing thin film coatings that is closest to the present invention, which includes an airlock chamber arranged in sequence, a processing chamber with a processing device inside, a buffer chamber and a planar substrate support designed to move along the chamber.

The disadvantages of this technical solution are as follows:

- The range of standard sizes of substrates that can be processed is limited, in particular flexible substrates such as thin glass cannot be processed because they cannot be reliably fixed and protected while moving along the production line;

- high costs, due to complex control systems and setup, especially for complex and high-precision coatings, as well as the consumption of large amounts of material, 30-50% of which does not reach the substrate, since uniformity of the deposited layer is provided at the expense of a larger processing area of the production equipment than the homogeneous area;

- The range of applicable technologies and processing equipment is limited, as the possible applications are restricted by the requirements for acceptable uniformity of the deposited layer.

Summary of the Invention

The challenge of the present group of inventions is to provide a high-throughput unified apparatus for processing substrates having a wide range of standard sizes.

When this challenge is solved, a technical result is achieved which ensures the processing of flexible large-scale substrates, as well as small-scale substrates, with a high degree of uniform coverage and the ability to use a wide range of technologies and processing equipment, as well as an efficient value-added use of the applied material.

The technical effect is achieved by providing a method for applying a thin film coating to a substrate, wherein the substrate is supported by a support and then moved with the support through a process chamber, wherein the coating is applied by a process apparatus positioned within the process chamber. Furthermore, the substrate support is configured as a rotating drum that moves through a process zone of the process apparatus parallel to the drum's axis of rotation and rotates at a constant linear velocity and angular velocity, wherein the ratio of the linear velocity to the angular velocity is selected such that each point on the drum surface performs at least two complete revolutions while passing through the process zone of the process apparatus.

The technical effects are achieved by providing a thin film coating production line comprising an airlock, a buffer chamber, at least one processing chamber having a processing device, a substrate holder mounted on a carriage (the carriage is mounted to enable passage through the chambers), and a conveyor system. Furthermore, the substrate holder, which moves through a processing zone of the processing device, is designed as a rotating drum, mounted coaxially on the carriage in the direction of carriage movement, and rotates at a constant angular velocity and linear velocity, ensuring that every point on the drum surface undergoes at least two complete revolutions as it passes through the processing zone of the processing device.

To achieve this technical effect, the production line may include inlet and outlet airlocks and a buffer chamber. In addition, the substrate support carriage may be designed as a rack or frame arranged above the substrate support, or a cart with linear guide rails arranged below the substrate support.

The production line can be equipped with at least one drive to rotate the substrate holder. The substrate holder can be equipped with a friction and/or magnetic detachable coupling and/or a low-voltage motor. In addition, each substrate holder can be equipped with a motor, the transport system can be equipped with rollers, and the carriage can be equipped with guide rails that contact the rollers.

The principle of achieving uniformity by design is explained below by describing the movement of a cylindrical support that rotates smoothly and moves forward through the treatment zone of a processing device. As the cylinder moves, a coating of thickness f(x) is applied to every point on the entire cylinder surface with each revolution. Each observation point A will move the cylinder by a step size d to point A' with each revolution, and in the following revolution, it will have the coating thickness corresponding to point A'. After passing through the entire treatment zone, the total thickness T applied at point A is obtained by summing the values of the point diagram for step size d. This sum is equal to the integral of the curve of the midpoint rule method for step size d. For another point B, the same sum is calculated, but it is obtained by selecting another set of steps. This means that for each point, an estimate of the total applied thickness is calculated as T ₀ = S/d, where S is the area under the curve. The accuracy of this estimate increases as the step size decreases, proportional to its square. An estimate of the relative error is given by the expression, where _fcp is the average value of f(x) _{and M2} is the maximum value of f″(x). This estimate is an assessment of the non-uniformity of the coating thickness under stable operating conditions of the processing equipment.

The above estimates remain valid when using N identical process devices, equally spaced around the substrate holder. They are repeatable for a single process device, numbered sequentially from 1 to N. Furthermore, for each point, the entry of the kth process device is determined by the total value of the point, relative to the first. If we now combine the sums of all points, this means we sum the values of the points with a step size of d/N. This means that using this device configuration is equivalent to integrating N times, thus improving N by a factor of ² .

The required uniformity can be achieved by:

- Several identical processing devices are symmetrically arranged around the substrate support;

- Along the path of the substrate support, several processing devices are arranged with the same step size S = (m + 1/n) * d, where m is an integer, n is the number of devices, and d is the linear displacement of the substrate support per revolution;

- A portion of the deposition area is shielded by a cover and controlled externally.

Regarding the principle of uniformity, it must also be noted that the substrate holder can be moved through the process chamber at different speeds if desired, and only at a constant speed within the process zone. The ability to move the substrate holder at different speeds within a process chamber: a uniform and constant speed within the process zone, and another speed outside the process zone, but within the confines of the process chamber, will increase production line productivity by enabling optimization of the line components using the desired process chamber design.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described with reference to the accompanying drawings, in which:

FIG1 shows a distribution curve of the thickness applied by a single treatment device during one revolution, shown in the figure (the X-axis coordinate is in mm starting from the center of the device);

FIG2 shows a structural diagram of a substrate support;

FIG3 shows a front view of the substrate support;

FIG4 shows a structural diagram of a magnetic coupling component;

FIG5 shows a front view of a magnetic coupling;

Figure 6 shows a general diagram of the production line.

DETAILED DESCRIPTION

The proposed application of thin film coatings on substrates can be illustrated by the example of a layout of a processing equipment line for applying four layers of antireflective coating on glass. The required layer uniformity is ±1% for the first and second layers and ±3% for the third and fourth layers.

The length of the substrate holder was 100 cm, and the speed at which the holder moved in the processing zone was 1 m/min, determined by the cycle of the production line.

To apply the coating, four treatment zones were set up, one for each layer. Medium-frequency magnetrons with a target distance of 800 mm were used as treatment equipment. The number of treatment units was determined by production requirements and layer thickness. One treatment unit 01 was used to apply the first layer (magnesium oxide), two treatment units 02 were used to apply the second layer (titanium oxide), and four treatment units 03 and 04 were used to apply the third (magnesium oxide) and fourth (titanium oxide) layers, respectively.

Since the first two layers have more stringent uniformity requirements, and a smaller number of processing devices are used to apply the first layer, the spin speed required to ensure uniformity will be determined by the first layer.

An example of the thickness distribution applied by one revolution of a single treatment device is shown in the graph ( FIG. 1 ), where the coordinate along the X-axis starting from the center of the device is in mm.

According to the curve shown, the length of the treatment zone is 120 cm, while the length of the edge region is approximately 10 cm, wherein the thickness of the edge region decreases to zero.

After the substrate holder has made two revolutions through the processing zone, the nonuniformity is approximately ±35%. The minimum thickness is located at points at the edge and center of the processing zone, and the maximum thickness is located at a point that has passed through the processing zone twice. The ratio of these thicknesses is approximately 1:2, resulting in a ±33% nonuniformity.

To achieve the required uniformity, this value needs to be reduced by a factor of 35, giving an estimate of the number of revolutions required:

A more accurate estimate using the above curves shows that over the above number of revolutions the non-uniformity is ±0.8%.

Based on this, the rotation speed of the substrate holder needs to be set so that the linear displacement of the holder per revolution does not exceed 120/12≈10 cm. If the forward speed is 1 m/min, the rotation speed should be at least 10 rpm.

Other layers can achieve better uniformity because using two or more identical processing devices proportionally increases the rotation speed, ie, improves uniformity.

The operation of the production line can be represented by an example of a linear arrangement with two-stage airlocks, which includes a substrate holder, a vacuum lock, a low vacuum inlet airlock, a high vacuum inlet airlock, an inlet buffer chamber, a processing chamber, an outlet buffer chamber, a high vacuum outlet airlock, a low vacuum outlet airlock, a conveyor system with driven rollers, a high vacuum pump, and processing equipment.

The substrate support consists of a drum (1) mounted on bearings of a carriage (2). The substrate, such as glass, is mounted on a plate (3) by any known method to ensure their secure fixation while the drum rotates.

The carriage is fitted with guide rails (10) located below the drum and is mounted on stands (11) made of dielectric material.

In many cases, according to different production processes, the slide (2) can be designed in the following forms:

- In the form of a cart, in which a linear guide is provided below the drum;

- suspended in air, with linear guides positioned above the drum;

- In the form of a frame in which linear guides are arranged along the sides of the drum.

- or other forms that ensure linear movement of the rotating cylinder.

Removable magnetic coupling parts (4) and (5) are mounted on the ends of the drum shaft. The design of the coupling is well known. The first part (4) of the removable coupling consists of a soft magnetic hollow material and magnets (6) are mounted along the inner surface. The magnets are mounted in alternating polarity with their magnetization directions shown in the figure. The mating part (5) of the magnetic coupling consists of a soft magnetic cylinder with magnets (7) mounted on its surface, the number of these magnets matching the number of magnets of the first part. The magnets are mounted in alternating polarity with their magnetization directions shown in the figure. There is a gap of about 5 mm between the magnets of the first and second parts, which ensures that no contact occurs when the coupling rotates in the case of an imprecise connection of the substrate holder.

A direct-acting electric motor is used to keep the drum rotating. The motor drive rotor (8) consists of a ring magnet with a magnet on it. The motor drive stator (9) with a control unit is placed on the frame of the carriage. The power for the motor is provided by a direct current through the linear guide (10) of the carriage. To this end, the linear guide is mounted on an insulating bracket (11) of the carriage. The power for the linear guide is provided by the rollers of the conveyor system.

The production line comprises a low vacuum inlet airlock (14), a high vacuum inlet airlock (15), an inlet buffer chamber (16), a processing chamber (17) containing a processing device, an outlet buffer chamber (18), a high vacuum outlet airlock (19) and a low vacuum outlet airlock (20).

Processing devices are mounted along the substrate support's direction of movement. The processing zone is defined by the area along which the processing devices are positioned, within the limits of which the majority (more than 90%) of the material deposited by the devices is deposited on the substrate support. Furthermore, several processing devices designed to deposit the same material, which partially or completely cover the processing zone, can be considered a single processing device. If desired, several processing devices involved in layer deposition can be mounted around the substrate support.

The support (22) with the substrate fixed thereon enters the inlet airlock (14), and then the door (21) of the airlock is closed. After the door is closed, the support is withdrawn and its detachable coupling (4) is connected to the mating part (23) of the coupling, which is mounted on the rotary shaft of the vacuum inlet, and the rotary shaft is driven by the motor (24) mounted on the airlock door.

The motor rotates the drum of the substrate holder to the desired rotation speed. Simultaneously, the airlock chamber is evacuated to a pressure of 10-20 Pa.

After the pumping and the drum rotation, the transfer gate (25) is opened, the carriage is transferred to the high vacuum inlet airlock chamber (15), and the gate (25) is closed. The high vacuum airlock chamber is equipped with a turbomolecular pump (26) and pumped to a pressure of less than 0.01 Pa.

After the high vacuum air lock chamber is evacuated, the transfer gate (27) opens and the substrate holder is transferred to the inlet buffer chamber (16), where the gate (27) closes. In the buffer chamber, the substrate holder is slowed down to process speed and connected to the substrate holder introduced into the production line in the previous step. The magnetic coupling of the substrate holders is connected, and the rotation of the introduced substrate holder is synchronized with the rotation of the substrate holder (28) passing through the processing chamber. In the processing chamber, power is provided to the rollers of the conveyor system, so that the motor of the substrate holder maintains the drum rotation.

The coating is applied to the substrate in the treatment chamber (17). During the treatment of the substrate (in the treatment zone), the drum rotates and moves uniformly along its axis. The substrate supports pass through the treatment zone with minimal clearance between them.

Since uniformity is primarily determined by the step size per revolution, the ratio of the substrate holder's linear displacement speed to its rotational speed is set so that each point on the substrate holder's surface undergoes at least two complete revolutions while passing through the processing zone. As a result, the step size per revolution is very small, enabling high uniformity of the applied coating to be achieved, regardless of the type of processing equipment used, including both linear and precision types.

To ensure the required rotational speed of the substrate holder while simultaneously moving linearly during processing, this challenge can be achieved by one of the following methods:

1. Using an external drive in one of the inlet chambers, rotate the substrate holder to the desired speed while the carriage is stationary, and then maintain its rotation due to inertia.

2. Each carriage is equipped with a low-voltage electric motor. The power of the motor is provided by the rollers of the conveyor system or the contact rollers on the linear guide of the carriage which are insulated from the carriage housing.

3. Using an external drive in one of the inlet chambers, the substrate holder is rotated to the desired speed, while the carriage is stationary and is equipped with a low voltage motor that is used to maintain the rotation and can be low powered.

To ensure that all substrate supports in the processing zone rotate at the same speed, they can be equipped with friction or magnetic detachable couplings, which ensure the transmission of rotation between adjacent substrate supports as they move with minimal clearance.

For applying metal-dielectric and composite metal-dielectric coatings, in addition to conventional devices for transmission devices, one of the following methods can be used, namely multiple application of thin metal or oxide layers followed by oxidation.

Oxidation in this context refers to any reaction that results in the formation of chemical bonds with, for example, oxygen, nitrogen, selenium, etc.

For this purpose, a special treatment zone is formed in which treatment means are mounted around the support for applying one or more metals, and treatment means for oxidation, representing a source of activated reactive gas (for example a plasma source).

A high vacuum pumping device is provided in the treatment zone to ensure gas separation between the treatment device for oxidation and the treatment device for applying the metal.

While passing through the treatment zone, each point of the treated surface passes multiple times through a treatment device for applying metal, where an ultra-thin layer of material is applied, and through a treatment device for oxidation, where this layer is completely oxidized. After passing through the treatment zone, the treated surface is uniformly coated with a metal-dielectric or composite metal-dielectric coating having a specified content.

The treatment device can apply one or a variety of materials. In the latter case, different speeds can be set to apply the materials to obtain the required coating content.

After passing through the processing chamber (17), the substrate holder enters the inlet buffer chamber (18).

The delivery gate (29) is opened, and the substrate holder is accelerated, away from another substrate holder behind it, and moves to the high vacuum inlet airlock chamber (19); then, the gate (29) is closed, and the delivery gate (30) is opened, and the substrate holder moves to the low vacuum outlet airlock chamber (20), wherein the front end part of the magnetic coupling of the holder is connected to the matching part (31) of the magnetic coupling installed on the door. The magnetic coupling part (31) is installed on a shaft, and the rotation of the shaft becomes difficult due to friction.

The gate (30) is closed, dry air is pumped into the chamber and the pressure is raised to atmospheric pressure. Simultaneously, the substrate support drum is stopped due to the coupling brake (31).

After the pressure within the outlet airlock chamber (20) is equalized to atmospheric pressure, the chamber door (32) is opened and the substrate support exits the production line.

Claims (9)

1. A method for applying a thin film on a substrate, according to the method - The substrates are located on substrate supports (22), each substrate support (22) is mounted on a carriage (2) and is configured such that they move through the processing chamber (17), and - The substrate support (22) moves sequentially through the processing chamber (17) and is coated within the processing chamber (17) by means of a processing device built into the processing chamber (17), and -The substrate support is in the form of a rotating drum. -And wherein the rotating drums move parallel to the rotation axis of the rotating drum through the processing area of the processing device, and as they pass through the processing chamber (17), they have a constant linear moving speed and rotate at a constant angular velocity. Its features - Each base plate support (22) is accelerated to the required angular velocity by an electric motor (24) in at least one inlet airlock (14), the carriage (2) is stationary, and then continues to rotate; - Each carriage (2) is equipped with a low-voltage motor for rotating the substrate support, the motor being powered by rollers of the conveying system or by the linear guide rails of the individual contact rollers and the carriage (2), the linear guide rails being insulated from the housing of the carriage; and - Select the ratio of the linear moving speed and the angular velocity such that each point on the surface of the rotating drum undergoes at least two complete rotations when passing through the processing area of the processing chamber (17). 2. A production line for applying thin films, which has -Inlet airlock chamber (14), - Buffer chambers (16, 18), and - At least one processing chamber (17) including processing devices, a substrate support (22) located on a carriage (2) and mounted such that they can move through the processing chamber (17). -and has a conveying system, - Each substrate support (22) is in the form of a rotating drum, and each substrate support (22) is mounted coaxially on the carriage (2) in its direction of movement. -The carriage is capable of moving at a constant linear speed. -The rotating drum is able to rotate at a constant angular velocity as it passes through the processing chamber (17). Its features - An electric motor (24) is provided in at least one inlet airlock (14), by means of which the base plate support (22) can be accelerated to the required angular velocity, the carriage (2) is stationary, and the base plate support (22) can continue to rotate thereafter; - Each carriage (2) is equipped with a low-voltage motor for rotating the substrate support, which is powered by the rollers of the conveying system or by the linear guide rails of the individual contact rollers and the carriage (2), the linear guide rails being insulated from the housing of the carriage; - Each point on the surface of the rotating drum undergoes at least two complete rotations as it passes through the processing area of the processing device. 3. The production line according to claim 2, Its features It includes an inlet airlock (14) and an inlet buffer chamber (16), as well as an outlet buffer chamber (18) and an outlet airlock (20). 4. The production line according to claim 2, Its features The slide (2) of the substrate support (22) is suspended above the substrate support. 5. The production line according to claim 2, Its features The slide (2) of the substrate support (22) is in the form of a frame. 6. The production line according to claim 2, Its features The slide (2) of the substrate support (22) is in the form of a transport slide with a linear guide rail, and the linear guide rail is located below the substrate support. 7. The production line according to claim 2, Its features It has at least one rotary drive with a substrate support (22). 8. The production line according to claim 7, Its features The substrate support (22) is equipped with a detachable friction coupling and/or magnetic coupling. 9. The production line according to claim 2, Its features The conveying system is equipped with rollers, and the carriage is equipped with guide rails. The guide rails and rollers work together.