DE102013110891B4 - Device and method for temperature control of substrates - Google Patents

Abstract

Device for controlling the temperature of substrates in a substrate treatment system, in which a substrate can be transported in the longitudinal extent of the substrate treatment system on a substrate transport plane, with• a heat-absorbing coolant arranged on one side of the substrate transport plane,• one arranged between the coolant and the substrate transport plane, transverse to the longitudinal extent of the substrate treatment system in sections , namely a central area and two edge areas, with which the coolant can be at least partially shielded from the substrate transport plane, and• a heating device arranged on the other side of the substrate transport plane, with which the temperature of the substrate can be controlled, characterized in that the shielding means (2 ) is formed separately in the edge areas and adjustable independently of the central area in such a way that the heat permeability of the shielding means (2) is separated and independent in the edge areas g is continuously controllable from the mid-range.

Description

The invention relates to a device for controlling the temperature of substrates in a substrate treatment system, in which a substrate can be transported on a substrate transport path in the longitudinal extent of the substrate treatment system, with a heat-absorbing coolant arranged on one side of the substrate transport path divided into sections transverse to the longitudinal extent of the substrate treatment system, and with a coolant between the coolant and Substrate transport path divided into sections transverse to the longitudinal extent of the substrate treatment system, with which the coolant can be at least partially shielded from the substrate transport path and with a heating device arranged on the other side of the substrate transport path, with which the temperature of the substrate can be controlled.

The invention further relates to a method for controlling the temperature of heated substrates using the device according to the invention.

For an optimal coating, it is necessary that the substrate surfaces to be coated are free of water. The substrates are heated for the purpose of desorption of adhering water, with homogeneous heating to temperatures of 150° C. with a tolerance of +/- 10 K being desirable.

In an already existing coating installation, the substrate heating can and should only be arranged on one side of the substrate, ie there is a one-sided heating device. In order to avoid heat losses through radiation, the substrate is faced on the substrate side facing away from the heating system by an arrangement of shielding plates, which are arranged in front of a coolant, for example a cooling plate. Due to the limited installation space in the existing system and the fact that the heater bushings cannot be arranged arbitrarily, only one-piece heating is possible. Ie the heating device extends transversely to the longitudinal extension of the coating system over the entire width of the system ( 1 ).

In order to be able to achieve homogeneous heating of the substrates with the corresponding homogeneity requirements, it is already known that the heating system can be divided into several separately controllable heating circuits. For example, a center heating circuit is formed directly under the substrate and edge heating circuits are formed next to the substrate. It should be noted that the heating system must be wider than the substrate so that adequate edge temperature control is possible ( 2 ).

The control circuits next to the substrate can also be omitted if it is possible to position the heater very close to the substrate. However, this option is usually ruled out because the heater does not represent a homogeneous surface, but is made up of heating rods that are arranged in a certain grid, e.g. in the case of jacketed tube heating elements. For the distance between the heating rods, certain minimum distances apply from a manufacturing point of view. If the heater is placed too close to the substrate, hotspots form on the substrate in the area of the heating rods, while the substrate in the area between the heating rods remains colder. This means that an inhomogeneous substrate heating is to be expected. Practical experience shows that the heater - substrate - distance should never be smaller than the distance between the heating rod and the heating rod.

Due to the limited installation space and the heating system that can only be implemented as a single part ( 1 ) a homogeneous substrate temperature control is not possible. This can be explained as follows: Assuming that the reflectance of the substrate surface is almost zero and the final temperature of the substrate is significantly lower than that of the heater, which is typically the case for heating processes, the heater radiation that hits the substrate is complete there absorbed. Due to the low substrate temperature (no significant radiation from the substrate) and the low degree of reflection of the substrate surface, hardly any radiant power falls on the areas of the heater in front of the substrate. In contrast, the overhang heater areas have a significant amount of radiation reflected back through the shields in front of the cooling plate, so that the radiation incident on the overhang heater area is significantly higher. Since the same power density is supplied to all points of the heater in a single-circuit heating system, the edge heating areas must be hotter than the central areas due to the additional higher incident radiation. The substrate will therefore become hotter at the edge than in the middle ( 3 ).

To counteract this thermal imbalance, a possible solution could be to remove all shielding in front of the cold plate in the heater overhang area and to cover the cold plate itself with a highly absorbent layer ( 4 ). A “highly absorbent layer” can be used, for example, as in the patent application filed DE 10 2013 101 696 A1 described to be produced. A copper cooling plate, the surface of which has been roughened, for example by blasting with normal corundum, is oxidized in a subsequent thermal treatment.

Under the same assumptions as above, ie the reflectivity of the substrate is almost zero and the substrate temperature is significantly lower than the heater temperature, the thermal radiation from the heater hits the substrate and is completely absorbed there. Due to the low substrate temperature (no significant radiation from the substrate) and the low degree of reflection of the substrate surface, hardly any radiation power falls on the areas of the heater in front of the substrate. Due to the lack of shielding in relation to the areas of the heater in the overhang, no radiation is reflected back to the heater either. The radiation arriving at the cooling plate is absorbed and carried away by the cooling water. Since the same power density is supplied to all points of the heater in a single-circuit heating system and no radiation impinges in any area (edge, middle), the edge heating areas must be just as hot as the middle areas. This means that the substrate will therefore be tempered homogeneously.

However, this structure is problematic if the substrates are provided with a (partially) reflective layer on the side to be heated, since a portion of the radiation (reflected on the substrate) then impinges on the central area of the heater and the heater in the central area becomes hotter than the edge area leaves. This means that the middle of the substrate becomes warmer ( 5 ).

In the DE 10 2009 049 954 A1 describes a device for controlling the temperature of substrates in a substrate treatment system, in which a substrate can be guided past a treatment device in the longitudinal extension of the substrate treatment system in a substrate transport plane within a vacuum chamber. In order to dynamically design a dynamic change in the thermal insulation for controlling the heat transfer in the substrate and in particular to reduce thermal inertia, a heat-absorbing coolant is provided on one side of the substrate transport plane, which in one configuration can be at least partially shielded from the substrate transport plane with an insulating means.

the U.S. 3,956,612 A relates to a modular radiant heater assembly of fast responding radiant heater units comprising a plurality of abutting heater element frame units, the intermediate frame units having open sides and the end frame units having closed outside sides. Means on the front and rear walls of the frame units support a plurality of thin foil radiant heating elements. Equal length link means connect the heating elements within each frame unit and from each of the abutting frame units to its adjacent unit, whereby all heating elements are evenly spaced laterally throughout the module to ensure even heating and eliminate heat streaks at the unit junctions. The radiant heater module is controlled by electronic feedback circuitry with optical temperature sensors, allowing the applied heat to be profiled to compensate for processing anomalies.

In the DE 10 2012 106 325 A1 describes a device and a method for heating and cooling a substrate treatment system and heating and cooling a substrate in the substrate treatment system, in which there is a vacuum chamber in which a transport device for transporting substrates is arranged, with inside the vacuum chamber on one side of the transport device a heating device and a thermal insulating device are arranged. It is based on the object of being able to quickly heat up and actively cool down a substrate in a substrate treatment system and the substrate treatment system itself. This is solved in that the thermal insulation device has a heat transfer path through which heat is transported. For this purpose, the heat transfer path can essentially be designed according to three different principles. In the first principle, the isolation device is designed with additional channels, through which a media flow is achieved both in the isolation device and in the vacuum chamber. In the second principle, the insulating device is modified in a suitable manner in order to form a volume in the insulating device, so that a flow within the insulating device and thus heat dissipation is realized. The third principle embodies heat conduction via mechanical heat-conducting elements. This creates thermal connections between the transport device, the insulating device and the chamber floor or chamber wall.

Finally describes the DE 10 2010 009 794 A1 a method and a corresponding arrangement for coating heated substrates in continuous vacuum coating systems, in which a substrate is moved continuously in a transport direction through a functional process chamber, with a coating particle stream being generated in the process chamber by means of coating sources, by means of which the substrate is coated in this process chamber will. In order to enable coating of substrates in continuous vacuum coating systems, in which the substrate temperature is influenced within the functional process chamber, the substrate is guided past at least one heater within the process chamber, with the substrate temperature, ie the Tempe temperature of the substrate in the transport direction after the heater, by means of a cascade control consisting of a master and a slave controller, in which the substrate is controlled as the controlled system of the master controller and the heater is controlled as the controlled system of the slave controller.

It is now the object of the invention to find a way of being able to heat any substrates with any precoatings homogeneously with a one-sided as well as a single-circuit heating system, with the temperature control being to take place fully automatically.

The object is achieved in that the shielding means is designed separately in the edge areas and adjustable independently of the central area in such a way that the heat permeability of the shielding means in the edge areas can be separately and continuously controlled independently of the central area. The shielding means are installed in front of the cooling plate instead of the previously permanently installed shielding in the protruding area of the heaters, i.e. in the edge areas of the substrate transport plane, in order to be able to influence the thermal transmission of the heat radiated by the heaters as required. The cooling plate itself is provided with a highly absorbent layer in order to dissipate excess heat, which would lead to a further increase in the temperature of the substrate due to the thermal inertia of the entire system.

In order to control the radiated heat of the heater in a targeted manner, the shielding means is formed from at least one adjustable reflector element in the edge areas of the substrate transport plane, so that the radiated heat of the single-circuit heater can be partly absorbed by the cooling plate and partly reflected back to the heater by the adjustable reflector element .

In one embodiment of the invention, in which the shielding means is formed from at least one adjustable reflector element, the adjustable reflector element is pivotable about an axis of rotation running parallel to the substrate transport plane.

In a further embodiment of the invention, the adjustable reflector element is arranged to be displaceable parallel to the substrate transport plane.

In a further embodiment of the invention, the adjustable reflector element is concave, extends partially around a tubular coolant and parallel to the substrate transport plane and is arranged rotatably.

• - Die Reflektorelemente sind vollständig geschlossen, d.h. die maximale Fläche der Reflektorelemente ist in Richtung des Heizers gerichtet, so dass die auftreffende Wärmestrahlung zurück in Richtung Heizer reflektiert wird. Die Reflektorelemente wirken analog zu den fest installierten Abschirmmitteln in der Mitte der Substrattransportebene.
• - Die Reflektorelemente sind teilweise geöffnet, d.h. nur ein Teil der Fläche der Reflektorelemente ist in Richtung Heizer gerichtet, so dass ein dem Öffnungsgrad bzw. der in Richtung Heizer gerichteten Reflexionsfläche entsprechender Anteil der Wärmestrahlung des Heizers zur Kühlplatte hindurchgelassen und dort absorbiert wird und der Rest der Wärmestrahlung des Heizers wieder zurück in Richtung Heizer reflektiert wird.
• - Sind die Reflektorelemente komplett geöffnet bzw. der Anteil der Reflexionsfläche in Richtung Heizer null, so wird die gesamte Wärmestrahlung des Heizers zur Kühlplatte durchgelassen, dort absorbiert und keine Wärmestrahlung in Richtung Heizer reflektiert.

Irrespective of the embodiment of the reflector elements, the controllable heat transmission is based on the principle that the heat radiation is reflected to different extents by adjusting the reflector elements either by pivoting about an axis of rotation, displacement in a plane or rotation about an axis of rotation. The following states can be set:

• - The reflector elements are completely closed, ie the maximum area of the reflector elements is directed in the direction of the heater, so that the incident thermal radiation is reflected back in the direction of the heater. The reflector elements act in the same way as the permanently installed shielding means in the middle of the substrate transport plane.
• - The reflector elements are partially open, i.e. only part of the surface of the reflector elements is directed in the direction of the heater, so that a proportion of the heat radiation from the heater that corresponds to the degree of opening or the reflection surface directed in the direction of the heater is let through to the cooling plate and absorbed there, and the rest of the heat radiation from the heater is reflected back towards the heater.
• - If the reflector elements are completely open or the proportion of the reflection surface in the direction of the heater is zero, the entire heat radiation from the heater is let through to the cooling plate, where it is absorbed and no heat radiation is reflected in the direction of the heater.

Advantageously, the adjustable reflector elements consist of a shielding plate that reflects the infrared range and has a reflectance greater than 0.8. If the degree of reflection is very high, the shielding plates can be made in one layer, e.g. this is the case with electropolished plates. If the reflector elements have a comparable degree of absorption or reflection as the shielding means installed in the middle area of the substrate transport plane in front of the cooling plate, then the adjustable reflector elements arranged in the edge areas should each comprise an arrangement of shielding plates, the number of plates of which is approximately the same as the number of plates of the shielding means arranged in the middle area .

In the device according to the invention, the heating device is designed in one piece transversely to the longitudinal extent of the substrate treatment system, the width of the heating device being greater than the width of the substrate to be treated.

At least two pyrometers with a Mes axis are arranged transversely to the substrate transport plane, with at least one pyrometer directed towards the central area of the substrate and at least one pyrometer towards an edge area of the substrate, the pyrometers being part of a control loop.

In terms of the method, the object of the invention is achieved in that at the end of a heating process, the substrate temperature is measured at at least one point in the central area and at at least one point in an edge area, and the temperature is measured via an adjustable heating output of the heating device and an adjustable heat permeability in the edge areas using adjustable reflector elements of the following substrate is controlled.

• - die Temperatur T_Mitte, ist wird im Mittenbereich gemessen,
• - aus der Temperatur T_Mitte, ist und einer Soll-Substrattemperatur T_{substrat, soll} als Führungsgröße wird für einen ersten Regelkreis eine erste Regelabweichung berechnet,
• - die erste Regelabweichung wird einem ersten Regler zugeführt und die Heizleistung der Heizeinrichtung eingestellt,
• - die Temperatur T_{Rand, ist} wird im Randbereich gemessen,
• - aus der Temperatur T_Rand, ist und der Temperatur T_Mitte, ist als Führungsgröße wird für einen zweiten Regelkreis eine zweite Regelabweichung berechnet,
• - die zweite Regelabweichung wird einem zweiten Regler zugeführt und die Wärmedurchlässigkeit der verstellbaren Reflektorelemente eingestellt.

The regulation of the temperature in order to bring the substrates to a homogeneous temperature includes the following process steps:

• - the temperature T _middle , is measured in the middle area,
• - a first control deviation is calculated from the temperature T _middle , actual and a setpoint substrate temperature T _{substrate , setpoint} as a reference variable for a first control loop,
• - the first control deviation is fed to a first controller and the heat output of the heating device is set,
• - the temperature T _{edge is} measured in the edge area,
• - a second control deviation is calculated from the temperature T _edge, actual and the temperature T _middle , actual as a reference variable for a second control loop,
• - The second control deviation is supplied to a second controller and the thermal transmittance of the adjustable reflector elements is set.

The adjustable reflector elements are adjusted depending on the control deviation between T _middle ,actual and T _{edge ,} actual in such a way that they fully reflect the heat, partially reflect the heat or allow the heat to pass completely.

The position of the adjustable reflector elements in the edge areas can be determined by a drive arranged outside the process area, which acts on the individual reflector elements, e.g. by means of a rotary feedthrough. The pivotable, displaceable or rotatable reflector elements can be connected, for example, by a chain and gear system. Furthermore, it is also possible to control the adjustable reflector elements on both sides of the substrate transport path both together and each side separately, i.e. to provide two independent drives for both sides.

The invention will be explained in more detail below using an exemplary embodiment.

• 1 Ein einteilig ausführbares Beheizungssystem durch Bauraumbegrenzung;
• 2 Eine Substrattemperierung mittels idealem Beheizungssystem, welches in getrennt regelbare Heizkreise aufgeteilt ist;
• 3 Eine inhomogene Substrattemperierung durch ein einkreisiges Beheizungssystem;
• 4 Eine homogene Substrattemperierung mit einem einkreisigen Beheizungssystem und hochabsorbierender Kühlplatte im Randbereich;
• 5 Eine inhomogene Substrattemperierung mit einem einkreisigen Beheizungssystem trotz hochabsorbierender Kühlplatte im Randbereich; Die Substratunterseite ist gut reflektierend;
• 6 Homogenisierung der Temperatur eines gut reflektierenden Substrates durch klappbaren Reflektor im Randbereich;
• 7 Weitere Ausführungsformen für Abschirmmittel mit steuerbarer Durchlässigkeit für Wärmestrahlung in den Randbereichen der Substrattransportbahn;
• 8 Aufbau einer vollautomatischen Regelung des Substrattemperierungssystems.

Show the accompanying drawings

• 1 A one-piece executable heating system by space limitation;
• 2 A substrate temperature control using an ideal heating system, which is divided into separately controllable heating circuits;
• 3 An inhomogeneous substrate temperature control by a single-circuit heating system;
• 4 A homogeneous substrate temperature control with a single-circuit heating system and a highly absorbent cooling plate in the edge area;
• 5 An inhomogeneous substrate temperature control with a single-circuit heating system despite a highly absorbent cooling plate in the edge area; The underside of the substrate is highly reflective;
• 6 Homogenization of the temperature of a well reflecting substrate by means of a foldable reflector in the edge area;
• 7 Further embodiments for shielding means with controllable permeability for thermal radiation in the edge areas of the substrate transport path;
• 8th Construction of a fully automatic control of the substrate temperature control system.

6 shows an embodiment of the device according to the invention for controlling the temperature of substrates 3, in which adjustable shielding means in the form of reflector elements 7 are arranged in the edge regions of the substrate transport path. The position of the reflector elements 7, which can be pivoted about an axis of rotation 8 parallel to the substrate transport path, can be adjusted in such a way that the thermal radiation emitted by the single-circuit heater 4 in the direction of the substrate 3 and shielding means is reflected or passed through and absorbed by a coolant 1 such that a homogeneous temperature over the entire surface of the substrate 3 to be treated is adjusted.

In a further embodiment of the device according to the invention ( 7a) are the shielding in the edge areas of the substrate transport path as parallel to the substrate transport path movable reflector elements 9 formed, so that by the position, ie the size of the directed towards the heating device 4 reflection surface, the proportion of reflected or transmitted Thermal radiation of the heating device 4 is adjusted in order to realize a homogeneous temperature over the entire surface of the substrate 3 to be treated.

7b shows a further embodiment of the device according to the invention, wherein the shielding means are designed as concave reflector elements 10 in the edge regions of the substrate transport path. The reflector elements 10 are arranged in sections parallel to the substrate transport path and rotatable about a tubular coolant 11 . Depending on the size of the reflection surface directed in the direction of heater 4, a corresponding proportion of the thermal radiation from the heating device 4 is let through to the cooling plate 11 and absorbed there, and the rest of the thermal radiation from the heating device 4 is reflected back in the direction of the heater 4, so that a homogeneous temperature can be realized over the entire substrate surface to be treated. In this embodiment, the coolant 1 in the form of a cooling plate is arranged only in the center of the substrate transport path and is designed as a tubular coolant 11 in the edge regions of the substrate transport path.

In terms of the method, the positioning of the pivoting, sliding or rotating reflector elements and thus the influencing of the temperature homogeneity of the substrate can be carried out manually by specifying a degree of opening.

However, it is more convenient to adjust both the heater output and the setting or positioning of the adjustable reflector elements via a fully automatic control system in such a way that the exact substrate temperature (by adjusting the heater output) and the required temperature homogeneity (by positioning the adjustable reflector elements) are achieved. In one embodiment of the method according to the invention, in the simplest case, two measuring devices are used to record the substrate temperature (eg pyrometers or temperature sensors) in order to determine the temperature level in the middle of the substrate and the current temperature of the edges. 8th shows the associated control scheme. If the measured substrate temperature in the middle is lower than the target value, for example, then the heater power P _heater must be increased accordingly. If the substrate temperatures at the edge are higher than in the middle of the substrate, for example, then the degree of opening of the adjustable reflector elements 7, 9, 10 must be increased. As a result, less radiation is reflected back onto the heating area in the overhang, as a result of which its temperature and consequently also the edge temperature of the substrate drop. A homogenization of the substrate temperature is achieved.

the inside 8th The algorithm shown for adjusting the edge temperature provides that the edge temperature is not immediately brought to the temperature setpoint T _{substrate,setpoint} , but rather that the edges always follow the current ACTUAL temperature value of the substrate center T _{middle,actual} . This ensures that there are no excessively large temperature differences between the edge and the center and, as a result, no impermissibly high stresses and deformations of the substrate occur.

Reference List

1

coolant

2

shielding means

3

substrate

4

heater

5

temperature of the heater

6

substrate temperature

7

reflector element

8th

axis of rotation

9

moveable reflector element

10

concave reflector element

11

tubular coolant

x

Location transverse to the longitudinal extent of the substrate treatment system

T

temperature

Claims (14)

Device for controlling the temperature of substrates in a substrate treatment system, in which a substrate can be transported in the longitudinal extent of the substrate treatment system on a substrate transport plane, with • a heat-absorbing coolant arranged on one side of the substrate transport plane, • one arranged between the coolant and the substrate transport plane, transverse to the longitudinal extent of the substrate treatment system in sections , namely a central area and two edge areas, with which the coolant can be at least partially shielded from the substrate transport plane, and • a heating device arranged on the other side of the substrate transport plane, with which the temperature of the substrate can be controlled, characterized in that the shielding means (2 ) is formed separately in the edge areas and adjustable independently of the central area in such a way that the heat permeability of the shielding means (2) in the edge areas is separated and independent can be steplessly controlled from the mid-range. setup after claim 1 , characterized in that the shielding means (2) is formed from at least one adjustable reflector element (7, 9, 10) in each edge area. setup after claim 2 , characterized in that the adjustable reflector element (7) is pivotable about an axis of rotation (8) running parallel to the substrate transport plane. setup after claim 2 , characterized in that the adjustable reflector element (9) is arranged displaceably parallel to the substrate transport plane. setup after claim 2 , characterized in that the adjustable reflector element (10) is concave, extends partially around a tubular coolant (11) and parallel to the substrate transport plane and is rotatably arranged. Setup according to one of claims 2 until 5 , characterized in that the adjustable reflector element (7, 9, 10) is formed from a metal sheet which reflects the infrared range and has a degree of reflection of greater than 0.8. setup after claim 6 , characterized in that the adjustable reflector elements (7, 9, 10) arranged in the edge areas each comprise an arrangement of shielding plates, the number of plates of which is approximately the same as the number of plates of the shielding means (2) arranged in the central area. setup after claim 1 , characterized in that the heating device (4) is formed in one piece transversely to the longitudinal extent of the substrate treatment system. setup after claim 8 , characterized in that the width of the heating device (4) is greater than the width of the substrate (3) to be treated. Device according to one of the preceding claims, characterized in that at least two pyrometers are arranged with a measuring axis transverse to the substrate transport plane, with at least one pyrometer being directed towards the central region of the substrate (3) and at least one pyrometer towards an edge region of the substrate (3), where the pyrometers are part of a control loop. Method for controlling the temperature of heated substrates (3) in substrate treatment systems, which are moved through a process area on a substrate transport level past a heating device (4), heat-absorbing coolants (1) being provided on the side of the substrate (3) facing away from the heating device (4) and shielding means (2,7,9,10) subdivided into sections, namely a central area and two edge areas, are arranged transversely to the longitudinal extension of the substrate treatment system, characterized in that at the end of a heating process the substrate temperatures at at least one point in the central area and at at least one Point measured in an edge area and the temperature of the following substrate (3) is regulated via an adjustable heat output of the heating device (4) and an adjustable heat permeability in the edge areas by adjustable reflector elements (7,9,10). Process for controlling the temperature of heated substrates (3). claim 11 , characterized in that - that the temperature T _middle ,actual is measured in the center area, - that a first control deviation is calculated from the temperature T _middle ,actual and a setpoint substrate temperature T _{substrate, setpoint} as a reference variable for a first control loop, - that the first control deviation is fed to a first controller and the heating power P _heater of the heating device (4) is set, - the temperature T _edge, actual is measured in the edge area, - the temperature T _edge, actual and the temperature T _middle ,actual as reference variable a second control deviation is calculated for a second control circuit, - that the second control deviation is supplied to a second controller and the thermal transmittance of the adjustable reflector elements (7,9,10) is adjusted. Process for controlling the temperature of heated substrates (3). claim 11 or 12 , characterized in that the adjustable reflector elements (7,9,10) are adjusted as a function of the control deviation between T _center and T _edge so that they fully reflect the heat, partially reflect the heat or fully transmit the heat . Method for controlling the temperature of heated substrates (3) according to one of Claims 11 until 13 , characterized in that the position of the adjustable reflector elements (7, 9, 10) in the edge areas is set via at least one drive arranged outside of the process area.

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