TREATMENT OF A SUBSTRATE

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to an apparatus for heat treatment of a substrate, and a method for heat treatment of a substrate. Embodiments of the present disclosure particularly relate to an apparatus for heat treatment of a substrate for reducing damage by residual heat in roll-to-roll (R2R) deposition systems.

BACKGROUND

[0001] Processing of flexible substrates, such as plastic films or foils, is in high demand in the packaging industry, semiconductor industries and other industries. Processing may consist of coating of a flexible substrate with a material, such as a metal, a semiconductor and a dielectric material, etching and other processing actions conducted on a substrate for the respective applications. Systems performing this task generally include a coating drum, e.g. a cylindrical roller, coupled to a processing system with a roller assembly for transporting the substrate, and on which at least a portion of the substrate is coated. Systems may alternatively include a free span between rolls or rollers, where at least a portion of the substrate is processed. Roll-to-roll (R2R) coating systems can provide a high throughput.

[0002] Therein, a coating process such as a CVD process, a PVD process, an OPV deposition process or an OLED deposition process, particularly a sputter process, can be utilized for depositing thin layers onto flexible substrates. Roll-to-roll deposition systems are understood in that a flexible substrate of a considerable length, such as one kilometre or more, is uncoiled from a storage spool, coated with a stack of thin layer(s), and recoiled again on a wind-up spool. In the manufacture of thin film batteries as well as in the display industry and the photovoltaic (PV) industry, the demand for roll-to-roll deposition systems is also increasing. For example, touch panel elements, flexible displays, and flexible PV modules result in an increasing demand for depositing suitable layers in R2R-coaters.

[0003] A challenge is posed in the heat treatment of a flexible substrate in an R2R coater. Specifically, when substrate heaters are used in a heat treatment process, films with a low heat capacity can be damaged when the film transport speed is altered. When film transport is slowed or stopped, residual heat from the heaters causes the material to overheat, which can damage or destroy the film. This situation can also occur during power outages, or emergency shutdowns of the R2R coater, as the heaters will remain heated and continue to radiate heat towards the substrate. [0002] In view of the above, solutions for reducing residual heat exposure of a flexible substrate and methods for operation of such devices that overcome at least some of the problems in the art are sought.

SUMMARY

[0003] In light of the above, an apparatus for heat treatment of a substrate, an apparatus for transporting a flexible substrate, and a method for heat treating a substrate are provided. Further aspects, benefits, and features of the present disclosure are apparent from the claims, the description, and the accompanying drawings.

According to a first aspect of the present disclosure, an apparatus for heat treatment of a substrate is provided. The apparatus comprises at least one heating element, and at least one shield, wherein the at least one shield is moveable between a first position and a second position between the substrate and the at least one heating element, and the at least one shield comprises at least one reflective surface.

According to a further aspect of the present disclosure, an apparatus for transporting a flexible substrate is provided. The apparatus comprises the apparatus for heat treatment of a substrate according to the first aspect above, a substrate transport controller, and a sensor, wherein the substrate is transported past the apparatus for heat treatment of a substrate. According to a further aspect of the present disclosure, a method for heat treatment of a substrate is provided. The method comprises emitting radiation towards the substrate, and temporarily reflecting the radiation to restrict the heating of the substrate.

[0004] Embodiments are also directed at apparatuses for carrying out the disclosed method and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIG. la shows a cross sectional side view of a heat treatment apparatus, with the at least one shield in the first position, according to embodiments described herein; FIG. lb shows a cross sectional side view of a heat treatment apparatus with the at least one shield in the second position, according to embodiments described herein;

FIG. 2 shows a schematic front view of a heat treatment apparatus according to embodiments described herein; FIG. 3a shows a cross sectional side view of a heat treatment apparatus, with the at least one shield in the first position, according to further embodiments described herein; FIG. 3b shows a cross sectional side view of a heat treatment apparatus, with the at least one shield in the second position, according to further embodiments described herein;

FIG. 4 shows a schematic front view of a heat treatment apparatus according to embodiments described herein;

FIG. 5 shows a cross sectional side view of a heat treatment apparatus according to embodiments described herein;

FIG. 6 shows a schematic side view of a substrate transport apparatus according to embodiments described herein; and FIG. 7 shows a flowchart for a method for operating a heat treatment apparatus according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0006] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0004] During the heat treatment of a flexible substrate in an R2R coater, specifically, when substrate heaters are used in a heat treatment process, films with a low heat capacity can be damaged when the film transport speed is altered. When film transport is slowed or stopped, residual heat from the heaters causes the material to overheat, which can damage or destroy the film. This situation can also occur during power outages, or emergency shutdowns of the R2R coater, as the heaters will remain heated and continue to radiate heat towards the substrate. One advantage of the present invention is that radiant heat from the heaters is restricted, reflected or blocked from radiating the substrate, which prevents the substrate from overheating and subsequently prevents damage or destruction of the substrate.

[0007] It is noted that a flexible substrate as used within the embodiments described herein is typically bendable. The term “flexible substrate” or “substrate” may be synonymously used with the term“foil” or the term“web”. In particular, it is to be understood that embodiments of the heat treatment apparatus described herein can be utilized for heat treatment of any kind of flexible substrate. For example, a flexible substrate as described herein may include materials like PET, HC-PET, PE, PI, PU, TaC, OPP, CPP, one or more metals, paper, thin glass, combinations thereof, and already coated substrates like Hard Coated PET (e.g. HC-PET, HC-TaC) and the like.

[0008] According to a first aspect of the present disclosure, an apparatus for heat treatment of a substrate is provided. Figs la and lb show cross sectional side views of heat treatment apparatus 100, and Fig. 2 shows a schematic front view of heat treatment apparatus 100.

[0009] Heat treatment apparatus 100 includes at least one heating element 102 and at least one shield 103, wherein the shield 103 is moveable between a first position and a second position between the substrate 101 and the at least one heating element 102, and the at least one shield 103 includes at least one reflective surface 104. The at least one shield 103 is shown in the first position in Fig. la, and in the second position in Fig. lb. When the at least one shield 103 is in the first position, the at least one shield 103 may be positioned away from the position between the substrate 101 and the at least one heating element 102, and radiation 105 from the at least one heating element 102 may be permitted to heat the substrate 101. When the at least one shield 103 is in the second position, the at least one shield 103 may be positioned between the substrate 101 and the at least one heating element 102, and radiation 105 from the at least one heating element 102 may be blocked, reflected or restricted from heating the substrate 101.

[0010] Since the at least one shield 103 is movable from the first position to the second position between the at least one heating element 102 and the substrate 101, the heat treatment apparatus 100 may be operated to prevent residual heat from undesirably heating the substrate 101, which prevents damage or destruction of the substrate 101.

[0011] The at least one heating element 102 may be any type of heating element suitable for applying heat to the substrate 101. Particularly, the heating element 102 may be an electric heater. The electric heater may include an electrically-heated bar element. The at least one heating element 102 may heat the substrate 101 primarily through infrared radiation 105. The at least one heating element 102 may include a single linear emitter, multiple linear emitters, a single coil emitter, or multiple coil emitters.

[0012] The substrate 101 may be transported past the at least one heating element 102, the substrate 101 and may be heated by infrared radiation 105. In a normal operating state, the substrate 101 may be transported at a nominal substrate transport speed. At the nominal substrate transport speed, the at least one heating element 102 may be active. The radiant heat being supplied to the substrate 101 at the nominal substrate transport speed may be sufficient to provide the desired heat treatment to the substrate 101, but may not be sufficient to damage or destroy the substrate 101.

[0013] Certain conditions may occur wherein the substrate transport speed is reduced or stopped completely. For example, the R2R coater may be slowed for a particular coating operation, the R2R coater may experience equipment failure which causes an emergency stop, or the R2R coater may experience a power outage. In the case where the substrate transport speed is reduced below the nominal substrate transport speed, such as for material handling or coil exchange, the at least one heating element 102 may be deactivated. However, even when in a deactivated state, the at least one heating element 102 retains residual heat, and may continue to emit infrared radiation 105. In the case where the substrate transport speed is stopped or below the nominal substrate transport speed, this residual heat and continued emission of infrared radiation 105 may damage or destroy the substrate 101.

[0014] In order to prevent damage or destruction of the substrate 101 in a condition of reduced substrate transport speed, the heat treatment apparatus 100 includes at least one shield 103. The at least one shield 103 may block, reflect or restrict radiation 105 from the at least one heating element 102 from heating the substrate 101 under certain conditions. The at least one shield 103 may include a metal, a ceramic, or a thermal-resistant polymer.

[0015] The at least one shield 103 further includes at least one reflective surface 104. Particularly, the at least one shield 103 may have a reflective surface 104 which faces the at least one heating element 102. The at least one reflective surface 104 may reflect radiation 105 from the at least one heating element 102, having the benefit of reflecting radiation 105 to block or restrict the heating of the substrate 101 by the at least one heating element 102 when the at least one shield 103 is in the second position. The at least one reflective surface 104 may have a further effect of preventing the at least one shield 103 from absorbing radiation 105 from the at least one heating element 102, so that the at least one shield 103 itself does not become heated. This effect is advantageous, as when the at least one shield 103 is positioned between the at least one heating element 102 and the substrate 101, the at least one shield 103 may undesirably radiate heat to the substrate 101 if the at least one shield 103 has been significantly heated by the at least one heating element 102.

[0016] According to some embodiments, which can be combined with other embodiments described herein, the at least one shield 103 may be moveable between the first position and the second position by rotation 106. For example, the at least one shield 103 may be positioned behind the at least one heating element 102 in the first position so as to allow radiation 105 from the at least one heating element 102 to heat the substrate 101. The at least one shield 103 may then be rotated approximately 180° around the at least one heating element 102 to the second position, such that the at least one shield 103 may be positioned between the at least one heating element 102 and the substrate 101. Alternatively, the at least one shield 103 may be positioned beside the heating element 102 in the first position, and may then be rotated approximately 90° around the at least one heating element 102 to the second position.

[0017] In the embodiments wherein the at least one shield 103 may be positioned behind the at least one heating element 102 in the first position, the reflective surface 104 may be the surface facing the at least one heating element 102 when the at least one shield 103 is in the first position. The radiation 105 which is radiated from the at least one heating element 102 in a direction away from the substrate 101 may be reflected by the at least one reflective surface 104 of the at least one shield 103, such that the efficiency of the at least one heating element 102 is improved.

[0018] The at least one shield 103 may be mounted on rotatable bearings 111. The at least one shield 103 may include axles 110 disposed along the rotation axis of the at least one shield 103. At least one of the axles 110 may have a hollow construction, such that electrical cables for supplying electricity to the at least one heating element 102 may pass through to allow the at least one shield 103 to rotate freely without contacting or becoming tangled with the electrical cables.

[0019] The at least one heating element 102 may be mounted on the at least one shield 103. In this arrangement, the at least one heating element 102 may be moveable, and the movement of the at least one heating element 102 may be coupled with that of the at least one shield 103. Alternatively, the at least one heating element 102 may be mounted decoupled from the at least one shield 103. In this arrangement, the at least one heating element 102 may remain in a fixed position and may not move with the at least one shield 103.

[0020] According to some embodiments, which may be combined with other embodiments described herein, the at least one shield 103 of heat treatment apparatus 100 may include a partial tube. The at least one shield 103 including a partial tube may partially surround the at least one heating element 102. The partial tube may have an arc- shaped cross section. The arc-shaped cross section may have a central angle in the range of 30° to 270°, particularly 90° to 180°. More particularly, the arc-shaped cross section may have a central angle of 180°.

[0021] According to some embodiments, which may be combined with other embodiments described herein, the at least one reflective surface 104 of the at least one shield 103 may be the inner surface of the partial tube.

[0022] The arc-shaped cross section of the partial tube may be a circular arc. In this case, the center of the circular arc may lie on a rotational axis of the at least one shield 103. When the heat treatment apparatus 100 includes multiple shields 103, a circular arc shape concentric with the rotational axis of the shield 103 has the benefit of allowing for the shields 103 to be positioned close together without the shields 103 contacting each other during rotation.

[0023] The arc-shaped cross section of the partial tube may be a parabolic arc. A parabolic arc has the advantage of reflecting radiation 105 from a point source (e.g. in the case where the at least one heating element 102 is a single linear emitter) in a direction normal to the substrate 101. Further, the parabolic arc may be positioned such that the focal point of the parabolic arc lies on the rotational axis of the at least one shield 103, which allows for precise positional control of the reflected radiation.

[0024] According to some embodiments, which may be combined with other embodiments described herein, heat treatment apparatus 200 may further include at least one counterweight 205 which may be attached to the at least one shield 203. Fig. 3a and 3b show cross sectional side views of the heat treatment apparatus 200, where the at least one shield 203 with at least one counterweight 205 is in the first position and the second position, respectively. Fig. 4 shows a schematic front view of the heat treatment apparatus 200. The at least one counterweight 205 has the benefit of allowing the at least one shield 203 to return to a neutral position in the event of, for example, an emergency shutdown, or an interruption of power to the heat treatment apparatus.

[0025] The neutral position of the at least one shield 203 with at least one counterweight 205 attached may substantially correspond to the second position, wherein the radiation 105 from the at least one heating element 102 may be blocked or restricted from heating the substrate 101. Such an arrangement may prevent the substrate 101 from being damaged or destroyed in the event of an emergency shutdown or an interruption of power, where the substrate transport is stopped and the at least one heating element 102 continues to radiate residual heat.

[0026] The at least one counterweight 205 may be integrated into the at least one shield 203. For example, the at least one counterweight 205 may include a weighted element made from a dense material attached to the at least one shield 203. The weighted element may be positioned on the at least one shield 203 such that when the at least one shield 203 is in the first position, the weighted element may be in an elevated position compared to when the at least one shield 203 is in the second position. [0027] According to some embodiments, which may be combined with other embodiments described herein, an insulating layer 306 may be provided over at least one surface of the at least one shield 303. Fig. 5 shows a cross sectional side view of a heat treatment apparatus 300 including at least one shield 303 with an insulating layer 306 provided thereon, wherein the at least one shield 303 is in the second position.

[0028] The at least one surface of the at least one shield 303 may be the surface opposite the at least one reflective surface 304 of the at least one shield 303, and the at least one surface may be the surface facing the substrate 101 when the at least one shield 303 is in the second position. Depending on the proportion of radiation reflected by the at least one reflective surface 304, the at least one shield 303 may be heated by the at least one heating element 102. A heated shield may radiate heat towards the substrate 101 when the at least one shield 303 is in the second position. Providing an insulating layer 306 over the surface facing the substrate 101 has the benefit of preventing heat radiation from the at least one shield 303 to the substrate 101 when the at least one shield 303 is in the second position. The insulating layer 306 may include a thermal barrier coating, particularly a ceramic thermal barrier coating.

[0029] According to some embodiments, which may be combined with other embodiments described herein, the heat treatment apparatus 100, 200, 300 may further include at least one actuator for moving the at least one shield 103, 203, 303 between the first position and the second position. The actuator may be a linear actuator, for example, a pneumatic cylinder, or the actuator may be a rotary actuator, for example, an electric motor.

[0030] It may be preferable that the actuator has a non-energized state which has no residual braking effect. The term“no residual braking effect” means that when the actuator is not activated, the actuator can be moved freely without applying significant load. If the actuator exhibits no residual braking effect, a counterweighted shield may freely return to the neutral second position in the event of an emergency stop or an interruption of power. [0031] According to some embodiments, which may be combined with other embodiments described herein, the at least one actuator may be at least one of the group including a pneumatic actuator, an electric actuator and a hydraulic actuator.

[0032] According to a further aspect of the present disclosure, an apparatus for transporting a flexible substrate 500 is provided. Fig. 6 shows a schematic side view of a transport apparatus 500. The transport apparatus 500 includes the apparatus for heat treatment of a substrate 100, 200, 300 according to aspects of the present invention, a substrate transport controller 501 and at least one sensor 502, wherein the substrate 101 is transported past the apparatus for heat treatment of the substrate 100, 200, 300.

[0033] The transport apparatus 500 may include a reel-to-reel (R2R) substrate transport apparatus, wherein a substrate 101 may be provided on a loading reel 510 and the substrate 101 may be transported to an unloading reel 511. The transport apparatus may include rollers 512 upon which the flexible substrate 101 may be transported. The transport apparatus 500 may include a substrate transport apparatus for a deposition system, wherein the flexible substrate 101 may be coated with one or more layers of material by at least one deposition apparatus provided therein.

[0034] The transport apparatus 500 includes the apparatus for heat treatment of a substrate 100, 200, 300 according to aspects of the present invention. The heat treatment apparatus 100, 200, 300 may perform a heat treatment process on the substrate. The heat treatment apparatus 100, 200, 300 may be positioned such that the substrate 101 passes the heat treatment apparatus 100, 200, 300 as the substrate 101 is transported. The distance between the heat treatment apparatus 100, 200, 300 and the substrate 101 may be sufficiently small such that the at least one heating element of the heat treatment apparatus 100, 200, 300 can effectively heat the substrate 101, and may be sufficiently large such that the at least one shield of the heat treatment apparatus 100, 200, 300 may be moved from the first position to the second position between the substrate 101 and the at least one heating element without coming into contact with the substrate 101.

[0035] As exemplarily shown in Fig. 6, the apparatus for heat treatment of the substrate 100, 200, 300 may include four heating elements and four shields. However, the apparatus for heat treatment of the substrate 100, 200, 300 may include any number of heating elements and shields. For example, the apparatus for heat treatment of a substrate 100, 200, 300 may include one heating element and one shield, six heating elements and six shields, or ten heating elements and ten shields. Further, the number of shields and number of heating elements may be different. For example, the apparatus for heat treatment of a substrate 100, 200, 300 may include four heating elements and two shields, wherein each of the two shields may block, restrict or reflect radiation from two heating elements.

[0036] The transport apparatus 500 further includes a substrate transport controller 501. The substrate transport controller 501 may be electrically coupled with components of the transport apparatus 500, including the at least one sensor 502. The substrate transport controller 501 may be electrically coupled to further components of the transport apparatus 500, such as the heat treatment apparatus 100, 200, 300, the at least one actuator, or user operated controls. The substrate transport controller 501 may further be electrically coupled to another controller or system of controllers, wherein such controllers are responsible for controlling other aspects of a processing system. [0037] Substrate transport controller 501 may include a CPU, a memory and input and output device in communication with components included within the substrate transport controller 501 and/or with components external to the substrate transport controller 501. The input and output device may include at least one of a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), and a pulse width modulator (PWM). [0038] The transport apparatus 500 includes at least one sensor 502. The at least one sensor 502 may be electrically coupled to the substrate transport controller 501, and may detect one or more attributes of the transport apparatus 500, the substrate 101 or the heat treatment apparatus 100, 200, 300.

[0039] According to some embodiments, which may be combined with other embodiments described herein, the at least one sensor 502 may include a substrate velocity sensor configured for measuring the transport velocity of the substrate. The substrate velocity sensor may be, for example, a rotational velocity sensor attached to a component of the transport apparatus 500, such as loading reel 510, unloading reel 511, roller 512 or a motor. The substrate velocity sensor may alternatively be an optical velocity sensor. The substrate velocity sensor may be electrically coupled to the substrate transport controller 501.

[0040] The substrate velocity sensor may provide the substrate transport controller 501 with a measurement of the substrate transport velocity. The substrate transport controller 501 may then control the transport apparatus 500, particularly the at least one shield and/or the at least one heating element, so as to control the heat radiated to the substrate 101. For example, in the case where the substrate transport velocity is reduced below a first predetermined threshold, the at least one heating element may be deactivated. In the case when the substrate transport velocity is reduced below a second predetermined threshold, the at least one shield may be moved from the first position to the second position to reflect radiation. Controlling the at least one shield and/or the at least one heating element based on a signal from the substrate velocity sensor has the benefit of allowing the transport apparatus 500 to prevent damage or destruction of the substrate 101 by controlling the amount of heat radiation applied to the substrate 101.

[0041] According to some embodiments, which may be combined with other embodiments described herein, the at least one sensor 502 may include a temperature sensor configured for measuring the surface temperature of the substrate 101. The temperature sensor may be positioned upstream of the heat treatment apparatus 100, 200, 300 to measure the surface temperature of the substrate 101 prior to heat treatment. Alternatively, the temperature sensor may be positioned downstream of the heat treatment apparatus 100, 200, 300 to measure the surface temperature of the substrate 101 after heat treatment. The temperature sensor may be, for example, an infrared pyrometer. The temperature sensor may be electrically coupled to the substrate transport controller 501.

[0042] The temperature sensor may provide the substrate transport controller 501 with a measurement of the surface temperature of the substrate 101. The substrate transport controller 501 may then control the transport apparatus 500, particularly the at least one shield and/or the at least one heating element, so as to control the heat radiated to the substrate 101. For example, in the case where the upstream surface temperature of the substrate 101 is above a first predetermined value, the at least one heating element may be deactivated. In the case where the upstream surface temperature of the substrate 101 is above a second predetermined value, the at least one shield may be moved from the first position to the second position to reflect radiation. Similarly, the same operations may be performed in the case where the downstream surface temperature of the substrate 101 is above a first predetermined value or a second predetermined value, respectively.

[0043] According to a further aspect of the present disclosure, a method for heat treatment of a substrate 600 is provided. The method includes emitting radiation towards the substrate, and temporarily reflecting the radiation.

[0044] Fig. 7 shows a flowchart of the method for heat treatment of a substrate 600. The method, beginning at start 601, includes emitting radiation towards the substrate in block 602 and temporarily reflecting the radiation in block 603. The method concludes at end 604.

[0045] Emitting radiation towards the substrate in block 602 may involve operating at least one heating element with the at least one shield positioned in the first position. The at least one shield may be positioned away from the position between the at least one heating element and the substrate, and subsequently the at least one shield may not block, restrict or reflect radiation being emitted from the at least one heating element from heating the substrate.

[0046] Temporarily reflecting the radiation in block 603 may involve moving the at least one shield from the first position to the second position. The at least one shield may then be positioned between the at least one heating element and the substrate, and subsequently the at least one shield may block, restrict or reflect the radiation being emitted from the at least one heating element from heating the substrate. Temporarily reflecting the radiation in block 603 may further involve deactivating the at least one heating element. However, in the case where the at least one heating element is deactivated, the at least one heating element may remain heated, emitting residual heat towards the substrate which may be blocked, restricted or reflected by the at least one shield in the second position.

[0047] According to some embodiments, which may be combined with other embodiments described herein, the method for heat treatment of a substrate 600 may further include detecting a change in substrate velocity in block 604, wherein temporarily reflecting the radiation 603 may be performed based on the substrate transport velocity. [0048] The substrate transport velocity may be detected in block 604 by a substrate velocity sensor. In the case where the substrate transport velocity is reduced below a predetermined threshold, the radiation may be temporarily reflected. In the case where the substrate transport velocity is subsequently increased above a predetermined threshold, the temporary reflection of the radiation may be suspended and emission of radiation may continue. Temporarily reflecting the radiation based on a signal from the substrate velocity sensor has the benefit of allowing the heat treatment apparatus to prevent damage or destruction of the substrate by controlling the amount of heat radiation applied to the substrate. [0049] According to some embodiments, which may be combined with other embodiments described herein, the method for heat treatment of a substrate 600 may further include detecting a surface temperature of the substrate in block 605, wherein temporarily reflecting the radiation 603 may be performed based on the surface temperature of the substrate. [0050] The surface temperature of the substrate may be detected in block 605 by a substrate temperature sensor. The substrate temperature sensor may be positioned to measure the surface temperature of the substrate downstream of the heat treatment apparatus, or may be positioned to measure the surface temperature of the substrate upstream of the heat treatment apparatus. In the case where the surface temperature of the substrate is increased above a predetermined threshold, the radiation may be temporarily reflected. In the case where the surface temperature of the substrate is subsequently decreased below a predetermined threshold, the temporary reflection of the radiation may be suspended and emission of radiation may continue. Temporarily reflecting the radiation based on a signal from the substrate temperature sensor has the benefit of allowing the heat treatment apparatus to prevent damage or destruction of the substrate by controlling the amount of heat radiation applied to the substrate.

[0051] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.