Heat treatment apparatus and method

Abstract

Disclosed herein is a thermal processing apparatus (1) for thermally processing a material (MTR) on a substrate (STR). The thermal processing apparatus includes a support plate (10) having a layer stack (12) provided on a first main surface (11) thereof, the layer stack (12) having a free surface (13) for supporting the substrate, the free surface defining a reference plane (x, y). The layer stack (12) includes a first resistive heating layer (121), a second resistive heating layer (122), and an electrical insulator layer (123) between the first resistive heating layer (121) and the second resistive heating layer (122). Each resistive heating layer (121) includes a plurality of mutually electrically insulated resistive heating strips (121_1, 121_2, ..., 121_n, ... 121_N) extending in mutually different directions. Each pair of the first and second resistive heating strips overlaps in a respective region.

Description

[Technical Field]

[0001] The present invention relates to a thermal processing apparatus for thermally processing structures, such as electronic and / or optical structures on a substrate.

[0002] The present invention further relates to a method for thermally processing a structure on a substrate. [Background technology]

[0003] background In the field of printed functional structures, such as printed electronics, functional components and interconnects are printed onto a substrate. Various printing methods are suitable for this purpose, such as screen printing, flexography, gravure printing, offset printing, and inkjet printing. Electrically functional electronic or optical inks are deposited onto a substrate to form active or passive devices, such as thin film transistors, capacitors, coils, resistors, etc. Functional inks may include solutions or dispersions of functional materials. Alternatively or additionally, functional inks may include polymerizable components. Exemplary materials used in the field of printed electronics are described at https: / / en.wikipedia.org / wiki / Printed_electronics#:~:text=Printed%20electronics%20is%20a%20set,%2C%20offset%20lithography%2C%20and%20inkjet

[0004] In the field of printed functional structures, most inks require thermal curing after deposition. Typically, conductive and dielectric inks require curing in a convection oven at approximately 120°C-150°C for 10-20 minutes. Convection heating is slow, limiting throughput and efficiency. A more time-efficient means of thermal processing is needed. Summary of the Invention [Means for solving the problem]

[0005] overview To address the above-mentioned needs, an improved thermal processing apparatus is provided for thermally processing printed features, such as electronic and / or optical features, on a substrate.

[0006] To address the above-mentioned needs, an improved thermal processing method for thermally processing printed functional structures, such as electronic and / or optical structures, on a substrate is also provided.

[0007] The improved thermal processing apparatus includes a support plate having a layer stack provided on a first major surface thereof, the layer stack having a free surface for supporting a substrate having printed functional structures, the free surface defining a reference plane, and the layer stack including a first resistive heating layer, a second resistive heating layer, and an electrical insulator layer between the first and second resistive heating layers.

[0008] The first resistive heating layer includes a first plurality of mutually electrically insulated resistive heating strips extending in a reference plane along a first axis, and the second resistive heating layer includes a second plurality of mutually electrically insulated resistive heating strips extending in a reference plane along a second axis different from the first axis, for example transverse to the reference axis or preferably perpendicular to the first axis.

[0009] Each of the first plurality of resistive heating strips and each of the second plurality of resistive heating strips are configured to be powered by a respective power source.

[0010] Respective pairs of the first and second plurality of resistive heating strips overlap in respective regions.

[0011] This improved thermal processing apparatus, with its configuration of first and second heating strips, each configured to be driven by a respective power supply, allows for the curing of printed substances in a substrate in a time-efficient and well-controlled manner. The free surface of the stack can be rapidly heated, while the independently driven resistive strips allow for precise control of the temperature distribution across the surface.

[0012] In one embodiment, each of the first plurality of resistive heating strips has a respective first end portion with a respective first electrical contact and a respective second end portion opposite the first end portion with a respective second electrical contact Similarly, each of the second plurality of resistive heating strips has a respective first further end portion with a respective first further electrical contact and a respective second further end portion with a respective second further electrical contact opposite the first further end portion.

[0013] In this example embodiment, the electrical contacts of the resistive heating strips extend laterally outside the stack for connection to a power source.

[0014] In another example of this embodiment, the support plate includes, on a second major surface side opposite the first major surface side at each first end portion and each second end portion of each of the first plurality of heating strips, respective first recesses and respective second recesses that taper inwardly toward the respective openings in the first major surface side of the support plate. In this example, the respective first electrical contacts at the respective first ends and respective second electrical contacts at the respective second ends are formed by respective conductive layers provided on the support plate within the respective first recesses and respective second recesses, and these electrical contacts are electrically connected to the respective first end portions and respective second end portions through the respective openings. The support plate on the second major surface side further includes, on each further first end portion and each further second end portion of each of the second plurality of heating strips, respective further first recesses and respective further second recesses that taper inwardly toward the respective openings in the first major surface side of the support plate. The respective first further electrical contacts at the respective first further end portions and the respective second further electrical contacts at the respective second further end portions are formed by respective conductive layers provided on the support plate within the respective first recesses and the respective second recesses. The respective first further electrical contacts and second further electrical contacts are electrically connected to the respective first further end portions and the respective second further end portions through the respective openings. In this latter example, the electrical contacts of the resistive heating strip can be efficiently connected by placing the support plate on a carrier with respective electrical contact pins (such as pogo pins) cooperating with the respective electrical contacts.

[0015] In one embodiment, the thermal treatment apparatus further includes a power supply source with a respective power supply unit for each of the first plurality of heating strips and each of the second plurality of heating strips, each power supply unit including a power supply section and a power controller for minimizing a difference between the power provided by the respective power supply unit and the power estimated to achieve a predetermined desired temperature value.

[0016] For serial production of printed structures, a single calibration of the simulation step is sufficient to estimate the required power. The estimated value can be stored, and the power controller can control the power supplied to the heating strip according to these stored values ​​each time. In this example embodiment, the power controller includes a temperature estimator for providing an estimate of the operating temperature of the resistive heating strip and a feedback controller for minimizing the difference between the estimated operating temperature and a predetermined desired temperature value. This embodiment does not require reliance on stored power settings. This allows the thermal processing apparatus to easily adjust power settings for different structures. Alternatively, the power controller can estimate the required power setting based on a predetermined stored power setting and adjust the stored power setting based on an output from the temperature estimator. In one example, the temperature estimator is configured to measure the electrical resistance of the resistive heating strip and calculate an estimate of the operating temperature based on the measured electrical resistance and the temperature coefficient of resistance of the resistive heating strip. This eliminates the need for a separate temperature sensor.

[0017] In one embodiment, a thermal processing apparatus including a temperature estimator as described above is operable in an operating mode selected from a calibration mode and a power control function mode. The thermal processing apparatus operable in the calibration mode is configured to perform a calibration in which a relationship between the power supplied by each of the power supply units as a function of time and a temperature distribution as a function of time is estimated. The thermal processing apparatus operable in the power control function mode controls the power supplied by each of the power supply units as a function of time to approximate a desired temperature distribution as a function of time based on the estimated relationship.

[0018] In one embodiment, a thermal processing device including the above-mentioned temperature estimation unit operable in a temperature control function mode controls the power supplied to each resistive heating strip to minimize the difference between the operating temperature of each heating strip indicated by the estimation and a predetermined desired temperature value as a function of time.

[0019] In these embodiments, the thermal processing device can control the temperature according to a predetermined, user-defined temperature profile, where the user can specify the rate at which the substrate with the electronic and / or optical structures is heated, the predetermined time interval that the substrate is maintained at the predetermined temperature, and optionally the rate at which the substrate is cooled following that time interval.

[0020] One embodiment of the thermal processing device may include a feedback control unit having a PWM controller for providing a PWM control signal to switch the power supply unit into a temperature control function mode. The PWM controller is configured to periodically initiate PWM cycles according to a clock signal and to terminate each PWM cycle whenever the operating temperature of the heating strip controlled by the PWM controller tends to exceed a predetermined desired temperature value as indicated by the estimation. In this manner, power is supplied to the heating strip at a fixed frequency and with a variable pulse duration.

[0021] To avoid spatial temperature differences, the operation of the PWM controllers of each heating strip can be synchronized. That is, the PWM controllers use the same clock signal to initiate PWM cycles. However, if the clock signals of the PWM controllers have a sufficiently high clock frequency, for example, at least 10 Hz, synchronization is not necessary. In practical embodiments, the PWM controllers use the same clock signal regardless of frequency, as this reduces material costs. For example, the PWM controllers may use a common clock signal with a frequency of 100 Hz or higher. In some embodiments, the PWM controllers of each heating strip are synchronized to a common clock generator but have different delays from each other. This reduces the fluctuation in the load imposed on the power supply by avoiding simultaneous operation of all heating strips.

[0022] In an alternative embodiment, the controller is configured to initiate a heating cycle when the estimated operating temperature of the heating strip is less than a first threshold temperature value and to terminate each heating cycle whenever the estimated operating temperature of the heating strip exceeds a second threshold temperature value greater than the first threshold temperature value. In this case, the temperature change can be limited to a predetermined temperature range specified by the first and second threshold temperatures, which can be specified as a function of time. Due to the fact that each controller operates independently of the other, a significant reduction in fluctuations in the load on the power supply can again be achieved.

[0023] In some embodiments, the thermal processing apparatus further includes a cooling unit and an actuator. The cooling unit has a cooling surface facing the second side of the support plate. The actuator is configured to position the cooling unit with its cooling surface away from the support plate in a first functional mode to activate the power supply to provide controlled power, and the actuator is configured to position the cooling unit with its cooling surface in thermal contact with the support plate in a second functional mode to rapidly cool the plate. This embodiment allows for even more time-efficient processing in that a substrate with structures printed thereon can be rapidly cooled upon hardening the structures, allowing subsequent structures to be printed or the substrate with the printed structures to be peeled off. In this example second functional mode, the cooling rate is mitigated by heating the plate with a resistive heating layer, thereby avoiding thermal shock effects. The cooling rate can be specified by a user in a temperature profile.

[0024] In one example, the heat treatment device including the cooling unit also includes a housing having a bottom wall and a peripheral wall extending from the bottom wall. In this example, a support plate is supported by the side of the peripheral wall opposite the bottom wall, and the cooling unit and actuator are disposed within a space enclosed by the bottom wall, the peripheral wall, and the plate. In this example, the plate is provided with exhaust openings extending through the support plate, and the cooling unit includes respective exhaust channels extending from the cooling surface to communicate with the space enclosed by the housing. Each exhaust channel is disposed opposite the exhaust opening to enable application of a vacuum on the first main surface side by communicating with the exhaust space on the second main surface side through the exhaust openings and exhaust channels of the support plate. The exhaust openings are provided, for example, at positions between the first plurality of pairs of subsequent resistive heating strips and the second plurality of pairs of subsequent resistive heating strips. The support plate may include one or more compensating heating strips on its periphery supported by the peripheral wall of the housing to compensate for heat flow toward the peripheral wall of the housing that occurs at the periphery of the plate. Each of the compensatory heating strips may have its own controlled power supply.

[0025] In one embodiment of the heat treatment device, the layer stack includes an additional electrical insulator layer between the first main surface side of the layer stack and the first resistive heating layer. This allows the heat treatment device to also be provided with a support plate made of an electrically non-insulating material. In one example, the support plate is a 1-0-0 oriented silicon wafer. This material is very suitable because it allows the support plate to be manufactured in a minimum of steps.

[0026] In one embodiment of the thermal processing device, the layer stack on the side facing away from the support plate includes an anti-stick layer, so that even if melting of the substrate accidentally occurs during the thermal processing, the substrate can still be easily peeled off from the anti-stick layer.

[0027] The improved method for heat treating structures on a substrate comprises the following steps: a) providing a layer stack on a support plate at a first major surface side, the layer stack having a free surface for supporting a substrate, the free surface defining a reference plane. a1) providing a first resistive heating layer having a first plurality of mutually electrically insulated resistive heating strips extending in a direction of a first axis in a reference plane; a2) providing an electrical insulator layer; a3) providing a second resistive heating layer having a second plurality of mutually electrically insulated resistive heating strips extending in a direction of a second axis in a reference plane different from the first axis, typically perpendicular to the first axis; b) supplying a respective controlled power to each of the first and second pluralities of resistive heating strips to heat the substrate with a controlled spatial distribution over an area of ​​the free surface.

[0028] Respective pairs of the first and second plurality of resistive heating strips overlap in respective regions.

[0029] One embodiment of the method includes providing a respective temperature indicator for each of the first and second pluralities of resistive heating strips, indicating an estimated average temperature of each resistive heating strip, and controlling a respective power supply for each of the resistive heating strips to minimize a difference between the power provided to each resistive heating strip and the power estimated to achieve a predetermined desired temperature value. In one example of this embodiment, the respective controlled power is provided to each heating strip in a pulse width controlled manner, with each PWM cycle initiated by a clock signal and ending when the respective temperature indicator for each heating strip indicates that the estimated average temperature of each heating strip is trending above the predetermined desired temperature value.

[0030] One embodiment of the improved method includes measuring the electrical resistance of each heating strip and calculating a respective temperature indicator for each heating strip based on the measured electrical resistance and the temperature coefficient of resistance of each resistive heating strip.

[0031] In one embodiment, the improved method then includes operating in a calibration mode a) and a power control function mode b). Operating in calibration mode a) includes: a1) individually supplying controlled power to each of the resistive heating strips so that, when there is no substrate on the free surface, a state is reached at a certain time when each of the temperature indicators of the resistive heating strips indicates that the temperature has a predetermined value and the temperature increases at a predetermined rate, for example, 150°C and the predetermined rate of increase is 100°C / sec. a2) determining a first magnitude of power supplied to each of the heating strips at which this condition is achieved; a3) determining a second respective magnitude of power supplied by each respective pair of the first plurality of resistive heating strips and the second plurality of heating strips; a4) Determining a first total power magnitude, which is the sum of the first magnitudes. For example, in the above case, the first total power magnitude is determined to be 920W. a5) Placing a substrate on the free surface of the layer stack. a6) individually supplying controlled power to achieve, with the substrate placed on the free surface, that at a certain point in time each of the temperature indicators of the resistive heating strips indicates that said condition has been reached, in which the temperature has a predetermined value and rises at the predetermined rate specified for step a1), thus in this example the predetermined value of the temperature is 150°C and the predetermined rate of rise is 100°C / s. a7) Determining a third respective magnitude of power supplied to each of the heating strips at which this condition is achieved. a8) determining a fourth respective magnitude of power supplied by each respective pair of the first plurality of resistive heating strips and the second plurality of heating strips; a9) determining a second total power magnitude that is the sum of the first magnitudes. For example, the second total power magnitude is determined to be 1140W. a10) determining the total power difference between the second total power magnitude and the first total power magnitude. In this example, the total power difference is 220W. a11) Determining the local power magnitude, which is the total power dissipated in the area of ​​the support plate covered by the substrate. For example, the local power magnitude is determined to be 195W. a12) Calculate the ratio between the total power difference and the local power magnitude. In this example, the ratio is 220W / 195W, which is thus equal to 1.128.

[0032] In power control function mode b), a substrate is placed on the free surface of the support plate, and power having a respective fifth magnitude is provided to each of the heating strips having an area covered by the substrate, the respective fifth magnitude being equal to the product of the respective third magnitude and the aforementioned ratio. Power of the respective third magnitude is provided to each of the heating strips having no area covered by the substrate.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects are described in more detail with reference to the drawings. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is a cross-sectional view showing a schematic diagram of one embodiment of an improved thermal processing apparatus. [Figure 2] This embodiment is shown in more detail in which FIG. 2 is a plan view. [Figure 3] This embodiment is shown in more detail in cross sections IIIA and IIB of FIG. 2, shown at A and B, respectively. [Figure 4] 1 illustrates an exemplary power supply unit for use with one embodiment of the improved thermal processing apparatus. [Figure 5] 1 is a cross-sectional view showing a schematic diagram of a further embodiment of an improved thermal processing apparatus; [Figure 6] FIG. 2 is a top view of exemplary components of one embodiment of an improved thermal processing apparatus. [Figure 7] 1 illustrates a schematic diagram of one embodiment of an improved method for thermally processing structures on a substrate. [Figure 8] 1 illustrates an exemplary controller in one embodiment of the improved thermal processing apparatus. [Figure 9A] 1 illustrates aspects relating to temperature control in one embodiment of the improved method. [Figure 9B] 1 illustrates aspects relating to temperature control in one embodiment of the improved method. [Figure 10A] The calibration procedure is shown. [Figure 10B] The calibration procedure is shown. [Figure 10C] The calibration procedure is shown. [Figure 11A] 1 shows an aspect of a simulation. [Figure 11B] 1 shows an aspect of a simulation. [Figure 11C] 1 shows an aspect of a simulation. DETAILED DESCRIPTION OF THE INVENTION

[0035] Detailed Description of the Embodiments Like reference symbols in the various drawings indicate like elements unless otherwise indicated.

[0036] Figure 1 shows a schematic cross-sectional view of an embodiment of an improved thermal processing apparatus 1 for thermally processing a material MTR on a substrate STR. Figures 2 and 3 show this embodiment in more detail. In this embodiment, Figure 2 is a plan view, and Figure 3 shows cross sections IIIA and IIB of Figure 2 at A and B, respectively.

[0037] The substrate STR can be either a rigid substrate such as glass or a flexible substrate of a polymer, e.g., PET or PEN. The material MTR to be heat-treated can be an electrically insulating and thermally insulating material, an electrically insulating and thermally conductive material, an electrically conductive and thermally insulating material, or an electrically conductive and thermally conductive material. The material MTR, also commonly referred to as an ink or paste, can include, for example, nanoparticles or microparticles or mixtures thereof suspended in a (high-boiling point) solvent. Epoxy-based materials, such as adhesives or conductive adhesives with silver microparticles, are also used. Alternatively or additionally, the substance can include one or more of solder, a mixture of eutectic materials, a positive or negative photoresist, a polymer solution, a molten polymer, a monomer, or a silicone-based material.

[0038] As shown in Figure 1, the thermal processing apparatus includes a support plate 10. The support plate 10 is provided on a first main surface side 11 with a layer stack having a free surface 13 for supporting a substrate. An example of the layer stack 12 is shown in detail in Figure 3.

[0039] The free surface 13 defines a reference plane x, y, and as shown in FIG. 3, the layer stack 12 includes a first resistive heating layer 121, a second resistive heating layer 122, and an electrical insulator layer 123 between the first resistive heating layer 121 and the second resistive heating layer 122.

[0040] As best seen in FIG. 2, the first resistive heating layer 121 includes a first plurality of mutually electrically insulated resistive heating strips 121_1, 121_2, ..., 121_n, ..., 121_N extending in the direction of a first axis x in a reference plane.

[0041] Similarly, the second resistive heating layer 122 includes a second plurality of mutually electrically insulated resistive heating strips 122_1, 122_2, ..., 122_m, ..., 122_M extending in the direction of a second axis y different from the first axis x in a reference plane.

[0042] Each of the first plurality of resistive heating strips 121_1, 121_2, ..., 121_n, ..., 121_N and each of the second plurality of resistive heating strips 122_1, 122_2, ..., 122_m, ..., 122_M is configured to be powered by a respective power supply.

[0043] As shown in FIG. 2, this is the case when the first plurality of resistive heating strips each have a respective first end portion 121a with a respective first electrical contact 151ac and a respective second end portion 121b with a respective second electrical contact 151bc opposite the first end portion, and similarly, the second plurality of resistive heating strips 122_1, 122_2, ..., 122_m, 122_M each have a respective further first end portion 122a with a respective further first electrical contact 152ac and a respective further second end portion 122b with a respective second further electrical contact 152bc opposite the further first end portion.

[0044] In this embodiment, the support plate 10 includes the following features on a second major side 14 opposite the first major side 11, as shown in FIG.

[0045] At each first end portion 121a and each second end portion 121b of each of the first plurality of heating strips 121_1, ..., 121_N, the support plate 10 has a respective first recess and a respective second recess 141b that taper inward toward a respective opening in the first main surface side 11 of the support plate 10. Each first electrical contact 151ac (not shown in FIGS. 2 and 3) at each first end portion 121a (not shown in FIGS. 2 and 3) and each second electrical contact 151bc at each second end portion 121b are formed by a respective conductive layer provided on the support plate 10 within each first recess and each second recess 141b. Each first electrical contact and each second electrical contact are electrically connected to each first end portion and each second end portion through each opening in the support plate 10.

[0046] Further, each of the further first end portions 122a and each of the further second end portions 122b of each of the second plurality of heating strips 122_1, ..., 122_N has a respective further first recess 142a and a respective further second recess 142b that taper inwardly toward the respective openings in the first main surface side 11 of the support plate 10. A respective further first electrical contact 152ac at each of the further first end portions 122a and a respective further second electrical contact 152bc at each of the further second end portions 122b are formed by respective conductive layers provided on the support plate 10 within the respective first recess 142a and the respective second recess 142b, and these further electrical contacts are electrically connected to the respective further first end portions and the respective further second end portions through the respective openings.

[0047] The layer stack 12 of the exemplary support plate shown in FIG. 3 includes an additional electrical insulator layer 124 between its first major surface side 11 and the first resistive heating layer 121. This eliminates the need for the support plate 10 itself to be an electrical insulator. The support plate 10 is intended for use with 1-0-0 oriented silicon wafers. This material is preferred because it allows for the manufacture of the support plate in a moderate number of process steps. The additional electrical insulator layer 124 can be provided by oxidizing the surface of the silicon wafer.

[0048] 3 includes an anti-stick layer 126 on the side facing away from the support plate 10. The presence of the anti-stick layer 126, e.g., a silicon dioxide, PTFE coating, fluoropolymer coating, or ceramic layer, facilitates removal of the substrate in the unlikely event that the substrate melts during heating.

[0049] In one embodiment, the thermal processing apparatus 1 further includes a power supply source having a respective power supply unit for each of the first plurality of heating strips and each of the second plurality of heating strips. For example, FIG. 4 shows a power supply unit 20 for one of the first plurality of heating strips and the electrical connection of the power supply unit 20 to that heating strip, shown in a cross-sectional view according to IV in FIG. 2. As shown in FIG. 4, the first and second electrical contacts 151ac and 151bc of the heating strip are electrically connected to contact elements 201ac and 201bc of the power supply unit 20. The power supply unit 20 includes a power supply section 21 and a power controller 22 for minimizing the difference between the power provided by each power supply unit 20 and the power estimated to achieve a predetermined desired temperature value Tdes.

[0050] In the embodiment shown in Figure 4, the power controller 22 includes a temperature estimator for estimating the operating temperature of the resistive heating strip to which the temperature estimator is connected, and a feedback controller for minimizing the difference between the estimated operating temperature and a predetermined desired temperature value Tdes. The temperature estimator is configured to measure the electrical resistance of the resistive heating strip and calculate an estimate of the operating temperature based on the measured electrical resistance and the temperature coefficient of resistance of the resistive heating strip. To that end, the power controller 22 receives input signals relating to the supplied current and voltage across the resistive heating strip. The supplied current is fed through a series resistor R disposed in series between the power supply 21 and the contacts 201ac, 201bc to which the resistive heating strip is connected. ser The series resistance R ser4, in this case, the power supply unit 20 has additional measurement contact elements 201acm, 201bcm electrically connected to the first and second electrical measurement contacts 151acm, 151bcm of the heating strip. A second voltage V2 is measured across these additional measurement contact elements 201acm, 201bcm. Using input signals indicative of the first voltage V1 and the second voltage V2, the temperature estimator of the power controller 22 is configured to estimate the current temperature of the heating strip based on a known relationship between the conductivity of the heating strip and its temperature, for example, using a look-up table or a polynomial approximation.

[0051] In the illustrated embodiment, the feedback control unit 22 includes a PWM controller. In the temperature control function mode, the PWM controller provides a PWM control signal for switching the power supply unit 21 to supply an appropriate amount of power, estimated based on the resistance of the heating strip, to achieve a desired temperature. In the illustrated embodiment, the feedback control unit 22 is configured to receive a clock signal and, as a result, periodically initiate a PWM cycle according to the clock signal. The feedback control unit 22 terminates each PWM cycle when the estimated operating temperature of the heating strip tends to exceed a predetermined desired temperature value Tdes. In an alternative embodiment, there is no external clock and the feedback control unit 22 initiates a PWM cycle when it detects that the estimated operating temperature of the heating strip is trending below the predetermined desired temperature value Tdes by a predetermined amount or has already fallen below the predetermined desired temperature value Tdes by more than the predetermined amount. Conversely, in this alternative embodiment, the feedback control unit 22 terminates the PWM cycle when it detects that the estimated operating temperature of the heating strip is trending toward or has already exceeded the predetermined desired temperature value Tdes by more than the predetermined amount.

[0052] The thermal processing device may also be capable of operating in a power control mode of operation. If the relationship between the operating temperature of the heating strip and the power supplied is known for a particular substrate having material thereon, for example from a calibration stage or from a model calculation, the thermal processing device can be operated in a power control mode of operation to supply the required power that is expected to result in the desired operating temperature. This is indicated as a feedforward control mode. In a variant, the thermal processing device may also be capable of operating in a hybrid mode of operation, where control is based on a combination of feedforward control based on the expected amount of power and feedback control based on sensed temperature data.

[0053] It should be noted that the temperature distribution may alternatively or additionally be estimated by a separate temperature sensor such as a thermocouple and / or by an IR camera monitoring the free surface of the substrate.

[0054] Typically, the desired temperature Tdes of the heating strip is specified as a function of time as part of a user-provided thermal treatment plan that specifies an exothermic phase, where the temperature is gradually increased, a curing phase, where the temperature is maintained at a predetermined level, and a cooling phase, where the temperature is reduced so that the next deposition phase can be performed or the substrate can be released for further processing in another apparatus.

[0055] In one embodiment of the thermal processing apparatus, such as that shown in FIG. 1, a cooling unit 30 is provided having a cooling surface 31 (see FIG. 5) on a side facing the second side 14 of the support plate 10. This embodiment also includes an actuator 40 configured to position the cooling unit 30 with the cooling surface 31 spaced apart from the support plate 10 in a first functional mode, as shown in FIG. 5. In the first functional mode, the power supply is activated to provide controlled power to the heating strip. In a second operating mode, as shown in FIG. 1, the actuator 40 is configured to position the cooling unit 30 with the cooling surface in thermal contact with the support plate 10 to quench the support plate 10. As shown in FIG. 1, the cooling unit 30 is coupled with flexible tubing 54a, 54b to a coolant inlet 55a and a coolant outlet 55b to provide active cooling via coolant flows Clin and Clout.

[0056] In one embodiment, as shown in FIGS. 1 and 5 , the heat treatment apparatus 1 further includes a housing 50 having a bottom wall 51 and a peripheral wall 52 extending from the bottom wall. The support plate 10 is supported by the side of the peripheral wall 52 opposite the bottom wall 51. The cooling unit 30 and the actuator 40 are disposed within a space 53 enclosed by the bottom wall 51, the peripheral wall 52, and the plate 10. As can be seen, for example, in FIGS. 3 and 4 , exhaust openings 16 extend through the support plate 10. The cooling unit 30 includes respective exhaust channels 32 extending from the cooling surface to communicate with the space enclosed by the housing. These exhaust channels 32 are disposed opposite the respective exhaust openings 16 to enable application of a vacuum on the first major surface side 11 by communicating with the sealed space on the second major surface side through the exhaust openings 16 and the exhaust channels 32 in the support plate. The sealed space is evacuated through an opening 56 coupled to a vacuum pump (not shown). During the first operating mode shown in FIG. 5 and the second operating mode shown in FIG. 4, a vacuum applied at the exhaust openings 16 of the support plate 10 makes it possible to press the substrate STR, on which the material MTR has been deposited, firmly against the surface of the support plate 10 so as to achieve good thermal contact with the surface of the support plate 10 during heating and cooling.

[0057] As shown in FIG. 2, the exhaust opening 16 is provided at a position between the first plurality of pairs of trailing resistive heating strips 121 and the second plurality of pairs of trailing resistive heating strips 122 .

[0058] 6 shows a top view of an example of a support plate 10 that includes one or more compensating heating strips 17 around the periphery of the support plate 10, which is supported by the peripheral wall 52 of the housing 50. The compensating heating strips 17 act to compensate for heat flow from the periphery of the support plate 10 to the peripheral wall 52, thereby achieving a more uniform temperature distribution across the surface of the support plate 10.

[0059] FIG. 7 shows a schematic diagram of a method for heat treating a structure on a substrate.

[0060] The method presented herein comprises a step S1 of providing a support plate 10 on a first major side 11 with a layer stack 12 having a free surface 13 for supporting a substrate. The free surface defines a reference plane having mutually orthogonal first and second axes x and y. Providing the layer stack 12 comprises the following steps:

[0061] In step S11, a first resistive heating layer 121 is provided, which has a first plurality of mutually electrically insulated resistive heating strips 121_1, 121_2, ..., 121_n, ..., 121_N extending in the direction of a first axis x in a reference plane.

[0062] An electrical insulator layer 123 is provided on the first resistive heating layer 121 in step S12;

[0063] A second resistive heating layer 122 is provided on the electrical insulator layer 123 in step S13. The second resistive heating layer 122 similarly includes a second plurality of mutually electrically insulated resistive heating strips 122_1, 122_2, ..., 122_m, ..., 122_M, which extend in the direction of a second axis y in a reference plane.

[0064] Following the support plate 10 on the first main surface side 11 with the layer stack 12, a substrate having the material to be cured is placed on the free surface 13 of the layer stack and respective controlled power is supplied to each of the first and second plurality of resistive heating strips 121_1, 121_2, ..., 121_n, ..., 121_N, 122_1, 122_2, ..., 122_m, ..., 122_M in step S2 to heat the substrate with a controlled spatial distribution over the area of ​​the free surface 13.

[0065] In one embodiment of the method, a substantially uniform temperature distribution is achieved in that the power supplied to the heating strips is controlled independently of one another. That is, each heating strip is provided with a respective power supply to supply the appropriate amount of power to achieve the desired temperature of the heating strip and / or the desired temperature change as a function of time. Note that this does not necessarily imply that the power supplied to each heating strip is the same, even if the temperature distribution is uniform. For example, in the case of a circular support plate 10, the heating strips have different lengths, as shown in FIG. 6. To maintain a uniform temperature distribution, the power supplied is approximately proportional to the length of the heating strip.

[0066] FIG. 8 illustrates a controller 60 configured to control the operation of various apparatus components in one embodiment of the improved thermal processing apparatus. In the illustrated example, the controller 60 is configured to provide a respective control signal S20,...,S20n to each of the power supply units 20,...,20n. Each power supply unit 20,...,20n is configured to autonomously control the heat generation rate of its appropriate heating strip in accordance with the control signal S20,...,S20n provided by the controller 60. The controller 60 also controls the actuator 40 using an actuator control signal S40. The controller 60 may also control a vacuum pump and / or a valve connecting the vacuum pump to the opening 56 using a control signal Svac. The controller 60 may also control a coolant supply unit using a control signal Sliq. In the example of FIG. 8, the controller 60 is coupled to a user interface 61, which allows an operator to specify a temperature profile as a function of time in which the thermal processing should be performed.

[0067] An exemplary operation is shown in FIGS. 9A and 9B. In FIGS. 9A and 9B, a temperature profile specified by an operator is shown as a dotted line. A temperature scale is shown on the left side of the graph. The controller 60 provides each power supply unit 20, ..., 20n with a respective control signal S20, ..., S20n that instructs the power supply unit to supply an appropriate amount of power to the heating strips connected to the power supply unit to approximate the specified temperature profile. A power scale is shown on the right side of the graph. FIGS. 9A and 9B illustrate how the exemplary power supply unit 20 shown in FIG. 4 supplies PWM-controlled power to the heating strips connected to the power supply unit 20. As described above, the exemplary power supply unit 20 of FIG. 4 operates at a fixed frequency according to a clock signal Cl. Each PWM cycle is initiated by the clock signal Cl and ends when the respective temperature indicators of each heating strip indicate that the estimated average temperature of each heating strip is trending above a predetermined desired temperature value Tdes, as defined by the temperature profile as a function of time. In Figure 9A, the solid curve shows the actual temperature as a function of time. In the illustrated embodiment, the power supply unit 20 estimates the temperature of the resistive heating strip by measuring the resistance of the resistive heating strip during the active phase of the PWM cycle. The estimated temperature during the active phase of the PWM cycle is shown in Figure 9B. The power supply unit 20 terminates the active phase of the PWM cycle when the temperature tends to exceed the desired temperature, and the resistive heating strip cools during the passive phase of the PWM cycle, so there is no need to know the temperature during the passive phase. That is, for short strips, the duty cycle will be relatively short compared to long strips.

[0068] If it is not desirable for the strips to have approximately the same duty cycle, it is possible to replace the short linear strips with serpentine strips.

[0069] Note that as a result of the temperature-based control, the appropriate amount of power is automatically supplied to each strip, regardless of the length of the strip.

[0070] 9A and 9B, forced cooling is applied following heating of the substrate. This is achieved by controller 60 providing a control signal S40 to actuator 40, which causes actuator 40 to move cooling unit 30 relative to support plate 10. In the illustrated example, the power supply unit is maintained in an active state, resulting in a temperature decrease at a slower rate (as defined by a user-defined temperature profile) than would otherwise be the case if the temperature of support plate 10 were determined solely by thermal contact with cooling unit 30.

[0071] If the substrate STR completely covers the support plate, it is sufficient for each of the heating strips to have the same temperature as a function of time. A different situation occurs if the substrate only partially covers the support plate. In this case, the temperature of the strip tends to be lower in the areas where the strip is covered by the substrate than in the remaining areas where the strip is not covered. Also, in this case, if calibration is performed, an appropriate temperature distribution can be achieved. This procedure and subsequent thermal processing of the substrate using calibration will now be described with reference to Figures 10A, 10B, and 10C.

[0072] As shown in Figure 10A, the first calibration stage is performed in the absence of a substrate at the free surface. A respective controlled power is supplied to each heating strip to achieve that each of the respective temperature indicators of the resistive heating strips indicates that a situation has been reached at a certain point in time, where the temperature has a predetermined value and increases at a predetermined rate.

[0073] As an example, the predetermined temperature value may be specified as 150° C. and the predetermined temperature ramp rate may be 100° C. / sec, as shown in the graph on the right side of Figure 10A. As an example, the graph on the right side of Figure 10A shows a measured relationship where a heating rate of 100° C. / sec is achieved at a temperature of 150° C. for a first region a at the periphery of the support plate and a second region b at the center of the support plate.

[0074] A first magnitude of power supplied to each of the heating strips that achieves this condition is then determined, and a second respective magnitude of power supplied by each pair of the first and second plurality of resistive heating strips and dissipated in the area where the pair of heating strips overlap is determined.

[0075] The left side of Figure 10A shows the first magnitude near each end of each heating strip and the second magnitude in each of the overlapping regions. As shown in Figure 10A, the first region a and the second region b require 15 W and 12 W of power, respectively, to achieve a heating rate of 100 °C / s at a temperature of 150 °C.

[0076] Also, a first total power magnitude is determined, which is the sum of the first magnitudes, in this case 920W.

[0077] 10B shows a second stage of the calibration phase, in which the substrate STR is placed on the free surface of the layer stack, and measurements are carried out as in the first stage, with the substrate STR placed on the free surface.

[0078] A respective controlled power is supplied to each heating strip to achieve that each of the respective temperature indicators of the resistive heating strips indicates that a situation has been reached at a certain point in time, in which the temperature has a predetermined value (150°C in this example) and rises at a predetermined rate (100°C / sec in this example).

[0079] 10B illustrates a third magnitude of power supplied to each of the heating strips at which this condition is achieved. Additionally, the left side illustrates a fourth respective magnitude of power supplied by each pair of the first plurality of resistive heating strips 121_1, 121_2, ..., 121_n, ..., 121_N and the second plurality of heating strips 122_1, 122_2, ..., 122_m, ..., 122_M.

[0080] A second total power magnitude is determined as the sum of the second magnitudes, which in this example is 1140W.

[0081] The difference in total power between the second total power magnitude and the first total power magnitude is then determined, which in this example is 220W.

[0082] The local power magnitude is also determined as the total power dissipated within the area of ​​the support plate covered by the substrate, which in this example is 195W.

[0083] The ratio of the total power difference to the local power magnitude is then calculated. In this example, the ratio is equal to 1.128. As shown in Figure 10C, the power supplied to the heating strip covered by the substrate is multiplied by this ratio to take into account the effect of the presence of the substrate on the temperature-power dependence during the processing stage.

[0084] As an example, simulation results are shown in Figures 11A-11C. These simulations show that a 675 μm thick silicon heater plate requires only 14 W / cm² to heat the center of the wafer at a rate of 115°C per second. On the side of the wafer in contact with the PTFE, the heat flux would need to be 19 W / cm² in² to reach the same heating rate. The total power to heat a 150 mm wafer would be approximately 2700 watts (1860 + 840). Heating to 250°C would require 5400 joules. Much less power is required to maintain the wafer at this temperature. After heating, the entire wafer can be cooled from 250°C to room temperature in 2 seconds by activating a water-cooled vacuum chuck. This allows for drying and / or curing (soldering) within 10 seconds.

[0085] If the substrate is placed on a wafer, e.g., a 525 μm thick silicon wafer, as shown in FIG. 11A, a heat flux of 24 W / cm2 is required to achieve the same heating rate of 115°C per second. FIG. 11C shows a simulation of temperature as a function of time, in which the substrate is heated at a rate of 115°C per second for 2 seconds, maintained at a temperature of 250°C for 3 seconds, and then cooled by thermal contact with a heat sink, as shown in FIG. 11B. The effect of placing a smaller substrate on the heater can be compensated for by calibration and heat flux correction, determined in the manner specified with reference to FIGS. 10A-10C.

[0086] Based on the measured thermal profile, it may also be possible to understand what kind of substrate is placed on the heater. For example, the heat capacity and thermal conductivity can be approximated / calculated. This additional information can be used to fine-tune the temperature profile on the top side of the substrate, especially for thicker substrates with poor thermal conductivity.

[0087] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single component or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. A heat treatment apparatus (1) for heat-treating a material (MTR) on a substrate (STR), the heat treatment apparatus includes a support plate (10) on which a layer stack (12) having a free surface (13) for supporting the substrate is provided on the first main surface side (11), the free surface defines a reference plane (x, y), and the layer stack (12) is The first resistive heating layer (121) and A second resistance heating layer (122) and The electrical insulating layer (123) between the first resistive heating layer (121) and the second resistive heating layer (122) This includes (see Figure 2), The first resistance heating layer (121) includes a first plurality of electrically insulated resistance heating strips (121_1, 121_2, ..., 121_n, ..., 121_N) extending in the direction of the first axis (x) within the reference plane, The second resistance heating layer (122) includes a second plurality of electrically insulated resistance heating strips (122_1, 122_2, ..., 122_m, ..., 122_M) extending in the direction of a second axis (y) different from the first axis within the reference plane, A heat treatment apparatus (1) characterized in that each of the first plurality of resistance heating strips (121_1, 121_2, ..., 121_n, ..., 121_N) and each of the second plurality of resistance heating strips (122_1, 122_2, ..., 122_m, ..., 122_M) is configured to be driven by its own power supply, and each pair of the first plurality of resistance heating strips and the second plurality of resistance heating strips overlaps in their respective regions.

2. The heat treatment apparatus (1) according to claim 1, wherein each of the first plurality of resistance heating strips (121_1, 121_2, ..., 121_n, ..., 121_N) has a first end portion (121a) having a first electrical contact (151ac) and a second end portion (121b) opposite to the first end portion having a second electrical contact (151bc), and each of the second plurality of resistance heating strips (122_1, 122_2, ..., 122_m, ..., 122_M) has a further first end portion (122a) having a further first electrical contact (152ac) and a further second end portion (122b) opposite to the further first end portion having a further second electrical contact (152bc).

3. The support plate (10) on the second main surface side (14) opposite to the first main surface side (11) is, Each of the first plurality of heating strips (121_1, ..., 121_N) has a first end portion (121a) and a second end portion (121b) that includes a first recess and a second recess (141b) that taper inward toward the respective openings on the first main surface side (11) of the support plate (10), and each of the first electrical contacts (151ac) at each first end portion (121a) and each of the second electrical contacts (151bc) at each second end portion (121b) is formed by a conductive layer provided on the support plate (10) within the respective first recess and the respective second recess (141b), the conductive layer being electrically connected to the respective first end portion and the respective second end portion through the respective openings. The support plate (10) includes, at each further first end portion (122a) and each further second end portion (122b) of each of the second plurality of heating strips (122_1, ..., 122_N), each further first recess (142a) and each further second recess (142b) that taper inward toward the respective openings on the first main surface side (11) of the support plate (10), and each further first electrical contact (152a) at each of the respective further first end portions (122a) c) and the respective further second electrical contacts (152bc) at each of the further second ends (122b) are formed by the respective conductive layers provided on the support plate (10) within the respective first recesses (142a) and the respective second recesses (142b), which are electrically connected to the respective further first end portions and the respective further second end portions, respectively, through the respective openings, the heat treatment apparatus (1) according to claim 2.

4. The heat treatment apparatus (1) according to claim 1, wherein each of the first plurality of resistance heating strips (121_1, 121_2, ..., 121_n, ..., 121_N) and each of the second plurality of resistance heating strips (122_1, 122_2, ..., 122_m, ..., 122_M) has a first electrical contact and a second electrical contact extending laterally from its respective first end portion and its respective second end portion.

5. The heat treatment apparatus (1) according to claim 1, further comprising a power supply source for each of the first plurality of heating strips and each of the second plurality of heating strips, each power supply unit (20), the power supply unit (20) comprising a power supply unit (21) and a power controller (22) for minimizing the difference between the power provided by each power supply unit (20) and the power estimated to be used to achieve a predetermined desired temperature value (Tdes).

6. The heat treatment apparatus (1) according to claim 5, wherein the power controller (22) includes a temperature estimation unit for estimating the operating temperature of the resistance heating strip and a feedback control unit for minimizing the difference between the operating temperature indicated by the estimation and a predetermined desired temperature value (Tdes).

7. The heat treatment apparatus (1) according to claim 5, wherein the temperature estimation unit is configured to measure the electrical resistance of the resistance heating strip, and calculates an estimated value of the operating temperature based on the measured electrical resistance and the temperature coefficient of the resistance of the resistance heating strip.

8. The heat treatment apparatus (1) according to claim 5 or 6, which is capable of operating in an operating mode selected from a calibration mode and a power control function mode, and when the heat treatment apparatus is capable of operating in the calibration mode, it is configured to perform a calibration that estimates the relationship between the power supplied as a function of time by each of the power supply units (20) and the temperature distribution as a function of time, and when the heat treatment apparatus is capable of operating in the power control function mode, it controls the power supplied as a function of time by each of the power supply units (20) to approximate a desired temperature distribution as a function of time based on the estimated relationship.

9. The heat treatment apparatus (1) according to claim 6 or 7, which is capable of operating in an operating mode selected from at least a temperature control function mode, and when the heat treatment apparatus is capable of operating in the temperature control function mode, controls the power supplied to each resistance heating strip to minimize the difference between the operating temperature of each heating strip indicated by the estimation and a predetermined desired temperature value (Tdes) as a function of time.

10. The heat treatment apparatus (1) according to claim 9, wherein the feedback control unit (22) includes a PWM controller for providing a PWM control signal to switch the power supply unit (21) to the temperature control function mode, the PWM controller is configured to periodically start PWM cycles according to a clock signal and to terminate each PWM cycle whenever the operating temperature of each heating strip indicated by the estimation tends to exceed a predetermined desired temperature value (Tdes).

11. A heat treatment apparatus (1) according to any one of claims 1 to 7, further comprising a cooling unit (30) and an actuator (40), wherein the cooling unit (30) has a cooling surface (31) on the side of the support plate (10) facing the second side (14), the actuator (40) is configured to position the cooling unit (30) such that the cooling surface (31) of the cooling unit (30) is away from the support plate in a first functional mode for operating the power source to provide the controlled power, and the actuator is configured to position the cooling unit (30) such that the cooling surface of the cooling unit (30) is in thermal contact with the plate in order to rapidly cool the support plate.

12. The heat treatment apparatus (1) according to claim 11, further comprising a housing (50) having a bottom wall (51) and a peripheral wall (52) extending from the bottom wall, wherein the support plate (10) is supported by the side of the peripheral wall opposite to the bottom wall, the cooling unit (30) and the actuator (40) are arranged in a space (53) enclosed by the bottom wall, the peripheral wall and the plate so that exhaust occurs when in operation, an exhaust opening (16) extends through the support plate, and each exhaust passage (32) extends from the cooling surface through the cooling unit (30) so as to communicate with the space enclosed by the housing, and each exhaust passage is arranged opposite to the exhaust opening so as to enable the application of vacuum on the first main surface side (11) by communicating with the sealed space on the second main surface side through the exhaust opening (16) in the support plate and the exhaust passage (32) in the cooling unit (30).

13. The heat treatment apparatus (1) according to claim 12, wherein the exhaust opening (16) is provided between the first plurality of subsequent pairs of subsequent resistance heating strips and the second plurality of subsequent pairs of subsequent resistance heating strips.

14. The heat treatment apparatus (1) according to claim 12 or 13, wherein the support plate (10) includes one or more compensating heat strips (17) on its periphery, which is supported by the surrounding wall (52) of the housing (50).

15. A method for heat-treating a structure on a substrate, The process includes providing a layer stack (12) having a free surface (13) for supporting the substrate on the first main surface side (11) of the support plate (10), wherein the free surface defines a reference plane (x, y), and providing the layer stack (12) is a subsequent step, namely, A first resistance heating layer (121) is provided, having a first plurality of electrically insulated resistance heating strips (121_1, 121_2, ..., 121_n, ..., 121_N) extending in the direction of the first axis (x) within the reference plane, By providing an electrical insulating layer (123), A second resistance heating layer (122) is provided, having a second plurality of electrically insulated resistance heating strips (122_1, 122_2, ..., 122_m, ..., 122_M) that extend in the direction of a second axis (y) different from the first axis within the reference plane, A method comprising supplying controlled power to each of the first and second plurality of resistance heating strips (121_1, 121_2, ..., 121_n, ..., 121_N, 122_1, 122_2, ..., 122_m, ..., 122_M) in order to heat the substrate in a controlled spatial distribution over the region of the free surface (13), wherein each pair of the first plurality of resistance heating strips and the second plurality of resistance heating strips overlaps in their respective regions.

Images