Patent Application
20120317993
1. Field of the Invention
The present invention generally relates to heating and cooling a workpiece in an atmospheric controlled chamber and, more particularly, to the application of a thermopile device in an atmospheric controlled chamber for achieving one or more of lower/higher workpiece temperatures, greater cooling/heating rates, and greater flexibility in the control of cooling/heating rates.
2. Description of Related Art
Generally speaking, a workpiece (e.g., a semiconductor wafer, a glass plate, or other plate-like object) can be processed to fabricate different devices, such as an integrated circuit, a memory, a liquid crystal display (LCD), a solar cell, and so on. Different processes sometimes require different processing environments. As room temperature and an atmospheric environment typically surround machines used for processing the workpiece, the workpiece is sometimes treated (e.g., cooled or heated) in an atmospheric controlled chamber in the machine to adjust the workpiece between the outside environment and the required processing environment within a process chamber.
For example, to minimize a non-uniform processing result distribution over a workpiece during an ongoing process, temperatures of different portions of the workpiece may be flexibly adjusted. For instance, lowering the workpiece temperature before implantation to reduce thermal diffusion of the dopants (such as implanted ions) induced by the kinetic energy of the dopants can render the distribution of the dopants more controllable.
Generally, the workpiece heating is accomplished with electric heaters or heated circulating fluid in a pedestal (or viewed as a workpiece holder) upon which the workpiece is placed, by near infrared heat lamps placed in proximity, by heated gas flowing around the workpiece, and so on. Similarly, the workpiece cooling is accomplished by a chilled fluid or gas circulated in the pedestal or around the workpiece. As usual, a chiller is used to provide the heated fluid with a specific temperature. Moreover, heat lamps may heat the workpiece by transmitting heat through an appropriate full spectrum window in the chamber wall. As usual, the workpiece is held by gravity on the pedestal or a partial vacuum is introduced between the workpiece and the pedestal to hold the workpiece close to the pedestal, and the pedestal transmits heat by radiation or a low pressure interfaces gas. In order to enhance the heat transfer rate between the workpiece and the pedestal, an electrostatic chuck or other equivalent device may be employed to hold the workpiece tightly to the pedestal, so that greater heating/cooling rates can be accomplished with minimal interface gas leaking into the surrounding vacuum.
These existing techniques are not without disadvantages.
First, in some cases, the materials allowed in the atmospheric controlled chamber may be restricted, thereby limiting the temperature that the workpiece can achieve. For instance, though popularly used in the semiconductor industry because of its relatively benign characteristics with respect to the device being created, aluminum has a service temperature sometimes below that designed for some processes, resulting in those processes not being properly operated when hardware being used is made of aluminum. Moreover, while static pedestal may present little problems, the dynamic pedestal capable of translating the workpiece in any direction, rotating the workpiece about any axis and/or tilting the workpiece about any axis during a period of processing the workpiece may experience appreciable design difficulties at temperatures below −60° C. and at elevated temperatures. As usual, at least a portion of the dynamic pedestal is made of elastomers to provide the required freedom of translation/rotation/tilting. However, the lower temperature affects elastomers in such a way as to make them brittle and unusable for sealing or structural purpose. Therefore, in chamber environments employing a dynamic pedestal and low workpiece temperature, the design of appropriate seals and mechanisms becomes very difficult if not impossible. The same problem occurs when the workpiece temperature is higher, because the quality of the material, such as metal and elastomer, is degraded under the higher temperature too.
One more disadvantage is the smaller (or limited) cooling/heating rates on the workpiece. The heat transferred between two surfaces is a function of temperature differential, distance apart, the fluid/gas in-between them, and so on. To avoid the degradation of the material, such as the elastomer, the available temperature range of a pedestal is limited. Therefore, when the workpiece is just moved from the atmospheric environment into the machine, the temperature differential between the pedestal and the workpiece is limited or finite, and then the cooling/heating rates of the workpiece is smaller (e.g., not fast enough for improving the throughput).
A consequential disadvantage is the smaller flexibility and precision on the adjustment of the workpiece temperature. A chiller outside the machine is popularly used to adjust the temperature of the pedestal. However, for many commercial chillers, the servo control of temperature can be affected but the time required to adjust temperature may be long and imprecise. Hence, the workpiece temperature may be not precisely controlled or even not flexibly adjusted to meet the different requirements of differential processes.
Furthermore, these existing techniques and other process(es) are typically performed separately. For example, the load lock venting process used when the workpiece is transported between a vacuum environment inside the process chamber and an atmospheric environment outside the machine is a single step, not used in parallel with any wafer change of state step. Hence, the total throughput is decreased, because the cooling/heating process usually is performed after/before other process(es).
For the aforementioned and other relative disadvantages associated with the existing techniques, a need has arisen to propose a novel approach that is capable of improving on the above disadvantages of the existing techniques.
In view of the foregoing, the present invention provides an atmospheric controlled chamber capable of controlling workpiece temperature and a method of controlling workpiece temperature in an atmospheric controlled chamber. The atmospheric controlled chamber may be evacuated, at a partial pressure, at atmospheric pressure, or in transition. The atmospheric controlled chamber may be a load lock chamber, a process chamber, or a separate chamber dedicated to bringing the workpiece to a desired temperature. In comparison with current practices, the invention may function to reduce heating and cooling times, achieve a greater workpiece temperature range, achieve a more precise final workpiece temperature, and/or adjust the workpiece to different temperatures more quickly.
According to one embodiment, an atmospheric controlled chamber capable of controlling workpiece temperature is provided inclusive of the following elements: a chamber wall surrounding a space, a support assembly located in the space and capable of holding a workpiece over a specific (e.g., special, or predetermined) surface of the support assembly, a heat-transfer assembly located close to the support assembly and capable of transferring heat to and from the exterior of the space, and at least one thermopile device disposed in the support assembly, wherein the thermopile device is configured to transfer heat between the specific surface of the support assembly and the heat-transfer assembly. Optionally, the thermopile device is a Peltier device including at least one p-type semiconductor element and at least one n-type semiconductor element connected in series, wherein at least one p-type and n-type semiconductor elements are driven by a power supply. Optionally, a gas assembly may be surrounded by the chamber wall and capable of controlling a gas on the specific surface of the support assembly, whereby the gas is used as a thermal medium between the held workpiece and the specific surface of the support assembly.
According to the other embodiment, a method of controlling workpiece temperature is disclosed. Initially, a workpiece is moved from a first environment into a chamber, wherein the workpiece has a first workpiece temperature. Next, the workpiece is located over a top surface of a support assembly positioned inside the chamber, wherein a heat-transfer assembly is disposed close to the support assembly and is capable of transferring heat to and from the exterior of the chamber, and wherein at least one thermopile device is disposed in the support assembly and is configured to transfer heat between the top surface of the support assembly and the heat-transfer assembly. Then, the temperature of the workpiece in the chamber is adjusted by using the thermopile device and using the heat-transfer assembly simultaneously. Finally, the workpiece is moved away from the chamber and into a second environment following the workpiece being adjusted to have a second workpiece temperature. Each of the environments may be or may comprise an atmospheric space, a cassette, a load lock chamber, a main chamber configured to connect at least one load lock chamber and at least one process chamber where the workpiece is processed, a chamber connected to the main chamber, or a process chamber.
The chamber wait 11 surrounds a space, and has one or more openings (not shown in the figure for brevity) disposed on different portions of the chamber wall 11, so that the workpiece 10 may be transferred into the space and/or transferred away from the space. The support assembly 12 is located in the space and is capable of holding the workpiece 10 over a specific (e.g., special, or predetermined) surface 125 of the support assembly 12. The workpiece 10 to be processed in, stored in and/or transferred through the atmospheric controlled chamber will be held by the support assembly 12 and located over the specific surface 125. The heat-transfer assembly 13 is located close to the support assembly 12 and is capable of transferring heat to and from the exterior of the space. As usual, the heat-transfer assembly 13 may be viewed as a portion of a heat sink mechanism. The at least one thermopile device 14 is disposed in the support assembly 12 and almost sits directly on the heat-transfer assembly 13 (e.g., almost directly in contact with the heat-transfer assembly 13), wherein the thermopile device 14 is configured to transfer heat between the specific surface 125 (e.g., the held workpiece 10) and the heat-transfer assembly 13. In other words, the at least one thermopile device 14 is in series between the specific surface 125 and the other surface of the support assembly 12 (e.g., in series between the workpiece 10 and the heat-transfer assembly 13). Hence, by using both the heat-transfer assembly 13 and the thermopile device 14, heat may be carried into or away from the workpiece 10 so that the temperature of the workpiece 10 is adjusted and controlled.
As an example, with reference to
Two ends of the coolant tube group 132 are connected to, respectively, the coolant body 131 and a chiller 15 located outside the atmospheric controlled chamber 11. Coolant agent or coolant fluid (such as cooling liquid or heating gas) circulates between the chiller 15 and the coolant body 131 through the coolant tube group 132, so that heat may be carried away or carried into the support assembly 12. That is, although not particularly shown in the figures, the coolant tube group 132 has at least one inlet tube and at least one outlet tube to ensure the circulation of the coolant agent or coolant fluid. In this way, the coolant body 131, the coolant tube group 132, and the chiller 15 together act as the heat sink mechanism.
The thermopile device 14 may be any electronic device capable of using an electric current for an electric voltage) to create a temperature differential between different sides of the thermopile device 14, i.e., the thermopile device 14 may be considered as a heat pump. Because the position of the thermopile device 14 is in series between the specific surface 125 and the other surface of the support assembly 12, the heat may be pumped between the heat-transfer assembly 13 and the specific surface 125. Accordingly, the temperature of the workpiece 10 close to the specific surface 125 may be adjusted to be different than the temperature of the heat-transfer assembly 13. In other words, when the heat-transfer assembly 13 for viewed as the heat sink mechanism including the heat-transfer assembly 13) is operated at a fixed temperature, the thermopile device 14 allows the temperature of the workpiece 10 to be lower or higher than the fixed temperature (dependent on the heat being pumped away or into the workpiece 10). Note that the materials and constructions of the thermopile devices 14 usually do not lend themselves to direct contact with the workpiece 10 close to the specific surface 125.
As shown in
Besides, in all cases, heating and cooling, the flexible operation of the thermopile device 14 can be used to servo control the temperature of the workpiece 10 to the desired final temperature. Optionally, the operation of the thermopile device 14 may be switched between on and off, or may be continuously varied within its capacity. Moreover, the thermal mass of each of the thermopile devices 14 and support assembly 12 usually is relatively smaller than the thermal mass of the heat sink mechanism, such as the thermal mass of the combination of the heat-transfer assembly 13 and the chiller. Hence, the response time for temperature change is shorter compared to the response time for temperature changes created in conventional ways. Even though the heat sink mechanism may change temperature slightly during the heat pumping operations, the thermopile device 14 may be servo operated to maintain the workpiece at the desired temperature, attenuating or nulling out any heat sink mechanism temperature changes.
Particular configurations of the thermopile device 14 are not intended to be limited herein. For example, embodiments of one or more thermopile devices 14 can comprise one or more Peltier devices which may be constructed so that the heat can be pumped in both directions (from the heat-transfer assembly 13 to the specific surface 125, and from the specific surface 125 to the heat-transfer assembly 13), and/or may be constructed so that one or more of the Peltier devices are installed in opposite direction pairs to pump heat in both directions.
In short, with the usage of the thermopile device 14, not only the temperature of the workpiece 10 inside the atmospheric controlled chamber may be enlarged, but also the control capability of the temperature of the workpiece 10 may be improved. Note that the thermopile device 14 is well-known to persons skilled in the pertinent art and has been used in the fabrication of integrated circuits. Therefore, when the invention proposes new applications of the thermopile device 14, details of the thermopile device(s) 14, such as the composition and the construction, are omitted for brevity.
To present how the throughput is improved by the atmospheric controlled chamber as discussed above,
Clearly, the adjusting rate of the workpiece temperature is a function of the pressure of the essentially static gas trapped under the workpiece 10 and above the specific surface 125. In addition, different atmospheric controlled chamber configurations and different workpiece configurations (such as diameter and thickness) may correspond to different suitable pressure range. Note that the use of gas pressure to control workpiece temperature is anticipated in view of the great cooling rates that can be achieved with a large temperature differential. For example, the gas pressure may be lowered or removed when the workpiece reaches the desired temperature even though that temperature is higher than the support assembly temperature. This pressure control in conjunction with modulation of the thermopile can control heat flow from the workpiece at the desired temperature as required by the process.
Therefore, to enhance the efficiency of the atmospheric controlled chamber, as shown in
Details on how the gas assembly 16 ensures the existence of the gas are not particularly limited. For example, the gas assembly 16 may be connected to an external gas source outside the atmospheric controlled chamber. Here, the external gas source could be a nitrogen source which is popularly used in the semiconductor industry for cleaning, venting, plasma generating, cooling, and so on. For example, to uniformly distribute the gas between the held workpiece and the support assembly 12, a portion of the gas assembly 16 may be embedded in the support assembly 12 so that the gas is delivered through the center of the specific surface 125 to be the essentially static gas trapped under the workpiece 10 and above the specific surface 125.
Furthermore, to enhance the interaction between the gas and both the held workpiece 10 and the support assembly 12 (e.g., to increase the heat transfer efficiency through the gas), the specific surface 125 may be not flat and some hardware designs may be assigned. For example, the top portion of the support assembly 12 may resemble a waffle having a series of ridges and valleys, so that numerous small interstices are formed. The gas that exists in the small interstices behaves as thermal medium between the upper portion and a workpiece held on the specific surface. Also, a raised flange may be positioned on the edge of the specific surface 125 to minimize the leakage of the gas into the portion of the atmospheric controlled chamber when a vacuum environment is required.
In addition, in
Further, the existence of the gas may apply a pressure (or viewed as a force) on the workpiece 10, and then the distance between the support assembly 12 and the workpiece 10 may fluctuate. Hence, as an example shown in
The invention can provide at least one of the following advantages.
First, the problem of elastomer functionality/composition being compromised under lower/higher temperature ranges may be improved. By locating the thermopile device(s) 14 close to the specific surface 125 but locating other devices close to the heat-transfer assembly 13 (such as the sealing devices, the tubes for conducting liquid and the electric lines), the temperature of the workpiece 10 close to the specific surface 125 may be significantly different (lower or higher) than the available temperature of the heat-transfer assembly 13 (such as the available temperature of the conventional chiller). Thus, scratch, fissure, particle contamination, brittleness, degradation, and other defects of the used materials (such as plastic, rubber, other elastomers, or metal) induced by lower/higher temperature may be avoided, especially in situations where the elastomer is popular material for the sealing devices, the tubes and so on. The advantage is more valuable when the workpiece 10 has to be moved and/or rotated inside the atmospheric controlled chamber, because the quality requirement of the elastomer is less strict in such conditions.
Second, the cooling rate (also the heating rate) of the workpiece 10 may be significantly improved. As discussed above, the temperature at the specific surface 125 may be further tower (or higher) than the available limitation of the conventional chiller. Hence, the available temperature differential between the specific surface 125 and the workpiece 10 may be larger than that of the conventional chiller, so that higher cooling/heating rates may be induced until the workpiece temperature is changed to be almost equal to the temperature at the specific surface 125. As the examples shown in
Third, the workpiece temperature may be flexibly and precisely adjusted. Thermopile device(s) 14 are driven by a power supply, and operation of the power supply can be switched between on and off immediately, even can be continuously varied with its capacity. Plus, the thermal mass of the thermopile device(s) 14 is smaller than the thermal mass of the connected heat sink mechanism. Therefore, by flexibly selecting and maintaining the temperature differential across the thermopile device with the thermopile device's capability, the heat pumping rate may be servo controlled during the cooling/heating process to flexibly and precisely adjust the workpiece temperature. In addition, the servo control can be slow because of the mass of the workpiece 10 being large, and it can take a while for it to cool down or heat up. And then, it may be the case that only the thermopile device(s) 14 is controllable with a rather fast response whereby heat can be moved away/into the workpiece 10 held by the support assembly 12 at almost any rate chosen within its capability.
Fourth, throughput may be further improved. The heat pump function of the thermopile device(s) 14 is dependent on some key factors, such as the operation of the connected power supply, the configuration of the thermopile device(s) 14 in the support assembly 12, and the essentially static gas between the workpiece 10 and the specific surface 125. Therefore, when the on-going process inside the atmospheric controlled chamber does not significantly affect the above key factors (such as does not affect the pressure of the essentially static gas), also when the accompanied adverse effect is acceptable (such as no more moisture formed on the workpiece 10), the cooling/heating process and the on-going process may be performed simultaneously. For example, owing to the popularly used N2 gas will not react with the held workpiece 10, the cooling/heating process and the vacuum venting process may be performed at the same time. Therefore, besides the greater cooling/heating rates provided, the throughput of a machine having the proposed atmospheric controlled chamber may be further improved.
As one example of the control of the workpiece temperature, when a workpiece is cooled (or heated) from an original temperature to a desired temperature, the heat pump function of the thermopile device(s) 14 can be temporarily turned off to avoid further adjustment on the workpiece temperature. Then, the thermopile device(s) 14 can be turned on again after the temperature differential between the workpiece temperature and the desired temperature exceeding a predetermined limitation. By alternately turning on and off the thermopile device(s), the workpiece temperature may be flexibly and precisely fixed at the desired temperature. As an alternative example of the control of the workpiece temperature, when a workpiece is moved into the proposed atmospheric controlled chamber, the thermopile device(s) may be operated with a maximum voltage to cool the workpiece down as quickly as possibly. Then, when the workpiece is at about the desired temperature, the voltage may be continuously varied in conventional servo system type operation to maintain that workpiece temperature. Herein, the voltage may be decreased to slowly cool the workpiece, even the voltage direction may be reversed to heat the workpiece, and the voltage may be increase to quickly cool the workpiece.
As one more example of the operational advantage of the proposed invention, the held workpiece may be moved away from the thermopile device(s) when the workpiece reaches about the desired temperature. For example, by using the extendable lift pins or other equivalent mechanism to change the relative distance between the workpiece and the support assembly. Here, the changed in relative distance will affect how the workpiece temperature is adjusted by the thermopile device(s). Therefore, even if the operation of the thermopile device(s) is fixed during the cooling/heating process, the workpiece temperature still may be effectively and precisely controlled. In this mode, the shortest temperature adjusting time is accomplished by setting both the heat-transfer assembly and the thermopile device(s) at their maximum lowest temperature, placing the workpiece on the support assembly for a prescribed time or until it reaches the desired temperature, then lifting the workpiece off the support assembly, the heat-transfer assembly and the thermopile device(s). In this way, the maximum cooling rate (or the maximum heating rate) and the minimum cooling time (or the minimum cooling time) can be achieved. Clearly, this way is more suitable for the pre-cooling activity and the pre-heating activity, because the workpiece usually is tightly held again the support assembly in a process chamber to transfer heat and maintain control of workpiece while the workpiece is manipulated.
Particulars on the atmospheric controlled chamber are not intended to be limited, besides according to some aspects the usage of the thermopile device(s). Therefore, the atmospheric controlled chamber may be any chamber in a machine capable of processing a workpiece, e.g., a load lock chamber, a process chamber, a main chamber configured to connect at least one load lock chamber and at least one process chamber, and any chamber connected to the main chamber,
According to aspects in which the heat-transfer assembly 13 is limited by function, the heat-transfer assembly 13 may not be connected to an external chiller but is thermally coupled with any mechanism capable of cooling/heating a workpiece. For example, the heat-transfer assembly 13 may be heated by one or more near infrared heat lamps placed in proximity thereto, with the thermopile device(s) 14 being applied to further adjust the workpiece temperature. By flexibly adjusting the operation of the thermopile device(s) 14, even by flexibly adjusting the heat pump direction of the thermopile device(s) 14, the workpiece temperature may be flexibly and precisely adjusted, with the mechanism capable of cooling/heating being stably operated.
Similarly, the atmospheric controlled chamber may be any chamber capable of performing any heating and/or cooling technique. Note that the combination of the thermopile device(s) 14 and the heat-transfer assembly 13 may be operable to achieve extreme temperatures as compared to the heat-transfer assembly 13 alone. Hence, when the temperature of the heat-transfer assembly 13 is controlled by any heating/cooling technique, to achieve the same adjustments on the workpiece temperature, the present invention may loosen the required working conditions of the heating/cooling technique. For example, when the desired workpiece temperature is −40° C. and a used thermopile device is capable of providing temperature differential at 35° C., the heat-transfer assembly 13 may be operated at only −5° C., which is more simple than being operated at −40° C.
One main characteristic of the exemplary implementation stems from performing the cooling/heating process, i.e., temperature adjustment process, during the movement of a workpiece inside a machine capable of processing the workpiece, so as to improve the total throughput. The chamber may be any chamber in the machine, and the timing of cooling/heating the workpiece is not particularly limited. Therefore, each of the first environment and the second environment may be or may comprise one or more of an atmospheric space outside the machine, a cassette outside the machine, a load lock chamber, a main chamber configured to connect at least one load lock chamber and at least one process chamber where the workpiece is processed, the process chamber, and a chamber connected to the main chamber and may be used to temporarily store or dedicate to be cool/heat the workpiece.
To keep the workpiece temperature at the desired temperature, in block 703, the thermopile device may be temporarily turned off following the workpiece temperature being essentially equal to the second workpiece temperature and re-turned on following the workpiece temperature being different significantly than the second workpiece temperature. Alternatively, in block 703, the operation of the thermopile device may be continuously varied when the workpiece temperature is about equal to the second workpiece, so that the workpiece is gradually cooled and/or heated and then the workpiece may be kept around the desired temperature. Further, the relative distance between the workpiece and the thermopile device(s) may be flexibly adjusted, so that the workpiece temperature may be quickly adjusted and then kept at desired temperature in sequence. Accordingly, even with the workpiece being not immediately processed in any process chamber or not immediately moved into the atmospheric environment, the temperature of the pre-adjusted workpiece still may be kept in an acceptable temperature range.
One popular practical configuration of the thermopile devices is the usage of Peltier device(s) including at least one p-type semiconductor element and at least one n-type semiconductor element connected in series. Moreover, besides the at least one p-type and n-type semiconductor elements being driven by a power supply, the Peltier device(s) may be constructed so that heat can be pumped in both directions and/or installed in opposite direction pairs to pump heat in both directions.
Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
