Patent Application
20060144584
The present invention relates to a cooling system for cooling a subject body to regulate a temperature of the subject body in the course of a surface treatment process utilizing vacuum.
To improve physical or chemical properties or add novel functions, various surface treatments on subject bodies utilizing vacuum are popularly practiced. As the surface treatments, film deposition, surface modification, surface nitriding, surface carbonization or carburisation, dry etching and such can be exemplified. The film deposition can be further categorized into two categories of so-called “Physical Vapor Deposition” (PVD hereinafter), in which film is grown under a physical process such as vacuum evaporation, and “Chemical Vapor Deposition” (CVD hereinafter), in which film is grown under a chemical process, in general. The surface treatments are processed with utilizing plasma in certain cases and CVD utilizing plasma is called “Plasma CVD”.
The surface treatments utilizing vacuum employs vacuum processing apparatuses which have constitutions preferable to the respective treatments.
The vacuum processing apparatus 100 is provided with a chamber 102, the interior of which is evacuated and then applied to a surface treatment, and a cooling system 104. The apparatus may be further provided with a heater, not shown in the drawings, for supplementary heating of a substrate. The cooling system 104 absorbs heat entering the substrate via a heat absorption portion 104A. The absorbed heat is conducted via a heat transfer portion 104C to a heat radiation portion 104B as indicated by an arrow AR10. The heat radiation portion 104B is provided with a water-cooling jacket 104D and the heat is radiated thereby so that the substrate is cooled.
One of technical problems of the prior vacuum processing apparatuses 100 and 120 is how properly regulating the temperature of the substrate. Supplied energy for surface treatment, such as heat injected into ingredient gases or plasma, may be changed as necessary and hence the heat entering the substrate is changed in each case. Radiation heat radiating to the substrate may also vary according to constitutions of auxiliary equipments housed in the chamber 102, and the same is true in a case of radiation heat radiating from the substrate. The temperature of the substrate depends on a balance among the aforementioned heats, the supplementary heat applied by the heater and heat drained by the cooling system 104.
In a case where the injected heat is relatively large, the supplementary heat by the heater comes to be nearly unnecessary so that the heater cannot effectively regulate the temperature of the substrate. On the other hand, the constitution of the cooling system 104 is uneasy to be changed so as to change the amount of heat draining therefrom. This leads to a complication of the constitution of the cooling system 104 so as to allow replacement of members thereof and further makes work on the replacement significantly laborious. More specifically, the prior vacuum processing apparatus has a problem of deficiency of controllability concerning with the substrate temperature.
The present invention is achieved in view of the above problem and intended for providing a cooling system for a vacuum processing apparatus, which can properly regulate a temperature of a subject body though simply constituted.
According to a first aspect of the present invention, a cooling system is provided with a heat pipe for transfer of heat entering a subject body which is treated with a vacuum treatment. Preferably the heat pipe is provided with a heat collection member. More preferably the heat collection member is surface-treated so as to have a larger radiation coefficient.
According to a second aspect of the present invention, a cooling system for a vacuum processing apparatus is provided with an internal heat conduction path for transferring heat entering a subject body, a heat radiation path for radiation of the transferred heat to an outside of the vacuum processing apparatus and a heat conduction path for regulation of quantity of heat transfer between the internal heat conduction path and the heat radiation path. Preferably, the heat conduction path is provided with a wall member, which isolates the inner heat conduction path and the heat radiation path so as to form a space, and a fluid regulation unit, which controllably fills a fluid for heat conduction into the space. More preferably, the fluid is gas. Further more preferably, the gas is one or more gases selected from a group of gases having high heat conduction coefficient. Still further preferably, the heat conduction path is so configured as to have 1/10 or less of the heat transfer quantity when the space is vacant compared with the heat transfer quantity when the space is filled with the fluid. Additionally preferably, the wall member is provided with an inner surface having a radiation coefficient of 0.7 or less. More preferably, an inner surface of the wall member is surface-treated so as to have a radiation coefficient of 0.7 or less. Further more preferably, the inner heat conduction path is provided with a heat pipe.
A first embodiment of the present invention will be described hereinafter with reference to
When depositing the thin film, a chamber 5 of the vacuum processing apparatus 1 includes ingredient gas in a depressurized state, for example, at less than 1000 Pa. Electricity is supplied thereto so as to generate plasma. A subject body W1 is closely attached to and supported by a holder 9 and receives heat input AR1 from the plasma. Against heating by the heat input AR1, the subject body W1 is cooled by the cooling system 3 so as to be a proper temperature. To give preferable quality to the thin film deposited on the subject body W1, it is an important technical problem to properly regulate the temperature and control a state of the plasma.
The cooling system 3 is provided with an inner heat conduction path composed of a heat pipe 7 so as to conduct the heat AR1 received by the subject body W1. One end 7A of the heat pipe 7 is thermally connected to the holder 9 and the other end 7B is thermally connected to one end 11A of a cooling member 11. The holder 9 and the cooling member 11 are made of any material having high thermal conductivity such as metal so as to effectively conduct heat.
The cooling member 11 is further provided with a heat radiation path 12 connecting with an outside of the vacuum processing apparatus 1. Through the heat radiation path 12, a cooling medium such as cooling water flows as indicated by an arrow AR2 in
Alternatively, the heat radiation path 12 can be constituted in accordance with a modified example shown in
A heat radiation path 12A according to a first modification shown in
A heat radiation path 12B according to a second modification shown in
According to any of the aforementioned modifications, a cooling medium for extraction of heat does not flow through the chamber 5. Thereby, when the thin film deposition is completed and hence cooling becomes unnecessary, possibility of unintended cooling of the interior of the chamber 5 by the cooling medium is reduced.
As shown in
The heat transfer space 13 is thermally connected to a fluid control unit 15 from which the fluid is injected. The fluid control unit 15 controls an amount and/or a pressure of the fluid so as to function as a heat conduction switch which turns heat conduction on and off. Meanwhile, when the fluid control unit 15 is operated so as to control variation and/or the pressure of the fluid, the fluid control unit 15 can control the heat flow passing through the heat transfer space 13. In this case, the heat transfer space 13 functions as a variable resistance to heat conduction.
Quantity of the heat transfer between the walls 13A and 13B can be changed dependently on thermal conductivity, which is determined by the cross-sectional area and the length of the heat transfer space 13, the coefficient of heat conductivity and the pressure or the volume of the fluid filled therein.
In view of improvement of controllability of the heat flow, certain advantages are given by a constitution in that a ratio of a heat transfer quantity when the heat transfer space 13 is filled with the fluid to a heat transfer quantity when the heat transfer space 13 is vacant is made larger. A heat transfer ratio is preferred to be smaller, preferably 1/10 or less and more preferably 1/20 or less, where the heat transfer ratio is defined as a ratio of a heat transfer quantity when the heat transfer space 13 is vacant to a heat transfer quantity when the heat transfer space 13 is filled with the fluid.
The heat transfer space 13 can be designed so that the heat transfer ratio is regulated to be an appropriate value by properly determining a gap d of the heat transfer space 13, respective radiation coefficient ε1, ε2 of the wall member 13A, 13B and a thermal conductivity k of the fluid filled therein. Calculation of heat transfer will be demonstrated hereinafter, in which the heat transfer quantity is calculated as a value divided by a unit area, namely, as a heat flux. For example, when the temperature of the wall member 13A is 150 degrees C. and the temperature of the wall member 13B is 200 degrees C., and provided that the gap d of the heat transfer space 13 is 2 mm and hydrogen gas (k=0.2 W/mK in approx.) is filled therein at an enough pressure, the heat flux is k×(200-150° C.)/d=5000 W/m2. Meanwhile, when the heat transfer space 13 is vacant, the heat flux can be calculated on the basis of proximity in which the heat is conducted only by radiation of the wall members 13A, 13B. Therefore, supposing the radiation coefficients ε1=ε2=0.4, the heat flux becomes 250 W/m2. Thus the heat transfer space 13 can be designed so that the heat transfer ratio is 1/20.
Either gas or liquid can be applied to the fluid.
The heat transfer space 13 is filled with gas supplied from the fluid regulation unit (gas regulation unit) 15. Any metal such as an In—Ga eutectic alloy, which is liquid at the working temperature, can be preferably applied to the fluid. In a case where the liquid incompletely fills the heat transfer space 13 as shown in
An operation of the cooling system 3, in accordance with a case where thin film is deposited on a planar subject body W1 in the vacuum processing apparatus 1, will be described hereinafter. In the following description, an example in which the heat transfer space 13 is filled with hydrogen gas is given.
During depositing thin film, as shown by an arrow AR1 in the drawing, heat enters the subject body W1 in surface-contact with and supported by the holder 9. The entering heat is conducted via the holder 9 to the end 7A of the heat pipe 7 and further conducted via the heat pipe 7 to the other end 7B.
Subsequently the heat is conducted from the other end 7B to the end 11A of the cooling member 11 and further conducted to the hydrogen gas filling the heat transfer space 13. The heat is further conducted to the other end 11B of the cooling member 11 and cooled by a cooling medium shown as an arrow AR2.
When completing the thin film deposition, the hydrogen gas is removed from the heat transfer space 13 by means of the fluid regulation unit 15 so that the resistance of the heat transfer space 13 to the heat flux is increased.
Subsequently, before disposing a next subject body to the holder 9 in the chamber 5, the interior of the chamber 5 is heated up to a temperature which is proper to the thin film deposition. The temperature of the holder 9 is immediately raised since the cooling system 3 is composed of the heat pipe 7 so as to have a small heat capacity and the resistance of the heat transfer space 13 to the heat flux is increased. Furthermore, because the resistance of the heat transfer space 13 to the heat flux is increased, even if the cooling medium shown as the arrow AR2 keeps flowing, the cooling medium is not obstructive to the temperature increase of the holder 9. Additionally, the cooling medium does not excessively cool the end 11A of the cooling member 11, thereby energy consumption in a standby state can be suppressed.
When the chamber 5 is heated up to the proper temperature, the heat transfer space 13 is filled with hydrogen gas and the thin film deposition and the cooling are repeated.
According to the cooling system 3 of the first embodiment, the temperature of the subject body can be properly regulated with such a simple constitution. Because of the simple constitution, when performing maintenance of the vacuum processing apparatus 1, uninstallation and installation of the cooling system 3 can be easily performed. Additionally the temperature of the subject body W1 can be immediately and properly regulated because the heat pipe 7 is employed.
Furthermore, because efficiency of cooling can be regulated by means of proper regulation of the gas in the heat transfer space 13 by the fluid regulation unit 15, the temperature of the subject body can be properly regulated independently of heat quantity input to the subject body. Thereby quality of the thin film can be improved.
Additionally, the holder 9 can be disposed in a vertical or slanted position though the holder 9 is disposed in a horizontal position according to the aforementioned cooling system 3, however, the cooling member 11 is preferably disposed in an upper position of the holder 9 because the heat pipe is suitable to heat conduction in a vertical direction.
In addition, to increase the resistance of the heat transfer space 13 to the heat flux, pressure of the gas filled therein may be decreased so that so-called molecular flow state in which mean free path of the gas is larger than sizes of the heat transfer space 13 is obtained.
Moreover, to further increase the resistance of the heat transfer space 13 to the heat flux, the wall member 13A, 13B, at least the inner surfaces thereof, may be surface-treated so as to have a smaller radiation coefficient. As such surface-treatments, coating by means of plating, ion-plating and such, or surface finishing such as finishing so as to decrease surface roughness, buffing, electrolytic polishing and such are preferable. Lowering the radiation coefficient results in increasing controllability of the heat flux and hence the radiation coefficient is preferably 0.7 or less and more preferably 0.4 or less.
A cooling system 33 and a vacuum processing apparatus 31 will be described hereinafter with reference to
According to the present embodiment, the subject body W1 is disposed distantly from a heat pipe 37. The heat pipe 37 is provided with a heat collection member 39 which is configured so as to effectively absorb heat AR6 by means of heat transfer and/or radiation via the gas in the vacuum processing apparatus 31.
For effective absorption of the heat AR6, the heat collection member 39 may be properly surface-treated so as to have a larger radiation coefficient. As such surface treatments, oxidation, nitriding, aluminum anodization, blasting, proper coating, spraying such as Al2O3, plating such as chromia, ceramics coating and such are preferable.
The subject body W1 and the heat collection member 39 are disposed in parallel with each other and in a vertical position.
The heat absorbed by the heat collection member 39 is conducted via the heat pipe 37 to the cooling member 11 and radiated as indicated by an arrow AR7 similarly to the aforementioned first embodiment.
The cooling system 33 of the present embodiment has the same effect as the cooling system 3 of the aforementioned first embodiment and has another effect of expanding freedom degrees of disposition because the subject body W1 is disposed distantly from the heat collection member 39. Furthermore, two of the subject bodies W1 may be simultaneously cooled.
Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. For example, a planar subject body has been exemplified, however, any subject body of various shapes can be applied. Further, if necessary, the shapes of the holder and the heat collection member can be properly modified. Furthermore, the present invention can be applied to various vacuum processing apparatuses such as a dry-etching apparatus, a sputtering apparatus, a vacuum evaporation apparatus, a cat-CVD apparatus and the like, not limited to the plasma CVD apparatus.
The present invention provides a cooling for cooling a subject body, the temperature of which can be effectively regulated by a simple constitution.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-038052 | Feb 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/00424 | 1/20/2004 | WO | 8/17/2005 |
