COOLING DEVICE, METHOD FOR COOLING A COOLING ELEMENT AND LAYER DEPOSITION APPARATUS

Abstract

Cooling device, layer deposition apparatus and method for cooling a cooling element. Therein, the cooling device comprises a cooling element having a cooling duct with an inlet and an outlet. With the inlet a compressed gas supply is connected via a supply line. Further a spray supply line is connected to the supply line, wherein a spray nozzle is connected to the spray supply line to nebulize a liquid coolant and feeding the nebulized coolant into the supply line.

Claims

1. A cooling device for a vacuum apparatus comprising: a cooling element having a cooling duct with an inlet and an outlet, wherein the inlet is connected to a compressed gas supply via a supply line, a spray supply line connected to the supply line, wherein a spray nozzle is connected to the spray supply line to nebulize a liquid coolant and feeding the nebulized coolant into the supply line.

2. The cooling device according to claim 1, wherein the cooling element comprises a sample holder or is built as baffle.

3. The cooling device according to claim 1, wherein the spray nozzle is a needle valve.

4. The cooling device according to claim 1, wherein the spray supply line has inlet valve, wherein the inlet valve is configured to increase the nebulized liquid coolant with decreasing temperature of the cooling element.

5. The cooling device according to claim 1, wherein the pressure of the spray supply line is controllable to be increased with decreasing temperature of the cooling element.

6. The cooling device according to claim 1, wherein the spray supply line has an inlet valve, wherein the inlet valve is configured to increase the duty cycle between an at least partially open position of the inlet valve and a closed position of the inlet valve to increase the nebulized liquid coolant with decreasing temperature of the cooling element.

7. The cooling device according to claim 4, wherein the spray nozzle is the inlet valve.

8. The cooling device according to claim 1, wherein a coolant supply line is connected to the supply line to supply a liquid coolant the cooling element, wherein the coolant supply line comprises a coolant inlet valve configured to open at a temperature of the cooling element below a threshold temperature and close at a temperature of the cooling element above the threshold temperature, wherein preferably the threshold temperature is below the boiling point of the liquid coolant.

9. A method for cooling a cooling element of a vacuum apparatus comprising: Providing compressed gas to the cooling element; and Providing a nebulized liquid coolant to the cooling element by the compressed gas.

10. The method according to claim 9, wherein the amount of nebulized coolant is increased with decreasing temperature of the cooling element.

11. The method according to claim 10, wherein the pressure of liquid coolant to be nebulized is increased with decreasing temperature of the cooling element.

12. The method according to claim 10, wherein an inlet valve of a spray supply line is opened further with decreasing temperature of the cooling element.

13. The method according to claim 10, wherein an inlet valve of a spray supply line is opened longer in a duty cycle with decreasing temperature of the cooling element.

14. The method according to claim 9, wherein below a threshold temperature of the cooling element a liquid coolant is provided to the cooling element, wherein preferably the threshold temperature is below the boiling point of the liquid coolant.

15. A layer deposition apparatus comprising a vacuum chamber, a sample holder disposed in the vacuum chamber and a deposition module, wherein the sample holder comprises a cooling device according to claim 1.

Description

DESCRIPTION OF THE DRAWINGS

[0040] In the following the present invention is described in more detail with reference to the accompanying figures.

[0041] The figures show:

[0042] FIG. 1 a cooling device according to the present invention and

[0043] FIG. 2 a detail of controlling the cooling device according to the present invention.

DETAILED DESCRIPTION

[0044] Referring to FIG. 1 showing a cooling device according to the present invention. The cooling device comprises a cooling element 10 which might be built as sample holder or baffle and disposed within a vacuum chamber of a vacuum apparatus. Alternatively, the cooling element 10 might be directly attached to a sample holder or baffle of the vacuum apparatus. The cooling element 10 comprises a cooling duct 12 having an inlet 14 and an outlet 16. The cooling duct 12 is running through the cooling element 10 in order to provide sufficient heat transfer from the cooling element 10 to the coolant provided to the cooling duct 12.

[0045] To the inlet 14 of the cooling duct 12 a supply line 18 is connected. The supply line 18 is connected to a compressed gas supply 20 via a compressed gas inlet valve 22. Thus, compressed gas from compressed gas supply is fed through the cooling duct 12 via the supply line 18 wherein the amount of compressed gas is controlled by the compressed gas inlet valve 22.

[0046] To the supply line 18 a spray supply line 24 is connected wherein a spray nozzle 26 is connected to the spray supply line or integrated into the spray supply line. By the spray nozzle 26 a liquid coolant provided by a liquid coolant supply 30 is nebulized or atomized and fed as mist or fog through the spray supply line into the supply line 18 and into the cooling duct 12 conveyed by the stream of compressed gas. Therein, an inlet valve 28 is disposed in the spray supply line 24. In the example of FIG. 1, the inlet valve 28 and the spray nozzle 26 are illustrated as two separate elements. However, the spray nozzle 26 can at the same time serve as inlet valve 28 integrating both functions. In particular, the spray nozzle 26 is built as needle valve. By the inlet valve 28 the amount of liquid coolant fed to the spray nozzle 26 or the amount of nebulized coolant provided to the cooling element 10 via the spray supply line 24 and the supply line 18 can be controlled and adjusted.

[0047] In an embodiment exemplified in FIG. 1, the cooling device might have further a coolant supply line 36 connected to a liquid coolant supply 32 in order to provide a liquid coolant to the cooling element 10. Therein, the coolant supply line 36 comprises a coolant inlet valve 34 in order to control whether liquid coolant is supplied from the liquid coolant 32 to the cooling element 10. However, the coolant supply line 36 is an optional feature. Thus, if the temperature of the cooling element 10 drops below a certain temperature threshold, the inlet valve 28 is closed, the compressed gas inlet valve 22 and the coolant inlet valve 34 is opened to supply a liquid coolant to the cooling element 10. Therein, the temperature threshold is below 100 C. and preferably 80 C. Thus, by use of a liquid coolant for lower temperatures of the cooling element 10, cooling efficiency can be further increased, decreasing cool down times further.

[0048] Further, the cooling element might comprise a heater or is directly connected to a heater in order to heat up the sample holder or the baffle. Preferably the heater is built as a resistive heater and is configured to heat up the sample holder or baffle to a temperature above 300 C., more preferably above 400 C. and most preferably above 500 C.

[0049] If then the sample is heated up to such high temperatures and in a next step low temperatures are required in the process of layer deposition or the sample shall be removed from the deposition apparatus, the sample must be cooled down. Therein, immediate venting of the vacuum chamber might lead to deteriorating the deposited layer. On the other hand, convectional cooling is inefficient in vacuum and requires a huge amount of time.

[0050] Thus, in accordance with the present invention and in particular in accordance to the method for cooling the cooling element, if the cooling element 10 is at high temperatures a compressed gas is provided to the cooling element 10 from the compressed gas supply 20 by opening the compressed gas inlet valve 22. At the same time the inlet valve 28 in the spray supply line 24 is at least partially opened such that liquid coolant from the liquid coolant supply 30 is nebulized/atomized by the spray nozzle 26 and then conveyed by the compressed gas through the cooling duct 12 of the cooling element. By the nebulized coolant a heat capacity of the mixture of compressed gas and nebulized coolant is increased improving the cooling effect and thereby reducing the cool down times of the cooling element 10 by a factor up to 10.

[0051] Therein, the temperature of the cooling element 10 might be detected and the amount of nebulized coolant is increased with decreasing temperature of the cooling element 10 by control of the inlet valve 28 and/or control of the compressed gas inlet valve 22. For lower temperatures immediate evaporation of the nebulized coolant is reduced thereby reducing the possibility of damages to the cooling element 10 and at the same time increasing the cooling efficiency of the cooling element 10.

[0052] Preferably, in order to increase the amount of nebulized coolant, the pressure of the liquid coolant provided by the liquid coolant supply 30 connected to the spray supply line 24 might be increased thereby increasing the amount of nebulized coolant in the stream of compressed gas and nebulized coolant. At the same time or alternatively, the pressure of the provided compressed air can be reduced preferably by the compressed gas inlet valve 22 in order to increase the difference between the pressures of the spray supply line and the compressed gas supply, thereby increasing the amount of nebulized coolant fed to the supply line 24.

[0053] Preferably, the amount of nebulized coolant is increased by further opening the at least partially opened inlet valve 28 in the spray supply line 24, increasing the amount of nebulized coolant provided to the cooling element 10.

[0054] Preferably, the inlet valve 28 is opened and closed periodically wherein one period of opening and closing may have a time of between 0.5 sec and 10 sec, more preferably between 1 sec and 5 sec and most preferably between 2 sec and 3 sec. The situation is depicted in FIG. 2 showing the temperature 40 for a high temperature section and the temperature 42 for a low temperature section. Signal 44 shows the control signal of the inlet valve 28 for the high temperature section wherein visibly the inlet valve 28 is open for a short amount of time of the overall period. Thus, the duty cycle is small. Therein, preferably the opening times of the inlet valve 28 are between 0.1 sec and 3 sec, more preferably between 0.2 sec and 2 sec and most preferably between 0.3 sec and 1 sec. If the temperature decreases overtime, more nebulized coolant can be fed to the cooling element 10. Thus, the duty cycle is increased as indicated by the control signal 46 for lower temperatures 42 depicted in FIG. 2 leading to an increased amount of nebulized coolant provided to the cooling element further improving the cooling efficiency of the cooling device. Therein, adjustment of the duty cycle can be performed stepwise or continuously in dependence on the temperature of the cooling element 10. Therein, opening times of the inlet valve might be calculated by

[00001]$t_{\mathrm{open}}\left[s\right]=t_{\mathrm{start}}\left[s\right]+\left(t_{\mathrm{period}}\left[s\right]-2*t_{\mathrm{start}}\left[s\right]\right)*\left(T_{\mathrm{init}}\left[C.\right]-T_{\mathrm{act}}\left[C.\right]\right)/\left(T_{\mathrm{init}}\left[C.\right]-T_{\mathrm{dest}}\left[C.\right]\right)$$\mathrm{and}$$t_{\mathrm{close}}\left[s\right]=t_{\mathrm{period}}\left[s\right]-t_{\mathrm{open}}\left[s\right],$

wherein t.sub.period is the total period time of the valve duty cycle, t.sub.open is the valve opening time, t.sub.close is the valve closing time, t.sub.start is the valve start opening time at the beginning of the cooling, T.sub.init is the initial heating temperature, T.sub.dest is the destination cool down temperature and T.sub.act is the actual temperature of the cooling element.

[0055] Therein, start time might be between 0.1 sec and 3 sec, more preferably between 0.2 sec and 2 sec and most preferably between 0.3 sec and 1 sec as indicated above. Initial temperature denotes the temperature of the cooling element 10 before cooling or at the beginning of the cool down process, and actual temperature denotes the current temperature of the cooling element 10. Period time denotes the length of a complete opening-closing cycle of the inlet valve 28 and might be between 0.5 sec and 10 sec, more preferably between 1 sec and 5 sec and most preferably between 2 sec and 3 sec.

[0056] Thus, for a specific example t.sub.period is set to be 2.8 s, t.sub.start is set to be 0.3 s, T.sub.init is set to be 300 C., T.sub.dest is set to be 80 C., then the valve opening times and valve closing times calculate to:

[00002]$t_{\mathrm{open}}\left[s\right]=0.3s+\left(300C.-T_{\mathrm{act}}\left[C.\right]\right)*s/100C.$$\mathrm{and}$$t_{\mathrm{close}}\left[s\right]=2.8s-t_{\mathrm{open}}\left[s\right],$

and thus, at the beginning of the cooling down procedure with T.sub.act=T.sub.init=300 C., the valve opening time and the valve closing time yields to t.sub.open=0.3 s, t.sub.close=2.5 s. Upon reaching the destination cool down temperature with T.sub.act=T.sub.dest=80 C., the valve opening time and the valve closing time yields to t.sub.open=2.5 s, t.sub.close=0.3 s.

[0057] Thus, by the present invention efficient cooling of a cooling element is provided by utilizing the increased heat capacity of a nebulized liquid coolant conveyed by a steam of compressed air to the cooling element 10. In order to further increase the cooling efficiency at decreasing temperatures, the amount of nebulized coolant fed to the cooling element is increased. As soon as the temperature of the cooling element 10 is below a temperature threshold, it is not necessary anymore to provide the coolant in a nebulized form and thus a liquid coolant is provided to the cooling element 10 in order to further enhance the cooling efficiency of the cooling element and provide cool downs up to 10 times shorter than of common cooling devices.

[0058] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0059] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.