JP3971123B2 - Fine structure drying equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fine structure drying apparatus capable of drying a fine structure while preventing the fine structure from being destroyed by surface tension in a drying process when producing a fine structure such as a micromachine.
[0002]
[Prior art]
When drying a microstructure formed by a wet etching method or the like using a fine structure drying apparatus, the fine structure is put in a drying chamber, and then, for example, liquefied carbon dioxide gas is used as a drying medium in the drying chamber. After being introduced as a drying medium source and removing the solvent contained in the fine structure, the temperature and pressure in the drying chamber are raised and increased so that the drying medium is in a supercritical state. When the drying chamber is in a supercritical state, the pressure in the drying chamber is reduced to atmospheric pressure by gradually exhausting the drying medium while keeping the drying chamber temperature above the critical temperature. Drying is finished at the point.
[0003]
When a fine structure is placed in the drying chamber, the drying chamber is opened to the atmosphere, and therefore the drying chamber temperature is controlled slightly higher than room temperature in order to prevent condensation on the walls of the drying chamber. On the other hand, the cylinder of the drying medium source is placed in the vicinity of the fine structure drying apparatus without controlling and controlling the temperature.
[0004]
[Problems to be solved by the invention]
In the conventional method for temperature control / control of the drying chamber and the cylinder of the fine layer drying layer apparatus, the temperature of the drying chamber is often higher than the temperature of the cylinder. Further, the initial introduction pressure of the drying medium into the drying chamber is always the vapor pressure of the drying medium depending on the temperature of the cylinder filled with the drying medium, and always fluctuates. For this reason, when the room temperature is low, the introduction pressure decreases, and even if the drying medium is introduced into the drying chamber where the object to be dried is placed, the liquid level of the drying medium is lower than the object to be dried. In some cases, the material to be dried is dried out of control and the fine structure is destroyed.
[0005]
In order to prevent the above-mentioned drying out of control, if the rise of the liquid level of the drying medium is confirmed immediately after the introduction of the drying medium into the drying chamber in the operation of the conventional apparatus, the temperature of the drying chamber is immediately lowered from room temperature. There are also cases where the liquid level of the drying medium is raised to prevent uncontrolled drying of the material to be dried.However, the confirmation of insufficient rise in the liquid level tends to be delayed or the room temperature is low. In winter, which tends to occur, the vapor pressure of the drying medium is too low, that is, the initial introduction pressure of the drying medium is too low, and the raising operation of the liquid level of the drying medium can be performed quickly and sufficiently by lowering the temperature of the drying chamber. In other words, uncontrolled drying of the material to be dried may be caused, and the fine structure may be destroyed.
[0006]
The remaining capacity of the cylinder is conventionally measured by measuring the initial introduction pressure into the drying chamber and the mass of the cylinder. However, since the initial introduction pressure is the vapor pressure of the drying medium, it easily changes depending on the room temperature. Since it is difficult to grasp accurately because the tension and mass of the piping is easily applied, the drying medium cannot be supplied as a liquid to the drying chamber immediately after the introduction of the drying medium, or as a gas instead of a liquid from the time of introduction. In other cases, the material to be dried could be dried out of control and the fine structure could be destroyed.
[0007]
The present invention addresses the above problems and prevents the destruction of the microstructure.
[0008]
[Means for Solving the Problems]
The present invention includes a drying chamber that accommodates a fine structure and is supplied with a liquefied gas, a filling container such as a cylinder that is a supply source of the liquefied gas, and a temperature measurement unit that measures the temperature of the filling container. The temperature of the drying chamber is controlled based on the measured value of the measuring means.
[0009]
More specifically, the present invention uses a filling container (cylinder) as a supply source of a liquefied gas used as a drying medium of a fine structure drying apparatus, and has a function of measuring the temperature of the cylinder. From the temperature, the pressure in the cylinder is derived before the vapor pressure of the known drying medium is introduced into the drying chamber, so that the liquid level of the drying medium in the drying chamber is higher than the object to be dried even at the pressure. A drying chamber temperature is calculated, and a mechanism capable of rapidly cooling the drying chamber temperature to the temperature immediately after introduction of the drying medium is provided.
[0010]
Further, the present invention is characterized in that a mechanism capable of controlling the temperature of the cylinder while measuring the temperature of the cylinder so that the temperature of the cylinder is always kept at a high vapor pressure of the drying medium in the cylinder is provided.
[0011]
Furthermore, the present invention has a function capable of measuring the pressure in the cylinder, measures the pressure before taking out the drying medium from the cylinder, and compares it with the vapor pressure specific to the drying medium derived from the temperature of the cylinder measured separately. And a mechanism capable of determining the remaining capacity.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. FIG. 1 is a diagram showing a configuration of a fine structure drying apparatus according to an embodiment of the present invention. In FIG. 1, a liquefied carbon dioxide gas cylinder 1 as a supply source of a drying medium is disposed in the vicinity of the fine structure drying apparatus. The liquefied carbon dioxide cylinder 1 has a pipe for taking out the carbon dioxide gas as a liquid by a siphon effect.
[0013]
When the cylinder head valve 2 of the liquefied carbon dioxide cylinder 1 is opened, the liquefied carbon dioxide flows out toward the pump 3 by the internal pressure P1 of the liquefied carbon dioxide cylinder 1. Since the pressure pump 3 functions as a check valve when the operation is stopped, the liquefied carbon dioxide gas that has flowed out passes through the pressure pump 3 and flows toward the safety valve 4, the on-off valve 5, and the on-off valve 6. When the on-off valve 5 is further opened, the liquefied carbon dioxide gas flows into the drying chamber (high pressure vessel) 13. The inflow of the liquefied carbon dioxide gas into the drying chamber (high pressure vessel) 13 ends when the internal pressure P2 of the drying chamber (high pressure vessel) 13 becomes equal to the internal pressure P1 of the liquefied carbon dioxide gas cylinder 1.
[0014]
Thereafter, the pressure feed pump 3 is further operated to feed the internal pressure P2 into the drying chamber (high pressure vessel) 13 until the internal pressure P2 becomes 72.8 atm or more which is the critical point pressure of the liquefied carbon dioxide gas. The internal pressure P2 of the drying chamber (high pressure vessel) 13 is confirmed by the pressure display / measurement device 12. When the internal pressure P2 of the drying chamber (high pressure vessel) 13 becomes 72.8 atm or higher, the operation of the pressure pump 3 is stopped and the on-off valve 5 is closed. Next, the temperature of the drying chamber (high pressure vessel) 13 is measured by the drying chamber temperature control unit 11 while the temperature of the drying chamber (high pressure vessel) 13 is measured by the drying chamber temperature display / measurement device 12. The temperature is raised to 31.9 ° C. or higher. By the operation so far, the liquefied carbon dioxide inside the drying chamber (high pressure vessel) 13 is in a supercritical state.
[0015]
Thereafter, while maintaining the temperature of the drying chamber (high pressure vessel) 13 at 31.9 ° C. or higher, the supercritical state (high pressure state) of liquefied carbon dioxide is reduced by the pressure reducing valve 16 and then the opening / closing valve 17 is opened. Then, the flow rate is adjusted by the flow rate control valve 18 so that the flow rate becomes an appropriate flow rate by the flow rate indicator 19, and then it is gradually discharged. When the discharge progresses and the pressure display / measuring instrument 12 displays 1 atm, the discharge of the liquefied carbon dioxide gas ends, that is, the drying ends.
[0016]
Here, in order to explain the liquid level height of the liquefied carbon dioxide gas introduced into the drying chamber (high pressure vessel) 13 before the operation of the pressure feed pump 3 is started, various conditions are assumed as follows.
[0017]
The temperature of the liquefied carbon dioxide cylinder 1 is 283.15 K (10 ° C.).
[0018]
The temperature of the drying chamber (high pressure vessel) 13 is 283.15 K (10 ° C.).
[0019]
The internal shape of the drying chamber (high pressure vessel) 13 is a cylindrical shape having a diameter of 3.57 cm, a height of 5 cm, and an internal capacity of 50 cc.
[0020]
If the internal volume of the pipe to the drying chamber (high pressure vessel) 13 is 1,726 cc and the liquefied carbon dioxide gas cylinder 1 is sufficiently filled with carbon dioxide, the temperature of the liquefied carbon dioxide gas cylinder 1 is 283.15K. The pressure P1 in 1 is 44.4 atm, which is the vapor pressure at 283.15K. The air that was originally present in the piping and in the drying chamber (high pressure vessel) 13 was compressed so that the liquid level of the liquefied carbon dioxide gas in the drying chamber (high pressure vessel) 13 would be 44.4 atm. Depends on the volume of time.
[0021]
The volume of the pipe internal volume + drying chamber (high pressure vessel) 13 is (1,726 + 50 = 1,776 cc (1 atm)), and when compressed to 44.4 atm, (1,776 ÷ 44.4 = 40 cc ( 44.4 atm)).
[0022]
Thereby, the liquid level height of the liquefied carbon dioxide gas introduced into the drying chamber (high pressure vessel) 13 is at a position of 1.00 cm from the bottom surface.
[0023]
At this time, if the temperature of the drying chamber (high pressure vessel) 13 is lowered from 283.15 K to 273.15 K, the compressed air volume becomes (40 × 273.15 ÷ 283.15 = 38.6 cc).
[0024]
As a result, the liquid level of the liquefied carbon dioxide gas introduced into the drying chamber (high pressure vessel) 13 is 1.14 cm from the bottom surface.
[0025]
On the other hand, when the temperature of the liquefied carbon dioxide cylinder 1 is 293.15K, the pressure P1 in the liquefied carbon dioxide cylinder 1 is 56.5 atm which is the vapor pressure at 293.15K, and the original volume 1,776 cc (1 atm) is obtained. When compressed to 56.5 atm, it becomes 1,776 ÷ 56.5 = 31.4 cc (56.5 atm).
[0026]
As a result, the liquid level of the liquefied carbon dioxide gas introduced into the drying chamber (high pressure vessel) 13 is 1.86 cm from the bottom surface.
[0027]
From these facts, as a method of increasing the liquid level of the liquefied carbon dioxide gas introduced into the drying chamber (high pressure vessel) 13 before starting the operation of the pressure pump 3, the temperature of the liquefied carbon dioxide cylinder 1 is increased. It turns out that it is effective.
[0028]
In the present invention, the temperature of the liquefied carbon dioxide gas cylinder 1 is measured by the cylinder temperature display / measurement device 7 (temperature measuring means), and the measured temperature is converted into the vapor pressure of the carbon dioxide gas by the control unit 20. If the result is low, carbon dioxide gas is introduced into the drying chamber (high pressure vessel) 13 using the drying chamber temperature control unit 11 (temperature control means) arranged so as to surround the drying chamber (high pressure vessel) 13. Immediately after starting, the temperature of the drying chamber (high pressure vessel) 13 is lowered.
[0029]
Alternatively, the temperature of the liquefied carbon dioxide cylinder 1 is increased by using the cylinder temperature control unit 7 arranged so as to surround the liquefied carbon dioxide cylinder 1 before the carbon dioxide gas is allowed to flow into the drying chamber (high pressure vessel) 13. Since the pressure in the liquefied carbon dioxide gas cylinder 1 can be increased, the liquid level of the liquefied carbon dioxide gas introduced into the drying chamber (high pressure vessel) 13 is increased before the operation of the pumping pump 3 is started. It becomes possible to prevent uncontrolled drying of the object to be dried.
[0030]
Further, when the liquefied carbon dioxide gas is introduced to the on-off valve 5, the pressure measured by the pressure display / measurement device 8 and the temperature measured by the cylinder temperature display / measurement device 7 (temperature measurement means) are used by the control unit 20 to generate carbon dioxide vapor. By comparing the pressure converted into the pressure, it can be determined whether or not carbon dioxide gas exists in the liquefied carbon dioxide cylinder 1 as a liquid. That is, if the measured pressure is less than the vapor pressure equivalent pressure, the carbon dioxide gas does not exist as a liquid in the liquefied carbon dioxide gas cylinder 1, and the liquefied carbon dioxide gas cylinder 1 needs to be replaced. In this way, the replacement time of the liquefied carbon dioxide cylinder 1 can be clearly determined, so that it is possible to prevent uncontrolled drying of the object to be dried due to the lack of liquefied carbon dioxide gas.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent the fine structure destruction of the object to be dried due to the non-control drying of the fine structure drying apparatus.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a fine structure drying apparatus according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquefied carbon dioxide cylinder, 2 ... Cylinder overhead valve, 3 ... Pressure feed pump, 4 ... Safety valve, 5 ... Open / close valve, 6 ... Open / close valve, 7 ... Cylinder temperature display / measurement instrument, 8 ... Pressure display / measurement instrument, 9 ... Cylinder temperature control unit, 10 ... drying chamber temperature display / measurement device, 11 ... drying chamber temperature control unit, 12 ... pressure display / measurement device, 13 ... drying chamber (high pressure vessel), 14 ... open / close valve, 15 ... safety valve, 16 DESCRIPTION OF SYMBOLS ... Pressure-reducing valve, 17 ... On-off valve, 18 ... Flow control valve, 19 ... Flow indicator, 20 ... Control part.

Claims (3)

In the fine structure drying apparatus using liquefied carbon dioxide as a drying medium for washing and drying the fine structure,
A drying chamber containing the microstructure and supplied with the liquefied carbon dioxide gas;
A filling container such as a cylinder which is a supply source of the liquefied carbon dioxide gas;
Temperature measuring means for measuring the temperature of the filling container;
A control unit for converting the temperature measured by the temperature measuring means into the vapor pressure of carbon dioxide,
Wherein it is lower than the vapor pressure of the liquefied carbon dioxide-filled container, the liquid level of the liquefied carbon dioxide immediately after the carbon dioxide began to flow into the drying chamber is lowered the temperature of the drying chamber to flow into the drying chamber
And a drying chamber temperature control unit for controlling the high to so that the height,
When liquefied carbon dioxide gas is introduced from the filling container into the drying chamber, the temperature of the drying chamber is made lower than the temperature of the filling container based on the measurement value of the temperature measuring means for the filling container. A drying apparatus for a fine structure, wherein the temperature of the drying chamber is controlled to be lowered by the drying chamber temperature control unit. In the fine structure drying apparatus using liquefied carbon dioxide as a drying medium for washing and drying the fine structure,
A drying chamber containing the microstructure and supplied with the liquefied carbon dioxide gas;
A filling container such as a cylinder which is a supply source of the liquefied carbon dioxide gas;
Temperature measuring means for measuring the temperature of the filling container;
A control unit for converting the measurement temperature into the vapor pressure of carbon dioxide gas by the temperature measuring means;
If it is lower than the vapor pressure of the liquefied carbon dioxide gas in the filling container, the temperature of the filling container is raised to increase the pressure in the filling container before flowing the carbon dioxide gas into the drying chamber, and the carbon dioxide gas flows into the drying chamber. and a cylinder temperature control unit for controlling the high to so that the liquid level of the liquefied carbon dioxide that,
When liquefied carbon dioxide gas is introduced from the filling container into the drying chamber, the temperature of the drying chamber is made lower than the temperature of the filling container based on the measurement value of the temperature measuring means for the filling container. An apparatus for drying a fine structure, wherein the temperature of the filling container is controlled to rise by the cylinder temperature control unit. In the drying apparatus of the fine structure according to claim 1 or 2,
Measuring the pressure in the filling container,
The measured pressure in the filling container is compared with the vapor pressure value of the liquefied carbon dioxide gas in the filling container calculated from the temperature measurement value of the filling container measured by the temperature measuring means for the filling container. Thus, the fine structure drying apparatus includes a control unit that determines whether or not the gas remaining in the filling container is present as liquefied carbon dioxide gas before the drying operation.

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