KR100706818B1 - cryo pump - Google Patents

Abstract

The present invention relates to a cryo pump.

The present invention has a two-stage configuration, comprising: a first stage for capturing water vapor; a cooling panel provided with adsorbent charcoal to condense and adsorb argon gas and nitrogen gas; and a second stage for mounting the cooling panel; In the cryopump comprising a housing having a two-stage cryogenic freezer, the heat transfer member is interposed between the second stage and the cooling panel mounted thereto.

According to the present invention, it is possible to raise the temperature range in the chamber to 330K or more without heat loss during the pump regeneration process, so that the material and gases with high evaporation heat in the chamber during the regeneration process are completely purified in a short time in a high temperature environment of 330K or more. Since this can extend the life of the adsorptive charcoal for the removal of gas in the chamber, the performance of the cooling panel is completely restored after regeneration, thereby extending the maintenance period of the pump according to the temperature rise inside the pump.

Cryopump, Stage 1, Stage 2, Cooling Panel, Sapphire

Description

Cryo pump

1 is a cross-sectional view schematically showing the overall configuration of a cryopump according to the prior art.

2 is a cross-sectional view schematically showing the overall configuration of the cryopump according to the present invention.

Figure 3 is a graph showing the difference between the thermal conductivity of oxygen-free copper and sapphire at low temperature to high temperature.

<Description of Signs of Major Parts of Drawings>

2: first stage 3: second stage

4: two stage freezer 5: housing

7: supply line 8: discharge line

9: relief valve 11: heat transfer member

12: bimetal 30: cooling panel

32: adsorptive charcoal 34: second stage heater

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryo pump used in an ion implantation process for manufacturing a semiconductor device, and shows a large difference in thermal conductivity between low temperature and high temperature between a second stage and a cooling panel mounted thereto. When the pump is regenerated by the heat transfer member, the chamber of the pump maintains a high temperature environment while purifying materials and gases with high evaporative heat in the second stage to completely discharge them to the outside to extend the regeneration efficiency and life of the device. It's about a cryopump.

The cryo pump generally refers to a freeze storage vacuum pump which performs vacuum extraction by condensing and adsorbing gas molecules at cryogenic temperatures, and is widely used as a means for making a processing chamber of a semiconductor manufacturing apparatus or the like into an ultra-high vacuum state.

1 is a schematic diagram of a typical cryopump 1 according to the prior art.

As shown in FIG. 1, the general cryopump 1 has a two-stage configuration, mainly comprising a first stage 2 that traps water vapor, and a second stage that condenses and adsorbs argon gas, nitrogen gas, and the like. The stage 3 and the housing | casing 5 in which the two stage cryogenic freezer 4 was built are included.

The first stage 2 consists of a housing 5 surrounding it except for the baffle 6 located between the second stage 3 and the chamber to be discharged.

This first stage 2 is cooled to a temperature in the range of 60K to 130K by the freezer (4). High boiling gas, such as water vapor coming from the working chamber, condenses on the baffle 6, while the remainder of the first stage 2 functions primarily to block the second stage 3 from radiant heat.

The second stage 3 is maintained at 4K to 25K by the refrigerator 4 and used to condense the low boiling gas passing through the baffle 6.

On the cold panner 30 of the second stage 3, an adsorbent charcoal capable of removing a gas having a particularly low boiling point, such as hydrogen, is bonded. For example, another panel may include a laminate with charcoal 32 on its base surface.

The cryogenic freezer 4 applied to the cryo pump is a two-stage freezer which achieves cooling through a Gifford-McMahon cooling cycle, and expands the compressed helium gas, the first and second stages. Take heat from (2,3) The refrigerator 4 is driven by a motor and purged nitrogen gas is supplied through a supply line.

In the cryopump having the above configuration, the first and second stages 2 and 3 essentially achieve a vacuum in the vacuum chamber by condensing gas molecules in the atmosphere. That is, when free floating gas molecules collide with the cryogenic stage, the stage takes heat energy from the gas molecules. When the gas molecules are sufficiently deprived of thermal energy, their phases are converted from vapor to solid condensate on the first and second stages 2 and 3. Thus, as the gas is condensed and / or adsorbed on the first and second stages 2 and 3, a high vacuum is created in both the vacuum chamber and the working chamber.

When such a high vacuum is achieved, the process product can be moved into and out of the working chamber through a partially vacuumed load lock (not shown). Additional gas enters the work chamber through each opening of the work chamber connected with the load lock. The gas is then condensed on the stage to evacuate the chamber again and provide the necessary low pressure for the process, which increases the efficiency of the cryo pump as the amount of condensate accumulated on the stage increases over time. The pump capacity will fall. In addition, there is a risk of damage to the process product in the working chamber, as well as to potential conditions and safety risks, due to the possibility of power supply interruption or other causes of rapid warming, which may result in sublimation of the condensate gas, which may include dangerous chemicals.

Therefore, a regeneration process for warming the first and second stages 2 and 3 under the control plan for discharging the condensed gas from the first and second stages 2 and 3 is necessary periodically about twice a month. .

Regeneration refers to the process of raising the temperature of the cryopump, releasing the gases that were adsorbed on charcoal and recharging them from the system.

In this regeneration process, hot nitrogen gas is introduced into the pump through a supply line (not shown) and condensed by heating the temperature in the pump to around 330K using an electric heater installed between the first and second stages. It is possible to increase the life and efficiency of the pump by purifying / discharging foreign substances, water, water vapor and other vapors generated in the process from the pump.

However, in the related art, there was a technical limitation that the temperature of the second stage including the cooling panel could not exceed 330K in relation to the physical factors of the components constituting the cryopump.

That is, in the second stage 3, the displacer (not shown) ultimately moves vertically, thereby absorbing heat and lowering the temperature. The displacer is made of very small lead balls to maintain a low temperature of 20K or less. Because of the low melting point of the lead (which spheronizes at 330K), there is a limitation that it may cause device defects when raised above 330K.

Therefore, conventionally, a regeneration process, that is, an inert gas such as nitrogen gas is introduced into the pump, and the low temperature temperature of the first and second stages 2 and 3 is raised to about room temperature, thereby regenerating the gas molecules collected therein. Substances and gases with high evaporation temperature (evaporation temperature 373K), such as water, attached to the first stage 2 while being cooled to the first stage 2 during the process of being discharged to the outside together with the solvent gas, are completely evaporated in the pump due to the low regeneration temperature. It does not flow in the form of moisture to contaminate the chamber or adhere to the adsorptive charcoal as it has a problem of shortening the life and maintenance time of the device.

The present invention has been made in view of the problems of the prior art as described above, and the thermal conductivity between the second stage and the cold panel (cold pannel) mounted thereon relatively different in the low temperature and high temperature environment, such as sapphire It is possible to raise the temperature range in the chamber to more than 330K without heat loss during the pump regeneration process through the heat transfer member having a very stable and very good mechanical properties without changing the state from cryogenic to ultra-high temperature.

Therefore, during the regeneration process, materials and gases with high evaporation heat in the chamber are purified and discharged completely in a high temperature environment of 330K or more, thereby extending the life of the adsorptive charcoal for gas removal in the chamber, and the performance of the cooling panel after regeneration is Its purpose is to provide a cryopump that can be completely returned to significantly improve the life of the pump.

As a technical means for achieving the above object, the present invention cryo pump is a housing, a refrigerator installed in the housing and consisting of two stages, the first stage is cooled in contact with the first stage of the freezer, the second stage of the freezer A second stage to be cooled in contact with the second stage, a heat transfer member for transferring heat by contacting the second stage, a cooling panel connected to the heat transfer member and capable of condensing and adsorbing gas during cooling, and between the heat transfer member and the cooling panel. An electric heater may be included in order to heat the regeneration.

In the present invention, the heat transfer member may be a sapphire excellent in mechanical properties that have a large difference in thermal conductivity at low and high temperatures and do not deform even within a wide temperature range.

In addition, a safety device may be further installed between the heat transfer member and the electric heater to stop the power supply of the heater when the heat transferred from the heater is excessively increased, and the safety device may be increased in accordance with a temperature increase. It may be a bimetal cut off.

In the present invention, between the heat transfer member and the second stage may further include a gasket made of a material having a good thermal conductivity to prevent heat loss due to the separation that may occur due to the thermal expansion coefficient between the metals according to a wide temperature range. The material of the gasket is made of indium (In) or silver (Silver) having a good thermal conductivity, and the coupling hole of the heater block to which the heat transfer member, the second stage and the heater are mounted is stainless or titanium having a low thermal conductivity. (Titanium) can be formed.

In the present invention, the heat transfer member may be controlled by a helium compressor (He-Compressure) or a cryopump controller (Cryopump controller) so that the electric heater provided in the second stage is supplied only during the pump operation.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to describing the present embodiment, in the present embodiment, the same reference numerals and names will be used for the same parts as the above-described conventional configurations.

2 is a cross-sectional view schematically showing the overall configuration of the cryopump according to the present invention.

As shown in FIG. 2, the cryopump 1 has a two-stage structure in which the first stage 2 and the second stage 3 are divided and partitioned by a heat dissipation film, and the second stage cryogenic temperature. It comprises a housing (5) in which the refrigerator (4) is built.

Specifically, the upper portion of the housing 5 is opened to allow gas to move, and a flange 50 for mounting it to a port on a container defining a working chamber is formed at the outer end of the housing based on the opened opening. .

In addition, a supply line 7 and a discharge line 8 are installed at the lower end of the housing 5 to supply or discharge helium gas into the chamber as an operating gas (refrigerant). The opening and closing of the supply line 7 and the discharge line 8 are controlled by the relief valve 9.

In the housing 5, a first stage 2 including a refrigerator 4 and a heat radiation film 22 for condensing gas and cooling to a temperature in the range of 35K to 130K is installed on the refrigerator 4, The second stage 3 is installed above the first stage 2 with the heat dissipation film 22 interposed therebetween.

On the second stage 3, a cooling panel 30 in which an adsorptive charcoal 32 is provided on its base surface is provided for the purpose of removing a gas having a low boiling point such as hydrogen. The cooling panel 30 has a multistage structure in the vertical direction in the chamber.

The second stage 3 is connected to the cryogenic freezer 4 having a two-stage structure, and the cooling panel 30 is maintained at 4K to 25K by the freezer 4.

That is, the cryogenic freezer 4 has a two-stage structure, and the first freezer comes into contact with the heat dissipation film 22 of the first stage to freeze the heat dissipation film 22, and the second freezer has a second stage 3. ) To freeze the cooling panel (30).

Meanwhile, the adsorptive charcoal 32 provided on the cooling panel 30 of the second stage 3 saturates various gases adsorbed in the chamber when the pump is driven, thereby increasing the degree of vacuum or the temperature of the second stage. In order to prevent such a temperature increase in the chamber, a regeneration process is required periodically, and in order to effectively regenerate, the temperature in the pump must be maintained at a high temperature of 330 K or more. And a heat transfer member 11 exhibiting a relatively large thermal conductivity in a low temperature and a high temperature environment between the cold pannel 30 mounted thereon.

As the heat transfer member 11, sapphire having a very stable and excellent mechanical properties is applied without changing the state from cryogenic to ultra-high temperature while having thermal conductivity comparable to metal.

The heat transfer member 11 is connected to a heater provided in the second stage 3 to form a safety device through a known bimetal 12 that operates at a specific temperature to block power supplied thereto.
On the other hand, since the heater is built in the heater block 13, it is not shown in the drawing.

That is, the bimetal 12 serves to prevent overheating of the second stage 3 by cutting off the power supply of the heater when the heat transferred from the heater rises more than necessary during the regeneration process.

The operation and effects of the cryopump of the present invention configured as described above will be described.

By condensing the gas molecules in the atmosphere with the drive of the refrigerator 4, the first and second stages 2, 3 essentially achieve a vacuum in the vacuum chamber. That is, when free floating gas molecules collide with the cryogenic stage, the stage takes heat energy from the gas molecules.

When the gas molecules are sufficiently deprived of thermal energy, their phases are converted from vapor to solid condensate on the first and second stages 2 and 3. Therefore, as the gas is condensed and / or adsorbed on the first and second stages 2 and 3, a high vacuum is created in both the vacuum chamber and the working chamber.

When this process is repeated, the adsorptive charcoal 32 provided on the cooling panel 30 of the second stage 3 accumulates and saturates various gases adsorbed in the chamber, thereby increasing the degree of vacuum or the second stage 3. The temperature of) increases, and a periodic regeneration process is necessary to prevent such a temperature increase in the chamber.

In the regeneration process, the temperature of the cooling panel 30 is 373K using the heater and the temperature sensor 36 provided in the first stage 2 and the second stage 3 while flowing N ₂ gas at room temperature or heated. It will be raised to (100 °) to perform the purification in the cryo pump.

Such a high temperature of 330 K or more is enabled by the sapphire 11 interposed between the second stage 3 and the cooling panel 30. This is because the cooling panel 30 and the second stage 3 is made of oxygen-free copper having a higher thermal conductivity than the sapphire 11 in the high temperature region, so that the heat conducted from the heater is more through the cooling panel 30 than the sapphire 11. Because much heat is conducted.

That is, as can be seen in Figure 3 showing the difference between the thermal conductivity of oxygen-free copper and sapphire according to the high temperature at low temperature, the sapphire 11 has a high thermal conductivity at low temperature, but has a low thermal conductivity compared to the oxygen-free copper at high temperature Therefore, as the temperature rises to the high temperature region, heat generated from the heater is first conducted into the chamber through sapphire, and when the high temperature region is reached, more heat is transferred to the chamber through the cooling panel made of oxygen-free copper.

 Therefore, due to the sapphire intervention based on this, the cooling panel 30 can maintain the high temperature 373K while the second stage 3 can be maintained at about 300K, thereby effectively purifying the cooling panel 30 inside the pump. .

2, the cooling panel 30 is connected to the upper surface of the sapphire 11 and the heater and the temperature sensor (between the upper surface of the sapphire 11 and the cooling panel 30). The heater block 13 to be installed 36 is made of oxygen-free copper, and the lower surface of the sapphire 11 is connected to the second stage 3 made of oxygen-free copper of the refrigerator.

Between the sapphire 11, the heater block 13 and the second stage 3, a gasket (not shown) made of indium (In) or silver (Silver) having a high thermal conductivity is installed to increase the thermal conductivity and according to a wide temperature range. It is possible to prevent heat loss due to the separation that can occur due to the thermal expansion rate between the metals.

The sapphire 11 is fixed as a bolt (not shown) between the heater block 13 and the second stage (3), the bolt is preferably made of a material of Stainless or Titanium which is not good thermal conductivity.

Due to such a configuration, the present invention provides a high temperature of the upper surface of the sapphire 11 which is in contact with the heater block 13 while the heater block 13 and the cooling panel 30 are formed at a high temperature during sapphire ( 11) is lowered, the temperature of the second stage (3) in contact with the lower surface of the sapphire 11 in accordance with the given temperature conditions and the thermal conductivity of the sapphire as shown in Figure 3 changes depending on the freezing capacity of the refrigerator As it rises, the cooling panel 30 is maintained at a predetermined temperature difference.

As a result, according to the present invention, while the cooling panel 30 is maintained at a high temperature (373K) due to the intervention of the sapphire 11, the second stage 3 can be maintained at about 300K, so that the cooling panel 30 inside the pump is It can be effectively purified. Therefore, if the temperature is maintained at this time, the purification effect can be further increased while the time is significantly reduced compared to the conventional purification rate, which was purified for 1 hour at 300K.

That is, in the low temperature state, in order to maintain the cooling vacuum state, which is the main function of the cryopump, the low temperature thermal conductivity is remarkably high, so that cooling can be effectively performed when the present function is performed.

However, in the high temperature state, the thermal conductivity is lower than that of the cooling panel and the second stage formed of oxygen-free copper, so that it is possible to prevent rapid heating of the mechanism other than the portion to be heated such as the cooling panel. ,

As described above, according to the present invention, the cryo pump includes a heat transfer member having a large temperature difference between low temperature and high temperature such as sapphire between the second stage and a cold pannel mounted thereon, thereby regenerating the pump. The temperature range in the chamber can be raised to more than 330K without heat loss. Therefore, during the regeneration process, materials and gases with high evaporation heat in the chamber can be completely purified and discharged in a short time in a high temperature environment of more than 330K. By further extending the life of the adsorptive charcoal for removal, the performance of the cooling panel after regeneration is fully restored, extending the maintenance period of the device as the temperature rises inside the pump.

In addition, by constructing a safety device such as an immetal, it is possible to prevent excessive heat transfer by unintentionally excessive heating as a heater and an excessive increase in temperature.

In addition, by including a gasket made of a material having a high thermal conductivity such as indium (In) or silver (Silver), the heat due to the separation between the heat transfer member and the second stage due to the thermal expansion coefficient between the metal according to a wide temperature range The loss can be prevented.

In addition, since the heat transfer member, the second stage, and the bolt of the heater block on which the heater is mounted are formed of stainless steel or titanium with low thermal conductivity, deformation due to temperature change is prevented and the apparatus is stably configured.

In addition, the heat transfer member is controlled by a helium compressor (He-Compressure) or a cryopump controller (Cryopump controller) so that the electric heater provided in the second stage is supplied only during pump operation, it is double with a safety device The operation of the cryopumps can be controlled.

Claims (7)

housing; A refrigerator provided in the housing and configured in two stages; A first stage that is cooled in contact with the first stage of the freezer; A second stage which is cooled in contact with the second stage of the refrigerator; A heat transfer member in contact with the second stage to transfer heat; A cooling panel connected to the heat transfer member and capable of condensing and adsorbing gas upon cooling; And The cryopump, characterized in that an electric heater is included between the heat transfer member and the cooling panel to apply heat during regeneration. The method of claim 1, The heat transfer member is a cryopump, characterized in that the difference in thermal conductivity at low and high temperatures is sapphire excellent mechanical properties that do not deform even within a wide temperature range. The cryo according to claim 1, further comprising a safety device between the heat transfer member and the electric heater to stop the power supply of the heater when the heat transferred from the heater is excessively raised. Pump. The cryopump according to claim 3, wherein the safety device is a bimetal that is cut off as the temperature rises. delete According to claim 1, Between the heat transfer member and the second stage further comprises a gasket made of a material having a good thermal conductivity to prevent heat loss due to the separation that may occur due to the thermal expansion coefficient between the metals according to a wide temperature range But The gasket is made of indium (In) or silver (Silver) having a high thermal conductivity, and the coupling hole of the heater block to which the heat transfer member, the second stage and the heater are mounted is stainless or titanium having low thermal conductivity. Cryopump, characterized in that formed by). The heat transfer member according to any one of claims 1 to 4 and 6, wherein the heat transfer member is provided with a he-compressure or a cryo compressor such that the electric heater provided in the second stage is supplied only during a pump operation. A cryopump, characterized in that it is controlled by a cryopump controller.

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