METHOD FOR VACUUM-EXHAUSTING BY MEANS OF CRYOPUMP

Abstract

A vacuum evacuation method to be performed by a cryopump includes: a process of receiving an injection signal of a process gas from a process gas injection device that injects a process gas into a processing chamber; a process of turning on a first heater based on the injection signal to increase a temperature of a first stage part; a process of measuring the temperature of the first stage part; a process of monitoring whether the temperature of the first stage part reaches a predetermined first stage reference temperature; and a process of vacuum-evacuating the process gas when the temperature of the first stage part reaches a predetermined first stage reference temperature.

Description

TECHNICAL FIELD

The present disclosure relates to a vacuum evacuation method using a cryopump.

BACKGROUND

Cryogenic cooling is widely used in industrial fields such as semiconductor manufacturing and testing. Herein, cryogenic temperatures may refer to temperatures below-200° C. A cooling process to achieve cryogenic temperatures is performed typically using a compressor, a condenser, an expander, and an evaporator in which a refrigerant evaporates to create a cryogenic environment.

In relation to technology for creating a cryogenic environment, Korean Patent Laid-open Publication No. 2020-0079062 discloses an ultra-cold freezer.

To create a cryogenic environment, GM (Gifford-McMahon) freezers, which are freezers for high-vacuum cryopumps, are mainly used. These cryopumps are used as main pumps in sputtering devices.

Since the cryopumps are configured to evacuate process gases through condensation and adsorption, the cryogenic surface temperature and vapor pressure significantly impact evacuation performance. If the temperature of a specific part is not suitable, the condensed argon (Ar) molecules repeatedly desorb and recondense or readsorb, which causes severe pressure fluctuations without dropping below a predetermined pressure and also causes instability when the sputtering devices evacuate Ar.

Hereinafter, the Ar equilibrium vapor pressure and Ar hang-up will be briefly described with reference to FIG. 1A and FIG. 1B.

FIG. 1A illustrates an example of the equilibrium vapor pressure of each process gas, and FIG. 1B illustrates an example of the conventional Ar hang-up and the Ar equilibrium vapor pressure.

FIG. 1A illustrates the equilibrium vapor pressure of each process gas. A cryopump evacuates most gases except for hydrogen, which is adsorbed onto an activated carbon array, by condensing them onto a cryogenic surface and gas molecules remain attached to the cryogenic surface without being expelled to the outside. Thus, it is unavoidable that it exhibits a certain level of vapor pressure depending on the surface temperature and attachment conditions. This action determines target pressures of the cryopump and the vacuum chamber.

Referring to FIG. 1A, when the surface temperature is 20K or less, the vapor pressure of argon 100 is 1E-10 Torr, when the surface temperature is 30K, the vapor pressure of the argon 100 is 1E-6 Torr, and when the surface temperature is 50K or more, the argon 100 cannot be condensed as the vapor pressure of the argon 100 becomes 1 Torr or more.

That is, when the vapor pressure of the argon 100 is 1 Torr or more, it may be meaningless from a practical standpoint.

FIG. 1B relates to Ar hang-up. Referring to FIG. 1B, the cryopump cools a first stage part using a freezer to maintain the temperature of the first stage part at 35K to 65K. Also, the cryopump cools a second stage part to maintain the temperature of the second stage part at 15K to 20K.

A thermal radiation shield CAN and a baffle are cooled by the first-stage part, and an activated carbon array is cooled by the second stage part. Herein, other gases than water molecules adsorbed on the thermal radiation shield or baffle, which have a relatively high temperature, are evacuated from the activated carbon array.

That is, the cylindrical thermal radiation shield cooled by the first stage part functions to protect the second stage part and activated carbon array from radiant heat of 300K radiant heat, and the baffle condenses moisture (water molecules) while maintaining some functions to shield heat and also functions as a passage for other gas molecules to enter the cryopump.

Herein, as described in FIG. 1A, argon can be condensed only when the temperature is 50K or less on a metal surface.

However, if the temperature of the first stage part is maintained at 30K to 50K, some of argon can be adsorbed and argon attached to a relatively high temperature area cannot be permanently fixed. Therefore, it is released again and then rapidly decreased depending on the ambient pressure. As this is repeated, instability appears. Such pressure instability of argon is called Ar hang-up in the cryopump.

Further, a sputtering device does not perform a sputtering process for 24 hours, but performs a sputtering process using argon as a process gas only when a substrate is supplied from a sputtering chamber through a transfer chamber. Therefore, a method to reduce power consumption is required.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The present disclosure is conceived to provide a vacuum evacuation method, including receiving an injection signal of a process gas from a process gas injection device that injects the process gas into a sputtering chamber and turning on a first heater based on the injection signal to increase a temperature of a first stage part.

Also, the present disclosure is conceived to provide a vacuum evacuation method, including measuring a temperature of a first stage part, monitoring whether the temperature of the first stage part reaches a predetermined first stage reference temperature, and vacuum-evacuating a process gas when the temperature of the first stage part reaches the predetermined first stage reference temperature.

The problems to be solved by the present disclosure are not limited to the above-described problems. There may be other problems to be solved by the present disclosure.

Means for Solving the Problems

As a means for achieving the above-described technical problem, an embodiment of the present disclosure provides a vacuum evacuation method to be performed by a cryopump which includes: a freezer equipped with a first stage part and a second stage part and configured to cool the first stage part and the second stage part; a cryopanel including a first stage panel cooled by the first stage part and a second stage panel cooled by the second stage part; a cryopump vessel surrounding the cryopanel; a first heater provided in the first stage part; and a second heater provided in the second stage part, and the vacuum evacuation method includes: a process of receiving an injection signal of a process gas from a process gas injection device that injects the process gas into a processing chamber; a process of turning on the first heater based on the injection signal to increase a temperature of the first stage part; a process of measuring the temperature of the first stage part; a process of monitoring whether the temperature of the first stage part reaches a predetermined first stage reference temperature; and a process of vacuum-evacuating the process gas when the temperature of the first stage part reaches the predetermined first stage reference temperature.

According to an embodiment, the process of increasing the temperature may include a process of gradually increasing the temperature of the first stage part from 35K to 60K by using the first heater.

According to an embodiment, the process of increasing the temperature in the vacuum evacuation method may include a process of gradually increasing the temperature of the first stage part by 5K.

According to an embodiment, a pressure of the process gas may increase based on the gradually increased temperature of the first stage part and decrease when the temperature of the first stage part reaches the predetermined first stage reference temperature, and the pressure of the process gas may be from 1E-10 Torr to 1E-6 Torr.

According to an embodiment, the vacuum evacuation method may further include a process of receiving a non-injection signal of the process gas from the process gas injection device that injects the process gas into the processing chamber and a process of turning off the first heater of the first stage part to maintain the temperature of the first stage part in an idle state.

The above-described aspects are provided by way of illustration only and should not be construed as liming the present disclosure. Besides the above-described embodiments, there may be additional embodiments described in the accompanying drawings and the detailed description.

Effects of the Invention

According to any one of the above-described means for solving the problems of the present disclosure, it is possible to provide a vacuum evacuation method, including receiving an injection signal of a process gas from a process gas injection device that injects the process gas into a sputtering chamber and turning on a first heater based on the injection signal to increase a temperature of a first stage part. Thus, the vacuum evacuation method can implement low power consumption with high evacuation performance by taking advantage of a phenomenon in which an evacuation speed of the process gas varies depending on the temperature of the first stage part.

Also, it is possible to provide a vacuum evacuation method, including measuring a temperature of a first stage part, monitoring whether the temperature of the first stage part reaches a predetermined first stage reference temperature, and vacuum-evacuating a process gas when the temperature of the first stage part reaches the predetermined first stage reference temperature. Thus, when the process gas is injected, the vacuum evacuation method can create optimization conditions for evacuation of the process gas and also suppress the occurrence of Ar hang-up.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an example of the equilibrium vapor pressure of each process gas.

FIG. 1B illustrates an example of the conventional argon hang-up and the argon equilibrium vapor pressure.

FIG. 2A illustrates an example of a cryopump system according to an embodiment of the present disclosure.

FIG. 2B illustrates an example of a cryopump according to an embodiment of the present disclosure.

FIG. 3 is a flowchart showing a vacuum evacuation method of the cryopump according to an embodiment of the present disclosure.

FIG. 4A illustrates a pressure of a process gas depending on an increase in temperature of a first stage part according to an embodiment of the present disclosure.

FIG. 4B illustrates a pressure of argon when argon is injected while the temperature of the first stage part is maintained at 50K according to an embodiment of the present disclosure.

FIG. 4C illustrates a pressure of argon when argon is injected while the temperature of the first stage part is maintained at 60K according to an embodiment of the present disclosure.

FIG. 4D illustrates a pressure of argon when argon is injected while the temperature of the first stage part is maintained at 65K according to an embodiment of the present disclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings to be readily implemented by a person with ordinary skill in the art to which the present invention belongs. However, it is to be noted that the present disclosure is not limited to the example embodiments but can be embodied in various other ways. In the drawings, parts irrelevant to the description are omitted in order to clearly explain the present disclosure, and like reference numerals denote like parts through the whole document.

Through the whole document, the term “connected to” or “coupled to” that is used to designate a connection or coupling of one element to another element includes both a case that an element is “directly connected or coupled to” another element and a case that an element is “electronically connected or coupled to” another element via still another element. Further, it is to be understood that the term” comprises or includes” and/or “comprising or including” used in the document means that one or more other components, steps, operation and/or existence or addition of elements are not excluded in addition to the described components, steps, operation and/or elements unless context dictates otherwise and is not intended to preclude the possibility that one or more other features, numbers, steps, operations, components, parts, or combinations thereof may exist or may be added.

In the document, the term “unit” includes units realized by hardware, units realized by software, and units realized by using both hardware and software. Moreover, one unit may be realized by using two or more hardware, and two or more units may be realized by one hardware.

Some of the operations or functions described as being performed by a terminal or device in the document may alternatively be performed by a server connected to the terminal or device. Similarly, some of the operations or functions described as being performed by a server may alternatively be performed by a terminal or device connected to the server.

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

FIG. 2A illustrates a cryopump system used in a sputtering process. The cryopump system may include a compressor 200, a cryopump 210, a sputtering device 220, and a process gas injection device 230.

The compressor 200 may be configured to compress a helium refrigerant to high pressure and supply the compressed high-pressure helium refrigerant to the cryopump 210 through a helium supply line.

The compressor 200 may recover a low-pressure helium refrigerant, which has undergone state transformation at high pressure by the cryopump 210, from the cryopump 210 through a helium recovery line and then may recompress the low-pressure helium refrigerant into a high-pressure helium refrigerant.

The cryopump 210 may create a cryogenic environment by using a freezer.

When a process gas is injected into a sputtering chamber 223, the cryopump 210 may evacuate the sputtering chamber 223 based on the temperature of the first stage part.

The sputtering device 220 may perform a sputtering process on a substrate 221 supplied through a transfer chamber in the sputtering chamber 223.

The sputtering process refers to a phenomenon in which atomic molecules acquire momentum greater than their binding energy due to ion impacts from argon or the like and thus scatter from a cathode surface into space, and also refers to a film forming method using the phenomenon.

The sputtering device 220 may receive the process gas injected from the process gas injection device 230 through a process gas inlet 231.

The sputtering device 220 may form a predetermined thin film on the substrate 221 through a sputtering source 222 by using argon as a process gas. For example, in the sputtering process, when an argon (Ar) gas, which is a process gas, is injected into the sputtering chamber 223 in a vacuum state, a voltage (−) is applied to a cathode, electrons are emitted from the cathode, and the emitted electrons collide with Ar gas atoms and ionize the Ar gas.

Herein, Ar is excited and emits electrons, which causes a glow discharge and generates plasma. Ar+ ions in the plasma may be accelerated by a potential difference and may collide with a target, and atoms of the collided target may bounce and move to the substrate. As a result, a thin film may be formed.

Referring to FIG. 2B, the cryopump 210 is equipped with a freezer 211, and may create a cryogenic environment by using the freezer 211. In this case, the cryopump 210 may be supplied with a helium refrigerant, which has been compressed to high pressure, from the compressor 200 through the helium supply line to create a cryogenic environment. The cryopump may include a first stage part 212 and a second stage part 213.

The cryopump 210 may include the freezer 211, the first stage part 212, the second stage part 213, a first heater 214, a second heater 215, a second stage panel 216, and a first stage panel 217. The cryopump 210 according to an embodiment of the present disclosure may be a GM (Gifford-McMahon) freezer equipped with the first stage part 212 and the second stage part 213.

The freezer 211 may be equipped with the first stage part 212 and the second stage part 213 which is cooled to a lower temperature than the first stage part 212. Herein, the first stage part 212 and the second stage part 213 may create a cryogenic environment by using a cooling principle that allows a displacer to reciprocate within a cylinder and expand a helium gas inside the cylinder.

A cryopump vessel 218 may surround a cryopanel. Herein, the cryopanel may include the first stage panel 217 and the second stage panel 216. The first stage panel 217 may include a first stage array (Can) and a baffle, and the first stage array may be directly cooled by the first stage part 212 and the baffle may be indirectly cooled by the first stage part 212. The second stage panel 216 may include a second stage array and may be cooled by the second stage part 213.

The first heater 214 may be provided in the first stage part 212 and may increase a temperature of the first stage part 212.

The second heater 215 may be provided in the second stage part 213 and may increase a temperature of the second stage part 213.

FIG. 3 is a flowchart showing a vacuum evacuation method of the cryopump according to an embodiment of the present disclosure. The vacuum evacuation method of the cryopump 210 illustrated in FIG. 3 includes the processes time-sequentially performed according to the embodiment illustrated in FIG. 2A and FIG. 2B. Therefore, the descriptions of the processes may also be applied to the vacuum evacuation method performed by the cryopump 210 according to the embodiment illustrated in FIG. 2A and FIG. 2B even though they are omitted hereinafter.

In a process S310, the cryopump 210 may receive an injection signal of a process gas from the process gas injection device 230 that injects the process gas into the sputtering chamber 223, which is a processing chamber. Herein, the process gas may be an argon (Ar) gas used in a sputtering process. To this end, the cryopump 210 used in the sputtering process is controllably connected to the process gas injection device 230 that injects the process gas, and, thus, the cryopump 210 may receive an injection signal of the process gas.

In a process S320, the cryopump 210 may turn on the first heater 214 based on the injection signal to increase the temperature of the first stage part 212.

For example, the cryopump 210 can gradually increase the temperature of the first stage part 212 from 35K to 60K by using the first heater 214. In this case, the cryopump 210 may gradually increase the temperature of the first stage part 212 by 5K.

In a process S330, the cryopump 210 may measure the temperature of the first stage part 212.

In a process S340, the cryopump 210 may monitor whether the temperature of the first stage part 212 reaches a predetermined first stage reference temperature. In this case, the predetermined first stage reference temperature may be 60K.

In a process S350, the cryopump 210 may vacuum-evacuate the process gas when the temperature of the first stage part 212 reaches the predetermined first stage reference temperature. In this case, a pressure of the process gas may be from 1E-10 Torr to 1E-6 Torr, and the pressure of the process gas may increase based on the gradually increased temperature of the first stage part 212 and decrease when the temperature of the first stage part 212 reaches the predetermined first stage reference temperature.

That is, the present disclosure can implement low power consumption with high evacuation performance by taking advantage of a phenomenon in which an evacuation speed of the process gas varies depending on the temperature of the first stage part 212 and thus can contribute to reducing power consumption during a sputtering process.

Also, it is possible to create optimization conditions for evacuation of an argon gas by suppressing the occurrence of Ar hang-up caused by the instability in pressure of argon during the sputtering process.

Although not shown in FIG. 3, the vacuum evacuation method of the cryopump 210 may further include a process of receiving a non-injection signal of the process gas from the process gas injection device 230 that injects the process gas into the sputtering chamber 223 and a process of turning off the first heater 214 of the first stage part 212 to maintain the temperature of the first stage part 212 in an idle state.

Accordingly, when the non-injection signal is received as the injection of the argon gas is completed, the temperature of the first stage part 212 is not controlled but maintained in an idle state. Thus, it is possible to reduce power consumption of the cryopump 210.

In the descriptions above, the processes S310 to S350 may be divided into additional processes or combined into fewer processes depending on an embodiment. In addition, some of the processes may be omitted and the sequence of the processes may be changed if necessary.

FIG. 4A is a graph showing a partial pressure of injected argon measured when the temperature of the first stage part is increased. The cryopump 210 may turn on the first heater 214 to increase the temperature of the first stage part 212 by 5K from the lowest temperature of 36K, and a partial pressure of argon injected as a process gas may be measured while the temperature of the first stage part 212 is increased.

In this case, it can be seen that a pressure drop of argon occurs when the temperature of the first stage part 212 is 60K instead of 50K, and the partial pressure continues to be low at 60K or more (400). This means that the first stage part 212 does not adsorb argon, and, thus, the second stage part 213 adsorbs argon. Therefore, it can be confirmed that Ar hang-up does not occur at 60K or more even when a large amount of argon is injected.

FIG. 4B illustrates a pressure of argon when argon is injected while the temperature of the first stage part is maintained at 50K according to an embodiment of the present disclosure, FIG. 4C illustrates a pressure of argon when argon is injected while the temperature of the first stage part is maintained at 60K according to an embodiment of the present disclosure, and FIG. 4D illustrates a pressure of argon when argon is injected while the temperature of the first stage part is maintained at 65K according to an embodiment of the present disclosure.

Referring to FIG. 4B, it can be seen that when the temperature of the first stage part 212 is maintained at 50K and argon is injected, the pressure is not dropped to 1E-7 Torr or less even after 1,000 minutes. This means that evacuation is not performed.

Referring to FIG. 4C, it can be seen that when the temperature of the first stage part 212 is maintained at 60K and argon is injected, evacuation can be performed to 3E-8 Torr in 5 minutes.

Referring to FIG. 4D, it can be seen that when the temperature of the first stage part 212 is maintained at 65K and argon is injected, evacuation can be performed to 3E-8 Torr in 5 minutes and saturation occurs at 60K or more.

That is, since saturation occurs at the temperature of the first stage part 212 of 60K or more, the temperature of the first stage part 212 is maintained at 60K and optimization conditions for evacuation of an argon gas can be created. Thus, it is possible to implement low power consumption with high evacuation performance.

The vacuum evacuation method performed by the cryopump as described above with reference to FIG. 2A to FIG. 4D can be implemented as a computer program stored in a medium to be executed by a computer or a storage medium including instructions executable by a computer. The vacuum evacuation method performed by the cryopump as described above with reference to FIG. 2A to FIG. 4D can be implemented as a computer program stored in a medium to be executed by a computer.

A computer-readable medium can be any available medium accessible by a computer, including volatile and non-volatile media, removable and non-removable media. Additionally, a computer-readable medium may include computer storage media. Computer storage media includes both volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data.

The above description of the present disclosure is provided for the purpose of illustration, and it would be understood by a person with ordinary skill in the art to which the present disclosure belongs that various changes and modifications may be made without changing technical conception and essential features of the present disclosure. Thus, it is clear that the above-described examples are illustrative in all aspects and do not limit the present disclosure. For example, each component described to be of a single type can be implemented in a distributed manner, likewise, components described to be distributed can be implemented in a combined manner.

The scope of the present disclosure is defined by the following claims rather than by the detailed description of the embodiment, and it should be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present disclosure.

Claims

1. A vacuum evacuation method to be performed by a cryopump which includes: a freezer equipped with a first stage part and a second stage part and configured to cool the first stage part and the second stage part; a cryopanel including a first stage panel cooled by the first stage part and a second stage panel cooled by the second stage part; a cryopump vessel surrounding the cryopanel; a first heater provided in the first stage part; and a second heater provided in the second stage part, the vacuum evacuation method comprising: a process of receiving an injection signal of a process gas from a process gas injection device that injects the process gas into a processing chamber;a process of turning on the first heater based on the injection signal to increase a temperature of the first stage part;a process of measuring the temperature of the first stage part;a process of monitoring whether the temperature of the first stage part reaches a predetermined first stage reference temperature; anda process of vacuum-evacuating the process gas when the temperature of the first stage part reaches the predetermined first stage reference temperature.

2. The vacuum evacuation method of claim 1, wherein the process of increasing the temperature includes a process of gradually increasing the temperature of the first stage part from 35K to 60K by using the first heater.

3. The vacuum evacuation method of claim 1, wherein the process of increasing the temperature includes a process of gradually increasing the temperature of the first stage part by 5K.

4. The vacuum evacuation method of claim 1, wherein a pressure of the process gas increases based on the gradually increased temperature of the first stage part and decreases when the temperature of the first stage part reaches the predetermined first stage reference temperature, andthe pressure of the process gas is from 1E-10 Torr to 1E-6 Torr.

5. The vacuum evacuation method of claim 1, further comprising: a process of receiving a non-injection signal of the process gas from the process gas injection device that injects the process gas into the processing chamber; anda process of turning off the first heater of the first stage part to maintain the temperature of the first stage part in an idle state.