WO2020146278A1

WO2020146278A1 - In-situ clean of turbo molecular pump

Info

Publication number: WO2020146278A1
Application number: PCT/US2020/012407
Authority: WO
Inventors: Wei Wu; Adam THORSNESS; Lai Wei; Jun Hee Han; Jisoo Kim
Original assignee: Lam Research Corp
Current assignee: Lam Research Corp
Priority date: 2019-01-11
Filing date: 2020-01-06
Publication date: 2020-07-16
Anticipated expiration: 2021-07-11

Abstract

A method for in-situ cleaning a turbomolecular pump for a plasma processing chamber is provided. A turbomolecular pump cleaning gas is flowed into the plasma processing chamber. The turbomolecular pump cleaning gas is formed into a plasma that provides turbomolecular pump cleaning radicals in the plasma processing chamber. The turbomolecular pump cleaning radicals are flowed to the turbomolecular pump. The plasma is maintained until the turbomolecular pump is cleaned.

Description

IN-SITU CLEAN OF TURBO MOLECULAR PUMP

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority of U.S. Application No. 62/791,364, filed January 11, 2019, which is incorporated herein by reference for all purposes.

BACKGROUND

[0002] The present disclosure relates to methods of manufacturing of

semiconductor devices. More specifically, the disclosure relates to methods for in- situ cleaning of turbomolecular pumps used in plasma processing chambers for manufacturing semiconductor devices.

[0003] During semiconductor wafer processing, plasma processing chambers for manufacturing semiconductor devices are cleaned. Turbomolecular pumps used on the plasma processing chambers also need to be cleaned.

SUMMARY

[0004] To achieve the foregoing and in accordance with the purpose of the present disclosure, a method for in-situ cleaning a turbomolecular pump for a plasma processing chamber is provided. A turbomolecular pump cleaning gas is flowed into the plasma processing chamber. The turbomolecular pump cleaning gas is formed into a plasma in the plasma processing chamber. The plasma provides turbomolecular pump cleaning radicals. The turbomolecular pump cleaning radicals are flowed to the turbomolecular pump. The plasma is maintained until the turbomolecular pump is cleaned.

[0005] In another manifestation, a method for processing a plurality of substrates in a plasma processing chamber with a turbomolecular pump is provided.

At least one cycle of a turbomolecular pump cleaning cycle is provided wherein each cycle comprises at least one substrate processing cycle and a turbomolecular pump in- situ clean. The at least one substrate processing cycle comprises placing a substrate in the plasma processing chamber, processing the substrate, and removing the substrate. The turbomolecular pump in-situ clean comprises providing a turbomolecular pump cleaning gas into the plasma processing chamber, forming the turbomolecular pump cleaning gas into a plasma that provides turbomolecular pump cleaning radicals in the plasma processing chamber, flowing the turbomolecular pump cleaning radicals to the turbomolecular pump, and maintaining the plasma until the turbomolecular pump is cleaned.

[0006] In another manifestation, a method for processing a plurality of substrates in a plasma processing chamber with a turbomolecular pump is provided. The process comprising at least one cycle of a turbomolecular pump cleaning cycle comprising at least one plasma processing chamber cycle and cleaning the turbomolecular pump. The at least one plasma processing chamber cycle comprises at least one substrate processing cycle comprising placing a substrate in the plasma processing chamber, processing the substrate, removing the substrate, and cleaning the plasma processing chamber. The cleaning the turbomolecular pump in-situ comprises providing a turbomolecular pump cleaning gas into the plasma processing chamber, forming the turbomolecular pump cleaning gas into a plasma that provides turbomolecular pump cleaning radicals in the plasma processing chamber, flowing the turbomolecular pump cleaning radicals to the turbomolecular pump, and maintaining the plasma until the turbomolecular pump is cleaned.

[0007] These and other features of the present disclosure will be described in more detail below in the detailed description of the disclosure and in conjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0009] FIG. 1 is a high level flow chart of an embodiment.

[0010] FIG. 2 is a more detailed flowchart of a step of in-situ pump cleaning.

[0011] FIG. 3 is a schematic view of a plasma processing chamber that may be used in an embodiment.

[0012] FIG. 4 is a computer system that may be used in an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure will now be described in detail with reference to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be apparent, however, to one skilled in the art, that the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present disclosure.

[0014] In the manufacturing of semiconductor devices, plasma processing chambers may be used to etch features or deposit layers over wafers or for other processes. Plasma processing chambers rely on pumps, such as a turbomolecular pump (TMP), to provide low pressure used in plasma processing. Plasma processing may create gas components, such as polymers. Such gas components may deposit in the TMP. Deposits in the TMP may cause the TMP to fail. If a TMP fails, a substrate being processed may be ruined. In order to clean a TMP, a user may remove the TMP from the plasma processing chamber. The TMP may be shipped off-site to be cleaned. A clean TMP is attached to the plasma processing chamber. The removal of the TMP may require that the plasma processing chamber is purged of any hazardous materials. The removal of a TMP and replacement of the TMP requires a significant amount of plasma processing chamber downtime.

[0015] An embodiment provides an in-situ cleaning of a pump, such as a TMP. To facilitate understanding, FIG. 1 is a high level flowchart of a process used in an embodiment. In this embodiment, a substrate is processed (step 104). The substrate processing may be a deposition process or an etching process or may be another substrate processing process. In an embodiment, the substrate processing forms polymers that deposit on the TMP and plasma processing chamber. The process may be repeated (step 108). One or more substrates may be processed. If the process is repeated, the substrate is removed from the plasma processing chamber and a new substrate is placed in the plasma processing chamber. [0016] The plasma processing chamber is then cleaned (step 112). In this embodiment, the cleaning of the plasma processing chamber may provide a plasma processing chamber cleaning gas. In this embodiment, the plasma processing chamber is maintained at a low pressure of less than 50 mTorr. The plasma processing chamber cleaning gas is formed into a plasma. The plasma cleans the plasma processing chambers. Cycles of processing substrates (step 104) and cleaning the plasma processing chamber (step 112) may be repeated (step 116) for one or more cycles until the pump needs to be cleaned. When the pump needs to be cleaned, an in-situ pump clean is provided (step 120). After the pump is cleaned, another substrate may be processed (step 104).

[0017] To more clearly illustrate the in-situ pump clean (step 120), FIG. 2 is a more detailed flowchart of the in-situ pump clean (step 120). A turbomolecular pump cleaning gas is provided in a plasma processing chamber (step 204). In an embodiment, the turbomolecular pump cleaning gas comprises oxygen (O₂), nitrogen (N₂), and nitrogen trifluoride (NF₃). The turbomolecular pump cleaning gas is formed into a plasma (step 208) that provides turbomolecular pump cleaning radicals. In some embodiments, the turbomolecular pump cleaning gas may be flowed for 1-100 seconds as a stabilization step before power is provided to form that turbomolecular pump cleaning gas into a plasma. In this example, a chamber pressure of about 100 mTorr is provided. Radio Frequency (RF) power of 1000-2200 watts at a frequency of 13.56 megahertz (MHz) is provided to form the cleaning gas into a plasma (step 208). The turbomolecular pump cleaning radicals from the plasma are flowed to the TMP (step 212). The plasma processing chamber is used as a remote plasma source for remote plasma and turbomolecular pump cleaning radicals provided to the TMP. The plasma is maintained until the TMP is cleaned (step 216). In this example, the plasma is maintained for 700 to 1000 seconds. After the TMP is cleaned the plasma is stopped (step 220).

[0018] In some embodiments, the processing of a substrate (step 104) causes polymer to deposit in the TMP. In some embodiments, the turbomolecular pump cleaning gas comprises an oxygen containing component. The oxygen containing component may comprise oxygen (O₂) or carbon dioxide (CO₂). Oxygen is used to bum off the polymer. In addition, the TMP cleaning gas may further comprise a halogen containing component, such as fluorine. In some embodiments, the halogen containing component is at least one of NF3, sulfur hexafluoride (SFr,), or carbon tetrafluoride (CF4). In some embodiments, the turbomolecular pump cleaning gas further comprises nitrogen (N2).

[0019] O2 may be useful for burning polymer from the TMP. Additionally, NF₃ and N2 may keep the plasma and radicals reactive while traveling to and through the TMP.

[0020] FIG. 3 schematically illustrates an example of a plasma processing chamber 300, which may be used in an embodiment. The plasma processing chamber 300 includes a plasma reactor 302 having a plasma processing confinement chamber 304 therein. A plasma power supply 306, tuned by a match network 308, supplies power to a transformer-coupled power (TCP) coil 310 located near a power window 312 to create a plasma 314 in the plasma processing confinement chamber 304 by providing an inductively coupled power. The TCP coil 310 may be configured to produce a uniform diffusion profile within the plasma processing confinement chamber 304.

For example, the TCP coil 310 may be configured to generate a toroidal power distribution in the plasma 314. The power window 312 is provided to separate the TCP coil 310 from the plasma processing confinement chamber 304 while allowing energy to pass from the TCP coil 310 to the plasma processing confinement chamber 304. A wafer bias voltage power supply 316, tuned by a match network 318, provides power to an electrode 320 to set the bias voltage on a substrate 364. The electrode 320 is used as a chuck to support the substrate 364. A controller 324 controls the plasma power supply 306, gas source/gas supply mechanism 330, and the wafer bias voltage power supply 316.

[0021] The plasma power supply 306 and the wafer bias voltage power supply 316 may be configured to operate at specific radio frequencies such as, for example, 13.56 megaHertz (MHz), 27 MHz, 2 MHz, 60 MHz, 200 kiloHertz (kHz), 2.54 gigaHertz (GHz), 400 kHz, and 1 MHz, or combinations thereof. Plasma power supply 306 and wafer bias voltage power supply 316 may be appropriately sized to supply a range of powers in order to achieve desired process performance. For example, in one embodiment, the plasma power supply 306 may supply the power in a range of 50 to 5000 Watts, and the wafer bias voltage power supply 316 may supply a bias voltage in a range of 20 to 2000 volts (V). For a bias voltage up to 4 kilovolts (kV) or 5 kV, a power of no more than 25 kilowatts (kW) is provided. In addition, the TCP coil 310 and/or the electrode 320 may be comprised of two or more sub-coils or sub electrodes, which may be powered by a single power supply or powered by multiple power supplies.

[0022] The gas source/gas supply mechanism 330 is in fluid connection with plasma processing confinement chamber 304 through a gas inlet 336, such as a showerhead. The gas inlet 336 may be located in any advantageous location in the plasma processing confinement chamber 304 and may take any form for injecting gas. Preferably, however, the gas inlet 336 may be configured to produce a“tunable” gas injection profile, which allows independent adjustment of the respective flow of the gases to multiple zones in the plasma process confinement chamber 304. The process gases and by-products are removed from the plasma process confinement chamber 304 via a pressure control valve 342 and a TMP 344, which also serve to maintain a particular pressure within the plasma processing confinement chamber 304. A Syndion® tool made by Lam Research Corp. of Fremont, CA, may be used to practice an embodiment.

[0023] In this embodiment, an exhaust pipe 346 is connected to an exhaust side of the TMP 344. The exhaust pipe 346 is in fluid connection with a first end of an isolation valve 370. A second end of the isolation valve 370 is connected to a first end of a chamber foreline 372 and foreline manometer 374. A second end of chamber foreline 372 is in fluid connection with a first end of a facility foreline 376. In this example, the facility foreline 376 is below a facility floor 378. A second end of the facility foreline 376 is in fluid connection with a rough pump 380. Exhaust from the rough pump 380 is flowed to a scrubber pipe 382. The scrubber pipe 382 may direct the exhaust to a scrubber. The scrubber may be used to clean the exhaust and remove chemicals from the exhaust.

[0024] FIG. 4 is a high-level block diagram showing a computer system 400, which is suitable for implementing a controller 324 used in embodiments. The computer system may have many physical forms ranging from an integrated circuit, a printed circuit board, and a small handheld device, up to a huge super computer. The computer system 400 includes one or more processors 402, and further can include an electronic display device 404 (for displaying graphics, text, and other data), a main memory 406 (e.g., random access memory (RAM)), storage device 408 (e.g., hard disk drive), removable storage device 410 (e.g., optical disk drive), user interface devices 412 (e.g., keyboards, touch screens, keypads, mice or other pointing devices, etc.), and a communication interface 414 (e.g., wireless network interface). The communication interface 414 allows software and data to be transferred between the computer system 400 and external devices via a link. The system may also include a communications infrastructure 416 (e.g., a communications bus, cross-over bar, or network) to which the aforementioned devices/modules are connected.

[0025] Information transferred via communications interface 414 may be in the form of signals such as electronic, electromagnetic, optical, or other signals capable of being received by communications interface 414, via a communication link that carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, a radio frequency link, and/or other communication channels. With such a communications interface, it is contemplated that the one or more processors 402 might receive information from a network, or might output information to the network in the course of performing the above-described method steps. Furthermore, method embodiments may execute solely upon the processors or may execute over a network such as the Internet in conjunction with remote processors that shares a portion of the processing.

[0026] The term“non-transient computer readable medium” is used generally to refer to media such as main memory, secondary memory, removable storage, and storage devices, such as hard disks, flash memory, disk drive memory, CD-ROM, and other forms of persistent memory and shall not be construed to cover transitory subject matter, such as carrier waves or signals. Examples of computer code include machine code, such as produced by a compiler, and files containing higher- level code that is executed by a computer using an interpreter. Computer readable media may also be computer code transmitted by a computer data signal embodied in a carrier wave and representing a sequence of instructions that are executable by a processor. [0027] During the processing of the substrate, contaminants, such as polymer, may build up in the TMP 344 and the chamber foreline 372. Processes for cleaning the plasma processing confinement chamber 304 do not sufficiently remove build up in the TMP 344 and the chamber foreline 372. The build-up in the TMP 344 and the chamber foreline 372 may reach a point that causes the processing of the substrate (step 104) to fail. The failure of the processing of the substrate (step 104) causes the processing of the substrate (step 104) to not sufficiently process the substrate so that the resulting substrate or semiconductor features on the substrate would be out of specification. The plasma may not need to reach the facility foreline 376, since heating the facility foreline 376 may be used to prevent buildup in the facility foreline 376.

[0028] Various embodiments provide in-situ cleaning of the TMP 344 and the chamber foreline 372. Oxygen radicals from the plasma are able to burn off polymer deposition in the TMP 344 and the chamber foreline 372. Flowing radicals from the plasma to the TMP 344 and the chamber foreline 372 (step 212) cleans the TMP 344 and the chamber foreline 372. The plasma is maintained for at least 450 seconds in order to allow plasma to sufficiently clean the TMP 344 and the chamber foreline 372. Various embodiments maintain the plasma for at least 450 seconds. Some embodiments maintain the plasma for at least 600 seconds. Other embodiments maintain the plasma for at least 900 seconds.

[0029] In other embodiments, the plasma processing chamber 300 may be other plasma processing devices. Such plasma processing devices may use a turbomolecular pump 344 to provide a desired chamber pressure. In some embodiments, exhaust from the turbomolecular pump 344 is flowed through a chamber foreline 372. The plasma processing chamber 300 may be a capacitively coupled device. The plasma processing chamber 300 may use other power systems to form a gas into a plasma in the plasma processing chamber 300.

[0030] In various embodiments, plasma from the turbomolecular pump cleaning gas and turbomolecular pump cleaning radicals may be used to simultaneously clean the plasma processing chamber 300 and the TMP 344. In various embodiments, a cleaning of the TMP 344 may be provided after each substrate is processed. In some embodiments, the plasma flows to the TMP 344.

[0031] In various embodiments, the plasma processing chamber has a pressure sufficiently high to allow turbomolecular pump cleaning radicals to reach and clean the TMP 344. It has been found that a pressure between 50 mTorr to 150 mTorr would provide the desired cleaning of the TMP 344 if the correct chemistry is provided. To provide the correct chemistry, in various embodiments, a turbomolecular pump cleaning gas has an oxygen (O2) to NF ratio in the range of 2:1 to 7:1. In addition, an 0₃:N₂ ratio is in the range of 10:1 to 30:1. In embodiments that use other fluorine containing components, oxygen and fluorine are provided in a ratio in the range of 10:3 to 20:1. In other embodiments that use halogen containing components, elemental oxygen and a halogen are provided in a ratio in the range of 10:3 to 20:1. Such ratios provide the correct chemistry for pump cleaning radicals.

[0032] While this disclosure has been described in terms of several preferred embodiments, there are alterations, permutations, modifications, and various substitute equivalents, which fall within the scope of this disclosure. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present disclosure. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and various substitute equivalents as fall within the true spirit and scope of the present disclosure.

Claims

CLAIMS What is claimed is:

1. A method for in-situ cleaning a turbomolecular pump for a plasma processing chamber, comprising:

providing a turbomolecular pump cleaning gas into the plasma processing chamber;

forming the turbomolecular pump cleaning gas into a plasma that provides turbomolecular pump cleaning radicals in the plasma processing chamber;

flowing the turbomolecular pump cleaning radicals to the turbomolecular pump; and

maintaining the plasma until the turbomolecular pump is cleaned.

2. The method, as recited in claim 1, wherein the plasma is maintained for at least 450 seconds.

3. The method, as recited in claim 1, wherein the turbomolecular pump cleaning gas comprises an oxygen containing component and a halogen containing component.

4. The method, as recited in claim 3, wherein the turbomolecular pump cleaning gas further comprises N2.

5. The method, as recited in claim 1, wherein the turbomolecular pump cleaning gas comprises O2 and at least one of NF₃, S Fr„ or CF4.

6. The method, as recited in claim 5, wherein the turbomolecular pump cleaning gas further comprises N2.

7. The method, as recited in claim 1, wherein the turbomolecular pump cleaning radicals pass through the turbomolecular pump to a foreline, wherein the

turbomolecular pump cleaning radicals clean polymer from the foreline.

8. The method, as recited in claim 1, wherein the plasma and the turbomolecular pump cleaning radicals clean the plasma processing chamber.

9. A method for processing a plurality of substrates in a plasma processing chamber with a turbomolecular pump, the process comprising at least one cycle of a turbomolecular pump cleaning cycle, comprising:

at least one substrate processing cycle, comprising:

placing a substrate in the plasma processing chamber; processing the substrate; and

removing the substrate; and

cleaning the turbomolecular pump in-situ, comprising:

maintaining the plasma until the turbomolecular pump is cleaned.

10. The method, as recited in claim 9, wherein the turbomolecular pump cleaning gas comprises an oxygen containing component and a halogen containing component.

11. The method, as recited in claim 10, wherein the turbomolecular pump cleaning gas further comprises N2.

12. The method, as recited in claim 9, wherein the turbomolecular pump cleaning gas comprises O2 and at least one of NF₃, S Fr„ or CF4.

13. The method, as recited in claim 12, wherein the turbomolecular pump cleaning gas further comprises N2.

14. The method, as recited in claim 9, wherein the turbomolecular pump cleaning radicals pass through the turbomolecular pump to a foreline, wherein the

turbomolecular pump cleaning radicals clean polymer from the foreline.

15. The method, as recited in claim 9, wherein the plasma and the turbomolecular pump cleaning radicals clean the plasma processing chamber.

16. A method for processing a plurality of substrates in a plasma processing chamber with a turbomolecular pump, the process comprising at least one cycle of a turbomolecular pump cleaning cycle, comprising:

at least one plasma processing chamber cycle, comprising:

at least one substrate processing cycle, comprising:

placing a substrate in the plasma processing chamber;

processing the substrate; and

removing the substrate; and

cleaning the plasma processing chamber; and

cleaning the turbomolecular pump in-situ, comprising:

maintaining the plasma until the turbomolecular pump is cleaned.

17. The method, as recited in claim 16, wherein the turbomolecular pump cleaning gas comprises an oxygen containing component and a halogen containing component.

18. The method, as recited in claim 17, wherein the turbomolecular pump cleaning gas further comprises N2.