WO2012052858A1

WO2012052858A1 - Etching of oxide materials

Info

Publication number: WO2012052858A1
Application number: PCT/IB2011/053625
Authority: WO
Inventors: Takashi Teramoto; Jun Sonobe; Terukuni Toge; Nicolas Blasco; Henrí CHEVREL
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2010-08-16
Filing date: 2011-08-16
Publication date: 2012-04-26
Anticipated expiration: 2013-02-16
Also published as: TW201213594A

Abstract

Oxide film deposits are removed from a film-forming apparatus. In the disclosed methods, a fluorine-containing gas, preferably plasma treated NF3, reacts with the oxide film deposits. The vapors of an organic compound, preferably t-butyl alcohol or acetylacetonate, react with the fluorinated oxide film deposits and generate volatile meta! species which are easily removed from the apparatus.

Description

ETCHING OF OXIDE MATERIALS

Cross-Reference to Related Applications

This application c!aims priority to U.S. provisional application nos. 61/373,952, filed August 16, 2010, and 61 /444,774, filed February 20, 201 1 , the entire contents of both being incorporated herein by reference.

Technical Field

The disclosed methods relate to gas cleaning methods for oxide film deposition chambers.

Background

Oxide materials including but not limited to ZrO₂, Ta₂O₅, HfO₂, and TiO₂ have attracted great attention for advanced generations of DRAM capacitors, Metal-In sulator-Metal architectures and as a substitute for SiO₂ as a gate dielectric material for metal oxide semiconductor (CMOS) technology. Among the materials mentioned, ZrO₂ is widely used in DRAM applications, combining such favorable properties as a high dielectric constant (k=20-42) and wide band gap (5-7eV).

Other oxide materials, such as TiO_2l ZnO₂, SnO₂, ln₂O3, CU2O3, and ITO, any of which may be doped with elements including but not limited to Ai, Ga, B, F, and/or Sn, have attracted attention as Transparent Conductive Oxides (TCOs) in the manufacture of photovoltaic thin-film cells or panels, flat panel displays, and LEDs. The TCO layers in photovoltaic cells serve to al!ow light to enter the light absorbing material from the front side and to collect the current created from both sides of the cells. The solar market is growing rapidly due to increased environmental awareness and associated grid parity policies led by governments. At present, crystalline-silicon based solar cell is main stream, but thin-film based solar cell is competitive. High-k materials or TCOs are typically deposited by thin films deposition techniques such as Physical Vapor Deposition (PVD), sputtering, Metal-Organic Chemical Vapor Deposition (MOCVD), Low Pressure CVD (LPCVD), or Atomic Layer Deposition (ALD).

During the deposition process, these oxide materials may also be deposited on the chamber hardware. For this reason the development of a dry cleaning process to maintain cleanliness in the oxide deposition chamber is indispensable.

The cleaning process will be carried out when the chamber has too much undesired oxide material or materials from the deposition precursors that may contaminate the substrates or affect the deposition parameters. The cleaning process may be scheduled based upon time, number of films deposited, particles detected on a wafer after a deposition, or any other schedule that the manufacturing site may develop in order to have high quality deposits produced in the oxide deposition chamber.

Currently, the oxide chamber cleaning process is typically done by opening the chamber and wiping the undesired deposits from the chamber wails or replacing the "dirty" sub-elements with clean ones. Such a cleaning process is time consuming, labor intensive, requires stopping and opening the chamber, and may expose the workers to potentially hazardous chemicals (residual precursors/acids/solvents/reaction products between the deposits and cleaning solutions/etc). After the undesired deposits are manually cleaned from the chamber wall, the chamber is closed and a vacuum is drawn. This "pump-down" process may be long due to evaporation of the residual cleaning solutions from the chamber walls. The entire cleaning process is non-productive time for the process tool and therefore any method of decreasing the downtime would be welcome in order to decrease the cost of production of oxide deposited films.

A gas phase (dry) cleaning method will decrease operator exposure to hazardous chemicals and process tool downtime. In a gas phase cleaning process, all of the undesired deposited materials on the chamber walls are chemically transformed, become volatile, and are extracted from the deposition chamber to the fab exhaust through a dry pump. Gas phase cleaning processes are widely used for many semiconductor processes such as SiO₂ PECVD deposition chambers or low-k deposition chambers. Gas phase cleaning is not commercially utilized for high-k oxide or zinc oxide deposition chambers because the correct gas chemistry to volatilize the materials on the chamber walls has not been developed.

In proposed dry cleaning processes following high-k deposition, EP

Pat. App. No. 1 ,382,716 utilizes chlorine compounds (BCI₃, COCl₂) in a thermal and or plasma process to remove chlorinated zirconium. JP Pat. App. Pub. No. 2009/188198 advocates a cleaning process using BCI₃ plus 0₂ plasma, as the boron element behaves as a reducing agent for Zr0₂. US Pat. No. 5,709,757 proposes using NCl₃ in a plasma cleaning process. UCLA discloses etching with BCI₃/CS₂ plasma and University of Korea teaches the use of BCI₃/Ar plasma (Plasma etching selectivity of ZrO? to Si in BCI₃/ CI2 plasmas, UCLA, Journal of vacuum science technology, A 21 (6), 1915 (2003) and On the etching mechanism of ZrO? thin films in inductivity coupled BCIg/Ar plasma, University of Korea, Microelectronics Engineering, 85, 348 (2008)). Almost all of the proposed dry cleaning processes rely on chlorine chemistry because chlorinated zirconium and hafnium have a higher volatility than fluorinated zirconium and hafnium. However, processes using CS₂ or BCI₃ in a plasma may be difficult to implement because of the material compatibility between C!, the plasma source, and chamber materials. In addition, highly reactive chlorinated compounds like NCI₃ may raise safety issues.

Another approach has been proposed by ASM in US Pat. App. Pub. No. 2010/099264. ASM sequentially contacts a high-k material with a vapor phase reducing agent and a volatilizing etchant in a cyclical process. A need remains for methods of decreasing the oxide film process tool downtime in order to decrease the cost of production of oxide deposited films. More especially, a dry cleaning method using fluorinated chemistry is desired.

Notation and Nomenclature

Certain abbreviations, symbols, and terms are used throughout the following description and claims and include:

As used herein, the abbreviation "ITO" refers to the film indium tin oxide or tin-doped indium oxide.

As used herein, the term "alkyl group" refers to saturated functional groups containing exclusively carbon and hydrogen atoms and the term "fluoroalkyi group" refers to saturated functional groups containing carbon, fluorine, and/or hydrogen atoms. Further, the term "alkyl group" and "fluoroalkyi group" may refer to linear, branched, or cyclic groups. Examples of linear alkyl groups include without limitation, methyl groups, ethyl groups, propyl groups, butyl groups, etc. Examples of branched alkyls groups include without limitation, isopropyl groups, f-butyi groups, etc. Examples of cyclic alkyl groups include without limitation, cyclopropyl groups, cyclopentyl groups, cyclohexyi groups, etc. One of ordinary skill in the art would recognize the equivalent linear, branched, or cyclic fluoroalkyi groups.

As used herein, the abbreviation "Me" refers to a methyl group; the abbreviation ΈΓ refers to an ethyl group; the abbreviation "iPr" refers to an isopropyl group; and the abbreviation "t-Bu" refers to a tertiary butyl group.

As used herein, the term "independently" when used in the context of describing R groups should be understood to denote that the subject R group is not only independently selected relative to other R groups bearing the same or different subscripts or superscripts, but is also independently selected relative to any additional species of that same R group. For example in the formula MR¹ _X (NR²R³)(_4-X), where x is 2 or 3, the two or three R groups may, but need not be identical to each other or to R² or to R³. Further, it should be understood that unless specifically stated otherwise, values of R groups are independent of each other when used in different formulas.

The standard abbreviations of the elements from the periodic table of elements are used herein, it should be understood that elements may be referred to by these abbreviations (e.g., Hf refers to hafnium, Zr refers to zirconium, Pd refers to palladium, Co refers to cobalt, etc).

Summary

Disclosed are cleaning processes for removing oxide film deposition from a film-forming apparatus. A fluorine-containing gas is introduced into the apparatus. The fluorine-containing gas reacts with the oxide film deposits to produce fluorinated oxide film deposits. The fluorinated oxide film deposits are exposed to vapors of an organic compound, which generates volatile metal species. The disclosed methods may include one or more of the following aspects:

• repeating the cleaning process until ali of the oxide film deposits have been removed from the apparatus;

• the fluorine-containing gas being selected from the group consisting of NF₃, F₂, HF, XeF₂, XeF₄, COF₂, NOF, SF₆, SF₄, CF₄, 2F6, C3F8, C4F-10, and combinations thereof;

• the fluorine-containing gas being NF₃;

• adding NO to the fluorine-containing gas;

• plasma-treating the fluorine-containing gas;

• introducing an inert purge gas between the introducing step and the exposing step;

• the organic compound being an alcohol;

• the organic compound being a tertiary alcohol;

• the organic compound being tert-butyl alcohol; • the alcohol being introduced by a carrier gas;

• the organic compound being selected from the group consisting of amines, beta-diketonates, and combinations thereof;

• the amine having the formula H_XNR₍₃._X> where x is an integer from 1 to 2 and R is an a!kyl group;

• the amine being selected from the group consisting of dimethyiamine, diethylamine, and combinations thereof;

• the beta-diketonate having the formula RC(0)CH₂C(0)R, with each R being independently selected from a C1 -C6 alkyl or fluoroaikyl group;

• the beta-diketonate being selected from the group consisting of tetramethylheptanedione, tetramethyloctanedione, acetylacetone, 1 ,1 ,1 ,5,5,5-hexafiuoroacetylacetone, and combinations thereof;

• the process being carried out at a temperature between approximately 50°C to approximately 500°C;

• the process being carried out at a temperature between approximately 180°C to approximately 300°C;

• the process being carried out at a pressure between approximately 1 mTorr (0.133 Pa) to approximately 400 Torr (53 kPa);

· the process being carried out at a pressure between approximately

1 Torr (133 Pa) to approximately 300 Torr (40 kPa);

• the oxide deposits comprising primarily at least one of Zr, Hf, Ta, Ti, Sn, Zn, In, O, and Si; and

• removing the volatile metal species from the apparatus via the exhaust line of the apparatus.

Also disclosed are cleaning processes for removing oxide film deposits from a film forming apparatus. A fluorine-containing gas is introduced into the apparatus to react with the oxide film deposits. An inert purge gas is introduced. A volatile metal species is generated by exposing the fiuorinated oxide film deposits to vapors of an organic compound. The volatile metal species are removed from the apparatus. The disclosed methods may include one or more of the following aspects:

• the fluorine-containing gas being selected from the group consisting of NF₃, F₂, HF, XeF₂, XeF₄, COF₂, NOF, SF₆, SF₄, CF₄, C₂F₆, C₃F₈, C Fio, and combinations thereof;

• the fluorine-containing gas being NF₃;

• adding NO to the fluorine-containing gas;

• piasma-treating the fluorine-containing gas;

• repeating the cleaning process until all of the oxide film deposits have been removed from the apparatus;

• the organic compound being an alcohol;

• the organic compound being a tertiary alcohol;

• the organic compound being a tert-butyl alcohol;

• the alcohol being introduced by a carrier gas;

• the amine having the formula H_XNR₍₃._X) where x is an integer from 1 to 2 and R is an a!kyi group;

• the amine being selected from the group consisting of dimethylamine, diethylamine, and combinations thereof;

• the beta-diketonate having the formula RC(O)CH₂C(O)R, with each R being independently selected from a Ci-C₆ alkyl or fiuoroalkyl group,

• the beta-diketonate being selected from the group consisting of tetramethylheptanedione, tetramethyloctanedione, acetylacetone, 1 , 1 , 1 ,6,6,6-hexafSuoroacetySacetonate, and combinations thereof;

• the process being carried out at a pressure between approximately 1 mTorr (0.133 Pa) to approximately 400 Torr (53 kPa); • the process being carried out at a pressure between approximately 1 Torr (133 Pa) to approximately 300 Torr (40 kPa);

• the oxide deposits comprising primarily at least one of Zr, Hf, Ta, Ti, Sn, Zn, In, O, and Si .

Brief Description of the Drawings

For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

FIG 1 is a schematic diagram of one apparatus capable of performing the disclosed methods;

FIG 2 is a schematic diagram of a second apparatus capable of performing the disclosed methods;

FIG 3 is a schematic diagram of a third apparatus that was not capable of performing the disclosed methods;

FIG 4 is a schematic diagram of a fourth apparatus capable of performing the disclosed methods;

FIG 5 is a schematic diagram of a fifth apparatus capable of performing the disclosed methods;

FIG 6a is a Scanning Electron Microscope (SEM) image of a ZnO ■ layer before etching;

FIG 6b is a SEM image of the ZnO layer after etching with plasma-treated NF₃ and acetylacetone; and

FIG 6c is a SEM image of the ZnO layer after etching with plasma-treated NF₃ alone. Detailed Description of Preferred Embodiments

Disclosed are cleaning processes for surfaces within a film-forming apparatus following oxide film deposition, the process comprising introducing a fluorine-containing gas into the apparatus to react with the oxide film deposits and exposing the fluorinated oxide film deposits to vapors of an organic compound to generate volatile metal species. The disclosed processes lead to uniform etching of oxide materials with a suitable etching rate.

The terms "after", "subsequent to" and "followed by" are used throughout the specification to indicate that the organic compound is not introduced into the film-forming apparatus at the same time as plasma-treatment, instead, introduction of the organic compound follows removal of the fluorine-containing gas.

The disclosed processes uniformly remove undesired oxide materials left on the surfaces of a film-forming apparatus. The disclosed processes enable the maintenance of clean deposition chambers and lead to the next process step with less downtime.

The oxide fi!m-forming apparatus includes, for example, a thin film vapor deposition chamber, for instance CVD, MOCVD, PECVD, or ALD reaction chambers, and associated introduction and exhaust lines (pipes) for gases. A member designed to hold a semiconductor wafer on which the oxide film is to be formed (for example, a boat in the case of a batch type fi!m-forming apparatus or a susceptor in the case of a singie wafer/substrate type film-forming apparatus) is arranged within the film-forming apparatus. The constituent members of the film-forming apparatus include the reaction chamber, the piping attached to the reaction chamber, and the member designed to hold a semiconductor wafer. The film-forming apparatus may be used to form an oxide film.

In general, the walls of the reaction chamber, whether a batch type or a single wafer/substrate type film-forming apparatus, may for example be formed of quartz, steel, stainless steel, anodized aluminum, bare aluminum, or aluminum oxide (AI₂O₃). The member designed to hold a semiconductor wafer/substrate is generally formed of quartz, silicon carbide (SiC), or a carbon material having its surface coated with silicon carbide. In some applications, such as the deposition of ZnO films, the member may be aluminum. The pipes are usually formed of quartz or stainless steel. The disclosed methods do not attack these chamber materials.

During the cleaning process, the temperature of the chamber may range from approximately 50°C to approximately 400°C, and preferably from approximately 180°C to approximately 300°C. The chamber may be maintained at a pressure ranging from approximately 1 mTorr (0.1 33 Pa) to approximately 400 Torr (53 kPa), and preferably from approximately 1 Torr ( 1 33 Pa) to approximately 300 Torr (40 kPa).

The disclosed cleaning process may be utilized before or after deposition of an oxide film. Suitable oxide films include but are not limited to ZnO, ZnO₂, SnO₂, Cu₂O₃, ln₂O₃, ITO, ZrO₂, Ta₂0₅, Hf0₂, TiO₂, and combinations thereof. Any of the oxide films may be doped with other elements including but not limited to Al, Ga, B, F, and/or Sn.

Preferably, the oxide film is ZnO, HfO₂, or ZrO₂, doped or not. One of ordinary skill in the art will recognize that parameters (e.g., temperature, pressure, flow rate, etc.) different than those disclosed herein may be necessary to remove oxide films other than ZnO, HfO , or ZrO₂ due to different reactivity and volatility characteristics. The disclosed cleaning process may be scheduled based upon time, number of films deposited, particles detected on a wafer after a deposition, or any other schedule that the manufacturing site may develop in order to have high quality deposits produced in the oxide deposition chamber.

In the first step of the disclosed cleaning process, a fluorine-containing gas is introduced into the apparatus and reacts with residual oxide film deposits. The fluorine-containing gas may be NF₃, F₂, HF, XeF₂, XeF₄, COF₂, NOF, SF₆, SF₄, CF₄, C₂F_6J C₃F₈, C₄F₁₀, or combinations thereof. In one alternative, the fluorine-containing gas is NF₃.

NO (nitrogen monoxide) may be added to the fluorine-containing gas. Applicants beiieve that NO may be used to help the fiuorine-containing gas react with the residua! deposits, particularly when the deposits contain doping agents, such as A!, Ga, B, F, and/or Sn. The fluorine-containing gas and NO may be mixed together prior to introduction into the apparatus. Alternatively, the fluorine-containing gas and NO may be introduced into the apparatus separately but simultaneous!y. In one embodiment, F₂ and NO are introduced into the apparatus to react with the oxide film deposits. In another embodiment, NF₃ and NO are introduced into the apparatus to react with the oxide film deposits. In yet another embodiment, XeF₂ and NO are introduced into the apparatus to react with oxide film deposits. These mixtures may contain reaction products of the two gases, but contain no other added gases.

The fluorine-containing gas and optional NO may be subject to plasma treatment. One of ordinary skill in the art will recognize that the plasma-treated fiuorine-containing gas may include the original gas molecule and radicals and ions of the same. For example, plasma-treated NF₃ may include NF₃, nitrogen and fluorine radicals, and negative and positive ions. The fluorine-containing gas and optional NO may be plasma-treated prior or subsequent to introduction into the reaction chamber. The fluorine-containing gas and optional NO may be plasma-treated by methods known in the art.

For example, introducing a fluorine-containing gas into the apparatus may include introducing NF₃ and generating the plasma-treated NF₃ in the apparatus, for example by the Titan™ PECVD System produced by Trion Technologies. The NF₃ may be introduced and held in the chamber prior to plasma processing. Alternatively, the plasma processing may occur simultaneously with the introduction of NF₃. In-situ plasma is typically a 13.56 MHz RF capacitively coupled plasma that is generated between the showerhead and the substrate holder. The substrate or the showerhead may be the powered electrode depending on whether positive ion impact occurs. Typical applied powers in in-situ plasma generators are from approximately 100 W to approximately 1000 W. The disassociation of NF₃ using in-situ plasma is typically less than achieved using a remote plasma source for the same power input and is therefore not as efficient in NF₃ disassociation as a remote plasma system. However, if the oxide film deposition step already utilizes a plasma, in situ plasma may be effectively used with NF₃, requiring only one plasma generator to perform the deposition and the cleaning steps.

Alternatively, introducing a fluorine-containing gas into the apparatus may include introduction of remotely generated plasma-treated NF₃. The MKS Instruments¹ ASTRON^®i reactive gas generator may be used to treat the NF₃ prior to passage into the reaction chamber. Operated at 2.45 GHz, 7kW plasma power, and a pressure ranging from approximately 3 Torr to approximately 10 Torr, NF₃ may be decomposed into three F^" radicals with more than 96% decomposing efficiency. One of ordinary skill in the art will recognize that the plasma treated NF₃ will not remain at 96% decomposing efficiency after departing the plasma apparatus. The plasma treated NF₃ introduced into the reaction chamber will include NF₃, nitrogen and fluorine radicals, and negative and positive ions because the radicals and ions will react during the transition from the apparatus to the reaction chamber. Preferably, the remote plasma may be generated with a power ranging from about 1 kW to about 10 kW, more preferably from about 2.5 kW to about 7.5 kW. Remote plasma-treated NF₃ may be introduced into the chamber at a flow rate between approximately 250 seem to approximately 1000 seem (1 slm) for a duration of between approximately 1 second and approximately 60 seconds. Applicants believe that fluorine radicals and ions in the

plasma-treated fluorine-containing gas react with the oxide film deposits remaining in the film-forming apparatus to form fluorinated oxide film deposits. For example, for oxide film deposits of Zr0₂, the

plasma-treated NF₃ may react to form ZrF_{1 -4} or zirconium oxyfluoride species. Applicants believe that a similar reaction occurs with Hf0₂ deposits. However, these reaction products do not appear to be volatile because test results reveal that, although the appearance of the film changed possibly indicating some type of reaction, the Zr0₂ film thickness does not change before and after introduction of the plasma-treated NF₃.

An inert gas purge may follow introduction of the plasma-treated fluorine-containing gas. The optional purge gas may be for instance N₂, Ar, or mixtures of the two. The optional purge gas may be introduced at flow rate between approximately 250 seem and 2 slm. The optional gas purge may last approximately 1 second to approximately 30 seconds.

An organic compound is subsequently introduced into the film-forming apparatus. Exposure of the fluorinated oxide film deposits to the organic compound generates volatile metal species. The organic compound may be an alcohol, amine, beta-diketonate, and mixtures thereof.

Gaseous organic compounds may be introduced directly into the film-forming apparatus. If the organic compound is a Iiquid, the organic compound may be fed to a vaporizer where it is vaporized before it is introduced into the film-forming apparatus. Alternatively, the Iiquid organic compound may be vaporized by passing a carrier gas into a container containing the organic compound or by bubbling the carrier gas into the organic compound. The carrier gas and organic compound are then introduced into the film-forming apparatus as a vapor. The carrier gas may include, but is not limited to, Ar, He, N₂, and mixtures thereof. In another alternative, a container of the iiquid organic compound may be heated to a temperature sufficient to produce a vapor of the organic compound and introduced into the film-forming apparatus without the use of a carrier gas. In either alternative, the container may be heated to a temperature that permits the organic compound to be in its liquid phase and to have sufficient vapor pressure. For example, the container may be maintained at a temperature between approximately 0°C and approximately 150°C. Those skilled in the art will recognize that the temperature of the container may be adjusted in a known manner to control the amount of organic compound vaporized.

The alcohol is preferably a tertiary alcohol and more preferably tert-butyl alcohol. The alcohol may be introduced into the chamber at a flow rate between approximately 5 seem to approximate!y 50 seem for a duration of between approximately 1 second and approximately 60 seconds. Although having identical introduction times in the following example, one of ordinary skill in the art will recognize that the introduction times of the plasma-treated NF₃ and alcohol may differ.

An inert gas, such as nitrogen, argon, or mixtures thereof, may be introduced with the alcohol if the alcohol exhibits low vapor pressure, as is the case for tert-butyl alcohol. In such cases, the nitrogen may be introduced at a flow rate between approximately 50 seem to approximately 250 seem simultaneously with and for the same duration as the alcohol.

The amine may be selected from compounds having the formula H_xNR(_3-x) where x is an integer from 1 to 2 and R is an alkyi group.

Exemplary amines include methylamine, ethylamine, isopropyl amine, dimethylamine, diethylamine, diisopropylamine, and mixtures thereof. Preferably, the amine may be selected from dimethylamine or

diethylamine. The amine may be introduced into the chamber at a flow rate between approximately 5 seem to approximately 50 seem for a duration of between approximately 1 second and approximately 60 seconds. Although having identical introduction times in the following example, one of ordinary skill in the art will recognize that the introduction times of the plasma-treated NF3 and amine may differ. The beta-diketonate may be selected from compounds of the formula RC(0)CH2C(0)R, with each R being independently selected from a Ci-C-6 alkyl or fluoroalkyl group. Exemplary beta-diketonates include tetramethylheptanedione, tetramethyloctanedione, acetylacetone,

1 ,1 ,1 ,5,5,5-hexafluoroacetylacetone, and mixtures thereof. The β-diketonate may be introduced into the chamber at a flow rate between approximately 5 seem to approximately 50 seem for a duration of between approximately 1 second and approximately 60 seconds. Although having identical introduction times in the following example, one of ordinary skill in the art will recognize that the introduction times of the plasma-treated NF₃ and β-diketonate may differ.

Applicants believe that the fluorine ions in the fluorinated oxide film deposits produced by the first process step react with the organic compound to produce volatile metal species.

The volatile metal species are removed from the chamber via the exhaust line of the chamber. In one embodiment, the flow rate of the organic compound and the pressure of the chamber force the volatile metal species from the chamber via the outlet port. In effect, the organic compound travels through the chamber, carrying the volatile metal species with it and through the chamber outlet port. in another embodiment, the organic compound may be introduced and retained in the chamber for a period of time. The chamber may then be evacuated under its own pressure, with the assistance of a vacuum, or with the assistance of a purge gas such as nitrogen, thereby removing the organic compound and volatile metal species from the chamber.

This process may be sufficient to remove the oxide film deposits from the apparatus or may be repeated until the oxide film deposits have been removed. Additionally, the disclosed process does not attack the chamber materials. The disclosed methods are capable of removing greater than 50 A (5000 pm) of metal oxide per cycle, preferably greater than 100 A (10,000 pm) of metal oxide per cycle, and more preferably greater than 200 A (20,000 pm) of metal oxide per cycle. One cycle Includes both the introduction of the fluorine-containing gas and exposure of the fluorinated oxide film deposits to vapors of an organic compound. Alternatively, one cycle includes both the introduction of the

fluorine-containing gas and generation of a volatile metal species. In either alternative, the process may include only one cycle or multiple cycles, depending upon the thickness of the oxide film deposits and the difficulty in removing them.

The disclosed processes may be performed in an apparatus similar to those disclosed in FIGS 1-5. However, in the example provided in FIG 3, the fluorine-containing gas and the organic compound are reacted prior to introduction into the deposition chamber. The resulting gas mixture did not remove the oxide deposits from the chamber. The disclosed process could be successfully formed in the apparatus of FIG 3 by keeping valve V2 closed during introduction of the fluorine-containing gas (depicted as NF3) and subsequently by keeping va!ve V1 closed during introduction of the organic compound (depicted as acetylacetone).

In FIGS 1 and 4, the fluorine-containing gas, depicted as NF3, is mixed with argon gas prior to introduction into a remote plasma system. Any of the other fluorine-containing gases disclosed herein may be used in place of NF₃. Valves V1 and V2 remain open and valve V3 is closed during the introduction of the fluorine-containing gas. Valve V2 is closed, but valve V1 remains open so that argon continuously flows into the apparatus in order to maintain the plasma. In FIG 1 , nitrogen flows through a cylinder of the organic compound, which is depicted as acetylacetone. In FIG 4, the organic compound, once again depicted as acetylacetone, is vaporized prior to introduction into the apparatus. One of ordinary skill in the art will recognize that argon, helium, or any combination of nitrogen, argon, and helium may be used in the place of nitrogen. Additionally, any of the other organic compounds disclosed herein may be used in place of acetylacetone. Valves V1 and V3 remain open and va!ve V2 is closed during the introduction of the organic compound. The process is repeated until the oxide deposits are removed from the chamber.

FIGS 2 and 5 are similar to FIGS 1 and 4, except that the fluorine-containing gas, depicted as NF₃, is not mixed with argon gas prior to introduction into the remote plasma system. As a result, the

fluorine-containing gas is diverted to exhaust via valve V1 during the second step of the process. The fluorine-containing gas passes through the plasma system and is introduced into the apparatus through valve V2. Valve V2 is closed and valves V1 and V3 are opened during introduction of the organic compound. The process is repeated until the desired results are obtained.

In FIG 3, the fluorine-containing gas, depicted as NF_3> and the organic compound, depicted as acetylacetone, were mixed prior to introduction to the apparatus. In other words, both valves V1 and V2 were open. The resulting gas mixture did not remove the oxide deposits from the chamber.

Examples

The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.

Example 1

A Zr0₂ sample was etched using plasma-treated NF₃ in

combination with alcohol at a low temperature.

Remotely generated piasma-treated NF₃ is introduced for 5 seconds into a chamber kept at 200°C. The Zr0₂ sample becomes fluorinated and Applicants believe that ZrF₄ (vapor pressure 400Torr at 873°C) is formed. It is stationary over the ZrO_≥ thin layer remaining on the substrate.

Alcohol is subsequently injected for 5 seconds. Applicants believe that the ZrF₄ reacts with the tertiary butyl alcohol (HO-CMe₃) and forms the volatile compound Zr-(OCMe₃)₄ (vapor pressure 400Torr at 200°C) and/or ZrF_x(OtBu)4_-)(, which is easily removed from the apparatus. In the end, a Zr0₂ surface appears again and the method is repeated until no ZrO₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the alcohol do not need to be identical. For example, for fiuorinated compounds having a higher vapor pressure than ZrF_4[ the plasma-treated NF₃ may be introduced for 5 seconds and the alcohol may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximately 10 seconds and removes approximately 50A (5000 pm) of ZrO₂ layer. ZrO₂ thin film is uniformly etched when

plasma-treated NF₃ and alcohol is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally.

Based upon the Scanning Electron Microscope (SEM) micrograph, uniformity after etching of ZrO₂ is tremendously improved as compared with plasma-treated NF₃ alone.

Comparative Example 1

Plasma-treated NF₃ alone (i.e., without subsequent introduction of alcohol) etched ZrO₂, but its surface after etching became uneven and ZrO₂ partly remained.

Comparative Example 2

ZrO₂ surface is not evenly etched if alcohol is mixed together with plasma-treated NF₃, whether the two are mixed in a remote plasma treatment device or the alcohol is mixed with the plasma-treated NF₃ downstream from the p!asma treatment device and upstream from the chamber.

Comparative Example 3

To verify the effectiveness of a different alcohol, a primary alcohol

(C₂H₅OH) also was tested, but no Zr0₂ etching resulted.

Exampie 2

A Zr0₂ sample was etched using plasma-treated NF₃ in

combination with alcohol at a low temperature.

Remoteiy generated plasma-treated NF₃ is introduced for 30 seconds into a chamber kept at 200°C and 2 Torr (267 Pa). The Zr0₂ sample becomes fluorinated and Appiicants be!ieve that ZrF₄ (vapor pressure 400Torr at 873°C) is formed, it is stationary over the Zr0₂ thin layer remaining on the substrate.

Aicohoi is subsequently injected for 30 seconds. Applicants believe that the ZrF₄ reacts with the tertiary butyi alcohol (HO-CMe₃) and forms the volatile compound Zr-(OCMe₃)4 and/or ZrF_x(OtBu)₄-x, which are easily removed from the apparatus. In the end, a Zr0₂ surface appears again and the method is repeated until no Zr0₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the alcohol do not need to be identical. For example, for fluorinated compounds having a higher vapor pressure than ZrF₄, the plasma-treated NF₃ may be introduced for 5 seconds and the alcohol may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximately 60 seconds and removes approximately 125A (12,500 pm) of Zr0₂ layer. Zr0₂ thin film is uniformly etched when plasma-treated NF₃ and alcohol is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally. Example 3

A Zr0₂ sample was etched using plasma-treated NF₃ in

combination with acetylacetone at a iow temperature.

Remotely generated piasma-treated NF₃ is introduced for 30 seconds into a chamber kept at 200°C and 2 Torr (267 Pa). The Zr0₂ sample becomes fluorinated and Applicants believe that ZrF₄ is formed. It is stationary over the Zr0₂ thin layer remaining on the substrate.

Acetylacetone is subsequently injected for 30 seconds. Applicants believe that the ZrF₄ reacts with the acetylacetone and forms volatile compounds which are easily removed from the apparatus, in the end, a ZrO₂ surface appears again and the method is repeated until no Zr0₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the acetylacetone do not need to be identical. For example, for fluorinated compounds having a higher vapor pressure than ZrF_4l the plasma-treated NF₃ may be introduced for 5 seconds and the acetylacetone may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximately 60 seconds and removes approximately 134A

(13,400 pm) of ZrO₂ layer. ZrO₂ thin film is uniformly etched when piasma-treated NF₃ and acetylacetone is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally.

Example 4

A ZrO₂ sample was etched using plasma-treated NF₃ in

combination with diethylamine at a low temperature.

Remotely generated piasma-treated NF₃ is introduced for 30 seconds into a chamber kept at 200°C and 2 Torr (267 Pa). The ZrO₂ sample becomes fluorinated and Applicants believe that ZrF₄ (vapor pressure 400Torr at 873°C) is formed. It is stationary over the ZrO₂ thin layer remaining on the substrate. Diethylamine is subsequently injected for 30 seconds. Applicants beiieve that the ZrF₄ reacts with the diethylamine and forms volatile compounds which are easily removed from the apparatus. In the end, a Zr0₂ surface appears again and the method is repeated until no Zr0₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the diethylamine do not need to be identical. For example, for fluorinated compounds having a higher vapor pressure than ZrF₄, the plasma-treated NF₃ may be introduced for 5 seconds and the diethylamine may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximately 60 seconds and removes approximately 240A (24,000 pm) of ZrO₂ layer. ZrO₂ thin film is uniformly etched when plasma-treated NF₃ and ethyiamine is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally.

Example 5

A HfO₂ sample was etched using plasma-treated NF₃ in

combination with alcohol at a low temperature.

Remotely generated plasma-treated NF₃ is introduced for 30 seconds into a chamber kept at 200°C and 2 Torr (267 Pa). The HfO₂ sample becomes fluorinated and Applicants believe that HfF₄ is formed. It is stationary over the HfO₂ thin layer remaining on the substrate.

Alcohol is subsequently injected for 30 seconds. Applicants believe that the HfF₄ reacts with the tertiary butyl alcohol (HO-CMe₃) and forms the volatile compound Hf-(OCMe₃)₄ and/or HfF_x(OtBu)₄,_x, which are easily removed from the apparatus. In the end, a HfO2 surface appears again and the method is repeated until no HfO₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the alcohol do not need to be identical.

For example, for fluorinated compounds having a higher vapor pressure than HfF₄, the plasma-treated NF₃ may be introduced for 5 seconds and the alcohol may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximately 60 seconds and removes approximately 79A (7,900 pm) of HfO₂ layer. Hf0₂ thin film is uniformly etched when

Example 6

A Hf0₂ sample was etched using plasma-treated NF₃ in

combination with acetylacetone at a low temperature.

Remotely generated plasma-treated NF₃ is introduced for 30 seconds into a chamber kept at 200°C and 2 Torr (267 Pa). The Hf0₂ sample becomes fluorinated and Applicants believe that HfF₄ is formed. It is stationary over the HfO₂ thin layer remaining on the substrate.

Acetylacetone is subsequently injected for 30 seconds. Applicants believe that the HfF₄ reacts with the acetylacetone and forms volatile compounds which are easily removed from the apparatus. In the end, a HfO₂ surface appears again and the method is repeated until no HfO₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the acetylacetone do not need to be identical. For example, for fluorinated compounds having a higher vapor pressure than HfF₄, the plasma-treated NF₃ may be introduced for 5 seconds and the acetylacetone may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximately 60 seconds and removes approximately 260A

(26,000 pm) of HfO₂ layer. HfO₂ thin film is uniformly etched when plasma-treated NF₃ and acetylacetone is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally. Example 7

A Hf0₂ sample was etched using plasma-treated NF₃ in

combination with diethy!amine at a low temperature.

Remotely generated plasma-treated NF₃ is introduced for 30 seconds into a chamber kept at 200°C and 2 Torr (267 Pa). The Hf0₂ sample becomes fluorinated and Applicants believe that HfF₄ is formed. It is stationary over the Hf0₂ thin layer remaining on the substrate.

Diethylamine is subsequently injected for 30 seconds. Applicants believe that the HfF₄ reacts with the diethylamine and forms volatile compounds which are easily removed from the apparatus. In the end, a Hf0₂ surface appears again and the method is repeated until no Hf0₂ remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the diethylamine do not need to be identical. For examp!e, for fluorinated compounds having a higher vapor pressure than HfF₄, the plasma-treated NF3 may be introduced for 5 seconds and the diethylamine may be introduced for 10 seconds.

This process may be repeated as necessary. One process cycle takes approximateiy 60 seconds and removes approximately 260A (26,000 pm) of HfO₂ layer. HfO₂ thin film is uniformly etched when plasma-treated NF₃ and alcohol is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally.

Example 8

A ZnO sample was etched using plasma-treated NF₃ in

combination with acetylacetone at a low temperature.

Remotely generated plasma-treated NF₃ is introduced for 10 seconds into a chamber kept at 200°C and 1 .8 Torr (240 Pa). The ZnO sample becomes fluorinated and Applicants believe that ZnF₂ is formed. St is stationary over the ZnO thin layer remaining on the substrate. Acetylacetone is subsequently injected for 10 seconds. Applicants believe that the ZnF₂ reacts with the acetylacetone and forms zinc acetylacetonate, a volatile compound which is easily removed from the apparatus, in the end, a ZnO surface appears again and the method is repeated until no ZnO remains.

One of ordinary skill in the art will recognize that the injection time for the plasma-treated NF₃ and the acetylacetone do not need to be identical. For example, for fluorinated compounds having a higher vapor pressure than ZnF₂, the plasma-treated NF₃ may be introduced for 5 seconds and the acetylacetone may be introduced for 10 seconds.

This process may be repeated as necessary. As shown in FIGS 6a and 6b, one process cycle takes approximately 20 seconds and removes approximately 243A (24,300 pm) of ZnO layer. Multiple trials resulted in an average ZnO removal rate of 1050 A/minute (105,000 pm/minute). ZnO thin film is uniformly etched when plasma-treated NF₃ and acetylacetone is sequentially introduced into the chamber. Thus each gas should be injected into chamber reciprocally.

Comparative Example 4

As shown in FIGS 6a and 6c, plasma-treated NF₃ alone (i.e., without subsequent introduction of acetylacetone) did not etch ZnO at 200°C. After a 20 minute exposure to 500 seem of NF₃ plasma at 1 .8 Torr (240 Pa), the ZnO film thickness only changed from 29,900 A

(2,990,000 pm) to 28,663 A (2,866,300 pm).

It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments examples given above and/or the attached drawings.

Claims

What is claimed is:

1 . A cleaning process for removing oxide film deposits from a film forming apparatus comprising the sequence of:

(a) introducing a fluorine-containing gas into the apparatus to react with the oxide film deposits; and

(b) exposing the fluorinated oxide film deposits to vapors of an organic compound to generate volatile metal species.

2. The process of claim 1 , wherein the fluorine-containing gas is selected from the group consisting of NF_3j F₂, HF, XeF_2l XeF₄, COF₂, NOF, SF₆, SF₄, CF₄₎ C₂F₆, C₃F₈, C₄F₁₀, and combinations thereof, preferably NF₃.

3. The process of claim 1 or 2, further comprising adding NO to the fluorine-containing gas.

4. The process of any one of claims 1 to 3, further comprising plasma-treating the fluorine-containing gas.

5. The process of any one of claims 1 to 4, further comprising repeating the cleaning process until all of the oxide film deposits have been removed from the apparatus.

6. The process of any one of claims 1 to 5, further comprising the step of introducing an inert purge gas between the introducing step and the exposing step.

7. The process of any one of claims 1 to 6, wherein the organic compound is an alcohol, preferably a tertiary alcohol, and more preferably tert-butyl alcohol.

8. The process of claim 7, wherein the aicohoi further comprises nitrogen.

9. The process of any one of claims 1 to 6, wherein the organic compound is selected from the group consisting of amines, beta-diketonaies, and combinations thereof.

10. The process of claim 9, wherein the amine has the formula HxNR(3-x₎ where x is an integer from 1 to 2 and R is an alkyl group.

1 1 . The process of claim 10, wherein the amine is selected from the group consisting of dimethylamine, diethylamine, and combinations thereof.

12. The process of claim 9, wherein the beta-diketonate has the formula RC(0)CH₂C(0)R, with each R being independently selected from a C-i-C-6 alkyl or fluoroalkyi group.

13. The process of claim 12, wherein the beta-diketonate is selected from the group consisting of tetramethylheptanedione, tetramethyloctanedione, acetylacetone, 1 , ,1 ,6,6,6-hexafluoroacetylacetonate, and combinations thereof.

14. The process of any one of claims 1 to 6, wherein the process is carried out at a temperature between approximately 50°C to approximately 500°C, preferably between approximately 180°C to approximately 300°C, and a pressure between approximately 1 mTorr (0.133 Pa) to approximately 400 Torr (53 kPa), preferably between approximately 1 Torr (133 Pa) to approximately 300 Torr (40 kPa).

1 5. The process of any one of claims 1 to 6, wherein the oxide deposits comprise primarily at least one of Zr, Hf, Ta, Ti, Sn, Zn, in, O, and Si .